JP3240477B2 - Engine evaporative fuel control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor control system for an engine, which controls the supply of fuel vapor generated in a fuel tank of a vehicle to an intake system.

[0002]

2. Description of the Related Art Evaporated fuel generated in a fuel tank or the like of a vehicle is directly adsorbed and collected in a canister provided with an adsorbent such as activated carbon, because if it is released into the atmosphere as it is, it will cause air pollution. The engine is detached (purged) from the canister by suction negative pressure during operation of the engine and is introduced into the intake system of the engine. As described in Japanese Utility Model Laid-Open Publication No. 64-41656, for example, the fuel vapor adsorbed by the canister is introduced into the intake system in the middle of a purge passage connecting the canister and the intake system. There is a known configuration in which a purge control valve is provided in the engine, and the amount of fuel vapor supplied to the engine is controlled by controlling the purge control valve in accordance with the operating state of the engine.

[0003]

By the way, when the fuel vapor is purged into the intake system of the engine, it may cause disturbance and adversely affect the air-fuel ratio of the engine. It is desirable not to do this unless possible. On the other hand, when the pressure in the fuel tank is reduced due to the influence of the outside air temperature and the outside air pressure, the vaporized fuel adsorbed and collected in the canister is returned to the fuel tank for processing without purging the fuel to the intake system (so-called processing). Back purge) is possible. For this reason, if the back purge can be used well to prevent unnecessary purge, adverse effects on the engine can be minimized.

However, in the above-described conventional purge system, the purge control valve is controlled to perform the purge to the intake system irrespective of the pressure fluctuation in the tank. Therefore, the purge causes the air-fuel ratio of the engine to fluctuate. However, there is a problem that the traveling performance and emission performance of the vehicle are deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and does not cause the fuel vapor to overflow from the canister. It is an object of the present invention to provide an evaporative fuel control device for an engine that can prevent a change in an air-fuel ratio due to supply.

[0006]

According to the present invention, as shown in FIG. 1, an evaporative fuel supply device for supplying evaporative fuel generated in a fuel tank to an intake system of an engine is provided. Operating state detecting means for detecting an operating state of the engine, an output of the operating state detecting means, and an evaporative fuel control means for controlling the evaporative fuel supply device in accordance with the operating state of the engine; A pressure-related parameter detecting means for detecting a parameter, and a supply restricting means for restricting the supply of evaporative fuel when a parameter value detected by the pressure-related parameter detecting means becomes equal to or less than a predetermined value , and in particular, Fuel tongue
A canister for adsorbing and collecting the evaporated fuel generated in the
Introduce the evaporated fuel desorbed from the canister into the intake system
A purge passage connecting the canister and the intake system;
The steam passing through the purge passage is provided in the middle of the purge passage.
A parameter that controls the flow rate of generated fuel according to the operating state of the engine.
Control valve and parameters related to fuel tank pressure
Pressure-related parameter detecting means for detecting
Parameter detected by force-related parameter detection means
The purge control valve is closed when the value falls below a predetermined value.
It is configured as follows.

[0007]

The evaporative fuel generated in the fuel tank is once collected in the evaporative fuel supply device and supplied to the intake system according to the operating state of the engine. When the parameter value related to the fuel tank pressure becomes equal to or less than a predetermined value, the supply of the fuel vapor to the intake system is restricted and the fuel vapor is positively returned to the fuel tank, thereby reducing the air-fuel ratio of the engine. Fluctuations are prevented. Further, when the pressure in the fuel tank is high, the evaporated fuel is supplied from the canister to the intake system, and the overflow of the evaporated fuel is prevented.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall system diagram of one embodiment of the present invention.

In this embodiment, an intake port 3 and an exhaust port 4 are opened in a combustion chamber 2 of the engine 1, and an intake valve 5 for opening and closing the intake port 3 and the exhaust port 4.
And an exhaust valve 6. The intake port 3 and the exhaust port 4 are connected to an intake passage 7 and an exhaust passage 8, respectively.

