JP3548031B2 - 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 vaporized fuel is sucked into the intake system of the internal combustion engine via the purge control valve to prevent the evaporated fuel from diffusing into the outside air (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.
That is, after measuring the operating current value of the air pump when air is pumped through a reference orifice having a reference diameter by an electric air pump as a determination level, the air pump bypasses the reference orifice and evaporative fuel processing apparatus. The operating current value of the air pump when air is pumped into the purge line is measured as a leak level, and this leak level is compared with a judgment level. When the leak level is smaller than the judgment level, it is diagnosed that there is a leak.
[0005]
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.
[0006]
[Problems to be solved by the invention]
However, in the above method, when the temperature is low at the time of measuring the determination level, and the temperature rises due to the self-heating of the motor portion of the electric air pump before the measurement of the leak level, it is actually diagnosed that a leak has occurred. Even when such holes are generated, the pump operating current increases due to the temperature characteristics of the electric air pump when measuring the leak level. There was a possibility of erroneous diagnosis that there was no leak. Such a tendency becomes remarkable when the outside air temperature is low, because the influence of the self-heating of the motor unit increases.
[0007]
In view of such a conventional problem, the present invention provides a leak diagnosis device for an evaporative fuel treatment device capable of improving the diagnosis accuracy by reliably avoiding the effect of temperature rise due to self-heating of an electric air pump. The purpose is to do.
[0008]
[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, together with fresh air introduced from the fresh air inlet. An evaporative fuel processing device for inhaling the evaporative fuel from a purge line from a fuel tank to a purge control valve through a canister through a canister, wherein the evaporative fuel processor is adapted to diagnose a leak of evaporative fuel from a purge line through a canister. A switching valve for selectively connecting an air introduction port to an atmosphere opening port and a discharge port of an electric air pump; and a fresh air introduction port of the canister from the discharge port of the air pump bypassing the switching valve. A bypass passage in which a reference orifice having a diameter is interposed, and turning on the air pump and switching the switching valve to the atmosphere opening port side. After the air pumped from the air pump passes through the reference orifice of the bypass passage, the operation current value of the air pump is measured as a determination level in a state where the air is released from the atmosphere opening port to the atmosphere via the switching valve. After the measurement of the determination level, the air pump is turned on, and the switching valve is switched to the air pump side, so that the air pumped from the air pump is passed through the switching valve from the fresh air inlet of the canister. A leak level measuring unit that measures an operating current value of the air pump as a leak level in a state of being supplied to the purge line, a leak determining unit that compares the leak level with the determination level to determine whether there is a leak, It is assumed that it is provided with.
[0009]
Here, in the invention according to claim 1, a judgment level remeasurement condition judgment means for judging whether or not a judgment level remeasurement condition is based on a temperature condition at the time of measuring the judgment level by the judgment level measurement means, and a judgment level remeasurement Under the condition, after the leak level is measured by the leak level measuring means, the judgment level remeasurement means for re-measuring the judgment level and the judgment level to be compared by the leak judging means are measured by the judgment level remeasuring means. And a judgment level updating means for updating the judgment level according to the determined judgment level.
[0010]
In the invention according to a second aspect, the determination level re-measurement condition determination means sets the determination level re-measurement condition that an outside air temperature detected by an outside air temperature sensor is equal to or less than a predetermined value.
[0011]
Further, in the invention according to claim 3, the determination level re-measurement condition determination means sets the determination level measured by the determination level measurement means within a predetermined range as a determination level re-measurement condition. And
[0012]
【The invention's effect】
According to the invention according to claim 1, under the determination level re-measurement condition determined by the temperature condition at the time of measurement of the determination level, the re-measurement of the determination level is performed after the measurement of the leak level, and the determination level is updated. In addition, erroneous diagnosis due to a change in the determination level due to self-heating of the pump can be prevented. Also, it can respond to environmental changes during diagnosis. In addition, when the temperature characteristics of the pump do not cause a problem, remeasurement is not performed, so that it is possible to prevent a diagnosis time from becoming unnecessarily long and an increase in power consumption.
