Control device for internal combustion engine and control method for internal combustion engine

Abstract

To provide a control device for an internal combustion engine and a control method for an internal combustion engine, which can improve an exhaust property when recovering from a fuel cut state and improve fuel consumption performance.SOLUTION: A control device for an internal combustion engine and a control method for an internal combustion engine are applied to the internal combustion engine including: a fuel injection device that injects fuel into the internal combustion engine; a recovered fuel processing device that recovers a fuel component and supplies gas containing the recovered fuel component to an intake passage of the internal combustion engine through a pipe having an electronic control type valve; and an exhaust emission control catalyst that is disposed in an exhaust passage of the internal combustion engine and has an oxygen storage capacity. During a fuel cut in which fuel injection by the fuel injection device is stopped, the valve is controlled to an open state.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine and a control method for an internal combustion engine.

Background Art

[0002] In the air-fuel ratio control device and air-fuel ratio control method of Patent Document 1, in an internal combustion engine having a catalyst with an oxygen storage ability to take in or release oxygen in exhaust gas according to the exhaust air-fuel ratio, fuel cut is performed when a predetermined condition is satisfied, and then fuel cut recovery is performed when another predetermined condition is satisfied. Further, rich spike processing is performed during fuel cut recovery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the rich spike processing during fuel cut recovery, since the fuel injection amount by the fuel injection device is increased, there is a concern about a decrease in fuel consumption performance. Further, when rich spike processing is performed in a state where the oxygen storage amount in the exhaust purification catalyst is saturated, it takes time until the oxygen storage amount decreases, and during this time, there is a possibility that the NOx emission amount increases due to a decrease in reduction performance.

[0005] The present invention has been made in view of the conventional situation, and an object thereof is to provide a control device for an internal combustion engine and a control method for an internal combustion engine that can improve the exhaust gas properties when returning from a fuel cut state and can also improve fuel consumption performance.

Means for Solving the Problems

[0006] Therefore, in one aspect of the present invention, in an internal combustion engine equipped with a recovered fuel treatment device that recovers a fuel component and supplies a gas containing the recovered fuel component to an intake passage of the internal combustion engine via a pipe equipped with an electronically controlled valve, during fuel cut in which fuel injection by a fuel injection device is stopped, the valve is controlled to an open state The valve is closed based on the output of an oxygen sensor that outputs a signal according to the oxygen concentration in the exhaust passage downstream of the exhaust purification catalyst having reversed from a lean output to a rich output.

Advantages of the Invention

[0007] According to the above invention, the exhaust gas properties when returning from the fuel cut state can be improved, and the fuel consumption performance can also be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram showing one aspect of an internal combustion engine. The internal combustion engine 101 shown in FIG. 1 is a spark ignition gasoline engine mounted on a vehicle such as an automobile.

[0010] The internal combustion engine 101 includes an ignition device 200, a fuel injection device 300, an electronically controlled throttle 108, and an exhaust gas 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.

[0011] The fuel injection device 300 includes a fuel injection valve 301 disposed 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 an air-fuel mixture is formed in the combustion chamber 110 by mixing the fuel injected from the fuel injection valve 301 with air. Note that the fuel injection device 300 may be a direct injection type into the cylinder in which the fuel injection valve 301 directly injects fuel into the combustion chamber 110.

[0012] The electronically controlled throttle 108 includes a throttle valve 108a that is a butterfly valve, a throttle motor 108b, and a throttle opening sensor 108c that detects the opening degree of the throttle valve 108a, and is a device that opens and closes the throttle valve 108a with the throttle motor 108b. The air that has passed through the air cleaner 107 has its flow rate adjusted by the throttle valve 108a.

[0013] The exhaust purification catalyst 112 is disposed in the exhaust pipe 103 (exhaust passage) of the internal combustion engine 101, and purifies the exhaust of the internal combustion engine 101 by the catalyst. The exhaust purification catalyst 112 includes a three-way catalyst having an oxygen storage capacity.

[0014] The internal combustion engine 101 also includes various sensors for detecting the operating state of the internal combustion engine 101. The air flow rate sensor 109 is disposed in the intake duct 104 upstream of the electronically controlled throttle 108, and detects 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 protrusions of the ring gear 114, and outputs a pulse signal that rises every predetermined rotation angle of the crankshaft 117.

