JP3548032B2 - 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]
By the way, in the above-mentioned method, since the inside of the fuel tank becomes a positive pressure by the leak diagnosis, after the leak diagnosis, as a post-diagnosis process, the air pump is turned off, and the switching valve is switched to the atmosphere opening port side, so that the fuel tank It is necessary to release the internal pressure from the air opening through the canister. At this time, the evaporated fuel is adsorbed on the canister and only the air is released.
[0009]
However, depending on the filling state of the canister, the adsorption efficiency is reduced, so the flow velocity when releasing the pressure in the fuel tank from the atmosphere opening port via the canister is too fast, and the canister can sufficiently adsorb the evaporated fuel. Therefore, there is a fear that the evaporated fuel may be released to the atmosphere (gasoline odor).
[0010]
In view of such a conventional problem, the present invention can reliably prevent evaporation of evaporated fuel into the atmosphere during post-diagnosis processing, regardless of the filling state of the canister, and fill the fuel tank as quickly as possible. It is an object of the present invention to be able to return to atmospheric pressure by reducing pressure.
[0011]
[Means for Solving the Problems]
The present invention is directed to a purge control valve that guides vaporized fuel from a fuel tank to a canister having a fresh air inlet and temporarily absorbs the vaporized fuel and the vaporized fuel adsorbed to the canister together with fresh air introduced from the fresh air inlet. In the evaporative fuel processing device to be sucked into the intake system of the internal combustion engine via the, after the engine is stopped, a leak diagnostic device for diagnosing the leak of the evaporative fuel from the purge line from the fuel tank through the canister to the purge control valve, 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. After switching to the mouth side, the air pumped from the air pump is passed through the reference orifice of the bypass passage, and then the operating current value of the air pump is determined in a state where the air is opened to the atmosphere from the atmosphere opening port via the switching valve. A determination level measuring means for measuring a level, and turning on the air pump, switching the switching valve to the air pump side, and purging air pumped from the air pump from the fresh air inlet of 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 line, a leak determining means for comparing the leak level with the determination level to determine whether or not there is a leak; After the determination, the air pump is turned off, and the switching valve is switched to the atmosphere opening port side so that the fuel tank is turned off. Assumes that the pressure of the inner in which and a diagnostic postprocessing means to escape from the air opening.
[0012]
Here, in the invention according to claim 1, when the canister filling state estimating means for estimating the filling state of the canister immediately before the engine is stopped and the post-diagnosis processing means operates according to the filling state of the canister, the switching is performed. Air opening opening limiting means for limiting the opening of the air opening side by the valve.
[0013]
That is, by restricting the opening degree on the atmosphere opening port side during the post-diagnosis processing (when the pressure in the fuel tank is released) according to the filling state of the canister, specifically, when the canister filling amount is large, Since the adsorption efficiency of the canister has decreased, the canister's adsorption efficiency (adsorption speed) has been reduced by reducing the degree of opening on the air opening side and decreasing the pressure release speed. By reducing the velocity of the gas passing through the canister to increase the contact time between the canister and the gas, the evaporated fuel can be sufficiently adsorbed. On the other hand, when the canister filling amount is small, the adsorption efficiency of the canister is high.Therefore, by increasing the opening degree on the side of the air opening and increasing the pressure release speed, the atmospheric pressure inside the fuel tank is quickly increased. It is returned to. This is because it is not preferable to keep the inside of the fuel tank in a positive pressure state.
[0014]
In the invention according to claim 2, the canister filling state estimating means is based on an air-fuel ratio deviation amount detecting means for detecting an air-fuel ratio deviation amount under a predetermined purge condition during engine operation, and based on the detected air-fuel ratio deviation amount. And a canister filling amount estimating means for estimating the canister filling amount.
[0015]
In the invention according to claim 3, the canister filling state estimating means calculates and integrates the amount of evaporative fuel generation based on the fuel temperature in the fuel tank during engine operation, and the evaporative fuel generation amount integrating means during engine operation. A purge amount integrating means for calculating and integrating the purge amount of the evaporative fuel based on the purge condition; and a canister charge amount for estimating the canister fill amount based on a value obtained by subtracting the integrated value of the purge amount from the integrated value of the evaporative fuel generation amount. And estimating means.
