JP3006126B2 - Fuel injection control device for 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 fuel injection control device for an internal combustion engine.

[0002]

2. Description of the Related Art A concave groove is formed on the inner wall surface of a cylinder head on the exhaust port side or on the top surface of a piston on the exhaust port side.
A first fuel injection valve and a first spark plug facing the concave groove are disposed on the inner wall surface of the cylinder head, and a second fuel injection valve and a second spark plug are disposed in the intake passage.
And a second ignition plug is disposed at the center of the inner wall surface of the cylinder head. During low engine load operation after completion of warm-up, the first fuel injection valve is disposed between the intake stroke and the compression stroke. The combustion chamber is stratified so that the air-fuel mixture gathers around the first ignition plug by injecting the fuel into the groove of the first fuel injection valve. Fuel is injected into the intake passage from the second fuel injection valve during an intake stroke earlier than the fuel injection timing from the valve, and thereafter fuel is injected into the concave groove from the first fuel injection valve during the intake stroke and the compression stroke. There is known a four-cycle internal combustion engine in which a uniform air-fuel mixture is formed in a combustion chamber (see JP-A-61-250354). In this four-cycle internal combustion engine, at the time of engine startup, fuel injection from the second fuel injection valve into the intake passage and fuel injection from the first fuel injection valve into the concave groove, as in the case of the above-described high engine load operation. To form a uniform mixture in the combustion chamber. As described above, when the engine is started, a large amount of fuel is injected by using the air in the entire combustion chamber for combustion to increase the engine output, and thus the engine speed is rapidly increased.

[0003]

However, even if an attempt is made to form a uniform air-fuel mixture throughout the combustion chamber when the engine is started as described above, the fuel injection valve is actually actually low at the beginning of the engine start because the engine temperature is particularly low. The fuel injected from the fuel is not easily atomized, and as a result, a good homogeneous mixture is not formed in the combustion chamber, and the liquid fuel is likely to be localized. In particular, when attempting to form a rich homogeneous mixture in the combustion chamber in order to ensure good ignitability at the time of starting the engine at such a low engine temperature, a larger amount of liquid fuel is localized in the combustion chamber. Becomes These liquid fuels move around the combustion chamber due to the flow of air in the combustion chamber and the like, and as a result, the ignition plug is covered with the liquid fuel to cause smoldering of the ignition plug, or the liquid fuel is transferred to the inner periphery of the cylinder bore. The adhesion on the wall surface causes a problem that the lubricating oil between the inner peripheral wall surface of the cylinder bore and the outer peripheral wall surface of the piston is diluted. In addition, the fuel localized in the combustion chamber is not satisfactorily burned, and as a result, a large amount of HC gas is generated.

[0004]

According to the present invention, a fuel is injected from a fuel injection valve disposed in a combustion chamber so that an air-fuel mixture is collected around an ignition plug. Internal combustion that can stratify the interior of the combustion chamber and form a uniform air-fuel mixture in the combustion chamber earlier than when stratifying the interior of the combustion chamber at the time of starting fuel injection from a fuel injection valve disposed in the combustion chamber or in the supply passage. In the engine, when the engine speed is lower than a predetermined speed at the time of engine start, the combustion chamber is stratified, and when it is detected that the engine speed becomes higher than the predetermined speed, the combustion chamber is uniformly strung. Provided is a fuel injection control device for an internal combustion engine that forms an air-fuel mixture.

[0005]

When the engine speed is lower than a predetermined speed when the engine is started, the combustion chamber is stratified so that a fuel-air mixture is gathered around the spark plug by fuel injected from a fuel injection valve disposed in the combustion chamber. When it is detected that the engine speed has become higher than a predetermined speed, the fuel injection start timing from the fuel injection valve arranged in the combustion chamber or the supply passage is advanced earlier than in the case of stratification. As a result, a uniform mixture is formed in the combustion chamber.

[0006]

4 to 7 show a case where the present invention is applied to a direct injection two-cycle internal combustion engine. 4 to 7, reference numeral 1 denotes a cylinder block, 2 denotes a piston reciprocating in the cylinder block 1, 3 denotes a cylinder head fixed on the cylinder block 1, 4 denotes an inner wall 3a of the cylinder head 3 and the piston. 2 shows a combustion chamber formed between the top surfaces of the two. A concave groove 5 is formed on the cylinder head inner wall surface 3a, and a pair of air supply valves 6 are arranged on the cylinder head inner wall surface portion 3b that forms the bottom wall surface of the concave groove 5. On the other hand, the cylinder head inner wall surface portion 3c excluding the concave groove 5 is inclined and substantially flat, and a pair of exhaust valves 7 is disposed on the cylinder head inner wall surface portion 3c. The cylinder head inner wall surface portion 3b and the cylinder head inner wall surface portion 3c are connected to each other via the peripheral wall 8 of the concave groove 5.

As shown in FIG. 5, the peripheral wall 8 of the concave groove is disposed very close to the peripheral edge of the air supply valve 6 and extends in a circular arc along the peripheral edge of the air supply valve 6; It comprises a fresh air guide wall 8b located between the air supply valves 6, and a pair of fresh air guide walls 8c located between the peripheral wall of the cylinder head inner wall surface 3a and the air supply valve 6. Each mask wall 8a extends toward the combustion chamber 4 below the intake valve 6 at the maximum lift position, so that the opening between the peripheral portion of the intake valve 6 located on the exhaust valve 7 side and the valve seat 9 is formed. The air supply valve 6 is closed by the mask wall 8a throughout the opening period of the air supply valve 6.

The ignition plug 10 is provided on the inner wall 3 of the cylinder head.
It is arranged on the cylinder head inner wall surface portion 3c so as to be located substantially at the center of the cylinder head a. On the other hand, the exhaust valve 7 is not provided with a mask wall that covers the opening between the exhaust valve 7 and the valve seat 11, so that when the exhaust valve 7 is opened, the exhaust valve 7 and the valve seat 11
The entire opening formed between the openings opens into the combustion chamber 4.