[0015] 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 gas. The oxygen sensor 116 is disposed in the exhaust pipe 103 downstream of the exhaust purification catalyst 112, and detects the richness and leanness of the exhaust air-fuel ratio 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.

[0016] Further, the internal combustion engine 101 includes a blow-by gas reflux device 400. The blow-by gas reflux device 400 is a device that refluxes the blow-by gas flowing 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.

[0017] The blow-by gas reflux device 400 includes a reflux pipe 401 that communicates the crank chamber 151 and the intake collector 152, and an electronically controlled reflux control valve 402 disposed in the reflux pipe 401 to adjust the blow-by gas flow rate. Note that the blow-by gas is composed of unburned fuel, combustion gas, and mist components of oil. That is, the blow-by gas reflux device 400 is a recovered fuel processing device that supplies the gas containing the fuel component recovered from the crank chamber 151 to the intake collector 152 of the internal combustion engine 101 via the reflux pipe 401 provided with the electronically controlled reflux control valve 402, and burns the unburned fuel component.

[0018] Further, the internal combustion engine 101 includes an evaporated fuel processing device 500. The evaporated fuel processing device 500 is a device that introduces the 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.

[0019] The evaporation fuel treatment device 500 includes a canister 501 filled with activated carbon for adsorbing evaporation fuel, an evaporation fuel pipe 502 that connects the canister 501 and the fuel tank 302, a purge pipe 503 that connects the canister 501 and the intake collector 152 (in other words, the intake passage) of the internal combustion engine 101, and an electronically controlled purge control valve 504 disposed in the purge pipe 503. When the evaporation fuel generated in the fuel tank 302 flows into the canister 501 through the evaporation fuel pipe 502, the canister 501 adsorbs and collects the evaporation fuel on the internal activated carbon.

[0020] When the purge control valve 504 is opened and the inside of the purge pipe 503 becomes negative pressure 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 introduction hole 501a, passes through the inside of the canister 501, and flows into the purge pipe 503. At this time, the evaporation fuel adsorbed on the activated carbon of the canister 501 desorbs, and the desorbed evaporation fuel is guided to the purge pipe 503 together with the outside air, merges with the intake air of the internal combustion engine 101 at the intake collector 152, flows into the combustion chamber 110, and is combusted in the combustion chamber 110.

[0021] That is, the evaporation fuel treatment device 500 is a recovered fuel treatment device that supplies the gas containing the fuel component recovered from the fuel tank 302 to the intake collector 152 of the internal combustion engine 101 through the purge pipe 503 provided with the electronically controlled purge control valve 504, and combusts the evaporation fuel generated in the fuel tank 302. Note that the reflux control valve 402 and the purge control valve 504 are, for example, electromagnetic valves.

[0022] The control device 600 includes an MPU (Microprocessor Unit) 601 and is an electronic control device that controls the operation of the internal combustion engine 101. Note that the MCU601 can be rephrased as a microcomputer, a processor, a processing device, an arithmetic device, etc.

[0023] 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 an operation amount for each control target based on the acquired signals. Specifically, the control device 600 controls the ignition coil 202 (ignition device 200), the fuel injection valve 301 (fuel injection device 300), the throttle motor 108b, the recirculation control valve 402, and the purge control valve 504.

[0024] The control device 600 controls fuel injection by the fuel injection valve 301 (fuel injection device 300) for forming an air-fuel mixture for each combustion cycle in the internal combustion engine 101. Further, the control device 600 performs fuel cut by stopping fuel injection by the fuel injection valve 301 when a predetermined fuel cut condition is satisfied, and restarting fuel injection by the fuel injection valve 301 when a predetermined fuel recovery condition is satisfied. The above fuel cut is implemented, for example, in a deceleration operation state of the internal combustion engine 101. Note that the fuel cut implemented during deceleration operation of the internal combustion engine 101 is also referred to as deceleration fuel cut.

