JP7145018B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to technology for controlling fuel cut.

The control device of Patent Document 1 is based on the air-fuel ratio feedback correction amount, the air-fuel ratio learning value, and the alcohol concentration learning value in a multi-fuel engine that can use a fuel of ethanol alone or a mixed fuel of ethanol and gasoline. It is determined whether or not the oil is diluted in an oil pan, and the fuel cut, which is performed when a predetermined fuel cut condition is satisfied, is prohibited when it is determined that the oil is diluted.

JP 2011-122543 A

When oil dilution occurs in which fuel mixes with the lubricating oil of the internal combustion engine, the fuel mixed with the lubricating oil is guided from the oil pan to the combustion chamber by the blow-by processing device.
Here, in an operating state in which fuel is injected by the fuel injection device and ignition is performed by the ignition device, the fuel guided to the combustion chamber by the blow-by processing device burns in the combustion chamber.

On the other hand, during the fuel cut, the fuel injection by the fuel injection device and the ignition by the ignition device are stopped, and the fuel guided to the combustion chamber by the blow-by processing device flows out to the exhaust system as it is without burning. Then, the fuel that has flowed out to the exhaust system may afterburn in the catalyst of the exhaust purification device, excessively increase the temperature of the catalyst, and damage the catalyst.
Here, if fuel cut is prohibited when oil dilution occurs, it is possible to suppress the increase in catalyst temperature due to afterburning of fuel, but the effect of improving fuel consumption by fuel cut cannot be obtained.

The fuel mixed in the lubricating oil evaporates as the engine continues to operate, and is led into the combustion chamber by the blow-by treatment device. Therefore, if the fuel cut is prohibited when the oil is diluted, there is a possibility that the fuel cut will be prohibited until the next oil change.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can cut fuel while suppressing an increase in catalyst temperature in an oil-diluted state. to do.

According to one aspect of the present invention, when starting a fuel cut, the fuel injection control device sets a higher return rotation speed, which is an engine rotation speed at which fuel injection by the fuel injection device is restarted, as the temperature of the catalyst increases, and Further, the higher the degree of oil dilution, which is the degree of mixing of fuel into the lubricating oil of the internal combustion engine, the higher the return rotation speed is set. Resume fuel injection by the injector.

According to the above invention, in an oil-diluted state, fuel cut can be performed while suppressing an increase in catalyst temperature, and fuel consumption can be improved as much as possible while protecting the catalyst.

1 is a system configuration diagram of an internal combustion engine; FIG. FIG. 3 is a diagram illustrating correlations between an operating time of an internal combustion engine, an oil dilution degree, and a fuel correction amount (air-fuel ratio correction amount); FIG. 10 is a flowchart showing a procedure of processing for changing return conditions in fuel cut; FIG. FIG. 5 is a diagram illustrating a map of catalyst temperature in steady state; FIG. 4 is a diagram showing the correlation between the degree of oil dilution and the amount of catalyst temperature rise; FIG. 3 is a graph showing the correlation among the degree of oil dilution, estimated maximum temperature TCAmax, and judgment temperatures TCAT1 and TCAT2; FIG. 10 is a flowchart showing a procedure of processing for changing return conditions in fuel cut; FIG.

Embodiments of the present invention will be described below.
FIG. 1 is a configuration diagram showing one aspect of an internal combustion engine to which a fuel injection control device according to the present invention is applied.
An internal combustion engine 1 shown in FIG. 1 is a spark ignition gasoline engine for a vehicle, and includes an ignition device 4 in an engine body 1a and a fuel injection valve 5 which is one aspect of a fuel injection device.

The fuel injection valve 5 is arranged in the intake pipe 2a and directs the intake valve 19 to inject fuel into the intake pipe 2a. That is, the internal combustion engine 1 shown in FIG. 1 is a so-called port injection internal combustion engine in which the fuel injection valve 5 injects fuel into the intake pipe 2a.
However, the internal combustion engine 1 may be a so-called in-cylinder direct injection internal combustion engine in which the fuel injection valve 5 directly injects fuel into the combustion chamber 10 .

The intake air of the internal combustion engine 1 passes through the air cleaner 7, and after the flow rate is adjusted by the throttle valve 8a of the electronically controlled throttle 8, it is mixed with the fuel injected into the intake pipe 2a by the fuel injection valve 5 to enter the combustion chamber. Flow into 10.
The electronically controlled throttle 8 is a device that opens and closes a throttle valve 8a with a throttle motor 8b, and includes a throttle opening sensor 8c that outputs a signal corresponding to the throttle opening TPS, which is the opening of the throttle valve 8a.

The rotation speed detection device 6 (crank angle sensor) detects the protrusion of the ring gear 14 and outputs a signal of the rotation angle POS for each predetermined rotation angle of the crankshaft 17 .
The water temperature sensor 15 outputs a signal corresponding to the temperature of cooling water (hereinafter referred to as water temperature TW) circulating in the water jacket 18 of the engine body 1a.

The flow rate detection device 9 (air flow sensor) is arranged upstream of the electronically controlled throttle 8 and outputs a signal corresponding to the intake air flow rate QAR of the internal combustion engine 1 .
Further, the exhaust purification device 12 (catalytic converter) is arranged in the exhaust pipe 3a and purifies the exhaust gas of the internal combustion engine 1 with a built-in catalyst 12a such as a three-way catalyst.

The air-fuel ratio sensor 11 is arranged in the exhaust pipe 3a on the upstream side of the exhaust purification device 12 and outputs a signal corresponding to the exhaust air-fuel ratio RABF.
A catalyst temperature sensor 16, which is one aspect of a catalyst temperature detector, outputs a signal corresponding to the temperature TCAT (° C.) of the catalyst 12a of the exhaust purification device 12. FIG.

An electronic control unit (ECU) 13 incorporating a microcomputer controls throttle opening TPS, intake air flow QAR, rotation angle POS, water temperature TW, exhaust air-fuel ratio RABF, catalyst temperature TCAT, etc., which are output by the various sensors described above. captures the detection signal of
The ECU 13, which is one aspect of the fuel injection control device, has a function of controlling the fuel injection valve 5 based on the received signal as software.
Further, the ECU 13 also outputs the manipulated variables to the ignition device 4 and the electronically controlled throttle 8 to control the ignition timing of the ignition device 4 and the opening degree of the throttle valve 8a, thereby controlling the operation of the internal combustion engine 1.

The ECU 13 includes an analog input circuit 20, an A/D conversion circuit 21, a digital input circuit 22, an output circuit 23, and an I/ An O circuit 24 is provided.
The ECU 13 also includes a microcomputer including an MPU (Microprocessor Unit) 26, a ROM (Read Only Memory) 27, and a RAM (Random Access Memory) 28 in order to perform data arithmetic processing.

An analog input circuit 20 receives sensor detection signals such as an intake air flow rate QAR, a throttle opening TPS, an exhaust air-fuel ratio RABF, a catalyst temperature TCAT, and a water temperature TW.
The A/D conversion circuit 21 converts various signals input to the analog input circuit 20 into digital signals and outputs them onto the bus 25 .

Also, the signal of the rotation angle POS input to the digital input circuit 22 is output to the bus 25 via the I/O circuit 24 .
MPU 26, ROM 27, RAM 28, timer/counter (TMR/CNT) 29 and the like are connected to bus 25. FIG. MPU 26 , ROM 27 and RAM 28 exchange data via bus 25 .

A clock signal is supplied from the clock generator 30 to the MPU 26, and the MPU 26 executes various calculations and processes in synchronization with the clock signal.
The ROM 27 is, for example, an EEPROM (Electrically Erasable Programmable Read-Only Memory) in which data can be erased and rewritten, and stores programs for operating the ECU 13, setting data, initial values, and the like.

Information stored in the ROM 27 is read into the RAM 28 and the MPU 26 via the bus 25 .
The RAM 28 is used as a work area for temporarily storing calculation results and processing results by the MPU 26 .

Note that the timer/counter 29 is used for measuring time and measuring various times.
The calculation results and processing results by the MPU 26 are output to the bus 25 and then supplied from the output circuit 23 to the ignition device 4, the fuel injection valve 5, the electronically controlled throttle 8 and the like via the I/O circuit 24. FIG.

