JP3575283B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention switches the combustion mode of the internal combustion engine by changing the fuel injection amount, and changes the engine output accompanying the switching of the combustion mode by changing the opening degree and the ignition timing of the throttle valve at the time of the switching. The present invention relates to a control device for an internal combustion engine that suppresses the internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an internal combustion engine that performs lean combustion that makes the air-fuel ratio leaner than the stoichiometric air-fuel ratio has been proposed. In such an internal combustion engine, the combustion mode is set to an engine operating state such as an engine load between the lean combustion and the stoichiometric combustion that sets the air-fuel ratio to the stoichiometric air-fuel ratio or the rich combustion that sets the air-fuel ratio richer than the stoichiometric air-fuel ratio. It is switched appropriately according to.
[0003]
In an internal combustion engine that performs such lean combustion, a nitrogen oxide (NOx) storage reduction catalyst (hereinafter abbreviated as "NOx catalyst") is used to purify exhaust gas. This NOx catalyst occludes NOx contained in exhaust gas during lean combustion, and reduces and releases NOx occluded by hydrocarbons and carbon monoxide contained in exhaust gas to nitrogen during rich combustion. To do.
[0004]
In an internal combustion engine equipped with such a NOx catalyst, when the amount of stored NOx increases to near the limit of the NOx catalyst, the combustion mode is forcibly switched to rich combustion by increasing the fuel injection amount. Processing, so-called rich spike processing, is performed. By executing this rich spike processing, the amounts of HC and CO contained in the exhaust gas temporarily increase, and the stored NOx is forcibly reduced and released, so that the predetermined NOx in the NOx catalyst is reduced. The storage capacity can be maintained.
[0005]
By the way, when such a rich spike process is executed, the engine output suddenly increases with an increase in the fuel injection amount, and for example, a driver may feel uncomfortable shock. Therefore, conventionally, as described in Japanese Patent Application Laid-Open No. 7-332071, a process of reducing the opening of the throttle valve by a predetermined amount when increasing the fuel injection amount and switching the combustion mode is performed. By performing such processing, an increase in engine output due to an increase in fuel injection amount can be offset by an increase in pumping loss.
[0006]
[Problems to be solved by the invention]
However, as shown in FIG. 12, the throttle opening (FIG. 12A) is reduced to suppress an increase in the engine output (FIG. 12D) due to the increase in the fuel injection amount (FIG. 12C). Even if this is done, there is usually a predetermined response delay time (Δt in the figure) until the intake pressure (FIG. 6 (b)) decreases and a predetermined pumping loss occurs. For this reason, conventionally, a sufficient pumping loss cannot be generated immediately after switching of the combustion mode, and a temporary increase in the engine output cannot be avoided.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can reliably suppress a rapid change in engine output due to switching of a combustion mode. .
[0008]
[Means for Solving the Problems]
In order to achieve this object, according to the first aspect of the present invention, the fuel injection amount control for changing the fuel injection amount of the internal combustion engine to a predetermined amount corresponding to the changed combustion mode in order to switch the combustion mode in the internal combustion engine. Combustion mode switching means including a combustion means, throttle opening control means for changing the opening of a throttle valve of the internal combustion engine to a predetermined opening in order to suppress a change in engine output due to switching of the combustion mode, and switching of the combustion mode. An ignition timing control means for changing the ignition timing of the internal combustion engine to a predetermined timing in order to suppress a change in the accompanying engine output.The combustion mode switching means switches from a combustion mode in which the air-fuel ratio of the internal combustion engine is leaner than the stoichiometric air-fuel ratio or a stoichiometric air-fuel ratio to a combustion mode in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio.The fuel injection amount control means controls the fuel injection amount when switching the combustion mode.Gradually increase from the fuel injection amount corresponding to the combustion mode before switching to the fuel injection amount corresponding to the combustion mode after switchingThings,The throttle opening control means controls the throttle valve opening from the opening of the throttle valve corresponding to the combustion mode before the switching to the throttle valve corresponding to the combustion mode after the switching to suppress the increase in the engine output accompanying the switching of the combustion mode. To the degree of opening,The ignition timing control means controls the ignition timing when switching the combustion mode.Slowly retard from the ignition timing corresponding to the combustion mode before switching to the ignition timing corresponding to the combustion mode after switchingAnd things.
[0009]
According to such a configuration,When performing rich spike processingFuel injection amountincreaseEngine outputincreaseIs slow, so even immediately after switching the combustion mode, the engine outputincreaseThe throttle openingDecreaseCan be offset by the change in pumping loss associated with. In addition to the throttle opening, the ignition timingRetardThe fuel injection amountincreaseEngine outputincreaseEven if is large,increaseThe ignition timingRetardWith the highest combustion pressureDeclineCan be surely offset.
[0010]
Also, the fuel injection amountFuel injection amount corresponding to the combustion mode after switchingGraduallyIncreaseThe fuel injection amountFuel injection amount corresponding to the combustion mode after switchingUntil combustion reachesExchangeThe transitional combustion mode does not belong to any of the preceding and following combustion modes. Therefore, if the ignition timing is instantaneously switched to a timing corresponding to the post-switching combustion mode when switching the combustion mode, the ignition timing may not be compatible with the engine combustion state and may cause a misfire.
[0011]
In this regard, in the above configuration, the ignition timingIgnition corresponding to the combustion mode after switchingSince the timing is gradually changed, the mismatch between the engine combustion state and the ignition timing is unlikely to occur..
