JPH04136468A - Evaporated fuel processing device - Google Patents

Abstract

PURPOSE:To prevent the erroneous judgement related to the trouble diagnosis for a purge system which is caused according to the quantity of the fuel vapor adsorption quantity by changing the trouble judging condition on the basis of the operation states of the purge system and an intake system in the direction in which the trouble judgement precision is improved, according to the increase of the fuel vapor pressure in a fuel tank. CONSTITUTION:In a charcoal canister 30, the fuel vapor introduced through a passage 33 which communicates to the upper part space of a fuel tank 32 is adsorbed on the activated carbon 31. In this case, a pressure sensor 34 for detecting the pressure of the fuel vapor in a fuel tank 32 is arranged midway in the passage 33. Further, the charcoal canister 30 communicates to a surge tank 6 through a purge passage 35. Further, a control unit 20 judges the trouble of a purge system on the basis of the signal outputted from an air-fuel ratio sensor 12, etc. The trouble judging condition which is determined on the basis of the operation states of the purge system and suction system is changed in the direction in which the trouble judgement precision is improved, according to the increase of the fuel vapor pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an evaporated fuel processing device that prevents fuel vapor evaporated from a fuel tank of a vehicle from escaping into the atmosphere.

(Prior art) In general gasoline engine vehicles, in order to prevent fuel vapor that evaporates from the fuel tank from dissipating into the atmosphere,
For example, as shown in Japanese Unexamined Patent Publication No. 57-52663, a charcoal canister for adsorbing the fuel gas is provided. The fuel vapor adsorbed in this charcoal canister is then drawn into the intake passage downstream of the engine throttle valve through a purge passage equipped with a duty solenoid valve that opens the passage under certain operating conditions, such as idle. It is now possible to do so.

Furthermore, a duty solenoid in the purge passage is installed so that if, for example, a pipe connecting the purge passage becomes disconnected and fuel vapor is released into the atmosphere, this can be immediately detected. When the control unit that controls the valve outputs an activation signal to the solenoid valve, it determines whether the purge system is operating normally or not, and if it is determined that the purge system is malfunctioning, For example, a warning light is turned on. That is, when an activation signal is output from the control unit to the solenoid valve, along with this,
If the air-fuel ratio sensor installed in the engine's exhaust system detects that the air-fuel ratio has become rich, it is determined that the purge system is operating normally, and the solenoid valve is stuck or the purge passage is blocked. If the connecting pipe is disconnected, fuel vapor will not be supplied to the intake system even if an activation signal is applied to the solenoid valve, and the air-fuel ratio will not become rich, so it can be determined that the purge system is malfunctioning. It is meant to be done.

However, even if the purge system is operating normally, if only a small amount of fuel vapor is adsorbed in the charcoal canister, or if no fuel vapor is adsorbed at all, even if an activation signal is applied to the solenoid valve, , the air-fuel ratio will not become rich. Therefore, in the purge system failure diagnosis method used in the conventional evaporative fuel processing apparatus of this type as described above, there is a risk that a failure determination may be made even though the purge system is normal.

(Objective of the Invention) Therefore, the present invention aims to prevent the above-mentioned erroneous judgments and improve the accuracy of failure detection when fault diagnosis of the purge system is performed based on the detection of changes in the air-fuel ratio of the engine. The purpose of the present invention is to provide an evaporated fuel processing device.

(Structure of the Invention) The evaporative fuel device according to the present invention includes a means for detecting fuel vapor pressure in a fuel tank, and a system for controlling the purge system and the intake system in response to an increase in the fuel evaporative pressure detected by the pressure detecting means. The apparatus is characterized by comprising a failure determination condition changing means for changing the failure determination condition determined according to the operating state of the apparatus in a direction that improves failure determination accuracy.

Further, in the evaporative fuel system according to the present invention, the purge system is provided with a valve that is operated according to the operating condition of the engine, and the judgment level in the failure judgment is further adjusted according to the operating condition of the valve and the operating condition of the engine. It is characterized by comprising means for correction.

(Effects of the Invention) According to the present invention, it is possible to prevent erroneous determinations caused by the amount of fuel vapor adsorbed by the fuel vapor adsorption means.

