Fuel vapor treatment canister

Details Fuel vapor treatment canister Fuel vapor treatment canister

2000-12-26

2003-01-07

Smith, Duane S. (Department: 1724)

Gas separation: apparatus

Solid sorbent apparatus

Plural solid sorbent beds

C096S135000, C096S144000, C123S519000

Reexamination Certificate

active

06503301

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in a fuel vapor treatment canister which is adapted to temporarily store therein fuel vapor generated in a fuel tank and the like and to release the stored fuel vapor at certain timings to be burnt in an engine in order to reduce the amount of fuel vapor emitted from the fuel tank and the like of a vehicle provided with the engine.
2. Description of the Prior Art
Hitherto most automotive vehicles are equipped with a fuel vapor treatment canister including fuel vapor adsorbing material (for example, crushed or granulated activated carbon) stored in a casing. Fuel vapor generated from a fuel tank is adsorbed by the fuel vapor adsorbing material, and then the adsorbed fuel vapor is desorbed from the fuel vapor adsorbing material at certain timings and carried to a combustion device (for example, combustion chambers of an engine, or a combustibles burning device of a vehicle equipped with a fuel cell) under the action of air flowing through the fuel vapor adsorbing material. This prevents fuel vapor from being released into the atmosphere. It will be understood that fuel vapor is generated in the fuel tank, for example, in the following cases:
(a) When an automotive vehicle is allowed to stand, fuel vapor is generated at a high temperature in the daytime under a temperature change between day and night.
(b) When the vehicle is stopped after its cruising (particularly after its high speed cruising), heat of an engine at a high temperature is transmitted to the fuel tank or the like. At this time, the temperature of the fuel tank or the like abruptly rises so that fuel vapor is generated in the fuel tank or the like.
(c) When fuel is supplied into the fuel tank, fuel vapor is generated in the fuel tank.
A typical example of such a conventional fuel vapor treatment canister is disclosed in Japanese Patent Provisional Publication No. 9-112356 and will be discussed with reference to FIG.
13
A.
The fuel vapor treatment canister
101
includes a casing
102
C. The casing
102
C includes a cylindrical casing body
102
which is provided at its one end with a first end wall
103
, and at the other end with a second end wall
104
. The first end wall
103
has a pipe defining therein a communication opening
103
a
which is in communication with the atmospheric. The second end wall
104
has an upper pipe defining therein a fuel vapor inlet opening
104
a
which is in communication with a fuel tank so that fuel vapor is flown in through the opening
104
a.
The second end wall
104
further has a lower pipe defining therein a fuel vapor outlet opening
104
b
which is in communication with an air intake passage of an intake system of an internal combustion engine (not shown) so that fuel vapor is flown out through the opening
104
b.
A perforated dish-like plate
107
is disposed inside the casing body
102
and located adjacent the second end wall
104
. The disk-like plate
107
is formed with a plurality of through-holes (not identified) and has a cylindrical flange section (not identified) which is fitted to the inner surface of the casing body
102
and in contact with the second end wall
104
so that a space
106
is defined between the dish-like plate
107
and the second end wall
104
. A sheet-like filter
108
formed of a non-woven fabric of polyester or a sheet of polyurethane foam is disposed inside the dish-like plate
107
so as to be in contact with the dish-like plate
107
.
A perforated plate
110
is disposed inside the casing body
102
and located adjacent the first end wall
103
. Two compression springs
112
,
112
are disposed between the perforated plate
110
and the first end wall
103
so as to define a space
109
inside the casing body
102
. A filter
111
similar to the filter
108
is disposed inside and in contact with the perforated plate
110
. A chamber or inside space Ra between the filter
108
and the filter
111
. The chamber Ra is filled with a fuel vapor adsorbing material A
1
a
and a heat-accumulative material A
2
a
which is higher in heat conductivity and specific heat than the fuel vapor-adsorbing material A
1
a
which are in a uniformly mixed state.
In operation, fuel vapor flowing in the canister
101
through the opening
104
a
is adsorbed by the fuel vapor adsorbing material A
1
a.
At this time, the distribution of concentration of the adsorbed fuel is as shown in
FIG. 13B
in which the concentration of the fuel vapor is gradually saturated from a side near the second end wall
104
to a side near the first end wall
103
. When the adsorption state has reaches a level at which fuel vapor is adsorbed by a portion of the fuel vapor adsorbing material A
1
a
located near the first end wall
103
, fuel vapor is released in an amount according to the concentration of the adsorbed fuel vapor at the portion through the opening
103
a.
It is to be noted that heat is generated so as to raise the temperature of the fuel vapor adsorbing material A
1
a
when fuel vapor is adsorbed by the fuel vapor adsorbing material A
1
a.
A fuel vapor amount corresponding to fuel vapor adsorbing ability of the fuel vapor adsorbing material A
1
a
increases as the temperature rises. However, the heat generated by the fuel vapor adsorbing material A
1
a
is adsorbed by the heat-accumulative material A
2
a
thereby preventing the temperature of the fuel vapor adsorbing material A
1
a
from rising. This prevents the fuel vapor amount corresponding to the fuel vapor adsorbing ability from being lowered.
In the intake stroke of an operational cycle of the engine, vacuum is generated in the air intake passage of the engine and transmitted through the opening
104
b
into the casing
102
C. Accordingly, atmospheric air is introduced through the opening
103
a
into the casing
102
C so as to develop air stream toward the opening
104
b.
Under the action of this air stream, fuel vapor (hydrocarbons) adsorbed by the fuel vapor adsorbing material A
1
a
is desorbed and sucked through the opening
104
b
and the air intake passage into the engine to be combusted in the engine.
As shown in
FIG. 14A
, during desorption of the fuel vapor adsorbed by the fuel vapor adsorbing material A
1
a
after fuel vapor adsorption indicated in
FIG. 13B
, the concentration of the adsorbed fuel vapor (or a fuel vapor residual level) takes a mode indicated by curves V
1
which indicates the case where the fuel vapor adsorbing material A
1
a
and the heat-accumulative material A
2
a
are disposed in the chamber Ra. For reference, a curve V
2
indicates a case where only the fuel vapor adsorbing material A
1
a
such as activated carbon is disposed in the chamber Ra.
Additionally, as shown in
FIG. 14B
, during adsorption of fuel vapor by the fuel vapor adsorbing material A
1
a
after fuel vapor desorption of
FIG. 14A
, the concentration of the adsorbed fuel vapor takes a mode indicated by a curve V
3
which indicates the case where the fuel vapor adsorbing material A
1
a
and the heat-accumulative material A
2
a
are disposed in the chamber Ra. For reference, a curve V
4
indicates a case where only the fuel vapor adsorbing material A
1
a
such as activated carbon is disposed in the chamber Ra.
FIG. 14B
reveals that the fuel vapor residual level (the concentration of the adsorbed fuel vapor) at the respective positions in an axial direction of the canister is low in the case where the fuel vapor adsorbing material A
1
a
and the heat-accumulative material A
2
a
are disposed in the chamber Ra as compared with that in the case where only the fuel vapor adsorbing material A
1
a
is disposed in the chamber Ra. This is because, in case that the fuel vapor adsorbing material A
1
a
and the heat-accumulative material A
2
a
are disposed in the chamber Ra, heat accumulated in the heat-accumulative material A
2
a
is transmitted to the fuel vapor adsorbing material A
1
a
during desorption of fuel vapor from the fuel vapor adsorbing material A
1
a,
so that the temperature of the fuel vapor adsorbing

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