JPH1068376A - Lean burn internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of knock after a driving mode is changed, by adjusting an ignition timing so as to prevent the knock of an engine by knock data from a knock sensor and a knock learning value and by changing a driving range in which the learning value is renewed between a stoichiometric driving mode and a lean driving mode. SOLUTION: While an engine is operated, a knock learning value corresponding to the driving state of an engine is determined by an ECU 23 based on knock data obtained from a knock sensor 36 and a fundamental ignition timing is corrected by the knock learning value and knock data to produce a suitable engine output while preventing the knock of the engine. In this respect, the renewal range of the learning value in the range of a lean suction driving is limited. That is, since the engine is apt to knock even in the range of the lean suction driving when a considerable load is imposed on the engine, the learning value is renewed at a prescribed range or more where a considerably heavy load is imposed on the engine and the learning value is renewed at the range or more where a considerably light load is imposed on the engine in the range of stoichiometric driving.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lean-burn internal combustion engine that performs knock determination based on an output of a knock sensor and a knock learning value corresponding to an operating state in order to prevent engine knock. The present invention relates to a lean-burn internal combustion engine that is suitable for use in a direct injection internal combustion engine that injects fuel and that performs knock control.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine (generally, a gasoline engine), if knocking (knocking) occurs excessively, it may cause a decrease in engine output or overheating, which is not preferable. On the other hand, in order to efficiently generate the output of the engine, it is preferable to control the ignition timing to a state immediately before knock occurs. For this reason, a technique (knock control) for controlling the occurrence of knock to a state immediately before the occurrence of knock has been developed.

[0003] This knock control usually means that when knock is detected based on an output from a knock sensor, ignition is performed in a direction (retard side) in which knock is not generated by feedback control based on the output of the knock sensor. If the timing is changed, and conversely, if knock occurrence is not detected, the ignition timing is changed in the direction in which knock occurs (advance side) by feedback control based on the output of the knock sensor, and no knock occurs but immediately before knock occurs This is a technique that attempts to control the ignition timing in the state described above.

In such knock control, the occurrence state of knock differs depending on the octane number and the individual difference of the engine. Therefore, as far as knock does not occur, the output of the engine immediately before knock occurs is brought as close as possible to a state in which the engine output can be generated efficiently. As described above, the learning value is obtained in accordance with the operating state of the engine by feedback control based on the knock sensor output, and while the learned value is updated, the appropriate ignition timing is always set so that the knock sensor output and It is known that the ignition timing is controlled based on the learned value (see Japanese Patent Application Laid-Open Nos. 60-16263 and 59-113267).

[0005]

The stoichiometric operation (operation for controlling the air-fuel ratio to the stoichiometric air-fuel ratio) and the lean operation (operation for controlling the air-fuel ratio to a leaner side than the stoichiometric air-fuel ratio) are currently available. The lean-burn internal combustion engine that switches the ignition timing in accordance with the operating state of the engine, in particular, those equipped with a three-way catalyst, suppresses the generation of NOx in the lean operation range, so that the ignition timing is retarded from the stoichiometric operation range. In this case, the operating range for updating the learning value for knock control is set to the same area for stoichiometric operation and for lean operation. When set, the learning value is updated even in an operation region where knock does not occur in the lean operation region.

That is, when the learning value is updated over a wide range covering the stoichiometric operation range and the lean operation range,
If the learning value is updated even in the operating range where knock does not occur in the lean operating range, and if the operating state in the operating range where knock does not occur continues, the ignition timing will be greatly changed to the advanced side, Since the advance angle is inappropriately adjusted by the updated learning value, knocking is extremely likely to occur when the operation state is switched from the lean operation range to the stoichiometric operation range in which knock is more likely to occur than in the lean operation range. turn into.

When a lean NOx catalyst is used in place of the three-way catalyst, if the NOx purification efficiency is high even in a lean operation region using the lean NOx catalyst, the ignition timing in the lean operation region is set to be more advanced than in the stoichiometric operation. In the stoichiometric operation region, the operation region in which knock does not occur may be wider in some cases. Further, in the lean-burn internal combustion engine, in order to perform engine control with higher accuracy, a volume efficiency Ev calculated from an output of an airflow sensor or the like is adopted as engine load information, and knock control is performed based on the volume efficiency Ev. In some cases. In this case, if the update region is set so that the learning value is updated at the same Ev level in the lean operation region and the stoichiometric operation region irrespective of the NOx purification, the substantial load level becomes lower than that in the stoichiometric operation region. Because the area is lower,
Even in the region where knock occurs in the stoichiometric operation, the learning value is updated in the region where knock does not easily occur in the lean operation, and the appropriate learning value cannot be updated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is liable to occur after the operation mode is switched by changing the operation region in which the learning value is updated between the stoichiometric operation region and the lean operation region. It is an object of the present invention to provide a lean burn internal combustion engine capable of suppressing knocking.

