JP3648864B2 - Lean combustion internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lean combustion internal combustion engine that performs knock determination from an output of a knock sensor and a knock learning value corresponding to an operating state in order to prevent engine knock, and more particularly, in-cylinder injection that directly injects fuel into a combustion chamber. The present invention relates to a lean combustion internal combustion engine suitable for use in an internal combustion engine that performs knock control.
[0002]
[Prior art]
In a spark ignition type internal combustion engine (generally, a gasoline engine), excessive occurrence of knocking (knocking) is not preferable because it causes engine output reduction and overheating. On the other hand, in order to efficiently generate engine output, it is preferable to control the ignition timing to a state immediately before the occurrence of knocking. For this reason, a technique (knock control) for controlling the occurrence of knocking to a state immediately before the occurrence has been developed.
[0003]
In this knock control, usually, when knocking is detected based on the output from the knock sensor, the ignition timing is changed in the direction in which knocking does not occur (retard side) by feedback control based on the knock sensor output. On the contrary, if knock occurrence is not detected, the ignition timing is changed in the direction in which knock occurs (advance angle side) by feedback control based on the knock sensor output so that no knock occurs but the state immediately before the occurrence of knock is reached. This is a technique for controlling the ignition timing.
[0004]
In such knock control, since the occurrence of knocks varies depending on the octane number and the individual difference of the engine, so that the engine output immediately before the occurrence of knocking can be efficiently generated as close as possible to the extent that knocking does not occur, A learning value is obtained according to the engine operating state by feedback control based on the knock sensor output, and while updating the learning value, an appropriate ignition timing is always set so that the knock sensor output and the learning value are It is known to control the ignition timing based on the above (refer to Japanese Patent Laid-Open Nos. 60-162063 and 59-113267).
[0005]
[Problems to be solved by the invention]
By the way, 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 be leaner than the stoichiometric air / fuel ratio) are switched according to the operating state of the engine. In a lean combustion internal combustion engine, particularly with a three-way catalyst, the ignition timing is set to be retarded from the stoichiometric operating range in order to suppress the generation of NOx in the lean operating range (from the ignition timing at which knocking occurs) In this case, if the operating range in which the learning value for knock control is updated is set to the same region for stoichiometric operation and lean operation, knocking in the lean operation region is set. The learning value is updated even in the driving region where it does not occur.
[0006]
In other words, if the learning value is updated over a wide range that covers the stoichiometric operation range and the lean operation region, the learning value is updated even in the operation region where knock does not occur in the lean operation region, and the operation region where knock does not occur If the driving state continues at, the ignition timing will be greatly changed to the advance side, and the advance angle will be adjusted inappropriately by the updated learning value, so from the lean operation range than this lean operation range When the operation state is switched to a stoichiometric operation region where knocking is likely to occur, knocking is extremely likely to occur.
[0007]
When a lean NOx catalyst is used instead of the three-way catalyst, if the NOx purification efficiency is high even in the lean operation region by the lean NOx catalyst, the ignition timing in the lean operation region is set to the advance side than during the stoichiometric operation. Therefore, there are cases where the stoichiometric operation region has a wider operation region where knock does not occur.
In a lean combustion internal combustion engine, in order to perform engine control with higher accuracy, volume efficiency Ev calculated from the output of an airflow sensor or the like is adopted as engine load information, and knock control is performed based on this volume efficiency Ev. There is a case. 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 regardless of the purification of NOx, the substantial load level is lean operation compared to the stoichiometric operation region. Since the range is lower, the learning value will be updated in the region where knocking will not occur in lean operation even in the region where knocking will occur in stoichiometric operation, and appropriate learning values can be updated. Absent.
[0008]
The present invention was devised in view of the above-described problems. In particular, the operation range in which the learning value is updated is changed between the stoichiometric operation range and the lean operation region, and in particular, the occurrence of knocking that is likely to occur after the operation mode is switched. An object of the present invention is to provide a lean-burn internal combustion engine that can suppress the above-described problem.
[0009]
[Means for Solving the Problems]
For this reason, the lean combustion internal combustion engine of the present invention according to claim 1 has a stoichiometric operation mode in which operation is performed in the vicinity of the theoretical air-fuel ratio and a lean operation mode in which operation is performed in an air-fuel ratio range that is leaner than the theoretical air-fuel ratio. A spark ignition type lean combustion internal combustion engine that can be switched in accordance with the engine operating state, comprising an exhaust purification catalyst in the exhaust system so that the basic ignition timing differs between the stoichiometric operation mode and the lean operation mode A knock sensor for detecting engine knock, knock data obtained from the knock sensor output, the knock data or the knock sensor output, and the stoichiometric operation mode and the lean operation mode. A control method for adjusting the ignition timing of the engine so as to suppress engine knock from the knock learning value commonly used in The learning region is updated separately in the stoichiometric operation mode and the lean operation mode, and the learning value is updated in the operation region corresponding to the selected operation mode. Configured The learning value is updated in one of the operation modes in which the operation region in which the learning value is updated is set at least according to the load of the internal combustion engine and knocking is likely to occur in the stoichiometric operation mode and the lean operation mode. Is set higher than the load response lower limit value in the wider mode of the operation region. It is characterized by having.
[0010]
The lean combustion internal combustion engine of the present invention according to claim 2 is the engine according to claim 1, wherein The internal combustion engine is configured to set the operation mode based on the intake air amount or the intake negative pressure data, and the load corresponding lower limit value of the operation region for updating the learning value is less than the region in the stoichiometric operation mode. The region in It is characterized by being set high.
[0011]
The lean combustion internal combustion engine of the present invention according to claim 3 The stoichiometric operation mode in which operation is performed in the vicinity of the theoretical air-fuel ratio and the lean operation mode in which operation is performed in an air-fuel ratio range that is leaner than the theoretical air-fuel ratio can be switched by the intake air amount or intake negative pressure data depending on the engine operation state. A spark ignition lean combustion internal combustion engine having an exhaust gas purification catalyst in an exhaust system, wherein the basic ignition timing is set to be different between the stoichiometric operation mode and the lean operation mode. A knock sensor for detecting the knock, a knock data obtained from the knock sensor output, a knock learning value that is obtained based on the knock data or the knock sensor output, and is commonly used in the stoichiometric operation mode and the lean operation mode, Control means for adjusting the ignition timing of the engine so as to suppress engine knock from The operating region to be updated, and another set between the stoichiometric operation mode and the lean operation mode, while being configured to perform the update of the learning value in the operating region corresponding to the operating mode selected, The load-corresponding lower limit value of the operation region for updating the learning value is set to be higher in the region in the lean operation mode than in the region in the stoichiometric operation mode.
[0013]
Claim 4 The lean burn internal combustion engine of the present invention described A spark ignition type lean combustion internal combustion engine that can switch between a stoichiometric operation mode that operates near the stoichiometric air-fuel ratio and a lean operation mode that operates in an air-fuel ratio range that is leaner than the stoichiometric air-fuel ratio depending on the engine operating state A knock sensor for detecting knocking of the engine, the engine having an exhaust purification catalyst in an exhaust system, wherein the basic ignition timing is set to be different between the stoichiometric operation mode and the lean operation mode; Suppressing engine knock from knock data obtained from the knock sensor output and the knock learning value that is obtained based on the knock data or the knock sensor output and is commonly used in the stoichiometric operation mode and the lean operation mode Control means for adjusting the ignition timing of the engine as described above, and the operating range in which the learning value is updated And another set in the Kio operation mode and the lean operation mode, while being configured to perform the update of the learning value in the operating region corresponding to the operating mode selected, The operation region in which the learning value is updated is set according to the load of the internal combustion engine. The operation region includes a retardation region in which the learning value is updated to the retard side, and the learning value is advanced to the advance side. Each of the advance angle areas to be updated is set, and the load corresponding lower limit value for setting the advance angle area is set lower than the load corresponding lower limit value for setting the retard angle area. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 to 5 show a lean combustion internal combustion engine as an embodiment of the present invention, which will be described based on these drawings.
As shown in FIG. 3, the lean combustion internal combustion engine is an internal combustion engine having four strokes of intake, compression, expansion, and exhaust in one operation cycle, that is, a spark ignition type, and combustion. This is configured as a cylinder injection engine (cylinder injection internal combustion engine) that directly injects fuel into the room.
[0015]
An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1 so as to communicate with each other. The intake passage 2 and the combustion chamber 1 are controlled to communicate with each other by an intake valve 4, and the exhaust passage 3 and the combustion chamber 1 are connected. The communication is controlled by the 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 purification catalytic converter 9 as an exhaust gas purification catalyst in order from the upstream side. A muffler (silencer) (not shown) is provided. The intake passage 2 is provided with a surge tank 2a.
[0016]
Further, an exhaust gas recirculation device (hereinafter referred to as an EGR device) 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 and the upstream side of the exhaust passage 3, and an EGR valve 10a is attached to the exhaust gas recirculation passage 10b.
The flow rate of exhaust gas (also referred to as exhaust gas, exhaust gas, or exhaust gas) from the exhaust passage 3 to the intake passage 2 can be controlled by the EGR valve 10a. The EGR valve 10a is controlled according to the operating state of the engine.
[0017]
Further, the opening degree 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, 16 is an idle speed control valve, which is provided in a bypass passage 16A that bypasses the throttle valve installation portion of the intake passage 2 and is driven to open and close by a stepper motor (not shown), and mainly the throttle valve 7 is fully closed or substantially fully closed. The idle speed at the time is finely adjusted.
[0018]
50 is an air bypass valve (ABV), which is provided in 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 the throttle valve 7 installation portion of the intake passage 2. 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, this injector 8 is provided for each cylinder. For example, if the engine of this embodiment is an in-line four-cylinder engine, four injectors 8 are provided.
[0019]
With such a configuration, the air sucked through the air cleaner 6 according to the opening of the throttle valve 7 is sucked into the combustion chamber 1 by opening the intake valve 4, and the sucked air and the injector 8 in the combustion chamber 1. The fuel directly injected from the fuel is mixed, and the ignition plug 35 is ignited at an appropriate timing in the combustion chamber 1 to be combusted to generate engine torque. CO, HC, NO in the exhaust gas is discharged to the exhaust passage 3 and discharged by a catalytic converter (hereinafter also simply referred to as catalyst) 9 _x After purifying such harmful components, they are silenced by a muffler and released to the atmosphere.
[0020]
In particular, this engine is a lean burn engine (lean combustion internal combustion engine) that can perform a saving operation while making the air-fuel ratio lean (fuel lean state), and is formed by injecting fuel uniformly into the combustion chamber 1. This is an engine that can switch between premixed combustion that can be performed and stratified lean combustion that can be established by making the injected fuel unevenly distributed around the spark plug 35 facing the combustion chamber 1 in accordance with the operating state.
[0021]
In this engine, as the engine operation mode, a late lean combustion operation mode (late lean mode) in which fuel injection is performed in the compression stroke to perform stratified lean combustion, and fuel injection is performed in the intake stroke to perform premixed combustion. There are four modes: a first-term lean combustion mode (first-term lean mode), a stoichiometric feedback combustion mode (stoichio mode), and an open-loop combustion mode (stoichio mode or enrichment mode). In each mode, the case where the EGR is operated and the case where the EGR is stopped is set, and any one of these modes is selected according to the operating state of the engine, the traveling state of the vehicle, etc. Control is performed.
[0022]
For this reason, as shown in FIG. 1, the engine operating state, that is, the engine load state Pe and the engine speed Ne of the engine are input to the ECU 23 based on the output of each sensor. The ECU 23 is provided with a function (mode selection unit) 102 for selecting each operation mode as described above in accordance with the engine operation state (Pe, Ne in this case) input from the operation state detection unit 101. ing. The ECU 23 further sets the air-fuel ratio according to the engine operating state (Pe, Ne) based on the selected operation mode, and 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.
[0023]
In general, the enrichment 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 late lean mode can achieve the leanest combustion (the air-fuel ratio is about 25 to 50), but in this mode, the fuel injection is a stage that is very close to the ignition timing as in the late stage of the compression stroke. In addition, the fuel is collected in the vicinity of the spark plug, and the fuel is partially saved to make it lean, and the fuel-saving operation is performed while ensuring ignition and combustion stability.
[0024]
In addition, lean combustion (the air-fuel ratio is about 18 to 22) can also be realized in the first lean mode, but in this mode, fuel injection is performed in the intake stroke before the second lean mode, and fuel is diffused into the combustion chamber as a whole. Saving operation is performed by ensuring a certain output while ensuring ignitability and combustion stability while making the air-fuel ratio lean.
[0025]
The stoichio operation mode is O ₂ By feedback control based on the output of the sensor, a sufficient engine output can be obtained efficiently while maintaining the air-fuel ratio at or near the stoichiometric state. This stoichiometric operation mode is also referred to as a stoichiometric feedback operation mode.
In the open loop combustion operation mode (enriched), combustion is performed at stoichiometric or richer air / fuel ratio by open loop control so that sufficient output can be obtained at the time of acceleration or starting.
[0026]
In order to control the engine in this way, various sensors are provided, and some of these sensors constitute the operating state detection means 101. First, on the intake passage 2 side, an air flow sensor 11 for detecting the intake air amount from Karman vortex information, an intake air temperature sensor 12 for detecting the intake air temperature, and an atmospheric pressure sensor 13 for detecting the atmospheric pressure are provided in the air cleaner portion. A potentiometer type throttle sensor 14 for detecting the opening degree of the throttle valve 7, an idle switch 15 for detecting an idling state, a knock sensor 36, and the like are provided in the throttle valve arrangement portion.
[0027]
Further, as other sensors, a water temperature sensor 19 for detecting the engine coolant temperature, a crank angle sensor 21 for detecting the crank angle (the crank angle sensor 21 also serves as a rotation speed sensor for detecting the engine rotation speed), and a second sensor. A TDC sensor (cylinder discrimination sensor) 22 for detecting the top dead center of one cylinder (reference cylinder) is provided. Detection signals from these sensors are input to an electronic control unit (ECU) 23.
[0028]
The ECU 23 is supplied with a voltage signal from an accelerator position sensor (not shown) for detecting the amount of depression of the accelerator pedal or a battery sensor (not shown) for detecting the voltage of the battery, and a cranking switch (or an ignition for detecting the start time). A signal from a switch (key switch)] (not shown) is also input.
[0029]
The engine performs various controls based on the input data from such various sensors. In particular, as shown in FIG. 1, the ECU 23 has a function of performing knock control [ignition timing for knock control. Control means (simply also referred to as control means)] 104 is provided.
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) ΘK (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 adjusted to the advance side or the retard side so that the output can be obtained while suppressing the engine knock. To do.
[0030]
By the way, in this engine, the operating state of the engine is defined from the engine speed Ne and the volume efficiency Ev calculated from the output of the air flow sensor or the like as engine load information, and the operating state of the engine is shown in FIG. As shown, the knock learning value K is updated for each of a plurality of matrix regions (regions separated by vertical and horizontal broken lines in FIG. 4) that are partitioned by the engine speed Ne and the volumetric efficiency Ev. The volumetric efficiency Ev is adopted in order to perform engine control more accurately.
[0031]
In addition, knock control is performed in intake lean operation (in the previous lean mode) and intake stoichiometric operation (in the stoichiometric operation mode) among the main operation modes (stoichio operation mode, previous lean mode, and late lean mode). Yes, and not during 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 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. The basic ignition timing ST1 is set from the target engine load Pe obtained from θth and the engine speed Ne and the engine speed Ne.
[0032]
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, the ignition timing is set to the retard side with a margin in order to suppress the generation of NOx in the lean operation region, but such processing is performed in the stoichiometric operation region. Absent.
[0033]
Therefore, knocking is unlikely to occur in the intake lean operation region, and the learning value K is set to be updated in the same operation region as in the stoichiometric operation under such a condition that the ignition timing is set on the retard side with a margin. In this case, when the operation is continuously performed in the intake lean operation region where the knock does not occur, the learning value K is updated to the advance side. For this reason, even if knock does not occur in the intake lean operation region, if the ignition timing is switched to the stoichiometric operation region that is not set to the retarded side with a margin, the ignition timing ST is significantly adjusted to the advanced side. Therefore, knocking is extremely likely to occur.
[0034]
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.
In other words, when the engine load is relatively high, knocking is likely to occur in the intake lean operation region as well as in the stoichiometric operation region (that is, in this case, the ignition timing set in consideration of NOx reduction becomes the knock generation limit). Therefore, if the engine load is equal to or higher than a predetermined region, the learning value K is appropriate as an update region. On the other hand, in the stoichiometric operation region, knocking is likely to occur since the engine load is relatively low. Therefore, if the engine load is equal to or higher than a predetermined region, the learning value K is appropriate as an update region.
[0035]
Further, the ignition timing is corrected to the retard side when it is attempted to suppress the knock when a knock occurs, whereas the ignition timing is corrected to the advance side when no knock occurs. Therefore, rather, the correction is made to the advance side where knocking is likely to occur, thereby achieving a good combustion state up to the knock generation limit retardation and obtaining an output. It can be said that the correction to the advance side is a correction that facilitates the occurrence of knocking. Therefore, if the ignition timing is positively corrected to the advance side, knocks are likely to occur frequently due to changes in the operating state, causing problems such as deterioration of drivability. The update should be set so as to be performed with priority over the update of the learning value corrected to the advance side.
[0036]
In this engine, the learning value for correcting the ignition timing to the retard side is updated from a region where the engine load is relatively low, and the learning value for correcting the ignition timing to the advance side is updated to the retard side. The setting is made so that the engine load region is relatively higher than that in the case of correction. That is, the update area for correcting the learning value to the advance side is made narrower than the update area for correcting the learning value to the retard side.
[0037]
In particular, in this engine, the volumetric efficiency Ev is set as an amount corresponding to the engine load. As shown in FIG. 4, in the stoichiometric operation region, the volumetric efficiency Ev level is relatively low in the region where the volumetric efficiency Ev11 or higher. The learning value update region is set so as to update the learning value for correcting the ignition timing to the retard side, and the learning value update for correcting the ignition timing to the advance side is set for learning to the retard side. The learning value update region is set so as to be performed in a region having a volume efficiency Ev01 (Ev01> Ev11) higher than the lower limit value Ev11 of the value update region.
[0038]
In the intake lean operation region, the learning value update region is constantly updated so that the learning value for correcting the ignition timing to the retarded angle side is constantly updated in the region where the volume efficiency Ev level is relatively high or higher. The learning value that is set and corrects the ignition timing to the advance side is updated in a region that is higher than the lower limit value Ev12 of the update region of the learning value to the retard side and that is higher than the volume efficiency Ev02 (Ev02> Ev12). In addition, a learning value update area is set.
[0039]
In the same operation mode, it is only necessary to set the lower limit value of the update range of the learning value to the advance side to a load region higher than the lower limit value of the update range of the learning value to the retard side. The lower limit value of the learning value update region toward the advance side at the time may be set to be higher than the lower limit value of the learning value update region toward the retard side during the intake lean operation.
Since the lean combustion internal combustion engine as one embodiment of the present invention is configured as described above, ignition timing control relating to knock control is performed, for example, as shown in FIG.
[0040]
That is, first, the target engine load Pe obtained from the throttle opening degree θth and the engine rotational speed Ne, the volume efficiency Ev calculated from the output of the airflow sensor, etc., and the engine rotational 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 engine is in 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. Accordingly, the basic ignition timing ST1 is set to the ignition timing ST (step S190), and an ignition timing signal is output according to the ignition timing ST to control the operation of the spark plug 35 (step S170).
[0041]
On the other hand, if it is not the compression lean mode, the intake lean mode or stoichiometric mode is set. In this case, first, the basic ignition timing ST2 is set from the volume efficiency Ev and the engine speed Ne (step S30), and then Then, knock data ΘK (t) is set in the knock sensor output (step S40). This knock data ΘK (t) is also used for updating the learning value ΘK of the corresponding operation region. If the knock occurrence tendency is in accordance with the knock occurrence state indicated by the knock sensor output, the knock data ΘK (t) is advanced to the retard side. Set to the corner side.
[0042]
Next, it is determined whether or not the stoichiometric mode (stoichiometric feedback mode) is set (step S50). If the stoichiometric mode is selected, the process proceeds to step S60 to determine whether or not the knock data ΘK is larger than the predetermined value α. This determination is to determine whether the knock data ΘK 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 by this determination, it should be corrected to the advance side, and the process proceeds to step S70, whether or not the volume efficiency Ev is equal to or higher than the lower limit value Ev01, that is, in the stoichiometric mode. It is determined whether or not it is a learning value update area toward the advance side.
[0043]
If the volumetric efficiency Ev is greater than or equal to the lower limit value Ev01 (in the stoichiometric mode, the learning value update region to the advance side), the learning value K is updated to the advance side by the correction amount β1 corresponding to the knock data ΘK. (Step S120), the process further proceeds to Step S160, where the ignition timing ST is obtained from the basic ignition timing ST2 based on the knock data ΘK and the learning value K updated to the advance side in Step S120, and the ignition timing ST In response to this, an ignition timing signal is output to control the operation of the spark plug 35 (step S170).
[0044]
If the volumetric efficiency Ev is not equal to or lower than the lower limit value Ev01 in step S70, the learning value K is not updated. In step S160, the ignition timing is based on the knock data ΘK and the learning value K that is not updated from the basic ignition timing ST2. ST is obtained, and an ignition timing signal is output according to the ignition timing ST to control the operation of the spark plug 35 (step S170).
[0045]
If the knock data ΘK is larger than the predetermined value α in step S60, it should be corrected to the retard side, and the process proceeds to step S80, in which whether or not the volume efficiency Ev is equal to or higher than the lower limit value Ev11, that is, stoichiometric. It is determined whether or not it is a learning value update region to the retard side in the mode.
If the volumetric efficiency Ev is equal to or greater than the lower limit value Ev11 (in the stoichiometric mode, the learning value update region to the retard side), the learned value K is updated to the retard side by the correction amount β2 corresponding to the knock data ΘK. (Step S130), the process further proceeds to step S160, the ignition timing ST is obtained from the basic ignition timing ST2 based on the knock data ΘK and the learning value K updated to the retard side in step S130, and the ignition timing ST In response to this, an ignition timing signal is output to control the operation of the spark plug 35 (step S170).
[0046]
If the volumetric efficiency Ev is not equal to or lower than the lower limit value Ev11 in step S80, the learning value K is not updated. In step S160, the ignition timing is based on the knock data ΘK and the learning value K that is not updated from the basic ignition timing ST2. ST is obtained, and an ignition timing signal is output according to the ignition timing ST to control the operation of the spark plug 35 (step S170).
[0047]
On the other hand, if it is not the stoichiometric mode in step S50, it is the intake lean mode, and the routine proceeds to step S90, where it is determined whether or not the knock data ΘK is larger than the predetermined value α. This determination is to determine whether the knock data ΘK is corrected to the advance side or to the retard side. In this determination, if the knock data ΘK is equal to or smaller than the predetermined value α, it should be corrected to the advance side, and the process proceeds to step S100, whether the volume efficiency Ev is equal to or greater than the lower limit value Ev02, that is, in the intake lean mode. It is determined whether or not it is a learning value update area toward the advance side.
[0048]
If the volumetric efficiency Ev is equal to or greater than the lower limit value Ev02 (in the learning value update region toward the advance angle side in the intake lean mode), the learned value K is updated toward the advance angle side by the correction amount β1 corresponding to the knock data ΘK. (Step S140), the process further proceeds to Step S160, where the ignition timing ST is obtained from the basic ignition timing ST2 based on the knock data ΘK and the learning value K updated to the advance side in Step S140, and the ignition timing ST In response to this, an ignition timing signal is output to control the operation of the spark plug 35 (step S170).
[0049]
If the volumetric efficiency Ev is not equal to or lower than the lower limit value Ev02 in step S100, the learning value K is not updated. In step S160, the ignition timing is based on the knock data ΘK and the learning value K that is not updated from the basic ignition timing ST2. ST is obtained, and an ignition timing signal is output according to the ignition timing ST to control the operation of the spark plug 35 (step S170).
[0050]
If the knock data ΘK is larger than the predetermined value α (α is an intermediate value between the maximum retard amount and 0) in step S90, the delay data should be corrected to the retard side, and step S110 is performed. Then, it is determined whether or not the volumetric efficiency Ev is equal to or greater than the lower limit value Ev12, that is, whether or not it is a learning value update region to the retard side in the intake lean mode.
If the volumetric efficiency Ev is equal to or greater than the lower limit value Ev12 (in the stoichiometric mode, the learning value update region to the retard side), the learned value K is updated to the retard side by the correction amount β2 corresponding to the knock data ΘK. (Step S150), the process further proceeds to Step S160, where the ignition timing ST is obtained from the basic ignition timing ST2 based on the knock data ΘK and the learning value K updated to the retard side in Step S150, and the ignition timing ST In response to this, an ignition timing signal is output to control the operation of the spark plug 35 (step S170).
[0051]
In step S110, if the volumetric efficiency Ev is not equal to or lower than the lower limit value Ev12, the learning value K is not updated. ST is obtained, and an ignition timing signal is output according to the ignition timing ST to control the operation of the spark plug 35 (step S170).
[0052]
In this way, according to the present apparatus, different learning value update regions are set in the stoichiometric mode and the intake lean mode, and further, learning value update regions that are different on the retard side and the advance side for each mode. Therefore, the learning value can be updated appropriately.For example, in the intake lean operation range, even when the ignition timing is set to the retard side with a margin to suppress the generation of NOx Therefore, updating of the learning value in a region where the knocking is unlikely to occur in the intake lean operation region (low load region) is prohibited, and the ignition timing ST is greatly advanced even when the stoichiometric operation region where knocking is likely to occur is switched. The occurrence of knocking can be suppressed without being adjusted to the corner side.
[0053]
Further, in this embodiment, since the learning value update to the retard side is set to have priority over the learning value update to the advance side, the occurrence of knock can also be suppressed in this respect.
In the present embodiment, the knock control in the enrich operation mode is not specifically described, but the knock control is performed by setting the learning update region wider than in the intake lean mode as in the stoichiometric mode. May be performed.
[0054]
Also, in this embodiment, there is a margin in the intake lean mode. To have The explanation is based on the assumption that the ignition timing is set to the retarded angle side, but depending on the system, this may be reversed, i.e., the intake lean mode is set to the advanced angle side than the stoichiometric mode. In this case, lower the lower limit value of the learning value update region in the intake lean mode, further increase the lower limit value of the learning value update region in the stoichiometric mode, and It is conceivable that the lower limit value is set higher than the lower limit value in the intake lean mode.
[0055]
In the above embodiment, the ignition timing is set differently in the lean operation range and the stoichiometric operation region in consideration of the NOx purification efficiency by the catalyst, etc., but the present invention is based on the intake air amount or the intake negative pressure data. When the learning value region is set on the basis of this, it is effective even when the optimal ignition timing is set in each operation mode regardless of the NOx purification by the catalyst.
[0056]
In other words, since lean operation is substantially smaller in stoichiometric operation than in stoichiometric operation at the same volumetric efficiency, knocking does not occur in the lean operation region when a learning value update region is set corresponding to stoichiometric operation. Since the generation region is included as the learning update region, knock learning becomes inappropriate. For this reason, even in such a case, it is effective to set a load-corresponding lower limit value (lower limit value of intake air amount or intake negative pressure data) for updating the learned value of lean operation higher than that in stoichiometric operation.
[0057]
Further, whether or not the knock data ΘK is larger than the predetermined value α determines whether it is an advance angle side or a retard angle side. With regard to this determination, a dead zone is provided, for example, α1 is a positive minute value. If ΘK <α−α1, the advance side may be determined, and if α + α1 <ΘK, the retard side may be determined.
[0058]
【The invention's effect】
As detailed above, claims 1 to 4. Any one of 4 According to the lean combustion internal combustion engine of the present invention, the operation range in which the knock learning value is updated is configured to be switched between the stoichiometric operation mode and the lean operation mode. It is possible to suppress the occurrence of knocking that is likely to occur after the operation mode is switched when they are different.
[0059]
Claim 2 or According to the lean combustion internal combustion engine of the present invention described in 3, since the operation mode is set based on the intake air amount or the intake negative pressure data, even if the load level is substantially different with the same intake air amount or intake negative pressure data. Switching of the operation mode according to the operation state can be performed reliably, and the load operation lower limit value is set higher in the lean operation mode region where the ignition timing is basically set to the retard side than in the stoichiometric operation mode region By doing so, the occurrence of knocking at the time of switching from the lean operation mode to the stoichiometric operation mode is suppressed.
[0060]
Claim 4 According to the lean combustion internal combustion engine of the present invention described above, it is possible to suppress frequent occurrence of knocking while ensuring the output in the specific operation region in the same operation region.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of a lean combustion internal combustion engine as an embodiment of the present invention.
FIG. 2 is a configuration diagram showing a lean combustion internal combustion engine as one embodiment of the present invention.
FIG. 3 is a diagram illustrating an operation mode of a lean combustion internal combustion engine as one embodiment of the present invention.
FIG. 4 is a diagram illustrating a lean combustion internal combustion engine as one embodiment of the present invention.
FIG. 5 is a flowchart showing a lean combustion internal combustion engine as one embodiment of the present invention.
[Explanation 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 air temperature sensor
13 Atmospheric pressure sensor
14 Throttle sensor
15 Idle switch
16 Idle speed control valve
16A bypass
23 ECU
35 Spark plug
36 knock sensor
50 Air bypass valve (ABV)
50A bypass
101 Output operation state detection means
102 Mode selection means
103 Fuel injection valve control means
104 Ignition timing control means (control means) for knock control

Claims (4)

A spark ignition type lean combustion internal combustion engine that can switch between a stoichiometric operation mode that operates near the stoichiometric air-fuel ratio and a lean operation mode that operates in an air-fuel ratio range that is leaner than the stoichiometric air-fuel ratio depending on the engine operating state An engine having an exhaust purification catalyst in an exhaust system and having a basic ignition timing set to be different between the stoichiometric operation mode and the lean operation mode.
A knock sensor for detecting engine knocking;
Suppressing engine knock from knock data obtained from the knock sensor output and the knock learning value that is obtained based on the knock data or the knock sensor output and is commonly used in the stoichiometric operation mode and the lean operation mode Control means for adjusting the ignition timing of the engine,
The operating range for updating the learning value, and another set between the stoichiometric operation mode and the lean operation mode, is configured to perform the update of the learning value in the operating region corresponding to the operating mode selected Rutotomoni ,
The operation range in which the learning value is updated is set at least according to the load of the internal combustion engine, and the learning value is updated in one of the operation modes having a narrow region where knocking is likely to occur between the stoichiometric operation mode and the lean operation mode. The lean combustion internal combustion engine, wherein the load-corresponding lower limit value in the operating region is set higher than the load-corresponding lower limit value in the wider mode of the region . The internal combustion engine is configured to set the operation mode based on intake air amount or intake negative pressure data,
Load corresponding lower limit of the operating range for updating the learning value, characterized in that towards the region is set higher in the stoichiometric above the lean operation mode than in the region in the operating mode, the lean burn according to claim 1, wherein Internal combustion engine. The stoichiometric operation mode in which operation is performed in the vicinity of the theoretical air-fuel ratio and the lean operation mode in which operation is performed in an air-fuel ratio range that is leaner than the theoretical air-fuel ratio can be switched by the intake air amount or intake negative pressure data depending on the engine operation state. A spark-ignition lean combustion internal combustion engine that includes an exhaust purification catalyst in an exhaust system, and the basic ignition timing is set to be different between the stoichiometric operation mode and the lean operation mode.
A knock sensor for detecting engine knocking;
Suppressing engine knock from knock data obtained from the knock sensor output and the knock learning value that is obtained based on the knock data or the knock sensor output and is commonly used in the stoichiometric operation mode and the lean operation mode Control means for adjusting the ignition timing of the engine,
The operation range in which the learning value is updated is set separately for the stoichiometric operation mode and the lean operation mode, and the learning value is updated in the operation region according to the selected operation mode. ,
The lean combustion internal combustion engine , wherein the load-corresponding lower limit value of the operation region for updating the learning value is set higher in the region in the lean operation mode than in the region in the stoichiometric operation mode. A spark ignition type lean combustion internal combustion engine that can switch between a stoichiometric operation mode that operates near the stoichiometric air-fuel ratio and a lean operation mode that operates in an air-fuel ratio range that is leaner than the stoichiometric air-fuel ratio depending on the engine operating state An engine having an exhaust purification catalyst in an exhaust system and having a basic ignition timing set to be different between the stoichiometric operation mode and the lean operation mode.
A knock sensor for detecting engine knocking;
Suppressing engine knock from knock data obtained from the knock sensor output and the knock learning value that is obtained based on the knock data or the knock sensor output and is commonly used in the stoichiometric operation mode and the lean operation mode Control means for adjusting the ignition timing of the engine,
The operation range in which the learning value is updated is set separately for the stoichiometric operation mode and the lean operation mode, and the learning value is updated in the operation region according to the selected operation mode. ,
The operation region in which the learning value is updated is set according to the load of the internal combustion engine. The operation region includes a retardation region in which the learning value is updated to the retard side, and the learning value is advanced to the advance side. The advance angle region to be updated is set, and the load corresponding lower limit value for setting the advance angle region is set lower than the load corresponding lower limit value for setting the retard angle region. , lean-burn internal combustion engine.

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