JPH07208234A - Combustion control device of two cycle engine - Google Patents

Abstract

PURPOSE:To provide a combustion control device of a two-cycle engine capable of the stable stratified charge combustion and stably improving the exhaust gas property and the fuel cost even when the engine speed is fluctuated by the external load. CONSTITUTION:In a combustion control device of a two-cycle engine 1 provided with an air volume control means 17 to control the air volume to be introduced in a cylinder 2a in response to the engine load, a first fuel injection valve 31 to directly inject the fuel in the cylinder 2a locally toward an ignition plug 9, and an engine control device 49 to control the fuel injection timing and the ignition timing in response to the crank angle, the fuel injection timing is relatively advanced with the ignition timing as the reference when the engine speed is incresed irrespective of the engine load in the low load operational zone. Even when the engine speed is fluctuated by the external load, the ignition is surely realized with excellent timing at the timepoint when the tip part of the fuel flow q1 to be injected from the first fuel injection valve 31 reaches in the vicinity of the ignition plug 9, and the sure stratified charge combustion is realized, and the exhaust gas property and the fuel cost are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for a two-cycle engine that performs stratified charge combustion in a low load operation range.

[0002]

2. Description of the Related Art A two-cycle engine has been developed which performs stratified combustion in a low load operation range for the purpose of measures against exhaust gas and improvement of fuel consumption.

In the above-mentioned stratified combustion, the cylinder is filled with air in a low load operation range, and the fuel is locally injected directly from the fuel injection valve to the vicinity of the spark plug to ignite the rich mixture formed around the fuel. It will be realized by
The fuel injection timing and the ignition timing are controlled according to the crank angle so that the ignition is performed when the tip of the fuel flow injected from the fuel injection valve reaches the vicinity of the spark plug.

[0004]

However, the time required for the tip of the fuel flow injected from the fuel injection valve to reach the vicinity of the spark plug is substantially constant irrespective of the engine speed, whereas the crank The time between the fuel injection timing and the ignition timing, which is uniquely controlled with respect to the angle, changes with the engine speed and becomes shorter as the engine speed increases. Therefore, depending on the engine speed, it may not be possible to reliably ignite the fuel at a timing when the tip of the fuel flow injected from the fuel injection valve reaches the vicinity of the spark plug.

For example, an external load may fluctuate on a vehicle due to road surface irregularities and on a small boat due to waves. In such a case, even if the engine is operated at a constant throttle opening, the engine speed may change. There is a possibility that the above-mentioned problems will occur due to the change, the reliable stratified charge combustion will not be performed, and the exhaust gas characteristics and the fuel economy will be deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to realize stable stratified combustion even if the engine speed changes due to an external load, thereby improving exhaust gas characteristics and fuel consumption. An object of the present invention is to provide a combustion control device for a two-cycle engine that can achieve improvement in a stable manner.

[0007]

In order to achieve the above object, the present invention provides an air amount control means for controlling the amount of air introduced into a cylinder in accordance with an engine load, and a fuel locally in the cylinder. In a combustion control device for a two-cycle engine, comprising: a fuel injection valve that directs a spark plug to directly inject fuel into the engine; and an engine control unit that controls fuel injection timing and ignition timing in accordance with a crank angle. In the low load operation range, a function of advancing the fuel injection timing relative to the ignition timing as the engine speed increases regardless of the engine load is provided.

Further, the present invention is characterized in that the fuel injection timing and the ignition timing in the low load operation range are controlled so that the crank angle difference between them increases as the engine speed increases.

[0009]

According to the present invention, in the low load operation range, the fuel injection timing is relatively advanced with respect to the ignition timing as the engine speed increases regardless of the engine load. Even if the number fluctuates, ignition is performed with good timing at the time when the tip of the fuel flow injected from the fuel injection valve reaches the vicinity of the spark plug, and as a result, reliable stratified combustion is stably performed. The exhaust gas characteristics and fuel consumption can be improved.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the structure of a combustion control device according to the present invention, FIG. 2 is a vertical sectional view of a two-cycle engine, FIG. 3 is a sectional view taken along the line AA of FIG. 2, and FIG. BB
5 is a sectional view taken along the line, FIG. 5 is an explanatory view of the operation of the air amount control means, FIG. 6 is an enlarged sectional view of a portion C of FIG. 1, and FIG.
8 is a sectional view taken along the line EE of FIG. 7, and FIG. 9 is an enlarged sectional view of the F portion of FIG.