[0009]

Therefore, the lean-burn internal combustion engine of the present invention according to the first aspect of the present invention operates in a stoichiometric operation mode in which the operation is performed near the stoichiometric air-fuel ratio and in an air-fuel ratio region leaner than the stoichiometric air-fuel ratio. Lean operation mode for driving
In a spark-ignition lean-burn internal combustion engine that can be switched according to the engine operating state, a knock sensor that detects knocking of the engine, knock data obtained from the knock sensor output and knock data based on the knock data or the knock sensor output Control means for adjusting the ignition timing of the engine so as to suppress the knock of the engine from the knock learning value obtained by the knocking learning value, and the operating region for updating the learning value is defined by the stoichiometric operation mode and the lean operation mode. It is characterized in that it is configured to switch over.

According to a second aspect of the present invention, there is provided the lean-burn internal combustion engine according to the first aspect, wherein the operating range in which the learning value is updated is set at least according to the load of the internal combustion engine. In the lean operation mode, the load corresponding lower limit of the operation region for updating the learning value in one of the operation modes in which the knock is likely to occur is set higher than the load corresponding lower limit in the wider mode of the region. It is characterized by having.

According to a third aspect of the present invention, there is provided a lean-burn internal combustion engine according to the first or second aspect, wherein the internal combustion engine is configured to set the operation mode based on intake air amount or intake negative pressure data. The load corresponding lower limit value of the operation region in which the learning value is updated is set higher in the region in the lean operation mode than in the region in the stoichiometric operation mode.

According to a fourth aspect of the present invention, there is provided a lean-burn internal combustion engine according to any one of the first to third aspects, wherein the internal combustion engine is a direct injection internal combustion engine which directly injects fuel into a combustion chamber. When the load of the internal combustion engine is equal to or more than a predetermined load, fuel is injected mainly in the intake stroke to perform premix combustion, and when the load of the internal combustion engine is equal to or less than the predetermined load, fuel is injected mainly in the compression stroke. Wherein the lower limit corresponding to the load of the internal combustion engine for updating the learning value is set to be equal to or more than the predetermined load.

According to a fifth aspect of the present invention, there is provided the lean-burn internal combustion engine according to the first aspect, wherein the operation range in which the learning value is updated is set according to the load of the internal combustion engine. In the above, a retard region where the learning value is updated to the retard side and an advance region where the learning value is updated to the advance side are respectively set, and a load-corresponding lower limit value in which the advance region is set. Is characterized in that the retard angle region is set lower than the load corresponding lower limit value set.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 5 show a lean-burn internal combustion engine as an embodiment of the present invention. Will be explained. The lean burn internal combustion engine is shown in FIG.
As shown in FIG. 1, an internal combustion engine which performs the intake, compression, expansion, and exhaust strokes in one operation cycle, that is, a four-stroke engine, of a spark ignition type and in which a fuel is directly injected into a combustion chamber. The engine is configured as an injection engine (a direct injection internal combustion engine).

An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1 so that they can communicate with each other. The communication between the intake passage 2 and the combustion chamber 1 is controlled by an intake valve 4.
The communication between the exhaust passage 3 and the combustion chamber 1 is controlled by an exhaust valve 5. The intake passage 2 is provided with an air cleaner 6 and a throttle valve 7 in order from the upstream side, and the exhaust passage 3 is provided with an exhaust gas purifying catalytic converter 9 as an exhaust gas purifying catalyst in order from the upstream side.
A muffler (muffler) not shown is provided.
Note that a surge tank 2a is provided in the intake passage 2.

