JP4075935B2 - Premixed compression self-ignition internal combustion engine - Google Patents

Description

The present invention relates to a premixed compression self-ignition internal combustion engine that utilizes a self-ignition phenomenon of a compressed air- fuel mixture .

  In order to improve the thermal efficiency of a gasoline engine, a method is known in which the air-fuel mixture is leaned to reduce pump loss and increase the specific heat ratio of the working gas to increase the theoretical thermal efficiency. However, in the conventional spark ignition engine, if the air-fuel ratio is made lean, the combustion period becomes longer and the combustion stability deteriorates. For this reason, there is a limit to the lean air-fuel ratio.

  As a technique for leaning the air-fuel ratio while avoiding such deterioration in combustion stability, compression self-ignition combustion is known. In compression self-ignition combustion, combustion reactions occur from multiple positions in the combustion chamber, so even when the air-fuel ratio is lean, the combustion period is not prolonged compared to spark ignition and stable even at a leaner air-fuel ratio. Combustion is possible. Further, since the air-fuel ratio is lean, the combustion temperature is lowered and NOx can be greatly reduced.

  As a conventional compression self-ignition gasoline engine, for example, the first prior art described in Patent Document 1 is known. In this example, in an engine that injects fuel into an intake port, the compression ratio is increased to the same level as that of a direct injection diesel engine, thereby increasing the temperature and pressure in the cylinder near the compression top dead center. The conditions for self-ignition are established, and compression self-ignition combustion is realized. As a result, the lean combustion limit and low fuel consumption that exceed the spark ignition gasoline engine are obtained.

Further, as a compression self-ignition engine in which conventional fuel injection is divided into two, for example, a second conventional technique described in Patent Document 2 is known.
In this conventional example, in order to avoid knocking at a high load in a diesel engine, fuel injection is divided into two injections, and the first injection is injected at an injection amount that does not cause knocking at a predetermined time in the second half of the compression stroke. Then, the combustion is started by the second injection thereafter.
JP-A-7-332141 JP-A-11-72038

However, in the first prior art, the condition of compression ignition is realized simply by increasing the compression ratio.
For this reason, in full load operation in which spark ignition is performed with a mixture near the stoichiometric air-fuel ratio, knocking is likely to occur due to a high compression ratio, and in order to avoid knocking, it is necessary to retard the ignition advance limit, There is a problem that the torque is greatly reduced as compared with a spark-ignition gasoline engine having a normal compression ratio.

  Further, the second prior art is devised in order to avoid knocking at the time of high load of early injection premixed compression self-ignition in a diesel engine, and it is thick enough not to cause knocking simply by the first injection. Therefore, in a compression self-ignition engine using gasoline with a low cetane number as a fuel, there is a problem that an adverse effect of worsening the ignitability, which is a problem, occurs.

  In view of the above problems, the object of the present invention is to obtain a high output torque without causing knocking at a high load, stabilize the ignitability at a low load, and achieve a stable compression self-ignition combustion at a wide range of engine speed and load. It is to provide an internal combustion engine that can be performed.

The invention of claim 1, wherein for solving the above problems is provided with a fuel injection valve for injecting fuel directly into the combustion chamber, premixed with a sealing period in which the intake and exhaust valves are both closed in the vicinity of exhaust top dead center In the compression self-ignition internal combustion engine, fuel is injected from the fuel injection valve during both the sealing period and the compression stroke in one combustion cycle , and the fuel injection amount during the sealing period is decreased as the load increases, The gist is to increase the fuel injection amount during the compression stroke as the load increases.

In order to solve the above-mentioned problem, the invention according to claim 2 is the premixed compression self-ignition internal combustion engine according to claim 1, wherein the fuel injection during the sealing period is from the exhaust valve closing timing to the exhaust top dead center. The main point is that

In order to solve the above-mentioned problems, a third aspect of the present invention is the premixed compression self-ignition internal combustion engine according to the first or second aspect, wherein the fuel injection timing during the compression stroke is advanced according to an increase in load. Is the gist.

