JP4038999B2 - Control device for direct-injection spark ignition engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a direct injection spark ignition engine.
[0002]
[Prior art]
As a method of suppressing knocking in a gasoline engine, a method of correcting the ignition timing when the knocking should be suppressed is generally used. However, when knocking is to be avoided only by such a method, the ignition timing is delayed. There is a problem that engine torque is greatly reduced due to corners.
[0003]
On the other hand, Japanese Patent Laid-Open No. 10-231744 injects a small amount of fuel during the intake stroke (an amount that does not self-ignite in the subsequent compression stroke) in the low-rotation and high-load operation region where knocking is likely to occur, The fuel is injected in the compression stroke. According to this method, the ignition timing can be set to the advance side as compared with the case where only the intake stroke injection is performed. Is going to improve.
[0004]
[Problems to be solved by the invention]
However, if compression stroke injection is performed during high load operation with a large amount of fuel injection, the amount of unburned fuel and smoke discharged tends to increase. Therefore, it is desirable to perform such control only when it is really necessary.
Furthermore, according to the experiments by the present inventors, the intake stroke injection is set to the knock limit by performing the intake stroke injection from the engine torque when the compression stroke injection is performed during the high load operation and the ignition timing is set to the knock limit. In some cases, the engine torque at that time may be larger, and it has been found that compression stroke injection is not always advantageous in terms of engine torque in the low rotation and high load operation region.
[0005]
In view of such a situation, the present invention is a direct injection spark ignition engine capable of minimizing deterioration of exhaust emission associated with knocking suppression and further suppressing a decrease in engine torque associated with knocking suppression. An object of the present invention is to provide a control device.
[0006]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, in a control device for a direct injection spark ignition engine having a fuel injection valve for directly injecting fuel into a cylinder and an ignition plug, a knocking detection means for detecting knocking strength, When the detected knocking strength exceeds the allowable range in the rotational high load operation region, the fuel injection timing is maintained at the first injection timing set in the intake stroke, and the ignition timing is set to be within the allowable range. The first knocking suppression control that corrects the retarded angle so as to be within the range, the fuel injection timing is changed to the second injection timing set in the compression stroke, and the ignition timing is within the allowable range. And control means for selectively executing either one of the second knocking suppression control and the second knocking suppression control for correcting the first knocking control. The retard correction amount engine torque from the second knock suppression control by correcting the ignition timing to the retard side at the grayed suppression control is expected to be small are stored as a predetermined value, In the first knocking suppression control, when the knocking intensity does not fall within the allowable range, a process of updating the retard correction amount with respect to the ignition timing to the increasing side is performed, and as a result, the first knocking suppression control is performed. On the condition that the retard correction amount of the ignition timing is larger than the predetermined value, The second knocking suppression control is executed.
[0009]
According to a second aspect of the present invention, in a control device for a direct injection spark ignition engine having a fuel injection valve for directly injecting fuel into a cylinder and an ignition plug, a knocking detection means for detecting knocking strength, a low rotation high load When the detected knocking strength exceeds the allowable range in the operation region, the fuel injection timing is maintained at the first injection timing set in the intake stroke, and the ignition timing is within the allowable range. The first knocking suppression control that corrects to the retarded angle side, and the fuel injection timing is changed to the second injection timing set in the compression stroke, and the ignition timing is set within the allowable range. Control means for selectively executing either one of the second knocking suppression control to be corrected to The control means performs the first knocking suppression control when it is determined that the engine torque when the second knocking suppression control is executed is smaller than the engine torque when the first knocking suppression control is executed. The engine torque when the second knocking suppression control is executed is greater than the engine torque when the first knocking suppression control is executed. Become When the determination is made, the second knocking suppression control is executed.
[0010]
Claim 3 In this invention, the initial value of the ignition timing at the time of switching from the first knocking suppression control to the second knocking suppression control is set to a predetermined knocking limit ignition timing at the second injection timing. Features.
[0011]
Claim 4 In this invention, the initial value of the ignition timing at the time of switching from the first knocking suppression control to the second knocking suppression control is from a predetermined knocking limit ignition timing at the second injection timing, immediately before the switching. The ignition timing is retarded by an amount corresponding to the retardation correction amount in the first knocking suppression control.
[0013]
【The invention's effect】
Claims 1, 2 According to the invention, the first knocking suppression control (ignition timing retarding control) and the second knocking suppression control (compression stroke injection) are performed according to the situation in the low-rotation and high-load operation region where knocking is likely to occur. Since the compression stroke injection is performed only when necessary, it is possible to minimize the deterioration of exhaust emission due to the suppression of knocking.
Also, Since it is possible to select and execute control that is advantageous in terms of engine torque, it is possible to minimize a decrease in engine torque due to knocking suppression.
[0014]
In particular, claim 1 According to the present invention, when the ignition timing retardation correction amount exceeds the predetermined range and the engine torque decrease due to the ignition timing retardation control becomes significant, the engine is switched to the compression stroke injection. Can be minimized.
Also, Claim 2 According to the invention, since the switching is performed by determining the magnitude of the engine torque by the two controls, it is possible to minimize the decrease in the engine torque accompanying the knocking suppression.
[0015]
Claim 3 According to the invention, since the reverse rotation of the engine torque is determined based on the engine torque at the knocking limit ignition timing when the fuel injection timing is changed to the second injection timing during the compression stroke, the second knocking is determined. Suppression control can be executed early, which can reduce engine torque reduction for suppressing knocking.
[0016]
Claim 4 According to the invention, since the reverse rotation of the engine torque is determined on the assumption that the same delay angle correction is performed in the two controls, the timing for executing the second knocking suppression control is relatively late. Since it is unlikely that knocking will continue even after the knocking suppression control 2 is executed, there is an advantage that knocking can be more reliably suppressed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
With respect to the first embodiment of the present invention, the configuration of a direct injection spark ignition gasoline engine will be described first with reference to FIG.
A combustion chamber 1 of the engine is defined by a cylinder head 2, a cylinder block 3, and a piston 4, and an intake port 5 and an exhaust port 6 connected to the combustion chamber 1 are formed in the cylinder head 2. The combustion chamber 1 side opening end of the intake port 5 is opened and closed by an intake valve 7 driven by an intake cam 9, and the combustion chamber 1 side opening end of the exhaust port 6 is opened and closed by an exhaust valve 8 driven by an exhaust cam 10. .
[0019]
A fuel injection valve 11 that directly injects fuel into the combustion chamber 1 is disposed below the intake port 5 of the cylinder head 2, and faces the combustion chamber 1 at a substantially central portion of the cylinder head 2. A spark plug 12 is provided.
This engine performs stratified lean operation in the low-rotation low-load operation region (region [3] in FIG. 2), and homogeneous stoichiometric operation or homogeneous rich operation in the other regions (regions [1] and [2] in FIG. 2). I do. In particular, the knocking suppression control according to the present invention is executed in a low-rotation and high-load operation region (region [1] in FIG. 2) where knocking is likely to occur.
[0020]
The engine control system will be described. An engine control unit (hereinafter referred to as an ECU) 13 for outputting a control signal to the fuel injection valve 11 and the spark plug 12 is provided. The ECU 13 is provided with knocking generated in the combustion chamber 1. A detection signal of a knocking sensor 14 that detects the strength as vibration of the cylinder block 3 and detection signals of a crank angle sensor, an accelerator opening sensor, and the like (not shown) are input.
[0021]
Of the various controls performed by the ECU 13, the control of the fuel injection timing and the ignition timing according to the present invention will be described based on the control flowcharts of FIGS.
The routine shown in the control flowchart of FIG. 3 is executed at predetermined time intervals to calculate the fuel injection timing IT.
In step 1 (hereinafter referred to as S1), whether or not the current engine operating conditions (engine speed NE, target engine torque tT) are in the low-rotation and high-load operating region, that is, the region [1] in FIG. Judging.
[0022]
If the vehicle is operating in the region [1], the process proceeds to S2, and it is determined whether or not the fuel injection timing flag fIT is 2. The fuel injection timing flag fIT is a flag indicating the setting of the fuel injection timing in the region [1], and fIT = 1 is set to the first injection timing, and fIT = 2 is set to the second injection timing. This is set by the flow of FIG. 5 described later.
[0023]
Here, the relationship between the fuel injection timing and the engine torque will be described with reference to FIG. FIG. 6 shows engine torque characteristics when the injection timing is changed while controlling the ignition timing to the knocking limit.
If fuel injection is performed at a predetermined time during the intake stroke, the maximum engine torque can be obtained. This is because the intake air temperature is lowered by the latent heat of vaporization when the injected fuel is vaporized, and the intake charging efficiency is improved. The engine torque decreases as the injection timing is set to the retard side. This is because the intake charging efficiency decreases and the mixing of the injected fuel and air deteriorates.
[0024]
When the injection timing is retarded to the first half of the compression stroke, the engine torque is once recovered, and when further retarded, the engine torque thereafter decreases monotonously. The engine torque is maximized in the first half of the compression stroke because the knocking limit ignition timing is advanced as the mixing of the injected fuel and air deteriorates.
The injection timing during the intake stroke at which the engine torque is maximum is the first injection timing, and the injection timing in the first half of the compression stroke at which the engine torque is maximum is the second injection timing.
[0025]
The engine torque characteristics of FIG. 6 are obtained when the engine is in a standard state (for example, there is no change over time such as deposit adhesion and the combustion chamber wall temperature is in a standard range). When the engine is actually operated, the knocking limit ignition timing with respect to each injection timing may fluctuate to change the characteristics.
Returning to the description of FIG. 3, if the fuel injection timing flag fIT is 2 in S2, the process proceeds to S3, where the fuel injection timing IT is set to the second injection timing in the first half of the compression stroke. Specifically, the map set value IT2m is looked up from the map of the second injection timing according to the engine operating conditions, and this value is set as the fuel injection timing IT.
[0026]
If the fuel injection timing flag fIT is not 2 in S2 (if fIT = 1), the routine proceeds to S4, where the fuel injection timing IT is set to the first injection timing in the intake stroke. Specifically, the map set value IT1m is looked up from the map of the first injection timing according to the engine operating conditions, and this value is set as the fuel injection timing IT.
If it is determined in S1 that the region is not the region [1], the process proceeds to S5, and it is determined whether or not the current engine operating condition is in the region [2].
[0027]
If the vehicle is operating in the region [2], the process proceeds to S6, and the fuel injection timing IT is set to the first injection timing during the intake stroke. The specific process is the same as the process in S4.
If it is determined that the region is not in the region [2] in S5 (that is, if the vehicle is operating in the region [3]), the process proceeds to S7, and the fuel injection timing IT is set to the third injection timing in the latter half of the compression stroke. Specifically, the map setting value IT3m is looked up from the map of the third injection timing according to the engine operating conditions, and this value is set to the fuel injection timing IT. When fuel injection is performed in the latter half of the compression stroke, most of the injected fuel is concentrated in the recess provided on the crown surface of the piston 4, and the air-fuel mixture is stratified in the combustion chamber 1.
[0028]
The fuel injection timing IT calculated by the above processing is stored in a memory in the ECU 13, and is read and used in a control routine (not shown) that outputs a fuel injection signal.
The routine shown in the control flowchart of FIG. 4 is executed at predetermined time intervals to calculate the ignition timing ADV.
[0029]
In S11, it is determined whether or not the current engine operating condition is in the low-rotation and high-load operating region, that is, the region [1] in FIG.
If the vehicle is operating in the region [1], the process proceeds to S12, and it is determined whether or not the fuel injection timing flag fIT is 2.
When the fuel injection timing flag fIT is 2, the process proceeds to S13, and the ignition timing ADV is calculated. Specifically, the map set value ADV2m is looked up from the ignition timing map for the second injection timing according to the engine operating conditions, and the retardation correction amount RTD for suppressing knocking from this ADV2m (according to the flow of FIG. 5 described later). Is subtracted to calculate the ignition timing ADV = ADV2m−RTD. The map set value ADV2m is the knocking limit ignition timing at the second injection timing, and a value obtained in advance by an experiment using an engine in a standard state is stored on the map.
[0030]
If the fuel injection timing flag fIT is not 2 in S12 (if fIT = 1), the process proceeds to S14, and the ignition timing ADV is calculated. Specifically, the map setting value ADV1m is looked up from the ignition timing map for the first injection timing according to the engine operating conditions, and the retard correction amount RTD is subtracted from this ADV1m to calculate the ignition timing ADV = ADV1m−RTD. To do. This map set value ADV1m is the knocking limit ignition timing at the first injection timing, and is a value obtained in advance by experiments in the same manner as ADV2m. If the engine operating conditions are the same, ADV2m is set to an advance side from ADV1m.
[0031]
If it is determined in S11 that the region is not the region [1], the process proceeds to S15, and it is determined whether or not the current engine operating condition is in the region [2].
When the operation is being performed in the region [2], the process proceeds to S16, and the ignition timing map set value ADV1m for the first injection timing is set to the ignition timing ADV.
If it is determined in S15 that the region is not in the region [2] (that is, if the vehicle is operating in the region [3]), the process proceeds to S17, and the ignition timing map set value ADV3m for the third injection timing is set to the ignition timing ADV. .
[0032]
The ignition timing ADV calculated by the above processing is stored in a memory in the ECU 13 like the fuel injection timing IT, and is read and used in a control routine (not shown) for outputting an ignition signal.
The routine shown in the control flowchart of FIG. 5 is executed at a predetermined timing, and sets the fuel injection timing flag fIT used in FIGS. 3 and 4 and calculates the ignition timing retardation correction amount RTD.
[0033]
The execution interval of this routine is at least every combustion cycle (for example, every 180 degrees in crank angle in the case of a 4-cylinder engine), and may be executed every several combustion cycles.
In S101, it is determined whether or not the current engine operating condition is in the low-rotation and high-load operating region, that is, the region [1] in FIG.
[0034]
If the vehicle is operating in the region [1], the process proceeds to S102, and it is determined whether or not the fuel injection timing flag fIT is 1. Since fIT is set to 1 when operating outside the region [1] (S115 described later), fIT = 1 at the beginning of the transition from outside the region [1] into the region [1]. .
When the fuel injection timing flag fIT is 1, the routine proceeds to S103, where it is determined whether or not the knocking strength KNO is greater than a predetermined first threshold value KNOthA. The knocking intensity KNO is a value calculated for each combustion based on the signal from the knocking sensor 14, and represents the knocking intensity of the previous combustion or the average of the knocking intensity of the past number of combustions including the previous combustion. . Since this routine is executed every combustion cycle at the shortest, the knocking strength KNO referred to this time is a value reflecting the result of the knocking suppression control performed in the previous routine. The first threshold value KNOthA is a threshold value for determining whether or not the current knocking strength is so strong as to require suppression by control.
[0035]
When it is determined that the knocking strength KNO is greater than the first threshold value KNOthA, the process proceeds to S104, and a process of updating the retard correction amount RTD with respect to the ignition timing to the increasing side (retarding side) is performed. Specifically, a new retardation correction amount RTD is calculated by adding a predetermined value (here, 2 degrees as a crank angle) to the current retardation correction amount RTD. This process corresponds to the first knocking suppression control. Since the RTD is set to 0 when the vehicle is operating outside the region [1] (S115 described later), RTD = 0 at the beginning of the transition from the outside of the region [1] into the region [1]. .
[0036]
In S105, it is determined whether or not the retardation correction amount RTD calculated in S104 is larger than a predetermined value RTDth. If it is determined that the retardation correction amount RTD is larger than the predetermined value RTDth, the process proceeds to S106 and the retardation correction amount. The RTD is reset to 0 and the fuel injection timing flag fIT is changed to 2. This process corresponds to the second knocking suppression control. If it is determined that the retardation correction amount RTD is equal to or less than the predetermined value RTDth, this routine is terminated as it is, so that it is determined that the first knocking suppression control is to be executed.
[0037]
The determination in S105 and the processing based on the result will be described with reference to FIG. FIG. 7 shows that the engine torque when the fuel injection timing is the first injection timing (fIT = 1) and the engine torque when the fuel injection timing is the second injection timing (fIT = 2) are respectively set to the ignition timing ADV. It is the figure shown correspondingly.
First, when the operating condition has shifted to the region [1], the fuel injection timing flag fIT is 1 and the retardation correction amount RTD is 0, so that the maximum engine torque can be obtained in the standard state. (Point A). If knocking occurs under this setting, the retardation correction amount RTD is increased twice by the process of S104. This means that the ignition timing ADV is set to point B. In this case, even if the injection timing is changed to the second injection timing, an engine torque greater than point B cannot be obtained, so the control from point A to point B (first knocking suppression control) is executed as it is. To do.
[0038]
On the other hand, if knocking occurs with the ignition timing set to point D (knocking cannot be avoided even if the retard control is advanced to point D), the retard correction amount RTD is further increased by 2 by the process of S104. This means that the ignition timing ADV is set to the point E. In this case, the engine torque at the point G with the retard correction amount RTD set to 0 with the injection timing as the second injection timing. Is larger than the engine torque at point E, so control from point D to point G (second knocking suppression control) is executed.
[0039]
Here, the engine torque characteristics of FIG. 7 can be obtained in advance by experiments, and it is possible to know in advance where the reversal of engine torque as described above occurs. Therefore, the retard correction amount RTD when the engine torque is reversed is stored as a predetermined value RTDth, the first knocking suppression control is performed while RTD ≦ RTDth, and when RTD> RTDth. Second knocking suppression control is performed.
[0040]
The characteristics shown in FIG. 7 are stored in the memory in the ECU 13, and the engine torque when the first knocking suppression control is performed and the engine torque when the second knocking suppression control is performed are calculated each time. Thus, the control for increasing the engine torque may be executed.
Returning to the description of FIG. 5, if it is determined in S103 that the knocking strength KNO is equal to or smaller than the first threshold value KNOthA, the process proceeds to S107, and it is determined whether or not the knocking strength KNO is smaller than the predetermined second threshold value KNOthB. To do. The second threshold value KNOthB is a threshold value set on the smaller side (weaker knocking) than the first threshold value KNOthA. If it is determined that the knocking strength KNO is smaller than the second threshold value KNOthB, the process proceeds to S108. The process advances and updates the retard correction amount RTD with respect to the ignition timing to the decrease side (advance side). Specifically, a new delay angle correction amount RTD is calculated by subtracting a predetermined value (here, 1 degree in crank angle) from the current delay angle correction amount RTD.
[0041]
If it is determined in S107 that the knocking strength KNO is greater than or equal to the second threshold value KNOthB, that is, if the knocking strength KNO is between the first threshold value KNOthA and the second threshold value KNOthB, a new retardation correction is performed. This routine is terminated without calculating the amount RTD.
If the fuel injection timing flag fIT is not 1 in S102 (if fIT = 2), the routine proceeds to S109, where it is determined whether or not the knocking strength KNO is greater than the first threshold value KNOthA.
[0042]
When it is determined that the knocking strength KNO is greater than the first threshold value KNOthA, the process proceeds to S110, and processing for updating the retard correction amount RTD to the increase side (retard side) is performed. That is, when knocking is not suppressed even after performing the second knocking suppression control, control is performed to further retard the ignition timing with the injection timing set to the second injection timing.
[0043]
If it is determined in S109 that the knocking strength KNO is equal to or smaller than the first threshold value KNOthA, the process proceeds to S111, and it is determined whether the knocking strength KNO is smaller than the second threshold value KNOthB.
When it is determined that the knocking strength KNO is smaller than the second threshold value KNOthB, the process proceeds to S112, and processing for updating the retard correction amount RTD to the decrease side (advance side) is performed.
[0044]
In S113, it is determined whether or not the retard correction amount RTD is smaller than 0. If the retard correction amount RTD is smaller than 0, the routine proceeds to S114, where the retard correction amount RTD is set to a predetermined value RTDth and the fuel injection timing flag is set. Change fIT to 1. That is, when knocking does not occur once the second knocking suppression control is performed, the ignition timing is gradually advanced. However, the ignition timing is set to advance beyond the point G in FIG. Since this is not a good strategy in terms of torque, control for changing the setting from point G to point D is executed.
[0045]
If it is determined in S101 that the region is not the region [1] (that is, the region [2] or the region [3]), the process proceeds to S115, the retard correction amount RTD is reset to 0, and the fuel injection timing flag fIT is set to 1. Set to.
Next, a second embodiment of the present invention will be described. The engine configuration (FIG. 1), fuel injection timing and ignition timing calculation flowcharts (FIGS. 3 and 4) are the same as those in the first embodiment.
[0046]
The control flowchart of FIG. 8 shows a routine for setting the fuel injection flag and calculating the ignition timing retardation correction amount in the second embodiment, and is used instead of FIG. 5 of the first embodiment. The difference between the steps is that the processes of S205, S206, S213, and S214 in FIG. 8 are performed with respect to S105, S106, S113, and S114 of FIG.
[0047]
The determination in S205 is a determination as to whether or not to shift from the first knocking suppression control to the second knocking control as in S105, and the determination method is the same (RTD> RTDth?), But the predetermined value RTDth is set. Is different from the case of the first embodiment.
The process of S206 is a process in the case of shifting to the second knocking suppression control as in S106, but the first implementation is that the retard correction amount RTD is not reset and only the fuel injection timing flag fIT is changed. It is different from the case of form.
[0048]
The determination in S213 is a determination as to whether or not to return from the second knocking suppression control to the first knocking control as in S113. Here, it is determined whether or not the retardation correction amount RTD is smaller than a predetermined value RTDth. This is different from the first embodiment.
The process of S214 is a process for returning to the first knocking suppression control as in S114, but here also the point that the retard correction amount RTD is not changed and only the fuel injection timing flag fIT is changed. This is different from the case of the first embodiment.
[0049]
These points will be described with reference to FIG. 9. In this embodiment, the first knocking suppression control is executed from point A to point E, and the setting is changed from point E to point L when further control is required. (Second knocking suppression control). This is because the engine torque at point L is greater than the engine torque at point F. That is, in this embodiment, it is assumed that the same ignition timing retardation correction is performed for both the first injection timing and the second injection timing, and the engine torque is larger when the second injection timing is selected under the conditions. The second knocking suppression control is executed when it can be determined that it is obtained, and the predetermined value RTDth is determined from such a viewpoint. If the predetermined value RTDth is not used, the engine torques at points B and H, points C and I, points D and J,... Are estimated and compared, and the engine torque increases. It is good to execute the other control.
[0050]
Here, the advantages and disadvantages of the two embodiments are compared. The influence of the engine state on the occurrence of knocking differs between when the first injection timing is selected and when the second injection timing is selected. The ignition timing is retarded at the first injection timing. Even in a state in which it is necessary, it is sufficiently conceivable that retardation correction is not necessary at the second injection timing (no knocking occurs at the map setting value ADV2m).
[0051]
For this reason, in the first embodiment, the reverse rotation of the engine torque is determined based on the engine torque at point G, and the second knocking suppression control is executed early. Thereby, there is a possibility that a decrease in engine torque for suppressing knocking can be further reduced.
On the other hand, in the second embodiment, since the reverse rotation of the engine torque is determined on the assumption that the same retard angle correction is performed, the timing for executing the second knocking suppression control becomes relatively late. However, since it is unlikely that knocking will continue after the second knocking suppression control is performed, there is an advantage that knocking can be more reliably suppressed.