First, the basic construction of the two-cycle engine 1 will be described with reference to FIG.

The two-cycle engine 1 according to this embodiment is
Which performs stratified charge combustion in a low load operation range,
A piston 3 is vertically slidably fitted in a cylinder 2a formed in the cylinder block 2. The piston 3 is connected via a connecting rod 5 to a crankshaft 4 arranged below the piston 3 in a direction perpendicular to the plane of FIG. A crank chamber 7 is formed inside the upper crankcase 2b integrally formed with the cylinder block 2 and the lower crankcase 6 connected to the lower surface of the upper crankcase 2b. 4 is rotatably supported and stored.

A cylinder head 8 is attached to the upper surface of the cylinder block 2, and the cylinder head 8 is attached.
A combustion recess 8a is formed in the combustion chamber 8a, and the combustion chamber S is defined by the combustion recess 8a and the piston 3. Furthermore,
A spark plug 9 is screwed onto the top of the cylinder head 8, and an electrode portion 9a of the spark plug 9 faces the combustion chamber S.

By the way, in the cylinder block 2,
As shown in FIG. 3, the two main scavenging ports 10, 11 and 1
One auxiliary scavenging port 12 and one exhaust port 13 are formed respectively. The above two main scavenging ports 1
0 and 11 are formed at positions facing each other, and the auxiliary scavenging port 12 is formed at a position facing the exhaust port 13. The upper end opening 12a of the auxiliary scavenging port 12 is open toward the upper side of the cylinder 2a, so that the scavenging air from the auxiliary scavenging port 12 is almost completely blown to the exhaust port 13. Absent.

On the other hand, an air introduction port 14 opening to the crank chamber 7 is formed in the lower portion of the cylinder block 2, and the air introduction port 14 allows only the flow of air toward the crank chamber 7. A reed valve 15 is provided.

An intake pipe 16 is connected to the air inlet 14, and an air amount adjusting device 17 is connected to the intake pipe 16.
The intake manifold 18 is connected via.

The air amount adjusting device 17 uses the operation amount (engine load) of an accelerator pedal (not shown) in the accelerator device 19 shown in FIG. 1 and the engine speed as parameters to crank the air from the air inlet 14 through the reed valve 15. The amount of air taken into the chamber 7 is controlled, and the intake ports 20a and 21a formed at the upper and lower sides are controlled.
Main valve 20 and sub valve 21 for opening and closing
have. The main valve 20 and the sub valve 21
Is always biased toward the closing side by a biasing means (not shown).

As shown in FIG. 4, the drive shafts 22 and 23 of the main valve 20 and the sub-valve 21 are provided with potentiometers 24 and 25 for detecting the openings of the valves 20 and 21, respectively. A motor 26 is connected to the drive shaft 23 of each sub-valve 21.

As shown in FIG. 5, the main valve 20
A first swing piece 27 is connected to one end of the drive shaft 22 of the above, and a second swing piece 28 is connected to one end of the drive shaft 23 of the sub valve 21. A groove 27a (see FIG. 4) and a locking hole 27b (see FIG. 5) are provided on the outer peripheral portion of the first swing piece 27.
The throttle wire 29 having one end connected to the accelerator device 19 is wound around the groove 27a, and the other end of the throttle wire 29 is the locking hole 27b of the first swinging piece 27. Is locked to.

Further, as shown in FIG.
The connecting rod 30 is disposed between the first swinging piece 27 and the second swinging piece 28.
The other end 30b is slidably engaged with an arcuate guide groove 28a formed in the second swing piece 28.

