Patent Publication Number: US-2015075380-A1

Title: Activated-carbon filter with storage volume for a fuel tank

Description:
The invention relates to an activated-carbon filter with a storage tank for a fuel tank. 
     Liquid-fuel tanks, in particular for motor vehicles, usually have a breather orifice enabling the internal pressure and atmospheric pressure to be equalized, for example when the fuel level changes as a result of the tank being filled or the fuel being used by the engine, or in the event of temperature changes. 
     There are a number of solutions used to ensure compliance with pollution regulations and to limit atmospheric emissions of hydrocarbon fumes. 
     A first solution, often used for hybrid motor vehicles, i.e. vehicles including heat and electric propulsion systems, involves closing the fuel tank using a calibrated valve. The fuel tank is then pressurized, which makes it more complex and expensive to build, as well as requiring means for opening and closing the valve. 
     A second solution involves fitting motor vehicles with a filter that traps and stores these fumes from the tank before recycling them in the engine. These filters, known as “canisters”, usually comprise a housing containing activated carbon. The recycling of fumes from the tank in the heat engine by purging the activated-carbon filter is controlled by a management system. Such purges must be performed regularly to ensure the filter works correctly. 
     Such filters may be used both in heat-engine vehicles and hybrid-engine vehicles. However, the heat engine in hybrid vehicles may not operate for several days in a row, or the operating mode of the heat engine may not command the filter to be purged, such that said filter is not purged for several days, which may result in emissions of hydrocarbon fumes into the atmosphere in contravention of pollution regulations. 
     To overcome this problem, a solution described in document WO2011/020627A1 involves providing an additional fume-storage tank located between the tank and the carbon filter, and outside the latter. This solution is nonetheless relatively cumbersome and may be difficult to implement, in particular in a hybrid vehicle in which the batteries and the electric motor occupy a significant volume. This solution is also relatively complex and requires pipes linking the additional tank to the fuel tank and to the activated-carbon filter, and valves isolating the additional tank, which increases the risks of leaks from the whole. 
     There is therefore a need for an activated-carbon filter of simple design and limited size that nonetheless provides high storage capacity, enabling compliance with prevailing regulations. 
     For this purpose, a first subject of the invention is an activated-carbon filter for a fuel tank supplying a heat engine of a motor vehicle, said carbon filter comprising a casing fitted with an input orifice that can be connected to said fuel tank, a purge orifice that can be connected to said heat engine and a breather orifice, characterized in that said casing includes at least one internal wall dividing the internal volume thereof into at least two chambers communicating with one another, at least one activated-carbon chamber containing the activated carbon able to trap gaseous hydrocarbons, and a storage chamber forming a storage volume for a gas flow entering via the input orifice of the casing. 
     Notably, the casing has at least two internal walls. 
     A first internal wall divides the internal volume thereof into at least two chambers communicating with one another, at least one activated-carbon chamber containing the activated carbon able to trap gaseous hydrocarbons, and a storage chamber forming a storage volume for a gas flow entering via the input orifice of the casing. 
     A second internal wall extends longitudinally such as to separate the purge orifice from at least one of the input and breather orifices. 
     The activated-carbon filter according to the invention therefore has a storage volume built into the casing of the filter, which saves space and simplifies assembly, this solution not requiring any pipes or valves to isolate the storage volume. The activated-carbon filter according to the invention is also less liable to leaks than a system incorporating an additional separate tank and a set of valves and pipes to connect this additional tank to the filter and/or to the fuel tank. 
     Furthermore, the presence of a storage chamber enables the saturation time of the activated-carbon filter to be delayed, thereby delaying the moment at which the activated-carbon filter has to be purged. The activated-carbon filter according to the invention can therefore be used in heat-engine vehicles to increase the saturation time if pollution regulations are made more stringent, or can be used to ensure compliance with these regulations when used in hybrid-engine vehicles. 
     The volume of the storage chamber may in particular be determined as a function of a target number of days before saturation of the activated carbon contained in the activated-carbon chamber or chambers. This number of days may be defined by prevailing regulations and may be from 1 to 3 days. The car manufacturer may also choose to increase the number of days as a function of the anticipated use of the heat engine. 