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which a control device for an internal combustion engine according to the present invention is applied to a four-cylinder gasoline engine will be described with reference to FIGS.
[0014]
FIG. 1 is a schematic configuration diagram illustrating a control device of an engine 10 according to the present embodiment.
A plurality of cylinders 15 (one of which is shown in FIG. 1) formed in the cylinder block 11 of the engine 10 are each provided with a piston 13 so as to be able to reciprocate. A combustion chamber 17 is defined by the upper surface of the piston 13, the inner wall surface of the cylinder 15, and the lower surface of the cylinder head 12, and an intake passage 18 and an exhaust passage 16 are connected to the combustion chamber 17.
[0015]
A surge tank 20 is provided in the intake passage 18, and a throttle valve 34 whose opening (throttle opening) is adjusted by a throttle motor 54 is provided upstream of the surge tank 20. This throttle valve 34 regulates the amount of intake air introduced into the combustion chamber 17.
[0016]
The cylinder head 12 is provided with an injector 50 for directly injecting fuel into the combustion chamber 17 and a spark plug 26 for igniting an air-fuel mixture in the combustion chamber 17 for each cylinder 15. The injector 50 has a built-in solenoid valve (not shown) for intermittently injecting fuel, and the amount of fuel injection is adjusted based on the opening and closing operation of the solenoid valve. The ignition timing of the ignition plug 26 is adjusted by an igniter 52 provided in the ignition coil 53.
[0017]
The exhaust passage 16 is provided with a three-way catalyst 22 and a NOx catalyst 24, respectively. The exhaust gas discharged from the combustion chamber 17 to the exhaust passage 16 is purified by the catalysts 22, 24. The exhaust passage 16 is connected to the intake passage 18 by an exhaust gas recirculation (EGR) passage 40, and a part of the exhaust gas (EGR gas) is returned to the intake passage 18 through the EGR passage 40. The EGR passage 40 is provided with an EGR valve 41 for adjusting the cross-sectional area of the passage 40. The amount of the EGR gas (EGR amount) is adjusted by the EGR valve 41.
[0018]
A brake booster 44 is connected to the surge tank 20 via a pressure passage 42. A negative pressure generated in the surge tank 20 according to the opening of the throttle valve 34 is supplied to the brake booster 44 through the pressure passage 42. The brake booster 44 accumulates the negative pressure supplied in this manner, and generates an auxiliary force for reducing the depressing force of a brake pedal (not shown) according to the magnitude of the accumulated negative pressure.
[0019]
An accelerator sensor 62 is provided near the throttle valve 34 in the intake passage 18. The accelerator sensor 62 is connected to an accelerator pedal 46 operated by a driver via a wire (not shown), and outputs a detection signal corresponding to the amount of depression of the accelerator pedal 46, that is, the accelerator opening ACCP.
[0020]
A crank sensor 64 is provided near the crankshaft 14 that rotates with the reciprocating motion of the piston 13, and a cam sensor 66 is provided near the camshaft 30 that rotates in synchronization with the rotation of the crankshaft 14. ing. These sensors 64 and 66 output detection signals corresponding to the rotation angle of the crankshaft 14, ie, the crank angle CA, and the rotation speed of the crankshaft 14, ie, the engine rotation speed NE.
[0021]
The surge tank 20 is provided with an intake pressure sensor 67, and the intake pressure sensor 27 outputs a detection signal corresponding to the pressure of the intake air in the intake passage 18, that is, the magnitude of the intake pressure PM.
[0022]
A pressure sensor 68 is attached to the brake booster 44, and the pressure sensor 68 outputs a detection signal corresponding to the magnitude of the negative pressure (actuation negative pressure BP) stored in the brake booster 44.
[0023]
The detection signals of these various sensors 62 to 68 are input to an electronic control unit (hereinafter abbreviated as “ECU”) 60 of the engine 10. The ECU 60 detects the accelerator opening ACCP, the crank angle CA, the engine rotation speed NE, the intake pressure PM, and the operating negative pressure BP based on these detection signals. The ECU 60 drives the solenoid valve, the igniter 52, the throttle motor 54, and the EGR valve 41 of the injector 50 based on each of these detected values, thereby setting the fuel injection amount, the ignition timing, the throttle opening, and the EGR amount to the engine operation state. Control to fit. The ECU 60 includes a memory 61 in which a control program and function data for executing such various controls based on predetermined procedures are stored in advance.
[0024]
The engine 10 in the present embodiment is configured to switch between the following five modes in which the combustion mode differs in the air-fuel ratio or the fuel injection method.
[Stratified Combustion] When the stratified combustion is selected as the combustion mode, the fuel is injected in the compression stroke. Therefore, at the time of ignition, the air-fuel mixture in the vicinity of the ignition plug 26 is in a rich state where partial ignition is possible. The average air-fuel ratio (A / F) of the air-fuel mixture is set to be leaner (A / F = 25 to 50) than the stoichiometric air-fuel ratio (A / F = 14.5).
[0025]
[Weakly stratified combustion] When the weakly stratified combustion is selected as the combustion mode, the fuel is split into two injections, an intake stroke and a compression stroke, and the air-fuel ratio is leaner (A) than the stoichiometric air-fuel ratio. / F = 20 to 30). Further, in this weak stratified combustion, since a part of fuel is injected in the intake stroke, the difference in the air-fuel ratio in the combustion chamber 17 at the time of ignition is smaller than that in the stratified combustion.
