Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-03-08
2001-05-15
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S520000, C123S557000
Reexamination Certificate
active
06230693
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates, in general, to the reduction of evaporative emissions from motor vehicles. More specifically, the invention relates to an evaporative emission control system employing a heated adsorber.
BACKGROUND OF THE INVENTION
Evaporative emissions of fuel vapor from a vehicle having an internal combustion engine occur principally due to venting of the fuel tank of the vehicle. When the vehicle is parked, diurnal changes in temperature or pressure of the ambient atmosphere cause air to waft into and out of the fuel tank. Some of the fuel inevitably evaporates into the air within the tank and thus takes the form of a vapor. If the air emitted from the fuel tank were allowed to flow untreated into the atmosphere, it would inevitably carry with it this fuel vapor. The fuel vapor, however, is a pollutant. For that reason, federal and state governments have imposed increasingly strict regulations over the years governing how much fuel vapor may be emitted from the fuel system of a vehicle.
One approach that automobile manufacturers have long employed to reduce the amount of fuel vapor that a vehicle emits to the atmosphere involves the use of a storage canister. In this approach, a tube, often referred to as a “tank tube,” is used to connect the air space in the fuel tank to the storage canister. Inside the storage canister is contained a sorbent material, typically activated carbon, whose properties enable it to adsorb the fuel vapor. Consequently, when air flows out of the tank, the tank tube carries it to the storage canister wherein the fuel vapor is adsorbed into the sorbent material There the fuel vapors are temporarily stored so that they can be burned later in the engine rather than being vented to the atmosphere when the engine is not operating.
FIGS. 1 and 2
illustrate one type of storage canister, generally designated
10
, typically used in the automotive industry.
FIG. 1
shows the canister in a perspective view, whereas
FIG. 2
shows it in cross-section. The storage canister
10
comprises a container
18
that is partially divided by partition
24
into two compartments
20
and
22
. An intercompartmental flow passage
26
connects these compartments.
The storage canister
10
has a tank port
12
and a purge port
14
, both of which communicate with the first compartment
20
. The tank port
12
connects to the tank tube
7
, and thereby allows the air space in the fuel tank
8
to communicate with the first compartment
20
. To the left of the tank port
12
as viewed from the perspective of
FIG. 2
, the purge port
14
connects to a purge line
19
. Through a purge valve
15
, the purge line
19
connects to the air intake passage
9
of the vehicle
11
. (Air flowing into the air intake passage
9
is mixed with fuel, and the mixture eventually drawn into the cylinders for combustion.) The purge valve
15
is closed when the engine is not running. When the engine is running, however, purge valve
15
is opened in and thereby allows the storage canister
10
via the first compartment
20
to communicate with the air intake
9
.
The storage canister
10
also features a vent port
16
that communicates with the second compartment
22
. The vent port
16
connects to a vent line
6
. The vent line
6
communicates with the ambient atmosphere through a vent valve
17
. Typically controlled via a solenoid, the vent valve
17
is normally held open. When opened, the vent valve
17
allows the storage canister
10
via the second compartment
22
, vent port
16
and vent line
6
to communicate with the atmosphere. The vent valve
17
is closed when the storage canister
10
is being tested for leaks.
Evaporative emission control systems of this type essentially have two phases of operation. During the storage phase when the engine is off, the system operates with the purge valve
15
closed and the vent valve
17
opened. When the pressure in the fuel tank
8
is high relative to atmospheric pressure, air from the tank and the fuel vapor it carries flows into tank tube
7
and through tank port
12
into storage canister
10
. Inside the storage canister
10
, the fuel vapor is adsorbed by the sorbent material
28
as the air that carried it flows not only through the first compartment
20
but also through the second compartment
22
via intercompartmental flow passage
26
. Although a high percentage of the fuel vapor is adsorbed into the sorbent material
28
, the air as it exits the canister
10
via vent port
16
carries with it some unadsorbed fuel vapor to atmosphere.
During the regenerative phase of operation when the engine
90
is running, the system operates with both the purge valve
15
and the vent valve
17
opened. A vacuum is developed within the intake manifold as a result of the combustion occurring within the cylinders of the engine
90
. This vacuum ultimately causes fresh air from the atmosphere to be drawn through vent valve
17
and into the storage canister
10
. Specifically, the air is pulled by vacuum through vent port
16
, second compartment
22
, flow passage
26
, first compartment
20
and out purge port
14
. Inside the storage canister
10
, as the fresh air flows through the sorbent material
28
, it strips it of the fuel vapor that it had adsorbed during the previous storage cycle. The sorbent material
28
is thus regenerated for the next storage phase. The purged fuel vapors are carried by the air stream through purge line
19
, purge valve
15
, air intake passage
9
and to the cylinders where they are consumed as fuel during combustion.
During the storage phase, the fuel vapors previously adsorbed by the sorbent material
28
may also return to the fuel tank
8
when the pressure in the tank lowers relative to atmospheric pressure. This happens when the temperature inside the fuel tank
8
drops and the fuel vapors condense. Being normally open, the vent valve
17
under such conditions allows air into the storage canister
10
and relieves any vacuum.
Due to the increasingly stringent air quality standards, the automotive industry has pondered several ways of further reducing the emissions of evaporated fuel. Thought has been given to increasing the size or number of compartments in the storage canister
10
. Those approaches have been deemed undesirable due to excessive cost and bulk. Various proposals for heating the storage canister
10
electrically have also been considered. Those approaches have also proved undesirable due to the electrical power they would require.
OBJECTIVES OF THE INVENTION
It is therefore an objective of the invention to reduce emissions of evaporated fuel from a motor vehicle to levels lower than previously achievable.
Another objective is to provide an evaporative emission control system having improved diurnal performance.
Still another objective is to capture minute breakthrough emissions from an evaporative emission control system.
A further objective is to enable the use of modern internal combustion engine fuels having increased volatility without increasing evaporative emissions.
An additional objective is to provide heat to assist the endothermic desorption process in an evaporative emission control system.
Yet another objective is to desorb adsorbed water from high retentivity carbon in an evaporative emission control system.
Yet another objective is to provide an evaporative emission control system for a motor vehicle having a superabsorber that is protected from contamination during fueling.
An additional objective is to provide an evaporative emission control system that employs heat to assist desorption of vapor and which minimizes electrical heating requirements.
Another objective is to provide an evaporative emission control system that reduces emissions to ultra-low levels, and one that is rugged and easy to maintain.
A further objective is to reduce the amount of partitioning needed in storage canisters used in such evaporative emission control systems.
Yet a further objective is to reduce the size of storage canisters used in such ev
Covert Charles Henry
Labine Susan Scott
Meiller Thomas Charles
Wagner Richard William
Cichosz Vincent A.
Delphi Technologies Inc.
Moulis Thomas N.
LandOfFree
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