On the other hand, as shown in FIG. 2, the side wall portion of the cylinder head 8 is mainly subjected to stratified charge combustion in a low load operation range, and fuel is supplementarily supplied also in other operation ranges. First fuel injection valve 31 for
Is mounted on the side wall of the cylinder block 2, and a second fuel injection valve 32 is mounted on the side wall of the cylinder block 2 for performing premixed combustion in the medium / high load range.

Here, the first fuel injection valve 31 is shown in FIG.
As shown in FIG. 8, one injection port 33 having a relatively large diameter is used.
And three relatively small diameter injection ports 34, 35, 36,
The injection port 35 is open on the axis center line, and the injection ports 34 and 36 are open on both sides of the injection port 35.

As shown in FIG. 6, the injection port 33 is formed so as to face upward in a direction forming an angle θ ₁ with respect to the axis in the longitudinal sectional view.
As shown in FIG.

On the other hand, as shown in FIG. 8, the injection ports 34 and 36 on both sides are formed in a direction that forms an angle θ ₂ with respect to the axis in the transverse sectional view, and the three injection ports 34 to 36. From this, fuel is injected toward the intermediate region between the spark plug 9 and the piston 3 of the combustion chamber S as shown in FIG.

By the way, in this embodiment, the flow rate Q _{1 of the} fuel (injected fuel flow q ₁ ) injected from the injection port 33 toward the ignition plug 9 is directed toward the intermediate region and the injection port 3
The injection port 3 is made smaller than the flow rate Q _{2 of the} fuel (injected fuel flow q ₂ ) injected from 4 to 36 (Q ₁ <Q ₂ ).
The diameters of 3 to 36 are determined (that is, the opening area of the injection port 33> the total opening area of the injection ports 34 to 36).

On the other hand, the second fuel injection valve 32 has, as shown in FIG. 9, two injection ports 37 and 38 that open at a predetermined angle θ _3, and the center line of the angle θ ₃ The direction corresponds to the installation position of the spark plug 9. Therefore, at the time of fuel injection, the fuel injected from each of the injection ports 37, 38 collides with each other and atomizes, and the fuel advances toward the spark plug 9 while diffusing into the cylinder 2a.

Next, the overall structure of the combustion control device will be described with reference to FIG. In FIG. 1, the same elements as those shown in FIGS. 2 to 5 are designated by the same reference numerals, and description thereof will be omitted below.

In FIG. 1, reference numeral 39 is an intake port of the intake manifold 18, arrow a indicates the flow of air taken in from the intake port 39, and arrow b indicates the exhaust gas discharged from the two-cycle engine 1. Each flow is shown.

By the way, the rotational power of the crankshaft 4 of the two-cycle engine 1 is transmitted to the external load 44 via the output shaft 40, the gears 41, 42 and the input shaft 43, but at the end of the crankshaft 4, A measurement gear 45 for detecting the engine speed and the crank angle is connected. A reference crank angle indicating tooth is formed on the measuring gear 45.

Further, in FIG. 1, 46 is a fuel supply device for supplying a constant pressure of fuel to the first fuel injection valve 31 and the second fuel injection valve 32, and 47 is the timing of ignition by the spark plug 9. An ignition timing control device for controlling, 48 is a rotation speed sensor which also serves as a crank angle sensor, and the rotation speed sensor 48 is arranged in the vicinity of the measuring gear 45.

An engine control unit (ECU: Engine Control Unit) 49 is provided in the combustion control device, and the engine control device 49 detects the engine speed detected by the speed sensor 48. Crank angle, each opening of the main valve 20 and the sub valve 21 detected by the potentiometers 24, 25 (in particular, the opening of the main valve 20, that is, the engine load)
Based on the air amount control device 17 (motor 26 (opening degree of the sub valve 21)) and the first and second fuel injection valves 31, 32.
By controlling (fuel injection timing and fuel injection amount) and ignition timing control device 47 (ignition timing), stratified charge combustion is performed in the low load operating range, and other operating ranges (medium / high load operating range). In the above, the premixed combustion is performed.

