JPH06159158A - Vaporized fuel leak diagnostic device of internal combustion engine - Google Patents

Abstract

PURPOSE:To execute the leak diagnostics of a vaporized fuel supply system which supplies the vaporized fuel to be generated in a fuel tank to the suction system without being affected by the fuel amount to be left in the fuel tank. CONSTITUTION:The inner space volume of a vaporized fuel supply system which consists of the space volume in vaporized fuel pipings 2a, 2b, a canister 3, and a fuel tank 1 is detected by the pressure dropping speed when suction is made by the negative pressure due to the engine suction, and the pressure rise speed when the negative pressure is raised toward the atmospheric pressure when a purge cut valve 4 is closed after suction by means of a pressure sensor 6. This constitution can presume the inner space volume which is changed by the change of the fuel amount to be left in the fuel tank 1, and the effect on the leak diagnostic accuracy by the residual fuel amount in the fuel tank 1 can be eliminated, enabling the leak diagnostics with good accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for diagnosing a leak state of evaporated fuel in a system for supplying evaporated fuel accumulated 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 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. So, for example, Environ
mental Protection Agency (EPA) and California Air Resources Board (CARB)
[California Atmosphere Resource Bureau]), etc. diagnoses whether the leak amount of the evaporated fuel from the evaporated fuel pipe or the like is below an allowable value, and if it exceeds the allowable value, take measures to prevent the evaporated fuel. It is required to prevent transpiration into the atmosphere, and a leak diagnosis device and a diagnosis method thereof are proposed.

FIG. 16 shows such a conventional evaporated fuel leak diagnostic device. According to FIG. 16, one end of the evaporated fuel pipe 2a is connected to the fuel tank 1, and the other end is connected to the canister 3 for adsorbing the evaporated fuel. A pressure sensor 6 for detecting the pressure inside the evaporated fuel pipe is provided in the middle of the evaporated fuel pipe 2a. The signal of the pressure sensor 6 is input to the engine control module 50,
The rate of pressure change in the evaporated fuel pipe is obtained based on the signal.

The engine control module 50 also stores a judgment value for leak diagnosis of evaporated fuel, and compares the judgment value with the pressure change speed described above to diagnose leakage of evaporated fuel. You can do it. One end of the evaporated fuel pipe 2b is connected to the canister 3, the other end is connected to the intake passage of the engine, and a purge cut valve 4 is provided in the middle thereof. The canister 3 is provided with a drain cut valve 5 that opens during normal engine operation and when introducing evaporated fuel into the intake passage to communicate with the atmosphere, and closes during leak diagnosis to shut off the atmosphere. ing.

With the conventional evaporated fuel leak diagnosis apparatus having such a configuration, the evaporated fuel leak diagnosis is performed based on the flowchart shown in FIG. In step 1 (indicated as S1 in the figure, the same applies hereinafter), the purge cut valve 4 is opened in a predetermined engine operating state, and the evaporated negative fuel adsorbed in the canister 3 is caused by the negative intake pressure of the engine. Is sucked into.

In step 2, the drain cut valve 5 is closed, so that the inside of the evaporated fuel passage, the inside of the fuel tank, and the like are pulled to a negative pressure by suction by the engine. In step 3, whether the pressure in the evaporated fuel pipe has reached a predetermined negative pressure,
Alternatively, it is determined whether suction has been performed for a predetermined time. In step 4, the purge cut valve 4 is closed. As a result, an internal space that maintains a negative pressure is formed.

In step 5, the pressure change in the internal space is monitored to detect the pressure change rate (pressure increase rate) toward the atmospheric pressure. In step 6, if the pressure change rate is larger than the pre-stored determination value, the process proceeds to step 7 and it is diagnosed that the leak amount of the evaporated fuel exceeds the allowable value, and the pressure change rate is determined as above. If it is less than the judgment value, the process proceeds to step 8 and it is diagnosed that the amount of leak of evaporated fuel is less than the allowable value.

After that, in step 9, the drain cut valve 5 is opened and the present flow chart ends.

[0010]

However, in such a conventional evaporated fuel leak diagnostic device, the rate of pressure change until the negative pressure in the internal space returns to atmospheric pressure depends on the amount of fuel remaining in the fuel tank. Since the volume of the internal space changes, the pressure change rate also changes depending on the amount of the remaining fuel (see FIG. 18), so that there is the inconvenience that the leakage diagnosis result varies depending on the internal space volume. It was For example, assuming that the leak determination value is set in accordance with a large amount of remaining fuel in the fuel tank, that is, when the internal space volume is small, the internal space volume is smaller when the remaining fuel amount is smaller than when the remaining fuel amount is large. Since the rate of change in pressure apparently decreases due to the increase, it is highly likely that there will be no leak of vaporized fuel even if the amount of leaked vaporized fuel actually exceeds the allowable value. It will end up.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and the vaporized fuel of an internal combustion engine capable of accurately performing leak diagnosis of the vaporized fuel without being affected by the remaining amount of the fuel in the fuel tank. An object of the present invention is to provide a leak diagnostic device. In addition to the above purpose, in consideration of the generation of fuel vapor depending on the temperature of the residual fuel in the fuel tank,
Another object of the present invention is to provide an evaporated fuel leak diagnosis device for an internal combustion engine, which can accurately perform a leak diagnosis of evaporated fuel.

[0012]

For this reason, the evaporated fuel leak diagnostic apparatus according to the first aspect of the present invention is shown in FIG.
As shown in (A), the evaporated fuel accumulated in the fuel tank is temporarily adsorbed by the adsorbing means, and the adsorbing means is made to communicate with the intake system of the engine under a predetermined engine operating condition. In an internal combustion engine equipped with an evaporated fuel transpiration prevention device that separates and sucks evaporated fuel from the adsorbing means and guides it to the intake system, the evaporated fuel that reaches the intake system from the fuel tank through the adsorbing means under predetermined conditions The pressure detecting means A for detecting the pressure in the supply system and the vaporized fuel supply system are communicated only with the intake system of the engine, and the pressure decrease rate in the vaporized fuel supply system at that time is used as a signal of the pressure detecting means A. Based on this, the evaporative fuel supply system, which has reached a predetermined negative pressure by communicating only with the intake system, is shut off from the intake system, and the rate of pressure increase in the evaporative fuel supply system at that time is detected by the pressure detecting means A. signal Based detected, configured to include a fuel vapor leakage diagnosis means B for diagnosing a leakage state of the evaporative fuel supply system on the basis of the these detected pressure drop velocity and pressure rise rate, a.

According to a second aspect of the present invention, there is provided an evaporated fuel leak diagnostic device, wherein the evaporated fuel leak diagnostic means B in the configuration of the first aspect of the invention has at least two measured pressure points in the evaporated fuel supply system that change in pressure. The leak state of the evaporated fuel supply system is diagnosed based on the change amount of either the pressure decrease rate or the pressure increase rate during the interval and the other pressure change rate.

As shown in FIG. 1B, the evaporative fuel leak diagnosis apparatus according to the third aspect temporarily adsorbs the evaporative fuel accumulated in the fuel tank by the adsorbing means, and in a predetermined engine operating state. Connecting the adsorption means to the intake system of the engine,
In an internal combustion engine equipped with an evaporated fuel transpiration prevention device adapted to separate and suck evaporated fuel from the adsorbing means by an intake negative pressure of the engine and guide it to an intake system for processing, from the fuel tank via the adsorbing means under predetermined conditions. Pressure detecting means A for detecting the pressure in the evaporated fuel supply system reaching the intake system; internal space volume detecting means C for detecting the internal space volume of the evaporated fuel supply system reaching the engine intake system from the fuel tank; The fuel supply system is set to a predetermined pressure condition, the pressure change speed at that time is detected based on the signal of the pressure detection means A, and based on the detected internal space volume of the evaporated fuel supply system and the pressure change speed. Evaporated fuel leak diagnosis means D is included so as to diagnose the leak state of the evaporated fuel.

According to a fourth aspect of the present invention, there is provided an evaporated fuel leak diagnostic apparatus, wherein the internal space volume detecting means C in the configuration of the third aspect of the invention detects the internal space by detecting the remaining amount of fuel in the fuel tank. I came to do it. The evaporated fuel leak diagnosis device according to a fifth aspect includes the evaporated fuel leak diagnosis means D in the configuration according to the third or fourth aspect of the invention.
The leak state of the evaporated fuel supply system is diagnosed based on the amount of change in the pressure change rate between at least two measurement pressure points in the evaporated fuel supply system where the pressure changes and the internal space volume.

According to a sixth aspect of the present invention, there is provided an evaporated fuel leak diagnosing device, wherein the vaporized fuel evaporation preventing device according to any one of the first to fifth aspects is provided between a fuel tank and an adsorbing means. A check valve that opens the valve at a predetermined pressure to send the evaporated fuel to the adsorbing means and prevents the reverse flow of the evaporated fuel at a pressure lower than the predetermined value.A bypass passage bypassing the check valve and a diagnosis in the middle of the bypass passage And a bypass valve that opens only when.

[0017]

According to the structure of the evaporated fuel leak diagnostic apparatus of claim 1, when the evaporated fuel supply system and the engine intake system are communicated with each other and the evaporated fuel supply system is sucked by the engine intake negative pressure,
The pressure decrease rate in the evaporated fuel supply system is detected based on the signal from the pressure detecting means A, the evaporated fuel supply system and the engine intake system are then shut off, and the evaporated fuel is supplied based on the signal from the pressure detecting means A. The pressure rise rate in the system is detected. Then, as shown in FIG. 4, when the amount of residual fuel in the fuel tank is large at the same leak amount, both the pressure decrease rate and the pressure increase rate are high, and the residual fuel amount in the fuel tank is high. In the case of a small amount, both the pressure decrease rate and the pressure increase rate become slow, and as shown in FIG.
When the amount of fuel remaining in the fuel tank is the same, when the leak amount is large, the pressure decrease speed is slow and the pressure increase speed is fast, and when the leak amount is small, on the contrary, the pressure decrease speed is By utilizing the characteristics that the fuel pressure is high and the pressure rising speed is slow, even if the amount of fuel remaining in the fuel tank is different, the leak diagnosis of the evaporated fuel is accurately performed.

Further, in the configuration of the evaporated fuel leak diagnosis apparatus according to the second aspect, either one of the pressure decrease rate or the pressure increase rate between at least two measured pressure points in the evaporated fuel supply system where the pressure changes. The amount of change (that is, the slope of the pressure velocity) is detected. As shown in FIG. 10, the change amount has a value that depends only on the internal space volume excluding the pressure increase due to the fuel vapor pressure. Therefore, the change amount is not detected. By combining the above, it becomes possible to eliminate the influence of the fuel vapor pressure and the amount of fuel remaining in the fuel tank, and to perform accurate leak diagnosis of evaporated fuel.

According to the constitution of the evaporated fuel leak diagnostic apparatus of the third aspect, the internal space volume detecting means C detects the internal space volume of the evaporated fuel supply system from the fuel tank to the engine intake system, while The vaporized fuel supply system is set to a predetermined pressure condition, and the pressure change speed at that time is detected based on the signal from the pressure detection means A. That is, even if the internal space volume is different by detecting the internal space volume,
From the relationship between the internal space volume and the pressure change rate, the influence of the amount of fuel remaining in the fuel tank can be eliminated and the leak diagnosis of the evaporated fuel can be performed accurately. In this case, the pressure change rate has the same effect at either the pressure decrease rate or the pressure increase rate in the evaporated fuel supply system.

In the structure of the evaporated fuel leak diagnosis apparatus according to the fourth aspect, the internal space volume is detected by detecting the remaining fuel amount in the fuel tank. In the configuration of the evaporated fuel leak diagnosis device according to the fifth aspect, in the configuration of the evaporated fuel leak diagnosis device according to the third or fourth aspect, the same operation as that of the above-described invention of the second aspect is performed. That is, the influence of the fuel vapor pressure and the amount of fuel remaining in the fuel tank is eliminated based on the amount of change in the pressure change rate between at least two measurement pressure points in the evaporative fuel supply system that changes in pressure and the internal space volume. It is possible to perform accurate leak diagnosis of evaporated fuel.

In the evaporated fuel leak diagnosis apparatus according to the sixth aspect, the bypass valve is opened and the check valve is bypassed only when the evaporated fuel leak is diagnosed. Therefore, the evaporated fuel leak diagnosis is performed. At this time, the influence of the valve opening pressure of the check valve can be eliminated, and more accurate vapor fuel leak diagnosis can be performed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the accompanying drawings. However, the same parts as those of the conventional example shown in FIG. 16 are denoted by the same reference numerals. In FIG. 2, one end of an evaporated fuel pipe 2a is connected to the upper wall of the fuel tank 1, and the other end of the evaporated fuel pipe 2a is connected to a canister 3 for temporarily adsorbing the evaporated fuel. A pressure sensor 6 for detecting the pressure inside the evaporated fuel pipe is provided in the middle of the evaporated fuel pipe 2a. Here, the pressure sensor 6 constitutes a pressure detecting means.

The check valve 7 may be omitted as in the conventional example, but if it is provided, the check valve 7 is opened at a predetermined pressure between the fuel tank 1 and the canister 3 to send the evaporated fuel to the canister 3. , Fuel tank for evaporated fuel at less than a specified pressure 1
Since the backflow to the canister 3 can be prevented, the evaporated fuel can be surely adsorbed to the canister 3. However, as shown in FIG. 15, the bypass passage 30 bypassing the check valve 7 and the midway of the bypass passage 30. If the bypass valve 31 is added to the check valve 7 and the bypass valve 31 is opened and the check valve 7 is bypassed at the time of vapor fuel leak diagnosis, the leak diagnosis is affected by the opening pressure of the check valve 7. It is also possible to eliminate the occurrence of an error in. After the leak diagnosis, by closing the bypass valve 31, the flow direction of the evaporated fuel can be regulated by the check valve 7.

The signal of the pressure sensor 6 is input to the engine control module 50, and the engine control module 50 monitors the pressure change based on the signal and can detect the pressure change speed. Further, the internal memory of the engine control module 50 stores a judgment table (FIG. 6) for leak diagnosis of evaporated fuel, and the leak diagnosis of evaporated fuel can be carried out based on the detected pressure change speed and the judgment table. You can do it.

By the way, the determination table of the present embodiment is set by utilizing the characteristics of the pressure decrease rate and the pressure increase rate, which vary depending on the amount of leak and the amount of fuel remaining in the fuel tank. There is. That is, when the amount of remaining fuel in the fuel tank is large (solid line) at the same leak amount shown in FIG. 4, the pressure decrease speed V ₁ and the pressure increase speed V are increased.
_When 1'is fast and the amount of fuel remaining in the fuel tank is small (broken line), both the pressure decrease rate V ₂ and the pressure increase rate V ₂ 'become slow, and the fuel shown in FIG. When the amount of fuel remaining in the tank is the same, when the leak amount is small (solid line), the pressure decrease speed V ₃ is fast, the pressure increase speed V ₃ 'is slow, and when the leak amount is large (broken line). On the contrary, the pressure decrease rate V ₄ is slow and the pressure increase rate V ₄ 'is fast.
Therefore, if the pressure decrease rate and the pressure increase rate are obtained, the leak amount can be determined. Therefore, a determination line corresponding to the leak amount serving as a reference for leak diagnosis is determined, and the region above the determination line in FIG. A region where a leak amount larger than the amount is generated) is stored as a leak generation region.

Then, one end of the evaporated fuel pipe 2b is connected to the canister 3, the other end is connected to the intake passage of the engine, and a purge cut valve 4 is provided in the middle thereof. Further, the canister 3 is provided with a drain cut valve 5 as in the conventional example. With the evaporated fuel leak diagnosis device having such a configuration, the engine control module 50 performs a leak diagnosis of the evaporated fuel pipe based on 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 negative pressure of the intake air of the engine. In step 11, by closing the drain cut valve 5, the evaporated fuel pipe 2a,
2b, canister 3, internal space of fuel tank 1, evaporative fuel supply system (hereinafter simply referred to as evaporative fuel supply system)
The engine suction negative pressure is introduced to.

In step 12, based on the signal from the pressure sensor 6, as shown in FIG. 4 or 5, 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 13
In, the judgment value of the pressure increase speed in the internal space volume formed when the purge cut valve 4 is closed with respect to the pressure decrease speed is read from the above-mentioned judgment table shown in FIG.

In step 14, the purge cut valve 4 is closed. In step 15, FIG. 4 or FIG.
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 16, when the detected pressure increase rate exceeds the determination value for the pressure decrease rate, the process proceeds to step 17, and it is diagnosed that the leak of evaporated fuel exceeds the allowable value.
If the pressure change rate is less than or equal to the judgment value, step 1
8 and it is diagnosed that the leak amount of the evaporated fuel is equal to or less than the allowable value. Here, step 13 and step 16, 1
Reference numerals 7 and 18 constitute evaporative fuel leak diagnosis means.

After that, in step 19, the drain cut valve 5 is opened, and this flowchart ends. According to the first embodiment of the present invention having such a configuration, the pressure decrease rate and the pressure increase rate are detected by using only one pressure sensor 6 as the detection means, and the pressure sensor 6 remains in the fuel tank. The influence of the amount of fuel can be eliminated and the leak diagnosis of evaporated fuel can be performed accurately.

When the bypass passage 30 bypassing the check valve 7 and the bypass valve 31 are added in the middle of the bypass passage 30, the bypass valve 31 is opened in step 11 to open the bypass valve 31. Since it is possible not to be influenced by the opening pressure of the check valve 7 at the time of leak diagnosis, the error caused by whether the leak position is on the fuel tank 1 side or the engine side of the check valve 7 is reduced. Therefore, it is possible to perform more accurate vapor fuel leak diagnosis.

Next, a second embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 7, the configuration of the second embodiment is different from the configuration of the first embodiment shown in FIG. 2 in that a fuel remaining amount gauge 20 for detecting the remaining amount of fuel is newly added to the fuel tank 1. The output signal from the fuel level gauge 20 is input to the engine control module 50. Since the other points are the same as those in the first embodiment, the description of the configuration will be omitted. In recent years, a fuel residual amount gauge is often provided in advance for the purpose of displaying the fuel residual amount, and in this case, the fuel residual amount gauge can be used.

The internal memory of the engine control module 50 in the present embodiment stores a judgment table for leak diagnosis of evaporated fuel, and the leak diagnosis of evaporated fuel is carried out based on the detected pressure change rate and the judgment table. You can do it. The determination table is shown in FIG.
It is set as shown in. That is, the fuel tank 1
Since the amount of fuel remaining in the fuel tank can be detected by the fuel gauge 20 (since the internal space volume of the evaporated fuel supply system is detected), the amount of fuel remaining in the fuel tank (in other words,
The determination line for the leak diagnosis is set based on the internal space volume) and the pressure change speed in the internal space volume (in the present embodiment, either the pressure increasing speed or the pressure decreasing speed may be used). You can

Next, based on the flowchart shown in FIG. 8, the fuel vapor leak diagnosis performed by the control module 50 will be described. In step 20, the purge cut valve 4 is opened in a predetermined engine operating state, so that the vaporized fuel adsorbed in the canister 3 is sucked into the engine by the negative pressure of the intake air of the engine.

In step 21, by closing the drain cut valve 5, the suction negative pressure negative pressure of the engine is introduced into the evaporated fuel supply system. In step 22, the amount of fuel remaining in the fuel tank is obtained based on the signal from the fuel amount gauge 20. Here, the fuel remaining amount gauge 20 constitutes an internal space volume detecting means.

In step 23, the judgment value of the pressure change speed in the internal space volume formed when the purge cut valve 4 is closed for the remaining fuel amount is read from the judgment table shown in FIG. In step 24, the purge cut valve 4 is closed. In step 25, as shown in FIG.
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 toward the atmospheric pressure.

In step 26, when the detected pressure change rate exceeds the judgment value for the remaining fuel amount, the routine proceeds to step 27, where it is diagnosed that the leak amount of evaporated fuel exceeds the allowable value. If the pressure change rate is equal to or lower than the determination value, the routine proceeds to step 28, where it is diagnosed that the leak amount of the evaporated fuel is equal to or lower than the allowable value. Here, step 23 and steps 26, 27 and 28 constitute the evaporated fuel leak diagnosis means.

Then, in step 29, the drain cut valve 5 is opened, and this flow chart ends.
According to the second embodiment of the present invention having such a configuration, it is possible to detect the internal space volume of the evaporated fuel pipe by detecting the amount of fuel remaining in the fuel tank with the fuel gauge 20. The leak diagnosis of the evaporated fuel can be performed accurately without being affected by the amount of fuel remaining in the fuel tank.

In the second embodiment, the pressure change speed toward the atmospheric pressure after the suction to the predetermined negative pressure is detected, but the pressure change speed at the time of suction to the predetermined negative pressure may be detected. Of course. Next, a third embodiment of the present invention will be described with reference to the accompanying drawings. Since the configuration of the third embodiment is similar to that of the second embodiment, the description thereof is omitted and FIG.
The leak diagnosis of the evaporated fuel performed by the control module 50 will be described based on the flowchart shown in FIG. Here, an example will be shown in which the leak diagnosis of the evaporated fuel is performed in consideration of the influence of the vapor pressure of the fuel vapor generated in the fuel tank in addition to the remaining amount of the fuel.

In step 30, 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 negative pressure of the intake air of the engine. In step 31, the drain cut valve 5 is closed, so that the inside of the evaporated fuel passage, the inside of the fuel tank, or the like is pulled to a negative pressure by suction by the engine.

In step 32, the amount of fuel remaining in the fuel tank is obtained based on the signal from the fuel amount gauge 20, as in the second embodiment. Here, the fuel remaining amount gauge 20 constitutes an internal space volume detecting means. (Here, as in the first embodiment, a method of detecting the pressure change rate in the evaporated fuel pipe based on the signal of the pressure sensor 6 may be used.) In step 33, the detection is performed. Fuel remaining in the fuel tank (or the pressure change rate)
Of the pressure change rate in the internal space volume formed when the purge valve 4 is closed (that is, ΔΔP = ΔP
The judgment value of (1-ΔP2) is read from the judgment table shown in FIG.

In step 34, the purge cut valve 4 is closed. In step 35, the pressure change in the internal space volume is monitored based on the signal of the pressure sensor 6 to measure the pressure change rate toward the atmospheric pressure. At that time, as shown in FIG. Pressure change rate (ΔP1) and pressure change rate near atmospheric pressure (ΔP
2) and at least are measured, and the difference (ΔΔP = ΔP1-ΔP2) between the pressure change rates at these two points is obtained. here,
In order to simplify the explanation, the difference between the pressure change rates at two points is used, but it is also possible to detect two or more points and obtain the slope by simple regression analysis or the like. Although the difference in the pressure change speed toward the atmospheric pressure is obtained here, the difference in the pressure change speed when the inside of the evaporated fuel pipe is pulled to a negative pressure may be obtained.

More specifically, even if the fuel vapor is generated and the fuel vapor pressure is added when the pressure of the internal space is detected, as shown in FIG. 12, the internal pressure of the internal space is increased. Straight line of pressure change rate with respect to pressure (ΔP1
And a straight line passing through ΔP2) have a tendency to move in parallel by the fuel vapor pressure, and it can be seen that there is little change in the gradient of the pressure change rate (difference in pressure change rate / ΔΔP = ΔP1−ΔP2). That is, the gradient of the pressure change rate is a value that is hardly influenced by the fuel vapor pressure and depends only on the internal space volume.

Therefore, using this characteristic, when the influence of the difference (ΔΔP) in the pressure change speed on the leak hole area is examined, the tendency shown in FIG. 13 is obtained. It is possible to set the determination table as shown in FIG. Subsequently, in step 36, when the difference (ΔΔP) in the pressure change rates exceeds the determination value for the remaining fuel amount, the process proceeds to step 37, and the leak amount of the evaporated fuel exceeds the allowable value. If it is determined that the pressure change rate is equal to or lower than the determination value, the process proceeds to step 38, and it is determined that the leak amount of the evaporated fuel is equal to or lower than the allowable value. Here, step 33 and steps 36, 37, and 38 constitute the evaporated fuel leak diagnosis means.

Thereafter, in step 39, the drain cut valve 5 is opened and the present flow chart ends.
Therefore, in the third embodiment, as described above, the amount of the fuel remaining in the fuel tank and the influence of the fuel vapor generated by the influence of the temperature of the fuel and the like are taken into consideration and the accuracy is improved. Evaporative fuel leak diagnosis can be performed.

In the third embodiment, as a method for eliminating the influence of the fuel remaining amount in the fuel tank, the fuel gauge 20 described in the second embodiment is used to detect the fuel remaining amount in the fuel tank. However, it goes without saying that a method of eliminating the influence of the remaining fuel amount in the fuel tank by combining the gradient of the pressure change rate with one of the pressure decrease rate and the pressure increase rate is also possible.

In each of the above embodiments, 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 due to the suction negative pressure of the engine). The internal space volume of the present invention can be detected by not performing the diagnosis when it decreases, and by performing the leak diagnosis only when the remaining fuel amount in the fuel tank reaches a predetermined remaining amount. Of course, it is included in this.

[0048]

As described above, according to the first aspect of the invention, the internal space volume of the evaporated fuel supply system, which changes depending on the amount of fuel remaining in the fuel tank, is estimated by the pressure change, Leakage of the evaporated fuel from the evaporated fuel supply system can be accurately diagnosed without being affected by the internal space volume.

According to the second aspect of the present invention, in addition to the above effects, the influence of the vapor pressure of the fuel vapor generated depending on the temperature of the fuel remaining in the fuel tank can be eliminated. Therefore, it is possible to perform more accurate leak diagnosis of the evaporated fuel. According to the invention described in claim 3, by detecting the internal space volume of the evaporated fuel supply system,
The leak diagnosis of the evaporated fuel from the evaporated fuel supply system can be accurately performed without being affected by the internal space volume.

According to the invention described in claim 4, it is possible to achieve the above effects more practically and economically. Claim 5
According to the invention described in (1), the same effects as those of the invention described in (2) can be obtained with respect to the invention described in (3) or (4). According to the invention described in claim 6, since it is possible to eliminate the influence of the opening pressure of the check valve provided in the middle of the evaporated fuel supply system, it is possible to perform a more accurate evaporated fuel leak diagnosis. it can.

[Brief description of drawings]

FIG. 1A is a block diagram showing a configuration of an evaporated fuel leak diagnosis device according to the invention of claim 1. (B)
FIG. 4 is a block diagram showing a configuration of an evaporated fuel leak diagnosis device according to a third aspect of the invention.

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

FIG. 3 is a flowchart according to the first embodiment of the present invention.

FIG. 4 is a time chart of negative pressure suction change and leak down pressure change at the same leak amount according to the first embodiment of the present invention.

FIG. 5 is a time chart of changes in negative pressure suction and changes in leakdown pressure when the same amount of remaining fuel is used according to the first embodiment of the present invention.

FIG. 6 is a determination table according to the first embodiment of the present invention.

FIG. 7 is an overall configuration diagram according to a second embodiment of the present invention.

FIG. 8 is a flowchart according to a second embodiment of the present invention.

FIG. 9 is a determination table according to the second embodiment of the present invention.

FIG. 10 is a flowchart according to the third embodiment of the present invention.

FIG. 11 is a diagram showing a pressure change rate (ΔP1) near a predetermined negative pressure and a pressure change rate (ΔP2) near atmospheric pressure according to the third embodiment of the present invention.

FIG. 12 is a diagram showing the relationship between the pressure in the evaporated fuel pipe and the pressure change rate in the internal space volume according to the third embodiment of the present invention.

FIG. 13 is a diagram showing a relationship between a leak area and a pressure change rate difference (ΔΔP) in an internal space volume according to a third example of the present invention.

FIG. 14 is a determination table according to the third embodiment of the present invention.

FIG. 15 is an overall configuration diagram in the case of bypassing the check valve of the present invention.

FIG. 16 is an overall configuration diagram according to a conventional example.

FIG. 17 is a flowchart according to a conventional example.

FIG. 18 is a time chart of changes in pressure in the internal space volume due to differences in the remaining fuel amount in the fuel tank.

[Explanation of symbols]

 1 Fuel Tank 2 Evaporative Fuel Pipe 2a Evaporative Fuel Pipe 2b Evaporative Fuel Pipe 3 Canister 4 Purge Cut Valve 5 Drain Cut Valve 6 Pressure Sensor 7 Check Valve 20 Fuel Level Gauge 30 Bypass Passage 31 Bypass Valve 50 Engine Control Module

Claims (6)

[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. In an internal combustion engine equipped with a vaporized fuel evaporation prevention device that separates and sucks vaporized fuel and guides it to the intake system, within the vaporized fuel supply system that reaches the intake system from the fuel tank through adsorption means under predetermined conditions A pressure detection means for detecting the pressure of the, and the evaporated fuel supply system is communicated only with the intake system of the engine, the pressure decrease rate in the evaporated fuel supply system at that time is detected based on the signal of the pressure detection means, The evaporative fuel supply system that has reached a predetermined negative pressure by communicating only with the intake system is shut off from the intake system, and the rate of pressure increase in the evaporative fuel supply system at that time is detected based on the signal from the pressure detection means. And an evaporative fuel leak diagnosis means for diagnosing a leak state of the evaporative fuel supply system based on the detected pressure decrease rate and pressure increase rate, and evaporative fuel for an internal combustion engine characterized by comprising: Leak diagnostic device. 2. The evaporative fuel leak diagnosing means is configured to change a pressure change rate or a pressure increase rate between at least two measured pressure points in the evaporative fuel supply system where the pressure changes, and a change in the other pressure. The evaporative fuel leak diagnosis apparatus for an internal combustion engine according to claim 1, wherein a leak state of the evaporative fuel supply system is diagnosed based on the speed. 3. Evaporated fuel accumulated in a fuel tank is temporarily adsorbed by an adsorbing means, and the adsorbing means is made to communicate with an intake system of the engine under a predetermined engine operating condition, and the adsorbing means is caused by an intake negative pressure of the engine. In an internal combustion engine equipped with a vaporized fuel evaporation prevention device that separates and sucks vaporized fuel and guides it to the intake system, within the vaporized fuel supply system that reaches the intake system from the fuel tank through adsorption means under predetermined conditions Pressure detection means for detecting the pressure of the fuel vapor, internal space volume detection means for detecting the internal space volume of the evaporated fuel supply system from the fuel tank to the engine intake system, and the evaporated fuel supply system is set to a predetermined pressure condition. , The pressure change rate at that time is detected based on the signal of the pressure detection means, and the leak state of the evaporated fuel is detected based on the detected internal space volume of the evaporated fuel supply system and the pressure change rate. Evaporative fuel leak diagnostic apparatus for an internal combustion engine to a fuel vapor leakage diagnosis means for disconnection, characterized in that it is configured to include. 4. The evaporated fuel leak diagnostic device according to claim 3, wherein the internal space volume detection means detects the internal space volume by detecting the amount of fuel remaining in the fuel tank. 5. The evaporative fuel supply system based on the amount of change in pressure change rate and the internal space volume between at least two measured pressure points in the evaporative fuel supply system where the pressure changes, in the evaporative fuel leak diagnosis means. 5. The evaporative fuel leak diagnosis device for an internal combustion engine according to claim 3, wherein the leak state is diagnosed. 6. A check valve for preventing the evaporative fuel from flowing backward when the evaporative fuel evaporation prevention device opens the valve between the fuel tank and the adsorbing means at a predetermined pressure to send the evaporated fuel to the adsorbing means and below the predetermined pressure. 6. A device comprising: a bypass passage for bypassing the check valve; and a bypass valve which is opened in the middle of the bypass passage only during a diagnosis. Evaporative fuel leak diagnostic device according to item 1.