JP2001020842A - Combustion control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To correct the amount of auxiliary energy to be applied to an air-fuel mixture in a combustion chamber or the timing of application of auxiliary energy in accordance with a change in combustion stability, and then to correct the fuel injection amount. As a result, the main combustion of the compression self-ignition is appropriately performed, thereby improving the thermal efficiency and realizing low emission. SOLUTION: A combustion pattern determination unit 21 of an ECU 11 is provided.
Selects spark ignition combustion or compression self-ignition combustion according to the operating region. The stability determination unit 22 detects and determines the stability. The auxiliary energy control unit 2 according to the stability determination
3 controls the amount of auxiliary energy or the timing of applying energy to the air-fuel mixture in the combustion chamber by the ignition plug 12 via the ignition control unit 25. When the auxiliary energy does not fall within a desired stability range, the fuel injection is performed. The controller 24 increases or decreases the fuel injection amount.

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 an internal combustion engine that switches between spark ignition combustion operation and compression self-ignition combustion operation according to operating conditions.

[0002]

2. Description of the Related Art In order to improve the thermal efficiency of a gasoline engine, there is known a method in which a mixture is made lean to reduce a pump loss and increase a specific heat ratio of a working gas to improve a theoretical thermal efficiency. However, in the conventional spark ignition engine, when 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 lean air-fuel ratio.

[0003] As a first prior art to solve the above problem,
Japanese Patent Application Laid-Open No. 7-71279 discloses a technique for causing homogeneous charge compression self-ignition combustion. According to this technology, near the exhaust port of a two-stroke engine,
An exhaust control valve capable of controlling the opening ratio of the exhaust port is provided, and by controlling the exhaust opening ratio in accordance with the engine speed and the opening degree of the intake throttle valve, the in-cylinder pressure is controlled to perform self-ignition combustion. It wakes up.

In such premixed compression self-ignition combustion,
Since combustion reactions occur from a plurality of positions in the cylinder, even when the air-fuel ratio becomes lean, combustion can be performed at a leaner air-fuel ratio without prolonging the combustion period as compared with spark ignition. Also, because the air-fuel ratio is lean, the combustion temperature drops,
NOx can also be significantly reduced.

[0005] Some compression self-ignition internal combustion engines include
As a third prior art, for example, Japanese Utility Model Application Laid-Open No. 58-154869.
As disclosed in Japanese Patent Application Laid-Open No. HEI 3-301944, an auxiliary ignition source is provided in a combustion chamber, and external ignition energy is supplied by the auxiliary ignition source in an operation region having a problem in ignitability and combustibility. There has been known a method of improving the combustion stability and the exhaust property by providing the composition.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 54-522006 as a fourth prior art, in a spark ignition type internal combustion engine, the air-fuel mixture is made leaner than a stoichiometric mixture ratio or exhaust gas recirculation. As a combustion improvement measure in the case of performing (EGR), induction discharge is performed on a spark plug provided in a combustion chamber from an intake stroke to a compression stroke to generate radicals, and a part of the air-fuel mixture is chemically activated. Technology has been proposed.

However, in the first prior art, since a normal two-stroke engine is used, there is no intake valve and exhaust valve for controlling gas exchange, and unburned gas blows through to reduce fuel consumption. Was getting worse.

[0007] Further, even in the case of a four-stroke engine in which there is no gas blow-through and which is expected to improve fuel economy, in a compression self-ignition internal combustion engine, fuel gas is heated to a high temperature during a compression stroke.
Maintains high pressure, pre-reacts the fuel to spontaneously ignite the fuel spontaneously, and has a combustion pattern characteristic in which main combustion is performed during the expansion stroke. The thermal efficiency is affected.

However, even if the auxiliary energy is applied in a specific operation range using the auxiliary ignition source as in the second and third prior arts, the main energy is not optimally applied when the auxiliary energy is not optimally applied. There has been a problem that the combustion is not performed well, and there is a risk of causing misfire or knocking.

In particular, when a fuel having a low cetane number, such as gasoline, is premixed and compression self-ignition is performed, this problem becomes remarkable because the fuel itself has low ignitability.

Further, as in the fourth prior art, in an internal combustion engine using a low cetane number fuel such as gasoline, compression self-ignition combustion is attempted in a low to medium load range in order to improve fuel efficiency and exhaust performance. In the case, even if the induction discharge is performed in the first half of the compression stroke from the bottom dead center of the intake air, the temperature and the fuel density in the cylinder are low, so that the generated radicals disappear before activating the air-fuel mixture and have a sufficient effect. Can not be obtained.

Further, even when the induction discharge is started from the middle stage of the compression stroke, the amount of radicals generated by the induction discharge is very small, and the amount of radicals generated until the mixture develops to a sufficient amount by the ignition timing at which compression ignition of the air-fuel mixture is to be generated. Since there is no delay in the reaction time, an effective combustion improvement effect cannot be obtained. Conversely, in a state where compression self-ignition is relatively easy to occur, such as at low rotation and high load, if an excessive amount of radicals is generated in the cylinder, combustion after compression ignition rapidly progresses, resulting in a sense of knock. Combustion causes the problem of increased vibration and noise.
In order to achieve the compression ignition combustion in a wide operating range as described above, it is necessary to appropriately control the amount of radicals generated in the cylinder according to the properties of the air-fuel mixture in the cylinder.

In view of the above problems, it is an object of the present invention to first correct the amount of auxiliary energy to be applied to the air-fuel mixture in the combustion chamber or the timing of applying the auxiliary energy in accordance with a change in combustion stability, and then to perform fuel injection. It is an object of the present invention to provide a combustion control apparatus for an internal combustion engine that corrects the amount of fuel, thereby appropriately performing the main combustion of the compression self-ignition, thereby improving thermal efficiency and realizing low emission.

[0013] Another object of the present invention is to optimize the amount of auxiliary energy or the timing of applying energy to the air-fuel mixture in the combustion chamber in accordance with the operating range, to enable compression auto-ignition combustion in a wide range of operating conditions, and to achieve combustion stability. Another object of the present invention is to provide a combustion control device for an internal combustion engine with improved fuel consumption rate.

[0014]

According to the first aspect of the present invention,
In order to solve the above-mentioned problem, in a combustion control apparatus for an internal combustion engine that ignites and burns an air-fuel mixture by compression of a piston, auxiliary energy applying means for activating the air-fuel mixture by applying auxiliary energy to the air-fuel mixture in a combustion chamber. A stability detecting means for detecting the combustion stability of the engine, and an auxiliary energy for controlling the amount or timing of the auxiliary energy applied by the auxiliary energy applying means according to the combustion stability detected by the stability detecting means. And control means.

According to a second aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the first aspect, wherein the fuel injection amount can be changed in accordance with an instruction from the auxiliary energy control means. When the combustion stability changes, the auxiliary energy control means first controls the effective increase or decrease of the auxiliary energy amount by changing the auxiliary energy amount or the energy application timing back and forth. If the control range exceeds the control amount of the auxiliary energy amount or the energy application timing, the gist is to instruct the fuel injection control means to change the fuel injection amount.

According to a third aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the first or second aspect, wherein a spark plug is provided as the auxiliary energy applying means. I do.

According to a fourth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the first or second aspect, wherein a laser beam irradiation device is provided as the auxiliary energy applying means. Make a summary.

