JP2009103017A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of extending a rich poisoning recovery time by fuel cutoff. <P>SOLUTION: In the internal combustion engine, fuel cutoff is started when the speed of the internal combustion engine is reduced, and the fuel cutoff can be terminated when the engine speed reaches the reset rotating speed. When the engine speed reaches the fuel cutoff reset rotating speed during fuel cutoff (step 118), whether an exhaust purifying catalyst is rich-poisoned is determined (step 122), and if it is still rich-poisoned, it is controlled to continue fuel cutoff by reducing the fuel cutoff reset rotating speed (steps 124, 126). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for executing control of an internal combustion engine mounted on a vehicle.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-163734, when the internal combustion engine is decelerated, the combustion cut is performed when the engine speed is higher than the permitted engine speed, and the fuel cut is terminated when the engine speed falls below the return engine speed. The institution is known. In addition, this publication discloses a function of setting the allowable rotational speed at the time of deceleration low according to the amount of oxygen released from the exhaust purification catalyst during the fuel increase operation.

  As described above, it is known that the fuel cut is executed when the permitted rotational speed is reached during deceleration of the internal combustion engine. An opportunity to recover rich poisoning can be obtained by performing a fuel cut. Further, if the permitted rotational speed is lowered, the fuel cut is executed even at a lower speed, so the frequency of executing the fuel cut increases. And if the frequency of fuel cut increases, the chance of recovery from rich poisoning increases.

JP 2005-163734 A

  However, in the case of rich poisoning, if the permitted rotational speed is decreased to increase the frequency of poisoning recovery, the permitted rotational speed is decreased and the width of the return rotational speed is reduced. Therefore, the time from the start of the fuel cut to the end of the fuel cut is shortened, and the time during which poisoning can be recovered once is shortened.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can extend the poisoning recovery time per time.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A fuel cut means for stopping the fuel supplied to the internal combustion engine when the engine speed is higher than the fuel cut permission speed during deceleration of the internal combustion engine;
Poisoning correlation value acquisition means for acquiring a poisoning correlation value having a correlation with a rich poisoning state of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine;
A poisoning judging means for comparing the poisoning correlation value with a judgment value to judge whether or not rich poisoning;
A first return speed changing means for reducing the fuel cut return speed when the engine speed reaches the fuel cut return speed when the internal combustion engine is decelerated and is rich poisoning;
Fuel cut return means for ending the fuel cut when the engine speed reaches the fuel cut return speed and is not rich poisoning;
It is characterized by providing.

The second invention is the first invention, wherein
When the engine speed is lower than the fuel cut permission speed and when the engine is richly poisoned, first permission speed changing means is provided for reducing the fuel cut permission speed.

A third aspect of the invention is a control device for an internal combustion engine in order to achieve the above object,
A fuel cut means for stopping the fuel supplied to the internal combustion engine when the engine speed is higher than the fuel cut permission speed during deceleration of the internal combustion engine;
Poisoning correlation value acquisition means for acquiring a poisoning correlation value having a correlation with a rich poisoning state of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine;
A poisoning judging means for comparing the poisoning correlation value with a judgment value to judge whether or not rich poisoning;
A first permission return that lowers the fuel cut return speed when the engine speed is smaller than the fuel cut permission speed determined by adding a fuel cut hysteresis value to the fuel cut return speed and is rich poisoning. Rotation speed changing means;
Fuel cut return means for ending the fuel cut when the engine speed reaches the fuel cut return speed;
It is characterized by providing.

Moreover, 4th invention is set in 3rd invention,
Engine stall determining means for determining whether or not the engine is likely to stall based on the operating state of the internal combustion engine;
A return speed reduction prohibiting means for prohibiting a decrease in the fuel cut return speed by the first permission return speed changing means when the engine is likely to stall;
Second permission return rotation speed changing means for lowering the fuel cut hysteresis value when the engine speed is smaller than the fuel cut permission speed, the rich poisoning, and the engine is likely to stall.
It is characterized by providing.

The fifth invention is the fourth invention, wherein
And a permission return rotation speed initialization means for returning the fuel cut hysteresis value to the initial value after the fuel cut return time.

Further, a sixth invention is any one of the first invention to the third invention,
Engine stall determining means for determining whether or not the engine is likely to stall based on the operating state of the internal combustion engine;
A return rotation speed change limiting means for reducing a reduction width of the fuel cut return rotation speed when compared with a case where it is difficult to stall the engine when engine stall is easy;
It is characterized by providing.

According to a seventh invention, in any one of the first invention to the sixth invention,
Fuel ignition means for igniting fuel in a cylinder of the internal combustion engine;
Ignition advance means for advancing the ignition timing at the time of fuel cut return when the fuel cut return speed is lower than the fuel cut return speed base value;
It is characterized by providing.

Further, an eighth invention is any one of the first invention to the seventh invention,
A throttle valve that changes the amount of air flowing into the internal combustion engine;
Inflow air amount control means for controlling the throttle valve opening during fuel cut based on the poisoning correlation value;
It is characterized by providing.

According to a ninth invention, in any one of the first invention to the eighth invention,
The fuel cut means includes fuel cut start means for starting a fuel cut after a predetermined delay time has elapsed after closing the throttle,
A delay time shortening means for shortening the previous delay time based on the poisoning correlation value;
It is characterized by providing.

A tenth aspect of the invention is a control device for an internal combustion engine to achieve the above object,
A fuel cut means for stopping fuel supplied to the internal combustion engine after a predetermined delay time has elapsed after the throttle is closed when the engine speed is higher than the fuel cut permission rotational speed during deceleration of the internal combustion engine; ,
Poisoning correlation value acquisition means for acquiring a poisoning correlation value having a correlation with a rich poisoning state of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine;
A poisoning judging means for comparing the poisoning correlation value with a judgment value to judge whether or not rich poisoning;
A delay time shortening means for shortening the previous delay time based on the poisoning correlation value when the rich poisoning is determined;
It is characterized by providing.

Further, an eleventh aspect of the invention is any one of the ninth to tenth aspects of the invention,
A delay shortening prohibiting means for prohibiting the shortening of the delay time until a predetermined time elapses after the fuel cut is restored.

  According to the first aspect of the present invention, when the internal combustion engine is decelerating, even if the engine speed reaches the return speed, the return speed can be lowered if the engine is still richly poisoned. By reducing the return rotational speed, the fuel cut (F / C) is continued until the lowered return rotational speed is reached. By continuing F / C, the time for recovering rich poisoning of the exhaust purification catalyst is extended. For this reason, according to the present invention, the poisoning recovery time per F / C can be extended by lowering the return rotational speed.

  According to the second invention, even if the engine speed is lower than the permitted rotational speed, the permitted rotational speed can be lowered in the case of rich poisoning. F / C can be started even if the engine speed is lower than the reference value by lowering the permitted speed. As a result, the opportunity to perform F / C increases, and the frequency of recovering rich poisoning can be increased. For this reason, according to the present invention, the frequency of poisoning recovery can be increased by lowering the permitted rotational speed.

  According to the third aspect of the invention, even if the engine speed is lower than the permitted engine speed, if the engine is richly poisoned, the permitted engine speed can be lowered and the return engine speed can be lowered. In the present invention, the permitted rotation speed is calculated by adding the fuel cut hysteresis value to the return rotation speed. Therefore, the permitted rotational speed can also be decreased by decreasing the return rotational speed. As described above, the frequency of poisoning recovery can be increased by lowering the permitted rotation speed. Moreover, the poisoning recovery time can be extended by lowering the return rotational speed. For this reason, according to the present invention, the poisoning recovery time can be extended while increasing the frequency of poisoning recovery by lowering the permitted rotational speed and lowering the return rotational speed in order to execute F / C from a low speed. Can do.

  According to the fourth aspect of the invention, under the condition that engine stall is likely to occur, it is possible to reduce only the permitted rotational speed without reducing the return rotational speed. Under conditions where the engine is likely to stall, it is more difficult to stall the engine if the return speed is not reduced. Also, the F / C frequency can be increased by lowering the permitted rotational speed even under conditions where the engine is likely to stall. For this reason, according to the present invention, it is possible to increase the frequency of poisoning recovery while suppressing engine stall even under conditions where engine stall is likely to occur.