In order to solve the above-mentioned problems, a fourth aspect of the present invention is the premixed compression self-ignition internal combustion engine according to any one of the first to third aspects, wherein the fuel injection amount during the sealing period is determined by the engine speed. The main point is to increase it according to the increase.

In order to solve the above-mentioned problems, a fifth aspect of the present invention is the premixed compression self-ignition internal combustion engine according to any one of the first to third aspects, wherein the fuel injection timing during the sealing period is determined by the engine speed. The main point is to advance the angle according to the increase of.

In order to solve the above-mentioned problems, a sixth aspect of the present invention is the premixed compression self-ignition internal combustion engine according to any one of the first to third aspects, wherein the fuel injection timing during the compression stroke is determined by the engine speed. The main point is to advance the angle according to the increase of.

According to the first aspect of the present invention, the premixed compression self-ignition internal combustion engine is provided with a fuel injection valve that directly injects fuel into the combustion chamber and has a closed period in which both the intake valve and the exhaust valve are closed near the exhaust top dead center. In the engine, fuel is injected from the fuel injection valve during both the sealing period and the compression stroke in one combustion cycle , and the fuel injection amount during the sealing period is decreased as the load increases, so that the fuel during the compression stroke is reduced. Since the injection amount is increased as the load increases, the amount of highly reactive reforming material necessary for ignition can be secured while keeping the fuel injection amount during this sealing period to a minimum. The fuel can be stably ignited together with the rich air-fuel mixture formed by the injection during the compression stroke.

  According to the invention of claim 2, in addition to the effect of the invention of claim 1, fuel injection during the sealing period is performed from the exhaust valve closing timing to the exhaust top dead center. The degree of reforming of the fuel injected at the first time due to the high temperature and high pressure inside can be increased, the amount of fuel injection during the sealing period can be minimized, the calorific value can be reduced, and the decrease in filling efficiency can be reduced .

  According to the invention of claim 3, in addition to the effects of the invention of claim 1 or 2, the fuel injection timing during the compression stroke is advanced according to the increase in load, so that the injection during the compression stroke is performed. The dispersed fuel can be diffused widely as the load increases, and the local decrease in the air-fuel ratio can be prevented, and the generation of particulate matter (particulates) accompanying the increase in the load can be suppressed.

  According to the invention of claim 4, in addition to the effects of the inventions of claims 1 to 3, the fuel injection amount during the sealing period is increased as the engine speed increases. Even if the actual time per crank angle is shortened along with the increase, the amount of fuel contributing to the chemical reaction of fuel reforming increases, and the amount of fuel reforming substance necessary for ignition can be ensured.

  According to the fifth aspect of the invention, in addition to the effects of the first to third aspects of the invention, the fuel injection timing during the sealing period is advanced according to the increase in the engine speed. Even if the actual time per crank angle is shortened as the engine speed increases, the chemical reaction time for fuel reforming is secured, and the fuel injection amount during the sealing period is kept to a minimum and stable regardless of the engine speed. The amount of fuel reforming material necessary for ignition can be secured.

  According to the invention of claim 6, in addition to the effects of the inventions of claims 1 to 3, the fuel injection timing during the compression stroke is advanced in accordance with the increase of the engine speed. Even if the actual time per crank angle is shortened with an increase in the amount of fuel, the amount that contributes to the chemical reaction of fuel reforming from the fuel injected during the compression stroke will increase, minimizing the fuel injection amount during the sealing period The amount of the fuel reforming material necessary for stable ignition can be ensured regardless of the engine speed.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system configuration diagram showing the configuration of a first embodiment of a compression self-ignition internal combustion engine according to the present invention.