The internal combustion engine 1 also includes a blow-by gas processing device 41 (blow-by gas recirculation device). The blow-by gas treatment device 41 is a device for returning blow-by gas containing vaporized fuel among unburned fuel leaked from the combustion chamber 10 of the internal combustion engine 1 into the crankcase 42 storing lubricating oil to the intake system of the internal combustion engine 1. is.
The blow-by gas treatment device 41 has a blow-by gas recirculation passage 43 that communicates the inside of the crankcase 42 with the inside of the intake collector portion 2b. The blow-by gas in the crankcase 42 is recirculated from the crankcase 42 through the blow-by gas recirculation passage 43 into the intake collector portion 2b, and the fuel in the blow-by gas is burned in the combustion chamber 10.

As fuel injection control, the ECU 13 calculates the fuel injection pulse width TI (fuel injection amount) based on the engine operating state, and sends a valve opening pulse signal of the fuel injection pulse width TI to the fuel injection valve 5 when the injection timing for each cylinder comes. Output. The fuel injection valve 5 opens during the ON period of the valve opening pulse signal, and injects an amount of fuel proportional to the valve opening time.
Here, in calculating the fuel injection pulse width TI, the ECU 13 first calculates a basic fuel injection pulse width TP (basic fuel injection amount) based on the measured value of the intake air amount of the internal combustion engine 1 .

Further, the ECU 13 performs air-fuel ratio feedback control to set the air-fuel ratio correction coefficient KAF for correcting the basic fuel injection pulse width TP so that the actual air-fuel ratio detected by the air-fuel ratio sensor 11 approaches the target air-fuel ratio. do.
Furthermore, the ECU 13 learns a correction amount based on the air-fuel ratio correction coefficient KAF as an air-fuel ratio learning correction value LAF for each engine operating range.
Then, the ECU 13 corrects the basic fuel injection pulse width TP with the air-fuel ratio correction amount consisting of the air-fuel ratio correction coefficient KAF and the air-fuel ratio learning correction value LAF to obtain the final fuel injection pulse width TI.

Further, when the operating state of the internal combustion engine 1 satisfies a predetermined fuel cut condition, the ECU 13 cuts the fuel to temporarily stop the fuel injection by the fuel injection valve 5 .
The predetermined fuel cut condition is a predetermined deceleration operation state of the internal combustion engine 1, and the ECU 13 determines that the engine rotation speed NE (rpm) when the accelerator opening is fully closed (accelerator off) is lower than the fuel cut start speed NES. is also high, the fuel injection by the fuel injection valve 5 is stopped.
Then, in the fuel cut state, the ECU 13 determines whether the accelerator pedal is depressed (the accelerator is turned on) or when the engine rotation speed NE decreases to the return rotation speed NER (NER<NES) at which fuel injection is restarted. Fuel injection by the fuel injection valve 5 is restarted.

Furthermore, the ECU 13 sets a recovery rotational speed NER (recovery rotational speed), which is a condition for restarting fuel supply from the fuel injection valve 5 from a fuel cut state, to an oil dilution rate, which is the degree of mixing of fuel in the lubricating oil of the internal combustion engine 1. It has the ability to change based on degree.
Oil dilution occurs when fuel entering the oil pan side from the combustion chamber 10 mixes with lubricating oil, and the degree of oil dilution can be estimated from the magnitude of the air-fuel ratio correction amount in the fuel injection amount.

As the amount of fuel mixed in the lubricating oil (degree of oil dilution) increases, the amount of fuel components volatilizing from the lubricating oil after the internal combustion engine 1 warms up increases. Since the fuel components volatilized in the crankcase 42 are returned to the intake system by the blow-by gas processing device 41, if the fuel components volatilized in the crankcase 42 increase, the air-fuel ratio will be enriched, resulting in air-fuel ratio feedback control. , the correction amount for reducing the amount of fuel injected from the fuel injection valve 5 increases.
Therefore, the ECU 13 can estimate an increase in the degree of oil dilution from the expansion of the correction amount that reduces the fuel injection amount.

FIG. 2 is a diagram schematically showing the correlation between the correction amount of the fuel injection amount (air-fuel ratio correction amount) by air-fuel ratio feedback control, the oil dilution degree (oil dilution level), and the operating time of the internal combustion engine 1. be.
FIG. 2 shows characteristics in which the degree of oil dilution gradually increases as the operating time of the internal combustion engine 1 increases, and the correction amount for reducing the fuel injection amount increases as the degree of oil dilution increases.

