JP7698570B2 - Control device for internal combustion engine and control method for internal combustion engine - Google Patents

Description

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

The air-fuel ratio control device and air-fuel ratio control method of Patent Document 1 performs fuel cut when a predetermined condition is met in an internal combustion engine having a catalyst with oxygen storage capacity that takes in or releases oxygen in the exhaust gas according to the exhaust air-fuel ratio, and then performs fuel cut recovery when another predetermined condition is met, and further performs rich spike processing when the fuel cut recovery is met.

JP 2009-162195 A

However, in the rich spike process at the time of fuel cut recovery, the fuel injection amount by the fuel injection device is increased, which raises concerns about a decrease in fuel economy.
Furthermore, when rich spike processing is performed when the oxygen storage amount in the exhaust purification catalyst is saturated, it takes time for the oxygen storage amount to decrease, and during this time, there is a risk that NOx emissions will increase due to a decrease in reduction performance.

The present invention was made in consideration of the current situation, and its purpose is to provide an internal combustion engine control device and an internal combustion engine control method that can improve exhaust properties when returning from a fuel cut state and also improve fuel efficiency.

Therefore, in one aspect of the present invention, in an internal combustion engine equipped with a recovered fuel processing device that recovers fuel components and supplies gas containing the recovered fuel components to an intake passage of the internal combustion engine via a pipe equipped with an electronically controlled valve, during a fuel cut in which fuel injection by a fuel injection device is stopped, the valve is controlled to an open state , and the valve is closed based on the output of an oxygen sensor that outputs a signal corresponding to the oxygen concentration in the exhaust passage downstream of an exhaust purification catalyst reversing from a lean output to a rich output.

The above invention improves exhaust characteristics when returning from a fuel cut state and also improves fuel economy.

FIG. 1 is a system configuration diagram of an internal combustion engine. 5 is a flowchart showing an example of a control procedure for blow-by gas recirculation or evaporated fuel processing during a fuel cut. 5 is a time chart showing an example of blow-by gas recirculation or evaporated fuel processing during a fuel cut.

An embodiment of the present invention will be described below.
FIG. 1 is a configuration diagram showing one embodiment of an internal combustion engine.
An internal combustion engine 101 shown in FIG. 1 is a spark-ignition gasoline engine mounted on a vehicle such as an automobile.

The internal combustion engine 101 includes an ignition device 200 , a fuel injection device 300 , an electronically controlled throttle 108 , and an exhaust purification catalyst 112 .
The ignition device 200 has an ignition plug 201 and an ignition coil 202 incorporating a power transistor, and ignites and burns the air-fuel mixture in the combustion chamber 110 by spark ignition.

The fuel injection device 300 has a fuel injection valve 301 arranged in the intake port 102 upstream of the intake valve 119, a fuel tank 302 that stores liquid fuel (gasoline) to be injected from the fuel injection valve 301, and a fuel pipe 304 that supplies the liquid fuel in the fuel tank 302 to the fuel injection valve 301.
When the fuel injection valve 301 opens, fuel is injected into the intake port 102 , and the fuel injected from the fuel injection valve 301 is mixed with air to form an air-fuel mixture in the combustion chamber 110 .
The fuel injection device 300 may be of a direct injection type in which the fuel injection valve 301 directly injects fuel into the combustion chamber 110 .

The electronically controlled throttle 108 has a throttle valve 108a which is a butterfly valve, a throttle motor 108b, and a throttle opening sensor 108c which detects the opening of the throttle valve 108a, and is a device which opens and closes the throttle valve 108a by the throttle motor 108b.
The air that has passed through the air cleaner 107 has its flow rate adjusted by a throttle valve 108a.

The exhaust purification catalyst 112 is disposed in an exhaust pipe 103 (exhaust passage) of the internal combustion engine 101, and purifies the exhaust gas from the internal combustion engine 101 by the catalyst.
The exhaust purification catalyst 112 includes a three-way catalyst having an oxygen storage capacity.

