JP6961307B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to a control device that controls an air-fuel ratio by adjusting a fuel injection amount in an internal combustion engine.

Generally, the exhaust passage of an internal combustion engine is equipped with a three-way catalyst that oxidizes / reduces _{harmful substances HC, CO, and NO x contained in the exhaust gas discharged from the cylinder to make them harmless.} In order to efficiently purify all of HC, CO, and NO _x , it is necessary to keep the air-fuel ratio of the air-fuel mixture within a certain range near the theoretical air-fuel ratio called a window. _{For this purpose, conventionally, O 2} sensors are arranged upstream and downstream of the catalyst, respectively, and a _{double feedback loop using the output signals of the O 2} sensors is constructed to feedback control the air-fuel ratio.

The ECU (Electronic Control Unit), which controls the operation of the internal combustion engine, has a feedback correction that changes according to the air-fuel ratio of the gas flowing into the catalyst to the basic injection amount proportional to the amount of air (fresh air) taken into the cylinder. The fuel injection amount from the injector is determined by multiplying by the coefficient.

_{As shown in FIG. 2, the ECU compares the output voltage of the front O 2} sensor that detects the air-fuel ratio of the gas on the upstream side of the catalyst with the determination voltage value corresponding to the stoichiometric air-fuel ratio or the air-fuel ratio in the vicinity thereof. If the output voltage is higher than the judgment voltage value, it is judged to be air-fuel ratio rich, and if it is lower than the judgment voltage value, it is judged to be air-fuel ratio lean. However, when _{the output voltage of the front O 2} sensor fluctuates so as to straddle the judgment voltage value, the judgment result of the air-fuel ratio is not immediately reversed, but the judgment result is reversed after waiting for the lapse of the delay time. That is, when _{the output voltage of the front O 2} sensor is switched from lean to rich (exceeds the judgment voltage value), it is determined that the air-fuel ratio is reversed from lean to rich after the rich judgment delay time TDR has elapsed. .. In addition, when _{the output voltage of the front O 2} sensor is switched from rich to lean (below the judgment voltage value), it is judged that the air-fuel ratio is reversed from rich to lean after the lean judgment delay time TDL has elapsed. ..

The ECU adjusts the feedback correction coefficient FAF in an increase or decrease based on the determination result of the air-fuel ratio of the gas on the upstream side of the catalyst. Specifically, while the air-fuel ratio is determined to be rich, the feedback correction coefficient FAF is gradually reduced by the lean integral value KIM, while the feedback correction coefficient FAF is determined to be lean while the air-fuel ratio is determined to be lean. Is gradually increased by the rich integral value KIP.

The rich determination delay time TDR and the lean determination delay time TDL are set according to the air-fuel ratio of the gas on the downstream side of the catalyst. _{As shown in FIGS. 3 and 4, the ECU compares the output voltage of the rear O 2} sensor that detects the air-fuel ratio of the gas on the downstream side of the catalyst with the judgment voltage value, and if the output voltage is higher than the judgment voltage value, If the air-fuel ratio is rich and lower than the judgment voltage value, it is judged to be air-fuel ratio lean. The longer the air-fuel ratio of the gas downstream of the catalyst is lean, the longer the rich determination delay time TDR is. On the contrary, the longer the period in which the air-fuel ratio of the gas on the downstream side of the catalyst is rich, the longer the lean determination delay time TDL is extended. As a result, _{the control center of the air-fuel ratio feedback control that refers to the output voltage of the front O 2} sensor, that is, the target for converging the air-fuel ratio of the gas by the feedback control changes (see the following patent documents).

The output voltage of the rear O ₂ sensor switches from rich to lean after oxygen has been occluded close to the catalyst's maximum oxygen occlusal capacity and oxygen has become excessive in the catalyst. If the oxygen in the catalyst is filled, the reduction of the NO _x becomes difficult, NO _x is easily discharged. On the other hand, _{the output voltage of the rear O 2} sensor switches from lean to rich after most of the oxygen stored in the catalyst is consumed and the oxygen in the catalyst is depleted. When oxygen is insufficient in the catalyst, it becomes difficult to oxidize HC and CO, and these are easily discharged.