[0026]
[Homogeneous Lean Combustion] When the homogeneous lean combustion is selected as the combustion mode, the fuel is injected in the intake stroke. In this homogeneous lean combustion, all the fuel is injected during the intake stroke, so that the air-fuel ratio in the combustion chamber 17 at the time of ignition becomes uniform. The air-fuel ratio is set leaner (A / F = 15 to 23) than the stoichiometric air-fuel ratio.
[0027]
[Homogeneous Stoichiometric Combustion] When homogeneous stoichiometric combustion is selected as the combustion mode, fuel is injected in the intake stroke, and the air-fuel ratio is set near the stoichiometric air-fuel ratio.
[Homogeneous rich combustion] When the homogeneous stoichiometric combustion is selected as the combustion mode, the fuel is injected in the intake stroke, and the air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio (A / F = 11 to 13). You.
[0028]
The determination of the combustion mode is performed by the ECU 60 based on the engine operating state, the NOx storage amount of the NOx catalyst 24, the negative pressure BP for operating the brake booster 44, and the like. Hereinafter, a procedure for determining the combustion mode by the ECU 60 will be described.
[0029]
FIG. 2 is a flowchart showing the processing of the "combustion mode determination routine". This "combustion mode determination routine" is executed by the ECU 60 as an interruption process for each predetermined crank angle CA.
[0030]
After setting the current combustion mode FMODE as the combustion mode tFMODE in the previous control cycle in step 110, the ECU 60 sets the combustion mode in the current control cycle based on the engine rotational speed NE and the basic fuel injection amount QBASE in step 112. Determine FMODE. The basic fuel injection amount QBASE is calculated based on the accelerator opening ACCP and the engine speed NE in a processing routine different from this routine.
[0031]
The combustion mode FMODE is a parameter for determining which of the above-described modes is selected as the combustion mode. For example, when the combustion mode FMODE is “0”, the above “stratified combustion” is selected as the combustion mode. Similarly, when the combustion mode FMODE is “4”, “weak stratified combustion” is selected as the combustion mode, when “8” is “homogeneous lean combustion”, and when “11”, it is “ "Homogeneous rich combustion" is selected, and if "12", "homogeneous stoichiometric combustion" is selected. Hereinafter, the procedure for determining the combustion mode FMODE will be described.
[0032]
The memory 61 of the ECU 60 stores function data that defines the relationship between the value of the combustion mode FMODE and the engine speed NE and the basic fuel injection amount QBASE. FIG. 3 is a function map schematically showing the function data.
[0033]
For example, when the engine speed NE and the basic fuel injection amount QBASE change from the state shown at the point A to the state shown at the point B along the one-dot chain line shown in the figure, the combustion mode FMODE changes from "0" to "4". , "8", and "12", and the combustion mode changes from "stratified combustion" to "weak stratified combustion", "homogeneous lean combustion", and "homogeneous stoichiometric combustion" in accordance with the change of the combustion mode FMODE. Will be done.
[0034]
Further, the ECU 60 calculates the NOx storage amount in the NOx catalyst 24 in a processing routine different from this routine, and in step 112, it is determined that the NOx storage amount has increased to near the limit storage amount of the NOx catalyst 24. If it is determined, the combustion mode is forcibly switched to “homogeneous rich combustion”. That is, the ECU 60 operates the combustion mode FMODE so as to maintain the predetermined NOx storage capacity of the NOx catalyst 24.
[0035]
When the rich spike processing is executed, in step 112, the ECU 60 sequentially changes the combustion mode FMODE until it becomes "11", and keeps it at "11" until a predetermined time elapses. Thereafter, the ECU 60 sequentially changes the combustion mode FMODE until it becomes equal to the combustion mode FMODE at the start of the rich spike processing again. For example, when the rich spike processing is started while “stratified combustion (FMODE =“ 0 ”)” is selected as the combustion mode, the combustion mode FMODE is changed from “0 → 4 → 8 → 11” and the predetermined mode is set. Conversely, the time is changed to "11 → 8 → 4 → 0" after the lapse of time.
[0036]
Further, in step 112, the ECU 60 compares the operation negative pressure BP with the determination pressure stored in the memory 61 in advance. Here, when it is determined that the operating negative pressure BP is higher than the determination pressure, the ECU 60 sequentially changes the combustion mode FMODE to "12" because the assisting force generated by the brake booster 44 has decreased. The combustion mode is forcibly switched to "homogeneous stoichiometric combustion". Then, the ECU 60 maintains the combustion mode as “homogeneous stoichiometric combustion” until a predetermined time has elapsed. As a result, the throttle opening decreases and the pressure in the surge tank 20 decreases, so that the operating negative pressure BP of the brake booster 44 decreases and a predetermined assisting force is secured. When the ECU 60 determines that the operating negative pressure BP has decreased to or below the determination pressure, the ECU 60 sequentially changes the combustion mode FMODE from “12” to a value at the time when it is determined that the operating negative pressure BP exceeds the determination pressure. . Hereinafter, the process of forcibly switching the combustion mode to secure the assisting force of the brake booster 44 is referred to as “negative pressure securing process”.
[0037]
As described above, in step 112, the ECU 60 appropriately sets the combustion mode FMODE according to the engine operating state (the engine speed NE and the basic fuel injection amount QBASE) or the necessity of the "rich spike processing" or the "negative pressure securing processing". decide.
