JPH0642413A - Failure diagnostic device for evaporative purge system - Google Patents

Abstract

PURPOSE:To prevent unsteadiness of an air fuel ratio when negative pressure is led in, in a device for diagnosing failure of an evaporative purge system formed in such constitution that evaporation fuel (vapor) in an internal combustion engine is discharged (purged) in an intake system so as to be burnt. CONSTITUTION:The atmosphere leading hole 33d of a canister 33 is communicated with a purge passage 39 through an atmosphere passage 35, a purge passage 40 and a failure detecting purge VSV41. A purge side VSV38 for communicating with a surge tank 26 is communicated with the purge port 33b of the canister 33 through a purge passage 37. When negative pressure is led in, a tank inter- pressure switching valve 34 is opened, a canister atmosphere hole VSV36 is shut out, the purge side VSV38 is shut out, and the failure detecting purge VSV41 is opened. As a result, since vapor in a tank is led in the purge passage 39 through activated carbons 33c in the canister 33, almost of vapor is absorbed by the activated carbons 33c.

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 an evaporative purge system, and more particularly to adsorbing evaporated fuel (vapor) of an internal combustion engine to an adsorbent in a canister, and adsorbing the adsorbed fuel to an internal combustion engine under a predetermined operating condition. The present invention relates to a device for diagnosing a failure of an evaporation purge system that discharges (purge) to an intake system of an engine and burns it.

[0002]

2. Description of the Related Art Fuel (vapor) evaporated in a fuel tank
In order to prevent air from being released to the atmosphere, each part is hermetically sealed, and the vapor is once adsorbed by the adsorbent in the canister, and the fuel adsorbed while the vehicle is running is sucked into the intake system and burned by evaporative purging. In an internal combustion engine equipped with a system, if the vapor passage is damaged for some reason or if the pipe is disconnected, the vapor is released to the atmosphere, and if the purge passage to the intake system is blocked,
The vapor in the canister overflows and leaks into the atmosphere through the canister air inlet. Therefore,
It is necessary to diagnose whether such an evaporative purge system has a failure.

Therefore, the present applicant previously filed Japanese Patent Application No. 3-138.
No. 002 has a first control valve that opens and closes a purge passage that purges the evaporated fuel stored in the canister into the intake system of the internal combustion engine, and a second control valve that opens and closes the atmospheric hole of the canister. After closing the second control valve during failure diagnosis,
Failure diagnosis of the evaporative purge system in which the first control valve is closed after a predetermined negative pressure is reached, the airtightness is maintained for a predetermined time, and whether or not a failure has occurred is diagnosed based on the degree of change in pressure at that time. Proposed a device.

[0004]

However, in the failure diagnosis device proposed by the present applicant, if a canister in which the vapor introduction port and the purge port are communicated in the same space is used, the failure diagnosis is performed. After the atmospheric hole of the canister is shut off by the second control valve, the first control valve is opened to introduce the negative pressure of the intake passage into the system, and the vapor generated in the fuel tank is generated. Is not passed through the activated carbon in the canister, but is sucked in a large amount into the intake passage. As a result, the air-fuel ratio becomes rough and drivability and exhaust emission deteriorate.

The present invention has been made in view of the above points,
An object of the present invention is to provide a failure diagnostic device for an evaporation purge system, which solves the above-mentioned problems by introducing a negative pressure so that the vapor in the fuel tank is passed through the adsorbent in the canister.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention for achieving the above object. As shown in the figure, according to the present invention, the evaporated fuel from the fuel tank 11 is transferred to the vapor passage 12
In the device for diagnosing the failure of the evaporative purge system in which the adsorbent in the canister 13 is adsorbed to the adsorbent in the canister 13 through the purge passage 14 to purge the adsorbed fuel in the canister 13 into the intake passage 15 of the internal combustion engine 10 in a predetermined operation. Pressure introducing means 16 for introducing a negative pressure into the fuel tank 11 through the adsorbent in the canister 13, pressure detecting means 17 for detecting the pressure in the evaporation system from the purge passage 14 to the fuel tank 11, and determining means 18 It is configured to have.

Here, the judging means 18 introduces a negative pressure into the evaporation system by the pressure introducing means 16, and the pressure detecting means 17
The degree of change in the pressure in the evaporation system is measured based on the negative pressure value detected by, and the presence or absence of a failure in the evaporation purge system is determined from the comparison result between the measured value and the determination value.