[0016]
In the invention according to claim 4, the atmosphere opening opening degree limiting means adjusts the opening degree of the atmosphere opening port side by the switching valve for a predetermined time according to the filling state of the canister when the post-diagnosis processing means is operated. It is characterized in that the opening is limited.
[0017]
In the invention according to claim 5, the air opening opening restriction means increases the opening of the switching valve on the air opening side with the passage of time after the predetermined time elapses, and makes the opening state fully open. It is characterized by the following.
[0018]
【The invention's effect】
According to the first aspect of the present invention, the amount of fuel evaporated when the pressure in the fuel tank is reduced by restricting the opening degree of the switching valve at the time of the post-diagnosis processing on the side of the atmosphere opening port according to the filling state of the canister. Can be reliably prevented from dispersing into the atmosphere, and the pressure in the fuel tank can be reduced to the atmospheric pressure as quickly as possible. More specifically, when the canister filling amount is large, the adsorption efficiency of the canister is reduced.Therefore, the evacuation fuel is reduced by reducing the opening degree on the air opening side and decreasing the pressure release rate. On the other hand, when the canister is sufficiently filled and the canister filling amount is small, the canister has a high adsorption efficiency.Therefore, by increasing the opening on the air opening side and increasing the pressure release rate, the fuel can be quickly removed. The inside of the tank can be returned to the atmospheric pressure.
[0019]
According to the second aspect of the present invention, the filling state of the canister can be accurately estimated by estimating the canister filling amount based on the air-fuel ratio deviation amount under predetermined purge conditions during engine operation.
[0020]
According to the invention according to claim 3, during the operation of the engine, the amount of evaporative fuel generation is calculated and integrated based on the fuel temperature in the fuel tank, and the purge amount of the evaporative fuel is calculated and integrated based on purge conditions, By estimating the charged amount of the canister based on the value obtained by subtracting the integrated value of the purge amount from the integrated value of the generated amount of evaporated fuel, the charged state of the canister can be accurately estimated.
[0021]
According to the invention according to claim 4, at the time of the post-diagnosis processing, the opening degree of the air opening port side by the switching valve is limited to the opening degree according to the filling state of the canister by the predetermined time, so that the predetermined time is managed. Easy to control.
[0022]
In the invention according to claim 5, after the elapse of the predetermined time, the degree of opening of the switching valve on the side of the atmosphere opening port is increased with the elapse of time to achieve a fully open state, thereby enabling smooth control.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
The various sensors include a crank angle sensor 21 that outputs a crank angle signal in synchronization with the rotation of the engine 1 and thereby detects the engine speed, an air flow meter 22 that measures the amount of intake air, and an air exhaust system in the engine exhaust system. An air-fuel ratio sensor (wide-range oxygen sensor) 23 for detecting a fuel ratio, a vehicle speed sensor 24 for detecting a vehicle speed, a fuel temperature sensor 25 for detecting a fuel temperature in the fuel tank 5, a fuel remaining amount in the fuel tank 5 (a tank remaining amount) ) Is provided, and a current sensor 27 for detecting the operating current value of the air pump 13 is provided.
[0032]
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.
[0033]
As shown in FIG. 2, the control unit 20 includes a judgment level measuring means, a leak level measuring means, a leak judging means, a post-diagnosis processing means and a canister filling state estimating means for the leak diagnosis of the fuel vapor processing apparatus. And a function as means for restricting the opening of the air opening is provided by software.
[0034]
Here, the canister filling state estimating means includes an air-fuel ratio deviation amount detecting means and a canister filling amount estimating means as shown in FIG. 2, or an evaporative fuel generation amount integrating means, a purge amount integrating means, and a canister It is configured to include a filling amount estimation unit.
[0035]
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), the canister filling amount Qc is estimated according to the flow of FIG. 4 or 5 during operation of the engine. This part corresponds to the canister filling state estimating means.
[0036]
The case of the flow of FIG. 4 will be described.
In step 101, it is determined whether or not a predetermined time has elapsed under a predetermined purge condition, and if YES, the process proceeds to step 102 and subsequent steps. Here, the predetermined purge condition is a target purge condition when the opening degree of the purge control valve 11 is controlled such that the purge amount Qp of the evaporated fuel becomes a predetermined ratio (target purge rate) with respect to the intake air amount Qa. It is assumed that the purge rate (Qp / Qa) is between a lower limit predetermined value and an upper limit predetermined value. Here, the predetermined time is a time required until the influence of the purge condition reaches the exhaust system.
[0037]
In step 102, the air-fuel ratio (A / F) is detected based on the signal of the air-fuel ratio sensor 23.
In step 103, the detected actual A / F is subtracted from the target A / F (14.7) to obtain the air-fuel ratio deviation amount ΔA / F to the rich side = target A / F-actual A / F.
[0038]
If the air-fuel ratio sensor (wide-range oxygen sensor) 23 is not provided, that is, if a normal oxygen sensor that detects only the rich / lean air-fuel ratio is used, the air-fuel ratio feedback control for the air-fuel ratio feedback control is performed. Based on the deviation Δα of the correction coefficient α from the reference value, the air-fuel ratio deviation amount ΔA / F to the rich side is obtained.
[0039]
In step 104, the canister filling amount Qc is estimated based on the air-fuel ratio deviation amount ΔA / F toward the rich side with reference to the table. If the air-fuel ratio deviation amount ΔA / F to the rich side is equal to or less than 0, the canister filling amount Qc can be estimated to be 0, and the larger the air-fuel ratio deviation amount ΔA / F to the rich side, the larger the canister filling amount Qc. This is because it can be estimated that
[0040]
In step 105, a weighted average of the canister filling amount Qc is calculated. That is, assuming that the canister filling amount estimated most recently in step 104 is Qcnew, the canister filling amount Qc is updated by the following equation.
[0041]
Qc = Qc × (1-K) + Qcnew × K
K is a weighted average weighting constant (0 <K <1).
Here, the steps 102 and 103 correspond to the air-fuel ratio deviation amount detecting means, and the steps 104 and 105 correspond to the canister filling amount estimating means.
[0042]
The case of the flow of FIG. 5 will be described.
In step 111, the fuel temperature is detected based on the signal of the fuel temperature sensor 25.
In step 112, the amount of evaporated fuel Qe is estimated based on the fuel temperature with reference to the table. If the fuel temperature is, for example, 10 ° C. or less, the amount of evaporated fuel Qe can be estimated to be 0, and it can be estimated that the higher the fuel temperature, the greater the amount of generated fuel Qe.
[0043]
In step 113, the amount of evaporated fuel Qe is integrated by the following equation to update the integrated value ΣQe.
ΣQe = ΣQe + Qe
In step 114, the purge amount Qp of the evaporated fuel is estimated from the intake air amount Qa detected by the air flow meter 22 and the target purge rate (Qp / Qa) based on the purge conditions.
[0044]
In step 115, the purge amount Qp is integrated by the following equation to update the integrated value ΣQp.
ΣQp = ΣQp + Qp
In step 116, the canister filling amount Qc is estimated based on a value (ΣQe- パ ー ジ Qp) obtained by subtracting the purge amount integrated value ΣQp from the evaporated fuel generation amount ΣQe with reference to the table. If ΣQe-ΣQp is 0 or less, the canister filling amount Qc can be estimated to be 0, and as ΣQe- 推定 Qp increases, the canister filling amount Qc can be estimated to increase.
[0045]
Here, steps 111 to 113 correspond to the evaporative fuel generation amount integrating means, steps 114 and 115 correspond to the purge amount integrating means, and step 116 corresponds to the canister filling amount estimating means.
[0046]
Returning to FIG. 3, the description will be continued.
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.
[0047]
(1) Engine speed ≦ predetermined value (2) Vehicle speed ≦ predetermined value
If it is not after the engine is stopped, that is, if the engine is operating, the process returns to step 1 to repeat the estimation of the canister charge amount Qc.
[0048]
If the engine has stopped, the process proceeds to step 3 and subsequent steps to execute a leak diagnosis. The canister filling amount Qc estimated at this time is a value immediately before the engine is stopped.
In addition, as the diagnosis execution conditions, the purge control valve 11 is diagnosed as having no failure in a separately executed failure diagnosis routine, the fuel temperature ≤ a predetermined value, the lower limit predetermined value ≤ the remaining amount of the tank ≤ If these conditions are not satisfied, in addition to the upper limit predetermined value, the diagnosis may be canceled.
[0049]
In step 3, 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.
[0050]
At this time, as shown in FIG. 7, the air sucked and discharged by the air pump 13 passes through the bypass passage 15, from the fresh air inlet 9 of the canister 7 to the inside of the canister 7, and passes through 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.
[0051]
As a result, the residual pressure (negative pressure) and the residual gas in the purge passage 10 are removed.
Next, in step 4, 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.
[0052]
At this time, as shown in FIG. 8, the air sucked and discharged by the air pump 13 passes through the bypass passage 15 (reference orifice 16), and then flows back through the switching valve 14 and is discharged into the atmosphere from the atmosphere opening port 12. .
[0053]
Then, after maintaining this state for a predetermined time, the operating current value of the air pump 13 is measured by the current sensor 27, 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.
[0054]
Next, at step 5, 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.
[0055]
At this time, as shown in FIG. 9, the air sucked and discharged by the air pump 13 passes through the switching valve 14 from the fresh air inlet 9 of the canister 7 to the inside of the canister 7, and from the fuel tank 5 to the purge control valve via the canister 7. 11 flows into the purge line (6, 10).
[0056]
Then, after maintaining this state for a predetermined time, the operating current value of the air pump 13 is measured by the current sensor 27, 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.
[0057]
Next, at step 6, the leak level (operating current value) AL measured at step 5 is compared with the determination level SL measured at step 4 to perform a leak diagnosis of the evaporated fuel. That is, referring to FIG. 11, when it is determined that the operating current value is larger than the determination level, it is diagnosed that there is no leak, but 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 7, a predetermined failure code is set.
[0058]
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.
[0059]
Finally, in step 8, post-diagnosis processing is performed according to the flow of FIG. This portion corresponds to post-diagnosis post-processing means.
In step 801, the purge control valve 11 is closed.
[0060]
In step 802, the air pump 13 is turned off.
In step 803, the canister filling amount Qc estimated and stored immediately before the engine is stopped is read, and the opening of the switching valve 14 on the side of the atmosphere opening port 12 (switching valve opening) is obtained by referring to the table. Initialize.
[0061]
That is, when the canister filling amount Qc is small, the opening degree (switching valve opening degree) of the switching valve 14 on the side of the atmosphere opening port 12 is increased, and as the canister filling amount Qc is larger, the switching valve 14 side of the atmosphere opening port 12 side. (Switching valve opening) is made smaller.
[0062]
In terms of control, when the canister filling amount Qc is small, the ON duty of the switching valve 14 is reduced, the opening degree of the switching valve 14 on the side of the atmosphere opening port 12 is increased, and as the canister filling amount Qc increases, the switching valve increases. The ON duty of the valve 14 is increased, and the opening degree of the switching valve 14 on the side of the atmosphere opening port 12 is reduced.
[0063]
In step 804, it is determined whether or not a predetermined time has elapsed, and the opening degree initially set in step 803 is maintained until the predetermined time has elapsed.
At this time, as shown in FIG. 10, the pressure in the fuel tank 5 escapes from the atmosphere opening port 12 via the switching valve 14 via the canister 7, the evaporated fuel is adsorbed by the canister 7, and only the air escapes. .
[0064]
In particular, by restricting the opening degree on the side of the atmosphere opening port 12 at the time of post-diagnosis processing (when the pressure in the fuel tank 5 is released) according to the filling state of the canister 7, specifically, the canister filling amount Qc When the pressure is large, the adsorption efficiency of the canister 7 is reduced. Therefore, by reducing the opening degree on the side of the atmosphere opening port 12 and decreasing the pressure release speed, the adsorption efficiency (adsorption speed) of the canister 7 is reduced. By reducing the velocity, the velocity of the gas passing through the canister 7 is reduced, so that the contact time between the adsorbent and the gas is prolonged, so that the fuel vapor is reliably adsorbed. On the other hand, when the canister filling amount Qc is small, the adsorption efficiency of the canister 7 is high. Therefore, by increasing the opening degree on the side of the atmosphere opening port 12 and increasing the pressure release speed, the fuel tank 5 The interior is decompressed and returned to atmospheric pressure.