Based on the characteristics described above, the ECU 13 can estimate the degree of oil dilution based on the correction amount of the fuel injection amount required immediately after the oil change, and from the amount of change in the air-fuel ratio correction amount according to the subsequent increase in operating time. . With such a configuration, it is possible to suppress deterioration in the accuracy of estimating the degree of oil dilution based on differences in air-fuel ratio correction amounts due to variations in parts and performance of the internal combustion engine 1 .
In addition, the ECU 13 stores the air-fuel ratio correction amount when the internal combustion engine 1 is stopped, and compares the stored value with the air-fuel ratio correction amount after the restart to determine the air-fuel ratio correction amount due to the oil change. If it is estimated that the oil needs to be changed by judging a stepwise change, the air-fuel ratio correction amount at that time is used as a base, and the subsequent change in the air-fuel ratio correction amount is used as the correction amount due to oil dilution to obtain the degree of oil dilution. can be done.

The fuel returned to the intake system by the blow-by gas processing device 41 during fuel cut flows directly into the exhaust system without burning, and is post-burned by the catalyst 12a of the exhaust purification device 12, thereby raising the temperature of the catalyst 12a.
For this reason, when the degree of oil dilution is high and a large amount of fuel is returned to the intake system by the blow-by gas processing device 41 during the fuel cut, if the fuel cut is performed for a long period of time, the temperature of the catalyst 12a will rise excessively and the catalyst 12a will may damage the

On the other hand, when the degree of oil dilution is relatively low, even if the fuel cut is performed for a long period of time, the temperature rise of the catalyst 12a is suppressed, and fuel consumption can be improved by cutting the fuel over a long period of time.
Therefore, the ECU 13 changes the return rotation speed NER, which is a condition for returning from the fuel cut state, based on the degree of oil dilution. To maximize the effect of fuel consumption improvement by executing fuel cut over an extended period of time.

The flowchart of FIG. 3 shows the procedure of processing for changing the return rotational speed NER in fuel cut control.
The routine shown in the flowchart of FIG. 3 is executed when the operating state of the internal combustion engine 1 satisfies the fuel cut condition in a predetermined deceleration operating state.

After starting fuel cut in step S101, the ECU 13 acquires data on the engine speed NE and the engine load (torque) at that time in the next step S102. Based on the load data, the temperature TCAb of the catalyst 12a at the start of the fuel cut is estimated.

FIG. 4 shows a map used by the ECU 13 for estimating the temperature TCAb.
The ECU 13 stores in memory a map (see FIG. 4) that stores the temperature TCAb of the catalyst 12a when the internal combustion engine 1 is in steady operation in each of a plurality of regions divided by the engine speed NE and the engine load. stored.
Then, in step S103, the ECU 13 refers to the map of FIG. 4 and searches for data on the temperature TCAb corresponding to the engine speed NE and the engine load at the start of the fuel cut.

Next, in step S104, the ECU 13 obtains the estimated maximum temperature TCAmax of the catalyst 12a in the fuel cut state.
If the fuel returned to the intake system by the blow-by gas treatment device 41 during fuel cut is afterburned in the catalyst 12a, the temperature of the catalyst 12a will rise, and an excessive temperature rise will damage the catalyst 12a. Therefore, the ECU 13 estimates to what extent the temperature of the catalyst 12a rises due to the fuel cut, thereby determining whether the fuel cut can be normally performed, in other words, whether it is necessary to shorten the fuel cut time. determine whether or not

The ECU 13 obtains the estimated maximum temperature TCAmax based on the temperature TCAb of the catalyst 12a at the start of the fuel cut and the temperature increase ΔTCA of the catalyst 12a from the start of the fuel cut.
FIG. 5 shows the correlation between the amount of temperature rise ΔTCA of the catalyst 12a from the start of fuel cut and the degree of oil dilution.

FIG. 5 shows a characteristic that the higher the degree of oil dilution, the greater the amount of fuel that flows out into the exhaust system during fuel cut, and the greater the amount of temperature rise ΔTCA due to afterburning in the catalyst 12a.
The ECU 13 obtains the temperature rise amount ΔTCA corresponding to the degree of oil dilution by referring to the table of FIG. is added to obtain the estimated maximum temperature TCAmax (TCAmax=TCAb+ΔTCA) of the catalyst 12a in the fuel cut state.

Next, in step S105, the ECU 13 compares the estimated maximum temperature TCAmax with the first judgment temperature TCAT1.
The first judgment temperature TCAT1 is the upper limit value of the allowable range of the estimated maximum temperature TCAmax, and is set to approximately 950° C., for example.

The fact that the estimated maximum temperature TCAmax is equal to or lower than the first judgment temperature TCAT1 indicates that the temperature of the catalyst 12a does not reach the temperature that damages the catalyst 12a even if the fuel cut is normally performed.
Therefore, when the estimated maximum temperature TCAmax is equal to or lower than the first judgment temperature TCAT1, the ECU 13 proceeds to step S106 and sets the standard return rotation speed NERst (NERst<NES) as the return rotation speed NER.

On the other hand, when the estimated maximum temperature TCAmax exceeds the first judgment temperature TCAT1, the ECU 13 proceeds to step S107 and compares the estimated maximum temperature TCAmax with the second judgment temperature TCAT2. The second judgment temperature TCAT2 is higher than the first judgment temperature TCAT1 (TCAT2>TCAT1), and is set at approximately 1000° C., for example.
The second determination temperature TCAT2 is set as a temperature that can prevent the temperature of the catalyst 12a from reaching a temperature that damages the catalyst 12a by shortening the fuel cut period.

Then, when the estimated maximum temperature TCAmax is lower than the second judgment temperature TCAT2, that is, when TCAT1<TCAmax<TCAT2, the ECU 13 proceeds to step S108 to shorten the period and cut fuel.
In step S108, the ECU 13 sets, as the return rotational speed NER, a return rotational speed NERsh for shortening the fuel cut period, which is higher than the standard return rotational speed NERst and lower than the fuel cut start speed NES (NERst < NERs < NES).

That is, the ECU 13 sets the temperature rise amount ΔTCA higher as the degree of oil dilution is higher, so that the higher the degree of oil dilution is, the higher the return rotation speed NER is changed.
Since the return rotation speed NERsh is higher than the return rotation speed NERst, the resumption of fuel injection based on the return rotation speed NERsh is earlier than the resumption of fuel injection based on the return rotation speed NERst. time) is shortened.

If the fuel cut period is shortened, the period (time) in which the fuel returned to the intake system by the blow-by gas processing device 41 flows into the exhaust system without being burned and is afterburned in the catalyst 12a is shortened. It is possible to suppress the temperature rise of the catalyst 12a within an allowable range (below the first judgment temperature TCAT1).
In addition, by executing the fuel cut while shortening the period, it is possible to obtain the effect of improving the fuel consumption due to the fuel cut.

When TCAT1<TCAmax<TCAT2, the ECU 13 divides the temperature range sandwiched between the first determination temperature TCAT1 and the second determination temperature TCAT2 into a plurality of temperature ranges. The return rotation speed NER can be set higher than the standard return rotation speed NERst.

On the other hand, when the estimated maximum temperature TCAmax is equal to or higher than the second judgment temperature TCAT2, the fuel cut is performed for a certain period or longer, and the temperature rise of the catalyst 12a during the fuel cut period is within the allowable range (below the first judgment temperature TCAT1). ) is difficult to suppress.
Therefore, when the estimated maximum temperature TCAmax is equal to or higher than the second judgment temperature TCAT2, the ECU 13 proceeds from step S107 to step S109 and prohibits fuel cut.
As a result, although the effect of fuel consumption improvement due to the fuel cut is reduced, it is possible to prevent the temperature of the catalyst 12a from rising and damaging the catalyst 12a during the fuel cut.

FIG. 6 shows the correlation among the degree of oil dilution, the estimated maximum temperature TCAmax, the first judgment temperature TCAT1, and the second judgment temperature TCAT2.
FIG. 6 shows that the higher the degree of oil dilution, the higher the temperature rise amount ΔTCA during fuel cut. is reached.

As the degree of oil dilution increases and a higher temperature is set as the estimated maximum temperature TCAmax, the ECU 13 changes the return rotational speed NER to a higher value to shorten the fuel cut period. A fuel cut can be implemented as much as possible while suppressing a rise.
3 does not use the measurement result of the catalyst temperature sensor 16, the process of changing the return rotation speed NER based on the estimated maximum temperature TCAmax can also be applied to the internal combustion engine 1 without the catalyst temperature sensor 16. Applicable and highly versatile.

By the way, in the case of the process of changing the return rotational speed NER based on the degree of oil dilution shown in the flowchart of FIG. Based on the catalyst temperature TCAT actually measured by the catalyst temperature sensor 16, the setting based on the estimated maximum temperature TCAmax can be changed.
The flow chart of FIG. 7 shows the procedure for changing the return condition based on the estimated maximum temperature TCAmax, and changing the setting of the return condition based on the estimated maximum temperature TCAmax based on the catalyst temperature TCAT actually measured by the catalyst temperature sensor 16. indicates

In the flowchart of FIG. 7, the ECU 13 performs the same processing as steps S101 to S108 in the flowchart of FIG.
In step S208, the ECU 13 sets the return rotation speed NER to the return rotation speed NERsh for shortening the fuel cut period.

In other words, the measured maximum temperature TCATmax is the catalyst temperature raised by the fact that the fuel returned to the intake system by the blow-by gas processing device 41 during the fuel cut does not burn but flows directly into the exhaust system and afterburns in the catalyst 12a. .
Then, in the next step S210, the ECU 13 compares the actually measured maximum temperature TCATmax with the third judgment temperature TCAT3.

The third judgment temperature TCAT3 is lower than the first judgment temperature TCAT1, preferably lower than the first judgment temperature TCAT1 (TCAT2>TCAT1≧TCAT3), and is set to about 920° C., for example.
If the measured highest temperature TCATmax is equal to or lower than the third judgment temperature TCAT3, the ECU 13 proceeds to step S211 and cuts fuel (resumes) until the engine speed NE drops to the return speed NERst.

When the return rotational speed NER is changed to a higher return rotational speed NERsh than the standard return rotational speed NERst and the fuel cut is completed in a shorter period than usual, the ECU 13 changes the measured maximum temperature TCATmax and the third It is compared with the judgment temperature TCAT3.
Here, if the measured maximum temperature TCATmax is equal to or lower than the third judgment temperature TCAT3 in a state where the fuel cut condition based on the standard return rotation speed NERst is established, the fuel cut is performed prior to the fuel injection restart determination based on the estimated maximum temperature TCAmax. can be implemented.

That is, due to an estimation error in the estimated maximum temperature TCAmax, the actual temperature rise is lower than the estimated maximum temperature TCAmax, and the actual measured maximum temperature TCATmax when the engine rotation speed is reduced to the return rotation speed NERsh and the fuel injection is to be restarted is If it is sufficiently low, the ECU 13 restarts (continues) the fuel cut.
As a result, the ECU 13 can prevent the fuel cut period from being excessively shortened due to an estimation error in the estimated maximum temperature TCAmax, so that a greater effect of improving fuel consumption by the fuel cut can be enjoyed.

Further, when the estimated maximum temperature TCAmax is equal to or higher than the second judgment temperature TCAT2, the ECU 13 proceeds from step S207 to step S212 and prohibits fuel cut.
Next, the ECU 13 obtains the actually measured maximum temperature TCATmax from the output of the catalyst temperature sensor 16 in step S213.

Then, in the next step S214, the ECU 13 compares the actually measured maximum temperature TCATmax with the third judgment temperature TCAT3.
Here, when the measured maximum temperature TCATmax is equal to or lower than the third determination temperature TCAT3, the ECU 13 proceeds to step S215, and cuts fuel (resumes) while the engine speed NE decreases to the return speed NERst.

That is, the ECU 13 prohibits fuel cut based on the estimated maximum temperature TCAmax, but implements (resumes) the fuel cut when the actually measured maximum temperature TCATmax is sufficiently low.
As a result, the ECU 13 can prevent the fuel cut from being unnecessarily prohibited due to the estimation error of the estimated maximum temperature TCAmax, and the effect of improving the fuel efficiency by the fuel cut can be enjoyed more.

In addition, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.
Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration.

For example, the ECU 13 can obtain the estimated maximum temperature TCAmax only when the degree of oil dilution exceeds the threshold value, and change the return rotation speed NER (return condition) based on the obtained estimated maximum temperature TCAmax.
Further, when the internal combustion engine 1 is equipped with the catalyst temperature sensor 16, the ECU 13 omits the process of obtaining the estimated maximum temperature TCAmax, monitors the catalyst temperature TCAT detected by the catalyst temperature sensor 16 after the fuel cut is started, and determines the catalyst temperature TCAT. When TCAT exceeds the set temperature or is estimated to exceed the set temperature, fuel cut is interrupted, in other words, when the catalyst temperature TCAT exceeds the set temperature or is estimated to exceed the set temperature, the return rotational speed The NER (return condition) can be changed higher.

Further, the ECU 13 can learn the correlation between the degree of oil dilution and the estimated maximum temperature TCAmax based on the measured value by the catalyst temperature sensor 16 .
In addition, the ECU 13 can appropriately employ a known estimation method as the process of estimating the degree of oil dilution. For example, the ECU 13 can estimate the degree of oil dilution from the operation time of the internal combustion engine 1 after oil replacement. .

DESCRIPTION OF SYMBOLS 1... Internal combustion engine 5... Fuel injection valve (fuel injection device) 12... Exhaust purification device 12a... Catalyst 13... ECU (fuel injection control device) 16... Catalyst temperature sensor (catalyst temperature detector) 41... blow-by gas treatment equipment

Claims (5)

Applied to the internal combustion engine provided with a fuel injection device for injecting fuel into the internal combustion engine and an exhaust purification device disposed in the exhaust system of the internal combustion engine and purifying exhaust gas with a catalyst , wherein the operating state of the internal combustion engine is fuel A fuel injection control device for an internal combustion engine that performs a fuel cut to stop fuel injection by the fuel injection device when a cut condition is satisfied ,
When starting the fuel cut, the higher the temperature of the catalyst, the higher the return rotation speed, which is the engine rotation speed at which the fuel injection by the fuel injection device is restarted, and the fuel to the lubricating oil of the internal combustion engine. The higher the degree of oil dilution, which is the degree of mixing of the oil, the higher the return rotation speed is set,
resuming fuel injection by the fuel injection device when the engine rotation speed decreases to the return rotation speed after the start of the fuel cut ;
A fuel injection control device for an internal combustion engine. A fuel injection control device for an internal combustion engine according to claim 1,
From the temperature of the catalyst when the fuel cut is started and the amount of temperature rise of the catalyst from the start time of the fuel cut, which is obtained based on the degree of oil dilution, the temperature of the catalyst when the fuel cut is performed. estimating the maximum temperature, and setting the return rotation speed higher as the maximum temperature is higher ;
A fuel injection control device for an internal combustion engine. A fuel injection control device for an internal combustion engine according to claim 1,
The internal combustion engine includes a catalyst temperature detector that detects the temperature of the catalyst,
If the temperature of the catalyst detected by the catalyst temperature detector is equal to or lower than a predetermined temperature when the return rotational speed is changed higher than the standard value, the fuel is supplied until the engine rotational speed decreases to the standard value. continue cutting
A fuel injection control device for an internal combustion engine. A fuel injection control device for an internal combustion engine according to claim 2,
when the maximum temperature is equal to or lower than the first judgment temperature, setting the return rotation speed to the first return rotation speed;
When the maximum temperature exceeds the first determination temperature and is lower than a second determination temperature higher than the first determination temperature, the return rotation speed is set to a second return rotation higher than the first return rotation speed. set to speed,
Prohibiting the fuel cut when the maximum temperature is equal to or higher than the second determination temperature;
A fuel injection control device for an internal combustion engine. A fuel injection control device for an internal combustion engine according to claim 4,
The internal combustion engine includes a catalyst temperature detector that detects the temperature of the catalyst,
When the temperature of the catalyst detected by the catalyst temperature detector is equal to or lower than the third judgment temperature which is equal to or lower than the first judgment temperature when the return rotation speed is set to the second return rotation speed, the Continuing the fuel cut until the engine rotation speed decreases to the first return rotation speed;
A fuel injection control device for an internal combustion engine.

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