JPH04237861A - Trouble detector for evaporative purge system - Google Patents

Abstract

PURPOSE:To provide such a trouble detector that adsorbs vapor to an adsorbent in a canister at trouble detection surely, and besides, the irreducible minimum of a requisition. CONSTITUTION:A purge trouble is judged on the basis of purge gas density at each time of purge stoppage and execution with a density detecting means 15. A purge stopping time before this trouble judgment execution is made variable according to the occurrence status of evaporated fuel in a fuel tank 13 by a purge stopping time variable means 17.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an abnormality detection device for an evaporative purge system, and in particular, it adsorbs evaporated fuel (vapor) generated in a vehicle to an adsorbent in a canister, and then releases the adsorbed fuel under predetermined operating conditions. The present invention relates to a device for detecting an abnormality in an evaporative purge system that discharges (purges) into an intake passage for combustion.

0002

[Prior art] Fuel evaporated in a fuel tank (vapor)
In order to prevent fuel from being released into the atmosphere, each part is sealed, and the vapor is adsorbed to an adsorbent inside the canister.Then, while the vehicle is running, the adsorbed fuel is sucked into the intake passage and burned. In an internal combustion engine equipped with a system, if the vapor supply passage is damaged or the piping is disconnected for some reason, vapor will be released into the atmosphere, and the purge passage to the intake passage of the internal combustion engine will be blocked. In this case, the vapor in the canister overflows and leaks into the atmosphere from the canister atmosphere inlet. Therefore, it is necessary to detect the occurrence of such an abnormality in the evaporative purge system.

On the other hand, in an internal combustion engine equipped with an electronically controlled fuel injection control device, for example, the basic fuel injection time is calculated from the intake pipe negative pressure (absolute pressure) and the engine speed, and the oxygen Equipped with an air-fuel ratio feedback system that corrects the basic fuel injection time based on the output detection signal of the concentration detection sensor so that the air-fuel mixture supplied into the engine combustion chamber has a predetermined target air-fuel ratio. . In this air-fuel ratio feedback system, the basic fuel injection time is multiplied by the air-fuel ratio feedback correction coefficient FAF and other coefficients obtained based on the output detection signal of the oxygen concentration detection sensor to correct the fuel injection time.

Conventionally, in an internal combustion engine equipped with such an air-fuel ratio feedback system, a purge control valve is opened and closed when the fuel tank internal pressure is above a predetermined value, and the change in the air-fuel ratio feedback correction coefficient FAF at that time is determined to be a predetermined value. There is known an abnormality detection device that determines that there is an abnormality in the evaporative purge system when the value is not exceeded (Japanese Patent Laid-Open No. 2-13
6558).

[0005] Here, the reason why abnormality detection is executed when the internal pressure of the fuel tank is above a predetermined value is to prevent erroneous detection due to vapor not being adsorbed to the canister.

[0006]

However, with the conventional abnormality detection device described above, the amount of vapor adsorbed in the canister may be small immediately after the internal pressure of the fuel tank reaches a predetermined value or higher, and in that case, Fuel ratio feedback correction coefficient F
The amount of change in AF is small, making it difficult to determine an abnormality, and in the worst case, erroneous detection may occur.

On the other hand, it is conceivable to stop purging for a relatively long period of time in order to secure a sufficient amount of vapor in the canister to determine an abnormality, but during this time the internal combustion temperature of the tank may become high or the amount of vapor generated may be reduced. When refueling with new fuel that contains a large amount of fuel, an unnecessarily large amount of vapor will be adsorbed into the canister, and if this is repeated, the vapor adsorption capacity of the canister will decrease, and the vapor generated in the fuel tank will be absorbed. leaks from the canister into the atmosphere.

[0008] The present invention has been made in view of the above points.
It is an object of the present invention to provide an abnormality detection device for an evaporative purge system that solves the above problems by stopping purge for a period of time depending on the vapor generation situation before abnormality detection is performed.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention, as shown in FIG. In an evaporative purge system equipped with a purge execution means 14 that alternately performs purging to discharge (purge) adsorbed fuel into the intake passage 12 of an internal combustion engine 11, the fuel gas discharged into the intake passage 12 by the purge execution means 14 is Concentration detection means 1 for substantially detecting concentration
5, an abnormality determination means 16 that determines a purge abnormality based on the purge gas concentration at the time of purge execution after the purge is stopped by the purge execution means 14;
The purge stop time variable means 17 is configured to vary the purge stop time according to the generation status of evaporated fuel in the fuel tank 3.

0010

[Effect] The amount of evaporated fuel (vapor) generated is
It changes depending on the fuel temperature in the fuel tank 13, the amount of new fuel supplied (refueling amount), the amount of fuel remaining in the fuel tank 13, etc. Therefore,
The present invention focuses on this point, and the purge stop time variable means 17
The vapor generation situation is estimated based on the parameters related to the vapor generation amount, and the purge stop time is variably controlled based on the estimation result.

