JP3755351B2 - Control device for direct-injection spark-ignition internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
In recent years, fuel has been configured to be directly injected into the combustion chamber of an engine. For example, fuel is usually injected during the intake stroke and burned in a homogeneous mixture (a state where fuel is evenly distributed throughout the combustion chamber) (homogeneous). In a predetermined operating state (low rotation, low load state, etc.), fuel is injected during the compression stroke to form a stratified stratified mixture consisting of an flammable mixture that can be ignited around the spark plug An internal combustion engine (direct injection spark ignition type internal combustion engine) that performs combustion (stratified lean combustion) at an extremely lean air-fuel ratio (an air-fuel ratio in the vicinity of the lean limit) is known (JP-A-62). No. 191622 and Japanese Patent Laid-Open No. 2-169834).
[0003]
For the direct-injection spark ignition internal combustion engine as described above, the local air-fuel ratio around the spark plug is made rich in the process from cold start to warm-up, creating a local shortage of air and generated by combustion Which promotes activation of the exhaust purification catalyst by reacting incomplete combustion product (CO) and a part of the unburned fuel with excess oxygen in the cylinder after the main combustion and raising the exhaust temperature (See JP-A-10-169488).
[0004]
In addition, the applicant of the present application forms a stratified mixture with a locally rich air-fuel ratio around the spark plug in view of the problem that ignition is unstable in the above-described technique, which in turn increases unburned fuel (HC) emissions. However, by nebulizing the atomized fuel sufficiently, for example by delaying the ignition timing from the normal stratified lean combustion, the combustion is stabilized and the activation of the exhaust purification catalyst due to the rise in the exhaust temperature is promoted. A technology for suppressing fuel (HC) emissions has been proposed (Japanese Patent Application No. 11-46612).
[0005]
[Problems to be solved by the invention]
By the way, in order to increase the exhaust gas temperature and promote the activation of the exhaust gas purification catalyst as described above, a stratified mixture having a rich air-fuel ratio is locally formed around the spark plug to perform stratified combustion. In this case, at the time of cold start, first, in order to ensure stable combustibility, homogeneous combustion is performed in which a homogeneous mixture is formed in the entire combustion chamber and then combustion is performed. After the exhaust purification catalyst is activated, it is switched to homogeneous lean combustion, and further switched to stratified lean combustion and homogeneous stoichiometric combustion according to operation requirements.
[0006]
However, since stratified combustion has lower thermal efficiency than homogeneous combustion in which fuel and air are sufficiently mixed, a torque step occurs when switching between stratified combustion for raising the exhaust temperature and homogeneous combustion before and after that. This causes a problem that drivability is impaired.
[0007]
The present invention has been made paying attention to such a conventional problem, and suppresses generation of a torque step at the time of switching between stratified combustion for raising the exhaust gas temperature and homogeneous combustion, and stable operability can be obtained. An object of the present invention is to provide a control apparatus for a direct injection spark ignition internal combustion engine.
[0009]
[Means for Solving the Problems]
  For this reason, as shown in FIG.
  A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
  The air-fuel ratio around the spark plug is greater than the stoichiometric condition due to fuel injection into the combustion chamber during the compression stroke under the conditions before the warm-up is completed.A rich air-fuel mixture is formed with an average air-fuel ratio in the combustion chamber that is substantially stoichiometric.Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
  A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
  Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
  Fuel injection timing correction means for correcting the injection timing in the fuel injection in the compression stroke in the stratified combustion in the direction of eliminating the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion;Composed and
When switching from the stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, the combustion switching means gradually increases the fuel injection timing in the compression stroke after the combustion switching request is generated and until the combustion is switched. Correct to the advance sideIt is characterized by.
[0010]
  Claim 1 Pertaining toAccording to the invention
  When there is a request to raise the exhaust gas temperature, the stratified charge combustion control means controls the fuel injection amount of the fuel injection valve, the fuel injection timing, and the ignition timing of the ignition plug).A stratified air-fuel mixture that is rich and has an average air-fuel ratio in the combustion chamber that is substantially stoichiometric is formed and burned.Thus, since the stratified mixture has an air-fuel ratio richer than stoichiometric, incompletely combusted matter (CO) is generated by main combustion, and the incompletely combusted product is recombusted in the combustion chamber and exhaust passage after main combustion. As a result, the exhaust temperature rises and the exhaust purification catalyst is activated.
[0011]
In addition, homogeneous combustion is required at low temperature starting or after the activation of the exhaust purification catalyst. (The homogeneous combustion control means controls the fuel injection amount, fuel injection timing, and ignition timing to produce a homogeneous mixture in the entire combustion chamber. To form and burn.
[0012]
  Then, when the demand is switched, the homogeneous combustion is switched to the stratified combustion for raising the exhaust gas temperature, and when the stratified combustion is switched to the homogeneous combustion, the torque by the combustion switching (by the fuel injection timing correcting means). The fuel injection timing in the compression stroke in the stratified combustion is corrected in the direction to eliminate the step.
  In particular, when switching from stratified combustion for raising the exhaust gas temperature to homogeneous combustion, the fuel injection timing in the compression stroke is gradually corrected to the advance side after the request for switching the combustion occurs until the combustion is switched. As a result, the ratio of air in the entire combustion chamber mixed with the fuel injected in the compression stroke increases and the ratio of homogenization increases, so that the torque is gradually increased by gradually approaching the combustion close to homogeneous combustion. In this way, since the torque is gradually increased and then switched to the homogeneous combustion, the torque step at the time of switching the combustion can be suppressed to be small, and the torque change due to the change in the injection timing before the switching of the combustion becomes gentle.
[0013]
  The invention according to claim 2 includes the same means as in claim 1,
  When switching from the homogeneous combustion to the stratified combustion for increasing the exhaust gas temperature, the combustion switching means gradually changes the fuel injection timing corrected to the advance side in the compression stroke after switching the combustion. It is characterized by returning to.
  In this way, when switching from homogeneous combustion to stratified combustion for raising the exhaust gas temperature, the reverse process is followed, and the fuel injection timing in the compression stroke is corrected to the advance side during combustion switching. As a result, the torque in stratified combustion increases, and the torque difference from the homogeneous combustion before switching can be suppressed to a small level, and then gradually returned to the retarded angle and fuel injection suitable for stratified combustion for raising the original exhaust gas temperature Since the timing can be approached, the torque change due to the injection timing change also becomes gradual.
  As described above, in claims 1 and 2,Generation of a torque step is suppressed at the time of combustion switching, and operability is stabilized. Further, simple control for correcting the fuel injection timing may be used.
  The invention according to claim 3
  The stratified combustion is performed by dividing fuel injection into an intake stroke and a compression stroke, and a fuel mixture in which the air-fuel ratio is leaner than stoichiometric is formed in the entire combustion chamber by fuel injection in the intake stroke, and fuel in the compression stroke is formed. It is characterized in that an air-fuel mixture having a richer air-fuel ratio than the stoichiometry is formed around the spark plug by injection, and the air-fuel mixture is combusted.
[0014]
A homogeneous mixture is formed in the entire combustion chamber by the fuel injected in the intake stroke, and then a stratified mixture whose air-fuel ratio is richer than stoichiometric is formed around the spark plug by the fuel injected in the compression stroke.
[0015]
According to the invention of claim 3,
The rich stratified mixture around the spark plug burns, and the incomplete combustion product (CO) generated by the main combustion is reburned together with the lean mixture, resulting in a good flame to every corner of the combustion chamber. Since it is propagated, the low temperature region (quenching area) in the combustion chamber can be made a small region that is not different from that during homogeneous combustion. Furthermore, since the excess oxygen in the region where the lean air-fuel mixture burns remains after the main combustion, the temperature of the remaining oxygen at the end of the main combustion is also relatively high, and the CO re-combustion is more Proceed quickly.
[0020]
  Further, the invention according to claim 4 is as shown in FIG.
  A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
  The air-fuel ratio around the spark plug is greater than the stoichiometric condition due to fuel injection into the combustion chamber during the compression stroke under the conditions before the warm-up is completed.A rich air-fuel mixture is formed with an average air-fuel ratio in the combustion chamber that is substantially stoichiometric.Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
  A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
  Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
  A fuel injection amount correcting means for correcting the fuel injection amount in a direction to eliminate a torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion;Including, and
  The combustion switching means, when switching from the stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, gradually increases and corrects the fuel injection amount until the combustion is switched after the combustion switching request is generated.It is characterized by.
[0021]
  According to claim 4According to the invention
  As described above, when there is a request to raise the exhaust gas temperature, the exhaust gas temperature rises and the exhaust purification catalyst is activated by burning the air-fuel ratio around the spark plug by forming a stratified mixture richer than the stoichiometric mixture. When homogeneous combustion is required at the time of low temperature starting or after the activation of the exhaust purification catalyst, a homogeneous mixture is formed in the entire combustion chamber and burned.
[0022]
Then, when the demand is switched, the homogeneous combustion is switched to the stratified combustion for raising the exhaust gas temperature, and when the stratified combustion is switched to the homogeneous combustion, the torque by the combustion switching (by the fuel injection amount correcting means). The fuel injection amount is corrected in the direction to eliminate the step.
[0023]
  In particular, when switching from stratified combustion for increasing exhaust gas temperature to homogeneous combustion, the fuel injection amount is gradually increased and corrected until the combustion is switched after the demand for combustion switching occurs, so that the torque is gradually increased. Then, the combustion is switched to homogeneous combustion, so that the torque step at the time of switching the combustion can be suppressed to a small level, and the torque change due to the change in the injection timing before the switching to the combustion becomes gentle.
  The invention according to claim 5 includes the same means as in claim 4,
  The combustion switching means, when switching from the homogeneous combustion to the stratified combustion for increasing the exhaust gas temperature, gradually returns the corrected fuel injection amount to the uncorrected state after switching the combustion. To do.
  According to the invention of claim 5,
  When switching from homogeneous combustion to stratified combustion for raising the exhaust temperature, the reverse process is followed, and the fuel injection amount is corrected to increase at the time of combustion switching, increasing the torque in stratified combustion, before switching. The torque difference from the homogeneous combustion can be suppressed to a small level, and the fuel injection amount is gradually reduced thereafter, so that the torque change due to the fuel injection amount change becomes moderate.
  If it is only to eliminate the torque step, it is only necessary to correct the fuel injection amount once at the time of combustion switching. However, the fuel injection amount before and after switching in the steady state (under the same operating conditions) should be set equal. Thus, the air-fuel ratio can be maintained at λ = 1 (theoretical air-fuel ratio) or the like to maintain good exhaust purification performance. In such a case, the fuel injection amount is gradually changed as described above. Thus, it is possible to control the fuel injection amount in the steady state to be equal while suppressing the torque step at the time of switching.
  As described above, in claims 4 and 5, theOccurrence of a torque step is suppressed at the time of combustion switching, and drivability is stabilized. In addition, simple correction of the fuel injection amountControl is sufficient.
[0028]
  Also,Claim 6The invention according to
  The fuel injection amount that is corrected to increase during the stratified combustion is a fuel injection amount that is injected during the compression stroke, a fuel injection amount that is injected during the intake stroke, or a fuel injection that is injected during the intake stroke and the compression stroke. It is characterized by being either of quantity.
[0029]
  Claim 6According to the invention according to
  When performing fuel injection in the intake stroke and fuel injection in the compression stroke during stratified combustion for increasing the exhaust gas temperature, the amount of fuel injected during the compression stroke and the amount of fuel injected during the intake stroke Alternatively, the torque step at the time of switching to the homogeneous combustion can be suppressed to be small by correcting the increase in any of the fuel injection amounts injected during the intake stroke and the compression stroke.
[0030]
  Also,The invention according to claim 7 includes the same means as in claim 4,
  The combustion switching meansWhen switching from the stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, after switching the combustion, the fuel injection amount that has been corrected for reduction is gradually increased to a state without correction.It is characterized by returning.
[0031]
  Claim 7According to the invention according to
  When switching from stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, the fuel injection amount is corrected to decrease when switching the combustion, the torque decreases, and the torque difference from the stratified combustion before switching can be suppressed to a small level. Is a state without correction by gradually increasing the fuel injection amount {for example, the aboveClaim 4The torque change can be moderately maintained by returning to the appropriate value (for example, a value corresponding to λ = 1)} in the steady state described in the above.
[0032]
  The invention according to claim 8 includes the same means as in claim 4,
  The combustion switching means, when switching from the homogeneous combustion to the stratified combustion for raising the exhaust gas temperature, gradually corrects the fuel injection amount until the combustion is switched after the combustion switching request is generated. It is characterized by.
  According to the invention of claim 8,
  When switching from homogeneous combustion to stratified combustion for raising the exhaust gas temperature, the reverse process is followed, and the fuel injection amount is gradually reduced and then switched to stratified combustion. In addition to being able to be suppressed, the torque change due to the fuel injection amount change before the combustion switching is also gradual.
  The invention according to claim 9 is
  The stratified combustion is performed by dividing fuel injection into an intake stroke and a compression stroke, and a fuel mixture in which the air-fuel ratio is leaner than stoichiometric is formed in the entire combustion chamber by fuel injection in the intake stroke, and fuel in the compression stroke is formed. It is characterized in that an air-fuel mixture having a richer air-fuel ratio than the stoichiometry is formed around the spark plug by injection, and the air-fuel mixture is combusted.
  According to the invention of claim 9,
  The operation and effect as described in the third aspect can be obtained.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
In FIG. 2 showing the system configuration of the first embodiment of the present invention, an air flow meter 3 for detecting the intake air flow rate Qa and a throttle valve 4 for controlling the intake air flow rate Qa are provided in the intake passage 2 of the engine 1. A fuel injection valve 5 is provided facing the combustion chamber of each cylinder.
[0034]
The fuel injection valve 5 is driven to open by a drive pulse signal set in a control unit 50, which will be described later, and burns fuel that is pumped from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator (not shown). It can be directly injected into the room.
[0035]
A spark plug 6 that is mounted facing the combustion chamber and ignites the intake air-fuel mixture based on an ignition signal from the control unit 50 is provided in each cylinder.
[0036]
On the other hand, in the exhaust passage 7, an air-fuel ratio sensor 8 (an oxygen sensor that performs rich / lean output) detects the air-fuel ratio of the exhaust gas mixture by detecting the concentration of a specific component (for example, oxygen) in the exhaust gas. Or a wide area air-fuel ratio sensor that linearly detects the air-fuel ratio over a wide area), and an exhaust purification catalyst 9 for purifying exhaust gas is provided downstream thereof. Has been. The exhaust purification catalyst 9 performs oxidation of CO, HC and reduction of NOx in the exhaust in the vicinity of stoichiometric, that is, the theoretical air-fuel ratio {λ = 1, A / F (air weight / fuel weight) · 14.7}. A three-way catalyst that can purify the exhaust gas or an oxidation catalyst that oxidizes CO and HC in the exhaust gas can be used.
[0037]
Further, a downstream oxygen sensor 10 that detects the concentration of a specific component (for example, oxygen) in the exhaust and outputs a rich lean gas is provided on the exhaust downstream side of the exhaust purification catalyst 9.
[0038]
Here, in order to suppress a control error associated with deterioration of the air-fuel ratio sensor 8 or the like by correcting the air-fuel ratio feedback control based on the detection value of the air-fuel ratio sensor 8 based on the detection value of the downstream oxygen sensor 10. Although the downstream oxygen sensor 10 is provided (for the so-called double air-fuel ratio sensor system), it is necessary to perform the air-fuel ratio feedback control based on the detected value of the air-fuel ratio sensor 8. The downstream oxygen sensor 10 can be omitted. When air-fuel ratio feedback control is not performed, both the air-fuel ratio sensor 8 and the downstream oxygen sensor 10 can be omitted.
[0039]
In the present embodiment, the crank angle sensor 11 is provided, and the control unit 50 counts a crank unit angle signal output from the crank angle sensor 11 in synchronization with the engine rotation for a predetermined time, or The engine rotational speed Ne can be detected by measuring the cycle of the crank reference angle signal.
[0040]
A water temperature sensor 12 that is provided facing the cooling jacket of the engine 1 and detects the cooling water temperature Tw in the cooling jacket is provided.
Further, a throttle sensor 13 (which can also function as an idle switch) for detecting the opening degree of the throttle valve 4 is provided.
[0041]
By the way, in this embodiment, the throttle valve control apparatus 14 which can control the opening degree of the said throttle valve 4 with actuators, such as a DC motor, is provided.
[0042]
The throttle valve control device 14 electronically controls the opening degree of the throttle valve 4 based on the drive signal from the control unit 50 so that the required torque calculated based on the driver's accelerator pedal operation amount and the like can be achieved. Can be configured.
[0043]
Detection signals from the various sensors are input to a control unit 50 including a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like. The opening of the throttle valve 4 is controlled via the throttle valve control device 14 in accordance with the operating state detected based on the signals from the sensors, and the fuel injection valve 5 is driven to drive the fuel injection amount (fuel The amount of supply) is controlled, the ignition timing is set, and the ignition plug 6 is ignited at the ignition timing.
[0044]
Note that, for example, stratified combustion can be performed by injecting fuel into the combustion chamber in a compression stroke in a predetermined operation state (low / medium load region, etc.) and forming a combustible air-fuel mixture in the vicinity of the spark plug 6 in the combustion chamber. On the other hand, in other operating conditions (high load region, etc.), fuel can be injected into the combustion chamber during the intake stroke, so that an air-fuel mixture with a substantially uniform mixing ratio can be formed in the entire cylinder so that homogeneous combustion can be performed. The fuel injection timing (injection timing) can also be changed according to the operating state.
[0045]
By the way, in the control unit 50 according to the present embodiment, the exhaust purification catalyst 9 can be activated early while suppressing the discharge of HC into the atmosphere from the start to the activation of the exhaust purification catalyst 9. In order to achieve this, input signals from various sensors such as the key switch 16 are received and, for example, the following control is performed. Note that, when performing stratified combustion for raising the exhaust gas temperature according to the present invention, the average air-fuel ratio in the combustion chamber is almost stoichiometric, so this combustion mode is expressed as stratified stoichiometric combustion.
[0046]
Specifically, for example, a flowchart as shown in FIG. 3 is executed.
In step (denoted as S in the figure, the same applies hereinafter) 1, whether or not the ignition signal of the key switch 16 is turned ON (whether the key position is set to the ignition ON position) is determined by a method similar to the prior art. To do. If YES, the process proceeds to Step 2, and if NO, this flow ends.
[0047]
In step 2, it is determined whether or not the start signal of the key switch 16 is turned ON (whether or not the key position is set to the start position) by a method similar to the conventional technique. That is, it is determined whether or not there is a cranking request by a starter motor (not shown).
[0048]
If YES, it is determined that there is a start cranking request, and the process proceeds to step 3. If NO, it is determined that there is no cranking request yet, and the process returns to step 1. In step 3, the starter motor is started and the engine 1 is cranked as in the prior art.
[0049]
In step 4, as in the prior art, fuel injection for start-up (direct fuel injection in the intake stroke, see FIG. 5B) is performed, and the engine 1 is operated (direct injection homogeneous combustion).
[0050]
In the next step 5, it is determined whether or not the exhaust purification catalyst 9 is not activated. The determination can be replaced by, for example, determining whether the downstream oxygen sensor 10 provided facing the exhaust passage 7 is not activated. That is, whether or not the exhaust purification catalyst 9 is activated can be determined based on the state of change in the detection value number of the downstream oxygen sensor 10.
[0051]
Further, the engine water temperature Tw or the oil temperature or the like is detected to estimate the temperature (or the outlet temperature) of the exhaust purification catalyst 9, and activation of the exhaust purification catalyst 9 can be determined based on the result, or directly. Further, it can also be determined by detecting the temperature (or outlet temperature) of the exhaust purification catalyst 9.
[0052]
If the catalyst is not activated (if YES), go to step 6.
On the other hand, if the catalyst is activated (if NO), it is determined that there is no need for control for promoting the catalyst activation, and the process proceeds to step 9 to improve fuel efficiency and the like according to the driving state. Combustion is performed in the combustion mode, and this flow is finished.
[0053]
In Step 6, it is determined whether or not the temperature of the piston 15 (particularly the surface temperature of the crown recess) is equal to or higher than a predetermined temperature (stratified stoichiometric combustion transition allowable temperature). Such a determination can be made by directly detecting with a thermocouple or the like embedded in the piston 15 (especially the crown), or by detecting the engine water temperature Tw or the oil temperature, the piston (especially the crown) temperature is determined. It is also possible to perform estimation and perform based on the result.
[0054]
Specifically, for example, the simulation can be performed based on the pseudo water temperature TWF correlated with the piston crown surface temperature, the pseudo water temperature TWF correlated with the piston crown surface temperature is estimated, and the result is a predetermined value. This can be done depending on whether TWF1 (stratified stoichiometric combustion transition permission temperature) has been reached or not (see FIGS. 6 and 7 of Japanese Patent Application No. 11-46612).
[0055]
In the case of YES, it is assumed that even if stratified stoichiometric combustion for promoting catalyst activation, which will be described later, is performed, good ignitability, combustibility, and engine stability (engine operability) are obtained. Proceed to
[0056]
On the other hand, in the case of NO, if the stratified stoichiometric combustion for promoting the catalyst activation described later is performed, the piston crown surface temperature is lower than the predetermined temperature. The transition to stratified stoichiometric combustion is prohibited as there is a possibility that ignition and vaporization promotion will not be carried out well, and there is a possibility that the ignitability, combustion stability and engine stability (engine driveability) will decrease. Then, the routine returns to step 4 in order to continue the direct fuel injection (direct injection homogeneous combustion) in the intake stroke.
[0057]
In Step 7, when the catalyst is not activated, it is necessary to promote the activation of the catalyst, and the piston crown surface temperature is equal to or higher than the predetermined temperature so that the stratified mixture can be generated satisfactorily. In order to prioritize the driving performance under the driving conditions that require high output, homogeneous combustion is performed. As shown in FIG. 4, it is set according to the operating range determined by the engine speed and load. A combustion method is determined according to a combustion switching map or the like. And if it is the operation range which performs stratified stoichiometric combustion in this map, it will progress to Step 8, and will shift to stratified stoichiometric combustion for catalyst activation promotion, and will perform stratified stoichiometric combustion. If homogeneous combustion is set in the operation region, the process proceeds to step 4 and homogeneous combustion is selected even after stratified stoichiometric combustion is once started.
[0058]
In step 8, stratified stoichiometric combustion is performed after control for eliminating a torque step, which will be described later, is performed. Specifically, for example, about 50 of the total fuel amount {fuel weight necessary to achieve a substantially stoichiometric (theoretical air-fuel ratio)} that can be almost completely burned with the amount of intake air per combustion cycle, for example, about 50 % To approximately 90% of the fuel weight is injected and supplied into the combustion chamber in the intake stroke to form a homogeneous mixture that is relatively leaner than the stoichiometric air in the entire combustion chamber {the fuel shown in FIG. 5B The remaining fuel weight of about 50% to about 10% is injected and supplied into the combustion chamber in the compression stroke, and the air-fuel mixture is relatively richer (higher fuel concentration) than the stoichiometry around the spark plug 6. Are formed in layers {see FIG. 5 (A)} and burned (see FIG. 6).
[0059]
The stratified stoichiometric combustion mode is such that the air-fuel ratio of the air-fuel mixture leaner than the stoichiometric air-fuel ratio formed in the combustion chamber during the intake stroke (by the intake stroke injection in this embodiment) is 16 to 28, and the fuel during the compression stroke The share ratio between the fuel injection amount during the intake stroke and the fuel injection amount during the compression stroke is set so that the air-fuel ratio of the air-fuel mixture richer than the stoichiometry formed around the spark plug by injection becomes 9-13. You may make it set.
[0060]
Further, if the air-fuel ratio of each air-fuel mixture is set in the above range, the average air-fuel ratio in the combustion chamber is set to an air-fuel ratio (for example, a range of 13.8 to 18) slightly deviated from the stoichiometric air-fuel ratio. Also good.
[0061]
According to the stratified stoichiometric combustion as described above, it is possible not only to raise the exhaust temperature as compared with the conventional homogeneous stoichiometric combustion, but also to reduce the amount of unburned HC discharged from the combustion chamber to the exhaust passage. .
[0062]
That is, according to the stratified stoichiometric combustion, the conventional combustion mode {combustion mode in which only homogeneous combustion, only stratified combustion, or additional fuel is injected after the later stage of combustion (after the expansion stroke or during the exhaust stroke)} Compared with the case where the engine is warmed up, the early activation of the exhaust purification catalyst 9 is greatly promoted while suppressing the emission of HC into the atmosphere between the start of start and the exhaust purification catalyst 9 being activated. It will be possible.
[0063]
Next, in step 9, as in step 5, it is determined whether or not the exhaust purification catalyst 9 has been activated (whether the warm-up has been completed). If yes, go to step 10. If NO, the routine returns to step 8 where stratified stoichiometric combustion is continued until the exhaust purification catalyst 9 is activated.
[0064]
In step 10, a combustion mode (homogeneous stoichiometric combustion, homogeneous lean combustion, stratified lean combustion, etc.) that can achieve desired exhaust performance, fuel efficiency performance, driving performance (output performance, stability, etc.), etc., depending on the operating conditions After shifting to, this flow ends. However, immediately after it is determined that the exhaust purification catalyst 9 has been activated, switching to homogeneous stoichiometric combustion is performed so that the torque step between homogeneous combustion, particularly stratified stoichiometric combustion, can be reduced.
[0065]
In the present embodiment, the transition to the stratified stoichiometric combustion is prohibited in an operating state that may adversely affect the flammability of the stratified stoichiometric combustion (for example, when the piston crown surface temperature is lower than a predetermined temperature). However, when it is desired to give the highest priority to the early activation of the exhaust purification catalyst 9, such a configuration may not be adopted (that is, step 6 in the flowchart of FIG. 3 is omitted). Can also be done).
[0066]
Next, the control according to the present invention for suppressing the torque step at the time of switching between the stratified stoichiometric combustion and the homogeneous combustion before and after that will be described.
First, an embodiment in which the torque step is suppressed by controlling the fuel injection timing in the compression stroke in the stratified stoichiometric combustion will be described.
[0067]
An embodiment based on the fuel injection timing control will be described with reference to the flowchart of FIG.
In step 11, it is determined whether the current combustion is homogeneous combustion or stratified stoichiometric combustion.
[0068]
When it is determined in step 11 that the combustion is homogeneous, the process proceeds to step 12 and it is determined whether or not stratified stoichiometric combustion is permitted (when stratified stoichiometric combustion is selected in step 7 of FIG. 3).
[0069]
When the stratified stoichiometric combustion is permitted, that is, when a request for switching from the current homogeneous combustion to the stratified stoichiometric combustion for raising the exhaust gas temperature is generated, the routine proceeds to step 13 and the current operation state (engine rotation) The fuel injection timing IT0 in the compression stroke of the stratified stoichiometric combustion according to the speed and the load) and the advance correction amount ITH for suppressing the torque step at the time of combustion switching are calculated by searching from a map or the like. That is, by advancing the fuel injection timing IT in the compression stroke, the amount of air in the combustion chamber mixed with the injected fuel is increased, the homogenization ratio of the air-fuel mixture is increased, and can be brought closer to homogeneous combustion. The torque step at the time of combustion switching can be reduced. Therefore, the advance angle correction amount ITH is set to a value that can sufficiently suppress the torque step at the time of combustion switching while ensuring the stratified combustion by the formation of the stratified mixture by the fuel injection in the compression stroke.
[0070]
In step 14, the combustion is switched from homogeneous combustion to stratified stoichiometric combustion. At this time, the fuel injection timing IT (advance value) in the compression stroke in the stratified stoichiometric combustion at the time of the combustion switching is advanced by the fuel injection timing IT0 corresponding to the operating state by the advance correction amount ITH for suppressing the torque step. Control the angle corrected value.
[0071]
As described above, the stratified stoichiometric combustion that is brought close to the homogeneous combustion is performed, so that a torque step at the time of switching the combustion is suppressed.
Next, every time the predetermined time elapses in step 15, the fuel injection timing IT in the compression stroke is retarded by the correction amount ΔITH in step 16. In step 17, the fuel injection timing IT corresponds to the operation state. It is determined whether or not the fuel injection timing IT0 has been reached. After the fuel injection timing IT0 has been reached, this flow is terminated, and thereafter the control of the fuel injection timing IT according to the operation state in the stratified stoichiometric combustion is continued. .
[0072]
On the other hand, when switching from stratified stoichiometric combustion to homogeneous combustion, the reverse of the above is followed. That is, when it is determined in step 11 that the current combustion is stratified stoichiometric combustion, the routine proceeds to step 18 where homogeneous combustion is permitted (when homogeneous combustion is selected in step 7 of FIG. 3). Determine whether.
[0073]
When the homogeneous combustion is permitted, that is, when a request for switching from the current stratified stoichiometric combustion to the homogeneous combustion is generated, the routine proceeds to step 19, where the compression stroke of the stratified stoichiometric combustion according to the current operating state is performed. An advance correction amount ITH for suppressing a torque level difference at the time of combustion switching with respect to the fuel injection timing IT0 is calculated.
[0074]
Each time a predetermined time elapse is determined in step 20, the fuel injection timing IT in the compression stroke is advanced by the correction amount ΔIT in step 21, and the total value ΣΔIT of the correction amount ΔIT is advanced in step 22 in step 22. It is determined whether the fuel injection timing IT has reached ITH, that is, whether the fuel injection timing IT has become a value obtained by correcting the fuel injection timing IT0 corresponding to the operating state by the advance angle correction amount ITH. In step 23, the combustion is switched to the homogeneous combustion. The fuel injection timing at the time of switching to the homogeneous combustion and the subsequent fuel injection are controlled according to the operation state.
[0075]
As described above, the stratified stoichiometric combustion approaching the homogeneous combustion is switched to the homogeneous combustion, thereby suppressing a torque step at the time of the combustion switching.
FIG. 8 shows a change in the fuel injection timing before and after the combustion switching in the first embodiment. In the figure, when switching from homogeneous combustion to stratified stoichiometric combustion, it is continuously from the lower side to the upper side of the figure. When changing from stratified stoichiometric combustion to homogeneous combustion, it changes continuously from the upper side to the lower side of the figure (the same applies to the figures corresponding to the following embodiments).
[0076]
Next, an embodiment in which the torque step at the time of combustion switching is suppressed by fuel injection amount control will be described.
First, an embodiment in which the torque step is suppressed by controlling the fuel injection amount in the compression stroke in the stratified stoichiometric combustion will be described with reference to the flowchart of FIG.
[0077]
In Steps 31 and 32, when it is determined that the current combustion is homogeneous combustion and stratified stoichiometric combustion is permitted in the same manner as in Steps 11 and 12, the process proceeds to Step 33 and the current operation state ( The fuel injection amount CTiS0 in the compression stroke of the stratified stoichiometric combustion according to the engine speed and the load) and the increase correction amount CTiSH for suppressing the torque step at the time of combustion switching are calculated by searching from a map or the like. That is, the torque step at the time of combustion switching can be reduced by increasing the torque by increasing the fuel injection amount CTiS in the compression stroke. Therefore, the increase correction amount CTiSH is set to a value that can sufficiently suppress the torque step at the time of combustion switching while ensuring the stratified combustion by the formation of the stratified mixture by the fuel injection in the compression stroke.
[0078]
In step 34, the combustion is switched from homogeneous combustion to stratified stoichiometric combustion. At this time, the fuel injection amount CTiS in the compression stroke in the stratified stoichiometric combustion at the time of the combustion switching is controlled to a value obtained by increasing the fuel injection amount CTiS0 corresponding to the operation state with the increase correction amount CTiSH for suppressing the torque step. .
[0079]
As described above, the stratified stoichiometric combustion in which the torque is increased and corrected at the time of the combustion switching is performed, so that the torque step is suppressed.
Next, every time a predetermined time elapse determination in step 35, the fuel injection amount CTiS in the compression stroke is decreased by a correction amount ΔCTiS in step 36, and in step 37, the fuel injection amount CTiS is a fuel corresponding to the operating state. It is determined whether or not the injection amount CTiS0 has been reached. After the fuel injection amount CTiS0 has been reached, the control of the fuel injection amount CTiS according to the operation state in the stratified stoichiometric combustion is continued.
[0080]
On the other hand, when switching from stratified stoichiometric combustion to homogeneous combustion, the reverse of the above is followed. That is, if it is determined in step 31 that the current combustion is stratified stoichiometric combustion and the process proceeds to step 38 and it is determined that homogeneous combustion is permitted, the process proceeds to step 39, where the stratified stoichiometric combustion corresponding to the current operating state is performed. An increase correction amount CTiSH for suppressing a torque step at the time of combustion switching with respect to the fuel injection amount CTiS0 in the compression stroke of combustion is calculated.
[0081]
Then, for each predetermined time elapsed determination in step 40, the fuel injection amount CTiS in the compression stroke is increased by the correction amount ΔCTiSH in step 41, and in step 42, the total value ΣΔCTiSH of the correction amount ΔCTiSH becomes the increase correction amount CTiSH. It is determined whether the fuel injection amount CTiS has reached the value obtained by correcting the fuel injection amount CTiS0 corresponding to the operating state with the increase correction amount CTiSH. At 43, combustion is switched to homogeneous combustion. The fuel injection amount at the time of switching to the homogeneous combustion and thereafter is controlled according to the operating state.
[0082]
In this way, after increasing the torque by stratified stoichiometric combustion, switching to homogeneous combustion suppresses the torque step at the time of combustion switching.
FIG. 10 shows how the fuel injection amount changes before and after the combustion switching in the second embodiment.
[0083]
Further, by correcting the fuel injection amount in the intake stroke as well as correcting the fuel injection amount in the compression stroke in the stratified stoichiometric combustion, the torque step can be suppressed. FIG. 11 shows a change in the fuel injection timing before and after the combustion switching in the third embodiment. Although the flowchart is omitted, the torque difference is suppressed only by the fuel injection amount increase correction in the compression stroke in the second embodiment, and the fuel injection amount increase correction and compression in the intake stroke are suppressed. What is necessary is just to set it as distributing and setting to the increase correction | amendment of the fuel injection quantity in a process. Here, an increase correction amount for each stroke can be set while maintaining a constant ratio (division ratio) between the fuel injection amount in the intake stroke and the fuel injection amount in the compression stroke. The change in combustibility due to can be reduced.
