JP2001082261A - Abnormality diagnostic apparatus for evaporated fuel discharge preventing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diagnostic apparatus capable of diagnosing abnormality in an evaporated fuel discharge preventing apparatus with high precision regardless of running or stopping of an internal combustion engine and of performing exact diagnosis even if stopping time is relatively short. SOLUTION: While an engine is running, a leak check A is performed, and while stopping, a leak check B is performed. In the leak check A, diagnosis waiting time is set according to the internal pressure PTANK of a tank (S12, S14, S32). In the leak check B, diagnosis waiting time for engine stopping is set. Abnormality diagnosis is performed based on a variance in the internal pressure of the tank within the diagnosis waiting time (S17, S20, S36, S37).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for diagnosing an abnormality in an evaporative fuel emission prevention device for preventing the emission of evaporative fuel generated in a fuel tank for supplying fuel to an internal combustion engine. The present invention relates to an abnormality diagnosis device for an evaporative fuel emission prevention device that prevents emission of evaporative fuel by maintaining the same.

[0002]

2. Description of the Related Art An evaporative fuel passage which directly connects an intake pipe of an internal combustion engine and a fuel tank is provided to maintain the inside of the fuel tank at a negative pressure (a pressure lower than the atmospheric pressure), thereby preventing the release of the evaporative fuel. For example, Japanese Patent Application Laid-Open No. 10-281
No. 019. Further, a method of diagnosing an abnormality of such an evaporative fuel emission prevention device is disclosed in
No. 8 discloses this.

According to the abnormality diagnosis method disclosed in this publication, a two-dimensional coordinate system defined by the fuel tank internal pressure and the fuel temperature in accordance with the fuel tank internal pressure at the time of stopping the internal combustion engine and the fuel temperature. When the combination of the fuel tank internal pressure and the fuel temperature detected at the time of the next engine start is within the abnormality determination region, the evaporative emission control device is determined to be abnormal.

[0004]

According to the above-mentioned conventional abnormality diagnosis method, the fuel tank internal pressure slightly increases when the evaporative fuel discharge device is normal, and reaches a steady state, that is, after the engine is stopped. It is assumed that the time until the next start is long, and when the engine is restarted in a relatively short time after the engine is stopped, an accurate determination cannot be made. In addition, the above publication does not disclose a method of diagnosing abnormality during operation of the internal combustion engine, and it has been desired to enable abnormality diagnosis even during operation of the internal combustion engine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and can accurately diagnose an abnormality of an evaporative emission control apparatus regardless of whether the internal combustion engine is operating or stopped. It is an object of the present invention to provide an abnormality diagnosis device capable of performing accurate diagnosis even when the time is relatively short.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an evaporative fuel passage connecting a fuel tank to an intake system of an internal combustion engine; And a control means for controlling the opening of the control valve so that the pressure in the fuel tank is lower than the atmospheric pressure at least during operation of the internal combustion engine. In the abnormality diagnosis device, an in-tank pressure detecting means for detecting a pressure in the fuel tank, an operation detecting means for detecting that the internal combustion engine is operating, and the in-tank pressure and the internal combustion engine are operating Diagnostic waiting time setting means for setting a diagnostic waiting time according to at least one of the following: pressure change amount detecting means for detecting a change amount of the tank internal pressure within the diagnostic waiting time; By comparing the amount of change in tank internal pressure and a predetermined threshold value, and having an abnormality judging means for judging an abnormality of the evaporative fuel emission preventing device.

According to this configuration, a diagnosis waiting time is set according to at least one of the tank internal pressure and whether or not the internal combustion engine is operating, and a change amount of the tank internal pressure during the diagnosis waiting time is detected. By comparing the change amount of the tank internal pressure with a predetermined threshold value, it is determined that the fuel vapor emission prevention device is abnormal. Therefore, it is determined whether the internal combustion engine is operating and / or the tank internal pressure is appropriate. By setting an appropriate diagnosis waiting time, it is possible to accurately diagnose the abnormality of the evaporative emission control device regardless of whether the internal combustion engine is operating or stopped, and accurately even if the stop time is relatively short. Diagnosis can be performed.

More specifically, it is desirable to make the diagnosis waiting time shorter during operation of the internal combustion engine than during stoppage, and to shorten the diagnosis waiting time as the internal pressure of the tank becomes lower during operation. Further, after the internal combustion engine is stopped, the predetermined threshold value is set based on a tank internal pressure and a fuel temperature at the time of the stop and a fuel temperature after a lapse of the diagnosis waiting time from the stop time of the internal combustion engine. Is desirable. It is preferable that the predetermined threshold value used during the operation of the internal combustion engine is set to an optimal value by an experiment so that the predetermined threshold value increases as the diagnosis waiting time increases.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an evaporative fuel release prevention device and an abnormality diagnosis device thereof according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an internal combustion engine having, for example, four cylinders (hereinafter simply referred to as "engine"), and a throttle valve 3 is disposed in the intake pipe 2 of the engine 1. The throttle valve 3 has a throttle valve opening (θT
H) The sensor 4 is connected, and outputs an electric signal corresponding to the opening degree of the throttle valve 3 and supplies it to an electronic control unit (hereinafter referred to as (ECU)) 5.

A fuel injection valve 6 is provided for each cylinder in the middle of the intake pipe 2 and slightly upstream of an intake valve (not shown) between the engine 1 and the throttle valve 3. Each fuel injection valve 6 is connected via a fuel supply pipe 7 to a fuel pump unit 8 provided in a sealed fuel tank 9. The fuel pump unit 8 includes a fuel pump, a fuel strainer, The pressure regulator is configured integrally with a pressure regulator that sets the reference pressure to the atmospheric pressure or the tank internal pressure. The fuel tank 9 has a filler port 10 for refueling, and a filler cap 11 is attached to the filler port 10.

The fuel injection valve 6 is electrically connected to the ECU 5, and the valve opening time is controlled by a signal from the ECU 5. Downstream of the throttle valve 3 of the intake pipe 2, an intake pipe absolute pressure (PBA) sensor 13 for detecting the intake pipe absolute pressure PBA and an intake temperature (TA) sensor 14 for detecting an intake air temperature TA as an outside air temperature are mounted. Have been. The fuel tank 9 has a tank pressure sensor 15 as a tank pressure detecting means for detecting the pressure in the fuel tank 9, that is, the tank pressure PTANK, and a fuel temperature (TGAS) for detecting the temperature TGAS of the fuel in the fuel tank 9. TGAS) sensors 16 are provided.

An engine speed (NE) sensor 17 for detecting the engine speed is mounted around a camshaft or crankshaft (not shown) of the engine 1. The engine speed sensor 17 outputs a pulse (TDC signal pulse) at a predetermined crank angle position every time the crankshaft of the engine 1 rotates 180 degrees. An engine water temperature sensor 18 for detecting a cooling water temperature TW of the engine 1 and an oxygen concentration sensor (hereinafter referred to as “LAF sensor”) 19 for detecting an oxygen concentration in exhaust gas of the engine 1 are provided. These sensors 13 to 19 are provided. Is supplied to the ECU 5. LAF
The sensor 19 functions as a wide-range air-fuel ratio sensor that outputs a signal that is substantially proportional to the oxygen concentration in the exhaust gas (the air-fuel ratio of the air-fuel mixture supplied to the engine 1). The ECU 5 is further connected to an atmospheric pressure sensor 40 for detecting an atmospheric pressure PA and a battery voltage sensor 41 for detecting a battery voltage VB.
Supplied to

Next, a configuration for reducing the internal pressure of the fuel tank 9 to a negative pressure will be described. The fuel tank 9 is connected to the intake pipe 2 on the downstream side of the throttle valve 3 via a first evaporative fuel passage 20. In the evaporative fuel passage 20, an evaporative fuel passage is provided to control the internal pressure of the fuel tank 9. A tank pressure control valve 30 is provided as a control valve that opens and closes 20. The tank pressure control valve 30 is an electromagnetic valve that controls the supply flow rate of the evaporated fuel generated in the fuel tank 9 to the intake pipe 2 by changing the on-off duty ratio of the control signal (the opening degree of the control valve). The operation of the control valve 30 is controlled by the ECU 5. The control valve 30 may be a linear control type solenoid valve whose opening can be continuously changed.

A cutoff valve 21 is provided at a connection between the fuel vapor passage 20 and the fuel tank 9. The cutoff valve 21 is a float valve that closes when the fuel tank 9 is full or when the inclination of the fuel tank 9 increases. Next, a configuration for preventing the evaporated fuel generated in the fuel tank 9 at the time of refueling from being released to the atmosphere will be described. A canister 33 is connected to the fuel tank 9 via a charge passage 31, and the canister 33 is connected to a downstream side of the throttle valve 3 of the intake pipe 2 via a purge passage 32.

A charge control valve 36 is provided in the middle of the charge passage 31. The charge control valve 36
The operation is controlled by the CU 5, and the valve is opened at the time of refueling, and otherwise closed, and the fuel vapor in the fuel tank 9 is guided to the canister 33 at the time of refueling.

The canister 33 has a built-in activated carbon for adsorbing the fuel vapor in the fuel tank 9 and has an open-to-atmosphere passage 3.
It can communicate with the atmosphere via 7. A vent shut valve (open / close valve) 38 is provided in the middle of the atmosphere opening passage 37. The vent shut valve 38 is a so-called normally-closed valve whose operation is controlled by the ECU 5 and is opened at the time of refueling or during execution of a purge, and closed at other times.

A purge control valve 34 is provided in the purge passage 32 between the canister 33 and the intake pipe 2. The purge control valve 34 is an electromagnetic valve configured so that the flow rate can be continuously controlled by changing the on-off duty ratio of the control signal (the opening degree of the control valve). It is controlled by the ECU 5.

The ECU 5 has a function of shaping input signal waveforms from various sensors and the like, correcting a voltage level to a predetermined level, converting an analog signal value into a digital signal value, and the like. "CPU"), a storage means for storing a calculation program executed by the CPU, a calculation result and the like, a fuel injection valve 6, a tank pressure control valve 30, a purge control valve 34, a charge control valve 36, and a vent shut valve 38. And an output circuit for supplying a drive signal to the control circuit.

The CPU of the ECU 5 responds to output signals from various sensors, such as an engine speed sensor 17, an intake pipe absolute pressure sensor 13, and an engine coolant temperature sensor 18, in accordance with output signals of the engine 1.
Control of the amount of fuel supplied to the vehicle. The CPU of the ECU 5
Controls the operation of the solenoid valve according to the situation such as during refueling or during normal operation of the engine 1 as follows. First, at the time of refueling, the charge control valve 36 and the vent shut valve 38 are opened as described above. As a result, the fuel vapor generated in the fuel tank 9 upon refueling is supplied to the charge control valve 36.
The air that has been occluded in the canister 33 through which the fuel component has been removed is discharged to the atmosphere through the vent shut valve 38. Therefore, it is possible to prevent the evaporative fuel from being released into the atmosphere during refueling.

Next, during normal operation of the engine 1, the charge control valve 36 is closed, the vent shut valve 38 is opened, the purge control valve 34 is opened, and the negative pressure in the intake pipe 2 is reduced. Acts on the canister 33. As a result, the atmosphere is supplied to the canister 33 via the vent shut valve 38, and the fuel adsorbed by the canister 33 is purged to the intake pipe 2 via the purge control valve 34. Therefore,
Evaporated fuel generated in the fuel tank 9 is supplied to the intake pipe 2 without being released to the atmosphere, and burns in the combustion chamber. Further, during normal operation of the engine 1, when a predetermined condition is satisfied, the tank pressure control valve 30 is opened, and the internal pressure PTANK of the fuel tank 9 becomes the target pressure P0 lower than the atmospheric pressure due to the negative pressure of the intake pipe 2. , A negative pressure control is performed. in this case,
As shown in, for example, Japanese Patent Application Laid-Open No. 10-281010, the target pressure P0 is expected to increase in the fuel tank internal pressure PTANK so that the negative pressure in the fuel tank 9 can be maintained even after the engine 1 is stopped. Is set by Also,
In addition to setting the target pressure P0 as an absolute pressure, the differential pressure between the tank internal pressure and the atmospheric pressure is a predetermined pressure (for example, 300
３５０350 mmHg).

Next, an abnormality diagnosis of the evaporative fuel emission prevention device configured as shown in FIG. 1 will be described with reference to FIGS. FIG. 2 is a flowchart of a process of performing an abnormality diagnosis (leak check A) while the engine 1 is operating, and FIG. 3 is a flowchart of a process of performing an abnormality diagnosis (leak check B) while the engine 1 is stopped. These processes are executed by the CPU of the ECU 5 every predetermined time (for example, 82 msec).

In step S11, an end flag FCHKAEN indicating "1" indicating that the leak check A has been completed.
It is determined whether or not D is “1”, and FCHKAEND =
When it is 0, the processing of step S12 and subsequent steps is executed,
When FCHKAEND = 1, this process is immediately terminated.

In step S12, the tank internal pressure PTAN
It is determined whether or not K is lower than a predetermined pressure PTANK0 (for example, set to 460 mmHg) for determining whether or not the pressure in the fuel tank has been sufficiently reduced to a negative pressure.
When TANK0 is attained and the pressure in the fuel tank is sufficiently reduced to a negative pressure, the tank pressure PTANK is set to perform abnormality diagnosis.
It is determined whether or not the value of a first down-count timer tmNPCSCHK0 for measuring a diagnosis waiting time for detecting a change amount of is less than or equal to 0 (step S13). At first tmNP
Since CSCHK0 = 0, this timer tmNPCS
CHK0 is set to a first predetermined time TNPCSCHK0 (for example, 15 seconds) and started (step S1).
4), measure the tank internal pressure PTANK at this time to the measurement start pressure P
It is stored as TANKC1 (step S33), and this processing ends.

When step S14 is executed, step S14 is executed.
Since the answer to 13 is negative (NO), the process proceeds to step S16, and it is determined whether or not the value of the timer tmNPSCSCHK0 is greater than the change amount measurement end time TCHK0 (for example, 1 second). At first this answer is affirmative (YES),
The tank pressure PTANK at this point and the measurement start pressure PTA
Differential pressure from NKC1, that is, a diagnosis waiting time for the tank internal pressure PTANK (tmNPSCSCH0 = TPCSCHK0)
~ TACK0), the change amount DPTANK (= PT
ANK-PTANC1) is determined to be greater than or equal to a first predetermined change amount α (for example, 30 mmHg) (step S).
17). At first, since DPTANK <α, the tank pressure control valve 30 is closed (step S18), and this processing ends.

If the tank pressure PTANK rises during the diagnosis waiting time and DPTANK ≧ α, the answer to step S17 becomes affirmative (YES), and the fuel tank 9, the evaporative fuel passage 30, or the charge passage 31 (hereinafter referred to as “fuel tank and It is determined that there is a leak in the "peripheral part" (step S20), the end flag FCHKAEND is set to "1" (step S21), and this processing ends.

If the answer to step S17 is negative (NO), the diagnosis waiting time ends, the process proceeds from step S16 to step S19, in which it is determined that there is no leakage in the fuel tank and its surroundings, and the process proceeds to step S21. . On the other hand, if PTANK ≧ PTANK0 in the step S12 and the negative pressure processing of the fuel tank is not completed,
The flow rate QNPC of the air-fuel mixture containing the evaporated fuel passing through the tank pressure control valve 30 (that is, flowing through the evaporated fuel passage 20)
It is determined whether S is larger than a predetermined flow rate QTH (for example, 10 liter / min) (step S31).

The flow rate QNPCS is the tank pressure PTANK.
Pressure difference ΔP between the pressure and the intake pipe absolute pressure PBA (= PTANK−
PBA) and the opening degree (valve opening duty ratio) of the tank pressure control valve 30 are calculated by searching a table shown in FIG. 4A and performing an interpolation operation as appropriate. FIG.
(A) shows a change characteristic of the flow rate QNPCS with respect to the differential pressure ΔP, in which the line L1 corresponds to the characteristic when the tank pressure control valve 30 is fully opened, and the opening decreases in the order of the lines L2, L3, and L4. It corresponds to the characteristic.

If QNPCS> QTH and the flow rate is large in step S31, a second timer t for measuring a diagnosis waiting time for detecting a change in the tank internal pressure PTANK.
The second predetermined time TNPCSCHK is added to mNPCSCHK1.
1 (for example, 30 seconds) and start, and the routine proceeds to step S33, where the tank pressure PTANK at that time is set.
Is stored as the measurement start pressure PTANKC1.

Thereafter, the negative pressure progresses, and the flow rate QNPCS ≦
When QTH is reached, the process proceeds from step S31 to step S34, in which it is determined whether the value of the timer tmNPCSCHK1 is 0 or less. Since tmNPCSCHK1> 0 at first, the amount of change in tank internal pressure DPTANK (= PTANK−
PTANKC1) is the second predetermined change amount β (for example, 30 m
mHg) or not (step S36), and the DP
When TANK <β, the present process is immediately terminated.
The tank pressure PTANK rises within the waiting time for diagnosis and DP
When TANK ≧ β, it is determined that there is a leak in the fuel tank and its surroundings (step S37), and the end flag FCHKAEND is set to “1” (step S3).
8), end this processing.

If the answer to step S36 is negative (NO), the diagnosis waiting time ends, the process proceeds from step S34 to step S35, where it is determined that there is no leak in the fuel tank and its surroundings, and the process proceeds to step S38. . The determination in step S12 is performed with hysteresis.
That is, if the width of the hysteresis is ± DPX, PTA
When the tank internal pressure PTANK decreases from the state of NK> PTANK0, PTANK <PTANK0-DP
At the point in time when X has been reached, the answer in step S12 changes from negative (NO) to positive (YES), while PTANK <PTAN.
When the tank internal pressure PTANK increases from the state of K0, the answer at step S12 is changed from affirmative (YES) to negative (N) when PTANK> PTAN0 + DPX.
O). Therefore, after the tank pressure control valve 30 is closed due to leakage, the tank internal pressure PTAN
Even if K increases, the answer in step S12 is affirmative (YES).
Is maintained.

When the fuel tank or the like has a hole, the lower the tank pressure PTANK is, the larger the pressure change amount per unit time becomes.
When it is lower than NK0, the diagnosis waiting time is set shorter than when it is higher than NK0, and by performing a leak check, it is possible to quickly and accurately determine the presence or absence of a leak.

FIG. 3 is a flowchart of a process for performing an abnormality diagnosis (leak check B) after the engine 1 is stopped.
In step S41, it is determined whether or not an end flag FCKBEND indicating that the leak check B has been completed is "1" is "1". When FCHKEND = 1, the present process is immediately terminated. If FCKBEND = 0, it is determined whether the filler cap 11 has been operated (step S42). This determination is performed, for example, based on a sensor output that detects whether or not the filler cap 11 has been removed. If the filler cap 11 has been operated, the present process is immediately terminated. If not, it is determined whether or not an ignition switch (not shown) has been turned off (step S4).
3).

When the ignition switch is on,
The current fuel temperature TGAS and tank pressure PTANK
Are stored as the fuel temperature TGASC2 and the tank internal pressure PTANKC2 at the end of the operation, respectively (step S4).
4) Then, a third predetermined time TNPCSCHK2 (for example, 3 minutes) is set in a down count timer tmNPSCSCHK2 for measuring the diagnosis waiting time after the engine is stopped, and the process is started (step S45), and this processing is ended.

When the ignition switch is turned off and the engine 1 is stopped, it is determined whether or not the value of the timer tmNPCSCHK2 is 0 or less (step S46). At first, since tmNPCSCHK2> 0, this process is immediately terminated. When the predetermined time TNPCSCHK2 elapses and tmNPCSCHK2 = 0, step S4
6 to step S47, and the stored value TGA of the fuel temperature
The a0 map is searched according to SC2 and the stored value PTANKC2 of the tank internal pressure, and the coefficient a0 used in the next step S48 is calculated. The a0 map shows that as the fuel temperature storage value TGASC2 increases as shown in FIG. 4 (b), the tank internal pressure storage value P decreases as shown in FIG. 4 (c).
It is set to increase as TANKC2 increases.

In the following step S48, a predicted value PTANKC3 of the tank internal pressure is calculated as a function of the fuel temperature TGAS at that time by the following equation (1). PTANKC3 = a2 × TGAS ² + a1 × TGAS + a0 (1) Here, the coefficients a2 and a1 are set to values experimentally obtained in advance, for example, about 0.1 and 5, respectively. The predicted value PTANKC3 is a minimum tank value which is a pressure at which a relief valve (not shown) provided to prevent the pressure in the fuel tank 9 from becoming excessively low and damaging the fuel tank 9 is opened. Internal pressure PTANL (for example, 350 mmHg)
Make sure that:

Next, it is determined whether or not the tank internal pressure PTANK is equal to or lower than the minimum tank internal pressure PTANL (step S4).
9) When PTANK ≦ PTANKL, it is determined that there is no leakage in the fuel tank and its surroundings (step S).
51), the end flag FCCHKBEND is set to “1” (step S53), and the process ends.

In step S49, PTANK> PTANK
When L, the tank internal pressure PTANK at that time,
Deviation DPC3 from prediction value PTANKC3 (= PTANKC3)
−PTANKC3) is equal to the predetermined deviation γ (for example, 15 mmH
g) It is determined whether or not it is equal to or greater than (step S50), and DPC3
If <γ, it is determined that there is no leakage (step S5).
1) When DPC3 ≧ γ, it is determined that there is a leak (step S52), and the process proceeds to step S53.

The left side of the judgment formula in step S50 in FIG. 3 is as follows: PTANK-PTANC3 = (PTANK-PTAN)
(KC2)-(PTANC3-PTANC2), so that the determination equation in step S50 can be modified as the following equation (2). (PTANK-PTANKC2)-(PTANKC3-PTANKC2) ≧ γ (2)

That is, according to the processing of FIG.
Tank pressure PTANKC2 and fuel temperature TGASC2 at the time of stoppage and a predetermined time TNPCS from the stop time
According to the fuel temperature TGAS after the passage of CHK2, the predicted value PTANKC3 of the tank internal pressure at that time is calculated (steps S47, S48), and the change amount DPTAN of the tank internal pressure is calculated.
K (= PTANK-PTANKC2) is the predicted value PTA
Reference change amount DPTANKREF obtained from NKC3
(= PTANKC3-PTANKC2) from the predetermined deviation γ
When it is larger than the above, it is determined that there is a leak in the fuel tank or its peripheral portion. Therefore, even after the engine is stopped, even before the tank internal pressure PTANK reaches a steady state, it is possible to make an accurate determination based on the state of the tank internal pressure and the fuel temperature at the time of the engine stop and subsequent changes.

The diagnosis waiting time after the engine is stopped, that is, the predetermined time TNPCSCHK2 is, for example, 3
Diagnostic waiting time during engine operation (TNPCSC)
By setting the time longer than (HK0, TNPCSCHK1), even a slight leak due to a small hole can be accurately determined.

In this embodiment, the abnormality diagnosis device is constituted by the tank internal pressure sensor 15 and the ECU 5. More specifically, step S43 in FIG. 3 corresponds to operation detection means, and steps S12, S14 and S14 in FIG. Steps S32 and S43 and S45 in FIG. 3 correspond to a diagnosis waiting time setting unit, steps S17 and S36 in FIG. 2 and step S50 in FIG. 3 correspond to a pressure change amount detecting unit, and steps S16, S17 and S17 in FIG. S19, S20, S34 to S37
Steps S46 to S52 in FIG. 3 correspond to an abnormality determination unit.

In the process of FIG. 2, the predetermined change amounts α, β
Corresponds to the “predetermined threshold value” in claim 1. In addition, the above equation (2) indicates that PTANK−PTANKC2 ≧ PTANKC
Since it can be transformed into 3-PTANC2 + γ, (PTANC3-PTANC2 + γ) in the processing of FIG. 3 corresponds to the “predetermined threshold value”.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the arrangement of the tank internal pressure sensor 15 is not limited to that shown in FIG. 1, and may be provided, for example, between the charge control valve 36 of the charge passage 31 and the fuel tank 9. The charge control valve 36 and the vent shut valve 38 may be provided with a relief valve as shown in Japanese Patent Application Laid-Open No. H11-50919.

[0044]

As described above in detail, according to the present invention, the diagnosis waiting time is set according to at least one of the tank internal pressure and whether or not the internal combustion engine is operating, and the tank within the diagnosis waiting time is set. The amount of change in the internal pressure is detected, and by comparing the amount of change in the tank internal pressure with a predetermined threshold value,
Since the abnormality of the evaporative fuel emission prevention device is determined, an appropriate diagnosis waiting time is set according to whether the internal combustion engine is operating and / or the tank internal pressure, and whether the internal combustion engine is operating,
Abnormality diagnosis of the evaporative emission control device can be accurately performed regardless of whether the apparatus is stopped, and accurate diagnosis can be performed even when the stop time is relatively short.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an evaporative fuel release prevention device and an abnormality diagnosis device thereof according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process for performing abnormality diagnosis during operation of an engine.

FIG. 3 is a flowchart of a process for performing abnormality diagnosis while the engine is stopped.

FIG. 4 is a diagram showing setting characteristics of a map used in the processing of FIG. 3 or 4;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 internal combustion engine 2 intake pipe 5 electronic control unit (control means, operation detection means, time setting means, pressure change detection means, abnormality determination means) 9 fuel tank 15 tank internal pressure sensor (tank pressure detection means) 16 fuel temperature sensor Reference Signs List 20 evaporative fuel passage 30 tank pressure control valve (control valve) 31 charge passage

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshiaki Ichiya 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Inventor Tohru Kitamura 1-4-1 Chuo, Wako-shi, Saitama Honda R & D Co., Ltd.

Claims (1)

[Claims] An evaporative fuel passage connecting a fuel tank to an intake system of an internal combustion engine, a control valve provided in the middle of the evaporative fuel passage to open and close the evaporative fuel passage, and at least during operation of the internal combustion engine A control means for controlling an opening degree of the control valve so that a pressure in the fuel tank becomes lower than an atmospheric pressure. Tank pressure detecting means, operation detecting means for detecting that the internal combustion engine is operating, and setting a diagnosis waiting time according to at least one of the tank internal pressure and whether or not the internal combustion engine is operating. Diagnostic wait time setting means, pressure change amount detecting means for detecting a change amount of the tank internal pressure within the diagnostic wait time, and comparing the change amount of the tank internal pressure with a predetermined threshold. It allows the abnormality diagnosis apparatus characterized by comprising an abnormality judging means for judging an abnormality of the evaporative fuel emission preventing device.