JPH07189825A - Failure diagnosing device for evaporative fuel treating device - Google Patents

Abstract

PURPOSE:To calculate a leakage area by using pressure values and times in decompression of a fuel component flow passage system reaching a purge passage via a canister from a fuel tank and in a recovery of the pressure after a stop of decompression as main parameters so as to precisely diagnose leakage from a dimension of the leakage area. CONSTITUTION:When an engine enters an operation area in which diagnosis can be carried, a drain cut valve 28 is closed while a bypass valve 32 and a purge cut valve 27 are opened, and in this way, an inlet negative pressure is introduced to a fuel component flow passage system 29 including an evaporative fuel passage 22 and a purge passage 24 via a collector 25. Then, a control unit 36 calculates a leakage area by using a pressure reduction valve and a pressure reduction time in decompression of the fuel component flow system 29 and a pressure increase value and a pressure increase time in a recovery of the pressure after a stop of decompression as main parameters, and it is determined whether it is in a normal condition or in an abnormal condition on the basis of a dimension of the leakage area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosing device for temporarily storing fuel evaporated from a fuel tank and diagnosing a leak state of an evaporated fuel processing device 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, vaporized fuel generated in a fuel tank is temporarily adsorbed by a canister, and a purge control valve is opened under a predetermined operating condition to purge gas from the canister. Is provided in the engine intake system.

By the way, such an evaporated fuel processing apparatus is for preventing the outflow of the fuel vapor in the fuel tank, but the tube forming the purge passage is pulled out, the sealing failure of the connecting portion, the pin hole, etc. occur. Then, the fuel component that is originally adsorbed by the canister and should be introduced into the engine intake system leaks to the outside, so that the function cannot be sufficiently exhibited.

Therefore, in order to prevent the leakage of the fuel vapor, it is required to develop an apparatus for self-diagnosing the leakage of the evaporated fuel processing apparatus. As this diagnostic device, a drain cut valve that opens and closes the fresh air intake of the canister, and a pressure sensor that detects the pressure of the fuel component flow path system from the inside of the fuel tank through the canister to the purge path are provided, and the intake of the engine After depressurizing the fuel component flow path system to a predetermined negative pressure using the negative pressure, the drain cut valve and the purge control valve are closed to maintain the negative pressure state, and the negative pressure state is changed to the atmospheric pressure state. The one configured to diagnose the leakage based on the pressure change at the time is proposed by CARB (California Air Resources Board) and the like.

[0005]

However, although the above-described diagnostic apparatus can qualitatively detect the presence or absence of leakage, it has not been possible to obtain the leakage area. Therefore, there is a possibility that accurate failure diagnosis cannot be performed.

[0006]

Therefore, the present invention estimates the leak area from the pressure value and time when the fuel flow path system is depressurized and the pressure value and time after the depressurization is stopped. When the value is equal to or more than the predetermined value, it is determined that the leakage state is abnormal. That is, as shown in FIG. 1, the evaporated fuel processing apparatus according to the present invention includes a canister 3 for temporarily adsorbing evaporated fuel introduced from the fuel tank 1 through the evaporated fuel passage 2, and a fresh air intake port 3A. A purge passage 5 for guiding the purge gas separated from the canister 3 to the engine intake system 4 together with the fresh air taken in through the purge passage 5 and a purge control valve 6 provided in the middle of the purge passage 5 for controlling the purge gas are provided. In an evaporation processing apparatus for an internal combustion engine, the canister 3
A drain cut valve 7 for closing the fresh air intake 3A, a pressure detecting means for detecting the pressure of a fuel component passage system 8 including the fuel tank 1, the evaporated fuel passage 2, the canister 3 and the purge passage 5. 9 and a pressure reducing means 1 for introducing the negative pressure of the engine intake system 4 into the fuel component passage system 8 by opening the purge control valve 6 with the drain cut valve 7 closed.
0, and the fuel component flow path system 8 by the pressure reducing means 10.
Of the first pressure value when the pressure of the pressure is reduced and the first time required to reach the first pressure value, and the pressure reducing means 10
Leakage for estimating the leak area of the fuel component flow channel system 8 with the second pressure value increased after the depressurization by is stopped and the second time required to reach the second pressure value as main parameters. The area estimation unit 11 and the determination unit 12 that determines an abnormal state when the leakage area estimated by the leakage area estimation unit 11 is equal to or larger than a predetermined value and determines a normal state when the leakage area is equal to or smaller than the predetermined value. .