[0065]
If the predetermined time has elapsed, the process proceeds to step 805.
In step 805, the opening degree of the switching valve 14 on the side of the atmosphere opening port 12 (switching valve opening degree) is gradually increased. That is, the ON duty of the switching valve 14 is gradually reduced, and the opening of the switching valve 14 on the side of the atmosphere opening port 12 is gradually increased.
[0066]
In step 806, it is determined whether or not the degree of opening of the switching valve 14 on the side of the atmosphere opening port 12 has been fully opened (ON duty of the switching valve 14 = 0%). If NO, the process returns to step 805; Ends the processing.
[0067]
Here, steps 803 to 806 correspond to the atmosphere opening opening degree limiting means.
By the post-diagnosis processing as described above, particularly, by controlling the opening degree of the air opening port 12 side by the switching valve 14 as shown in FIG. 12, the evaporation fuel is released to the atmosphere when the pressure in the fuel tank 5 is released. (Generation of gasoline odor) can be reliably prevented, and the pressure in the fuel tank 5 can be reduced to the atmospheric pressure as quickly as possible.
[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. 4 is an estimate of a canister filling amount (first embodiment). FIG. 5 is a detailed flowchart of canister filling amount estimation (second embodiment). FIG. 6 is a detailed flowchart of post-diagnosis processing. FIG. 7 is a diagram showing a flow of air when a purge line atmosphere is initialized. FIG. 9 shows the air flow at the time of determination level measurement. FIG. 9 shows the air flow at the time of leak level measurement. FIG. 10 shows the air flow at the time of post-diagnosis processing. FIG. 12 is a diagram showing a pump operating current value of FIG. 12. FIG. 12 is a diagram showing a state of opening control during post-diagnosis processing.
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 Fuel temperature sensor 26 Tank remaining amount sensor 27 Current sensor

Claims (5)

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;
Leak determining means for comparing the leak level and the determination level to determine whether or not there is a leak,
After the leak determination, the air pump is turned off, and the switching valve is switched to the atmosphere opening port side, and post-diagnosis processing means for releasing the pressure in the fuel tank from the atmosphere opening port,
Canister filling state estimating means for estimating the filling state of the canister immediately before stopping the engine,
Depending on the state of filling of the canister, during the operation of the post-diagnosis processing means, atmosphere opening opening degree limiting means for limiting the opening degree of the air opening side by the switching valve,
A leak diagnostic device for an evaporative fuel treatment device, comprising: The canister filling state estimating means includes an air-fuel ratio deviation amount detecting means for detecting an air-fuel ratio deviation amount under a predetermined purge condition during engine operation, and a canister for estimating a canister filling amount based on the detected air-fuel ratio deviation amount. 2. The leak diagnosis device for an evaporative fuel treatment apparatus according to claim 1, further comprising a filling amount estimation unit. The canister filling state estimating means includes an evaporative fuel generation amount integrating means for calculating and integrating the amount of evaporative fuel generated based on the fuel temperature in the fuel tank during operation of the engine, and an evaporative fuel amount integrating means based on purge conditions during operation of the engine. A purge amount integrating means for calculating and integrating the purge amount, and a canister filling amount estimating means for estimating the canister filling amount based on a value obtained by subtracting the integrated value of the purge amount from the integrated value of the evaporative fuel generation amount. 2. The leak diagnosis device for an evaporative fuel treatment device according to claim 1, wherein: The open-to-atmosphere opening limiter limits the opening of the open-to-atmosphere side by the switching valve to an opening according to the filling state of the canister for a predetermined period of time when the post-diagnosis processing means operates. The leak diagnosis device for an evaporative fuel treatment device according to any one of claims 1 to 3, wherein: 5. The air opening opening restriction means for increasing the opening of the air opening on the side of the air opening by the switching valve with the passage of time after the lapse of the predetermined time to bring the opening to the fully open state. A leak diagnostic device for the evaporative fuel treatment device according to the above.

Images