Furthermore, the internal combustion engine 101 is equipped with various sensors for detecting the operating state of the internal combustion engine 101 .
The air flow sensor 109 is disposed in the intake duct 104 upstream of the electronically controlled throttle 108 to detect the intake air flow rate of the internal combustion engine 101 .
The crank angle sensor 106 is a sensor for measuring the rotation angle of the crankshaft 117, detects the protrusion of the ring gear 114, and outputs a pulse signal that rises every time the crankshaft 117 rotates by a predetermined angle.

The air-fuel ratio sensor 111 is disposed in the exhaust pipe 103 upstream of the exhaust purification catalyst 112, and detects the exhaust air-fuel ratio based on the oxygen concentration in the exhaust.
The oxygen sensor 116 is disposed in the exhaust pipe 103 downstream of the exhaust purification catalyst 112, and detects whether the exhaust air-fuel ratio is rich or lean based on the oxygen concentration in the exhaust pipe 103 (in the exhaust passage) downstream of the exhaust purification catalyst 112.
The water temperature sensor 118 is disposed in the cooling water jacket 105 of the internal combustion engine 101 and detects the temperature of the cooling water in the cooling water jacket 105 .

The internal combustion engine 101 also includes a blow-by gas recirculation device 400 .
The blow-by gas recirculation device 400 is a device that recirculates the blow-by gas that flows out from the combustion chamber 110 into the crank chamber 151 to the intake collector 152 (in other words, the intake passage) downstream of the electronically controlled throttle 108.

The blow-by gas recirculation device 400 has a recirculation pipe 401 that connects the crank chamber 151 and the intake collector 152, and an electronically controlled recirculation control valve 402 that is disposed in the recirculation pipe 401 and adjusts the flow rate of the blow-by gas.
Blow-by gas is composed of unburned fuel, combustion gas, and oil mist components.
In other words, the blow-by gas recirculation device 400 is a recovered fuel treatment device that supplies gas containing fuel components recovered from the crank chamber 151 to the intake collector 152 of the internal combustion engine 101 via a recirculation piping 401 equipped with an electronically controlled recirculation control valve 402, and combusts and treats the unburned fuel components.

The internal combustion engine 101 also includes an evaporated fuel treatment device 500 .
The evaporated fuel processing device 500 is a device that introduces evaporated fuel (gasoline vapor) recovered from the fuel tank 302 into the intake collector 152 (in other words, the intake passage) downstream of the electronically controlled throttle 108 .

The evaporative fuel treatment device 500 has a canister 501 filled with activated carbon for adsorbing evaporative fuel, an evaporative fuel piping 502 connecting the canister 501 with the fuel tank 302, a purge piping 503 connecting the canister 501 with the intake collector 152 (in other words, the intake passage) of the internal combustion engine 101, and an electronically controlled purge control valve 504 arranged in the purge piping 503.
When evaporated fuel generated in the fuel tank 302 flows into the canister 501 through the evaporated fuel pipe 502, the canister 501 adsorbs and collects the evaporated fuel on activated carbon inside.

When the purge control valve 504 is controlled to be open and the pressure inside the purge piping 503 becomes negative due to the intake negative pressure of the internal combustion engine 101, outside air (atmosphere) is sucked into the canister 501 through the outside air inlet hole 501a, passes through the inside of the canister 501, and flows into the purge piping 503.
At this time, the evaporated fuel that had been adsorbed on the activated carbon in the canister 501 is desorbed, and the desorbed evaporated fuel is guided to the purge piping 503 together with the outside air, merges with the intake air of the internal combustion engine 101 in the intake collector 152, flows into the combustion chamber 110, and is combusted in the combustion chamber 110.

In other words, the evaporated fuel treatment device 500 is a recovered fuel treatment device that supplies gas containing fuel components recovered from the fuel tank 302 to the intake collector 152 of the internal combustion engine 101 via a purge piping 503 equipped with an electronically controlled purge control valve 504, and combusts the evaporated fuel generated in the fuel tank 302.
The reflux control valve 402 and the purge control valve 504 are, for example, electromagnetic valves.

