JPH05223019A - Diagnosing device for evaporation purge system - Google Patents

Abstract

PURPOSE:To provide a diagnosing device for always diagnosing a failure of an evaporation purge system in which evaporated fuel is adsorbed to an adsorb ent in a canister in an internal combustion engine, and the adsorbed fuel is purged, for combustion, into the intake passage of the internal combustion engine under a predetermined condition. CONSTITUTION:A purge side VSV is opened, and a canister atmospheric hole VSV us opened (steps 104, 105). Thereafter, a variation in pressure in the system for X seconds is calculated (steps 106 to 111). If this calculated variation rate is less than a predetermined value Y, a large leakage is present, and accordingly, a failure is detected (steps 112, 124, 125). Meanwhile, if the calculated variation rate exceeds the predetermined value Y (step 112), the purge side VSV and the canister atmospheric hole VSV are closed after the vacuum in a tank reaches Z(Pa), and then a diagnosis is carried out in view of a pressure variation rate in the system for a predetermined time alpha (sec) (steps 114 to 125).

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 evaporative purge system that discharges (purges) and burns the intake air of an engine.

[0002]

2. Description of the Related Art Fuel evaporated in a fuel tank (vapor)
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 an evaporative purge. 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,
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 applicant of the present invention has previously proposed a first control valve for opening and closing the purge passage for purging the evaporated fuel stored in the canister into the intake system of the internal combustion engine, and a second control valve for opening and closing the atmospheric hole of the canister. It has a control valve, and it has a second
After closing the control valve of the
Of the evaporative purging system (Japanese Patent Application No. 3-138002), in which the control valve is closed to maintain the airtightness 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. A failure diagnosis device for an evaporative purge system (Japanese Patent Laid-Open No. 2-275608), which simply determines whether or not a predetermined negative pressure is reached and then determines whether or not there is a leak after closing the second control valve. Proposed.

[0004]

However, in the former failure diagnosis device, if the leak is large, it takes a long time for the internal pressure of the fuel tank to reach the preset negative pressure, and if the leak is very large, the preset negative pressure is set. Since it does not reach, failure diagnosis itself cannot be performed. In the latter failure diagnosis device, it is difficult to detect small leaks due to changes in the purge flow rate, fuel evaporation, and the like.

The present invention has been made in view of the above points,
Failure diagnosis of the evaporative purge system that solves the above problems by determining an abnormality when the predetermined negative pressure is not reached within the predetermined time or when the predetermined negative pressure is reached and the pressure change after sealing the system is large The purpose is to provide a device.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, the evaporation fuel from the fuel tank 10 is adsorbed to the adsorbent in the canister 12 through the vapor passage 11, and the adsorbed fuel in the canister 12 is purged into the intake passage 14 of the internal combustion engine through the purge passage 13 during a predetermined operation. In the failure diagnosing device for a purge system, the present invention provides a first control valve 15, a second control valve 16, a first valve control means 17, a first determination means 18, and a second valve control means 1.
9 and the second determination means 20 are provided.

Here, the first control valve 15 is the purge passage 1
3 is turned on or off. The second control valve 16 opens and closes the atmosphere hole of the canister 12. Also, the first valve control means 17
Closes the second control valve 16 and closes the first control valve 15
Is opened to introduce the pressure in the intake passage 14 into the system from the purge passage 13 to the fuel tank 10 for a first predetermined time. The first determining means 18 determines whether or not there is a failure in the evaporative purge system based on the degree of change in pressure in the system during the first predetermined time. The second valve control means 19 is the first determination means 1
When it is determined that there is no failure in the evaporative purge system by No. 8, it is monitored whether the pressure in the system reaches a predetermined value, and when the pressure in the system reaches a predetermined value, the first control valve 15
Are closed together with the second control valve 16.

The second judging means 20 is provided when a second predetermined time has elapsed from the time when the second valve control means 19 received the closing command for both the first and second control valves 15 and 16, The degree of change of the pressure in the system during the second predetermined time is measured, and the presence or absence of a failure of the evaporative purge system is determined from the measurement result.

[0009]

According to the present invention, the first valve control means 17 closes the second control valve 16 and opens the first control valve 15 to adjust the pressure in the intake passage 14 from the purge passage 13. It is introduced into the system up to the tank 10 for a first predetermined time, and the degree of change in the pressure in the system during the first predetermined time is measured. When there is no leakage or it is extremely small, the degree of change in pressure in the system is larger than a predetermined threshold value, whereas when leakage is large, there is no change in the system even after the first predetermined time has elapsed. The degree of change in pressure is smaller than the above-mentioned predetermined threshold value.

Therefore, the first determining means 18 determines that the evaporative purge system has failed when the degree of change in pressure in the system is smaller than the predetermined threshold value. And
Only when it is determined by the first determining means 18 that the evaporative purge system is not in failure, the second valve control means 19 and the second determining means 20 introduce a negative pressure into the system in a closed state. Is held for a second predetermined time, and a failure of the evaporative purge system is determined from the degree of change in pressure at that time.

[0011]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. In the figure, the air from which dust, dust and the like in the atmosphere have been removed by the air cleaner 22 has its intake air amount measured by an air flow meter 23, and its flow rate is controlled by a throttle valve 25 in an intake pipe 24. Further, it flows through a surge tank 26 and an intake manifold 27 (which constitutes the intake passage 14 together with the intake pipe 24) into a combustion chamber (both not shown) of an internal combustion engine during a period in which an 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 31 in the fuel tank 30 into the air flow passing through the intake manifold 27 for a time designated by the microcomputer 21.

The fuel tank 30 is the fuel tank 10 described above.
The fuel 31 is accommodated and the evaporated fuel (vapor) generated inside is sent to the canister 33 (corresponding to the canister 12 described above) through the vapor passage 32 (corresponding to the vapor passage 11). The canister 33 is filled with an adsorbent such as activated carbon inside and a part of the canister 33 is provided with an atmosphere hole 34.

The atmosphere hole 34 is connected to a canister atmosphere hole vacuum switching valve (VSV) 36 through an atmosphere passage 35. Canister vent V
The SV 36 is a control valve that connects or disconnects the atmosphere introducing hole 36 a and the atmosphere passage 35 based on a control signal from the microcomputer 21, and constitutes the second control valve 16.
Further, the canister 33 communicates with the purge-side VSV 38 via the purge passage 37. The purge-side VSV 38 is a control valve for connecting or disconnecting the other end of the purge passage 39, one end of which communicates with the surge tank 26, and the other end of the purge passage 37, based on a control signal from the microcomputer 21. The first control valve 15 is configured.

The pressure sensor 40 is provided in the middle of the vapor passage 32, and is provided to detect the pressure in the vapor passage 32 to substantially detect the internal pressure of the fuel tank 30. The warning lamp 41 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

In such a structure, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon in the canister 33 through the vapor passage 32 and prevented from being released into the atmosphere. Normally, the canister atmosphere hole VSV36 is opened, and when the evaporative purge system is operating, the purge side VS
V38 is also open. As a result, the negative pressure of the intake manifold 27 is used during operation, and the air inlet 36a
The atmosphere is introduced into the canister 33 through the canister atmosphere hole VSV 36, the atmosphere passage 35, and the atmosphere hole 34.

Then, the fuel adsorbed on the activated carbon is desorbed, and the fuel is purged by the purge passage 37 and the purge side VSV3.
8 and the purge passage 39, respectively, to be sucked into the surge tank 26. In addition, the activated carbon is regenerated by the above desorption and prepared for the next adsorption of vapor.

The microcomputer 21 is the above-mentioned first
Is a control device that realizes the valve control means 17, the first determination means 18, the second valve control means 19, and the second determination means 20 by software processing, and has a known hardware configuration as shown in FIG. is doing. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 3, the microcomputer 21 is a central processing unit (CP
U) 50, read-only storage of processing program
A memory (ROM) 51, 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, and an input / output interface circuit. 55 and the like, which are connected via a 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 40, and the like, and is a serial signal synthesized in time series. And a single A / D converter 56
To the bus 57 after analog-to-digital conversion
To sequentially send to.

The input / output interface circuit 55 receives the detection signal from the throttle position sensor 28 and inputs it to the CPU 50 via the bus 57, while the signals input from the bus 57 are supplied to the fuel injection valve 29 and the canister. The porosity VSV 36, the purge side VSV 38, and the warning lamp 41 are selectively sent to control them.

The CPU 50 of the microcomputer 21 having the above-mentioned configuration executes the processing of the flowchart described below according to the program stored in the ROM 51. FIG. 4 is a flow chart for explaining the operation of an embodiment of the main part of the present invention, which is activated by interruption every 65 ms, for example. In the figure, first, it is checked whether the execution flag is set (the value is "1") (step 101). The execution flag is cleared by the initial routine at engine startup (value is "0")
Since it is already set, it is not set at first, so the process proceeds to the next step 102.

In step 102, it is checked whether a leak determination flag, which will be described later, is set. Since this leak determination flag is also cleared by the initial routine,
Initially it is not set, then the next step 103
Go to. At step 103, it is judged if the negative pressure setting flag is "1". Since the negative pressure setting flag is cleared by the initial routine, the negative pressure setting flag is "0" at first, so the routine proceeds to the next step 104, where the canister atmosphere hole VSV36 is shut off (closed), and the subsequent step Open the VSV38 on the purge side at 105 (open valve)
Put in a state. Closing of the canister atmospheric hole VSV36 is performed at time t ₁ as shown in FIG. 5 (B), the valve opening of the purge side VSV38 is carried out in substantially the same time t ₁ as shown in FIG. 5 (A) If the negative pressure to the engine combustion chamber is set, the purge passage 39, the purge side VSV shown in FIG.
38, purge passage 37, canister 33, vapor passage 3
2 to the fuel tank 30. As a result, the internal pressure of the fuel tank 30 (tank internal pressure) is the time t as shown by the solid line in FIG. 5C when there is no relatively large leak in the system.
_{After 1 the} pressure rises rapidly in the negative direction (pressure decreases).

Then, it is judged whether or not the timer A is 0 second (step 106). Since this timer A is also cleared to 0 seconds by the initial routine executed after the engine is started, when this step 106 is executed for the first time, the routine proceeds to step 107, where the sensor value P _S1 of the pressure sensor 40 at that time is set. This is stored in the RAM 52 of FIG. 3, and in the next step 108, the value of the timer A is added by a predetermined value, and this routine is once ended.

Thereafter, until the timer A reaches X seconds (corresponding to the above-mentioned first predetermined time), step 10 is performed every 65 ms.
1 to 106, 109, 108 are repeatedly executed, and the sensor value P _E1 of the pressure sensor 40 is stored in the RAM 52 at the time when it is determined in step 109 that the timer A has reached X seconds (step 110). Then, the above-mentioned memory sensor value P
_{From S1} and P _E1 and the known time X (seconds), (P _E1 −
The change rate is calculated by the formula P _S1 ) / X (step 11
1) It is determined whether the calculated change rate is equal to or greater than a predetermined set value Y (step 112).

Here, after the time t ₁ is a period in which the negative pressure is introduced into the engine combustion chamber in the system, and the pressure value in the system at the time t _{2 when} X seconds have elapsed after the introduction of the negative pressure The rate of change is greater than or equal to the set value Y because the pressure in the system changes greatly in the negative pressure direction when there is not much leakage in the system. On the other hand, when the leak in the system is relatively large, the pressure in the system during the time from time t _{1 to} time t ₂ is, for example, as shown in FIG.
As indicated by the chain double-dashed line in (C), the change in the negative pressure direction is extremely gentle, so the rate of change calculated in step 111 is less than the set value Y.

Therefore, when the rate of change is equal to or greater than the set value Y, it is roughly determined that there is no relatively large failure in the evaporative purge system, and the negative pressure setting flag is set to "1" (step 113). The above steps 103 to 109 are the processes for realizing the first valve control means 17, and step 110
˜112 are processes for realizing the first determination means 18.

Subsequently, in step 114 of FIG. 4, the negative pressure in the tank is set to Z (Pa) based on the detection signal of the pressure sensor 40.
It is determined whether or not it is less than or equal to Z. If it is less than Z (Pa), the negative pressure is being set, so this routine is ended. The above steps 101, 102, 103 and 114 are repeatedly executed every 65 ms until the tank internal pressure becomes larger than Z (Pa) on the negative pressure side. Then, when it is determined in step 114 that the tank internal pressure has become greater than Z (Pa) on the negative pressure side,
The purge-side VSV 38 is shut off at time t ₃ as shown in FIG. 5 (A) (step 115).

Since the two VSVs 36 and 38 are both closed at the time point t ₃ , the pressure in the system from the VSV 38 on the purge side to the fuel tank 30 is kept closed if there is no failure in the system and is extremely gentle. The pressure drops to atmospheric pressure.

As shown in FIG. 5C, at time t ₃ , the negative pressure in the tank is determined to be larger than Z (Pa), and VSV on the purge side is determined.
When the valve 38 is closed, it is determined whether the leak determination timer is "0" (step 116). Since the leak determination timer is cleared to "0" by the initial routine described above, when the determination at step 116 is first made, it is determined as "0" and the routine proceeds to step 117, where the current pressure is judged. The detection value of the sensor 40 is used as the diagnosis start pressure value P.
_It is stored in the RAM 52 as _S2 .

Then, the value of the leak determination timer is added by a predetermined value (step 118), the leak determination flag is set to "1" (step 119), and this routine is ended. Then, when this routine is started again next time, since it is determined in step 102 that the leakage is being determined, steps 103 to 114 are jumped, and further step 115 is reached to step 116.

This time, it is determined in step 116 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 120), if the time α has not yet come, this routine is ended via steps 118 and 119.

In this way, steps 101, 10
The processes of 2, 115, 116, 120, 118, and 119 are repeated every 65 ms, and when the value of the leak determination timer reaches a value corresponding to the leak determination time α, the detection value of the pressure sensor 40 at that time is set to the diagnostic end pressure. The value P _E2 is stored in the RAM 52 (step 121). Then, based on the pressure values P _S2 and P _E2 read from the RAM 52, (P _E2 −
The rate of change in pressure is calculated from the expression P _S2 ) / α (seconds) (step 122).

Then, it is judged whether or not the calculated change rate is equal to or larger than a predetermined threshold value β (step 123). , Turn on the warning lamp 41 (step 12
4) 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 125), and step 12
Go to 6. The leakage failure fail code is read out 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, when it is determined that the calculated change rate is less than β, it is determined that the leakage is normal because the leakage is less than the specified value, and steps 124 and 125 are jumped to step 126. In step 126, the canister atmosphere hole VSV36 is opened (valve opened). Then, the timer A and the leak determination timer are cleared (step 127), the execution flag is set to "1" (step 128), and the leak determination flag and the negative pressure setting flag are cleared to "0" ( In step 129), the failure diagnosis process ends. After that, even if this routine is started, the execution flag is determined to be "1" in step 101, so this routine is not executed until it is restarted thereafter.

In step 126, the canister atmosphere hole VSV
When time 36 is opened is assumed to be t _5, Fig. 5
As shown in (C), the tank internal pressure reaches atmospheric pressure in a short time due to the atmosphere introduced from the atmosphere inlet 36a.

The above steps 114 and 115 are processes for realizing the second valve control means 19, and step 1
16 to 123 are processes for realizing the second determination means 20. Since the negative pressure introduced into the purge passage 37, the vapor passage 32, and the fuel tank 30 is hermetically held for the time α seconds by the above steps 114 to 123, even a small leak can be detected.

When it is determined in step 112 that the rate of change is less than the predetermined set value Y, it is determined that there is a large leak in the system, and the valve control and determination processing in steps 113 to 123 are not performed. Immediately, the routine proceeds to step 124, the warning lamp 41 is turned on, and the leak failure fail code is stored in the backup RAM 53 (step 125).

As described above, according to this embodiment, a large leak can be detected from the degree of change in the negative pressure in the system within a predetermined time after the start of introduction of the negative pressure, and a small leak can be detected in the system. Can be detected from the degree of change in negative pressure when the container is sealed for a predetermined time.

The present invention is not limited to the above embodiment, and for example, the evaporated fuel may be purged near the throttle valve 25.

[0040]

As described above, according to the present invention, a large leak in the system can be detected from the pressure change in the system for a predetermined time after the negative pressure is introduced into the system, and a large leak cannot be detected. In this case, the negative pressure in the system is hermetically maintained and a small leak in the system can be detected from the pressure change in the system for a predetermined time.Therefore, fault diagnosis can always be performed, and small leaks to large leaks can be accurately detected. It has features such as detection.

[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 for explaining the operation of the embodiment of the main part of the present invention.

5 is a time chart explaining the operation of each part of FIG. 4. FIG.

[Explanation of symbols]

10, 30 Fuel tank 11, 32 Vapor passage 12, 33 Canister 13, 37, 39 Purge passage 14 Intake passage 15 First control valve 16 Second control valve 17 First valve control means 18 First determination means 19 Second valve control means 20 Second determination means 21 Microcomputer 36 Canister atmosphere hole vacuum switching valve (VSV) 38 Vapor side vacuum switching valve (V
SV) 40 pressure sensor

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[Procedure amendment]

[Submission date] November 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Failure diagnosis device for evaporative purge system

[Claims]

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 evaporative purge system that discharges (purges) and burns the intake air of an engine.

[0002]

2. Description of the Related Art Fuel evaporated in a fuel tank (vapor)
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 an evaporative purge. 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,
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 applicant of the present invention has previously proposed a first control valve for opening and closing the purge passage for purging the evaporated fuel stored in the canister into the intake system of the internal combustion engine, and a second control valve for opening and closing the atmospheric hole of the canister. It has a control valve, and it has a second
After closing the control valve of the
Of the evaporative purging system (Japanese Patent Application No. 3-138002), in which the control valve is closed to maintain the airtightness 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. just after closing the first control valve, the trouble diagnosis device for the evaporative emission control system adapted to determine the presence or absence of leakage by detecting whether a predetermined negative pressure after a predetermined time (Japanese Patent Application Rights 2- 27560 No. 7) was proposed.

[0004]

However, in the former failure diagnosis device, if the leak is large, it takes a long time for the internal pressure of the fuel tank to reach the preset negative pressure, and if the leak is very large, the preset negative pressure is set. Since it does not reach, failure diagnosis itself cannot be performed. In the latter failure diagnosis device, it is difficult to detect small leaks due to changes in the purge flow rate, fuel evaporation, and the like.

The present invention has been made in view of the above points,
Failure diagnosis of the evaporative purge system that solves the above problems by determining an abnormality when the predetermined negative pressure is not reached within the predetermined time or when the predetermined negative pressure is reached and the pressure change after sealing the system is large The purpose is to provide a device.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, the evaporation fuel from the fuel tank 10 is adsorbed to the adsorbent in the canister 12 through the vapor passage 11, and the adsorbed fuel in the canister 12 is purged into the intake passage 14 of the internal combustion engine through the purge passage 13 during a predetermined operation. In the failure diagnostic device for the purge system, the present invention is directed to the pressure detection means 15, the negative pressure introduction control means 17, the first determination means 18, the sealing holding means 19, and the second determination means 2.
0 is provided.

Here, the pressure detecting means 15 is not a diagnosis target.
The pressure value in the evaporation path can be detected. Negative pressure introduction control hand
The stage 17 opens the purge control valve 16 for a first predetermined time.
Valve to introduce the negative pressure of the intake passage 14 into the evaporation path.
It The first determining means 18 is detected by the pressure detecting means 15.
Degree of change in pressure value issued during the first predetermined time
The abnormality of the evaporation route is determined based on the agreement. Closed
The holding means 19 is judged by the first judging means 18 to be normal.
The negative pressure introduced in the evaporative pathway.
Monitor whether or not the specified negative pressure value has been reached.
When the value is reached, the evaporative passage, the intake passage, and the atmosphere
Communication is cut off for a second predetermined time to keep the introduced negative pressure sealed
To do.

The second judgment means 20 is set to the second predetermined time.
Based on the degree of change in the detected pressure value within the
Determine the abnormality of the Vapo route.

[0009]

In the present invention , the pressure in the intake passage 14 is introduced into the system from the purge passage 13 to the fuel tank 10 for the first predetermined time, and the degree of change in the pressure in the system during the first predetermined time is measured. To do. When there is no leakage or it is extremely small, the degree of change in pressure in the system is larger than a predetermined threshold value, whereas when leakage is large, there is no change in the system even after the first predetermined time has elapsed. The degree of change in pressure is smaller than the above-mentioned predetermined threshold value.

Therefore, the first determining means 18 determines that the evaporative purge system has failed when the degree of change in pressure in the system is smaller than the predetermined threshold value. And
Only when it is judged by the first judging means 18 that the evaporative purge system is not in failure, the airtight holding means 19 is provided.
The second determining means 20 holds the closed state in which the negative pressure is introduced into the system for the second predetermined time, and determines the failure of the evaporative purge system from the degree of pressure change at that time.

[0011]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. In the figure, the air from which dust, dust and the like in the atmosphere have been removed by the air cleaner 22 has its intake air amount measured by an air flow meter 23, and its flow rate is controlled by a throttle valve 25 in an intake pipe 24. Further, it flows through a surge tank 26 and an intake manifold 27 (which constitutes the intake passage 14 together with the intake pipe 24) into a combustion chamber (both not shown) of an internal combustion engine during a period in which an 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 31 in the fuel tank 30 into the air flow passing through the intake manifold 27 for a time designated by the microcomputer 21.

The fuel tank 30 is the fuel tank 10 described above.
The fuel 31 is accommodated and the evaporated fuel (vapor) generated inside is sent to the canister 33 (corresponding to the canister 12 described above) through the vapor passage 32 (corresponding to the vapor passage 11). The canister 33 is filled with an adsorbent such as activated carbon inside and a part of the canister 33 is provided with an atmosphere hole 34.

The atmosphere hole 34 is connected to a canister atmosphere hole vacuum switching valve (VSV) 36 through an atmosphere passage 35. Canister vent V
The SV 36 is a control valve that connects or disconnects the atmosphere introducing hole 36 a and the atmosphere passage 35 based on a control signal from the microcomputer 21 . Further, the canister 33 communicates with the purge-side VSV 38 via the purge passage 37. One end of the purge-side VSV 38 is, for example, the surge tank 2
6 is a control valve that connects or disconnects the other end of the purge passage 39 communicating with 6 and the other end of the purge passage 37 based on a control signal from the microcomputer 21 .

The pressure sensor 40 is provided in the middle of the vapor passage 32, and is provided to detect the pressure in the vapor passage 32 to substantially detect the internal pressure of the fuel tank 30. The warning lamp 41 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

In such a structure, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon in the canister 33 through the vapor passage 32 and prevented from being released into the atmosphere. Normally, the canister atmosphere hole VSV36 is opened, and when the evaporative purge system is operating, the purge side VS
V38 is also open. As a result, the negative pressure of the intake manifold 27 is used during operation, and the air inlet 36a
The atmosphere is introduced into the canister 33 through the canister atmosphere hole VSV 36, the atmosphere passage 35, and the atmosphere hole 34.

Then, the fuel adsorbed on the activated carbon is desorbed, and the fuel is purged by the purge passage 37 and the purge side VSV3.
8 and the purge passage 39, respectively, to be sucked into the surge tank 26. In addition, the activated carbon is regenerated by the above desorption and prepared for the next adsorption of vapor.

The microcomputer 21 uses the negative pressure described above.
This is a control device that realizes the introduction control means 17, the first determination means 18, the hermetically-sealing means 19, and the second determination means 20 by software processing, and has a known hardware configuration as shown in FIG. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 3, the microcomputer 21 is a central processing unit (CP
U) 50, read-only storage of processing program
A memory (ROM) 51, 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, and an input / output interface circuit. 55 and the like, which are connected via a 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 40, and the like, and is a serial signal synthesized in time series. And a single A / D converter 56
To the bus 57 after analog-to-digital conversion
To sequentially send to.

The input / output interface circuit 55 receives the detection signal from the throttle position sensor 28 and inputs it to the CPU 50 via the bus 57, while the signals input from the bus 57 are supplied to the fuel injection valve 29 and the canister. The porosity VSV 36, the purge side VSV 38, and the warning lamp 41 are selectively sent to control them.

The CPU 50 of the microcomputer 21 having the above-mentioned configuration executes the processing of the flowchart described below according to the program stored in the ROM 51. FIG. 4 is a flow chart for explaining the operation of an embodiment of the main part of the present invention, which is activated by interruption every 65 ms, for example. In the figure, first, it is checked whether the execution flag is set (the value is "1") (step 101). The execution flag is cleared by the initial routine at engine startup (value is "0")
Since it is already set, it is not set at first, so the process proceeds to the next step 102.

In step 102, it is checked whether a leak determination flag, which will be described later, is set. Since this leak determination flag is also cleared by the initial routine,
Initially it is not set, then the next step 103
Go to. At step 103, it is judged if the negative pressure setting flag is "1". Since the negative pressure setting flag is cleared by the initial routine, the negative pressure setting flag is "0" at first, so the routine proceeds to the next step 104, where the canister atmosphere hole VSV36 is shut off (closed), and the subsequent step Open the VSV38 on the purge side at 105 (open valve)
Put in a state. Closing of the canister atmospheric hole VSV36 is performed at time t ₁ as shown in FIG. 5 (B), the valve opening of the purge side VSV38 is carried out in substantially the same time t ₁ as shown in FIG. 5 (A) If the negative pressure to the engine combustion chamber is set, the purge passage 39, the purge side VSV shown in FIG.
38, purge passage 37, canister 33, vapor passage 3
2 to the fuel tank 30. As a result, the internal pressure of the fuel tank 30 (tank internal pressure) is the time t as shown by the solid line in FIG. 5C when there is no relatively large leak in the system.
_{After 1 the} pressure rises rapidly in the negative direction (pressure decreases).

Then, it is judged whether or not the timer A is 0 second (step 106). Since this timer A is also cleared to 0 seconds by the initial routine executed after the engine is started, when this step 106 is executed for the first time, the routine proceeds to step 107, where the sensor value P _S1 of the pressure sensor 40 at that time is set. This is stored in the RAM 52 of FIG. 3, and in the next step 108, the value of the timer A is added by a predetermined value, and this routine is once ended.

Thereafter, until the timer A reaches X seconds (corresponding to the above-mentioned first predetermined time), step 10 is performed every 65 ms.
1 to 106, 109, 108 are repeatedly executed, and the sensor value P _E1 of the pressure sensor 40 is stored in the RAM 52 at the time when it is determined in step 109 that the timer A has reached X seconds (step 110). Then, the above-mentioned memory sensor value P
_{From S1} and P _E1 and the known time X (seconds), (P _E1 −
The change rate is calculated by the formula P _S1 ) / X (step 11
1) It is determined whether the calculated change rate is equal to or greater than a predetermined set value Y (step 112).

Here, after the time t ₁ is a period in which the negative pressure is introduced into the engine combustion chamber in the system, and the pressure value in the system at the time t _{2 when} X seconds have elapsed after the introduction of the negative pressure The rate of change is greater than or equal to the set value Y because the pressure in the system changes greatly in the negative pressure direction when there is not much leakage in the system. On the other hand, when the leak in the system is relatively large, the pressure in the system during the time from time t _{1 to} time t ₂ is, for example, as shown in FIG.
As indicated by the chain double-dashed line in (C), the change in the negative pressure direction is extremely gentle, so the rate of change calculated in step 111 is less than the set value Y.

Therefore, when the rate of change is equal to or greater than the set value Y, it is roughly determined that there is no relatively large failure in the evaporative purge system, and the negative pressure setting flag is set to "1" (step 113). The above steps 103 to 109 are negative.
In the process for realizing the pressure introduction control means 17, step 110
˜112 are processes for realizing the first determination means 18.

Subsequently, in step 114 of FIG. 4, the negative pressure in the tank is set to Z (Pa) based on the detection signal of the pressure sensor 40.
It is determined whether or not it is less than or equal to Z. If it is less than Z (Pa), the negative pressure is being set, so this routine is ended. The above steps 101, 102, 103 and 114 are repeatedly executed every 65 ms until the tank internal pressure becomes larger than Z (Pa) on the negative pressure side. Then, when it is determined in step 114 that the tank internal pressure has become greater than Z (Pa) on the negative pressure side,
The purge-side VSV 38 is shut off at time t ₃ as shown in FIG. 5 (A) (step 115).

Since the two VSVs 36 and 38 are both closed at the time point t ₃ , the pressure in the system from the VSV 38 on the purge side to the fuel tank 30 is kept closed if there is no failure in the system and is extremely gentle. The pressure drops to atmospheric pressure.

As shown in FIG. 5C, at time t ₃ , the negative pressure in the tank is determined to be larger than Z (Pa), and VSV on the purge side is determined.
When the valve 38 is closed, it is determined whether the leak determination timer is "0" (step 116). Since the leak determination timer is cleared to "0" by the initial routine described above, when the determination at step 116 is first made, it is determined as "0" and the routine proceeds to step 117, where the current pressure is judged. The detection value of the sensor 40 is used as the diagnosis start pressure value P.
_It is stored in the RAM 52 as _S2 .

Then, the value of the leak determination timer is added by a predetermined value (step 118), the leak determination flag is set to "1" (step 119), and this routine is ended. Then, when this routine is started again next time, since it is determined in step 102 that the leakage is being determined, steps 103 to 114 are jumped, and further step 115 is reached to step 116.

This time, it is determined in step 116 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 120), if the time α has not yet come, this routine is ended via steps 118 and 119.

In this way, steps 101, 10
The processes of 2, 115, 116, 120, 118, and 119 are repeated every 65 ms, and when the value of the leak determination timer reaches a value corresponding to the leak determination time α, the detection value of the pressure sensor 40 at that time is set to the diagnostic end pressure. The value P _E2 is stored in the RAM 52 (step 121). Then, based on the pressure values P _S2 and P _E2 read from the RAM 52, (P _E2 −
The rate of change in pressure is calculated from the expression P _S2 ) / α (seconds) (step 122).

Then, it is judged whether or not the calculated change rate is equal to or larger than a predetermined threshold value β (step 123). , Turn on the warning lamp 41 (step 12
4) 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 125), and step 12
Go to 6. The leakage failure fail code is read out 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, when it is determined that the calculated change rate is less than β, it is determined that the leakage is normal because the leakage is less than the specified value, and steps 124 and 125 are jumped to step 126. In step 126, the canister atmosphere hole VSV36 is opened (valve opened). Then, the timer A and the leak determination timer are cleared (step 127), the execution flag is set to "1" (step 128), and the leak determination flag and the negative pressure setting flag are cleared to "0" ( In step 129), the failure diagnosis process ends. After that, even if this routine is started, the execution flag is determined to be "1" in step 101, so this routine is not executed until it is restarted thereafter.

In step 126, the canister atmosphere hole VSV
When time 36 is opened is assumed to be t _5, Fig. 5
As shown in (C), the tank internal pressure reaches atmospheric pressure in a short time due to the atmosphere introduced from the atmosphere inlet 36a.

[0036] Step 114 and 115 of the said dense
This is a process for realizing the closing holding means 19, and step 116
˜123 are processes for realizing the second determination means 20. Since the negative pressure introduced into the purge passage 37, the vapor passage 32, and the fuel tank 30 is hermetically held for the time α seconds by the above steps 114 to 123, even a small leak can be detected.

When it is determined in step 112 that the rate of change is less than the predetermined set value Y, it is determined that there is a large leak in the system, and the valve control and determination processing in steps 113 to 123 are not performed. Immediately, the routine proceeds to step 124, the warning lamp 41 is turned on, and the leak failure fail code is stored in the backup RAM 53 (step 125).

As described above, according to this embodiment, a large leak can be detected from the degree of change in the negative pressure in the system within a predetermined time after the start of introduction of the negative pressure, and a small leak can be detected in the system. Can be detected from the degree of change in negative pressure when the container is sealed for a predetermined time.

[0039] The present invention is not limited to the above embodiments, for example the purge point of the evaporative fuel is rather good even throttle valve 25 near, also VSV36 is a ball
A mechanical check valve composed of a spring may be used.

[0040]

As described above, according to the present invention, a large leak in the system can be detected from the pressure change in the system for a predetermined time after the negative pressure is introduced into the system, and a large leak cannot be detected. In this case, the negative pressure in the system is hermetically maintained and a small leak in the system can be detected from the pressure change in the system for a predetermined time.Therefore, fault diagnosis can always be performed, and small leaks to large leaks can be accurately detected. It has features such as detection.

[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 for explaining the operation of the embodiment of the main part of the present invention.

5 is a time chart explaining the operation of each part of FIG. 4. FIG.

[Explanation of reference numerals] 10,30 Fuel tank 11,32 Vapor passage 12,33 Canister 13,37,39 Purge passage 14 Intake passage 15 Pressure detection means 16 Control valve 17 Negative pressure introduction control means 18 First determination means 19 Closed Holding means 20 Second judging means 21 Microcomputer 36 Canister atmosphere hole vacuum switching valve (VSV) 38 Vapor side vacuum switching valve (V
SV) 40 pressure sensor

[Procedure amendment]

[Submission date] November 2, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

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 above, a first control valve that connects or disconnects the purge passage, a second control valve that opens and closes an atmosphere hole of the canister, and a valve that closes the second control valve Valve control means for opening the control valve to introduce the pressure in the intake passage into the system from the purge passage to the fuel tank for a first predetermined time, and the system at the first predetermined time. First determining means for determining whether or not there is a failure in the evaporative purge system based on the degree of change in the internal pressure, and the first determining means determines that there is no failure in the evaporative purge system. When the pressure in the system reaches a predetermined value, the first control valve is closed together with the second control valve when the pressure in the system reaches the predetermined value. Second valve control means and the second predetermined time after the second predetermined time elapses from the time when both the first and second control valves receive the closing command by the second valve control means. And a second judging means for judging the presence or absence of the failure of the evaporative purge system from the measurement result of the degree of change of the pressure in the system.