Therefore, according to the present invention, the abnormality determining means 1
When determining an abnormality according to 6, the adsorbent in the canister can reliably adsorb the amount of vapor necessary for the determination.
Moreover, since the purge stop time can be minimized, the vapor can be adsorbed to the adsorbent in the canister in just the right amount.

0012

Embodiment FIG. 2 shows a system configuration diagram of an embodiment of the present invention. This embodiment is an example in which the internal combustion engine 11 is applied to a 4-cylinder, 4-cycle, spark ignition internal combustion engine, and is controlled by a microcomputer 21, which will be described later.

In FIG. 2, a surge tank 24 is provided downstream of the air cleaner 22 via a throttle valve 23. An intake air temperature sensor 25 is installed near the air cleaner 22 to detect the intake air temperature, and a throttle position sensor 26 is installed on the throttle valve 23 to detect the opening (throttle opening) and idle state of the throttle valve 23. ing. In addition, the surge tank 24 includes a diaphragm type vacuum sensor 27.
is installed.

The surge tank 24 is communicated with a combustion chamber 31 of an engine 30 (corresponding to the internal combustion engine 11) via an intake manifold 28 corresponding to the intake passage 12 and an intake valve 29. A fuel injection valve 32 is disposed for each cylinder so that a portion thereof protrudes into the intake manifold 28, and this fuel injection valve 32 injects fuel into the airflow passing through the intake manifold 28 into the microcomputer 2.
Inject for the time specified by 1.

The combustion chamber 31 is communicated with a catalyst device 35 via an exhaust valve 33 and an exhaust manifold 34. Further, 36 is a spark plug, which is provided so that a part thereof protrudes into the combustion chamber 31. Also, 37 is a piston,
In the figure, it reciprocates in the vertical direction. A distributor 38 distributes and supplies the high voltage generated by the igniter to the spark plugs 36 of each cylinder, and detects the crank angle reference position and crank angle from the rotation of the shaft.

A water temperature sensor 39 is provided so as to penetrate through the engine block 40 and partially protrude into the water jacket, and detects the temperature of engine cooling water and outputs a water temperature sensor signal. Further, the oxygen concentration detection sensor (O2 sensor) 41 is arranged so that a part thereof protrudes through the exhaust manifold 34, and is connected to the catalyst device 3.
5. Detects the oxygen concentration in the exhaust gas before entering the exhaust gas. Also,
The exhaust temperature sensor 48 detects the catalyst temperature within the catalyst device 35.

Reference numeral 42 denotes a fuel tank, which corresponds to the fuel tank 13 in FIG. The canister 44 is filled with an adsorbent such as activated carbon, and an air inlet 44 is provided at the bottom of the canister 44 .
A is provided. The canister 44 also communicates with the intake pipe near the throttle valve 23 via a purge passage 45. Note that the purge passage 45 is connected to the surge tank 24.
It may be communicated with.

Furthermore, a vacuum switching valve (VSV) 46 is provided in the middle of the purge passage 45, and its opening degree is adjusted by a control signal from the microcomputer 21, so that air can be drawn from the canister 44. Adjust the flow rate of purge gas to the pipe. The above vapor passage 43, canister 44, purge passage 45 and VS
The V46 together with the microcomputer 21 constitutes the purge execution means 14 described above.

The vapor generated in the fuel tank 42 is adsorbed by the activated carbon in the canister 44 via the vapor passage 43, and is prevented from being released into the atmosphere. Then, during operation, the canister 4 is
Air is introduced from the air inlet 44a of No. 4, whereby the fuel adsorbed on the activated carbon is desorbed, and the fuel is sucked into the intake pipe via the purge passage 45 and the VSV 46. Furthermore, the activated carbon is regenerated by the above-described desorption and is ready for the next vapor adsorption.

Further, 47 is a warning light which, when the microcomputer 21 determines that there is an abnormality, notifies the driver of the abnormality. Further, 49 is a fuel gauge, which is a gauge that measures the amount of fuel in the fuel tank 42,
It consists of a sender and a receiver and is electrically operated.

The microcomputer 21 that controls the operation of each part of such a configuration has a hardware configuration as shown in FIG. In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. In FIG. 3, the microcomputer 21 is a central processing unit (CPU) 50.
, read-only memory that stores processing programs (
ROM) 51, random access memory (RAM) 52 used as a work area, backup RAM 53 that retains data even after the engine is stopped, input interface circuit 54, A/D converter with multiplexer 5
6 and an input/output interface circuit 55, which are connected to each other via a bus 57.