In the cylinder head 3, an air supply port 12 is formed for the air supply valve 6, and an exhaust port is formed for the exhaust valve 7.
13 is formed. In addition, a first fuel injection valve 14a and a second fuel injection valve 14b are arranged on the peripheral portion of the cylinder head inner wall surface 3a near the pair of supply valves 6, respectively. The first fuel injection valve 14a and the second fuel injection valve 14b are attached to the cylinder head 3 in parallel with each other. As shown in FIGS. 8, 11 and 13, the first fuel injection valve 14a and the second
Fuel is injected from the fuel injection valves 14b into the combustion chamber 4 below the ignition plug 10, respectively. The first embodiment of the present invention
The fuel injection valve 14a and the second fuel injection valve 14b are each electromagnetically controlled to open and close by a solenoid (not shown).

As shown in FIGS. 6 and 7, a second fuel injection valve 14b is provided on the top surface of the piston 2 from below the spark plug 10.
A concave groove 15 is formed to extend to below the front end portion. In the embodiment shown in FIGS. 6 and 7, this groove 15 is a vertical plane K- including the spark plug 10 and the nozzle port 20 of the second fuel injection valve 14b.
It has a substantially spherical shape symmetric with respect to K. Also, piston 2
A concave portion 16 having a spherical shape with a smaller radius of curvature than that of the concave groove 15 is formed at the center of the top surface. This recess 16 also has a vertical plane K
−K, and the recess 16 is opened above the concave inner wall surface of the groove 15. As shown in FIG. 7, when the piston 2 reaches the top dead center, the ignition plug 10 enters the recess 16. On the other hand, the top surface portion 2a of the piston 2 on the opposite side of the recess 16 from the first fuel injection valve 14a and the second fuel injection valve 14b.
Is formed from an inclined substantially flat surface, and as shown in FIG. 7, when the piston 2 reaches the top dead center, a squish area is provided between the cylinder head inner wall surface portion 3c and the piston top surface portion 2a.
17 is formed.

As shown in FIG. 4, the air supply port 12 is connected to a surge tank 23 via a corresponding air supply branch 22.
The surge tank 23 is connected to the discharge side of an engine-driven mechanical supercharger 25 via an air supply duct 24, and the suction side of the mechanical supercharger 25 is connected to an air supply duct 26. The air supply duct 26 is connected to an air cleaner 28 via an air flow meter 27, and a throttle valve 29 is disposed in the air supply duct 26. Further, a bypass passage 31 is branched from the air supply duct 26 upstream of the throttle valve 29, and the bypass passage 31 is connected to the air supply duct 26 between the throttle valve 29 and the mechanical supercharger 25. In the bypass passage 31, a bypass control valve 32 for controlling the amount of air flowing in the bypass passage 31 is arranged. The bypass control valve 32 is driven by, for example, a step motor, and the step motor is controlled by an output signal of the electronic control unit 40.

The electronic control unit 40 is composed of a digital computer, and a ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, and a backup RAM 45 interconnected by a bidirectional bus 41. , An input port 46 and an output port 47. The air flow meter 27 generates an output voltage proportional to the intake air amount Q, and this output voltage is input to an input port 46 via an AD converter 48. A water temperature sensor 35 that generates an output voltage proportional to the engine cooling water temperature TW is attached to the cylinder block 1, and the output voltage of the water temperature sensor 35 is input to an input port 46 via an AD converter 49. Further, the input port 46 is connected to a rotation speed sensor 36 that generates an output signal indicating the engine rotation speed N. On the other hand, output port 47
Represents the first fuel injection valve 14a and the second
It is connected to the fuel injection valve 14b. Further, the output port 47 is connected to the ignition plug 10 and the bypass control valve 32 via corresponding drive circuits 52 and 53, respectively.

As shown in FIG. 9, in the embodiment shown in FIGS. 4 to 8, the exhaust valve 7 opens before the air supply valve 6, and the exhaust valve 7 closes before the air supply valve 6. I do. 4 to 8
In the embodiment shown in FIG. 2, when stratifying the inside of the combustion chamber 4 so that the air-fuel mixture gathers around the ignition plug 10, the second fuel injection valve 14b
Fuel injection is performed only from the first fuel injection valve 14a, and when a uniform mixture is formed in the combustion chamber 4, fuel injection is performed only from the first fuel injection valve 14a. In Figure 9 I _t shows an example of a fuel injection timing of the second fuel injection valve 14b in the case of stratified combustion chamber 4, in a case I _h is to form a homogeneous mixture in the combustion chamber 4 An example of the fuel injection timing from the first fuel injection valve 14a is shown. The fuel injection I _t from the second fuel injection valve 14b in the case of stratified combustion chamber 4 as shown in FIG. 9 performed in the end of the compression stroke, in the case of forming a homogeneous mixture in the combustion chamber 4 the fuel injection I _h from the first fuel injection valve 14a is started by the time the exhaust valve 7 is closed.

FIG. 3 shows an engine operating region T in which the combustion chamber 4 is stratified so that the air-fuel mixture gathers around the ignition plug 10 in the operation state after the completion of the engine start, and a uniform air-fuel mixture is formed in the combustion chamber 4. An engine operation region H is shown. As shown in FIG. 3, in the embodiment shown in FIGS. 4 to 8, after the start of the engine is completed, the combustion is performed by stratifying the inside of the combustion chamber 4, or a uniform mixture is formed in the combustion chamber 4 for combustion. Is determined from the engine load Q / N and the engine speed N. 3, the combustion chamber 4 is stratified at the time of low engine load operation after completion of the engine start, and the combustion chamber 4 at the time of high engine load operation.
It can be seen that a uniform air-fuel mixture is formed therein. The relationship shown in FIG. 3 is stored in the ROM 42 in advance.