  According to the fifth aspect, the fuel cut hysteresis value can be returned to the reference value when the F / C is restored. In the present invention, the permitted rotation speed is calculated by adding the fuel cut hysteresis value to the return rotation speed. If the hysteresis value is kept low, the interval between the permitted rotation speed and the return rotation speed becomes narrower at the next and subsequent F / Cs. As a result, the start / end of F / C is frequently executed, and hunting of engine rotation is likely to occur. On the other hand, if the hysteresis value is returned to the initial value, the interval between the permitted rotation speed and the return rotation speed can be returned to the reference value in the next and subsequent F / Cs. Therefore, according to the present invention, it is possible to realize an internal combustion engine suitable for recovery from poisoning that can suppress hunting of engine rotation as compared with the fourth aspect of the invention.

  According to the sixth aspect of the invention, the range of decrease in the return rotational speed can be reduced under conditions where engine stall is likely to occur. For this reason, according to the present invention, it is possible to extend the poisoning recovery time while avoiding engine stall.

  According to the seventh aspect, when the return rotational speed is lowered, the ignition timing at the time of F / C return can be advanced. By advancing the ignition timing, the torque at the time of F / C return can be increased. If the torque increases, engine stall can be suppressed. For this reason, according to the present invention, it is possible to realize an internal combustion engine suitable for poisoning recovery while preventing engine stall even when the return rotational speed is lowered.

  According to the eighth invention, the throttle can be opened during F / C according to the rich poisoning situation. By opening the throttle, more air than usual can be sent to the exhaust purification catalyst. By sending more air, the recovery speed of rich poisoning can be increased, and the time required for recovery can be shortened. For this reason, according to the present invention, it is possible to realize an internal combustion engine suitable for poisoning recovery that can reduce the time required for rich poisoning recovery.

  According to the ninth or tenth invention, the delay time from the closing of the throttle to the start of F / C can be shortened. If the delay time is shortened, the F / C can be started even if the time from when the throttle is closed until the F / C is started is short. By starting F / C, it is possible to obtain time to recover rich poisoning. Therefore, according to the present invention, the poisoning recovery time can be obtained even when the time from when the throttle is closed to when the F / C is started is short.

  According to the eleventh aspect, it is possible to prohibit the delay time from being shortened for a predetermined period after the F / C due to the shortening of the delay time. By prohibiting the reduction of the delay time for a predetermined period, it is possible to suppress the F / C from being repeated in a short time when the throttle ON / OFF is repeated quickly. As a result, drivability and emission can be prevented from deteriorating. For this reason, according to the present invention, an internal combustion engine suitable for recovery from poisoning can be realized while preventing deterioration of drivability and emission due to shortening of the delay time.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 has a plurality (four in FIG. 1) of cylinders 12. The cylinder 12 is provided with a fuel injection valve 14 for injecting fuel into the intake port and an ignition plug 16 for igniting the air-fuel mixture in the combustion chamber. In the vicinity of the crankshaft of the internal combustion engine 10, a crank angle sensor 18 is provided for detecting the rotation angle (crank angle) and the rotation speed (engine speed NE) of the crankshaft. An intake passage 20 and an exhaust passage 22 communicate with the internal combustion engine 10.

  An air cleaner 24 is disposed upstream of the intake passage 20. An air flow meter 26 that outputs a signal corresponding to the inflow air amount GA is provided in the vicinity of the air cleaner 24. A throttle valve 28 is disposed downstream of the air cleaner 24. In the vicinity of the throttle valve 28, a throttle opening sensor 30 for outputting a signal corresponding to the throttle opening TA is provided.

  An exhaust purification catalyst 32 is disposed in the exhaust passage 22. For example, a three-way catalyst is used as the exhaust purification catalyst 32. Upstream of the exhaust purification catalyst 32, an air-fuel ratio sensor 34 that outputs a signal corresponding to the air-fuel ratio of the exhaust discharged from the internal combustion engine 10, and an exhaust temperature sensor 36 that outputs a signal corresponding to the temperature of the exhaust are provided. ing. An oxygen concentration sensor 38 that outputs a signal corresponding to the oxygen concentration in the exhaust is provided downstream of the exhaust purification catalyst 32.

  The internal combustion engine 10 is provided with an ECU (Electronic Control Unit) 50. The aforementioned fuel injection valve 14, spark plug 16, and throttle valve 28 are connected to the output side of the ECU 50. On the input side of the ECU 50, in addition to the crank angle sensor 18, the air flow meter 26, and the throttle opening sensor 30, the accelerator opening sensor 52 that detects the accelerator opening AA, and the water temperature that detects the temperature of the cooling water of the internal combustion engine. A sensor 54 is connected.

  Further, the ECU 50 stops the fuel supplied to the internal combustion engine 10 when it is determined that the engine speed NE is higher than the fuel cut permission rotational speed (hereinafter referred to as the permitted rotational speed) when the internal combustion engine 10 is decelerated. To do. Further, the ECU 50 ends the fuel cut (hereinafter referred to as F / C) when the engine speed NE reaches the fuel cut return speed (hereinafter referred to as the return speed). Thus, the ECU 50 functions as a fuel cut control means by starting and ending F / C.

[Air-fuel ratio control in Embodiment 1]
As described above, the ECU 50 in FIG. 1 stops the fuel supplied to the internal combustion engine 10 by executing F / C. When the fuel supply is stopped, the sucked air passes through the fuel exhaust passage as it is. As a result, the rich poisoning of the exhaust purification catalyst 32 can be recovered. Eventually, when the engine speed NE reaches the return speed, the F / C ends. However, if the exhaust purification catalyst 32 is still richly poisoned even when the return rotational speed is reached, it is preferable to continue the F / C to achieve further poisoning recovery.

  Therefore, in the system of the present embodiment, when the engine speed reaches the return speed and rich poisoning, the return speed is lowered to extend the poisoning recovery time.

  A more specific outline of control will be described with reference to FIGS. FIG. 2 is a timing chart for explaining the contents of characteristic operations executed in the system of this embodiment.

A waveform indicated by a solid line in FIG. 2A indicates the in-catalyst oxygen storage amount OSA calculated by the ECU 50 based on the inflow air amount GA, the measured A / F, and the like. In addition, a center line indicated by a broken line in FIG. 2A indicates a poisoning threshold in which a lower part than the center line is a rich poisoning area and an upper part from the center line is a non-rich poisoning area.
A waveform indicated by a solid line in FIG. 2B indicates the engine speed NE. Moreover, the center line shown with a broken line in FIG. 2 (B) shows the base value FCRTNB of the return rotation speed. Note that a lower line indicated by a broken line in FIG. 2B indicates the return rotational speed FCRTN1 lowered by the ECU 50.
In FIG. 2, time t0 represents the F / C start time. Time t1 represents the time when it is determined that the engine speed NE has reached FCRTNB. Time t2 represents the F / C end time.

  At time t0, F / C is started. At this stage, OSA in FIG. 2A is lower than the poisoning threshold value, and the catalyst is in a rich poisoning state. Further, since NE in FIG. 2B has not reached FCRTNB and F / C is continued, poisoning recovery proceeds.

  At time t1, the NE in FIG. 2B has reached FCRTNB. However, OSA in FIG. 2A is lower than the poisoning threshold, and the exhaust purification catalyst 32 is still in a rich poisoning state. Therefore, in order to further recover the poisoning, the ECU 50 lowers the return rotational speed (FCRTN1) and continues the F / C.

  At time t2, the NE in FIG. 2B has reached FCRTN1. 2A is higher than the poisoning threshold value, and the rich poisoning of the exhaust purification catalyst 32 is sufficiently recovered. Therefore, the ECU 50 ends the F / C. After the completion of the F / C, the engine speed NE increases thereafter.

  As described above, as shown in FIG. 2, after the fuel cut is started by the ECU 50, the exhaust purification catalyst 32 is still richly poisoned even when the engine speed NE reaches the return speed. Reduce the return speed to further recover the poisoning. Thereafter, the poisoning is recovered and the F / C is ended when the above-described lowered return rotational speed is reached.

  The in-catalyst oxygen storage amount OSA used in the determination of the poisoning situation will be described with reference to FIG. FIG. 3 is a map showing the relationship between the deterioration degree of the exhaust purification catalyst 32 and OSA. The upper limit of OSA is α, and the lower limit is β. As shown in FIG. 3, the width between α and β decreases as the degree of deterioration of the exhaust purification catalyst 32 increases. In this embodiment, a poisoning threshold A that is determined to be poisoned is determined for each degree of deterioration between α and β. When the oxygen storage amount OSA in the catalyst falls below the poisoning threshold A (OSA <A), it is determined that the catalyst is poisoned, and this is referred to as “rich poisoning”. The ECU 50 stores the map shown in FIG. 3 described above. The same applies to the embodiments described below.

