JP4120292B2 - Knock learning control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a knock learning control device for an internal combustion engine that calculates a knock learning value according to an output of a knock sensor.
[0002]
[Prior art]
In an 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 engine output, it is preferable to advance the ignition timing to a state immediately before the occurrence of knocking. For this reason, a technique (knock control) for controlling the ignition timing immediately before the occurrence of knocking has been developed.
[0003]
When knocking is detected based on the output from the knock sensor, this knock control is performed by changing the ignition timing in a direction (retarding side) in which knocking does not occur by feedback control based on the knock sensor output. In addition, when knock occurrence is not detected, the ignition timing is changed in a direction (advance side) where knock occurs by feedback control based on the knock sensor output, and the ignition timing is controlled to a state immediately before the occurrence of knock. .
[0004]
By the way, because the occurrence of knocks varies depending on the fuel properties (especially octane number), atmospheric conditions, and differences in the engine, etc., in knock control, engine output immediately before the occurrence of knocks is generated efficiently within the range where knocks do not occur. The learning value is obtained according to the operating state of the engine by feedback control based on the output of the knock sensor so as to be as close as possible to the state that can be caused. It is known that the ignition timing is controlled based on the knock sensor output and the learning value so that an appropriate ignition timing is always set while the learning value is updated (Japanese Patent Laid-Open No. 60-162063). No., JP-A-59-113267).
[0005]
Hereinafter, the change of the knock learning value will be briefly described with reference to the drawings. The engine 1 shown in FIG. 5 is configured as an in-cylinder injection engine (in-cylinder injection internal combustion engine) that directly injects fuel into a combustion chamber, and an injector (not shown) is disposed in the combustion chamber. An intake passage 2 and an exhaust passage 3 are connected to the chamber.
The intake passage 2 is provided with an air cleaner 6 and a throttle valve 7 in order from the upstream side, and further, a surge tank 2a is provided downstream thereof. Further, the exhaust passage 3 is provided with an exhaust purification catalytic converter 9 and a muffler (not shown).
[0006]
An exhaust gas recirculation device (hereinafter referred to as an EGR device) 10 is disposed between the exhaust passage 2 and the intake passage 3. The EGR device 10 includes an exhaust recirculation passage 10b that connects the surge tank 2a and the exhaust passage 3, and an EGR valve 10a provided in the exhaust recirculation passage 10b. The recirculation amount of the 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.
[0007]
The throttle valve 7 is a so-called drive-by-wire throttle valve (ETV) that is electrically connected to the accelerator pedal. The throttle valve 7 has an opening degree that depends on the engine operating state in addition to the driver's accelerator depression amount. It has been changed.
The engine 1 includes an air flow sensor 11 that detects the intake air amount, a throttle opening sensor (TPS) 12 that detects the opening of the throttle, and a crank angle sensor that detects the engine speed by detecting the crank angle. 13. A knock sensor 14 for detecting engine knock and an accelerator opening sensor (not shown) for detecting the accelerator depression amount of the driver are attached.
[0008]
These sensors are connected to a controller (ECU) 20, and the ECU 20 outputs an operation control signal to the EGR valve 10a, the throttle valve 7, the injector, the ignition coil, and the like based on information from these sensors. It has become.
Then, as shown in FIG. 6, when a knock signal is detected from the knock sensor 14 as the driver depresses the accelerator and the engine speed increases, the ECU 20 updates the knock learning value until the knock is suppressed. The ignition timing correction amount (retard amount in this case) is set in accordance with the updated knock learning value.
[0009]
As a result, the ignition timing is controlled to a timing immediately before the occurrence of knocking, and the engine can be burned efficiently.
[0010]
[Problems to be solved by the invention]
By the way, as described above, the update of the knock learning value is executed in order to cope with changes in fuel properties and atmospheric conditions. However, such conventional techniques have the following problems.
