JP3548026B2 - Leak diagnosis device for evaporative fuel treatment equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a leak diagnosis device for an evaporative fuel treatment device for an internal combustion engine for a vehicle.
[0002]
[Prior art]
In a conventional evaporative fuel processing apparatus for an internal combustion engine, evaporative fuel generated in a fuel tank is guided to a canister to be temporarily adsorbed, and the evaporative fuel adsorbed by the canister is supplied to a fresh air introduced from a fresh air inlet of the canister. At the same time, the fuel is sucked into the intake system of the internal combustion engine via the purge control valve to prevent the evaporated fuel from being diffused into the atmosphere (see Japanese Patent Application Laid-Open No. H5-215020).
[0003]
By the way, in the above-mentioned device, if a crack is generated in the pipe of the purge line from the fuel tank to the purge control valve through the canister, or if there is a poor seal at the joint of the pipe, a leak of the evaporated fuel occurs, and The effect of preventing radiation cannot be sufficiently exhibited.
[0004]
Therefore, the following method has been considered as a leak diagnosis device for diagnosing the presence or absence of a leak of fuel vapor from the purge line.
A switching valve for selectively connecting a fresh air introduction port of the canister to an atmosphere opening port and a discharge port of an electric air pump; and a fresh air introduction port of the canister bypassing the switching valve from the discharge port of the air pump. And a bypass passage in which a reference orifice having a reference diameter is interposed.
[0005]
After the engine is stopped, first, the air pump is turned on, and the switching valve is switched to the atmosphere opening port side to allow the air pumped from the air pump to pass through the reference orifice of the bypass passage. , The operating current value of the air pump is measured as a determination level.
[0006]
Next, while the air pump is turned on, the switching valve is switched to the air pump side, and the air pumped from the air pump is supplied to the purge line from the fresh air inlet of the canister via the switching valve, and the operating current value of the air pump is reduced. Measure as leak level. Then, this leak level is compared with the judgment level, and when the leak level is smaller than the judgment level, it is diagnosed that there is a leak.
[0007]
According to this method, diagnosis can be performed with high accuracy even when a small amount of leakage occurs, such as when a fine hole is formed in a pipe.
[0008]
[Problems to be solved by the invention]
However, in the above-described method, when the engine is stopped immediately after high-speed running (high-speed running) or steep-climbing running (high-load running), the fuel pressure generated in the purge line increases the fuel pressure in the purge line due to the fuel generated after the engine stops. High, and even in a case where a hole or the like that is actually diagnosed as a leak is occurring, the drive current of the electric pump increases due to the effect of the increase in the evaporative fuel pressure, There was a possibility of erroneous diagnosis that there was no leak.
[0009]
Further, when the purge line atmosphere initialization process (scavenging process) is performed prior to the leak diagnosis, there is a possibility that the fuel vapor is released to the atmosphere at this time.
The present invention has been made in view of such a problem, and provides a leak diagnosis device for an evaporative fuel treatment apparatus that can prevent erroneous diagnosis due to the effect of an increase in evaporative fuel pressure and improve diagnostic accuracy. The purpose is to:
[0010]
[Means for Solving the Problems]
For this reason, in the invention according to claim 1, the evaporated fuel from the fuel tank is guided to the canister having the fresh air inlet to be temporarily adsorbed, and the evaporated fuel adsorbed by the canister is introduced from the fresh air inlet. In the evaporative fuel processing device for inhaling the fresh air into the intake system of the internal combustion engine via the purge control valve, after the engine is stopped, a diagnosis is made of a leak of evaporative fuel from a purge line from the fuel tank to the purge control valve via the canister to the purge control valve. A leak diagnostic device, comprising: a leak level measuring means for measuring, as a leak level, an operating current value of the air pump when air is pressure-fed to the purge line via the fresh air inlet by an electric air pump; Is compared with a predetermined determination level to determine whether or not there is a leak.
An operation history detecting means for detecting a frequency of an operating state in which a large amount of evaporative fuel is generated before the engine is stopped; and a leak level measuring means and a leak determination in a case where the frequency of the operating state in which a large amount of evaporative fuel is generated is large. Means for prohibiting leak diagnosis by the means.