Here, the operation of the two-cycle engine 1 will be outlined.

As shown in FIG. 2, when the piston 3 is located at the bottom dead center, the main scavenging ports 10 and 11, the auxiliary scavenging port 12 and the exhaust port 13 are open, and at this time, the crank in the previous cycle is used. The air introduced into the chamber 7 and compressed by the piston 3 flows into the cylinder 2a through the main scavenging ports 10 and 11 and the auxiliary scavenging port 12, and the exhaust gas remaining in the cylinder 2a is exhausted from the exhaust port 13 to the cylinder 2a. Performs scavenging action that pushes out.

Next, when the piston 3 moves upward in the cylinder 2a from the bottom dead center, first, the main scavenging ports 10 and 11 are released.
And the auxiliary scavenging port 12 is closed by the piston 3,
Although the air is introduced into the cylinder 2a, a transition is made to a compression stroke in which the fuel is locally discharged from the first fuel injection valve 31 during the compression stroke after the scavenging stroke in the low load operation region where the accelerator operation amount is small. Will be jetted.

FIG. 10 shows a timing chart at the time of idle operation (engine speed: 700 rpm). As shown in FIG. 10, the engine control device 49 is located before the top dead center with respect to the first fuel injection valve 31 ( BTDC) When a drive pulse signal is transmitted from 24 ° (crank angle), the actual fuel injection starts from the same 20 °, and as described above, the fuel is injected from the injection port 33 of the first fuel injection valve 31 to the spark plug 9. The fuel is injected in a direct direction, and the fuel is injected from the other injection ports 34 to 36 in an intermediate region between the spark plug 9 and the piston 3.

The ignition period by the ignition plug 9 starts from 17 ° before the top dead center, and the tip of the injected fuel flow q ₁ reaches the vicinity of the ignition plug 9 at 16 °.

Therefore, ignition by the spark plug 9 is started immediately before the tip of the injected fuel flow q ₁ reaches the vicinity of the spark plug 9 (17 ° before top dead center).

By the way, the fuel flow q ₁ injected toward the spark plug 9 forms a combustible air-fuel mixture in the vicinity of the spark plug 9 (see m _{1 in} FIG. 11), but the fuel amount is restricted. Since the air-fuel mixture is too rich, it does not go out of the flammable range, and when sparks fly to the spark plug 9, the air-fuel mixture immediately ignites and burns.

On the other hand, the flow rate Q ₂ of the fuel flow q ₂ injected toward the intermediate region is larger than the flow rate Q ₁ of the fuel flow q ₁ injected toward the spark plug 9 (Q ₂ > Q
₁ ) Therefore, the air-fuel mixture in the intermediate region is rich (see G in FIG. 11).

However, when the combustible air-fuel mixture near the ignition plug 9 is ignited and burned as described above, the flame becomes a nucleus and spreads to the surroundings, and is injected toward the intermediate region between the ignition plug 9 and the piston 3. It heats and vaporizes more fuel.

The vaporized fuel takes in oxygen from the surroundings to form a combustible mixture, and the combustible mixture is ignited and burned, the flame further heats and vaporizes the surrounding fuel, and the vaporized fuel surrounds it. The action of taking in oxygen to form a combustible mixture is repeated, and the fuel injected toward the intermediate region gradually takes in oxygen at a slow temperature while taking in oxygen, achieving stable stratified combustion and achieving exhaust gas emission. The amount of NO _{x in it} can be kept low.

Further, the piston 3 is larger than m ₂ shown in FIG.
Since there is no fuel on the side, the injected fuel does not fly out of the flammable region more than necessary, which suppresses the generation of unburned gas and keeps the amount of HC in the exhaust gas low. Fuel efficiency is improved.

FIG. 11 is a diagram showing the mixture concentration distribution in the cylinder.

