JP2965797B2 - Abnormality detection device for fuel supply system of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an abnormality in a fuel supply system of an internal combustion engine, and more particularly to an air-fuel ratio correction which is set according to an output value of an exhaust gas concentration detector provided in an exhaust system of the internal combustion engine. The present invention relates to an abnormality detection device for a fuel supply system of an internal combustion engine that detects an abnormality that has occurred in a fuel supply system based on an average value of coefficients.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting an abnormality in a fuel supply system of an internal combustion engine, that is, a clogging of a fuel injection valve, a foreign substance bite or a deviation from a controllable range of a fuel supply amount due to aging, for example, Japanese Unexamined Patent Application Publication No. 3-249348
Was disclosed in Japanese Patent Publication No.

[0003] The fuel supply system abnormality detection device disclosed in this publication initializes the previous value of the abnormality determination coefficient KO2AVE calculated based on the air-fuel ratio correction coefficient KO2 for correcting the amount of fuel supplied to the internal combustion engine. Calculating a learning average of the KO2 value as a value, and determining that an abnormality has occurred in the fuel supply system when the current value of the KO2AVE calculated based on the learning average exceeds a predetermined range. It is.

Further, in the device disclosed in this publication, the air-fuel ratio fluctuates due to the effect of vapor supplied to the intake system of the engine, and the KO2AVE value becomes smaller. Thus, the fuel supply system is abnormal although it is normal. In consideration of the possibility of erroneous detection, when the engine operation area such as the engine speed is within a specific area and the fuel supply system failure diagnosis condition is satisfied, the vapor engine A means for performing a purge cut for stopping the supply (purge) to the intake system is provided. During the purge cut, the abnormal determination target coefficient KO2AVE is calculated.

[0005]

However, in the fuel supply system abnormality detecting device disclosed in the above publication, the purge cut needs to be performed every time the failure diagnosis condition is satisfied. In addition, torque fluctuations occur in the engine due to fluctuations in the air-fuel ratio due to the purge cut.

That is, if a purge cut is performed while a large amount of vapor is being purged, the fuel correction by the air-fuel ratio correction coefficient KO2 cannot keep up with the air-fuel ratio that sharply leans thereafter, and a rapid change in the air-fuel ratio may occur. As a result, there is a problem that the engine vibrates to deteriorate the drivability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an abnormality detection device for a fuel supply system of an internal combustion engine that can prevent erroneous detection due to purge and prevent deterioration in operability due to purge cut. And

[0008]

According to a first aspect of the present invention, an exhaust gas concentration detecting means provided in an exhaust system of an internal combustion engine and an internal combustion engine based on an output of the exhaust gas concentration detecting means are provided. Air-fuel ratio correction coefficient calculating means for calculating an air-fuel ratio correction coefficient for correcting an amount of fuel supplied to the engine so that the air-fuel mixture supplied to the engine has a predetermined air-fuel ratio; and an operation for detecting an operation state of the internal combustion engine. State detection means, average value calculation means for calculating an average value of the air-fuel ratio correction coefficient when the internal combustion engine is in a predetermined operation state by the operation state detection means, Abnormality determining means for determining that the fuel supply system of the engine is abnormal when exceeding a range defined by predetermined upper and lower limits; and intake air for the internal combustion engine of fuel vapor generated in the fuel tank. An abnormality detection device for a fuel supply system of an internal combustion engine having a purge control unit that controls supply to the internal combustion engine, wherein the average value calculation unit includes a predetermined average value of the calculated correction coefficient that is larger than the predetermined lower limit value. When the value is smaller than the threshold value, an instruction to stop the supply of the fuel vapor is issued,
The purge control means includes a purge cut means for stopping the supply of the fuel vapor based on an instruction to stop the supply of the fuel vapor.

In a second aspect based on the first aspect, the average value of the air-fuel ratio correction coefficient calculated by the average value calculating means is set to the predetermined threshold after the supply of the evaporated fuel is stopped by the purge cut means. When the value is larger than the above, an abnormality detection stopping means for giving an instruction to stop the purge cut and stopping the abnormality detection of the fuel supply system is provided.

[0010]

[0011]

According to the first aspect of the present invention, the supply of evaporative fuel is cut off only when the average value of the air-fuel ratio correction coefficient is smaller than a predetermined value, so that erroneous detection due to the effect of the evaporative fuel is accurately prevented. In addition, unnecessary supply of fuel vapor is not cut off.

According to the second aspect of the invention, when the average value exceeds a predetermined value after the supply of evaporative fuel is cut off in the first aspect, the abnormality detection of the fuel system is interrupted. In addition to preventing erroneous detection due to the influence, the interruption of the evaporated fuel is not performed according to the instruction of the abnormality detection device after the interruption, so that the fluctuation of the engine torque due to the switching between the shutoff / execution of the evaporated fuel is prevented.

