JP2636310B2 - Fuel evaporative gas leak prevention device - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a fuel evaporative gas leakage prevention device provided with a canister that adsorbs evaporative fuel gas when the operation of an engine body is stopped and during idling operation. .

(Prior Art) In general, exhaust gas from a gasoline engine mounted on a vehicle such as an automobile is divided into exhaust gas, blow-by gas, and evaporative gas. In this case, the evaporative gas is
It is gasoline vapor that evaporates from a fuel tank, a carburetor, etc., and its components are all HC (hydrocarbon) itself, which is a main component of raw gasoline.

By the way, as a means of purifying exhaust gas, a fuel evaporative gas leakage prevention device for preventing gasoline vapor evaporating from a fuel tank, a carburetor or the like from being released to the atmosphere has been developed. This provides a fuel evaporative gas passage connecting the fuel tank side and the intake pipe side of the engine body, and provides a canister for adsorbing the evaporative fuel gas in the fuel evaporative gas passage. A purge control valve is provided in the purge air supply passage between the two.

When the operation of the engine is stopped and the engine is idling, the purge control valve is kept closed to adsorb the fuel vapor by the activated carbon in the canister, thereby preventing the gasoline vapor from being released to the atmosphere. doing.

Further, during an acceleration operation other than the idling operation of the engine body, the purge control valve is switched to the open state, and outside air is introduced into the canister, and the evaporated fuel gas is purged from the activated carbon in the canister,
The fuel vapor gas is introduced from the purge control valve into the intake pipe via the purge air supply passage, and is supplied to the cylinder side.

However, in the above conventional configuration, when the engine body is switched from the idling operation state to the acceleration operation state and the purge control valve is switched from the closed state to the open state, it is adsorbed on the activated carbon in the canister. Since a large amount of evaporated fuel gas is supplied into the intake pipe via the purge control valve in a relatively short time, immediately after the engine body is switched from the idling operation state to the acceleration operation state, the fuel gas remains in the cylinder of the engine body. There has been a problem that the gasoline concentration in the supplied air-fuel mixture becomes extremely high. Therefore, especially immediately after the engine body is switched from the idling operation state to the acceleration operation state, the air-fuel ratio deteriorates, and the HC (hydrocarbon) concentration and CO (carbon monoxide) concentration in the exhaust gas are lower than appropriate values. However, there was a problem in pursuing exhaust gas purification measures.

(Problems to be Solved by the Invention) That is, in the conventional configuration, when the engine body is switched from the idling state to the acceleration state,
Since the evaporated fuel gas in the canister is simply supplied to the intake pipe irrespective of the change in the air-fuel ratio, there is a problem in pursuing measures for purifying the exhaust gas.

The present invention has been made in view of the above problems,
For example, in an exhaust gas deterioration state where the air-fuel ratio is not at the stoichiometric air-fuel ratio,
It is an object of the present invention to provide a fuel evaporative gas leakage prevention device that is advantageous in pursuing exhaust gas purification measures without performing a large amount of evaporative fuel gas purge.

[Structure of the Invention] (Means and Actions for Solving the Problems) That is, the fuel evaporative gas leakage prevention device according to the present invention is provided in a purge fuel supply passage between a canister and an intake pipe to supply the purge fuel. a duty control valve for opening and closing the passage, and holding the O ₂ sensor for detecting the change in the air-fuel ratio is provided in an exhaust pipe of the engine body, the duty control valve at the time when the operation stop of the engine body and idling operation is closed , together with the state of the stoichiometric air-fuel ratio is detected by the O ₂ sensor at the time of acceleration operation other than idling of the engine body to maximize the flow rate of the purge fuel introduced into the intake pipe side is fully opened the duty control valve A control unit that performs duty control in accordance with the feedback integrated value of the air-fuel ratio when a substantially stoichiometric air-fuel ratio is not detected. In a state the air-fuel ratio is not the stoichiometric air-fuel ratio without large amounts purging of evaporated fuel gas is obtained by so as to prevent further deterioration of the exhaust gas.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a main part of a fuel evaporative gas leakage prevention device, wherein 1 is a fuel tank, 2 is an engine body,
Denotes an intake pipe of the engine body 2. Reference numeral 4 denotes a fuel evaporative gas passage of the fuel evaporative gas leakage prevention device. One end of the fuel evaporative gas passage 4 is connected to the fuel tank 1 via the reservoir tank 5. Further, the other end of the fuel evaporative gas passage 4 is connected to a purge hole 6 of the intake pipe 3 of the engine body 2. The fuel evaporative gas passage 4
Inside, a canister 7 for adsorbing the evaporated fuel gas is provided.