Next, referring to FIG. 10 to FIG. 13, the operation in the case where the inside of the combustion chamber 4 is stratified in the operation state after the completion of the engine start, that is, the operation in the stratified combustion operation region T shown in FIG. The operation in the case of forming a uniform mixture in the chamber 4, that is, the operation in the uniform combustion operation region H shown in FIG. 3 will be described.

As shown in FIG. 10, the supply valve 6 and the exhaust valve 7
Is opened, air flows into the combustion chamber 4 via the air supply valve 6. At this time, since the opening of the air supply valve 6 on the exhaust valve 7 side is covered by the mask wall 8a, the air flows into the combustion chamber 4 from the opening of the air supply valve 6 on the side opposite to the mask wall 8a. This air descends along the inner wall surface of the cylinder bore below the air supply valve 6 as indicated by the arrow W, and then travels along the top surface of the piston 2 and rises along the inner wall surface of the cylinder bore below the exhaust valve 7, and Will flow in a loop in the combustion chamber 4. The air W flowing in the loop shape causes the combustion chamber 4
The burned gas inside is exhausted through the exhaust valve 7, and the swirling flow X swirling in a vertical plane is generated in the combustion chamber 4 by the air W flowing in the loop. Next, when the piston 2 starts rising after passing through the bottom dead center BDC and the exhaust valve 7 closes, the first fuel injection valve 14a or the second fuel injection valve 14
The fuel injection from b is performed.

FIGS. 11 and 12 show an operation region T (see FIG. 3) in which the inside of the combustion chamber 4 is stratified after the completion of the start of the engine, that is, at the time of engine low load operation, and FIG. Operating region H in which a uniform mixture is formed in combustion chamber 4
3 (see FIG. 3), that is, during high engine load operation.

The operating range T for stratified combustion chamber 4 after the completion of engine startup, i.e. low engine load during operation fuel injection from the second fuel injection valve 14b of the compression stroke as shown by I _t in FIG. 9 It takes place at the end. The state of fuel injection at this time is shown in FIG. That is, at the end of the compression stroke, fuel is injected from the second fuel injection valve 14b toward the concave inner wall surface of the concave groove 15 as shown in FIG. In this embodiment, the second
The spray of the injected fuel F _b from the fuel injection valve 14b is for example with a conical shape as shown in FIGS. 11 and 8, the injection axis Z _b of the injected fuel F _b is the vertical plane shown in FIG. 6 K-
It is located in K. The injected fuel along the injection axis Z _b, as shown in FIG. 11 impinges on the concave inner wall of the groove 15 obliquely at an acute angle theta. In this way, the injected fuel is
Obliquely collides with the concave inner wall surface of
As shown by G in FIG. 12, the gas is vaporized along the concave inner wall surface of the concave groove 15 by inertia and proceeds below the ignition plug 10, and is then sent into the concave portion 16. At the time of engine low load operation, the injection amount is small, but at this time most of the injected fuel is carried below the spark plug 10, so that an ignitable mixture G is formed around the spark plug 10. That is, at the time of engine low load operation, the surroundings of the air-fuel mixture G are filled with air and residual burned gas. Thus, even if the fuel injection amount is small, the air-fuel mixture is not
Since the mixture does not spread over the entire interior and becomes an extremely lean mixture, and is concentrated in a part of the region inside the combustion chamber 4, that is, the inside of the combustion chamber 4 is stratified, so that good ignition and subsequent Good combustion will be obtained.

Further, as shown in FIG. 10, the swirling flow X generated in the combustion chamber 4 is attenuated as the piston 2 rises, and the turning radius gradually decreases while decreasing, and as the piston 2 approaches the top dead center, the swirling flow X as shown in FIG. As shown in FIG. 7, a swirling flow X along the concave inner wall surface of the concave groove 15 is obtained. The injected fuel _Fb is also given by this swirling flow X with a force directed downward of the ignition plug 10. When the piston 2 further approaches the top dead center, a squish flow spouts from the squish area 17 as indicated by an arrow S in FIG. 12, and the squish flow S also advances along the concave inner wall surface of the groove 15. Thus the injected fuel F _b the squish flow S
This also applies a downward force to the spark plug 10. Further, the fuel flowing down the spark plug 10 along the concave inner wall surface of the concave groove 15 is vaporized by the swirling flow X and the squish flow S, and thus the fully vaporized combustible mixture G around the spark plug 10 Will gather. Thus, even during low engine load operation with a small injection amount, good ignition and subsequent good combustion can be obtained. From another point of view, since the combustible mixture G is collected around the ignition plug 10 without diffusing the injected fuel throughout the combustion chamber 4, the fuel injection amount can be reduced, and the fuel consumption rate can be reduced. Can be improved.

On the other hand, after the start of the engine shown in FIG.
Operating region H in which a uniform mixture is formed in the combustion chamber 4
That is, during high engine load operation, the fuel from the first fuel injection valve 14a
Injection is I in FIG._hThe exhaust valve 7 closes as shown by
It is started immediately before or after the exhaust valve 7 is closed. This
FIG. 13 shows the state of the fuel injection at this time. That is,
At this time, as shown in FIG.
When low, the fuel injection I from the first fuel injection valve 14a_hIs line
The injection fuel F_aIs directed to the entire top surface of the piston 2.
I will. As shown in FIG. 13 and FIG.
_aInjection axis Z _aIs directed below the spark plug 10.
This injected fuel F_aOver a wide area on the top surface of piston 2
Collision occurs, and at this time, the piston 2_aTo
Therefore, it is cooled and the injected fuel F_aReceives heat from piston 2
Fuel F_aGasification will be promoted.
You. At this time, a swirl as shown in FIG.
Injection fuel F_aAnd air is good
And the injection timing
F_aAllow enough time for the fuel to evaporate
You. Therefore, before the ignition by the spark plug 10 is performed, the combustion chamber
4, a uniform air-fuel mixture is formed, and
A high output can be obtained. Note that the fuel
Injection I_hIs performed before and after the exhaust valve 7 closes.
And the injected fuel F _aInto the exhaust port 13 via the exhaust valve 7
There is no blow through.

Next, referring to FIGS. 1 and 2, the engine is started.
The operation at the time will be described. In this specification,
As shown in FIG. 1, an ignition switch (shown in FIG.
Is turned on, the engine speed N is determined in advance.
Engine start completion rotation speed N _ThreeTime to rise to
This is referred to as "when the engine is started". In this embodiment, as shown in FIG.
When the engine is started, the bypass control valve 32
(See FIG. 4) is held in a fully open position, and therefore a considerable amount
Intake air flows through the bypass passage 31 and the mechanical supercharger 25.
And supplied into the engine cylinder. In this embodiment,
Engine stops, i.e., the ignition switch is
Step for driving the bypass control valve 32 when it becomes FF
The motor is driven to open the bypass control valve 32 fully.
The bypass control valve 32 remains fully open during engine startup
It is kept in a state. Thus, when the engine is started, the bypass system
Since the control valve 32 is kept fully open, the engine load Q / N
The engine load Q / N at the time of starting the engine and
The engine speed after the completion of the engine start shown in FIG.
Applying this to the map of the region,
This corresponds to an operation region in which a uniform mixture is to be formed in the sintering chamber 4.
You. Conventionally, when the engine is started, it is uniformly mixed in the combustion chamber 4.
In the combustion chamber 4
Injects a large amount of fuel by using the whole air for combustion
The engine output is increased to increase the engine speed N
It was common practice to try to raise swiftly.

However, as described above, even if an attempt is made to form a uniform mixture in the combustion chamber 4 when the engine is started, the fuel injected from the fuel injection valve is actually low because the engine temperature is low at the beginning of the engine start. It is difficult to atomize satisfactorily, and as a result, a good homogeneous mixture is not formed in the combustion chamber 4, and the liquid fuel is localized in the combustion chamber 4. In the state where the liquid fuel is localized in various parts of the combustion chamber 4 without forming a good homogeneous mixture in the combustion chamber 4 as described above, the air-fuel mixture around the ignition plug 10 can be satisfactorily ignited. Since it is difficult to form a fuel ratio, good ignitability cannot be ensured, and good combustion cannot be obtained, so that a large amount of HC gas is generated. Further, since these liquid fuels move in the combustion chamber 4 due to the flow of air in the combustion chamber 4 and the like, the ignition plug 10 is covered with the liquid fuel and the smolder of the ignition plug 10 occurs, or There is also a problem that the liquid fuel adheres to the inner peripheral wall surface of the cylinder bore and the lubricating oil between the inner peripheral wall surface of the cylinder bore and the outer peripheral wall surface of the piston 2 is diluted.

In order to solve these problems, according to the present invention,
In one embodiment, as shown in FIG.
The engine speed N is set to a predetermined combustion mode.
Revolution N_TwoLower, that is, at the beginning of the engine startup
Stratified inside combustion chamber 4 so that air-fuel mixture gathers around spark plug 10
And the engine speed N becomes the combustion mode switching speed N described above. _Two
Higher, i.e., in the latter half of the engine startup, the combustion chamber 4
So that a uniform mixture is formed.

Referring to FIG. 1, when starting the engine,
The engine is not shown when the NISCHON switch is turned ON.
Cranking speed N by starter motor₁For example
Rotated at 200rpm. At the beginning of engine startup,
Same as the operation in the stratified combustion operation region T shown in FIG.
In addition, the fuel injection from the second fuel injection valve 14b is_tso
This is done at the end of the compression stroke as shown. This fuel injection
I_tInjected fuel F _bIs a concave groove as shown in FIG.
15 obliquely collided on the concave inner wall surface, and the collided fuel
Inertia of fuel, swirl flow X and squish flow S
As shown by G in FIG. 12, the concave inner wall surface of the groove 15
Is transported below the ignition plug 10 while evaporating along the path. Engine start
At the beginning of the time, the injected fuel F_bAtomization of
Is bad, but all injected fuel F_bIs caught in the groove 15
And then this injected fuel F_bIs mostly in the concave shape of the groove 15.
As it is carried under the ignition plug 10 while evaporating along the wall,
Around the spark plug 10, an air-fuel mixture G having an appropriate ignitable air-fuel ratio
Are easily formed. Therefore, the starter motor
Operation by combustion of the engine early during
When the operation by combustion is started, FIG.
As shown, the engine speed N is equal to the cranking speed N.₁
And rises smoothly.

When the engine is started, the bypass control valve 32 is kept fully open as shown in FIG. 1 (b), so that a considerably large amount of air flows around the air-fuel mixture G shown in FIG. It is filled with the residual burned gas, and the air in the combustion chamber 4 is in an excessive state. As described above, even if the air in the combustion chamber 4 is in an excessive state, the air-fuel mixture G does not spread to the entire inside of the combustion chamber 4 and becomes an extremely lean air-fuel mixture. In the combustion chamber 4
Since the inside is stratified, good ignition and subsequent good combustion are obtained. Even if liquid fuel remains before the ignition is performed, the liquid fuel is
The liquid fuel does not float and move in the combustion chamber 4 because it adheres to the concave inner wall surface of the fifteenth embodiment. Therefore, the smoldering of the ignition plug 10 is prevented by the ignition plug 10 being covered with the liquid fuel, and the liquid fuel is adhered on the inner peripheral wall surface of the cylinder bore, and the smolder is formed between the inner peripheral wall surface of the cylinder bore and the outer peripheral surface of the piston 2 Is prevented from being diluted. Further, since almost no fuel adheres to the inner peripheral wall surface of the cylinder bore or the inner wall surface 3a of the cylinder head, HC
Gas generation is reduced.

