JP2002332890A - Fuel feeding controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel feed controller of an internal combustion engine, capable of preventing catalyst having, in particular a perovskite structure, from deteriorating by limiting the fuel amount increase time. SOLUTION: This fuel feed controller of the internal combustion engine comprises a catalytic converter disposed in the exhaust system of the internal combustion engine; a high-load operating state detection means for detecting the high-load operating state of the internal combustion engine; a catalyst temperature predicating means for predicting the temperature of the catalytic converter, and an air-fuel ratio control means for implementing increase of fuel, when the predicted catalyst temperature is increased to a first temperature or higher and stopping to increase the fuel, when the predicted catalyst temperature is lowered to a second temperature or below lower than the first temperature; and a rich continuation time limiting means, which stops to increase the fuel, even if the predicted catalyst temperature is not lowered, to the second temperature or below, when the predicted catalyst temperature is lower than the first temperature, and the continuation time for increasing the fuel is a specified time or longer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device which suppresses catalyst deterioration in an internal combustion engine having a catalyst disposed in an exhaust system.

[0002]

2. Description of the Related Art In a fuel supply apparatus for an internal combustion engine, when it is determined that the engine is in a high load operation state, the amount of fuel supplied to the internal combustion engine is increased to enrich the air-fuel ratio of an air-fuel mixture to increase the high load operation. It is common practice to increase the output of the internal combustion engine in this state and to suppress the temperature rise of the catalyst for purifying the exhaust gas by lowering the combustion temperature to prevent the deterioration and heat loss of the catalyst.

An example of such an apparatus is disclosed in Japanese Patent Application Laid-Open No.
Japanese Patent No. 205375 discloses a fuel supply control device that executes fuel increase at a time suitable for the temperature of a catalyst by using an estimated catalyst temperature value. According to this, even when it is determined that the engine is in the high load operation state, if the catalyst temperature is low and does not immediately reach the temperature at which the catalyst is likely to deteriorate or lose heat, the fuel increase is not performed. It is possible to prevent catalyst deterioration and heat loss while improving fuel efficiency.

[0004]

In recent years, perovskite oxides have been used as catalysts or cocatalysts. These perovskite-type catalysts have lower durability than conventional noble metal-based three-way catalysts, and the perovskite structure is destroyed when rich operation is continued for a long time, resulting in deterioration of catalyst characteristics. There is.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel supply control device for an internal combustion engine that can prevent deterioration of a catalyst having a perovskite structure in particular by limiting a fuel increase time. I do.

[0006]

SUMMARY OF THE INVENTION The present invention comprises a catalytic converter disposed in an exhaust system of an internal combustion engine, high load operating state detecting means for detecting a high load operating state of the internal combustion engine, and a temperature of the catalytic converter. A catalyst temperature judging means for judging whether or not the fuel temperature is increased when the catalyst temperature becomes equal to or higher than a first temperature, and when the catalyst temperature becomes equal to or lower than a second temperature lower than the first temperature. A fuel supply control device for an internal combustion engine including: an air-fuel ratio control unit that stops increasing the fuel; a measuring unit that measures a time during which the fuel is increased; and a catalyst temperature that is equal to or lower than the second temperature. And a rich continuation time limiter for stopping the fuel increase when the catalyst temperature is lower than the first temperature and the measurement time has reached a predetermined time, even if the fuel supply control device has not reached the first temperature. To provide.

According to the present invention, since the rich operation time for executing the fuel increase is limited by providing the rich continuation time limiting means, the destruction of the perovskite structure due to the enrichment of the air-fuel ratio is prevented even in the catalyst having the structure. Thus, deterioration of the catalyst and, consequently, deterioration of the emission can be prevented.

[0008]

FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as an engine) 1 having a fuel supply control device according to an embodiment of the present invention. Intake pipe to engine 1
In the middle of 2, a throttle valve 3 is arranged. A throttle valve opening (TH) sensor 4 is connected to the throttle valve 3, and outputs an electric signal corresponding to the opening of the throttle valve 3 and supplies it to an electronic control unit (hereinafter referred to as an ECU) 5. The configuration of the ECU 5 will be described later.

The fuel injection valve 6 is electrically connected to the ECU 5, and a signal from the ECU 5 controls a valve opening time of fuel injection. The injected fuel is mixed with air from the intake pipe 2 to form an air-fuel mixture, which is supplied to the engine 1.

The intake pipe 2 has an intake pipe absolute pressure (PBA) sensor 7
And an intake air temperature (TA) sensor 8 for detecting an intake pipe absolute pressure and an intake air temperature, respectively, and supplying them to the ECU 5 as electric signals.

