JP2004270504A - Idle speed controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an idle speed controller for an internal combustion engine by which occurrence of such a trouble can be suppressed that when misfire has happened, an overcorrection is made in a feedback control, which triggers a sharp rise in the rotational speed of the engine. <P>SOLUTION: In the idle speed controller, feedback control on an intake air flow is performed so that a rotational speed of the engine in idle operation agrees with a set rotational speed. Occurrence of a misfire in the internal combustion engine is judged, and execution of feedback control is inhibited (step S210) when a judgement on occurrence of a misfire is made (step S206:YES). Thus, in the control device, execution of such a control is inhibited that the intake air-flow is changed to the side of increasing the rotational speed of the engine. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an idle speed control device for an internal combustion engine.
[0002]
[Prior art]
In general, during idling operation of a vehicle-mounted internal combustion engine, a target rotation speed for the engine rotation speed is set. Then, so-called idle speed control control (hereinafter referred to as "ISC control") in which an engine control amount such as an intake air amount or a fuel injection amount is feedback-controlled so that the actual rotation speed matches the target rotation speed. (See, for example, Patent Document 1).
[0003]
In this ISC control, a rotational speed as low as possible is set as the target rotational speed under conditions that stable operation of the internal combustion engine during idle operation is maintained. Thereby, engine noise and fuel consumption rate are suppressed as much as possible while maintaining idle stability.
[0004]
[Patent Document 1]
JP-A-9-189252 (page 3-4, FIG. 3-4)
[0005]
[Problems to be solved by the invention]
By the way, during the execution of the ISC control, if a misfire occurs due to, for example, use of poor fuel or some abnormality of the engine system, the following inconvenience occurs.
[0006]
As shown in FIG. 6, at time t21, if a misfire occurs after the start of the internal combustion engine is completed ([a] in FIG. 6), the engine rotational speed is reduced by an amount corresponding to the decrease in the engine torque due to the misfire. It becomes lower ([d] in the figure). Therefore, in order to compensate for the decrease, the feedback correction amount rapidly increases from the time t21 to the time t22 ([b] in the figure).
[0007]
Then, when the occurrence of misfire stops at time t22, the engine control amount (in this example, the intake air amount: [c] in the drawing, which is corrected by the increased feedback correction amount even though the misfire has not occurred. ), The engine control is executed.
[0008]
As a result, the engine torque sharply increases, and accordingly, the engine rotational speed also sharply increases ([d] in the figure). This leads to a significant overshoot of the engine rotation speed from the target rotation speed, and reduces drivability.
[0009]
In an apparatus in which the ISC control for setting the target rotation speed to a high speed when the engine is cold is performed, since the engine rotation speed is set to be high when the engine is cold where misfiring easily occurs, the above-described disadvantages are caused. Particularly easy to occur. In addition, in order to increase the purification performance of the catalytic converter in the exhaust passage at an early stage, the target rotation speed in the ISC control is set to a higher speed when the engine is cold, and the exhaust gas temperature in the exhaust passage is increased, so that the catalytic converter can be quickly operated. In this case, the temperature is raised. However, when the target rotational speed is set to a higher value, the tendency of the drivability to deteriorate as described above becomes more remarkable.
[0010]
The present invention has been made in view of the above circumstances, and an object of the invention is to suppress an excessive correction in feedback control due to the occurrence of a misfire, thereby suppressing a sudden increase in engine speed due to the correction. It is an object of the present invention to provide an idle speed control device for an internal combustion engine that can perform the operation.
[0011]
[Means for Solving the Problems]
Hereinafter, the means for achieving the above object and the effects thereof will be described.
First, an invention according to claim 1 is an idle speed control apparatus for an internal combustion engine that performs feedback control of an engine control amount so that the engine speed during idling operation and its target speed match. Misfire determining means for determining occurrence of the engine, and limiting the change of the engine control amount to the side for increasing the engine rotational speed through the feedback control when the misfire determination means determines that the misfire has occurred. The gist of the present invention is to provide a restriction means for performing the above.
[0012]
In the above configuration, basically, when the engine rotation speed is lower than the target rotation speed, the correction amount (feedback correction amount) applied to the feedback control sets the engine rotation speed in order to make the engine rotation speed coincide with the target rotation speed. It is changed to the value of the side to raise. However, when a misfire occurs, such a change in the feedback correction amount is suppressed. Therefore, according to the above configuration, it is possible to suppress an excessive correction in the ISC feedback control due to the occurrence of a misfire, thereby suppressing a sudden increase in the engine speed due to the correction.
[0013]
According to a second aspect of the present invention, in the idle speed control device for an internal combustion engine according to the first aspect, the limiting unit stops execution of the feedback control and prohibits a change of the engine control amount by the control. That is the gist.
[0014]
According to the above configuration, it is possible to prohibit the change of the feedback correction amount when a misfire occurs, and prevent the increase. Therefore, when the occurrence of misfire stops thereafter and the feedback control is started, it is possible to preferably suppress the engine speed from increasing.
[0015]
According to a third aspect of the present invention, in the idle speed control device for an internal combustion engine according to the first aspect, the limiting unit sets an upper limit value for a feedback correction amount when correcting the engine control amount through the feedback control. The setting is the gist.
[0016]
According to the configuration described above, when a misfire occurs, the feedback correction amount changes to a value on the side that increases the engine rotation speed, but the change can be limited by the limit value. Therefore, when the change in the feedback correction amount reaches the limit value, the change in the feedback correction amount can be suppressed by the amount limited by the limit value.
[0017]
According to a fourth aspect of the present invention, in the idle speed control device for an internal combustion engine according to the first or third aspect, the limiting means reduces a control gain of the feedback control.
[0018]
According to the above configuration, the rate of change of the feedback correction amount when a misfire occurs can be made lower than when the misfire does not occur. Therefore, if the change in the feedback correction amount is not saturated, the change can be suppressed.
[0019]
Here, the engine speed does not decrease so much when the misfire occurs only once or sporadic. In other words, when misfires occur frequently, the engine speed is significantly reduced. Therefore, in this case, the inconvenience is likely to occur. On the other hand, the restriction is executed when the occurrence of misfire is determined a plurality of times or more, thereby accurately determining that misfire occurs frequently enough to cause the inconvenience. As a result, it is possible to appropriately limit an excessive change in the feedback correction amount.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
First, a schematic configuration of an engine system to which the idle speed control device according to the present embodiment is applied will be described with reference to FIG.
[0021]
As shown in FIG. 1, an intake passage 14 and an exhaust passage 16 are connected to a combustion chamber 12 of the internal combustion engine 10, respectively. A throttle valve 20 that is opened and closed by a motor 18 is provided in the intake passage 14. This throttle valve 20 regulates the amount of air taken into the combustion chamber 12.
[0022]
A fuel injection valve 22 is provided in the intake passage 14. The fuel injection valve 22 injects fuel into the intake passage 14. The injected fuel is mixed with the intake air and is introduced into the combustion chamber 12 with the opening of the intake valve 24.
[0023]
Then, a mixture of fuel and air introduced into the combustion chamber 12 is ignited by the ignition plug 26 and burns. Thereafter, the combustion gas is discharged to the exhaust passage 16 with the opening of the exhaust valve 28.
[0024]
The exhaust passage 16 is provided with a catalytic converter 30 having an exhaust purification function. The exhaust gas discharged to the exhaust passage 16 is purified by the catalytic converter 30 and then discharged to the outside of the exhaust passage 16. The catalytic converter 30 is of a type that is activated by its own temperature rise.
[0025]
The internal combustion engine 10 is provided with various sensors for detecting an engine operating state and the like. For example, an intake air amount sensor for detecting an intake air amount GA, a crank sensor for detecting a rotation phase (crank angle) and a rotation speed (engine rotation speed NE) of a crankshaft of the internal combustion engine 10, an engine cooling water Is provided with a water temperature sensor for detecting the temperature THW. Further, an idle switch and the like for detecting the presence or absence of depression of an accelerator pedal are also provided.
[0026]
The output signals of these various sensors are taken into an electronic control unit 32 that controls and executes various controls of the internal combustion engine 10. The electronic control unit 32 performs various controls related to engine control, such as controlling the motor 18, the fuel injection valve 22, and the spark plug 26 based on these detection signals. Note that the electronic control unit 32 executes the above-described ISC control as the various controls.
[0027]
Hereinafter, a processing procedure of the feedback control, which is one processing mode of the ISC control according to the present embodiment, will be specifically described with reference to a flowchart shown in FIG.
[0028]
Note that a series of processes shown in this flowchart is a process executed by the electronic control device 32 as a process for each predetermined cycle, provided that a precondition described later is satisfied.
[0029]
As shown in FIG. 2, in this process, first, a target rotation speed TNE for the engine rotation speed NE is calculated based on the cooling water temperature THW (step S102). Here, the lower the cooling water temperature THW, the more the engine combustion state tends to be unstable. Therefore, the target rotation speed TNE is set to a higher value to avoid this.
[0030]
Next, an expected control amount ISCbse for the feedback control is calculated based on the engine speed NE and the intake air amount GA (step S104).
This expected control amount ISCbse is output as a control signal to the throttle valve 20, more precisely, to the motor 18 that opens and closes the throttle valve 20, and as this value is set to a larger value, the opening degree of the throttle valve 20 becomes larger. growing. As a result, the amount of intake air passing through the throttle valve 20 increases, and the engine speed NE also increases due to the increase in fuel injection amount accompanying the increase. This is the same for the feedback correction amount ISCFB, the correction amount KH, and the final control amount ISCFIN to be described later.
[0031]
Next, the feedback correction amount ISCB is calculated (step S106).
Specifically, first, a speed difference ΔNE (= NE−TNE) between the engine rotation speed NE and the target rotation speed TNE is calculated. Then, a correction term proportional to the speed difference ΔNE, a correction term proportional to the integral value of the speed difference ΔNE, and a correction term proportional to the rate of change of the speed difference ΔNE are calculated and added. Thus, the feedback correction amount ISCB is calculated. The opening of the throttle valve 20 is increased or decreased based on the feedback correction amount ISCB. That is, in the present process, the intake air amount GA is controlled by proportional integral derivative (PID) based on the speed difference ΔNE.
[0032]
The feedback correction amount ISCB basically changes with the following tendency. When the engine rotational speed NE is lower than the target rotational speed TNE, the feedback correction amount ISCFB increases to obtain a larger engine torque. On the other hand, when the engine rotation speed NE is higher than the target rotation speed TNE, the feedback correction amount ICSFB becomes small in order to reduce the engine torque. In addition, the coolant temperature THW is also used to calculate the feedback correction amount ISCB. As the cooling water temperature THW is lower, the rate of increase of the feedback correction amount ISCFB increases, and the rate of decrease of the feedback correction amount ISCFB decreases. Become smaller.
[0033]
Next, an upper limit value GDH and a lower limit value GDL for the feedback correction amount ISCFB are calculated, and a guard process is performed on the feedback correction amount ISCFB based on the upper limit value GDH and the lower limit value GDL (step S108). Both the upper limit value GDH and the lower limit value GDL are values calculated based on the cooling water temperature THW, and the higher the cooling water temperature THW, the higher the value is set. The reason why such guard processing is performed is to prevent the feedback correction amount ISCFB from becoming excessively large or small when any abnormality occurs in the apparatus.
[0034]
Next, a correction amount KH for the load of the auxiliary equipment that is drivingly connected to the crankshaft is calculated (step S110).
Then, based on the expected control amount ISCbse, the feedback correction amount ISCFB, and the correction amount KH, a final control amount ISCFIN is calculated from the following equation (step S112).
ISCFIN = ISCbse + ISCB + KH
After the motor 18 is controlled based on the final control amount ISCFIN and the opening of the throttle valve 20 is controlled (step S114), the present process is temporarily terminated.
[0035]
Now, in the device of the present embodiment, it is determined whether or not a misfire has occurred in the internal combustion engine 10. This determination process is performed as follows.
That is, first, in the combustion stroke of each cylinder of the internal combustion engine 10, the time T required for the crankshaft to rotate by 30 ° CA starting from the compression top dead center is detected. Then, a difference (= T−Ti) between the time T and the same time (Ti) detected last time is calculated as the rotation fluctuation amount ΔT. Then, when the rotation fluctuation amount ΔT exceeds a predetermined threshold value, it is determined that a misfire has occurred. In the present embodiment, this determination process functions as a misfire determination unit that determines the occurrence of a misfire in the internal combustion engine.
[0036]
In the ISC control according to the present embodiment, the execution of the feedback control is prohibited when it is determined that misfire has occurred in the determination processing.
[0037]
Hereinafter, the processing procedure of such ISC control will be described with reference to the flowchart shown in FIG.
It should be noted that a series of processes shown in this flowchart is a process including the above-described feedback control process (Step S208 in the figure), and is executed by the electronic control unit 32 as a process at predetermined intervals.
[0038]
As shown in FIG. 3, in this process, first, it is determined whether or not the internal combustion engine 10 is in an idle operation state based on an output signal of an idle switch or the like (step S202).
[0039]
Then, when the vehicle is in the idling operation state (step S202: YES), it is determined whether the precondition is satisfied (step S204). This precondition is a condition for determining that the feedback control can be executed in a stable state, such as "starting of the internal combustion engine 10 has been completed" or "no abnormality has occurred in the engine system". .
[0040]
If the precondition is satisfied (step S204: YES), it is next determined whether or not misfire has occurred in the internal combustion engine 10 (step S206). If no misfire has occurred (step S206). : NO), and the feedback control (FIG. 2) is executed (step S208).
[0041]
On the other hand, when the misfire has occurred (step S206: YES), the execution of the feedback control is prohibited. At this time, the so-called open control, in which the estimated control amount ISCo is calculated based on the engine operation state such as the cooling water temperature THW and the load of various auxiliary devices, and the motor 18 is controlled based on the estimated control amount ISCo. Is executed (step S210). Therefore, although misfire has occurred at this time, the feedback correction amount ISCB does not increase due to the misfire. The misfire occurrence can be appropriately suppressed by adding the misfire occurrence state to the calculation parameter of the expected control amount ISCo. In the present embodiment, the process in S210 functions as a limiting unit that limits the change of the engine control amount to the side that increases the engine speed.
[0042]
Then, after the execution of the feedback control or the execution of the open control as described above, the present process is temporarily terminated.
When the vehicle is not in the idling operation state (step S202: NO), it is determined that there is no need to perform the ISC control in the first place, and this process is temporarily ended. When the precondition is not satisfied (step S204: NO), it is determined that the situation is such that the feedback control is not stably executable, and the open control is also executed in this case (step S210). The process is temporarily terminated.
[0043]
Hereinafter, an operation of executing the ISC control according to the present embodiment will be described with reference to FIG.
FIG. 4 is a timing chart showing an example of the processing mode of the ISC control processing when a misfire occurs immediately after the start of the internal combustion engine 10 is completed.
[0044]
Also, in FIG. 4, [a] shows the selection status of the processing mode of the ISC control, [b] shows the transition of the misfire occurrence state, [c] shows the transition of the feedback correction amount ICSFB, and [d] Represents the transition of the intake air amount GA, and [e] represents the transition of the engine speed NE.
[0045]
As shown in FIG. 4, when the precondition is satisfied after the engine start is completed at time t11, execution of the feedback control of the ISC control process is prohibited because misfire has occurred at this time (FIG. 4B). Then, the open control is executed ([a] in the figure).
[0046]
Therefore, the feedback correction amount ISFB is not updated during a period during which misfire occurs (time t11 to t12) ([c] in FIG. 3). Further, during the same period, the intake air amount GA is maintained at a substantially constant value ([d] in the figure).
[0047]
When the occurrence of misfire stops at time t12 ([b] in the figure), the execution of the open control is stopped and the execution of the feedback control is started ([a] in the figure).
[0048]
At this time, although the misfire occurred in the above period, the feedback correction amount ISCFB and the intake air amount GA do not increase because the feedback correction amount ISCFB has not been updated ([c] and [d] in FIG. ]). Therefore, in this example, unlike the conventional ISC control in which the feedback control is executed even when a misfire occurs (see FIG. 6), the engine rotational speed NE does not suddenly increase with the stop of the misfire occurrence (see FIG. 6E). ).
[0049]
As described above, according to the present embodiment, the following effects can be obtained.
-The execution of the feedback control in the ISC control is prohibited when it is determined that a misfire has occurred. As a result, it is possible to prohibit the change of the feedback correction amount ICSFB when a misfire occurs, and prevent the increase thereof. For this reason, the occurrence of a misfire causes an excessive correction in the feedback control, and it is possible to suppress a sudden increase in the engine speed NE due to this.
[0050]
The above embodiment may be implemented with the following modifications.
In the above-described embodiment, the determination process is performed such that the misfire is determined when “the number of times the rotation fluctuation ΔT exceeds a predetermined threshold / the predetermined number of determinations” is equal to or greater than a predetermined value. It may be executed. Here, the engine speed NE does not decrease so much when the misfire occurs only once or sporadic. In other words, when misfires occur frequently, the engine speed NE is significantly reduced. Therefore, in this case, the inconvenience is likely to occur. On the other hand, according to the above-described determination processing, it is possible to accurately determine that misfire has occurred frequently enough to cause the above-described inconvenience, and thereby to appropriately limit an excessive change in the feedback correction amount ICSFB. Can be. Further, it is also possible to adopt a configuration in which the execution of the feedback control is prohibited when the determination that the misfire has occurred is continuously performed for a predetermined time or more. In short, as long as the occurrence of misfire can be accurately determined, the above-described determination processing can be appropriately changed.
[0051]
In the above embodiment, the execution of the feedback control is prohibited when a misfire occurs. However, the present invention is not limited to this, and the feedback control can be executed. Even in such a configuration, by newly providing a configuration for suppressing a change in the feedback correction amount ISCFB when a misfire occurs, it is possible to avoid a rapid increase in the engine speed NE due to the stoppage of the misfire. Examples of such a configuration include the following.
[0052]
(Configuration A) A limit value for limiting a change in the feedback correction amount ISCFB when a misfire occurs is set. For example, in the above embodiment, the upper limit value GDH may be changed to a small value when a misfire occurs, and the changed upper limit value GDH may be set as the limit value. According to such a configuration, when a misfire occurs, the feedback correction amount ICSFB increases, but the change can be limited by the upper limit value GDH. Therefore, when the change of the feedback correction amount ISCB reaches the upper limit value GDH, the change of the feedback correction amount ISCFB can be suppressed by an amount limited by the upper limit value GDH.
[0053]
(Configuration B) When a misfire occurs, the control gain for the feedback control is reduced. In the above embodiment, the change amount of the feedback correction amount ISCFB every time the feedback control process is performed may be reduced by a predetermined amount. According to such a configuration, the rate of change of the feedback correction amount ICSFB when a misfire occurs can be made lower than when the misfire does not occur (FIG. 3C). For this reason, as shown by a solid line in FIG. 5, an example of the transition is shown before the change in the feedback correction amount ISCB is saturated, as compared with the case where the control gain shown by the one-dot chain line is not reduced. A change in the correction amount ISCB can be suppressed. Further, in such a configuration, the predetermined amount can be variably set according to a misfire occurrence situation. According to this configuration, by setting a smaller value as the predetermined value as misfires occur more frequently, it is possible to suppress an excessive change in the feedback correction amount ISCFB while suppressing misfires.
[0054]
(Configuration C) When a misfire occurs, the target rotation speed TNE is reduced. In the above embodiment, for example, an upper limit value for the target rotation speed TNE may be newly set. According to such a configuration, the speed difference ΔNE can be reduced, and consequently, the changing speed of the feedback correction amount ISCFB can be reduced.
[0055]
In the above embodiment, the processing method of the feedback control can be appropriately changed. In short, whatever the processing method is used, the present invention is an apparatus in which the intake air amount GA is feedback-controlled so that the engine rotational speed NE and the target rotational speed TNE coincide with each other. It suffices if the change in the amount ISCB can be suppressed.
[0056]
In the above embodiment, the present invention is applied to the device that executes the ISC control through the opening control of the throttle valve 20. The present invention is also applicable to a device in which a bypass passage bypassing the throttle valve and an idle speed control valve (ISCV) are separately provided, and the ISC control is executed through the opening control of the ISCV.
[0057]
In the above embodiment, the present invention is applied to the internal combustion engine 10 that injects fuel into the intake passage 14. However, the present invention is applied to an internal combustion engine that injects fuel into the combustion chamber 12. It can also be applied. In some of such internal combustion engines, in the ISC control, feedback control of the fuel injection amount is performed so that the engine rotation speed NE and the target rotation speed TNE match. Even in this case, when the ISC control is performed, a change in the feedback correction amount related to the feedback control may be suppressed using a method according to any of the above-described methods.
[0058]
The present invention is also applicable to a device that employs ISC control such that the engine ignition timing is feedback-controlled so that the engine speed NE and the target speed TNE match.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an engine system to which an embodiment of the present invention is applied.
FIG. 2 is an exemplary flowchart showing a processing procedure when executing feedback control according to the embodiment;
FIG. 3 is an exemplary flowchart showing a processing procedure when executing ISC control according to the embodiment;
FIG. 4 is a timing chart showing an example of a processing mode of the ISC control.
FIG. 5 is a timing chart showing an example of a transition of a feedback correction amount according to another embodiment.
FIG. 6 is a timing chart showing an example of a processing mode of the conventional ISC control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Fuel chamber, 14 ... Intake passage, 16 ... Exhaust passage, 18 ... Motor, 20 ... Throttle valve, 22 ... Fuel injection valve, 24 ... Intake valve, 26 ... Spark plug, 28 ... Exhaust valve, 30: catalytic converter, 32: electronic control unit.

Claims (5)

An idle speed control device for an internal combustion engine that performs feedback control of an engine control amount such that the engine speed during idling and the target speed match.
Misfire determining means for determining misfire occurrence in the internal combustion engine,
Limiting means for limiting a change in the engine control amount to a side that increases the engine rotational speed through the feedback control when the misfire determination means has determined that a misfire has occurred. An idle speed control device for an internal combustion engine. 2. The idle speed control device for an internal combustion engine according to claim 1, wherein the limiting unit stops executing the feedback control and prohibits a change in the engine control amount by the control. 2. The idle speed control device for an internal combustion engine according to claim 1, wherein the limiting unit sets a limit value for a feedback correction amount when correcting the engine control amount through the feedback control. The idle speed control device for an internal combustion engine according to claim 1 or 3, wherein the limiting means reduces a control gain of the feedback control. The idle speed control device for an internal combustion engine according to any one of claims 1 to 4, wherein the restriction means executes the restriction when the occurrence of a misfire is determined a plurality of times by the misfire determination means.

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