A fuel tank 9 for storing gasoline fuel is provided. An upper space of the fuel tank 9 is connected to an introduction port 13 of a canister 12 having an adsorbent 11 such as activated carbon through an introduction passage 10. ing. A pressure sensor 14 for detecting the pressure of the evaporated fuel in the fuel tank 9 is provided in the middle of the introduction passage 10. The purge port 15 of the canister 12 communicates with the intake passage 7 through a purge passage 16, and a solenoid valve 17 for controlling the flow rate of fuel vapor passing through the passage 16 is provided in the middle of the purge passage 16. (Purge control valve) . An atmosphere port 18 communicating with the atmosphere is provided below the canister 12.

The solenoid valve 17 is actuated by a control signal from a control unit 19 constituted by a microcomputer, and linearly changes the passage area of the purge passage 16 to adjust the passage amount of the evaporated fuel. The control unit 19 includes, as information for calculating the control signal, an engine speed signal from an engine speed sensor, an intake air amount signal from an air flow meter,
An engine water temperature signal from a water temperature sensor attached to a cooling water jacket of the engine 1, an evaporative fuel pressure signal from a pressure sensor 14, and the like are input.

In the present embodiment, the pressure in the fuel tank 9 is detected by the pressure sensor 14, and when the detected value falls below a predetermined value, the evaporated fuel adsorbed and collected in the canister 12 is directed to the fuel tank 9 side. Therefore, the purge to the intake system is cut by closing the solenoid valve 17 and the evaporated fuel is positively returned to the fuel tank 9.

Next, a flowchart for executing the control of this embodiment will be described with reference to FIG. In the figure, S1 to S
Reference numeral 6 denotes each step.

In this flow, when starting, first, various signals such as the intake air amount and the engine speed are read (S1). Next, whether the purge execution condition is satisfied, that is, whether the engine is in the idling state or when the engine is in the idling state, It is determined whether or not the engine is not in a region where combustion stability is poor such as when the engine is cold (S2).

If the above determination is YES, in the next step, it is determined whether or not the tank pressure detected by the pressure sensor 14 is equal to or less than a predetermined value (α) (S3). Sometimes, the control amount (D) of the purge solenoid (solenoid valve 17) is set to zero (S
4) Output to the purge solenoid (S5).

On the other hand, if the determination in S2 is NO, that is, if the purge execution condition is not satisfied, it means that the purge is in a region where the combustibility is adversely affected.
Proceeding to S4 without making the determination of 3, the control amount D of the purge solenoid is also set to zero at S4.

If the determination in S3 is NO, that is, if the tank pressure is greater than the predetermined value α, a control amount D according to the engine operating state is set (S6) and output to the purge solenoid (S5). ).

In the above-described embodiment, the purge solenoid is controlled by directly detecting the pressure in the fuel tank. However, the control is performed by controlling other parameters related to the pressure in the tank such as temperature. You may make it perform by detecting.

Further, in the above-described embodiment, the case in which the purge to the intake system is completely cut off when the tank pressure becomes equal to or lower than the predetermined value has been described. May be limited to limit the purge amount.

[0021]

The present invention is configured as described above.
When the fuel tank pressure drops, the fuel vapor adsorbed by the canister is made to flow back to the fuel tank.Therefore, without causing the fuel vapor to overflow from the canister, the air-fuel ratio of the fuel vapor supply to the intake system can be reduced. Fluctuations can be prevented, and adverse effects on traveling performance can be eliminated. Also, due to the backflow of the evaporated fuel,
Since the concentration in the upper space in the fuel tank increases, the amount of fuel vapor generated in the tank can be reduced, and the capacity of the canister can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is an overall system diagram of an embodiment of the present invention.

FIG. 3 is a flowchart for executing control of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 7 Intake passage 9 Fuel tank 12 Canister 14 Pressure sensor 17 Solenoid valve 19 Control unit

Claims (1)

(57) [Claims] 1. A method for adsorbing and evaporating fuel generated in a fuel tank.
Collecting canister and evaporation desorbed from the canister
The canister and the intake system are connected so that fuel is introduced into the intake system.
A purge passage to be connected, and a purge passage provided in the middle of the purge passage.
The flow rate of the evaporated fuel passing through the purge passage is controlled by the engine operation.
A purge control valve for controlling in accordance with the rolling conditions, and a pressure-related parameter detecting means for detecting a parameter related to the fuel tank pressure, the parameter value detected by the pressure related parameter detecting means becomes less than a predetermined value When
An evaporative fuel control device for an engine, wherein the purge control valve is closed .