[0011]
In the invention according to claim 2, the evaporated fuel from the fuel tank is guided to the canister having the fresh air inlet to be temporarily adsorbed, and the evaporated fuel adsorbed by the canister is introduced from the fresh air inlet. And a leak diagnostic device for diagnosing a leak of evaporated fuel from a purge line from a fuel tank through a canister to a purge control valve after the engine is stopped in the evaporative fuel processing device for inhaling the fuel into an intake system of an internal combustion engine via a purge control valve. A switching valve for selectively connecting a fresh air introduction port of the canister to an air opening port and a discharge port of an electric air pump; and a switching valve for bypassing the switching valve from the discharge port of the air pump to the canister. A bypass passage that reaches a fresh air inlet and is provided with a reference orifice having a reference diameter, and turns on the air pump, After switching the switching valve to the atmosphere opening port side, the air pumped from the air pump is passed through the reference orifice of the bypass passage, and then the air pump is operated in a state where the air is released from the atmosphere opening port to the atmosphere through the switching valve. A determination level measuring means for measuring a current value as a determination level, and turning on the air pump and switching the switching valve to the air pump side to introduce air pumped from the air pump into the canister via the switching valve. A leak level measuring means for measuring an operating current value of the air pump as a leak level in a state of being supplied to the purge line from a mouth, and a leak determining means for comparing the leak level with the determination level to determine the presence or absence of a leak And those comprising:
An operation history detecting means for detecting a frequency of an operation state in which a large amount of evaporative fuel is generated before the engine is stopped, and the determination level measuring means when the frequency of the operation state in which a large amount of evaporative fuel is generated is large; A leak diagnosis prohibiting unit for prohibiting a leak diagnosis by the measuring unit and the leak determining unit.
[0012]
In the invention according to claim 3, the operating history detecting means detects, as the frequency of the operating state where the amount of evaporated fuel is large, the accumulated time of the operating state where the amount of evaporated fuel is large before stopping the engine. It is characterized by being.
[0013]
The invention according to claim 4 is characterized in that the operation history detecting means detects a high-speed high-load operation as an operation state in which the amount of generated fuel vapor is large.
[0014]
【The invention's effect】
According to the first or second aspect of the present invention, the frequency of an operating state in which a large amount of evaporative fuel is generated before the engine is stopped is detected, and when this frequency is high, the leak diagnosis is prohibited. It is possible to prevent erroneous diagnosis due to the influence of the increase in the pressure and improve the diagnosis accuracy. Further, it is possible to prevent the fuel vapor from being released into the atmosphere due to the execution of the diagnosis.
[0015]
According to the third aspect of the present invention, the frequency of the operating state where the amount of evaporated fuel is large is detected as the accumulated time of the operating state where the amount of evaporated fuel is large before the engine is stopped.
[0016]
According to the invention according to claim 4, high-speed high-load operation is detected as an operation state in which a large amount of fuel vapor is generated, so that the operation can be easily performed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a system diagram showing one embodiment of the present invention.
[0018]
The intake system of the internal combustion engine 1 is provided with a throttle valve 2 for controlling the amount of intake air. An electromagnetic fuel injection valve 4 is provided for each cylinder in a manifold portion of the intake pipe 3 downstream of the throttle valve 2. The fuel injection valve 4 is opened by a drive pulse signal output in synchronization with the engine rotation from the control unit 20 to perform fuel injection, and the injected fuel burns in the combustion chamber of the engine 1.
[0019]
The evaporative fuel processing apparatus includes a canister 7 that guides evaporative fuel generated in the fuel tank 5 through the evaporative fuel introduction passage 6 and temporarily absorbs the evaporative fuel. The canister 7 has a container filled with an adsorbent 8 such as activated carbon.
[0020]
A fresh air inlet 9 is formed in the canister 7 and a purge passage 10 is led out. The purge passage 10 is connected to the intake pipe 3 downstream of the throttle valve 2 via a purge control valve 11. The purge control valve 11 is opened by a signal output from the control unit 20.
[0021]
Therefore, the evaporated fuel generated in the fuel tank 5 while the engine 1 is stopped or the like is guided to the canister 7 by the evaporated fuel introduction passage 6 and is absorbed therein. When the engine 1 is started and a predetermined purge permission condition is satisfied, the purge control valve 11 is opened, and the negative suction pressure of the engine 1 acts on the canister 7. As a result, the evaporated fuel adsorbed on the canister 7 is desorbed, and the purge gas containing the desorbed evaporative fuel is sucked into the intake pipe 3 through the purge passage 10, and thereafter, the combustion process is performed in the combustion chamber of the engine 1. Is done.
[0022]
The following device is provided as a leak diagnostic device of the evaporative fuel processing device on the fresh air inlet 9 side of the canister 7.
An air opening 12 is provided, and an electric air pump 13 is provided. An electromagnetic switching valve 14 for selectively connecting the fresh air introduction port 9 of the canister 7 to the atmosphere opening port 12 and the discharge port 13a of the air pump 13 is provided. A bypass passage 15 is provided from the discharge port 13a of the air pump 13 to the fresh air introduction port 9 of the canister 7 by bypassing the switching valve 14, and the bypass passage 15 has a reference diameter having a reference diameter (for example, 0.5 mm). An orifice 16 is provided. An air filter 17 is provided at the atmosphere opening port 12 and the suction port 13b of the air pump 13.
[0023]
The switching valve 14 is switched to the air opening port 12 side in the OFF state and to the air pump 13 side in the ON state. Normally, the switching valve 14 is switched to the air opening port 12 side to OFF, and the fresh air introduction port of the canister 7 is opened. 9 communicates with the air opening 12.
[0024]
The control unit 20 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, and receives signals from various sensors.
[0025]
The various sensors include a crank angle sensor 21 that outputs a crank angle signal in synchronization with the rotation of the engine 1 to detect the engine speed Ne, an air flow meter 22 that measures an intake air amount Qa, and an engine exhaust system. An air-fuel ratio sensor (oxygen sensor) 23 for detecting an air-fuel ratio, a vehicle speed sensor 24 for detecting a vehicle speed VSP, and the like, and a current sensor 25 for detecting an operating current value of the air pump 13 are provided.
[0026]
Here, the control unit 20 controls the operation of the fuel injection valve 4 based on the engine operating conditions, and controls the operation of the purge control valve 11 based on the engine operating conditions. Further, after the engine is stopped, the operation of the air pump 13 and the switching valve 14 serving as a leak diagnosis device is controlled to perform a leak diagnosis of the fuel vapor treatment device.
[0027]
As shown in FIG. 2, the control unit 20 includes a determination level measurement unit, a leak level measurement unit, a leak determination unit, an operation history detection unit, and a prohibition of leak diagnosis. The function as the means is provided by software.
[0028]
Next, the leak diagnosis of the evaporated fuel processing device by the control unit 20 will be described with reference to the flowchart of FIG.
In step 1 (referred to as S1 in the figure, the same applies hereinafter), during engine operation, diagnosis prohibition flag processing based on the operation history is performed according to the flow of FIG. This part corresponds to the operation history detection means.
[0029]
Description will be made according to the flow of FIG.
In step 101, it is determined whether or not the engine is in a high-rotation, high-load operation region in which a large amount of evaporated fuel is generated. Specifically, using the engine speed Ne and the load (for example, the basic fuel injection amount Tp = K × Qa / Ne) as parameters, it is determined whether or not the engine is in a high-speed high-load operation region indicated by hatching in FIG. I do. As the load, a boost, an intake air amount, or the like may be detected.
[0030]
In the case of the high rotation and high load operation region, the process proceeds to step 102.
In step 102, the counter CNTINH is incremented by one (CNTINH = CNTINH + 1).
[0031]
Then, in step 103, it is determined whether or not the counter CNTINH is equal to or greater than a predetermined value. If CNTINH <the predetermined value, the process returns.
If CNTINH ≧ predetermined value, the process proceeds to step 104.
[0032]
In step 104, the diagnosis prohibition flag is set to 1, and in step 105, the counter CNTCLR is reset to 0, and the routine returns.
If it is not the high-rotation high-load operation region, the process proceeds to step 106.
[0033]
At step 106, the counter CNTCLR is incremented by one (CNTCLR = CNTCLR + 1).
Then, in step 107, it is determined whether or not the counter CNTCLR ≧ predetermined value. If CNTCLR <predetermined value, the process returns.
[0034]
If CNTCLR ≧ predetermined value, the process proceeds to step 108.
In step 108, the diagnosis prohibition flag is reset to 0, and in step 109, the counter CNTINH is reset to 0, and the routine returns.
[0035]
In this way, if the frequency of the high-speed high-load operation, that is, the cumulative time (CNTINH) is equal to or more than the predetermined value, the diagnosis inhibition flag is set to 1.
Returning to FIG. 3, the description will be continued.
[0036]
In step 2, it is determined whether or not the engine is stopped after a predetermined diagnosis execution condition, based on whether or not all of the following conditions (1) and (2) are satisfied.
(1) Engine speed Ne ≦ predetermined value (2) Vehicle speed VSP ≦ predetermined value.
[0037]
If the engine has not been stopped, that is, if the engine is operating, the process returns to step 1 and repeats the diagnosis prohibition flag process based on the operation history.
If the engine has stopped, the process proceeds to step 3.
[0038]
In step 3, it is determined whether the diagnosis prohibition flag = 1 or not. If the diagnosis prohibition flag = 1, that is, the frequency (accumulation) of the operation state (high-speed high-load operation) in which a large amount of evaporative fuel is generated before the engine stops. If the time is large, the process is terminated without performing the leak diagnosis to prevent erroneous diagnosis. This part corresponds to a leak diagnosis prohibiting unit.
[0039]
The diagnosis of the purge control valve 11 may be prohibited even when it is determined that a failure has occurred in a separately executed failure diagnosis routine.
When the diagnosis prohibition flag = 0, the process proceeds to step 4 to execute the leak diagnosis.
[0040]
In step 4, the purge line atmosphere is initialized. Specifically, (1) the purge control valve 11 is opened, (2) the switching valve 14 is turned off to switch to the atmosphere opening port 12 side, and (3) the air pump 13 is turned on. Then, this state is maintained for a predetermined time.
[0041]
At this time, as shown in FIG. 6, the air sucked and discharged by the air pump 13 passes through the bypass passage 15, passes through the fresh air inlet 9 of the canister 7, the inside of the canister 7, and the purge control valve 11 of the purge passage 10. After that, it flows out into the intake pipe 3. After passing through the bypass passage 15, a part of the air flows backward through the switching valve 14 and is discharged into the atmosphere from the atmosphere opening port 12.
[0042]
As a result, the residual pressure (negative pressure) and the residual gas in the purge passage 10 are removed.
Next, in step 5, the determination level for leak diagnosis is measured. Specifically, (1) the purge control valve 11 is closed, (2) the switching valve 14 is turned off to switch to the atmosphere opening port 12 side, and (3) the air pump 13 is turned on. Then, this state is maintained for a predetermined time.
[0043]
At this time, as shown in FIG. 7, after the air sucked and discharged by the air pump 13 passes through the bypass passage 15 (reference orifice 16), it flows back through the switching valve 14 and is discharged into the atmosphere from the atmosphere opening port 12. .
[0044]
Then, after maintaining this state for a predetermined time, the operating current value of the air pump 13 is measured by the current sensor 25, and this is set as a determination level SL. That is, the operation current value of the air pump 13 when the air pumped from the air pump 13 is released to the atmosphere through the reference orifice 16 having the reference diameter is measured as the determination level SL. This part corresponds to the determination level measuring means.
[0045]
Next, at step 6, the leak level is measured. Specifically, (1) the purge control valve 11 is closed, (2) the switching valve 14 is turned on to switch to the air pump 13 side, and (3) the air pump 13 is turned on. Then, this state is maintained for a predetermined time.
[0046]
At this time, as shown in FIG. 8, the air sucked and discharged by the air pump 13 passes through the switching valve 14, passes through the fresh air inlet 9 of the canister 7, passes through the canister 7, and flows from the fuel tank 5 through the canister 7 to the purge control valve. 11 flows into the purge line (6, 10).
[0047]
Then, after maintaining this state for a predetermined time, the operating current value of the air pump 13 is measured by the current sensor 25, and this is set as the leak level AL. That is, the operating current value of the air pump 13 when the air pumped from the air pump 13 is supplied to the purge line is measured as the leak level AL. This part corresponds to a leak level measuring unit.
[0048]
Next, at step 7, the leak level (operating current value) AL measured at step 6 is compared with the determination level SL measured at step 5 to perform a leak diagnosis of the evaporated fuel. That is, referring to FIG. 9, when it is determined that the operating current value is larger than the determination level, it is diagnosed that there is no leak. When it is determined that the operating current value is equal to or less than the determination level, it is diagnosed that there is a leak. At step 8, a predetermined failure code is set.
[0049]
That is, when the operating current value at the time of the leak level measurement is smaller than the operating current value of the air pump 13 required for the air pumped from the air pump 13 to flow through the reference orifice 16 having the reference diameter, that is, the air pump 13 When the drive load of the motor decreases, a failure equivalent to the opening of a hole larger than the reference diameter in the purge line (6, 10) occurs, and it is diagnosed that a leak exceeding the determination level has occurred. If not, diagnose that there is no leak (normal). This part corresponds to a leak determination unit.
[0050]
The leak diagnosis is performed as described above. As described above, if the frequency (cumulative time) of the operation state where the amount of evaporated fuel is large (high-speed high-load operation) before the engine is stopped is large, Leak diagnosis is prohibited because there is a possibility of erroneous diagnosis due to the effect of the increase in pressure.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing a leak diagnosis function of a control unit. FIG. 3 is a flowchart of a leak diagnosis. FIG. FIG. 5 is a diagram showing a high-rotation high-load region where a large amount of fuel vapor is generated. FIG. 6 is a diagram showing an air flow when the purge line atmosphere is initialized. FIG. 7 is a diagram showing an air flow when a judgment level is measured. FIG. 8 is a diagram showing the flow of air when measuring a leak level. FIG. 9 is a diagram showing a pump operating current value when measuring a leak level.
DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Throttle valve 3 Intake pipe 4 Fuel injection valve 5 Fuel tank 6 Evaporated fuel introduction passage 7 Canister 8 Adsorbent 9 Fresh air introduction port 10 Purge passage 11 Purge control valve 12 Atmospheric opening 13 Air pump 14 Switching valve 15 Bypass passage 16 Reference Orifice 17 Air Filter 20 Control Unit 21 Crank Angle Sensor 22 Air Flow Meter 23 Air Fuel Ratio Sensor 24 Vehicle Speed Sensor 25 Current Sensor

Claims (4)

The vaporized fuel from the fuel tank is guided to a canister having a fresh air inlet to be temporarily adsorbed, and the vaporized fuel adsorbed by the canister and the fresh air introduced from the fresh air inlet are subjected to internal combustion through a purge control valve. In a vaporized fuel processing device to be sucked into an intake system of an engine, a leak diagnostic device for diagnosing a vaporized fuel leak from a purge line from a fuel tank to a purge control valve via a canister after stopping the engine,
A leak level measuring means for measuring an operating current value of the air pump as a leak level when air is supplied to the purge line via the fresh air inlet by an electric air pump, and comparing the leak level with a predetermined determination level And a leak determining means for determining whether or not there is a leak.
Operating history detecting means for detecting the frequency of an operating state in which a large amount of evaporative fuel is generated before the engine is stopped
A leak diagnosis prohibiting unit that prohibits a leak diagnosis by the leak level measuring unit and the leak determining unit when the frequency of the operation state in which the amount of generated fuel is large is high;
A leak diagnostic device for an evaporative fuel treatment device, comprising: The vaporized fuel from the fuel tank is guided to a canister having a fresh air inlet to be temporarily adsorbed, and the vaporized fuel adsorbed by the canister and the fresh air introduced from the fresh air inlet are subjected to internal combustion through a purge control valve. In a vaporized fuel processing device to be sucked into an intake system of an engine, a leak diagnostic device for diagnosing a vaporized fuel leak from a purge line from a fuel tank to a purge control valve via a canister after stopping the engine,
A switching valve for selectively connecting a fresh air introduction port of the canister to an atmosphere opening port and a discharge port of an electric air pump; and a fresh air introduction port of the canister bypassing the switching valve from the discharge port of the air pump. And a bypass passage in which a reference orifice having a reference diameter is interposed.
While turning on the air pump, the switching valve is switched to the atmosphere opening port side to allow the air pumped from the air pump to pass through the reference orifice of the bypass passage, and then to the atmosphere from the atmosphere opening port via the switching valve. In an open state, a judgment level measuring means for measuring an operation current value of the air pump as a judgment level,
While the air pump is turned on, the switching valve is switched to the air pump side, and the air pumped from the air pump is supplied to the purge line from the fresh air inlet of the canister via the switching valve. Leak level measuring means for measuring an operating current value as a leak level;
A leak determining unit that compares the leak level with the determination level to determine the presence or absence of a leak.
Operating history detecting means for detecting the frequency of an operating state in which a large amount of evaporative fuel is generated before the engine is stopped
Leak diagnosis prohibiting means for prohibiting leak diagnosis by the determination level measuring means, the leak level measuring means and the leak determining means when the frequency of the operation state in which the amount of generated fuel is large is large;
A leak diagnostic device for an evaporative fuel treatment device, comprising: The operating history detecting means detects, as the frequency of the operating state in which the amount of evaporated fuel is large, the accumulated time of the operating state in which the amount of evaporated fuel is large before stopping the engine. 3. The leak diagnosis device for an evaporative fuel treatment device according to claim 1 or 2. The evaporative fuel processing according to any one of claims 1 to 3, wherein the operation history detecting means detects a high-speed high-load operation as an operation state in which the amount of generated evaporative fuel is large. Equipment leak diagnostic device.

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