According to a fifth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to any one of the second to fourth aspects, wherein the combustion stability is lower than an allowable value. In this case, the auxiliary energy amount is increased or the energy application timing is sequentially advanced to increase the effective auxiliary energy amount until the maximum, and even at the maximum energy amount or the maximum advance timing, the combustion stability falls below the allowable value. If so, the gist is to increase the fuel injection amount.

According to a sixth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to any one of the second to fifth aspects, in which the combustion stability is improved to be higher than an allowable value. In this case, the auxiliary energy amount is reduced or the energy application timing is sequentially retarded until the effective auxiliary energy amount is minimized, and even at the minimum energy amount or the maximum retard timing, the combustion stability is improved from the allowable value. If so, the gist is to reduce the fuel injection amount.

According to a seventh aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the fifth aspect, further comprising an in-cylinder temperature estimating means for estimating an in-cylinder temperature.
When the predicted cylinder temperature at the energy application time is lower than a predetermined value, the increase of the effective energy amount due to the advance of the energy application time is prohibited, the auxiliary energy amount is increased, and the auxiliary energy amount is increased to the maximum. The gist is also to increase the fuel injection amount when the in-cylinder temperature predicted value is lower than a predetermined value.

According to an eighth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to any one of the first to seventh aspects, in order to solve the above-mentioned problem. The gist of the present invention is to learn the amount of auxiliary energy or the timing of applying energy when providing auxiliary energy in accordance with the engine speed and load.

According to a ninth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to any one of the first to eighth aspects, wherein the stability detecting means is provided for each cylinder. Based on the combustion stability for each cylinder, the control means performs control of whether or not to apply the auxiliary energy and control of the amount of auxiliary energy or energy application timing for each cylinder based on the combustion stability for each cylinder. That is the gist.

According to a tenth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine in which an air-fuel mixture is self-ignited by compression of a piston to burn the air-fuel mixture. An ignition system including at least one spark plug for activating an air-fuel mixture, and an ignition system including the spark plug is capable of performing at least two types of discharges having different capacity discharge characteristics. The gist of the present invention is to control the amount or to control the energy application timing by the discharge timing from the spark plug.

According to an eleventh aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the tenth aspect, wherein the ignition system includes at least two ignition coils. The gist is to control the amount of auxiliary energy by changing the number of ignition coils for supplying electric energy to the ignition plug.

According to a twelfth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the tenth aspect, wherein the ignition system includes at least two spark plugs in each cylinder and supplies current to each cylinder. The gist is to control the amount of auxiliary energy by changing the selection or the number of plugs.

According to a thirteenth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to the twelfth aspect, wherein the first ignition plug is disposed substantially at the center of the combustion chamber, and the second ignition plug is provided. Place the plug around the periphery of the combustion chamber and
The gist of the capacity discharge characteristic of the ignition plug is that the rise time of the secondary voltage of the capacity discharge is shorter than that of the second ignition plug or that the capacity discharge voltage is set to be higher.

According to a fourteenth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine according to any one of the tenth to thirteenth aspects, wherein the first spark plug is provided substantially in the combustion chamber. In the center, the second spark plug is arranged in the periphery of the combustion chamber. In stratified charge combustion, the mixture is ignited by the discharge of the first spark plug, and in the case of homogeneous lean combustion or homogeneous EGR combustion, the first mixture is ignited. Prior to the ignition of the air-fuel mixture by the discharge of the spark plug, the supplementary energy is applied by discharging the second spark plug.

According to a fifteenth aspect of the present invention, there is provided a stratified combustion region, a homogeneous lean combustion region, and a homogeneous E region.
A combustion control device for an internal combustion engine having a GR combustion region, wherein a first spark plug is disposed substantially at the center of a combustion chamber, and a second spark plug is disposed at a peripheral portion of the combustion chamber. The mixture is ignited by the discharge of the spark plug 1;
At the time of homogeneous lean combustion or homogeneous EGR combustion, the gist is to perform discharge by the second spark plug prior to ignition of the air-fuel mixture by discharge of the first spark plug.

[0029]

According to the first aspect of the present invention, in a combustion control apparatus for an internal combustion engine in which an air-fuel mixture is self-ignited by compression of a piston and burned, the stability detection means detects the combustion stability of the engine. The auxiliary energy applying means controls the amount of auxiliary energy or the timing of applying energy to the air-fuel mixture according to the combustion stability, so that the combustion stability can be reliably increased even when the external environment or fuel properties change. There is an effect that it can be improved.

According to the second aspect of the present invention, in addition to the effect of the first aspect, the fuel injection control apparatus further includes a fuel injection control means capable of changing a fuel injection amount in accordance with an instruction from the auxiliary energy control means. When the combustion stability changes, the auxiliary energy control means controls the increase or decrease of the effective auxiliary energy amount by first changing the auxiliary energy amount or the energy application timing back and forth, and controls the auxiliary energy amount or the energy application timing. When the control range is exceeded, the fuel injection amount is changed by instructing the fuel injection control means, so that it is possible to prevent frequent changes in the fuel amount from causing torque fluctuation and deteriorating drivability. This has the effect.

According to the third aspect of the present invention, since the ignition plug system which is generally used for the ignition means of a gasoline engine internal combustion engine and whose technology has been established is adopted as the auxiliary energy applying means, engine design is easy. In addition to the advantages obtained in terms of cost, there is an effect that durability and reliability can be improved.

According to the fourth aspect of the present invention, as the auxiliary energy applying means, a laser beam irradiating device capable of assisting linear ignition rather than ignition as a point in the air-fuel mixture is used. Energy assistance can be performed over a wide range, and there is an effect that stable ignition combustion can be performed.

According to the fifth aspect of the present invention, when the combustion stability becomes lower than the allowable value, the auxiliary energy amount is increased or the energy application timing is sequentially advanced until the effective auxiliary energy becomes maximum. The fuel injection amount is increased when the stability is worse than the allowable value even at the maximum auxiliary energy amount or the maximum advance timing. This allows
There is an effect that it is possible to prevent the operability from being deteriorated due to the torque fluctuation due to the frequent fuel amount change.

According to the sixth aspect of the invention, when the combustion stability becomes higher than the allowable value, the auxiliary energy amount is reduced or the energy application timing is sequentially delayed until the effective auxiliary energy becomes minimum. The fuel injection amount is reduced when the combustion stability is improved beyond the allowable value even at the minimum auxiliary energy amount or the maximum retard timing. This allows
There is an effect that it is possible to prevent the operability from being deteriorated due to the torque fluctuation due to the frequent fuel amount change.

According to the seventh aspect of the present invention, the in-cylinder temperature is predicted by the in-cylinder temperature predicting means, and when the in-cylinder temperature at the energy applying time is lower than the judgment value, the advance of the energy applying time is prohibited. Then, the fuel injection amount is increased. by this,
There is an effect that it is possible to prevent the timing of applying the energy from being advanced too much and the combustion stability from suddenly deteriorating and the drivability from deteriorating.

According to the eighth aspect of the present invention, whether or not to apply auxiliary energy and the amount of auxiliary energy or the timing of applying energy when performing auxiliary energy addition are learned according to the engine speed and load. Thereby, when the fuel property or the like changes, the time until the combustion stability is improved under each operating condition can be shortened, and the drivability can be improved.