In the second aspect, the leak area estimating means estimates the leak area based on a predetermined arithmetic expression.

Further, in claim 3, the purge control valve 6 is configured as a variable orifice valve capable of adjusting the orifice, and when the first time is less than a predetermined time, the orifice of the purge control valve is Is adjusted to reduce the pressure by the pressure reducing means.

[0009]

The first pressure value when the pressure of the fuel component flow path system 8 is reduced, the first time required to reach the first pressure value, and the second time after the pressure reduction is stopped. The leak area estimation means 11 can estimate the leak area of the fuel component flow path system 8 with the pressure value and the second time required to reach the second pressure value as the main parameters. As a result, the determination means 12 can determine whether it is normal or abnormal by comparing the leakage area with the predetermined value.

Further, the leakage area estimating means 11 can estimate the leakage area based on a predetermined arithmetic expression.

Furthermore, if the purge control valve 6 is configured as a variable orifice valve and the orifice of the purge control valve 6 is adjusted and the pressure is reduced again when the first time is less than the predetermined time, the first time is optimized. It is possible to improve the accuracy of the estimated area value by the leakage area estimation means 11.

[0012]

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

First, FIG. 2 is a structural explanatory view of an evaporative fuel processing apparatus equipped with a failure diagnosing 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. There is. In addition, this evaporated fuel passage 2
A bypass passage 22A is provided in the middle of 2.

The canister 23 is composed of an adsorbent, a filter (neither is shown), etc., and has a fresh air intake port 23A open to the atmosphere at the bottom thereof. Also,
The purge gas outlet of the canister 23 is connected via a purge passage 24 to a collector 25 on the downstream side of the throttle valve of the intake passage, and a purge control valve 26 driven by a stepping motor is provided in the middle of the purge passage 24. There is. The purge control valve 26 is capable of variably adjusting the lift amount of the valve body by a control signal (pulse signal) from a control unit 36 described later, and is configured as a variable orifice valve.

In the middle of the purge passage 24, a purge cut valve 27 consisting of a solenoid valve is provided upstream of the purge control valve 26 (upstream side in the state where the purge gas is introduced into the engine). On the other hand, the fresh air intake 2 of the canister 23
3A is provided with a drain cut valve 28 which is an electromagnetic valve. The drain cut valve 28 is operated by a control signal from the control unit 36, and is closed together with the purge cut valve 27 during self-diagnosis so that the fuel tank 21, the evaporated fuel passage 22, the canister 2 are closed.
3. The fuel component passage system 29 including the purge passage 24 is kept in a sealed state.

The pressure sensor 30 as pressure detecting means is
It is provided in the bypass passage 22A of the evaporated fuel passage 22. The pressure sensor 30 is composed of, for example, a semiconductor type pressure sensor or the like, and detects the pressure of the evaporated fuel passage 22 as the pressure P of the fuel component flow passage system 29 and outputs it to the control unit 36 at the time of self-diagnosis. is there.

A check valve 31 is provided in the vaporized fuel passage 22 to allow the vaporized fuel to flow only toward the canister 23. A bypass valve 22A bypassing the check valve 31 is provided in the bypass passage 22A. A bypass valve 32, which is an electromagnetic valve, is interposed. This bypass valve 32 is opened at the time of self-diagnosis, so that the collector 2
The suction negative pressure of 5 is introduced into the fuel tank 21.