[0038]
After determining the combustion mode FMODE as described above, the ECU 60 shifts the processing to step 114. In step 114, the ECU 60 determines whether the combustion mode tFMODE in the previous control cycle is “8” and the combustion mode FMODE in the current control cycle is “11”. That is, the ECU 60 determines whether the combustion mode has been switched from “homogeneous lean combustion” to “homogeneous rich combustion”. Incidentally, as described above, when the combustion mode is switched from “homogeneous lean combustion” to “homogeneous rich combustion”, the combustion mode is one of “stratified combustion”, “weak stratified combustion”, and “homogeneous lean combustion”. This corresponds to the case where the rich spike processing is executed when the mode is set.
[0039]
If it is determined in step 114 that the combustion mode has been switched from “homogeneous lean combustion” to “homogeneous rich combustion”, in step 116, the ECU 60 sets the gradual change processing execution flag XQINJR to “1”. After executing the processing of step 116 or when a negative determination is made in step 114, the ECU 60 temporarily ends the processing of this routine.
[0040]
In the present embodiment, when the combustion mode is switched from “homogeneous lean combustion” to “homogeneous rich combustion”, the fuel injection amount injected into the combustion chamber 17 is changed from the amount corresponding to “homogeneous lean combustion” to “homogeneous rich combustion”. The amount is not instantaneously increased to the amount corresponding to "combustion", but is gradually increased. The gradual change process execution flag XQINJR is a flag for determining whether or not to perform the process of gradually increasing the fuel injection amount (hereinafter, referred to as “fuel injection amount gradual change process”).
[0041]
Hereinafter, the processing procedure in the “fuel injection amount gradual change processing” will be described with reference to the flowcharts of FIGS. 4 and 6.
FIG. 4 is a flowchart showing the processing of the “fuel injection amount correction routine”. FIG. 6 is the “fuel correction amount calculation routine” for calculating the fuel correction amount QINJR used in the processing of the “combustion injection amount correction routine”. 5 is a flowchart showing the processing of FIG. These processing routines are executed by the ECU 60 as interrupt processing for each predetermined crank angle CA.
[0042]
First, the process of the "combustion injection amount correction routine" will be described. In this routine, the amount of fuel injected from the injector 50 into the combustion chamber 17 (final fuel injection amount QINJ) is calculated.
[0043]
In step 310 shown in FIG. 4, the ECU 60 calculates a rich spike correction coefficient FRSPK based on the combustion mode FMODE, the engine speed NE, and the indicated fuel injection amount QINJ0. The rich spike correction coefficient FRSPK indicates the increase rate of the fuel injection amount when the combustion mode is switched to “homogeneous rich combustion” by “rich spike processing”.
[0044]
The command fuel injection amount QINJ0 is calculated based on the combustion mode FMODE, the engine speed NE, the basic fuel injection amount QBASE, and the like in a processing routine different from this routine. As shown in FIG. 5, the memory 61 of the ECU 60 stores function data that defines the relationship between the indicated fuel injection amount QINJ0, the basic fuel injection amount QBASE, and the engine speed NE for each combustion mode FMODE, The ECU 60 calculates the indicated fuel injection amount QINJ0 corresponding to each combustion mode FMODE with reference to the function data.
[0045]
For example, in this other processing routine, if the combustion mode FMODE is set to any one of “0”, “4”, “8”, and “11”, the ECU 60 makes the aforementioned basic fuel injection amount QBASE (engine rotation The command fuel injection amount QINJ0 is calculated based on the speed NE and the accelerator opening ACCP) and the engine speed NE.
[0046]
On the other hand, when the combustion mode FMODE is set to “12”, the ECU 60 calculates the basic fuel injection amount QBASE based on the engine rotation speed NE and the intake pressure PM, and calculates the basic fuel injection amount QBASE and the engine rotation speed NE. The command fuel injection amount QINJ0 is calculated based on the command fuel injection amount QINJ0.
[0047]
Then, in step 310, the rich spike correction coefficient FRSPK is calculated based on the command fuel injection amount QINJ0 or the like calculated as described above. For example, when the combustion mode FMODE is set to a value other than “11”, the ECU 60 sets the rich spike correction coefficient FRSPK to “1”.
[0048]
On the other hand, when the combustion mode FMODE is set to “11”, the ECU 60 calculates the rich spike correction coefficient FRSPK based on the engine speed NE and the indicated fuel injection amount QINJ0. In this case, the rich spike correction coefficient FRSPK is calculated as a value larger than “1”. The memory 61 of the ECU 60 stores function data that defines the relationship between the rich spike correction coefficient FRSPK, the engine speed NE, and the indicated fuel injection amount QINJ0. When the ECU 60 calculates the rich spike correction coefficient FSPK, , Refer to this function data. This function data is set in advance by experiments or the like so that the actual air-fuel ratio becomes a predetermined value (for example, “11”) when the combustion mode is changed to “homogeneous rich combustion” by “rich spike processing”. I have.
[0049]
Next, in step 312, the ECU 60 calculates the increased fuel injection amount tQINJ based on the following equation (1).
tQINJ = QINJ0 × FRSPK (1)
Here, the increased fuel injection amount tQINJ is a fuel injection amount corresponding to “homogeneous rich combustion”, and when the “fuel injection amount gradual change process” is completed, the final fuel injection amount QINJ becomes equal to the increased fuel injection amount tQINJ. Will be consistent.
