JP2921307B2 - Evaporative fuel leak diagnostic system for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel leak diagnostic system for an internal combustion engine for diagnosing a leak state of evaporative fuel in a system for supplying evaporative fuel stored in a fuel tank to an engine intake system.

[0002]

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

However, in such a device, if a leak hole is formed in the middle of the fuel vapor pipe, or a defective seal is formed at the joint of the fuel vapor pipe, the fuel vapor is vaporized into the atmosphere. that Do not. So, for example, Env
ironmental Protection Agency (EPA) and the California Air Resources Board (CARB)
[California Atmospheric Resources Bureau]), etc., diagnoses whether the amount of fuel vapor leak from the fuel vapor piping etc. is below an allowable value, and takes measures if the amount exceeds the allowable value. It is required to prevent transpiration into the atmosphere beforehand, and a leak diagnostic device and a diagnostic method thereof are proposed.

[0004] Such conventional fuel vapor leak diagnosis is as follows.
It was done like that. In other words, the size of the canister
Close the drain cut valve to shut off air communication.
The evaporative fuel pipe that connects the canister and the intake system.
Open the interposed purge cut valve and set the engine
As a result, the evacuation fuel passage and the fuel tank are pulled to a negative pressure.
So that And, the pressure in the fuel vapor pipe is
Negative pressure is reached or suction is performed for a predetermined time
While holding the drain cut valve closed,
Close the purge cut valve.

Here, after the purge cut valve is closed,
The pressure change in the internal space is monitored, and the
The pressure change speed (pressure rise speed) is detected. Soshi
Thus, the pressure change speed is compared with a judgment value stored in advance.
If it is too large, the amount of fuel vapor leak exceeds the allowable value.
The pressure change rate is equal to the determination value.
In the following cases, the amount of fuel vapor leak is below the allowable value.
Was to be diagnosed.

[0006]

THE INVENTION Problems to be Solved] However, within the
The pressure change rate until the negative pressure in the space returns to atmospheric pressure is
Emission of fuel vapor depending on the temperature of remaining fuel in the fuel tank
Fuel variation in raw and fuel remaining in fuel tank
The volume of the internal space changes depending on the amount of
Pressure change rate changes even with conventional leak diagnosis.
The diagnostic accuracy depends on the fuel vapor generation state, fuel remaining amount, etc.
There is a problem that there is a possibility that is reduced.

Therefore, the present invention has been made in view of such a conventional problem, and has been made to reduce the temperature of the remaining fuel in a fuel tank.
It is an object of the present invention to provide an evaporative fuel leak diagnostic device for an internal combustion engine that can accurately perform an evaporative fuel leak diagnosis while eliminating the influence of dependent fuel vapor . In addition, inside the fuel tank
Remaining amount of fuel in the evaporative fuel supply system
It is another object of the present invention to provide an evaporative fuel leak diagnostic device for an internal combustion engine that can accurately perform evaporative fuel leak diagnosis in consideration of changes in space volume .

[0008]

[SUMMARY OF To this end, the evaporation fuel leakage diagnosis apparatus according to the invention of claim 1, the shown <br/> Suyo 1, adsorbing the fuel vapor accumulated in the fuel tank Means for temporarily adsorbing the fuel, allowing the adsorbing means to communicate with the intake system of the engine in a predetermined engine operating state, separating and sucking the evaporated fuel from the adsorbing means by the negative pressure of the intake air of the engine, and guiding the fuel to the intake system. in an internal combustion engine having a fuel vapor evaporative emission apparatus, and the pressure detection <br/> means to detect the pressure before Symbol evaporative fuel supply system from the fuel tank to the intake system via the suction means, the fuel vapor The pressure in the fuel vapor supply system is reduced by shutting off the supply system from the atmosphere and communicating with the intake system of the engine.
After the pressure is reduced by the intake negative pressure of the engine,
Intake system and shut-off of engine while maintaining shut-off condition between system and atmosphere
Pressure to increase and change the pressure in the evaporative fuel supply system
Change control means, and the evaporation by the pressure change control means.
The change in pressure in the fuel supply system is
The pressure at each of two different points in time
In addition to determining the rate of change of the pressure detected by the detection means,
Of the pressure change rate determined at each of the two points in time
Evaporative fuel leak diagnosis means for determining a difference and diagnosing a leak state of the evaporative fuel supply system based on the difference in the pressure change speed .

According to a second aspect of the present invention, there is provided an evaporative fuel leak diagnostic device, wherein the evaporative fuel leak diagnostic means includes the one pressure change.
Of the rate of change in pressure determined during
The leak state of the evaporative fuel supply system is diagnosed based on the pressure change speed obtained during the force change .

According to a third aspect of the present invention, there is provided an evaporative fuel leak diagnostic apparatus, as shown by a dotted line in FIG.
Detect the internal space volume of the evaporative fuel supply system leading to the intake system
An internal space volume detection means, wherein the fuel vapor leak diagnosis is performed.
Means for detecting the difference between the pressure change rates and the internal space volume detection;
Based on the internal space volume detected by the discharge means.
The system is configured to diagnose the leak state of the feed system .

According to a fourth aspect of the present invention, there is provided an evaporative fuel leak diagnostic apparatus, wherein the internal space volume detecting means detects an internal space volume by detecting a remaining amount of fuel in a fuel tank. An evaporative fuel leak diagnostic device according to claim 5 is
The evaporative fuel evaporation prevention device opens the valve at a predetermined pressure between the fuel tank and the adsorbing means and sends the evaporative fuel to the adsorbing means,
In a device provided with a check valve for preventing a backflow of fuel vapor at a pressure lower than a predetermined pressure, a bypass passage for bypassing the check valve and a bypass valve which is opened in the middle of the bypass passage only at the time of diagnosis are provided.

[0012]

In the configuration of the fuel vapor leak diagnosis apparatus according to the first aspect, the fuel vapor supply system is shut off while the communication with the atmosphere is cut off.
And the engine intake system to communicate the engine fuel in the evaporative fuel supply system.
The pressure is reduced by suction using air negative pressure, and then
Suction by suction negative pressure while keeping the air shut off
Shut off and increase pressure. Here, the intake negative pressure is applied
During and after the negative pressure decrease
During the rising change since then,
When the rate of change of pressure is determined at each of the two
The leak condition based on the difference between these pressure change rates
Diagnose. This difference in pressure change rate is
Depends only on the internal space volume excluding the pressure rise due to
Value, eliminating the effects of fuel vapor pressure
Good evaporative fuel leak diagnosis is possible.

[0013] The fuel vapor leak according to claim 2
In the configuration of the diagnostic device, the pressure determined during the one pressure change is
The pressure determined during the other pressure change, along with the difference in force change rate
A leak diagnosis is performed based on the change speed. Of the same leak volume
If the remaining fuel amount in the fuel tank is large,
Both the pressure drop rate and the pressure rise rate are
If the amount of remaining fuel in the fuel tank is small,
And the rate of pressure rise are both slow.
Therefore, the effect of the amount of fuel remaining in the fuel tank is eliminated.
Thus, accurate leak diagnosis of the evaporated fuel becomes possible.

According to the structure of the evaporative fuel leak diagnostic apparatus according to the third aspect, the fuel pressure difference and the fuel tank speed are different from each other.
Internal space of the evaporative fuel supply system from the tank to the engine intake system
The product is detected, and a leak state is diagnosed based on the products.
That is, the amount of fuel remaining in the fuel tank
Even if the space volumes are different, it is necessary to detect the internal space volume.
By eliminating the effect of the amount of fuel remaining in the fuel tank
Accurate evaporative fuel leak diagnosis is possible.

In the configuration of the evaporated fuel leak diagnosis device according to the fourth aspect, the internal space volume is detected by detecting the remaining fuel amount in the fuel tank. In the evaporative fuel leak diagnostic apparatus according to claim 5, the bypass valve opens only when the leakage diagnosis of the fuel vapor. Thus so as to bypass the check valve, the check at the time of leakage diagnosis of fuel vapor Eliminating the influence of the valve opening pressure makes it possible to perform a more accurate vapor fuel leak diagnosis.

[0016]

EXAMPLES Hereinafter, will be described with reference to embodiments of the present invention in the accompanying drawings. In FIG. 2, one end of an evaporative fuel pipe 2a is connected to an upper wall of the fuel tank 1, and the other end of the evaporative fuel pipe 2a is connected to a canister 3 for temporarily absorbing the evaporative fuel. A pressure sensor 6 for detecting the pressure in the fuel vapor pipe is provided in the middle of the fuel vapor pipe 2a. Here, the pressure sensor 6 constitutes a pressure detecting means.

Further , the fuel vapor pipe 2 is connected to the canister 3.
b is connected at one end and the other end is connected to the intake passage (intake
(Manifold).
A jiccat valve 4 is provided. The canister 3
During normal engine operation and when fuel vapor is
When entering, open the valve and communicate with the atmosphere.
Drain cut valve 5 that can be closed and shut off from the atmosphere is provided
Have been.

Further, the remaining amount of fuel in the fuel tank 1 is detected.
A fuel remaining gauge 20 is provided. Shows fuel remaining
If a fuel gauge is provided in advance for the purpose of
In such a case, the fuel gauge can be used.
Although it may be the check valve 7 is rather free, if provided, the feed evaporated fuel opens at a predetermined pressure between the fuel tank 1 and the canister 3 to the canister 3, the fuel vapor is less than the predetermined pressure Can be prevented from flowing back to the fuel tank 1, so that the evaporated fuel can be reliably adsorbed to the canister 3. As shown in FIG. 3 , a bypass passage 30 that bypasses the check valve 7, and a bypass valve 31 is added in the middle of the bypass passage 30,
If the bypass valve 31 is opened and the check valve 7 is bypassed at the time of evaporative fuel leak diagnosis, it is possible to eliminate an error in the leak diagnosis due to the influence of the valve opening pressure of the check valve 7. It is. Then, the post-leakage diagnosis for closing the bypass valve 31, the flow direction of the evaporated fuel Ru can restricted by the check valve 7.

An apparatus for preventing evaporation of fuel vapor having such a configuration.
In FIG. 4, based on the flowchart shown in FIG.
The gin control module 50 is a
Make a diagnosis. In step 30, by opening the purge cut valve 4 in a predetermined engine operating state, the fuel vapor adsorbed in the canister 3 is sucked into the engine by the negative intake air pressure of the engine.

In step 31, by closing the drain cut valve 5, suction by the engine intake negative pressure is performed.
Negative pressure in the evaporative fuel passage, fuel tank, etc.
Is the pressure in the evaporation fuel supply system will decrease. Step 32 Te odor, based on a signal retardant Ryozanryou gauge 20 obtains the amount of fuel remaining in the fuel tank. Where fuel
Depending on the amount of fuel remaining in the tank 1, fuel is absorbed from the fuel tank.
The internal space volume of the evaporative fuel supply system leading to the gas system may change.
Therefore, the fuel remaining amount gauge 20 constitutes the internal space volume detecting means.

Here, the remaining fuel amount is detected.
Instead of giving the pressure, the pressure
The rate of pressure change in the fuel vapor pipe during the drop change (negative
Pressure suction speed) may be detected. Specifically, a predetermined negative
Measure the time it takes to reach pressure as the pressure drop rate.
In such a configuration, the fuel level gauge
It is no longer necessary to have 20.

In step 33, according to the detected remaining fuel amount in the fuel tank , that is, the internal space volume,
FIG. 5 shows the determination value of the pressure change speed difference ΔΔP described later.
Read from the judgment table. In step 32,
If a pressure drop rate (negative pressure suction rate) is detected,
Based on the pressure drop rate (negative pressure suction rate),
Let it be set.

In step 34, the purge cut valve 4 is closed. Here, steps 30, 31, and 34 correspond to pressures.
It constitutes force change control means. In step 35, the pressure change in the internal space volume is monitored based on the signal of the pressure sensor 6, and the pressure change rate (pressure
The rate of pressure change during the rising change) is measured.
As shown in FIG. 6 , the pressure change rate near the predetermined negative pressure (ΔP
1) and at least the pressure change rate (ΔP2) in the vicinity of the atmospheric pressure, and at each of these two different points in time,
The difference between the determined pressure change rates ΔP1 and ΔP2 (ΔΔP =
ΔP1−ΔP2) is obtained.

Here, the operation will be described in detail.
When the fuel vapor pressure is generated and the internal space volume pressure is detected
Even if added to the figure7As shown in the above internal empty
The line of the pressure change rate with respect to the pressure in the inter-volume (ΔP1 and
ΔP2) is translated by the fuel vapor pressure.
And the slope of the pressure change rate (pressure change
There is little change in the speed difference (ΔΔP = ΔP1-ΔP2)
You can see that. That is, the slope of the pressure change rateΔΔP
Is hardly affected by the fuel vapor pressure,
That is, the value depends only on the product.

Therefore, by examining the effect of the difference (ΔΔP) in the pressure change rate on the leak hole area using this characteristic, as shown in FIG. 8, the leak hole area is large.
The above ΔΔP is shown to be larger, and
The smaller the space volume (the more fuel remaining) the larger
The internal space volume as shown in FIG.
By setting a judgment table according to (fuel remaining amount),
Eliminates the effects of fuel vapor pressure and internal volume
Diagnosis can be performed. Subsequently, when the difference (ΔΔP) of the pressure change speeds exceeds the determination value for the fuel remaining amount in Step 36, Step 37
The procedure proceeds to step 38, where it is diagnosed that the leak amount of the evaporated fuel exceeds the allowable value. If the pressure change rate is equal to or less than the determination value, the procedure proceeds to step 38, where it is determined that the leak amount of the evaporated fuel is less than the allowable value. I do. Here, step 33 and step 3
6, 37 and 38 constitute evaporative fuel leak diagnosis means.

Thereafter, in step 39, the drain cut valve 5 is opened, and this flow chart is terminated.
Thus, in the above embodiment, as described above, the fuel
Influence on fuel vapor generated by temperature
The leak diagnosis is performed based on the ΔΔP that is not received.
Leak diagnosis with high accuracy regardless of combustion steam generation state
Can be turned off. Also, the internal space affected by the ΔΔP
Since the judgment value is set according to the volume, the fuel
Diagnostic accuracy is determined by changes in the internal space volume due to changes in the remaining amount.
The degree can be prevented from lowering.

As described above, the remaining fuel amount is detected,
The determination value according to the internal space volume product deduced from the fuel remaining amount
Instead of setting the pressure drop rate (negative pressure suction rate)
Alternatively, a configuration may be used in which a determination value is set. That is, the figure
In the case of the same leak amount shown in Fig. 9, the remaining amount in the fuel tank
When the amount of stored fuel is large (the internal space volume is small) (solid line)
The pressure drop speed V ₁ and the pressure rise speed V ₁ ′
Both are fast and the amount of remaining fuel in the fuel tank is small
(The inter-volume is large) (broken line), the pressure drop rate
V ₂ and the pressure rise rate V ₂ 'and characteristics that are both slow
There is.

Also, as shown in FIG.
When the amount of remaining fuel is the same and the amount of leak is large
The pressure drop rate is low and the pressure rise rate is high.
If the leak rate is small, the pressure drop rate
And the pressure rise speed is slow. I
Therefore, the pressure change speed during negative pressure change (negative pressure suction speed)
The higher the degree, the higher the fuel level (the smaller the internal space volume)
) And the determination value of ΔΔP in the same manner as in FIG.
, The leak amount is large and the pressure drop rate is small.
If it becomes low, it is considered that the volume of space is small and judged
Set the value to a smaller value (in a direction that makes leak diagnosis easier).
This is the same as detecting the internal space volume from the remaining fuel.
In the same way, the effects of the internal space volume (remaining fuel) are eliminated.
Diagnosis is possible.

Further , in the above embodiment, ΔΔP is set so that the pressure is large.
Determined during pressure rise change toward atmospheric pressure
Is the rate of pressure change when the evacuation fuel pipe is pulled to a negative pressure.
ΔΔP from this, and from this and the fuel remaining amount or the pressure rise speed
A configuration for performing leak diagnosis by comparing with the obtained judgment value
It may be.

In the above embodiment, the accuracy of the leak diagnosis is determined by the amount of fuel remaining in the fuel tank (for example, when the fuel itself is sucked up from the fuel tank by the negative suction pressure of the engine). In the case of a decrease, the diagnosis is not performed, and the leak diagnosis is performed only when the remaining amount of fuel in the fuel tank reaches a predetermined remaining amount. Of course, this is included.

[0031]

As described above, according to the first aspect of the present invention, the temperature of the fuel remaining in the fuel tank is controlled.
Eliminates the effect of fuel pressure on fuel vapor
High-precision evaporative fuel leak diagnosis
Can do it. According to the second and third aspects of the invention
Depends on the amount of fuel remaining in the fuel tank.
The effect of the internal space volume of the evaporative fuel supply system
More accurate diagnosis of evaporative fuel leaks
Can be performed.

According to the fourth aspect of the present invention, the above effects can be obtained more practically and economically. Claim 5
According to the invention described in (1), the influence of the valve opening pressure of the check valve provided in the middle of the evaporative fuel supply system can be eliminated, so that a more accurate evaporative fuel leak diagnosis can be performed.

[Brief description of the drawings]

FIG. 1 shows a configuration of an evaporative fuel leak diagnostic apparatus according to the present invention .
FIG.

FIG. 2 is an overall configuration diagram according to an embodiment of the present invention.

FIG. 3 shows a case where the check valve of the present invention is bypassed.
FIG.

FIG. 4 is a flowchart according to the embodiment of the present invention.

FIG. 5 is a determination table according to the embodiment of the present invention.

FIG. 6 shows a pressure in the vicinity of a predetermined negative pressure according to the embodiment of the present invention .
The rate of change (ΔP1) and the rate of pressure change near atmospheric pressure (ΔP1)
The figure showing P2).

FIG. 7 shows the pressure in the fuel vapor pipe according to the embodiment of the present invention;
The figure which shows the relationship of a pressure change speed.

FIG. 8 shows a leak area and a pressure change according to the embodiment of the present invention .
The figure which shows the relationship of a speed difference ((DELTA) P).

FIG. 9 shows a change in negative pressure suction at the same leak amount (pressure drop speed).
Degree) and leak down pressure change (pressure rise rate)
5 is a time chart showing a change due to a difference in amount.

FIG. 10 shows a negative pressure suction change (pressure drop) when the remaining fuel amount is the same .
Speed) and leak down pressure change (pressure rise speed) of fuel
5 is a time chart showing a change due to a difference in remaining amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Evaporated fuel pipe 2a Evaporated fuel pipe 2b Evaporated fuel pipe 3 Canister 4 Purge cut valve 5 Drain cut valve 6 Pressure sensor 7 Check valve 20 Fuel remaining gauge 30 Bypass passage 31 Bypass valve 50 Engine control module

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-256214 (JP, A) JP-A-5-223019 (JP, A) JP-A-6-129311 (JP, A) 79408 (JP, A) JP-A-6-42414 (JP, A) JP-A-6-173789 (JP, A) JP-A-5-256215 (JP, A) JP-A 5-180093 (JP, A) JP-A-5-240117 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 25/08

Claims (5)

(57) [Claims] An adsorbing means temporarily adsorbs evaporated fuel accumulated in a fuel tank, and communicates the adsorbing means with an intake system of the engine in a predetermined engine operating state. in an internal combustion engine having a fuel vapor evaporative emission control system which is adapted evaporated fuel disengaged suction processes led to the intake system, the pressure in the evaporative fuel supply system from the previous SL fuel tank through to the intake system via the suction means a pressure detecting means for detecting, intake of the engine the pressure in the evaporative fuel supply system is communicated intake system and communicating the engine together with the fuel vapor supply system is shut off from the atmosphere
After being reduced by the negative air pressure, the fuel vapor supply system and the atmosphere
And shut off the intake system of the engine while maintaining the
Pressure change control to increase and change the pressure in the evaporative fuel supply system
Means in the evaporative fuel supply system by the pressure change control means.
The pressure changes during a falling or rising change.
At two points in time, the pressure is detected by the pressure detecting means.
And the rate of change of the pressure to be determined.
The difference between the pressure change speeds determined for each is determined, and the pressure
An evaporative fuel leak diagnostic device for an internal combustion engine, comprising: evaporative fuel leak diagnostic means for diagnosing a leak state of the evaporative fuel supply system based on a difference in force change speed . 2. The apparatus according to claim 2, wherein said fuel vapor leak diagnosis means is provided for said one side.
Difference between the pressure change speed obtained during the pressure change of the
2. The evaporative fuel leak diagnostic device for an internal combustion engine according to claim 1, wherein a leak state of the evaporative fuel supply system is diagnosed based on a pressure change speed obtained during the other pressure change . 3. Evaporation from the fuel tank to an engine intake system.
Internal space volume detection that detects the internal space volume of the fuel supply system
Means, wherein the fuel vapor leak diagnosis means includes a difference in the pressure change rate.
And the internal space volume detected by the internal space volume detecting means.
Diagnosing a leak state of the fuel vapor supply system based on the product
The fuel vapor leak diagnosis device for an internal combustion engine according to claim 1, wherein 4. The evaporative fuel leak diagnosis apparatus according to claim 3, wherein said internal space volume detecting means detects the internal space volume by detecting a remaining amount of fuel in a fuel tank. 5. A check valve for opening a valve between a fuel tank and an adsorbing device at a predetermined pressure to feed the evaporative fuel to the adsorbing device and preventing a backflow of the evaporative fuel at a pressure lower than the predetermined pressure. in those and a bypass passage bypassing the check valve, either a bypass valve to be opened only at the time of diagnosis in the middle of the bypass passage, from claim 1 comprising the claims 4 1 The fuel vapor leak diagnostic device according to any one of the above.