As described above, stratified combustion in which the inside of the combustion chamber 4 is stratified is performed at the initial stage of the engine start, and the engine speed N is set to a predetermined combustion mode switching speed N ₂ , for example, 450 r.
When the engine temperature reaches pm, that is, when the engine temperature rises to some extent, a uniform air-fuel mixture is formed in the combustion chamber 4 to perform combustion.

That is, in the latter half of the engine start-up, as shown in FIG.
Similarly to the operation in the uniform combustion operation region H, the first fuel
The fuel injection from the fuel injection valve 14a corresponds to I in FIG._hWill be indicated by
This is performed before and after the exhaust valve 7 is closed. This fuel
Injection I_hInjected fuel F _aIs as shown in FIG.
Towards the entire top surface of the piston 2 and therefore the injected fuel F_aBut
It is diffused throughout the combustion chamber 4. Also as mentioned above
In the latter half of the engine start, the engine temperature has risen considerably
The atomization of the injected fuel has been improved by the
In FIG. 4, a swirling flow X as shown in FIG.
Injected fuel F_aAnd air are mixed well. Also
Because the injection timing is early, the injected fuel F_aFuel vaporizes against
Have enough time to do so. Thus, the spark plug 10
Before the ignition by
Will be formed. In this way, the engine temperature
In the late stage of starting the rising engine, a large amount of fuel
The injection fuel F is injected from the fuel injection valve 14a._aBut the combustion chamber
4 and mixed well with the air inside the combustion chamber 4
A homogeneous mixture is formed. Thus, the engine power is increased
As a result, the engine speed N is rapidly increased.

[0028] During for the engine start rises to thus engine startup of the engine start completion speed to form a homogeneous mixture combustion is performed in the combustion chamber 4 by the engine rotational speed N is predetermined in the later N ₃ Is completed, and then the operation shifts to the engine idling operation as shown in FIG. Note that the engine start completion rotational speed N ₃ in this embodiment is a function of engine coolant temperature TW, as shown in FIG. 2, the engine coolant temperature TW is lower completion of engine startup rotation speed N ₃ than at high Become. As can be seen from FIG. 2, the engine start completion speed N ₃
For example, when the engine cooling water temperature TW is 25 ° C, about 1400 rpm
Is set to about 900r when the engine cooling water temperature TW is 80 ° C.
Set to pm. The relationship between the engine coolant temperature TW and the engine start completion rotational speed N ₃ of FIG. 2 is stored in the ROM 42. The time t ₃ to time t _3, i.e. completion of engine startup until engine speed N is increased to completion of engine startup rotation speed N ₃ in FIG. 1, for example, about 4 seconds.

The combustion mode switching rotation speed N ₂ is set to, for example, 450 rpm at the time of transition from stratified combustion in the combustion chamber 4 to combustion in which a uniform mixture is formed in the combustion chamber 4. On the other hand, when the engine speed N has decreased due to some reason after a shift to the combustion in which a uniform mixture is formed, the combustion in returning the combustion to the stratified combustion in the combustion chamber 4 again. the value of the mode switching rotational speed N ₂ is set to 250rpm, for example. By to have such a combustion mode hysteresis switching rotational speed N _2, the switching to the formation of the homogeneous mixture combustion from the combustion with stratified combustion chamber 4 so that smoothly.

Next, a description will be given engine idling the engine speed N is followed after rising to the engine start completion speed N _3. After the engine idling operation, the engine load Q / N and the engine speed N are used to perform stratified combustion in the combustion chamber 4 or to perform combustion based on the combustion mode map shown in FIG. It is determined whether or not to perform combustion in which a uniform air-fuel mixture is formed.

As shown in FIG. 1B, the engine speed N
Is the engine start completion speed N_ThreeReaches the bypass control valve
Estimated idling open from 32
Degree V ₀It is gradually reduced toward. This bypass
Estimated idling opening V of control valve 32₀Is the previous engine operation
The bypass control valve 32 during idling operation at the time of
And the estimated idling opening V₀Is back
It is stored in the up RAM 45. As shown in FIG.
Thus, the engine speed N is equal to the engine start completion speed N. _ThreeReach
The opening degree of the bypass control valve 32 is
And then gradually decrease by a certain opening degree for a certain period of time.
The amount of intake air Q supplied into the engine cylinder
As a result, the engine speed N is shown in FIG.
It gradually decreases as it does. In addition, bypass control
The opening of the valve 32 is the estimated idling opening V₀Reduced to
Time t_FourEngine warm-up before and after
ing. Further, the engine start completion time t_ThreeFrom the bypass
The opening of the control valve 32 is the estimated idling opening V₀When
t_FourThe time until is, for example, about 3 to 5 minutes.

Next, after the opening of the bypass control valve 32 has been reduced to the estimated idling opening V ₀ , that is, FIG.
Time t ₄ in the subsequent engine idle operation shown in the engine speed N is the target idling speed N _i, the opening degree of the bypass control valve 32 so as for example to 600rpm is feedback controlled. That is, the opening degree of the bypass control valve is made to increase if the engine speed N for some reason is lower than the target idling speed N _i, the fuel injection amount is made to increase by increasing its resulting engine load Q / N Therefore, the engine speed N increases. Whereas opening of the bypass control valve is made to decrease when the engine speed N for some reason becomes higher than the target idling speed N _i, the fuel injection amount is decreased as a result the engine load Q / N is used to lower The engine speed N decreases. Thus to the engine speed N is maintained at the target idling speed N _i.