  FIG. 4 is a flowchart of a routine executed by the ECU 50 in order to realize the above-described operation. This routine is repeatedly executed at a predetermined cycle during operation of the internal combustion engine 10. In the routine shown in FIG. 4, it is first determined whether or not F / C is being performed (step 100). The start of F / C is performed in another routine.

  If it is determined in step 100 that F / C is not being performed, there is no room for lowering the return rotational speed because F / C is not performed. In this case, in order to calculate the current in-catalyst oxygen storage amount OSA used in the next routine, first, the oxygen adsorption / desorption amount DOSA of the exhaust purification catalyst 32 from the previous routine to the current calculation time is calculated (step 102). Specifically, the air flow meter 26 detects the inflow air amount GA, and the air-fuel ratio sensor 34 detects the measurement A / F (ABYF). Next, a value GA * 23% obtained by multiplying the inflowing air amount GA by 23% which is the oxygen ratio in the air is calculated. Further, (ABYF-14.6) / ABYF is calculated from the measured A / F (ABYF) and the theoretical air-fuel ratio (14.6 as an example). Then, the oxygen adsorption / desorption amount DOSA is calculated by multiplying them.

  Next, the current in-catalyst oxygen storage amount OSA used in the next routine is calculated (step 104). Specifically, the current oxygen storage amount OSA in the catalyst is calculated by adding the oxygen storage / desorption amount DOSA calculated in step 102 to the OSA calculated in the previous routine.

  Next, upper and lower limit processing of the oxygen storage amount OSA in the catalyst is performed (step 106). Specifically, when OSA is equal to or higher than the upper limit value α shown in FIG. 3, OSA is set as the upper limit value α. When OSA is equal to or lower than the lower limit value β shown in FIG. 3, OSA is set as the lower limit value β.

  If it is determined in step 100 that F / C is being performed, then the oxygen adsorption / desorption amount DOSA during fuel cut is calculated (step 108). Specifically, the inflow air amount GA is detected by the air flow meter 26, and a value obtained by multiplying GA by an oxygen ratio of 23% in the air is calculated. Next, the current in-catalyst oxygen storage amount OSA is calculated for use in poisoning determination (step 110). Specifically, the current OSA is calculated by adding the DOSA calculated in step 108 to the OSA calculated in the previous routine.

  Next, it is determined whether or not idling is OFF (step 112). Here, when the accelerator pedal is depressed, it is determined that the idle is OFF.

  If it is determined that the idling is OFF, the accelerator pedal is depressed and F / C is terminated (step 114). Next, in order to initialize the return speed FCRTN, the return speed base value FCRTNB is substituted into FCRTN (step 116). Thereafter, the process of step 106 is performed.

  If it is determined in step 112 that the idling is ON, F / C is being continued, and then it is determined whether or not the engine speed NE is equal to or lower than the return speed FCRTN (step 118). It should be noted that the return rotational speed FCRTN is the same value as the base value FCRTNB from the start of F / C until step 118 is established for the first time.

  While the engine speed NE is still greater than the return speed FCRTN, it is determined that the condition of step 118 is not satisfied, and F / C is continued (step 120). Thereafter, the process of step 106 is performed.

As F / C continues, the engine speed NE decreases and eventually becomes lower than the return speed FCRTN. In this case, the condition of step 118 (NE ≦ FCRTN) is satisfied, and next, the exhaust purification catalyst 32 is richly poisoned, and whether or not the return speed FCRTN is larger than the return speed lower limit guard value C. Is determined (step 122).
Here, whether or not the exhaust purification catalyst 32 is richly poisoned is determined when the current in-catalyst oxygen storage amount OSA calculated in step 110 is lower than the poisoning threshold A shown in FIG. Judged to be rich poison. Note that the ECU 50 stores a map representing the relationship between the OSA and the poisoning threshold A as shown in FIG. Further, it is determined whether or not the return rotational speed FCRTN is larger than the return rotational speed lower limit guard value C. Here, while FCRTN is not lowered to the lower limit guard value C, it is determined that there is room for lowering FCRTN.

  If it is determined in step 122 that rich poisoning has been recovered or the return rotational speed FCRTN has reached the lower limit guard value C, the F / C is terminated (step 114). Thereafter, the processing in steps 116 and 106 is performed.

On the other hand, in the above-described step 122, under the condition where the rich poisoning is still in progress and the return rotational speed FCRTN has not reached the lower limit guard value C, the F / C is continued to perform further poisoning recovery (step 124). In this case, FCRTN is lowered by a predetermined value B (step 126). Specifically, the ECU 50 stores a map that defines the relationship between the in-catalyst oxygen storage amount OSA and the predetermined value B as shown in FIG. 5, and lowers the value of FCRTN by the predetermined value B calculated according to the map. . Thereafter, the process of step 106 is performed.
In the routine after the next time, the condition of step 118 is not satisfied until the currently lowered FCRTN is reached. As a result, the F / C is continued until the condition of Step 118 is satisfied (Step 120, Step 106), and during that time, the poisoning recovery time is also extended.

As the F / C is continued in the routine after the next time (step 120), the engine speed NE decreases. Eventually, when NE reaches the return rotational speed FCRTN lowered in step 126, the condition of step 118 is satisfied (NE ≦ FCRTN), and then the condition of step 122 is determined.
If it is determined that the poisoning has been recovered at this stage, the F / C is terminated because the purpose of the poisoning recovery has been reached (step 114), and then the processing of steps 116 and 106 is performed. If FCRTN has reached the lower limit guard value C, the F / C is terminated even if the poisoning has not recovered to prevent engine stall (step 114). Thereafter, the processing of steps 116 and 106 is performed. Do.

  On the other hand, the engine speed NE has reached the return speed FCRTN reduced in step 126. However, in step 122, it is determined that rich poisoning has not yet recovered and FCRTN is higher than the lower limit guard value C. If so, since there is room to further reduce FCRTN, F / C is continued (step 124), and FCRTN is further reduced according to the map shown in FIG. 5 (step 126). Thereafter, the process of step 106 is performed.

  As described above, according to the routine shown in FIG. 4, if the rich poisoning is not recovered even when the engine speed reaches the return speed during F / C, the return speed is decreased and F / C can continue. For this reason, according to the system of this embodiment, the poisoning recovery time per F / C can be extended.

  In the first embodiment described above, the poisoning situation is calculated by calculating the in-catalyst oxygen storage amount OSA. However, the method for calculating the poisoning situation is not limited to this. Absent. For example, the following first to fourth calculation methods may be used. The same applies to the embodiments described below.

  The first calculation method can be applied to a system including a main O2 sensor upstream of the exhaust purification catalyst 32 and a sub O2 sensor downstream of the exhaust purification catalyst 32. In this system, when the exhaust purification catalyst 32 is richly poisoned, if the rich exhaust gas is blown, it is easy to blow through without being sufficiently purified. In this case, the sub O2 sensor easily outputs a rich value. Here, if the output integrated value of the sub O2 sensor is measured, the steady state of the catalyst can be understood, and it is considered that the rich poisoning is caused as the state is inclined toward the rich side. Therefore, the poisoning situation may be calculated from the rich output integrated value of the sub O2 sensor.

  The second calculation method can be applied to a system including a rear O2 sensor upstream of the underfloor converter (UF) and a sub O2 sensor downstream of the UF. Here, in the case where the catalyst is richly poisoned, when rich exhaust gas is blown, the exhaust gas is easily purified without being sufficiently purified. In this case, as soon as a rich value is detected by the rear O2 sensor, a rich value is also detected by the sub O2 sensor. Therefore, the poisoning situation may be calculated by detecting the synchronization of the rear O2 sensor and the sub O2 sensor.

  The third calculation method can be applied to a system including a main O2 sensor or an A / F sensor upstream of the exhaust purification catalyst 32 and a sub O2 sensor downstream of the exhaust purification catalyst 32. In this system, when a rich value is detected by the sub O2 sensor by the sub feedback control, the air-fuel ratio is corrected to the lean side. In addition, when a lean value is detected by the sub O2 sensor, the air-fuel ratio is corrected to the rich side. Here, if the rich-lean integrated value is measured from the correction value, it can be determined how much the state of the catalyst is inclined to the rich or lean side. Therefore, the poisoning situation may be calculated from the rich lean integrated value of the sub feedback (SFB) correction amount.

  The fourth calculation method is based on a change in the maximum oxygen storage amount Cmax (Capacity Max) of oxygen stored in the exhaust purification catalyst 32. Cmax decreases as the deterioration of the exhaust purification catalyst 32 proceeds. Here, when Cmax has decreased in the past short period, it may have decreased due to poisoning. Therefore, the poisoning status may be calculated based on the change in Cmax.

  In the first embodiment described above, the F / C starts when the ECU 50 determines that the engine speed NE is higher than the permitted engine speed when the internal combustion engine 10 is decelerated as described in the description of FIG. Is done. Here, the ECU 50 determines the start of F / C while maintaining the above-described permitted rotational speed at the normal permitted rotational speed, but the determination method is not limited to this. That is, even if NE is lower than the normal permitted rotational speed, if the exhaust purification catalyst 32 is richly poisoned, the start of F / C may be determined after lowering the permitted rotational speed. Good.

  In Embodiment 1 described above, the bed temperature of the exhaust purification catalyst 32 is fixed in FIG. 3 and the poisoning area A for a certain degree of deterioration is determined. However, the method of determining the poisoning area A is not limited to this. It is not something that can be done. That is, the poisoning area A may be determined by adding the bed temperature as a parameter.

In the first embodiment described above, the ECU 50 stops the fuel supplied to the internal combustion engine 10 when it is determined that the engine rotational speed NE is higher than the permitted rotational speed when the internal combustion engine is decelerated. The “fuel cutting means” according to the first aspect of the invention is realized. Further, here, the oxygen storage amount OSA in the catalyst corresponds to the “poisoning correlation value”, and in addition to the air flow meter 26 and the air-fuel ratio sensor 34, the ECU 50 executes the processing of steps 102 to 110 to obtain the “poisoning correlation value”. "Acquisition means" is realized. Furthermore, here, the “poisoning determination means” is realized by the ECU 50 executing the processing of step 122. In addition, here, the “first return rotational speed changing means” is realized by the ECU 50 executing the processing of steps 112, 118, 122 to 126. In addition, the “fuel cut return means” is realized by the ECU 50 executing steps 122 and 114 here.
In addition, in the above-described first embodiment, when the engine speed NE is lower than the normal permitted rotational speed and the exhaust purification catalyst 32 is richly poisoned, the ECU 50 decreases the permitted rotational speed. Thus, the “first permitted rotational speed changing means” in the second invention is realized.

Embodiment 2. FIG.
[System Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 8 described later in the configuration shown in FIG.

[Air-fuel ratio control in Embodiment 2]
In the first embodiment described above, even if the return rotational speed is reached when the internal combustion engine is decelerated, if the exhaust purification catalyst 32 is still richly poisoned, the return rotational speed is lowered and F / C is continued. can do. By continuing F / C, the time for recovery from rich poisoning can be extended. In the first embodiment, the F / C is executed on condition that the engine speed exceeds the permitted speed. Therefore, even if rich poisoning is performed, if the engine speed is equal to or lower than the permitted rotational speed, the F / C is not executed, and the rich poisoning due to the F / C is not recovered. However, even when the engine speed is lower than the permitted engine speed, it is preferable to start the F / C and obtain an opportunity to recover the rich poisoning when the engine is richly poisoned.

  Therefore, in the present embodiment, in the case of rich poisoning, even if the engine speed is lower than the permitted rotational speed, F / C is started by lowering the permitted rotational speed to recover the poisoning. We decided to increase the frequency.

  A more specific outline of the control will be described with reference to FIGS. FIG. 6 shows a method for calculating the permitted rotational speed in this embodiment. In the present embodiment, it is assumed that the permitted rotational speed is calculated by adding an F / C hysteresis value (hereinafter referred to as a hysteresis value) to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed). Therefore, if the return rotation speed is lowered, the permitted rotation speed can be lowered. Further, if the hysteresis value is lowered, the permitted rotational speed can be lowered without changing the return rotational speed.

FIG. 7 is a timing chart for explaining the contents of characteristic operations executed in the system of this embodiment.
A waveform indicated by a solid line in FIG. 7A indicates the in-catalyst oxygen storage amount OSA calculated by the ECU 50 based on the inflow air amount GA, the measured A / F, and the like. Further, the center line indicated by a broken line in FIG. 7A indicates a poisoning threshold value in which the lower part from the center line is a rich poisoning area and the upper part from the center line is a non-rich poisoning area.
A waveform indicated by a solid line in FIG. 7B indicates the engine speed NE. On the other hand, an upper line 90 indicated by a thin broken line in FIG. 7B indicates the permitted rotational speed (FCRTN + FCHYS) before time t0. Similarly, an underline 92 indicated by a thin broken line indicates the return rotational speed FCRTN before time t0. On the other hand, an upper line 94 indicated by a thick broken line in FIG. 7B indicates the permitted rotation speed after time t0. Similarly, an underline 96 indicated by a thick broken line indicates the return rotational speed after time t0.
In FIG. 2, the time t0 represents the time when it is determined that the idling is ON. Time t1 represents the F / C end time.

  At time t0, it is determined that an idle ON state has been established. At this time, since NE is below the permitted rotational speed, F / C is not started at the normal permitted rotational speed. However, in the present embodiment, the permitted number of revolutions (FCRTN + FCHYS) can be lowered by performing a control to lower the return speed FCRTN. As a result, the F / C is started exceeding the permitted rotational speed at which NE is lowered. At this stage, the OSA in FIG. 7A is lower than the poisoning threshold, and the catalyst is in a rich poisoning state. Further, since NE in FIG. 7B has not reached FCRTN and F / C is continued, recovery of poisoning proceeds.

  At time t1, the NE in FIG. 7B has reached the lowered FCRTN. Further, OSA in FIG. 7A is higher than the poisoning threshold value, and the rich poisoning of the exhaust purification catalyst 32 is sufficiently recovered. In this case, the ECU 50 ends the F / C. After the completion of F / C, the engine speed NE then increases.

  As described above, as shown in FIG. 7, when the engine speed at the time of idling is lower than the permitted rotational speed and rich poisoning, the ECU 50 reduces the permitted rotational speed by reducing the return rotational speed FCRTN ( FCRTN + FCHYS) can be reduced. As a result, F / C can be performed even from a low rotation, and the poisoning recovery frequency can be increased to recover the poisoning. Thereafter, the poisoning is recovered and the F / C is finished when the lowered return rotational speed is reached.

  FIG. 8 is a flowchart of a routine executed by the ECU 50 in order to realize the above-described operation. In particular, it shows control until F / C is started. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. Since this routine includes the same processing as steps 102 to 110 shown in FIG. 4, common steps are denoted by common reference numerals, and description thereof is simplified or omitted.

  In the routine shown in FIG. 8, it is first determined whether or not the engine speed NE is smaller than the permitted engine speed (FCRTNB + FCHYS) and the engine is richly poisoned (step 130). If NE is equal to or higher than the permitted rotational speed or is not rich poisoning, the base value FCRTNB is substituted into the return rotational speed FCRTN to determine the start of F / C at the normal permitted rotational speed (step 132). On the other hand, when NE is smaller than the permitted rotation speed and rich poisoning is performed, a value obtained by subtracting the predetermined value B from the base value FCRNTB is set as a new return rotation speed FCRTN (step 133). Note that the ECU 50 stores a map that defines a reduction range of the return rotational speed (the predetermined value B) using the OSA indicating the poisoning status as a parameter. In this step 133, the predetermined value B corresponding to the OSA is calculated according to the map, and a value obtained by lowering the predetermined value B from FCRTNB is calculated as a new return rotational speed FCRTN.

  Subsequent to step 132 or 133, F / C start determination and OSA calculation are performed (step 134). The process of step 134 is realized by a series of processes from steps 136 to 106.

  First, in step 136, it is determined whether or not idle ON and NE is greater than the permitted rotational speed. Here, when the idling OFF or NE is equal to or lower than the permitted rotation speed, F / C cannot be started, the processing of steps 102 to 106 is performed, and this routine ends.

  In the above-mentioned step 136, when the idle is ON and NE is larger than the permitted rotational speed, F / C is started (step 138). Rich poisoning can be recovered by starting F / C. Thereafter, a series of processes in steps 108 to 106 are performed, and this routine is terminated.

  As described above, the permitted rotational speed is calculated by adding a hysteresis value to the return rotational speed. Here, if the return rotational speed FCRTN is lowered, the permitted rotational speed (FCRTN + FCHYS) is also lowered. Therefore, when the return rotational speed is decreased in step 133, the F / C start condition is determined in step 136 based on the decreased allowable rotational speed. As a result, F / C from low rotation becomes possible, and the frequency of rich poisoning recovery by F / C increases. On the other hand, if the return rotational speed FCRTN is set to the base value FCRTNB in step 132, the F / C start condition is determined in step 136 based on the normal permitted rotational speed.

  As described above, according to the routine shown in FIG. 8, even when the engine speed NE is equal to or lower than the permitted engine speed and normally does not satisfy the F / C start condition, the vehicle is richly poisoned. Can lower the return rotational speed and lower the permitted rotational speed to start F / C. For this reason, according to the system of the present embodiment, it is possible to increase the poisoning recovery frequency by F / C.

  In the second embodiment described above, the “fuel cut means” according to the third aspect of the present invention is realized by the ECU 50 executing the processing of steps 136 to 138. Further, here, the oxygen storage amount OSA in the catalyst corresponds to the “poisoning correlation value”, and in addition to the air flow meter 26 and the air-fuel ratio sensor 34, the ECU 50 executes the processing of steps 102 to 110 to obtain the “poisoning correlation value”. "Acquisition means" is realized. Further, here, the “poisoning determination means” is realized by the ECU 50 executing the process of step 130. In addition, here, the “first permission return rotational speed changing means” is realized by the ECU 50 executing the processing of steps 130 and 133. In addition, here, the “fuel cut return means” is realized by the ECU 50 ending the fuel cut when the engine speed reaches the return speed.

Embodiment 3 FIG.
[System Configuration of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 9 described later in the configuration shown in FIG. In the present embodiment, as in the second embodiment, the permitted rotational speed is calculated by adding the hysteresis value to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed). Therefore, if the return rotation speed is lowered, the permitted rotation speed can be lowered. Further, if the hysteresis value is lowered, the permitted rotational speed can be lowered without changing the return rotational speed.

[Air-fuel ratio control in Embodiment 3]
In the second embodiment described above, even if the engine speed NE is equal to or lower than the permitted rotational speed, if the exhaust purification catalyst 32 is richly poisoned, the return rotational speed is decreased and the permitted rotational speed is decreased. F / C from low rotation is enabled. The frequency of rich poisoning recovery increases because F / C can be performed from low rotation. However, it is preferable to increase the frequency of poisoning recovery while suppressing engine stall under conditions where engine stall is likely to occur (for example, when the engine is cold before complete warm-up).

  Therefore, in the system of the present embodiment, under the condition that the engine is likely to stall, only the permitted rotation speed is decreased without decreasing the return rotation speed.

  FIG. 9 is a flowchart of a routine executed by the ECU 50 in order to realize the above-described operation. In particular, it shows control until F / C is started. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. Further, since this routine includes the same processes as steps 102 to 110 shown in FIG. 4 and steps 134 to 138 shown in FIG. 8, common steps are denoted by common numbers, and description thereof is simplified or omitted.

  In the routine shown in FIG. 9, it is first determined whether or not the engine speed NE is smaller than the permitted engine speed (FCRTNB + FCHYS) and rich poisoning (step 140). If NE is equal to or higher than the permitted rotation speed or is not rich poisoning, F / C start determination and OSA calculation are performed (step 134). On the other hand, if NE is smaller than the permitted rotation speed and rich poisoning is made, it is determined whether or not the engine is likely to stall (step 144). As to the determination of whether or not the engine stalls easily, for example, it is determined that the engine stalls easily when it is cold before complete warming (for example, the water temperature is 70 ° C. or lower).

  If it is determined in step 144 that it is difficult to stall the engine, a value obtained by subtracting the predetermined value B from the return rotation speed base value FCRTNB is set as a new return rotation speed FCRTN. The base value FCHYSB is substituted (step 146). Note that the ECU 50 stores a map that defines a reduction range of the return rotational speed (the predetermined value B) using the OSA indicating the poisoning status as a parameter. In step 146, the predetermined value B corresponding to the OSA is calculated according to the map, and a value obtained by lowering the predetermined value B from FCRTNB is calculated as a new return rotational speed FCRTN.

  If it is determined in step 144 that the engine is likely to stall, the value obtained by subtracting the predetermined value B from the hysteresis base value FCHYSB is used as a new hysteresis value FCHYS. The value FCRTNB is substituted (step 148). The predetermined value B is calculated from the same map as in step 146.

  When step 140 is not established or following the processing of step 146 or 148, F / C start determination and OSA calculation are performed (step 134 above). The process of Step 134 is realized by a series of processes from Steps 136 to 106 described above.

  As described above, the permitted rotational speed is calculated by adding a hysteresis value to the return rotational speed. Here, if the hysteresis value FCHYS is decreased, the permitted rotational speed (FCRTB + FCHYS) is decreased without decreasing the return rotational speed FCRTN. Therefore, when the hysteresis value is lowered in step 148, in step 136, the F / C start condition is determined by lowering only the permitted rotational speed without lowering the return rotational speed. As a result, while preventing engine stall due to a decrease in the return rotational speed, F / C from a low rotational speed is possible due to the lowered permitted rotational speed, and the frequency of rich poisoning recovery by F / C increases.

  On the other hand, if the return rotational speed FCRTN is lowered, the permitted rotational speed (FCRTN + FCHYS) is also lowered. Therefore, when the return rotational speed is decreased in step 146, the F / C start condition is determined in step 136 based on the decreased allowable rotational speed. As a result, F / C from low rotation becomes possible, and the frequency of rich poisoning recovery by F / C increases.

  As described above, according to the routine shown in FIG. 9, compared to the second embodiment, under conditions where engine stall is likely to occur, the F / C is reduced by reducing only the permitted rotational speed without reducing the return rotational speed. You can start. For this reason, according to the system of the present embodiment, it is possible to increase the poisoning recovery frequency while suppressing engine stall.

  By the way, in Embodiment 3 mentioned above, although it is using the time of the cold before complete warm-up as a condition which is easy to stall an engine, the condition is not limited to this. That is, it is good on condition that the poor fuel is used. Further, it may be a condition that the rate of decrease in the engine speed is fast (when the clutch is disengaged at F / C or MT from a high speed).

  In the third embodiment described above, a map in which the common predetermined value B is determined in steps 146 and 148 is used, but the map is not limited to this. That is, a map in which different predetermined values are determined in steps 146 and 148 may be used.

  In the third embodiment described above, the “engine stall determination means” according to the fourth aspect of the present invention is realized by the ECU 50 executing the process of step 144. Further, here, the ECU 50 executes the processing of steps 140, 144, and 148, thereby realizing “return rotation speed reduction prohibiting means” and “second permitted return rotation speed changing means”.

Embodiment 4 FIG.
[System Configuration of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 10 described later in the configuration shown in FIG. In the present embodiment, as in the second embodiment, the permitted rotational speed is calculated by adding the hysteresis value to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed).

[Control in Embodiment 4]
Generally, a predetermined delay time is provided from when the throttle is closed until F / C is started. This is to prevent the start / end of F / C from being repeated and maintain good drivability when the throttle ON / OFF is repeated in a short time. However, when the exhaust purification catalyst 32 is richly poisoned, even if the time from when the throttle is closed until the F / C is started is short, the time for starting the F / C and recovering the rich poisoning is reduced. It is preferable to obtain.

  Therefore, in the system of the present embodiment, the delay time is reduced according to the poisoning situation.

  FIG. 10 is a flowchart of a routine executed by the ECU 50 in order to realize the above-described operation. In particular, it shows control until F / C is started. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. Further, since this routine includes the same processing as Steps 102 to 110 shown in FIG. 4 and Step 138 shown in FIG. 8, common steps are denoted by common numbers and description thereof is simplified or omitted.

  In this routine, first, a value obtained by lowering the predetermined value B from the delay base time FCDELAYB according to the poisoning situation is set as a new delay time FCDELAY (step 150). Note that the ECU 50 stores a map that defines the decrease width B of the delay time FCDELAY using the OSA indicating the poisoning status as a parameter. Specifically, a map for increasing the reduction width B as OSA is low, or a map for increasing the reduction width B only when rich poisoning is determined (OSA <A) is stored.

  Next, based on the calculated delay time, F / C start determination and OSA are calculated (step 152). The process of step 152 is realized by a series of processes from steps 154 to 106.

  In step 154, it is determined whether the idle is ON, NE is larger than the permitted rotation speed, and the delay time has elapsed. When the idle OFF or NE is equal to or lower than the permitted rotation speed or the delay time has not elapsed, F / C cannot be started. In this case, the processing of steps 102 to 106 is performed, and this routine ends.

  In step 154, if the idle is ON, NE is larger than the permitted rotation speed, and the delay time has elapsed, F / C is started (step 138). Here, whether or not the delay time has elapsed is determined by whether or not the delay time FCDELAY calculated in step 150 has elapsed since the throttle was closed. In step 150, the delay time is shortened according to the poisoning situation, so that F / C is easily started, and poisoning recovery by F / C is promoted. Thereafter, the processing of steps 108, 110, and 106 is performed, and this routine ends.

  As described above, according to the routine shown in FIG. 10, the delay time can be shortened and F / C can be started in accordance with the poisoning situation. For this reason, according to the system of the present embodiment, the poisoning recovery time by F / C can be obtained even when the time from when the throttle is closed to when F / C is started is short.

  By the way, in the above-described fourth embodiment, the present embodiment is realized by performing the F / C start determination after only reducing the delay time in the routine of FIG. It is not limited to. In other words, in the routine of FIG. 8 shown in the second embodiment, step 136 may be replaced with step 154, and step 150 may be added before step 154. Further, in the routine of FIG. 9 shown in the third embodiment, step 136 may be replaced with step 154, and step 150 may be added before step 154.

In the fourth embodiment described above, the “fuel cut start means” according to the ninth aspect of the present invention is realized by the ECU 50 executing the processing of steps 154 and 138. Here, the “delay time shortening means” is realized by the ECU 50 executing the processing of step 150.
In addition, in the above-described fourth embodiment, the “fuel cut means” according to the tenth aspect of the present invention is realized by the ECU 50 executing the processing of steps 154 and 138. Further, here, the oxygen storage amount OSA in the catalyst corresponds to the “poisoning correlation value”, and in addition to the air flow meter 26 and the air-fuel ratio sensor 34, the ECU 50 executes the processing of steps 102 to 110 to obtain the “poisoning correlation value”. "Acquisition means" is realized. Further, here, the “poisoning determination means” is realized by the ECU 50 executing the processing of step 150. In addition, the “delay time shortening means” is realized by the ECU 50 executing the processing of step 150 here.

Embodiment 5 FIG.
[System Configuration of Embodiment 5]
Next, a fifth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 4 in the first embodiment and the routine of FIG. 11 described later in the configuration shown in FIG.

[Air-fuel ratio control in the fifth embodiment]
In the first and second embodiments, it is possible to achieve a preferable recovery of rich poisoning by extending the poisoning recovery time by F / C by lowering the return rotational speed. However, if the return rotational speed is lowered, the possibility of causing an engine stall increases. Therefore, it is preferable to prevent engine stall while reducing the return rotational speed.

  Therefore, in the system according to the present embodiment, when the return rotational speed (FCRTN) is lower than the base value (FCRTNB), a drop in the rotational speed is prevented by advancing at the time of F / C return.

  FIG. 11 is a flowchart of a routine executed by the ECU 50 in order to realize the above-described operation. In particular, control from F / C to F / C return is shown. It should be noted that the processing for starting F / C and lowering the return rotational speed FCRTN below the base value FCRTNB is performed in another routine. In the routine shown in FIG. 11, it is first determined whether or not the return rotational speed FCRTN is lower than the base value FCRTNB (step 160).

  If the return rotational speed is higher than the base value, it is not necessary to advance to prevent engine stall, and the return advance flag is set to OFF (step 162). On the other hand, if the return rotational speed is lower than the base value, the possibility of engine stall is high, so the return advance flag is set to ON (step 164).

  Subsequent to step 162 or 164, it is determined whether the F / C is being performed and the F / C return condition is satisfied (step 166). Specifically, the F / C return condition is satisfied if the engine speed NE has reached the return speed FCRTN.

  If the F / C is not in progress or the F / C return condition is not satisfied, this routine is terminated. If F / C is not in progress, it is not necessary to return to F / C. On the other hand, if the F / C return condition is not satisfied, F / C is continued.

  If it is determined in step 166 that F / C is being performed and the F / C return condition is satisfied, it is next determined whether or not the return advance flag is ON (step 168). If the return advance flag is turned OFF in step 162, the F / C is returned without advance at the return (step 170), and this routine is terminated.

  If the return advance flag is ON in step 168, the ignition timing is advanced (step 172). Here, the advance angle is increased as the FTCTN is lowered. Thereafter, the F / C is returned and the return rotational speed FCRTN is returned to the base value FCRTNB (step 170). If the ignition timing is advanced, the torque increases, and the rotation speed can be prevented from dropping.

  As described above, according to the routine shown in FIG. 11, even when the return rotational speed is lowered, the engine speed can be prevented from dropping and the engine stall can be suppressed by advancing at the time of F / C return. it can.

  In the fifth embodiment described above, the control for lowering the return rotational speed FCRTN below the base value FCRTNB is performed by the routine of FIG. 4 shown in the first embodiment, but the control method is limited to this. It is not a thing. That is, the control may be performed by either the routine of FIG. 8 shown in the second embodiment or the routine of FIG. 9 shown in the third embodiment.

  In the fifth embodiment described above, the spark plug 16 corresponds to the “fuel ignition means” of the seventh invention. Here, the “ignition advancement means” is realized by the ECU 50 executing the processing of steps 160 to 172.

Embodiment 6 FIG.
[System Configuration of Embodiment 6]
Next, a sixth embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 12 described later in the configuration shown in FIG. In the present embodiment, as in the second embodiment, the permitted rotational speed is calculated by adding the hysteresis value to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed). Therefore, if the return rotation speed is lowered, the permitted rotation speed can be lowered. Further, if the hysteresis value is lowered, the permitted rotational speed can be lowered without changing the return rotational speed.

[Air-fuel ratio control in Embodiment 6]
In Embodiment 2, rich poisoning can be recovered by performing F / C. The rich poisoning is recovered by sending air to the exhaust purification catalyst 32. Here, it is preferable that the amount of air per unit time sent to the exhaust purification catalyst 32 can be increased, because the poisoning recovery speed can be improved and the time required for rich poisoning recovery can be shortened.

  Therefore, in the system of the present embodiment, the throttle opening is controlled according to the poisoning situation after the start of F / C.

  FIG. 12 is a flowchart of a routine executed by the ECU 50 to realize the above-described operation. In particular, the control up to the start of F / C is shown. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. Further, in this routine, step 182 is inserted between steps 132 to 134, step 184 is inserted between steps 133 to 134, and step 188 is inserted between steps 110 to 106. This is similar to the routine shown. In the following, steps common to both are denoted by common numbers, and description thereof is simplified or omitted.

  In the routine shown in FIG. 12, after the process of step 132, the throttle opening (QFC) during F / C is set to the throttle opening base value (QFCB) during F / C (step 182). Further, after the process of step 135, the correction value X is added to the throttle opening base value (QFCB) during F / C according to the poisoning situation to obtain the throttle opening (QFC) during F / C (step 184). ). Note that the ECU 50 stores a map in which a correction value X as shown in FIG. 13 is defined using the OSA indicating the poisoning status as a parameter.

  Subsequent to step 182 or 184, F / C start determination and OSA calculation are performed (step 134). The process of step 134 is realized by a series of processes from steps 136 to 106.

  When the condition of step 136 is satisfied, F / C is started (step 138), and steps 108 and 110 are performed as OSA calculation. Next, the throttle valve 28 is controlled based on the throttle opening (QFC) during F / C calculated in step 182 or 184 (step 188). Thereafter, the above step 106 is performed and this routine is terminated.

  As described above, when the throttle opening during F / C is set to the base value in step 182, the throttle valve 28 is opened by the normal throttle opening in step 188. On the other hand, when the correction value X corresponding to the poisoning situation is added to the normal throttle opening in the step 184, the throttle valve 28 is opened to the normal throttle opening by the correction value X in the step 188. Here, the amount of air per unit time that passes through the exhaust purification catalyst 32 during F / C can be increased by increasing the correction value X as it is poisoned (lower OSA). The poisoning recovery time is shortened by increasing the amount of air passing through the catalyst.

  As described above, according to the routine shown in FIG. 12, it is possible to control the throttle opening during the F / C according to the poisoning situation, and to shorten the time required for the poisoning recovery. Further, since the torque at the time of F / C return can be increased by opening the throttle and increasing the inflow air amount, the effect of suppressing engine stall even when the return rotational speed is lowered in the first to third embodiments. Can also hope.

  In the sixth embodiment described above, the present embodiment is realized by adding steps 182 to 188 to the routine of FIG. 8 shown in the second embodiment. However, the implementation method is not limited to this. Absent. That is, in the routine of FIG. 4 shown in the first embodiment, step 182 is added between steps 116 to 106, step 184 is added between steps 126 to 106, and step 188 is added after steps 182 and 184. It is good to do. In the routine of FIG. 9 shown in the third embodiment, step 182 is added between steps 148 to 134, step 184 is added between steps 146 to 134, and step 188 is added between steps 110 to 106. It is also good to do.

  In the above-described sixth embodiment, the throttle valve 28 corresponds to the “throttle valve” in the eighth invention. Here, in addition to the throttle opening sensor 30, the ECU 50 executes the processes of steps 130, 182, 184, 136, and 188 to realize “inflow air amount control means”.

Embodiment 7 FIG.
[System Configuration of Embodiment 7]
Next, a seventh embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 14 described later in the configuration shown in FIG. In the present embodiment, as in the second embodiment, the permitted rotational speed is calculated by adding the hysteresis value to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed). Therefore, if the return rotation speed is lowered, the permitted rotation speed can be lowered. Further, if the hysteresis value is lowered, the permitted rotational speed can be lowered without changing the return rotational speed.

[Air-fuel ratio control in Embodiment 7]
In the first and second embodiments, the poisoning recovery time can be further extended by lowering the return rotational speed and extending F / C. However, under conditions where engine stall is likely to occur, it is preferable not to reduce the return rotational speed too much in order to suppress engine stall.

  Therefore, in the system according to the present embodiment, the reduction range of the return rotational speed is limited under the condition that the engine is likely to stall.

  FIG. 14 is a flowchart of a routine executed by the ECU 50 to realize the above-described operation. In particular, the control up to the start of F / C is shown. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. Further, this routine is the same as the routine shown in FIG. 8 except that step 133 is replaced with step 190. In the following, steps common to both are denoted by common numbers, and description thereof is simplified or omitted.

  In the routine shown in FIG. 14, the determination in step 130 is first made. When the engine speed NE is smaller than the permitted engine speed (FCRTN + FCHYS) and the engine is poisoned, a predetermined value B (calculated from the map shown in FIG. And a correction value X is added to obtain a new return rotational speed FCRTN (step 190). Note that the ECU 50 stores a map in which a correction value X as shown in FIG. 15 is defined using whether or not the engine stall is likely to occur as a parameter. According to this map, the correction value X increases as the engine stalls more easily. In addition, as to whether or not the engine is likely to stall, for example, it is determined that the engine is likely to stall when cold before complete warming (for example, when the water temperature is 70 ° C. or lower).

  As described above, in step 190, the engine stall due to the F / C can be suppressed by increasing the correction value X and decreasing the reduction range of the return rotational speed as the engine stalls more easily.

  As described above, according to the routine shown in FIG. 14, it is possible to extend the poisoning recovery time while limiting the reduction range of the return rotational speed in accordance with the poisoning situation and suppressing the engine stall.

  In the seventh embodiment described above, the present embodiment is realized by replacing step 133 of the routine of FIG. 8 shown in the second embodiment with step 190. However, the implementation method is limited to this. is not. That is, in the routine of FIG. 4 shown in the first embodiment, step 126 may be replaced with step 190.

  In the above-described seventh embodiment, the condition that the engine is easily stalled is that it is cold before complete warm-up, but the condition is not limited to this. That is, it is good on condition that the poor fuel is used. Further, it may be a condition that the rate of decrease in the engine speed is fast (when the clutch is disengaged at F / C or MT from high rotation).

  In the above-described seventh embodiment, the correction value X is added to the predetermined value B in order to reduce the reduction range of the return rotational speed FCRTN. However, the calculation method is not limited to this. That is, the predetermined value B may be multiplied by the correction value X in order to reduce the amount of decrease in the return rotational speed FCRTN. Here, the correction value X is set so that the range is 0 ≦ X ≦ 1 and the engine stalls easily.

  In the above-described seventh embodiment, the “engine stall judging means” and the “return rotational speed change restricting means” according to the sixth aspect of the present invention are realized by the ECU 50 executing the processing of steps 130 and 190.

Embodiment 8 FIG.
[System Configuration of Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 16 described later in the configuration shown in FIG. In the present embodiment, as in the second embodiment, the permitted rotational speed is calculated by adding the hysteresis value to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed). Therefore, if the return rotation speed is lowered, the permitted rotation speed can be lowered. Further, if the hysteresis value is lowered, the permitted rotational speed can be lowered without changing the return rotational speed.

[Air-fuel ratio control in the eighth embodiment]
In the third embodiment, the F / C can be performed from a low speed even under a condition where the engine stalls easily by lowering the F / C hysteresis value without lowering the return speed. However, if the F / C hysteresis value is kept lowered after the completion of the F / C, the range between the permitted rotation speed and the return rotation speed is small, which may cause hunting of the engine rotation at the next and subsequent F / Cs. .

  Therefore, in the system of this embodiment, the hysteresis value after F / C is returned to the base value.

  FIG. 16 is a flowchart of a routine executed by the ECU 50 in order to realize the above-described operation. In particular, it shows control from idle ON to F / C start. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. Further, the routine shown in FIG. 16 is the same as the routine shown in FIG. 9 except that step 200 is inserted between steps 110 and 106. In the following, steps common to both are denoted by common numbers and description thereof is omitted.

  In the routine shown in FIG. 16, after starting the F / C (the above step 138), OSA is calculated (the above steps 108 and 110). Thereafter, the hysteresis value FCHYS is returned to the base FCHYSB value (step 200). Thereafter, the process of step 106 is performed.

  As described above, the hysteresis value can be returned to the base value in step 200. Thereby, in the routine after the next time, the interval between the permitted rotation speed and the return rotation speed can be returned to the reference value for processing. In particular, when it is determined in step 140 that the condition is not satisfied, that is, when the engine speed NE that should not lower the permitted engine speed is sufficiently high or not poisoned, the hysteresis value is returned to the base value. , F / C start determination (step 136) can be determined and processed appropriately based on the normal permitted rotational speed.

  As described above, according to the routine shown in FIG. 16, in addition to the control shown in the third embodiment, the hunting of the engine rotation can be suppressed by returning the hysteresis value to the base value.

  Incidentally, in the above-described eighth embodiment, the hysteresis value is returned to the base value by the processing of step 200, but the processing method is not limited to this. That is, instead of step 200, when the condition of step 140 is not satisfied, a process of setting the hysteresis value FCHYS as the base value FCHYSB may be inserted, and then the process of step 134 may be performed.

  In the eighth embodiment described above, the “permission return rotation speed initialization means” according to the fifth aspect of the present invention is realized by the ECU 50 executing the process of step 200.

Embodiment 9 FIG.
[System Configuration of Embodiment 9]
Next, a ninth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 17 described later in the configuration shown in FIG. In the present embodiment, as in the second embodiment, the permitted rotational speed is calculated by adding a hysteresis value to the return rotational speed (return rotational speed + hysteresis value = permitted rotational speed). Therefore, if the return rotational speed is lowered, the permitted rotational speed can be lowered. Further, if the hysteresis value is lowered, the permitted rotational speed can be lowered without changing the return rotational speed.

[Control in Embodiment 9]
In the fourth embodiment, the delay time can be shortened according to the poisoning situation. By shortening the delay time, the F / C can be performed even when the time from when the throttle is closed until the F / C is started is short. . However, if the throttle ON / OFF is repeated quickly, the F / C is repeated in a short time, and drivability and emissions deteriorate. For this reason, it is preferable to suppress that F / C is repeated in a short time.

  Therefore, in the system according to the present embodiment, shortening of the delay time is prohibited for a predetermined period after F / C.

  FIG. 17 is a flowchart of a routine that the ECU 50 executes to realize the above-described operation. It should be noted that the F / C return and the process of returning the return rotational speed FCRTN to the base value FCRTNB after the F / C return are performed in other routines. In the routine shown in FIG. 17, except that steps 210 to 212 are inserted between the routine start and step 154 and steps 216 to 222 are inserted between step 110 and the routine end. This is the same as the routine shown in FIG. In the following, steps common to both are denoted by common numbers, and description thereof is simplified or omitted.

  In this routine, first, it is determined whether or not the prohibition flag is OFF (step 210). When the prohibition flag is ON, the base value FCDEYALB is substituted for the delay time FCDELAY in order to adopt the normal delay time without reducing the delay time (step 212). On the other hand, when the prohibition flag is OFF, the processing of step 150 is performed to shorten the delay time.

  Next, based on the delay time calculated in step 212 or 150, F / C start determination and OSA calculation are performed (step 214). The process of step 214 is realized by a series of processes of steps 154 to 222.

  In step 154, it is determined whether the idle is ON, NE is larger than the permitted rotation speed, and the delay time has elapsed. When the idle OFF or NE is equal to or lower than the permitted rotation speed or the delay time has not elapsed, F / C cannot be started. In this case, OSA is then calculated (steps 102 to 106 above).

  In step 154, if the idle is ON, NE is larger than the permitted rotation speed, and the delay time has elapsed, F / C is started (step 138). Here, whether or not the delay time has elapsed is determined by whether or not the delay time FCDELAY calculated in step 150 or 212 has elapsed since the throttle was closed. In step 150, when the delay time elapses according to the poisoning situation, the F / C is easily started, and the poisoning recovery by the F / C is promoted. Thereafter, OSA is calculated (steps 108 and 110).

  Next, it is determined whether F / C has been started in the previous routine (step 216). When the F / C is performed in the previous routine, the process of step 106 is performed. On the other hand, when F / C is started in the current routine, after the prohibition flag is turned on (step 218), the processing of step 106 is performed.

  Following step 106, it is determined whether a predetermined time has elapsed since the prohibition flag was turned on (step 220). Here, when the prohibition flag is OFF or when the predetermined time has not elapsed since the prohibition flag is ON, this routine is terminated. As a result, the shortening of the delay time can be prohibited until a predetermined time has elapsed since the prohibition flag was turned on.

  On the other hand, if a predetermined time has elapsed since the prohibition flag was turned on in step 220, the prohibition flag is turned OFF to cancel the delay time reduction prohibition (step 222).

  As described above, by turning on the prohibition flag in step 218, the routine ends with the prohibition flag being turned on without satisfying the condition of step 220 until a predetermined time has elapsed since the prohibition flag was turned on. As a result, the condition of step 210 is not satisfied in the next routine, and the delay time is not shortened (step 212).

  As described above, according to the routine shown in FIG. 17, the delay time shown in the fourth embodiment is prohibited from being shortened for a predetermined time after the execution of the F / C, and deterioration of drivability and emission can be suppressed.

  In the ninth embodiment described above, the “delay reduction prohibiting means” according to the eleventh aspect of the present invention is realized by the ECU 50 executing the processing of steps 210 to 212 and 216 to 222.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a timing chart for demonstrating an example of the operation | movement implement | achieved in the control apparatus of Embodiment 1 of this invention. It is a figure which shows the map used for poisoning determination in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the correction map used in Embodiment 1 of this invention. It is a relationship diagram of the return rotation speed and permission rotation speed which are used in Embodiment 2 of this invention. It is a timing chart for demonstrating an example of the operation | movement implement | achieved in Embodiment 2 control apparatus of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention. It is a flowchart of the routine performed in Embodiment 6 of this invention. It is a figure which shows the correction map used in Embodiment 6 of this invention. It is a flowchart of the routine performed in Embodiment 7 of this invention. It is a figure which shows the correction map used in Embodiment 7 of this invention. It is a flowchart of the routine performed in Embodiment 8 of this invention. It is a flowchart of the routine performed in Embodiment 9 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder 14 Fuel injection valve 16 Spark plug 18 Crank angle sensor 20 Intake passage 22 Exhaust passage 24 Air cleaner 26 Air flow meter 28 Throttle valve 30 Throttle opening sensor 32 Exhaust purification catalyst 34 Air fuel ratio sensor 36 Exhaust temperature sensor 38 Oxygen concentration Sensor 50 ECU
52 Accelerator opening sensor 54 Water temperature sensor

Claims (11)

A fuel cut means for stopping the fuel supplied to the internal combustion engine when the engine speed is higher than the fuel cut permission speed during deceleration of the internal combustion engine;
Poisoning correlation value acquisition means for acquiring a poisoning correlation value having a correlation with a rich poisoning state of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine;
A poisoning judging means for comparing the poisoning correlation value with a judgment value to judge whether or not rich poisoning;
A first return speed changing means for reducing the fuel cut return speed when the engine speed reaches the fuel cut return speed when the internal combustion engine is decelerated and is rich poisoning;
Fuel cut return means for ending the fuel cut when the engine speed reaches the fuel cut return speed and is not rich poisoning;
A control device for an internal combustion engine, comprising: 2. The first permitted rotational speed changing means for lowering the fuel cut permitted rotational speed when the engine rotational speed is lower than the fuel cut permitted rotational speed and the rich poisoning. Control device for internal combustion engine. A fuel cut means for stopping the fuel supplied to the internal combustion engine when the engine speed is higher than the fuel cut permission speed during deceleration of the internal combustion engine;
Poisoning correlation value acquisition means for acquiring a poisoning correlation value having a correlation with a rich poisoning state of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine;
A poisoning judging means for comparing the poisoning correlation value with a judgment value to judge whether or not rich poisoning;
A first permission return that lowers the fuel cut return speed when the engine speed is smaller than the fuel cut permission speed determined by adding a fuel cut hysteresis value to the fuel cut return speed and is rich poisoning. Rotation speed changing means;
Fuel cut return means for ending the fuel cut when the engine speed reaches the fuel cut return speed;
A control device for an internal combustion engine, comprising: Engine stall determining means for determining whether or not the engine is likely to stall based on the operating state of the internal combustion engine;
A return speed reduction prohibiting means for prohibiting a decrease in the fuel cut return speed by the first permission return speed changing means when the engine is likely to stall;
Second permission return rotation speed changing means for lowering the fuel cut hysteresis value when the engine speed is smaller than the fuel cut permission speed, the rich poisoning, and the engine is likely to stall.
The control device for an internal combustion engine according to claim 3, further comprising: 5. The control device for an internal combustion engine according to claim 4, further comprising permission return rotation speed initialization means for returning the fuel cut hysteresis value to an initial value after the fuel cut return time. Engine stall determining means for determining whether or not the engine is likely to stall based on the operating state of the internal combustion engine;
A return rotation speed change limiting means for reducing a reduction width of the fuel cut return rotation speed when compared with a case where it is difficult to stall the engine when engine stall is easy;
The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising: Fuel ignition means for igniting fuel in a cylinder of the internal combustion engine;
Ignition advance means for advancing the ignition timing at the time of fuel cut return when the fuel cut return speed is lower than the fuel cut return speed base value;
The control apparatus for an internal combustion engine according to any one of claims 1 to 6, further comprising: A throttle valve that changes the amount of air flowing into the internal combustion engine;
Inflow air amount control means for controlling the throttle valve opening during fuel cut based on the poisoning correlation value;
The control device for an internal combustion engine according to any one of claims 1 to 7, further comprising: The fuel cut means includes fuel cut start means for starting a fuel cut after a predetermined delay time has elapsed after closing the throttle,
A delay time shortening means for shortening the previous delay time based on the poisoning correlation value;
The control device for an internal combustion engine according to any one of claims 1 to 8, further comprising: A fuel cut means for stopping fuel supplied to the internal combustion engine after a predetermined delay time has elapsed after the throttle is closed when the engine speed is higher than the fuel cut permission rotational speed during deceleration of the internal combustion engine; ,
Poisoning correlation value acquisition means for acquiring a poisoning correlation value having a correlation with a rich poisoning state of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine;
A poisoning judging means for comparing the poisoning correlation value with a judgment value to judge whether or not rich poisoning;
A delay time shortening means for shortening the previous delay time based on the poisoning correlation value when the rich poisoning is determined;
A control device for an internal combustion engine, comprising: 11. The control device for an internal combustion engine according to claim 9, further comprising: a delay reduction prohibiting unit that prohibits the reduction of the delay time until a predetermined time elapses after the fuel cut is restored. .

Images