[0025] In the above deceleration fuel cut, when the engine rotational speed NE when the electronic control throttle 108 is closed (in other words, when the driver releases the accelerator pedal) exceeds the fuel cut rotational speed NE1, the control device 600 stops fuel injection by the fuel injection valve 301. Then, after the control device 600 stops fuel injection by the fuel injection valve 301, when the electronic control throttle 108 is opened (in other words, when the driver depresses the accelerator pedal), the control device 600 restarts fuel injection by the fuel injection valve 301. Further, after the control device 600 stops fuel injection by the fuel injection valve 301, when the engine rotational speed falls below the fuel recovery rotational speed NE2 which is lower than the fuel cut rotational speed NE1, the control device 600 restarts fuel injection by the fuel injection valve 301.

[0026] When such fuel cut is performed, air flows into the exhaust purification catalyst 112 during the fuel cut, and thus the oxygen storage amount of the exhaust purification catalyst 112 may increase and reach a saturated state. In a state where the oxygen storage amount of the exhaust purification catalyst 112 is saturated, the reduction ability of NOx in the exhaust purification catalyst 112 decreases. Therefore, when the fuel injection by the fuel injection valve 301 is restarted, the NOx emission amount increases.

[0027] Here, as a control for suppressing the NOx emission amount when the fuel injection is restarted, there is a rich spike which is a control for temporarily increasing the fuel injection amount by the fuel injection valve 301 to perform rich combustion. If the control device 600 performs a rich spike when restarting the fuel injection, rich exhaust with a large amount of HC and CO flows into the exhaust purification catalyst 112, thereby promoting a decrease in the oxygen storage amount of the exhaust purification catalyst 112 and enabling the early restoration of the NOx reduction ability.

[0028] However, since the rich spike is a fuel increase correction, there is a concern about a decrease in fuel consumption performance due to the rich spike. Further, although the NOx emission amount decreases due to the implementation of the rich spike, the NOx emission amount still increases during the process in which the oxygen storage amount decreases from the saturated state. Therefore, the control device 600 supplies a fuel component to the intake collector 152 (intake passage) by the blow-by gas reflux device 400 and / or the evaporated fuel treatment device 500 during the fuel cut, thereby suppressing the oxygen storage amount of the exhaust purification catalyst 112 from saturating during the fuel cut.

[0029] If it is possible to suppress the saturation of the oxygen storage amount, it is possible to reduce the fuel increase amount in the rich spike required to reduce the oxygen storage amount to an appropriate value, and it is also possible to reduce the oxygen storage amount to an appropriate value at an early stage, thereby suppressing the NOx emission amount. That is, during fuel cut, the control device 600 supplies a fuel component to the intake collector 152 (intake passage) by the blow-by gas reflux device 400 and / or the evaporated fuel treatment device 500, thereby improving the exhaust characteristics when returning from the fuel cut state and also improving the fuel consumption performance.

[0030] Note that fuel cut can include idle stop (idle reduction). Idle stop is a control for automatically stopping the internal combustion engine 101 by stopping the fuel injection by the fuel injection valve 301 (fuel injection device 300) during signal waiting of the vehicle or the like. Then, during idle stop, the control device 600 supplies a fuel component to the intake collector 152 (intake passage) by the blow-by gas reflux device 400 and / or the evaporated fuel treatment device 500, thereby improving the exhaust characteristics when restarting the operation of the internal combustion engine 101 and also improving the fuel consumption performance.

[0031] The flowchart of FIG. 2 shows an aspect of the control procedure of the blow-by gas reflux device 400 and / or the evaporated fuel treatment device 500 during fuel cut implemented by the control device 600. In step S701, the control device 600 determines whether fuel cut has started. If the fuel cut has not started (in other words, if it is not during fuel cut), the control device 600 proceeds to step S711 and performs normal control of the blow-by gas reflux device 400 and the evaporated fuel treatment device 500.

[0032] As normal control of the blow-by gas reflux device 400, for example, the control device 600 performs open control of the reflux control valve 402 when the pressure in the crankcase 151 is higher than a threshold value. Also, as normal control of the evaporated fuel treatment device 500, for example, based on the load, rotational speed, etc. of the internal combustion engine 101, the control device 600 adjusts the opening degree of the purge control valve 504 by duty control so that the purge rate is proportional to the intake air amount of the internal combustion engine 101.

[0033] On the other hand, when fuel cut is started, the control device 600 proceeds to step S702 and obtains the oxygen storage amount OSC of the exhaust purification catalyst 112 based on 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 rate sensor 109 (in other words, the flow rate of the exhaust flowing into the exhaust purification catalyst 112).