The control device 600 is an electronic control device that includes an MPU (Microprocessor Unit) 601 and controls the operation of the internal combustion engine 101 .
The MCU 601 can be referred to as a microcomputer, a processor, a processing device, an arithmetic device, or the like.

The control device 600 acquires signals output by the various sensors described above (in other words, information regarding the operating state of the internal combustion engine 101), and calculates and outputs manipulated variables for each controlled object based on the acquired signals.
Specifically, the control device 600 controls the ignition coil 202 (the ignition device 200 ), the fuel injection valve 301 (the fuel injection device 300 ), the throttle motor 108 b , the reflux control valve 402 , and the purge control valve 504 .

The control device 600 controls fuel injection by the fuel injection valve 301 (fuel injection device 300 ) to form an air-fuel mixture for each combustion cycle in the internal combustion engine 101 .
In addition, the control device 600 performs fuel cut by stopping fuel injection by the fuel injection valve 301 when a predetermined fuel cut condition is met, and resuming fuel injection by the fuel injection valve 301 when a predetermined fuel recovery condition is met.
The above-mentioned fuel cut is performed, for example, when the internal combustion engine 101 is in a deceleration operation state. Note that the fuel cut performed when the internal combustion engine 101 is in a deceleration operation state is also called a deceleration fuel cut.

In the above-mentioned deceleration fuel cut, if the engine speed NE exceeds the fuel cut speed NE1 when the electronically controlled throttle 108 is closed (in other words, when the driver releases the accelerator pedal), the control device 600 stops fuel injection by the fuel injection valve 301.
Then, after stopping fuel injection by the fuel injection valve 301, the control device 600 resumes fuel injection by the fuel injection valve 301 when the electronically controlled throttle 108 is opened (in other words, when the driver depresses the accelerator pedal).
Furthermore, after stopping fuel injection by the fuel injection valve 301, the control device 600 restarts fuel injection by the fuel injection valve 301 when the engine speed falls below a fuel recovery speed NE2 that is lower than the fuel cut rotation speed NE1.

When such a fuel cut is performed, air flows into the exhaust purification catalyst 112 during the fuel cut, and the amount of oxygen storage in the exhaust purification catalyst 112 increases, and may reach a saturated state.
When the oxygen storage amount of the exhaust purification catalyst 112 is saturated, the NOx reduction ability of the exhaust purification catalyst 112 decreases, so that the amount of NOx emissions increases when fuel injection by the fuel injection valve 301 is resumed.

Here, as a control for suppressing the amount of NOx emissions when fuel injection is resumed, there is a rich spike, which is a control for temporarily increasing the amount of fuel injected by the fuel injection valve 301 to perform rich combustion.
If the control device 600 performs a rich spike when resuming fuel injection, rich exhaust gas containing a large amount of HC and CO will flow into the exhaust purification catalyst 112, which will promote a reduction in the amount of oxygen storage in the exhaust purification catalyst 112 and enable the NOx reduction ability to be restored quickly.

However, since a rich spike is a fuel increase correction, there is concern that a rich spike may result in a decrease in fuel efficiency.
In addition, although the NOx emissions are reduced by implementing a rich spike, the NOx emissions still increase as the oxygen storage amount decreases from the saturated state.
Therefore, during fuel cut, the control device 600 prevents the oxygen storage amount of the exhaust purification catalyst 112 from becoming saturated during fuel cut by supplying fuel components to the intake collector 152 (intake passage) via the blow-by gas recirculation device 400 and/or the evaporated fuel treatment device 500.

If the oxygen storage amount can be prevented from becoming saturated, the amount of fuel increase required in a rich spike to reduce the oxygen storage amount to an appropriate value can be reduced. In addition, the oxygen storage amount can be reduced to an appropriate value earlier, thereby suppressing NOx emissions.
In other words, during fuel cut, the control device 600 supplies fuel components to the intake collector 152 (intake passage) via the blow-by gas recirculation device 400 and/or the evaporated fuel treatment device 500, thereby improving exhaust properties when returning from a fuel cut state and also improving fuel economy.