The A/D converter 56 is connected to the intake air temperature sensor 25.
Intake temperature detection signal from, throttle position sensor 2
6, an intake pipe pressure (PM) detection signal from the vacuum sensor 27, a water temperature detection signal from the water temperature sensor 39, an oxygen concentration detection signal from the O2 sensor 41, and an output measurement signal from the fuel gauge 49. The signals are sequentially switched and taken in through the bus 54, converted into analog/digital data, and sequentially sent to the bus 57.

The input/output interface circuit 55 receives a detection signal from the throttle position sensor 26 and a rotational speed signal corresponding to the engine rotational speed (NE) from the distributor 38, and sends them to the CPU via a bus 57.
At the same time, each signal input from the bus 57 is sent to the fuel injection valve 32 and the VSV 46 to control them. Thereby, the fuel injection time TAU of the fuel injection valve 32 is controlled. The CPU 50 in the microcomputer 21 having the above configuration executes the processing of the flowchart described below in accordance with the program stored in the ROM 51, and realizes the concentration detection means 15, the abnormality determination means 16, the purge stop time variable means 17, etc. do.

Next, the abnormality detection process of this embodiment will be explained. The abnormality detection processing performed by the microcomputer 21 can be roughly divided into: ■ provisional abnormality determination, ■ purge stop time control, and ■
Diagnosis is performed in the order of diagnosis, and control of the VSV 46 is performed in parallel. Therefore, these will be explained one by one.

■ Temporary abnormality determination FIGS. 4 to 6 are flowcharts showing the temporary abnormality determination routine. First, step 1 in FIG.
01, the provisional abnormality determination end flag FKDiAGEND is “1”.
” or not. This provisional abnormality determination end flag FKD
iAGEND is cleared to "0" in advance by an initial routine (not shown), and is set to "1" at step 128 in FIG. 6, which will be described later, when the temporary abnormality determination is completed. If the temporary abnormality determination has not been completed, the process advances to step 102 in FIG. 4 and the diagnostic determination end flag FDiAGE is set.
It is determined whether ND is "1" or not. This diagnostic determination end flag FDiAGEND is also cleared to "0" in advance by the initial routine. Steps 101, 10
If it is determined that the provisional abnormality determination is complete or the diagnostic determination is complete in either of 2, the process proceeds to step 131 in FIG. 6, clears the purge stop processing flag XKPURGE to "0", executes the purge, and then ends this routine. do.

[0026] In step 102, FDiAGEND is set to “0”.
” (diagnosis judgment not completed), then the engine cooling water temperature THW is determined based on the detection signal of the water temperature sensor 39.
The throttle valve 23 is fully closed based on the detection signal of the throttle position sensor 26 (step 104). (idle) or not (step 105), and the vehicle speed sensor (
(not shown) indicates that the vehicle speed SPD is 5km/
It is sequentially determined whether or not it is less than H (step 106).

The conditions in steps 103 to 106 are operating conditions under which the value of the air-fuel ratio (A/F) feedback correction coefficient FAF, which will be described later, is stable and appropriately obtained, and when all of these conditions are satisfied, step 107 is performed. Proceed to step 108 to determine whether the value of the FAF average value calculation flag FFAFOFF at the time of purge stop is "1", and if the FAF average value at the time of purge stop has not been calculated yet (FFAFOFF=0), proceed to step 108. Purge stop processing flag XKPUR
When the purge is stopped by setting GE to "1" and the FAF average value at the time of the purge stop has been calculated (
FFAFOFF=1), the process advances to step 109, where the purge stop processing flag XKPURGE is cleared to "0" and purge is executed.

If any of the conditions in steps 103 to 106 are not satisfied, it is assumed that the conditions for executing the temporary abnormality determination are not met, and the process proceeds to step 129 in FIG. 6, clears the flags etc. described later, and ends this routine. do.

When the purge is stopped with the flag XKPURGE set to "1" in step 108, the process proceeds to step 110 in FIG. 5, where the value of the air-fuel ratio feedback correction coefficient FAF is changed from one of the values indicating lean and the value indicating rich to the other. Determine whether the FAF has changed (this is referred to as "FAF inversion"). If FAF has not been inverted, proceed to step 1.
The routine advances to step 14, where the flag FFAFOFF is cleared to "0" and this routine ends. On the other hand, when it is determined that the FAF has reversed, the process proceeds to step 111, where the current FAF is added to the FAF integrated value FAFOFF at the time of the previous purge stop, and FAFOFF is updated. The data counter NOFF is counted up, and in step 113 it is determined whether the value of NOFF is "8" or more.

If the value of NOFF is less than "8", the value of the FAF average value calculation flag FFAFOFF at the time of purge stop is set to "0" (step 114), this routine is terminated, and the value of NOFF is set to "8". ” or more, divide the FAF integrated value FAFOFF by 8 to calculate the average value FAFAVOFF (step 115), and then calculate the FAF value when the purge is stopped.
The average value calculation flag FFAFOFF is set to "1" (step 116). On the other hand, in step 109 the flag
When executing purge with KPURGE set to “0”,
Proceeding to step 117 in FIG. 5, it is determined whether or not the FAF is inverted. At the time of FAF inversion, steps 111~
Similarly to 116, the FAF average value FAFA during purge execution
When VON is calculated, FAF average value calculation flag FF
AFON is set to "1" and when FAF is not inverted, the flag FFAFON is cleared to "0" and this routine ends (steps 117 to 123). In step 123, the FAF average value calculation flag FFA at the time of purge execution is set.
When FON is set to "1", the process proceeds to step 124 in FIG.
Difference between F average value FAFAVOFF and FAFAVON DLF
AF is calculated.

By the way, the air-fuel ratio feedback correction coefficient FAF is calculated by a conventionally known A/F feedback control routine shown in FIG. When the routine of FIG. 7 is activated every 4 ms, for example, the microcomputer 21 first performs A/F feedback (F/B feedback) in step 201.
) Determine whether the condition is met. When the F/B condition is not satisfied (for example, the cooling water temperature is below a predetermined value, the engine is starting, increasing after starting, warming up, increasing power, cutting fuel, etc.), the air-fuel ratio feedback correction coefficient FAF The value of is set to 1.0 (step 210), and this routine ends (step 211). This allows A/
Open loop control of F is performed. On the other hand, when the F/B condition is satisfied (other than when the above F/B condition is not satisfied), the process proceeds to step 202, and the detected voltage V1 of the O2 sensor 41 is
Convert and import.

Next, in step 203, it is determined whether the detected voltage V1 is less than or equal to the comparison voltage VR1, thereby determining whether the air-fuel ratio is rich or lean. When rich (V1
>VR1), it is determined whether the state has reversed from lean to rich (
Step 204), when the reversal is to rich, the value obtained by subtracting the skip constant RSL from the value of the previous air-fuel ratio feedback correction coefficient FAF is set as the new air-fuel ratio feedback correction coefficient FAF (step 205); If the rich condition continues, the integral constant KI is subtracted from the previous FAF value to obtain a new FAF value (step 206), and this routine is exited (step 211).

On the other hand, when it is determined in step 203 that the fuel is lean (V1≦VR1), it is determined whether the state has reversed from the rich state to lean (step 207). When reversing to lean, the value obtained by adding the skip constant RSR from the previous FAF value is used as the new air-fuel ratio feedback correction coefficient FAF.
(step 208), and on the other hand, when it is determined that the lean state is still lean in the previous time, the integral constant K is added to the value of FAF.
Add I to create a new FAF value (step 209)
, this routine ends (step 211). Here, the above skip constants RSL and RSR are integral constants KI
is set to a value that is sufficiently large compared to .

As a result, when the air-fuel ratio changes as schematically shown in FIG. 8(A), the air-fuel ratio feedback correction coefficient FAF changes when the air-fuel ratio is reversed from lean to rich as shown in FIG. 8(B). When the air-fuel ratio is reversed from rich to lean, the fuel injection time is greatly attenuated by the skip constant RSL in a skip-like manner, and when the air-fuel ratio is reversed from rich to lean, the fuel injection time is greatly increased by the skip constant RSR in a skip-like manner. Change TAU to a larger value. Furthermore, when the air-fuel ratio remains the same, FAF gradually changes from a larger value when lean to a smaller value when rich, according to the integral constant (time constant) KI, as shown in Figure 8 (B). do.

This air-fuel ratio feedback correction coefficient FAF
The basic fuel injection time determined by the engine speed and intake pipe negative pressure is multiplied together with other coefficients to determine the final fuel injection time TAU, thereby controlling the intake air-fuel mixture to the target air-fuel ratio.

The above air-fuel ratio feedback correction coefficient FA
Using F, a tentative abnormality determination is performed in step 125 of FIG. 6 based on the following principle.

That is, when the aforementioned VSV 46 is turned on and purge is enabled, if the evaporative purge system is normal, the fuel adsorbed in the canister 44 is purged into the intake passage through the VSV 46 and the purge passage 45, so the purge amount is Therefore, in order to correct this, the air-fuel ratio feedback correction coefficient FAF changes to the decreasing side (lean side) as shown by a in FIG. 9. Furthermore, when the purge execution is stopped, the FAF changes to the increasing side as shown by b in FIG.

Therefore, in step 125 following step 124 in FIG. 6, a provisional abnormality determination is made to determine whether or not the difference DLFAF between the average values of the air-fuel ratio feedback correction coefficients FAF before and after the purge has shifted to the lean side by 5% or more. , if it deviates to the lean side by 5% or more, it is determined to be normal and step 1
Proceed to 26 and set the provisional abnormality determination flag FKDiAGPURGE.
On the other hand, if it does not shift toward the lean side by 5% or more, it is determined to be abnormal and the process proceeds to step 127, where the provisional abnormality determination flag FKDiAGPURGE is set to "1".