[0034] After the start of fuel cut, the internal combustion engine 101 rotates inertially, and by such inertial rotation, the internal combustion engine 101 sucks in air and sends the air out to the exhaust passage, and air flows into the exhaust purification catalyst 112 to increase the oxygen storage amount OSC. Therefore, the control device 600 estimates, in step S702, the increase change in the oxygen storage amount OSC due to fuel cut based on the operating state of the internal combustion engine 101 (exhaust air-fuel ratio, intake air flow rate).

[0035] Next, the control device 600 compares, in step S703, the oxygen storage amount OSC estimated in step S702 with a predetermined amount OSCSL. The predetermined amount OSCSL is a value 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 in a substantially saturated state, or whether it is in a state predicted to reach the saturated state.

[0036] If the oxygen storage amount OSC exceeds the predetermined amount OSCSL and the oxygen storage amount OSC is in a substantially saturated state, or in a state predicted to reach the saturated state, the control device 600 proceeds from step S703 to step S704. On the one hand, when the oxygen storage amount OSC is less than or equal to a predetermined amount OSCSL and there is a margin until the oxygen storage amount OSC reaches the saturated state, in other words, when the increase change in the oxygen storage amount OSC due to fuel cut is still small, the control device 600 returns from step S703 to step S701. That is, when the oxygen storage amount OSC is less than or equal to the predetermined amount OSCSL, the control device 600 waits without starting the control of the blow-by gas reflux device 400 and / or the evaporated fuel treatment device 500 (in other words, by keeping the reflux control valve 402 and the purge control valve 504 in the closed state).

[0037] In step S704, the control device 600 supplies the gas containing the fuel component recovered from the crankcase 151 or the fuel tank 302 to the internal combustion engine 101 by opening the reflux control valve 402 and / or the purge control valve 504. That is, after stopping the fuel injection by the fuel injection valve 301, the control device 600 opens the reflux control valve 402 and / or the purge control valve 504 after the oxygen storage amount OSC rises to the predetermined amount OSCSL.

[0038] Here, intake negative pressure is generated while the internal combustion engine 101 rotates by inertia even when fuel cut is implemented. At this time, when the reflux control valve 402 and / or the purge control valve 504 is opened, the gas containing the fuel component is introduced into the intake manifold 152 of the internal combustion engine 101 (in other words, the intake passage).

[0039] The fuel component (HC) introduced into the intake manifold 152 of the internal combustion engine 101 passes through the combustion chamber 110 and flows into the exhaust purification catalyst 112. Then, the exhaust purification catalyst 112 oxidizes the fuel component (HC) using oxygen. That is, the exhaust purification catalyst 112 oxidizes the fuel component supplied to the internal combustion engine 101 by the opening control of the reflux control valve 402 and / or the purge control valve 504, whereby the oxygen storage amount OSC decreases.

[0040] While the internal combustion engine 101 is rotating by inertia after the fuel cut is started, air flows into the exhaust purification catalyst 112, so that the oxygen storage amount OSC in the exhaust purification catalyst 112 immediately reaches the saturation amount. At this time, if a fuel component is allowed 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 treatment of the fuel component.

[0041] When the control device 600 performs open control of the reflux control valve 402 and / or the purge control valve 504 in step S704, in the next step S705, it determines whether or not the output of the oxygen sensor 116 has reversed from the lean output to the rich output, thereby determining whether or not the exhaust air-fuel ratio downstream of the exhaust purification catalyst 112 has switched from lean to rich. When the control device 600 detects that the output of the oxygen sensor 116 has reversed from the lean output to the rich output, it proceeds to step S706.

[0042] In step S706, the control device 600 closes the reflux control valve 402 and / or the purge control valve 504 that was opened in step S704, and returns the reflux control valve 402 and the purge control valve 504 to the closed state. That is, when the control device 600 detects that the output of the oxygen sensor 116 has reversed from the lean output to the rich output, it determines that no further supply of the fuel component is required, closes the reflux control valve 402 and / or the purge control valve 504 that was opened for the supply of the fuel component, and shuts off the supply of the fuel component.