[0084]
In addition, it is natural that the torque step can be suppressed by correcting only the fuel injection amount during the intake stroke in the stratified stoichiometric combustion, and the fuel before and after the combustion switching in the fourth embodiment thus configured. FIG. 12 shows how the injection amount changes.
[0085]
In addition, the above has been shown to suppress the torque step by increasing the fuel injection amount at the time of stratified stoichiometric combustion. However, the torque step is also suppressed by correcting the decrease in the fuel injection amount in homogeneous combustion. be able to. FIG. 13 shows how the fuel injection timing changes before and after the combustion switching in the fifth embodiment. In FIG. 13, at the time of switching from homogeneous combustion to stratified stoichiometric combustion, the fuel injection amount corresponding to the operation state in homogeneous combustion is gradually reduced and corrected to a torque step equivalent at the time of combustion switching, and then stratified. Switch to stoichiometric combustion. The fuel injection amount in the intake stroke and the compression stroke in the stratified stoichiometric combustion at the time of switching and after switching is controlled to a steady-state value corresponding to the operating state.
[0086]
When switching from stratified stoichiometric combustion to homogeneous combustion, the reverse process is followed, and immediately after switching to homogeneous combustion, the fuel injection amount is reduced by an amount corresponding to the torque step, and then gradually increased to increase steady state fuel injection. Increase to volume.
[0087]
Thus, the torque step at the time of combustion switching can be suppressed even by correcting the amount of fuel injection in homogeneous combustion to be reduced.
In the above embodiment, the fuel injection amount in the steady state in the same operation state (the engine speed and load are the same) in the homogeneous combustion and the stratified stoichiometric combustion (in the stratified stoichiometric combustion, the sum of the intake stroke and the compression stroke) The fuel injection amount) is controlled equally, so that the fuel injection amount before or after switching is gradually changed. Thereby, in a steady state, each combustion is stoichiometric (λ = 1), and the exhaust purification performance by the exhaust purification catalyst can be maintained well. However, if it is only to eliminate the torque step, the fuel injection amount is corrected once when the combustion is switched (increased when switching from homogeneous combustion to stratified stoichiometric combustion, decreased when switching from stratified stoichiometric combustion to homogeneous combustion) It is good.
[0088]
  Further, in the above embodiment, the stratified stoichiometric combustion is shown in which fuel injection is performed twice in the intake stroke and the compression stroke, but the present invention performs injection only in the compression stroke in the stratified stoichiometric combustion, and the spark plug The present invention can also be applied to a case where an air-fuel mixture layer that is richer than stoichiometric is formed around it and the outer combustion chamber space is an air layer. In this case as well, the average air-fuel ratio in the combustion chamber is close to the stoichiometric range.To do.
[0089]
FIG. 14 (fuel injection timing control) and FIG. 15 (stratified stoichiometric combustion fuel) show changes in the fuel injection timing or fuel injection amount in each embodiment applied to the fuel that performs stratified stoichiometric combustion in which fuel is injected only in the compression stroke. The injection amount is corrected to increase), and FIG. 16 (homogeneous combustion fuel injection amount is corrected to decrease).
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an invention according to claim 2 and claim 6;
FIG. 2 is a system configuration diagram according to the embodiment of the present invention.
FIG. 3 is a flowchart for explaining control in the embodiment.
FIG. 4 is a combustion switching map used for switching combustion according to an operation region in the embodiment.
FIG. 5A is a schematic diagram for explaining direct injection compression stroke injection. (B) is a schematic diagram for explaining direct injection intake stroke injection. (C) is a top view at the time of fuel injection.
FIG. 6 is a view for explaining the state of air-fuel mixture formation in the combustion chamber of the stratified stoichiometric combustion mode according to the present invention.
FIG. 7 is a flowchart showing fuel injection timing correction control in a compression stroke of stratified stoichiometric combustion at the time of combustion switching according to the first embodiment.
FIG. 8 is a time chart showing a change in fuel injection timing in the first embodiment.
FIG. 9 is a flowchart showing fuel injection amount correction control in a compression stroke of stratified stoichiometric combustion at the time of combustion switching according to a second embodiment.
FIG. 10 is a time chart showing how the fuel injection amount changes in the second embodiment.
FIG. 11 is a time chart showing a change in the fuel injection amount in the fuel injection amount correction control in the intake stroke and compression stroke of stratified stoichiometric combustion at the time of combustion switching according to the third embodiment.
FIG. 12 is a time chart showing a change in the fuel injection amount in the fuel injection amount correction control in the intake stroke of stratified stoichiometric combustion at the time of combustion switching according to the fourth embodiment.
FIG. 13 is a time chart showing a change in the fuel injection amount in the fuel injection amount correction control for homogeneous combustion at the time of combustion switching according to the fifth embodiment.
FIG. 14 is a time chart showing a change in fuel injection timing of stratified stoichiometric combustion in which fuel is injected only during the compression stroke at the time of combustion switching according to the sixth embodiment.
FIG. 15 is a time chart showing a change in the fuel injection amount of stratified stoichiometric combustion in which fuel is injected only during the compression stroke at the time of combustion switching according to the seventh embodiment.
FIG. 16 is a time chart showing the state of change in the fuel injection amount of homogeneous combustion, in which stratified stoichiometric combustion in which fuel is injected only during the compression stroke at the time of combustion switching according to the seventh embodiment is performed.