[0013]

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device including a fuel supply system abnormality detection device according to an embodiment of the present invention. 1 shows a four-cycle internal combustion engine of a type in which six cylinders are arranged. A throttle body 3 is provided in the middle of an intake pipe 2 of an engine 1 and a throttle valve 3 ′ is disposed inside the throttle body 3. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 ′, and outputs an electric signal corresponding to the opening of the throttle valve 3 ′ to an electronic control unit (hereinafter referred to as “ECU”) 5. Supply.

A fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 'and slightly upstream of an intake valve (not shown) in the intake pipe 2. Each injection valve is provided via a fuel pump 7. Connected to the fuel tank 8 and the ECU
The valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

On the other hand, immediately downstream of the throttle valve 3 ', an intake pipe absolute pressure (PBA) sensor 10 is provided via a pipe 9. The absolute pressure signal converted into an electric signal by the absolute pressure sensor 10 is It is supplied to the ECU 5. Further, an intake air temperature (TA) sensor 11 is mounted downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies the electric signal to the ECU 5.

An engine water temperature (Tw) sensor 12 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects an engine water temperature (cooling water temperature) Tw, outputs a corresponding temperature signal, and supplies it to the ECU 5. Engine speed (Ne)
The sensor 13 and the cylinder discrimination (CYL) sensor 14 are mounted around a camshaft (not shown) of the engine 1 or around a crankshaft. The engine speed sensor 13 is the engine 1
A signal pulse (hereinafter referred to as a "TDC signal pulse") is output at a predetermined crank angle position every time the crankshaft rotates 180 degrees, and the cylinder discriminating sensor 14 outputs a signal pulse at a predetermined crank angle position of a specific cylinder. These signal pulses are supplied to the ECU 5.

The three-way catalyst 15 is disposed in the exhaust pipes 17 of the exhaust pipes 16L and 16R provided respectively in the left and right cylinder groups of the engine 1, and HC, CO, N in the exhaust gas.
Purify components such as Ox. O ₂ sensors 18L and 18R as exhaust gas concentration detectors are respectively mounted on the exhaust pipes 16L and 16R for each of the left and right cylinder groups, and detect the oxygen concentration in the exhaust gas for each of the left and right cylinder groups and detect the respective detected values. And outputs the signal to the ECU 5. The ECU 5
Is connected to an LED (Light Emitting Diode) 19 for issuing a warning when an abnormality in the fuel supply system is detected by the method shown in FIG.

Between the upper part of the sealed fuel tank 8 and the intake pipe 2 immediately after the throttle valve 3 ', a two-way valve 20 and a canister 2 constituting a fuel evaporative emission control device are provided.
1. A purge control valve 22 is provided. Purge control valve 22
Is connected to the ECU 5 and is controlled by a signal from the ECU 5. That is, when the evaporative gas generated in the fuel tank 8 reaches a predetermined set pressure, it pushes open the positive pressure valve of the two-way valve 20, flows into the canister 21, and is stored. ECU5
When the purge control valve 22 is opened in response to a control signal from the engine, the evaporative gas temporarily stored in the canister 21 is
Is sucked into the intake pipe 2 together with the outside air sucked from the outside air intake port provided in the canister 21 and sent to the cylinder. When the fuel tank 8 is cooled by the influence of the outside air and the negative pressure in the fuel tank increases, the two-way valve 20
, And the evaporative gas temporarily stored in the canister 21 is returned to the fuel tank 8. In this way, the fuel evaporative gas generated in the fuel tank 8 is prevented from being released to the atmosphere.

The ECU 5 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, and converts an analog signal value to a digital signal value. 5b, storage means 5c for storing various calculation programs executed by the CPU 5b, calculation results, and the like, the fuel injection valve 6, the purge control valve 22, an output circuit 5d for supplying a drive signal to the LED 19, and the like. Is done.

The CPU 5b determines various engine operating states such as a feedback control operating area and an open loop control operating area according to the oxygen concentration in the exhaust gas based on the above-mentioned various engine parameter signals, and responds to the engine operating state. Based on the following equation (1), the fuel injection time TOUT of the fuel injection valve 6 synchronized with the TDC signal pulse
Is calculated.

TOUT = Ti × K ₁ × KO ₂ + K ₂ (1) Here, Ti is a reference value of the injection time TOUT of the fuel injection valve 6 and depends on the engine speed Ne and the intake pipe absolute pressure PBA. It is read from the set Ti map.

KO ₂ is an air-fuel ratio feedback correction coefficient, which is set in accordance with the oxygen concentration in the exhaust gas detected by the O ₂ sensors 18L and 18R during feedback control. In the control operation region, it is a coefficient set according to each operation region. The correction coefficient KO ₂ is set for each of the left and right cylinder groups. For example, the correction coefficient KO ₂ R of the right cylinder group is obtained by adding a well-known proportional term (P term) when the output level of the O ₂ sensor 18R of the right cylinder group is inverted. When the output level is not inverted, it is calculated by integration control by addition of a well-known integration term (I term).
37633, JP-A-63-189639, etc.). The correction coefficient KO ₂ L for the left cylinder group is calculated in the same manner as described above based on the output voltage of the O ₂ sensor 18L for the left cylinder group.

K ₁ and K ₂ are other correction coefficients and correction variables calculated in accordance with various engine parameter signals, respectively. Optimization of various characteristics such as a fuel consumption characteristic and an engine acceleration characteristic according to an engine operating state is performed. The predetermined value is determined as shown.

The CPU 5b supplies a drive signal for opening the fuel injection valve 6 to the fuel injection valve 6 via the output circuit 5d based on the fuel injection time TOUT obtained as described above.

FIGS. 2 and 3 show a flowchart of a program for detecting an abnormality in the fuel supply system to which the present invention is applied.
b.

In FIG. 2, first, in step 101,
It is determined whether or not a flag FFMPASS indicating that fuel supply system abnormality detection (monitoring) should be performed is "1" is "1", and the answer is affirmative (YES), that is, the fuel supply system abnormality detection is performed. If there is no instruction to perform, the process proceeds to step 102.

In step 102, a monitor condition duration timer tCON for setting a duration of a monitor condition described later.
T, a post-purge cut stabilization timer tFMPGS for setting a post-purge cut stabilization time, and an air-fuel ratio correction coefficient K
A KAV calculation timer tCHKAVE for setting the calculation time of the integrated value KAV of O2 is initialized to a predetermined value and started. Note that these timers are constituted by down counters.

In the following step 103, it is determined whether or not a flag FPGSCNT indicating by "1" that purge cutting should be performed to detect an abnormality in the fuel supply system is "0". The flag FPGSCNT is used in a process of calculating an abnormally determined coefficient KO2AVE, which will be described later, and is a flag for executing a purge cut when a purge cut instruction for eliminating erroneous detection due to the influence of the purge is issued. (Set to “1” in step 220 described later.)

If the answer to step 103 is affirmative (YES), that is, if the flag FPGSCNT is "0" and the purge cut has not been performed, this routine is terminated. When the answer is negative (NO), that is, when the purge cut is performed, the flag FPGS indicating that purge control should be performed is set to “1” and the flag FPGSCNT is set to “0”. After the setting, the process is returned so that the purge can be performed again, and the present routine is terminated (step 104).

On the other hand, if the answer in step 101 is negative (N
O), that is, when an instruction to detect an abnormality in the fuel supply system is issued, the determination processes of steps 105, 106, and 107 are sequentially performed. That is, in step 105, it is determined whether or not a flag FFMPGPASS indicating "1" indicating that monitoring should be prohibited to eliminate erroneous detection due to the influence of the purge is "1". This flag FFMPG
PASS is set to “1” in step 120 described later.

In step 106, it is determined whether or not a flag FFMNG indicating an abnormality of the fuel supply system by "1" is "1". This flag FFMNG is set to “1” when an abnormality of a fuel supply system described later is determined (step 113 described later).

In step 107, this monitor is
Since the detection is performed using the two sensors 18L and 18R, it is determined whether or not the O2 sensors 18L and 18R are abnormal.

If at least one of the results of these determination processes is affirmative (Y
ES), that is, when the flag FFMPGPASS = "1", the flag FFMNG = "1", or when the O2 sensor is abnormal, the processing of steps 102, 103, and 104 is described assuming that the abnormality detection of the fuel supply system is not performed. Execute similarly.

Steps 105 to 107
If the answer is all negative (NO), that is, the flag FFMPGPASS = "0" and the flag F
If FMNG = “0” and the O2 sensor is not abnormal, the process proceeds to the next step 108 assuming that abnormality of the fuel supply system is to be detected, and the process of calculating an abnormal determination coefficient KO2AVE shown in a subroutine described later is performed.

After the process of calculating the abnormal determination target coefficient KO2AVE in step 108, the process proceeds to step 109. In step 109, the abnormal determination target coefficient KO
Flag FKO indicating that 2AVE has been calculated by "1"
It is determined whether or not 2AVECHK is "1". If the answer is negative (NO), that is, if the abnormal determination coefficient KO2AVE has not been calculated, this routine ends. When the answer is affirmative (YES), that is, when the abnormal discrimination coefficient KO2AVE has been calculated, the process proceeds to step 111 in FIG. 3, and the calculated abnormal discrimination coefficient KO2AVE is calculated as the KO2AVE.
It is determined whether or not the value is larger than the upper limit value KO2AVEFSH.