In short, _{there was a delay in the feedback referring to the output signal of the rear O 2} sensor, and the delay caused a limit to the suppression of the emission of harmful substances.

Japanese Unexamined Patent Publication No. 2010-138791

An object of the present invention is to further reduce the amount of harmful substances emitted from an internal combustion engine.

In order to solve the above-mentioned problems, the present invention is a control device that feedback-controls the air-fuel ratio of the gas flowing into the exhaust gas purification catalyst mounted in the exhaust passage of the internal combustion engine, and is an amount of air sucked into the cylinder. , and wherein the output signal of the air-fuel ratio sensor installed upstream of the catalyst based on the exhaust passage, was estimated a deviation between the amount of oxygen and its target storage amount occluded in the catalyst of the air-fuel ratio of the gas The first target, which is the target, is set, and the second target, which is the target of the air-fuel ratio of the gas, is separately set based on the output signal of the air-fuel ratio sensor installed downstream of the catalyst in the exhaust passage. By comparing the first target and the second target, a control device for an internal combustion engine that changes the target of the air-fuel ratio of the gas to be converged by the feedback control is configured.

Further, when the deviation between the first target and the second target widens beyond a certain level, feedback control is performed so that the air-fuel ratio of the gas is converged on the second target instead of the first target. It is also preferable.

When you are carrying out feedback control so as to converge the air-fuel ratio to the second target, wherein when the interrupting fuel cut for a predetermined time or more fuel injection for the cylinder occurs, the air-fuel ratio for the subsequent first target Feedback control can be implemented to converge.

According to the present invention, the amount of harmful substances emitted from the internal combustion engine can be further reduced.

The figure which shows the schematic structure of the internal combustion engine for a vehicle and the control device in one Embodiment of this invention. A timing diagram showing a pattern of air-fuel ratio feedback control with reference to the output signal of the air-fuel ratio sensor on the upstream side of the catalyst. The graph which illustrates the relationship between the control center correction amount FACF and the delay time TDR, TDL. A timing diagram showing a pattern of air-fuel ratio feedback control with reference to the output signal of the air-fuel ratio sensor on the downstream side of the catalyst. The flow chart which shows the procedure which the control device of the same embodiment calculates the control center correction amount FACF.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to the present embodiment. The internal combustion engine in the present embodiment is a spark-ignition 4-stroke engine, and includes a plurality of cylinders 1 (one of which is illustrated in FIG. 1). An injector 11 for injecting fuel is provided in the vicinity of the intake port of each cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives an induction voltage generated by the ignition coil to induce a spark discharge between the center electrode and the ground electrode.

The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream on the intake passage 3.

The exhaust passage 4 for discharging the exhaust guides the exhaust gas generated as a result of burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4.

Air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the gas flowing through the exhaust passage 4 are installed upstream and downstream of the catalyst 41 in the exhaust passage 4. _{Each of the air-fuel ratio sensors 43 and 44 may be an O 2} sensor having a non-linear output characteristic with respect to the air-fuel ratio of the exhaust gas, and is a linear A / F sensor having an output characteristic proportional to the air-fuel ratio of the exhaust gas. There may be. In the present embodiment, it is assumed that the air-fuel ratio sensors 43 and 44 on the upstream side and the downstream side of the catalyst 41 are O ₂ sensors that output voltage signals according to the oxygen concentration in the exhaust gas. The characteristics of the output voltages f and g of the O ₂ sensors 43 and 44 show a steep slope with a large rate of change in output with respect to the air-fuel ratio in a certain range (window) near the stoichiometric air-fuel ratio, and the air-fuel ratio is larger than that. A so-called Z characteristic curve is drawn in which the low saturation value is asymptotic in the region and the high saturation value is asymptotic in the rich region where the air-fuel ratio is small.