According to the ninth aspect of the present invention, the stability detecting means detects the combustion stability of each cylinder, determines whether or not to provide auxiliary energy according to the combustion stability of each cylinder, and determines whether or not to provide auxiliary energy. Is performed for each cylinder. Thereby, even when the combustion conditions such as the cylinder inner wall temperature for each cylinder of the multi-cylinder engine are different, the energy application is optimally controlled,
The combustion stability of each cylinder can be set optimally. As a result, there is an effect that the drivability can be improved and the fuel efficiency can be improved.

According to a tenth aspect of the present invention, in the combustion control apparatus for an internal combustion engine in which the air-fuel mixture is self-ignited by compression of the piston and burns, the auxiliary air is supplied to the air-fuel mixture in the combustion chamber to activate the air-fuel mixture. An ignition system including at least one ignition plug capable of performing at least two types of discharges having different capacity discharge characteristics, and controlling the amount of auxiliary energy by selecting different capacity discharge characteristics. Alternatively, the energy application timing is controlled by the discharge timing from the spark plug,
There is an effect that radicals are generated in the cylinder in a larger amount more rapidly than the radical generation by the conventional induction discharge, and the compression self-ignition operation is enabled in a wide operating region, thereby improving the fuel consumption rate.

Further, by selecting different capacity discharge characteristics and controlling the discharge timing, the temperature in the cylinder at the time of low load, etc.,
Effective mixture activation can be achieved even when the mixture density is low or when the radical growth time during high rotation is short.

According to the eleventh aspect of the present invention, the first aspect is provided.
0, the ignition system includes at least two ignition coils, and the amount of auxiliary energy is changed by selecting these ignition coils or changing the number of ignition coils that supply electric energy to the ignition plug. Since the control is performed, an appropriate amount of radicals can be supplied into the cylinder according to the variation of the load and the engine speed, and the compression self-ignition combustion operation can be stably performed in a wide operation range. There is.

According to the twelfth aspect, the first aspect
In addition to the effects of the invention described in Item 0, the ignition system includes at least two spark plugs in each cylinder, and controls the amount of auxiliary energy by changing the selection or the number of spark plugs to be energized. An appropriate amount of radicals can be supplied into the cylinder according to changes in load and engine speed,
There is an effect that the compression self-ignition combustion operation can be stably performed in a wide operation range.

According to the thirteenth aspect, according to the first aspect,
In addition to the effects of the invention described in 2, the first spark plug is arranged substantially at the center of the combustion chamber, the second spark plug is arranged at the periphery of the combustion chamber, and the capacity discharge characteristic of the first spark plug is Since the rise time of the secondary voltage of the capacity discharge is shorter than that of the second spark plug or the capacity discharge voltage is set to be higher, the flame generated during the capacity discharge of the second spark plug Since the nucleus is held by the energy supplied by the subsequent induction discharge, a flame can be formed even in a state where the fuel density is low.

According to the fourteenth aspect of the present invention, the first aspect
In addition to the effects of the present invention, the first spark plug is disposed substantially at the center of the combustion chamber, and the second spark plug is disposed at the periphery of the combustion chamber.
In the case of homogeneous lean combustion or homogeneous EGR combustion, auxiliary energy is applied by discharging the second ignition plug prior to ignition of the mixture by the first ignition plug during homogeneous lean combustion or homogeneous EGR combustion. Therefore, the flame nucleus generated at the time of the capacity discharge of the second spark plug is retained by the energy supplied by the subsequent induction discharge, so that the flame can be formed even in a state where the fuel density is low. Further, when the temperature in the cylinder rises, the first spark plug discharges the gas, so that reliable and rapid combustion can be realized. Therefore, the combustion stability and the fuel consumption rate during lean burn combustion or large EGR combustion can be reduced. Improvements can also be made possible.

According to a fifteenth aspect of the present invention, there is provided a combustion control apparatus for an internal combustion engine having a stratified combustion region, a homogeneous lean combustion region, and a homogeneous EGR combustion region, wherein the first spark plug is provided substantially at the center of the combustion chamber. The first spark plug ignites the air-fuel mixture during stratified charge combustion and is used for homogeneous lean combustion or homogeneous EG combustion.
At the time of R combustion, prior to the ignition of the air-fuel mixture by the first spark plug, the discharge by the second spark plug is performed, so that the flame nucleus generated at the time of the capacity discharge of the second spark plug causes the subsequent induction discharge. The flame is formed even when the fuel density is low because the fuel is held by the energy supplied by the fuel cell. When the temperature in the cylinder further increases, the first
By performing discharge by the spark plug, reliable and rapid combustion can be realized.
It is also possible to improve combustion stability and fuel consumption rate during GR combustion.

[0045]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an engine showing a first embodiment of a combustion control device for an internal combustion engine according to the present invention. In the engine of this embodiment, a combustion chamber 4 is formed by a cylinder block 1, a cylinder head 2, and a piston 3 in FIG.

The cylinder head 2 has at least one intake port 5, an intake valve 6 located downstream of the intake port 5 at the inlet of the combustion chamber 4, at least one exhaust port 7, and an upstream of the exhaust port 7. And an exhaust valve 8 located at the outlet of the combustion chamber, and the intake valve 6 and the exhaust valve 8 are opened and closed in conjunction with the crank angle of the engine by a valve train driving system (not shown).

A fuel injection valve 9 is provided at the intake port 5, and an air amount adjusting throttle (not shown), an intake air amount measuring air flow meter, and an intake air temperature measuring temperature sensor are provided upstream of the intake port 5. And an intake system comprising an air cleaner and piping.

A fuel having a low cetane number such as gasoline can be injected from the fuel injection valve 9 toward the intake valve 6. Specifically, the fuel is injected from the fuel injection valve 9 in such a manner as to directly hit the intake valve 6, whereby the vaporization is promoted by the intake valve 6 sufficiently heated by the heat transmitted from the combustion chamber 4. It is. Note that the fuel injection valve 9 may be installed at a position where fuel is directly injected into the cylinder.

The fuel injection valve 9 is controlled by an engine control unit (hereinafter abbreviated as ECU) 11 to a fuel injection timing and a fuel injection amount according to the engine operating conditions.
The fuel injection valve 9 may be provided at a position where fuel is directly injected into the cylinder.

Further, in the present invention, the auxiliary energy applying means 12 is provided in the combustion chamber 4, and by applying the auxiliary energy, the air-fuel mixture is reformed to improve its ignitability.

In this embodiment, an ignition plug used as an ignition device of a general gasoline internal combustion engine is used as the above-mentioned auxiliary energy applying means 12 and the ignition plug 1 is used.
2 is arranged in the central part of the combustion chamber 4.

The ECU 11 receives detection signals from a load sensor 14 for detecting an engine load and a crank angle sensor 15 for detecting an engine speed and its fluctuation, and operates the fuel injection valve 9 based on the detection signals. At the same time, the ignition plug 12 is operated via the ignition circuit 13.

Further, the ECU 11 detects and determines the combustion stability of the engine (hereinafter, simply referred to as stability) by selecting a combustion pattern determining section 21 for selecting spark ignition combustion or compression self-ignition combustion according to the operating range. The stability determination unit 22 determines the ignition plug 1 according to the stability detected and determined by the stability determination unit 22.
2, an auxiliary energy control unit 23 for controlling the amount of auxiliary energy or energy application timing, a fuel injection control unit 24 capable of increasing or decreasing the fuel injection amount in accordance with an instruction from the auxiliary energy control unit, and an ignition for controlling the ignition timing. The control unit 25 is provided.