     This storage volume inside the casing of the activated-carbon filter also allows less activated carbon to be used when compared to a conventional activated-carbon filter of equal casing volume (without internal storage volume), while keeping the saturation time constant. It is therefore possible to reduce costs, since activated carbon is relatively expensive, which may be beneficial, in particular for heat-engine vehicles. 
     Advantageously, said storage chamber is placed upstream of an activated-carbon chamber in relation to the gas flow entering via the input orifice and exiting via the breather orifice. This arrangement requires the gas flow entering the activated-carbon filter to fill the storage chamber before passing through the activated carbon, delaying entry of the gas flow into the activated-carbon chamber, which delays saturation of the activated carbon. 
     Specifically, the casing of the activated-carbon filter may include at least two activated-carbon chambers containing activated carbon, said storage chamber being placed upstream of one activated-carbon chamber and downstream of another activated-carbon chamber in relation to the gas flow entering via the input orifice and exiting via the breather orifice. Notably, this arrangement enables different types of activated carbon to be used in the two activated-carbon chambers, thereby improving adsorption of the hydrocarbon gas flows. It also helps to reduce pressure drops through the activated-carbon filter, enabling more activated carbon to be used than in the embodiment described below. 
     Advantageously, if the activated-carbon filter according to the invention includes at least one activated-carbon chamber and at least one storage chamber, and in particular one activated-carbon chamber and one storage chamber, the activated-carbon chamber and the storage chamber are separated by a gas-impermeable internal wall that extends along most of the length of the casing, the input orifice of the casing leading to one extremity of the storage chamber along the length of said casing and said storage chamber communicating with the activated-carbon chamber at an extremity opposite said input orifice. 
     This arrangement enables the input orifice of the activated-carbon filter to be placed in a low position when it is connected to the fuel tank, the longitudinal axis of the carbon filter being for example close to vertical, enabling any condensed fuel vapors to return to the fuel tank. 
     To provide a gas flow path inside the activated-carbon chamber, an internal gas-impermeable wall may be placed inside this chamber, extending along some of the length of the casing, in particular from the purge orifice side. 
     The purge orifice usually communicates with the activated-carbon chamber. For example, the input orifice and the purge orifice of the casing may be arranged at opposing extremities of the casing along the length of the casing. 
     The breather orifice also usually communicates with the activated-carbon chamber. For example, it may be located on the same extremity of the casing as the purge orifice of the casing or on the extremity of the casing opposite the extremity with the purge orifice of the casing. 
     In the latter case, the breather orifice may then be placed in a low position of the activated-carbon filter, if the longitudinal axis of the latter is close to vertical when in use. 
     In this case, water may penetrate this breather orifice, which may disturb operation or purging of the activated-carbon filter. To overcome this drawback, the breather orifice may lead to another chamber separated from the activated-carbon chamber by a gas-impermeable wall extending along most of the length of the casing, one extremity of said other chamber being connected to the activated-carbon chamber via the breather orifice, and the other extremity of this other chamber communicating with the atmosphere. 
     Furthermore, the volume of this other chamber may be used to contain a supplementary adsorbent agent to improve the gas hydrocarbon retention of the activated-carbon filter. 
     If the activated-carbon filter according to the invention includes at least two activated-carbon chambers, and in particular two activated-carbon chambers, the two activated-carbon chambers may be separated by a gas-impermeable internal wall extending along the length of the casing as far as a gas-permeable transverse internal wall extending along the entire width of the casing. This arrangement has the advantage of being particularly compact, enabling it to be used in hybrid-engine vehicles. It also enables the use of different types of activated carbon in each of the chambers and causes limited pressure drops. 
     The gas-permeable internal wall may for example also be used to support the activated carbon contained in each of the activated-carbon chambers. For this purpose, it may be held in position by pressurizing means, such as springs. 
     Another subject of the invention is a motor vehicle with a heat engine supplied by a fuel tank, and incorporating an activated-carbon filter according to the invention. 
    