Further, according to the present invention, failure detection accuracy can be improved by accurately predicting the operating state of the purge system.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of an engine equipped with an evaporative fuel processing device according to the present invention.In the intake passage 2 of the engine 1, from the upstream side to the downstream side, there is an air cleaner 3, which detects the amount of intake air. An air flow meter 4, a throttle valve 5, a surge tank 6 that absorbs pulsation of intake air, and a fuel injection valve 7 are arranged in this order, and the air-fuel mixture is supplied into a combustion chamber 9 via an intake valve 8. The exhaust of engine 1 is in combustion chamber 9
The exhaust gas is discharged from the inside through an exhaust valve 10 into an exhaust passage 11, and this exhaust passage 11 is equipped with an air-fuel ratio sensor 12 that detects the residual oxygen concentration in the exhaust gas and measures the air-fuel ratio, and a catalytic converter 13 that purifies the exhaust gas. is installed.

Further, the intake passage 2 is provided with a bypass passage 14 for supplying air into the combustion chamber 9 by bypassing the throttle valve 5 during idling operation. A duty solenoid valve 15 is provided for controlling the.

16 is an igniter that generates the high voltage necessary for ignition, 17
Reference numeral 19 is a distributor that operates in conjunction with a crankshaft (not shown) and distributes the high voltage generated in the igniter 16 to the spark plugs 18 of each cylinder, and 19 is installed in the distributor 17 to generate pulses according to the rotation of the crankshaft. An engine rotation speed sensor generates a signal, and 20 is a control unit.

The control unit 20 includes an engine speed sensor 1
9. Air flow meter 4, intake temperature sensor 21, throttle opening sensor 22 equipped with an idle switch to determine whether the throttle valve 5 is fully closed, air-fuel ratio sensor 12, engine water temperature proportional to engine temperature. Based on the signal output from the water temperature sensor 24 etc. to be detected,
In addition to controlling the amount of fuel injected from the fuel injection valve 7, during idling operation, the duty solenoid valve 15 is duty-controlled so as to adjust the amount of air passing through the bypass passage 14 and bring the idling speed close to a set value. .

30 is a charcoal canister equipped with activated carbon 31, and the activated carbon 31 adsorbs fuel vapor brought through a passage 33 that communicates the upper space of the fuel tank 32 and the charcoal canister 30. A pressure sensor 34 is disposed in the middle of the passage 33 to detect the pressure of fuel vapor within the fuel tank 32. charcoal canister 3
0 communicates with the surge tank 6 through a purge passage 35, and this purge passage 3 is located in the middle of the purge passage 35.
A duty solenoid valve 36 is disposed for controlling the flow rate of fuel vapor drawn into the intake system through the intake system.

The control unit 20 outputs an activation signal to the duty solenoid valve 36 to activate the purge system, and also includes an engine speed sensor 19, an intake air temperature sensor 21, a throttle opening sensor 22, a water temperature sensor 24,
Failure of the purge system is determined based on signals output from the air-fuel ratio sensor 12, pressure sensor 34, and the like.

FIG. 2 shows a flowchart of a purge system failure determination routine executed by the control unit 20. First, in steps S1 and S2, a start determination and a catalyst warm-up timer are performed to warm up the catalytic converter 13. Then, in step S3, it is checked whether the purge system failure determination condition I is satisfied.

The requirements for the failure determination condition I to be satisfied are that the purge execution condition is satisfied, the engine is in idling operation, and the intake air temperature is equal to or higher than a predetermined value. The above purge execution condition is when the engine water temperature reaches a predetermined value or higher. If the determination in step S3 is YES, in step $4 the duty solenoid valve 36 is turned on to open the purge passage 35, and the fuel vapor adsorbed in the charcoal canister 30 is sucked into the surge tank 6, and then in step S5 Check whether the air-fuel ratio has become rich. If it is determined in step S5 that the air-fuel ratio is rich, the process proceeds to step S6 and it is determined that the purge system is operating normally.

