JPH0712013A - Vaporized fuel leak diagnostic device for internal combustion machine and outside air temperature recognizing device in internal combustion engine-mounted vehicle - Google Patents

Abstract

PURPOSE:To prevent a wrong diagnosis according to decreasing air-tightness of a seal material of a drain cut valve by inhibiting a leak diagnosis in the case that a temperature of the outside air is a prescribed value or less. CONSTITUTION:By a fuel temperature sensor and a water temperature sensor, a difference (DELTATstop) between a fuel temperature and a cooling water temperature at engine stop time is obtained (step S2), and a difference (DELTATstart) between a fuel temperature and a cooling water temperature at engine restart time is obtained (step S4), to permit a leak diagnosis (step S6) only when the DELTATstop is 40 deg.C or more further with the DELTATstart 5 deg.C or less and further only when the fuel temperature (Tf2) at engine restart time is 15 deg.C or more. Thus by surely detecting the outside air temperature to be -10 deg.C or more, an erroneous diagnosis according to decreasing air-tightness by hardening a seal material of a drain cut valve at a low temperature can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when diagnosing a leak state of evaporated fuel in a system for supplying evaporated fuel accumulated in a fuel tank to an engine intake system, prevents misdiagnosis based on the outside air temperature. The present invention relates to an evaporated fuel leak diagnosis device. The present invention also relates to a device for recognizing the outside air temperature necessary for preventing the erroneous diagnosis based on the engine cooling water temperature of the internal combustion engine mounted on the vehicle and the fuel temperature in the fuel tank.

[0002]

2. Description of the Related Art Conventionally, in order to prevent vaporized fuel vaporized in a vehicle fuel tank or the like from being released into the atmosphere and causing environmental damage, the vaporized fuel adsorbed by an adsorption means (canister). Is provided with an evaporated fuel transpiration prevention device that is guided to the intake passage by using the intake negative pressure of the engine, whereby the evaporated fuel is sucked into the combustion chamber together with the intake air and burned, and It has been proposed to prevent evaporation of evaporated fuel.

However, in such a device, if a leak hole is formed in the middle of the vaporized fuel pipe or a defective seal is formed at the joint of the vaporized fuel pipe, the vaporized fuel will be evaporated into the atmosphere. In some cases, the effects of the device could not be fully exerted. Therefore, the applicants of the present application
Japanese Patent Application No. 4-31507, Japanese Patent Application No. 4-335859,
Japanese Patent Application No. 4-337306 proposes a leak diagnosis device for diagnosing the leak state of the evaporated fuel supply system from the fuel tank to the engine intake system via the canister.

In such a leak diagnosis apparatus, a drain cut valve (communication / cutoff means) is provided in a drain pipe (a discharge portion of separated air in the canister) provided in the canister, and the drain cut valve is closed to close the drain cut valve. By disconnecting the communication between the evaporated fuel supply system and the outside air to make the evaporated fuel supply system a closed space, and utilizing the fact that the pressure in the closed space changes according to the leak state of the evaporated fuel supply system, The leak state of the evaporated fuel supply system is diagnosed.

[0005]

However, the conventional leak diagnosing device for evaporated fuel has the following problems. That is, the drain cut valve used in the conventional device is a general drain cut valve 3b as shown in FIG. 4, and when the terminal 37 receives the valve closing signal from the control module, the coil 32 is energized and the plunger is depressed. 33 is moved to the right in the figure by overcoming the urging force of the spring 38, and the valve 31 (for example, acrylonitrile butadiene rubber [NBR] or the like for ensuring airtightness) is provided at the left end of the plunger 33 in the figure. The sealing surface is formed of a sealing material) and is pressed against the valve seat 36 provided in the main body 30. As a result, the communication between the inflow-side opening 34 and the discharge-side opening 35 provided in the main body 30 is blocked, so that the communication between the inside of the canister and the atmosphere is blocked and a closed space is formed in the evaporated fuel supply system. It is formed, but at this time the outside air temperature is
For example, when the temperature is -10 ° C or lower, the NBR on the sealing surface of the valve 31 is hardened at a low temperature, so that the valve seat
The adhesiveness with 36 is reduced and the airtightness is reduced.

Therefore, when the closed space is formed in the evaporated fuel supply system and the leak diagnosis is performed based on the pressure change in the closed space as in the conventional example in the state where the airtightness is lowered, the inside of the closed space is reduced. Although the pressure is caused by the poor airtightness of the NBR, the pressure changes as if there were a leak hole in the vaporized fuel supply system, and there is a high possibility of erroneous diagnosis.

Therefore, in order to improve the low temperature curing temperature range of the NBR of the valve 31, the material is changed at the expense of other characteristics (durability, oil resistance, etc.), or the NBR is forcibly heated. Then, it is possible to prevent the deterioration of the airtightness, but the problem of the deterioration of the airtightness is a problem peculiar to the leak diagnosis, that is, the outside air and the canister are the air after the fuel vapor separation except the time of the leak diagnosis. Is always communicated (valve 31 is opened) so as to be discharged to the outside air, so that even if the outside air temperature is low and the NBR is hardened at a low temperature, there is no problem. Therefore, the problem is only when the outside air temperature is equal to or lower than the predetermined temperature and at the time of leak diagnosis, which is a very limited time. However, it is not desirable from the standpoint of increasing the product cost.

Therefore, in view of the above conventional circumstances, the present invention performs leak diagnosis when the outside air temperature is equal to or lower than a predetermined temperature at which the sealing material forming the drain cut valve is hardened at a low temperature to lower the airtightness. It is a first object of the present invention to provide an evaporated fuel leak diagnosis device for an internal combustion engine, in which leak diagnosis is prohibited in order to prevent erroneous diagnosis. by the way,
It is not desirable to separately provide a new outside air temperature sensor to detect the outside air temperature in terms of complication of the configuration, increase of product cost, and the like. Therefore, for example, the above-mentioned Japanese Patent Application No. 4-3
The outside air temperature is determined based on the fuel temperature and the cooling water temperature obtained from the fuel temperature sensor used in the devices of 35859 and Japanese Patent Application No. 4-337306, and the cooling water temperature sensor used for normal engine control. It is a second object of the present invention to provide an outside air temperature recognition device that recognizes the outside air temperature.

[0009]

Therefore, as shown in FIG. 1, the evaporated fuel leak diagnostic apparatus for an internal combustion engine according to the first aspect of the present invention temporarily absorbs the evaporated fuel accumulated in the fuel tank by the adsorbing means. Adsorption and communication of the adsorbing means with the intake system of the engine in a predetermined engine operating state, and evaporative fuel is separated from the adsorbing means by suction negative pressure of the engine to be sucked and guided to the intake system to prevent evaporation of evaporated fuel The apparatus is provided with an adsorbing means for introducing outside air into the adsorbing means at the time of separating and sucking the evaporated fuel, and for discharging separated air after adsorbing the evaporated fuel into the outside air from the adsorbing means. The outside air circulation unit is provided with a communication / interruption means having a seal material capable of communicating / interrupting with the outside air.
A closed space is formed in the vaporized fuel supply system from the fuel tank to the intake system via the adsorption means by shutting off the shutoff means, and the vaporized fuel leaks from the vaporized fuel supply system based on the pressure change in the closed space. In an evaporative fuel leak diagnostic device for an internal combustion engine configured to diagnose a state, an outside air temperature detecting means for detecting an outside air temperature and an outside air temperature detected by the outside air temperature detecting means are: And a leakage diagnosis prohibiting means for prohibiting the diagnosis of the leakage state when the temperature is lower than a predetermined temperature at which the property deteriorates.

As shown in FIG. 2, an outside air temperature recognition device for a vehicle equipped with an internal combustion engine according to a second aspect of the present invention is a device provided in a vehicle equipped with an internal combustion engine to recognize the outside air temperature. Cooling water temperature detecting means for detecting the cooling water temperature of the engine, fuel temperature detecting means for detecting the fuel temperature in the fuel tank, and cooling water temperature and fuel temperature when the engine is stopped detected by the temperature detecting means. And the difference between the cooling water temperature and the fuel temperature at the time of the next start, the temperature state of at least one of the cooling water temperature and the fuel temperature at the time of the next start is substantially stable. When estimated, the outside air temperature estimating means estimates the outside air temperature based on the one of the substantially stable temperatures.

According to a third aspect of the invention, there is provided an evaporated fuel leak diagnostic apparatus for an internal combustion engine, wherein the outside air temperature detecting device for a vehicle equipped with an internal combustion engine according to the second invention is used as the outside air temperature detecting means according to the first invention. It was configured.

[0012]

In the evaporated fuel leak diagnostic apparatus for an internal combustion engine according to the first aspect of the invention, the evaporated fuel leak diagnostic apparatus forms a closed space in the evaporated fuel supply system by shutting off the communication / cutoff means having the sealing material. When diagnosing the leak state of the evaporated fuel based on the pressure change in the closed space,
When the outside air temperature detecting means detects the outside air temperature at which the sealing material is hardened at a low temperature and the airtightness is lowered, the leak diagnosis is prohibited by the leak diagnosis inhibiting means to reduce the airtightness of the sealing material. Prevent the accompanying misdiagnosis.

According to a second aspect of the present invention, there is provided an outside air temperature recognition device for a vehicle equipped with an internal combustion engine, wherein the cooling water temperature detecting means and the fuel temperature detecting means detect the cooling water temperature and the fuel temperature when the engine is stopped. And the difference between the cooling water temperature and the fuel temperature at the time of the next start, the outside air temperature estimating means determines whether at least one of the cooling water temperature and the fuel temperature at the time of the next start is a temperature with respect to time. The amount of change is estimated to be substantially stable below a predetermined value, and the left time from engine stop to the next start is estimated, and when the estimated left time is a predetermined time or more, the outside air temperature is estimated based on the stable one temperature. .

According to a third aspect of the present invention, there is provided an evaporated fuel leak diagnosing device for an internal combustion engine, wherein the outside air temperature detecting device according to the second invention is used as the outside air temperature detecting means according to the second invention. By recognizing the outside temperature,
Prevent erroneous diagnosis of leak diagnosis. This avoids the use of separate and independent outside air temperature detecting means such as an outside air temperature sensor, thereby reducing the product cost and the like.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the accompanying drawings. In FIG. 3, a communication passage 1b that connects the upper space of the fuel tank 1 and the upper space of the fuel injection hole 1a is provided, and one end of the evaporated fuel pipe 2a is provided in the upper space of the fuel injection hole 1a. And the other end of the evaporated fuel pipe 2a is connected to a canister 3 for temporarily adsorbing evaporated fuel. In the middle of the vaporized fuel pipe 2a, an engine intake system from a fuel tank 1 via a canister 3
A pressure sensor 6 for detecting the pressure in the evaporated fuel supply system up to 10 is provided, and the output signal of the pressure sensor 6 is input to the control module 50. The pressure sensor 6 constitutes pressure detecting means.

Then, the canister 3 is provided with the evaporated fuel pipe 2b.
One end is connected and the other end is connected to the intake passage 10 of the engine, and the purge cut valve 4 is provided on the engine side and the purge control valve 5 is provided on the canister 3 side of the fuel vapor piping 2b. The purge cut valve 4 is an on-off valve that connects and disconnects the engine intake system 10 and the evaporated fuel supply system at the time of a later-described leak diagnosis, and the purge control valve 5 causes the evaporated fuel adsorbed by the canister 3 to be stored in the engine. This is a flow rate control valve whose opening degree is controlled for air-fuel ratio control and the like when suctioning (purging). Each of these valves is controlled based on a signal from the control module 50.

In addition, the outside air is introduced into the canister 3 at the time of purging the evaporated fuel, and the separated air after the evaporated fuel is temporarily adsorbed is discharged from the canister into the outside air. A drain pipe 3a is provided as a distribution unit, and the drain pipe 3a is provided.
A drain cut valve 3b is provided as a shut-off / communication means for opening and closing. The drain cut valve 3b
Is controlled to open and close based on a signal from the control module 50, and is controlled to be closed during a leak diagnosis and to be opened during other operations (normal operation and evaporated fuel purge). By the way, the drain cut valve 3b is similar to the above-mentioned conventional example (FIG. 4).
reference).

By the way, the check valve 7 provided in the vaporized fuel pipe 2a includes a fuel tank 1 and a canister 3.
Between the fuel tank 1 and the fuel tank 1 at a predetermined pressure to send evaporated fuel to the canister 3,
This is a check valve for preventing backflow of the evaporated fuel to the side and reliably adsorbing the evaporated fuel to the canister 3. In addition,
Bypass passage 8 that bypasses the check valve 7
The bypass valve 9 is provided in the middle of the bypass passage 8, and the leak diagnosis is performed in a state where the bypass valve 9 is opened and the check valve 7 is bypassed only during the leak diagnosis of the evaporated fuel. It is designed to eliminate the occurrence of an error in the leak diagnosis under the influence of the valve opening pressure.

A fuel temperature sensor 20 for detecting the temperature (T _f ) of the fuel is provided at the bottom of the fuel tank 1, and the output signal from the fuel temperature sensor 20 is a control module.
Entered in 50. The fuel temperature sensor 20 constitutes a fuel temperature detecting means. In addition, engine cooling water temperature (Tw)
A water temperature sensor 21 for detecting is provided facing the cooling system path 10 of the engine, and the detection signal is input to the control module 50. The water temperature sensor 21 constitutes cooling water temperature detection means.

By the way, in this embodiment, the outside air temperature (T
When a) is equal to or lower than a predetermined temperature (for example, −10 ° C.), the outside air temperature recognition according to the second aspect of the present invention is performed in order to prevent the leak diagnosis of the evaporated fuel from being performed in order to prevent the above-mentioned erroneous diagnosis. The device detects the outside air temperature, and based on the outside air temperature, the leak diagnosis inhibiting means determines whether to inhibit the leak diagnosis.

Here, the outside air temperature recognition device according to the second aspect of the present invention as the outside air temperature detecting means for detecting the outside air temperature will be described. When the fuel temperature (T _f ) and the cooling water temperature (Tw) have a predetermined temperature difference when the engine is stopped, the outside air temperature recognition device keeps the temperature difference within a predetermined range as a result of being left for a predetermined time. When the fuel temperature (T _f ) and the cooling water temperature (Tw) become relatively stable (the temperature change is small with respect to time) when the temperature becomes small, It is configured to include an outside air temperature estimating means for estimating the outside air temperature (Ta) based on the substantially stable fuel temperature (T _f ) or the cooling water temperature (Tw).

Next, the outside air temperature estimating means and the leak diagnosis inhibiting means for making a leak diagnosis inhibition determination based on the outside air temperature recognized by the outside air temperature recognizing device,
A description will be given based on the flowchart shown in FIG. In addition,
As described above, the reference temperature for recognizing the outside air temperature (Ta) is the substantially stable fuel temperature (T _f ).
It may be either the cooling water temperature (Tw) or the cooling water temperature (Tw), but the fuel temperature ( _Tf ) at which the substantially stable state appears faster (that is, the temperature rise range of the fuel temperature is higher than that of the cooling water temperature). This is because the number of fuel tanks 1 is small and the fuel tank 1 is not formed of a thick member such as a cooling jacket and is disposed in a place where it is in direct contact with the outside air. Will be described as the reference temperature.

Step 1 (indicated as S1 in the figure).
The same applies hereinafter), the fuel temperature sensor 20, the water temperature sensor
21 detection signals are input to the control module 50,
Fuel temperature (Tf) and cooling water temperature (Tw) are monitored. In step 2, it is detected that the engine is stopped (key OFF) based on a signal from a key switch (not shown), and the temperature difference between the fuel temperature (Tf ₁ ) and the cooling water temperature (Tw ₁ ) at that time is detected. ΔTstop (= | Tf ₁ −Tw
₁ )) before the control module 50 self-shuts.

In step 3, the temperature difference ΔTstop is
It is determined whether or not the temperature is equal to or higher than a predetermined temperature (for example, 40 ° C. or higher). If the temperature is equal to or higher than the predetermined temperature (for example, 40 ° C. or higher), the process proceeds to step 4. If the temperature difference ΔTstop is less than 40 ° C., the process proceeds to step 8 and the leak diagnosis is not performed. Here, when the temperature difference ΔTstop is less than 40 ° C., for example, when the engine is stopped without being warmed up sufficiently, in such a state, the fuel temperature (Tf ₁ ) and the cooling water temperature (Tw ₁ ) Since the temperature difference is originally small, it is highly likely that the temperature difference is determined to be within the predetermined range in step 5 described later even if it is not left for a predetermined time. In this state, the fuel temperature (Tf ₁ ) Is not in a substantially stable state (a temperature change with time is small), and if the outside air temperature (Ta) is recognized based on the fuel temperature (Tf ₁ ) that is not substantially stable, the error becomes large, so Cannot recognize the outside air temperature (Ta). Therefore, in order to completely eliminate the case where the outside air temperature (Ta) is −10 ° C. or lower, the leak diagnosis is not performed.

In step 4, the fuel temperature (Tf ₂ ) and the cooling water temperature (Tw) at the time of starting the engine this time (when the key is ON).
₂ ) and the temperature difference ΔTstart (= | Tf ₂ −Tw
₂ |) is calculated. In step 5, the temperature difference ΔTst
Determine if art is below 5 ° C. The temperature difference Δ
If Tstart is 5 ° C. or lower, proceed to step 6. On the other hand, if the temperature difference ΔTstart is larger than 5 ° C., the process proceeds to step 8 and the leak diagnosis is not performed.
That is, the when the temperature difference ΔTstart is greater than 5 ° C., the time the engine was stopped (standing time) is short, not therefore fuel temperature (Tf ₂₎ of substantially stable state, the fuel temperature (Tf ₂ ) Is used to recognize the outside air temperature (Ta), the outside air temperature (Ta) cannot be accurately recognized. Therefore, also in this case, the outside air temperature (T
In order to completely eliminate the case where a) is -10 ° C or lower, leak diagnosis is not performed.

In step 6, when it is determined in step 5 that the engine has been left for a predetermined time and the fuel temperature (Tf ₂ ) is in a substantially stable state, the current fuel temperature (Tf ₂ )
To detect. Then, the fuel temperature (Tf ₂ ) is 15 ° C.
If it is above, it is determined that the outside air temperature (Ta) is higher than −10 ° C., and the process proceeds to step 7. On the other hand, the current fuel temperature (T
If f ₂ ) is lower than 15 ° C, the outside air temperature (Ta) is -1.
When it is determined that the temperature is 0 ° C. or lower, the process proceeds to step 8 and the leak diagnosis is prohibited.

The reason why it is judged that the outside air temperature (Ta) is -10 ° C or lower when the fuel temperature (Tf ₂ ) is lower than 15 ° C will be described below. That is, when the outside air temperature (Ta) is detected, the fuel temperature (Tf ₂ ) and the cooling water temperature (Tw ₂ ) should be the same temperature after a sufficient time, and these and the outside air temperature (Ta) should be the same. The fuel temperature (Tf ₂ ) or the cooling water temperature (Tw ₂ ) that matches the outside air temperature (Ta) can be detected as the outside air temperature (Ta) by waiting until When the remaining fuel amount in the tank 1 is large and the heat capacity is large, or it is necessary to leave it for a very long time due to the influence of latent heat or the like, the judgment opportunity is lost and it is not practical at all. Therefore, in the present embodiment, in order to make the judgment opportunity practical, that is, to provide many judgment opportunities, as described above, the fuel temperature (Tf) or the cooling water temperature (Tf) after the engine is stopped.
At the stage when w) is in a substantially stable state, the outside air temperature (Ta) is estimated based on the fuel temperature (Tf ₂ ) at that time, so that the fuel temperature (Tf ₂ ) and the outside air are actually measured. There is a temperature difference with the temperature (Ta). Since the temperature difference is greatly affected by the heat capacity of the residual fuel in the fuel tank 1 as described above, for example, when the residual fuel amount is large and the heat capacity is large, the outside air temperature (Ta) is -10 ° C.
Even below, there are cases where the fuel temperature (Tf ₂ ) is near 15 ° C., which is lower than 15 ° C. Therefore, in order to reliably determine that the outside air temperature (Ta) is higher than −10 ° C. in consideration of all the conditions, it is necessary to determine that the fuel temperature (Tf ₂ ) is 15 ° C. or higher. This is because it was confirmed by experiments and simulations.

In step 7, if it is determined in step 6 that the fuel temperature (Tf ₂ ) is 15 ° C. or higher, the outside air temperature (Ta) is definitely determined to be higher than −10 ° C.
Allows execution of fuel vapor leak diagnosis performed in another routine. Control module that performs the above flow
50 constitutes a leak diagnosis prohibition means. The above steps 1 to 6 constitute the outside air temperature estimating means. Of course, as described in the present embodiment, it is not necessary to use the outside air temperature recognition device according to the second invention as the outside air temperature detecting means in the first invention, and the outside air temperature sensor or the like directly detects the outside air temperature. May be used.

Next, the leak diagnosis control of the evaporated fuel will be described. The signal of the pressure sensor 6 is input to the control module 50, and the control module 50
In this case, the pressure change rate based on the signal is monitored, and the pressure change rate (the pressure decrease rate V ₁ , the pressure increase rate V ₁ 'in FIG. 8) can be obtained.

And the engine control module
In the internal memory of the fuel cell 50, the fuel vapor fuel is stored as shown in FIG.
A judgment table for network diagnosis is stored, and the judgment table
Table and the rate of pressure change detected above
It is possible to diagnose fuel leaks. By the way
Therefore, the judgment table shows that the leak amount and the fuel tank remain.
Pressure drop rate and pressure rise rate, depending on the amount of fuel present
Are set by utilizing the fact that
The rate of pressure change is affected by the amount of fuel remaining in the tank
I am getting rid of. That is, the same list as shown in FIG.
If the amount of residual fuel in the fuel tank is large,
(Solid line), the pressure decrease rate V₁And pressure rise rate
V ₁’, And the remaining fuel amount in the fuel tank is small.
If not (broken line), the pressure decrease rate V₂And pressure rise
Speed V₂'Is delayed together, and shown in FIG.
When the amount of fuel remaining in the fuel tank is the same,
When the amount of suction is small (solid line), the pressure decrease speed V₃Is fast
The pressure rise rate V₃When ’becomes slow and the amount of leak is large
In the case of (dashed line), on the contrary, the pressure decrease speed V_FourIs late
The pressure rise rate V_Four′ Becomes faster.
Therefore, the pressure decrease rate and the pressure increase rate are required.
In this case, the leak amount can be determined, which is the basis for leak diagnosis.
Find the judgment line corresponding to the leak amount, and use the judgment line in Fig. 7.
Area above the leak level (leakage larger than the standard leak amount)
The area that produces the amount) is stored as the leak occurrence area.
It

Further, the pressure change rate is greatly affected by the amount of fuel vapor generated (in other words, the fuel vapor pressure) in addition to the effect of the amount of fuel remaining in the fuel tank. In order to eliminate the influence, the control module 50 uses the detected fuel temperature (T _f ).
Based on the above, the fuel vapor generation amount is predicted and detected, and the determination line is corrected. In other words, when the fuel temperature (T _f ) is high, the fuel vapor pressure is high, so that the negative pressure suction speed decreases and the pressure increase speed increases at the same time. Therefore, the determination line is moved upward in the figure. To do. Further, when the fuel temperature (Tf) is low, the tendency tends to be opposite to that when the fuel temperature (Tf) is high, so the movement is corrected to the lower side in the figure (see the broken line in FIG. 7).

The leak diagnosis control of the evaporated fuel performed by the control module 50 will now be described with reference to the flowchart shown in FIG. In step 10, the purge cut valve 4 is opened in a predetermined engine operating state, so that the evaporated fuel adsorbed in the canister 3 is sucked into the engine by the intake negative pressure of the engine.

In step 11, the drain cut valve 5 is closed and the bypass valve 9 is opened, so that the evaporative fuel supply system constituted by the evaporative fuel pipes 2a and 2b, the canister 3, and the inner space of the fuel tank 1 can suck the engine suction negative. Pressure is introduced. In step 12, the fuel temperature (T _f ) in the fuel tank is detected based on the signal from the fuel temperature sensor 20.

In step 13, based on the signal from the pressure sensor 6, as shown in FIG. 8 or 9, the pressure decrease rate in the evaporated fuel pipe during the suction is detected. In particular,
It may be a time until reaching a predetermined negative pressure. Step 14
In FIG. 7, the determination value set based on the fuel temperature (T _f ) and the pressure increase rate in the internal space volume formed when the purge cut valve 4 is closed with respect to the pressure decrease rate is described above. Read from the judgment table.

In step 15, the purge cut valve 4 is closed. 8 or 9 in step 16.
As shown in, the pressure change in the internal space volume is monitored based on the signal from the pressure sensor 6 to detect the pressure change speed (pressure increase speed) toward the atmospheric pressure. In step 17, when the detected pressure increase rate exceeds the determination value for the pressure decrease rate, the process proceeds to step 18, and it is diagnosed that the leak of the evaporated fuel exceeds the allowable value,
If the pressure change rate is less than or equal to the judgment value, step 1
9 and it is diagnosed that the leak amount of the evaporated fuel is equal to or less than the allowable value.

After that, in step 20, the drain cut valve 5 is opened and the bypass valve 9 is closed to end this flow. In this way, according to the leak diagnosis apparatus having such a configuration, the pressure decrease rate and the pressure increase rate are detected by using one pressure sensor 6 to detect the amount of fuel remaining in the fuel tank. In addition to eliminating the influence, the fuel temperature sensor 20 detects the fuel temperature (T _f ) of the fuel remaining in the fuel tank, predicts the fuel vapor generation amount in accordance with the detected fuel temperature, and determines the fuel based on the prediction. Since the correction is made in consideration of the vapor pressure amount, it is possible to perform accurate vapor fuel leak diagnosis without being affected by the remaining fuel amount and the vapor pressure of the vaporized fuel.

As described above, according to this embodiment,
By closing the drain cut valve 3b configured by providing the valve 31 with a sealing material such as NBR, a closed space is formed in the evaporated fuel supply system from the fuel tank 1 to the intake system through the canister 3 to close the closed space. In a leak diagnostic device for diagnosing a leak state of vaporized fuel in the vaporized fuel supply system based on a pressure change in a space, a leak diagnostic is performed only when the ambient temperature is detected and the ambient temperature is higher than a low temperature curing temperature of the NBR. Therefore, it is possible to prevent an erroneous leak diagnosis due to a decrease in the airtightness of the drain cut valve 3b.

Further, in this embodiment, when detecting the outside air temperature, the outside air temperature is estimated from the fuel temperature (Tf) and the cooling water temperature (Tw) obtained from the fuel temperature sensor 20 and the water temperature sensor 21. Therefore, it is not necessary to separately provide a new outside air temperature sensor or the like, and therefore, the cost can be reduced without inviting a complicated structure.

[0039]

As described above, according to the evaporated fuel leak diagnostic apparatus for the internal combustion engine according to the first aspect of the present invention, the communication / interruption means having the sealing material is interrupted so that the fuel tank is adsorbed through the adsorption means. When a closed space is formed in the evaporated fuel supply system leading to the intake system and the leak state of the evaporated fuel in the evaporated fuel supply system is diagnosed based on the pressure change in the closed space, the outside air temperature is detected by the outside air temperature detecting means. However, when the detected outside air temperature is equal to or lower than the low temperature curing temperature of the seal material, the leak diagnosis is prohibited by the leak diagnosis prohibiting means. Can be prevented.

According to the outside air temperature recognizing device for the vehicle equipped with the internal combustion engine according to the second aspect of the invention, based on the fuel temperature and the cooling water temperature obtained from the cooling water temperature detecting means and the fuel temperature detecting means. Since it is possible to recognize the outside air temperature, there is no need to provide an independent outside air temperature detecting means for detecting only the outside air temperature, the configuration can be simplified, and an increase in product cost can be suppressed. be able to.

If the outside air temperature recognizing device of the vehicle equipped with the internal combustion engine according to the second invention is used as the outside air temperature detecting means according to the first aspect of the invention, the outside air temperature required for the prohibition determination of the leak diagnosis is detected. It is not necessary to provide a separate and independent outside air temperature detection means, the configuration is simplified, and an increase in product cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an evaporated fuel leak diagnosis device according to a first invention.

FIG. 2 is a block diagram showing a configuration of an outside air temperature recognition device according to a second invention.

FIG. 3 is an overall configuration diagram according to an embodiment of the first invention.

FIG. 4 is an enlarged sectional view of the drain cut valve 3b.

FIG. 5 is a leak diagnosis prohibition determination control according to the first invention;
3 is a flowchart for explaining the outside air temperature recognition control according to the second aspect of the invention.

FIG. 6 is a flowchart illustrating a leak diagnosis control according to an embodiment of the first invention.

FIG. 7 is a determination table according to an example of the first invention.

FIG. 8 is a time chart of the pressure decrease rate and the pressure increase rate when the leak amount is the same according to the first embodiment of the present invention.

FIG. 9 is a time chart of the pressure decrease rate and the pressure increase rate when the remaining fuel amount is the same according to the first embodiment of the present invention.

[Explanation of symbols]

 1 Fuel Tank 2a Evaporative Fuel Pipe 2b Evaporative Fuel Pipe 3 Canister 3a Drain Pipe 3b Drain Cut Valve 4 Purge Cut Valve 5 Purge Control Valve 6 Pressure Sensor 10 Engine Intake System 20 Fuel Temperature Sensor 21 Water Temperature Sensor 31 Valve 50 Control Module

Claims (3)

[Claims] 1. An evaporative fuel accumulated in a fuel tank is temporarily adsorbed by an adsorbing means, the adsorbing means is made to communicate with an intake system of the engine in a predetermined engine operating state, and the adsorbing means is caused by an intake negative pressure of the engine. While being equipped with a vaporized fuel evaporation prevention device that separates and sucks the evaporated fuel and guides it to the intake system, outside air is introduced into the adsorbing means when the evaporated fuel is separated and sucked, and the evaporated fuel is temporarily adsorbed. An external air circulation unit provided in the adsorption unit for discharging the separated air from the adsorption unit into the external air is provided with a communication / interruption unit having a sealing material capable of communicating / interrupting with the external air. A closed space is formed in the vaporized fuel supply system from the fuel tank to the intake system via the adsorption means by shutting off the shutoff means, and the vaporized fuel leaks from the vaporized fuel supply system based on the pressure change in the closed space. In an evaporative fuel leak diagnostic device for an internal combustion engine configured to diagnose a state, an outside air temperature detecting means for detecting an outside air temperature and an outside air temperature detected by the outside air temperature detecting means are a sealing material that is hardened at a low temperature and is airtight. And a leak diagnosis prohibiting means for prohibiting the diagnosis of the leak state when the temperature is lower than a predetermined temperature at which the vaporized fuel leak diagnosis apparatus for an internal combustion engine is characterized. 2. An apparatus for recognizing an outside air temperature, which is provided in a vehicle equipped with an internal combustion engine, comprising: a cooling water temperature detecting means for detecting a cooling water temperature of the internal combustion engine; and a fuel temperature in a fuel tank. Fuel temperature detection means, based on the difference between the cooling water temperature and the fuel temperature at the time of engine stop detected by the temperature detection means, and the difference between the cooling water temperature and the fuel temperature at the next start, When it is estimated that at least one of the cooling water temperature and the fuel temperature at the time of the next start is substantially stable,
An outside air temperature recognizing device in a vehicle equipped with an internal combustion engine, comprising: an outside air temperature estimating means for estimating the outside air temperature based on the one of the substantially stable temperatures. 3. The evaporation of an internal combustion engine according to claim 1, wherein the outside air temperature detecting device in the vehicle equipped with the internal combustion engine according to claim 2 is used as the outside air temperature detecting means according to claim 1. Fuel leak diagnostic device.