Next, the fuel injection control and the like will be described with reference to the main routine shown in FIGS. 14 to 16 and the interruption routine at regular intervals shown in FIG. Figure 14 to Figure
Referring to FIG. 16, first, at step 60, the engine load Q / N (intake air amount Q / engine speed N) is calculated based on the output signals of the air flow meter 27 and the speed sensor 36.

Next, at step 61, the start processing flag SF is set.
Is determined as to whether or not the value is zero. This startup processing flag
Is activated when the ignition switch is turned on.
Is reset to 0 and the engine speed is
Number N is engine start completion rotation speed N _ThreeLater when it rises
In step 69, the value is switched to 1. That is,
During the start of the seki, the start processing flag SF takes the value 0, while
When the engine is not started, the start processing flag SF changes to a value of 1.
Take. In step 61, the start processing flag SF is not 0.
If not, the process proceeds to step 70, while the start processing flag SF
Is 0, the routine proceeds to step 62.

In step 62, it is determined whether or not the value of the combustion mode flag HF is 0. The combustion mode flag HF is set when the engine is started, that is, when the time t in FIG.
_This flag is used only in the period up to ₃ . This combustion mode flag HF is set when the ignition switch is turned on.
When the engine speed N is reset to 0, the internal combustion chamber 4 should be stratified so that air-fuel mixture gathers around the ignition plug 10 at the time of engine start, that is, the engine speed N becomes the combustion mode shown in FIG. combustion mode flag HF when less than the switching rotation speed N ₂ takes the value 0. On the other hand, when to form a homogeneous mixture in the combustion chamber 4 at the time of engine startup, i.e., when the engine speed N is higher than the combustion mode switching rotational speed N ₂ is the combustion mode flag HF has the value 1. In the present embodiment has a combustion mode switching rotational speed N ₂ hysteresis as described above, the combustion mode switching rotational speed N ₂ is to form a homogeneous mixture from the combustion were stratified combustion chamber 4 For example, 450 rpm is set at the time of transition to combustion, and 250 rpm is set at the time of the opposite transition.

In step 62, the combustion mode flag HF
Is zero, the routine proceeds to step 63, where the engine speed N
Is greater than or equal to 450 rpm. Engine speed N
If is equal to or greater than 450 rpm, the routine proceeds to step 64, where 1 is set in the combustion mode flag HF, and then proceeds to step 67. On the other hand, if the engine speed N is equal to or less than 450 rpm, the process directly proceeds to step 67. On the other hand, if the combustion mode flag HF is not 0 at step 62, the routine proceeds to step 65, where it is determined whether or not the engine speed N is 250 rpm or less. If the engine speed N is equal to or less than 250 rpm, the routine proceeds to step 66, where the combustion mode flag HF is set to 0, and then the routine proceeds to step 67. On the other hand, when the engine speed N is 25
If the speed is 0 rpm or more, the process directly proceeds to step 67.

[0037] At step 67, the engine start completion rotational speed N ₃ from the relationship shown in FIG. 2 is calculated based on the engine coolant temperature TW detected by the water temperature sensor 35. Then the engine speed N at step 68 is whether or not the engine start completion rotational speed N ₃ or more is discriminated. 1 is set to start processing flag SF proceeds to step 69 if the engine speed N is the engine start completion rotational speed N ₃ or more, then the routine proceeds to step 70. On the other hand, the process proceeds to step 70 if the engine rotational speed N is equal to or less than the engine start completion speed N _3.

In step 70, it is determined whether or not the value of the start processing flag SF is 0. Start processing flag SF is 0
, Ie, when the engine is started, the routine proceeds to step 71. As described above, when the engine is started, the bypass control valve 32
Is held in the fully open state, the drive signal for the drive step motor of the bypass control valve 32 is not output to the output port 47.

In step 71, it is determined whether or not the value of the combustion mode flag HF is 0. Combustion mode flag HF
Is zero, that is, when the engine is started and the combustion chamber 4 is to be stratified so that the air-fuel mixture gathers around the ignition plug 10, the routine proceeds to step 72. In step 72, the fuel injection time TAU is calculated based on the data of the fuel injection time TAU stored in advance in the ROM 42 in the form of a map relating to the engine load Q / N and the engine speed N, for example. Then the injection start timing of the fuel injection I _t is calculated from the data stored in advance in ROM 42 in step 73, the injection completion timing of the fuel injection I _t is calculated from the injection start timing and the injection time TAU. Then the data to be completed inject injected to be data and the injection completion time starts the injection start timing in step 74 is output to the output port 47, the fuel injection I _t is performed on the basis of these data.

On the other hand, if the value of the combustion mode flag HF is not 0 in step 71, that is, if the engine is started and a uniform air-fuel mixture is to be formed in the combustion chamber 4, the routine proceeds to step 75. In step 75, the fuel injection time TAU is calculated based on the data of the fuel injection time TAU stored in advance in the ROM 42 in the form of a map relating to the engine load Q / N and the engine speed N, for example. Next, at step 76,
Injection start timing of the fuel injection I _h is calculated from the data stored in the ROM 42, the injection start timing and the injection time T
Injection completion timing of the fuel injection I _h is calculated from the AU. Next, at step 77, data to start the injection at the injection start timing and data to complete the injection at the injection completion timing are output to the output port 47, and the fuel injection _Ih is performed based on these data.

On the other hand, if the start processing flag SF is not 0 in step 70, that is, if the engine start is completed, the routine proceeds to step 78.