The external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high-pressure loop EGR, and has an EGR passage 21 that communicates between the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The EGR cooler 22 provided on the EGR passage 21 and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined position downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined position downstream of the throttle valve 32 in the intake passage 3, specifically, a surge tank 33.

The ECU 0, which is a control device for the internal combustion engine of the present embodiment, is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

The input interface of ECU0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crank shaft and the engine rotation speed, and an accelerator pedal. Accelerator opening signal c output from a sensor that detects the amount of depression or the opening of the throttle valve 32 as the accelerator opening (so to speak, the engine load ratio required for the internal combustion engine), the intake passage 3 (particularly, the surge tank 33). ), The intake air temperature / intake pressure signal d output from the temperature / pressure sensor that detects the intake air temperature and the intake pressure, and the cooling water temperature signal e that is output from the water temperature sensor that detects the cooling water temperature that suggests the temperature of the internal combustion engine. The air-fuel ratio signal f output from the air-fuel ratio sensor 43 that detects the air-fuel ratio of the exhaust gas on the upstream side of the catalyst 41, and the air output from the air-fuel ratio sensor 44 that detects the air-fuel ratio of the exhaust gas on the downstream side of the catalyst 41. The fuel ratio signal g, the atmospheric pressure signal h output from the atmospheric pressure sensor that detects the atmospheric pressure, and the like are input.

From the output interface of the ECU 0, the ignition signal i for the igniter 13 of the spark plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening for the EGR valve 23. Outputs the operation signal l and the like.

The processor of ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine via the input interface, obtains the engine speed, and is sucked into the cylinder 1. Estimate the amount of air (fresh air). Then, based on the engine speed and the amount of air, various operations such as required fuel injection amount, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, required EGR rate, ignition timing, etc. Determine the parameters. The ECU 0 applies various control signals i, j, k, l corresponding to the operation parameters via the output interface.

In determining the fuel injection amount, the ECU 0 first obtains the amount Ga of the air sucked into the cylinder 1, and is proportional to the intake air amount Ga (the stoichiometric air-fuel ratio or the air in the vicinity thereof according to the intake air amount Ga). Determine the basic amount TP of the fuel injection amount (so that the fuel ratio can be realized). The intake air amount Ga is estimated based on the engine speed and the intake pressure in the surge tank 33. If necessary, the estimated value can be corrected according to the intake air temperature, atmospheric pressure, and the like. If an air flow meter is installed in the intake passage 3, it is possible to directly measure the intake air amount Ga via the air flow meter.

Next, this basic injection amount TP is corrected by a feedback correction coefficient FAF determined according to the output signal f of the air-fuel ratio sensor 43 on the upstream side of the catalyst 41. The feedback correction coefficient FAF is a positive number that increases or decreases around 1. Further, the final fuel injection time (energization time for the injector 11) T is calculated by taking into consideration various correction coefficients K determined according to the situation and the invalid injection time TAUV of the injector 11. The fuel injection time T is
T = TP x FAF x K + TAUV
Will be. Then, a signal j is input to the injector 11 for the fuel injection time T, and the injector 11 is opened to inject fuel.

Further, the ECU 0 executes a fuel cut that temporarily suspends the fuel supply to the cylinder 1 according to the operating condition. When the predetermined fuel cut condition is satisfied, the ECU 0 stops the fuel cut, that is, the fuel injection from the injector 11. The ECU 0 determines that the fuel cut condition is satisfied when at least the amount of depression of the accelerator pedal is 0 or equal to or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permitted speed.

During the fuel cut, the throttle valve 32 is opened to an opening degree that does not depend on the amount of depression of the accelerator pedal (0 or close to 0). This operation is performed in order to reduce the pumping loss of the internal combustion engine during fuel cutting and delay the deceleration of the engine rotation. The opening degree of the throttle valve 32 at this time may be a constant value or may be increased or decreased according to the vehicle speed or the like, but in any case, the opening degree is relatively large.

Then, when the predetermined fuel cut end condition is satisfied, the ECU 0 decides to end the fuel cut and restarts the fuel injection (and ignition). The ECU 0 determines that the fuel cut end condition is satisfied when the accelerator pedal depression amount exceeds the threshold value, the engine speed has decreased to the fuel cut return speed, or the like.