It should be noted that the fuel cut can include idle stop (idle reduction).
The idle stop is a control for automatically stopping the internal combustion engine 101 by stopping fuel injection from the fuel injection valve 301 (fuel injection device 300) while the vehicle is waiting at a traffic light or the like.
Furthermore, the control device 600 supplies fuel components to the intake collector 152 (intake passage) via the blow-by gas recirculation device 400 and/or the evaporated fuel treatment device 500 during idle stop, thereby improving the exhaust properties when the internal combustion engine 101 resumes operation and also improving fuel efficiency.

The flowchart in FIG. 2 shows one embodiment of a control procedure executed by the control device 600 for the blow-by gas recirculation device 400 and/or the evaporated fuel treatment device 500 during a fuel cut.
In step S701, the control device 600 determines whether or not a fuel cut has been started.
If a fuel cut has not been started (in other words, if the fuel cut is not in progress), the control device 600 proceeds to step S711 and performs normal control of the blow-by gas recirculation device 400 and the evaporated fuel processing device 500.

As a normal control of the blow-by gas recirculation device 400, the control device 600 controls the recirculation control valve 402 to open when the pressure in the crank chamber 151 is higher than a threshold value, for example.
In addition, as a normal control of the evaporative fuel treatment device 500, the control device 600 adjusts the opening degree of the purge control valve 504 by duty control based on the load, rotational speed, etc. of the internal combustion engine 101 so that the purge rate is proportional to the amount of intake air of the internal combustion engine 101.

On the other hand, when the fuel cut is started, the control device 600 proceeds to step S 702 , and obtains the oxygen storage amount OSC of the exhaust purification catalyst 112 on the basis of the operating state of the internal combustion engine 101 .
The control device 600 estimates the oxygen storage amount OSC based on the exhaust air-fuel ratio upstream of the exhaust purification catalyst 112 detected by the air-fuel ratio sensor 111 (in other words, the air-fuel ratio of the exhaust flowing into the exhaust purification catalyst 112) and the intake air flow rate of the internal combustion engine 101 detected by the air flow sensor 109 (in other words, the flow rate of the exhaust flowing into the exhaust purification catalyst 112).

From the start of the fuel cut, the internal combustion engine 101 rotates by inertia, and due to this inertial rotation, the internal combustion engine 101 takes in air and sends the air out into the exhaust passage, causing the air to flow into the exhaust purification catalyst 112 and increasing the oxygen storage amount OSC.
Therefore, in step S702, the control device 600 estimates the increase or change in the oxygen storage amount OSC due to the fuel cut based on the operating state of the internal combustion engine 101 (exhaust air-fuel ratio, intake air flow rate).

Next, in step S703, the control device 600 compares the oxygen storage amount OSC estimated in step S702 with a predetermined amount OSCSL.
The predetermined amount OSCSL is a value that is set based on the saturation amount (maximum oxygen storage amount) of the oxygen storage amount OSC in the exhaust purification catalyst 112, and is a value for determining whether the oxygen storage amount OSC is approximately saturated or is in a state predicted to reach saturation.

If the oxygen storage amount OSC exceeds a predetermined amount OSCSL and determines whether the oxygen storage amount OSC is substantially saturated or is predicted to reach saturation, the control device 600 proceeds from step S703 to step S704.
On the other hand, if the oxygen storage amount OSC is equal to or less than the predetermined amount OSCSL and there is a margin before the oxygen storage amount OSC becomes saturated, in other words, if the increase and change in the oxygen storage amount OSC due to the fuel cut is still small, the control device 600 returns from step S703 to step S701.
In other words, when the oxygen storage amount OSC is less than or equal to a predetermined amount OSCSL, the control device 600 waits without starting control of the blow-by gas recirculation device 400 and/or the evaporated fuel treatment device 500 (in other words, keeps the recirculation control valve 402 and the purge control valve 504 in a closed state).