  1, a compression self-ignition internal combustion engine of the present invention includes an electronic control unit (hereinafter abbreviated as ECU) 1, an engine body 10, a combustion chamber 11, a piston 12, an intake port 13, and an intake valve 14. An intake valve variable valve device 15, an exhaust port 16, an exhaust valve 17, an exhaust valve variable valve device 18, a fuel injection valve 19 provided facing the combustion chamber 11, and spark ignition. A spark plug 20 for performing spark ignition during combustion and a crank angle sensor 21 are provided.

  The ECU 1 includes an operation region determination unit 2 that determines whether to perform spark ignition combustion or compression self-ignition combustion in accordance with the load and the engine speed, and spark ignition combustion control that performs spark ignition combustion at high load or high speed. And a self-ignition combustion control unit 4 that performs self-ignition combustion during medium-low load and medium-low rotation.

  The self-ignition combustion control unit 4 controls the fuel injection during the sealing period at the time of low load or low rotation and the fuel injection during the compression stroke at the time of medium or low load or medium / low rotation. A compression stroke injection control unit 6 and an intake stroke injection control unit 7 that controls fuel injection during the intake stroke during medium load or medium rotation are provided.

  Further, the ECU 1 inputs an accelerator opening signal detected by an accelerator opening sensor provided on an accelerator pedal (not shown) and a crank angle sensor signal detected by a crank angle sensor 21, while an intake valve variable valve gear 15 and A valve timing switching signal is output to the exhaust valve variable valve device 18, a fuel injection control signal is output to the fuel injection valve 19, and an ignition signal is output to the spark plug 20.

  FIG. 2 is a diagram illustrating an example of valve timings of the intake valve and the exhaust valve in the present embodiment. As shown in the valve timing example (1) in FIG. 2A, there are two valve timings: a normal spark ignition combustion valve timing indicated by a solid line and a compressed self ignition combustion valve timing indicated by a broken line. have.

  The valve timing of the solid line in FIG. 2 (a) is the intake valve lift and exhaust valve lift for spark ignition combustion similar to the valve timing of a gasoline engine in a normal four-stroke cycle, and the intake valve 14 and the exhaust in the vicinity of the exhaust TDC. There is an overlap period in which the valves 17 open together.

  The valve timings indicated by broken lines in FIG. 2A are intake valve lift and exhaust valve lift indicating valve timings for compression self-ignition combustion, and a sealing period in which both the exhaust valve 17 and the intake valve 14 are closed near the exhaust TDC. (So-called minus overlap period) is formed, and the lift amount is reduced in consideration of the middle and low loads and the middle and low rotation speed.

  FIG. 2B shows a valve timing example (2), which has a valve timing during normal spark ignition combustion indicated by a solid line and a negative overlap period during compression self-ignition combustion indicated by a broken line. 2b in that it has two valve timings, but the maximum lift amount is equal to that of the solid spark ignition combustion, and the cam profile remains the same without changing the cam profile. It is realized just by changing.

  A variable valve operating device for intake valve 15 for switching the opening / closing timing of the intake and exhaust valves between a valve timing for spark ignition and a valve timing for compression self-ignition by control from the valve timing control unit 5 of the ECU 1; As the exhaust valve variable valve device 18, for example, as disclosed in Japanese Patent Laid-Open No. 9-203307, a cam switching mechanism that switches cams with different profiles, or an electromagnetic that controls opening and closing of the intake and exhaust valves by electromagnetic force. A drive valve is available.

Next, the operation of this embodiment will be described.
FIG. 3 is a schematic cross-sectional view for each stroke of the engine for explaining the operation of the engine at the partial load in the present embodiment. (A) Exhaust stroke, (b) Sealing period (minus overlap) near the exhaust TDC, (C) The intake stroke, (d) the compression stroke, and (e) the vicinity of the compression TDC are shown.

  At the time of partial load, by operating the variable valve device 15 for the intake valve and the variable valve device 18 for the exhaust valve, the valve timing for self-ignition combustion that forms a sealed period near the exhaust top dead center is selected, and the exhaust TDC Form a sealing period in the vicinity.