[0050]
After calculating the increased fuel injection amount tQINJ in this manner, in step 314, the ECU 60 determines whether the gradual change process execution flag XQINJR is “1”, that is, executes the “fuel injection amount gradual change process”. Determine if it is necessary.
[0051]
If it is determined in step 314 that the “fuel injection amount gradual change process” needs to be executed, the ECU 60 executes the process from step 316 to step 324 sequentially. The series of processes in steps 316 to 324 determines the fuel injection amount at the start of the “fuel injection amount gradual change process”, in other words, when the combustion mode FMODE is changed from “8” to “11”. This is executed only once after the gradual change processing execution flag XQINJR is set to “1”.
[0052]
That is, the ECU 60 resets the gradual change process execution flag XQINJR to “0” in step 316, and then sets the start-time correction amount tQINT to a constant predetermined value γ in step 318. This initial correction amount tQINT is a correction amount when the final fuel injection amount QINJ is reduced at the start of the “fuel injection amount gradual change process”. Accordingly, the larger the initial correction amount tQINT is set, the smaller the fuel injection amount at the start of the “fuel injection amount gradual change process”.
[0053]
In step 320, the ECU 60 calculates the initial correction amount tQINT from the final fuel injection amount QINJ calculated in the previous control cycle and the fuel injection amount at the start of the “fuel injection amount gradual change process”, that is, the increasing fuel injection amount tQINJ. Compare the subtracted value (tQINJ-tQINT). Here, when it is determined that the final fuel injection amount QINJ is larger than the subtraction value (tQINJ-tQINT), that is, when the combustion mode is switched from “homogeneous lean combustion” to “homogeneous rich combustion”, the fuel injection amount decreases. If it is determined that the correction has been made, in step 322, the ECU 60 corrects the initial correction amount tQINT based on the following equation (2).
tQINT = tQINJ-QINJ (2)
After executing the processing of step 322, or when it is determined in step 320 that the final fuel injection amount QINJ is equal to or smaller than the subtraction value (tQINJ-tQINT), the ECU 60 shifts the processing to step 324 and performs initial correction. The amount tQINT is set as the fuel correction amount QINJR. After executing the process of step 324, or if it is determined in step 314 that it is not necessary to execute the “fuel injection amount gradual change process”, the ECU 60 shifts the process to step 326.
[0054]
In step 326, the ECU 60 subtracts the fuel correction amount QINJR from the increased fuel injection amount tQINJ, and sets the value after the subtraction (tQINJ-QINJR) as the final fuel injection amount QINJ. Then, the ECU 60 once ends the processing of this routine.
[0055]
The fuel correction amount QINJR is used to reduce the final fuel injection amount QINJ during the execution of the “fuel injection amount gradual change process” and to correct the final fuel injection amount QINJ to an amount smaller than the increasing fuel injection amount tQINJ. It is. Hereinafter, a procedure for calculating the fuel correction amount QINJR will be described.
[0056]
In step 410 shown in FIG. 6, the ECU 60 subtracts a predetermined amount α from the fuel correction amount QINJR, and determines whether or not the subtraction value (QINJR−α) is less than “0”. If it is determined that the subtraction value (QINJR-α) is equal to or greater than “0”, the ECU 60 sets the subtraction value (QINJR-α) as a new fuel correction amount QINJR in step 414.
[0057]
On the other hand, if it is determined in step 410 that the subtraction value (QINJR-α) is less than “0”, the ECU 60 sets the fuel correction amount QINJR to “0”. Accordingly, the fuel correction amount QINJR is obtained by subtracting the final fuel injection amount QINJ from the predetermined value γ or the increasing fuel injection amount tQINJ in the above-described “fuel injection amount correction routine” by the processes of steps 410 to 414 (tQINJ). −QINJ), the amount is reduced by a predetermined amount α until it becomes “0”. After calculating the fuel correction amount QINJR in step 412 or step 414, the ECU 60 once ends the processing of this routine.
[0058]
In the control device according to the present embodiment, in addition to the control related to the fuel injection amount described above, in order to suppress a sudden increase in torque due to switching of the combustion mode from “homogeneous lean combustion” to “homogeneous rich combustion”. In addition, control is performed to decrease the throttle opening and to retard the ignition timing. Hereinafter, the control related to the throttle opening and the control related to the ignition timing will be sequentially described.
[0059]
FIG. 7 is a flowchart showing the processing of the “throttle opening calculation routine”. This routine is executed by the ECU 60 as an interruption process for each predetermined crank angle CA.
[0060]
In step 210, the ECU 60 calculates a target throttle opening TATRG, which is a target value related to the throttle opening, based on the engine speed NE, the basic fuel injection amount QBASE or the accelerator opening ACCP, and the combustion mode FMODE. As shown in FIG. 8, the memory 61 of the ECU 60 stores function data that defines the relationship between the target throttle opening TATRG and the basic fuel injection amount QBASE or the accelerator opening ACCP and the engine speed NE for each combustion mode FMODE. The ECU 60 calculates the target throttle opening degree TATRG corresponding to each combustion mode FMODE by referring to the function data.
[0061]
For example, when the combustion mode FMODE is set to one of “0”, “4”, “8”, and “11”, the ECU 60 determines the basic fuel injection amount QBASE (based on the engine speed NE and the accelerator opening ACCP). And the target throttle opening TATRG is calculated based on the engine speed NE.