The engine water temperature (TW) sensor 9 mounted on the main body of the engine 1 is composed of a thermistor or the like.
(Cooling water temperature) is detected and supplied to the ECU 5 as an electric signal.

The engine 1 further includes an engine speed (N
E) A sensor 10 and a cylinder determination (CYL) sensor 11 are mounted. The engine speed sensor 10 outputs a pulse (hereinafter referred to as a TDC pulse signal) at a predetermined crank angle position every time the crankshaft of the engine 1 rotates by 180 degrees, and the cylinder determination sensor 11 outputs a predetermined crank angle position of a specific cylinder. Outputs a signal pulse. Both pulses are supplied to the ECU 5.

The ECU 5 is electrically connected to a vehicle speed sensor 20 for detecting a vehicle speed V.

A catalytic converter (hereinafter referred to as a three-way catalyst) 14
Is disposed in the exhaust pipe 13 of the engine 1 and purifies components such as HC, CO, and NOx in the exhaust gas. Three-way catalyst 14
An oxygen concentration sensor 15 (hereinafter, referred to as an O2 sensor) is provided as an air-fuel ratio sensor in the exhaust pipe on the upstream side of. The O2 sensor 15 detects the oxygen concentration in the exhaust gas, outputs an electric signal corresponding to the detected value, and supplies the electric signal to the ECU 5.

The ECU 5 is composed of a computer, which stores a ROM for storing programs and data, a RAM for storing programs and data required at the time of execution to provide an arithmetic work area, a CPU for executing programs, and a CPU for receiving various types of sensors. It has an input interface for processing input signals and a drive circuit for sending control signals to valves and the like. The signals from each of the above-mentioned sensors are received by the input interface and processed according to a program stored in the ROM. In FIG. 1, the ECU 5 is shown by functional blocks based on such a hardware configuration.

The ECU 5 includes functional blocks of operating state detecting means 21, catalyst temperature determining means 22, air-fuel ratio setting means 23, rich continuation time limiting means 24, and fuel injection control means 25.

The operating state detecting means 21 determines various operating states of the engine 1 based on the output of each sensor signal.
When the intake pipe absolute pressure PBA or the throttle valve opening TH exceeds a predetermined value, the operating state detecting means 21
Is determined to be in the high load operation state (WOT).

The catalyst temperature determining means 22 is an operating state detecting means.
The temperature of the three-way catalyst 14 is determined based on the operating state information obtained from 21, and the determined catalyst temperature TCT is returned to the operating state detecting means 21. The catalyst temperature TCT can be determined based on an output of a sensor provided with a temperature sensor in the catalytic converter.

When it is determined that the engine 1 is in the high-load operation state, the operation state detecting means 21 stops the air-fuel ratio feedback control based on the various operation states and changes the engine speed NE and the absolute pressure PBA in the intake pipe. Based on the catalyst temperature TCT, it is determined whether or not to start the fuel increase control based on the temperature.
When the catalyst temperature TCT becomes equal to or higher than a first predetermined value, fuel increase control, that is, enrichment of the air-fuel ratio is started, and when the catalyst temperature TCT becomes equal to or lower than a second predetermined value smaller than the first predetermined value due to the enrichment, the fuel is increased. The increase control is stopped.

The air-fuel ratio setting means 23 sets a target air-fuel ratio according to various operating conditions. When the operating state detecting means 21 determines that the engine 1 is in the high load operating state and executes the fuel increase control, the air-fuel ratio is made rich.

The rich continuation time limiter 24 determines that the fuel temperature will not exceed the first predetermined value and the fuel increase execution time will not exceed the predetermined value even if the catalyst temperature does not fall below the second predetermined value during the fuel increase control. Is reached, the air-fuel ratio setting means 23 is instructed to stop increasing the fuel.

The fuel injection control means 25 is an operating state detecting means.
Engine operating state and air-fuel ratio setting means detected at 21
The fuel injection time is calculated according to the target air-fuel ratio set in 23, and the fuel injection valve 6 is driven.

FIG. 2 is a flowchart showing a process for setting the catalyst temperature determination flag FCATWOT. This series of processing is executed by the ECU 5 at predetermined intervals (in this embodiment, 0.5 sec). The catalyst temperature determination flag FCATWOT is a flag that is set not to increase the amount of fuel when the catalyst temperature is low even in a high-load operation state and there is no danger of the catalyst being deteriorated or thermally damaged immediately.

First, in step 31, it is determined whether or not the engine is in a start mode. If the engine is in the start mode, FCATWOT is set to 1 in step 33, and this processing is terminated.

If it is not the start mode, it is determined in step 32 whether or not a fail-safe (for example, abnormality of the absolute pressure sensor or the like) has been detected. If it has been detected, it is difficult to determine the catalyst temperature in step 34. , Step 33
To set FCATWOT to 1 and end this processing.

In step 34, a subroutine for calculating the catalyst temperature TCT is executed. In this subroutine, the catalyst temperature obtained from the catalyst temperature map value set based on the engine speed NE and the intake pipe absolute pressure PBA is calculated based on the atmospheric pressure, the intake air temperature TA, the water temperature TW, the ignition timing correction amount, etc. And the catalyst temperature TCT is calculated.

In step 35, it is determined whether or not the engine speed NE is equal to or lower than a predetermined speed NECATWO. If it is larger than the predetermined number of revolutions, 1 is set to FCATWOT in step 37, and this processing ends. If the rotation speed is equal to or lower than the predetermined rotation speed, it is determined whether or not the determined catalyst temperature TCT is equal to or higher than the predetermined temperature TCTH (step 36). Hysteresis is added to the predetermined temperature TCTH, and its upper limit is set to 900 ° C. and its lower limit is set to 870 ° C.

When the catalyst temperature TCT is equal to or higher than the upper limit of the predetermined temperature TCTH, the three-way catalyst is in a high temperature state, and it is necessary to enrich the air-fuel ratio to cool the catalyst. It is set (step 37), and the process ends. If the catalyst temperature TCT is lower than the upper limit of the predetermined temperature TCTH, there is no need to cool the catalyst by enrichment,
Set the catalyst temperature determination flag FCATWOT to 0 (step 3
8), this process ends. Once the flag FCATWOT is set to 1, the flag FCATWOT continues to be set to 1 until the catalyst temperature TCT falls below the lower limit of the predetermined temperature TCTH. That is, the flag FCATWOT has a hysteresis function.

Next, a process of calculating the high load increase coefficient KWOT used in the fuel increase control will be described with reference to FIGS. The high load increase coefficient KWOT is the fuel injection control
When calculating the fuel injection amount in 25, this is a coefficient for executing the fuel increase by multiplying the preset basic fuel amount by KWOT.

First, at step 41, a high load increase coefficient map value KWOTMAP is calculated by a map search based on the engine speed NE and the intake pipe absolute pressure PBA.

In step 42, a subroutine for setting a threshold value PBWOT for judging a high load operation state of the engine is executed. This subroutine is executed every time the TDC signal is generated. In this subroutine, a PBWOT table corresponding to the engine speed NE is searched, and the obtained value is corrected by the atmospheric pressure to obtain a threshold value PBWOT.

In step 43, it is determined whether or not traction control is being performed. If YES, a delay timer tmWOTDLY for reducing the preset count value with time is set in step 44. The load determination flag FWOT is set to 0, and the fuel is not increased.

If traction control is not being performed, it is determined in step 45 whether or not fail safe has been detected. If detected, the process proceeds to step 48. If fail-safe has not been detected, in step 46, the threshold value THWOT of the throttle valve opening TH is calculated by searching a THWOT table. The threshold value THWOT is set to a larger value as the engine speed NE is higher.

In step 47, it is determined whether or not the throttle valve opening TH is equal to or less than a threshold value THWOT. If the threshold value is exceeded, it is determined that the vehicle is in the high load operation state, and the process proceeds to a rich continuation time restriction process described later. If the engine speed NE is equal to or less than the threshold value THWOT, the engine speed NE is increased to a predetermined speed NW in step 48.
Judge whether it is OTO or more.

If the engine speed NE is equal to or higher than the predetermined engine speed NWOTO, it is determined in step 49 whether the water temperature TW is equal to or lower than the predetermined water temperature TWWOTE. Hysteresis is added to the predetermined water temperature TWWOTE. In the present embodiment, the upper limit is 105 ° C. and the lower limit is 90 ° C.

If the water temperature TW is lower than the predetermined water temperature, the step
At 50, it is determined whether or not a lean burn operation is being performed. If the lean burn operation is not being performed, it is determined in step 51 whether the intake pipe absolute pressure PBA is equal to or less than the threshold value PBWOT calculated in step 42. Absolute pressure PBA in intake pipe is threshold value PBW
If greater than OT, go to step 54. Absolute pressure in intake pipe
If PBA is equal to or smaller than the threshold value PBWOT, a predetermined time is set in a delay timer tmWOTDLY in step 52.

If the lean burn operation is being performed in step 50, the delay timer tmWOTDLY is set directly without determining the intake pipe absolute pressure PBA. In this case, the high load determination flag FWOT is set to 0 in step 53 of FIG. 4, and the fuel increase control is not performed.

When the engine speed NE is lower than the predetermined speed NWOTO, or when the water temperature TW is higher than the predetermined water temperature TWWOTE, the routine proceeds to step 57 in FIG. Here, the absolute pressure PB in the intake pipe
It is determined whether or not A is equal to or greater than the threshold value PBWOT calculated in step 42.

If the absolute pressure PBA in the intake pipe is not equal to or greater than the threshold value PBWOT, the delay timer tmWOTDLY is set to 0.
(Step 59), set 0 to the high load determination flag FWOT
(Step 60), the fuel increase control is not performed.

If the absolute pressure PBA in the intake pipe is equal to or higher than the threshold value PBWOT, it is determined whether or not the flag FENKWOT which is set to 1 when the vehicle enters the low-load operation state at the time of restart after the engine stall in step 58 is 1. Is determined. Flag FENKWOT
If is not 1, the routine proceeds to step 59 and on, and the fuel increase control is not performed.

If the flag FENKWOT is 1, the water temperature TW is increased to a predetermined water temperature TWWOTO (step 105 in this embodiment) at step 61.
° C) is determined. If the water temperature is equal to or lower than the predetermined water temperature, it is determined in step 62 whether the water temperature increase coefficient KTW is equal to or higher than the high load increase coefficient KWOT.

If the water temperature increase coefficient KTW is equal to or higher than the high load increase coefficient KWOT, the delay timer tmWOTDLY is set to 0 (step 63), the high load determination flag FWOT is set to 1 (step 64), and the fuel increase is performed. Will run.
In this case, the fuel increase coefficient KWOT is set to 1.0 (step 65).

If the engine water temperature is higher than the predetermined water temperature in step 61, or if the water temperature increase coefficient KTW is smaller than the high load increase coefficient KWOT in step 62, step 66
Performs the process of correcting the value of KWOT. The higher the water temperature TW, the higher the KW
OT is corrected to a large value. The fuel increase is performed by multiplying the basic fuel amount by the calculated KWOT.

In step 67, the delay timer tmWOTDLY is set to 0.
, And at step 68, the high load determination flag FWOT is set to 1. Subsequently, at step 69, the water temperature increase coefficient KTW is set to 1.0.
Is set to

Returning to FIG. 3, if the intake pipe absolute pressure PBA is larger than the threshold value PBWOT calculated in step 42 in step 51, the vehicle speed V is increased to a predetermined speed VTMWOT (5 km / h in this embodiment) in step 54. It is determined whether or not this is the case. If the speed is equal to or higher than the predetermined speed, the catalyst temperature determination flag is determined in step 55.
Determine whether FCATWOT is set to 1.

If the catalyst temperature determination flag FCATWOT is 1, it is determined in step 56 whether a value obtained by subtracting the value of the delay timer tmWOTDLY from the predetermined time FF (1.0 second in this embodiment) is equal to or longer than the basic delay time tmWOT. judge. Basic delay time tmW
The OT is obtained by searching a tmWOT table corresponding to the engine speed NE. If the calculated value is equal to or longer than the basic delay time, the process shifts to the rich continuation time limit process of FIG. 5 to execute the fuel increase. The same applies when the vehicle speed V is lower than the predetermined value in step 54.

In step 55, the catalyst temperature determination flag FCATWOT
Is 0, or if the calculated value is smaller than the basic delay time tmWOT in step 56, the FWOT is set to 0 in step 43, so that the fuel increase is not executed.

As described above, when the catalyst temperature is equal to or lower than the predetermined value, there is no need to cool the catalyst by enriching the air-fuel ratio.
No fuel boosting is performed. That is, even if it is determined that the intake pipe absolute pressure PBA is higher than the threshold value PBWOT and the engine is in the high load operation state, if the catalyst temperature TCT is lower than the predetermined temperature TCTH, the ECU 5 performs the processing shown in FIG. Since FCATWOT is set to 0, the high load judgment flag F
WOT is set to 0 and operates so as not to execute fuel increase. When the catalyst temperature TCT becomes equal to or higher than the predetermined temperature TCTH,
The ECU 5 sets the catalyst temperature determination flag FCATWOT to 1,
The high load determination flag FWOT is set to 1 to execute the fuel increase.

Next, the rich duration limiting process will be described with reference to FIG.

In the prior art, the air-fuel ratio is enriched by increasing the fuel so that the catalyst temperature does not exceed the upper limit value of TCTH (for example, 900 ° C.), and the enrichment reduces the catalyst temperature to the lower limit value (for example, 870 ° C.). When it fell, it was controlled to return to the stoichiometric air-fuel ratio. In this technique, as the load increases and the catalyst temperature increases, the duration of the fuel increase (rich operation time) required for the catalyst temperature to decrease to the lower limit value is controlled to be longer.

However, particularly in the case of a catalyst having a perovskite structure, there is a problem that the perovskite structure is destroyed unless the rich operation time is limited to a predetermined time or less, resulting in a reduction in purification performance. Therefore, the rich continuation time limit process described below, even if the catalyst temperature does not fall below the lower limit, if it falls below the upper limit, so as not to continue the rich time more than a predetermined time,
This is for avoiding the destruction of the perovskite structure.

First, at step 70, it is determined whether or not the previous routine was in the high load operation state (WOT). If the current state is the high load operation state, the timer tmWOT2 for rich operation time measurement is started in step 71. Subsequently, the process proceeds to the process after step 62 in FIG. 4, and the fuel increase is started.

Next, when entering the rich continuation time limit process, the process proceeds from step 70 to step 72, and it is determined whether or not the count value of the timer tmWOT2 has exceeded a predetermined value TMWOT2.
The predetermined value TMWOT is set in advance to a time during which the perovskite structure is not destroyed even when the rich operation (fuel increase) is continued. If it does not exceed the predetermined value, the process proceeds to step 62 and subsequent steps.

If the count value of the timer tmWOT2 exceeds the predetermined value TMWOT in step 72, the catalyst temperature TCT is set in step 73.
Is lower than the upper limit temperature (in the present embodiment, 900 ° C.). If not, the routine proceeds to step 62 and thereafter to continue the fuel increase. If it falls below, the timer is reset to 0 in step 74, and the routine proceeds to step 53 in FIG. 4 to stop the fuel increase.

When the count value of the timer tmWOT2 is equal to the predetermined value TMWOT
If the catalyst temperature TCT becomes lower than the lower limit even when the temperature does not reach the lower limit, the process proceeds to NO in step 36 shown in FIG.
Is set to 0, the fuel increase ends.

As described above, in the present invention, when the air-fuel ratio is enriched by increasing the amount of fuel, even if the catalyst temperature does not fall below the predetermined temperature, control is performed so that the rich operation is not continued for more than the predetermined time. Prevents structural destruction.

[0057]

According to the present invention, the rich operation time for executing the fuel increase is limited by the provision of the rich continuation time limiting means. Therefore, even in the case of the catalyst having the perovskite structure, the structure by the air-fuel ratio enrichment is particularly provided. Of the catalyst can be prevented, and the deterioration of the catalyst and the deterioration of the emission can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an internal combustion engine including a fuel supply control device according to one embodiment of the present invention.

FIG. 2 is a flowchart showing a setting process of a catalyst temperature determination flag FCATWOT.

FIG. 3 is a flowchart illustrating a calculation process of a high load increase coefficient KWOT.

FIG. 4 is a flowchart showing a calculation process of a high load increase coefficient KWOT.

FIG. 5 is a flowchart showing a rich continuation time limit process.

[Explanation of symbols]

 1 Internal combustion engine (engine) 5 Electronic control unit (ECU) 6 Fuel injection valve 14 Catalytic converter (three-way catalyst) 21 Operating state detecting means 22 Catalyst temperature judging means 23 Air-fuel ratio setting means 24 Rich continuation time limiting means 25 Fuel injection control means

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) FB12 FC08 GA06 GB00W HA36 HA39 3G301 HA01 HA15 JA02 JA21 JA33 KA09 LB02 MA13 NA08 NB11 NC02 NE01 NE13 NE17 NE19 NE21 NE24 NE26 PA07Z PA10Z PA11Z PD04Z PD12Z PE04Z PE05Z PE08Z PF01Z

Claims (1)

[Claims] A catalytic converter disposed in an exhaust system of the internal combustion engine; a high load operating state detecting means for detecting a high load operating state of the internal combustion engine; and a catalyst temperature determining means for determining a temperature of the catalytic converter. Air-fuel ratio control for executing fuel increase when the catalyst temperature becomes equal to or higher than a first temperature and stopping the fuel increase when the catalyst temperature becomes equal to or lower than a second temperature lower than the first temperature. A fuel supply control device for an internal combustion engine, comprising: a measuring unit configured to measure a time during which the fuel increase is performed; and even when the catalyst temperature does not fall below the second temperature, A fuel supply control device further comprising: a rich continuation time limiter that stops the fuel increase when the temperature is lower than the first temperature and the measurement time reaches a predetermined time.