After the processing in step 126 or 127, the tentative abnormality determination end flag FKDiAGEND is set to "1" (step 128), and the FAF at the time of the above purge is set.
Average value FAFAVON, FAF average value F when purge is stopped
AFAVOFF, data counter NON when purge is executed
and the data counter NOFF at the time of purge stop are cleared to zero (step 129), and furthermore, the data counter NOFF at the time of purge execution is cleared to zero.
AF average value calculation flag FFAFON, F when purge is stopped
After clearing the AF average value calculation flag FFAFOFF and the FAF integrated values FAFON and FAFOFF during purge execution and stop to zero (step 130), the purge stop processing flag XKPURGE is set to zero (step 13).
1) This routine ends with the purge enabled.

In this way, the temporary abnormality determination routines shown in FIGS. 4 to 6 are executed only when the temporary abnormality determination or the diagnosis determination described below has not been completed after the initial routine is activated, and when the purge is stopped and when the purge is executed. Average value of air-fuel ratio feedback correction coefficient FAF at time FAFAVOFF and FA
A provisional abnormality determination is made based on whether the difference in FAVON shifts toward the lean side by 5% or more.

■Purge stop time control FIGS. 10 to 12 are processing routines related to purge stop time control, which are the main parts of the present invention, in which FIG. 10 is a refueling amount correction coefficient calculation routine, FIG. 11 is a purge stop time calculation routine, FIG. 12 shows the vapor accumulation processing routine.

First, to explain the flowchart showing the refueling amount correction coefficient calculation routine in FIG. 10, the CPU 50 in the microcomputer 21
Immediately after starting the engine, the AD conversion value ADFU of the previous output
After reading EL (which, as will be described later, indicates the output of the fuel gauge 49 immediately before the previous engine stop) from the backup RAM 53 and moving it to the variable ADFUELOLD (step 301), the output signal of the fuel gauge 49 is shown in FIG. The current AD conversion value ADFUEL obtained by A/D conversion by the A/D converter 56 is taken in (step 302).

[0043] Next, the above-mentioned distributor 38
Based on the rotational speed signal from the engine, it is determined whether or not it is time to start the engine (step 303). When starting the engine, the counter value N
It is determined whether STA is zero (step 304). The counter value NSTA has been cleared to zero by the initial routine, so the first time it is determined that the engine has started, it is determined that NSTA=0 in step 304, and the process proceeds to step 305, where the counter value NSTA is set to "1". After that, in step 306, the refueling amount coefficient DFUEL is calculated from the following equation.

DFUEL=(ADFUEL−ADFUELO
LD)/ADFULL However, in the above formula, ADFULL is the AD conversion value when the fuel tank 42 is full, and is known (constant).

Next, it is determined whether the refueling amount coefficient DFUEL is positive or not (step 307), and if it is positive, it means that refueling has been performed.
) Based on the two-dimensional map shown in
Calculate UEL (step 308). On the other hand, when the refueling amount coefficient DFUEL is zero or negative, it means that no refueling is being performed, so after setting the refueling amount coefficient DFUEL to zero (step 3
09), proceed to step 308 above and set the oil supply amount correction coefficient K.
Calculate NFUEL.

As can be seen from FIG. 13(D), the refueling amount correction coefficient KNFUEL changes when the refueling amount is zero (DFUE
L=0) is set to be the maximum value at 1.0, and becomes smaller as the amount of refueling increases (as DFUEL becomes a positive value). This is to shorten the purge stop time T, which will be described later, since vapor is more likely to be generated as the amount of oil supplied increases. After calculating the refueling amount correction coefficient KNFUEL in step 308, this routine ends (step 310).
.

Furthermore, when it is determined in step 303 that it is not time to start, or even if it is determined in step 303 that it is time to start, NSTA is determined to be "1" in step 304 when this routine is started for the second time or later. Therefore, in these cases, the refueling amount correction coefficient KNFUEL is not calculated and the process ends (step 310). However, since steps 301 and 302 are executed every time this routine is started, the value immediately before the engine is stopped is stored in the AD conversion value ADFUEL.

Next, a flowchart showing the purge stop time calculation routine shown in FIG. 11 will be explained. First, the intake air temperature detection signal from the intake air temperature sensor 25 described above is converted into an A/D
Based on the value THA obtained by A/D conversion by the converter 56, the intake air temperature correction coefficient KTHA is calculated by interpolation with reference to the two-dimensional map shown in FIG. 13(A) stored in the ROM 51 in advance (step 401). The above two-dimensional map is set so that the higher the intake air temperature is, the smaller the coefficient KTHA becomes. This is to shorten the purge stop time T, since vapor is more likely to be generated as the intake air temperature is higher.

Next, in the same way as above, A of the water temperature sensor 39 is
Based on the D conversion value THW, the cooling water temperature correction coefficient KTHW is calculated by interpolation with reference to the two-dimensional map shown in FIG. 13(B).
is calculated (step 402), and a fuel amount correction coefficient KFUEL is calculated by interpolation calculation with reference to the two-dimensional map shown in FIG. 13(C) (step 403). As shown in FIG. 13(C), the fuel amount correction coefficient KFUEL is the AD conversion value ADFUE of the current output signal of the fuel gauge 49.
It is calculated based on the ratio between L and the AD conversion value ADFULL when the tank is full.The smaller the remaining fuel amount (the closer the above ratio approaches 0), the more likely vapor is generated, so the value proportional to the above ratio is calculated. By calculating the fuel amount correction coefficient KFUEL, the purge stop time T is shortened when the remaining fuel amount is small.

[0050] Note that the above-mentioned cooling water temperature correction coefficient KTHW
As shown in Fig. 13(B), when the engine cooling water temperature THW is 7
In the range of 0°C to 120°C, the value is inversely proportional to the engine cooling water temperature. This is because when the engine cooling water temperature THW is high, the fuel temperature is high and vapor is likely to be generated.

Next, in step 404, the stop time TN is calculated using the following equation. TN=30×KTHA×KTHW×K
BUEL be. This constant needs to be adapted to each vehicle because the required amount of vapor adsorption varies depending on the capacity, shape, vehicle type, etc. of the fuel tank 42. In the above equation, "KNFUEL" is the oil supply amount correction coefficient calculated in step 308 of FIG. 10 above.

Next, the process advances to step 405 in FIG. 11, where the average value of the previous purge stop time T and the new stop time TN calculated in step 404 is taken, and this is determined as the new purge stop time T (minutes). After storing it in the RAM 52 as , this routine ends (step 406). This is because the operating conditions change from moment to moment, so it is necessary to update the purge stop time T.

Next, the vapor accumulation processing routine shown in FIG. 12 will be explained. First, the provisional abnormality determination flag FKDiA
It is determined whether GPURGE is "1" (that is, it is determined that there is a temporary abnormality) (step 501), and only when it is "1", it is determined whether or not the diagnosis determination end flag FDiAGEND is "1" (that is, the diagnosis determination is completed). Step 502)
, when the diagnosis judgment is not completed, the flag FSTRAGE indicating that vapor is stored in the canister 44 is set to “1”.
” (step 503).This flag F
STRAG is previously cleared to zero by the initial routine.

When the value of the flag FSTRAGE is "0", the purge stop flag XSTRAGE is set to "1", and then the timer is counted up (steps 504 and 5).
05), it is determined whether the elapsed time of the timer is the vapor stop time T calculated in step 405 of FIG. 11 (step 506). If the purge stop time T has not elapsed, this routine is ended (step 509),
On the other hand, when the purge stop time T has elapsed, the vapor accumulation state flag FSTRAGE is set to "1" (step 507), and this routine is ended (step 509).
).

[0055] If it is determined to be normal in the provisional abnormality determination (step 501), if the diagnostic determination has been completed (step 502), or if the vapor accumulation state flag FST
When RAGE is "1", it is not determined whether the purge stop time T has elapsed, and the purge stop flag XSTR is
AGE is set to "0" (step 508), and this routine exits (step 509).

Therefore, by the vapor accumulation processing routine of FIG. 12, the purge stop time T is determined only when a temporary abnormality is determined in the temporary abnormality determination routine of FIGS. During the period, the purge stop flag XSTRAGE is set to "1" to cause the purge to be stopped as described below. At this time, as mentioned above, this purge stop time T is determined by the following: ■ When the amount of refueling is large, ■ When the fuel temperature is high (when the intake air temperature and engine cooling water temperature are high), and ■ When the remaining fuel amount is low, vapor is generated. Since it is calculated to be a short value in consideration of these factors, the purge can be stopped for a period corresponding to the amount of vapor generated.

The above-described purge stop time variable means 17 can be realized by each of the routines shown in FIGS. 10 to 12.

①Diagnostic Judgment FIGS. 14 to 16 show flowcharts of the diagnostic judgment routine, respectively. This diagnostic determination routine is approximately the same as the above-described temporary abnormality determination routine. First, in step 601 of FIG. 14, the provisional abnormality determination flag FKDiAGPU
It is determined whether RGE is “1” (step 601), and “1” is determined.
”, it means that a tentative abnormality has been determined in step 125 of FIG. 6, so the process proceeds to step 602 to perform diagnostic determination again, and a diagnostic determination completion flag FD indicating whether or not the determination by this diagnostic determination routine has been completed is set.
Determine whether iAGEND is "1". When the temporary abnormality determination flag FKDiAGPURGE is “0” (normal),
Or, the value of the diagnosis end flag FDiAGEND is “
1”, set the purge stop processing flag XPURGE to “0”.
” and exit this routine (step 601).
, 602, 632, 633).

Next, in steps 603 to 606, it is determined whether the operating conditions are such that a stable and appropriate FAF value can be obtained, as in steps 103 to 106, and if all of these operating conditions are satisfied, the process proceeds to step 607. Proceeding, it is determined whether the vapor accumulation state flag FSTRAGE is "1". This flag FSTRAGE is a flag that is set to "1" after the purge is stopped for the purge stop time T in step 507 of the vapor accumulation processing routine in FIG. 12, and when it is "1", the purge is stopped in step 608. It is determined whether the FAF average value calculation flag FFAFOFF at the time is "1".

When the flag FFAFOFF is "0", it means that the FAF average value has not yet been calculated, and the process proceeds to step 609 where the purge stop processing flag XPURG is set.
Set E to "1" to stop the purge. When the flag FFAFOFF is "1", it means that the FAF average value has been calculated, and in this case, step 610
The program then proceeds to clear the purge stop processing flag XPURGE to "0" and execute the purge.

At step 609, the flag XPURGE is set to “
1” when the purge is stopped, steps 611 to 617 in FIG. 15 cause steps 110 to 11 in FIG.
6, calculate the average value FAFAVOFF of the values when the air-fuel ratio feedback correction coefficient FAF is reversed eight times, and set the FAF average value calculation flag FFAFOFF when the purge is stopped.
is set to “1”.

On the other hand, in step 610 the flag XPURG
When executing purge with E set to "0", steps 618 to 624 in FIG. 15 perform steps 117 to 117 in FIG.
123, calculate the average value FAFAVON of the values when the air-fuel ratio feedback correction coefficient FAF is reversed eight times, and set the FAF average value calculation flag FFAFON at the time of purge execution.
is set to “1”.

After completing any one of steps 615, 617, and 622, the routine exits. On the other hand, when the process in step 624 is completed, the process proceeds to step 625 in FIG.
After calculating the difference DLFAF between AVOFF and FAFAVON, it is determined whether DLFAF has deviated to the lean side by 5% or more based on the above-mentioned principle (step 62
6).

When the above difference DLFAF deviates to the lean side by 5% or more, it is determined to be normal and the process proceeds to step 627 where the diagnosis determination flag FDiAGPURGE is set to "0".On the other hand, following the provisional abnormality determination, the DLFAF is is 5
If it does not shift toward the lean side by more than %, it is determined that there is an abnormality, and the process proceeds to step 628 where the diagnosis determination flag FDiAGP is set.
Set URGE to “1”. When the diagnosis flag FDiAGPURGE is "1", the CPU 50 turns on the warning light 47 shown in FIG. 2 to notify the driver of an abnormality in the evaporative purge system.

When the process of step 627 or 628 is completed, the value of the diagnostic determination end flag FDiAGEND is set to "1" (step 629), and then this routine is ended (step 633).

On the other hand, if any of the operating conditions in steps 603 to 606 in FIG. 14 are not satisfied, or if the vapor accumulation state flag FSTRAGE is "0" (purge stop time T has not elapsed) 607
If it is determined, the process advances to step 630 in FIG.
Each FAF average value FAF when executing and stopping the purge described above
The values of AVON and FAFAVOFF are each cleared to zero, and the values of data counters NON and NOFF are also cleared to zero. Next, each flag FFAFO described above is
N, FFAFOFF and FAF integrated value FAFON and FA
After each FOFF is cleared to zero (step 631)
, the purge stop processing flag XPURGE is set to "0" (step 632), and this routine is ended with the purge enabled (step 633).

In this manner, the diagnostic determination routines shown in FIGS. 14 to 16 are routines that execute the above-described abnormality determination means 16 and concentration detection means 15, and are performed when a temporary abnormality is determined in the above-described temporary abnormality determination routine, and , is executed when the diagnostic determination by this diagnostic determination routine is not completed, and the diagnostic determination is executed after the vapor is reliably adsorbed in the canister 44 to the extent that it does not become excessive due to the elapse of the purge stop time T. It is possible to prevent false detections that occur in the past. Furthermore, the purge stop time T for adsorbing vapor to the activated carbon in the canister 44 can be minimized according to the amount of vapor generated, thereby preventing a decrease in the adsorption capacity of the canister 44 due to adsorption of a large amount of vapor. be able to.

① VSV Control FIG. 17 is a flowchart showing a control routine of the VSV 46, which implements the purge execution means 14 of FIG. In FIG. 17, it is determined whether the engine cooling water temperature THW is 50°C or higher based on the detection signal of the water temperature sensor 39 (step 701), and when the engine cooling water temperature THW is warmed up to 50°C or higher, the purge stop processing flag XKPURGE in the temporary abnormality determination routine is A determination is made as to whether the value of
When KPURGE is “0”, the value of the purge stop processing flag XPURGE in the diagnostic judgment routine is as shown in Figure 1.
Is it set to “1” in step 609 of 4?
In step 610 and step 632 in FIG. 16, it is determined whether the value is set to "0" (step 70).
3).

[0069] The above purge stop processing flag XPURGE
When the value of is "0", it is determined whether the purge stop flag XSTRAGE obtained in steps 504 and 508 in the vapor accumulation processing routine of FIG. 12 is "1" (step 7
04), when it is "0", the microcomputer 21 outputs a control signal to turn on the VSV 46 to the VSV 46 (step 705), and purge is executed.

On the other hand, during a cold start when the engine cooling water temperature THW is less than 50°C (step 701), or when at least one of the purge stop processing flags XKPURGE and XPURGE is "1", or when the purge stop flag XSTR
When AGE is "1", a control signal to turn off the VSV 46 is output from the microcomputer 21 to the VSV 46 (step 706), and the purge is stopped.

Note that the present invention is not limited to the above-mentioned embodiment, and in the embodiment, FAF is used to detect the purge gas concentration in view of the fact that the air-fuel ratio feedback correction coefficient FAF changes depending on the purge gas concentration. However, the point is that it is sufficient to detect changes in the purge gas concentration, and therefore, for example, an HC sensor or the like may be provided in the middle of the purge passage 45 to directly detect the purge gas concentration.

[0072]

As described above, according to the present invention, the purge stop time is variably controlled depending on the vapor generation situation to ensure that the vapor is adsorbed to the adsorbent in the canister. The change in the purge gas concentration is large, making it possible to reliably detect abnormalities and reduce false detections.Also, the amount of vapor adsorbed by the adsorbent in the canister can be constantly monitored regardless of differences in the amount of refueling or remaining fuel. Since it can be minimized, it has the advantage of being able to prevent a decrease in the vapor adsorption capacity of the canister due to adsorption of a large amount of vapor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of the present invention.

FIG. 3 is a diagram showing the hardware configuration of the microcomputer in FIG. 2;

FIG. 4: Temporary abnormality determination routine according to an embodiment of the present invention (
It is a flowchart showing part 1).

FIG. 5: Temporary abnormality determination routine according to an embodiment of the present invention (
It is a flowchart showing part 2).

FIG. 6: Temporary abnormality determination routine according to an embodiment of the present invention (
It is a flowchart showing part 3).

FIG. 7 is a flowchart showing an A/F feedback control routine.

8 is a diagram illustrating changes in FAF in FIG. 7. FIG.

FIG. 9 is a diagram illustrating changes in FAF due to turning on and off of the purge system.

FIG. 10 is a flowchart showing a refueling amount correction coefficient calculation routine according to an embodiment of the present invention.

FIG. 11 is a flowchart showing a purge stop time calculation routine according to an embodiment of the present invention.

FIG. 12 is a flowchart showing a vapor accumulation processing routine according to an embodiment of the present invention.

[Figure 13] Coefficients KTHA,K in Figures 10 and 11
It is a figure which shows the two-dimensional map for calculation of THW, KFUEL, and KNFUEL.

FIG. 14 is a flowchart showing a diagnostic determination routine (Part 1) according to an embodiment of the present invention.

FIG. 15 is a flowchart showing a diagnostic determination routine (Part 2) according to an embodiment of the present invention.

FIG. 16 is a flowchart showing a diagnostic determination routine (part 3) according to an embodiment of the present invention.

FIG. 17 is a flowchart showing a VSV control routine according to an embodiment of the present invention.

[Explanation of symbols]

11 Internal combustion engine 12 Intake passage 13,42 Fuel tank 14 Purge execution means 15 Concentration detection means 16 Abnormality determination means 17 Purge stop time variable means 21 Microcomputer

Claims (1)

[Claims] 1. A purge that alternately performs a purge stop in which evaporated fuel from a fuel tank is adsorbed on an adsorbent in a canister, and a purge in which the adsorbed fuel in the adsorbent in the canister is released into an intake passage of an internal combustion engine. In an evaporative purge system equipped with an execution means, a concentration detection means for substantially detecting the gas concentration of the fuel discharged into the intake passage by the purge execution means, and a concentration detection means that detects the gas concentration of the fuel discharged into the intake passage by the purge execution means, and Abnormality determining means for determining purge abnormality based on purge gas concentration during purge execution after purge stop; and purge stop for varying the purge stop time of the purge execution means in accordance with the generation status of evaporated fuel in the fuel tank. An abnormality detection device for an evaporative purge system, characterized in that it has a time variable means.