JP2002276475A - Leak deciding device for evaporated fuel processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leak deciding device of an evaporated fuel processing system capable of improving accuracy of the decision of sway of fuel and thereby properly and accurately performing a leak decision according to the presence or absence of sway of fuel. SOLUTION: An ECU 2 of the leak deciding device 1 decides the presence or absence of leak of the evaporated fuel processing system 20 (Step 56 and 77), calculates estimated pressure PM' by using a pressure estimated coefficient a calculated from tank internal pressure PTANK at two points of time in leak check modes (Step 41), decides the presence or absence of slosh by comparing differential pressure DPM of actual pressure PM and the estimated pressure PM' and a threshold value PTG for slosh decision (Step 43) and inhibits the leak decision when slosh is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention determines whether or not there is a leak in an evaporative fuel processing system of an internal combustion engine, in which evaporative fuel generated in a fuel tank is temporarily stored in a canister and supplied to an intake system as appropriate. The present invention relates to a leak determination device for a fuel vapor processing system.

[0002]

2. Description of the Related Art Conventionally, as this kind of leak determination device,
For example, one described in JP-A-6-159157 is known. This evaporative fuel processing system includes a canister,
It is composed of a charge passage, a purge passage and the like.
The canister is connected to a fuel tank via a charge passage, and connected to an intake pipe of an internal combustion engine via a purge passage. A pressure sensor is provided in the charge passage, and the pressure sensor detects a pressure in a space on the upstream side of the canister formed by the charge passage and the fuel tank (hereinafter, referred to as “tank internal pressure”).

[0003] In this leak determination device, the presence or absence of a leak in the evaporative fuel processing system is determined, and during that time, a fuel swing (hereinafter referred to as "slosh") may occur in which a large amount of evaporative fuel is generated. Therefore, the presence or absence of slosh is also determined. In this case, in the slosh determination for determining the presence or absence of slosh, the tank internal pressure is detected at predetermined time intervals, and when the difference between the current value and the previous value of the detected value is less than the predetermined value, it is determined that slosh has not occurred. On the other hand, if it is equal to or greater than the predetermined value, it is determined that slosh has occurred. When it is determined that the slosh has occurred, the leak determination is stopped to prevent an erroneous determination due to the occurrence of the slosh.

[0004]

In the above-described conventional leak determination device, the slosh determination is performed only based on the deviation between two detection values of the tank internal pressure detected at predetermined time intervals. There is a problem that the leak determination cannot be performed with high accuracy due to the low accuracy of the determination result. In other words, depending on the detection cycle (sampling cycle) of the tank internal pressure, the state of the change in the tank internal pressure due to the slosh is not properly reflected in the above-mentioned deviation, so that it is erroneously determined that the slosh does not occur despite the slosh. In some cases, the determination may be made, and the wrong determination may be made in the opposite direction. For example, if the detection cycle is too short, when the tank internal pressure temporarily rises slightly for a reason other than slosh, it may be erroneously determined that slosh has occurred, even though slosh has not occurred. In such a case, the leak determination is stopped. On the other hand, if the detection cycle is too long, when the tank internal pressure gradually rises due to leakage or the like, it may be erroneously determined that slosh has occurred even though slosh has not occurred. Will be aborted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can improve the accuracy of the fuel swing determination, whereby the leak determination can be performed appropriately and properly in accordance with the presence or absence of the fuel swing. It is an object of the present invention to provide a leak determination device for an evaporative fuel processing system that can be performed with high accuracy.

[0006]

In order to achieve this object, according to the first aspect of the present invention, the fuel vapor generated in the fuel tank 21 is temporarily adsorbed to the canister 24 and the intake air of the internal combustion engine 3 is taken. A leak determination device 1 for an evaporative fuel processing system 20 that determines the presence or absence of a leak from an evaporative fuel processing system 20 supplied to a system (intake pipe 5), and detects a pressure (tank pressure PTANK) in the evaporative fuel processing system 20. Pressure detection means (pressure sensor 26), and a predetermined leak determination period (time t1 to time t1).
According to the pressure in the evaporative fuel treatment system 20 detected during (during t7) (the comparison result between the third differential pressure DP3 and the third threshold value PT3, or the deviation (DP3-DP4) and the fourth threshold). A leak determining unit (ECU2, steps 56 to 58, 77 to 79) for determining whether or not there is a leak in the evaporated fuel processing system 20; and at least one after the start of the leak determination period. In accordance with the state of the pressure in the evaporative fuel treatment system 20 detected at the predetermined first timing (time t2, t3) (the current value PX of the reference pressure, the previous value PY of the reference pressure, the pressure estimation coefficient a), A predetermined second timing after the first timing during the determination period (time t3 and time t5
Pressure estimating means (ECU2, step 41) for estimating the pressure (estimated pressure PM ') in the evaporative fuel processing system 20 at any timing during the period), the estimated pressure (estimated pressure PM') and the second According to the comparison result (comparison result between differential pressure DPM for slosh determination and threshold value PTG for slosh determination) with the pressure (detected pressure PM for slosh determination) in vaporized fuel processing system 20 detected at the timing. The fuel sway determining means (ECU2, step 43) for determining whether fuel sway has occurred in the fuel tank 21 and the fuel sway determining means determine that fuel sway has occurred in the fuel tank 21. (When the determination result of step 43 is YE
(In the case of S), a leak determination prohibiting means (ECU2) for prohibiting the leak determination by the leak determining means (skips steps 6 and 7).