[0043] In the next step S707, the control device 600 performs a setting to eliminate the rich spike when restarting the fuel injection by the fuel injection valve 301. The fact that the output of the oxygen sensor 116 has reversed from the lean output to the rich output indicates that the oxygen storage amount OSC in the exhaust purification catalyst 112 has decreased, the efficiency of the oxidation treatment of the fuel component has decreased, while the efficiency of the reduction treatment of NOx is in a sufficiently high state.

[0044] And, if the oxygen storage capacity OSC in the exhaust purification catalyst 112 is small enough for the reduction treatment of NOx to be performed with high efficiency, a rich spike for reducing the oxygen storage capacity OSC becomes unnecessary. 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, it shuts off the supply of the fuel component in step S706, and also sets not to perform a rich spike when restarting the fuel injection by the fuel injection valve 301 in step S707.

[0045] When the control device 600 holds the reflux control valve 402 and the purge control valve 504 in the closed state during fuel cut, the oxygen storage capacity OSC of the exhaust purification catalyst 112 becomes saturated, and the fuel injection by the fuel injection valve 301 is restarted in a state where the purification efficiency of NOx is low. Therefore, in order to suppress the NOx emission amount when the fuel injection by the fuel injection valve 301 is restarted, the control device 600 needs to perform a rich spike to rapidly reduce the oxygen storage capacity OSC.

[0046] However, since the rich spike is a process of increasing the fuel injection amount by the fuel injection valve 301, it deteriorates the fuel consumption performance, and NOx emissions increase until the oxygen storage capacity OSC decreases due to the rich spike. On the other hand, since the fuel component supplied to the internal combustion engine 101 by the opening control of the reflux control valve 402 and / or the purge control valve 504 is recovered from the crank chamber 151 or the fuel tank 302, the influence on the fuel consumption performance is small.

[0047] Further, if the control device 600 performs the opening control of the reflux control valve 402 and / or the purge control valve 504 during fuel cut, the fuel injection can be restarted in a state where the oxygen storage capacity OSC of the exhaust purification catalyst 112 is small. Therefore, the exhaust gas purification catalyst 112 can efficiently reduce NOx immediately after the resumption of fuel injection, and can suppress the NOx emission amount.

[0048] On the other hand, when the control device 600 determines in step S705 that the output of the oxygen sensor 116 is held at the lean output, it proceeds to step S708. In step S708, the control device 600 determines whether or not the condition for resuming fuel injection is satisfied, in other words, whether or not the continuation of fuel cut is predicted.

[0049] Here, when the control device 600 determines that the condition for resuming fuel injection is not satisfied, it returns to step S705 and determines whether or not the output of the oxygen sensor 116 has reversed from the lean output to the rich output. On the other hand, when the control device 600 determines that the condition for resuming fuel injection is satisfied, it 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 open-controlled in step S704, returns the reflux control valve 402 and the purge control valve 504 to the closed state, and then resumes fuel injection.

[0050] That is, if the output of the oxygen sensor 116 reverses from the lean output to the rich output, the control device 600 returns the reflux control valve 402 and the purge control valve 504 to the closed state, but if the condition for resuming fuel injection is satisfied before reaching the reversal, it returns the reflux control valve 402 and the purge control valve 504 to the closed state without waiting for the reversal. In other words, the control device 600 closes the reflux control valve 402 and the purge control valve 504 at the latest before the fuel injection by the fuel injection device 300 is resumed.

[0051] When the reflux control valve 402 and / or the purge control valve 504 is in the open state, the combustion stability of the internal combustion engine 101 decreases due to a decrease in the control accuracy of the air-fuel ratio, etc., and it becomes difficult to stably return the internal combustion engine 101 to self-sustained operation. Therefore, after returning the reflux control valve 402 and the purge control valve 504 to the closed state, the control device 600 can stably return the internal combustion engine 101 to the self-operating state by restarting fuel injection.

[0052] Next, the control device 600 proceeds to step S710 and makes a setting to perform a rich spike when restarting fuel injection by the fuel injection valve 301. When the output of the oxygen sensor 116 is not inverted and remains at a lean output, although the increase in the oxygen storage amount OSC can be suppressed to some extent by the opening control of the reflux control valve 402 and / or the purge control valve 504, it means that the maximum suppression has not been achieved.

[0053] Therefore, the control device 600 performs a rich spike when restarting fuel injection in order to quickly restore the reduction in the NOx purification efficiency due to the increase in the oxygen storage amount OSC. Note that the control device 600 can variably set the increased amount of the fuel injection amount in the rich spike according to the oxygen storage amount OSC, the exhaust air-fuel ratio upstream of the exhaust purification catalyst 112, and the like.

[0054] FIG. 3 is a time chart illustrating changes in the engine speed, fuel injection amount, oxygen storage amount OSC, etc. when the control device 600 performs opening control of the reflux control valve 402 and / or the purge control valve 504 during fuel cut. When the fuel cut condition is satisfied at time t1, the control device 600 stops the fuel injection by the fuel injection valve 301 (fuel injection device 300).

[0055] Due to the stop of fuel injection, the rotational speed of the internal combustion engine 101 begins to decrease. At this time, air flows into the exhaust purification catalyst 112, and thus the oxygen storage amount OSC of the exhaust purification catalyst 112 increases. At time t2, which is the timing when the estimated value of the oxygen storage amount OSC exceeds a predetermined amount OSCSL, the control device 600 switches the reflux control valve 402 and / or the purge control valve 504 from closed to open.

[0056] When the reflux control valve 402 and / or the purge control valve 504 is switched from closed to open, gas containing a fuel component is introduced into the intake passage of the internal combustion engine 101, and the gas flowing into the exhaust purification catalyst 112 becomes rich. When rich gas flows into the exhaust purification catalyst 112, a reduction process of the fuel component is performed, and the oxygen storage amount OSC starts to decrease.

[0057] Then, when the purification efficiency of the fuel component decreases due to the 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, the control device 600 closes the reflux control valve 402 and / or the purge control valve 504 that has been opened at the timing when the estimated value of the oxygen storage amount OSC exceeds a predetermined amount OSCSL, and stops the supply of the fuel component from the blow-by gas reflux device 400 and the evaporative fuel treatment device 500.

[0058] By opening the reflux control valve 402 and / or the purge control valve 504, the oxygen storage amount OSC when returning from fuel cut can be made smaller than when the reflux control valve 402 and / or the purge control valve 504 is not opened. If the oxygen storage amount OSC when fuel injection is restarted (time t4) is small, the fuel increase amount during the rich spike from time t4 to time t5 can be reduced or made zero, and NOx can be purified with high efficiency immediately after the restart of fuel injection. Therefore, by the control device 600 opening the reflux control valve 402 and / or the purge control valve 504 during fuel cut, it is possible to suppress a decrease in fuel consumption performance due to a rich spike and to suppress the NOx emission amount when returning from the fuel cut state.

[0059] Each technical idea described in the above embodiments can be used in appropriate combination as long as no contradiction occurs. In addition, although the content of the present invention has been specifically described with reference to the preferred embodiments, it is obvious that those skilled in the art can adopt various modified forms based on the basic technical idea and teaching of the present invention.

[0060] It is obvious that the control device for an internal combustion engine according to the present invention can also be applied to an internal combustion engine provided with either one of the blow-by gas reflux device 400 and the evaporated fuel treatment device 500. Further, the evaporated fuel treatment device 500 may be a device that pumps the evaporated fuel recovered from the fuel tank 302 into the intake passage of the internal combustion engine 101 by a pump.

[0061] In addition, the control device 600 can switch between a state in which either one of the reflux control valve 402 and the purge control valve 504 is opened and a state in which both the reflux control valve 402 and the purge control valve 504 are opened. For example, the control device 600 maintains the purge control valve 504 in a closed state and only opens the reflux control valve 402. When it determines a shortage of the fuel component flowing into the exhaust purification catalyst 112 based on the exhaust air-fuel ratio upstream of the exhaust purification catalyst 112 in such a state, the control device 600 can further open the purge control valve 504. Note that the control device 600 can also additionally open the reflux control valve 402 after opening the purge control valve 504.

[0062] In addition, the control device 600 respectively learns the fuel concentration of the blow-by gas in the blow-by gas reflux device 400 and the fuel concentration of the purge gas in the evaporated fuel treatment device 500, and can switch which one of the reflux control valve 402 and the purge control valve 504 to open based on the learned fuel concentration. In addition, the control device 600 can open the reflux control valve 402 and / or the purge control valve 504 at the start of fuel cut or after a predetermined time has elapsed since the start of fuel cut.

[0063] Further, when the rotational speed of the internal combustion engine 101 is lower than a predetermined rotational speed (predetermined rotational speed > 0), or when the rotational speed of the internal combustion engine 101 becomes zero, the control device 600 can perform closing control on the opened reflux control valve 402 and / or the purge control valve 504. That is, in the case of a system in which the blow-by gas reflux device 400 and the evaporated fuel processing device 500 supply a gas containing a fuel component to the intake passage of the internal combustion engine 101 by utilizing the intake negative pressure of the internal combustion engine 101, when the rotation of the internal combustion engine 101 stops after fuel cut and the intake negative pressure no longer occurs, even if the reflux control valve 402 and / or the purge control valve 504 is controlled to be in an open state, the supply of the gas containing the fuel component will be interrupted.

[0064] Therefore, the control device 600 can determine the timing to close the reflux control valve 402 and / or the purge control valve 504 based on the rotational speed of the internal combustion engine 101 (in other words, the intake negative pressure of the internal combustion engine 101). Specifically, when the rotational speed of the internal combustion engine 101 becomes a predetermined rotational speed (predetermined rotational speed ≥ 0 rpm) or less than the predetermined rotational speed, the control device 600 can close the reflux control valve 402 and / or the purge control valve 504.

Explanation of Reference Numerals

[0065] 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 reflux device (recovered fuel processing device), 401... Reflux pipe, 402... Reflux control valve (electrically controlled valve), 500... Evaporated fuel processing device (recovered fuel processing device), 503... Purge pipe, 504... Purge control valve (electrically controlled valve), 600... Control device

Claims

1. A fuel injection device for injecting fuel into an internal combustion engine; A recovered fuel treatment device that recovers fuel components and supplies a gas containing the recovered fuel components to an intake passage of the internal combustion engine via a pipe equipped with an electronically controlled valve; An exhaust gas purification catalyst having an oxygen storage capacity, disposed in an exhaust passage of the internal combustion engine; An oxygen sensor that outputs a signal according to the oxygen concentration in the exhaust passage downstream of the exhaust gas purification catalyst; A control device for an internal combustion engine applied to the internal combustion engine provided with the above, During fuel cut-off in which fuel injection by the fuel injection device is stopped, the valve is controlled to be in an open state, Based on the output of the oxygen sensor having reversed from a lean output to a rich output, the valve is closed, A control device for an internal combustion engine.

2. The control device for an internal combustion engine according to Claim 1, The recovered fuel treatment device, Includes a blow-by gas reflux device that refluxes blow-by gas to the intake passage, A control device for an internal combustion engine.

3. The control device for an internal combustion engine according to Claim 1, The recovered fuel treatment device, Includes an evaporated fuel treatment device that introduces evaporated fuel recovered from a fuel tank into the intake passage, A control device for an internal combustion engine.

4. The control device for an internal combustion engine according to Claim 1, When the condition for restarting fuel injection by the fuel injection device is satisfied before the output of the oxygen sensor reverses to a rich output, the valve is closed without waiting for the reversal to a rich output, A control device for an internal combustion engine.

5. A fuel injection device for injecting fuel into an internal combustion engine; A recovered fuel treatment device that recovers fuel components and supplies a gas containing the recovered fuel components to an intake passage of the internal combustion engine via a pipe equipped with an electronically controlled valve; An exhaust gas purification catalyst having an oxygen storage capacity, disposed in an exhaust passage of the internal combustion engine; An oxygen sensor that outputs a signal according to the oxygen concentration in the exhaust passage downstream of the exhaust gas purification catalyst; A control method for an internal combustion engine executed by a control device applied to the internal combustion engine provided with the above, During fuel cut-off in which fuel injection by the fuel injection device is stopped, the valve is controlled to be in an open state, Based on the output of the oxygen sensor having reversed from a lean output to a rich output, the valve is closed, A control method for an internal combustion engine.

6. The control method for an internal combustion engine according to Claim 5, When the condition for restarting fuel injection by the fuel injection device is satisfied before the output of the oxygen sensor reverses to a rich output, the valve is closed without waiting for the reversal to the rich output. A method for controlling an internal combustion engine.

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