In step S704, the control device 600 controls the recirculation control valve 402 and/or the purge control valve 504 to open, thereby supplying the gas containing the fuel components recovered from the crank chamber 151 or the fuel tank 302 to the internal combustion engine 101.
That is, after the control device 600 stops fuel injection by the fuel injection valve 301, the control device 600 opens the recirculation control valve 402 and/or the purge control valve 504 after the oxygen storage amount OSC increases to a predetermined amount OSCSL.

Here, even if a fuel cut is performed, as long as the internal combustion engine 101 is rotating by inertia, a negative intake pressure is generated.
At this time, if the recirculation control valve 402 and/or the purge control valve 504 are controlled to be opened, gas containing fuel components is introduced into the intake collector 152 (in other words, the intake passage) of the internal combustion engine 101 .

The fuel components (HC) introduced into the intake collector 152 of the internal combustion engine 101 pass through the combustion chamber 110 and flow into the exhaust purification catalyst 112 .
The exhaust purification catalyst 112 oxidizes the fuel components (HC) using oxygen.
In other words, the exhaust purification catalyst 112 oxidizes the fuel components supplied to the internal combustion engine 101 by the opening control of the recirculation control valve 402 and/or the purge control valve 504, thereby reducing the oxygen storage amount OSC.

While the internal combustion engine 101 is rotating by inertia after the start of fuel cut, air flows into the exhaust purification catalyst 112, so that the oxygen storage amount OSC in the exhaust purification catalyst 112 quickly reaches a saturation amount.
At this time, if the fuel components are made to flow into the exhaust purification catalyst 112, the oxygen storage amount OSC in the exhaust purification catalyst 112 can be reduced from the saturation amount by the amount of oxygen used for the oxidation process of the fuel components.

When the control device 600 controls the recirculation control valve 402 and/or the purge control valve 504 to open in step S704, in the next step S705, it determines whether the output of the oxygen sensor 116 has reversed from a lean output to a rich output, thereby determining whether the exhaust air-fuel ratio downstream of the exhaust purification catalyst 112 has switched from lean to rich.
Then, when the control device 600 detects that the output of the oxygen sensor 116 has reversed from a lean output to a rich output, the process proceeds to step S706.

In step S706, the control device 600 closes the reflux control valve 402 and/or the purge control valve 504 that were opened in step S704, and returns the reflux control valve 402 and the purge control valve 504 to their closed states.
In other words, when the control device 600 detects that the output of the oxygen sensor 116 has reversed from a lean output to a rich output, it determines that no further supply of fuel components is necessary, and closes the reflux control valve 402 and/or the purge control valve 504, which have been controlled to be open to supply the fuel components, thereby cutting off the supply of the fuel components.

In the next step S707, the control device 600 performs a setting so that a rich spike is not required when fuel injection by the fuel injection valve 301 is resumed.
The reversal of the output of the oxygen sensor 116 from a lean output to a rich output indicates that the oxygen storage amount OSC in the exhaust purification catalyst 112 has decreased and the efficiency of the oxidation process of the fuel components has decreased, while the efficiency of the reduction process of NOx is sufficiently high.

If the oxygen storage amount OSC in the exhaust purification catalyst 112 is small enough that the reduction process of NOx can be performed with high efficiency, there is no need for a rich spike to reduce the oxygen storage amount OSC.
Therefore, when the control device 600 detects in step S705 that the output of the oxygen sensor 116 has reversed from a lean output to a rich output, in step S706, it cuts off the supply of fuel components, and also sets in step S707 not to perform a rich spike when fuel injection by the fuel injection valve 301 is resumed.

When the control device 600 keeps the recirculation control valve 402 and the purge control valve 504 closed during fuel cut, the oxygen storage amount OSC of the exhaust purification catalyst 112 becomes saturated, and fuel injection by the fuel injection valve 301 is resumed in a state where the NOx purification efficiency is low.
Therefore, in order to suppress the amount of NOx emissions when fuel injection by the fuel injection valve 301 is resumed, the control device 600 needs to perform a rich spike and quickly reduce the oxygen storage amount OSC.