  In the first half of the exhaust stroke, as shown in FIG. 3A, the exhaust gas of the cylinder is discharged from the exhaust valve 17 to the exhaust port 16 as in a normal engine.

  In the latter half of the exhaust stroke, as shown in FIG. 3 (b), unlike the normal engine, the exhaust valve 17 is closed, the exhaust gas is closed in the cylinder, and compression is performed again to form a high temperature and high pressure state.

  The first gasoline injection from the fuel injection valve 19 into the high-temperature gas causes a combustion prereaction, and the composition of gasoline is reformed to a more reactive composition containing aldehyde. The degree of this reforming can be continuously controlled by the time that gasoline is held in the hot gas. When the fuel injection timing is advanced, the fuel is highly reformed until just before the start of combustion, and when the injection timing is delayed, the reformed state is close to that of gasoline.

  In the first half of the intake stroke, the reformed air-fuel mixture is expanded to near atmospheric pressure while the intake and exhaust valves are closed, and in the second half of the intake stroke, the intake valve 14 is opened and a new one is opened as shown in FIG. Inhale air from the intake port 13.

  In the compression process, as shown in FIG. 3D, the compressed air is compressed in a mixed state with the high-temperature reformed air-fuel mixture. Further, a second fuel injection is performed here. Since the fuel injected here has a high density of gas in the cylinder, so-called stratification is performed in which diffusion is suppressed and a locally rich mixture is formed.

As a result, due to the synergistic effect of the fuel reforming effect and fuel stratification, gasoline is used instead of light oil in the case of the known example, and at a compression ratio lower than the compression ratio in the known example, FIG. Compressive self-ignition can be achieved as shown in FIG. For this reason, torque reduction due to the knocking limit is less likely to occur even at full load operation with spark ignition.
Although not shown in the expansion stroke, the self-ignited and burned gas pushes down the piston to generate shaft torque.

  FIG. 4 is a cross-sectional view for each stroke of the engine for explaining the operation of the engine at the full load in this embodiment. (A) Exhaust stroke, (b) Intake stroke, (c) Compression stroke, (d) Compression The vicinity of TDC is shown.

  During full-load operation, the ECU 1 operates the intake valve variable valve device 15 and the exhaust valve variable valve device 18 to select the valve timing for spark ignition combustion, and to set the spark plug 20 at an appropriate ignition timing. The mixture is ignited by sparks. At this time, the operation is the same as that of a normal spark ignition gasoline engine over four strokes.

Next, compression auto-ignition combustion at partial load will be described in detail.
The compression self-ignition as described above is affected by the temperature, pressure, fuel concentration, and the degree of reforming of the fuel in the combustion chamber. On the other hand, from the viewpoint of the thermal efficiency of the engine, the start time of compression self-ignition needs to be in the vicinity of compression TDC.

  FIG. 5 is a conceptual diagram showing the relationship between the fuel injection timing and the degree of fuel reforming during the sealing period. As shown here, the earlier the injection timing during the sealing period, the longer the time during which the fuel is exposed to high temperature and pressure, and the degree of reforming of the fuel increases.

  FIG. 6 shows the relationship between the fuel injection amount and the charging efficiency during the sealing period. As the amount of fuel injected during the sealing period increases, heat generation during the sealing period increases, so that the intake amount in the subsequent intake stroke decreases and the charging efficiency decreases. Therefore, from the viewpoint of charging efficiency, the smaller the fuel injection amount during the sealing period, the better. In order to obtain a large reforming effect with a small amount of fuel, the fuel injection timing during the sealing period is exhausted from the exhaust valve closing timing. The range up to the top dead center will be used.