Further, an exhaust gas recirculation device (hereinafter, EGR)
10) is provided. That is, the exhaust gas recirculation passage 10b is provided so as to connect the surge tank 2a portion of the intake passage 2 with the upstream side of the exhaust gas passage 3, and the exhaust gas recirculation passage 10b is provided with the EGR valve 10a. The flow rate of exhaust gas (also referred to as exhaust gas or exhaust gas or exhaust gas) from the exhaust passage 3 to the intake passage 2 can be controlled by the EGR valve 10a. The control of the EGR valve 10a is performed according to the operating state of the engine.

The opening of the throttle valve 7 changes in accordance with the amount of depression of an accelerator pedal (not shown), whereby the amount of air introduced into the combustion chamber 1 is adjusted. Further, reference numeral 16 denotes an idle speed control valve, which is provided in a bypass passage 16A which bypasses a portion where the throttle valve is provided in the intake passage 2 and is driven to open and close by a stepper motor (not shown). The idle speed at the time is finely adjusted.

Reference numeral 50 denotes an air bypass valve (ABV), which is connected to a bypass passage 50A that connects the intake passage 2 upstream of the throttle valve 7 and the surge tank 2a so as to bypass a portion of the intake passage 2 where the throttle valve 7 is provided. Provided,
The air-fuel ratio can be adjusted by adjusting the intake air amount separately from the throttle valve 7. The injector (fuel injection valve) 8 is arranged so that its opening faces the combustion chamber 1 so as to directly inject fuel toward the combustion chamber 1 in the cylinder. Naturally, the injectors 8 are provided for each cylinder. For example, if the engine of the present embodiment is an in-line four-cylinder engine, four injectors 8 are provided.

With this configuration, the air sucked through the air cleaner 6 in accordance with the opening of the throttle valve 7 is sucked into the combustion chamber 1 by opening the intake valve 4, and the air sucked in the combustion chamber 1 And the fuel directly injected from the injector 8 are mixed, and the ignition plug 35
Is ignited at an appropriate timing to cause combustion and generate engine torque.
The exhaust gas is exhausted from the inside to the exhaust passage 3, and a catalytic converter (hereinafter, also simply referred to as a catalyst) 9 emits C in the exhaust gas.
O, HC, since the purifying harmful components such as NO _x,
The sound is muted by the muffler and released to the atmosphere.

In particular, the present engine is a lean burn engine (lean-burning internal combustion engine) capable of performing economizing operation while keeping the air-fuel ratio lean (fuel-lean state), and injects fuel uniformly into the combustion chamber 1. This is an engine that can switch between premixed combustion that can be realized by the above and stratified lean combustion that can be realized by unevenly distributing the injected fuel around the ignition plug 35 facing the combustion chamber 1 according to the operating state. .

The engine is operated in a late lean burn operation mode in which fuel is injected in a compression stroke to perform stratified lean combustion (late lean mode), and in a premixed fuel injection mode in which fuel is injected in an intake stroke. Four modes are provided: a first-half lean combustion operation mode for performing combustion (first-half lean mode), a stoichiometric feedback combustion operation mode (stoichiometric operation mode), and an open-loop combustion operation mode (stoichiometric operation mode or enriched operation mode). In each mode,
A case where the EGR is operated and a case where the EGR is stopped are set. One of these modes is selected according to the operating state of the engine or the running state of the vehicle, and the fuel supply control is performed.

For this reason, as shown in FIG.
The output of each sensor empty, the operating state of the engine,
That is, the load state Pe of the engine and the engine speed Ne of the engine are input, and the ECU 23 inputs the operating state (here, Pe, Ne) of the engine input from the operating state detecting means 101. (Mode selection means) 1 for selecting each operation mode as described above according to
02 is provided. The ECU 23 further sets the air-fuel ratio in accordance with the operation state of the engine (Pe, Ne) based on the selected operation mode, and sets the fuel injection provided for each cylinder based on the set air-fuel ratio. A function (fuel injection valve control means) 103 for controlling fuel supply by the valve 8 is provided.

In general, the enriched operation mode, the stoichiometric operation mode, the first lean mode, and the second lean mode are set with respect to the engine speed Ne and the engine load Pe in a region tendency as shown in FIG. Of the above-mentioned modes, the latter lean mode can realize the leanest combustion (air-fuel ratio is about 25 to 50), but in this mode, the fuel injection is performed at a stage very close to the ignition timing as in the latter half of the compression stroke. In addition, the fuel is collected near the spark plug to make it partially rich and lean as a whole so that the fuel-saving operation is performed while ensuring the ignitability and the combustion stability.