However, the rich spike is a process for increasing the amount of fuel injected by the fuel injection valve 301, which results in a decrease in fuel efficiency. In addition, the amount of NOx emissions increases until the oxygen storage amount OSC is reduced by the rich spike.
In contrast, the fuel components supplied to the internal combustion engine 101 by controlling the opening of the recirculation control valve 402 and/or the purge control valve 504 are recovered from the crank chamber 151 or the fuel tank 302, and therefore have little effect on fuel economy.

Furthermore, if the control device 600 controls to open the recirculation control valve 402 and/or the purge control valve 504 during fuel cut, it is possible to resume fuel injection when the oxygen storage amount OSC of the exhaust purification catalyst 112 is small.
Therefore, the exhaust purification catalyst 112 can efficiently reduce NOx immediately after fuel injection is restarted, and can suppress the amount of NOx emissions.

On the other hand, if the control device 600 determines in step S705 that the output of the oxygen sensor 116 is being held at a lean output, the process proceeds to step S708.
In step S708, the control device 600 determines whether or not the conditions for resuming fuel injection are met, in other words, whether or not the state is such that the continuation of fuel cut is predicted.

If the control device 600 determines that the condition for resuming fuel injection is not satisfied, the process returns to step S705, and the control device 600 determines whether the output of the oxygen sensor 116 has reversed from a lean output to a rich output.
On the other hand, if the control device 600 determines that the conditions for resuming fuel injection are met, the process proceeds to step S709.
In step S709, before resuming fuel injection, the control device 600 closes the reflux control valve 402 and/or the purge control valve 504 that were controlled to be open in step S704, and returns the reflux control valve 402 and the purge control valve 504 to a closed state, and then resumes fuel injection.

In other words, when the output of the oxygen sensor 116 reverses from a lean output to a rich output, the control device 600 returns the recirculation control valve 402 and the purge control valve 504 to a closed state, but if the conditions for resuming fuel injection are met before the output of the oxygen sensor 116 reverses, the control device 600 returns the recirculation control valve 402 and the purge control valve 504 to a closed state without waiting for the output to reverse.
In other words, the control device 600 closes the reflux control valve 402 and the purge control valve 504 at the latest before fuel injection by the fuel injector 300 is resumed.

If the reflux control valve 402 and/or the purge control valve 504 are open, the combustion stability of the internal combustion engine 101 decreases due to factors such as a decrease in the control accuracy of the air-fuel ratio, making it difficult to stably return the internal combustion engine 101 to independent operation.
Therefore, the control device 600 closes the recirculation control valve 402 and the purge control valve 504 and then resumes fuel injection, thereby enabling the internal combustion engine 101 to stably return to an independent operating state.

Next, the control device 600 proceeds to step S710, and performs setting so that a rich spike will be performed when fuel injection by the fuel injection valve 301 is resumed.
If the output of the oxygen sensor 116 does not invert and is maintained at a lean output, the increase in the oxygen storage amount OSC can be suppressed to some extent by opening the reflux control valve 402 and/or the purge control valve 504, but the maximum suppression has not been achieved.

Therefore, the control device 600 performs a rich spike when restarting fuel injection in order to quickly recover the NOx purification efficiency that has decreased due to an increase in the oxygen storage amount OSC.
The control device 600 can variably set the increase in the fuel injection amount during a rich spike in accordance with the oxygen storage amount OSC, the exhaust air-fuel ratio upstream of the exhaust purification catalyst 112, and the like.

FIG. 3 is a time chart showing an example of changes in the engine speed, the fuel injection amount, the oxygen storage amount OSC, etc. when the control device 600 controls to open the recirculation control valve 402 and/or the purge control valve 504 during a fuel cut.
When the fuel cut condition is satisfied at time t1, the control device 600 stops fuel injection by the fuel injection valve 301 (fuel injection device 300).

