JP3250351B2 - Failure diagnosis device for evaporative fuel treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis apparatus for temporarily storing fuel evaporated from a fuel tank and diagnosing a leaked state of an evaporative fuel treatment system which is introduced into an engine intake system under a predetermined operating condition. .

[0002]

2. Description of the Related Art Generally, in an internal combustion engine of an automobile, a purge gas from a canister is temporarily absorbed by a canister by temporarily adsorbing fuel vapor generated in a fuel tank and opening a purge control valve under a predetermined operating condition. Is introduced into the engine intake system.

[0003] Such an evaporative fuel treatment apparatus is for preventing fuel vapor from flowing out of a fuel tank. However, a tube constituting a purge passage may come off, a poor seal at a connection portion, and a pinhole may occur. Then, a fuel component that is originally adsorbed by the canister and introduced into the engine intake system leaks to the outside, so that the function cannot be sufficiently exhibited.

[0004] Therefore, in order to prevent the leakage of the fuel vapor, there is a demand for the development of a device for self-diagnosing the leakage of the fuel vapor treatment device. The diagnostic device includes a drain cut valve that opens and closes a fresh air intake of a canister, and a pressure sensor that detects a pressure of a fuel component flow path system from a fuel tank through a canister to a purge passage. After reducing the fuel component flow path system to a predetermined negative pressure by using a negative pressure, the drain cut valve and the purge control valve are closed to maintain the negative pressure state, and from this negative pressure state to the atmospheric pressure state A configuration for diagnosing a leak based on a change in pressure at that time has been proposed by, for example, CARB (California Air Resources Bureau) and the like.

[0005]

However, in the above-described diagnostic apparatus, the strength is improved by the stress caused by the negative pressure generated in the fuel tank, the purge passage, etc., because the structure is such that the negative suction pressure of the engine is introduced into the fuel component flow path system. Need to be performed, which increases costs.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention has a configuration for performing a leak diagnosis of a device without giving a forced pressure change to a fuel flow path system. That is, as shown in FIG. 1, a failure diagnosis device for an evaporative fuel processing apparatus according to the present invention includes a canister 3 for temporarily adsorbing evaporative fuel introduced from the inside of a fuel tank 1 via an evaporative fuel passage 2, A purge passage 5 for guiding the purge gas released from the canister 3 together with fresh air taken in through the intake 3A to the engine intake system 4,
A drain cut valve for closing a fresh air intake port of the canister; and a fuel cut-off valve for closing the fresh air inlet of the internal combustion engine, the drain cut valve being provided in the middle of the purge passage and having a purge control valve for controlling a purge gas. 1, a pressure detecting means 9 for detecting a pressure of a fuel component flow path system 8 including a fuel passage 2, a canister 3, and a purge passage 5, and a purge control valve 6 and a drain cut valve 7, which are closed and closed. a passage sealing means 10 for holding the fuel component flow passage system 8 in a sealed state, the pressure
Based on the output signal of the force detecting means 9, the initial pressure before the fuel component flow path system 8 is closed by the flow path closing means 10 and the pressure after sealing after the fuel component flow path system 8 is closed are read. Sealed
A pressure change detecting means 11 for detecting a pressure change between the post-pressure and the initial pressure; and a normal state when the pressure change exceeds a predetermined reference value, and an abnormal state when the pressure change falls below the predetermined reference value. The determination means 12 determines the state.

In the configuration of the second aspect, fuel temperature detecting means 13 for detecting a fuel temperature is provided, and the determining means 12
It is characterized in that a comparison is made between a reference value prepared in advance according to the fuel temperature and the pressure change to determine whether the state is a normal state or an abnormal state. Contract
In the configuration of claim 3, in order to enable more accurate diagnosis
In the meantime, the fuel component flow path system 8 is closed by the flow path sealing means 10.
Measurement means for measuring the elapsed time since the
The determining means 12 determines that the elapsed time has reached a predetermined maximum measurement time.
If the pressure change exceeds a predetermined reference value before
It is characterized in that it is determined to be in a normal state. Claim 4
In order to prevent erroneous diagnosis,
Until the predetermined maximum measurement time is reached.
It is characterized by the need for repetition.

[0008]

When the fuel component flow path system 8 is kept closed by the flow path sealing means 10, the pressure of the fuel component flow path system 8 is increased by the purge gas and vapor. On the other hand, the degree of the pressure rise changes according to the leakage area of the fuel component flow path system 8. Accordingly, the pressure change before and after the fuel component flow path system 8 is closed is determined by the pressure change detecting means 11.
, The determination means 12 can determine the presence or absence of leakage based on the change in pressure.

