Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-11-27
2002-07-09
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S516000
Reexamination Certificate
active
06415772
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 11-362735 filed on Dec. 21, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an evaporative emission control system and, more particularly, to an evaporative emission control system for a fuel tank installed in a motor vehicle, such as an automobile.
2. Description of Related Art
It has been known in the art that a fuel tank installed in a motor vehicle, such as an automobile, be equipped with an evaporative emission control system which prevents fuel evaporative emission (fuel vapors) generated in the fuel tank from flowing or escaping to the outside of the tank. One example of such a system is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. HEI 8-276757.
In such an evaporative emission control system, as shown in
FIG. 10
by way of example, a back pressure chamber
74
and a tank chamber
76
of a differential pressure valve
72
mounted in a fuel tank
70
are separated or partitioned from each other by a diaphragm, constituting a valve portion
80
. A communicating hole
82
for communication between the back pressure chamber
74
and the tank chamber
76
of the differential pressure valve
72
is formed through the valve portion
80
. With this arrangement, liquid fuel that has flown into he back pressure chamber
74
of the differential pressure valve
72
may be returned into the fuel tank
70
through the communicating hole
82
.
In the above evaporative emission control system, if the liquid surface
84
A of the fuel
84
in the fuel tank
70
is inclined such that its level becomes higher on the side of a fuel fill pipe
86
than on the other side of the tank, during a vehicle turn or other mode of running of the vehicle, as shown in
FIG. 10
, the air pressure in the back pressure chamber
74
escapes or releases into the tank chamber
76
through the communicating hole
82
, as indicated by an arrow W
1
in FIG.
10
. Thus, a large amount of fuel
84
is likely to flow into the fuel fill pipe
86
and a recirculation conduit
88
formed in communication with the fill pipe
86
.
When the fuel tank
70
shifts from the state as shown in
FIG. 10
, to the state in which the liquid surface
84
A of the fuel
84
in the fuel tank
70
is inclined such that its level is lower on the side of the fuel fill pipe
86
than on the other side as shown in
FIG. 11
, a relatively long period of time is required until a large amount of fuel
84
that has entered the fill pipe
86
and the recirculation conduit
88
returns to the inside of the fuel tank
70
. During the period of time in which the large amount of fuel
84
that has entered the fill pipe
86
and the recirculation conduit
88
takes to return to the inside of the fuel tank
70
, a negative pressure builds up in the back pressure chamber
74
of the differential pressure valve
72
, whereby the valve portion
80
is placed in the open position. As a result, a large amount of evaporative fuel flows from the fuel tank
70
to a canister (not shown).
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an evaporative emission control system capable of reducing the amount of evaporative fuel that flows into a canister during running of the vehicle.
To accomplish the above object, the present invention provides an evaporative emission control system. A differential pressure valve controls fluid communication between a canister and a fuel tank. The differential pressure valve includes a diaphragm that separates a first chamber and a second chamber of the differential pressure valve from each other, and a valve seat that faces the diaphragm, the differential pressure valve being placed in a selected one of an open state in which the diaphragm is spaced apart from the valve seat, and a closed state in which the diaphragm rests on the valve seat. The diaphragm has a communicating hole formed therethrough. A closure member is positioned and configured to close the communicating hole of the diaphragm when the differential pressure valve is placed in the closed state, the communicating hole communicating with the first and second chambers when the differential pressure valve is placed in the open state.
In the aforementioned evaporative emission control system, when the liquid surface of fuel within the fuel tank is inclined during a vehicle turn or other running mode of the vehicle, such that the level of the liquid surface becomes higher on the side of a fuel fill pipe than on the other side of the fuel tank, the differential pressure valve is placed in the closed state with the diaphragm resting upon the valve seat, and therefore the communicating hole formed through the diaphragm is closed by the closure member. As a result, the air pressure in the back pressure chamber is inhibited from escaping into the tank chamber through the communicating hole, and therefore only a small amount of fuel is introduced into the fuel fill pipe. If the liquid surface of fuel within the fuel tank is subsequently inclined such that the level of the liquid surface becomes lower on the side of the fuel fill pipe than on the other side of the fuel tank, a negative pressure is produced in the back pressure chamber of the differential pressure valve, whereby the diaphragm is lifted away from the valve seat. In this state, since the communicating hole communicates with the back pressure chamber and the tank chamber, the small amount of fuel that has entered the fill pipe can return to the fuel tank within a short period of time. Although the diaphragm is spaced apart from the valve seat (the differential pressure valve is held in the open state) while the fuel that has entered the fill pipe
12
is returning to the fuel tank, it is possible to restrict or reduce the amount of evaporative fuel flowing toward the canister during running of the vehicle because only a short period of time is required to drain the fill pipe.
To accomplish the above object, the present invention also provides a differential pressure valve that controls fluid communication between a canister and a fuel tank. The differential pressure valve includes a diaphragm that separates a back pressure chamber and a tank chamber of the differential pressure valve from each other, and a valve seat that faces the diaphragm, the differential pressure valve being opened when the diaphragm is moved away from the valve seat. The differential pressure control valve includes a communicating portion that communicates with the back pressure chamber and the tank chamber, and a closure member positioned and configured to close the communicating portion when a pressure within the back pressure chamber is higher than a pressure within the tank chamber. The closure member permits the communicating portion to communicate with the back pressure chamber and the tank chamber before opening of the differential pressure valve when the pressure within the back pressure chamber becomes lower than the pressure within the tank chamber.
In one preferred embodiment of the invention, the closure member as indicated just above may be a check valve.
In the aforementioned evaporative emission control system, when the liquid surface of fuel within the fuel tank is inclined during a vehicle turn or other running mode of the vehicle, such that the level of the liquid surface becomes higher on the side of the fuel fill pipe than on the other side of the fuel tank, a pressure higher than at least the pressure in the tank chamber is applied to the back pressure chamber of the differential pressure valve, and the communicating portion between the back pressure chamber and the tank chamber is closed by the check valve. As a result, the air pressure in the back pressure chamber is kept from escaping into the tank chamber through the communicating portion, and therefore only an extremely small amount of fuel flows into the fuel fill pipe. If the liquid
Taga Takanori
Yoshioka Mamoru
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Miller Carl S.
Toyota Jidosha & Kabushiki Kaisha
LandOfFree
Evaporative emission control system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Evaporative emission control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evaporative emission control system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2871159