In other words, the fuel properties (especially octane number) differ greatly from regular gasoline and high-octane (premium) gasoline. It will change suddenly. For this reason, it is preferable to update the knock learning value quickly if priority is given to the response to the change in the fuel properties, but in this case, the change in the knock learning value with respect to the change in the atmospheric condition becomes sensitive and the control stability may be lowered. There is.
[0011]
On the other hand, when updating the knock learning value for factors such as atmospheric conditions and engine deterioration, it is necessary to learn carefully. In such careful learning, knock learning when the fuel property changes takes time, There is a problem that knocks cannot be quickly suppressed.
In addition, the change in the flow rate of the exhaust gas recirculation amount by the EGR device 10 and the mismatch between the control ignition and the required ignition timing due to the excessive change in the EGR device 10 have a large effect on knocking, and when exhaust gas recirculation is being executed There is a problem that it is difficult to accurately grasp the fuel properties by knock learning.
[0012]
The present invention has been devised in view of such problems. Even when the fuel property changes suddenly, knock learning can be performed quickly in accordance with the change in the fuel property, so that the knock can be made promptly. An object of the present invention is to provide a knock learning control apparatus for an internal combustion engine that can be suppressed.
[0013]
[Means for Solving the Problems]
  For this reason, the knock learning control apparatus for an internal combustion engine according to the first aspect of the present invention calculates a knock learning value according to detection information of a knock detection means for detecting the knock intensity of the internal combustion engine, and according to the knock learning value. In the knock learning control device for an internal combustion engine for controlling the operation of the internal combustion engine, an oil supply detection means for detecting that the oil supply is performed,An exhaust gas recirculation adjusting means for adjusting an exhaust gas recirculation amount for recirculating a part of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine;When it is detected by the above-described refueling detecting means that refueling has been performed,An exhaust gas recirculation control means for controlling the operation of the exhaust gas recirculation adjustment means to limit the exhaust gas recirculation;It is characterized by having.
[0014]
  Therefore, for a predetermined period after it is detected that refueling has been performed,Since exhaust gas recirculation is limited, factors other than fuel properties that affect knocking can be reduced. For this reason, it is possible to quickly reflect the change in the knock status due to the change in fuel properties in the knock learning value, and when the newly supplied fuel differs from the previous fuel, the property of the fuel supplied to the engine changes suddenly. Even so, it is possible to quickly learn according to changes in fuel properties. Further, since exhaust gas recirculation is restricted for a predetermined period after refueling, exhaust gas recirculation appropriate for exhaust gas purification performance can be performed after the predetermined period, and the exhaust gas purification performance does not deteriorate.
[0015]
  The learning gain changing means further changes the learning gain of the knock learning value based on the detection information of the knock detecting means, and the learning gain changing means detects that refueling has been performed by the refueling detecting means. In this case, it is preferable that the learning gain is increased during the predetermined period.
[0016]
  In this case, since the learning gain of the knock learning value based on the detection information of the knock detection means is increased for a predetermined period after it is detected that fueling has been performed, the newly supplied fuel has the same characteristics as the previous fuel. Even in different cases, that is, when the fuel property of the internal combustion engine changes suddenly, knock learning can be quickly performed in accordance with the change in fuel property. Further, since the learning gain is increased for a predetermined period after refueling, stable learning can be performed after the predetermined period, and control stability does not deteriorate.
[0017]
  Note that the predetermined period is preferably a period from when it is detected that the fuel supply is detected to when the knock learning value converges. In this case, knock learning can be performed appropriately in accordance with the change in fuel properties during refueling.
  And claims1 to 3In the configuration described above, the internal combustion engine is configured to be capable of switching between 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 region that is leaner than the theoretical air-fuel ratio, The exhaust gas recirculation control means may be configured to execute the exhaust gas recirculation restriction in the stoichiometric operation mode.
[0018]
In this case, since exhaust gas recirculation is limited in the stoichiometric operation mode in which knocking is likely to occur, rapid learning can be performed in accordance with changes in fuel properties without deteriorating exhaust gas performance in the lean operation mode.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a knock learning control apparatus for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of the internal combustion engine to which the present invention is applied, and FIG. FIG. 3 and FIG. 4 are flowcharts for explaining the operation.
[0020]
An internal combustion engine (engine) 1 shown in FIG. 1 is configured as a spark ignition type in-cylinder injection engine that directly injects fuel into a combustion chamber (not shown), and is configured in substantially the same manner as the engine described with reference to FIG. ing. That is, an injector (not shown) is disposed in the combustion chamber, and the intake passage 2 and the exhaust passage 3 are connected to the combustion chamber.
[0021]
The intake passage 2 is provided with an air cleaner 6 and a throttle valve 7 in order from the upstream side, and further, a surge tank 2a is provided downstream thereof. Further, the exhaust passage 3 is provided with an exhaust purification catalytic converter 9 and a muffler (not shown).
An exhaust gas recirculation device (hereinafter referred to as an EGR device) 10 is disposed between the exhaust passage 2 and the intake passage 3. The EGR device 10 includes an exhaust recirculation passage 10b that connects the surge tank 2a and the exhaust passage 3, and an EGR valve (exhaust recirculation adjustment means) 10a provided in the exhaust recirculation passage 10b. The recirculation amount of exhaust gas (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.
[0022]
The throttle valve 7 is a so-called drive wire type throttle valve (ETV) that is electrically connected to the accelerator pedal. The throttle valve 7 has an opening degree that depends on the engine operating state in addition to the accelerator depression amount. It has been changed.
The engine 1 includes an air flow sensor 11 that detects the intake air amount, a throttle opening sensor (TPS) 12 that detects the opening of the throttle, and a crank angle sensor that detects the engine speed by detecting the crank angle. 13. A knock sensor 14 for detecting engine knock and an accelerator opening sensor (not shown) for detecting the accelerator depression amount of the driver are attached.
[0023]
Further, in the present embodiment, a sensor (fuel supply port switch) 21 that detects opening / closing of a fuel supply port (not shown) is provided, and this fuel supply port switch 21 is also connected to the ECU 20. The fuel filler port switch 21 functions as a fuel filler detecting means for detecting that fuel has been supplied (fuel supply). When the fuel filler switch 21 detects that the fuel filler port has been opened, the ECU 20 Then, it is determined that fuel is supplied (fuel supply).
[0024]
By the way, the engine 1 has a lean operation mode in which operation is performed at least in an air-fuel ratio range that is leaner than the stoichiometric air-fuel ratio, and a stoichiometric feedback combustion operation mode (stoichio operation mode) in which operation is performed in the vicinity of the stoichiometric air-fuel ratio. These operation modes can be switched.
In the engine 1, operation mode switching control and various controls are performed by the ECU 20 based on input data from various sensors as described above.
[0025]
Next, when focusing attention on the main part of the present invention, the ECU 20 is provided with a function of performing knock control. Specifically, the ECU 20 obtains a knock learning value K corresponding to the operating state of the engine based on the knock data (detection information) output from the knock sensor 14, and performs basic ignition based on the knock learning value K and the knock data. By correcting the timing to the advance side or the retard side, knocking of the engine 1 is suppressed. It should be noted that methods for calculating and updating the knock learning value K are well known (see, for example, Japanese Patent Laid-Open No. 10-68376), and thus detailed description thereof is omitted here.
[0026]
Further, the ECU 20 includes a learning gain changing unit 201 that increases the learning gain of the knock learning value K based on detection information from the knock sensor 14 and an exhaust gas recirculation control unit 202 that controls the operation of the EGR valve 10a to limit the exhaust gas recirculation. Is provided.
When the ECU 20 detects or determines refueling based on the information from the refueling port switch 21, the learning gain changing means 201 increases the learning gain of the knock learning value K for a predetermined period, and the exhaust gas recirculation control means 202 again. The exhaust gas recirculation is stopped by closing the EGR valve 10a for a predetermined period.
[0027]
The reason why the learning gain of the post-refueling knock learning value K is increased is that fuel characteristics (for example, octane number) can be greatly changed during refueling. This is because it is necessary to update the knock learning value K promptly when it is changed at a stroke.
That is, generally, when the knock learning value K is updated for factors such as atmospheric conditions and engine deterioration, it is necessary to carefully update the knock learning value K. Therefore, the learning gain of the knock learning value K is relatively small. Is set. Therefore, with such a learning gain, the update of the learning value K is delayed when the fuel property changes greatly, and it may take a long time to suppress knocking of the engine.
[0028]
Therefore, in the present embodiment, when the opening of the fuel filler opening is detected by the fuel filler switch 21, it is determined that the fuel has been refilled, and the knock learning value K can be quickly updated even if the fuel property changes. As shown, the learning gain is increased.
On the other hand, the reason why the EGR valve 10a is closed for a predetermined period after refueling to stop the exhaust gas recirculation is to reduce the requirement affecting the knock as much as possible. In other words, exhaust gas recirculation has the advantages of suppressing NOx and improving fuel efficiency, but if the exhaust gas recirculation amount fluctuates, it causes the knock learning value K to vary.
[0029]
Therefore, by stopping (or limiting) exhaust gas recirculation for a predetermined period after it has been detected that fueling has been performed, the factors affecting knocking are reduced, and knock learning due to changes in fuel properties is knocked. The value K is promptly reflected. Since EGR is restricted for a predetermined period after refueling, exhaust gas recirculation appropriate for exhaust purification performance can be performed after the predetermined period, and the exhaust purification performance does not deteriorate.
[0030]
Further, the exhaust gas recirculation restriction by the exhaust gas recirculation control means 202 is executed in the stoichiometric operation mode of the engine 1 and is not performed in the lean operation mode. This is because knocking is less likely to occur in the lean operation region, and knocking is more likely to occur in the stoichiometric operation region. In other words, among the modes in which knock control is performed, the stoichiometric operation mode and the lean operation mode are set so that the basic ignition timing (basic ignition timing) itself is different. Hard to happen. Therefore, even after refueling, the exhaust gas recirculation amount is controlled based on the operating state during the lean operation, and the exhaust gas recirculation is stopped during the stoichiometric operation.
[0031]
By the way, the predetermined period is a period from when it is detected that the fuel filler switch 21 has been refueled until the knock learning value K converges. In this embodiment, the knock learning value K is equal to or longer than a certain time. It is determined that the knock learning value has converged at the point in time when no change in the number is detected. The convergence determination of the knock learning value K is not particularly limited, and various determination methods can be applied.
[0032]
Since the knock learning control apparatus for an internal combustion engine according to an embodiment of the present invention is configured as described above, its operation will be described as follows.
As shown in the time chart of FIG. 2, first, when the opening / closing of the filler opening is detected based on the information from the filler switch 21, it is determined that the ECU 20 has been refueled. Simultaneously with this refueling determination, the learning gain for updating the knock learning value is increased, and during the stoichiometric operation, the EGR valve 10a is closed and the exhaust gas recirculation is stopped. Note that, during the lean operation, the EGR valve 10a is controlled according to the operating state of the engine (normal EGR control).
[0033]
Thereafter, as shown in FIG. 2, when the driver depresses the accelerator and the engine speed increases and knock is detected, the knock learning value K is updated accordingly. Although not shown, the ignition timing is also retarded according to the knock learning value K.
Further, at the time of updating the knock learning value K, the learning value of the knock learning value K is greatly corrected, so that the knock learning value K quickly converges. Furthermore, since the retard amount of the ignition timing is set according to the knock learning value K, the ignition timing is quickly corrected and knocking is suppressed.
[0034]
Further, when the convergence of the knock learning value K is determined, the learning gain is returned to the value before the change, and normal knock learning accompanying a change in the atmospheric condition or the like is executed relatively carefully as before.
Here, the gain of the knock learning value refers to the learning value update amount Δk and the knock learning value cycle time Δt in the time chart of FIG. 2, and increasing the knock learning gain means increasing at least | Δk | Or Δt is reduced, and in the present embodiment, at the time of fuel supply determination, | Δk | is increased and Δt is decreased.
[0035]
That is, by increasing | Δk |, the update amount of one knock learning value can be increased, and quick knock learning can be performed. Further, by reducing Δt, the number of updates of the knock learning value K per unit time can be increased, so that quick knock learning can also be performed.
Next, the operation of the knock learning control apparatus according to the present embodiment will be described with reference to the flowcharts of FIGS. 3 and 4. First, in step S11 of FIG. 3, the opening / closing of the filler opening is detected based on the information from the filler switch 21. If it is determined whether or not the fuel filler opening / closing is determined, the fuel property detection flag is turned on in step S12 and the process returns. Further, when it is not determined that the fuel filler opening / closing has been determined, the process directly returns from step S1.
[0036]
On the other hand, in step S21 of FIG. 4, it is determined whether or not the fuel property detection flag is on. If the flag is not on, the process proceeds to step S26, in which normal knock learning is performed and the engine operation state is set. The control of the corresponding normal EGR valve 10a is executed and the process returns.
On the other hand, if the fuel property detection flag is on, the process proceeds to step S22 to increase the knock learning gain, and then, in step S23, if the stoichiometric operation is being performed, the EGR valve 10a is closed to stop the exhaust gas recirculation. If it is during lean operation, step S23 is cancelled.
[0037]
Next, in step S24, it is determined whether or not the knock learning value has converged. Here, step S24 is repeatedly executed until it is determined that the knock learning value has converged. If it is determined that the knock learning value has converged, the process proceeds to step S25, the fuel property detection flag is turned off, and the process returns. .
Therefore, according to the knock learning control apparatus for an internal combustion engine according to the embodiment of the present invention, the learning gain of the knock learning value based on the detection information of the knock sensor 14 is increased for a predetermined period after the refueling is detected. Even when the fuel supplied to the engine 1 is different from the previous fuel and the property of the fuel supplied to the engine 1 changes suddenly, it is possible to quickly learn according to the change in the fuel property. Further, since the learning gain is increased for a predetermined period after refueling, stable learning can be performed after the predetermined period, and the control stability is not lowered.
[0038]
In addition, since exhaust gas recirculation by the EGR device 10 is limited (stopped) during the predetermined period, factors other than the fuel properties that affect knocking can be reduced. For this reason, a knock situation change due to a change in fuel properties can be quickly reflected in the knock learning value. Further, since exhaust gas recirculation is restricted for a predetermined period after refueling, after the predetermined period, exhaust gas recirculation appropriate for exhaust gas purification performance can be performed as usual, and the exhaust gas purification performance does not deteriorate.
[0039]
In addition, the predetermined period is a period from when it is detected that the fuel filler switch 21 has been refueled until the knock learning value converges, so that the knocking can be appropriately performed according to the change in the fuel property at the time of fueling. Learning can be done.
Further, since the exhaust gas recirculation by the EGR device 10 is stopped in the stoichiometric operation mode in which the engine 1 is likely to be knocked, the fuel property is reduced without deteriorating the exhaust gas performance in the lean operation mode. There is an advantage that quick learning according to change can be performed.
[0040]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, a fuel filler switch as a fuel filler detection means may be attached to a fuel filler opener provided near the driver's seat to detect the operation of the opener, or provided near the fuel filler opening and turned on and off by opening and closing the fuel filler opening. It may be a sensor. Further, the refueling detection means may be configured as a sensor that detects refueling in accordance with fluctuations in the level gauge of the fuel gauge.
[0041]
Further, in the present embodiment, the case where the ignition timing is corrected to the retard side (retard side) has been described. However, the present invention may be applied when the ignition timing is advanced until just before the occurrence of knocking due to a change in fuel properties. Good.
Furthermore, in this embodiment, both the increase of the knock learning gain and the stop of the exhaust gas recirculation of the EGR device 10 are executed after refueling, but at least one of them may be executed.
[0042]
【The invention's effect】
  As described above in detail, according to the knock learning control device for an internal combustion engine of the present invention according to claim 1, during a predetermined period after it is detected that refueling has been performed.Since exhaust gas recirculation is limited, factors other than fuel properties that affect knocking can be reduced. For this reason, it becomes possible to quickly reflect the change in the knock status due to the change in fuel properties in the knock learning value,Even when the newly supplied fuel is different from the previous fuel and the property of the fuel supplied to the engine changes suddenly, it is possible to quickly learn according to the change in the fuel property.Further, since exhaust gas recirculation is restricted for a predetermined period after refueling, exhaust gas recirculation appropriate for exhaust purification performance can be performed after the predetermined period, and deterioration of exhaust purification performance can be prevented.
[0043]
  Further, according to the knock learning control apparatus for an internal combustion engine of the present invention according to claim 2, during a predetermined period after it is detected that fuel has been supplied.Since the learning gain of the knock learning value based on the detection information of the knock detection means is increased, the learning gain increases for a predetermined period after refueling,Even when the newly supplied fuel is different from the previous fuel and the property of the fuel supplied to the engine changes suddenly, it is possible to quickly learn according to the change in the fuel property.Further, since the learning gain is increased for a predetermined period after refueling, stable learning can be performed after the predetermined period, and the control stability can be prevented from being lowered.
[0044]
Further, according to the knock learning control apparatus for an internal combustion engine of the present invention according to claim 3, knock learning can be appropriately performed in accordance with the change in the fuel property during refueling.
Further, according to the knock learning control device for an internal combustion engine of the present invention according to claim 4, since the exhaust gas recirculation is restricted in the swift operation mode in which knock is likely to occur, without reducing the exhaust gas performance in the lean operation mode, There is an advantage that rapid learning can be performed in accordance with changes in fuel properties.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine to which a knock learning control device for an internal combustion engine according to an embodiment of the present invention is applied.
FIG. 2 is a time chart for explaining the operation of the knock learning control apparatus for an internal combustion engine according to the embodiment of the present invention.
FIG. 3 is a flowchart for explaining the operation of the knock learning control apparatus for an internal combustion engine according to the embodiment of the present invention.
FIG. 4 is a flowchart for explaining the operation of the knock learning control apparatus for an internal combustion engine according to the embodiment of the present invention.
FIG. 5 is a schematic diagram showing a configuration of a general internal combustion engine.
FIG. 6 is a time chart for illustrating conventional knock control.
[Explanation of symbols]
1 engine (internal combustion engine)
10 EGR device (exhaust gas recirculation device)
10a EGR valve (exhaust gas recirculation adjustment means)
20 ECU (control means)
21 Refueling port switch (Fueling detection means)
201 Learning gain changing means
202 Exhaust gas recirculation control means

Claims (4)

In a knock learning control device for an internal combustion engine that calculates a knock learning value according to detection information of a knock detection means for detecting knock intensity of the internal combustion engine and controls the operation of the internal combustion engine according to the knock learning value.
Refueling detection means for detecting that refueling has been performed;
An exhaust gas recirculation adjusting means for adjusting an exhaust gas recirculation amount for recirculating a part of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine;
Exhaust gas recirculation control means for controlling the operation of the exhaust gas recirculation adjusting means so as to limit the exhaust gas recirculation for a predetermined period of time when it is detected that the fuel supply is detected by the oil supply detection means. A knock learning control device for an internal combustion engine. Learning gain changing means for changing the learning gain of the knock learning value based on the detection information of the knock detecting means;
The learning gain changing unit according to claim 1, wherein the learning gain changing unit increases the learning gain during the predetermined period when the refueling detecting unit detects that refueling has been performed . A knock learning control device for an internal combustion engine. 3. The knock of the internal combustion engine according to claim 1, wherein the predetermined period is a period from when it is detected that the fuel supply is detected by the fuel supply detection means until the knock learning value converges. Learning control device. The internal combustion engine is configured to be able to switch between 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 region that is leaner than the theoretical air-fuel ratio,
The knock learning control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas recirculation control means performs the exhaust gas recirculation restriction in the stoichiometric operation mode.

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