  FIG. 7 shows an example of the relationship between the load, the fuel injection amount during the sealing period, and the fuel injection amount during the compression stroke in the embodiment. Gasoline has lower ignitability than light oil, and the compression ratio of a gasoline engine must be lower than the compression ratio of a diesel engine because of the demand for full load performance. Experience has shown that in order to ensure the ignition of gasoline under such conditions, a certain amount of fuel reforming product represented by aldehyde is required depending on the engine speed and compression ratio. .

  FIG. 7 shows that in order to secure this constant amount of reformed product, the fuel injection amount during the sealing period is kept constant regardless of the load, and the fuel injection amount during the compression stroke is increased as the load increases. An example is shown. According to this example, the injection control unit 5 during the sealing period in FIG. 1 always sets the fuel injection amount during the sealing period to a constant amount regardless of the load, and the injection control unit 6 during the compression stroke sets the fuel injection amount during the compression stroke. The control to be increased according to the increase in load is performed, and the control structure of the self-ignition combustion control unit 4 as a whole is simplified.

  FIG. 8 is another example showing the relationship between the load, the fuel injection amount during the sealing period, and the fuel injection amount during the compression stroke in the embodiment. When the fuel injection amount during the compression stroke is increased in accordance with the increase in the load, the ignitability of the air-fuel mixture is thereby increased, so that the amount of fuel reformed product necessary for ignition is reduced. In accordance with this, the fuel injection amount during the sealing period is gradually reduced. According to this example, the injection control unit 5 during the sealing period in FIG. 1 decreases the fuel injection amount during the sealing period as the load increases, and the injection control unit 6 during the compression stroke reduces the fuel injection amount during the compression stroke to the load. Increase with increase. Thereby, both the injection control unit 5 and the injection control unit 6 during the compression stroke need to perform fuel injection amount control according to the load during the sealing period, but the intake charging efficiency is improved.

  FIG. 9 is an example of setting the fuel injection timing for the load in the embodiment. The internal combustion engine of the present embodiment includes four operation regions according to the load. That is, from the region where the load L is small to the large region, the fuel reforming self-ignition region (L <L1) by the sealing period injection and the compression stroke injection, the stratified self-ignition region (L1 <L <L2) by only the compression stroke injection ), A homogeneous auto-ignition region (L2 <L <L3) by intake stroke injection, and a homogeneous spark ignition region (L3 <L) by intake stroke injection and spark ignition. In the vicinity of the boundary loads L1, L2, and L3, in order to prevent frequent control switching, the combustion region switching control has some hysteresis characteristics so as to continue the previous combustion region.

  When the load is smaller than L1, fuel injection is performed during the first sealing period and the second compression stroke, and the gasoline is reformed to obtain an appropriate heat generation time.

  The engine load increases to some extent, and the fuel concentration is locally increased by stratifying the air-fuel mixture without relying on fuel reforming during the sealing period, and compression self-ignition can be caused. For this reason, stratified self-ignition combustion with only compression stroke injection can be performed at the load L in the range of L1 <L <L2.

  Comparing compression auto-ignition due to fuel reforming during the sealing period and compression auto-ignition due to mixed gas stratification, compressed self-ignition due to mixed gas stratification has the advantage that HC emissions due to wall quenching are less For this reason, in this embodiment, compression self-ignition by mixed gas stratification is included in the operation region.

  In the stratified self-ignition region, the injection control unit 6 during the compression stroke performs control to advance the injection timing during the compression stroke as the load increases. This is because the fuel injection amount during the compression stroke increases as the load increases, but if the fuel injection timing is fixed at this time, the local air-fuel ratio at the time of combustion becomes too high, and NOx and smoke are generated. To avoid this, increase the fuel injection amount and simultaneously advance the fuel injection timing, inject the fuel at a time when the compression pressure is low and there is time to the top dead center, and diffusion of the injected fuel This is because it is necessary to make the local air-fuel ratio during combustion almost constant.

When the load further increases and exceeds L2, fuel injection is performed during the intake stroke, and the process proceeds to compression self-ignition with a homogeneous mixture.
In a region where the load is larger (L3 <L), the intake / exhaust valve timing is changed to the timing for spark ignition, and intake stroke injection and spark ignition are performed.

