Device for recovering gasoline vapors

The device includes a filter containing a material which adsorbs the vapors coming from a tank. The filter is connected through a first duct to the upper part of the tank, through a second duct to a source of depression and through a third duct to a source of air for regenerating the adsorbent material. Apparatus is provided for heating the regenerating air. The device further includes apparatus for regulating the temperature of the air flowing in the third duct, this apparatus has a temperature response control element disposed in the filter. The device is particularly useful in automobile vehicles.

The present invention relates to devices for recovering gasoline vapors 
coming from the gasoline tank of a motor vehicle. 
Such devices are known which comprise a filter for adsorbing said gasoline 
vapors, this filter being connected through a first duct to the upper part 
of the tank, through a second duct to a source of depression which is 
generally constituted by the intake circuit of the engine, and through a 
third duct to a source of air for regenerating the adsorbent material, 
means being provided if desired for heating this regenerating air. 
Such a device fixes the gasoline vapors which come from the tank owing to 
the evaporation of the gasoline, in particular in hot weather, or to the 
displacement of the mass of gas overlying the liquid in the tank when the 
latter is being filled. 
The material adsorbing said gasoline vapors may be activated carbon which 
becomes charged with the gasoline vapors when the gas flows from the first 
duct to the second duct via the filter and which is regenerated when it is 
swept through by a counter-current of the regenerating air flowing from 
the third duct to the second duct. This sweeping occurs by aspiration in 
the second duct which is due in particular to the depression prevailing in 
the intake circuit of the engine when the latter is running. 
The effectiveness of the regeneration is improved if the sweeping or 
purging air has sufficient temperature and this is why a heating of this 
air has been proposed in a known arrangement. However, such a heating is 
liable to cause an overheating of the activated carbon and consequently to 
rapidly deteriorate the latter. 
An object of the invention is to improve the operating capacity of a filter 
incorporated in a device for recovering gasoline vapors, without running 
the risk of a rapid deterioration of the active material contained in this 
filter. The invention also proposes, owing to the improvement of this 
capacity, reducing the dimension of the filter and consequently the price 
and overall size thereof. 
The invention therefore provides a device for recovering gasoline vapors 
from a tank, comprising a filter containing a material for adsorbing said 
vapors, said filter being connected through a first duct to the upper part 
of the tank, through a second duct to a source of depression, and through 
a third duct to a source of air for regenerating the adsorbent material, 
and means for heating the regenerating air, wherein regulating means are 
provided which act on the regenerating air heating means and comprise a 
temperature responsive control element disposed in the filter. 
According to other features of the invention: 
the control element is carried by a metal plate embedded in the mass of 
adsorbent material; 
the heating and regulating means comprise a heating resistor connected in 
series with the control element; 
the third duct is connected to a source of cold air and to a source of hot 
air under the control of a closure member; 
the closure member is actuated by a depression capsule connected to an 
intake pipe of the engine through a thermovalve constituting the control 
element; 
an electrical valve controlled as a function of at least one operating 
parameter of the engine is placed between the thermovalve and the intake 
pipe; 
an electrical valve controlled as a function of at least one operating 
parameter of the engine is placed in the second duct; 
the control element and/or said electrical valves are controlled by a 
computer which controls and manages the operation of the engine.