The fuel injection timing of the first fuel injection valve 31 and the ignition timing of the spark plug 9 are controlled by the engine control device 49 (ignition timing control device 47) in accordance with the crank angle. Then, as shown in FIG. 13, the engine speed increases as the external load is reduced with the engine load kept constant in the low load operation range.
Along with this, the fuel injection timing is relatively advanced with reference to the ignition timing.

Further, in the present embodiment, the fuel injection timing and the ignition timing in the low load operation range not only increase the crank angle difference between the two as the engine speed increases, but also determine both the fuel injection timing and the ignition timing. Controlled to advance.

In FIG. 13, is a drive pulse transmission period of the fuel injection valve 31 (that is, injection drive period), is an actual injection period of fuel, is a period during which the fuel flow q ₁ passes through the ignition plug 9, and is an ignition period. is there.

As can be seen from FIG. 13, the crank angle difference between the beginning and the end of each period ~ increases as the engine speed increases. Further, the ratio of the advance angle with the increase of the engine speed is larger at the beginning than at the end of each period.

Further, since the period and the period are made to overlap at least partly on the crank angle,
During ignition, the fuel injection flow q ₁ passes through the spark plug 9, and reliable ignition is obtained. If the end time of is delayed from the end time of while satisfying the condition that a part of this overlaps, the fuel will pass after ignition, and this fuel burns surely and slowly, so reliable stratified combustion Is possible.

By advancing or matching the timing of the beginning of the period with the timing of the beginning of the fuel, the fuel always exists around the spark plug 9 during the period of, and reliable ignition can be obtained.

As described above, since the fuel injection timing and the ignition timing in the low load operation range are controlled by using only the engine speed as a parameter, when the engine speed is constant (2000 rpm) as shown in FIG. Irrespective of the throttle opening α (engine load), the timing of the beginning of each of the fuel injection timing and the ignition timing is kept constant. In this case, the crank angle difference between the beginning and end of each period of ~ increases with increasing engine load.

Thus, according to the present embodiment, as described above, in the low load operation range, the crank angle difference between the fuel injection timing and the ignition timing is increased as the engine speed increases regardless of the engine load. Since it is increased, even if the engine speed fluctuates due to an external load, the fuel flow q ₁ injected from the first fuel injection valve 31 can be reliably timed at the time when the tip of the fuel flow q ₁ reaches the vicinity of the spark plug 9. Since ignition is performed, reliable stratified combustion is stably performed, and exhaust gas characteristics and fuel economy are improved.

On the other hand, in the medium / high load operating range where the engine load is larger than the predetermined value, fuel injection into the cylinder 2a from the first and second fuel injection valves 31 and 32 has already started during the scavenging stroke. The fuel injection ends before the compression stroke, and a combustible mixture is formed in the cylinder 2a due to sufficient diffusion of the fuel. When the piston 3 reaches near the top dead center, the spark of the spark plug 9 causes the combustible air-fuel mixture in the combustion chamber S to ignite and burn, which is what is called premixed combustion.

By the way, a negative pressure is generated in the crank chamber 7 due to the rise of the piston 3, and the negative pressure causes air to flow into the intake manifold 18, the air amount control device 17, and the intake pipe 1.
6 and the reed valve 15, and is introduced into the crank chamber 7 from the air introduction port 14.

When the piston 3 descends past the top dead center by the explosive force due to the combustion of the air-fuel mixture in the combustion chamber S, the air introduced into the crank chamber 7 is compressed by the piston 3 and compressed. The air is used for scavenging and mixture formation in the next cycle. Then, when the piston 3 descends to near the bottom dead center, the exhaust port 13 is first opened, and the exhaust gas generated by the combustion of the air-fuel mixture is discharged from the exhaust port 13. After that, continue to main scavenging port 1
When 0, 11 and the auxiliary scavenging port 12 open, the crank chamber 7
The air compressed therein flows into the cylinder 2a from the main scavenging ports 10 and 11 and the auxiliary scavenging port 12 to perform the scavenging action.

Thereafter, the same operation as described above is repeated, and 2
The cycle engine 1 is continuously operated.

