JP5195742B2 - Engine ignition timing control device - Google Patents

Description

  The present invention relates to an ignition timing control device for an engine provided with a variable valve mechanism that changes an opening / closing characteristic (at least one of valve opening timing and valve closing timing) of an intake valve.

  In general, the variable valve mechanism includes at least one of a valve timing variable mechanism that changes the valve timing of the intake valve and a maximum valve lift amount variable mechanism that changes the maximum valve lift amount of the intake valve. Patent Document 1 proposes a variable valve mechanism that includes both the variable valve timing mechanism and the maximum valve lift amount variable mechanism.

JP-A-2001-263015

  By the way, in an engine equipped with a variable valve mechanism, the temperature / pressure in the combustion chamber changes as the opening / closing characteristics are changed. Therefore, in order to ensure a good combustion state, it is necessary to set the ignition timing in consideration of such changes in temperature / pressure.

However, an ignition timing control device that sets the ignition timing by paying attention to the relationship between the opening / closing characteristics of the intake valve and the temperature / pressure in the combustion chamber has not yet been proposed.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an engine ignition timing control device capable of setting an appropriate ignition timing regardless of changes in the opening / closing characteristics of the intake valve. There is.

  (1) The first means is “an engine ignition timing control device including a control unit that controls the ignition timing in accordance with the operating state of the engine, wherein the engine has a valve opening timing as an open / close characteristic of the intake valve, and A variable valve mechanism for changing a valve closing timing, wherein the control unit defines an ignition timing used for combustion of an air-fuel mixture as a base ignition timing, and operates the engine for which the suitable base ignition timing is set. A state is defined as a basic operating state, a current operating state of the engine is defined as a current operating state, an open / close characteristic of the intake valve in the basic operating state is defined as a basic open / close characteristic, and the current operating state is defined. The open / close characteristic of the intake valve in the state is defined as the current open / close characteristic, and is the amount of change in the compression end pressure or the compression end temperature in the combustion chamber, the compression end pressure of the combustion chamber in the basic operation state Alternatively, the difference between the compression end temperature and the compression end pressure or the compression end temperature of the combustion chamber in the current operating state is defined as a state change amount, and the opening timing and closing timing of the intake valve in the basic opening / closing characteristics And calculating the state change amount based on the opening and closing timings of the intake valve in the current opening / closing characteristics, and correcting the base ignition timing suitable for the basic operating state according to the state change amount And an engine ignition timing control device that sets the corrected base ignition timing as a base ignition timing suitable for the current operating state.

In the above configuration, the ignition timing is set taking into account changes in the temperature or pressure in the combustion chamber that accompany changes in the opening / closing characteristics of the intake valve, so an appropriate ignition timing is set regardless of changes in the opening / closing characteristics of the intake valve. Will be able to.
Further, it has been confirmed that the compression end temperature / compression end pressure is more sensitive to changes in the opening / closing characteristics of the intake valve than the temperature / pressure in the combustion chamber at other crank angles. Therefore, by adopting the above configuration, the change in the state change amount with respect to the change in the opening / closing characteristics can be grasped more accurately, so that the correction accuracy of the ignition timing based on the state change amount can be improved. Become.
Further, the temperature or pressure in the combustion chamber changes with a certain correlation with the opening timing of the intake valve. Therefore, by adopting the above configuration, the compression end pressure or the compression end temperature in the combustion chamber can be appropriately estimated.
Further, the temperature or pressure in the combustion chamber changes with a certain correlation with the intake valve closing timing. Therefore, by adopting the above configuration, the compression end pressure or the compression end temperature in the combustion chamber can be appropriately estimated.

  (2) The second means is “an ignition timing control device for an engine including a control unit that controls the ignition timing in accordance with the operating state of the engine. The control unit has a variable valve mechanism for changing the valve closing timing, and the control unit uses the ignition timing used for combustion of the air-fuel mixture as an ignition timing that suppresses the occurrence of knocking and provides the best output torque and fuel consumption rate. A plurality of base ignition timings prepared in advance for each engine operating state are defined as basic base ignition timings, and the engine operating states corresponding to the selected basic base ignition timings are defined as basic timings. The current operating state of the engine is defined as the current operating state, and the open / close characteristics of the intake valve in the basic operating state are basically opened. The open / close characteristic of the intake valve in the current operating state is defined as the current open / close characteristic, and the amount of change in the compression end pressure or compression end temperature in the combustion chamber, the combustion chamber in the basic operation state The difference between the compression end pressure or the compression end temperature of the combustion chamber and the compression end pressure or the compression end temperature of the combustion chamber in the current operation state is defined as a state change amount, and the current change amount is included in the plurality of basic base ignition timings. When an ignition timing suitable for the operating condition exists, this ignition timing is selected as a base ignition timing appropriate for the current operating condition, and an ignition suitable for the current operating condition is selected from among the plurality of basic base ignition timings. When no timing is present, select any one of the plurality of basic base ignition timings, the basic operating state corresponding to the selected basic base ignition timing, and The amount of state change corresponding to the current operation state is based on the valve opening timing and valve closing timing of the intake valve in the basic opening / closing characteristics, and the valve opening timing and valve closing timing of the intake valve in the current opening / closing characteristics. An engine ignition timing control device that calculates, corrects the basic base ignition timing according to the state change amount, and sets the corrected ignition timing as a base ignition timing suitable for the current operating state.

  (3) The third means is that “the control unit defines the operating state of the engine for setting the valve overlap as the first operating state, and sets the operating state of the engine for which the valve overlap is not set to the second operating state. The base ignition timing that conforms to the first operating state is defined as the first base ignition timing, the base ignition timing that conforms to the second operating state is defined as the second base ignition timing, and the first operation A correction amount of the ignition timing according to the valve overlap amount in the state is calculated based on the first base ignition timing and the second base ignition timing, and the calculated correction amount is set to the valve overlap amount in the current operating state. The base ignition timing suitable for the current operating state is calculated based on the corrected correction amount and the first base ignition timing after conversion. Including an ignition timing control system "for an engine according.

  (4) A fourth means is that “the control unit opens and closes the state change amount when the opening and closing characteristics of the intake valve change from the opening and closing characteristics of the first operating state to the opening and closing characteristics of the second operating state. The amount of change is calculated, a correction amount of the ignition timing corresponding to the amount of change in the open / close state is calculated, the first base ignition timing is retarded by an amount corresponding to the second base ignition timing, and the amount of change in the open / close state The ignition timing control device for an engine according to claim 3, wherein an ignition timing correction amount corresponding to the valve overlap amount in the first operating state is calculated by performing correction based on an ignition timing correction amount corresponding to including.

  (5) The fifth means is an engine ignition timing control device including a control unit that controls the ignition timing according to the operating state of the engine, wherein the engine has a valve opening timing as an opening / closing characteristic of the intake valve and The control unit has a variable valve mechanism for changing the valve closing timing. The control unit defines an ignition timing used for combustion of the air-fuel mixture as a base ignition timing, and determines an ignition timing at which the best output torque and fuel consumption rate can be obtained by MBT. The ignition timing that is the most advanced of the ignition timings that can suppress the occurrence of knocking is defined as the knock limit ignition timing, and the MBT ignition timing and the knock limit ignition timing that are suitable are determined. The set operating state of the engine is defined as a basic operating state, the current operating state of the engine is defined as the current operating state, and the intake valve in the basic operating state is defined. The open / close characteristic of the combustion chamber is defined as a basic open / close characteristic, the open / close characteristic of the intake valve in the current operating state is defined as a current open / close characteristic, and the amount of change in the compression end pressure or compression end temperature in the combustion chamber, The difference between the compression end pressure or compression end temperature of the combustion chamber in the present operation state and the compression end pressure or compression end temperature of the combustion chamber in the current operation state is defined as a state change amount, and the intake valve in the basic switching characteristics The state change amount is calculated based on the opening timing and closing timing of the intake valve and the opening timing and closing timing of the intake valve in the current opening / closing characteristics, and the MBT ignition timing and the The knock limit ignition timing is corrected based on the state change amount, and the retarded ignition timing of the corrected MBT ignition timing and knock limit ignition timing is set as the ignition timing. Including an ignition timing control apparatus for an engine "to be set as a matching base ignition timing to the operating state of the resident.

  (6) The sixth means is "an engine ignition timing control device including a control unit that controls the ignition timing in accordance with the operating state of the engine, wherein the engine has a valve opening timing as an open / close characteristic of the intake valve and The control unit has a variable valve mechanism for changing the valve closing timing. The control unit defines an ignition timing used for combustion of the air-fuel mixture as a base ignition timing, and determines an ignition timing at which the best output torque and fuel consumption rate can be obtained by MBT. The ignition timing that is the most advanced of the ignition timings that can suppress the occurrence of knocking is defined as the knock limit ignition timing, and the MBT ignition timing and the knock limit ignition timing that are suitable are determined. The set operating state of the engine is defined as a basic operating state, the current operating state of the engine is defined as the current operating state, and the intake valve in the basic operating state is defined. The open / close characteristic of the engine is defined as a basic open / close characteristic, the open / close characteristic of the intake valve in the current operating state is defined as a current open / close characteristic, and a plurality of MBT ignition timings prepared in advance for each operating state of the engine and The plurality of knock limit ignition timings are defined as a basic MBT ignition timing and a basic knock limit ignition timing, respectively, and are common to any one of the selected basic MBT ignition timings and any one of the basic knock limit ignition timings The engine operating state corresponding thereto is defined as the basic operating state, and is the amount of change in the compression end pressure or the compression end temperature in the combustion chamber, the compression end pressure or the compression end of the combustion chamber in the basic operation state. The difference between the temperature and the compression end pressure or compression end temperature of the combustion chamber in the current operating state is defined as a state change amount, and the plurality of basic MBT ignition times When there is a basic MBT ignition timing and a basic knock limit ignition timing that match the current operating state among the plurality of basic knock limit ignition timings, a delay of the basic MBT ignition timing and the basic knock limit ignition timing is included. An ignition timing on the corner side is set as a base ignition timing suitable for the current operation state, and an ignition timing suitable for the current operation state among the plurality of basic MBT ignition timings and the plurality of basic knock limit ignition timings Is selected, one of the plurality of basic MBT ignition timings and one of the plurality of basic knock limit ignition timings are selected, and the selected basic MBT ignition timing and basic knock limit ignition timing are selected. The corresponding basic operating state, and the state change amount corresponding to the current operating state, in the basic switching characteristics The basic MBT ignition timing and the basic knock limit ignition timing selected based on the opening timing and closing timing of the intake valve, and the opening timing and closing timing of the intake valve in the current opening / closing characteristics Ignition control of the engine which corrects based on the amount of change and sets the retarded ignition timing of the corrected basic MBT ignition timing and basic knock limit ignition timing as the base ignition timing suitable for the current operating state Equipment ".

  (7) The seventh means is that “the control unit defines the operating state of the engine for setting valve overlap as a first operating state and sets the operating state of the engine for which valve overlap is not set as a second operating state. The MBT ignition timing suitable for the first operating state is defined as the first MBT ignition timing, the MBT ignition timing suitable for the second operating state is defined as the second MBT ignition timing, A correction amount of the ignition timing corresponding to the valve overlap amount is calculated based on the first MBT ignition timing and the second MBT ignition timing, and the calculated correction amount is a correction amount corresponding to the valve overlap amount in the current operating state The MBT ignition timing suitable for the current operating state is calculated based on the corrected amount after conversion and the first MBT ignition timing. Including an ignition timing control system "for an engine according.

  (8) The eighth means is that “the control unit opens and closes the state change amount when the open / close characteristic of the intake valve changes from the open / close characteristic of the first operation state to the open / close characteristic of the second operation state”. The ignition timing correction amount is calculated according to the opening / closing state change amount, the first MBT ignition timing is retarded by an amount corresponding to the second MBT ignition timing, and the opening / closing state change amount is determined. The engine ignition timing control device according to claim 7, wherein an ignition timing correction amount corresponding to a valve overlap amount in the first operating state is calculated by performing correction based on the ignition timing correction amount. .

  (9) Ninth means is: “The control unit defines the operating state of the engine for setting valve overlap as a first operating state, and sets the operating state of the engine not to set valve overlap as a second operating state. And defining the knock limit ignition timing suitable for the first operating state as the first knock limit ignition timing, defining the knock limit ignition timing suitable for the second operating state as the second knock limit ignition timing, An ignition timing correction amount corresponding to the valve overlap amount in the first operating state is calculated based on the first knock limit ignition timing and the second knock limit ignition timing, and the calculated correction amount is calculated in the current operating state. Is converted to a correction amount corresponding to the valve overlap amount of the engine, and based on the converted correction amount and the first knock limit ignition timing, the knock limit point suitable for the current operating state Timing including the ignition timing control apparatus "for an engine according to any one of claims 5-8 calculated.

  (10) The tenth means is “the control unit opens and closes the state change amount when the opening / closing characteristic of the intake valve changes from the opening / closing characteristic of the first operating state to the opening / closing characteristic of the second operating state. The amount of change is defined, the correction amount of the ignition timing corresponding to the amount of change in the open / close state is calculated, the first knock limit ignition timing is retarded by an amount corresponding to the second knock limit ignition timing, and the open / close state is The engine ignition timing control according to claim 9, wherein a correction amount of the ignition timing according to the valve overlap amount in the first operating state is calculated by performing correction based on a correction amount of the ignition timing according to the change amount. Equipment ".

  (11) The eleventh means is that “the controller changes the state change amount when the opening timing of the intake valve changes from the opening timing of the first operating state to the opening timing of the second operating state. Is defined as the valve opening side state change amount, and the state change amount when the valve closing timing of the intake valve changes from the valve closing timing of the first operation state to the valve closing timing of the second operation state is closed. A side state change amount, the valve opening side state change amount is calculated based on the valve opening timing of the first operation state and the valve opening timing of the second operation state, and the valve closing timing of the first operation state The valve closing side state change amount is calculated based on the valve closing timing of the second operation state, and the opening / closing state change amount is calculated based on the valve opening side state change amount and the valve closing side state change amount. The engine ignition timing control device according to claim 4, 8, or 10 ”.

  (12) The twelfth means is that the control unit defines the valve opening timing of the basic opening / closing characteristics as a basic valve opening timing, the valve opening timing of the current switching characteristics as a current valve opening timing, The engine ignition timing control device according to any one of claims 1 to 11, wherein the state change amount is calculated based on a valve opening timing and the current valve opening timing.

  (13) The thirteenth means is that “the control unit defines the opening timing of the top dead center of the intake valve as a reference opening timing, and the opening timing of the intake valve is determined from the reference opening timing to the basic opening timing. The state change amount when the valve opening timing is changed is defined as a first valve opening state change amount, and the state when the intake valve opening timing is changed from the reference valve opening timing to the current valve opening timing is defined. The amount of change is defined as a second valve opening state change amount, the first valve opening state change amount is calculated based on the reference valve opening timing and the basic valve opening timing, and the reference valve opening timing and the current valve opening time are calculated. The engine according to claim 12, wherein the second valve opening state change amount is calculated based on a timing, and the state change amount is calculated based on the first valve opening state change amount and the second valve opening state change amount. Ignition timing control device ".

  (14) The fourteenth means is that the control unit defines the closing timing of the basic opening / closing characteristics as a basic closing timing, defines the closing timing of the current opening / closing characteristics as a current closing timing, and The engine ignition timing control device according to any one of claims 1 to 13, wherein the state change amount is calculated based on a valve closing timing and the current valve closing timing.

  (15) The fifteenth means is that the control unit defines the closing timing of the bottom dead center of the intake valve as a reference closing timing, and the closing timing of the intake valve is changed from the reference closing timing to the basic closing timing. The state change amount when changing to the valve closing timing is defined as a first valve closing state change amount, and the state when the intake valve closing timing is changed from the reference valve closing timing to the current valve closing timing. A change amount is defined as a second valve closing state change amount, the first valve closing state change amount is calculated based on the reference valve closing timing and the basic valve closing timing, and the reference valve closing timing and the current valve closing time are calculated. The engine according to claim 14, wherein the second valve closing state change amount is calculated based on a timing, and the state change amount is calculated based on the first valve closing state change amount and the second valve closing state change amount. Ignition timing control device ".

  (16) The sixteenth means is that “the control unit defines the closing timing of the intake valve having the maximum charging efficiency as a maximum charging closing timing, and the closing timing of the intake valve is the maximum charging closing timing. The amount of state change when changing from the timing to the basic valve closing timing is defined as a third valve closing state change amount, and the valve closing timing of the intake valve changes from the maximum filling valve closing timing to the current valve closing timing. The state change amount at the time of operation is defined as a fourth valve closing state change amount, the third valve closing state change amount is calculated based on the maximum filling valve closing timing and the basic valve closing timing, and the maximum filling closing amount is calculated. The fourth valve closing state change amount is calculated based on the valve timing and the current valve closing timing, and the state change amount is calculated based on the third valve closing state change amount and the fourth valve closing state change amount. 15. An engine ignition timing control device according to claim 14. .

  (17) The seventeenth means is the “engine ignition timing control device according to any one of claims 1 to 16, wherein the control unit calculates the state change amount based on a rotational speed of the engine”. Including.

  (18) The eighteenth means is "the engine ignition timing control device according to any one of claims 1 to 17, wherein the control unit calculates the state change amount based on an intake air amount of the engine". including.

  (19) The nineteenth means is "the engine ignition timing control device according to any one of claims 1 to 18, wherein the control unit calculates the state change amount based on an effective intake pipe length of the engine". including.

The block diagram which shows the structure of an engine about 1st Embodiment which actualized the ignition timing control apparatus of the engine concerning this invention. The figure which shows the change aspect of the intake valve timing by the intake valve timing variable mechanism of the embodiment. The figure which shows the change aspect of the exhaust valve timing by the exhaust valve timing variable mechanism of the embodiment. The figure which shows the change aspect of the intake maximum valve lift amount by the intake maximum valve lift amount variable mechanism of the embodiment. The figure which shows an example of the intake cam selection map of the embodiment. The graph which shows the relationship between intake valve opening timing and the temperature / pressure in a combustion chamber. The graph which shows the relationship between the intake valve closing timing and the temperature / pressure in the combustion chamber. The graph which shows the relationship between valve overlap amount and residual gas rate. The figure which shows the structure of the "base ignition timing setting process" performed in order to set a base ignition timing in the same embodiment. The structure of the "base ignition timing setting process" performed in order to set a base ignition timing in the same embodiment is shown. The figure which shows the relationship of each parameter calculated through the "base ignition timing setting process" of the embodiment. The figure which shows the relationship of each parameter calculated through the "base ignition timing setting process" of the embodiment. 9 is a flowchart showing a processing procedure of “variable valve mechanism driving process” executed in order to drive the variable valve mechanism in the embodiment. 6 is a flowchart showing a processing procedure of “target cam setting processing” executed in order to set a target cam in the embodiment. 6 is a flowchart showing a processing procedure of “base ignition timing setting processing” executed to set the base ignition timing in the embodiment. 6 is a flowchart showing a processing procedure of “base ignition timing setting processing” executed to set the base ignition timing in the embodiment. 7 is a flowchart showing a processing procedure of “compression end pressure change amount calculation processing [1]” executed in order to calculate a current cam total pressure change amount in the embodiment. 9 is a flowchart showing a processing procedure of “IVO compression end pressure change amount calculation process [1]” executed in order to calculate a current cam IVO pressure change amount in the embodiment. 9 is a flowchart showing a processing procedure of “IVC compression end pressure change amount calculation process [1]” executed in order to calculate a current cam IVC pressure change amount in the embodiment. 7 is a flowchart showing a processing procedure of “compression end pressure change amount calculation process [2]” executed to calculate the initial cam total pressure change amount in the embodiment. 9 is a flowchart showing a processing procedure of “IVO compression end pressure change amount calculation process [2]” executed in order to calculate an initial cam IVO pressure change amount in the embodiment. 7 is a flowchart showing a processing procedure of “IVC compression end pressure change amount calculation process [2]” executed in order to calculate an initial cam IVC pressure change amount in the embodiment. 9 is a flowchart showing a processing procedure of “overlap ratio calculation processing” executed in order to calculate an overlap ratio in the embodiment. 9 is a flowchart showing a processing procedure of “current cam MBT ignition timing setting processing” executed in order to calculate a current cam MBT ignition timing in the embodiment. 9 is a flowchart showing a processing procedure of a “first MBT correction amount calculation process” that is executed to calculate a first MBT correction amount in the embodiment. 9 is a flowchart showing a processing procedure of “second MBT correction amount calculation processing” executed to calculate a second MBT correction amount in the embodiment. 9 is a flowchart showing a processing procedure of a “compression end temperature change amount calculation process [1]” executed to calculate the current cam total temperature change amount in the embodiment. 7 is a flowchart showing a processing procedure of “IVO compression end temperature change amount calculation process [1]” executed in order to calculate a current cam IVO temperature change amount in the embodiment. 9 is a flowchart showing a processing procedure of “IVC compression end temperature change calculation process [1]” executed to calculate the current cam IVC temperature change in the embodiment. 9 is a flowchart showing a processing procedure of “compression end temperature change calculation process [2]” executed to calculate the initial cam total temperature change in the embodiment. 9 is a flowchart showing a processing procedure of “IVO compression end temperature change calculation process [2]” executed to calculate an initial cam IVO temperature change in the embodiment. 9 is a flowchart showing a processing procedure of “IVC compression end temperature change calculation process [2]” executed in order to calculate the initial cam IVC temperature change in the embodiment. 9 is a flowchart showing a processing procedure of a “current cam knock limit ignition timing setting process” executed to calculate a current cam knock limit ignition timing in the embodiment. 7 is a flowchart showing a processing procedure of “first knock limit correction amount calculation processing” executed to calculate a first knock limit correction amount in the embodiment. 9 is a flowchart showing a processing procedure of a “second knock limit correction amount calculation process” executed to calculate a second knock limit correction amount in the embodiment. The figure which shows an example of the IVO compression end pressure calculation map which set the relationship between intake valve opening timing, engine rotation speed, and compression end pressure in the embodiment. The graph which shows the relationship between the intake valve opening timing and compression end pressure in equal engine rotational speed about the IVO compression end pressure calculation map of the embodiment. The figure which shows an example of the IVC compression end pressure calculation map which set the relationship between intake valve closing timing, engine rotation speed, and compression end pressure in the same embodiment. The graph which shows the relationship between the intake valve closing timing and compression end pressure in equal engine rotation speed about the IVC compression end pressure calculation map of the embodiment. The figure which shows an example of the 1st MBT correction amount calculation map which set the relationship between the compression end pressure change amount and the 1st MBT correction amount in the same embodiment. The figure which shows an example of the optimal cam MBT ignition timing calculation map which set the relationship between an intake air rate, an engine speed, and the optimal cam MBT ignition timing in the embodiment. The graph which shows the relationship between the intake air rate and MBT ignition timing in equal engine rotational speed about the optimal cam MBT ignition timing calculation map of the embodiment. The figure which shows an example of the initial cam MBT ignition timing calculation map which set the relationship between an intake air rate, an engine speed, and the initial cam MBT ignition timing in the same embodiment. The graph which shows the relationship between the intake air rate and MBT ignition timing in equal engine rotational speed about the initial cam MBT ignition timing calculation map of the embodiment. The figure which shows an example of the ignition timing correction ratio calculation map which set the relationship between the overlap ratio and the ignition timing correction ratio in the same embodiment. The figure which shows an example of the IVO compression end temperature calculation map which set the relationship between intake valve opening timing, an engine speed, and compression end temperature in the same embodiment. The graph which shows the relationship between the intake valve opening timing and compression end temperature in equal engine rotational speed about the IVO compression end temperature calculation map of the embodiment. The figure which shows an example of the IVC compression end temperature calculation map which set the relationship between intake valve closing timing, an engine speed, and compression end temperature in the same embodiment. The graph which shows the relationship between the intake valve closing timing and compression end temperature in equal engine rotation speed about the IVC compression end temperature calculation map of the embodiment. The figure which shows an example of the 1st knock limit correction amount calculation map which set the relationship between the compression end temperature variation | change_quantity and the 1st knock limit correction amount in the same embodiment. The figure which shows an example of the optimal cam knock limit ignition timing calculation map which set the relationship between an intake air rate, an engine speed, and the optimal cam knock limit ignition timing in the same embodiment. The graph which shows the relationship between the intake air rate in the same engine speed, and a knock limit ignition timing about the optimal cam knock limit ignition timing calculation map of the embodiment. The figure which shows an example of the initial cam knock limit ignition timing calculation map which set the relationship between the intake air rate, the engine speed, and the initial cam knock limit ignition timing in the same embodiment. The graph which shows the relationship between the intake air rate and knock limit ignition timing in equal engine rotational speed about the initial cam knock limit ignition timing calculation map of the embodiment. Processing procedure of “IVC compression end pressure change amount calculation process [3]” executed to calculate the current cam IVC pressure change amount for the second embodiment that embodies the engine ignition timing control device according to the present invention. The flowchart which shows. 9 is a flowchart showing a processing procedure of “IVC compression end pressure change amount calculation process [4]” executed in order to calculate an initial cam IVC pressure change amount in the embodiment. 7 is a flowchart showing a processing procedure of “IVC compression end temperature change amount calculation process [3]” executed in order to calculate the current cam IVC temperature change amount in the embodiment. 9 is a flowchart showing a processing procedure of “IVC compression end temperature change calculation process [4]” executed in order to calculate the initial cam IVC temperature change in the embodiment. In a third embodiment that embodies an ignition timing control device for an engine according to the present invention, the first knock limit correction amount calculation map [2] in which the relationship between the compression end pressure change amount and the first knock limit correction amount is set. The figure which shows an example. The figure which shows an example of 1st MBT correction amount calculation map [2] which set the relationship between compression end temperature variation | change_quantity and 1st MBT correction amount about 4th Embodiment which actualized the ignition timing control apparatus of the engine concerning this invention. .