The determining means compares the reference value corresponding to the fuel temperature detected by the fuel temperature detecting means with the pressure change detected by the pressure change detecting means,
The presence or absence of leakage can be diagnosed in consideration of the amount of vapor generated differently depending on the fuel temperature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS.

First, FIG. 2 is an explanatory view of a configuration of an evaporative fuel processing apparatus provided with a failure diagnosis device according to an embodiment of the present invention. A fuel tank 21 is connected to a canister 23 via an evaporative fuel passage 22. I have.

The canister 23 is composed of an adsorbent, a filter (both not shown) and the like, and a bottom thereof is provided with a fresh air intake 23A open to the atmosphere. Also,
A purge gas outlet of the canister 23 is connected via a purge passage 24 to a collector 25 downstream of the throttle valve in the intake passage. A purge control valve 26, which is an electromagnetic valve, is provided in the purge passage 24.

On the other hand, the fresh air inlet 23A of the canister 23
Is provided with a drain cut valve 27 composed of an electromagnetic valve. The drain cut valve 27 is operated by a control signal from a control unit 34 to be described later, and is closed together with the purge control valve 26 at the time of a self-diagnosis, so that the fuel tank 21, the evaporative fuel passage 22, the canister 2
3. The fuel component flow path system 28 including the purge passage 24 is kept closed. Here, the closed state in the present embodiment refers to a substantially closed state except for a leak within an allowable range from a gap between a valve body and a valve seat, and there is a natural leak to be allowed. Also grasped as a closed state.

A pressure sensor 29 as a pressure detecting means includes:
It is provided in the middle of the evaporative fuel passage 22. The pressure sensor 29 includes, for example, a semiconductor pressure sensor, and detects the pressure of the fuel vapor passage 22 as the pressure P of the fuel component flow path system 28 and outputs this to the control unit 34 at the time of self-diagnosis. is there.

A temperature sensor 30 as a fuel temperature detecting means is provided in the fuel tank 21. This temperature sensor 30
Is composed of, for example, a thermistor, a thermocouple, and the like, and detects the temperature of the fuel in the fuel tank 21.

Reference numeral 31 denotes a throttle sensor for detecting a valve opening of a throttle valve, 32 denotes an air flow meter for measuring an intake air amount, and 33 denotes a crank angle sensor for detecting a crank angle. A water temperature sensor, an ignition switch, and the like are connected to the control unit 34.

A control unit 34 for electrically centrally controlling the internal combustion engine is configured as a microcomputer system, and includes a purge control valve 26 and a drain cut valve 27.
Is provided with a drive circuit (both not shown) for driving.

Next, the operation of the embodiment will be described.

First, the pressure change when the fuel component flow path system 28 is kept in a closed state will be described with reference to FIG.

If the purge control valve 26 and the drain cut valve 27 are closed when the engine enters the operation range where self-diagnosis is possible, the inside of the fuel component flow path system 28 is maintained in a substantially sealed state. Will be. On the other hand, due to the closed state, the destination of the evaporated fuel (vapor) generated in the fuel tank 21 and the purge gas stored in the canister 23 disappear. Therefore, at the time of normal no leakage locations other than the natural leakage is acceptable, as indicated by a solid line S ₁ in FIG. 3, the fuel component flow channel system 2
The pressure of 8 gradually increases.

On the other hand, if there is an unacceptable leak in the fuel component flow path system 28, the evaporated fuel generated in the fuel tank 21 flows out of the leak location to the outside, so that the two-dot chain line S in FIG. _As shown in FIG. ₂ , the degree of pressure rise is lower than in the normal state where there is no leakage.

[0022] Thus, in this embodiment, as described later, the pressure difference occurring before and after the sealing is judged to be normal state once exceeds the predetermined reference value [Delta] P _S, it adapted to determine an abnormal state if falls below.

By the way, when the fuel temperature is high, the amount of the fuel vapor generated in the fuel tank 21 increases, while when the fuel temperature is low, the amount of the fuel vapor decreases. Accordingly, since the pressure difference between the fuel component flow path system 28 before and after sealing varies depending on the fuel temperature, in the present embodiment, the above-described reference value ΔP _{S is set} to the fuel value as shown by the dotted line S ₃ in FIG. It is adjusted according to the temperature.

Next, the self-diagnosis method according to this embodiment will be described with reference to the flowchart of FIG.

First, when the engine enters a predetermined operating region in which self-diagnosis is possible, it is determined in step 1 whether or not an initial pressure value P ₁ described later has already been read. Since it is just after the start of the program, "NO" is determined in this step 1.

Next, in step 2, reads the current pressure P of the fuel component flow channel system 28 from the output signal of the pressure sensor 29, and stores this value as the initial pressure value P _1. And
In step 3, the purge control valve 26 and the drain cut valve 27 are closed to keep the fuel component flow path system 28 in a closed state. In step 4, the pressure after sealing is determined based on an output signal from the pressure sensor 29. It reads the P _2.

Next, in step 5, after detecting the fuel temperature from the output signal of the temperature sensor 30, and sets the reference value [Delta] P _S corresponding to the current fuel temperature based on the characteristic diagram shown in FIG. 4, the the differential pressure between the sealing after the pressure value P ₂ and the initial pressure value P ₁ determines whether exceeds a predetermined reference value [Delta] P _S.
As described above, in a normal state with no leakage, the pressure difference ΔP (= P ₂ −P ₁ ) between the two is determined by the reference value ΔP _S according to the fuel temperature.
Therefore, it is determined to be “YES” and step 8 described later is performed.
Move to On the other hand, if there is a leak in the fuel component flow path system 28, the differential pressure ΔP falls below the reference value ΔP _S , so that “N
O "is determined, and the process proceeds to the next step 6.

Here, even if the purge control valve 26 and the drain cut valve 27 are closed to keep the fuel component flow path system 28 in a closed state, the pressure does not increase immediately.
Therefore, when the program is started, “NO” is determined in step 5 and the process proceeds to step 6.

In step 6, the timer t is started, and in the next step 7, it is determined whether or not the timer t has reached the maximum measurement time t _max . That is, as shown in FIG. 3, the pressure P after sealing rises with the passage of time. Therefore, when self-diagnosis is performed immediately after the sealing of the fuel component flow path system 28, it is determined that the fuel component is normal but abnormal. May be Therefore, in the present embodiment, the maximum measurement time t is used as the time during which the presence or absence of leakage can be reliably determined from the differential pressure ΔP.
By setting _max and repeatedly obtaining the differential pressure ΔP before and after sealing until the maximum measurement time t _max is reached, erroneous diagnosis is prevented.

As a result, if "NO" is determined in step 7, step 1 → step 4 → step 5 →
Returning to step 7 through step 6, while repeating this loop, when the differential pressure [Delta] P exceeds the reference value [Delta] P _S, it is determined as "YES" in step 5 proceeds to step 8, a normal state (OK ) Is diagnosed. Therefore, when the maximum measurement time t _max is not a set time for simply waiting for a time, and it is convinced that it is in a normal state, the determination can be made immediately in step 5 described above.

On the other hand, if "NO" is determined in the step 7, even if the timer t reaches the set maximum measurement time _tmax with a sufficient margin, the differential pressure ΔP will still be equal to the reference value ΔP _S
Is not exceeded, that is, it can be regarded as an abnormal state with leakage. Therefore, in this case, the process proceeds to step 9 to determine an abnormal state (NG), and turns on an alarm lamp or the like on an indicator (not shown) to alert the driver. The alarm means is not limited to the alarm lamp, but may be an alarm buzzer, a warning message by a sound generator, or the like.

As described above, according to the present embodiment, the fuel component passage system 28 including the fuel tank 21, the evaporative fuel passage 22, the canister 23, and the purge passage 24 is sealed by the purge control valve 26 and the drain cut valve 27. And a pressure difference (ΔP) between before and after sealing detected through the pressure sensor 29 is compared with a reference value ΔP _S to diagnose the presence or absence of leakage. The life of the fuel vapor treatment device can be greatly improved without applying stress due to negative pressure.

Further, since the difference between the pressure difference ΔP between the initial pressure value P ₁ and the pressure value after sealing P ₂ and the reference value ΔP _S is determined, it is possible to determine whether or not there is a leak from a pressure gradient or the like. The program can be simplified, and the overall control configuration can be made compact.

Further, since the reference value _tmax is adjusted in accordance with the fuel temperature, erroneous diagnosis due to a change in the fuel temperature can be prevented. In addition to this, the fuel temperature range in which self-diagnosis can be performed can be expanded, so that a diagnosis opportunity can be increased and the reliability of the device can be improved.

In the above embodiment, the pressure sensor 30 as the pressure detecting means is provided in the fuel vapor passage 22. However, the present invention is not limited to this.
Or in the middle of the purge passage 24 or in the canister 23.

In the above-described embodiment, the temperature sensor 30 is used as the fuel temperature detecting means, and the temperature sensor 30 directly measures the fuel temperature in the fuel tank 21. However, the present invention is not limited to this. Alternatively, a temperature sensor may be provided on the outer wall or the like of the fuel tank 21 to measure the fuel temperature indirectly, or the fuel temperature may be estimated from the cooling water temperature, the number of revolutions, or the like of the engine. In this case, a map indicating the correlation between the coolant temperature, the number of revolutions, and the like and the fuel temperature may be prepared in advance.

Further, in the above embodiment, the maximum measurement time t
_{The case} where the differential pressure ΔP and the reference value ΔP _S are compared up to _max has been described as an example. However, when the measurement time is not limited, steps 6 and 7 in FIG. A configuration may be adopted in which a predetermined time is waited for before performing the above processing.

In the above-described embodiment, the determination is made by comparing the pressure difference ΔP with the reference value ΔP _S.
In some cases, the determination may be made based on the magnitude of the gradient of the pressure change due to the fuel vapor, or may be determined based on the length of time required to reach a predetermined pressure determined for each fuel temperature.

[0039]

As described above in detail, according to the failure diagnosis system for an evaporative fuel treatment system according to the present invention, the fuel component passage system from the fuel tank to the purge passage via the canister is maintained in a sealed state. By comparing the pressure difference before and after sealing with the reference value to diagnose the presence or absence of leakage, there is no need to improve the strength of the fuel component flow path system to cope with stress due to negative pressure, thus reducing costs can do.

Further, since the reference value is adjusted in accordance with the fuel temperature, erroneous diagnosis due to a change in the fuel temperature can be prevented beforehand. You get the opportunity.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of a failure diagnosis device according to the present invention.

FIG. 2 is a configuration explanatory diagram of a failure diagnosis device according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a passage of time after passage sealing and a pressure change.

FIG. 4 is a characteristic diagram showing a relationship between a fuel temperature and a pressure change.

FIG. 5 is a flowchart illustrating a failure diagnosis process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... Fuel tank 22 ... Evaporation fuel passage 23 ... Canister 23A ... Fresh air intake 24 ... Purge passage 25 ... Collector (engine intake system) 26 ... Purge control valve 27 ... Drain cut valve 28 ... Fuel component flow passage system 29 ... Pressure Sensor (pressure detecting means) 30 ... Temperature sensor (fuel temperature detecting means) 34 ... Control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 25/08 G05B 23/02

Claims (4)

(57) [Claims] A canister for temporarily adsorbing fuel vapor introduced from a fuel tank through a fuel vapor passage, and a purge gas separated from the canister together with fresh air taken in through a fresh air inlet. In an evaporating apparatus for an internal combustion engine, comprising: a purge passage leading to an intake system; and a purge control valve provided in the middle of the purge passage and controlling a purge gas, a drain cut valve for closing a fresh air intake of the canister Pressure detecting means for detecting the pressure of a fuel component flow path system including the fuel tank, the evaporative fuel passage, the canister, and the purge passage; and closing the purge control valve and the drain cut valve to close the fuel component flow. A flow path sealing means for maintaining a passage system in a closed state, and an initial pressure before the fuel component flow path system is closed by the flow path sealing means based on an output signal of the pressure detection means. Reads and closed after the pressure after being sealed with the force, after they closed
Pressure change detecting means for detecting a pressure change between the pressure and the initial pressure; determining that the pressure change exceeds a predetermined reference value as a normal state, and determining that the pressure change is below a predetermined reference value as an abnormal state. A failure diagnosis device for an evaporative fuel treatment device, comprising: a determination means for determining; 2. A fuel temperature detecting means for detecting a fuel temperature, wherein said judging means compares the pressure change with a reference value prepared in advance according to the fuel temperature to determine whether the state is normal or abnormal. The failure diagnosis device for an evaporative fuel treatment device according to claim 1, wherein the failure diagnosis device is configured to determine whether the state is a state. 3. The fuel component flow path system according to claim 1, wherein the fuel component flow path system is formed by flow path sealing means.
Measurement means for measuring the time elapsed since the
In addition, the determination unit determines that the elapsed time reaches a predetermined maximum measurement time.
If the pressure change exceeds a predetermined reference value before reaching
3. The method according to claim 1, wherein the normal state is determined.
A failure diagnosis device for the fuel vapor treatment device according to any one of the preceding claims. 4. The elapsed time reaches a predetermined maximum measurement time.
Until the pressure change is repeatedly required
4. A failure of the fuel vapor treatment device according to claim 3,
Diagnostic device.