Reference numeral 33 is a throttle sensor for detecting the valve opening of the throttle valve, 34 is an air flow meter for measuring the amount of intake air, and 35 is a crank angle sensor for detecting the crank angle. These sensors are not shown. It is connected to the control unit 36 together with a water temperature sensor, an ignition switch and the like.

The control unit 36 for electrically centrally controlling the internal combustion engine is constructed as a microcomputer system and includes a purge control valve 26 and a drain cut valve 2.
8. A drive circuit for driving the bypass valve 32 and a pulse generator (not shown) for driving the purge control valve 26 including a stepping motor are provided.

Next, the operation of the structure of this embodiment will be described.

First, the pressure change when the pressure of the fuel component flow path system 29 is reduced will be described with reference to FIG.

When the engine enters the diagnosable range, the drain cut valve 28 is closed, while the bypass valve 32, the purge cut valve 27 and the purge control valve 26 are opened.
Since the negative pressure in 5 is introduced into the fuel component flow channel system 29, the pressure in the fuel component flow channel system 29 decreases. If the purge cut valve 27 is closed in the state where this pressure is reduced, the fuel component flow path system 29 will be in a closed state while temporarily maintaining a low pressure.

Now, when there is no leak point in the fuel component flow system 29, that is, when there is only an allowable natural pressure leak, as shown by the solid line S ₁ in FIG. 3, the fuel component flow system 29 is shown. The pressure rises gradually over a relatively long period of time.

On the other hand, when there is a leakage spot in the fuel component passage system 29 that is larger than the naturally allowed leakage, as shown by the alternate long and two short dashes line S ₂ in FIG. Upon entry, the pressure rises in a relatively short time.

Therefore, although it is possible to diagnose the presence or absence of leakage to some extent only by knowing such a tendency of pressure change, as a result of further research, the fluid movement shown in the following mathematical formula 1 was independently found. It has been found that the leak area can be presumedly measured as a function of pressure and time based on

[0026]

[Equation 2]

"K" is the first correction coefficient for ensuring linearity, and "C" is the second correction coefficient for aligning the units of the parameters (for example, C = 26.695).
7). Further, “DP _P ” is a depressurized value (mmHg) as the first pressure value, which is a pressure change amount from the depressurization start to the depressurization end. Further, “DP _L ” is a pressure increase value (mmHg) as the second pressure value, and is a pressure change amount after the pressure reduction is completed and the purge cut valve 27 is closed.

Further, "t _P " is the depressurization time (sec) as the first time, which is the time required from the start of depressurization to the end of depressurization. Further, “t _L ” is the pressure rising time (sec) as the second time, and shows the time elapsed from the end of the pressure reduction. On the other hand, the unit of “A _C ” in Formula 1 is square mm.

That is, the leak area AL is the reduced pressure value DP _P.
And the two pressure values of the boost value DP _{L and} the two times of the depressurization time t _P and the boost value DP _L.

Next, the diagnosis method will be described with reference to the flow charts of FIGS.

First, in step 1 (abbreviated as S1 in the drawing), it is determined whether or not the self-diagnosis of the evaporated fuel processing apparatus is possible based on the operating state of the engine and the like.

When it is determined that the self-diagnosis is possible, the routine proceeds to step 2, where the drain cut valve 28 is closed and the bypass valve 32 is opened, and in the next step 3, a flag "F" indicating the number of depressurizations. Determines whether is standing. If "YES" is determined in this step 3, if the flag "F" is not set, that is, it is the first pressure reduction, the process moves to step 4, and a pulse signal is applied to the stepping motor of the purge control valve 26, Purge control valve 2
The valve opening of No. 6, that is, the orifice is set to the initial value A _C1 . On the other hand, when it is determined to be "NO" in the step 3, since it is the second pressure reduction, a pulse signal is output to the purge control valve 26 and set to the adjustment value A _C2 of the orifice smaller than the initial value A _C1. Do it again.

Since preparation for depressurization is completed as described above, in step 6, the purge cut valve 27 is opened and the collector 25 is opened.
The suction negative pressure therein is introduced into the fuel component flow path system 29. As a result, the pressure P of the fuel component flow system 29 decreases, so in step 7, whether the pressure P of the fuel component flow system 29 has reached the predetermined maximum depressurization value DP _Pmax based on the output signal of the pressure sensor 30. Monitor whether or not. "YES" in this step 7
If it is determined that the pressure P of the fuel component flow path system 29 has reached the maximum depressurization value DP _max , step 1 described later is performed.
Move to 0.

On the other hand, if "NO" is determined in this step 7, the timer T ₁ is started in step 8 in order to measure the pressure reduction time t _P. Even if the purge cut valve 27 is opened, the pressure is not instantaneously reduced.
Immediately after the processing in step 8, the clocking is started in step 8.

In step 9, it is monitored whether or not the timer T ₁ has reached a predetermined maximum depressurization time t _Pmax . That is, when there is a large leakage point in the fuel component flow path system 29, as shown by the dotted line S ₃ in FIG. 3, the pressure P does not decrease so much even if the pressure reduction is started, so even if the pressure is reduced for a long period of time, the predetermined pressure is maintained. The maximum depressurization value DP _Pmax has not been reached, and the diagnosis process will stop at step 7. Therefore, in step 9, the timer T ₁ is monitored so that the pressure P after the elapse of the predetermined maximum pressure reduction time t _Pmax becomes the pressure reduction value DP _P.

Next, in step 10, the leakage area A
In order to improve the calculation accuracy of L, it is determined whether the timer T ₁ is shorter than a predetermined minimum depressurization time t _Pmin . That is, as shown in the above equation 2, the pressure reducing time t _P is equal to the pressure increasing time t _L
Since it is divided by, if this value is too small, the leakage area A
The error of L becomes large.

Therefore, when it is judged "NO" in this step 10, it means that the depressurization time t _P is small because the suction negative pressure is too strong, etc., so the routine moves to step 11 and the flag "F" is set. , Return. As a result, the self-diagnosis starts from the beginning again, and in step 5, the orifice of the purge control valve is reset to the adjustment value A _C2 of the small orifice.

Then, in step 12, since the pressure reduction of the fuel component flow path system 29 is completed, the purge cut valve 27 is closed in order to temporarily hold this pressure reduced state and observe the pressure change, and as shown in FIG. In step 13 shown, the pressure sensor 30
Depressurization value D based on the detected pressure P and the contents of timer T _1.
Set P _P and depressurization time t _P.

[0039] That is, when the detected pressure P of the fuel component flow path system 29 reaches the maximum vacuum value DP _Pmax, while the maximum vacuum value DP _Pmax is set as the pressure reduction value DP _P, the maximum vacuum value DP _Pmax Even if it does not reach the maximum decompression time t
_{When Pmax} has elapsed, the pressure P at the maximum depressurization time t _Pmax is set as the depressurization value DP _P. Further, the depressurization time t _P is the value of the timer T ₁ when the pressure P reaches the maximum depressurization value DP _Pmax , or the maximum depressurization time t
_Pmax is set.

Next, at step 14, the pressure P of the fuel component flow path system 29 in the closed state is set to a predetermined maximum boost value DP.
Whether or not _Lmax is reached is monitored, and at the same time as this, in step 15, the second timer T _{2 is used} to measure the boosting time t _L.
In the next step 16, it is determined whether or not this timer T ₂ has reached a predetermined maximum boosting time t _Lmax in order to stop monitoring the pressure change in a predetermined time.

When the determination in step 14 is "YES", the pressure P of the fuel component passage system 29 rises due to the invasion of the outside air from the leakage point, and the maximum pressure rise value DP
_{Since Lmax} has been reached, the process _proceeds to step 17 described later. On the other hand, even if it is determined "NO" in step 14, when the timer T ₂ has reached the maximum boost time t _Lmax, in order to with a pressure P in the maximum boost time t _Lmax and the boost value DP _L, Step 17 Move to.

As a result, in step 17, the boosted value D
P _L , pressurization time t _L, and orifice value A _C of the purge control valve 26 are set. That is, as the boost value DP _L , the maximum boost value DP _Lmax or the pressure P at the maximum boost time t _Lmax is set, and as the boost time t _L , the timer T when the pressure P reaches the maximum boost value DP _Lmax. A value of ₂ or the maximum boosting time t _Lmax is set. Also,
As the orifice value A _C of the purge control valve 26, the initial value A _C1 or the adjustment value A _C2 is set.

Next, in step 18, each step 1
By substituting the parameters set in Nos. 3 and 17 into the equation for fluid movement shown in Formula 2, the total leak area AL at the leak point is calculated.

Then, in step 19, it is judged whether or not the presumably detected leak area AL exceeds a reference leak area AL _SP corresponding to the area of a hole having a diameter of about 1 mm, for example. If "NO" is determined in this step 19, there is a leak in the fuel component flow path system 29, but this is a case where the leakage remains at a natural level that should be tolerated, so that a normal state (OK) is obtained in step 20. judge. On the other hand, if "YES" is determined in the step 19, it means that the leakage is equal to or larger than the reference leakage area AL _SP , so the process proceeds to step 21 and is determined to be an abnormal state (NG), and an indicator not shown is shown. Call the driver's attention by turning on the alarm lamp etc. above. The alarm means is not limited to the alarm lamp, but may be an alarm buzzer, a warning message generated by a voice generator, or the like.

As described above, according to this embodiment, the fuel component flow system 29 including the fuel tank 21, the evaporated fuel passage 22, the canister 23, and the purge passage 24 is decompressed by utilizing the suction negative pressure of the engine. The pressure reduction value DP _P when the pressure is reduced by temporarily maintaining the closed state, the pressure reduction time t _P required for this pressure reduction, the pressure increase value DP _L when the pressure goes toward recovery, and the pressure increase required for recovery Since the leak area AL is calculated from an independently found fluid movement equation mainly based on the time t _L, and whether the leak area AL is normal or abnormal is determined based on the gradient of pressure change or the like. In addition to being able to detect the presence or absence of leakage more accurately than the conventional diagnostic method, it is possible to know the leakage area.

When the pressure reduction time t _L is less than the predetermined minimum pressure reduction time t _Pmax , the orifice of the purge control valve 26 is changed to perform the self-diagnosis again.
The calculation accuracy of the leak area AL can be significantly improved.

Further, since the stepping motor is used as the drive source of the purge control valve 26, the orifice can be easily changed and the self-diagnosis can be performed with a relatively simple structure.

In the above embodiment, the pressure sensor 30 as the pressure detecting means is provided in the bypass passage 22A of the evaporated fuel passage 22, but the present invention is not limited to this.
For example, it may be incorporated in the fuel tank 21, the purge passage 24, or in the canister 23.

In the above embodiment, the purge control valve 26
The case where the orifice of No. 2 is changed in two steps of the initial value A _C1 and the adjustment value A _C2 is illustrated, but the present invention is not limited to this, and for example, a plurality of adjustment values are provided and the adjustment values are sequentially switched. Alternatively, the adjustment value may be calculated directly from the pressure gradient at the time of depressurization obtained at the initial value, the operating state of the engine, and the like, and the orifice of the purge control valve 26 may be adjusted to this value.

Further, in the above-mentioned embodiment, the purge control valve using a stepping motor as a drive source is described as an example of the variable orifice valve, but the present invention is not limited to this, and for example, forward / reverse rotation is possible using a servo motor as a drive source. An electric motor or a variable throttle valve may be used.
It is also possible to provide a plurality of bypass passages having different flow passage areas, and switch each of these passages by an electromagnetic valve or the like.

In the above-described embodiment, the case where the result of the leak area AL is divided into two types, that is, normal and abnormal, and the result is output is shown. However, in some cases, there are a plurality of abnormal states depending on the size of the leak area AL. It is also possible to divide into levels and issue a warning according to the degree of each abnormality.

[0052]

As described above in detail, according to the failure diagnosis apparatus for the evaporated fuel processing apparatus of the present invention, the fuel component passage system from the fuel tank to the purge passage to the purge passage is affected by the negative pressure of the engine intake system. Main parameters are the first pressure value when the pressure is reduced and the first time required for the pressure reduction, and the second pressure value when the pressure goes toward recovery after the pressure reduction is stopped and the second time required for the pressure increase. Detecting the leaked area presumably,
Since it is configured to determine whether the leakage is normal or abnormal based on the size of the leakage area, it is possible to more accurately determine the presence or absence of leakage and also to obtain the leakage area.

The leak area estimating means can detect the leak area presumably based on a predetermined arithmetic expression.

Furthermore, by adjusting the orifice of the purge control valve, the reliability of the estimated value of the leak area can be improved.

[Brief description of drawings]

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

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

FIG. 3 is a characteristic diagram showing a relationship between leakage and pressure change.

FIG. 4 is a flowchart showing a failure diagnosis process.

FIG. 5 is a flowchart following FIG. 4;

[Explanation of symbols]

 21 ... Fuel tank 22 ... Evaporative fuel passage 23 ... Canister 23A ... Fresh air intake 24 ... Purge passage 25 ... Collector (engine intake system) 26 ... Purge control valve 28 ... Drain cut valve 29 ... Fuel component passage system 30 ... Pressure Sensor (pressure detection means) 36 ... Control unit

Claims (3)

[Claims] 1. A canister for temporarily adsorbing vaporized fuel introduced from the inside of a fuel tank through an vaporized fuel passage, and a purge gas separated from the canister together with fresh air taken in through a fresh air inlet. An evaporation processing 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 for controlling a purge gas, wherein a drain cut valve for closing a fresh air intake of the canister. A pressure detecting means for detecting the pressure of the fuel component flow path system including the fuel tank, the evaporated fuel passage, the canister, and the purge passage; and the purge control valve opened with the drain cut valve closed. To reduce the pressure of the fuel component flow path system by the pressure reducing means for introducing the negative pressure of the engine intake system into the fuel component flow path system. The pressure value and the first time required to reach the first pressure value, the second pressure value increased after the pressure reduction by the pressure reducing means is stopped, and the second time required to reach the second pressure value. 2 is a main parameter, and a leak area estimating means for estimating a leak area of the fuel component flow path system; and when the leak area estimated by the leak area estimating means is equal to or more than a predetermined value, it is determined as an abnormal state, A failure diagnosing device for an evaporated fuel processing device, comprising: a determining unit that determines a normal state when the value is equal to or less than a predetermined value. 2. The leak area estimating means comprises a first pressure value DP _P , a first time t _P , a second pressure value _{D P L} , a second time t _L and a purge control valve. Orifice area is A _C ,
The failure diagnosis device for an evaporated fuel processing apparatus according to claim 1, wherein the leakage area is estimated based on the following expression 1 where K is the first correction coefficient and C is the second correction coefficient. . [Equation 1] 3. The purge control valve is configured as a variable orifice valve capable of adjusting an orifice, and when the first time is shorter than a predetermined time, the orifice of the purge control valve is adjusted to reduce pressure. The failure diagnosis apparatus for an evaporated fuel processing apparatus according to claim 1 or 2, wherein the failure diagnosis apparatus is configured to reduce the pressure.