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the present invention is applied to an engine having a variable valve mechanism that can change the valve characteristics (valve timing and maximum valve lift amount) of the intake valve.

<Engine configuration>
FIG. 1 shows a cross-sectional structure of the engine 1.
The engine 1 includes a cylinder block 2 and a cylinder head 3.

The cylinder block 2 is provided with a cylinder 21.
A piston 22 is accommodated in the cylinder 21 so as to reciprocate.
A combustion chamber 23 is defined in the cylinder 21 by being surrounded by the inner peripheral surface of the cylinder 21, the top surface of the piston 22, and the cylinder head 3.

The cylinder head 3 is provided with an intake port 31 and an exhaust port 32.
An intake pipe 33 is connected to the intake port 31. In addition, an intake valve 35 that changes the connection state between the intake pipe 33 and the combustion chamber 23 by opening and closing the intake port 31 is disposed.

  An exhaust pipe 34 is connected to the exhaust port 32. Further, an exhaust valve 36 that changes the connection state between the exhaust pipe 34 and the combustion chamber 23 by opening and closing the exhaust port 32 is disposed.

An ignition plug 37 that sparks and ignites an air-fuel mixture formed by fuel and air is disposed at a position where the top of the combustion chamber 23 is formed in the cylinder head 3.
The intake pipe 33 is provided with a throttle valve 38 that adjusts the flow rate of air flowing through the intake pipe 33. A port injection injector 39 that injects fuel toward the intake port 31 is disposed.

The cylinder head 3 is provided with a variable valve mechanism 5 that changes the valve characteristics of the intake valve 35 and the exhaust valve 36.
The variable valve mechanism 5 includes an intake valve timing variable mechanism 51, an exhaust valve timing variable mechanism 52, and an intake maximum valve lift amount variable mechanism 53.

  The intake valve timing variable mechanism 51 changes the valve timing of the intake valve 35 (intake valve timing INVT). That is, the relative rotational phase of the camshaft of the intake valve 35 with respect to the crankshaft of the engine 1 is changed. By changing the valve timing, the opening timing of the intake valve 35 (intake valve opening timing IVO) and the closing timing of the intake valve 35 (intake valve closing timing IVC) are advanced or retarded by the same crank angle.

  As shown in FIG. 2, the intake valve timing INVT is between the most advanced valve timing (most advanced intake valve timing INVTmax) and the most retarded valve timing (most retarded intake valve timing INVTmin). Continuously changed. Further, the intake valve opening timing IVO and the intake valve closing timing IVC are maintained in a state in which the valve opening period of the intake valve 35 (crank angle from the intake valve opening timing IVO to the intake valve closing timing IVC) is maintained constant. Is changed. Hereinafter, the valve opening period of the intake valve 35 is referred to as an intake valve working angle INCAM.

  The exhaust valve timing variable mechanism 52 changes the valve timing of the exhaust valve 36 (exhaust valve timing EXVT). That is, the relative rotational phase of the camshaft of the exhaust valve 36 with respect to the crankshaft of the engine 1 is changed. By changing the valve timing, the opening timing of the exhaust valve 36 (exhaust valve opening timing EVO) and the closing timing of the exhaust valve 36 (exhaust valve closing timing EVC) are advanced or retarded by the same crank angle.

  As shown in FIG. 3, the exhaust valve timing EXVT is between the most advanced valve timing (most advanced exhaust valve timing EXVTmax) and the most retarded valve timing (most retarded exhaust valve timing EXVTmin). Continuously changed. Further, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are maintained in a state where the valve opening period of the exhaust valve 36 (crank angle from the exhaust valve opening timing EVO to the exhaust valve closing timing EVC) is maintained constant. Is changed. Hereinafter, the valve opening period of the exhaust valve 36 is referred to as an exhaust valve working angle EXCAM.

  The intake maximum valve lift amount varying mechanism 53 changes the maximum valve lift amount (intake maximum valve lift amount INVL) of the intake valve 35. Further, the intake valve working angle INCAM is changed together with the intake maximum valve lift amount INVL.

  As shown in FIG. 4, the maximum intake valve lift amount INVL is continuously between the largest maximum valve lift amount (upper limit maximum valve lift amount INVLmax) and the smallest maximum valve lift amount (lower limit maximum valve lift amount INVLmin). Changed to Correspondingly, the intake valve working angle INCAM is continuously changed from the largest valve working angle (maximum intake valve working angle INCAMmax) to the smallest valve working angle (minimum intake valve working angle INCAMmin). The

  In the engine 1, when the valve characteristics of the intake valve 35 are changed by the intake valve timing variable mechanism 51 and the intake maximum valve lift amount variable mechanism 53, the opening / closing characteristics of the intake valve 35 (the intake valve opening timing IVO and the intake valve closing) At least one of the times IVC) is changed.

The engine 1 is provided with an electronic control unit 9 that comprehensively controls fuel injection amount, ignition timing, valve characteristics (combination of valve timing and maximum valve lift amount), and the like. The control unit includes an electronic control device 9.

  The electronic control unit 9 includes a CPU that executes arithmetic processing for engine control, a memory for storing programs and information necessary for engine control, and an input port and an output port for inputting / outputting signals to / from the outside. Configured.

The following various sensors that detect engine operating conditions are connected to the input port of the electronic control unit 9.
The rotational speed sensor 91 detects the rotational speed of the crankshaft of the engine 1 (engine rotational speed NE).
The throttle opening sensor 92 detects the throttle valve opening (throttle opening TA).
The air flow meter 93 detects the flow rate of air flowing through the intake pipe 33 (intake air amount GA).
The intake valve timing sensor 94 detects the intake valve timing INVT.
The exhaust valve timing sensor 95 detects the exhaust valve timing EXVT.
The intake maximum valve lift amount sensor 96 detects the intake maximum valve lift amount INVL.

  An ignition plug 37, a throttle valve 38, a port injection injector 39, an intake valve timing variable mechanism 51, an exhaust valve timing variable mechanism 52, an intake maximum valve lift amount variable mechanism 53, and the like are connected to the output port of the electronic control unit 9. ing.

  The electronic control unit 9 adjusts the intake air amount through coordinated control of the intake valve timing variable mechanism 51, the maximum intake valve lift amount variable mechanism 53, and the throttle valve 38, so that the actual intake air amount (intake air amount GA) is adjusted. Is converged to the required value of the intake air amount (required intake air amount GAreq). The required intake air amount GAreq is calculated based on the accelerator operation amount and the like.

<Valve characteristics of the engine>
In the present embodiment, each valve characteristic (valve timing and maximum valve lift amount) of the engine 1 used for control of the intake maximum valve lift amount variable mechanism 53, ignition timing control, and the like will be described.
[A] The target cam Ctrg indicates a target value of the valve characteristic set based on the operating state of the engine 1.
[B] The optimum cam Cbst indicates a valve characteristic that provides the best fuel consumption rate. The optimum cam Cbst is set to a value where the valve overlap amount OVLP is larger than “0”. The optimum cam Cbst corresponds to the valve characteristic in the first operating state.
[C] The initial cam Cdfl shows a valve characteristic that can suppress the deterioration of the emission when the engine 1 is cold. Note that the valve overlap amount OVLP of the initial cam Cdfl is set to “0”. The initial cam Cdfl corresponds to the valve characteristic in the second operation state.
[D] The reference cam Ctdc indicates a valve characteristic in which the intake valve opening timing IVO is top dead center (TDC) and the intake valve closing timing IVC is bottom dead center (BDC). In the present embodiment, the crank angle at the top dead center is set to “0 deg”.
[E] The current cam Cnow indicates the current valve characteristic.

Each parameter in each of the above valve characteristics is defined as follows.
[1] "Optimum cam"
Intake valve opening timing IVO of the optimal cam Cbst: Optimal cam intake valve opening timing IVObst.
Intake valve closing timing IVC of optimum cam Cbst: Optimal cam intake valve closing timing IVCbst.
Exhaust valve closing timing EVC for optimum cam Cbst: Optimal cam exhaust valve closing timing EVCbst.
-Optimal cam Cbst valve overlap amount OVLP ... Optimal cam overlap amount OVLPbst.

[2] "Initial cam"
Intake valve opening timing IVO of initial cam Cdfl: Initial cam intake valve opening timing IVOdfl.
Intake valve closing timing IVC of initial cam Cdfl: Initial cam intake valve closing timing IVCdfl.
Exhaust valve closing timing EVC of initial cam Cdfl ... Initial cam exhaust valve closing timing EVCdfl.

[3] "Reference cam"
Intake valve opening timing IVO of reference cam Ctdc ... Reference cam intake valve opening timing IVOtdc.
Intake valve closing timing IVC of reference cam Ctdc ... Reference cam intake valve closing timing IVCtdc.
Exhaust valve closing timing EVC of reference cam Ctdc ... Reference cam exhaust valve closing timing EVCtdc.

[4] “Current Cam”
The intake valve opening timing IVO of the current cam Cnow ... The current cam intake valve opening timing IVOnow.
The intake valve closing timing IVC of the current cam Cnow ... The current cam intake valve closing timing IVCnow.
-Exhaust valve closing timing EVC of current cam Cnow ... Current cam exhaust valve closing timing EVCnow.
-The valve overlap amount OVLP of the current cam Cnow ... The current cam overlap amount OVLPnow.

  The optimum cam intake valve opening timing IVObst corresponds to the basic valve opening timing. The optimum cam intake valve closing timing IVCbst corresponds to the basic valve closing timing. The reference cam intake valve opening timing IVOtdc corresponds to the reference valve opening timing. The reference cam intake valve closing timing IVCtdc corresponds to the reference valve closing timing. The current cam intake valve opening timing IVOnow corresponds to the current valve opening timing. The current cam intake valve closing timing IVCnow corresponds to the current valve closing timing.

<Valve characteristic setting mode>
The electronic control unit 9 sets the initial cam Cdfl as the target cam Ctrg when the engine 1 is cold. Further, after the warm-up of the engine 1 is completed, the optimum cam Cbst is basically set as the target cam Ctrg. When a special request is detected, the valve characteristic corresponding to the request is set as the target cam Ctrg.

The intake valve 35 characteristics (intake valve timing INVT and intake valve working angle INCAM) and the exhaust valve 34 characteristics (exhaust valve timing EXVT) are changed as follows.
[A] When the engine 1 is cold, the intake valve timing INVT and the intake valve working angle INCAM (intake maximum valve lift amount INVL) are maintained at the characteristics of the initial cam Cdfl. Further, the exhaust valve timing EXVT is also maintained at the characteristics of the initial cam Cdfl.
[B] After the warm-up of the engine 1 is completed, the intake valve timing INVT and the intake valve working angle INCAM are basically changed according to the required intake air amount GAreq. Further, the exhaust valve timing EXVT is maintained at a constant valve timing (steady exhaust valve timing EXVTst) unless there is a special request.

  The electronic control unit 9 selects the intake cam with the intake valve 35 characteristics (the intake valve timing INVT and the intake valve working angle INCAM) of the optimum cam Cbst, the initial cam Cdfl, and the reference cam Ctdc set on the valve timing-valve operating angle diagram. The characteristics of the intake valve 35 corresponding to the operating state of the engine 1 are selected through the map. The intake cam selection map is stored in advance in the electronic control unit 9.

FIG. 5 shows an example of the intake cam selection map.
In the intake cam selection map, the intake valve operating angle INCAM changes from the maximum intake valve operating angle INCAMmax to the minimum intake valve operating angle INCAMmin as the intake valve timing INVT goes from the most advanced intake valve timing INVTmax to the most retarded intake valve timing INVTmin. The line inclined in the direction to indicate the equal intake valve opening timing line (valve characteristics with the same intake valve opening timing IVO).

  Further, as the intake valve timing INVT moves from the most advanced intake valve timing INVTmax to the most retarded intake valve timing INVTmin, the intake valve operating angle INCAM is inclined in a direction to change from the minimum intake valve operating angle INCAMmin to the maximum intake valve operating angle INCAMmax. This line shows an equal intake valve closing timing line (valve characteristics with the same intake valve closing timing IVC).

On the intake cam selection map, the optimum cam Cbst, the initial cam Cdfl, and the reference cam Ctdc are indicated as follows.
The intake valve timing INVT and the intake valve working angle INCAM of the optimum cam Cbst are indicated by a curve AA.
The intake valve timing INVT and the intake valve working angle INCAM of the initial cam Cdfl are indicated by a point B.
The intake valve timing INVT and the intake valve working angle INCAM of the reference cam Ctdc are indicated by a point C.

  In addition to the intake cam selection map, the electronic control unit 9 stores in advance an exhaust cam selection map in which the exhaust valve 34 characteristics (exhaust valve timing EXVT) of the optimum cam Cbst, the initial cam Cdfl, and the reference cam Ctdc are set. Yes. The exhaust valve 34 characteristics of the optimum cam Cbst, the initial cam Cdfl, and the reference cam Ctdc are set in association with the intake valve 35 characteristics of the optimum cam Cbst, the initial cam Cdfl, and the reference cam Ctdc, respectively.

  When setting the target cam Ctrg based on the operating state of the engine 1, the electronic control unit 9 selects the intake valve 35 characteristic corresponding to the operating state of the engine 1 from the intake cam selection map. Further, the exhaust valve 34 characteristic corresponding to the operating state of the engine 1 is selected from the exhaust cam selection map.

  Then, a target cam Ctrg is set from the intake valve 35 characteristics and the exhaust valve 34 characteristics, and the intake valve timing variable mechanism 51, the exhaust valve timing variable mechanism 52, and the intake maximum valve are set so that the current cam Cnow matches the target cam Ctrg. Each actuator of the variable valve lift amount mechanism 53 is driven.

<Ignition timing setting mode>
In the electronic control unit 9, a map in which the MBT ignition timing and the knock limit ignition timing suitable for the optimum cam Cbst are set, and a map in which the MBT ignition timing and the knock limit ignition timing suitable for the initial cam Cdfl are set in advance. It is remembered. The optimum cam Cbst and the initial cam Cdfl correspond to valve characteristics in an operating state (basic operating state) in which a suitable base ignition timing is known in advance.

  When the electronic control unit 9 sets the optimal cam Cbst as the target cam Ctrg, the electronic control device 9 finally sets the retarded ignition timing among the MBT ignition timing of the optimal cam Cbst and the knock limit ignition timing of the optimal cam Cbst. It is set as an ignition timing (base ignition timing) to be applied to the ignition plug 37.

  On the other hand, when the initial cam Cdfl is set as the target cam Ctrg, the ignition timing on the retard side of the MBT ignition timing of the initial cam Cdfl and the knock limit ignition timing of the initial cam Cdfl is finally set to the ignition plug 37. Is set as the ignition timing (base ignition timing) for application to

  The MBT ignition timing indicates the ignition timing at which the output torque and the fuel consumption rate are the best in the current operating state. The knock limit ignition timing indicates the most advanced ignition timing among the ignition timings capable of suppressing the occurrence of knocking in the current operating state.

  Incidentally, in the engine 1, the variable valve mechanism 5 is basically controlled so that the current cam Cnow moves on the curve AA of the intake cam selection map, but the intake valve timing variable mechanism 51 and the intake maximum Due to the difference in responsiveness with the variable valve lift amount mechanism 53, the current cam Cnow may be out of the optimum cam Cbst (curve AA in the intake cam selection map). At this time, since the state in the combustion chamber 23 is different from the state assumed when the optimum cam Cbst MBT / knock limit ignition timing is adapted, the base ignition timing is based on the MBT / knock limit ignition timing of the optimum cam Cbst. When is set, output torque drops or knocks.

  Such a problem is not limited to the case where the current cam Cnow does not coincide with the optimum cam Cbst, but the valve characteristics in which the MBT / knock limit ignition timing is adapted in advance (in this embodiment, the optimum cam Cbst and the initial cam Cdfl are the valves). This also occurs if the current valve characteristics do not match the current valve characteristics. That is, when there is no ignition timing suitable for the cam Cnow in the MBT / knock limit ignition timing stored in advance, the above problem is caused.

  Further, the above problem may occur due to factors other than the difference in response between the intake valve timing variable mechanism 51 and the intake maximum valve lift amount variable mechanism 53. Incidentally, in the engine 1, the target cam Ctrg may be actively set to a valve characteristic different from the optimum cam Cbst and the initial cam Cdfl. For example, when the required intake air amount GAreq increases suddenly and significantly, in order to ensure the response of the actual intake air amount to the required intake air amount GAreq, a valve characteristic that can meet such a request is set as the target cam Ctrg. Set. Also in this case, since the current cam Cnow is different from the optimum cam Cbst and the initial cam Cdfl, the above problem occurs.

  When the current cam Cnow deviates from the optimum cam Cbst, the following difference occurs between the state in the combustion chamber 23 at the optimum cam Cbst and the state in the combustion chamber 23 at the current cam Cnow. .

  [A] Since the valve timing (intake valve opening timing IVO and intake valve closing timing IVC) of the intake valve 35 differs between the current cam Cnow and the optimum cam Cbst, there is a difference in temperature / pressure in the combustion chamber 23. Arise.

  [B] Since the valve overlap amount OVLP differs between the current cam Cnow and the optimum cam Cbst, a difference occurs in the residual gas amount in the combustion chamber 23. Note that the residual gas includes the internal EGR gas that once flows out of the combustion chamber 23 into the exhaust pipe 34 and then flows into the combustion chamber 23 from the exhaust pipe 34 and stays in the combustion chamber 23 without being discharged into the exhaust pipe 34. Continuing with gas.

  Therefore, in the present embodiment, the difference between the state in the combustion chamber 23 at the optimum cam Cbst and the state in the combustion chamber 23 at the current cam Cnow is grasped, and the base ignition timing is set in consideration of this difference. Yes.

<Relationship between valve timing and temperature / pressure in combustion chamber>
[1] “Relationship between intake valve opening timing and combustion chamber temperature / pressure”
FIG. 6 shows the relationship between the intake valve opening timing IVO and the temperature / pressure in the combustion chamber 23.

  In the intake stroke of the engine 1, when the valve lift amount of the intake valve 35 is small, the opening area of the intake port 31 is small, so the direction of air flow is in the vicinity of the intake valve 35 (the relationship between the combustion chamber 23 and the intake port 31 After being bent largely in the vicinity of the boundary), air is drawn into the combustion chamber 23 through a minute gap between the intake valve 35 and the cylinder wall. At this time, since the airflow direction changes more rapidly as the flow velocity of the air flowing into the combustion chamber 23 is larger, the amount of heat energy generated increases with the change in the airflow direction (the temperature rise of the air in the combustion chamber 23 increases). Will occur).

  Accordingly, the intake valve 35 is opened in a state where the negative pressure in the combustion chamber 23 increases as the intake valve opening timing IVO increases toward the retard side on the ATDC side (conditions in which the air flow rate increases). Therefore, the temperature / pressure in the combustion chamber 23 tends to increase.

  When the maximum intake valve lift amount INVL is large, the state immediately after the intake port 31 is opened and immediately before the intake port 31 is closed corresponds to the above-described state where the valve lift amount is small. When the maximum intake valve lift amount INVL is small, the entire valve lift region of the intake valve 35 corresponds to the above-described state where the valve lift amount is small.

[2] “Relationship between intake valve closing timing and combustion chamber temperature / pressure”
FIG. 7 shows the relationship between the intake valve closing timing IVC and the temperature / pressure of the combustion chamber 23.
In the intake stroke of the engine 1, when the pressure in the vicinity of the intake port 31 is increased due to the intake pulsation, the flow velocity of the air flowing into the combustion chamber 23 is increased.

  Therefore, when the intake valve 35 is closed when the charging efficiency is maximized by the intake pulsation, the flow velocity of the air flowing into the combustion chamber 23 becomes large when the valve lift amount is small, so that the air flow direction suddenly changes. As a result of the change, the amount of heat energy generated in accordance with the change in the direction of airflow increases.

Thereby, the temperature / pressure in the combustion chamber 23 changes as follows with respect to the intake valve closing timing IVC.
[A] At the intake valve closing timing IVC (maximum charging valve closing timing IVCmax) at which the charging efficiency is maximized, the temperature / pressure in the combustion chamber 23 becomes the largest. In addition, since the inertia of the air drawn into the combustion chamber 23 increases as the engine speed NE increases, the maximum filling valve closing timing IVCmax tends to increase toward the retard side as the engine speed NE increases.