FIG. 10 is a diagram for explaining the fuel injection timing characteristics of the second embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment shown in FIG.
In the present embodiment, the fuel injection timing during the compression stroke is advanced as the load increases in the fuel reforming auto-ignition region (L <L1) by the closed period injection. The other injection timing control is the same as in FIG.

  Even in the fuel reforming self-ignition region due to closed period injection, the fuel injection amount during the compression stroke increases with the load, but if the fuel injection timing is fixed at this time, the local air-fuel ratio during combustion becomes too dense. NOx and smoke are generated. In order to avoid this, it is necessary to increase the fuel injection amount and simultaneously advance the fuel injection timing to keep the local air-fuel ratio at the time of combustion substantially constant. For this reason, in the present embodiment, in the fuel reforming auto-ignition region (L <L1) by the closed period injection, the fuel injection timing during the compression stroke from the injection control unit 6 during the compression stroke is advanced according to the increase in load. ing.

Next, the relationship between engine speed and fuel reforming will be described.
Even if the rotational speed of the engine is changed, the time of the chemical change of the compression self-ignition is constant, so that the compression self-ignition timing relative to the crank angle changes relatively. That is, when the engine speed is slowed down, the compression self-ignition timing is advanced. Conversely, when the engine speed is fastened, the compression self-ignition timing is delayed. Therefore, in order to obtain an appropriate compression autoignition timing for a wide range of engine speeds, it is necessary to control the degree of reforming of the fuel or the amount of reformed product. One method for this is to increase the amount of fuel injection during the sealing period and increase the amount of reformed product of the fuel as the engine speed increases.

  FIG. 11 is a diagram illustrating the fuel injection characteristics of the third embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment shown in FIG. This embodiment is an example in which the fuel injection timing during the sealing period by the injection control unit 5 during the sealing period is advanced according to the increase in the engine speed and the degree of fuel reforming is increased as the engine speed increases.

  In FIG. 11, the internal combustion engine of the present embodiment has four operating regions according to the engine speed. That is, from the region where the engine speed V is small to the large region, the fuel reforming self-ignition region (V <V1) by the sealed period injection and the compression stroke injection, and the stratified autoignition region (V1 <V <) by only the compression stroke injection. V2), a homogeneous auto-ignition region (V2 <V <V3) by intake stroke injection, and a homogeneous spark ignition region (V3 <V) by intake stroke injection and spark ignition. In the vicinity of the boundary engine speeds V1, V2, and V3, in order to prevent frequent control switching, the combustion region switching control has some hysteresis characteristics so as to continue the previous combustion region. .

  When the engine speed is lower than V1, fuel injection can be performed during the first sealing period and the second compression stroke, and the gasoline can be reformed to obtain an appropriate heat generation time.

  The engine speed of the engine increases to some extent, and the fuel concentration can be locally increased by stratifying the air-fuel mixture without relying on fuel reforming during the sealing period, and compression self-ignition can be caused. For this reason, at an engine speed V in the range of V1 <V <V2, stratified self-ignition combustion with only compression stroke injection can be performed.

  Comparing compression auto-ignition due to fuel reforming during the sealing period and compression auto-ignition due to mixed gas stratification, compressed self-ignition due to mixed gas stratification has the advantage that HC emissions due to wall quenching are less For this reason, in this embodiment, compression self-ignition by mixed gas stratification is included in the operation region.

  Further, in the stratified self-ignition region, the injection control unit 6 during the compression stroke performs control to advance the injection timing during the compression stroke as the engine speed increases. This is because if the fuel injection timing during the compression stroke is fixed with respect to the increase in engine speed, the local air-fuel ratio at the time of combustion becomes excessively high, and NOx and smoke are generated. In order to avoid this, the fuel injection timing is advanced, the fuel is injected at a time when the compression pressure is low, and there is sufficient time to top dead center, and the diffusion of the injected fuel is facilitated. The local air-fuel ratio at the time of combustion can be kept substantially constant.

When the engine speed further increases and exceeds V2, fuel injection is performed during the intake stroke, and the process proceeds to compression self-ignition with a homogeneous mixture.
Further, in a region where the engine speed is high (V3 <V), the intake / exhaust valve timing is changed to the timing for spark ignition, and intake stroke injection and spark ignition are performed.

  FIG. 12 is a diagram illustrating the fuel injection characteristics of the fourth embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment shown in FIG. This embodiment is an embodiment in which the fuel injection timing during the compression stroke in the fuel reforming auto-ignition region by the sealed period injection is advanced as the engine speed increases.

  Even if the engine speed is changed, the time of chemical change required for compression self-ignition is constant, so if the fuel injection timing is fixed, the ignition timing is delayed as the engine speed increases, and eventually misfiring occurs. To do. In order to avoid this, the ignition timing is kept substantially constant at the timing near the compression top dead center by advancing the fuel injection timing during the compression stroke by the injection control unit 6 during the compression stroke as the engine speed increases. be able to.

It is a system configuration figure showing the composition of a 1st embodiment. It is a figure which shows the valve timing in 1st Embodiment. It is a schematic diagram explaining the state of the air-fuel mixture in the engine in each stroke at the time of partial load. It is a schematic diagram explaining the state of the engine air-fuel mixture in each stroke at the time of full load. It is a graph which shows the relationship between the fuel-injection timing in a sealing period, and a fuel reforming grade. It is a graph which shows the relationship between the fuel injection quantity and filling efficiency in a sealing period. It is a graph which shows the relationship between the load and each fuel injection quantity in 1st Embodiment. It is a graph which shows the other example of the relationship between the load in 1st Embodiment, and each fuel injection quantity. It is a graph which shows the relationship between the load in 1st Embodiment, and each fuel-injection time. It is a graph which shows the relationship between the load in 2nd Embodiment, and each fuel-injection time. It is a graph which shows the relationship between the engine speed and each fuel injection timing in 3rd Embodiment. It is a graph which shows the relationship between the engine speed and each fuel-injection time in 4th Embodiment.

Explanation of symbols

1 ECU
DESCRIPTION OF SYMBOLS 2 Operation area | region determination part 3 Spark ignition combustion control part 4 Self ignition combustion control part 5 Injection control part during sealing period 6 Injection control part during compression stroke 7 Injection control part 10 during intake stroke 10 Engine main body 11 Combustion chamber 12 Piston 13 Intake port 14 Intake valve 15 Intake valve variable valve device 16 Exhaust port 17 Exhaust valve 18 Exhaust valve variable valve device 19 Fuel injection valve 20 Spark plug 21 Crank angle sensor

Claims (6)

In a premixed compression self-ignition internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber and having a sealing period in which both an intake valve and an exhaust valve are closed near the exhaust top dead center,
Fuel is injected from the fuel injection valve both during the sealing period and during the compression stroke in one combustion cycle , and the fuel injection amount during the sealing period is decreased as the load increases, so that the fuel injection amount during the compression stroke is reduced. A premixed compression self-ignition internal combustion engine characterized by increasing the engine as the load increases. 2. The premixed compression self-ignition internal combustion engine according to claim 1, wherein the fuel injection during the sealing period is performed from an exhaust valve closing timing to an exhaust top dead center. The premixed compression self-ignition internal combustion engine according to claim 1 or 2, wherein the fuel injection timing during the compression stroke is advanced according to an increase in load. The premixed compression self-ignition internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection amount during the sealing period is increased as the engine speed increases. The premixed compression self-ignition internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection timing during the sealing period is advanced in accordance with an increase in engine speed. The premixed compression self-ignition internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection timing during the compression stroke is advanced as the engine speed increases.

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