[Explanation of symbols]
1 Internal combustion engine
5 Fuel injection valve
6 Spark plug
7 Exhaust passage
8 Air-fuel ratio sensor
9 Exhaust gas purification catalyst
10 Downstream oxygen sensor
11 Crank angle sensor
50 Control unit

Claims (9)

A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber;
Under the conditions before the completion of warm-up, fuel mixture is injected into the combustion chamber in the compression stroke to form an air-fuel mixture around the spark plug that is richer in air / fuel ratio than stoichiometric and whose average air / fuel ratio in the combustion chamber is substantially stoichiometric Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
Comprising fuel injection timing correction means for correcting the injection timing in the fuel injection in the compression stroke in the stratified combustion in the direction of eliminating the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion ; and
When switching from the stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, the combustion switching means gradually increases the fuel injection timing in the compression stroke after the combustion switching request is generated and until the combustion is switched. A control device for a direct-injection spark-ignition internal combustion engine , wherein correction is made to the advance side . A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
Under the conditions before the completion of warm-up, fuel mixture is injected into the combustion chamber in the compression stroke to form an air-fuel mixture around the spark plug that is richer in air / fuel ratio than stoichiometric and in which the average air / fuel ratio in the combustion chamber is substantially stoichiometric. Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
Comprising fuel injection timing correction means for correcting the injection timing in the fuel injection in the compression stroke in the stratified combustion in the direction of eliminating the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion; and
When switching from the homogeneous combustion to the stratified combustion for increasing the exhaust gas temperature, the combustion switching means gradually changes the fuel injection timing corrected to the advance side in the compression stroke after switching the combustion. A control device for a direct-injection spark-ignition internal combustion engine, wherein   The stratified combustion is performed by dividing fuel injection into an intake stroke and a compression stroke, and a fuel mixture in which the air-fuel ratio is leaner than stoichiometric is formed in the entire combustion chamber by fuel injection in the intake stroke, and fuel in the compression stroke is formed. 3. The direct injection spark ignition type internal combustion engine according to claim 1, wherein an air-fuel ratio is formed around the spark plug by injection and the air-fuel ratio is richer than stoichiometric, and the air-fuel mixture is combusted. Control device. A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
Under the conditions before the completion of warm-up, fuel mixture is injected into the combustion chamber in the compression stroke to form an air-fuel mixture around the spark plug that is richer in air / fuel ratio than stoichiometric and whose average air / fuel ratio in the combustion chamber is substantially stoichiometric Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
Comprising fuel injection amount correction means for correcting the fuel injection amount in a direction to eliminate the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion , and
The combustion switching means, when switching from the stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, gradually increases and corrects the fuel injection amount until the combustion is switched after the combustion switching request is generated. A control apparatus for a direct-injection spark ignition type internal combustion engine. A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
Under the conditions before the completion of warm-up, fuel mixture is injected into the combustion chamber in the compression stroke to form an air-fuel mixture around the spark plug that is richer in air / fuel ratio than stoichiometric and in which the average air / fuel ratio in the combustion chamber is substantially stoichiometric. Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
Comprising fuel injection amount correction means for correcting the fuel injection amount in a direction to eliminate the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion, and
The combustion switching means, when switching from the homogeneous combustion to the stratified combustion for increasing the exhaust gas temperature, gradually returns the corrected fuel injection amount to the uncorrected state after switching the combustion. Control device for direct-injection spark-ignition internal combustion engine. The fuel injection amount that is corrected to increase during the stratified combustion is a fuel injection amount that is injected during the compression stroke, a fuel injection amount that is injected during the intake stroke, or a fuel injection that is injected during the intake stroke and the compression stroke. 6. The control device for a direct injection spark ignition type internal combustion engine according to claim 4 or 5, wherein the control device is a quantity. A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
Under the conditions before the completion of warm-up, fuel mixture is injected into the combustion chamber in the compression stroke to form an air-fuel mixture around the spark plug that is richer in air / fuel ratio than stoichiometric and in which the average air / fuel ratio in the combustion chamber is substantially stoichiometric. Stratified combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to perform stratified combustion for increasing the exhaust gas temperature;
A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
Comprising fuel injection amount correction means for correcting the fuel injection amount in a direction to eliminate the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion, and
When switching from the stratified combustion for raising the exhaust gas temperature to the homogeneous combustion, the combustion switching means gradually increases the fuel injection amount that has been corrected for reduction and returns it to the state without correction after switching combustion. A control device for a direct-injection spark-ignition internal combustion engine. A fuel injection valve that directly injects fuel into the combustion chamber of the engine, and an ignition plug that sparks the air-fuel mixture in the combustion chamber,
Under the conditions before the completion of warm-up, fuel mixture is injected into the combustion chamber in the compression stroke to form an air-fuel mixture around the spark plug that is richer in air / fuel ratio than stoichiometric and in which the average air / fuel ratio in the combustion chamber is substantially stoichiometric. , Fuel injection amount, fuel injection timing, ignition timing to cause stratified combustion for exhaust gas temperature rise Stratified combustion control means for controlling
A homogeneous combustion control means for controlling the fuel injection amount, the fuel injection timing, and the ignition timing so as to form and burn a homogeneous mixture in the entire combustion chamber by fuel injection only in the intake stroke;
Combustion switching means for switching between stratified combustion by the stratified combustion control means and homogeneous combustion by the homogeneous combustion control means according to the engine operation request;
Comprising fuel injection amount correction means for correcting the fuel injection amount in a direction to eliminate the torque step due to the switching at the time of switching between the stratified combustion and the homogeneous combustion, and
The combustion switching means, when switching from the homogeneous combustion to the stratified combustion for raising the exhaust gas temperature, gradually corrects the fuel injection amount until the combustion is switched after the combustion switching request is generated. Characterized by
Control device for a direct injection spark ignition internal combustion engine. The stratified combustion is performed by dividing fuel injection into an intake stroke and a compression stroke, and a fuel mixture in which the air-fuel ratio is leaner than stoichiometric is formed in the entire combustion chamber by fuel injection in the intake stroke, and fuel in the compression stroke is formed. The direct eruption according to any one of claims 4 to 8 , wherein an air-fuel ratio is formed around the spark plug by injection and the air-fuel ratio is richer than stoichiometric, and the air-fuel mixture is combusted. A control device for a flower ignition type internal combustion engine.

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