If the answer to the determination in step 111 is affirmative (Y
ES), that is, the abnormal discrimination coefficient KO2AVE is
If it is larger than the upper limit of the AVE value, it is determined that there is an abnormality in the fuel supply system, and in step 112, the flag FFMPGS indicating that purge cut should be performed is set to "0". At 113, the flag F
FMNG is set to "1" and this routine ends.

If the answer to the determination in step 111 is negative (NO), the flow proceeds to step 114. In step 114, it is determined whether or not the current KO2AVE value is smaller than a threshold value KO2AVEPGL for determining whether there is a possibility of erroneous detection due to the influence of the purge. Here, the threshold value KO2AVEPGL is KO2AVEPGL as shown in FIG.
It is set slightly larger than the lower limit value KO2AVEFSL of the 2AVE value. This is because if the threshold value KO2AVEGPL is set to the same value as the lower limit value KO2AVEFSL, the fuel supply system may be determined to be abnormal before the fluctuation of the KO2AVE value occurs when a purge cut described later is performed.

If the answer to the determination in step 114 is affirmative (YE
S), that is, when it is determined that the KO2AVE value is smaller than the threshold value KO2AVEGPL (A1 in FIG. 8) and there is a possibility of erroneous detection due to the influence of the purge, the process proceeds to step 115, and the flag FFMPGS is set to “1”. Instruct the next monitor to perform a purge cut (this purge cut is performed in steps 219 and 220 described later). As described above, by performing the purge cut only when the abnormality determination coefficient KO2AVE falls below the threshold value KO2AVEGPL, not only the erroneous detection due to the influence of the purge can be accurately prevented, but also unnecessary purge cut is not performed. This eliminates the need to perform frequent purge cut / purge switching as in the related art, thereby preventing deterioration in drivability.

Next, the routine proceeds to step 116, where KO2AV
E value is lower limit value KO2AVEFSL of the KO2AVE value
It is determined whether the answer is affirmative (YE
S), that is, the KO2AVE value is the lower limit value KO2AVEFSL
If it is smaller than this, it is determined that there is an abnormality in the fuel supply system, and the routine is terminated through the processing of steps 112 and 113. The answer is negative (NO), ie KO2
If the AVE value is larger than the lower limit value KO2AVEFSL, it is determined that there is no abnormality in the fuel supply system, and the flag F indicating "1" indicating that there is no abnormality in the fuel supply system in step 117.
FMOK is set to "1", and this routine ends.

On the other hand, in the next monitor, step 114 is executed.
Is negative (NO), that is, KO2
If the AVE value is larger than the threshold value KO2AVEPGL (the KO2AVE value increases due to the previous purge cut; A2 in FIG. 8), the process proceeds to step 118, and whether the purge cut was instructed last time (step 115) is determined. And the answer is affirmative (YES), that is, the flag F
If FMPGS is “1” and the previous purge cut was instructed, the flag FFMPGS is set to “0” in step 119 and the purge cut is stopped (A in FIG. 8).
3).

In such a case, the execution of the monitor is judged to be in a state where accurate monitoring cannot be performed due to the influence of the purge (the reason will be described later with reference to FIG. 9). FFMPGPA
SS is set to “1”, and an instruction to prohibit monitoring is issued (A4 in FIG. 8). Thereafter, the routine proceeds to step 116, and after the same processing as described above, the present routine ends.

The abnormality detection routine of the fuel supply system is as follows.
First, after the operation is performed in the right cylinder group, the left cylinder group is similarly executed.

Next, referring to the flow charts of FIGS. 4 to 7, the abnormal discrimination coefficient KO2A in step 108 will be described.
A detailed calculation method of VE will be described.

In FIG. 4, first, in step 201,
It is determined whether the engine operation is in the specific operation region.
That is, when the engine speed Ne is equal to the lower limit speed NEAVEL (for example, 15
04 rpm) and the upper limit rotational speed NAVEL (for example, 2496 rpm) (the upper and lower limit rotational speeds may be set to different values for AT and MT vehicles), and the absolute pressure PBA in the intake pipe is lower than the lower limit pressure PBAVEL.
(Eg 263mmHg) and upper limit pressure PBAVEH (eg 435mmHg)
(The upper and lower pressures may be set to different values for the AT and MT vehicles), and the intake air temperature TA is set to the lower limit temperature TAAVEL (for example, 20 ° C.) and the upper limit temperature TWAVEH (for example, 70 ° C.). And the engine coolant temperature Tw is between the lower limit temperature TAAVEL (for example, 70 ° C.) and the upper limit temperature (for example, 90 ° C.)
The vehicle speed V is between the lower limit speed VAVEL and the upper limit speed VAVEH, and the throttle valve opening θTH is equal to the lower limit opening θTHAV.
It is assumed that the engine is in the specific operation range when it is between EL and the upper limit opening θTHAVEH.

If the answer to step 201 is affirmative (YES), that is, if the engine operation is in the specific operating region, step 2
Proceeding to 02, it is determined whether the air-fuel ratio feedback control is being performed. Step 201 or step 202
Is negative (NO), that is, when the engine operation is not in the specific operation range, or when the air-fuel ratio feedback control is not performed, the calculation of the air-fuel ratio correction coefficient KO2 according to the outputs of the O2 sensors 18L and 18R is performed. Not done, so K
The processing of steps 203 to 209 shown in FIG. 5 is performed without executing the O2AVE value calculation processing, and the present subroutine ends.

That is, in steps 203 to 205, the monitor condition duration timer tCONT, the purge cut stabilization timer tFMPGS, and the KAV calculation timer tCHKAVE are sequentially initialized to predetermined values and started. Further, at step 206, the flag F
KO2AVECHK is set to “0”, and it is determined in the following step 207 whether or not the flag FPGSCNT is “0”. If the answer is negative (NO), that is, if the flag FPGSCNT is not "0", the process proceeds to step 208, and the flag FPGS is set to "1".
The flag FPGSCNT is returned to "0", and in step 209, the flag FVO2ST is set to "0", and this subroutine is terminated. Here, the flag FVO2ST is
O2 sensor 18L (or 18R) in another control routine
Is set to "1" when the output value VO2 is inverted (set to "1" in step 217 described later). If the answer to the step 207 is affirmative (YES), that is, if the flag FPGSCNT is "0", the step 208 is skipped, and the subroutine is terminated via the step 209.

Returning to FIG. 4, if the answer to step 201 and step 202 is affirmative (YES), that is, if the engine operation is in the specific operation range and the air-fuel ratio feedback control is being performed, the routine proceeds to step 210, where the flag FK is set.
It is determined whether or not O2AVECHK is “1”. If the answer is negative (NO), that is, the flag FKO2AVECHK
Is 0 "and the abnormal discriminated coefficient KO2AVE has not been calculated yet, the routine proceeds to the next step 211, where the timer tC
It is determined whether or not ONT is “0”.

If the answer to step 210 is affirmative (YE
S), that is, if the flag FKO2AVECHK is "1" and the KO2AVE value has already been calculated, or the answer to step 211 is negative (NO), that is, the timer tCONT
Is not "0", the processing of the steps 207 to 209 is performed in the same manner, and this subroutine is terminated.

If the answer to step 210 is negative (NO),
That is, if the KO2AVE value has not been calculated and the answer to step 211 is affirmative (YES), that is, if the timer tCONT is "0" and the air-fuel ratio feedback control state in which the engine operation is in the specific operation area has continued for a predetermined time, ,
Since the monitoring condition is satisfied, the process of calculating the abnormal discriminated coefficient KO2AVE is actually performed in step 212 and subsequent steps.

First, at step 212, the flag F
It is determined whether or not FMPGS is “1”. The first time,
Since the answer is negative (NO), that is, the flag FFMPGS is "0" and no purge cut instruction has been issued, the process proceeds to step 213 in FIG.

In FIG. 6, in step 213, it is determined whether or not the timer tFMPGS has become "0", and the answer is negative (NO), that is, the timer tFMPGS started in step 205 becomes "0". If not, the process proceeds to step 214 on the assumption that the predetermined time has not elapsed since the start of the purge. In this step 214, the flag FVO2ST is set to "0", and this subroutine ends.

If the answer in step 213 is affirmative (YE
S), that is, if the timer tFMPGS has become "0" and a predetermined time has elapsed since the start of purging, the routine proceeds to step 215, where it is determined whether or not the flag FVO2ST is "1". In the first time, the answer is negative (NO), that is, since the flag FVO2ST is “0” and the inversion of the VO2 value has not been confirmed, it is determined in step 216 whether or not the VO2 value has been inverted. The answer is negative (N
O), that is, if the VO2 value has not been inverted, this subroutine is terminated. If affirmative (YES), that is, the VO2 value has been inverted, the flag FV is determined in step 217.
O2ST is set to "1", and the current KO2 value is set as the initial value of the integrated value KAV in step 218, and this subroutine is terminated.

Returning to FIG. 4, after the second time, the answer to step 212 is affirmative (YES), that is, the flag FFM
If the PGS becomes “1” and a purge cut instruction for eliminating erroneous detection due to the influence of the purge is issued, the process proceeds to step 219. In this step 219, it is determined whether or not the flag FPGS is "1". The answer is affirmative (YES), that is, the flag FPGS is "1" despite the fact that the purge cut instruction has been issued. If the purge cut has not been performed, the process proceeds to step 220.

In step 220, the flag FPGS
Is set to "0" to instruct purge cut, and the flag FPGSCNT is set to "1" to execute purge cut. Then, the routine proceeds to step 213 shown in FIG. If the answer to step 219 is negative (NO), and the purge cut has been performed according to the purge cut instruction, the process proceeds directly to step 213. In this step 213,
After performing the same processing as described above, the process proceeds to step 215.

In the determination of step 215, VO2
If the value is inverted, the flag FVO2ST is "1", so the answer is affirmative (YES), that is, the inversion of the VO2 value is confirmed, and the routine proceeds to step 221 and again VO2
It is determined whether or not the two values are inverted. The answer is affirmative (YES), i.e. VO2 value is inverted, the following equation when the air-fuel ratio feedback correction coefficient KO ₂ is calculated by the proportional control by adding process known proportional term (P term) (2)
Integral value KAV a learned average value of the correction coefficient KO ₂ based on the calculated (steps 222).

[0058]

(Equation 1) However, CO ₂ AV is a variable that is set to a relatively large value in 1 to 100H in order to improve the followability to the change of the correction coefficient KO ₂ in the specific operation region, and KAV ′ is the last variable of the integral value KAV. The initial value is the last KO2 obtained and stored the last time the engine was in the specified operating area.
When the vehicle enters the specific operation region for the first time after starting the engine, the initial value of the coefficient KO2AVE is used.

If the answer in step 221 is negative (N
O), that is, if the VO2 value is not inverted, the step 222 is skipped, and the previous value is adopted as the integral value KAV.

In the following step 223, the timer tCHK
It is determined whether or not AVE is "0". If the answer is negative (NO), that is, if the timer tCHKAVE is not "0", this subroutine is terminated. If the answer is affirmative (YES), that is, if the timer tCHKAVE becomes “0” and the calculation of the KAV value has been performed for a predetermined time, FIG.
Go to step 224.

In step 224, it is determined whether or not the integrated value KAV thus determined is larger than the value obtained by adding the aging change deviation ΔKO ₂ AVE (for example, 800H) to the previous KO ₂ AVE value. The initial value of the coefficient KO ₂ AVE is a known average value K REF of KO ₂ determined by another control routine. If the answer to this step 224 is affirmative (Yes), the current value of the abnormal discrimination coefficient KO ₂ AVE is calculated and updated based on the following equation (3) (step 225).

KO ₂ AVE = KO ₂ AVE ′ + α × ΔKO ₂ AVE (3) where KO ₂ AVE ′ indicates the previous value of the coefficient KO ₂ AVE, and the coefficient α on the right side is a coefficient set according to the operation state. (≦ 1.0), for example, set to 0.5.

Next, at step 226, the flag FKO ₂ AVERCHK
Is set to 1 and the process proceeds to step 227. In this step 227, it is determined whether or not the flag FPGSCNT is "0". If the answer is affirmative (YES), that is, if the purge cut for detecting an abnormality in the fuel supply system has not been performed, the main routine proceeds to step 227. The subroutine ends, and the answer is negative (N
O), that is, when the purge cut for detecting the abnormality of the fuel supply system has been performed, the process proceeds to step 228.

In step 228, the flag FPGS
Is set to “1” and the flag FPGSCNT
Is set to "0", the purge is returned to the original state, and this subroutine is terminated.

If the answer to step 224 is negative (No), it is determined whether or not the integrated value KAV is smaller than a value obtained by subtracting the aging difference ΔKO ₂ AVE from the previous KO ₂ AVE value (step). 229). This answer is affirmative (Yes)
If so, the current value of the abnormal discrimination coefficient KO ₂ AVE is calculated and updated based on the following equation (4) (step 230).

KO ₂ AVE = KO ₂ AVE′−α × ΔKO ₂ AVE (4) Thereafter, the processing of steps 226, 227, and 228 is performed in the same manner as described above, and the present subroutine ends. If the answer to step 229 is negative (NO), step 230 is skipped and the present subroutine ends.

FIG. 9 shows the KO2 value at the time of the purge cut,
It is a figure showing a change situation of a KAV value and a KO2AVE value.

In the figure, until the purge cut,
The KO2 value is slightly moving below the threshold value KO2AVEGPL, and accordingly, the KO2AVE value is also reduced to the threshold value KO2AVE.
Below PGL. However, when the purge cut occurs, the KO2 value fluctuates greatly in excess of the threshold value KO2AVEGPL in a short time, while the KO2AVE value takes a long time to calculate and cannot quickly follow the fluctuation (shift upward in B1 in FIG. 9). Do). Accordingly, the integral values KAV and KO2 located substantially at the center of the fine movement range of the KO2 value
The deviation B2 from the AVE value increases. As described above, if the KO2 value fluctuates extremely during the purge cut, accurate monitoring can no longer be performed due to the influence of the purge. Therefore, the purge cut is stopped and the purge is restarted. Is prohibited (step S120). As a result, the reliability of the abnormality detection is improved, and the purge cut is not performed according to the instruction of the abnormality detection device after the monitoring is prohibited, so that the deterioration of the operability due to the switching of the purge cut / purge is prevented.

By the way, at the time of switching between purge cut / purge in the above-described abnormality detection processing of the fuel supply system,
Since the air-fuel ratio fluctuates, drivability is expected to deteriorate. Therefore, in the present embodiment, a function is provided for suppressing fluctuations in the air-fuel ratio when the purge cut / purge is switched. Hereinafter, this point will be described with reference to FIGS.
This will be described with reference to FIG.

In step 115 of FIG. 3, the flag FFMPGS is set to "1" and an instruction is issued to execute a purge cut in the next monitor.
In step 220, the flag FPGS is set to "0" and the process is executed. At this time, the ECU 5 sets the purge control valve 22
Is closed to cut off the supply of vapor to the intake pipe 2. Thereafter, in step 228, the flag FPGS is returned to "1" and the purge is opened. At this time, the ECU
5 opens the purge control valve 22 to supply vapor to the intake pipe 2.

FIG. 10 is a flowchart of the purge control when the purge control valve 22 is a duty solenoid valve.

In the figure, first, in step 301,
It is determined whether or not the flag FPGS is set to “0”, and the answer is affirmative (YES), that is, the flag FPGS
Is set to “0” and a purge cut instruction is issued, in subsequent steps S302 to 304,
At a timing when the correction of the KO2 value is sufficiently in time, the duty ratio DUTY is gradually reduced to a predetermined value DERDUTY, set to "0", and the purge control valve 22 is closed.

Thereafter, if the answer to step 301 is negative (NO), that is, if the flag FPGS becomes "1" and the purge is opened again, steps S305 to S306 are executed.
And the duty ratio DUTY until the target duty ratio is reached.
Is gradually increased to DELDUTY, and the purge control valve 22 is opened. Thereby, as is clear from FIG. 11, the fluctuation of the air-fuel ratio A / F is suppressed.

FIG. 12 is a flowchart of the purge control when the purge control valve 22 is an on / off solenoid valve.

In the figure, first, at step 401,
It is determined whether or not the flag FPGS is set to “0”, and the answer is affirmative (YES), that is, the flag FPGS
Is set to “0” and a purge cut instruction is issued, in subsequent steps 402 and 403,
At the same time that the purge control valve 22 is closed, the KO2 value is set to × 1.
After returning to 0 (corresponding to the stoichiometric air-fuel ratio), the air-fuel ratio feedback control is continued.

Thereafter, when the answer to step 401 is negative (NO), that is, when the flag FPGS becomes "1" and the purge is opened again, the purge control valve 22 is opened in steps 404 and 405 at the same time. K
The O2 value is set to the cruise learning value KREF1, and the air-fuel ratio feedback control is continued. As a result, FIG.
As is apparent from the above, the fluctuation of the air-fuel ratio A / F is suppressed.

[0077]

As described above, according to the first aspect, the exhaust gas concentration detecting means provided in the exhaust system of the internal combustion engine, and the exhaust gas concentration is supplied to the internal combustion engine based on the output of the exhaust gas concentration detecting means. Air-fuel ratio correction coefficient calculating means for calculating an air-fuel ratio correction coefficient for correcting the amount of fuel supplied to the engine such that the air-fuel mixture has a predetermined air-fuel ratio; and operating state detecting means for detecting an operating state of the internal combustion engine. Average value calculating means for calculating an average value of the air-fuel ratio correction coefficient when the operating state detecting means detects that the internal combustion engine is in a predetermined operating state; Abnormality determining means for determining that the fuel supply system of the engine is abnormal when the value exceeds a range determined by a value;
A purge control unit for controlling supply of evaporative fuel generated in a fuel tank to an intake system of the internal combustion engine, wherein the average value calculating unit includes the calculated correction value. When the average value of the coefficient is smaller than a predetermined threshold value that is larger than the predetermined lower limit value, an instruction to stop the supply of the evaporated fuel is issued, and the purge control unit performs the operation based on the instruction to stop the supply of the evaporated fuel. Since the purge cut means for stopping the supply of fuel is provided, it is possible to prevent an erroneous detection due to the supply of the evaporated fuel in the abnormality determination of the fuel supply system, and to stop the supply of the evaporated fuel only when necessary for the abnormality determination. As a result, it is possible to prevent the operability of the engine from deteriorating due to a rapid change in the air-fuel ratio.

According to a second aspect, in the first aspect, after the supply of the evaporated fuel is stopped by the purge cut means, the average value of the air-fuel ratio correction coefficient calculated by the average value calculation means is set to the predetermined threshold value. When it is larger than the above, an abnormality detection stopping means for giving an instruction to stop the purge cut and stopping the abnormality detection of the fuel supply system is provided, so that the erroneous detection of the abnormality determination of the fuel supply system due to the supply of the evaporated fuel is accurately performed. In addition to the prevention, the frequency of stopping the supply of the evaporated fuel can be further reduced, so that the deterioration of the operability of the engine can be prevented.

[0079]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel supply control device including an abnormality detection device according to an embodiment of the present invention.

FIG. 2 is a flowchart of an abnormality detection program.

FIG. 3 is a flowchart of an abnormality detection program.

FIG. 4 is a detailed program flowchart of step 108 shown in FIG. 2;

FIG. 5 is a flowchart that follows the detailed program of step 108 shown in FIG. 2;

FIG. 6 is a flowchart of a detailed program of step 108 shown in FIG. 2;

FIG. 7 is a continued flowchart of the detailed program of step 108 shown in FIG. 2;

FIG. 8 is an abnormal discrimination coefficient KO2AV due to the influence of purge.
FIG. 9 is a diagram showing a change in E.

FIG. 9 shows KO2 value, KAV value and KO at the time of purge cut.
It is a figure showing a 2AVE value fluctuation situation.

FIG. 10 is a flowchart of the purge control when the purge control valve 22 is a duty solenoid valve.

FIG. 11 is a diagram showing the effect of the purge control shown in FIG.

FIG. 12 is a flowchart of purge control when the purge control valve 22 is an on / off solenoid valve.

FIG. 13 is a diagram showing the effect of the purge control shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake pipe 5 ECU 6 Fuel injection valve 18L Left cylinder group side O2 sensor 18R Right cylinder group side O2 sensor

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroshi Maruyama 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-3-249348 (JP, A) JP-A Heisei JP-A-2-33443 (JP, A) JP-A-2-33442 (JP, A) JP-A-61-43236 (JP, A) JP-A-63-1753 (JP, A) JP-A-63-8833 (JP, A) A) JP-A-63-113158 (JP, A) JP-A-63-85237 (JP, A) JP-A-4-318251 (JP, A) JP-A-5-163983 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) F02D 41/02 F02D 41/14 310 F02D 41/22 F02M 25/08

Claims (2)

(57) [Claims] An exhaust gas concentration detecting means provided in an exhaust system of an internal combustion engine, and an engine is provided such that an air-fuel mixture supplied to the internal combustion engine has a predetermined air-fuel ratio based on an output of the exhaust gas concentration detecting means. Air-fuel ratio correction coefficient calculating means for calculating an air-fuel ratio correction coefficient for correcting the supplied fuel amount,
Operating state detecting means for detecting an operating state of the internal combustion engine; and average value calculating means for calculating an average value of the air-fuel ratio correction coefficient when the operating state detecting means detects that the internal combustion engine is in a predetermined operating state. Abnormality determination means for determining that the fuel supply system of the engine is abnormal when the average value of the correction coefficients exceeds a range defined by predetermined upper and lower limits ; An abnormality detection device for a fuel supply system of the internal combustion engine having purge control means for controlling supply of the evaporated fuel to an intake system of the internal combustion engine, wherein the average value calculation means includes a correction coefficient of the calculated correction coefficient.
The average value is smaller than a predetermined threshold value larger than the predetermined lower limit value
At the time, an instruction to stop the supply of the evaporated fuel is given, and the purge control unit issues an instruction to stop the supply of the evaporated fuel.
An abnormality detection device for a fuel supply system of an internal combustion engine, comprising a purge cut means for stopping supply of evaporative fuel based on the purge cut means. 2. The average value calculating means calculates after the supply of evaporated fuel is stopped by the purge cut means.
When the average value of the air-fuel ratio correction coefficient is larger than the predetermined threshold
Huang, abnormality detection of the fuel supply system of an internal combustion engine according to claim 1, comprising the abnormality detection stopping means for stopping the fuel supply system of the abnormality detecting co If an instruction to stop the purge cut apparatus.