As a result of the fuel injection being stopped, the rotation speed of the internal combustion engine 101 starts to decrease, and at this time, air flows into the exhaust purification catalyst 112, so that the oxygen storage amount OSC of the exhaust purification catalyst 112 increases.
The control device 600 switches the reflux control valve 402 and/or the purge control valve 504 from closed to open at time t2, which is the timing when the estimated value of the oxygen storage amount OSC exceeds a predetermined amount OSCSL.

When the recirculation control valve 402 and/or the purge control valve 504 is switched from closed to open, gas containing fuel components is introduced into the intake passage of the internal combustion engine 101, so that the gas flowing into the exhaust purification catalyst 112 becomes rich.
When rich gas flows into the exhaust purification catalyst 112, the reduction process of the fuel components is performed, and the oxygen storage amount OSC starts to decrease.

Then, when the purification efficiency of the fuel components drops due to a decrease in the oxygen storage amount OSC of the exhaust purification catalyst 112, the exhaust air-fuel ratio downstream of the exhaust purification catalyst 112 reverses from lean to rich.
When the control device 600 detects at time t3 that the exhaust air-fuel ratio downstream of the exhaust purification catalyst 112 has reversed from lean to rich based on the output of the oxygen sensor 116, it closes the recirculation control valve 402 and/or the purge control valve 504, which were controlled to be open, at the timing when the estimated value of the oxygen storage amount OSC exceeds a predetermined amount OSCSL, and stops the supply of fuel components from the blow-by gas recirculation device 400 and the evaporated fuel treatment device 500.

By controlling the recirculation control valve 402 and/or the purge control valve 504 to be open, the oxygen storage amount OSC when returning from a fuel cut can be made smaller than when the recirculation control valve 402 and/or the purge control valve 504 are not controlled to be open.
If the oxygen storage amount OSC is small when fuel injection is resumed (at time t4), the fuel increase during the rich spike from time t4 to time t5 can be reduced or reduced to zero, and NOx can be purified with high efficiency immediately after fuel injection is resumed.
Therefore, by the control device 600 controlling the opening of the recirculation control valve 402 and/or the purge control valve 504 during fuel cut, it is possible to prevent a decrease in fuel efficiency due to a rich spike, and also to reduce NOx emissions when returning from a fuel cut state.

The technical ideas described in the above embodiments can be used in any suitable combination as long as no contradiction occurs.
Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical concept and teachings of the present invention.

It is clear that the control device for an internal combustion engine according to the present invention can also be applied to an internal combustion engine equipped with either the blow-by gas recirculation device 400 or the evaporated fuel processing device 500.
The evaporated fuel processing device 500 may be a device that pumps evaporated fuel recovered from the fuel tank 302 into the intake passage of the internal combustion engine 101 using a pump.

In addition, the control device 600 can switch between a state in which either the reflux control valve 402 or the purge control valve 504 is controlled to be open, and a state in which both the reflux control valve 402 and the purge control valve 504 are controlled to be open.
For example, the control device 600 can maintain the purge control valve 504 in a closed state and open only the recirculation control valve 402, and when it determines that there is a shortage of fuel components flowing into the exhaust purification catalyst 112 based on the exhaust air-fuel ratio upstream of the exhaust purification catalyst 112 in this state, it can further open the purge control valve 504.
After controlling the purge control valve 504 to open, the control device 600 can additionally control the reflux control valve 402 to open.

In addition, the control device 600 learns the fuel concentration of the blow-by gas in the blow-by gas recirculation device 400 and the fuel concentration of the purge gas in the evaporated fuel treatment device 500, and can switch between controlling the opening of the recirculation control valve 402 and the purge control valve 504 based on the learned fuel concentrations.
Furthermore, the control device 600 can control the recirculation control valve 402 and/or the purge control valve 504 to open at the start of fuel cut, or after a predetermined time has elapsed since the start of fuel cut.