Next, the operation of the combustion control device will be described with reference to FIGS.
It will be described based on 2. Incidentally, FIG. 12 shows the main valve 20.
5 is a diagram showing a change in the opening area of the intake port 20a with respect to the opening α (engine load) of FIG.

When the two-cycle engine 1 is in the stopped state, both the main valve 20 and the sub-valve 21 are in the fully closed state, and in the idling state, the motor 26 is driven by the control signal from the engine control device 49, and the sub-valve is driven. 21 is opened by a predetermined angle in the direction of the arrow as shown by the chain line in FIG.

Therefore, in the idling state of the engine 1 (opening α = 0 of the main valve 20), the opening area of the intake port shows the value indicated by the point ID in FIG. 12 (opening area of the intake port 21a), The air that has passed through the idle port and the sub valve 21 (not shown) is reed valve 15
The air is introduced into the crank chamber 7 through the air introduction port 14 through the passage, whereby a larger amount of air than in the conventional idling state is introduced into the cylinder 2a and supplied to the scavenging.
The scavenging efficiency during idling is improved.

In FIG. 12, the broken line J indicates the opening area of the intake port 20a of the main valve 20, and the chain line K indicates the total opening area of the intake ports 20a and 21a of both valves 20 and 21. Further, a broken line L represents a change in the opening area of the intake port 21a of the sub-valve 21 when the engine speed is maintained at 1500 rpm, and a solid line M
Shows changes in the opening area of the intake port 21a of the sub-valve 21 when the engine speed is kept at 4000 rpm.

Thus, the amount of depression of the accelerator pedal in the accelerator device 19 is small, and the throttle wire 2
Since the turning angle between the first swinging piece 27 and the main valve 20 which are turned by 9 is small, the potentiometer 2
In the low load range (α <α ₀ ) where the opening α of the main valve 20 detected by 4 is smaller than the set value α ₀ (this value α ₀ changes depending on the engine speed), the engine control device 49 Instead of driving and controlling the sub-valve 21 by the connecting rod 30, the motor 26 is driven and controlled to rotate the sub-valve 21 in the arrow direction as shown by the solid line in FIG. 31 and the ignition timing control device 47 are controlled to perform stratified combustion of the air-fuel mixture in the combustion chamber S.

Therefore, in the low load region where the stratified charge combustion is executed, when the accelerator pedal of the accelerator device 19 is gradually depressed, the main valve 20 gradually opens and
Without being directly driven by the operation of the main valve 20, the engine control device 49 reads the operation (engine load) of the main valve 20 by the potentiometer 24, and feeds back the potentiometer 25 so as to set a predetermined opening based on this value. Motor 26 while hanging
To control. Then, the sub valve 21 is opened by the drive control of the motor 26, and the intake port 2 of the sub valve 21 is opened.
The opening area of 1a is the broken line L in FIG. 12 (when the engine speed is 1
500 rpm) or solid line M (engine speed is 4)
000 rpm). in this way,
In the low load region where stratified charge combustion is performed, air is also supplied through the sub-valve 21, so that a large amount of air is temporarily supplied to the scavenging air in the cylinder 2a, and scavenging efficiency and exhaust gas characteristics are improved.

Thereafter, the opening α of the main valve 20 is set to a set value α ₀ (α ₀ = 1 when the engine speed is 1500 rpm).
At 5 ° and 4000 rpm, α ₀ = 25 °) is reached,
Since the engine control device 49 releases the drive control of the motor 26, the sub valve 21 is rapidly closed in the closing direction until the end of the guide groove 28a formed in the second swing piece 28 comes into contact with the end 30b of the connecting rod 30. Turn to. As a result, as shown in FIG. 12, the intake port 21a of the sub-valve 21 is
When the opening α of the main valve 20 increases by depressing the accelerator pedal thereafter, the second swinging piece 28 is driven by the connecting rod 30 to rotate the first swinging piece 27. Interlock with the movement. As a result, the sub-valve 21 rotates integrally with the main valve 20 in the opening direction, and the intake ports 20a, 21 of both valves 20, 21 are rotated.
The sum of the opening areas of a increases along the dashed line K in FIG.
The hatched area in FIG. 12 indicates the stratified combustion area.