Next, the operation of the first embodiment will be described. FIG. 2 shows a combustion mode according to the present embodiment, and the ECU 1
1 includes a combustion mode map in which a spark ignition combustion region and a compression self-ignition combustion region determined according to the engine speed and load as shown in FIG. 2 are stored in advance.

The combustion pattern determination section 21 of the ECU 11
Based on the input signals of the load sensor 14 and the crank angle sensor 15, a combustion mode map stored in advance is referred to,
It is determined whether to operate in the combustion pattern of spark ignition combustion or compression ignition combustion.

When performing spark ignition combustion, the ignition control unit 2
5 controls the ignition circuit 13 to generate an appropriate ignition signal, and instructs a valve timing control mechanism (not shown) to set the valve timing to a compression ratio suitable for spark ignition combustion.

In the case of performing the compression self-ignition combustion, the auxiliary energy control unit 2 controls the air-fuel mixture in the cylinder so that an appropriate auxiliary energy is applied and the compression self-ignition combustion is performed stably.
3 controls the ignition control unit 25 to control the discharge timing or the amount of discharge energy from the spark plug 12 as auxiliary energy application. In addition, although not particularly limited, a valve timing control mechanism (not shown) is instructed to set a valve timing that provides a compression ratio and an internal EGR rate suitable for compression self-ignition combustion.

FIG. 3 shows a heat generation pattern when the energy application timing is changed. When the energy application timing is advanced, the heat generation timing approaches TDC (top dead center), and the temperature and pressure in the cylinder increase, so that combustion is stabilized.

FIG. 4 shows the heat generation timing when the fuel properties change. When the fuel property changes from light (relatively low octane number) to heavy (relatively high octane number), the heat generation time becomes T
It is retarded from DC and the stability is deteriorated. In addition to fuel properties,
When parameters that affect combustion, such as intake air temperature and intake pressure, change, the heat generation timing changes.

Therefore, when a parameter affecting combustion changes, it is necessary to control the stability by changing the energy application timing to correct the heat generation timing.

FIG. 5 shows the stability with respect to the ignition timing in spark ignition combustion. In spark ignition combustion, the ignition timing is set to MBT
(Minimum Advance for Best Torque) The stability improves as the angle advances. Further, even if the angle is advanced from the MBT, the stability does not greatly deteriorate.

FIG. 6 shows the relationship between the timing of applying energy and the degree of stability in compression self-ignition combustion. The stability with respect to the energy application time is an upwardly convex curve having a maximum value at a certain application time. Although the stability increases as the energy application timing is sequentially advanced from the retard side, the stability sharply decreases when the energy is advanced from the timing at which the stability is maximum. Therefore, it is necessary to control or correct the energy application timing by grasping the timing of the stability with respect to the above tendency.

FIG. 7 shows the relationship between the energy application timing and the stability change. As an index indicating the degree of stability, a change rate of engine rotation (rotation fluctuation rate) is taken. For example, the engine speed is sampled for 50 rotations, and a value obtained by dividing the standard deviation σ of the engine speed at each rotation at this time by the average engine speed n is set as σn as an index of stability.

[0064]

Σn = σ / n σ: standard deviation, n: average engine speed.

When the change in the stability with respect to the change in the energy application timing, that is, dσn / dθ is large, the stability is improved by advancing the energy application timing (θ is assumed to be positive in the advance direction). Can be improved. On the other hand, if the change in the stability with respect to the change in the energy application timing, that is, dσn / dθ, is small, the stability may suddenly deteriorate if the energy application timing is advanced. Therefore, in the latter case, it is necessary to increase the fuel injection amount instead of correcting the energy application timing.

As described above, in the compression self-ignition combustion, the change characteristic of the stability with respect to the change of the energy application timing is different from that of the spark ignition. Focusing on the tendency of the stability change characteristics, when the factors that affect combustion such as fuel properties, intake air temperature, and cooling water temperature are changed by optimally correcting the energy application timing and correcting the fuel injection amount. In this case, the stability can always be kept optimal.

FIG. 8 is a flow chart showing a control flow according to the first embodiment. First, in step 10 (hereinafter, step is abbreviated as S), signals from the crank angle sensor and the load sensor are detected. Next, at S11, the engine speed and the load T are calculated. Next, in S12, a combustion pattern is determined according to the engine speed N and the load T. That is, it is determined from the engine speed N and the load T whether to perform the spark ignition combustion operation or the compression self-ignition combustion operation based on the map of FIG.

If the spark ignition combustion operation is to be performed, the process proceeds to S13, where control of the spark ignition combustion operation is started. When performing the self-ignition combustion operation, the process proceeds to S14, and the self-ignition combustion control is started.

Next, the stability is detected in S15. For example, based on the signal of the crank angle sensor, the above-mentioned σn is calculated as an index indicating the rotation fluctuation. In S16, the stability is determined. If the degree of stability is better than the judgment value, no control is required and the control is terminated. To determine the degree of stability, the determination value is determined according to the characteristics of the mounted vehicle, which is the field of use of the internal combustion engine, and for example, the following equation is used.

[0070]

Σn <a, for example, a = 5%.

If σn is smaller than 5%, it is determined that the stability is good. When σn is larger than 5%, the process proceeds to S17 to improve the stability. In S17, the energy application timing is advanced. For example, it is advanced by 1 ° CA (crank angle). At S18, the stability is detected again. In S19, a stability change allowance is determined. When the stability change allowance is large, it is determined that the effect of the energy application timing correction is large, and the process returns to S15, and the correction of the energy application timing is continued until the stability is improved. Here, the above-mentioned dσn /
It is determined by the following equation using dθ.

[0072]

## EQU3 ## dσn / dθ> b, for example, b = 0.5% / CA.

When the stability change margin is small, it is determined that the effect of the energy application timing correction is small, and the fuel injection amount is corrected in S20.

Next, a second embodiment of the present invention will be described. The configuration of the second embodiment is the first embodiment (FIG. 1).
Is the same as In the second embodiment, in order to reduce the fuel injection amount when the stability is better than the judgment value, the fuel injection amount is retarded and the fuel injection amount reduction correction is performed.

FIG. 9 shows the relationship between the energy application timing and the stability change. As an index indicating a change in stability, dσ described above is used.
n / dθ is used. Stability change allowance, that is, dσn / dθ
Is large, the stability of delaying the energy application timing is reduced. Therefore, the stability can be corrected by correcting the energy application timing. On the other hand, the stability does not change with respect to the change in the energy application timing, that is, dσn / dθ. Therefore, it can be determined that the stability is better as the fuel injection amount can be reduced. Therefore, in the latter case, fuel consumption is improved by reducing the fuel injection amount instead of correcting the energy application timing.

As described above, in the compression self-ignition combustion, the change of the stability with respect to the change of the energy application timing is different from that of the spark ignition. By paying attention to this tendency of the stability change, and by optimally correcting the energy application timing and the fuel injection amount, even when factors affecting the combustion such as the fuel property and the intake air temperature change, the correction is always performed. Stability can be kept optimal.