On the other hand, if the determination in step S5 is NO, that is, if the air-fuel ratio is not determined to be rich, the process proceeds to step S7, and it is determined whether the conditions for increasing the internal pressure of the fuel tank 32 are satisfied. When this tank internal pressure increase condition is met,
This refers to when the engine water temperature, intake temperature, engine speed, and intake air filling efficiency each exceed a predetermined value. When the determination in step S7 is YES, the process advances to step S8, and when the determination in step S7 is NO, the process advances to step S8.
Proceed to 11.

In step S8, it is determined whether the fuel vapor pressure detected by the pressure sensor 34 is equal to or higher than a set value. If the determination in step S8 is YES, it is clear that a failure has occurred in the purge system, so step S9
Turn on the warning light.

Further, when the determination in step S8 is NO, that is, when the detected pressure of the pressure sensor 34 is lower than the set value, the process proceeds to step S10, sets a flag F to check whether or not the purge system is actually out of order, and steps Sll Proceed to.

In step Sll, it is checked whether failure determination condition (2) is satisfied. This failure determination condition (2) includes, in addition to the failure determination condition I in step S3 described above, the requirement that the tank internal pressure is a certain value or more, and the predicted amount A of the fuel vapor amount in the charcoal canister 30, This adds the requirement that the amount of adsorption exceeds the minimum adsorption amount that enables determination. Here, the predicted amount A of the fuel vapor amount in the charcoal canister 30 is calculated by subtracting the fuel vapor amount C supplied from the charcoal canister 30 to the intake system from the fuel vapor amount B supplied from the fuel tank 32 to the charcoal canister 30. It is calculated as the integral value of the calculated value. The fuel vapor tB is set to a predetermined value when the tank internal pressure is higher than a certain value, and is set to zero otherwise. Further, the fuel vapor amount C is determined as a value obtained by multiplying the map value of the fuel vapor amount B using the intake air filling efficiency and the engine rotational speed as parameters by the current duty ratio of the duty solenoid 36 and a correction coefficient. Further, when the predicted amount A obtained in this way is larger than the minimum adsorption amount in the charcoal canister 30 or smaller than the minimum adsorption amount in the charcoal canister 30,
The value of the maximum adsorption amount or the minimum adsorption amount is set respectively.

If it is determined in step Sll that the failure determination conditions set as described above are satisfied, step S1
In Step 2, the duty solenoid valve 36 is turned ON again, and in the next step S13, it is determined whether the air-fuel ratio has become rich. If the determination in step S13 is YES, it is determined in step S6 that the purge system is operating normally; if NO, it is determined that there is a failure, and a warning light is turned on in step S9. Further, when the determination in step S11 is No, the process advances to step S14 to check whether the flag F is set, and when this determination is YES, the process returns to step 811, and when the determination is NO, step S
Return to 7.

It is clear that by performing failure determination in the manner described above, it is possible to prevent erroneous determinations caused by the amount of fuel vapor adsorbed in the charcoal canister 30, and to improve the accuracy of failure detection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an engine equipped with an evaporative fuel processing device according to the present invention, and FIG. 2 is a flowchart of a purge system failure determination routine executed by a control unit. 1...Engine 2...Intake passage 6...
Surge tank 20... Control unit 30... Charcoal canister 32... Fuel tank 34... Pressure sensor 35
...Purge passage 36...Duty solenoid valve

Claims (1)

[Scope of Claims] 1. A system comprising an adsorption means for fuel vapor evaporated from a fuel tank and a purge system for supplying the fuel vapor adsorbed by the adsorption means to the intake system of an engine, and capable of diagnosing failures of this purge system. In an evaporative fuel processing system that performs processing based on the detection of a change in the air-fuel ratio of an engine, there is provided a means for detecting the fuel vapor pressure in the fuel tank, and an increase in the fuel vapor pressure detected by the pressure detecting means. Accordingly, the evaporative fuel treatment is characterized by comprising a failure determination condition changing means for changing the failure determination condition determined according to the operating state of the purge system and the intake system in a direction that improves the failure determination accuracy. Device. 2. The purge system is provided with a valve that is operated according to the operating condition of the engine, and includes means for further correcting the judgment level in the failure judgment according to the operating condition of the valve and the operating condition of the engine. The evaporative fuel processing device according to claim 1, characterized in that: