JP2014074332A - Control device for internal combustion engine - Google Patents

Abstract

The present invention relates to a control device for an internal combustion engine, and it is an object of the present invention to suitably adjust a fuel cut duration so that fuel efficiency can be reliably improved when fuel cut is performed.
A fuel injection valve for supplying fuel to an internal combustion engine and an exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine are provided. An increase in fuel injection for eliminating the lean air-fuel ratio of the catalyst atmosphere caused by the fuel cut is performed when returning from the fuel cut state. Based on the predicted fuel cut duration, a fuel efficiency improvement A due to continued fuel cut and a first fuel efficiency deterioration B associated with the increase in fuel injection are calculated. The fuel cut duration is adjusted so that the fuel efficiency improvement A is greater than the first fuel efficiency deterioration B.
[Selection] Figure 3

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, for example, Patent Document 1 discloses a driving force control device for a vehicle including an internal combustion engine. In this conventional control device, the longest duration of fuel cut is set based on the operating conditions of the internal combustion engine. Specifically, the longest duration is set longer in the low rotation / low load region and shorter in the high rotation / high load region.

JP-A-8-61108 JP 2012-57576 A JP 2011-163303 A JP 2007-56718 A JP 2006-233828 A JP 2011-111899 A Japanese Patent Laid-Open No. 1-113550

  During operation of the internal combustion engine, in order to improve fuel efficiency, fuel cut is performed when a predetermined execution condition is satisfied during deceleration or the like. On the other hand, when the fuel cut is performed, fresh air having a high oxygen concentration is supplied to the exhaust purification catalyst disposed in the exhaust passage. For this reason, as the fuel cut duration time becomes longer, the air-fuel ratio of the atmosphere of the exhaust purification catalyst becomes leaner. Further, when returning from the fuel cut state, generally, in order to eliminate the lean air-fuel ratio of the exhaust purification catalyst atmosphere caused by the execution of the fuel cut (for example, when the exhaust purification catalyst is a three-way catalyst) The fuel injection is increased in order to return the catalyst atmosphere to the stoichiometric air-fuel ratio. Therefore, if the fuel cut duration time is increased, the increase in fuel injection at the time of return increases. This is a factor that deteriorates fuel consumption.

  The present invention has been made to solve the above-described problems. When the fuel cut is performed, the internal combustion engine capable of suitably adjusting the fuel cut duration so that the fuel consumption can be reliably improved. An object of the present invention is to provide an engine control device.

A first invention is a control device for an internal combustion engine,
A fuel injection valve for supplying fuel to the internal combustion engine;
An exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine;
A return fuel increase execution means for executing an increase in fuel injection for eliminating the lean air-fuel ratio of the atmosphere of the exhaust purification catalyst caused by the execution of fuel cut when returning from the fuel cut state;
Fuel cut duration acquisition means for acquiring fuel cut duration; and
Fuel efficiency improvement calculating means for calculating a fuel efficiency improvement due to continuation of the fuel cut based on the fuel cut duration;
First fuel consumption deterioration calculation means for calculating a first fuel consumption deterioration due to an increase in fuel injection by the return fuel increase execution means based on the fuel cut duration;
Fuel cut duration adjusting means for adjusting the fuel cut duration so that the fuel efficiency improvement is greater than the first fuel consumption deterioration;
It is characterized by providing.

The second invention is the first invention, wherein
An air-fuel ratio sensor disposed in the exhaust passage, having a heater for heating the sensor element, and detecting an air-fuel ratio of the exhaust gas flowing through the exhaust passage;
Heater energization stopping means for stopping energization of the heater when fuel cut is executed,
Based on the fuel cut duration, a second fuel consumption that calculates a second fuel consumption deterioration associated with the power consumption of the heater required to raise the temperature of the sensor element to the activation temperature when returning from the fuel cut state Deterioration calculation means,
Further comprising
The fuel cut duration adjusting means adjusts the fuel cut duration so that the fuel consumption improvement is larger than the sum of the first fuel consumption deterioration and the second fuel consumption deterioration. .

The third invention is the second invention, wherein
The fuel cut duration acquisition means includes means for predicting a return time from the fuel cut state,
Heater energization restarting means for resuming energization of the heater during fuel cut is further provided so that the temperature of the sensor element reaches the activation temperature when the return time from the predicted fuel cut state arrives. It is characterized by.

  According to the first aspect of the invention, based on the comparison result between the fuel consumption improvement amount and the first fuel consumption deterioration amount, the fuel cut duration is adjusted so that the fuel consumption improvement amount becomes larger than the first fuel consumption deterioration amount. . As the fuel cut duration increases, the air-fuel ratio of the atmosphere of the exhaust purification catalyst becomes leaner. For this reason, if the fuel cut duration time becomes longer, a situation may occur in which the first fuel consumption deterioration due to the increase in fuel injection for eliminating the leaning exceeds the fuel consumption improvement due to continued fuel cut. According to the present invention, even when the above situation occurs, the fuel cut duration is adjusted so that the condition that the fuel consumption improvement is larger than the first fuel consumption deterioration is maintained. As a result, the fuel cut duration can be determined so that the fuel consumption can be reliably improved regardless of the length of the fuel cut duration.

  According to the second invention, in consideration of the second fuel consumption deterioration, the fuel cut duration is adjusted so that the fuel consumption improvement is larger than the sum of the first fuel consumption deterioration and the second fuel consumption deterioration. Is done. As a result, when control is performed to stop energization of the heater included in the air-fuel ratio sensor during execution of fuel cut, fuel consumption is reliably ensured regardless of the length of fuel cut duration compared to the first aspect of the invention. The fuel cut duration can be determined more appropriately so that it can be improved.

  According to the third aspect of the present invention, the sensor element is activated at the return time from the predicted fuel cut state by appropriately adjusting the time to stop energizing the heater during the fuel cut. Can be. As a result, while maintaining the effect of reducing power consumption by stopping the energization of the heater during the fuel cut, the air / fuel ratio sensor can be used to quickly obtain an accurate air / fuel ratio at the time of return from the fuel cut state. Can be detected.

It is a schematic diagram for demonstrating the system configuration | structure of the internal combustion engine of Embodiment 1 of this invention. It is a figure for demonstrating the difference between synchronous injection and asynchronous injection. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the characteristic heater energization control implemented in Embodiment 3 of this invention.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a schematic diagram for explaining a system configuration of an internal combustion engine 10 according to a first embodiment of the present invention. The system of this embodiment includes a spark ignition type internal combustion engine (for example, a gasoline engine) 10. A piston 12 is provided in each cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in each cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. An electronically controlled throttle valve 22 is provided downstream of the air flow meter 20. A fuel injection valve 24 for injecting fuel into the intake port is provided in the intake passage 16 (intake manifold portion) after branching toward each cylinder. Each cylinder is provided with a spark plug 26 for igniting the air-fuel mixture in the combustion chamber 14.

A catalyst 28 is disposed in the exhaust passage 18 as an exhaust purification catalyst for purifying the exhaust gas. Here, as an example, the catalyst 28 is assumed to be a three-way catalyst. An air-fuel ratio sensor 30 for detecting the air-fuel ratio of the exhaust gas flowing into the catalyst 28 (that is, the air-fuel ratio in the atmosphere of the catalyst 28) is disposed in the exhaust passage 18 upstream of the catalyst 28. As such an air-fuel ratio sensor 30, an A / F sensor that emits an almost linear output with respect to the air-fuel ratio of the exhaust gas flowing into the catalyst 28, or the exhaust gas flowing into the catalyst 28 is rich with respect to the stoichiometric air-fuel ratio. It is possible to use an O ₂ sensor or the like that generates a rich output when the exhaust gas is low and generates a lean output when the exhaust gas is lean with respect to the stoichiometric air-fuel ratio. The air-fuel ratio sensor 30 is assumed to include a heater (not shown) for heating the sensor element.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the air flow meter 20 and the air-fuel ratio sensor 30 described above, various sensors for detecting the operating state of the internal combustion engine 10 such as a crank angle sensor 42 for detecting the engine speed are connected to the input portion of the ECU 40. ing. Further, an input portion of the ECU 40 includes an accelerator opening sensor 44 for detecting a depression amount (accelerator opening) of an accelerator pedal (not shown) of the vehicle on which the internal combustion engine 10 is mounted, road surface information (for example, an uphill road ahead) A navigation system 46 capable of obtaining a corner) and an inter-vehicle distance sensor 48 for detecting an inter-vehicle distance from a vehicle traveling ahead are connected. Further, various actuators for controlling the operation state of the internal combustion engine 10 such as the throttle valve 22, the fuel injection valve 24, and the spark plug 26 are connected to the output portion of the ECU 40. The ECU 40 performs predetermined engine control such as fuel injection control and ignition control by operating various actuators in accordance with the outputs of the various sensors described above and a predetermined program.

(Fuel cut control and fuel injection control when returning from fuel cut)
During the operation of the internal combustion engine 10, a fuel cut is performed when a predetermined execution condition is satisfied during deceleration or the like in order to improve fuel consumption. On the other hand, when the fuel cut is performed, fresh air having a high oxygen concentration is supplied to the catalyst 28 disposed in the exhaust passage 18. For this reason, the air-fuel ratio of the atmosphere of the catalyst 28 becomes leaner as the fuel cut duration time becomes longer. Further, when returning from the fuel cut state, generally, the leaning of the air-fuel ratio of the atmosphere of the catalyst 28 caused by the fuel cut is eliminated, and the air-fuel ratio of the atmosphere of the catalyst 28 is changed to the stoichiometric air-fuel ratio (stoichiometric). An increase in fuel injection for returning is performed. In the case of the catalyst 28 which is a three-way catalyst, the NOx purification function can be recovered thereby. Therefore, if the fuel cut duration time is increased, the increase in fuel injection at the time of return increases. This is a factor that deteriorates fuel consumption.

  In general, in an internal combustion engine having a port injection type fuel injection valve such as the fuel injection valve 24, the timing of fuel injection can be switched between synchronous injection and asynchronous injection during operation as required. It has become. FIG. 2 is a diagram for explaining the difference between synchronous injection and asynchronous injection. As shown in FIG. 2, the synchronous injection is fuel injection performed for each cylinder in a predetermined crank angle period in synchronization with the rotation (crank angle) of the crankshaft. On the other hand, asynchronous injection is fuel injection that is executed immediately when an injection request is detected regardless of the crank angle (that is, not synchronized with the crank angle). Generally done.

  When returning from the fuel cut state due to the occurrence of an acceleration request or the like during the fuel cut, it is necessary to instantaneously supply the fuel corresponding to the rapidly increasing intake air amount. Thus, it is necessary to quickly return the air-fuel ratio of the atmosphere of the catalyst 28 in the lean state to stoichiometric. For this reason, in this case, asynchronous injection is executed. Then, by changing the amount of asynchronous injection at the time of fuel cut return according to the value of the air-fuel ratio of the atmosphere of the catalyst 28 at the time of return, the air-fuel ratio of the atmosphere of the catalyst 28 can be appropriately returned to stoichiometric. The reason why asynchronous injection is used in this case will be explained more specifically. Since the engine speed changes suddenly during acceleration, the fuel injection amount is calculated in a manner synchronized with the crank angle and reflected in the synchronous injection. This is because there is little time for making it possible to perform such calculation and reflection.

[Characteristic Control in Embodiment 1]
As described above, at the time of deceleration or the like that does not require the internal combustion engine 10 to generate torque, it is possible to suppress fuel consumption during the fuel cut. This basically contributes to an improvement in fuel consumption. On the other hand, as the fuel cut duration time is longer, the amount of asynchronous injection at the time of return increases as the air-fuel ratio of the atmosphere of the catalyst 28 becomes leaner. This becomes a factor of deterioration in fuel consumption.

  Therefore, in the present embodiment, the fuel cut continuation time is predicted at the start of the fuel cut, and the fuel efficiency improvement A due to the continuation of the fuel cut is calculated based on the predicted fuel cut continuation time. Furthermore, based on the predicted fuel cut duration, the first fuel consumption deterioration B associated with the increase in asynchronous injection at the time of return is calculated. In addition, the fuel cut duration is adjusted so that the calculated fuel efficiency improvement A is greater than the first fuel efficiency deterioration B.

FIG. 3 is a flowchart showing a control routine executed by the ECU 40 in order to realize characteristic control in the first embodiment of the present invention.
In the routine shown in FIG. 3, first, it is determined whether or not the FC execution is started based on whether or not a predetermined execution condition for fuel cut (hereinafter sometimes referred to as “FC”) is satisfied (see FIG. 3). Step 100).

  When it is determined in step 100 that the FC execution is started, calculation of a predicted value of the FC continuation time is executed (step 102). The FC duration can be predicted based on a known method. For example, the return time from the fuel cut can be predicted, and the FC duration can be calculated based on the difference between the predicted return time and the start time of the fuel cut. In this case, the return timing can be predicted based on, for example, the difference between the current engine speed and a predetermined return speed (in the case of natural return), the reduction speed of the current engine speed, or the like. Even in the case of FC return based on an acceleration request (so-called forced return), for example, the road surface information using the above-described navigation system 46 (specifically, the vehicle has entered an uphill after a certain time has passed). The acceleration request timing is predicted and the FC return timing is predicted based on, for example, that the inter-vehicle distance from the forward traveling vehicle obtained by using the inter-vehicle distance sensor 48 is more than a predetermined value. can do.

  Next, based on the FC continuation time calculated in step 102, the fuel efficiency improvement A due to the continuation of FC is calculated (step 104). This fuel efficiency improvement A is calculated, for example, as the product of the predicted number of fuel injections during the FC continuation time and a predetermined fuel injection amount per time when no FC is performed under the same operating conditions. be able to. The estimated number of fuel injections during the FC continuation time is estimated based on, for example, a result of predicting the transition of the engine speed during the FC continuation using the engine speed at the start of FC or its decreasing speed. be able to.

  Next, based on the FC duration calculated in step 102, the air-fuel ratio of the atmosphere of the catalyst 28 at the time of FC recovery is calculated (step 106). The air-fuel ratio can be calculated based on, for example, the value of the air-fuel ratio immediately before the start of FC (the value detected by the air-fuel ratio sensor 30) and the amount of fresh air flowing into the catalyst 28 during FC execution. . The fresh air amount is, for example, the air amount, the FC duration (predicted value), the vehicle speed, the intake air amount (the value detected by the air flow meter 20), and the valve that is stopped during FC. It can be calculated by referring to a map defined in relation to the number of (reversely, the number of valves opened during FC may be used). The vehicle speed is used because the intake air amount changes depending on the vehicle speed during FC.

  Next, based on the air-fuel ratio of the catalyst atmosphere at the time of FC return calculated in step 106, the first fuel consumption deterioration amount B accompanying the increase in asynchronous injection for returning the catalyst 28 to the stoichiometric state at the time of FC return is calculated. (Step 108). According to the air-fuel ratio calculated in step 106, it is possible to grasp how lean the air-fuel ratio of the catalyst atmosphere at the time of FC recovery predicted is lean. The ECU 40 stores a map that defines the fuel injection amount (first fuel consumption deterioration B) necessary for returning the catalyst 28 to the stoichiometric state at the time of FC recovery in relation to the air-fuel ratio of the catalyst atmosphere at the time of FC recovery. Yes. In this step 108, referring to such a map, the first fuel consumption deterioration amount B is calculated based on the air-fuel ratio calculated in step 106.

  Next, the FC continuation time is adjusted so that the fuel efficiency improvement A calculated in step 104 is larger than the first fuel efficiency deterioration B calculated in step 108 (step 110). Specifically, in this step 110, when the fuel efficiency improvement A is equal to or less than the first fuel efficiency deterioration B based on the comparison result between the calculated fuel efficiency improvement A and the first fuel efficiency deterioration B, The FC duration is shortened with respect to the value calculated in step 102 so that the fuel efficiency improvement A becomes larger than the first fuel efficiency deterioration B. On the other hand, if the fuel efficiency improvement A is already larger than the fuel efficiency deterioration, the FC duration calculated in step 102 is used as it is.

  Thereafter, when the FC continuation time after the adjustment in the process of step 110 has elapsed, a return from the FC state (resumption of fuel injection) is executed (step 112).

  According to the routine shown in FIG. 3 described above, the fuel efficiency improvement A is calculated based on the comparison result between the fuel efficiency improvement A calculated based on the FC duration and the first fuel efficiency deterioration B. The FC duration is adjusted to be greater than B. As described above, the leaner the air-fuel ratio of the atmosphere of the catalyst 28 progresses as the FC duration time becomes longer. For this reason, if FC continuation time becomes long, the first fuel consumption deterioration B due to the increase in fuel injection for eliminating the leaning and making the air-fuel ratio of the catalyst atmosphere stoichiometric exceeds the fuel consumption improvement A due to FC continuation. Can happen. On the other hand, according to the processing of the above routine, when the above situation occurs, the FC continuation time is adjusted so that the condition that the fuel efficiency improvement A is larger than the first fuel efficiency deterioration B is maintained. The As a result, regardless of the length of the FC duration, the FC duration can be determined so that the fuel consumption can be reliably improved.

  In the first embodiment described above, the ECU 40 increases the amount of asynchronous injection when returning from the FC state, thereby realizing the “recovery fuel increase execution means” according to the first aspect of the present invention. By executing the processing of 102, the “fuel cut duration acquisition means” in the first invention is realized, and the ECU 40 executes the processing of step 104 to perform the “fuel efficiency improvement calculation” in the first invention. Means "is realized, and the ECU 40 executes the processing of steps 106 and 108, whereby the" first fuel consumption deterioration calculating means "in the first invention is realized, and the ECU 40 executes the processing of step 110. As a result, the “fuel cut duration adjusting means” in the first aspect of the invention is realized. .

Embodiment 2. FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 4 described later instead of the routine shown in FIG. 3 using the hardware configuration shown in FIG.

  A zirconia element is generally used for the air-fuel ratio sensor 30 provided in the internal combustion engine 10, and the sensor element is not activated unless the temperature exceeds a certain temperature, and the air-fuel ratio cannot be detected correctly. For this reason, the air-fuel ratio sensor 30 is also provided with a heater, and consideration is given so that the sensor element temperature can maintain a predetermined activation temperature by controlling energization to the heater.

  However, power consumption due to energization of the heater is large, and it is desired to suppress energization of the heater as small as possible in view of the recent need for improved fuel consumption. For this reason, in the present embodiment, by utilizing the fact that air-fuel ratio feedback control using the air-fuel ratio sensor 30 is not performed during FC execution, the heater is turned off during FC execution to reduce power consumption. We are going to plan.

  On the other hand, during the execution of the FC, fresh air at normal temperature flows through the exhaust passage 18 so that the sensor element is cooled by the fresh air. For this reason, when the energization to the heater is turned off during the execution of FC, the element temperature of the air-fuel ratio sensor 30 decreases toward a certain convergence temperature as the FC duration time increases. The heater energization time required to raise the element temperature to the activation temperature when returning from the FC state becomes longer as the element temperature is lower. For this reason, in addition to the first fuel consumption deterioration amount B in the first embodiment described above, the second fuel consumption deterioration amount C due to the increase in power consumption due to energization of the heater at the time of return as the FC duration time increases. growing.

  Therefore, in the present embodiment, the first fuel consumption deterioration portion B and the second fuel consumption deterioration portion C are assumed on the premise that control for stopping energization of the heater included in the air-fuel ratio sensor 30 is performed during the execution of FC. The fuel cut duration is adjusted so that the fuel efficiency improvement A is greater than the sum of

  In the present embodiment, while the energization of the heater of the air-fuel ratio sensor 30 is OFF during the execution of FC (that is, while the air-fuel ratio cannot be detected by the air-fuel ratio sensor 30), the air-fuel ratio immediately before the start of FC. Based on the value of the air-fuel ratio detected by the sensor 30 and the amount of fresh air flowing into the catalyst 28 during the execution of FC, the sensor element is detected by restarting energization to the heater during the execution of FC and after returning from the FC state. The air-fuel ratio until activation is calculated (estimated). The amount of fresh air during the execution of FC includes, for example, the air amount, the FC duration, the vehicle speed, the intake air amount (value detected by the air flow meter 20), and the valve that is stopped during FC. It can be calculated by referring to a map defined in relation to the number of (reversely, the number of valves opened during FC may be used). This makes it possible to grasp the air-fuel ratio of the catalyst atmosphere when returning from the FC state even when the heater is turned off during FC execution.

  In the present embodiment, the asynchronous injection amount at the time of return from the FC state is changed based on the air-fuel ratio value estimated as described above. More specifically, the asynchronous injection amount is increased as the air-fuel ratio of the atmosphere of the catalyst 28 at the time of FC recovery becomes leaner. Thereby, even in a situation where the elements of the air-fuel ratio sensor 30 are not activated, it is possible to determine an appropriate asynchronous injection amount according to the air-fuel ratio of the catalyst atmosphere. However, if the amount of asynchronous injection is excessively increased according to the lean degree of the air-fuel ratio in the catalyst atmosphere, there is a risk that the amount of unburned fuel discharged from the cylinder will increase. For this reason, an upper limit is set for the amount of increase in asynchronous injection corresponding to the air-fuel ratio. On the other hand, when the FC is continued for a long time, the air-fuel ratio of the atmosphere of the catalyst 28 may be in an extremely lean state. In such a case, there is a possibility that the air-fuel ratio of the atmosphere of the catalyst 28 cannot be returned to the stoichiometric state only by increasing the amount of asynchronous injection within a range up to a certain upper limit. Therefore, in this embodiment, when the asynchronous injection amount to be injected at the time of FC recovery exceeds a predetermined upper limit value, the synchronous injection amount of the next cycle is increased only by the insufficient increase amount. As a result, even when the air-fuel ratio of the catalyst atmosphere becomes an extremely lean state during the execution of the FC, the stoichiometric state can be quickly restored.

  FIG. 4 is a flowchart illustrating a control routine executed by the ECU 40 in order to realize characteristic control for adjusting the fuel cut duration in the second embodiment of the present invention. In FIG. 4, the same steps as those shown in FIG. 3 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 4, after the first fuel consumption deterioration amount B is calculated in step 108, the second fuel consumption deterioration amount C due to energization of the heater at the time of FC return is calculated based on the predicted FC duration time. (Step 200). As shown in FIG. 5 to be described later, the temperature reduction allowance of the sensor element due to the continuation of FC can be calculated based on the FC continuation time by defining the relationship with the FC continuation time as a map in advance. . When the temperature reduction allowance of the sensor element is known, the electric power required for the temperature increase for reactivating the sensor element can be calculated according to a predetermined relational expression. Further, the maintenance power required when energization of the heater is maintained in order to maintain the element temperature during the predicted FC duration time at the activation temperature is calculated. Then, after calculating the difference between the power required for reactivation of the sensor element at the time of FC recovery and the maintenance power, this difference is calculated according to a predetermined relational expression and the fuel efficiency improvement A and the first fuel efficiency deterioration B Is converted into a conversion value that can be compared with the second fuel consumption deterioration amount C.

  Next, the FC continuation time is adjusted so that the fuel efficiency improvement A becomes larger than the sum of the first fuel efficiency deterioration B and the second fuel efficiency deterioration C (step 202). Specifically, in this step 202, based on the comparison result of the fuel efficiency improvement A and the sum of the first fuel efficiency deterioration B and the second fuel efficiency deterioration C, the fuel efficiency improvement A is the sum (B + C). In the following cases, the FC continuation time is shortened with respect to the value calculated in step 102 so that the fuel efficiency improvement A becomes larger than the sum (B + C). On the other hand, if the fuel efficiency improvement A is already greater than the sum (B + C), the FC duration calculated in step 102 is used as it is.

  According to the routine shown in FIG. 4 described above, the fuel efficiency improvement A is larger than the sum of the first fuel efficiency deterioration B and the second fuel efficiency deterioration C in consideration of the second fuel efficiency deterioration C. The FC duration is adjusted. As a result, when control for stopping energization of the heater included in the air-fuel ratio sensor 30 is performed during execution of FC, fuel efficiency is improved regardless of the length of FC continuation time compared to the control of the first embodiment described above. It will be possible to determine the FC duration more appropriately so as to ensure improvement.

  In the second embodiment described above, the “heater energization stopping means” in the second aspect of the present invention is realized by the ECU 40 stopping energization of the heater of the air-fuel ratio sensor 30 during execution of FC. The "second fuel consumption deterioration calculating means" in the second invention is realized by the ECU 40 executing the process of step 200, and the ECU 40 executes the process of step 202 to realize the second invention. "Fuel cut duration adjusting means" is realized.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment additionally performs the control described below with reference to FIG. 5 with respect to the system of the second embodiment described above.

FIG. 5 is a diagram for explaining the characteristic heater energization control performed in the third embodiment of the present invention.
As shown in FIG. 5, when the heater is de-energized with the start of FC, the temperature of the sensor element decreases with time. However, the element temperature does not continue to decrease, but is balanced at a constant temperature. It takes a certain amount of time to raise the temperature of the sensor element, which has decreased during FC execution, to the activation temperature.

  Therefore, in this embodiment, after the return time from the FC state is predicted by the method described above, the temperature of the sensor element is activated when the return time from the predicted FC state arrives as shown in FIG. Energization to the heater was resumed during FC execution to reach the control temperature. In other words, based on the FC continuation time, the time for turning off the power to the heater during FC execution is controlled.

  More specifically, in the present embodiment, the energization time to the heater necessary to re-activate the sensor element at the time of FC recovery is calculated during the period in which energization to the heater is stopped during FC execution. The This energization time can be calculated based on a predetermined map or the like as a value according to the temperature reduction allowance of the sensor element that is executing FC obtained by referring to the map or the like as described above. In addition, energization of the heater is resumed at a timing earlier by the energization time calculated with respect to the predicted return timing.

  According to the heater energization control of the present embodiment described above, the sensor element can be activated at the predicted return time from the FC state. As a result, while maintaining the effect of reducing power consumption by stopping energization of the heater during FC execution, the air-fuel ratio sensor 30 is used to quickly detect the accurate air-fuel ratio at the return timing from the FC state. become able to.

  In the above-described third embodiment, as shown in FIG. 5, the ECU 40 executes the FC so that the temperature of the sensor element reaches the activation temperature when the return time from the predicted FC state arrives. The “heater energization restarting means” according to the third aspect of the present invention is realized by resuming energization of the heater.

  By the way, in Embodiment 1 etc. which were mentioned above, the duration of this fuel cut is estimated at the time of the start of execution of fuel cut, and fuel consumption improvement A and 1st fuel consumption deterioration are based on the predicted fuel cut duration. The example which calculates B and also the 2nd fuel consumption deterioration part C was demonstrated. However, the prediction of the fuel cut duration is not limited to the start of execution, and the fuel consumption improvement A and the fuel consumption deterioration B and C are sequentially calculated and compared while sequentially predicting the duration during execution of the fuel cut. The fuel cut duration time may be sequentially adjusted based on the above. Further, the adjustment of the fuel cut duration in the present invention is not limited to the method based on the predicted fuel cut duration. That is, for example, the fuel cut duration time is actually measured and acquired during execution of the fuel cut. Then, the fuel consumption improvement A and the fuel consumption deterioration B and C may be sequentially calculated and compared while measuring the fuel cut duration, and the fuel cut duration may be adjusted sequentially based on the result.

  Moreover, in Embodiment 1 etc. which were mentioned above, the example where asynchronous injection was increased at the time of a return from a fuel cut state was demonstrated. However, the mode of fuel injection executed when returning from the fuel cut state is not necessarily limited to asynchronous injection, and may be synchronous injection if possible.

  Further, in the first to third embodiments described above, the fuel cut performed at the time of deceleration or the like has been described as an example. However, the fuel cut that is the subject of the present invention is not limited to a fuel cut intended for all cylinders during deceleration or the like, but may be a fuel cut intended for some cylinders for reduced-cylinder operation. .

  In the first to third embodiments described above, the port injection type fuel injection valve 24 has been described as an example. However, the fuel injection valve that is the subject of the present invention is not limited to the port injection type as long as it supplies fuel to the internal combustion engine, and may be a direct injection type in-cylinder type.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Air flow meter 22 Throttle valve 24 Fuel injection valve 26 Spark plug 28 Exhaust purification catalyst 30 Air-fuel ratio sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Accelerator opening sensor 46 Navigation system 48 Inter-vehicle distance sensor

Claims (3)

A fuel injection valve for supplying fuel to the internal combustion engine;
An exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine;
A return fuel increase execution means for executing an increase in fuel injection for eliminating the lean air-fuel ratio of the atmosphere of the exhaust purification catalyst caused by the execution of fuel cut when returning from the fuel cut state;
Fuel cut duration acquisition means for acquiring fuel cut duration; and
Fuel efficiency improvement calculating means for calculating a fuel efficiency improvement due to continuation of the fuel cut based on the fuel cut duration;
First fuel consumption deterioration calculation means for calculating a first fuel consumption deterioration due to an increase in fuel injection by the return fuel increase execution means based on the fuel cut duration;
Fuel cut duration adjusting means for adjusting the fuel cut duration so that the fuel efficiency improvement is greater than the first fuel consumption deterioration;
A control device for an internal combustion engine, comprising: An air-fuel ratio sensor disposed in the exhaust passage, having a heater for heating the sensor element, and detecting an air-fuel ratio of the exhaust gas flowing through the exhaust passage;
Heater energization stopping means for stopping energization of the heater when fuel cut is executed,
Based on the fuel cut duration, a second fuel consumption that calculates a second fuel consumption deterioration associated with the power consumption of the heater required to raise the temperature of the sensor element to the activation temperature when returning from the fuel cut state Deterioration calculation means,
Further comprising
The fuel cut duration adjusting means adjusts the fuel cut duration so that the fuel consumption improvement is larger than the sum of the first fuel consumption deterioration and the second fuel consumption deterioration. The control apparatus for an internal combustion engine according to claim 1. The fuel cut duration acquisition means includes means for predicting a return time from the fuel cut state,
Heater energization restarting means for resuming energization of the heater during fuel cut is further provided so that the temperature of the sensor element reaches the activation temperature when the return time from the predicted fuel cut state arrives. The control apparatus for an internal combustion engine according to claim 2.

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