  [B] In the region where the intake valve closing timing IVC is advanced from the maximum filling valve closing timing IVCmax, the intake pulsation is increased as the intake valve closing timing IVC is advanced from the maximum filling valve closing timing IVCmax. The degree of pressure increase due to is reduced. Therefore, the temperature / pressure in the combustion chamber 23 decreases as the intake valve closing timing IVC is advanced with reference to the maximum charging valve closing timing IVCmax.

  [C] In the region where the intake valve closing timing IVC is retarded from the maximum filling valve closing timing IVCmax, as the intake valve closing timing IVC is retarded from the maximum filling valve closing timing IVCmax, the combustion chamber The actual compression ratio of the air-fuel mixture in 23 becomes small. Therefore, the temperature / pressure in the combustion chamber 23 decreases as the intake valve closing timing IVC is retarded with reference to the maximum charging valve closing timing IVCmax. Incidentally, the maximum filling valve closing timing IVCmax is basically retarded from BDC.

<Relationship between valve overlap and residual gas>
FIG. 8 shows the relationship between the valve overlap amount OVLP and the residual gas ratio EGrate. The residual gas rate EGrate indicates the ratio of the residual gas amount to the intake air amount GA.

  As the valve overlap amount OVLP increases, the amount of internal EGR gas flowing from the exhaust pipe 34 into the combustion chamber 23 increases. Therefore, the residual gas ratio EGrate basically increases with the valve overlap amount OVLP. However, in the region where the valve overlap amount OVLP is less than the reference overlap amount OVLPX, the exhaust efficiency of the combustion gas increases due to the increase of the valve overlap amount OVLP, and therefore the residual gas ratio EGrate with respect to the increase of the valve overlap amount OVLP. Shows a tendency to decrease.

  That is, in the region where the valve overlap amount OVLP is less than the reference overlap amount OVLPX, the residual gas ratio EGRate decreases as the valve overlap amount OVLP increases, and in the region where the valve overlap amount OVLP is greater than or equal to the reference overlap amount OVLPX, As the valve overlap amount OVLP increases, the residual gas ratio EGrate increases.

<MBT / knock limit ignition timing correction mode>
In the present embodiment, the temperature / pressure and the residual gas ratio in the combustion chamber 23 are adopted as parameters indicating the difference in the state in the combustion chamber 23 between the optimum cam Cbst and the current cam Cnow, and the optimum cam Cbst is based on these parameters. By correcting the MBT ignition timing and the knock limit ignition timing separately, the MBT / knock limit ignition timing of the optimum cam Cbst is converted into an ignition timing suitable for the current cam Cnow.

In the following, the above parameters in each valve characteristic will be shown as follows.
[Optimum cam combustion chamber temperature Tbst] The temperature in the combustion chamber 23 of the optimal cam Cbst.
[Optimum cam combustion chamber pressure Pbst] The pressure in the combustion chamber 23 of the optimal cam Cbst.
[Optimum cam residual gas ratio Gbst] The residual cam ratio in the combustion chamber 23 of the optimal cam Cbst.
[Current cam combustion chamber temperature Tnow] The temperature in the combustion chamber 23 of the current cam Cnow.
[Current cam combustion chamber pressure Pnow]... Pressure in the combustion chamber 23 of the current cam Cnow.
[Current cam residual gas ratio Gnow] A residual gas ratio in the combustion chamber 23 of the current cam Cnow.

[1] “Correction of MBT ignition timing based on pressure change in combustion chamber”
When the current cam Cnow deviates from the optimum cam Cbst, the optimum cam combustion chamber pressure Pbst and the current cam combustion chamber pressure Pnow are determined according to the difference between the optimum cam intake valve opening timing IVObst and the current cam intake valve opening timing IVOnow. There is a difference between them. Further, a difference occurs between the optimum cam combustion chamber pressure Pbst and the current cam combustion chamber pressure Pnow according to the difference between the optimum cam intake valve closing timing IVCbst and the current cam intake valve closing timing IVCnow.

  Therefore, in order to set an appropriate MBT ignition timing when the current cam Cnow deviates from the optimum cam Cbst, the difference between the optimum cam combustion chamber pressure Pbst and the current cam combustion chamber pressure Pnow is grasped. It is necessary to set the MBT ignition timing in consideration of the difference.

  In the present embodiment, as the index values of the optimum cam combustion chamber pressure Pbst and the current cam combustion chamber pressure Pnow, the pressure in the combustion chamber 23 when the piston 22 reaches the compression top dead center in a state where the mixture is not ignited. (Compression end pressure) is used.

  Then, the change amount of the compression end pressure (IVO compression end pressure change amount) when the intake valve opening timing IVO changes from the optimal cam intake valve opening timing IVObst to the current cam intake valve opening timing IVOnow, and the intake valve closing timing. Based on the amount of change in the compression end pressure when the IVC changes from the optimum cam intake valve closing timing IVCbst to the current cam intake valve closing timing IVCnow (IVC compression end pressure change amount), the optimum cam Cbst changes to the current cam Cnow. A change amount of the compression end pressure accompanying the change (a pressure change amount in the combustion chamber 23) is calculated.

  By correcting the MBT ignition timing of the optimum cam Cbst based on this change amount, the deviation of the MBT ignition timing of the optimum cam Cbst from the optimum value caused by the pressure change in the combustion chamber 23 is compensated. ing.

[2] “Correction of knock limit ignition timing based on temperature change in combustion chamber”
When the current cam Cnow deviates from the optimum cam Cbst, the optimum cam combustion chamber temperature Tbst and the current cam combustion chamber temperature Tnow are changed according to the difference between the optimum cam intake valve opening timing IVObst and the current cam intake valve opening timing IVOnow. There is a difference between them. Further, a difference occurs between the optimum cam combustion chamber temperature Tbst and the current cam combustion chamber temperature Tnow according to the difference between the optimum cam intake valve closing timing IVCbst and the current cam intake valve closing timing IVCnow.

  Therefore, in order to set an appropriate knock limit ignition timing when the current cam Cnow deviates from the optimum cam Cbst, the difference between the optimum cam combustion chamber temperature Tbst and the current cam combustion chamber temperature Tnow is grasped. In consideration of this difference, it is necessary to set the knock limit ignition timing.

  In the present embodiment, as the index values of the optimum cam combustion chamber temperature Tbst and the current cam combustion chamber temperature Tnow, the temperature in the combustion chamber 23 when the piston 22 reaches the compression top dead center in a state where the air-fuel mixture is not ignited. (Compression end temperature) is used.

  Then, the change amount of the compression end temperature (IVO compression end temperature change amount) when the intake valve opening timing IVO changes from the optimal cam intake valve opening timing IVObst to the current cam intake valve opening timing IVOnow, and the intake valve closing timing. Based on the change amount of the compression end temperature (IVC compression end temperature change amount) when IVC changes from the optimal cam intake valve closing timing IVCbst to the current cam intake valve closing timing IVCnow, the optimum cam Cbst changes to the current cam Cnow. A change amount of the compression end temperature accompanying the change (a temperature change amount in the combustion chamber 23) is calculated.

  By correcting the knock limit ignition timing of the optimum cam Cbst based on this change amount, the deviation from the optimum value caused by the temperature change in the combustion chamber 23 is compensated for the knock limit ignition timing of the optimum cam Cbst. I am doing so.

[3] “Correction of MBT / knock limit ignition timing based on change in residual gas ratio”
When the current cam Cnow deviates from the optimum cam Cbst, the difference between the optimum cam overlap amount OVLPbst and the current cam overlap amount OVLPnow is between the optimum cam residual gas rate Gbst and the current cam residual gas rate Gnow. There is a difference.

  Therefore, in order to set an appropriate MBT / knock limit ignition timing when the current cam Cnow deviates from the optimum cam Cbst, the difference between the optimum cam residual gas rate Gbst and the current cam residual gas rate Gnow is grasped. In consideration of this difference, it is necessary to set the MBT / knock limit ignition timing.

  In the present embodiment, the ratio (overlap ratio) between the optimal cam overlap amount OVLPbst and the current cam overlap amount OVLPnow is used as an index value of the difference between the optimal cam residual gas rate Gbst and the current cam residual gas rate Gnow. I have to.

  Based on the overlap ratio, the overlap correction amount (correction amount for the optimal cam overlap amount OVLPbst) included in the MBT ignition timing of the optimal cam Cbst is converted into a correction amount corresponding to the current cam overlap amount OVLPnow. Through this correction amount, the MBT / knock limit ignition timing of the optimum cam Cbst is corrected. As a result, the MBT / knock limit ignition timing is compensated for a deviation from the optimum value caused by the difference between the optimum cam residual gas rate Gbst and the current cam residual gas rate Gnow.

<Overview of ignition timing setting process>
In this embodiment, the base ignition timing is set through the “base ignition timing setting process” (FIG. 15).

9 and 10 show the structure of the “base ignition timing setting process”.
The “base ignition timing setting process” includes the following processes.
[FIG. 24] Current cam MBT ignition timing setting process.
[FIG. 33] Current cam knock limit ignition timing setting processing.
[FIG. 17]... Compression end pressure change amount calculation process [1].
[FIG. 20]... Compression end pressure change amount calculation process [2].
[FIG. 27]... Compression end temperature change calculation process [1].
[FIG. 30]... Compression end temperature change calculation process [2].
[FIG. 23] ... Overlap ratio calculation processing.

The “current cam MBT ignition timing setting process” includes the following processes.
[FIG. 25]... First MBT correction amount calculation processing.
[FIG. 26] Second MBT correction amount calculation processing.

The “current cam knock limit ignition timing setting process” includes the following processes. [FIG. 34]... First knock limit correction amount calculation processing.
[FIG. 35] Second knock limit correction amount calculation processing.

The “compression end pressure change amount calculation process [1]” includes the following processes.
[FIG. 18]... IVO compression end pressure change calculation process [1].
[FIG. 19]... IVC compression end pressure change amount calculation process [1].

The “compression end pressure change amount calculation process [2]” includes the following processes.
[FIG. 21]... IVO compression end pressure change calculation process [2].
[FIG. 22]... IVC compression end pressure change amount calculation process [2].

The “compression end temperature change calculation process [1]” includes the following processes.
[FIG. 28]... IVO compression end temperature change calculation process [1].
[FIG. 29]... IVC compression end temperature change calculation process [1].

The “compression end temperature change calculation process [2]” includes the following processes.
[FIG. 31]... IVO compression end temperature change calculation process [2].
[FIG. 32]... IVC compression end temperature change calculation process [2].

With reference to FIGS. 9-12, the outline | summary of said each process is demonstrated.
11 and 12 show the relationship between the parameters calculated through the above processes.
[1] “Base ignition timing setting process”
In this process, the current cam MBT ignition timing MBTnow calculated through the “current cam MBT ignition timing setting process” and the current cam knock limit ignition timing TKnow calculated through the “current cam knock limit ignition timing setting process” are retarded. Is set as the base ignition timing BseF.

[Base ignition timing BseF] An ignition timing at which the occurrence of knocking is suppressed and the output torque and the fuel consumption rate are the best in the operation state in which the cam Cnow is currently selected.
[Current cam MBT ignition timing MBTnow] An ignition timing at which the output torque and the fuel consumption rate are the best in the operation state in which the current cam Cnow is selected.

  [Current cam knock limit ignition timing TKnow]... The most advanced ignition timing among the ignition timings in which the occurrence of knocking can be suppressed in the operation state in which the current cam Cnow is selected.

[2] “Current cam MBT ignition timing setting process”
In this processing, based on the first MBT correction amount MBTcompnb calculated through the “first MBT correction amount calculation processing”, the second MBT correction amount MBTOVLPnb calculated through the “second MBT correction amount calculation processing”, and the optimal cam MBT ignition timing MBTbst. The current cam MBT ignition timing MBTnow is calculated.

  [Optimum cam MBT ignition timing MBTbst] An ignition timing at which the output torque and the fuel consumption rate are the best in the operation state in which the optimal cam Cbst is selected. The optimum cam MBT ignition timing MBTbst corresponds to the first MBT ignition timing.

[First MBT correction amount MBTcompnb] A correction amount of the optimal cam MBT ignition timing MBTbst corresponding to the pressure difference in the combustion chamber 23 between the optimal cam Cbst and the current cam Cnow.
[Second MBT correction amount MBTOVLPnb]... Correction amount of the optimal cam MBT ignition timing MBTbst according to the difference in the residual gas rate between the optimal cam Cbst and the current cam Cnow.

[3] “First MBT correction amount calculation process”
In this process, the first MBT correction amount MBTcompnb is calculated based on the current cam total pressure change amount compALLnb calculated through the “compression end pressure change amount calculation process [1]”.

  [Current cam total pressure change amount compALLnb]... An estimated value of the change amount of the compression end pressure when the valve characteristic changes from the optimum cam Cbst to the current cam Cnow. The current cam total pressure change amount compALLnb corresponds to the state change amount.

[4] “Second MBT correction amount calculation process”
In this process, the overlap MBT correction amount MBTOVLPbst is extracted from the optimum cam MBT ignition timing MBTbst through the initial cam MBT ignition timing MBTdfl and the initial cam MBT correction amount MBTcompdb. Then, the second MBT correction amount MBTOVLPnb is calculated based on the overlap MBT correction amount MBTOVLPbst and the ignition timing correction ratio MBTTKratio.

  [Initial cam MBT ignition timing MBTdfl] An ignition timing at which the output torque and the fuel consumption rate are the best in the operation state in which the initial cam Cdfl is selected. The initial cam MBT ignition timing MBTdfl corresponds to the second MBT ignition timing.

  [Initial cam MBT correction amount MBTcompdb] A correction amount of the initial cam MBT ignition timing MBTdfl corresponding to the pressure difference (initial cam total pressure change amount compALLdb) in the combustion chamber 23 between the optimum cam Cbst and the initial cam Cdfl.

  [Initial cam total pressure change amount compALLdb]... Estimated value of the change amount of the compression end pressure caused by the change of the valve characteristic from the optimum cam Cbst to the initial cam Cdfl. The initial cam total pressure change amount compALLdb corresponds to the open / close state change amount.

  [Overlap MBT correction amount MBTOVLPbst] A correction amount of the MBT ignition timing according to the valve overlap amount (residual gas ratio) of the optimum cam Cbst. The optimum cam MBT ignition timing MBTbst indicates a value adapted including this correction amount.

  [Ignition timing correction ratio MBTTKratio] A correction coefficient for converting the ignition timing correction amount of the optimum cam Cbst into an ignition timing correction amount corresponding to the valve overlap amount of the current cam Cnow.

[5] “Knock limit ignition timing setting process”
In this process, the first knock limit correction amount TKtempnb calculated through the “first knock limit correction amount calculation process”, the second knock limit correction amount TKOVLPnb calculated through the “second knock limit correction amount calculation process”, and the optimum Based on the cam knock limit ignition timing TKbst, the current cam knock limit ignition timing TKnow is calculated.

  [Optimum cam knock limit ignition timing TKbst]... The most advanced ignition timing among the ignition timings in which the occurrence of knocking can be suppressed in the operating state in which the optimal cam Cbst is selected. The optimal cam knock limit ignition timing TKbst corresponds to the first knock limit ignition timing.

  [First knock limit correction amount TKtempnb] A correction amount of the optimal cam knock limit ignition timing TKbst corresponding to the temperature difference in the combustion chamber 23 between the optimal cam Cbst and the current cam Cnow.

  [Second knock limit correction amount TKOVLPnb]... A correction amount of the optimal cam knock limit ignition timing TKbst corresponding to the difference in valve overlap amount between the optimal cam Cbst and the current cam Cnow.

[6] “First knock limit correction amount calculation process”
In this process, the first knock limit correction amount TKtempnb is calculated based on the current cam total temperature change amount tempALLnb calculated through the “compression end temperature change amount calculation process [1]”.

  [Current cam total temperature change amount tempALLnb] An estimated value of the change amount of the compression end temperature due to the change of the valve characteristic from the optimum cam Cbst to the current cam Cnow. Note that the current cam total temperature change amount tempALLnb corresponds to the state change amount.

[7] “Second knock limit correction amount calculation process”
In this process, the overlap knock limit correction amount TKOVLPbst is extracted from the optimum cam knock limit ignition timing TKbst through the initial cam knock limit ignition timing TKdfl and the initial cam knock limit correction amount TKtempdb. Then, the second knock limit correction amount TKOVLPnb is calculated based on the overlap knock limit correction amount TKOVLPbst and the ignition timing correction ratio MBTTKratio.

  [Overlap knock limit correction amount TKOVLPbst]... Knock limit ignition timing correction amount according to the valve overlap amount of the optimum cam Cbst. The overlap knock limit correction amount TKOVLPbst indicates a value that is adapted including this correction amount.

  [Initial cam knock limit ignition timing TKdfl]... The most advanced ignition timing among the ignition timings in which the occurrence of knocking can be suppressed in the operating state in which the initial cam Cdfl is selected. The initial cam knock limit ignition timing TKdfl corresponds to the second knock limit ignition timing.

  [Initial cam knock limit correction amount TKtempdb] A correction amount of the initial cam knock limit ignition timing TKdfl corresponding to the temperature difference (initial cam total temperature change amount tempALLdb) in the combustion chamber 23 between the optimum cam Cbst and the initial cam Cdfl.

  [Initial cam total temperature change amount tempALLdb]... Estimated value of the change amount of the compression end temperature due to the change of the valve characteristic from the optimum cam Cbst to the initial cam Cdfl. The initial cam total temperature change amount tempALLdb corresponds to the open / close state change amount.

[8] “Compression end pressure change calculation process [1]”
In this process, the current cam IVO pressure change amount compIVOnb calculated through the “IVO compression end pressure change calculation process [1]” and the current cam IVC pressure calculated through the “IVC compression end pressure change calculation process [1]”. A current cam total pressure change amount compALLnb is calculated based on the change amount compIVCnb.

  [Current cam IVO pressure change amount compIVOnb] The intake valve opening timing IVO is the optimal cam Cbst opening timing (optimal cam intake valve opening timing IVObst) to the current cam Cnow opening timing (current cam intake valve opening timing IVOnow). Estimated amount of change in compression end pressure due to change to.

  [Current cam IVC pressure change amount compIVCnb] The intake valve closing timing IVC changes from the closing timing of the optimal cam Cbst (optimal cam intake closing timing IVCbst) to the closing timing of the current cam Cnow (current cam intake closing timing IVCnow). Estimated amount of change in compression end pressure due to change to.

[9] “IVO compression end pressure change calculation process [1]”
In this process, the current cam IVO pressure change amount compIVOnb is calculated based on the first reference IVO pressure change amount compIVObt and the second reference IVO pressure change amount compIVOnt.

  [First reference IVO pressure change amount compIVObt]... The intake valve opening timing IVO changes from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the optimal cam Cbst (optimum cam intake valve opening timing IVObst). ) Estimated value of the amount of change in compression end pressure associated with the change to. The first reference IVO pressure change amount compIVObt corresponds to the first valve opening state change amount.

  [Second reference IVO pressure change amount compIVOnt]... The intake valve opening timing IVO changes from the opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the opening timing of the current cam Cnow (current cam intake valve opening timing IVOnow). ) Estimated value of the amount of change in compression end pressure associated with the change to. Note that the second reference IVO pressure change amount compIVOnt corresponds to the second valve opening state change amount.

[10] “IVC compression end pressure change calculation process [1]”
In this process, the current cam IVC pressure change amount compIVCnb is calculated based on the first reference IVC pressure change amount compIVCbt and the second reference IVC pressure change amount compIVCnt.

  [First reference IVC pressure change amount compIVCbt] The intake valve closing timing IVC changes from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the optimal cam Cbst (optimal cam intake closing timing IVCbst). ) Estimated amount of change in compression end pressure due to change to. The first reference IVC pressure change amount compIVCbt corresponds to the first valve closing state change amount.

  [Second reference IVC pressure change amount compIVCnt]... The intake valve closing timing IVC changes from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the current cam Cnow (current cam intake closing timing IVCnow). ) Estimated value of the amount of change in compression end pressure associated with the change to. The second reference IVC pressure change amount compIVCnt corresponds to the second valve closing state change amount.

[11] “Compression end pressure change calculation process [2]”
In this process, the initial cam IVO pressure change amount compIVOdb calculated through the “IVO compression end pressure change calculation process [2]” and the initial cam IVC pressure calculated through the “IVC compression end pressure change calculation process [2]”. Based on the change amount compIVCdb, an initial cam total pressure change amount compALLdb is calculated.

  [Initial cam IVO pressure change amount compIVOdb]... The intake valve opening timing IVO is from the optimal cam Cbst valve opening timing (optimal cam intake valve opening timing IVObst) to the initial cam Cdfl valve opening timing (initial cam intake valve opening timing IVOdfl). Estimated amount of change in compression end pressure due to change to. The initial cam IVO pressure change amount compIVOdb corresponds to the valve opening side state change amount.

  [Initial cam IVC pressure change amount compIVCdb]... The intake valve closing timing IVC is changed from the optimal cam Cbst closing timing (optimal cam intake closing timing IVCbst) to the initial cam Cdfl closing timing (initial cam intake closing timing IVCdfl). Estimated amount of change in compression end pressure due to change to. The initial cam IVC pressure change amount compIVCdb corresponds to the valve closing side state change amount.

[12] “IVO compression end pressure change calculation process [2]”
In this process, the initial cam IVO pressure change amount compIVOdb is calculated based on the first reference IVO pressure change amount compIVObt and the third reference IVO pressure change amount compIVOdt.

  [First reference IVO pressure change amount compIVObt]... The intake valve opening timing IVO changes from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the optimal cam Cbst (optimum cam intake valve opening timing IVObst). ) Estimated value of the amount of change in compression end pressure associated with the change to.

  [Third reference IVO pressure change amount compIVOdt] The intake valve opening timing IVO is from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the initial cam Cdfl (initial cam intake valve opening timing IVOdfl). ) Estimated value of the amount of change in compression end pressure associated with the change to.

[13] “IVC compression end pressure change calculation process [2]”
In this process, the initial cam IVC pressure change amount compIVCdb is calculated based on the first reference IVC pressure change amount compIVCbt and the third reference IVC pressure change amount compIVCdt.

  [First reference IVC pressure change amount compIVCbt] The intake valve closing timing IVC changes from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the optimal cam Cbst (optimal cam intake closing timing IVCbst). ) Estimated value of the amount of change in compression end pressure associated with the change to.

  [Third reference IVC pressure change amount compIVCdt] The intake valve closing timing IVC changes from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the initial cam Cdfl (initial cam intake closing timing IVCdfl). ) Estimated value of the amount of change in compression end pressure associated with the change to.

[14] “Compression end temperature change calculation process [1]”
In this process, the current cam IVO temperature change amount tempIVOnb calculated through the “IVO compression end temperature change calculation process [1]” and the current cam IVC temperature calculated through the “IVC compression end temperature change calculation process [1]”. A current cam total temperature change amount tempALLnb is calculated based on the change amount tempIVCnb.

  [Current cam IVO temperature change amount tempIVOnb] The intake valve opening timing IVO is the optimal cam Cbst opening timing (optimal cam intake valve opening timing IVObst) to the current cam Cnow opening timing (current cam intake valve opening timing IVOnow). Estimated amount of change in compression end temperature due to change to.