FIG. 1 shows diagrammatically a fuel tank 1 in an automobile vehicle. This 
tank comprises a filling pipe 2 and, extending from a point located in the 
upper part of the pipe, is a first duct 3 connected to a filter 4 
containing a material 5 capable of adsorbing the gasoline vapors, for 
example activated carbon. Extending from this filter is a second duct 6 
connected to a source 7 of depression which is preferably the intake pipe 
of the engine (not shown) of the vehicle. 
The filter is connected through a third duct 8 to a source 9 of air for 
regenerating the activated carbon. 
Placed in this duct 8 is an electric resistor 10 which may be supplied with 
current by the battery of the vehicle. This resistor is connected in 
series with a switch 11 which is closed when the engine is running and 
with a cell 12 having a positive temperature coefficient carried by a 
metal plate 13, for example composed of aluminum, embedded in the mass of 
activated carbon. The cell 12 constitutes a probe whose resistance varies 
as a function of the temperature of the mass of activated carbon. The 
metal plate 13 performs the function of a radiator whereby it is possible 
to bring the temperature of the cell to the temperature of the 
environment. 
The resistance of the cell 12 varies as a function of the temperature in 
accordance with the curve shown in Fig. 2. Above T.sub.a , this resistance 
very rapidly increases. The operation of the device is then as follows: 
The gasoline vapors coming from the tank through the duct 3 are fixed in 
the filter by adsorption on the activated carbon 5, in particular when 
filling the tank or when the vehicle is operating in very hot weather. 
When the engine of the vehicle is running, the activated carbon is 
regenerated, since a stream of air, coming from the duct 8 and aspirated 
through the duct 6, flows therethrough. The fact of heating this airstream 
by means of the resistor 10 facilitates this regeneration and increases 
the operating capacity of the activated carbon. It will be recalled in 
this respect that this operating capacity is measured by the difference 
between the mass of the filter in the saturated state and its mass in the 
purged or regenerated state. 
During the regenerating stage, the cell 12 having a positive temperature 
coefficient responds to the temperature prevailing in the mass of 
activated carbon. So long as this temperature remains lower than the value 
T.sub.a , its electric resistance is low so that the current can pass 
therethrough and the resistor 10 gives off by the Joule effect a 
relatively large amount of heat causing the heating of the activated 
carbon. 
On the other hand, when the temperature of the activated carbon exceeds the 
value T.sub.a , the resistance of the cell 12 increases and renders the 
amount of heat given off by the resistor 10 by the Joule effect very low 
or even negligible. The heating of the activated carbon is interrupted and 
its temperature becomes stabilized. 
It will be understood that the characteristics of the cell 12 are so 
determined that its own heating by the Joule effect is negligible relative 
to that due to the heating resistor 10. 
By way of example, an order of magnitude of the electrical power given off 
by the heating resistor 10 may be a few tens of watts. 
The diagram of FIG. 3 shows the supply circuit of the heating resistor 10 
and the cell 12 having a positive temperature coefficient, this circuit 
being controlled for example by a computer 20 which controls and manages 
the operation of the engine and is so arranged as to allow the purge or 
the regeneration of the filter only when a number of conditions related to 
the operation of the engine are in effect satisfied. Thus, the computer 
may be connected to suitable means 21, 22, 23 known per se which deliver 
thereto signals representing the temperature of the coolant water of the 
engine, the load on the latter and the control of the richness of the 
mixture fed to the engine. By way of example, the purge will only be 
allowed if the engine is sufficiently warm, if the load thereon exceeds a 
given value, and if the richness of the intake mixture is controlled and 
regulated at a given value. 
In the diagrams of FIGS. 1 and 3, the cell 12 having a positive temperature 
coefficient may be replaced by a thermocontact carried by the metal plate 
which is normally closed and opens when the temperature exceeds a given 
value. 
In another embodiment shown in FIG. 4, the duct 8 may be connected, under 
the action of a flap 30, either to a source 31 of cold air or to a source 
32 of hot air. In the last mentioned case, the air may be heated by 
putting it in contact with the exhaust pipe of the engine. This flap 30 is 
controlled by a depression capsule 33 controlled by a thermovalve 34 
mounted on the metal plate 13 embedded in the mass 5 of activated carbon. 
For this purpose, the capsule 33 is connected through a duct 35 to the 
thermovalve 34, itself connected through a second duct 36 to a source of 
depression obtained by a branch connection 37 to the intake circuit 38 of 
the engine. In the case of FIG. 4, this branch connection is located on 
the downstream side of the gasoline control butterfly valve 39 so that it 
is constantly subjected to a depression when the engine is running. 
Placed in the duct 36 is an electrical valve 40 controlled by a computer 41 
controlling and managing the operation of the engine, this computer being, 
as before, arranged to process data representing the temperature of the 
coolant liquid of the engine, the load and the richness of the mixture, 
delivered by probes or other suitable means 42, 43, 44. 
Provided in the duct 6 leading to the same branch connection 37 is an 
electrical valve 45 controlled by the same computer. This control of the 
electrical valve 45 has for purpose to purge or regenerate the filter 
under such conditions that this purge does not create a substantial 
disturbance in the feeding of fuel to the engine, since the gasoline 
vapors coming from the filter are thereafter transmitted to the intake of 
the engine. 
In the case of FIG. 5, the same main arrangements of the diagram of FIG. 4 
are found except that the branch connection 37a is located on the upstream 
side of the gasoline control butterfly valve when the latter is closed; 
The location of this branch connection is so chosen that the depression 
created therein when the butterfly valve is opened corresponds to the 
desired level of the load on the engine for allowing the purge in the 
filter 4. In this case, the computer merely has to take into account the 
temperature of the coolant liquid of the engine and the regulation of the 
richness of the mixture fed to this engine. 
The device then operates in the following manner: 
With the filter charged with gasoline vapors through the duct 3, in 
particular when filling the tank or when the vehicle is stationary in very 
hot weather, the filter is regenerated when the conditions of operation of 
the engine allow the purge through the duct 6, the computer 41 then 
delivering to the electrical valves 40 and 45 an opening signal. This puts 
the capsule 33 under depression and causes the displacement of the flap 30 
to a position in which it closes the cold air supply duct 31 and opens the 
hot air supply duct 32. A stream of hot air then flows through the filter 
toward the duct 6 and this stream is regulated by the thermovalve 34 which 
acts through he medium of the capsule 33 on the flap 30 to ensure that the 
temperature of the activated carbon does not exceed a given value. 
In the various illustrated embodiments in which modifications may of course 
be made, the operating capacity of the activated carbon filter is improved 
and it is consequently possible to reduce its dimensions and even its cost 
and overall size. This is of particular interest in the envisaged 
application in which it is associated with an automobile vehicle tank.