Needless to say, after the fuel cut end condition is satisfied, the throttle valve 32 is operated to have an opening degree corresponding to the amount of depression of the accelerator pedal.

Hereinafter, the air-fuel ratio feedback control performed by ECU 0 will be described in detail. The air-fuel ratio feedback control converges the air-fuel ratio of the air-fuel mixture filled in the cylinder 1, and eventually the air-fuel ratio of the exhaust gas discharged from the cylinder 1 and led to the catalyst 41 to a desired target air-fuel ratio, and thus the catalyst 41. It maximizes the purification efficiency of harmful substances.

_{As shown in FIG. 2, the ECU 0 determines that the output voltage f of the front O 2} sensor 43, which is a sensor for detecting the air-fuel ratio of the gas on the upstream side of the catalyst 41, corresponds to the stoichiometric air-fuel ratio or the air-fuel ratio in the vicinity thereof. Compared with the voltage value (represented by the alternate long and short dash line), if it is higher than the judgment voltage value, it is judged to be rich, and if it is lower than the judgment voltage value, it is judged to be lean. Then, the ECU 0 adjusts the feedback correction coefficient FAF by increasing or decreasing based on the determination result of the air-fuel ratio of the gas on the upstream side of the catalyst 41.

Specifically, when the determination result of the air-fuel ratio is reversed from lean to rich (the following delay time TDR has elapsed), the feedback correction coefficient FAF is reduced by the skip value RSM. In addition, while it is determined that the air-fuel ratio is rich, the feedback correction coefficient FAF is gradually reduced by the lean integral value KIM per calculation cycle (control cycle). The cycle of the calculation cycle is equal to the cycle in which each cylinder 1 included in the internal combustion engine enters a new cycle (a series of intake stroke-compression stroke-expansion stroke-exhaust stroke).

On the other hand, when the determination result of the air-fuel ratio is reversed from rich to lean (the following delay time TDL has elapsed), the feedback correction coefficient FAF is increased by the skip value RSP. In addition, while determining that the air-fuel ratio is lean, the feedback correction coefficient FAF is incremented by the rich integral value KIP per calculation cycle.

When the feedback correction amount FAF multiplied by the basic injection amount TP decreases, the fuel injection amount by the injector 11 is reduced, and the air-fuel ratio of the air-fuel mixture becomes lean. On the contrary, when the feedback correction amount FAF increases, the fuel injection amount by the injector 11 is increased, and the air-fuel ratio of the air-fuel mixture becomes rich.

However, when _{the output voltage f of the front O 2} sensor 43 fluctuates so as to cross the target voltage value, the determination result of the air-fuel ratio of the gas on the upstream side of the catalyst 41 is not immediately reversed, but the delay times TDL and TDR. After waiting for the progress of, the judgment result is inverted. That is, when _{the output voltage f of the front O 2} sensor 43 is switched from rich to lean (below the target voltage value), it is determined that the air-fuel ratio is reversed from rich to lean after the lean determination delay time TDL has elapsed. .. Further, when _{the output voltage f of the front O 2} sensor 43 is switched from lean to rich (exceeds the target voltage value), it is determined that the air-fuel ratio is reversed from lean to rich after the rich determination delay time TDR has elapsed. ..

The lean judgment delay time TDL and the rich judgment delay time TDR are provided so that _{when noise is mixed in the output signal f of the O 2} sensor 43, the lean / rich judgment result of the air-fuel ratio is inverted multiple times in a short period of time. The intention is to prevent chattering, which increases or decreases so that the fuel injection amount vibrates.

The delay times TDL and TDR increase or decrease according to the control center correction amount FACF. FIG. 3 illustrates the relationship between the control center correction amount FACF and the delay times TDL and TDR. As the control center correction amount FACF increases, the lean determination delay time TDL (represented by a broken line) is shortened, and the rich determination delay time TDR (represented by a solid line) is extended. Then, the time when the feedback correction coefficient FAF changes from an increase to a decrease is delayed, and the time when the feedback correction coefficient FAF changes from a decrease to an increase is advanced. As a result, the fuel injection amount increases on average, and the control center of the air-fuel ratio feedback control, in other words, the target of the air-fuel ratio of the gas to be converged by the feedback control is displaced to the rich side.

On the other hand, as the control center correction amount FACF becomes smaller, the lean determination delay time TDL is extended and the rich determination delay time TDR is shortened. Then, the time when the feedback correction coefficient FAF changes from an increase to a decrease is advanced, and the time when the feedback correction coefficient FAF changes from a decrease to an increase is delayed. As a result, the fuel injection amount is reduced on average, and the control center of the air-fuel ratio feedback control is displaced to the lean side.

The ECU 0 also calculates the control center correction amount FACF during the air-fuel ratio feedback control. As shown in FIG. 5, ECU0, first, from the feedback correction coefficient FAF _n calculated in the current operation cycle by subtracting a feedback correction coefficient FAF _n-1 calculated in the previous calculation cycle, the difference between them DerutaFAF _n (Step S1). n is a subscript representing the calculation cycle.

Next, the ECU 0 obtains a value Σ (ΔFAF _{n ) obtained by integrating ΔFAF n} calculated in a plurality of consecutive past calculation cycles (step S2).

Then, ECU0 was calculated in the current operation cycle, the air amount Ga _n sucked into the cylinder 1, since the integrated value of ΔFAF _n Σ (ΔFAF _n), obtaining the DerutaOS _n shown in the following equation (step S3) ..
_{ΔOS n = -Ga n × Σ (} ΔFAF n) / {1 + Σ (ΔFAF n)}
This ΔOS _n is an approximate value of the amount of change (increase or decrease) in the amount of oxygen stored in the catalyst 41, which increases or decreases as the gas discharged from the cylinder 1 flows into the catalyst 41.

Further, a value Σ (ΔOS _{n ) obtained by integrating ΔOS n} calculated in a plurality of consecutive past arithmetic cycles is obtained (step S4). This integrated value Σ (ΔOS _n ) is a deviation indicating how much the amount of oxygen currently occluded by the catalyst 41 deviates from the desired target occluded amount. When the oxygen storage amount in the current catalyst 41 matches the target storage amount, the deviation Σ (ΔOS _n ) becomes 0. The positive value of the deviation Σ (ΔOS _n ) means that the amount of oxygen stored in the catalyst 41 is larger than the target amount of stored oxygen. On the contrary, when the deviation Σ (ΔOS _n ) is a negative value, it means that the amount of oxygen stored in the catalyst 41 is less than the target amount of stored oxygen.

It is desirable to set the target occlusion amount to a size such that the oxidation reaction of harmful substances HC and CO and _{the reduction reaction of NO x in the catalyst 41 occur most efficiently.} For example, the target storage amount is obtained by multiplying the maximum oxygen storage capacity of the catalyst 41 by a constant ratio (value of about 0.5 to 0.6) smaller than 1. The maximum oxygen storage capacity of the catalyst 41 gradually declines due to aging, but a specific method for estimating the maximum oxygen storage capacity is known as a diagnosis (self-diagnosis) function of the catalyst 41 (for example, Japanese Patent Application Laid-Open No. 2016). (Refer to Japanese Patent Application Laid-Open No. 070156, etc.), so the explanation is omitted here.

Then, the ECU 0 adjusts the control center correction amount FACF according to the positive / negative of the deviation Σ (ΔOS _{n) (steps S5 and S6).} When the deviation Σ (ΔOS _n ) is a positive value, the control center correction amount FACF is made larger (step S7), and the control center of the air-fuel ratio feedback control is changed to the richer side. When the deviation Σ (ΔOS _n ) is a negative value, the control center correction amount FACF is made smaller (step S8), and the control center of the air-fuel ratio feedback control is changed to a leaner side.

In steps S5 to S8, while the deviation Σ (ΔOS _n ) is a negative value, the control center correction amount FACF is gradually reduced by the lean integral value FACFKIM per operation cycle, while the deviation Σ (ΔOS _n ) is a positive value. , The control center correction amount FACF can be gradually increased by the rich integral value FACFKIP per calculation cycle. Alternatively, more simply, the control center correction amount FACF when the _{deviation Σ (ΔOS n} ) is a positive value is set to a value larger than that when the _{deviation Σ (ΔOS n) is 0, and the deviation Σ (ΔOS n) is set.} The control center correction amount FACF when _n ) is a negative value may be set to a value smaller than that when the _{deviation Σ (ΔOS n) is 0.}

The ECU 0 repeats steps S1 to S8 each time a calculation cycle arrives (each time any cylinder 1 enters a new cycle).

Incidentally, in the conventional air-fuel ratio feedback control, the control center correction amount FACF is determined according to the output signal g of the air-fuel ratio sensor 44 on the downstream side of the catalyst 41. _{That is, as shown in FIG. 4, the output voltage g of the rear O 2} sensor 44, which is a sensor for detecting the air-fuel ratio of the gas on the downstream side of the catalyst 41, is compared with the determination voltage value (represented by a chain line), and the determination voltage is compared. If it is higher than the value, it is judged to be rich, and if it is lower than the judgment voltage value, it is judged to be lean. Note that this determination voltage value may not match the determination voltage value compared with the output signal f _{of the front O 2 sensor 43.}

Then, the control center correction amount FACF is increased or decreased based on the determination result of the air-fuel ratio of the gas on the downstream side of the catalyst 41. Specifically, while the air-fuel ratio is determined to be rich, the control center correction amount FACF is gradually reduced by the lean integral value FACFKIM per calculation cycle, while the air-fuel ratio is determined to be lean. The control center correction amount FACF is gradually increased by the rich integral value FACFKIP per calculation cycle. As already described, when the control center correction amount FACF decreases, the air-fuel ratio control center moves toward lean, and when the control center correction amount FACF increases, the air-fuel ratio control center moves toward rich.

In the present embodiment, there is provided a control apparatus 0 for feedback-controlling the air-fuel ratio of gas flowing into the catalyst 41 for exhaust gas purification which is attached to the exhaust passage 4 of an internal combustion engine, the amount of air sucked into the cylinder 1 Ga _n, Based on the output signal f of the air-fuel ratio sensor 43 installed upstream of the catalyst 41 in the exhaust passage 4, the deviation Σ (ΔOS _n ) between the amount of oxygen stored in the catalyst 41 and its target storage amount is estimated. Then, the control device 0 of the internal combustion engine was configured to change the target of the air-fuel ratio to be converged by the feedback control according to the deviation Σ (ΔOS _n).

According to this embodiment, it is possible to converge the amount of oxygen currently occluded in the catalyst 41 to the desired target occluded amount. Therefore, it is possible to prevent the catalyst 41 from being filled with oxygen and _{discharging NO x,} or the catalyst 41 being depleted of oxygen and discharging HC and CO, which is effective in improving emissions. _{By using the O 2} sensor 43, which is cheaper than the linear A / F sensor, the amount of harmful substances emitted can be further reduced, which is also advantageous in terms of cost.

The present invention is not limited to the embodiments described in detail above. In the above embodiment, the air-fuel ratio to be converged by feedback control is adjusted by adjusting the control center correction amount FACF according to _{the deviation Σ (ΔOS n} ) between the amount of oxygen stored in the catalyst 41 and the target storage amount thereof. I was changing my goals. However, instead of or together with this, the target value to be compared with the output signal f of the air-fuel ratio sensor 43 on the upstream side of the catalyst 41, in other words, the determination voltage to be compared with the output voltage f of the _{front O 2 sensor 43.} By adjusting the value itself, the target of the air-fuel ratio to be converged may be changed by feedback control. In that case, when the deviation Σ (ΔOS _n ) is a positive value, the judgment voltage value is raised to displace the target value to the richer side, and when the deviation Σ (ΔOS _n ) is a negative value, the judgment voltage value. To shift the target value to the lean side.

Further, the ECU 0, which is a control device of the internal combustion engine, _{performs the calculation of the control center correction amount FACF based on the deviation Σ (ΔOS n} ) (without referring to the output signal g of the air-fuel ratio sensor 44 downstream of the catalyst 41). It is also possible to execute the calculation of the control center correction amount FACF with reference to the output signal g of the air-fuel ratio sensor 44 downstream of the catalyst 41, which is similar to the air-fuel ratio feedback control of the above. Each of these control center correction amounts indicates a target of the air-fuel ratio of the gas to be converged by feedback control.

Then, the divergence between the former control center correction amount FACF and the latter control center correction amount FACF widened beyond a certain level (the absolute value of the difference between the two became more than a certain value, or the ratio between the two deviated from a certain range. (When the ratio of the two becomes larger than the upper limit of the range or becomes smaller than the lower limit of the range), the control center correction amount FACF of the latter is used instead of the control center correction amount FACF of the former. It is conceivable to use the air-fuel ratio feedback control to perform the air-fuel ratio feedback control, that is, to perform feedback control for converging the air-fuel ratio to a target set based on the output signal g of the air-fuel ratio sensor 44 downstream of the catalyst 41. Then, even if a _{large error is mixed in the deviation Σ (ΔOS n} ), it is possible to appropriately avoid an increase in the amount of harmful substances emitted.

If the fuel cut that interrupts the fuel injection to the cylinder 1 for a predetermined time (for example, several seconds) or more occurs while the air-fuel ratio is feedback-controlled using the latter control center correction amount FACF, the former control thereafter. It is possible to return to the feedback control in which the central correction amount FACF is used, that is, the air-fuel ratio is converged to the target according to the _{deviation Σ (ΔOS n).} This is because the fuel cut causes oxygen to be occluded up to the maximum oxygen occlusal capacity of the catalyst 41, and the calculation error is reset (resolved). _{The initial value of the deviation Σ (ΔOS n} ) when returning to the air-fuel ratio feedback control using the former control center correction amount FACF can be obtained by subtracting the target storage amount from the maximum oxygen storage capacity of the catalyst 41.

In addition, the specific configuration of each part, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

The present invention can be applied to the control of an internal combustion engine mounted on a vehicle.

0 ... Control device (ECU)
1 ... Cylinder 11 ... Injector 3 ... Intake passage 4 ... Exhaust passage 41 ... Catalyst 43 ... Air-fuel ratio sensor upstream of catalyst (O ₂ sensor)
b ... Crank angle signal d ... Intake air temperature / intake pressure signal f ... Air-fuel ratio signal j ... Fuel injection signal

Claims (3)

It is a control device that feedback-controls the air-fuel ratio of the gas flowing into the exhaust gas purification catalyst installed in the exhaust passage of the internal combustion engine.
The amount of air sucked into the cylinder, and on the basis of the output signal of the air-fuel ratio sensor installed upstream of the catalyst in the exhaust passage, the deviation between the oxygen amount and the target storage amount occluded in the said catalyst Set the first target, which is the target of the air-fuel ratio of the gas estimated from
Based on the output signal of the air-fuel ratio sensor installed downstream of the catalyst in the exhaust passage, a second target, which is the target of the air-fuel ratio of the gas, is separately set.
A control device for an internal combustion engine that compares the first target and the second target and changes the target of the air-fuel ratio of the gas to be converged by the feedback control. Said first target, when the deviation between the second target has spread to more than a certain implements a feedback control so as to converge the air-fuel ratio of the gas to the first target rather than the second target, wherein Item 1. The control device for an internal combustion engine according to item 1. When you are carrying out feedback control so as to converge the air-fuel ratio to the second target, wherein when the interrupting fuel cut for a predetermined time or more fuel injection for the cylinder occurs, the air-fuel ratio for the subsequent first target The control device for an internal combustion engine according to claim 2, wherein feedback control is performed so as to converge.

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