In the first lean mode, lean combustion (air-fuel ratio of about 18 to 22) can be realized. In this mode, fuel is injected in the intake stroke before the second lean mode to diffuse fuel into the combustion chamber. In this way, while maintaining the ignitability and combustion stability while keeping the overall air-fuel ratio lean, a certain amount of output is ensured, thereby performing the economizing operation.

In the stoichiometric operation mode, a sufficient engine output can be efficiently obtained while maintaining the air-fuel ratio at or near the stoichiometric ratio by feedback control based on the output of the O ₂ sensor. This stoichiometric operation mode is also referred to as a stoichiometric feedback operation mode. In the open-loop combustion operation mode (enrich), combustion is performed by stoichiometry or an air-fuel ratio richer than the stoichiometric ratio by open-loop control so that a sufficient output can be obtained during acceleration or starting.

In order to control the engine in this manner, various sensors are provided, and some of these sensors constitute the operating state detecting means 101. First, on the intake passage 2 side, an air flow sensor 11, which detects an intake air amount from Karman vortex information, an intake air temperature sensor 12, which detects an intake air temperature, and an atmospheric pressure sensor 13, which detects an atmospheric pressure, are provided at the portion where the air cleaner is provided. The throttle valve is provided with a potentiometer type throttle sensor 14 for detecting the opening of the throttle valve 7, an idle switch 15 for detecting an idling state, a knock sensor 36, and the like.

Further, as other sensors, a water temperature sensor 19 for detecting an engine cooling water temperature and a crank angle sensor 21 for detecting a crank angle (the crank angle sensor 21 also serves as a rotation speed sensor for detecting an engine rotation speed). ) And a TDC sensor (cylinder discrimination sensor) 22 for detecting the top dead center of the first cylinder (reference cylinder). And the detection signals from these sensors are:
The information is input to an electronic control unit (ECU) 23.

The ECU 23 is provided with an accelerator position sensor (not shown) for detecting the amount of depression of the accelerator pedal.
Sensor (not shown) for detecting battery voltage
And a signal from a cranking switch (or an ignition switch (key switch)) (not shown) for detecting the start-up time.

In the present engine, various controls are performed based on input data from such various sensors and the like. In particular, as shown in FIG. Ignition timing control means (also simply referred to as control means)] 104. The control means 104 obtains a knock learning value K corresponding to the operating state of the engine based on the knock data (detection information) （K (t) output from the knock sensor 36 as shown in FIGS. By correcting the basic ignition timing ST based on the knock learning value K and the knock data ΘK (t), the ignition timing of the engine is advanced or retarded so as to obtain an output while suppressing the engine knock. I do.

In the present engine, the operating state of the engine is determined by the engine speed Ne and the volumetric efficiency E calculated from the output of an airflow sensor or the like as load information of the engine.
v, a plurality of matrix regions (FIG. 4) formed by dividing the operating state of the engine by the engine speed Ne and the volumetric efficiency Ev as shown in FIG. 4.
The knock learning value K is updated for each of the areas divided by vertical and horizontal broken lines. The reason why the volume efficiency Ev is adopted is to perform engine control with higher accuracy.

In the knock control, among the main operation modes (stoichiometric operation mode, first-half lean mode, and second-half lean mode), the intake lean operation (first half-lean mode) and the intake stoichiometric operation (stoichiometric operation mode) ), And not during the compression lean operation (late lean mode). This is because, during the compression lean operation, the ignition timing is limited and extremely stable combustion is performed, so that there is no risk of knocking, so that knock control is not performed. In the stoichiometric operation mode and the intake lean mode, the basic ignition timing ST2 is set from the volume efficiency Ev calculated from the output of the airflow sensor and the engine speed Ne, whereas in the compression lean mode, the throttle opening degree is set. θth and engine speed Ne
The basic ignition timing ST1 is set from the target engine load Pe and the engine speed Ne obtained from the above.

In the knock control mode,
The basic ignition timing (basic ignition timing) ST2 itself is set to be different between the stoichiometric operation and the intake lean operation. That is, if the catalyst 9 is a three-way catalyst,
In the lean operation region, the ignition timing is set to the retard side with a margin in order to suppress the generation of NOx, but such a process is not performed in the stoichiometric operation region.

Therefore, in the intake lean operation region, knock is unlikely to occur, and the learning value K is updated in the same operation region as in the stoichiometric operation under such a situation that the ignition timing is set to the retard side with a margin. Is set, the learning value K is updated to the advanced side when the operation is continuously performed in the region where the knock does not occur in the intake lean operation region. Therefore, even if knock does not occur in the intake lean operation range, if the ignition timing is switched to the stoichiometric operation range in which the ignition timing is not set to the retard side with a margin, the ignition timing S
T is largely adjusted to the advance side, and knock is extremely likely to occur.

Therefore, in order to avoid such a problem related to the update of the learning value K in the intake lean operation region, the update region of the learning value K in the intake lean operation region is limited. That is, when the engine load is relatively high, knock is likely to occur in the intake lean operation range as well as in the stoichiometric operation range (that is, in this case, the ignition timing set in consideration of NOx reduction is Therefore, if the engine load is equal to or more than a predetermined region where the engine load is relatively high, the learning value K is appropriate as an update region. On the other hand, in the stoichiometric operation range, knock is likely to occur when the engine load is relatively low. Therefore, if the engine load is equal to or more than a predetermined region where the engine load is relatively low, the learning value K is appropriate as an update region.

The reason for correcting the ignition timing to the retard side is as follows.
When knocking occurs, it is intended to suppress the knocking.On the other hand, correcting the ignition timing to the advance side means that the knocking does not occur, but rather to the advance side where knocking is likely to occur. This is to achieve a favorable combustion state up to the knock generation limit retard to obtain an output. It can also be said that the correction to the advance angle side is a correction that makes knock more likely to occur. Therefore, if the ignition timing is positively corrected to the advance side, knocks are likely to occur frequently due to a change in the operating state, causing problems such as deterioration in drivability. Updating should be set so as to take precedence over updating of the learning value corrected to the advance side.

In this engine, updating of the learning value for correcting the ignition timing to the retard side is performed from a region where the engine load is relatively low, and updating of the learning value for correcting the ignition timing to the advance side is performed based on this retardation. It is set so as to be performed in a relatively high engine load region as compared with the case of the correction to the side. That is, the update area for correcting the learning value toward the advance angle side is made narrower than the update area for correcting the learning value toward the retard angle side.

In particular, in the present engine, the volume efficiency Ev is set as an amount corresponding to the engine load. As shown in FIG. 4, in the stoichiometric operation region, the level of the volume efficiency Ev is at least a relatively low volume efficiency Ev11 or more. In the region of, a learning value update region is set so as to update the learning value for correcting the ignition timing to the retard side, and the updating of the learning value for correcting the ignition timing to the advance side is performed on the retard side. The volume efficiency Ev01 (Ev0) higher than the lower limit Ev11 of the learning value update area
1> Ev11) The learning value update region is set so as to be performed in the region equal to or greater than Ev11).

In the intake lean operation region, the volumetric efficiency E
In the region where the level of v is relatively higher than the volumetric efficiency Ev12, the learning value update region is set so that the learning value for correcting the ignition timing is constantly updated to the retard side, and the ignition timing is set to the advance side. The learning value update region is set so that the learning value to be corrected is updated in a region where the volume efficiency Ev02 (Ev02> Ev12) is higher than the lower limit value Ev12 of the learning value update region to the retard side or higher. ing.

In the same operation mode, the lower limit of the update range of the learning value on the advance side should be set to a load region higher than the lower limit of the update range of the learning value on the retard side. Alternatively, the lower limit value of the learning value update region on the advance side during the stoichiometric operation may be set to be higher than the lower limit value of the learning value update region on the retard side during the intake lean operation. Since the lean burn internal combustion engine as one embodiment of the present invention is configured as described above, ignition timing control related to knock control is performed, for example, as shown in FIG.

That is, first, the target engine load P obtained from the throttle opening θth and the engine speed Ne is obtained.
e, the volume efficiency Ev calculated from the output of the air flow sensor or the like, and the engine speed Ne are read (step S10). Then, it is determined whether or not the engine is in the compression lean mode (step S20). If the mode is the compression lean mode, the basic ignition timing ST1 is set from the target engine load Pe and the engine speed Ne (step S180), and knock control is performed. Instead, the basic ignition timing ST1 is changed to the ignition timing ST
(Step S190), and outputs an ignition timing signal in accordance with the ignition timing ST to control the operation of the ignition plug 35 (step S170).

On the other hand, if the mode is not the compression lean mode, the mode is the intake lean mode or the stoichiometric mode. In this case, first, the basic ignition timing ST2 is set from the volumetric efficiency Ev and the engine speed Ne (step S30). ,next,
Knock data ΘK (t) is set in the knock sensor output (step S40). This knock data ΘK (t) is
It is also used to update the learning value ΘK of the corresponding operation region, but if the knocking tendency is in accordance with the knocking occurrence state indicated by the knock sensor output, it is set to the retard side if not, and to the advance side otherwise.

Next, it is determined whether or not the stoichiometric mode (stoichiometric feedback mode) is set (step S5).
0), if in the stoichiometric mode, proceed to step S60,
It is determined whether knock data ΔK is greater than a predetermined value α.
This determination is to determine whether knock data ΔK is to be corrected to the advance side or to the retard side. If it is determined that the knock data ΘK is equal to or less than the predetermined value α, it is to be corrected to the advanced angle side, and the process proceeds to step S70 to determine whether or not the volumetric efficiency Ev is equal to or more than the lower limit value Ev01, that is, It is determined whether or not it is a learning value update area on the advance side.

If the volumetric efficiency Ev is equal to or larger than the lower limit value Ev01 (in the stoichiometric mode, the learning value update area on the advance side is advanced), the learning value K is advanced by the correction amount β1 corresponding to the knock data ΘK. Side (step S120), and further proceeds to step S160 to obtain the ignition timing ST based on the knock data ΘK from the basic ignition timing ST2 and the learning value K updated to the advanced side in step S120, The ignition plug 3 outputs an ignition timing signal in accordance with the ignition timing ST.
5 is controlled (step S170).

If the volume efficiency Ev is not equal to or greater than the lower limit value Ev01 in step S70, the learning value K is not updated, and in step S160, the knock data 点火 K from the basic ignition timing ST2 and the learning value K which is not updated are used. To determine the ignition timing ST and output an ignition timing signal in accordance with the ignition timing ST to control the operation of the spark plug 35 (step S
170).

In step S60, knock data ノ
If K is larger than the predetermined value α, it is to be corrected to the retard side, and the process proceeds to step S80 to determine whether or not the volume efficiency Ev is equal to or more than the lower limit value Ev11, that is, to the retard side in the stoichiometric mode. It is determined whether or not the area is a learning value update area. If the volumetric efficiency Ev is equal to or more than the lower limit value Ev11 (if the learning value updating region for the retard side in the stoichiometric mode), the learning value K
Is updated to the retard side by the correction amount β2 according to the knock data ΘK (step S130), and furthermore, step S16
0, the knock data ΘK
The ignition timing ST is obtained based on the learning value K updated to the retard side in step S130, and an ignition timing signal is output in accordance with the ignition timing ST to control the operation of the ignition plug 35 (step S170).

In step S80, if the volumetric efficiency Ev is not equal to or greater than the lower limit value Ev11, the learning value K is not updated. In step S160, based on the knock data ΘK and the learning value K not updated from the basic ignition timing ST2. To determine the ignition timing ST and output an ignition timing signal in accordance with the ignition timing ST to control the operation of the spark plug 35 (step S
170).

On the other hand, if the stoichiometric mode is not set in step S50, the intake lean mode is set, and step S9
The process proceeds to 0, and it is determined whether or not knock data ΘK is greater than a predetermined value α. This determination is to determine whether knock data ΔK is to be corrected to the advance side or to the retard side. If the knock data ΘK is equal to or smaller than the predetermined value α in this determination, it is to be corrected to the advance side, and step S1
Then, it is determined whether or not the volume efficiency Ev is equal to or greater than the lower limit value Ev02, that is, whether or not the learning value update area for the advance side in the intake lean mode is set.

If the volumetric efficiency Ev is equal to or greater than the lower limit value Ev02 (in a learning value update area on the advance side in the intake lean mode), the learning value K is advanced by a correction amount β1 corresponding to the knock data ΘK. Side (step S140), and further proceeds to step S160 to determine the ignition timing ST based on the knock data ΘK from the basic ignition timing ST2 and the learned value K updated to the advanced side in step S140. The ignition plug 3 outputs an ignition timing signal in accordance with the ignition timing ST.
5 is controlled (step S170).

In step S100, if the volumetric efficiency Ev is not equal to or greater than the lower limit value Ev02, the learning value K is not updated. In step S160, the learning data K is obtained from the basic ignition timing ST2 based on the knock data し な い K and the learning value K which is not updated. Then, an ignition timing signal is output according to the ignition timing ST to control the operation of the ignition plug 35 (step S170).

In step S90, knock data Θ
If K is larger than a predetermined value α (α is an intermediate value between the maximum retardation amount and 0), it should be corrected to the retard side.
Proceeding to step S110, the volumetric efficiency Ev falls to the lower limit Ev1.
It is determined whether or not it is 2 or more, that is, whether or not it is a learning value update area on the retard side in the intake lean mode. Volumetric efficiency Ev
Is equal to or more than the lower limit value Ev12 (in the stoichiometric mode, the learning value update area on the retard side), the learning value K is updated to the retard side by the correction amount β2 corresponding to the knock data ΘK ( Step S150), and further proceeds to step S160 to obtain the ignition timing ST based on the knock data ΘK from the basic ignition timing ST2 and the learning value K updated to the retard side in step S150, and according to the ignition timing ST An operation of the ignition plug 35 is controlled by outputting an ignition timing signal (step S170).

In step S110, if the volume efficiency Ev is not equal to or greater than the lower limit value Ev12, the learning value K is not updated. In step S160, the learning data K is obtained from the basic ignition timing ST2 based on the knock data ΘK and the learning value K which is not updated. Then, an ignition timing signal is output according to the ignition timing ST to control the operation of the ignition plug 35 (step S170).

As described above, according to the present apparatus, different learning value update areas are set for the stoichiometric mode and the intake lean mode, and further, different learning values are set for the retard side and the advance side for each mode. Since the value update region is set, the learning value is appropriately updated. For example, in the intake lean operation region, the ignition timing is set to the retard side with a margin to suppress the generation of NOx. In this case as well, the learning value update in the region where the knock is unlikely to occur in the intake lean operation region (low load region) is prohibited, and even if the ignition switch ST is switched to the stoichiometric operation region where knock is likely to occur, the ignition timing ST is not changed. Knock generation can be suppressed without being significantly adjusted to the advance side.

In the present embodiment, the learning value update to the retard side is set to have priority over the learning value update to the advance side. Can be. In the present embodiment, knock control in the enriched operation mode is not particularly described, but the knock update control is performed by setting the learning update region wider than in the intake lean mode as in the case of the stoichiometric mode. May be performed.

Further, in the present embodiment, the description has been made on the assumption that the ignition timing is set to the retard side with a margin in the intake lean mode. In some cases, the lean mode sets the ignition timing on the more advanced side than the stoichiometric mode.In this case, the lower limit value of the learning value update area in the intake lean mode is further reduced, and the lean mode is set in the stoichiometric mode. It is conceivable that the lower limit of the learning value update region is further increased so that the lower limit in the stoichiometric mode is set higher than the lower limit in the intake lean mode.

Further, in the above embodiment, the catalyst NO
x Although the ignition timing is set differently in the lean operation region and the stoichiometric operation region in consideration of the purification efficiency and the like, the present invention sets the learning value region based on the intake air amount or the intake negative pressure data. In this case, it is effective even when the optimal ignition timing is set in each operation mode, regardless of the NOx purification by the catalyst.

That is, since the load level is substantially lower in the lean operation than in the stoichiometric operation at the same volumetric efficiency, when the learning value update region is set corresponding to the stoichiometric operation, Since the region where knock does not occur is included as a learning update region,
Knock learning becomes inappropriate. Therefore, even in such a case, it is effective to set the load-related lower limit (the lower limit of the intake air amount or the intake negative pressure data) for updating the learning value of the lean operation to be higher than that in the stoichiometric operation.

Further, it is determined whether the knock data 大 K is greater than a predetermined value α to determine whether it is on the advance side or on the retard side. For this determination, a dead zone is provided, for example, α1
As a positive minute value, if ΔK <α−α1, the advance side, α
If + α1 <ΘK, it may be determined to be on the retard side.

[0058]

As described above in detail, according to the lean-burn internal combustion engine of the present invention, the operating range for updating the knock learning value is switched between the stoichiometric operation mode and the lean operation mode. With such a configuration, it is possible to suppress the occurrence of knock, which is likely to occur after the operation mode is switched, particularly when the occurrence of knock differs depending on the operation mode.

According to the third aspect of the present invention, since the operation mode is set based on the intake air amount or the intake negative pressure data, the load is substantially changed by the same intake air amount or intake negative pressure data. Even if the level is different, it is possible to reliably switch the operation mode according to the operation state.
By setting the lower limit value corresponding to the load in the lean operation mode in which the ignition timing is basically set to the retard side higher than the range in the stoichiometric operation mode, the knock at the time of switching from the lean operation mode to the stoichiometric operation mode is reduced. Generation is suppressed.

According to the lean burn internal combustion engine of the fifth aspect of the present invention, frequent knocking can be suppressed in the same operating range while ensuring output in a specific operating range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a lean burn internal combustion engine as one embodiment of the present invention.

FIG. 2 is a configuration diagram showing a lean burn internal combustion engine as one embodiment of the present invention.

FIG. 3 is a diagram illustrating an operation mode of a lean burn internal combustion engine as one embodiment of the present invention.

FIG. 4 is a diagram illustrating a lean burn internal combustion engine as one embodiment of the present invention.

FIG. 5 is a flowchart showing a lean burn internal combustion engine as one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Intake passage 3 Exhaust passage 4 Intake valve 5 Exhaust valve 6 Air cleaner 7 Throttle valve 8 Injector (fuel injection valve) 9 Exhaust gas purification catalytic converter (catalyst) 2a Surge tank 10 Exhaust gas recirculation device (EGR device) 10a EGR valve 10b Exhaust gas recirculation passage 11 Air flow sensor 12 Intake temperature sensor 13 Atmospheric pressure sensor 14 Throttle sensor 15 Idle switch 16 Idle speed control valve 16A Bypass passage 23 ECU 35 Spark plug 36 Knock sensor 50 Air bypass valve (ABV) 50A Bypass passage DESCRIPTION OF SYMBOLS 101 Output operation state detection means 102 Mode selection means 103 Fuel injection valve control means 104 Ignition timing control means for knock control (control means)

Claims (5)

[Claims] 1. A spark ignition that can switch between a stoichiometric operation mode in which operation is performed near the stoichiometric air-fuel ratio and a lean operation mode in which operation is performed in an air-fuel ratio region leaner than the stoichiometric air-fuel ratio, according to the engine operation state. In the lean-burn internal combustion engine of the formula, a knock sensor that detects knocking of the engine, a knock data obtained from the knock sensor output and a knock learning value obtained based on the knock data or the knock sensor output are used to determine the knock of the engine. Control means for adjusting the ignition timing of the engine so as to suppress, the operating range for updating the learning value is configured to be switched between the stoichiometric operation mode and the lean operation mode. A lean-burn internal combustion engine. 2. An operation range in which the learning value is updated is set at least according to a load of the internal combustion engine, and the operation range in one of the operation modes in which knock is likely to occur in the stoichiometric operation mode and the lean operation mode is narrow. 2. The lean-burn internal combustion engine according to claim 1, wherein a lower limit value corresponding to a load in an operation range in which a learning value is updated is set higher than a lower limit value corresponding to a load in a mode in a wider range of the range. 3. The internal combustion engine is configured to set the operation mode based on intake air amount or intake negative pressure data, and a load corresponding lower limit of an operation region in which the learning value is updated is a region in the stoichiometric operation mode. 3. The lean burn internal combustion engine according to claim 1, wherein the region in the lean operation mode is set higher than the lean operation mode. 4. The internal combustion engine is a direct injection internal combustion engine that injects fuel directly into a combustion chamber. When the load of the internal combustion engine is equal to or greater than a predetermined load, fuel is injected mainly during an intake stroke to perform premixing. Combustion is performed, and when the load of the internal combustion engine is equal to or less than a predetermined load, stratified combustion is mainly performed by injecting fuel in the compression stroke, and the load corresponding lower limit of the internal combustion engine for updating the learning value is:
The lean-burn internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is set to the predetermined load or more. 5. An operating region in which the learning value is updated is set in accordance with a load of the internal combustion engine. The operating region includes a retarding region in which the learning value is updated to a retard side, and the learning value. And an advance angle region in which the angle is updated to the advance angle side is set, and the load corresponding lower limit value in which the advance angle region is set is set lower than the load corresponding lower limit value in which the retard angle region is set. The lean-burn internal combustion engine according to claim 1, wherein: