JPH11324825A - Leak diagnostic device for fuel evaporative gas purge system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent erroneous diagnosis that there is leak in a fuel evaporative gas purge system by the opening of the filler cap of a fuel tank. SOLUTION: In the case of diagnosis that there is leak in a purge system, if an idle operation condition is set up, a canister closing valve is fully closed, and a purge control valve is opened, then intake pipe negative pressure is introduced to the inside of the purge system under atmospheric pressure (steps 141-143). After this, it is judged whether or not fuel tank inner pressure PT is set to set pressure (for example, -5 mmHg) or below within reference time (steps 144, 145), and when the PT is set to the set pressure or below within the reference time, it is judged that a filler cap is not opened, therefore diagnosis that there is leak is fixed and a warning lamp is lighted (steps 146, 147). If the PT is not set to the set pressure or below within the reference time from the start of introducing negative pressure, it is judged that the filler cap is opening (step 148), therefore diagnosis that there is leak is canceled (step 149).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel evaporation system for diagnosing the presence or absence of a leak in a fuel evaporation gas purging system for purging (discharging) fuel evaporation gas generated by evaporating fuel in a fuel tank into an intake pipe of an internal combustion engine. The present invention relates to a leak diagnostic device for a gas purge system.

[0002]

2. Description of the Related Art Conventionally, in a fuel evaporative gas purging system, a fuel evaporative gas generated in a fuel tank is adsorbed into a canister through a fuel evaporative gas passage in the fuel tank in order to prevent the fuel evaporative gas from leaking into the atmosphere. At the same time, a purge control valve is provided in the middle of a purge passage for purging fuel evaporative gas adsorbed in the canister to an intake pipe of the internal combustion engine, and opening and closing of the purge control valve is controlled according to an operation state of the internal combustion engine. Thus, the purge flow rate of the fuel evaporative gas purged from the canister to the intake pipe is controlled. It is necessary to detect the leakage of the fuel evaporative gas at an early stage in order to prevent the abnormality in which the fuel evaporative gas leaks from the fuel evaporative gas purge system into the atmosphere from being left for a long time.

[0003] Therefore, as shown in, for example, Japanese Patent Application Laid-Open No. 5-125997, the atmospheric pressure or the negative pressure of an intake pipe is introduced into a purge system including a fuel tank and a canister, and the pressure of the purge system or the pressure after the intake system is closed. In some cases, the presence or absence of a leak in the purge system is diagnosed based on the pressure change amount.

Since the leak diagnosis may be performed even during idling, the filler cap of the fuel tank may be opened due to refueling or the like during the execution of the leak diagnosis. The system may be open to the atmosphere. At self-service refueling stations, which are increasing in Japan recently, it is expected that refueling will be performed with the engine running while the driver himself opens the fuel tank filler cap to refuel. Therefore, it is expected that the possibility that the filler cap is opened during the leak diagnosis is increased. If the filler cap is opened during the leak diagnosis and the purge system is opened to the atmosphere, the leak is erroneously diagnosed as the purge system.

In order to prevent such erroneous diagnosis, a fuel temperature sensor is provided in the fuel tank as shown in Japanese Patent Application Laid-Open No. Hei 9-137756, and the presence or absence of a decrease in the fuel temperature is monitored. Sometimes, it is determined that refueling is in progress and the leak diagnosis is prohibited.

[0006]

However, the configuration disclosed in the above publication requires the installation of a fuel temperature sensor in the fuel tank, which leads to an increase in the number of parts and an increase in the number of assembling steps, resulting in an increase in cost.

Further, when the temperature difference between the temperature of the fuel in the fuel tank and the temperature of the fuel to be supplied is small, it cannot be determined that the fuel is being supplied. Further, if the leak diagnosis is completed after the filler cap is opened and before refueling is started, it is not determined that the fuel is being refueled. It will not be canceled and will result in a misdiagnosis. In short, in the refueling determination based on the fuel temperature, erroneous diagnosis due to the opening of the filler cap may not be prevented, and the reliability of leak diagnosis cannot be sufficiently improved.

The present invention has been made in view of such circumstances, and an object of the present invention is to reliably prevent erroneous diagnosis due to opening of a filler cap of a fuel tank and improve reliability of leak diagnosis. It is an object of the present invention to provide a leak estimating apparatus for a fuel evaporative gas purge system which can be improved and can satisfy the demands of reducing the number of parts, reducing the number of assembling steps, and reducing costs.

[0009]

According to a first aspect of the present invention, there is provided a leak diagnosis apparatus for a fuel evaporative gas purge system. In the idle operation state, an operation of introducing a predetermined pressure into the purge system (hereinafter referred to as “re-pressure introduction operation”) is performed again to determine the degree of pressure introduction into the purge system, and based on the determination result, To cancel the diagnosis result with the leak. In general, the hole that causes a leak in the purge system is small, and the filler port of the fuel tank is much larger. Therefore, when the filler cap is opened, an opening that is much larger than the hole that causes the leak is opened. . Therefore, the pressure introduction into the purge system when the filler cap is opened is extremely slow as compared with the time when a leak occurs.If the pressure introduction into the purge system becomes extremely slow during the re-pressure introduction operation, the filler Judge that the cap is open and cancel the result of the leak diagnosis. As a result, erroneous diagnosis due to the opening of the filler cap can be reliably prevented,
The reliability of leak diagnosis can be improved. In addition, the degree of pressure introduction into the purge system during the re-pressure introduction operation is determined (that is, whether the filler cap is opened or closed).
Can be performed using a pressure sensor used for leak diagnosis, so that a new sensor such as a fuel temperature sensor is not required, and it is possible to satisfy the demands of reducing the number of parts, the number of assembly steps, and the cost.

In this case, the degree of pressure introduction into the purge system at the time of the re-pressure introduction operation is determined, for example, by the pressure change rate at the time of the re-pressure introduction operation, the pressure change amount for a predetermined time, and the time required for the predetermined pressure change. Although it may be determined by the following method, etc.
It is determined whether the pressure in the purge system changes to the set pressure within the reference time by the re-pressure introduction operation, and if the pressure does not change to the set pressure within the reference time, the diagnosis result of the leak is determined. It may be canceled. This makes it possible to easily perform processing from the determination of the degree of pressure introduction during the re-pressure introduction operation to the determination of whether or not the diagnosis result can be canceled.

The reference time used for determining the degree of pressure introduction at the time of the re-pressure introduction operation may be a predetermined fixed time. The setting may be made based on at least one of the concentration learning value, the remaining amount of fuel in the fuel tank, the pressure in the purge system before the re-pressure introduction operation, and the degree of pressure change in the purge system at the time of leak diagnosis. Since each of these influences the degree of pressure introduction during the re-pressure introduction operation, by setting a reference time based on at least one of these,
The reference time can be optimized.

According to a fourth aspect of the present invention, it is determined whether the remaining amount of fuel in the fuel tank has increased based on the detection value of the remaining fuel amount detecting means. Leak diagnosis of the system may be stopped, or the result of the leak diagnosis performed at that time may be canceled. That is,
Since an increase in the remaining amount of fuel means that refueling has been performed, when the increase in the remaining amount of fuel is detected, the leak diagnosis of the purge system should be stopped or the result of the leak diagnosis performed at that time should be canceled. By doing so, erroneous diagnosis due to refueling can be reliably prevented.

In the vehicle equipped with the automatic transmission, when the shift position detected by the shift position detecting means is the neutral position or the parking position, the leak diagnosis of the purge system is stopped, or The diagnosis result of the leak made at that time may be canceled. That is, when the shift position is the parking position, the vehicle is parked, and in the neutral position, there is a possibility that the vehicle is stopped or parked. Since it is considered that the opening of the filler cap is performed during parking or stopping, the leak diagnosis of the purge system is stopped when the shift position is the neutral position or the parking position, or the result of the leak existence diagnosis performed at that time is stopped. By canceling, the erroneous diagnosis due to the opening of the filler cap can be reliably prevented.

[0014]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
First, a schematic configuration of the entire system will be described with reference to FIG. An air cleaner 13 is provided on the upstream side of an intake pipe 12 of the engine 11, and air passing through the air cleaner 13 is drawn into each cylinder of the engine 11 through a throttle valve 14. The opening of the throttle valve 14 is adjusted by the amount of depression of the accelerator pedal 15. Also,
A fuel injection valve 16 is provided in the intake pipe 12 for each cylinder. Fuel (gasoline) in a fuel tank 17 is sent to each fuel injection valve 16 via a fuel pipe 19 by a fuel pump 18. The fuel tank 17 is provided with a pressure sensor 20 such as a semiconductor pressure sensor for detecting the pressure in the fuel tank 17.

Next, the configuration of the purge system 21 will be described. The canister 23 is connected to the fuel tank 17 through a communication pipe 22.
Is connected. In the canister 23, an adsorbent 24 such as activated carbon for adsorbing fuel evaporative gas is accommodated. At the bottom of the canister 23, an atmosphere communication pipe 25 communicating with the atmosphere is provided, and a canister closing valve 26 is attached to the atmosphere communication pipe 25.

The canister closing valve 26 is constituted by an electromagnetic valve. In an off state, the canister closing valve 26 is kept open by a spring (not shown), and the canister 23 is kept open to the atmosphere. Dripping. When a predetermined voltage is applied to the canister closing valve 26, the canister closing valve 26 is switched to a closed state, and the atmosphere communication pipe 25 is closed.

On the other hand, between the canister 23 and the intake pipe 12, a purge passage 30a for purging (discharging) the fuel evaporative gas adsorbed by the adsorbent 24 into the intake pipe 12 is provided.
A purge control valve 31 for adjusting a purge flow rate is provided between the purge passages 30a and 30b. This purge control valve 31 is constituted by an electromagnetic valve.

A voltage is applied to a solenoid coil (not shown) of the purge control valve 31 in the form of a pulse signal. By adjusting the ratio of the pulse width to the cycle of the pulse signal (duty ratio), the purge control is performed. The purge flow rate of the fuel evaporative gas from the canister 23 to the intake pipe 12 is controlled by adjusting the ratio of the valve opening time to the opening / closing cycle of the valve 31.

A filler cap 38 with a relief valve is attached to the fuel supply port 17a of the fuel tank 17 so that the internal pressure of the fuel tank is -40 mmHg to 150 mmHg.
When the internal pressure exceeds (relief pressure), the relief valve opens to release the pressure. Therefore, the section from the fuel tank 17 to the canister 23 is always kept at a pressure within this relief pressure range.

Next, the configuration of the control system will be described. The control circuit 39 is configured by mutually connecting a CPU 40, a ROM 41, a RAM 42, an input / output circuit 43, and the like via a common bus 44. The input / output circuit 43 includes a throttle sensor 45, an idle switch 46, a vehicle speed sensor 47,
Various sensors, such as an atmospheric pressure sensor 48, an intake pipe pressure sensor 49, a cooling water temperature sensor 50, and an intake temperature sensor 51, for detecting an engine operating state are connected, and signals input from these various sensors via the input / output circuit 43 are provided. And ROM 41
The fuel injection control, ignition control, fuel evaporative gas purge control, abnormality diagnosis of the fuel evaporative gas purge system 21 and the like are executed based on programs and data stored in the RAM 42 and the like, and the fuel injection valve 16, the ignition plug 52, the canister A drive signal is output to the closing valve 26, the purge control valve 31, and the like via the input / output circuit 43. When an abnormality in the purge system 21 is detected, a warning lamp 53 is turned on to notify the driver.

Hereinafter, the purge system 2 executed by the control circuit 39
The abnormality diagnosis program 1 will be described with reference to the flowcharts of FIGS. This abnormality diagnosis program is repeatedly executed at predetermined time intervals (for example, at every 256 msec) when an ignition switch (not shown) is turned on, and plays a role as a leak diagnosis means in the claims. When this program is started, first, in step 101 of FIG. 2, it is determined whether or not an abnormality diagnosis execution condition is satisfied. Here, the abnormality diagnosis execution condition is satisfied when the engine operation state is stable.
Even during the idling operation, if the engine operation state is stable, the abnormality diagnosis execution condition is satisfied.

If the abnormality diagnosis execution condition is not satisfied, the abnormality diagnosis is prohibited, and the subsequent processing is not performed.
Exit this program.

On the other hand, if it is determined in step 101 that the condition for executing the abnormality diagnosis is satisfied, the process proceeds to steps 110 to 112, and the process branches to various steps while determining to what stage the current process has progressed. I do. The processing is performed in four stages of first to fourth stages, and the first to third flags F1 to F3
The processing stage can be determined from the setting state of. The first stage is when all the flags F1 to F3 are set to “0”, that is, when all of the steps 110 to 712 are “No”, and the process proceeds to step 113.

In the first stage, first, in step 113, the purge control valve 31 is fully closed, and then, in step 114, the canister closing valve 26 is fully closed to open the purge system 21 from the fuel tank 17 to the intake pipe 12. Keep tightly closed. That is,
As shown in FIG. 5, first, when the canister closing valve 26 is in the open state, the purge control valve 31 is fully closed at time T1 so that the purge path from the fuel tank 17 to the purge control valve 31 is connected to the atmosphere communication pipe 25. , The canister closing valve 26 is fully closed at time T2 with a slight delay, thereby forming a closed purge path maintained at atmospheric pressure.

Then, in the next step 115, the fuel tank internal pressure P1a at time T2 in FIG. 5 is read, and the timer T is reset and started. Then, the routine proceeds to step 116, where the count value of the timer T becomes 10 seconds or more. Is determined. If 10 seconds have not elapsed, the process proceeds to step 117,
The first flag F1 is set to "1" and the program ends.

Thereafter, the process of the second stage is performed. In the second stage, "Yes" is determined in step 110, and the processing is repeated in the order of step 101 → step 110 → step 116 →. During this time, the value detected by the pressure sensor 20 rises from 0 mmHg according to the amount of fuel evaporative gas generated in the fuel tank 17 between time T2 and time T3 in FIG.

Thereafter, when 10 seconds have elapsed from time T2 (the time point of detection of P1a), the routine proceeds to step 118 in FIG. 2, where the input signal from the pressure sensor 20 is read, and the fuel tank internal pressure P1b at this time is stored. In the following step 119,
After calculating the pressure change amount ΔP1 for 10 seconds, step 1
At 20, the first flag F1 is reset. Thus, the processing in the second stage is completed, and the process proceeds to the third stage.

In this third stage, first, step 1 in FIG.
At 21, the purge control valve 31 is switched from the fully closed state to the fully open state, and the intake pipe negative pressure introduction control is started.
At 22, the timer T is reset and started. Here, when the purge control valve 31 is fully opened, the intake pipe negative pressure starts to be introduced into the purge system 21 under the atmospheric pressure before that (time T3 in FIG. 5). Therefore, if there is no abnormality such as a leak in the purge system 21, the detection value of the pressure sensor 20 starts to decrease.

In the next step 123, the pressure sensor 20
It is determined whether or not the fuel tank internal pressure PT has become, for example, −20 mmHg or less based on the input signal from
If it is 20 mmHg, the routine proceeds to step 132, where it is determined whether two seconds have elapsed after the purge control valve 31 has been fully opened.
If two seconds have not elapsed, the process proceeds to step 137, where the second flag F2 is set to "1", and the program ends.

As described above, when the second flag F2 is set to "1", "No" in step 110 and "Y" in step 111 when the program is executed next time.
es ", and steps 101 to 11
The processing is repeated in the order of 1 → step 123 →. This state ends when step 123 or step 132 becomes “Yes”. Step 132 is "Yes" first
In this case, it is considered that the intake pipe negative pressure cannot be sufficiently introduced into the purge system 21, and it is considered that somewhere in the purge system 21 is clogged. In this case, the routine proceeds to step 133, in which the purge system clogging flag Fclose is set to "1" indicating that the purge system 21 is clogged, and in the next step 134, the warning lamp 53 is turned on to inform the driver of the purge system 21. Warning of abnormal of and ends this program.

On the other hand, in step 123, "Ye
s ", the process proceeds to step 124, where the second flag F2 is reset. In step 125, the purge control valve 31 is fully closed again.
The input signal from the pressure sensor 20 is read, the fuel tank internal pressure P2a immediately after the purge system 21 is set to the negative pressure sealed state is stored, and the timer T is reset and started. Thereby, the process moves from the third stage to the fourth stage.

By executing the processing of steps 124 to 126, as shown in FIG. 5, at time T4, the purge system 21 is closed at a negative pressure of -20 mmHg. Thereafter, the detection value of the pressure sensor 20 becomes the time T
From 4 to time T5, the pressure rises from -20 mmHg according to the amount of fuel evaporative gas generated in the fuel tank 17.

Then, in the next step 127, it is determined whether or not 10 seconds have elapsed after the reading of P2a. Before 10 seconds have elapsed, the process proceeds to step 135, and the third flag F3 is set to "1". And exit this program. Thus, the next time this program is executed, step 11
"No" is determined at 0 and 111, and "Yes" is determined at step 112, and the processing is repeated from step 101 to 112 → step 127 →.

Thereafter, when 10 seconds have elapsed from the reading of P2a, the routine proceeds to step 128, where the input signal from the pressure sensor 20 is read, and the fuel tank internal pressure P at time T6 is read.
2b, and the pressure change amount ΔP2 (= P
2b-P2a) is calculated. Thereafter, in step 130, it is determined whether or not there is a leak based on a leak determination condition represented by the following equation.

ΔP2> α · ΔP1 + β (1) where α is a coefficient for correcting the difference in fuel evaporation due to the difference between atmospheric pressure and negative pressure, β is the detection accuracy of the pressure sensor 20, and the canister closing valve 26 Is a coefficient for correcting a leak or the like. If the above expression (1) is satisfied, it is determined that "there is a leak".
That is, if there is a leak cause in the closed section of the purge system 21 from the fuel tank 17 to the purge control valve 31, the outflow from the closed section to the atmosphere occurs under the positive pressure, while the air flows from the atmosphere to the closed section under the negative pressure. Air inflow occurs. Therefore, "(pressure change under negative pressure)-(amount of fuel evaporative gas generated from fuel tank 17)-(outflow from closed section to atmosphere)" ΔP
2) = (Amount of fuel evaporative gas generated from fuel tank 17)
+ (The amount of inflow from the atmosphere to the closed section) ”is larger. From this relationship, the leak determination condition of the above equation (1) is derived.

If the leak determination condition of the above equation (1) is not satisfied, it is determined that there is no leak, and the routine proceeds to step 131, where the first to third flags F1 to F3 are forcibly reset. Proceeding to 138, the time T5 in FIG.
The canister closing valve 26 is fully opened, and the purge control valve 3
1 is returned to the normal control state, and the program ends.

On the other hand, when the leak determination condition of the above equation (1) is satisfied, it means that there is a hole causing a leak somewhere in the closed section of the purge system 21 from the fuel tank 17 to the purge control valve 31. Then, it is determined that there is a leak. In this case, the process proceeds to step 136, where the leak flag Fle
After setting ak to “1” meaning that there is a leak, the process proceeds to step 139. At time T5 in FIG. 5, the canister closing valve 26 is fully opened to return the inside of the purge system 21 to the atmospheric pressure.
The leak check processing after step 141 in FIG. 4 is executed.

This leak confirmation process is a process for preventing erroneous diagnosis due to the opening of the filler cap 38 of the fuel tank 17. More specifically, first, at step 138, it is determined whether or not the engine is in the idling operation state by the idle switch 46. And the input signal from the vehicle speed sensor 47, and when the vehicle is not in the idling operation state (that is, when the vehicle is traveling), it can be determined that the filler cap 38 is not opened.
Proceeding to step 146, the diagnosis of the presence of a leak (leak flag Fleak = 1) made in the previous process is determined, and in the next step 147, the warning lamp 53 is turned on to warn the driver of the leak of the purge system 21. , End this program.

On the other hand, if it is determined in step 141 that the engine is in the idling operation state, the routine proceeds to step 142, where the canister closing valve 26 is fully closed at time T6 in FIG. Purge system 21 up to
Is closed, the purge control valve 31 is opened, a re-pressure introduction operation for introducing the intake pipe negative pressure into the purge system 21 under the atmospheric pressure is started, and the timer T is reset and started (step 143). . At this time, if the filler cap 38 is not opened, the fuel tank internal pressure PT starts to decrease by the re-pressure introduction operation.

Thereafter, in step 144, it is determined whether or not the reference time has elapsed since the reset start of the timer T. If the reference time has not elapsed, the process waits until the reference time has elapsed. And when the reference time has passed,
Proceeding to step 145, based on the input signal from the pressure sensor 20, the fuel tank internal pressure PT is set to a set pressure, for example, -5.
It is determined whether or not the pressure has become equal to or less than mmHg. If the pressure does not decrease to −5 mmHg, the intake pipe negative pressure cannot be introduced into the purge system 21 very much. In this case, the process proceeds to step 148, where it is determined that the filler cap 38 is being opened, and the process proceeds to step 149, where the leak flag Fleak is reset to “0” meaning no leak and the diagnosis of the leak is canceled. Thereafter, the routine proceeds to step 150, and at time T7 in FIG. 5, the canister closing valve 26 is fully opened, the purge control valve 31 is returned to the normal control state, and the program ends.

On the other hand, if it is determined in step 145 that the internal pressure PT of the fuel tank has decreased to −5 mmHg or less within the reference time, it is in a state where the intake pipe negative pressure can be sufficiently introduced into the purge system 21. It can be determined that the cap 38 has not been opened. In this case, step 14
Then, the flow advances to step 6 to determine the leak diagnosis (leak flag Fleak = 1) made in the previous process.
Then, the warning lamp 53 is turned on to warn the driver of the leak of the purge system 21, and the program is terminated.

Here, the reference time used in step 144 may be set by any of the following methods (1) to (6). (1) The reference time is set to a predetermined time (for example, 5 seconds).
c). (2) Focusing on the fact that the degree of pressure drop of the purge system 21 at the time of the re-pressure introduction operation changes in accordance with the remaining amount of fuel in the fuel tank 17, a reference time in which the remaining amount of fuel in the fuel tank 17 is used in advance Is set as shown in Table 1 below, and a reference time is obtained from the map of Table 1 according to the current fuel remaining amount.

[0043]

[Table 1]

Alternatively, the reference time may be calculated by the following equation. Reference time = T1 × A1 / B1 where T1 is the base time, A1 is the current fuel remaining, B
1 is the reference fuel remaining.

(3) Paying attention to the point that the degree of pressure reduction of the purge system 21 at the time of the re-pressure introduction operation changes in accordance with the concentration of the fuel evaporative gas in the fuel tank 17, the fuel evaporative gas concentration learning value is used as a parameter in advance. A reference time map is set in advance, and the reference time is determined from the map according to the current fuel evaporative gas concentration learning value. Alternatively, the reference time may be calculated by the following equation. Reference time = T2.times.A2 / B2 where T2 is the base time, A2 is the current learned value of the fuel vapor concentration, and B2 is the reference fuel vapor concentration.

(4) Purge system 21 immediately before re-pressure introduction operation
Paying attention to the point that the degree of pressure decrease of the purge system 21 at the time of the re-pressure introduction operation changes according to the pressure (= atmospheric pressure), a map of a reference time using the atmospheric pressure as a parameter is set in advance, and the current time is set. The reference time is obtained from the map according to the atmospheric pressure. Alternatively, the reference time may be calculated by the following equation. Reference time = T3 × A3 / B3 where T3 is the base time, A3 is the current atmospheric pressure, and B3
Is the reference atmospheric pressure.

Instead of the atmospheric pressure, the pressure of the purge system 21 immediately before the re-pressure introduction operation or the pressure of the purge system 21 before the abnormality diagnosis may be used.

(5) Paying attention to the point that the degree of pressure drop of the purge system 21 at the time of the re-pressure introduction operation changes in accordance with the pressure change amounts ΔP 1 and ΔP 2 of the purge system 21 at the time of leak diagnosis.
A reference time map is set using P1 or ΔP2 as a parameter, and the reference time is determined from the map according to the current ΔP1 or ΔP2. Alternatively, the reference time may be calculated by the following equation. Reference time = T4.times.A4 / B4 Here, T4 is a base time, A4 is .DELTA.P1 or .DELTA.P2 at the time of the current leak diagnosis, and B4 is a reference pressure change amount.

(6) The purge system 21 during the re-pressure introduction operation according to the negative pressure introduction time of the purge system 21 at the time of leak diagnosis (the time from the start of the introduction of the negative pressure until the pressure drops to −20 mmHg).
Focusing on the point where the degree of pressure drop changes, a map of a reference time is set in advance using the negative pressure introduction time as a parameter, and the reference time is determined from the map according to the current negative pressure introduction time. Alternatively, the reference time may be calculated by the following equation. Reference time = T5 × A5 / B5 Here, T5 is the base time, A5 is the negative pressure introducing time at the time of the current leak diagnosis, and B4 is the reference negative pressure introducing time.

It should be noted that the fuel remaining amount, the fuel evaporation gas concentration learning value,
Atmospheric pressure, pressure change amount ΔP of purge system 21 at the time of leak diagnosis
1, a combination of two or more parameters of ΔP 2, a negative pressure introduction time at the time of leak diagnosis, a pressure of the purge system 21 immediately before the re-pressure introduction operation, and a pressure of the purge system 21 before the abnormality diagnosis are obtained by using a map or a mathematical formula. The reference time may be obtained.

In the embodiment (1) described above, when the filler cap 38 of the fuel tank 17 is opened, the opening (the refueling port 17) is much larger than the hole causing the leak.
Focusing on the point that a) is opened, if the purge system 21 is diagnosed as having a leak and is in an idling operation state (that is, a situation where the filler cap 38 may be opened), the purge system 21 is re-established. When the internal pressure of the purge system 21 does not decrease to the set pressure (for example, −5 mmHg) within the reference time, it is determined that the filler cap 38 is being opened, and a leak is detected. Canceled the result of diagnosis. As a result, erroneous diagnosis due to the opening of the filler cap 38 can be reliably prevented, and the reliability of leak diagnosis can be improved. Moreover, the determination of the degree of pressure introduction into the purge system 21 at the time of the re-pressure introduction operation (that is, the determination of the opening / closing of the filler cap 38) is based on the pressure sensor 20 used for leak diagnosis.
Therefore, a new sensor such as a fuel temperature sensor is not required, and the demand for reduction in the number of parts, reduction in the number of assembly steps, and cost reduction can be satisfied.

In the above embodiment (1), when judging the degree of pressure introduction into the purge system 21 during the re-pressure introduction operation, it is determined whether or not the fuel tank internal pressure falls to the set pressure within a reference time. Is determined, for example, the determination may be made based on the pressure change rate during the re-pressure introduction operation, the pressure change amount during a predetermined time, and the time required for the predetermined pressure change.

In the embodiment (1), the intake pipe negative pressure is introduced into the purge system 21 at the time of abnormality diagnosis and the re-pressure introduction operation. However, at the time of abnormality diagnosis and / or the re-pressure introduction operation. The positive pressure adjusted to a constant pressure is supplied to the purge system 21.
It may be introduced inside.

[Embodiment (2)] In the embodiment (2) of the present invention, it is determined whether or not the remaining fuel amount in the fuel tank 17 has increased during the idling operation. Then, it is determined that refueling is being performed, and the leak diagnosis of the purge system 21 is stopped (prohibited), or the result of the leak diagnosis performed at that time is canceled. This process is executed by the leak diagnosis confirmation program shown in FIG.

This program is repeatedly executed at predetermined time intervals when an ignition switch (not shown) is turned on, and plays a role as a leak diagnosis means in the claims. When the program is started, first, in step 201, it is determined whether or not the vehicle is in an idling operation state based on input signals from the idle switch 46 and the vehicle speed sensor 47. If the vehicle is not idling (that is, the vehicle is traveling), it can be determined that the fuel is not being supplied.
It is determined whether or not a leak has been diagnosed by the same leak diagnosis process as above, and if it has been diagnosed that there is no leak, the program is terminated as it is. The diagnosis of the presence of the leak is determined, and in the next step 207, the warning lamp 53 is turned on and the present program ends.

On the other hand, if it is determined in step 201 that the engine is in the idling operation state, the process proceeds to step 202, where the remaining fuel amount is determined based on the detection value of the remaining fuel amount detecting means such as a float type fuel gauge. It is determined whether the fuel level has increased by a certain amount or more or the fuel level in the fuel tank 17 has increased to a specified level or more. Here, the reason for determining whether or not the remaining fuel amount has increased by a predetermined amount or more is to avoid erroneously determining that the apparent increase in the remaining fuel amount due to the inclination or shaking of the vehicle is refueling. The reason for determining whether the fuel level in the fuel tank 17 has increased to a specified level is as follows.
When the fuel level rises above the specified level, the space volume in the fuel tank 17 decreases, so that the fuel tank internal pressure detected by the pressure sensor 20 is susceptible to the influence of fuel evaporative gas and the inclination and sway of the fuel liquid level. And pressure sensor 2
This is because it becomes difficult to accurately detect the fuel tank internal pressure at 0.

If "Yes" is determined in step 202, the process proceeds to step 203, in which it is determined that refueling is in progress, and the process proceeds to step 204, in which the leak diagnosis of the purge system 21 is stopped, or the leak performed at that time is determined. Cancel the existing diagnosis and end this program. Thereby, it is possible to reliably prevent erroneous diagnosis due to refueling during leak diagnosis.

On the other hand, if "No" is determined in step 202, it is determined that refueling is not being performed. In this case, as in the case of the idle operation state described above, the process proceeds to step 205, where it is determined whether or not a leak has been diagnosed. If it is diagnosed that there is a leak, the process proceeds to step 206, where the diagnosis of the presence of a leak is determined. In the next step 207, the warning lamp 53 is turned on, and this program ends.

The processing in step 201 of this program may be omitted, and the processing in and after step 202 may be performed during traveling.

Further, in the present embodiment (2), it is determined whether or not the fuel remaining amount has increased (during refueling) at predetermined time intervals during the idling operation. The presence / absence of an increase in the remaining fuel amount (during refueling) may be determined based on the amount of change from the remaining fuel amount at the end of the diagnosis (or after a lapse of a predetermined time from the end).

[Embodiment (3)] In the embodiment (3) of the present invention, in a vehicle equipped with an automatic transmission, when the shift position detected by the shift position detecting means is the neutral position or the parking position, the purge system is operated. The leak diagnosis of step 21 is stopped, or the result of the leak diagnosis performed at that time is canceled. That is, when the shift position is the parking position, the vehicle is parked, and in the neutral position, there is a possibility that the vehicle is stopped or parked. Since the opening of the filler cap 38 is performed while the vehicle is parked or stopped, the leak diagnosis of the purge system 21 is stopped when the shift position is the neutral position or the parking position, or the result of the leak diagnosis performed at that time is canceled. By doing so, erroneous diagnosis due to opening of the filler cap 38 can be reliably prevented.

The suspension / cancellation / confirmation of the leak diagnosis based on the shift position is executed by a leak diagnosis confirmation program shown in FIG. This program is the same as the program of FIG. 6 described in the embodiment (2) except for steps 202a and 203a. This program is also repeatedly executed at a predetermined time interval when an ignition switch (not shown) is turned on, and plays a role as a leak diagnosis unit referred to in the claims. When the program is started, it is first determined in step 201 whether or not the engine is in an idling operation state. If the operation is in the idling operation state, the process proceeds to step 202a, and the shift position of the automatic transmission is set to the neutral position (N range). Alternatively, it is determined whether or not the vehicle is at the parking position (P range).

If it is determined in step 202a that the shift position is the neutral position or the parking position, the process proceeds to step 203a, where it is determined that the filler cap 38 may be opened. The diagnosis is stopped, or the diagnosis with the leak made at that time is canceled and the program is terminated. As a result, erroneous diagnosis due to the opening of the filler cap 38 can be reliably prevented.

On the other hand, if it is determined in step 202a that the shift position is neither the neutral position nor the parking position, the process proceeds to step 205, where it is determined whether or not a leak has been diagnosed. If so, the process proceeds to step 206, where the diagnosis of the presence of a leak is determined, and in the next step 207, the warning lamp 53 is turned on, and the program ends. The other processing is the same as the program of FIG. 6 described in the embodiment (2).

It should be noted that the processing in step 201 of this program may be omitted, and the processing in and after step 202a may be performed during traveling.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire system showing an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 1);

FIG. 3 is a flowchart showing the flow of processing of an abnormality diagnosis program (part 2);

FIG. 4 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 3);

FIG. 5 is a time chart for explaining the behavior of the purge control valve, the canister closing valve, and the fuel tank internal pressure at the time of abnormality diagnosis.

FIG. 6 is a flowchart showing a flow of processing of a leak diagnosis confirmation program according to the embodiment (2) of the present invention.

FIG. 7 is a flowchart showing a flow of processing of a leak diagnosis confirmation program according to the embodiment (3) of the present invention.

[Explanation of symbols]

Reference Signs List 11 engine (internal combustion engine), 12 intake pipe, 14 throttle valve, 16 fuel injection valve, 17 fuel tank, 18 fuel pump, 20 pressure sensor, 21 purge system, 22 communication pipe, 23 ... Canister, 24 ... Adsorbent, 26 ... Canister closing valve, 30a, 30b ... Purge passage, 31 ... Purge control valve, 39 ... Control circuit (leak diagnostic means), 46 ... Idle switch, 47 ... Vehicle speed sensor, 48 ... Large Atmospheric pressure sensor, 49 ... intake pipe pressure sensor, 5
0: cooling water temperature sensor, 51: intake air temperature sensor, 53: warning lamp.

Claims (5)

[Claims] 1. A canister for adsorbing fuel evaporative gas generated by evaporating fuel in the fuel tank in a passage connecting a fuel tank and an intake pipe of an internal combustion engine, and a fuel from the canister to the intake pipe. A purge control valve for controlling the purge of the evaporative gas is provided, and a predetermined pressure is introduced into a purge system including at least the fuel tank and the canister at the time of leak diagnosis, and the pressure of the purge system when sealing is performed or the subsequent pressure A leak diagnostic device for a fuel evaporative gas purge system, comprising: a leak diagnostic device that detects a change amount and diagnoses the presence or absence of a leak in the purge system based on the detected value, wherein the leak diagnostic device has a leak in the purge system. If it is an idling operation state when it is diagnosed, the operation of introducing a predetermined pressure into the purge system (hereinafter referred to as “re-pressure introducing operation”) is performed again. What determines the pressure introduction state to the purge system within leak diagnostic apparatus for a fuel evaporative emission purge system characterized by cancel the diagnosis result of the leakage there based on the determination result. 2. The leak diagnosing means determines whether or not the pressure in the purge system changes to a set pressure within a reference time by a re-pressure introduction operation, and does not change to the set pressure within the reference time. 2. The leak diagnosis apparatus for a fuel evaporative gas purge system according to claim 1, wherein the diagnosis result of the presence of the leak is sometimes canceled. 3. The leak diagnosis means includes: an atmospheric pressure, a learned value of a fuel evaporating gas concentration, a remaining amount of fuel in the fuel tank, a pressure in the purge system before a re-pressure introduction operation, and a purge system at the time of leak diagnosis. 3. The reference time is set based on at least one of pressure changes in the inside.
A leak diagnostic device for a fuel evaporative gas purging system according to claim 1. 4. A canister for adsorbing fuel evaporative gas generated by evaporating fuel in the fuel tank in a passage communicating the fuel tank with an intake pipe of the internal combustion engine, and a fuel from the canister to the intake pipe. A purge control valve for controlling the purge of evaporative gas is provided, and a predetermined pressure is introduced into a purge system including at least the fuel tank and the canister at the time of leak diagnosis, and the pressure of the purge system at the time of sealing or a subsequent pressure A leak diagnostic device for a fuel evaporative gas purge system comprising a leak diagnostic means for detecting a change amount and diagnosing the presence or absence of a leak in the purge system based on the detected value, wherein a fuel for detecting a remaining amount of fuel in the fuel tank is provided. The fuel cell system further includes a remaining amount detecting unit, wherein the leak diagnosing unit determines whether or not the remaining amount of fuel in the fuel tank has increased based on a detection value of the remaining fuel amount detecting unit. And when the remaining fuel amount increases, the leak diagnosis of the purge system by the leak diagnosis means is stopped, or the result of the leak diagnosis performed at that time is canceled. Diagnostic device. 5. A canister for adsorbing fuel evaporative gas generated by evaporating fuel in a fuel tank into a passage communicating a fuel tank mounted on a vehicle equipped with an automatic transmission and an intake pipe of an internal combustion engine. And a purge control valve for controlling the purging of fuel evaporative gas from the canister to the intake pipe, and a predetermined pressure is introduced into a purge system including at least the fuel tank and the canister at the time of leak diagnosis to seal the leak. A leak diagnosing device for a fuel evaporative gas purge system, comprising: a leak diagnosing means for detecting a pressure of the purge system at the time or a subsequent pressure change amount and diagnosing a leak of the purge system based on the detected value. Shift position detection means for detecting a shift position of the automatic transmission, wherein the leak diagnosis means includes a shift position detected by the shift position detection means. When in the neutral position or parking position, the leak diagnostic means according to cancel the leakage diagnosis of the purge system, or leak diagnostic apparatus for a fuel evaporative emission purge system characterized by cancel the diagnostic result made a leakage there at that time.