According to the evaporative fuel processing system leak judging device, the presence or absence of a leak in the evaporative fuel processing system is judged according to the pressure in the evaporative fuel processing system detected during a predetermined leak judging period. Further, according to the state of the pressure in the evaporative fuel processing system detected at at least one predetermined first timing after the start of the leak determination period, at a predetermined second timing after the first timing during the leak determination period. The pressure in the evaporative fuel processing system is estimated, and it is determined whether or not the fuel has swayed in the fuel tank according to the comparison result between the estimated pressure and the pressure detected at the second timing. Is done. As a result, when it is determined that fuel sway has occurred, the leak determination is prohibited. As described above, the pressure in the evaporative fuel processing system at the second timing is estimated based on the state of the pressure detected at the earlier first timing, so that the estimation is performed while reflecting the tendency of the pressure change. be able to. Therefore, by comparing the estimated pressure reflecting the tendency of the pressure change with the actual detected pressure in this way, compared with the conventional method of simply determining based on the deviation of the detected pressure between the two points, the fuel The presence or absence of shaking can be more accurately determined. As a result, erroneous determination of leak due to erroneous determination of fuel swing can be prevented, and leak determination can be performed accurately.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an evaporative fuel processing system according to an embodiment of the present invention; FIG. 1 shows a schematic configuration of an evaporative fuel processing system to which the leak determination device of the present embodiment is applied, and an internal combustion engine including the same. This leak determination device 1
Is for determining whether or not there is a leak in the evaporated fuel processing system 20 of the internal combustion engine (hereinafter referred to as “engine”) 3.
U2 is provided. Details of the evaporated fuel processing system 20 and the ECU 2 will be described later.

The engine 3 is a gasoline engine and is mounted on a vehicle (not shown). An engine speed sensor 12 is attached to the main body of the engine 3. The engine speed sensor 12 detects the engine speed NE and sends a detection signal to the ECU 2.

A throttle valve 6 is provided in an intake pipe 5 (intake system) of the engine 3, and a throttle valve 6 is provided downstream thereof.
An intake pipe absolute pressure sensor 13 is attached. The intake pipe absolute pressure sensor 13 detects an intake pipe absolute pressure PBA in the intake pipe 5 and sends a detection signal to the ECU 2.

An injector 7 is attached to a portion of the intake pipe 5 downstream of the intake pipe absolute pressure sensor 13 so as to face an intake port (not shown). The fuel injection time TOU which is the valve opening time of the injector 7
T is controlled by the ECU 2. The injector 7 is connected to a fuel tank 21 via a fuel supply pipe 8. A fuel pump 9 for pumping fuel to the injector 7 is provided in the middle of the fuel supply pipe 8.

On the other hand, an O2 sensor 14 is attached to a portion of the exhaust pipe 10 of the engine 3 upstream of the catalyst device 11. The O2 sensor 14 detects the oxygen concentration in the exhaust gas on the upstream side of the catalyst device 11, and outputs a detection signal corresponding to the oxygen concentration to the ECU 2. The ECU 2
Based on the detection signal of the O2 sensor 14, the air-fuel ratio correction coefficient KO2 used for calculating the fuel injection time TOUT described above.
Ask for.

Further, a detection signal indicating the vehicle speed (vehicle speed) VP is input from the vehicle speed sensor 15 to the ECU 2.

The evaporative fuel processing system 20 temporarily stores the evaporative fuel generated in the fuel tank 21 in the canister 24 and discharges the evaporative fuel into the intake pipe 5 as appropriate. It is composed of a bypass passage 23, a canister 24, a purge passage 25, and the like.

The canister 24 is connected to the fuel tank 21 via the charge passage 22 and is connected to the fuel tank 2.
The fuel vapor generated in 1 is sent to the canister 24 via the charge passage 22. A pressure sensor 26 (pressure detecting means) is disposed in a portion of the charge passage 22 near the fuel tank 21. The pressure sensor 26 is formed of, for example, a piezoelectric element, detects the pressure in the charge passage 22, and outputs a detection signal to the ECU 2. Normally, the pressure in the charge passage 22 is substantially equal to the pressure in the fuel tank 21, and is hereinafter referred to as a tank internal pressure PTANK.

The pressure sensor 26 in the charge passage 22
A two-way valve 27 is provided between the canister 24 and the canister 24. Each of the two-way valves 27 is constituted by a mechanical valve combining a diaphragm type positive pressure valve and a negative pressure valve. This positive pressure valve is configured to open when the tank internal pressure PTANK becomes higher than the atmospheric pressure by a predetermined pressure, whereby the fuel vapor in the fuel tank 21 is sent to the canister 24 by the opening. . Further, the negative pressure valve is configured to open when the tank internal pressure PTANK becomes lower by a predetermined pressure than the pressure on the canister 24 side, and by the opening, the fuel vapor stored in the canister 21 is opened. Is returned to the fuel tank 21.

Further, the bypass passage 23 is provided with a two-way valve 2.
7, a portion of the charge passage 22 closer to the canister 24 than the two-way valve 27 and the pressure sensor 2
It is connected to the 6-side part. This bypass passage 2
In the middle of 3, a bypass valve 30 is provided. The bypass valve 30 is constituted by a normally closed type electromagnetic valve, and normally closes the bypass passage 23 and opens when excited by the control of the ECU 2 to open the bypass passage 23.

The fuel tank 21 has a float valve 2
1a is provided. The float valve 21a opens and closes a port of the charge passage 22 on the fuel tank 21 side.
When the fuel cell 1 is full or when the fuel in the tank sways, the port is closed to prevent the fuel from flowing into the charge passage 22 side.

On the other hand, the canister 24 contains activated carbon, and the activated carbon adsorbs fuel vapor. The canister 24 has an atmosphere passage 2 opening to the atmosphere side.
The air passage 29 is provided with a vent shut valve 31 for opening and closing the passage. The vent shut valve 31 is constituted by a normally open type electromagnetic valve, and normally keeps the atmosphere passage 29 open and closes the atmosphere passage 29 when excited by the control of the ECU 2.

In the middle of the purge passage 25, a purge control valve 32 for opening and closing the purge passage 25 is provided. The purge control valve 32 is configured by an electromagnetic valve whose opening degree continuously changes according to the duty ratio of the drive signal from the ECU 2. When the purge control valve 32 opens when the vent shut valve 31 is in the open state, the fuel vapor adsorbed by the canister 24 is removed.
The air is sent into the intake pipe 5 by the negative pressure in the intake pipe 5. E
The CU 2 controls the flow rate of the evaporated fuel sent from the canister 24 into the intake pipe 5, that is, the purge flow rate, by performing duty control on the opening of the purge control valve 32.

On the other hand, the ECU 2 (leak determining means, pressure estimating means, fuel fluctuation determining means, leak determining prohibiting means)
I / O interface, CPU, RAM and ROM
It consists of a microcomputer consisting of
The detection signals of the various sensors 12 to 15 are input to the CPU after being subjected to A / D conversion and shaping by the I / O interface. The CPU determines the operating state of the engine 3 according to these input signals,
In accordance with a control program stored in advance in the CPU or data stored in the RAM, the above-described various valves 30 to 32 are driven, and a leak determination process of the evaporated fuel processing system 20 described below is executed.

Hereinafter, this leak determination processing will be described with reference to FIGS. This processing is performed by the two-way valve 2 of the fuel vapor processing system 20 including the fuel tank 21.
This is to determine the presence or absence of a leak in a portion on the upstream side of the bypass valve 7 and the bypass valve 30. FIG. 2 shows a main routine of this processing. This process is executed every predetermined time (for example, 80 msec) by setting a timer, and the leak determination according to this process is executed only once from the start to the end of the operation of the engine 3.

First, in step 1 (abbreviated as S1 in the figure, the same applies hereinafter), it is determined whether or not the monitoring execution condition is satisfied. The monitor execution condition is for determining whether or not the execution condition of the leak determination process is satisfied. For example, when all of the following conditions (1) to (4) are satisfied, the monitor execution condition is determined. It is determined that the execution condition is satisfied. (1) The purge control by the purge control valve 32 is being performed. (2) The engine 3 is in a predetermined steady operation state (for example, it is determined based on the intake pipe absolute pressure PBA, the engine speed NE, and the like). (3) Cruising operation in which the change in vehicle speed VP is small. (4) The air-fuel ratio correction coefficient KO2 is equal to or greater than a predetermined value, and the effect of the purge fuel on the air-fuel ratio A / F is small.

If the decision result in the step 1 is YES and all of the above conditions (1) to (4) are satisfied, the routine proceeds to a step 2, in which a leak determination prohibition flag FENOC is set.
It is determined whether or not OUNT is “1”. The leak determination prohibition flag FNOCOUNT is, as described later,
This is set to “1” when it is determined in the leak check mode that a slosh, which is a fuel shake, such that a large amount of evaporated fuel is generated in the fuel tank 21, has occurred. If the determination result is NO, it is determined that slosh has not occurred and the leak determination can be performed, and it is determined that the air release mode processing, the pressure reduction mode processing, the leak check mode processing, and the pressure return mode processing in steps 3 to 7 have been performed. After executing the correction check mode process in order, the process ends. The contents of these various mode processes will be described later.

On the other hand, if the decision result in the step 1 is NO and the monitor execution condition is not satisfied, or
Is YES and it is determined that slosh has occurred in the evaporative fuel processing system 20, the routine proceeds to step 8, where an initialization process is executed.

In this initialization process, although not shown, the timer value T of the leak determination timer and the timer value TKINJ of the slosh determination timer are both set to 0.
Each of the leak determination timer and the slosh determination timer is configured by an up-count timer. Then, the process proceeds to a step 9, wherein the leak determination prohibition flag FNOCOUNT is set to "0", followed by terminating the present process.

On the other hand, in the open-to-atmosphere mode process in step 3 described above, the bypass valve 30 and the vent shut valve 31 are kept open and the purge control valve 32 is kept closed, so that the tank internal pressure PTANK is almost equal to the atmospheric pressure. The state is equal.

In the pressure reduction mode process of step 4 following step 3, the bypass valve 30 is kept open, the vent shut valve 31 is kept closed, and the purge control valve 32 is kept at a predetermined pressure reduction time T1 and the duty control. By doing so, the pressure inside the evaporated fuel processing system 20 is reduced. After the pressure reduction, the timer value T of the leak determination timer is set to 0, and the leak check mode execution permission flag F_EVAP2 is set to “1” to indicate that the leak check mode processing can be executed.
Set to.

Next, the contents of the leak check mode processing in step 5 will be described with reference to FIG. First, in step 11, it is determined whether or not the leak check mode execution permission flag F_EVAP2 is "1". When the result of this determination is NO, this process is terminated, while the result of this determination is YES, indicating that the evaporative fuel processing system 20
Is in a state in which the leak check mode can be executed, the process proceeds to step 12, and the bypass valve (“BP
S ”. The same applies hereinafter; 30, a vent shut valve (abbreviated as "VSSV" in the figure, the same applies hereinafter) 31, and a purge control valve (abbreviated as "PCS" in the figure, same applies hereinafter) 32. Thereby, the evaporative fuel processing system 20 shifts to the leak check mode.

Then, the process proceeds to a step 13, wherein the timer value T of the leak determination timer is set to a first predetermined time T21 (for example, 0.
It is determined whether it is 5 seconds or more. When the result of this determination is NO, that is, when the first predetermined time T21 has not elapsed after the transition to the leak check mode, steps 20 to 24 described below are executed, and this processing ends.

That is, the tank internal pressure (hereinafter referred to as “the current value of the tank internal pressure”) PTANK detected by the pressure sensor 26 at the present time is changed to the first and second detection pressures P1,
Set as P2 (steps 20, 21), then
The timer value TKINJ of the slosh determination timer is set to a value of 0 (step 22), and the estimation coefficient calculation end flag FK
INJ is set to "0" (step 23), the current value PTANK of the tank internal pressure is set as the third detection pressure P3 (step 24), and the process is terminated.

On the other hand, if the decision result in the step 13 is YES.
The first predetermined time T after the shift to the leak check mode.
When 21 has elapsed, the routine proceeds to step 14, where the timer value T is set to the second predetermined time T2 longer than the first predetermined time T21.
It is determined whether it is 2 (for example, 5 seconds) or more. When the determination result is NO, that is, when the second predetermined time T22 has not elapsed after the shift to the leak check mode, the above-described steps 21 to 24 are executed, and then the present process ends. On the other hand, if the determination result of step 13 is YE
In S, when the second predetermined time T22 has elapsed, the routine proceeds to step 15, where a slosh determination process described later is executed.

Next, the routine proceeds to step 16, where the timer value T
Is a third predetermined time T23 longer than the second predetermined time T22
(For example, 30 seconds) or more. If the determination result is NO, that is, if the third predetermined time T23 has not elapsed after the shift to the leak check mode, the above-described step 24 is executed, and then the present process ends. On the other hand, if the determination result is YES and the third predetermined time T23 has elapsed, the routine proceeds to step 17, where the timer value T is equal to or longer than the predetermined leak check time T2 (for example, 30.5 sec) longer than the third predetermined time T23. It is determined whether or not.

When the result of this determination is NO, that is, when the predetermined leak check time T2 has not elapsed after the transition to the leak check mode, this processing is terminated. On the other hand, if the decision result in the step 17 is YES and the predetermined leak check time T2 has elapsed, the routine proceeds to a step 18, wherein the step 2
The value obtained by subtracting the second detection pressure P2 set at 1 (PTAN
K-P2) is set as the second differential pressure DP2. As described above, the second differential pressure DP2 is the tank pressure PTA between the time when the second predetermined time T22 has elapsed from the start of the leak check mode and the time when the leak check mode ends.
This represents the amount of fluctuation of NK.

Then, the process proceeds to a step 19, wherein the leak check mode execution permission flag F_EVAP2 is set to "0" to indicate that the leak check mode has ended, to indicate that the pressure return mode can be executed. After setting the pressure return mode execution permission flag F_EVAP3 to “1” and setting the timer value T to 0,
This processing ends. In step 19, the leak check mode execution permission flag F_EVAP2 is set to "0", so that in the next and subsequent loops of the present process, the determination result of step 11 is NO. The process skips and proceeds to the pressure return mode processing of step 6 described above.

Next, the contents of the slosh determination processing in step 15 will be described with reference to FIG. In this slosh determination process, the slosh is
It is determined whether or not the error has occurred within. In the present process, as shown in the figure, first, in a step 31, it is determined whether or not the estimation coefficient calculation end flag FKINJ is “1”.

First, since the estimation coefficient calculation end flag FKINJ is set to "0" in step 23, the determination result is NO. In this case, the process proceeds to step 32, where the timer of the slosh determination timer is set. Value TKI
NJ is a predetermined slosh determination time T5 (for example, 5 seconds)
It is determined whether or not this is the case. When the result of this determination is NO, that is, when the predetermined slosh determination time T5 has not elapsed after the start of this processing, this processing is ended.

On the other hand, if the result of this determination is YES and the predetermined slosh determination time T5 has elapsed after the start of this process, the second detected pressure P2 (ie, the present value PTANK of the tank internal pressure before the current time by the predetermined slosh determination time T5) )
Is set as the previous value PY of the reference pressure, and the current value PTANK of the tank internal pressure is set as the current value PX of the reference pressure (steps 33 and 34).