The canister 7 has an activated carbon storage chamber 9 formed in a substantially cylindrical container 8 and a fuel evaporative gas introduction chamber 10.
And a purge fuel discharge chamber 11 are formed. In this case, in the container 8 of the canister 7, there is provided a gas-permeable partition plate 12 for partitioning the activated carbon storage chamber 9 from the fuel evaporative gas introduction chamber 10 and the purge fuel discharge chamber 11. This partition plate 12,
For example, it is formed of a punching metal having a large number of ventilation holes formed in a flat plate surface. Furthermore, activated carbon storage room 9
A filter 13 is provided on the inner bottom of the
Activated carbon 14 is filled between the filter 13 and the filter 13.

Further, a fuel inlet 10a of the fuel evaporative gas introduction chamber 10 and a purge fuel discharge port 11a of the purge fuel discharge chamber 11 are formed on one end plate of the container 8 of the canister 7, and the other end plate is formed on the other end plate. An outside air inlet 15 is formed. In this case, the fuel inlet 10a of the canister 7 is connected to the fuel tank 1 via the reservoir tank 5, and the purge fuel outlet 11a of the canister 7 is connected to the intake pipe 3 via a duty control valve 16 which will be described later. Is connected to the purge hole 6 of the first embodiment.
Further, the outside air inlet 15 of the canister 7 is opened to the atmosphere.

On the other hand, the duty control valve 16 is provided with a duty solenoid 18 in a valve case 17 and a plunger 19 driven by the duty solenoid 18. Further, the plunger 19 is connected to a valve element 20 for opening and closing the purge fuel introduction port 17a of the valve case 17. Further, the duty solenoid 18 of the duty control valve 16 is connected to a control unit 21 constituted by, for example, a microcomputer. Further, the control unit 21
Is connected to, for example, an accelerator pedal switch 22 and an O ₂ sensor 24 provided in an exhaust pipe 23 of the engine body 2. Then, based on the output signal from the accelerator pedal switch 22 and the O ₂ sensor 24, the control unit 21 detects the operating state of the engine body 2, the duty control valve 16 is opened and closed. Where 3a is the air cleaner and 3b
Is a throttle valve, 25 is an injector (fuel injection valve)
The injector 25 is driven by a control signal from the control unit 21.

That is, when the movement of the engine body 2 is stopped and the idling operation is performed, the duty control valve 16 is held in the closed state, so that the activated carbon 14 in the canister 7 adsorbs the evaporated fuel gas and prevents its leakage into the atmosphere. In addition, during an acceleration operation other than the idling operation of the engine body 2, outside air is introduced into the container 8 from the outside air inlet 15 of the canister 7, and the activated air
The fuel vapor adsorbed from the fuel cell is released (purged), and the duty control valve 16 is opened and closed to control the flow rate of purge fuel guided from the canister 7 to the intake pipe 3 during acceleration of the vehicle. In this case, the control unit 21, the air-fuel ratio detected by the O ₂ sensor 24, the stoichiometric air-fuel ratio (≒ 14.
In the state of 7), the duty control valve 16 is controlled so that the purge flow rate is maximized. That is, when the air-fuel ratio is near the stoichiometric air-fuel ratio, the duty ratio set by the control unit 21 is
The duty control valve 16 is set to 100% and the duty control valve 16 is fully opened. The duty ratio is reduced and the purge flow rate is reduced as the air-fuel ratio deviates from the stoichiometric air-fuel ratio.

FIG. 2 shows a duty control pulse signal given from the control unit 21 to the duty control valve 16, and its duty ratio D = {drive time t / control cycle T} × 100 (%) 4
As shown in FIGS. 3A to 3C, the duty ratio (D) is determined by the filling efficiency (Mpt) determined according to the engine speed and the water temperature coefficient (K). _WT ) and the air-fuel ratio coefficient (K _IV ).
That is, for example, if the engine speed is 3000 (rpm) and the engine load is large, and the water temperature is 80 (° C) or less,
_{When WT} is 100 (%), the duty ratio (D) is determined by the air-fuel ratio coefficient (K _IV ). Here, the air-fuel ratio coefficient (K _IV ) is a feedback integral value (F / A) of the air-fuel ratio (A / F) where the stoichiometric air-fuel ratio (14.7) is “1.0”.
/ B), for example, each air-fuel ratio (A /
Feedback integral value for F) (F / B), as shown in FIG. 4, the air-fuel ratio coefficient (K _IV) is an air-fuel ratio (A / F of the feedback integration value (F / B) is 0.95 to 1.05 ) Is 14.0
The duty ratio (D) is set to "1.0", and is set to 100 (%) only between .about.15.4, that is, in the vicinity of the stoichiometric air-fuel ratio (14.7).

 Next, the operation of the above configuration will be described.

First, in the engine body 2 operation on the basis of the output signal from the accelerator pedal switch 22 and the O ₂ sensor 24, the operating state of the engine body 2 is detected by the control unit 21.

When the operation of the engine body 2 is stopped and the idling state of the engine body 2 is detected by the control unit 21, the purge fuel introduction port 17a of the valve case 17 is closed by the valve body 20 of the duty control valve 16. Will be retained. In this case, the evaporative fuel gas introduced from the fuel tank 1 into the fuel evaporative gas passage 4 is activated carbon in the canister 7.
Since the fuel vapor is adsorbed by the fuel cell 14, it is possible to prevent the fuel vapor from leaking into the atmosphere.

Further, when the engine body 2 is switched from the idling operation state to the acceleration operation state, external air is introduced into the container 8 from the outside air inlet 15 of the canister 7, and the fuel vapor adsorbed from the activated carbon 14 by the introduced air. The gas is released (purged), and the duty of the duty control valve 16 is controlled by the controller 21. In this case, the opening operation time of the duty control valve 16 is set by the duty ratio (D) as shown in FIG. 2 and FIG. 3, and for example, a map (Map) and a water temperature coefficient (K _WT ), the duty ratio (D) is 100 (%), and the duty ratio (D) is the remaining air-fuel ratio coefficient (K _IV )
Will change depending on That is, when the air-fuel ratio detected by the O ₂ sensor 24 is near the stoichiometric air-fuel ratio (14.7), the air-fuel ratio coefficient (K _IV ) becomes “1.0”, and the duty control valve 16 = 100 (%), and the purge fuel is supplied to the intake pipe 3 at the maximum flow rate.

Further, the accelerator operation, or engine load, or by something like of influence of the intake system or the like, when the air-fuel ratio detected deviates greatly stoichiometric air-fuel ratio (14.7) by O ₂ sensor 24, the first Accordingly The feedback integrated value (F / B) of the air-fuel ratio (A / F) in FIGS. 3 (C) and 4 is “1.
0 ”. Then, the air-fuel ratio coefficient (K _IV ) becomes“ 1.
0 ", and the duty ratio (D) of the drive signal to the duty control valve 16 becomes, for example, 80 (%) → 50 (%) →
By decreasing to 20 (%), the supply amount of the purge fuel to the intake pipe 3 is reduced, and the fluctuation of the air-fuel ratio is prevented from being promoted.

Therefore, in the above configuration, when the engine body 2 is in an acceleration operation other than the idling operation,
When the air-fuel ratio (A / F) detected by the O ₂ sensor 24 is approximately the stoichiometric air-fuel ratio (≒ 14.7), as shown in FIG.
When the duty control valve 16 is fully opened from the feedback integrated value (F / B) “1.0” to supply a large amount of purge fuel, and the detected air-fuel ratio (A / F) greatly deviates from the stoichiometric air-fuel ratio. The duty control valve according to the difference
Since the drive duty ratio (D) of 16 is reduced to suppress the supply amount of purge fuel, it is possible to prevent the air-fuel ratio (A / F) from being adversely affected while supplying sufficient purge fuel. Thus, for example, when the vehicle is accelerating, the concentration of gasoline in the air-fuel mixture supplied into the cylinder of the engine body 2 can be prevented from becoming extremely high due to the supply of the purge fuel. It is possible to prevent hydrocarbon (hydrocarbon) concentration and CO (carbon monoxide) concentration from deviating from appropriate values, which is advantageous in advancing exhaust gas purification measures.

In the above embodiment, the configuration of the fuel evaporative gas leakage prevention device for a vehicle without a supercharger (turbo) has been described. However, for a vehicle with a supercharger, for example, a configuration as shown in FIG. Then, the same effect of preventing the exhaust gas from being deteriorated can be obtained.

That is, a supercharger 26 is provided from the exhaust pipe 23 of the engine body 2 to the intake pipe 3, and the purge fuel discharge port 11 a of the canister 7 and the purge hole 6 for the intake pipe 3 upstream of the supercharger 26 are provided. Between them, a valve 27 that opens and closes in conjunction with the duty control valve 16 is provided. The valve 27 has an intake inlet 27a communicating with the intake pipe 3 downstream of the supercharger 26. That is, with the driving of the duty control valve 16 according to the acceleration operation of the engine body 2, the valve body of the valve 27
When the opening operation of the turbocharger 28 is performed,
6, the positive pressure intake air is introduced, and the purged fuel from the canister 7 is discharged together with the introduced positive pressure air from the discharge port 27.
This is supplied to the intake pipe 3 through b.

[Effects of the Invention] As described above, according to the present invention, a duty control valve interposed in a purge fuel supply passage between a canister and an intake pipe to open and close the purge fuel supply passage, and an exhaust pipe of an engine body and O ₂ sensor for detecting the change in the air-fuel ratio provided, the duty control valve held in the closed state during the time of operation stop of the engine body and the idling operation, the on time of acceleration operation other than idling of the engine body O ₂
In a state where the sensor detects the substantially stoichiometric air-fuel ratio, the duty control valve is fully opened to maximize the flow rate of the purge fuel guided to the intake pipe, and in a state where the substantially stoichiometric air-fuel ratio is not detected, the feedback integration of the air-fuel ratio is performed. And a control unit that performs duty control in accordance with the value, for example, in a state where the air-fuel ratio is not at the stoichiometric air-fuel ratio, without performing a large amount purge of the evaporated fuel gas, accurately controlling the stoichiometric air-fuel ratio. Further, it is possible to provide a fuel evaporative gas leakage prevention device that can prevent further deterioration of exhaust gas and is advantageous in promoting exhaust gas purification measures.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a fuel evaporative gas leak preventing device according to one embodiment of the present invention, and FIG. 2 is a drive pulse signal output from a control unit to a duty control valve in the fuel evaporative gas leak preventing device. FIG. 3 (A) to FIG.
(C) respectively shows the map and temperature coefficient and the air-fuel ratio coefficient determines the duty ratio of the drive pulse signal in the second view, sky Figure 4 is obtained by the O ₂ sensor of the fuel evaporative emission leak preventing device The figure which shows the feedback integral value and the drive signal duty ratio with respect to a fuel ratio, FIG.
FIG. 6 is a diagram showing a duty control operation of a duty control valve with respect to a feedback integral value according to an air-fuel ratio of the fuel evaporative gas leakage prevention device, and FIG. 6 is a diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Engine body, 3 ... Intake pipe, 4 ... Fuel evaporative gas passage, 5 ... Reservoir tank,
6 ... purge hole, 7 ... canister, 9 ... activated carbon storage chamber, 10 ... fuel evaporative gas introduction chamber, 11 ... purge fuel discharge chamber, 12 ... partition plate, 13 ... filter, 14 ... activated carbon , 15
…… Outside air inlet, 16… Duty control valve, 21… Control unit, 22 …… Accel pedal switch, 23 …… Exhaust pipe, 24
…… O ₂ sensor, 26 …… Supercharger, 27 …… Valve, 27a ……
Inlet, 27b …… Discharge port.

Claims (1)

(57) [Claims] A fuel evaporative gas passage connecting the fuel tank and an air supply pipe of the engine main body; a canister for adsorbing the evaporative fuel gas is interposed in the fuel evaporative gas passage; At the time of operation stop and idling operation, the evaporated fuel gas is adsorbed by the activated carbon in the canister, and during the acceleration operation other than the idling operation of the engine body, the evaporated fuel gas adsorbed by the activated carbon in the canister is purged, In the fuel evaporative gas leakage prevention device in which the purge evaporative fuel gas is supplied into the intake pipe, a duty control valve interposed in a purge fuel supply path between the canister and the intake pipe to open and close the purge fuel supply path When the O ₂ sensor for detecting the change in the air-fuel ratio is provided in an exhaust pipe of the engine body, engine During shut-down and idling of the main body holding the duty control valve in a closed state, the duty control valve in a state in which the stoichiometric air-fuel ratio is detected by the O ₂ sensor at the time of acceleration operation other than idling of the engine body And a control unit for performing a duty control in accordance with a feedback integral value of the air-fuel ratio in a state where substantially no stoichiometric air-fuel ratio is detected, while fully opening the valve and maximizing a flow rate of the purge fuel guided to the intake pipe side. A device for preventing leakage of fuel evaporative gas.