Referring to the flow chart shown in FIG. 17, the period (see FIG. 1) from the time t ₃ when the engine start is completed to the time t ₄ when the opening of the bypass control valve 32 reaches the estimated idling opening V ₀ . The driving process of the bypass control valve 32 in the above will be described. The control routine shown in FIG. 17 is executed by interruption every predetermined time. When this interrupt is executed, first, at step 100, it is determined whether or not the start processing flag SF is "1". The start processing flag SF is a common flag to the start processing flag SF used in the main routine shown in FIGS. If the start processing flag SF is 1, that is, after the completion of the engine start, the routine proceeds to step 101, where it is determined whether or not the feedback flag FBF is 0. The feedback flag FBF is reset to a value of 0 when the ignition switch is turned on, and as shown in FIG. 1, during the engine idling operation following the engine start, the opening of the bypass control valve 32 becomes the estimated idling opening V. ₀ step 10 described later at time t ₄ when was reduced to
At 5 the value is switched to 1. That is, the feedback flag FBF takes a value 0 before the time t ₄ shown in FIG. 1, and takes a value 1 after the time t ₄ . The feedback flag FBF is a feedback flag FB used in the main routine shown in FIGS.
This flag is common to F. If the feedback flag FBF is 0 in step 101, step 102
Proceed to. Therefore, after the completion of the engine start and when the opening of the bypass control valve 32 has not yet been reduced to the estimated idling opening V ₀ , that is, between the time t ₃ and the time t ₄ shown in FIG. To step 102.

In step 102, the target opening V of the bypass control valve 32 is reduced by a predetermined value ΔV from the target opening V in the previous processing cycle. Next, at step 103, the step motor of the bypass control valve 32 is driven such that the opening of the bypass control valve 32 becomes the target opening V. Next, at step 104, it is determined whether or not the target opening V of the bypass control valve 32 is equal to or more than (V ₀ -ΔV / 2) and equal to or less than (V ₀ + ΔV / 2).
Incidentally, the estimated idling opening degree V ₀ which bypass control valve as described above is a degree of opening of the bypass control valve 32 at the time of idling when the previous engine operation, the estimated idling opening degree V ₀ is the backup RAM 45 in Is stored in If an affirmative determination is made in step 104, the routine proceeds to step 105, where the value 1 is set in the feedback flag FBF
Is set, and this interrupt routine ends. On the other hand, if a negative determination is made in step 104, the present interrupt routine ends.

On the other hand, when it is determined in step 100 that the start processing flag SF is not 1, or in step 10
If it is determined in step 1 that the feedback flag FBF is not 0, the present interrupt routine ends. That is, when the time t ₃ when shown in Figure 1 except the period until time t ₄ is not substantially perform any processing in this interrupt routine.

Returning to the main routine shown in FIG. 15, in step 78, based on the engine load Q / N and the engine speed N, the current engine operation state is changed to the stratified combustion operation region T based on the relationship shown in FIG. Or the uniform combustion operation region H
Is determined. If the engine operation state corresponds to the stratified combustion operation region T, that is, if the combustion chamber 4 should be stratified so that the air-fuel mixture gathers around the ignition plug 10, the routine proceeds to step 79, where the feedback flag FBF is 1. Is determined. Feedback flag FBF is 1
When it is, i.e., at time t ₄ after that shown in Figure 1 is the target opening degree V of the bypass control valve 32 is calculated proceeds to step 80. In this case, feedback control of the opening degree of the bypass control valve 32 based on the engine speed N as the engine speed N is maintained at the target idling rotational speed N _i if the current engine operating condition is idling The target opening degree V is calculated in order to achieve this. On the other hand, when the current engine operation state corresponds to the stratified combustion operation region T that is not the idling operation, the target opening degree V is calculated from the data stored in the ROM 42 in advance. Next, at step 81, the step motor of the bypass control valve 32 is driven so that the opening of the bypass control valve 32 becomes the target opening V, and then the routine proceeds to step 82. On the other hand, if the feedback flag FBF is not 1 in step 79, the process directly proceeds to step 82.

In step 82, the fuel injection time TAU is calculated based on the fuel injection time TAU data stored in advance in the ROM 42 in the form of a map relating to the engine load Q / N and the engine speed N, for example. Next, at step 83,
Injection start timing of the fuel injection I _t is calculated from the data stored in the ROM 42, the injection start timing and the injection time T
Injection completion timing of the fuel injection I _t is calculated from the AU. Then the data to be completed inject injected to be data and the injection completion time starts the injection start timing in step 84 is output to the output port 47, the fuel injection I _t is performed on the basis of these data.

On the other hand, in step 78, the current engine operation state is not the stratified combustion operation area T but the uniform combustion operation area H
In other words, if a uniform air-fuel mixture is to be formed in the combustion chamber 4, the routine proceeds to step 85, where it is determined whether or not the feedback flag FBF is 1. When the feedback flag FBF is 1, i.e., at time t ₄ after that shown in Figure 1 proceeds to step 86, pre-ROM 42
The target opening V of the bypass control valve 32 is calculated from the data stored therein. Next, at step 87, the bypass control valve is controlled so that the opening of the bypass control valve 32 becomes the target opening V.
32 step motors are driven, then step
Continue to 88. On the other hand, if the feedback flag FBF is not 1 in step 85, the flow directly proceeds to step 88.

In step 88, the fuel injection time TAU is calculated based on the fuel injection time TAU data stored in advance in the ROM 42 in the form of a map relating to the engine load Q / N and the engine speed N, for example. Next, in step 89,
Injection start timing of the fuel injection I _h is calculated from the data stored in the ROM 42, the injection start timing and the injection time T
Injection completion timing of the fuel injection I _h is calculated from the AU. Next, at step 90, data to start the injection at the injection start timing and data to complete the injection at the injection completion timing are output to the output port 47, and the fuel injection _Ih is performed based on these data.

In this embodiment, when a uniform air-fuel mixture is formed in the combustion chamber 4, one fuel injection from the first fuel injection valve 14a before and after the exhaust valve 7 closes as shown in FIG. I am doing the I _h. Instead, as shown in FIG. 18, the fuel injection is performed in two separate steps, that is, the first fuel injection _Ih1 is performed from the first fuel injection valve 14a before and after the exhaust valve 7 closes, and thereafter, The second fuel injection _Ih2 may be performed from the second fuel injection valve 14b toward the concave inner wall surface of the concave groove 15.

In this embodiment, as shown in FIGS. 5 to 8, the first fuel injection valve 14a and the second fuel injection valve 14b
Are used. Alternatively, to place one of the fuel injection valve to the periphery of the cylinder head inner wall surface 3a, both the fuel injection I _h and grooves 15 in toward the fuel injection I _t toward the entire piston 2 top surface this It can also be performed from one fuel injection valve.

In this embodiment, when a uniform air-fuel mixture is formed in the combustion chamber 4, the fuel injection I is directed from the first fuel injection valve 14a disposed on the inner wall surface 3a of the cylinder head toward the entire top surface of the piston 2. _h has gone. Alternatively, if the first fuel injection valve is disposed in the air supply port to form a uniform mixture in the combustion chamber 4, the first fuel injection valve disposed in the air supply port during the air supply stroke The present invention can be similarly applied to an internal combustion engine in which fuel is injected from an injection valve into an air supply port.

In this embodiment, as shown in FIG. 3, after the engine start is completed, the ignition plug
The case where the present invention is applied to a two-stroke internal combustion engine that stratifies the inside of the combustion chamber 4 so that the air-fuel mixture gathers around 10 and forms a uniform air-fuel mixture in the combustion chamber 4 during high engine load operation has been described. However, after completion of the engine start, the internal combustion engine that always stratifies the inside of the combustion chamber 4 regardless of the engine load Q / N and the engine speed N, or the internal combustion engine that always forms a uniform mixture in the combustion chamber 4 However, the present invention can be similarly applied. Further, the present invention can be applied to a four-cycle internal combustion engine.

[0053]

According to the present invention, when the engine speed is lower than a predetermined speed at the time of starting the engine, that is, at the beginning of the engine starting, the atomization of the injected fuel is relatively poor due to the low engine temperature. Since the injected fuel is collected around the plug, a mixture that can be ignited well around the ignition plug is easily formed. Thus, the startability of the engine can be improved. Further, even if liquid fuel exists in the combustion chamber due to poor atomization of the injected fuel, the liquid fuel does not move over a wide range in the combustion chamber. Therefore, the liquid fuel is prevented from adhering to the spark plug and the inner peripheral wall surface of the cylinder bore, and the ignition plug is prevented from being smoldered and the lubricating oil between the inner peripheral wall surface of the cylinder bore and the outer peripheral wall surface of the piston is diluted. on the other hand,
When the engine speed is higher than the above-described predetermined speed at the time of starting the engine, a uniform air-fuel mixture is formed in the combustion chamber and the engine output is increased, so that the engine speed can be rapidly increased.

[Brief description of the drawings]

FIG. 1 is a time chart showing an engine speed and an opening degree of a bypass control valve at the time of engine start and subsequent engine idling operation.

FIG. 2 is a diagram showing a relationship between an engine cooling water temperature and an engine start completion rotation speed.

FIG. 3 is a diagram showing an operation region in which the combustion chamber is stratified after completion of the engine start and an operation region in which a uniform mixture is formed in the combustion chamber.

FIG. 4 is an overall view of a two-cycle internal combustion engine.

FIG. 5 is a bottom view of the cylinder head.

FIG. 6 is a plan view of a piston.

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 5;

FIG. 8 is a bottom view of the cylinder head showing a fuel injection direction.

FIG. 9 is a diagram showing a valve opening timing and a fuel injection timing of a supply / exhaust valve.

10 is a cross-sectional view taken along line VII-VII of FIG. 5 for explaining a state inside the combustion chamber when the supply valve and the exhaust valve are opened.

11 is a sectional view taken along the line VII-VII of FIG. 5 for explaining a state of fuel injection when stratifying the inside of the combustion chamber.

12 is a cross-sectional view taken along the line VII-VII of FIG. 5 for explaining a state of formation of an air-fuel mixture when the combustion chamber is stratified.

13 is a cross-sectional view taken along line XIII-XIII of FIG. 5 for explaining a state of fuel injection when a uniform air-fuel mixture is formed in the combustion chamber.

FIG. 14 is a first part of a flowchart showing a main routine.

FIG. 15 is a second part of the flowchart showing the main routine.

FIG. 16 is a third part of the flowchart showing the main routine.

FIG. 17 is a flowchart illustrating a control routine of the bypass control valve.

FIG. 18 is a diagram showing another example of the fuel injection timing when a uniform mixture is formed in the combustion chamber.

[Explanation of symbols]

 2 Piston 4 Combustion chamber 6 Supply valve 7 Exhaust valve 10 Spark plug 14a First fuel injection valve 14b Second fuel injection valve 15 Groove 16 Groove

──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A-60-56146 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/06 F02B 17/00 F02D 41 / 02

Claims (1)

(57) [Claims] 1. A fuel chamber that can be stratified so that an air-fuel mixture gathers around an ignition plug by fuel injected from a fuel injection valve disposed in a combustion chamber, and a fuel disposed in the combustion chamber or an air supply passage. In an internal combustion engine that can form a uniform mixture in the combustion chamber earlier than the case where the fuel injection start timing from the injection valve is stratified in the combustion chamber, the engine rotation speed at the time of engine start is higher than a predetermined rotation speed. A fuel injection control device for an internal combustion engine, which stratifies the combustion chamber when the engine speed is low, and forms a uniform air-fuel mixture in the combustion chamber when detecting that the engine speed is higher than a predetermined engine speed.