[0013]
According to the second aspect of the present invention, by determining that the outside air temperature detected by the outside air temperature sensor is equal to or lower than a predetermined value as the determination level re-measurement condition, the determination is made under the condition that the temperature characteristic of the pump becomes a problem. The re-measurement of the level can improve the diagnostic accuracy.
[0014]
According to the invention according to claim 3, the temperature at the time of measuring the determination level is estimated to be low by setting the determination level measured first within a predetermined range as the determination level re-measurement condition. By remeasurement of the determination level, the diagnostic accuracy can be improved, and the determination can be performed more easily without using an outside air temperature sensor or the like.
[0015]
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.
[0016]
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.
[0017]
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.
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
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 a vehicle speed sensor that detects the vehicle speed 23, a fuel temperature sensor 24 for detecting the fuel temperature in the fuel tank 5, a tank remaining sensor 25 for detecting the remaining fuel (tank remaining) in the fuel tank 5, an outside air temperature sensor 26 for detecting the outside air temperature, and the like. A current sensor 27 for detecting an operating current value of the air pump 13 is further provided.
[0024]
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.
[0025]
As shown in FIG. 2, the control unit 20 includes a judgment level measuring unit, a leak level measuring unit, a leak judging unit, a judgment level remeasurement condition judging unit, a judgment level Functions as re-measurement means and determination level updating means are provided in software.
[0026]
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. This flow is started after the engine key switch is turned ON → OFF.
[0027]
In step 1 (referred to as S1 in the figure, the same applies hereinafter), it is determined whether or not predetermined diagnosis execution conditions, specifically, all of the following conditions (1) to (5) are satisfied.
(1) Engine speed ≦ predetermined value (2) vehicle speed ≦ predetermined value (3) For the purge control valve 11, it is diagnosed that there is no failure in a separately executed failure diagnosis routine. (4) Fuel temperature ≦ predetermined value (5) Lower limit predetermined value ≦ remaining tank amount ≦ upper limit predetermined value.
[0028]
When it is determined that the diagnosis execution condition is satisfied, the process proceeds to step 2.
In step 2, the atmosphere of the purge line 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.
[0029]
At this time, as shown in FIG. 4, 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 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.
[0030]
As a result, the residual pressure (negative pressure) and the residual gas in the purge passage 10 are removed.
Next, in step 3, 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.
[0031]
At this time, as shown in FIG. 5, 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. .
[0032]
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 SL1. 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 SL1. This part corresponds to the determination level measuring means.
[0033]
Next, at step 4, the judgment level SL is set as the judgment level SL measured at this time as the judgment level SL (SL = SL1).
Next, in step 5, it is determined whether a predetermined determination level re-measurement condition, specifically, the following condition (1) or (2) is satisfied.
[0034]
(1) Outside temperature ≦ predetermined value (for example, 20 ° C.)
(2) Lower limit predetermined value ≦ judgment level SL1 ≦ upper limit predetermined value.
As a result, if the determination level re-measurement condition is not satisfied, the retry flag #RETRY is set to 0 in step 6, and if the determination level re-measurement condition is satisfied, the retry flag #RETRY is set in step 7 Set to 1.
[0035]
That is, when the outside air temperature detected by the outside air temperature sensor 26 is equal to or less than the predetermined value, the temperature characteristic of the pump is a condition that causes a problem. Therefore, the retry flag #RETRY is set so that the determination level is re-measured later. Set to 1.
[0036]
Alternatively, when the initially measured determination level SL1 is within a predetermined range, it is estimated that the temperature at the time of measurement of the determination level is low, and the retry flag #RETRY is set to 1 so that the determination level is re-measured later. To
[0037]
Here, the steps 5 to 7 correspond to the judgment level re-measurement condition judging means. The determination level re-measurement condition may be that (1) outside air temperature ≦ predetermined value and (2) lower limit predetermined value ≦ determination level SL1 ≦ upper limit predetermined value.
[0038]
Next, at step 8, 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.
[0039]
At this time, as shown in FIG. 6, 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).
[0040]
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.
[0041]
Next, in step 9, the value of the retry flag #RETRY is determined. If # RETRY = 0, the process proceeds to the leak determination (step 12) without performing the determination level remeasurement (steps 10 and 11). If RETRY = 1, determination level remeasurement (steps 10 and 11) is performed prior to leak determination (step 12).
[0042]
In step 10, the determination level is re-measured.
First, the purge control valve 11 is opened (fully opened) for a predetermined time. In order to completely eliminate the influence from the tank side, the pressure is once set to the atmospheric pressure.
[0043]
Next, in the same manner as in step 3, (1) the purge control valve 11 is closed, (2) the switching valve 14 is turned off to switch to the atmosphere opening port 12, and (3) the air pump 13 is turned on. Then, this state is maintained for a predetermined time.
[0044]
Also at this time, as shown in FIG. 5, after the air sucked and discharged by the air pump 13 passes through the bypass passage 15 (reference orifice 16), the air flows backward through the switching valve 14 and is discharged into the atmosphere from the atmosphere opening port 12. Is done.
[0045]
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 SL2. That is, the operating 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 SL2. This part corresponds to the determination level remeasurement means.
[0046]
After the re-measurement of the determination level, in step 11, the re-measured determination level SL2 is set as the determination level SL, and the determination level SL is updated (SL = SL2). This part corresponds to the judgment level updating means.
[0047]
Finally, in step 12, the leak level (operating current value) AL measured in step 8 is compared with the determination level SL measured in step 3 or step 10 to perform a leak diagnosis of the fuel vapor. That is, when it is determined that the operating current value is equal to or lower than the determination level, it is diagnosed that there is a leak, and a predetermined failure code is set in step S13, followed by terminating the present flow. When it is determined that the operating current value is larger than the determination level, it is diagnosed that there is no leak, and this flow is terminated.
[0048]
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 If the drive load of the engine is reduced, 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. Otherwise, it is diagnosed that there is no leak (normal) (see FIG. 7). This part corresponds to a leak determination unit.
[0049]
With the above-described leak diagnosis, it is possible to reliably avoid the influence of temperature rise due to self-heating of the electric air pump, and to improve diagnosis accuracy.
[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 leak diagnosis. FIG. 4 is a flow of air when a purge line atmosphere is initialized. FIG. 5 is a diagram showing an air flow at the time of determination level measurement. FIG. 6 is a diagram showing an air flow at the time of leak level measurement. FIG. 7 is a diagram showing a pump operating current value at the time of leak level measurement. Explanation of code]
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 Vehicle Speed Sensor 24 Fuel Temperature Sensor 25 Tank Remaining Sensor 26 Outside Temperature Sensor 27 Current Sensor

Claims (3)

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 leak of vaporized fuel from a purge line from a fuel tank to a purge control valve via a canister,
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,
After the determination level was measured, the air pump was turned on, the switching valve was switched to the air pump side, and air supplied from the air pump was supplied to the purge line from the fresh air inlet of the canister via the switching valve. In the state, a leak level measuring means for measuring an operating current value of the air pump 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.
A judgment level remeasurement condition judging unit for judging whether or not a judgment level remeasurement condition is determined based on a temperature condition at the time of measurement of the judgment level by the judgment level measurement unit; A determination level remeasurement means for remeasurement of the determination level after measuring the level, and a determination level updating means for updating a determination level to be compared by the leak determination means with the determination level measured by the determination level remeasurement means A leak diagnostic device for an evaporative fuel treatment device, comprising: 2. The leak of the evaporated fuel processing apparatus according to claim 1, wherein the determination level re-measurement condition determination unit sets the determination level re-measurement condition that an outside air temperature detected by an outside air temperature sensor is equal to or less than a predetermined value. Diagnostic device. 3. The judgment level remeasurement condition judging means sets a judgment level measured by the judgment level measurement means within a predetermined range as a judgment level remeasurement condition. Diagnostic device for evaporative fuel processing equipment.

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