Next, the routine proceeds to step 35, where the pressure estimation coefficient a is calculated by the following equation (1).

[0040]

(Equation 1)

Next, the routine proceeds to step 36, where the timer value T
Set KINJ to the value 0, then go to step 37,
After setting the estimation coefficient calculation end flag FKINJ to “1”, the present process ends.

By executing this step 37, in the next and subsequent loops, the result of the determination in step 31 becomes YE
In step S38, the process proceeds to step S38, where it is determined whether the timer value TKINJ is equal to or longer than the predetermined slosh determination time T5, as in step S32. When the result of this determination is NO, that is, when the predetermined slosh determination time T5 has not elapsed after the calculation of the pressure estimation coefficient a, the routine proceeds to step 40, where the present value PTAN of the tank internal pressure is set.
K is set as a detection pressure PM for slosh determination.

Then, the process proceeds to a step 41, wherein the estimated pressure P is calculated by the following equation (2) using the present value PX of the reference pressure and the pressure estimation coefficient a calculated before the predetermined slosh determination time T5.
M ′ is calculated (estimated).

[0044]

(Equation 2)

Then, the process proceeds to a step 42, wherein the estimated pressure PM 'is determined from the detected pressure PM for the slosh determination in the step 40.
Is subtracted to obtain a differential pressure DPM for slosh determination.
(= PM−PM ′) is calculated.

Then, the process proceeds to a step 42, wherein it is determined whether or not the slosh determination differential pressure DPM is equal to or greater than a slosh determination threshold value PTG. The result of this determination is N
In the case of O, it is determined that slosh has not occurred, and the present process is terminated.

On the other hand, if the result of this determination is YES, then DPM ≧
At the time of PTG, slosh has occurred,
Proceeding to step 44, the leak determination prohibition flag FNOCOUNT is set to "1" to indicate this. Next, due to the occurrence of the slosh, it is determined that there is no state where the leak determination should be performed in the pressure return mode and the correction check mode in the steps 6 and 7, and the process exits from this process and FIG.
Then, by skipping the steps 6 and 7, the leak determination is prohibited, and the leak determination process ends. Thus, in the next loop, the determination result of step 2 becomes YES, and in that case, the above-described steps 8 and 9 are executed. Thereafter, when the determination result of step 2 is YES, that is, when the monitoring execution condition is satisfied, the various mode processes of steps 3 to 7 including the leak check mode are sequentially executed.

On the other hand, if the decision result in the step 38 is YES.
When the predetermined slosh determination time T5 elapses after the calculation of the pressure estimation coefficient a, the process proceeds to step 39, where the current value PX of the reference pressure is set as the previous value PY of the reference pressure, and then the current value PX of the reference pressure is set. Update (step 34),
The pressure estimation coefficient a is updated (step 35). Then
After executing steps 36 and 37, the present process is terminated. As described above, from the start of the leak check mode to the elapse of the predetermined leak check time T2, the estimated pressure P is increased every time the predetermined slosh determination time T5 elapses.
The value of the pressure estimation coefficient a used for calculating M ′ is updated.

Next, the contents of the pressure return mode processing in step 6 will be described with reference to FIG. This pressure return mode processing is performed by the bypass valve 3 as described below.
0 and the vent shut valve 31 are set to a predetermined pressure return time T.
3. By releasing the tank, the tank internal pressure PTANK is returned to the atmospheric pressure state, and at that time, the presence or absence of a leak is determined.

As shown in the figure, in this processing, first, in step 51, the pressure return mode execution permission flag F_EV
It is determined whether or not AP3 is “1”. When the result of this determination is NO, it is determined that the evaporative fuel processing system 20 is not in a state in which the pressure recovery mode can be executed, and this processing is ended.
On the other hand, when the result of the determination is YES, the routine proceeds to step 52, where it is determined whether or not the timer value T of the leak determination timer is equal to or longer than a predetermined pressure recovery time T3 (for example, 10 seconds). When the determination result is NO, that is, when the predetermined pressure return time T3 has not elapsed after the shift to the pressure return mode, the process proceeds to step 53, where the bypass valve 30 and the vent shut valve 31 are opened, and the vent shut valve is opened. 31 is kept in the closed state, and the process is terminated.

On the other hand, if the decision result in the step 52 is YES.
After the shift to the pressure return mode, the predetermined pressure return time T3
Has elapsed, the routine proceeds to step 54, where a value obtained by subtracting the first detection pressure P1 set in step 20 from the current value PTANK of the tank internal pressure is defined as a first differential pressure DP1.
A value obtained by subtracting the third detection pressure P3 set in step 24 from the current value PTANK of the tank internal pressure is used as a third differential pressure DP.
Set as 3, respectively. As described above, the first differential pressure DP1 represents the amount of change in the tank internal pressure PTANK between the time when the first predetermined time T21 has elapsed from the start of the leak check mode and the time when the pressure return mode ends, and the third differential pressure DP1. DP3 is the third from the start of the leak check mode.
It represents the amount of change in the tank internal pressure PTANK between the time when the predetermined time T23 has elapsed and the time when the pressure return mode ends.

Next, the routine proceeds to step 55, where the second differential pressure DP2 calculated in step 18 is equal to the second threshold PT2.
It is determined whether or not it is less than. This determination result is YES
If the change in the tank internal pressure PTANK during the leak check mode is small, the routine proceeds to step 56, where the third
It is determined whether or not the differential pressure DP3 is less than the third threshold value PT3. If the determination result is NO and the tank internal pressure PTANK is lower than the atmospheric pressure PATM by a predetermined pressure or more at a predetermined time (for example, time t4 in FIG. 7) before the end of the leak check mode, the pressure is sufficiently reduced in the pressure reduction mode. And the change in the tank internal pressure PTANK is small, it is determined that there is no leak in the evaporative fuel processing system 20, and the routine proceeds to step 57, where a leak determination flag FLEAK is indicated.
Is set to “0”.

On the other hand, if the result of this determination is YES, the tank pressure PTAN at a predetermined time before the end of the leak check mode is set.
When K is close to the atmospheric pressure PATM, that is, when the degree of pressure reduction during the pressure reduction mode is small and the change in the tank internal pressure PTANK during the leak check mode is small, a relatively large amount of leak has occurred in the evaporative fuel processing system 20. Then, the process proceeds to a step 58, and the leak determination flag FLEAK is set to "1" in order to indicate this. In a step 61 following these steps 57 and 58, a leak determination end flag F is set to indicate that the leak determination has been completed.
After setting DONE to “1”, the present process is terminated.

On the other hand, if the decision result in the step 55 is NO,
If the change in the tank internal pressure PTANK during the leak check mode is large, the routine proceeds to step 59, where it is determined whether or not the first differential pressure DP1 is larger than the first threshold value PT1. When the result of this determination is YES, the degree of pressure reduction of the tank internal pressure PTANK in the pressure reduction mode is too large,
Since it is assumed that the float valve 21a is in the closed state because the fuel tank 21 is full, the evaporative fuel processing system 20 is determined not to be in a state in which the correction check mode can be executed, and the process exits from this process. Return to steps 6 and 7
Is skipped, the leak determination is prohibited, and the leak determination process ends.

On the other hand, if the decision result in the step 59 is NO, it is determined that the correction check mode is executable, the process proceeds to a step 60, the pressure return mode execution permission flag F_EVAP3 is set to "0", and the correction check is performed. After the mode execution permission flag F_EVAP4 is set to “1” and the timer value T of the leak determination timer is set to 0, the process ends. This step 6
Since the pressure return mode execution permission flag F_EVAP3 is set to “0” at 0, the determination result of step 51 is NO in the next and subsequent loops of this processing, and in that case, steps 52 to 60 are skipped. Then, the process proceeds to the correction check mode of step 7.

Next, the contents of the correction check mode processing in step 7 will be described with reference to FIG. As described below, this correction check mode processing is performed by setting all three valves 30 to 32 to a predetermined correction check time T4,
This is to maintain the closed state and to determine the presence or absence of a leak at that time.

As shown in the figure, in this processing, first, in step 71, a correction check mode execution permission flag F_
It is determined whether or not EVAP4 is "1". If the result of this determination is NO, it is determined that the correction check mode is not being executed, and the present process is terminated. On the other hand, when the result of the determination is YES, the routine proceeds to step 72, where the bypass valve 30, the vent shut valve 31 and the purge control valve 32 are all kept closed.

Next, the process proceeds to a step 73, wherein the timer value T of the leak determination timer is set to a predetermined delay time T41 (for example, 0.5
sec) It is determined whether it is equal to or longer than sec. If the determination result is NO and the predetermined delay time T41 has not elapsed after the shift to the correction check mode, the routine proceeds to step 74, where the current value PTANK of the tank internal pressure is set as the fourth detection pressure P4, and then the present processing is performed. To end.

On the other hand, if the decision result in the step 73 is YES.
After a shift to the correction check mode, a predetermined delay time T4
When 1 has elapsed, the routine proceeds to step 75, where it is determined whether or not the timer value T is equal to or longer than a predetermined correction check time T4 (for example, 30 seconds). If the result of this determination is NO, and after the shift to the correction check mode, a predetermined correction check time T
If 4 has not elapsed, this processing is terminated. On the other hand, if the result of this determination is YES and the predetermined correction check time T4 has elapsed after the shift to the correction check mode, the routine proceeds to step 76, where the present value PTAN of the tank internal pressure is set.
A value obtained by subtracting the fourth detection pressure P4 from K is set as the fourth differential pressure DP4. As described above, the fourth differential pressure DP4 indicates the amount of change in the tank internal pressure PTANK between the time when the predetermined delay time T41 has elapsed from the start of the correction check mode and the time when the correction check mode ends.

Then, the process proceeds to a step 77, wherein a difference (DP3-DP4) between the third differential pressure DP3 and the fourth differential pressure DP4 calculated in the step 56 is smaller than a fourth threshold value PT4. Is determined. If the determination result is YES and the difference between the change amount of the tank pressure PTANK during the pressure return mode and the change amount of the tank pressure PTANK during the correction check mode is small, the cause of the increase in the tank pressure PTANK during the leak check mode is determined. Is determined to be because there is a large amount of fuel vapor, it is determined that there is no leak in the fuel vapor processing system 20, and the routine proceeds to step 78, where a leak determination flag FLEAK is set to "0" to indicate this. Then, the process proceeds to a step 80, wherein the leak determination end flag FDONE is set to "1" to indicate that the leak determination has been completed, and then the present process is terminated.

On the other hand, if the decision result in the step 77 is YES.
When the difference between the change in the tank pressure PTANK during the pressure return mode and the change in the tank pressure PTANK in the correction check mode is large, the tank pressure PTANK during the leak check mode despite the small amount of fuel vapor.
It is determined that the cause of the rise is mainly due to the leak, and it is determined that a leak equivalent to a state where there is a hole having a predetermined diameter is generated in the evaporative fuel processing system 20, and step 79.
And a leak determination flag FLEA
Set K to "1". Next, after executing the step 80, the present process is terminated.

Next, an example of the transition of the tank internal pressure PTANK obtained when the above-described leak determination processing is executed will be described with reference to timing charts shown in FIGS. FIG. 7 shows the transition of the tank internal pressure PTANK when slosh does not occur during the leak check mode, and FIG. 8 shows the transition of the tank internal pressure PTANK when slosh occurs during the leak check mode. In both figures, the curve shown by the solid line indicates the actually detected tank internal pressure PTANK, and the curve shown by the broken line indicates the estimated pressure PM 'estimated by the approximate expression (2).

As shown in both figures, first, when pressure reduction is started in the pressure reduction mode (time t0, t10), the tank internal pressure P
TANK decreases. Thereafter, when the tank internal pressure PTANK decreases to a predetermined negative pressure and the predetermined pressure reduction time T1 has elapsed (time t1, t11), the purge control valve 32 is closed, the evaporated fuel processing system 20 is closed, and the leak check mode is set. Transition. Thereafter, when the tank internal pressure PTANK gradually increases and the first predetermined time T21 elapses, the first detection pressure P1 is sampled. Next, at the time when the second predetermined time T22 has elapsed (time t2, t12), the second detection pressure P2 is sampled, and at the time when the predetermined slosh determination time T5 has elapsed from this time (time t3, t13), Using the second detected pressure P2 and the tank internal pressure PTANK at that time, the pressure estimation coefficient a is calculated by equation (1).

Thereafter, the slosh determination is repeatedly executed at a predetermined cycle (for example, every 80 msec). That is, the estimated pressure PM 'calculated by the pressure estimation coefficient a and the approximate expression (2) and the tank internal pressure P at that time.
The differential pressure DPM with TANK is calculated, and this differential pressure DPM is compared with a slosh determination threshold value PTG.

Each time the predetermined slosh determination time T5 elapses, the value of the pressure estimation coefficient a is updated, and thereafter, the differential pressure DPM calculated using the updated pressure estimation coefficient a is set to a threshold value. By comparing with the PTG, the slosh determination is continuously performed. Then, as shown in FIG. 8, when a slosh occurs during the leak check mode, the differential pressure DPM increases, and DPM ≧ PTG is established at a certain timing (time tx) (step 43 in FIG. 4; YES) ). As a result, in the current leak determination process, the leak determination is prohibited, and the execution of the pressure return mode and the correction check mode is prohibited. afterwards,
After waiting for the monitor execution condition to be satisfied, the leak determination process is executed again sequentially from the open-to-atmosphere mode.

On the other hand, if no slosh occurs during the leak check mode as shown in FIG.
Since TG is continuously established, the slosh determination is continuously performed. Then, when the third predetermined time T23 has elapsed (time t4), the third detection pressure P3 is sampled, and when the predetermined leak check time T2 has elapsed (time t5), the leak check mode is ended. Then, the pressure return mode is started.

In the pressure return mode, as described above, when the second differential pressure DP2 is less than the second threshold value PT2, a leak determination is performed based on the third differential pressure. on the other hand,
When the second differential pressure DP2 is equal to or greater than the second threshold value PT2,
On the condition that the leak determination is not performed and the first differential pressure DP1 is less than the first threshold value PT1, the correction check mode is started at the time when the predetermined pressure return time T3 has elapsed (time t6). Thereafter, when the predetermined delay time T41 has elapsed, the fourth detection pressure P4 is sampled. Then, when the predetermined correction check time T4 has elapsed (time t
In 7), the fourth differential pressure DP4 is calculated, and a leak determination is performed by comparing the deviation (DP3-DP4) between the third differential pressure DP3 and the fourth differential pressure DP4 with the fourth threshold value PT4. You.

As described above, according to the leak determination device 1 of the present embodiment, the evaporated fuel processing system 20 during the leak determination processing
Using the first to fourth differential pressures DP1 to DP4 calculated from the internal tank pressure PTANK, the presence / absence of a leak in the evaporated fuel processing system 20 is determined. Further, in the leak check mode, based on the two tank internal pressures PTANK detected at predetermined time intervals (predetermined slosh determination time T5), the pressure estimation coefficient a is calculated by the approximate expression (1),
Thereafter, at predetermined time intervals, by comparing the detected pressure PM, which is the detected tank internal pressure, with the estimated pressure PM ′ calculated by the approximate expression (2) using the pressure estimation coefficient a,
Slosh determination is repeatedly performed. When it is determined that slosh has occurred, the leak determination is prohibited.

As described above, since the estimated pressure PM ′ is estimated based on the tank pressure PTANK detected at two points before the slosh determination point, the tank pressure PTA is determined.
The estimation can be performed while reflecting the tendency of the NK change. Therefore, the estimated pressure PM ′ reflecting the tendency of the change in the tank internal pressure PTANK and the actual detected pressure P
By comparing with M, the slosh determination can be performed more accurately than in the conventional method of simply determining based on the difference between the two detected pressures. In addition, since the pressure estimation coefficient a used for estimating the estimated pressure PM ′ is updated every predetermined time (predetermined slosh determination time T5), the estimated pressure PM ′ can be more accurately estimated. . As described above, erroneous determination of leak due to erroneous slosh determination can be prevented, and leak determination can be performed accurately.

The leak determination prohibiting means is not limited to the embodiment in which the leak determination is prohibited when the slosh occurs, and the leak determination is stopped when it is determined that the slosh has occurred during the leak determination. It is also possible to invalidate the result of the determination once and then make the determination result invalid.

The determination of the presence or absence of the slosh is not limited to the method of the embodiment in which the differential pressure DPM between the detected pressure PM and the estimated pressure PM ′ is compared with the threshold value DPM. May be compared with a predetermined value.

Further, the embodiment is an example in which the bypass valve 30 is closed during the leak check mode, so that the space on the fuel tank 21 side of the bypass valve 30 and the two-way valve 27 is subjected to the leak determination. Alternatively or additionally, the bypass valve 3 is in the leak check mode.
By leaving 0 open, the entire evaporated fuel processing system 20 including the canister 24 side may be subjected to the leak determination. In this case, by performing both of the two types of leak determination, the location of the leak is determined by the bypass valve 30.
It is possible to specify which one is the canister 24 side or the fuel tank 21 side.

[0073]

As described above, according to the leak determination processing of the evaporative fuel processing system of the present invention, the accuracy of the fuel swing determination can be improved. Can be appropriately and accurately performed according to the conditions.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an evaporated fuel processing system to which a leak determination device according to an embodiment of the present invention is applied and an internal combustion engine including the same.

FIG. 2 is a flowchart illustrating a main routine of a leak determination process executed by the leak determination device.

FIG. 3 is a flowchart showing a subroutine of a leak check mode in FIG. 2;

FIG. 4 is a flowchart illustrating a subroutine of a slosh determination process of FIG. 3;

FIG. 5 is a flowchart showing a subroutine of a pressure return mode of FIG. 2;

FIG. 6 is a flowchart showing a subroutine of a correction check mode in FIG. 2;

FIG. 7 is a timing chart showing an example of transition of the tank internal pressure PTANK when slosh does not occur during execution of the leak determination processing.

FIG. 8 is a timing chart showing an example of a transition of the tank internal pressure PTANK when a slosh occurs during the execution of the leak determination process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Leak determination apparatus 2 ECU (leak determination means, pressure estimation means, fuel fluctuation determination means, leak determination inhibition means) 3 Internal combustion engine 5 Intake pipe (intake system) 20 Evaporated fuel processing system 21 Fuel tank 24 Canister 25 Purge passage 26 Pressure Sensor (pressure detection means) PTANK Tank internal pressure (pressure in evaporative fuel processing system) PM Detection pressure for slosh determination (pressure in evaporative fuel processing system detected at second timing) PM 'estimated pressure (estimated evaporation A Pressure estimation coefficient (coefficient for estimating pressure) PX Current value of reference pressure (pressure value for estimating pressure) PY Previous value of reference pressure (pressure for estimating pressure) Value) DPM Differential pressure for slosh judgment (differential pressure for judging fuel sway) PTG Threshold pressure for slosh judgment (threshold for fuel sway judging) DP1 to DP4 1st to 1st Differential pressure PT1~PT4 first to fourth threshold pressure (differential pressure for leak determination) (threshold value for leak determination)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shoichi Kitamoto 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3G044 BA22 EA32 EA40 EA53 EA55 EA67 FA04 FA05 FA20 FA27 FA32 FA39 GA01 GA25

Claims (1)

[Claims] An evaporative fuel processing system leak judging device for temporarily adsorbing evaporative fuel generated in a fuel tank to a canister and determining whether or not there is a leak in an evaporative fuel processing system to be supplied to an intake system of an internal combustion engine. Pressure detecting means for detecting the pressure in the fuel vapor processing system, and a pressure detecting means for detecting a pressure in the fuel vapor processing system according to the pressure in the fuel vapor processing system detected during a predetermined leak determination period. A leak determination unit that determines the presence or absence of the leak determination period; and a leak determination unit that determines the presence or absence of the leak determination period according to a pressure state in the evaporative fuel processing system detected at at least one predetermined first timing after the start of the leak determination period. Pressure estimating means for estimating a pressure in the evaporative fuel processing system at a predetermined second timing after the first timing; and the evaporative fuel detected at the second timing and the estimated pressure. Fuel sway determining means for determining whether or not fuel sway has occurred in the fuel tank according to a result of comparison with the pressure in the processing system; and A leak determination device for a fuel vapor processing system, comprising: a leak determination prohibition unit for prohibiting a leak determination by the leak determination unit when it is determined that the shaking has occurred.