[0062]
On the other hand, when the combustion mode FMODE is set to “12”, the ECU 60 calculates the target throttle opening TATRG based on the accelerator opening ACCP and the engine speed NE.
[0063]
Further, when the combustion mode FMODE is set to “11” and “homogeneous rich combustion” is selected as the combustion mode, the target throttle opening TATRG is relatively smaller than when “homogeneous lean combustion” is selected. The function data is set so as to be calculated smaller. Therefore, if the combustionLeanCombustion to homogeneousrichWhen switching to "combustion", the throttle valve 34 is closed and the intake pressure PM in the intake passage 18 decreases, so that the pumping loss of the engine 10 increases. This pumping loss offsets the increase in torque associated with the increase in the final fuel injection amount QINJ.
[0064]
After calculating the target throttle opening TATRG as described above, the ECU 60 temporarily ends the processing of this routine.
Next, control regarding the ignition timing will be described.
[0065]
FIG. 9 is a flowchart showing the processing of the “ignition timing calculation routine”. This routine is executed by the ECU 60 as an interruption process for each predetermined crank angle CA. In this routine, an ignition signal is output from the ECU 60 to the igniter 52, and a final ignition timing ESAOUT, which is a timing at which the ignition of the air-fuel mixture by the ignition plug 26 is performed, is calculated. The final ignition timing ESAOUT is set based on the crank angle CA when the piston 13 of each cylinder 15 is at the top dead center position, and is set as an advance amount from the reference crank angle CA. That is, the ignition timing by the spark plug 26 is advanced as the final ignition timing ESAOUT is set larger, and the ignition timing is retarded as the final ignition timing ESAOUT is set smaller.
[0066]
In step 510, the ECU 60 calculates an instruction ignition timing tESAOUT, which is a target value related to the ignition timing, based on the engine speed NE, the basic fuel injection amount QBASE or the intake pressure PM, and the combustion mode FMODE. As shown in FIG. 10, the memory 61 of the ECU 60 stores function data defining the relationship between the instruction ignition timing tESAOUT and the basic fuel injection amount QBASE or the intake pressure PM and the engine speed NE for each combustion mode FMODE. The ECU 60 refers to the function data to calculate the designated ignition timing tESAOUT corresponding to each combustion mode FMODE.
[0067]
For example, when the combustion mode FMODE is set to one of “0”, “4”, “8”, and “11”, the ECU 60 determines the basic fuel injection amount QBASE (based on the engine speed NE and the accelerator opening ACCP). The calculated ignition timing tESAOUT is calculated based on the engine speed NE.
[0068]
On the other hand, when the combustion mode FMODE is set to “12”, the ECU 60 calculates the command ignition timing tESAOUT based on the intake pressure PM and the engine speed NE.
[0069]
When the combustion mode FMODE is set to “11” and “homogeneous rich combustion” is selected as the combustion mode, the command ignition timing tESAOUT is relatively smaller than when “homogeneous lean combustion” is selected. The function data is set so as to be calculated as the timing on the retard side. Therefore, if the combustionLeanCombustion to homogeneousrichWhen the mode is switched to "combustion", the ignition timing of the ignition plug 26 is retarded, and the maximum combustion pressure in the combustion chamber 17 decreases, so that the torque of the engine 10 decreases. Then, the decrease in the torque cancels the increase in the torque due to the increase in the final fuel injection amount QINJ.
[0070]
Next, in step 512, the ECU 60 determines whether or not the combustion mode FMODE is set to "11", in other words, whether or not the combustion mode is set to "homogeneous rich combustion". If it is determined that the combustion mode is not set to “homogeneous rich combustion”, the ECU 60 shifts the processing to step 518. Then, in step 518, the ECU 60 sets the designated ignition timing tESAOUT as the final ignition timing ESAOUT. On the other hand, when it is determined in step 512 that the combustion mode is set to “homogeneous rich combustion”, the ECU 60 shifts the processing to step 514.
[0071]
In step 514, the ECU 60 delay-corrects the final ignition timing ESAOUT0 in the previous control cycle by a predetermined value β, and compares the corrected timing (ESAOUT0-β) with the designated ignition timing tESAOUT. Here, if it is determined that the instruction ignition timing tESAOUT is a timing that is more retarded than the corrected timing (ESAOUT0-β), the ECU 60 determines in step 516 the corrected timing (ESAOUT0-β). It is set as the final ignition timing ESAOUT. On the other hand, if it is determined in step 514 that the designated ignition timing tESAOUT is at the same time as the correction timing (ESAOUT0-β) or is on the advance side, the ECU 60 executes the processing of step 518 described above.
[0072]
After executing the processing of step 516 or step 518, the ECU 60 sets the final ignition timing ESAOUT in the current control cycle as the final ignition timing ESAOUT0 in the previous control cycle, and ends the processing of this routine once.
[0073]
FIG. 11 is a timing chart showing an example of how the combustion mode FMODE, the final fuel injection amount QINJ, the target throttle opening TATRG, the intake pressure PM, and the final ignition timing ESAOUT change.
[0074]
As shown in FIG. 7A, when the combustion mode FMODE is changed from “8” to “11” at timing t1 by executing “rich spike processing”, the final fuel injection amount QINJ becomes “homogeneous”. The amount corresponding to “lean combustion” is changed to the amount (tQINJ−tQINT (= tQINJ−γ)) corresponding to the start of the “fuel injection gradual change process”. Thus, in this embodiment, even if the combustion mode is switched from “homogeneous lean combustion” to “homogeneous rich combustion”, the final fuel injection amount QINJ instantaneously increases to an amount corresponding to “homogeneous rich combustion”. Absent. After the timing t1, the final fuel injection amount QINJ is increased by a predetermined amount α. When the final fuel injection amount QINJ becomes equal to the increasing fuel injection amount tQINJ at the timing t3, thereafter, it is maintained equal to the increasing fuel injection amount tQINJ.
[0075]
Further, as shown in FIG. 9C, at timing t1, the target throttle opening TATRG is changed to an opening corresponding to “homogeneous rich combustion” and is reduced by a predetermined amount. As a result, after the timing t1, the intake pressure PM decreases and the pumping loss increases as shown in FIG.
[0076]
Here, since there is a response delay in the change of the intake pressure PM, the intake pressure PM does not instantaneously decrease to a value (= PM1) corresponding to the target throttle opening TATRG. For this reason, when the final fuel injection amount QINJ is changed, for example, in a manner indicated by a two-dot chain line in FIG. Cannot be offset by an increase in pumping loss accompanying a decrease in the throttle opening.
[0077]
In this regard, in the present embodiment, the final fuel injection amount QINJ is gradually increased from the amount corresponding to “homogeneous lean combustion” to the amount corresponding to “homogeneous rich combustion”. The increase of the torque with the increase of the amount becomes slow. Therefore, an increase in pumping loss due to a decrease in the throttle opening can offset an increase in torque due to an increase in the final fuel injection amount QINJ.
[0078]
Further, in the present embodiment, in addition to the change of the throttle opening, the final ignition timing ESAOUT is set to “homogeneous lean combustion” during the period from the timing t1 to the timing t2 when the combustion mode is switched as shown in FIG. ) To a time corresponding to “homogeneous rich combustion”.
[0079]
Therefore, the increase in torque due to the increase in the final fuel injection amount QINJ can be offset by such retard control of the ignition timing, and even if the increase in torque due to switching of the combustion mode becomes large, Compared to a configuration in which the increase in torque is simply offset by an increase in pumping loss, the increase in torque can be more reliably offset.
[0080]
(1) As a result, according to the present embodiment, it is possible to reliably suppress a sudden increase in torque due to switching of the combustion mode from “homogeneous lean combustion” to “homogeneous rich combustion”. For this reason, it is possible to prevent the driver from feeling uncomfortable shock.
[0081]
When the final fuel injection amount QINJ is gradually increased from the amount corresponding to “homogeneous lean combustion” to the amount corresponding to “homogeneous rich combustion” as described above, the period during the increase (FIG. 11) During the period from the timing t1 to the timing t3), the combustion mode is a transient one that does not belong to any of the above-mentioned “homogeneous lean combustion” and “homogeneous rich combustion”.
[0082]
Further, when the combustion mode is switched from “homogeneous lean combustion” to “homogeneous rich combustion”, the EGR amount is usually reduced to “0” or a predetermined amount. There is a delay. For this reason, in the engine 10 according to the present embodiment, the combustion mode tends to be more transient as described above.
[0083]
For this reason, the final ignition timing ESAOUT is instantaneously retarded from the timing corresponding to “homogeneous lean combustion” to the timing corresponding to “homogeneous rich combustion” as shown by a two-dot chain line in FIG. Then, the ignition timing does not match the combustion state of the engine, and immediately after the switching of the combustion mode (for example, at timing t1), the ignition timing suitable for the combustion state of the engine and the actual timing may be greatly different, and a misfire may occur. There is.
[0084]
In this regard, according to the present embodiment, the final ignition timing ESAOUT is gradually retarded from the timing corresponding to “homogeneous lean combustion” to the timing corresponding to “homogeneous rich combustion”. Incompatibility between the state and the ignition timing is less likely to occur.
[0085]
(2) As a result, according to the present embodiment, it is possible to prevent the occurrence of misfire due to the mismatch between the engine combustion state and the ignition timing.
The embodiment described above can be implemented by changing the configuration as follows.
[0086]
In the above embodiment, the case where the combustion mode of the engine 10 is switched from “homogeneous lean combustion” to “homogeneous rich combustion” is described, but the fuel injection is also performed when the combustion mode is switched from “homogeneous stoichiometric combustion” to “homogeneous rich combustion”. By performing the same control with respect to the amount, the throttle opening, and the ignition timing, it is possible to obtain the same operational effects as those of the above embodiment.
[0089]
In the above embodiment, the predetermined value γ corresponding to the reduction correction amount of the final fuel injection amount QINJ at the start of the “fuel injection amount gradual change process” corresponds to the rate of change of the final fuel injection amount QINJ during execution of the process. The predetermined amount α and the predetermined value β corresponding to the rate of change of the final ignition timing ESAOUT when the ignition timing is gradually retarded have been set to constant values, but these are set as follows, for example. Is also good.
[0090]
First, the ECU 60 estimates a response delay time related to a change in the intake pressure PM based on the engine operating state (for example, the engine rotational speed NE and the intake pressure PM). In the memory 61 of the ECU 60, function data that defines the relationship between the response delay time and the engine rotational speed NE and the intake pressure PM is obtained and stored in advance by experiments or the like, and the response delay time is determined by referring to the function data. Is estimated. Next, the ECU 60 calculates each of the values α, β, and γ based on the response delay time. At the time of this calculation, similarly, reference is made to the function data that defines the relationship between the response delay time and each of the values α, β, and γ stored in the memory 61 of the ECU 60 in advance. The function data is set such that the values α, β, and γ are calculated to be smaller as the response delay time is longer.
[0091]
According to this configuration, even if the response delay time related to the change in the intake pressure PM changes according to the engine operating state, the change can be reflected in the fuel injection control and the ignition timing control. As a result, it is possible to more surely suppress a sudden increase in torque associated with the combustion, and to quickly switch the combustion mode from “homogeneous lean combustion” to “homogeneous rich combustion”. Note that the response delay time related to the change in the EGR amount can be reflected in the fuel injection control and the ignition timing control in the same manner as described above.
[0092]
In the above embodiment, the control device according to the present invention is applied to the engine 10 in which the combustion mode is switched between the five modes described above. For example, “stratified combustion” and “weak stratified combustion” It can also be applied to engines that do not perform this.
[0093]
As described above, the embodiment embodying the present invention has been described. The technical idea that can be grasped from this embodiment will be described below together with its effects.
(1) ClaimsIn oneIn the control device for an internal combustion engine described,
Detecting means for detecting an engine operating state of the internal combustion engine,
Estimating means for estimating a response delay time related to a change in pumping loss due to a change in the opening degree of the throttle valve based on the detected engine operating state;
Set a gradual change speed when gradually changing the fuel injection amount to the predetermined amount and a gradual change speed when gradually changing the ignition timing to the predetermined time based on the estimated response delay time. Setting means and
A control device for an internal combustion engine, further comprising:
[0094]
According to such a configuration, it is possible to more reliably suppress a sudden increase in torque due to the switching of the combustion mode, and it is possible to quickly switch the combustion mode.
[0095]
【The invention's effect】
As explained above, the claimsIn oneAccording to the described invention, it is possible to reliably suppress a sudden change in engine output due to switching of the combustion mode, and to prevent the occurrence of misfire due to incompatibility between the engine combustion state and the ignition timing. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an engine control device according to an embodiment.
FIG. 2 is a flowchart illustrating a procedure for determining a combustion mode.
FIG. 3 is a graph showing a relationship between each mode of a combustion mode, an engine speed, and a basic fuel injection amount.
FIG. 4 is a flowchart illustrating a procedure for correcting a fuel injection amount.
FIG. 5 is a conceptual diagram showing function data for calculating an instruction fuel injection amount.
FIG. 6 is a flowchart for explaining a calculation procedure of a fuel correction amount.
FIG. 7 is a flowchart illustrating a procedure for calculating a target throttle opening.
FIG. 8 is a conceptual diagram showing function data for calculating a target throttle opening.
FIG. 9 is a flowchart illustrating a procedure for calculating an ignition timing.
FIG. 10 is a conceptual diagram showing function data for calculating an ignition timing.
FIG. 11 is a timing chart showing how the final fuel injection amount and the like change.
FIG. 12 is a timing chart showing a conventional manner of changing an engine output and the like.
[Explanation of symbols]
Reference Signs List 10 engine, 11 cylinder block, 12 cylinder head, 13 piston, 14 crankshaft, 15 cylinder, 16 exhaust passage, 17 combustion chamber, 18 intake passage, 20 surge tank, 22 three Source catalyst, 24 NOx catalyst, 26 spark plug, 30 camshaft, 34 throttle valve, 40 EGR passage, 41 electromagnetic valve, 42 pressure passage, 44 brake booster, 46 accelerator pedal, 50 Injector, 52: igniter, 53: ignition coil, 54: throttle motor, 60: ECU, 61: memory, 62: accelerator sensor, 64: crank sensor, 66: cam sensor, 67: intake pressure sensor, 68: pressure sensor.

Claims (1)

Combustion mode switching means including fuel injection quantity control means for changing the fuel injection quantity of the internal combustion engine to a predetermined quantity corresponding to the post-switching combustion mode in order to switch the combustion mode in the internal combustion engine; and Throttle opening control means for changing the opening of the throttle valve of the internal combustion engine to a predetermined opening in order to suppress a change in engine output; and a throttle opening control means for suppressing the change in engine output accompanying the switching of the combustion mode. An ignition timing control means for changing the ignition timing to a predetermined timing, a control device for an internal combustion engine,
The combustion mode switching means switches from a combustion mode in which the air-fuel ratio of the internal combustion engine is leaner than the stoichiometric air-fuel ratio or a stoichiometric air-fuel ratio to a combustion mode in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio.
The fuel injection amount control means gradually increases the fuel injection amount from the fuel injection amount corresponding to the combustion mode before the switching to the fuel injection amount corresponding to the combustion mode after the switching when switching the combustion mode. And
The throttle opening control means changes the opening of the throttle valve from the opening of the throttle valve corresponding to the combustion before switching to the combustion after the switching in order to suppress an increase in engine output due to the switching of the combustion. To the opening of the throttle valve corresponding to
The ignition timing control means gradually retards the ignition timing from the ignition timing corresponding to the combustion mode before the switching to the ignition timing corresponding to the combustion mode after the switching when switching the combustion mode. A control device for an internal combustion engine, comprising:

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