In addition, the control device 600 can close the reflux control valve 402 and/or the purge control valve 504, which have been controlled to be open, when the rotational speed of the internal combustion engine 101 falls below a predetermined rotational speed (predetermined rotational speed > 0) or when the rotational speed of the internal combustion engine 101 becomes zero.
In other words, if the blow-by gas recirculation device 400 and the evaporated fuel treatment device 500 are systems that utilize the intake negative pressure of the internal combustion engine 101 to supply gas containing fuel components to the intake passage of the internal combustion engine 101, when the rotation of the internal combustion engine 101 stops after a fuel cut and the intake negative pressure is no longer generated, the supply of gas containing fuel components will be cut off even if the recirculation control valve 402 and/or the purge control valve 504 are controlled to an open state.

Therefore, the control device 600 can determine the timing to close the recirculation control valve 402 and/or the purge control valve 504 based on the rotation speed of the internal combustion engine 101 (in other words, the intake negative pressure of the internal combustion engine 101).
In detail, the control device 600 can close the reflux control valve 402 and/or the purge control valve 504 when the rotational speed of the internal combustion engine 101 becomes a predetermined rotational speed (predetermined rotational speed ≧0 rpm) or becomes less than the predetermined rotational speed.

101... internal combustion engine, 112... exhaust purification catalyst, 116... oxygen sensor, 152... intake collector (intake passage), 300... fuel injection device, 301... fuel injection valve, 302... fuel tank, 400... blow-by gas recirculation device (recovered fuel processing device), 401... recirculation piping, 402... recirculation control valve (electronically controlled valve), 500... evaporated fuel processing device (recovered fuel processing device), 503... purge piping, 504... purge control valve (electronically controlled valve), 600... control device

Claims (6)

A fuel injection device that injects fuel into an internal combustion engine;
a recovered fuel processing device that recovers fuel components and supplies a gas containing the recovered fuel components to an intake passage of the internal combustion engine through a pipe having an electronically controlled valve;
an exhaust purification catalyst having an oxygen storage capability, which is disposed in an exhaust passage of the internal combustion engine;
an oxygen sensor that outputs a signal corresponding to an oxygen concentration in an exhaust passage downstream of the exhaust purification catalyst;
A control device for an internal combustion engine, which is applied to the internal combustion engine comprising:
During a fuel cut in which fuel injection by the fuel injection device is stopped, the valve is controlled to an open state ;
closing the valve based on the inversion of the output of the oxygen sensor from a lean output to a rich output;
A control device for an internal combustion engine. 2. The control device for an internal combustion engine according to claim 1,
The recovered fuel processing device includes:
A blow-by gas recirculation device for recirculating blow-by gas to the intake passage,
A control device for an internal combustion engine. 2. The control device for an internal combustion engine according to claim 1,
The recovered fuel processing device includes:
and a fuel vapor treatment device that introduces fuel vapor recovered from a fuel tank into the intake passage.
A control device for an internal combustion engine. 2. The control device for an internal combustion engine according to claim 1,
when a condition for restarting fuel injection by the fuel injection device is satisfied before the output of the oxygen sensor is inverted to a rich output, the valve is closed without waiting for the output to be inverted to a rich output.
A control device for an internal combustion engine. A fuel injection device that injects fuel into an internal combustion engine;
a recovered fuel processing device that recovers fuel components and supplies a gas containing the recovered fuel components to an intake passage of the internal combustion engine through a pipe having an electronically controlled valve;
an exhaust purification catalyst having an oxygen storage capability, which is disposed in an exhaust passage of the internal combustion engine;
an oxygen sensor that outputs a signal corresponding to an oxygen concentration in an exhaust passage downstream of the exhaust purification catalyst;
A control method for an internal combustion engine, which is executed by a control device applied to the internal combustion engine comprising:
During a fuel cut in which fuel injection by the fuel injection device is stopped, the valve is controlled to an open state ;
closing the valve based on the inversion of the output of the oxygen sensor from a lean output to a rich output;
A method for controlling an internal combustion engine. A method for controlling an internal combustion engine according to claim 5, comprising the steps of:
when a condition for restarting fuel injection by the fuel injection device is satisfied before the output of the oxygen sensor is inverted to a rich output, the valve is closed without waiting for the output to be inverted to a rich output.
A method for controlling an internal combustion engine.