[0052]
In order to further suppress the suppression of knocking, when the setting is changed from the point E to the point L in the second embodiment, the setting is temporarily changed to the point M, and the point M is gradually monitored while monitoring the knocking strength KNO. The setting may be changed from point to point L.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a direct-injection spark ignition engine showing a first embodiment of the present invention.
FIG. 2 is a diagram showing an operation region
FIG. 3 is a control flowchart for calculating fuel injection timing.
FIG. 4 is a control flowchart for calculating ignition timing.
FIG. 5 is a control flowchart for setting a fuel injection timing flag and calculating an ignition timing retardation correction amount.
FIG. 6 is a graph showing the relationship between fuel injection timing and engine torque
FIG. 7 is an explanatory diagram of control in the first embodiment.
FIG. 8 is a control flowchart for setting a fuel injection timing flag and calculating an ignition timing retard correction amount according to a second embodiment of the present invention.
FIG. 9 is an explanatory diagram of control in the second embodiment.
[Explanation of symbols]
1 Combustion chamber
11 Fuel injection valve
12 Spark plug
13 ECU
14 Knocking sensor

Claims (4)

In a direct-injection spark-ignition engine control device comprising a fuel injection valve that injects fuel directly into a cylinder and an ignition plug,
Knocking detection means for detecting knocking strength;
When the detected knocking intensity exceeds a permissible range in the low-rotation high-load operation region, the fuel injection timing is maintained at the first injection timing set in the intake stroke, and the ignition timing is set to the knocking intensity First knocking suppression control that corrects to the retard side so as to be within the allowable range, and the fuel injection timing is changed to the second injection timing that is set in the compression stroke, and the ignition strength is set to the allowable range. Control means for selectively executing any one of the second knocking suppression control and the second knocking suppression control that corrects to be within,
The control means stores, as a predetermined value, a retard correction amount that is predicted to cause the engine torque to be smaller than that in the second knock suppression control by correcting the ignition timing to the retard side in the first knock suppression control. In the first knocking suppression control, when the knocking strength does not fall within the allowable range, a process of updating the retard correction amount with respect to the ignition timing to the increasing side is performed, and as a result, the first knocking control is performed. A control device for a direct-injection spark-ignited engine , wherein the second knocking suppression control is executed on the condition that the retard correction amount of the ignition timing is greater than the predetermined value in the knocking suppression control. In a control device for a direct-injection spark-ignition engine having a fuel injection valve for directly injecting fuel into a cylinder and an ignition plug,
Knocking detection means for detecting knocking strength;
When the detected knocking intensity exceeds the allowable range in the low-rotation and high-load operation region, the fuel injection timing is maintained at the first injection timing set in the intake stroke, and the ignition timing is set to the knocking intensity The first knocking suppression control for correcting the retarded angle so as to be within the allowable range, and the fuel injection timing is changed to the second injection timing set in the compression stroke, and the ignition timing is set to the allowable range. Control means for selectively executing any one of the second knocking suppression control and the second knocking suppression control for correcting the internal control,
The control means performs the first knocking suppression control when it is determined that the engine torque when the second knocking suppression control is executed is smaller than the engine torque when the first knocking suppression control is executed. And executing the second knocking suppression control when it is determined that the engine torque when the second knocking suppression control is executed is equal to or greater than the engine torque when the first knocking suppression control is executed. A control device for a direct-injection spark-ignited engine.   The initial value of the ignition timing at the time of switching from the first knocking suppression control to the second knocking suppression control is a predetermined knocking limit ignition timing at the second injection timing. The control apparatus for a direct-injection spark ignition engine according to claim 1 or 2.   The initial value of the ignition timing at the time of switching from the first knocking suppression control to the second knocking suppression control is the first value immediately before switching from the predetermined knocking limit ignition timing at the second injection timing. 3. The direct-injection spark ignition engine control device according to claim 1, wherein the ignition timing is retarded by an amount corresponding to the retardation correction amount in the knocking suppression control.

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