FIG. 10 shows a flow of control in the second embodiment. The control of the second embodiment is the same as that of the first embodiment (FIG. 8).
However, the difference is that the energy application timing is retarded when the stability is better than the judgment value.

The operation up to the detection of the stability in S35 of the third embodiment is the same as the operation up to S15 of the first embodiment. Next, at step 36, the degree of stability is determined. If the stability is lower than the judgment value, there is no need for correction, and the control ends.

For example, the following equation is used for determining the stability.

[0080]

Σn <c, for example, c = 3%.

If σn is larger than 3%, it is determined that the stability is not good enough to be corrected. When σn is smaller than 3%, the process proceeds to S37. In S37, the energy application timing is retarded. For example, 1 ° CA is retarded. In S38, the stability is detected again. In S39, a stability change allowance is determined. When the stability change allowance is large, it is determined that the effect of the energy application timing correction is large, and the process returns to S35, and the correction of the energy application timing is continued until the stability becomes optimum.

Here, the above-mentioned d is used for correcting the stability change allowance.
Using σn / dθ, determination is made by the following equation.

[0083]

(5) dσn / dθ> e, for example, e = 0.5% / CA.

When the stability change margin is small, it is determined that the effect of the energy application timing correction is small, and the fuel injection amount is reduced in S40.

Next, a third embodiment of the present invention will be described. FIG. 11 shows the configuration of the third embodiment. The difference between the configuration of the third embodiment and the configuration of the first embodiment (FIG. 1) is that the ignition plug 12 and the ignition circuit 13 of the first embodiment are different.
Instead, the laser beam irradiation device 16 is used as an energy applying device. With the change of the energy applying device, the ECU 11 is provided with a laser light control unit 27 instead of the ignition control unit 25 of the first embodiment. By changing the timing, the effective amount of auxiliary energy can be controlled. Other configurations are the same as in the first embodiment.

The laser beam irradiating device 16 is provided so as to irradiate the laser beam from a position other than the intake valve 6 and the exhaust valve 8 of the cylinder head 2, for example, from the center of the combustion chamber into the combustion chamber 4. By changing the amount of energy or the laser light irradiation timing as the energy application timing,
The same operation and effect as those of the above embodiment can be obtained.

In the third embodiment, the ignition of the air-fuel mixture is not ignited by a point as in the case of using the ignition plug 12, but is performed by linear ignition by laser light. To provide energy assistance over
It is possible to stably apply the auxiliary energy.

Further, as a modified example of the third embodiment, a spark ignition combustion operation and a compression self-ignition combustion operation capable of providing auxiliary energy by laser light irradiation are provided by providing both an ignition device and a laser light irradiation device. Switching can also be performed depending on the operation area.

Next, a fourth embodiment of the present invention will be described. FIG. 12 shows the configuration of the fourth embodiment. The configuration of the fourth embodiment is different from the configuration of the first embodiment (FIG. 1) in that an intake air temperature sensor 17 is added to the intake port 5 and an in-cylinder temperature calculator 26 is added to the ECU 11. Other components are the same as those of the first embodiment, and the same components are denoted by the same reference numerals, and redundant description will be omitted.

In the fourth embodiment, the in-cylinder temperature calculating section 26 predicts the in-cylinder temperature at the time of energy application based on the intake air temperature measured by the intake air temperature sensor 17, and the energy provision in accordance with the predicted in-cylinder temperature. It is characterized in that the presence and absence of energy and the timing of energy application are controlled.

The reason why the combustion timing approaches TDC when the auxiliary energy is applied to the air-fuel mixture and the combustion stability is improved is that a part of the vaporized fuel reacts with oxygen to cause radicals having high chemical activity. Is generated. The presence of these radicals promotes main combustion, which is the main heat-generating chemical reaction, and improves the stability of combustion.

FIG. 13 shows the amount of radicals after applying energy. The longer the elapsed time after the energy application, the more radicals. This indicates that radicals generated by the application of energy promote the reaction of the vaporized fuel to generate new radicals. Therefore, when energy is applied earlier in time, that is, on the advance side, T
Since there is time before DC, the radical growth time is secured, and the amount of radicals increases.

FIG. 14 shows the relationship between the in-cylinder temperature and the amount of generated radicals. As shown in the figure, the amount of generated radicals when a certain amount of energy is applied depends on the in-cylinder temperature. If the in-cylinder temperature is equal to or higher than a certain value Ta, the radical amount sharply increases as the temperature rises. At a temperature exceeding Tb higher than Ta, the amount of radicals increases gently as the temperature rises. In this embodiment, a temperature region equal to or higher than Tb is used.

However, the in-cylinder temperature has a certain value Ta.
If it is lower, radicals are hardly generated even when the auxiliary energy is applied. Therefore, if the energy application timing is advanced too much, the meaning of energy application is lost, and no radical is generated.

Therefore, by predicting the in-cylinder temperature and, if the energy application timing is advanced too much without improving the stability, the advance of the energy application timing is prohibited and the fuel amount is increased. Deterioration of stability can be prevented.

FIG. 15 is a flow chart showing a control flow according to the fourth embodiment. The control of the fourth embodiment is the same as that of the first embodiment (FIG. 8).
It is almost the same as Only different points will be described.

First, at step 50, the crank angle sensor 1
5. The difference is that the signal of the intake air temperature sensor 17 is detected in addition to the load sensor 14. Next, S51 to S56,
This is the same as S11 to S16 of the first embodiment.

If it is determined in S56 that the stability is lower than the determination value, the energy application timing is corrected to the advanced side in S57. Next, in S58, the in-cylinder temperature at the time of energy application is calculated. To calculate the in-cylinder temperature, first, the in-cylinder compression start temperature T0 is calculated from the intake air temperature Tin detected in S50. For example, T0 is calculated by the following equation.

[0099]

## EQU6 ## T0 = Tin + f, for example, f = 300K.

Next, the in-cylinder temperature T1 at the time of energy application is calculated from the compression start temperature T0 by the following equation.

[0101]

T1 = T0 × ε ＾ (n−1) ε: compression ratio at the time of energy application, n: polytropic index, and “＾” represents a power.

The compression ratio ε of the energy application timing is calculated from the energy application timing using, for example, a map shown in FIG. The compression ratio ε can also be obtained by calculation from the crank angle of the intake valve closing timing, the crank angle of the energy applying timing, and the shape of the combustion chamber. The polytropic index is, for example, n = 1.33. The polytropic index may be given according to the load.

Next, at S59, the in-cylinder temperature T1 is determined.
If the in-cylinder temperature T1 is higher than a predetermined judgment value, energy is actually applied in S60. The following equation is used to determine the in-cylinder temperature T1.

[0104]

T1> f, for example, f = 700K.

If T1 is higher than the judgment value f, S60
To give energy. When T1 is lower than f, the effect of the energy application is small and the stability is deteriorated. Therefore, the advance of the energy application timing is prohibited, and the fuel increase is performed in S63.

By controlling in this way, it is possible to prevent the energy application timing from being advanced too much and the effect of the energy application to be lost and the stability from deteriorating.

Next, a fifth embodiment of the present invention will be described. The configuration of the fifth embodiment is the same as the configuration of the first embodiment (FIG. 1). The fifth embodiment is characterized in that the energy application timing is learned according to the engine speed and the load.

In the embodiments described above, the energy application timing is corrected every time when the operating conditions change. When the stability is deteriorated, the drivability deteriorates while the energy application timing is being corrected. Therefore, in the present embodiment, the energy application timing is learned and stored.

FIG. 17 shows a map of the energy application timing for the engine speed N and the load T. FIG. 17 (a)
FIG. 17B is a map of the standard energy application timing stored in advance as an initial value, and FIG. 17B is a correction value of the energy application timing by learning. When performing spark ignition combustion, the ignition timing is controlled with reference to another map.

In the compression self-ignition combustion region, FIG.
As shown in (a), a map of standard energy application timing Eij (i is division by engine speed, j is division by load) is stored in advance for engine speed N and load T. Also, as shown in FIG. 17B, a similar storage area is prepared for an energy application timing correction value αij (i is division by engine speed, j is division by load), which are learning values. When controlling the energy application timing, [Eij + αij] is set as the control value.

The standard energy application timing Ei shown in FIG.
j is set to the advance side as the engine speed increases. Thereby, even at each engine rotation, the chemical reaction time for the radical generation by applying the auxiliary energy is secured, and the combustion stability can be surely improved.

FIGS. 18 and 19 show the control flow of the fifth embodiment. The energy application timing is learned and stored in the flow of FIG. 18, and the energy application timing stored in the flow of FIG. 19 is called and used for control.

First, the flow of FIG. 18 for learning the energy application timing and storing the learning value will be described. Step 90
Detects signals from the crank angle sensor and the load sensor. Next, in S91, the engine speed N and the load T are calculated. Next, in S92, a combustion pattern is determined according to the engine speed N and the load T. When performing spark ignition operation, S
The program proceeds to 93 and control of the spark ignition operation is started. When the self-ignition operation is performed, the process proceeds to S94 and the self-ignition combustion control is started.

Next, the stability is detected in S95. S96
To judge the stability. If the stability is lower than the determination value, the correction is being performed, and the learning value is not stored. If the stability is good, a steady judgment is made in S97. If the operating condition is not steady, the learning value is not stored because the transient control is being performed. When the operating condition is steady, the energy application timing is checked in S98, and the energy application timing correction value αij, which is the learning value, is determined in S99 in FIG.
It is stored at the position of i, j determined by the corresponding rotation speed N load T in the correction value map of (b).

Next, a learning value is called and used in FIG.
Will be described. The flow of FIG. 19 is almost the same as the flow of the first embodiment (FIG. 8). Only different points will be described. After starting the compression self-ignition combustion control in S74, the energy application timing is called from the map in FIG. 20 in S75, and the energy is applied in S76.

Next, a sixth embodiment of the present invention will be described. The configuration of the sixth embodiment is the same as the configuration of the first embodiment (FIG. 1), except that the stability determining unit 22 determines the stability of each cylinder, and the auxiliary energy control unit 23 determines that the It is characterized in that control of the amount of auxiliary energy or energy application timing is performed, and that the fuel injection control unit 24 corrects the fuel injection amount for each cylinder.

In the compression self-ignition combustion, the influence of combustion control factors such as the in-cylinder temperature, the in-cylinder pressure, the residual gas amount, and the cooling water temperature is strongly affected. Therefore, when the above factors differ for each cylinder, the combustion state differs for each cylinder. Therefore, the stability can be improved by performing the energy application and the correction of the fuel injection amount for each cylinder.

At this time, the stability of each cylinder is detected by a crank angle sensor. That is, based on the crank angle sensor signal, the angular velocity of the crankshaft in the expansion stroke of each cylinder at the time of combustion of each cylinder is taken out, and the σn of each cylinder can be detected by statistical processing. Then, σn of each cylinder is determined, and the presence / absence of energy application and the energy application timing are controlled for each cylinder.

FIGS. 20 and 21 show the control flow of the sixth embodiment. FIG. 20 is a flowchart of the control for each cylinder. FIG.
Will be described. In S100, signals from the crank angle sensor and the load sensor are detected. Next, in S101, the engine speed and the load T are calculated. Next, in S102, the control of the individual cylinder is determined. That is, if the cylinder-by-cylinder control is not to be performed during warm-up after start or near full opening, etc.
8 is the same control for all cylinders. When performing cylinder-specific control, cylinder discrimination is performed in S103. S104 to S1 for each cylinder
At 07, the energy application timing and the fuel injection amount are corrected according to the stability of each cylinder.

FIG. 21 shows a flow for controlling the energy application timing and the fuel injection amount for each cylinder. The control flow of FIG. 21 is the same as the control flow of the first embodiment except that the stability is detected for each cylinder, and that the auxiliary energy is applied and the fuel injection amount is increased or decreased based on the stability for each cylinder. Same as 8). According to the present embodiment, in a multi-cylinder engine, even when the combustion control factor differs for each cylinder,
It is possible to optimally control the energy application and enhance the stability.

In the first to sixth embodiments described above, by controlling the energy application timing of the auxiliary energy for generating radicals in the combustion chamber, the effective auxiliary energy is controlled according to the operating conditions or the detected stability. By controlling the amount of energy, appropriate compression self-ignition was realized. However, in the present invention, the control of the amount of auxiliary energy, such as the discharge voltage, is not limited to the control of the energy application timing.
For example, when the auxiliary energy is applied by the discharge of the spark plug, the primary coil current conduction time is controlled, and when the laser light is irradiated, the appropriate compression self-ignition combustion is realized by controlling the laser light intensity and the irradiation time. Obviously you can.

Next, a seventh embodiment of the present invention will be described.
FIG. 22 is an engine configuration diagram showing the seventh embodiment.
The combustion chamber 4 in the present device is formed by the cylinder head 2, the cylinder block 1 and the piston 3.
The cylinder head 2 has at least one intake port 5
An intake valve 6 located downstream of the intake port 5 at the inlet of the combustion chamber 4, and at least one exhaust port 7,
An exhaust valve 8 is provided upstream of the exhaust port 7 at the outlet of the combustion chamber. The intake valve 6 and the exhaust valve 8 are opened and closed by a valve operating system (not shown) in conjunction with the crank angle of the engine.

A fuel injection valve 9 is provided in the intake port 5, and an air amount adjusting throttle (not shown), an intake air amount measuring air flow meter, and an intake air temperature measuring temperature sensor are provided upstream of the intake port 5. And an intake system comprising an air cleaner and piping.

Further, the ignition plug 1 is attached to the cylinder head 2.
2 are screw-connected, and the ignition plug 12 is connected to an ignition circuit 13 in which ignition coils 18a and 18b having different capacity discharge characteristics are connected in parallel.

Here, it is assumed that the capacity discharge characteristic of the ignition coil 18a is larger than that of the ignition coil 18b. The capacity discharge characteristics can be changed by changing the number of turns on the primary side and the secondary side to change the secondary voltage value and the secondary voltage rise time, or by changing the discharge energy amount of the ignition coil 18 itself. It is feasible. Further, the two ignition coils 18a and 18b are connected to the battery 19 via the ECU 11, and the presence or absence of discharge and the discharge timing are individually controlled by the ECU 11.

Further, the engine of the seventh embodiment controls substantial changes in the compression ratio, intake air temperature and pressure, self EGR, external EGR amount, and the like in the low to medium load range of the engine.
The configuration is such that a high temperature and high pressure state capable of performing the compression self-ignition operation can be realized.

Next, the relationship between the discharge waveform and the amount of radicals generated by the discharge will be described with reference to FIG. The discharge from the spark plug is broadly classified into a high-voltage capacitive discharge that causes dielectric breakdown between the electrodes of the spark plug 12 and a subsequent low-voltage and relatively long-time induced discharge. At this time, the amount of chemically active intermediate products and radicals generated between the electrodes of the ignition plug 12 is generated in large quantities during the capacity discharge,
The amount of radicals generated during the induction discharge is relatively small. Therefore, it is important to change the characteristics of the capacity discharge in order to control the amount of radicals generated by the discharge.

The discharge timing of the spark plug 12 and the subsequent transition of the radical amount will be described with reference to FIG. In the internal combustion engine, the substantial compression starts almost at the point where the intake valve 6 is closed, and as the piston 3 moves up, the temperature in the combustion chamber 4 and the mixture density rise. The subsequent increase or decrease of the radicals generated by the discharge is determined by the temperature of the combustion chamber and the density of oxygen and fuel in the air-fuel mixture. In the compression self-ignition region when the load is low, the temperature and density in the cylinder in the first half of the compression stroke are low, so that the radicals generated by the discharge decrease and disappear without maintaining the activated state.

However, when the discharge is performed in the latter half of the compression stroke, the temperature and pressure in the cylinder are high, so that the radicals generated by the discharge multiply in a chain reaction with time, and the main combustion accompanied by full-scale heat generation occurs. Cause the necessary pre-reaction.

FIG. 25 shows the relationship between the discharge timing to the spark plug 12 and the amount of generated radicals at the required timing of the occurrence of the pre-reaction determined by the thermal efficiency.

The amount of generated radicals at the time of requesting the start of the pre-reaction has a maximum value depending on the discharge timing and tends to be upwardly convex due to the decrease and increase of the radicals. At this time, on the left side (early discharge side) of the discharge timing having the maximum value, the radical amount changes sharply with respect to the discharge timing, so that control based on the timing on the right side of the maximum side is necessary from the viewpoint of control robustness.

Therefore, two or more ignition coils capable of performing discharges having different capacity discharge characteristics are provided, and three types of discharges are performed in the order of discharge by the low-capacity discharge coil 12b, discharge by the high-capacity discharge coil 12a, and simultaneous discharge by both coils. By changing the discharge timing from late to early, it becomes possible to control the amount of radicals over a wide range with high accuracy.

FIG. 26 shows the required amount of radicals for the engine speed and load in the compression self-ignition operation region. At low engine speed and high load, there is ample reaction time for radicals to increase, and the appropriate amount of radicals decreases due to high fuel and air densities. Conversely, when the engine speed is high and the load is low, the reaction time is short and the fuel and air densities are low, so that the amount of radicals required for the occurrence of self-ignition increases.

The actual discharge control is performed by the ECU 1 shown in FIG.
1 is performed. The ECU 11 stores the engine speed measured by a sensor (not shown) as the operating state of the engine,
The intake air amount, the fuel injection amount, and the EGR amount are determined according to the crank angle and the required load, and the coil to be charged for the discharge and the discharge timing are determined based on a map prepared in advance. This makes it possible to achieve the compression self-ignition combustion in a wide operating range.

Next, an eighth embodiment of the present invention is shown in FIG. In the eighth embodiment, an ignition plug 1 having a different capacity discharge characteristic is used.
2 a and 12 b are arranged at the center and side of the combustion chamber 4. At this time, the spark plug 12a arranged substantially at the center of the combustion chamber 4 is set to have a higher capacity discharge voltage than the spark plug 12b arranged laterally,
The ignition coil 18 is set so that the induction discharge time of the ignition plug 12b is longer than that of the ignition plug 12a. The capacity discharge voltage can be changed depending on the distance between the electrodes and the shape of the electrodes.

This embodiment is an example of a direct-injection gasoline engine that supplies fuel directly into the combustion chamber. On the crown of the piston 3, a stratified charge combustion is performed in which a locally rich mixture is formed in the combustion chamber and burned. (Piston cavity) 3a is provided.

With this configuration, the amount of radicals during compression self-ignition combustion of the engine can be performed in the same manner as in the seventh embodiment, and the generation of radicals is spatially dispersed in the combustion chamber. The stability of ignition combustion can be improved.

When the engine is in the stratified charge combustion operation, the combustion chamber 4
And is ignited by an ignition plug 12a provided substantially at the center of the cylinder to perform combustion by flame propagation. Generally, during stratified charge combustion, the mixture near the spark plug 12a is rich, so that carbon is deposited near the electrodes and plug smoldering is likely to occur. However, by enhancing the capacity discharge as in the present embodiment, the capacity discharge is enhanced. Since the carbon in the vicinity of the electrode burns during combustion, the combustion stability at the time of spark ignition can be maintained.

Further, in the case of lean burn combustion in which the mixture concentration is lower than the stoichiometric air-fuel ratio or in the case of spark ignition combustion in which a large amount of exhaust gas is recirculated, ignition is first performed by the ignition plug 12b arranged on the side of the combustion chamber 4. After a predetermined time, the ignition is performed by the ignition plug 12a disposed substantially at the center of the combustion chamber 4. In the ignition by the ignition plug 12b, the flame nucleus generated at the time of the capacity discharge is held by the energy supplied by the subsequent induction discharge, so that the flame can be formed even when the fuel density is low. Further, when the temperature in the cylinder rises, by performing ignition by the ignition plug 12a, reliable and rapid combustion can be realized, so that the combustion stability and the fuel consumption rate during lean burn combustion or a large amount of EGR combustion can be improved. Can also be possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of an engine to which a combustion control device for an internal combustion engine according to the present invention is applied.

FIG. 2 is an explanatory diagram of a combustion pattern for selecting spark ignition combustion or compression self-ignition combustion with respect to operating conditions.

FIG. 3 is a diagram for explaining a relationship between energy application timing and heat generation during compression self-ignition.

FIG. 4 is a diagram illustrating the effect of fuel properties on heat generation timing.

FIG. 5 is a diagram illustrating the relationship between ignition timing and stability in spark ignition combustion.

FIG. 6 is a diagram illustrating the relationship between the timing of energy application and the degree of stability in compression self-ignition combustion.

FIG. 7 is a diagram illustrating a change rate of stability with respect to a change in energy application timing when the energy application timing is advanced.

FIG. 8 is a control flowchart illustrating the operation of the first embodiment.

FIG. 9 is a diagram for explaining a rate of change in stability with respect to a change in energy application timing when the energy application timing is retarded.

FIG. 10 is a control flowchart illustrating the operation of the second embodiment.

FIG. 11 is a configuration diagram of a third embodiment.

FIG. 12 is a configuration diagram of a fourth embodiment.

FIG. 13 is a diagram illustrating the relationship between the elapsed time after energy application and the amount of radicals.

FIG. 14 is a diagram illustrating the relationship between the in-cylinder temperature and the amount of generated radicals.

FIG. 15 is a control flowchart illustrating the operation of the fourth embodiment.

FIG. 16 is a diagram illustrating the relationship between the energy application timing and the compression ratio.

FIG. 17 is a diagram illustrating an energy application timing standard map (a) and an energy application timing correction value map (b) for the engine speed and load.

FIG. 18 is a control flowchart illustrating the operation of the fifth embodiment.

FIG. 19 is a control flowchart illustrating the operation of the fifth embodiment.

FIG. 20 is a control flowchart illustrating the operation of the sixth embodiment.

FIG. 21 is a control flowchart illustrating the operation of the sixth embodiment.

FIG. 22 is a schematic diagram of an engine configuration showing a seventh embodiment.

FIG. 23 is a diagram showing a discharge waveform and a generated radical amount in an ignition plug.

FIG. 24 is a diagram showing a transition of the amount of radicals in a cylinder depending on a discharge timing to an ignition plug.

FIG. 25 is a diagram showing the influence of the number of spark plugs to be discharged and the discharge timing on the amount of generated radicals.

FIG. 26 is a diagram showing a control state of a supplied radical amount during a compression self-ignition operation of the engine.

FIG. 27 is a schematic diagram of an engine configuration showing an eighth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 3 Piston 4 Combustion chamber 9 Fuel injection valve 11 Engine control unit (ECU) 12 Spark plug 13 Ignition circuit 14 Load sensor 15 Crank angle sensor 16 Laser light irradiation device 17 Intake air temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02P 15/08 301 F02P 15/08 301M 301A 23/04 23/04 A (72) Inventor ▲ Yoshi ▼ Sawa Kodai Nissan Motor Co., Ltd. (72) Inside the Nissan Motor Co., Ltd. (72) Inventor Koji Hiratani Nissan Motor Co., Ltd. (72) Inventor Go Taniyama Kanagawa-ku, Yokohama, Kanagawa 2 Takaracho Nissan Motor Co., Ltd. F-term (reference) 3G019 AA07 AA08 AA09 BA00 KA15 3G023 AA01 AA02 AA06 AB03 AB06 AB08 AC02 AC04 AG01 AG02 AG03

Claims (15)

[Claims] 1. A combustion control device for an internal combustion engine that self-ignites and burns an air-fuel mixture by compression of a piston, wherein auxiliary energy applying means for applying auxiliary energy to the air-fuel mixture in a combustion chamber to activate the air-fuel mixture. Stability detecting means for detecting the combustion stability of the engine, and auxiliary energy control means for controlling the amount or timing of the auxiliary energy applied by the auxiliary energy applying means according to the combustion stability detected by the stability detecting means. And a combustion control device for an internal combustion engine. 2. The fuel cell system according to claim 1, further comprising a fuel injection control unit configured to change a fuel injection amount in accordance with an instruction from the auxiliary energy control unit. The effective amount of auxiliary energy is controlled to be increased or decreased by changing the energy amount or the energy application timing back and forth, and when the control range of the auxiliary energy amount or the energy application timing is exceeded, the fuel injection control unit is instructed. 2. The fuel injection amount is varied.
A combustion control device for an internal combustion engine according to the above. 3. The apparatus according to claim 1, wherein an ignition plug is provided as the auxiliary energy applying means.
A combustion control device for an internal combustion engine according to the above. 4. A combustion control apparatus for an internal combustion engine according to claim 1, further comprising a laser beam irradiation device as said auxiliary energy applying means. 5. When the combustion stability falls below an allowable value, the amount of auxiliary energy is increased or the energy application timing is sequentially advanced to increase the amount of auxiliary energy until the effective amount of auxiliary energy becomes maximum. The combustion of the internal combustion engine according to any one of claims 2 to 4, wherein the fuel injection amount is increased when the combustion stability is lower than the allowable value even at the maximum advance timing. Control device. 6. When the combustion stability is higher than an allowable value, the auxiliary energy amount is reduced or the energy application timing is sequentially retarded to reduce the auxiliary energy amount until the effective auxiliary energy amount is minimized. The combustion of the internal combustion engine according to any one of claims 2 to 5, wherein the fuel injection amount is reduced when the combustion stability is higher than the allowable value even at the maximum retard timing. Control device. 7. An in-cylinder temperature estimating means for estimating an in-cylinder temperature, wherein when the in-cylinder temperature predicted value at the energy application timing is lower than a predetermined value, the effective energy amount is increased by advancing the energy application timing. 6. The internal combustion engine according to claim 5, wherein even if the auxiliary energy amount is increased to a maximum and the in-cylinder temperature predicted value is lower than a predetermined value, the fuel injection amount is increased. Engine combustion control device. 8. The method according to claim 1, wherein whether or not the auxiliary energy is to be applied and the amount or timing of the auxiliary energy when the auxiliary energy is to be applied are learned according to the engine speed and the load. Any one of item 7
A combustion control device for an internal combustion engine according to claim 1. 9. The stability detection means detects the combustion stability of each cylinder, and the control means determines the combustion stability of each cylinder based on the combustion stability.
The combustion of the internal combustion engine according to any one of claims 1 to 8, wherein the control of whether or not to apply the auxiliary energy and the control of the amount of auxiliary energy or the timing of applying the energy are performed for each cylinder. Control device. 10. A combustion control device for an internal combustion engine that self-ignites and burns an air-fuel mixture by compression of a piston, wherein at least one spark plug that applies auxiliary energy to the air-fuel mixture in the combustion chamber to activate the air-fuel mixture. The ignition system including the ignition plug is capable of performing at least two types of discharges having different capacity discharge characteristics, and controlling the amount of auxiliary energy by selecting different capacity discharge characteristics, or according to the discharge timing from the ignition plug. A combustion control device for an internal combustion engine, which controls a timing of applying energy. 11. The ignition system includes at least two ignition coils, and the amount of auxiliary energy is controlled by selecting these ignition coils or changing the number of ignition coils that supply electric energy to the ignition plug. The combustion control device for an internal combustion engine according to claim 10, wherein 12. The ignition system according to claim 10, wherein the ignition system includes at least two ignition plugs in each cylinder, and controls the amount of auxiliary energy by changing the selection or the number of ignition plugs to be energized. A combustion control device for an internal combustion engine. 13. The first spark plug is disposed substantially at the center of the combustion chamber, the second spark plug is disposed at a periphery of the combustion chamber, and the first spark plug has a capacity discharge characteristic of a second ignition plug. 13. The combustion control apparatus for an internal combustion engine according to claim 12, wherein the rise time of the secondary voltage of the capacity discharge is shorter than that of the plug, or the capacity discharge voltage is set higher. 14. A first spark plug is disposed substantially at the center of a combustion chamber, and a second spark plug is disposed at a peripheral portion of the combustion chamber. 11. The method according to claim 10, wherein, during ignition, homogeneous lean combustion or homogeneous EGR combustion, auxiliary energy is applied by discharging the second spark plug prior to ignition of the air-fuel mixture by discharging the first spark plug. A combustion control apparatus for an internal combustion engine according to any one of claims 13 to 13. 15. A combustion control device for an internal combustion engine having a stratified combustion region, a homogeneous lean combustion region, and a homogeneous EGR combustion region, wherein a first spark plug is disposed substantially at the center of a combustion chamber, and a second spark plug is provided. At the periphery of the combustion chamber, ignites the mixture by the discharge of the first spark plug during stratified charge combustion, and ignites the mixture by the discharge of the first spark plug during homogeneous lean burn or homogeneous EGR combustion A combustion control device for an internal combustion engine, wherein the discharge is performed by a second spark plug prior to the ignition.