Thus, in the medium / high load range in which the opening α of the main valve 20 becomes equal to or larger than the set value α ₀ (α ≧ α ₀ ), the premix combustion is performed as described above. First, when the opening degree α of the main valve 20 is less than a certain set value α ₁ (> α ₀ ) (α <α ₁ ), that is, until the sub-valve 21 opens abruptly until it opens, it is low. As in the load region, fuel is injected only from the first fuel injection valve 31, and the ignition timing control device 47 forms an ignition timing sufficiently retarded from the value in the low load region and formed by sufficiently diffused fuel. The air-fuel mixture is ignited, and the air-fuel mixture is ignited and burned to perform premixed combustion.

When the opening degree α of the main valve 20 exceeds the set value α ₁ (α> α ₁ ), the first fuel injection valve 3
Fuel is supplied from both the first fuel injection valve 32 and the second fuel injection valve 32, and the ignition timing is controlled by the ignition timing control device 47 to ignite the air-fuel mixture formed by the sufficiently diffused fuel for premixed combustion. Done.

[0066]

As is apparent from the above description, according to the present invention, the air amount control means for controlling the amount of air introduced into the cylinder in accordance with the engine load, and the fuel locally in the cylinder are provided. Fuel injection valve that directs the spark plug to direct injection,
In a combustion control device for a two-cycle engine including engine control means for controlling a fuel injection timing and an ignition timing in correspondence with a crank angle, in a low load operation range, the ignition timing is increased regardless of the engine load as the engine speed increases. Since the fuel injection timing has been relatively advanced as a reference,
Even if the engine speed fluctuates due to an external load, it is possible to achieve stable stratified combustion and achieve an improvement in exhaust gas characteristics and fuel efficiency in a stable manner.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a combustion control device according to the present invention.

FIG. 2 is a vertical sectional view of a two-cycle engine.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view taken along line BB in FIG.

FIG. 5 is a diagram illustrating the operation of the air amount control means.

FIG. 6 is an enlarged cross-sectional view of a C part of FIG.

7 is a view in the direction of arrow D in FIG.

8 is a cross-sectional view taken along the line EE of FIG.

FIG. 9 is an enlarged cross-sectional view of an F portion of FIG.

FIG. 10: During idle operation (engine speed: 700r
pm) timing chart

FIG. 11 is a diagram showing a mixture concentration distribution in a cylinder.

FIG. 12 is a diagram showing changes in the opening area of the intake port with respect to the opening of the main valve (engine load).

FIG. 13 is a diagram showing a control example of the engine speed of fuel injection timing and ignition timing during low load operation.

FIG. 14 is a diagram showing an example of control of throttle opening (engine load) of fuel injection timing and ignition timing when the engine speed is constant during low load operation.

[Explanation of symbols]

 1 2 cycle engine 2a cylinder (cylinder) 9 spark plug 17 air amount control device (air amount control means) 31 first fuel injection valve (fuel injection valve) 47 ignition timing control device 49 engine control device (engine control means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02D 43/00 J F02P 5/15

Claims (2)

[Claims] 1. An air amount control means for controlling the amount of air introduced into a cylinder in response to an engine load, and a fuel injection valve for directly injecting fuel into the cylinder by directing fuel locally toward an ignition plug. In a combustion control device for a two-cycle engine, which comprises an engine control means for controlling a fuel injection timing and an ignition timing in correspondence with a crank angle, the engine control means includes:
A combustion control device for a two-cycle engine, which is provided with a function of advancing the fuel injection timing relative to the ignition timing as the engine speed increases regardless of the engine load in a low load operation range. 2. The two-cycle engine according to claim 1, wherein the fuel injection timing and the ignition timing in the low load operation range are controlled so that the crank angle difference between the two increases as the engine speed increases. Combustion control device.