[0008]

In the failure diagnosis, the negative pressure of the intake air is supplied by the pressure introducing means 16 through the adsorbent in the canister 13 to the fuel tank 1.
Introduced in 1. Therefore, in the present invention, the fuel tank 11
The vapor (evaporated fuel) therein is sucked into the intake passage 15 from the purge passage 14 through the adsorbent in the canister 13 as the negative pressure is introduced.

[0009]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. In the figure, after the air cleaner 22 measures the amount of intake air of the air from which dust, dust, etc. in the atmosphere have been removed, the flow rate thereof is controlled by the throttle valve 25 in the intake pipe 24. Further, it flows through a surge tank 26 and an intake manifold 27 (which constitutes the intake passage 15 together with the intake pipe 24) into a combustion chamber (both not shown) of the internal combustion engine during a period in which the intake valve is open.

The opening of the throttle valve 25 is controlled in conjunction with an accelerator pedal (not shown), and the opening is detected by a throttle position sensor 28. Further, a fuel injection valve 29 is provided for each cylinder so that a part thereof projects into the intake manifold 27. The fuel injection valve 29 injects the fuel 45 in the fuel tank 30 into the air flow passing through the intake manifold 27 for a time instructed by the microcomputer 21.

The fuel tank 30 is the fuel tank 11 described above.
Corresponding to, and contains the fuel 45. Reference numeral 31 denotes a fuel tank internal pressure control valve, which is a mechanical control valve for connecting (opening) or shutting off between the vapor passages 32a and 32c and 32d, and when the tank internal pressure is a value in the positive pressure direction from the set pressure of the spring 31a, The diaphragm 31b is positioned as shown in the drawing to communicate between the vapor passages 32a, 32c and 32d, and when the tank internal pressure is a value in the negative pressure direction from the set pressure of the spring 31a, the diaphragm 31b moves downward to move the vapor passage 32a. And between 32c and 32d.
As a result, the tank internal pressure of the fuel tank 30 is maintained at a positive pressure, and the amount of vapor generation is suppressed as low as possible. In addition, 31c is an atmospheric opening.

Further, one end of the vapor passage 32a is
Together with the vapor passage 32b, it communicates with the vapor introduction port 33a of the canister 33. This canister (corresponding to the canister 13) is of a type in which a vapor introduction port 33a and a purge port 33b are communicated in the same space, the inside thereof is filled with activated carbon 33c as an adsorbent, and part of the atmosphere An introduction hole 33d is provided.

Further, in the present embodiment, at the time of failure diagnosis, the tank internal pressure control by the fuel tank internal pressure control valve 31 is prohibited and the negative pressure is introduced into the fuel tank 30. Vapor passage 32 between the exits
A tank internal pressure switching valve (VSV) 34 is provided to bypass (b) and 32c and to conduct (open) or shut off between the vapor passages 32b and 32c. The tank internal pressure switching valve 34 is an electromagnetic valve that is turned on or off by an output control signal from the microcomputer 21.

The atmosphere introducing hole 33d of the canister 33 communicates with a canister atmosphere hole vacuum switching valve (VSV) 36 through an atmosphere passage 35. The canister atmosphere hole VSV36 is a microcomputer 21.
Based on the control signal of the
It is a control valve that connects or disconnects between and.

Further, the purge port 33 of the canister 33
b is communicated with the purge-side VSV 38 via the purge passage 37. One end of the purge side VSV 38 is connected to the surge tank 26, for example, and the other end of the purge passage 39 and the other end of the purge passage 37 are connected to the microcomputer 2
It is a control valve that conducts or shuts off based on a control signal from 1.

The atmosphere passage 35 is connected to the surge tank 26 via a purge passage 40, a failure diagnosis detection purge vacuum switching valve (VSV) 41 and a purge passage 39. Failure detection purge VSV4
Reference numeral 1 is an electromagnetic valve that opens (conducts) or shuts off between the purge passages 39 and 40 based on a control signal from the microcomputer 21.

The pressure sensor 42 is provided in the middle of the vapor passage 32d, and is provided to detect the pressure in the vapor passage 32d to substantially detect the internal pressure of the fuel tank 30, and the pressure detecting means 17 is provided. Are configured.
The warning lamp 43 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

The microcomputer 21 is a control device for realizing the pressure introducing means 16 and the judging means 18 together with the VSVs 34, 36 and 41 by software processing, and has a known hardware configuration as shown in FIG. In the figure, the same components as those in FIG.
The description is omitted. In FIG. 3, the microcomputer 21 includes a central processing unit (CPU) 50, a read only memory (ROM) 51 storing a processing program,
It is composed of a random access memory (RAM) 52 used as a work area, a backup RAM 53 that retains data even after the engine is stopped, an input interface circuit 54 with a multiplexer, an A / D converter 56, an input / output interface circuit 55, and the like. And they are connected via a bidirectional bus 57.

The input interface circuit 54 sequentially switches the intake air amount detection signal from the air flow meter 23, the detection signal from the throttle position sensor 28, the pressure detection signal from the pressure sensor 42, etc., and synthesizes them in time series. The signal is supplied to a single A / D converter 56 for analog-to-digital conversion, and then sequentially sent to the bus 57.

The input / output interface circuit 55 is provided with a detection signal from the throttle position sensor 28 and the starter 4
4, the starter signal is input to the CPU 50 via the bus 57, and each signal input from the bus 57 is processed as appropriate to inject the fuel injection valve 29, the tank internal pressure switching valve 34, the canister atmosphere hole VSV 36. , Purge side VS
V38, failure detection purge VSV41 and warning lamp 43 are selectively sent to control them.

Next, the evaporative purge operation of the system configuration will be described. The evaporative purge is performed by the microcomputer 21 according to the purge control routine of FIG. The purge control routine is executed, for example, as a part of the main routine, and whether the engine cooling water temperature THW of the internal combustion engine has warmed up to a predetermined value A or more by the output of a water temperature sensor (not shown) (step 101), or the air-fuel ratio feedback (F /
B) It is judged whether it is being executed (step 102) or not being idling (step 103) based on the output of the throttle position sensor 28, and if any one of these cases is not satisfied, the purge side VSV 38 is shut off. (Step 104) When all of these conditions are satisfied, the purge side VSV 38 is opened (Step 105).

When step 104 or 105 is processed, the failure detection purge VSV41 is subsequently shut off (step 106), and the canister atmosphere hole VSV36 is opened (step 107). The tank internal pressure switching valve 34 is always closed. This will result in step 10 above.
Purge is not executed unless the operating condition satisfies all of the three conditions determined by 1 to 103. When the operating condition satisfies all of the three conditions, the purge can be executed. This routine is not executed during failure diagnosis (step 100).

That is, the tank internal pressure in the fuel tank 30 increases according to the amount of vapor generated, but when the internal pressure of the fuel tank 30 is equal to or lower than the positive pressure set by the fuel tank internal pressure control valve 31, the fuel tank internal pressure control valve 31 is shut off. Therefore, the vapor is not supplied to the canister 33. When the amount of vapor generated in the fuel tank 30 becomes large and the tank internal pressure becomes higher than the pressure set by the fuel tank internal pressure control valve 31, the fuel tank internal pressure control valve 31 is opened, so that the vapor in the fuel tank can be transferred to the vapor passage 32d. , Sent to the canister 33 through the fuel tank internal pressure control valve 31 and the vapor passage 32a,
It is adsorbed by the activated carbon 33c and prevented from being released into the atmosphere.

By sending the vapor to the canister 33,
When the tank internal pressure in the fuel tank 30 becomes equal to or lower than the set pressure of the fuel tank internal pressure control valve 31, the fuel tank internal pressure control valve 31
Is cut off again. By repeating the above operation, the pressure in the fuel tank 30 is maintained at the set pressure of the fuel tank internal pressure control valve 31.

On the other hand, in the vapor adsorbed on the activated carbon 33c in the canister 33, the negative pressure of the intake system in the above-mentioned predetermined operating state is introduced into the canister 33 through the purge passage 39, the purge side VSV 38 and the purge passage 37, whereby the atmosphere is released. Canister atmosphere hole VSV3 from the inlet 36a
6, the atmosphere is sent into the canister 33 through the atmosphere passage 35 and the atmosphere introduction hole 33d.

Then, the fuel adsorbed on the activated carbon 33c is desorbed, and the fuel is sucked into the surge tank 26 from the purge port 33b through the purge passage 37, the purge side VSV 38 and the purge passage 39. In addition, the activated carbon 33c is regenerated by the above desorption and prepared for the next adsorption of vapor.

Next, the failure diagnosis of the evaporative purge system that performs the above operation will be described. In this case, the CPU 50 of the microcomputer 21 activates the failure diagnosis routine shown in FIG. 5 every 65 ms, for example, according to the program stored in the ROM 51. In the figure, first, it is checked whether the execution flag is set (the value is "1") (step 201). Since the execution flag has been cleared (the value is "0") by the initial routine at the time of starting the engine, it is not initially set, so the routine proceeds to the next step 202.

In step 202, it is determined whether or not the engine has just started by the presence or absence of a starter signal from the starter 44. Immediately after starting, it is judged whether the internal pressure of the fuel tank 30 (tank internal pressure) is equal to or higher than the positive pressure Y (Pa) (step 203). When the tank internal pressure is Y (Pa) or more, the amount of fuel vapor generated is large, it is estimated that there is no leakage, and since accurate failure diagnosis is impossible, it is necessary not to perform failure diagnosis until the next starting opportunity. Set the flag (step 225) and clear the leak determination flag (step
226), and ends this routine.

When it is determined in step 202 that it is not immediately after starting, or when the tank internal pressure is less than Y (Pa) in step 203, that is, the tank internal pressure is an atmospheric pressure or a negative pressure side value of Y (Pa), the amount of vapor generation is It is judged that the number is small and accurate failure diagnosis is possible, and the process proceeds to the next step 204.

In step 204, it is checked whether a leak determination flag, which will be described later, is set. Since the leak determination flag is also cleared by the initial routine, it is not initially set, and the purge side VSV 38 is initially shut off (step 205), the canister atmosphere hole VSV 36 is shut off (step 206), and the tank internal pressure switching valve is set. The VSV switching control is performed in the order of opening 34 (step 207) and opening the failure detection purge VSV 41 (step 208).

As a result, the negative pressure of the surge tank 26 is reduced by the purge passage 39, the failure detection purge VSV 41, the purge passage 40, the atmosphere passage 35, the canister 33, and the vapor passage 32.
b, tank internal pressure switching valve 34, vapor passages 32c and 32
They are introduced into the fuel tank 30 through the respective d. As a result, in the normal state where there is no leakage in the evaporation system from the purge passage 37 to the fuel tank 30, the tank internal pressure changes rapidly in the negative pressure direction. Steps 205-208 above are VS
The pressure introducing means 16 is configured with V34, 36 and 41, and the negative pressure is introduced into the atmosphere introducing hole 3 of the canister 33.
3d to the vapor introduction port 33a. Therefore, since the vapor from the fuel tank 30 reaches the atmosphere introduction hole 33d from the vapor introduction port 33a through the activated carbon 33c by the introduction of the negative pressure, most of the vapor is adsorbed to the activated carbon 33c. To be done. Therefore, the amount of vapor taken into the engine combustion chamber in the fuel tank 30 can be reduced as compared with the apparatus proposed by the applicant.

Then, in step 209 of FIG. 5, the tank internal pressure is set to the diagnostic start pressure X based on the detection signal of the pressure sensor 42.
It is determined whether or not (Pa) or less, and when it is X (Pa) or less, the negative pressure setting is further continued, so this routine is once ended. The above steps 201 to 209 are repeatedly executed every 65 ms until the tank internal pressure becomes larger than X (Pa) on the negative pressure side. When it is determined in step 209 that the tank internal pressure has become larger than X (Pa) on the negative pressure side, the failure detection purge VSV41 is shut off (step 210).

Failure detection purge VS in step 210 above
By shutting off V41, three VSVs 36, 38 and 41
Are closed, the pressure in the evaporative system from the purge passage 37 to the fuel tank 30 is kept closed when there is no malfunction in the system, and gradually decreases to the atmospheric pressure side. When the failure detection purge VSV 41 is shut off in step 210, the processing of the determination means 18 is realized in steps 211 to 218.

That is, first, it is determined whether or not the leak determination timer is "0" (step 211). Since the leak determination timer has been cleared to "0" by the initial routine described above, when the determination at step 211 is first made, it is determined as "0" and the routine proceeds to step 212, where the pressure sensor 42 The current detection value of the diagnostic start pressure value P
_It is stored in the RAM 52 as _S.

Subsequently, the value of the leak determination timer is added by a predetermined value (step 213), the leak determination flag is set to "1" (step 214), and this routine is ended. The next time this routine is started again, the step
Since it is determined in 204 that the leak is being determined, steps 205 to 20
Jump 9 and step through 210
It reaches to 211.

This time, it is determined in step 211 that the leak determination timer is not "0", so it is determined whether the value of the leak determination timer is equal to the diagnostic time (leak determination time) α (step 215), if the time α has not yet come, this routine is ended via steps 213 and 214.

In this way, steps 201-204, 21
The processing of 0, 211, 215, 213, and 214 is repeated every 65 ms.
And the value of the leak determination timer corresponds to the leak determination time α.
When it reaches a value, the detected value of the pressure sensor 42 at that time is diagnosed.
End pressure value P_EStored in the RAM 52 as (step
216). The pressure value read from the RAM 52
P _S, P_EBased on (P_E-P_S) / Α (seconds)
The rate of change in pressure is calculated from the equation (step 217).

Subsequently, it is determined whether the calculated change rate is equal to or more than a predetermined threshold value β (step 218). When it is equal to or more than β, it is determined that the leakage is large and abnormal because the change in pressure is large. Then, the warning lamp 43 is turned on (step 21
9) Then, after notifying the driver of the failure occurrence of the evaporative purge system, the leak failure fail code is stored in, for example, the backup RAM 53 (step 220), and the process proceeds to step 221. The leak failure fail code is read from the backup RAM 53 at the time of subsequent repair, and informs the cause of failure of the evaporative purge system. On the other hand, the calculated rate of change is β
If it is judged to be less than the specified value, it is judged to be normal because the leakage is below the specified value, and steps 219 and 220 are jumped to step 221.

When the presence or absence of a failure of the evaporative purge system is determined as described above, subsequently, in order to make the operation of the fuel tank internal pressure control valve 31 effective, the tank internal pressure switching valve 3
4 is shut off (step 221), and the canister atmosphere hole VSV36 is opened (step 222).
At the same time, the purge side VSV 38 is opened (step 223) to release the negative pressure closed state of the evaporation system.

As a result, the atmosphere is introduced into the system from the atmosphere introducing port 36a of FIG. 2 through the canister atmosphere hole VSV36 and the canister 33, so that the tank internal pressure is a positive pressure depending on the state of vapor generation via atmospheric pressure in a short time. Changes to.

Thereafter, the leak determination timer is cleared (step 224) and the execution flag is set to "1" (step
225), the leakage determination flag is further cleared to "0" (step 226), and the failure diagnosis process is terminated. After that,
Even if this routine is started, the execution flag is determined to be "1" in step 201, so this routine will not be executed until it is restarted thereafter.

As described above, according to this embodiment, when the negative pressure of the intake system is introduced into the evaporative system at the time of failure diagnosis,
Since the negative pressure is made to pass through the activated carbon 33c in the canister 33, most of the vapor in the fuel tank 30 will be adsorbed by the activated carbon 33c and then sucked into the intake system. Even in the type in which the purge port 33b and the purge port 33b are communicated in the same space, it is possible to reduce the roughness of the air-fuel ratio when the negative pressure is introduced as compared with the device proposed by the applicant.

The present invention is not limited to the above embodiment, and for example, the canister may be of a type in which the vapor introducing port and the purge port do not communicate in the same space. Further, the pressure sensor 43 may be directly attached to the fuel tank 30, or the vapor purging portion may be an intake passage portion near the throttle valve 25.

[0044]

As described above, according to the present invention, since the vapor in the fuel tank is sucked into the intake passage through the adsorbent in the canister when the negative pressure is introduced, most of the vapor is adsorbed by the adsorbent. Therefore, it is possible to reduce the vapor intake amount of the intake passage when the negative pressure is introduced, as compared with the device previously proposed by the applicant, and thus it is possible to prevent the air-fuel ratio from becoming rough when the negative pressure is introduced, and the drivability and the exhaust emission are reduced. It has features such as prevention of deterioration.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of the present invention.

FIG. 3 is a configuration diagram of an example of hardware of the microcomputer in FIG.

FIG. 4 is a flowchart showing a purge control routine.

FIG. 5 is a flowchart showing an embodiment of a failure diagnosis routine which is a main part of the present invention.

[Explanation of symbols]

10 Internal Combustion Engine 11,30 Fuel Tank 12,32a to 32d Vapor Passage 13,33 Canister 14,37,39,40 Purge Passage 15 Intake Passage 16 Pressure Introducing Means 17 Pressure Detecting Means 18 Judging Means 21 Microcomputer 31 Fuel Tank Internal Pressure Control Valve 34 Tank pressure switching valve (VSV) 35 Atmosphere passage 36 Canister Atmospheric hole Vacuum switching valve (VSV) 38 Purge side vacuum switching valve (V
SV) 41 Failure detection Purge vacuum switching valve (VSV) 42 Pressure sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Kisho 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A failure of an evaporation purge system for adsorbing evaporated fuel from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister through a purge passage into an intake passage of an internal combustion engine during a predetermined operation. In the device for diagnosing, the pressure introducing means for introducing the negative pressure in the intake passage into the fuel tank through the adsorbent in the canister, and the pressure in the evaporation system from the purge passage to the fuel tank are detected. Pressure detection means, by introducing a negative pressure in the evaporation system by the pressure introducing means, based on the negative pressure value detected by the pressure detection means, to measure the degree of change in the pressure in the evaporation system, An evaporation system having a judgment means for judging the presence / absence of a failure of the evaporative purge system from the result of comparison between the measured value and the judgment value. System diagnostic device.