  [Current cam IVC temperature change amount tempIVCnb] The intake valve closing timing IVC changes from the closing timing of the optimal cam Cbst (optimal cam intake closing timing IVCbst) to the closing timing of the current cam Cnow (current cam intake closing timing IVCnow). Estimated amount of change in compression end temperature due to change to.

[15] “IVO compression end temperature change calculation process [1]”
In this process, the current cam IVO temperature change amount tempIVOnb is calculated based on the first reference IVO temperature change amount tempIVObt and the second reference IVO temperature change amount tempIVOnt.

  [First reference IVO temperature change amount tempIVObt]... The intake valve opening timing IVO changes from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the optimal cam Cbst (optimum cam intake valve opening timing IVObst). ) Estimated value of the amount of change in compression end temperature due to the change to.

  [Second reference IVO temperature change amount tempIVOnt] ... The intake valve opening timing IVO is from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the current cam Cnow (current cam intake valve opening timing IVOnow). ) Estimated value of the amount of change in compression end temperature due to the change to.

[16] “IVC compression end temperature change calculation process [1]”
In this process, the current cam IVC temperature change amount tempIVCnb is calculated based on the first reference IVC temperature change amount tempIVCbt and the second reference IVC temperature change amount tempIVCnt.

  [First reference IVC temperature change amount tempIVCbt] The intake valve closing timing IVC is changed from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the optimal cam Cbst (optimal cam intake closing timing IVCbst). ) Estimated value of the amount of change in compression end temperature due to the change to.

  [Second reference IVC temperature change amount tempIVCnt]... The intake valve closing timing IVC changes from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the current cam Cnow (current cam intake closing timing IVCnow). ) Estimated value of the amount of change in compression end temperature due to the change to.

[17] “Compression end temperature change calculation process [2]”
In this process, the initial cam IVO temperature change amount tempIVOdb calculated through the “IVO compression end temperature change calculation process [2]” and the initial cam IVC temperature calculated through the “IVC compression end temperature change calculation process [2]”. Based on the change amount tempIVCdb, the initial cam total temperature change amount tempALLdb is calculated.

  [Initial cam IVO temperature change amount tempIVOdb]... The intake valve opening timing IVO is from the optimal cam Cbst valve opening timing (optimal cam intake valve opening timing IVObst) to the initial cam Cdfl valve opening timing (initial cam intake valve opening timing IVOdfl). Estimated amount of change in compression end temperature due to change to. The initial cam IVO temperature change amount tempIVOdb corresponds to the valve opening side state change amount.

  [Initial Cam IVC Temperature Change Amount tempIVCdb]... The intake valve closing timing IVC is from the optimal cam Cbst closing timing (optimal cam intake closing timing IVCbst) to the initial cam Cdfl closing timing (initial cam intake closing timing IVCdfl). Estimated amount of change in compression end temperature due to change to. The initial cam IVC temperature change amount tempIVCdb corresponds to the valve closing side state change amount.

[18] “IVO compression end temperature change calculation process [2]”
In this process, the initial cam IVO temperature change amount tempIVOdb is calculated based on the first reference IVO temperature change amount tempIVObt and the third reference IVO temperature change amount tempIVOdt.

  [First reference IVO temperature change amount tempIVObt]... The intake valve opening timing IVO changes from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the optimal cam Cbst (optimum cam intake valve opening timing IVObst). ) Estimated value of the amount of change in compression end temperature due to the change to.

  [Third reference IVO temperature change amount tempIVOdt] The intake valve opening timing IVO is from the valve opening timing of the reference cam Ctdc (reference cam intake valve opening timing IVOtdc) to the valve opening timing of the initial cam Cdfl (initial cam intake valve opening timing IVOdfl). ) Estimated value of the amount of change in compression end temperature due to the change to.

[19] “IVC compression end temperature change calculation process [2]”
In this process, the initial cam IVC temperature change amount tempIVCdb is calculated based on the first reference IVC temperature change amount tempIVCbt and the third reference IVC temperature change amount tempIVCdt.

  [First reference IVC temperature change amount tempIVCbt] The intake valve closing timing IVC is changed from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the optimal cam Cbst (optimal cam intake closing timing IVCbst). ) Estimated value of the amount of change in compression end temperature due to the change to.

  [Third reference IVC temperature change amount tempIVCdt] The intake valve closing timing IVC changes from the closing timing of the reference cam Ctdc (reference cam intake closing timing IVCtdc) to the closing timing of the initial cam Cdfl (initial cam intake closing timing IVCdfl). ) Estimated value of the amount of change in compression end temperature due to the change to.

[20] “Overlap ratio calculation process”
In this process, the ratio (overlap ratio OVLPratio) between the optimum cam overlap amount OVLPbst and the current cam overlap amount OVLPnow is calculated.

[Optimum cam overlap amount OVLPbst] The valve overlap amount of the optimum cam Cbst.
[Current cam overlap amount OVLPnow] ... The valve overlap amount of the current cam Cnow.

<Driving mode of variable valve mechanism>
Here, prior to detailed description of the base ignition timing setting process, a control mode of the variable valve mechanism 5 will be described with reference to FIGS. 13 and 14.

[1] "Variable valve mechanism drive process"
This process is executed at predetermined intervals through the electronic control unit 9 during operation of the engine 1.
[Step S10] "Target cam setting process" is executed. Through this process, the valve characteristic (target cam Ctrg) corresponding to the operating state of the engine 1 is set.

[Step S20] It is determined whether or not the current cam Cnow matches the target cam Ctrg. In this process, the current intake valve timing INVT, exhaust valve timing EXVT, and intake maximum valve lift amount INVL are compared with the intake valve timing INVT, exhaust valve timing EXVT, and intake maximum valve lift amount INVL of the target cam Ctrg, The above determination is performed based on this result.
When the current cam Cnow matches the target cam Ctrg, the process proceeds to step S30.
When the current cam Cnow does not coincide with the target cam Ctrg, the process proceeds to step S40.

  [Step S30] The drive states of the intake valve timing variable mechanism 51, the exhaust valve timing variable mechanism 52, and the intake maximum valve lift amount variable mechanism 53 are maintained. That is, the intake valve timing INVT, the exhaust valve timing EXVT, and the maximum intake valve lift amount INVL are maintained in the current state.

  [Step S40] The intake valve timing variable mechanism 51, the exhaust valve timing variable mechanism 52, and the intake maximum valve lift amount variable mechanism 53 are driven so that the current cam Cnow matches the target cam Ctrg.

[2] “Target cam setting process”
This process is executed as the process of step S10 of the “variable valve mechanism driving process”.
[Step S12] It is determined whether or not the engine 1 has been warmed up.
When the engine 1 has not been warmed up, the process proceeds to step S14.
When the engine 1 has been warmed up, the process proceeds to step S16.

[Step S14] The initial cam Cdfl is set as the target cam Ctrg.
[Step S16] It is determined whether or not there is an interrupt request for the setting of the target cam Ctrg. That is, when setting the target cam Ctrg, it is determined whether or not there is a request that needs to be handled with priority over the request for the fuel consumption rate. In addition, as a request | requirement which should respond with priority, the request | requirement regarding the response property of the intake air amount mentioned above is mentioned, for example.
When there is no interrupt request for the setting of the target cam Ctrg, the process proceeds to step S18.
When there is an interrupt request for setting the target cam Ctrg, the process proceeds to step S1A.

[Step S18] The optimum cam Cbst corresponding to the required intake air amount GAreq is set as the target cam Ctrg.
[Step S1A] The valve characteristic corresponding to the interrupt request is set as the target cam Ctrg.

<Base ignition timing setting mode>
The electronic control unit 9 sets the base ignition timing at every predetermined period during the operation of the engine 1. The base ignition timing is set through one of the following processes (A) to (C) according to the current cam Cnow.

  (A) When the current cam Cnow matches the optimum cam Cbst, that is, when the MBT / knock limit ignition timing suitable for the current cam Cnow can be selected from the optimum cam Cbst and the MBT / knock limit ignition timing of the initial cam Cdfl. Of the optimum cam MBT ignition timing MBTbst and the optimum cam knock limit ignition timing TKbst, the retarded ignition timing is set as the base ignition timing BseF.

  (B) When the current cam Cnow coincides with the initial cam Cdfl, the ignition timing on the retard side of the initial cam MBT ignition timing MBTdfl and the initial cam knock limit ignition timing TKdfl is set as the base ignition timing BseF.

  (C) When the current cam Cnow does not coincide with either the optimum cam Cbst or the initial cam Cdfl, that is, the MBT / knock limit ignition timing adapted to the current cam Cnow is determined from the MBT / knock limit ignition timing of the optimum cam Cbst and the initial cam Cdfl. When the selection cannot be made, the base ignition timing BseF is set through the “base ignition timing setting process” shown in FIGS. 15 and 16.

<Base ignition timing setting process: FIG. 15 / FIG. 16>
[Step S100] For the optimal cam Cbst that is the current cam Cnow and the target cam Ctrg, the valve opening timing of the intake valve 35 (intake valve opening timing IVO), the valve closing timing of the intake valve 35 (intake valve closing timing IVC), And the valve closing timing (exhaust valve closing timing EVC) of the exhaust valve 36 is calculated. In this process, the intake valve opening timing IVO, the intake valve closing timing IVC, and the exhaust valve closing timing EVC are calculated based on the following [A] and [B].
[A] The present intake valve timing INVT, exhaust valve timing EXVT, and intake maximum valve lift amount INVL (intake valve operating angle INCAM) detected through each sensor.
[B] Relationship between the maximum intake valve lift amount INVL and the intake valve working angle INCAM stored in advance in the electronic control unit 9 (the relationship shown in FIG. 4).

  [Step S200] "Compression end pressure change calculation process [1]" (FIG. 17) is executed. Through this process, an estimated value of the change amount of the compression end pressure (current cam total pressure change amount compALLnb) when the valve characteristic changes from the optimum cam Cbst to the current cam Cnow is calculated.

  [Step S300] "Compression end pressure change calculation process [2]" (FIG. 20) is executed. Through this processing, an estimated value of the amount of change in the compression end pressure (initial cam total pressure change amount compALLdb) due to the change in the valve characteristic from the optimum cam Cbst to the initial cam Cdfl is calculated.

  [Step S400] "Overlap ratio calculation processing" (FIG. 23) is executed. Through this process, the ratio (overlap ratio OVL Ratio) between the optimum cam overlap amount OVLPbst and the current cam overlap amount OVLPnow is calculated.

  [Step S500] "Current cam MBT ignition timing setting process" (FIG. 24) is executed. Through this process, the ignition timing (current cam MBT ignition timing MBTnow) at which the output torque of the engine 1 and the fuel consumption rate are the best in the current cam Cnow operation state is calculated.

  [Step S600] "Compression end temperature change calculation process [1]" (FIG. 27) is executed. Through this processing, an estimated value of the change amount of the compression end temperature (current cam total temperature change amount tempALLnb) due to the change of the valve characteristic from the optimum cam Cbst to the current cam Cnow is calculated.

  [Step S700] "Compression end temperature change calculation process [2]" (FIG. 30) is executed. Through this processing, an estimated value of the change amount of the compression end temperature (initial cam total temperature change amount tempALLdb) due to the change of the valve characteristic from the optimum cam Cbst to the initial cam Cdfl is calculated.

  [Step S800] "Current cam knock limit ignition timing setting process" (FIG. 33) is executed. Through this process, the most advanced ignition timing (current cam knock limit ignition timing TKnow) is calculated among the ignition timings at which knocking of the engine 1 can be suppressed in the current cam Cnow operation state.

[Step S900] Of the current cam MBT ignition timing MBTnow and the current cam knock limit ignition timing TKnow, the ignition timing on the retard side is set as the base ignition timing BseF. That is, the following processing

BseF ← min {MBTnow, TKnow}

Through the base ignition timing BseF.

<Compression end pressure change calculation process [1]: FIG. 17>
This process is executed as the process of step S200 of the “base ignition timing setting process”.
[Step S210] "IVO compression end pressure change amount calculation process [1]" (FIG. 18) is executed. Through this process, the estimated value of the change amount of the compression end pressure (current cam IVO pressure change amount compIVOnb) due to the change of the intake valve opening timing IVO from the optimal cam intake valve opening timing IVObst to the current cam intake valve opening timing IVOnow. Is calculated.

  [Step S220] "IVC compression end pressure change amount calculation process [1]" (FIG. 19) is executed. Through this process, the estimated value of the change amount of the compression end pressure (current cam IVC pressure change amount compIVCnb) when the intake valve closing timing IVC is changed from the optimal cam intake valve closing timing IVCbst to the current cam intake valve closing timing IVCnow. Is calculated.

[Step S230] Based on the current cam IVO pressure change amount compIVOnb and the current cam IVC pressure change amount compIVCnb, a current cam total pressure change amount compALLnb is calculated. That is, the following processing

compALLnb ← compIVOnb + compIVCnb

Then, the cam total pressure change amount compALLnb is calculated.

<IVO compression end pressure change calculation process [1]: FIG. 18>
This process is executed as the process of step S210 of the “compression end pressure change amount calculation process [1]”.

  [Step S212] An estimated value of the change amount of the compression end pressure (the first reference IVO pressure change amount compIVObt when the intake valve opening timing IVO changes from the reference cam intake valve opening timing IVOtdc to the optimum cam intake valve opening timing IVObst). ) Is calculated. Here, the first reference IVO pressure change amount compIVObt is calculated through the following processes [1] to [4].

  [1] By applying the reference cam intake valve opening timing IVOtdc and the current engine speed NE to the IVO compression end pressure calculation map (FIG. 36), the intake valve opening timing IVO is set to the reference cam intake valve opening timing IVOtdc. The estimated value of the compression end pressure at that time (reference cam IVO compression end pressure compIVOtdc) is calculated.

  [2] Applying the optimum cam intake valve opening timing IVObst and the current engine speed NE to the IVO compression end pressure calculation map (FIG. 36), the intake valve opening timing IVO is set to the optimum cam intake valve opening timing IVObst. The estimated value of the compression end pressure at that time (optimal cam IVO compression end pressure compIVObst) is calculated.

[3] The difference between the optimum cam IVO compression end pressure compIVObst and the reference cam IVO compression end pressure compIVOtdc (optimum-reference IVO pressure change amount ΔcompIVObt) is calculated. That is, the following processing

ΔcompIVObt ← compIVObst-compIVOtdc

Then, the optimal-reference IVO pressure change amount ΔcompIVObt is calculated.

[4] The first reference IVO pressure change amount compIVObt is calculated based on the optimal-reference cam IVO pressure change amount ΔcompIVObt and the intake air rate KL. That is, the following processing

compIVObt ← ΔcompIVObt × (KL / 100)

Then, the first reference IVO pressure change amount compIVObt is calculated.

  The intake air rate KL indicates the ratio of the current intake air amount GA to the maximum air amount that can be taken into the engine 1 (maximum intake air amount GAmax). That is, the value calculated through “GA / GAmax” is shown. The intake air rate KL corresponds to the load factor of the engine 1.

  Since the relationship between the intake valve opening timing IVO and the compression end pressure when the intake air ratio KL is 100% is set in the IVO compression end pressure calculation map, the optimum-reference IVO pressure change amount ΔcompIVObt is suctioned By multiplying the air rate KL (a dimensionless value), the amount of change in the compression end pressure corresponding to the current intake air rate KL can be calculated.

FIG. 37 shows the relationship between the intake valve opening timing IVO and the compression end pressure compIVO at the same engine speed NE.
As the intake valve opening timing IVO is retarded on the ATDC side, the intake valve 35 is opened in a state in which the negative pressure in the combustion chamber 23 is larger, so that the intake valve opening timing IVO depends on the retardation of the intake valve opening timing IVO. As a result, the compression end pressure compIVO increases.

  On the other hand, the compression end pressure compIVO (pressure in the combustion chamber 23) changes under the influence of the intake pulsation according to the engine speed NE. For this reason, the magnitude of the compression end pressure compIVO with respect to the intake valve opening timing IVO differs for each engine speed NE. Note that the change tendency of the compression end pressure compIVO with respect to the intake valve opening timing IVO at the same engine speed NE is common to any engine speed NE.

  Therefore, in the present embodiment, the relationship between the intake valve opening timing IVO and the compression end pressure compIVO for each engine rotation speed NE is grasped in advance, and the intake valve opening timing IVO and the engine rotation speed NE are parameters of the compression end pressure compIVO. As shown in FIG. 36, an IVO compression end pressure calculation map (FIG. 36) is set.

  In the IVO compression end pressure calculation map, the compression end pressure compIVO of each intake valve opening timing IVO is set as a relative value with respect to the compression end pressure compIVO of the reference cam intake valve opening timing IVOtdc (0 kPa in the map). When calculating the compression end pressure compIVO through the IVO compression end pressure calculation map, if the intake valve opening timing IVO is on the BTDC side, the intake valve opening timing IVO is regarded as “0 deg (TDC)” and the compression end pressure is calculated. CompIVO is calculated.

  [Step S214] An estimated value of the amount of change in the compression end pressure (second reference IVO pressure change amount compIVnt) when the intake valve opening timing IVO changes from the reference cam intake valve opening timing IVOtdc to the current cam intake valve opening timing IVOnow. ) Is calculated. Here, the second reference IVO pressure change amount compIVOnt is calculated through the following processes [1] to [3].

  [1] By applying the current cam intake valve opening timing IVOnow and the current engine speed NE to the IVO compression end pressure calculation map (FIG. 36), the intake valve opening timing IVO is set to the current cam intake valve opening timing IVOnow. The estimated value of the compression end pressure at this time (current cam IVO compression end pressure compIVOnow) is calculated.

[2] The difference between the current cam IVO compression end pressure compIVOnow and the reference cam IVO compression end pressure compIVOtdc (current-reference IVO pressure change amount ΔcompIVOnt) is calculated. That is, the following processing

ΔcompIVOn ← compIVOnnow-compIVOtdc

Then, the present-reference IVO pressure change amount ΔcompIVOnt is calculated.

[3] The second reference IVO pressure change amount compIVOnt is calculated on the basis of the current-reference IVO pressure change amount ΔcompIVOnt and the intake air rate KL. That is, the following processing

compIVOnt ← ΔcompIVOnt × (KL / 100)

Then, the second reference IVO pressure change amount compIVOnt is calculated.

[Step S216] A difference between the second reference IVO pressure change amount compIVOnt and the first reference IVO pressure change amount compIVObt (current cam IVO pressure change amount compIVOnb) is calculated. That is, the following processing

compIVOnb <-compIVOnt-compIVObt

Then, the current cam IVO pressure change amount compIVOnb is calculated.

<IVC compression end pressure change calculation process [1]: FIG. 19>
This process is executed as the process of step S220 of the “compression end pressure change amount calculation process [1]”.

  [Step S222] An estimated value of the change amount of the compression end pressure (the first reference IVC pressure change amount compIVCbt when the intake valve closing timing IVC changes from the reference cam intake valve closing timing IVCtdc to the optimum cam intake valve closing timing IVCbst. ) Is calculated. Here, the first reference IVC pressure change amount compIVCbt is calculated through the following processes [1] to [4].

  [1] Applying the reference cam intake valve closing timing IVCtdc and the current engine speed NE to the IVC compression end pressure calculation map (FIG. 38), the intake valve closing timing IVC is set to the reference cam intake valve closing timing IVCtdc. The estimated value of the compression end pressure at this time (reference cam IVC compression end pressure compIVCtdc) is calculated.

  [2] Applying the optimum cam intake valve closing timing IVCbst and the current engine speed NE to the IVC compression end pressure calculation map (FIG. 38), the intake valve closing timing IVC is set to the optimum cam intake valve closing timing IVCbst. The estimated value of the compression end pressure at that time (optimum cam IVC compression end pressure compIVCbst) is calculated.

[3] The difference between the optimum cam IVC compression end pressure compIVCbst and the reference cam IVC compression end pressure compIVCtdc (optimum-reference IVC pressure change amount ΔcompIVCbt) is calculated. That is, the following processing

ΔcompIVCbt ← compIVCbst-compIVCtdc

Then, the optimal-reference IVC pressure change amount ΔcompIVCbt is calculated.

[4] The first reference IVC pressure change amount compIVCbt is calculated based on the optimum-reference IVC pressure change amount ΔcompIVCbt and the intake air rate KL. That is, the following processing

compIVCbt ← ΔcompIVCbt × (KL / 100)

Then, the first reference IVC pressure change amount compIVCbt is calculated.

  In the IVC compression end pressure calculation map, since the relationship between the intake valve closing timing IVC and the compression end pressure when the intake air ratio KL is 100% is set, the intake to the optimum-reference IVC pressure change amount ΔcompIVCbt is set. By multiplying the air rate KL (a dimensionless value), the amount of change in the compression end pressure corresponding to the current intake air rate KL can be calculated.

FIG. 39 shows the relationship between the intake valve closing timing IVC and the compression end pressure compIVC at the same engine speed NE.
[A] When the intake valve closing timing IVC is set to the maximum filling valve closing timing IVCmax, the flow velocity of air with respect to the intake valve closing timing IVC is maximized, so that the compression end pressure compIVC becomes the largest.

  [B] In the region where the intake valve closing timing IVC is on the more advanced side than the maximum charging valve closing timing IVCmax, as the intake valve closing timing IVC is advanced based on the maximum charging valve closing timing IVCmax, Since the degree of increase in pressure becomes small, the compression end pressure compIVC becomes small according to the advance angle of the intake valve closing timing IVC.

  [C] In the region where the intake valve closing timing IVC is retarded from the maximum filling valve closing timing IVCmax, the combustion chamber 23 increases as the intake valve closing timing IVC is retarded with reference to the maximum filling valve closing timing IVCmax. Since the actual compression ratio of the air-fuel mixture becomes smaller, the compression end pressure compIVC becomes smaller according to the retardation of the maximum filling valve closing timing IVCmax.

  On the other hand, the compression end pressure compIVC changes under the influence of the intake pulsation according to the engine speed NE. For this reason, the magnitude of the compression end pressure compIVC with respect to the intake valve closing timing IVC differs for each engine speed NE. Note that the change tendency (the above [A] to [C]) of the compression end pressure compIVC with respect to the intake valve closing timing IVC at the same engine speed NE is common to any engine speed NE.

  Therefore, in the present embodiment, the relationship between the intake valve closing timing IVC and the compression end pressure compIVC for each engine rotation speed NE is grasped in advance, and the intake valve closing timing IVC and the engine rotation speed NE are set as parameters of the compression end pressure compIVC. The IVC compression end pressure calculation map (FIG. 38) is set.

  In the IVC compression end pressure calculation map, the compression end pressure compIVC of each intake valve closing timing IVC is set as a relative value with respect to the compression end pressure compIVC (0 kPa in the map) of the maximum filling valve closing timing IVCmax.

  [Step S224] An estimated value of the amount of change in the compression end pressure due to the change in the intake valve closing timing IVC from the reference cam intake valve closing timing IVCtdc to the current cam intake valve closing timing IVCnow (second reference IVC pressure change amount compIVCnt ) Is calculated. Here, the second reference IVC pressure change amount compIVCnt is calculated through the following processes [1] to [3].

  [1] Applying the current cam intake valve closing timing IVCnow and the current engine speed NE to the IVC compression end pressure calculation map (FIG. 38), the intake valve closing timing IVC is set to the current cam intake valve closing timing IVCnow. The estimated value of the compression end pressure (current cam IVC compression end pressure compIVCnow) is calculated.

[2] The difference (current-reference IVC pressure change amount ΔcompIVCnt) between the current cam IVC compression end pressure compIVCnow and the reference cam IVC compression end pressure compIVCtdc is calculated. That is, the following processing

ΔcompIVCnt ← compIVCnow-compIVCtdc

Then, the current-reference IVC pressure change amount ΔcompIVCnt is calculated.

[3] The second reference IVC pressure change amount compIVCnt is calculated based on the current-reference IVC pressure change amount ΔcompIVCnt and the intake air rate KL. That is, the following processing

compIVCnt ← ΔcompIVCnt × (KL / 100)

Then, the second reference IVC pressure change amount compIVCnt is calculated.

[Step S226] The difference (current cam IVC pressure change amount compIVCnb) between the second reference IVC pressure change amount compIVCnt and the first reference IVC pressure change amount compIVCbt is calculated. That is, the following processing

compIVCnb ← compIVCnt-compIVCbt

Then, the current cam IVC pressure change amount compIVCnb is calculated.

<Compression end pressure change calculation process [2]: FIG. 20>
This process is executed as the process of step S300 of the “base ignition timing setting process”.
[Step S310] "IVO compression end pressure change calculation process [2]" (FIG. 21) is executed. Through this process, the estimated value of the change amount of the compression end pressure (initial cam IVO pressure change amount compIVOdb) when the intake valve opening timing IVO is changed from the optimal cam intake valve opening timing IVObst to the initial cam intake valve opening timing IVOdfl. Is calculated.

  [Step S320] "IVC compression end pressure change amount calculation process [2]" (FIG. 22) is executed. Through this process, the estimated value of the change amount of the compression end pressure (initial cam IVC pressure change amount compIVCdb) due to the change of the intake valve closing timing IVC from the optimum cam intake valve closing timing IVCbst to the initial cam intake valve closing timing IVCdfl. Is calculated.

[Step S330] The initial cam total pressure change amount compALLdb is calculated based on the initial cam IVO pressure change amount compIVOdb and the initial cam IVC pressure change amount compIVCdb. That is, the following processing

compALLdb ← compIVOdb + compIVCdb

Then, the initial cam total pressure change amount compALLdb is calculated.

<IVO compression end pressure change calculation process [2]: FIG. 21>
This process is executed as the process of step S310 of the “compression end pressure change amount calculation process [2]”.

  [Step S312] An estimated value of the amount of change in the compression end pressure (the third reference IVO pressure change amount compIVOdt when the intake valve opening timing IVO changes from the reference cam intake valve opening timing IVOtdc to the initial cam intake valve opening timing IVOdfl. ) Is calculated. Here, the third reference IVO pressure change amount compIVOdt is calculated through the following processes [1] to [3].

  [1] By applying the initial cam intake valve opening timing IVOdfl and the current engine speed NE to the IVO compression end pressure calculation map (FIG. 36), the intake valve opening timing IVO is set to the initial cam intake valve opening timing IVOdfl. The estimated value of the compression end pressure at this time (current cam IVO compression end pressure compIVOdfl) is calculated.

[2] The difference between the initial cam IVO compression end pressure compIVOdfl and the reference cam IVO compression end pressure compIVOtdc (initial-reference IVO pressure change amount ΔcompIVOdt) is calculated. That is, the following processing

ΔcompIVOdt ← compIVOdfl-compIVOtdc

Then, the initial-reference IVO pressure change amount ΔcompIVOdt is calculated.

[3] A third reference IVO pressure change amount compIVOdt is calculated based on the initial-reference IVO pressure change amount ΔcompIVOdt and the intake air rate KL. That is, the following processing

compIVOdt ← ΔcompIVOdt × (KL / 100)

Then, the third reference IVO pressure change amount compIVOdt is calculated.

[Step S314] A difference (initial cam IVO pressure change amount compIVOdb) between the third reference IVO pressure change amount compIVOdt and the first reference IVO pressure change amount compIVObt is calculated. That is, the following processing

compIVOdb ← compIVOdt-compIVObt

Then, the initial cam IVO pressure change amount compIVOdb is calculated.

<IVC compression end pressure change calculation process [2]: FIG. 22>
This process is executed as the process of step S320 of the “compression end pressure change amount calculation process [2]”.

  [Step S322] Estimated value of change amount of compression end pressure due to change of intake valve closing timing IVC from reference cam intake valve closing timing IVCtdc to initial cam intake valve closing timing IVCdfl (third reference IVC pressure change amount compIVCdt ) Is calculated. Here, the third reference IVC pressure change amount compIVCdt is calculated through the following processes [1] to [3].

  [1] By applying the initial cam intake valve closing timing IVCdfl and the current engine speed NE to the IVC compression end pressure calculation map (FIG. 38), the intake valve closing timing IVC is set to the initial cam intake valve closing timing IVCdfl. The estimated value of the compression end pressure at that time (initial cam IVC compression end pressure compIVCdfl) is calculated.

[2] The difference between the initial cam IVC compression end pressure compIVCdfl and the reference cam IVC compression end pressure compIVCtdc (initial-reference IVC pressure change amount ΔcompIVCdt) is calculated. That is, the following processing

ΔcompIVCdt ← compIVCdfl-compIVCtdc

Then, the initial-reference IVC pressure change amount ΔcompIVCdt is calculated.

[3] The third reference IVC pressure change amount compIVCdt is calculated based on the initial-reference IVC pressure change amount ΔcompIVCdt and the intake air rate KL. That is, the following processing

compIVCdt ← ΔcompIVCdt × (KL / 100)

Then, the third reference IVC pressure change amount compIVCdt is calculated.

[Step S324] A difference (initial cam IVC pressure change amount compIVCdb) between the third reference IVC pressure change amount compIVCdt and the first reference IVC pressure change amount compIVCbt is calculated. That is, the following processing

compIVCdb ← compIVCdt-compIVCbt

Then, the initial cam IVC pressure change amount compIVCdb is calculated.

<Overlap ratio calculation processing: FIG. 23>
This process is executed as the process of step S400 of the “ignition timing setting process”.
[Step S410] The optimum cam overlap amount OVLPbst is calculated. The optimum cam overlap amount OVLPbst is calculated through one of the following processes [1] and [2] according to the optimum cam intake valve opening timing IVObst.

[1] “When optimal cam intake valve opening timing IVObst is BTDC”
The crank angle from the optimum cam intake valve opening timing IVObst to the optimum cam exhaust valve closing timing EVCbst is calculated as the optimum cam overlap amount OVLPbst. That is, the following processing

OVLPbst ← IVObst + EVCbst

Then, the optimum cam overlap amount OVLPbst is calculated. For example, when the optimum cam intake valve opening timing IVObst is 10 deg (BTDC side) and the optimum cam exhaust valve closing timing EVCbst is 10 deg (ATDC side), the optimum cam overlap amount OVLPbst is “20 deg”.

[2] “When optimal cam intake valve opening timing IVObst is ATDC”
The crank angle from TDC to the optimum cam exhaust valve closing timing EVCbst is calculated as the optimum cam overlap amount OVLPbst. That is, the following processing

OVLPbst ← EVCbst

Then, the optimum cam overlap amount OVLPbst is calculated. For example, when the optimum cam intake valve opening timing IVObst is 10 deg (ATDC side) and the optimum cam exhaust valve closing timing EVCbst is 20 deg (ATDC side), the optimum cam overlap amount OVLPbst is “20 deg”.

  [Step S420] A current cam overlap amount OVLPnow is calculated. The current cam overlap amount OVLPnow is calculated through one of the following processes [1] and [2] according to the current cam intake valve opening timing IVOnow.

[1] "When the current cam intake valve opening timing IVOnow is BTDC"
The crank angle from the current cam intake valve opening timing IVOnow to the current cam exhaust valve closing timing EVCnow is calculated as the current cam overlap amount OVLPnow. That is, the following processing

OVLPnow ← IVOnow + EVCnow

Then, the current cam overlap amount OVLPnow is calculated.

[2] “When the current cam intake valve opening timing IVOnow is ATDC”
The crank angle from TDC to the current cam exhaust valve closing timing EVCnow is calculated as the current cam overlap amount OVLPnow. That is, the following processing

OVLPnow ← EVCnow

Then, the current cam overlap amount OVLPnow is calculated.

  [Step S430] The ratio (overlap ratio OVLPratio) between the optimal cam overlap amount OVLPbst and the current cam overlap amount OVLPnow is calculated. The overlap ratio OVLPratio is calculated through one of the following processes [1] and [2] according to the relationship between the optimum cam overlap amount OVLPbst and the reference overlap amount OVLPX.

[1] “When OVLPbst ≧ OVLPX”
Based on the current cam overlap amount OVLPnow and the optimum cam overlap amount OVLPbst, an overlap ratio OVL Ratio is calculated. That is, the following processing

OVLPratio ← OVLPnow / OVLPbst

Then, the overlap ratio OVL Ratio is calculated.

[2] “When OVPLbst <OVLPX”
The overlap ratio OVLPratio is set to “0”. That is, the following processing

OVLPratio ← 0

Then, the overlap ratio OVL Ratio is calculated.

  When the optimal cam overlap amount OVLPbst is equal to or larger than the reference overlap amount OVLPX, the electronic control unit 9 is in a state where the correction accuracy of the optimal cam MBT ignition timing MBTbst with respect to the optimal cam overlap amount OVLPbst can be sufficiently secured. Determination is made, and the overlap ratio OVL Ratio is calculated. That is, it is considered that the optimum cam MBTbst / optimum cam knock limit ignition timing TKbst includes an ignition timing correction amount corresponding to the valve overlap amount.

  On the contrary, when the optimum cam overlap amount OVLPbst is less than the reference overlap amount OVLPX, it is determined that the correction accuracy of the optimum cam MBT ignition timing MBTbst with respect to the optimum cam overlap amount OVLPbst cannot be sufficiently secured. The overlap ratio OVL Ratio is not calculated ("0" is set as the overlap ratio OVL Ratio). In other words, it is considered that the optimum cam MBTbst / optimum cam knock limit ignition timing TKbst does not include the ignition timing correction amount corresponding to the valve overlap amount.

<Current cam MBT ignition timing setting process: FIG. 24>
This process is executed as the process of step S500 of the “base ignition timing setting process”.
[Step S510] The optimal cam MBT ignition timing MBTbst corresponding to the current engine speed NE and the intake air ratio KL is calculated through the optimal cam MBT ignition timing calculation map (FIG. 41). FIG. 42 shows the relationship between the intake air rate KL and the optimum cam MBT ignition timing MBTbst at the same engine speed NE. In the present embodiment, each optimum cam MBT ignition timing MBTbst set in the optimum cam MBT ignition timing calculation map corresponds to a plurality of basic MBT ignition timings.

  [Step S520] “First MBT correction amount calculation processing” (FIG. 25) is executed. Through this process, a first MBT correction amount MBTcompnb, which is a correction term for the optimum cam MBT ignition timing MBTbst, is calculated.

  [Step S530] "Second MBT correction amount calculation processing" (FIG. 26) is executed. Through this process, a second MBT correction amount MBTOVLPnb, which is a correction term for the optimal cam MBT ignition timing MBTbst, is calculated.

[Step S540] An MBT ignition timing correction amount MBTnb is calculated based on the first MBT correction amount MBTcompnb and the second MBT correction amount MBTOVLPnb. That is, the following processing

MBTnb ← MBTcompnb + MBTOVLPnb

Then, the MBT ignition timing correction amount MBTnb is calculated.

[Step S550] Based on the optimum cam MBT ignition timing MBTbst and the MBT ignition timing correction amount MBTnb, a current cam MBT ignition timing MBTnow is calculated. That is, the following processing

MBTnow ← MBTbst + MBTnb

Then, the current cam MBT ignition timing MBTnow is calculated.

<First MBT Correction Amount Calculation Processing: FIG. 25>
This process is executed as the process of step S520 of the “MBT ignition timing setting process”.
[Step S522] The first MBT correction amount MBTcompnb corresponding to the current cam total pressure change amount compALLnb is calculated through the first MBT correction amount calculation map (FIG. 40).

  The first MBT correction amount calculation map includes an MBT correction amount (first MBT correction amount MBTcompnb / initial value) according to the change amount of the compression end pressure (current cam total pressure change amount compALLnb / initial cam total pressure change amount compALLdb) as follows. The cam MBT correction amount MBTcompdb) is set.

  (A) In the region where the amount of change in the compression end pressure is a positive value, that is, in the region where the current cam combustion chamber pressure Pnow is larger than the optimum cam combustion chamber pressure Pbst, the MBT correction amount is set to a negative value. . Further, the MBT correction amount is set so as to decrease (increase toward the negative side) as the change amount of the compression end pressure increases toward the positive side.

  (B) The MBT correction amount is set to a positive value in a region where the amount of change in the compression end pressure is a negative value, that is, in a region where the current cam combustion chamber pressure Pnow is smaller than the optimum cam combustion chamber pressure Pbst. . Further, the MBT correction amount is set to increase (increase to the positive side) as the change amount of the compression end pressure increases to the negative side.

  (C) When the change amount of the compression end pressure is “0”, that is, when the current cam combustion chamber pressure Pnow is equal to the optimum cam combustion chamber pressure Pbst, the MBT correction amount is set to “0”.

  The optimum cam MBT ignition timing MBTbst (MBT ignition timing correction amount MBTnb) is corrected as follows according to the current cam total pressure change amount compALLnb (steps S540 / S550).

  (A) When the current cam total pressure change amount compALLnb is a positive value, the first MBT correction amount MBTcompnb is a negative value, so the optimal cam MBT ignition timing MBTbst (MBT ignition timing correction amount MBTnb) is the first MBT correction amount MBTcompnb. Is delayed by an amount corresponding to the absolute value of.

  (B) When the current cam total pressure change amount compALLnb is a negative value, the first MBT correction amount MBTcompnb is a positive value, so that the optimal cam MBT ignition timing MBTbst (MBT ignition timing correction amount MBTnb) is the first MBT correction amount MBTcompnb. Is advanced by an amount corresponding to the absolute value of.

  (C) When the current cam total pressure change amount compALLnb is “0”, the first MBT correction amount MBTcompnb is “0”, so that the optimal cam MBT ignition timing MBTbst (MBT ignition timing correction amount MBTnb) is advanced and retarded. It is not changed to either corner.

<Second MBT Correction Amount Calculation Processing: FIG. 26>
This process is executed as the process of step S530 of the “MBT ignition timing setting process”.
[Step S532] The initial cam MBT ignition timing MBTdfl corresponding to the current engine speed NE and the intake air ratio KL is calculated through the initial cam MBT ignition timing calculation map (FIG. 43). FIG. 44 shows the relationship between the intake air rate KL and the initial cam MBT ignition timing MBTdfl at the same engine speed NE.

  [Step S534] The initial cam MBT correction amount MBTcompdb corresponding to the initial cam total pressure change amount compALLdb is calculated through the first MBT correction amount calculation map (FIG. 40).

[Step S536] An MBT ignition timing correction amount (overlap MBT correction amount MBTOVLPbst) corresponding to the optimal cam overlap amount OVLPbst is extracted from the optimal cam MBT ignition timing MBTbst. That is, the following processing

MBTOVLPbst ← MBTbst + MBTcompdb−MBTdfl

Then, the overlap MBT correction amount MBTOVLPbst is calculated.

An extraction mode of the overlap MBT correction amount MBTOVLPbst will be described.
There is the following difference between the optimum cam MBT ignition timing MBTbst and the initial cam MTB ignition timing MBTdfl.

  (A) The optimal cam MBT ignition timing MBTbst is adapted including the correction amount of the ignition timing with respect to the valve overlap amount of the optimal cam Cbst. On the other hand, the initial cam MTB ignition timing MBTdfl is adapted to a state where the valve overlap amount of the initial cam Cdfl, that is, the valve overlap amount is “0”. Therefore, there is a difference between the optimum cam MBT ignition timing MBTbst and the initial cam MBT ignition timing MBTdfl according to the valve overlap amount of the optimum cam Cbst.

  (B) The optimal cam MBT ignition timing MBTbst is adapted including the correction amount of the ignition timing with respect to the optimal cam combustion chamber pressure Pbst. On the other hand, the initial cam MBT ignition timing MBTdfl is adapted including the correction amount of the ignition timing with respect to the initial cam combustion chamber pressure Pdfl. Therefore, there is a difference between the optimum cam MBT ignition timing MBTbst and the initial cam MBT ignition timing MBTdfl according to the difference between the optimum cam combustion chamber pressure Pbst and the initial cam combustion chamber pressure Pdfl.

  Here, when the optimum cam MBT ignition timing MBTbst is used as a reference, the optimum cam MBT ignition timing MBTbst does not include the ignition timing correction amount for the pressure change in the combustion chamber 23. On the other hand, the initial cam MBT ignition timing MBTdfl includes an ignition timing correction amount (initial cam MBT correction amount MBTcompdb) corresponding to the amount of pressure change from the optimum cam combustion chamber pressure Pbst to the initial cam combustion chamber pressure Pdfl. Will be.

  Therefore, the ignition timing obtained by adding the overlap MBT correction amount MBTOVLPbst to the initial cam MBT ignition timing MBTdfl is equal to the ignition timing obtained by adding the initial cam MBT correction amount MBTcompdb to the optimum cam MBT ignition timing MBTbst.

  Therefore, by removing the initial cam MBT ignition timing MBTdfl from the ignition timing obtained by adding the initial cam MBT correction amount MBTcompdb to the optimal cam MBT ignition timing MBTbst, the correction amount corresponding to the valve overlap amount from the optimal cam MBT ignition timing MBTbst. Only can be extracted.

  [Step S538] The ignition timing correction ratio MBTTKratio corresponding to the overlap ratio OVL Ratio is calculated through the ignition timing correction ratio calculation map (FIG. 45).

The ignition timing correction ratio MBTTKratio is set in the ignition timing correction ratio calculation map as follows.
(A) In a region where the overlap ratio OVP Ratio is greater than “1”, that is, in a region where the current cam overlap amount OVLPnow is greater than the optimum cam overlap amount OVLPbst, the ignition timing correction ratio MBTTKratio is greater than “1”. Is set to Further, the ignition timing correction ratio MBTTKratio is set so as to increase as the overlap ratio OVLPratio increases.

  (B) In the region where the overlap ratio OVL Ratio is smaller than “1”, that is, in the region where the current cam overlap amount OVLPnow is smaller than the optimum cam overlap amount OVLPbst, the ignition timing correction ratio MBTTKratio is smaller than “1”. Is set to Further, the ignition timing correction ratio MBTTKratio is set to be smaller as the overlap ratio OVP Ratio becomes smaller.

  (C) When the overlap ratio OVLPratio is “0”, that is, when the optimum cam overlap amount OVLPbst is less than the reference overlap amount OVLPX, the ignition timing correction ratio MBTTKratio is set to “0”.

  (D) When the overlap ratio OVLPratio is “1”, that is, when the current cam overlap amount OVLPnow is equal to the optimum cam overlap amount OVLPbst, the ignition timing correction ratio MBTTKratio is set to “1”.

[Step S53A] A second MBT correction amount MBTOVLPnb is calculated based on the overlap MBT correction amount MBTOVLPbst and the MBT ignition timing correction amount MBTTKratio. That is, the following processing

MBTOVLPnb ← MBTOVLPbst × (MBTTKratio-1)

Then, the second MBT correction amount MBTOVLPnb is calculated.

  The optimum cam MBT ignition timing MBTbst (MBT ignition timing correction amount MBTnb) is corrected as follows according to the overlap ratio OVL Ratio (steps S540 / S550).

  (A) Since the second MBT correction amount MBTOVLPnb is a positive value when the overlap ratio OVP Ratio is greater than “1”, the optimal cam MBT ignition timing MBTbst advances by an amount corresponding to the absolute value of the second MBT correction amount MBTOVLPnb. Horned.

  (B) Since the second MBT correction amount MBTOVLPnb has a negative value when the overlap ratio OVLPRatio is smaller than “1”, the optimal cam MBT ignition timing MBTbst is delayed by an amount corresponding to the absolute value of the second MBT correction amount MBTOVLPnb. Horned.

  (C) Since the second MBT correction amount MBTOVLPnb becomes a negative overlap MBT correction amount MBTOVLPbst when the overlap ratio OVLPLatio is “0”, the optimal cam MBT ignition timing MBTbst is the overlap MBT correction amount MBTOVLPbst (second MBT correction amount). It is retarded by an amount corresponding to the absolute value of MBTOVLPnb).

  (D) When the overlap ratio OVLPratio is “1”, the second MBT correction amount MBTOVLPnb is “0”, so the optimal cam MBT ignition timing MBTbst is not changed to either the advance side or the retard side.

<Compression end temperature change calculation process [1]: FIG. 27>
This process is executed as the process of step S600 of the “base ignition timing setting process”.
[Step S610] “IVO compression end temperature change calculation process [1]” (FIG. 28) is executed. Through this process, the estimated value of the change amount of the compression end temperature (the current cam IVO temperature change amount tempIVOnb) due to the change of the intake valve opening timing IVO from the optimal cam intake valve opening timing IVObst to the current cam intake valve opening timing IVOnow. Is calculated.

  [Step S620] "IVC compression end temperature change calculation process [1]" (FIG. 29) is executed. Through this process, the estimated value of the change amount of the compression end temperature (the current cam IVC temperature change amount tempIVOnb) due to the change of the intake valve close timing IVC from the optimum cam intake valve close timing IVCbst to the current cam intake valve close timing IVCnow. Is calculated.

[Step S630] A current cam total temperature change amount tempALLnb is calculated based on the current cam IVO temperature change amount tempIVOnb and the current cam IVC temperature change amount tempIVCnb. That is, the following processing

tempALLnb ← tempIVOnb + tempIVCnb

Then, the current cam total temperature change amount tempALLnb is calculated.

<IVO compression end temperature change calculation process [1]: FIG. 28>
This process is executed as the process of step S610 of the “compression end temperature change calculation process [1]”.

  [Step S612] Estimated value of change amount of compression end temperature due to change of intake valve opening timing IVO from reference cam intake valve opening timing IVOtdc to optimal cam intake valve opening timing IVObst (first reference IVO temperature change amount tempIVObt ) Is calculated. Here, the first reference IVO temperature change amount tempIVObt is calculated through the following processes [1] to [4].

  [1] By applying the reference cam intake valve opening timing IVOtdc and the current engine speed NE to the IVO compression end temperature calculation map (FIG. 46), the intake valve opening timing IVO is set to the reference cam intake valve opening timing IVOtdc. The estimated value of the compression end temperature (reference cam IVO compression end temperature tempIVOtdc) is calculated.

  FIG. 47 shows the relationship between the intake valve opening timing IVO and the compression end temperature tempIVO at the same engine speed NE. Similar to the IVO compression end pressure calculation map, the IVO compression end temperature calculation map of FIG. 46 is set based on the relationship between the intake valve opening timing IVO and the compression end temperature tempIVO for each engine speed NE. Further, in the IVO compression end temperature calculation map, the compression end temperature tempIVC of each intake valve opening timing IVO is set as a relative value with respect to the compression end temperature tempIVO (0 ° C. in the map) of the reference cam intake valve opening timing IVOtdc. .

  [2] Applying the optimum cam intake valve opening timing IVObst and the current engine speed NE to the IVO compression end temperature calculation map (FIG. 46), the intake valve opening timing IVO is set to the optimum cam intake valve opening timing IVObst. The estimated value of the compression end temperature (optimal cam IVO compression end temperature tempIVObst) is calculated.

[3] The difference between the optimum cam IVO compression end temperature tempIVObst and the reference cam IVO compression end temperature tempIVOtdc (optimum-reference IVO temperature change ΔtempIVObt) is calculated. That is, the following processing

△ tempIVObt ← tempIVObst-tempIVOtdc

Then, the optimum-reference IVO temperature change amount ΔtempIVObt is calculated.

[4] The first reference IVO temperature change amount tempIVObt is calculated based on the optimum-reference IVO temperature change amount ΔtempIVObt and the intake air rate KL. That is, the following processing

tempIVObt ← ΔtempIVObt × (KL / 100)

Then, the first reference IVO temperature change amount tempIVObt is calculated.

  Since the relationship between the intake valve opening timing IVO and the compression end temperature when the intake air ratio KL is 100% is set in the IVO compression end temperature calculation map, the intake to the optimal-reference IVO temperature change amount ΔtempIVObt is taken. By multiplying the air rate KL (a dimensionless value), the compression end temperature change amount corresponding to the current intake air rate KL can be calculated.

  [Step S614] An estimated value of the amount of change in the compression end temperature (the second reference IVO temperature change amount tempIVOnt) when the intake valve opening timing IVO has changed from the reference cam intake valve opening timing IVOtdc to the current cam intake valve opening timing IVOnow. ) Is calculated. Here, the second reference IVO temperature change amount tempIVOnt is calculated through the following processes [1] to [3].

  [1] Applying the current cam intake valve opening timing IVOnow and the current engine speed NE to the IVO compression end temperature calculation map (FIG. 46), the intake valve opening timing IVO is set to the current cam intake valve opening timing IVOnow. The estimated value of the compression end temperature at this time (current cam IVO compression end temperature tempIVOnow) is calculated.

[2] The difference between the current cam IVO compression end temperature tempIVOnnow and the reference cam IVO compression end temperature tempIVOtdc (current-reference IVO temperature change amount ΔtempIVOnt) is calculated. That is, the following processing

△ tempIVOn ← tempIVOnnow-tempIVOtdc

Then, the present-reference IVO temperature change amount ΔtempIVOnt is calculated.

[3] The second reference IVO temperature change amount tempIVOnt is calculated based on the current-reference IVO temperature change amount ΔtempIVOnt and the intake air rate KL. That is, the following processing

tempIVOnt ← △ tempIVOnt × (KL / 100)

Then, the second reference IVO temperature change amount tempIVOnt is calculated.

[Step S616] A difference between the second reference IVO temperature change amount tempIVOnt and the first reference IVO temperature change amount tempIVObt (current cam IVO temperature change amount tempIVOnb) is calculated. That is, the following processing

tempIVOnb ← tempIVOnt-tempIVObt

Then, the current cam IVO temperature change amount tempIVOnb is calculated.

<IVC compression end temperature change calculation process [1]: FIG. 29>
This process is executed as the process of step S620 of the “compression end temperature change calculation process [1]”.

  [Step S622] An estimated value of the change amount of the compression end temperature (the first reference IVC temperature change amount tempIVCbt associated with the change of the intake valve close timing IVC from the reference cam intake valve close timing IVCtdc to the optimum cam intake valve close timing IVCbst) ) Is calculated. Here, the first reference IVC temperature change amount tempIVCbt is calculated through the following processes [1] to [4].

  [1] The reference cam intake valve closing timing IVCtdc and the current engine speed NE are applied to the IVC compression end temperature calculation map (FIG. 48) to set the intake valve closing timing IVC to the reference cam intake valve closing timing IVCtdc. The estimated value of the compression end temperature (reference cam IVC compression end temperature tempIVCtdc) is calculated.

  FIG. 49 shows the relationship between the intake valve closing timing IVC and the compression end temperature tempIVC at the same engine speed NE. Similar to the IVC compression end pressure calculation map, the IVC compression end temperature calculation map of FIG. 48 is set based on the relationship between the intake valve closing timing IVC and the compression end temperature tempIVC for each engine speed NE. In the IVC compression end temperature calculation map, the compression end temperature tempIVC of each intake valve closing timing IVC is set as a relative value with respect to the compression end temperature tempIVO (0 ° C. in the map) of the maximum filling valve closing timing IVCmax.

  [2] Applying the optimum cam intake valve closing timing IVCbst and the current engine speed NE to the IVC compression end temperature calculation map (FIG. 48), the intake valve closing timing IVC is set to the optimum cam intake valve closing timing IVCbst. The estimated value of the compression end temperature at that time (optimum cam IVC compression end temperature tempIVCbst) is calculated.

[3] The difference (optimum-reference IVC temperature change amount ΔtempIVCbt) between the optimum cam IVC compression end temperature tempIVCbst and the reference cam IVC compression end temperature tempIVCtdc is calculated. That is, the following processing

△ tempIVCbt ← tempIVCbst-tempIVCtdc

Then, the optimum-reference IVC temperature change amount ΔtempIVCbt is calculated.

[4] The first reference IVC temperature change amount tempIVCbt is calculated based on the optimum-reference IVC temperature change amount ΔtempIVCbt and the intake air rate KL. That is, the following processing

tempIVCbt ← ΔtempIVCbt × (KL / 100)

Then, the first reference IVC temperature change amount tempIVCbt is calculated.

  In the IVC compression end temperature calculation map, since the relationship between the intake valve closing timing IVC and the compression end temperature when the intake air ratio KL is 100% is set, the intake to the optimal-reference IVC temperature change amount ΔtempIVCbt is set. By multiplying the air rate KL (a dimensionless value), the compression end temperature change amount corresponding to the current intake air rate KL can be calculated.

  [Step S624] Estimated value of change amount of compression end temperature due to change of intake valve closing timing IVC from reference cam intake valve closing timing IVCtdc to current cam intake valve closing timing IVCnow (second reference IVC temperature change amount tempIVCnt ) Is calculated. Here, the second reference IVC temperature change amount tempIVCnt is calculated through the following processes [1] to [3].

  [1] The current cam intake valve closing timing IVCnow and the current engine speed NE are applied to the IVC compression end temperature calculation map (FIG. 48) to set the intake valve closing timing IVC to the current cam intake valve closing timing IVCnow. The estimated value of the compression end temperature (current cam IVC compression end temperature tempIVCnow) is calculated.

[2] A difference (current-reference IVC temperature change amount ΔtempIVCnt) between the current cam IVC compression end temperature tempIVCnow and the reference cam IVC compression end temperature tempIVCtdc is calculated. That is, the following processing

△ tempIVCnt ← tempIVCnow-tempIVCtdc

Then, the current-reference IVC temperature change amount ΔtempIVCnt is calculated.

[3] The second reference IVC temperature change amount tempIVCnt is calculated based on the current-reference IVC temperature change amount ΔtempIVCnt and the intake air rate KL. That is, the following processing

tempIVCnt ← △ tempIVCnt × (KL / 100)

Then, the second reference IVC temperature change amount tempIVCnt is calculated.

[Step S626] A difference (current cam IVC temperature change amount tempIVCnb) between the second reference IVC temperature change amount tempIVCnt and the first reference IVC temperature change amount tempIVCbt is calculated. That is, the following processing

tempIVCnb ← tempIVCnt-tempIVCbt

Then, the current cam IVC temperature change amount tempIVCnb is calculated.

<Compression end temperature change calculation process [2]: FIG. 30>
This process is executed as the process of step S700 of the “base ignition timing setting process”.
[Step S710] “IVO compression end temperature change calculation process [2]” (FIG. 31) is executed. Through this process, the estimated value of the change amount of the compression end temperature (the initial cam IVO temperature change amount tempIVOdb) due to the change of the intake valve opening timing IVO from the optimum cam intake valve opening timing IVObst to the initial cam intake valve opening timing IVOdfl. Is calculated.

  [Step S720] "IVC compression end temperature change calculation process [2]" (FIG. 32) is executed. Through this process, the estimated value of the change amount of the compression end temperature (initial cam IVC temperature change amount tempIVCdb) due to the change of the intake valve close timing IVC from the optimal cam intake valve close timing IVCbst to the initial cam intake valve close timing IVCdfl. Is calculated.

[Step S730] The initial cam total temperature change amount tempALLdb is calculated based on the initial cam IVO temperature change amount tempIVOdb and the initial cam IVC temperature change amount tempIVCdb. That is, the following processing

tempALLdb ← tempIVOdb + tempIVCdb

Then, the initial cam total temperature change amount tempALLdb is calculated.

<IVO compression end temperature change calculation process [2]: FIG. 31>
This process is executed as the process of step S710 of the “compression end temperature change calculation process [2]”.

  [Step S712] An estimated value of the amount of change in the compression end temperature (the third reference IVO temperature change amount tempIVOdt when the intake valve opening timing IVO changes from the reference cam intake valve opening timing IVOtdc to the initial cam intake valve opening timing IVOdfl. ) Is calculated. Here, the third reference IVO temperature change amount tempIVOdt is calculated through the following processes [1] to [3].

  [1] By applying the initial cam intake valve opening timing IVOdfl and the current engine speed NE to the IVO compression end temperature calculation map (FIG. 46), the intake valve opening timing IVO is set to the initial cam intake valve opening timing IVOdfl. The estimated value of the compression end temperature at that time (initial cam IVO compression end temperature tempIVOdfl) is calculated.

[2] The difference between the initial cam IVO compression end temperature tempIVOdfl and the reference cam IVO compression end temperature tempIVOtdc (initial-reference IVO temperature change amount ΔtempIVodt) is calculated. That is, the following processing

△ tempIVOdt ← tempIVOdfl-tempIVOtdc

Then, the initial-reference IVO temperature change amount ΔtempIVodt is calculated.

[3] A third reference IVO temperature change amount tempIVodt is calculated based on the initial-reference IVO temperature change amount ΔtempIVODt and the intake air rate KL. That is, the following processing

tempIVOdt ← △ tempIVOdt × (KL / 100)

Then, the third reference IVO temperature change amount tempIVodt is calculated.

[Step S714] A difference (initial cam IVO temperature change amount tempIVOdb) between the third reference IVO temperature change amount tempIVOdt and the first reference IVO temperature change amount tempIVObt is calculated. That is, the following processing

tempIVOdb ← tempIVOdt-tempIVObt

Then, the initial cam IVO temperature change amount tempIVOdb is calculated.

<IVC compression end temperature change calculation process [2]: FIG. 32>
This process is executed as the process of step S720 of the “compression end temperature change calculation process [2]”.

  [Step S722] An estimated value of the amount of change in the compression end temperature due to the change in the intake valve closing timing IVC from the reference cam intake valve closing timing IVCtdc to the initial cam intake valve closing timing IVCdfl (third reference IVC temperature change amount tempIVCdt ) Is calculated. Here, the third reference IVC temperature change amount tempIVCdt is calculated through the following processes [1] to [3].

  [1] By applying the initial cam intake valve closing timing IVCdfl and the current engine speed NE to the IVC compression end temperature calculation map (FIG. 48), the intake valve closing timing IVC is set to the initial cam intake valve closing timing IVCdfl. The estimated value of the compression end temperature (initial cam IVC compression end temperature tempIVCdfl) is calculated.

[2] The difference (initial-reference IVC temperature change amount ΔtempIVCdt) between the initial cam IVC compression end temperature tempIVCdfl and the reference cam IVC compression end temperature tempIVCtdc is calculated. That is, the following processing

ΔtempIVCdt ← tempIVCdfl-tempIVCtdc

Then, the initial-reference IVC temperature change amount ΔtempIVCdt is calculated.

[3] The third reference IVC temperature change amount tempIVCdt is calculated based on the initial-reference IVC temperature change amount ΔtempIVCdt and the intake air rate KL. That is, the following processing

tempIVCdt ← ΔtempIVCdt × (KL / 100)

Then, the third reference IVC temperature change amount tempIVCdt is calculated.

[Step S724] The difference between the third reference IVC temperature change amount tempIVCdt and the first reference IVC temperature change amount tempIVCbt (initial cam IVC temperature change amount tempIVCdb) is calculated. That is, the following processing

tempIVCdb ← tempIVCdt-tempIVCbt

Then, the initial cam IVC temperature change amount tempIVCdb is calculated.

<Current cam knock limit ignition timing setting process: FIG. 33>
This process is executed as the process of step S800 of the “base ignition timing setting process”.
[Step S810] The optimal cam knock limit ignition timing TKbst corresponding to the current engine speed NE and the intake air ratio KL is calculated through the optimal cam knock limit ignition timing calculation map (FIG. 51). FIG. 52 shows the relationship between the intake air ratio KL and the optimum cam knock limit ignition timing TKbst at the same engine speed NE. In the present embodiment, each optimum cam knock limit ignition timing TKbst set in the optimum cam knock limit ignition timing calculation map corresponds to a plurality of basic knock limit ignition timings.

  [Step S820] "First knock limit correction amount calculation processing" (FIG. 34) is executed. Through this process, a first knock limit correction amount TKtempnb, which is a correction term for the optimal cam knock limit ignition timing TKbst, is calculated.

  [Step S830] "Second knock limit correction amount calculation processing" (FIG. 35) is executed. Through this process, a second knock limit correction amount TKOVLPnb, which is a correction term for the optimal cam knock limit ignition timing TKbst, is calculated.

[Step S840] The knock limit ignition timing correction amount TKnb is calculated based on the first knock limit correction amount TKtempnb and the second knock limit correction amount TKOVLPnb. That is, the following processing

TKnb ← TKtempnb + TKOVLPnb

Then, the knock limit ignition timing correction amount TKnb is calculated.

[Step S850] Based on the optimum cam knock limit ignition timing TKbst and the knock limit ignition timing correction amount TKnb, the current cam knock limit ignition timing TKnow is calculated. That is, the following processing

TKnow ← TKbst + TKnb

Then, the current cam knock limit ignition timing TKnow is calculated.

<First knock limit correction amount calculation processing: FIG. 34>
This process is executed as the process of step S820 of the “knock limit ignition timing setting process”.

  [Step S822] The first knock limit correction amount TKtempnb corresponding to the current cam total temperature change amount tempALLnb is calculated through the first knock limit correction amount calculation map (FIG. 50).

  The first knock limit correction amount calculation map includes a knock limit correction amount (first knock limit) as follows according to the amount of change in compression end temperature (current cam total temperature change amount tempALLnb / initial cam total temperature change amount tempALLdb). Correction amount TKtempnb / initial cam knock limit correction amount TKtempdb) is set.

  (A) In the region where the change amount of the compression end temperature is a positive value, that is, the region where the current cam combustion chamber temperature Tnow is higher than the optimum cam combustion chamber temperature Tbst, the knock limit correction amount is set to a negative value. Yes. Further, the knock limit correction amount is set so as to decrease (increase to the negative side) as the change amount of the compression end temperature increases to the positive side.

  (B) In the region where the change amount of the compression end temperature is a negative value, that is, the region where the current cam combustion chamber temperature Tnow is smaller than the optimum cam combustion chamber temperature Tbst, the knock limit correction amount is set to a positive value. Yes. Further, the knock limit correction amount is set to increase (increase to the positive side) as the change amount of the compression end temperature increases to the negative side.

  (C) When the change amount of the compression end temperature is “0”, that is, when the current cam combustion chamber temperature Tnow is equal to the optimum cam combustion chamber temperature Tbst, the knock limit correction amount is set to “0”.

  The optimum cam knock limit ignition timing TKbst (knock limit ignition timing correction amount TKnb) is corrected as follows according to the current cam total temperature change amount tempALLnb (steps S840 / S850).

  (A) Since the first knock limit correction amount TKtempnb is a negative value when the current cam total temperature change amount tempALLnb is a positive value, the optimal cam knock limit ignition timing TKbst (knock limit ignition timing correction amount TKnb) is the first value. The angle is retarded by an amount corresponding to the absolute value of knock limit correction amount TKtempnb.

  (B) When the current cam total temperature change amount tempALLnb is a negative value, the first knock limit correction amount TKtempnb is a positive value, so the optimal cam knock limit ignition timing TKbst (knock limit ignition timing correction amount TKnb) is the first value. The angle is advanced by an amount corresponding to the absolute value of knock limit correction amount TKtempnb.

  (C) Since the first knock limit correction amount TKtempnb is “0” when the current cam total temperature change amount tempALLnb is “0”, the optimal cam knock limit ignition timing TKbst (knock limit ignition timing correction amount TKnb) is advanced. No change is made to either the side or the retard side.

<Second knock limit correction amount calculation processing: FIG. 35>
This process is executed as the process of step S830 of the “knock limit ignition timing setting process”.

  [Step S832] The initial cam knock limit ignition timing TKdfl corresponding to the current engine speed NE and the intake air rate KL is calculated through the initial cam knock limit ignition timing calculation map (FIG. 53). FIG. 54 shows the relationship between the intake air ratio KL and the initial cam knock limit ignition timing TKdfl at the same engine speed NE.

  [Step S834] The initial cam knock limit correction amount TKtempdb corresponding to the initial cam total temperature change amount tempALLdb is calculated through the first knock limit correction amount calculation map (FIG. 50).

[Step S836] A knock limit ignition timing correction amount (overlap knock limit correction amount TKOVLPbst) corresponding to the valve overlap amount of the optimal cam Cbst is extracted from the optimal cam knock limit ignition timing TKbst. That is, the following processing

TKOVLPbst ← TKbst + TKtempdb−TKdfl

Then, the overlap knock limit correction amount TKOVLPbst is calculated.

An extraction mode of the overlap knock limit correction amount TKOVLPbst will be described.
There is the following difference between the optimal cam knock limit ignition timing TKbst and the initial cam knock limit ignition timing TKdfl.

  (A) The optimal cam knock limit ignition timing TKbst is adapted including the correction amount of the ignition timing with respect to the valve overlap amount (residual gas ratio) of the optimal cam Cbst. On the other hand, the initial cam knock limit ignition timing TKdfl is adapted to a state where the valve overlap amount of the initial cam Cdfl, that is, the valve overlap amount is “0”. Therefore, there is a difference between the optimum cam knock limit ignition timing TKbst and the initial cam knock limit ignition timing TKdfl according to the valve overlap amount of the optimum cam Cbst.

  (B) The optimal cam knock limit ignition timing TKbst is adapted including the correction amount of the ignition timing with respect to the temperature of the combustion chamber 23 of the optimal cam Cbst. On the other hand, the initial cam knock limit ignition timing TKdfl is adapted including the correction amount of the ignition timing with respect to the temperature of the combustion chamber 23 of the initial cam Cdfl. Therefore, there is a difference between the optimal cam knock limit ignition timing TKbst and the initial cam knock limit ignition timing TKdfl according to the difference between the temperature of the combustion chamber 23 of the optimal cam Cbst and the temperature of the combustion chamber 23 of the initial cam Cdfl. There is.

  Here, when the optimum cam knock limit ignition timing TKbst is used as a reference, the optimum cam knock limit ignition timing TKbst does not include the ignition timing correction amount for the temperature change of the combustion chamber 23. On the other hand, the initial cam knock limit ignition timing TKdfl includes an ignition timing correction amount (initial cam knock limit correction amount) according to the temperature change amount from the temperature of the combustion chamber 23 of the optimal cam Cbst to the temperature of the combustion chamber 23 of the initial cam Cdfl. TKtempdb) is included.

  Therefore, the ignition timing obtained by adding the overlap knock limit correction amount TKOVLPbst to the initial cam knock limit ignition timing TKdfl is equal to the ignition timing obtained by adding the initial cam knock limit correction amount TKtempdb to the optimum cam knock limit ignition timing TKbst.

  Accordingly, by removing the initial cam MBT ignition timing MBTdfl from the ignition timing obtained by adding the initial cam knock limit correction amount TKtempdb to the optimal cam knock limit ignition timing TKbst, the correction amount corresponding to the valve overlap amount from the optimal cam knock limit ignition timing TKbst. Only can be extracted.

[Step S838] Based on the overlap knock limit correction amount TKOVLPbst and the ignition timing correction ratio MBTTKratio, a second knock limit correction amount TKOVLPnb is calculated. That is, the following processing

TKOVLPnb ← TKOVLPdb × (MBTTKratio-1)

Then, the second knock limit correction amount TKOVLPnb is calculated.

  The optimal cam knock limit ignition timing TKbst (knock limit ignition timing correction amount TKnb) is corrected as follows according to the overlap ratio OVL Ratio (steps S840 / S850).

  (A) When the overlap ratio OVLPratio is greater than “1”, the second knock limit correction amount TKOVLPnb has a positive value, so the optimum cam knock limit ignition timing TKbst depends on the absolute value of the second knock limit correction amount TKOVLPnb. Is advanced by a certain amount.

  (B) When the overlap ratio OVLPratio is smaller than “1”, the second knock limit correction amount TKOVLPnb has a negative value, so the optimum cam knock limit ignition timing TKbst depends on the absolute value of the second knock limit correction amount TKOVLPnb. The amount is retarded.

  (C) When the overlap ratio OVLPratio is “0”, the second knock limit correction amount TKOVLPnb is a negative overlap knock limit correction amount TKOVLPbst, so that the optimum cam knock limit ignition timing TKbst is the overlap knock limit correction amount TKOVLPbst ( The second knock limit correction amount TKOVLPnb) is retarded by an amount corresponding to the absolute value.

  (D) When the overlap ratio OVLPratio is “1”, the second knock limit correction amount TKOVLPnb is “0”, so the optimal cam knock limit ignition timing TKbst is not changed to either the advance side or the retard side.

<Effect of embodiment>
As described above in detail, according to the engine ignition timing control apparatus according to the first embodiment, the effects listed below can be obtained.

  (1) In the present embodiment, the current cam MBT ignition timing MBTnow and the current cam knock limit ignition timing TKnow are calculated in consideration of the temperature / pressure change in the combustion chamber 23 accompanying the change in the intake valve opening timing IVO. ing. As a result, an appropriate base ignition timing BseF can be set regardless of changes in the intake valve opening timing IVO.

  (2) In the present embodiment, the current cam MBT ignition timing MBTnow and knock limit ignition timing TKnow are calculated in consideration of the temperature / pressure change in the combustion chamber 23 accompanying the change in the intake valve closing timing IVC. Yes. As a result, an appropriate base ignition timing BseF can be set regardless of changes in the intake valve closing timing IVC.

  (3) In the present embodiment, the current cam MBT ignition timing MBTnow and the knock limit ignition timing TKnow are calculated in consideration of the change in the residual gas ratio in the combustion chamber 23 accompanying the change in the valve overlap amount OVLP. . As a result, an appropriate base ignition timing BseF can be set regardless of the change in the valve overlap amount OVLP.

  (4) In this embodiment, the compression end temperature / compression end pressure is employed as the temperature / pressure index value in the combustion chamber 23, and the compression end associated with changes in the intake valve opening timing IVO and the intake valve closing timing IVC. Based on the change amount of the temperature / compression end pressure, the MBT ignition timing and the knock limit ignition timing of the optimum cam Cbst are corrected. Incidentally, it is confirmed that the compression end temperature / compression end pressure is more sensitive to changes in the intake valve opening timing IVO and the intake valve closing timing IVC than the temperature / pressure in the combustion chamber 23 at other crank angles. ing. Therefore, by adopting the above configuration, the amount of change in temperature / pressure in the combustion chamber 23 with respect to changes in the intake valve opening timing IVO and the intake valve closing timing IVC can be grasped more accurately. The timing correction accuracy can be improved.

  (5) In the present embodiment, the MBT ignition timing correction amount corresponding to the optimal cam overlap amount OVLPbst is extracted from the optimal cam MBT ignition timing MBTbst, and the MBT ignition timing corresponding to the current cam overlap amount OVLPnow is extracted through this correction amount. The amount of correction is calculated. Accordingly, it is possible to appropriately correct the MBT ignition timing with respect to the change in the valve overlap amount OVLP without previously adjusting the correction amount of the MBT ignition timing corresponding to each valve overlap amount OVLP.

  (6) In the present embodiment, the knock limit ignition timing correction amount corresponding to the optimal cam overlap amount OVLPbst is extracted from the optimal cam knock limit ignition timing TKbst, and the knock limit corresponding to the current cam overlap amount OVLPnow is extracted through this correction amount. The correction amount of the ignition timing is calculated. As a result, it is possible to appropriately correct the knock limit ignition timing with respect to the change in the valve overlap amount OVLP without previously adjusting the correction amount of the knock limit ignition timing corresponding to each valve overlap amount OVLP. .

  (7) In the present embodiment, when extracting the correction amount according to the optimum cam overlap amount OVLPbst, the initial cam MBT ignition timing MBTdfl and the initial cam knock limit ignition timing TKdfl that are preliminarily adapted to the initial cam Cdfl are used. ing. Incidentally, when calculating the correction amount according to the valve overlap amount OVLP, the ignition timing of the valve characteristic in which the valve overlap is set and the ignition timing of the valve characteristic in which the valve overlap is not set are required. In the above configuration, since the ignition timing of the initial cam Cdfl that is preliminarily adapted for when the engine 1 is cold is used, separately, the MBT ignition timing and the valve characteristics for which no valve overlap is set are used. It is no longer necessary to adapt the knock limit ignition timing.

  (8) In the present embodiment, the optimal cam MBT ignition timing MBTbst and the optimal cam knock limit ignition timing are based on the difference in the state (temperature / pressure and residual gas rate) in the combustion chamber 23 between the optimal cam Cbst and the current cam Cnow. By correcting TKbst, the MBT / knock limit ignition timing suitable for the current cam Cnow is calculated. As a result, if the MBT / knock limit ignition timing of the optimum cam Cbst and the initial cam Cdfl is previously adapted, the MBT / knock limit ignition timing suitable for other valve characteristics can be calculated. The construction of the “ignition timing setting process” can be performed more efficiently.

  (9) Even when the MBT ignition timing and knock limit ignition timing suitable for the current cam Cnow cannot be selected from the ignition timings set in the map, the optimum cam MBT ignition timing MBTbst and optimum Appropriate MBT ignition timing and knock limit ignition timing can be set through correction of the cam knock limit ignition timing TKbst. Thus, even if the current cam Cnow deviates from the optimum cam Cbst due to a difference in response between the intake valve timing variable mechanism 51 and the intake maximum valve lift amount variable mechanism 53, the base adapted to the current cam Cnow. The ignition timing can be set.

  (10) In this embodiment, the relationship between the intake valve opening timing IVO and the compression end temperature / compression end pressure is ascertained for each engine speed NE, and the change amount of the compression end temperature / compression end pressure is determined based on this relationship. I try to estimate. Since the temperature / pressure in the combustion chamber 23 changes under the influence of the intake pulsation, the compression end temperature / compression end pressure is more appropriately set by using the intake valve opening timing IVO and the engine rotational speed NE as parameters. Can be estimated.

  (11) In this embodiment, the compression end temperature / compression end pressure is corrected according to the intake air rate KL. Since the amplitude of the intake pulsation varies according to the intake air rate KL (intake air amount), the compression end temperature / compression end pressure also changes accordingly. Therefore, by adopting the above configuration, it is possible to further improve the estimation accuracy of the compression end temperature / compression end pressure.

  (12) In this embodiment, when the intake valve opening timing IVO and the exhaust valve closing timing EVC are on the ATDC side, the period from the top dead center to the exhaust valve closing timing EVC is calculated as the valve overlap amount. ing. Incidentally, when the exhaust valve closing timing EVC is on the ATDC side, the residual gas rate tends to increase even if the intake valve 35 is not opened due to an increase in the negative pressure in the combustion chamber 23 as the piston 22 descends. Show. Therefore, by calculating the valve overlap amount OVLP in the above manner, the change in the residual gas ratio can be grasped more appropriately.

  (13) In the present embodiment, when the optimum cam overlap amount OVLPbst is less than the reference overlap amount OVLPX, the overlap ratio OVL Ratio is set to “0”. Thereby, since the fall of the correction precision of the ignition timing according to the valve overlap amount is suppressed, more appropriate MBT ignition timing and knock limit ignition timing can be set.

<Example of change>
In addition, the said 1st Embodiment can also be implemented as the following forms which changed this suitably, for example.

  Prepare “IVO compression end pressure calculation map”, “IVC compression end pressure calculation map”, “IVO compression end temperature calculation map”, and “IVC compression end temperature calculation map” for each effective length of the intake pipe 33. You can also. When the effective length of the intake pipe 33 changes, the period of the intake pulsation changes accordingly, so that the temperature / pressure in the combustion chamber 23 is also affected. Therefore, by adopting the above configuration, it is possible to improve the estimation accuracy of the compression end temperature / compression end pressure.

  “IVO compression end pressure change calculation process [1]”, “IVO compression end pressure change calculation process [2]”, “IVO compression end temperature change calculation process [1]”, and “IVO compression end temperature change amount” In the calculation process [2], the amount of change in the compression end pressure / compression end temperature can be calculated based on the intake valve opening timing IVO other than the reference cam intake valve opening timing IVOtdc.

  "IVC compression end pressure change calculation process [1]", "IVC compression end pressure change calculation process [2]", "IVC compression end temperature change calculation process [1]" and "IVC compression end temperature change amount" In the calculation process [2], the amount of change in the compression end pressure / compression end temperature can be calculated based on the intake valve closing timing IVC other than the reference cam intake valve closing timing IVCtdc.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment, the change amount of the compression end pressure (first reference IVC pressure change amount bt, second reference IVC pressure change amount nt, third reference IVC pressure change amount dt with reference to the reference cam intake valve closing timing IVCtdc. ) Is calculated.

On the other hand, in the present embodiment, the amount of change in the compression end pressure is calculated based on the maximum filling valve closing timing IVCmax.
Since the maximum filling valve closing timing IVCmax corresponds to the inflection point of the change tendency of the compression end pressure (see FIG. 8), the change tendency of the compression end pressure is the same by using the maximum filling valve closing timing IVCmax as a reference. The amount of change in the compression end pressure is calculated at. Thereby, since the estimation accuracy of the amount of change in the compression end pressure is improved, the correction accuracy of the MBT ignition timing and the knock limit ignition timing can be improved.

  Hereinafter, the compression end pressure change amount calculation process and the compression end temperature change amount calculation process in the present embodiment will be described. The present embodiment is the same as the first embodiment except for the configuration described below.

<Compression end pressure change calculation process [1]: FIG. 17>
In step S220 of this process, an “IVC compression end pressure change calculation process [3]” described below is executed instead of the “IVC compression end pressure change calculation process [1]”.

<IVC compression end pressure change calculation process [3]: FIG. 55>
This process is executed as the process of step S220 of the “compression end pressure change amount calculation process [1]”.

  [Step T222] Estimated value of change amount of compression end pressure when intake valve closing timing IVC has changed from maximum filling valve closing timing IVCmax to optimum cam intake valve closing timing IVCbst (first maximum IVC pressure change amount compIVCbm) Is calculated. Here, the first maximum IVC pressure change amount compIVCbm is calculated through the following processes [1] to [4].

  [1] When the maximum charging valve closing timing IVCmax and the current engine speed NE are applied to the IVC compression end pressure calculation map (FIG. 39), the intake valve closing timing IVC is set to the maximum charging valve closing timing IVCmax. An estimated value of the compression end pressure (maximum filling IVC compression end pressure compIVCmax) is calculated.

  [2] The optimum cam intake valve closing timing IVCbst and the current engine speed NE are applied to the IVC compression end pressure calculation map (FIG. 39) to set the intake valve closing timing IVC to the optimum cam intake valve closing timing IVCbst. The estimated value of the compression end pressure at that time (optimum cam IVC compression end pressure compIVCbst) is calculated.

[3] The difference between the optimal cam IVC compression end pressure compIVCbst and the maximum filling IVC compression end pressure compIVCmax (optimal-maximum IVC pressure change amount ΔcompIVCbm) is calculated. That is, the following processing

ΔcompIVCbm ← compIVCbst-compIVCmax

Then, the optimal-maximum IVC pressure change amount ΔcompIVCbm is calculated.

[4] The first maximum IVC pressure change amount compIVCbm is calculated based on the optimum-maximum IVC pressure change amount ΔcompIVCbm and the intake air rate KL. That is, the following processing

compIVCbm ← ΔcompIVCbm × (KL / 100)

Then, the first maximum IVC pressure change amount compIVCbm is calculated. The first maximum IVC pressure change amount compIVCbm corresponds to the third valve closing state change amount.

  [Step T224] An estimated value of the change amount of the compression end pressure when the intake valve closing timing IVC changes from the maximum charging valve closing timing IVCmax to the current cam intake valve closing timing IVCnow (second maximum IVC pressure change amount compIVCnm). Is calculated. Here, the second maximum IVC pressure change amount compIVCnm is calculated through the following processes [1] to [3].

  [1] Applying the current cam intake valve closing timing IVCnow and the current engine speed NE to the IVC compression end pressure calculation map (FIG. 39), the intake valve closing timing IVC is set to the current cam intake valve closing timing IVCnow. The estimated value of the compression end pressure (current cam IVC compression end pressure compIVCnow) is calculated.

[2] The difference between the current cam IVC compression end pressure compIVCnow and the maximum filling IVC compression end pressure compIVCmax (current-maximum IVC pressure change amount ΔcompIVCnm) is calculated. That is, the following processing

△ compIVCnm ← compIVCnow-compIVCmax

Then, the present-maximum IVC pressure change amount ΔcompIVCnm is calculated.

[3] The second maximum IVC pressure change amount compIVCnm is calculated based on the current-maximum IVC pressure change amount ΔcompIVCnm and the intake air rate KL. That is, the following processing

compIVCnm ← ΔcompIVCnm × (KL / 100)

Then, the second maximum IVC pressure change amount compIVCnm is calculated. The second maximum IVC pressure change amount compIVCnm corresponds to the fourth valve closing state change amount.

[Step T226] A difference (current cam IVC pressure change amount compIVCnb) between the second maximum IVC pressure change amount compIVCnm and the first maximum IVC pressure change amount compIVCbm is calculated. That is, the following processing

compIVCnb ← compIVCnm-compIVCbm

Then, the current cam IVC pressure change amount compIVCnb is calculated.

<Compression end pressure change calculation process [2]: FIG. 20>
In the present embodiment, in step S320, “IVC compression end pressure change calculation process [4]” described below is executed instead of “IVC compression end pressure change calculation process [2]”.

<IVC compression end pressure change calculation process [4]: FIG. 56>
This process is executed as the process of step S320 of the “compression end pressure change amount calculation process [2]”.

  [Step T322] An estimated value of the amount of change in compression end pressure when the intake valve closing timing IVC changes from the maximum charging valve closing timing IVCmax to the initial cam intake valve closing timing IVCdfl (third maximum IVC pressure change amount compIVCdm). Is calculated. Here, the third maximum IVC pressure change amount compIVCdm is calculated through the following processes [1] to [3].

  [1] By applying the initial cam intake valve closing timing IVCdfl and the current engine speed NE to the IVC compression end pressure calculation map (FIG. 39), the intake valve closing timing IVC is set to the initial cam intake valve closing timing IVCdfl. The estimated value of the compression end pressure at that time (initial cam IVC compression end pressure compIVCdfl) is calculated.

[2] The difference between the initial cam IVC compression end pressure compIVCdfl and the maximum filling IVC compression end pressure compIVCmax (initial-maximum IVC pressure change amount ΔcompIVCdm) is calculated. That is, the following processing

ΔcompIVCdm ← compIVCdfl-compIVCmax

Then, the initial-maximum IVC pressure change amount ΔcompIVCdm is calculated.

[3] The third maximum IVC pressure change amount compIVCdm is calculated based on the initial-maximum IVC pressure change amount ΔcompIVCdm and the intake air rate KL. That is, the following processing

compIVCdm ← ΔcompIVCdm × (KL / 100)

Then, the third maximum IVC pressure change amount compIVCdm is calculated.

[Step T324] The difference (initial cam IVC pressure change amount compIVCdb) between the third maximum IVC pressure change amount compIVCdm and the first maximum IVC pressure change amount compIVCbm is calculated. That is, the following processing

compIVCdb ← compIVCdm-compIVCbm

Then, the initial cam IVC pressure change amount compIVCdb is calculated.

<Compression end temperature change calculation process [1]: FIG. 27>
In step S620 of this process, an “IVC compression end temperature change calculation process [3]” described below is executed instead of the “IVC compression end temperature change calculation process [1]”.

<IVC compression end temperature change calculation process [3]: FIG. 57>
This process is executed as the process of step S620 of the “compression end temperature change calculation process [1]”.

  [Step T622] Estimated value of change amount of compression end temperature (first maximum IVC temperature change amount tempIVCbm) due to change of intake valve closing timing IVC from maximum charging valve closing timing IVCmax to optimum cam intake valve closing timing IVCbst Is calculated. Here, the first maximum IVC temperature change amount tempIVCbm is calculated through the following processes [1] to [4].

  [1] When the maximum charging valve closing timing IVCmax and the current engine speed NE are applied to the IVC compression end temperature calculation map (FIG. 49), the intake valve closing timing IVC is set to the maximum charging valve closing timing IVCmax. An estimated value of the compression end temperature (maximum filling IVC compression end temperature tempIVCmax) is calculated.

  [2] The optimum cam intake valve closing timing IVCbst and the current engine speed NE are applied to the IVC compression end temperature calculation map (FIG. 49) to set the intake valve closing timing IVC to the optimum cam intake valve closing timing IVCbst. The estimated value of the compression end temperature at that time (optimum cam IVC compression end temperature tempIVCbst) is calculated.

[3] The difference between the optimum cam IVC compression end temperature tempIVCbst and the maximum filling IVC compression end temperature tempIVCmax (optimal-maximum IVC temperature change amount ΔtempIVCbm) is calculated. That is, the following processing

△ tempIVCbm ← tempIVCbst-tempIVCmax

Then, the optimum-maximum IVC temperature change amount ΔtempIVCbm is calculated.

[4] The first maximum IVC temperature change amount tempIVCbm is calculated based on the optimum-maximum IVC temperature change amount ΔtempIVCbm and the intake air rate KL. That is, the following processing

tempIVCbm ← △ tempIVCbm × (KL / 100)

Then, the first maximum IVC temperature change amount tempIVCbm is calculated.

  [Step T624] Estimated value of change amount of compression end temperature due to change of intake valve closing timing IVC from maximum filling valve closing timing IVCmax to current cam intake valve closing timing IVCnow (second maximum IVC temperature change amount tempIVCnm) Is calculated. Here, the second maximum IVC temperature change amount tempIVCnm is calculated through the following processes [1] to [3].

  [1] By applying the current cam intake valve closing timing IVCnow and the current engine speed NE to the IVC compression end temperature calculation map (FIG. 49), the intake valve closing timing IVC is set to the current cam intake valve closing timing IVCnow. The estimated value of the compression end temperature (current cam IVC compression end temperature tempIVCnow) is calculated.

[2] The difference between the current cam IVC compression end temperature tempIVCnow and the maximum filling IVC compression end temperature tempIVCmax (current-maximum IVC temperature change amount ΔtempIVCnm) is calculated. That is, the following processing

△ tempIVCnm ← tempIVCnow-tempIVCmax

Then, the current-maximum IVC temperature change amount ΔtempIVCnm is calculated.

[3] The second maximum IVC temperature change amount tempIVCnm is calculated based on the current-maximum IVC temperature change amount ΔtempIVCnm and the intake air rate KL. That is, the following processing

tempIVCnm ← △ tempIVCnm × (KL / 100)

Then, the second maximum IVC temperature change amount tempIVCnm is calculated.

[Step T626] A difference (current cam IVC temperature change amount tempIVCnb) between the second maximum IVC temperature change amount tempIVCnm and the first maximum IVC temperature change amount tempIVCbm is calculated. That is, the following processing

tempIVCnb ← tempIVCnm-tempIVCbm

Then, the current cam IVC temperature change amount tempIVCnb is calculated.

<Compression end temperature change calculation process [2]: FIG. 30>
In step S720 of this process, an “IVC compression end temperature change calculation process [4]” described below is executed instead of the “IVC compression end temperature change calculation process [2]”.

<IVC compression end temperature change calculation process [4]: FIG. 58>
This process is executed as the process of step S720 of the “compression end temperature change calculation process [2]”.

  [Step T722] Estimated value of amount of change in compression end temperature due to change in intake valve closing timing IVC from maximum charging valve closing timing IVCmax to initial cam intake valve closing timing IVCdfl (third maximum IVC temperature change amount tempIVCdm) Is calculated. Here, the third maximum IVC temperature change amount tempIVCdm is calculated through the following processes [1] to [3].

  [1] By applying the initial cam intake valve closing timing IVCdfl and the current engine speed NE to the IVC compression end temperature calculation map (FIG. 49), the intake valve closing timing IVC is set to the initial cam intake valve closing timing IVCdfl. The estimated value of the compression end temperature (initial cam IVC compression end temperature tempIVCdfl) is calculated.

[2] A difference (initial-maximum IVC temperature change amount ΔtempIVCdm) between the initial cam IVC compression end temperature tempIVCdfl and the maximum filling IVC compression end temperature tempIVCmax is calculated. That is, the following processing

△ tempIVCdm ← tempIVCdfl-tempIVCmax

Then, the initial-maximum IVC temperature change amount ΔtempIVCdm is calculated.

[3] The third maximum IVC temperature change amount tempIVCdm is calculated based on the initial-maximum IVC temperature change amount ΔtempIVCdm and the intake air rate KL. That is, the following processing

tempIVCdm ← △ tempIVCdm × (KL / 100)

Then, the third maximum IVC temperature change amount tempIVCdm is calculated.

[Step T724] A difference (initial cam IVC temperature change amount tempIVCdb) between the third maximum IVC temperature change amount tempIVCdm and the first maximum IVC temperature change amount tempIVCbm is calculated. That is, the following processing

tempIVCdb ← tempIVCdm-tempIVCbm

Then, the initial cam IVC temperature change amount tempIVCdb is calculated.

<Effect of embodiment>
As described above in detail, according to the ignition timing control apparatus for an engine according to the second embodiment, in addition to the effects (1) to (13) according to the first embodiment, the following is shown. An effect comes to be acquired.

  (14) In the present embodiment, the change amount of the compression end temperature / compression end pressure is calculated based on the maximum filling valve closing timing IVCmax. Thereby, since the estimation accuracy of the compression end temperature / compression end pressure is improved, the correction accuracy of the MBT ignition timing and the knock limit ignition timing can be improved.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG.
In the first embodiment, the first knock limit correction amount calculation map in which the first knock limit correction amount TKtempnb / initial cam knock limit correction amount TKtempdb is adapted to the current cam total temperature change amount tempALLnb / initial cam total temperature change amount tempALLdb. (FIG. 50) is stored in advance in the electronic control unit 9.

  On the other hand, in the present embodiment, the first knock limit correction in which the first knock limit correction amount TKcompnb / initial cam knock limit correction amount TKcompdb is adapted to the current cam total pressure change amount compALLnb / initial cam total pressure change amount compALLdb. The quantity calculation map [2] (FIG. 59) is stored in the electronic control device 9 in advance.

  When such a configuration is adopted, “compression end temperature change calculation [1]” (FIG. 27), “compression end temperature change calculation processing [2]” (FIG. 30), IVO compression end temperature calculation map (FIG. 46) and the IVC compression end temperature calculation map (FIG. 48) can be omitted.

<Effect of embodiment>
As described above in detail, according to the ignition timing control apparatus for an engine according to the third embodiment, in addition to the effects (1) to (13) according to the first embodiment, the following is shown. An effect comes to be acquired.

(15) According to this embodiment, the structure of the “base ignition timing setting process” can be simplified.
<Example of change>
In addition, the said 3rd Embodiment can also be implemented as the following forms which changed this suitably, for example.

The third embodiment can be applied to the second embodiment.
(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIG.

  In the first embodiment, the first MBT correction amount calculation map in which the first MBT correction amount MBTcompnb / the initial cam MBT correction amount MBTcompdb is adapted to the current cam total pressure change amount compALLnb / initial cam total pressure change amount compALLdb (FIG. 40). Is stored in the electronic control device 9 in advance.

  In contrast, in the present embodiment, the first MBT correction amount calculation map in which the first MBT correction amount MBTtempnb / the initial cam MBT correction amount MBTtempdb is adapted to the current cam total temperature change amount tempALLnb / initial cam total temperature change amount tempALLdb [ 2] (FIG. 60) is stored in advance in the electronic control unit 9.

  When such a configuration is adopted, “compression end pressure change calculation [1]” (FIG. 17), “compression end pressure change calculation processing [2]” (FIG. 20), IVO compression end pressure calculation map (FIG. 36) and the IVC compression end pressure calculation map (FIG. 38) can be omitted.

<Effect of embodiment>
As described above in detail, according to the ignition timing control apparatus for an engine according to the fourth embodiment, in addition to the effects (1) to (13) according to the first embodiment, the following is shown. An effect comes to be acquired.

(16) According to the present embodiment, the structure of the “base ignition timing setting process” can be simplified.
<Example of change>
In addition, the said 4th Embodiment can also be implemented as the following forms which changed this suitably, for example.

The fourth embodiment can be applied to the second embodiment and the third embodiment.
(Other embodiments)
In addition, elements that can be changed in common with each of the above embodiments are listed below.

Each calculation map in the “base ignition timing setting process” is not limited to the configuration exemplified in each of the above embodiments, and can be changed as appropriate.
The setting mode of the target cam Ctrg is not limited to the mode illustrated in the above embodiments, and can be changed as appropriate.

  The base ignition timing suitable for each optimum cam Cbst can be set in a map, and this map can be stored in advance in the electronic control unit 9, and the base ignition timing can be calculated through the map. Also in this case, the base ignition timing suitable for the current cam Cnow can be calculated by correcting the base ignition timing of the optimal cam Cbst in a manner according to the above embodiments. In the above configuration, the base ignition timing set in the map corresponds to a plurality of basic base ignition timings. Further, the base ignition timing adapted to the optimum cam Cbst corresponds to the first base ignition timing, and the base ignition timing adapted to the initial cam Cdfl corresponds to the second base ignition timing.

  In each of the above embodiments, the amount of change in the temperature in the combustion chamber 23 due to the residual gas is estimated based on the residual gas rate and the temperature of the exhaust port 32, and this is taken into account to correct the knock limit ignition timing. You can also Thereby, the correction accuracy of the knock limit ignition timing can be further improved.

-If it is the engine 1 provided with the variable valve mechanism 5, the structure of the engine 1 can be changed suitably.
The configuration of the variable valve mechanism 5 can be changed to a configuration including at least one of an intake valve timing variable mechanism, an exhaust valve timing variable mechanism, an intake maximum valve lift amount variable mechanism, and an exhaust maximum valve lift amount variable mechanism. it can. The exhaust maximum valve lift amount variable mechanism changes the exhaust valve working angle together with the maximum valve lift amount of the exhaust valve.

  The present invention is applied to any engine as long as the engine has a variable valve mechanism that changes at least one of the intake valve opening timing and the intake valve closing timing. can do.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder block, 21 ... Cylinder, 22 ... Piston, 23 ... Combustion chamber, 3 ... Cylinder head, 31 ... Intake port, 32 ... Exhaust port, 33 ... Intake pipe, 34 ... Exhaust pipe, 35 ... Intake Valve 36, Exhaust valve, 37 ... Ignition plug, 38 ... Throttle valve, 39 ... Port injection injector, 5 ... Variable valve mechanism, 51 ... Intake valve timing variable mechanism, 52 ... Exhaust valve timing variable mechanism, 53 ... Intake maximum Valve lift variable mechanism, 9 ... electronic control device, 91 ... rotational speed sensor, 92 ... throttle opening sensor, 93 ... air flow meter, 94 ... intake valve timing sensor, 95 ... exhaust valve timing sensor, 96 ... intake maximum valve lift Quantity sensor.

Ctrg: target cam, Cbst: optimum cam, Cdfl: initial cam, Ctdc: reference cam, Cnow: current cam.
NE: engine rotation speed, TA: throttle opening, GA: intake air amount, GAreq: required intake air amount, KL: intake air rate, EGrate: residual gas rate.

  INVT: Intake valve timing, INVTmax: Most advanced intake valve timing, INVTmin: Most retarded intake valve timing, EXVT: Exhaust valve timing, EXVTmax: Most advanced exhaust valve timing, EXVTmin: Most retarded exhaust valve timing.

  INVL: Maximum intake valve lift, INVLmax: Upper intake maximum valve lift, INVLmin: Lower intake maximum valve lift, INCAM: Intake valve operating angle, INCAMmax: Maximum intake valve operating angle, INCAMmin: Minimum intake valve operating angle, EXCAM ... Exhaust valve working angle.

  IVO ... intake valve opening timing, IVC ... intake valve closing timing, IVOnow ... current cam intake valve opening timing, IVObst ... optimal cam intake valve opening timing, IVOdfl ... initial cam intake valve opening timing, IVOtdc ... reference cam intake valve opening Timing, IVCnow: current cam intake valve closing timing, IVCbst: optimum cam intake valve closing timing, IVCdfl: initial cam intake valve closing timing, IVCtdc: reference cam intake valve closing timing, IVCmax: maximum charging valve closing timing.

  EVO ... exhaust valve opening timing, EVC ... exhaust valve closing timing, EVCnow ... current cam exhaust valve closing timing, EVCbst ... optimal cam exhaust valve closing timing, EVCdfl ... initial cam exhaust valve closing timing, EVCtdc ... reference cam exhaust valve closing timing season.

  OVLP ... valve overlap amount, OVLPbst ... optimum cam overlap amount, OVLPnow ... current cam overlap amount, OVLPX ... reference overlap amount, OVLPratio ... overlap ratio.

  BseF: Base ignition timing, MBTnow: Current cam MBT ignition timing, MBTbst: Optimal cam MBT ignition timing, MBTdfl: Initial cam MBT ignition timing, MBTcompnb: First MBT correction amount, MBTtempnb: First MBT correction amount, MBTOVLPnb: Second MBT correction amount , MBTOVLPbst ... overlap MBT correction amount, MBTcompdb ... initial cam MBT correction amount, MBTtempdb ... initial cam MBT correction amount, MBTTKratio ... ignition timing correction ratio.

  TKnow: current cam knock limit ignition timing, TKbst: optimal cam knock limit ignition timing, TKdfl: initial cam knock limit ignition timing, TKtempnb: first knock limit correction amount, TKcompnb: first knock limit correction amount, TKOVLPnb: second knock limit correction amount , TKOVLPbst ... overlap knock limit correction amount, TKtempdb ... initial cam knock limit correction amount, TKcompdb ... initial cam knock limit correction amount.

  compIVOnow ... current cam IVO compression end pressure, compIVObst ... optimal cam IVO compression end pressure, compIVOtdc ... reference cam IVO compression end pressure, compIVCnow ... current cam IVC compression end pressure, compIVCbst ... optimal cam IVC compression end pressure, compIVCtdc ... reference cam IVC Compression end pressure.

  compALLnb ... current cam total pressure change amount, compIVOnb ... current cam IVO pressure change amount, compIVCnb ... current cam IVC pressure change amount, compIVObt ... first reference IVO pressure change amount, compIVOnt ... second reference IVO pressure change amount, compIVOdt ... first 3 reference IVO pressure change amount, compALLdb ... initial cam total pressure change amount, compIVOdb ... initial cam IVO pressure change amount, compIVCdb ... initial cam IVC pressure change amount, compIVCbt ... first reference IVC pressure change amount, compIVCnt ... second reference IVC Pressure change amount, compIVCdt ... third reference IVC pressure change amount.

  ΔcompIVOTt—optimal-reference IVO pressure change amount, ΔcompIVOnt—current—reference IVO pressure change amount, ΔcompIVodt—initial—reference IVO pressure change amount, ΔcompIVCbt—optimal—reference IVC pressure change amount, ΔcompIVCnt—current—reference IVC pressure change amount, ΔcompIVCdt... Initial-reference IVC pressure change amount.

  tempIVOnow ... current cam IVO compression end temperature, tempIVObst ... optimal cam IVO compression end temperature, tempIVOtdc ... reference cam IVO compression end temperature, tempIVCnow ... current cam IVC compression end temperature, tempIVCbst ... optimal cam IVC compression end temperature, tempIVCtdc ... reference cam IVC Compression end temperature.

  tempALLnb ... current cam total temperature change amount, tempIVOnb ... current cam IVO temperature change amount, tempIVCnb ... current cam IVC temperature change amount, tempIVObt ... first reference IVO temperature change amount, tempIVOnt ... second reference IVO temperature change amount, tempIVOdt ... first 3 reference IVO temperature change amount, tempALLdb ... initial cam total temperature change amount, tempIVOdb ... initial cam IVO temperature change amount, "tempIVCdb ... initial cam IVC temperature change amount, tempIVCbt ... first reference IVC temperature change amount, tempIVCnt ... second reference IVC temperature change amount, tempIVCdt ... third reference IVC temperature change amount.

  ΔtempIVObt: Optimal-reference IVO temperature change amount, ΔtempIVOnt: current-reference IVO temperature change amount, ΔtempIVodt: initial-reference IVO temperature change amount, ΔtempIVCbt ... optimal-reference IVC temperature change amount, ΔtempIVCnt ... current-reference IVC temperature change amount, ΔtempIVCdt... Initial-reference IVC temperature change amount.

  Tbst: optimal cam combustion chamber temperature, Tnow: current cam combustion chamber temperature, Pbst: optimal cam combustion chamber pressure, Pnow: current cam combustion chamber pressure, Gbst: optimal cam residual gas rate, Gnow: current cam residual gas rate.

Claims (19)

  An ignition timing control device for an engine including a controller that controls the ignition timing according to the operating state of the engine,
  The engine has a variable valve mechanism for changing a valve opening timing and a valve closing timing as an opening / closing characteristic of an intake valve,
  The controller is
  The ignition timing used to burn the mixture is defined as the base ignition timing,
  The operating state of the engine for which the suitable base ignition timing is set is defined as a basic operating state,
  The current operating state of the engine is defined as the current operating state,
  The opening / closing characteristics of the intake valve in the basic operation state are defined as basic opening / closing characteristics,
  The opening and closing characteristics of the intake valve in the current operating state are defined as the current opening and closing characteristics,
  The amount of change in the compression end pressure or compression end temperature in the combustion chamber, the compression end pressure or compression end temperature of the combustion chamber in the basic operation state, and the compression end pressure or compression end of the combustion chamber in the current operation state The difference from temperature is defined as the amount of state change,
  The state change amount is calculated based on the opening timing and closing timing of the intake valve in the basic opening / closing characteristics, and the opening timing and closing timing of the intake valve in the current opening / closing characteristics,
  Correcting the base ignition timing suitable for the basic operating state according to the state change amount;
  Set the corrected base ignition timing as the base ignition timing suitable for the current operating state.
  Engine ignition timing control device.   An ignition timing control device for an engine including a controller that controls the ignition timing according to the operating state of the engine,
  The engine has a variable valve mechanism for changing a valve opening timing and a valve closing timing as an opening / closing characteristic of an intake valve,
  The controller is
  The ignition timing used for the combustion of the air-fuel mixture is defined as the base ignition timing as the ignition timing that suppresses the occurrence of knocking and provides the best output torque and fuel consumption rate.
  A plurality of base ignition timings prepared in advance for each engine operating state are defined as basic base ignition timings, respectively.
  The operating state of the engine corresponding to the selected basic base ignition timing is defined as a basic operating state,
  The current operating state of the engine is defined as the current operating state,
  The opening / closing characteristics of the intake valve in the basic operation state are defined as basic opening / closing characteristics,
  The opening and closing characteristics of the intake valve in the current operating state are defined as the current opening and closing characteristics,
  The amount of change in the compression end pressure or compression end temperature in the combustion chamber, the compression end pressure or compression end temperature of the combustion chamber in the basic operation state, and the compression end pressure or compression end of the combustion chamber in the current operation state The difference from temperature is defined as the amount of state change,
  When there is an ignition timing suitable for the current operating state among the plurality of basic base ignition timings,
  This ignition timing is selected as a base ignition timing suitable for the current operating state,
  When there is no ignition timing suitable for the current operating state among the plurality of basic base ignition timings,
  Selecting any one of the plurality of basic base ignition timings;
  The basic operating state corresponding to the selected basic base ignition timing, and the state change amount corresponding to the current operating state are expressed as the valve opening timing and closing timing of the intake valve in the basic opening / closing characteristics, and the current Calculated based on the opening and closing timing of the intake valve in the opening and closing characteristics,
  Correcting the basic base ignition timing according to the state change amount;
  Set the corrected ignition timing as the base ignition timing that matches the current operating condition.
  Engine ignition timing control device.   The controller is
  The engine operating state for setting valve overlap is defined as a first operating state,
  The operation state of the engine that does not set valve overlap is defined as a second operation state,
  A base ignition timing suitable for the first operating state is defined as a first base ignition timing,
  A base ignition timing suitable for the second operating state is defined as a second base ignition timing,
  Calculating a correction amount of the ignition timing according to the valve overlap amount in the first operating state based on the first base ignition timing and the second base ignition timing;
  The calculated correction amount is converted into a correction amount according to the valve overlap amount in the current operating state,
  Based on the corrected correction amount and the first base ignition timing, a base ignition timing suitable for the current operating state is calculated.
  The engine ignition timing control device according to claim 1 or 2.   The controller is
  The state change amount when the opening / closing characteristic of the intake valve changes from the opening / closing characteristic in the first operating state to the opening / closing characteristic in the second operating state is defined as an opening / closing state change amount,
  Calculate the ignition timing correction amount according to the open / close state change amount,
  By delaying the first base ignition timing by an amount corresponding to the second base ignition timing and correcting the first base ignition timing based on the correction amount of the ignition timing according to the opening / closing state change amount, the valve in the first operation state Calculate the ignition timing correction amount according to the overlap amount
  The engine ignition timing control device according to claim 3.   An ignition timing control device for an engine including a controller that controls the ignition timing according to the operating state of the engine,
  The engine has a variable valve mechanism for changing a valve opening timing and a valve closing timing as an opening / closing characteristic of an intake valve,
  The controller is
  The ignition timing used to burn the mixture is defined as the base ignition timing,
  The ignition timing that provides the best output torque and fuel consumption rate is defined as the MBT ignition timing,
  Among the ignition timings that can suppress the occurrence of knocking, the most advanced ignition timing is defined as the knock limit ignition timing,
  The engine operating state in which the suitable MBT ignition timing and the knock limit ignition timing are set is defined as a basic operating state,
  The current operating state of the engine is defined as the current operating state,
  The opening / closing characteristics of the intake valve in the basic operation state are defined as basic opening / closing characteristics,
  The opening and closing characteristics of the intake valve in the current operating state are defined as the current opening and closing characteristics,
  The amount of change in the compression end pressure or compression end temperature in the combustion chamber, the compression end pressure or compression end temperature of the combustion chamber in the basic operation state and the compression end pressure or compression end temperature of the combustion chamber in the current operation state Is defined as the amount of state change,
  The state change amount is calculated based on the opening timing and closing timing of the intake valve in the basic opening / closing characteristics, and the opening timing and closing timing of the intake valve in the current opening / closing characteristics,
  Correcting the MBT ignition timing and the knock limit ignition timing suitable for the basic operating state based on the state change amount;
  The retarded ignition timing of the corrected MBT ignition timing and knock limit ignition timing is set as the base ignition timing that matches the current operating state.
  Engine ignition timing control device.   An ignition timing control device for an engine including a controller that controls the ignition timing according to the operating state of the engine,
  The engine has a variable valve mechanism for changing a valve opening timing and a valve closing timing as an opening / closing characteristic of an intake valve,
  The controller is
  The ignition timing used to burn the mixture is defined as the base ignition timing,
  The ignition timing that provides the best output torque and fuel consumption rate is defined as the MBT ignition timing,
  Among the ignition timings that can suppress the occurrence of knocking, the most advanced ignition timing is defined as the knock limit ignition timing,
  The engine operating state in which the suitable MBT ignition timing and the knock limit ignition timing are set is defined as a basic operating state,
  The current operating state of the engine is defined as the current operating state,
  The opening / closing characteristics of the intake valve in the basic operation state are defined as basic opening / closing characteristics,
  The opening and closing characteristics of the intake valve in the current operating state are defined as the current opening and closing characteristics,
  A plurality of MBT ignition timings and a plurality of knock limit ignition timings prepared in advance for each operating state of the engine are defined as a basic MBT ignition timing and a basic knock limit ignition timing, respectively.
  Defining the operating state of the engine corresponding to any one of the selected basic MBT ignition timings and any one of the basic knock limit ignition timings as a basic operating state;
  The amount of change in the compression end pressure or compression end temperature in the combustion chamber, the compression end pressure or compression end temperature of the combustion chamber in the basic operation state and the compression end pressure or compression end temperature of the combustion chamber in the current operation state Is defined as the amount of state change,
  When there is a basic MBT ignition timing and a basic knock limit ignition timing that match the current operating state among the plurality of basic MBT ignition timings and the plurality of basic knock limit ignition timings,
  Of the basic MBT ignition timing and the basic knock limit ignition timing, the retarded ignition timing is set as a base ignition timing suitable for the current operating state,
  When there is no ignition timing suitable for the current operating state among the plurality of basic MBT ignition timings and the plurality of basic knock limit ignition timings,
  Selecting any one of the plurality of basic MBT ignition timings and any one of the plurality of basic knock limit ignition timings;
  The basic operation state corresponding to the selected basic MBT ignition timing and the basic knock limit ignition timing, and the state change amount corresponding to the current operation state are determined based on the opening timing and closing timing of the intake valve in the basic opening / closing characteristics. Calculated based on the valve timing, and the opening timing and closing timing of the intake valve in the current opening / closing characteristics,
  Correcting the selected basic MBT ignition timing and basic knock limit ignition timing based on the state change amount;
  Of the corrected basic MBT ignition timing and basic knock limit ignition timing, the retarded ignition timing is set as the base ignition timing suitable for the current operating state.
  Engine ignition timing control device.   The controller is
  The engine operating state for setting valve overlap is defined as a first operating state,
  The operation state of the engine that does not set valve overlap is defined as a second operation state,
  The MBT ignition timing suitable for the first operating state is defined as the first MBT ignition timing,
  The MBT ignition timing suitable for the second operating state is defined as the second MBT ignition timing,
  Calculating a correction amount of the ignition timing according to the valve overlap amount in the first operating state based on the first MBT ignition timing and the second MBT ignition timing;
  The calculated correction amount is converted into a correction amount according to the valve overlap amount in the current operating state,
  Based on the corrected amount after conversion and the first MBT ignition timing, an MBT ignition timing suitable for the current operating state is calculated.
  The engine ignition timing control device according to claim 5 or 6.   The controller is
  The state change amount when the opening / closing characteristic of the intake valve changes from the opening / closing characteristic in the first operating state to the opening / closing characteristic in the second operating state is defined as an opening / closing state change amount,
  Calculate the ignition timing correction amount according to the open / close state change amount,
  The first MBT ignition timing is retarded by an amount corresponding to the second MBT ignition timing, and corrected based on the correction amount of the ignition timing corresponding to the open / close state change amount, whereby the valve overlap in the first operating state is corrected. Calculate the ignition timing correction amount according to the amount
  The engine ignition timing control device according to claim 7.   The controller is
  The engine operating state for setting valve overlap is defined as a first operating state,
  The operation state of the engine that does not set valve overlap is defined as a second operation state,
  The knock limit ignition timing suitable for the first operating state is defined as the first knock limit ignition timing,
  A knock limit ignition timing suitable for the second operating state is defined as a second knock limit ignition timing;
  Calculating a correction amount of the ignition timing according to the valve overlap amount in the first operating state based on the first knock limit ignition timing and the second knock limit ignition timing;
  The calculated correction amount is converted into a correction amount according to the valve overlap amount in the current operating state,
  Based on the corrected correction amount and the first knock limit ignition timing, a knock limit ignition timing suitable for the current operating state is calculated.
  The engine ignition timing control device according to any one of claims 5 to 8.   The controller is
  The state change amount when the opening / closing characteristic of the intake valve changes from the opening / closing characteristic in the first operating state to the opening / closing characteristic in the second operating state is defined as an opening / closing state change amount,
  Calculate the ignition timing correction amount according to the open / close state change amount,
  By delaying the first knock limit ignition timing by an amount corresponding to the second knock limit ignition timing and correcting the first knock limit ignition timing based on the correction amount of the ignition timing according to the open / close state change amount, the first operating state The ignition timing correction amount according to the valve overlap amount
  The engine ignition timing control device according to claim 9.   The controller is
  The state change amount when the valve opening timing of the intake valve changes from the valve opening timing of the first operation state to the valve opening timing of the second operation state is defined as a valve opening side state change amount;
  The state change amount when the valve closing timing of the intake valve changes from the valve closing timing of the first operating state to the valve closing timing of the second operating state is defined as a valve closing side state changing amount,
  Based on the valve opening timing of the first operating state and the valve opening timing of the second operating state, the valve opening side state change amount is calculated,
  Based on the valve closing timing of the first operating state and the valve closing timing of the second operating state, the valve closing side state change amount is calculated,
  The opening / closing state change amount is calculated based on the valve opening side state change amount and the valve closing side state change amount.
  The engine ignition timing control device according to claim 4, 8 or 10.   The controller is
  The valve opening timing of the basic opening / closing characteristics is defined as the basic valve opening timing,
  The valve opening timing of the current opening / closing characteristics is defined as the current valve opening timing,
  The state change amount is calculated based on the basic valve opening timing and the current valve opening timing.
  The engine ignition timing control device according to any one of claims 1 to 11.   The controller is
  The opening timing of the top dead center of the intake valve is defined as a reference opening timing,
  The state change amount when the valve opening timing of the intake valve changes from the reference valve opening timing to the basic valve opening timing is defined as a first valve opening state change amount;
  The state change amount when the valve opening timing of the intake valve changes from the reference valve opening timing to the current valve opening timing is defined as a second valve opening state change amount,
  Based on the reference valve opening timing and the basic valve opening timing, the first valve opening state change amount is calculated,
  Based on the reference valve opening timing and the current valve opening timing, the second valve opening state change amount is calculated,
  The state change amount is calculated based on the first valve opening state change amount and the second valve opening state change amount.
  The engine ignition timing control device according to claim 12.   The controller is
  The closing timing of the basic opening / closing characteristics is defined as the basic closing timing,
  The closing timing of the current opening / closing characteristics is defined as the current closing timing,
  Based on the basic valve closing timing and the current valve closing timing, the state change amount is calculated.
  The engine ignition timing control device according to any one of claims 1 to 13.   The controller is
  The closing timing of the bottom dead center of the intake valve is defined as a reference closing timing,
  The state change amount when the valve closing timing of the intake valve changes from the reference valve closing timing to the basic valve closing timing is defined as a first valve closing state change amount;
  The state change amount when the valve closing timing of the intake valve changes from the reference valve closing timing to the current valve closing timing is defined as a second valve closing state change amount,
  Based on the reference valve closing timing and the basic valve closing timing, the first valve closing state change amount is calculated,
  Based on the reference valve closing timing and the current valve closing timing, the second valve closing state change amount is calculated,
  The state change amount is calculated based on the first valve closing state change amount and the second valve closing state change amount.
  The engine ignition timing control device according to claim 14.   The controller is
  The closing timing of the intake valve having the maximum charging efficiency is defined as the maximum charging valve closing timing,
  The state change amount when the intake valve closing timing is changed from the maximum filling valve closing timing to the basic valve closing timing is defined as a third valve closing state change amount;
  The state change amount when the intake valve closing timing changes from the maximum filling valve closing timing to the current valve closing timing is defined as a fourth valve closing state change amount,
  Based on the maximum filling valve closing timing and the basic valve closing timing, the third valve closing state change amount is calculated,
  Based on the maximum filling valve closing timing and the current valve closing timing, the fourth valve closing state change amount is calculated,
  The state change amount is calculated based on the third valve closing state change amount and the fourth valve closing state change amount.
  The engine ignition timing control device according to claim 14.   The controller is
  The state change amount is calculated based on the rotation speed of the engine.
  The engine ignition timing control device according to any one of claims 1 to 16.   The controller is
  The state change amount is calculated based on the intake air amount of the engine.
  The engine ignition timing control device according to any one of claims 1 to 17.   The controller is
  The state change amount is calculated based on the effective intake pipe length of the engine.
  The engine ignition timing control device according to any one of claims 1 to 18.

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