    
     
       The invention is described below with reference to the attached drawings, which are non-limiting, in which: 
         FIG. 1   a  is a top view of an activated-carbon filter according to the invention, 
         FIG. 1   b  is a cross-section taken from  FIG. 1   a  along the line A-A in  FIG. 1   a,    
         FIG. 2  is a cross-section similar to  FIG. 1   b  of another embodiment of the invention, 
         FIG. 3  is a cross-section similar to  FIG. 1   b  according to another embodiment of the invention, 
         FIG. 4  is a perspective view of another embodiment of the invention, 
         FIG. 5  is a cross-section of the embodiment shown in  FIG. 4 . 
     
    
    
     The terms “upper” and “lower” relate to a vertical position of the carbon filter, i.e. when the longitudinal axis of the carbon filter is vertical. 
       FIG. 1   a  shows an activated-carbon filter  10  for a fuel tank supplying a heat engine of a motor vehicle. 
     This activated-carbon filter  10  includes a casing  12  fitted with an input orifice  14  that can be connected to said fuel tank. The casing  12  is also fitted with a purge orifice  16  that can be connected to a heat engine, and a breather orifice  18 . 
     According to the invention, the casing  12  includes at least one internal wall dividing the internal volume thereof into at least two chambers communicating with one another. 
     In the example shown in  FIGS. 1   a  and  1   b , an internal wall  20  separates the internal volume of the casing into an activated-carbon chamber  22  and a storage chamber  24  forming a storage volume for a gas flow entering via the input orifice  14  of the casing. 
     The activated-carbon filter  10  is arranged such that the storage chamber  24  is placed upstream of the activated-carbon chamber  22  in relation to the gas flow entering via the input orifice  14  and exiting via the breather orifice  18 . 
     In the example shown, the activated-carbon chamber  22  has a generally cylindrical shape, while the storage chamber  24  has a general parallelepiped rectangle shape ( FIG. 1   a ). The invention is however not limited to these specific shapes. 
     The internal wall  20  separating the two chambers  22 ,  24  is a gas-impermeable wall that extends along most of the length of the casing  12 . 
     “Most” means that this wall  20  extends along 80% of the length of the casing, or even along 90-95% of the length of the casing  12 . 
     The input orifice  14  of the casing  12  leads to one extremity of the storage chamber  24  along the length of the casing  12 , located in the lower zone of the casing  12  in the example. 
     The storage chamber  24  communicates with the activated-carbon chamber  22  at an extremity opposite this input orifice  14 , in the upper zone of the casing  12 . The breather orifice  18  and the purge orifice  16  are located at the same extremity of the casing  12 , opposite the input orifice  14 . 
     In the example shown, the activated-carbon chamber  22  is also separated substantially into two by an internal wall  26  extending along most of the length of the casing from the extremity of the activated-carbon chamber  22  connected to the breather orifice  18  and the purge orifice  16 . This wall  26  extends longitudinally between the purge orifice  16  and the breather orifice  18  ( FIG. 1   b ). 
     The activated carbon contained in the activated-carbon chamber  22  is held in position by means of gas-permeable walls  28 ,  30 . These may be perforated plates or grilles, for example. 
     These perforated plates or grilles  28 ,  30  are arranged substantially perpendicular to the longitudinal axis of the casing  12 . The upper grille  28  is preferably fixed while the lower grille  30  is removable and held in position by a cover  32  and a retaining spring  34  located between the cover  32  and this lower grille  30 . 
     The purge orifice  16  and the breather orifice  18  are arranged above the grille  28  along the length of the casing, such that the activated-carbon chamber communicates with these two orifices. The internal wall  20  stops level with the grille  28 , thereby communicating the storage chamber  24  with the activated-carbon chamber  22 . 
     The activated-carbon filter shown in  FIGS. 1   a  and  1   b  works as follows: 
     During the charging phases (broken-line arrow), the fumes from the fuel tank enter via the input orifice  14  and fill the storage chamber  24 , before entering the activated-carbon chamber  22  via the grille  28  and passing through the activated-carbon chamber  22  along a substantially U-shaped path as far as the breather orifice  18 . 
     During the purge phases of the activated-carbon filter, the fumes move in the opposite direction (following the solid-line arrow) to the purge orifice  16 . 
     The embodiment shown in  FIG. 2  differs from the embodiment shown in  FIG. 1  in the position of the purge orifice and of the breather orifice. 
     In this embodiment, the activated-carbon filter  110  includes a casing  112 , an input orifice  114 , a purge orifice  116 , and a breather orifice  118 . An internal wall  120  separates the inside of the volume of the casing  112  into an activated-carbon chamber  122  and a storage chamber  124 . The input orifice  114  is located at a lower extremity of the casing  112 , while the purge orifice  116  is located at the opposite extremity of the casing  112 . The breather orifice  118  is located on the extremity opposite the purge orifice  116 , beneath the activated-carbon chamber  122 . 
     Plates  128 ,  130  hold the activated carbon placed inside the activated-carbon chamber  122 , and the entire surface area of the lower grille  130  leads to the breather orifice  118 , which may be formed in a cover  132 . 
     The internal wall  120  stops level with the grille  128 , thereby communicating the storage chamber  124  with the activated-carbon chamber  122 . 
     An internal wall  126  extends longitudinally inside the activated-carbon chamber  122  for a short distance from this grille  128 , such as to separate the purge orifice  116  and the communicating passage between the storage chamber  124  and the activated-carbon chamber  122 . This internal wall  126  extends for example along at least half of the length of the casing, or at least one third or at least one quarter of this length. 
     On the upper extremity of the casing  112 , the grille  128  thus leads from one side of the internal wall  126  to the storage chamber  124 , and from the other side of the internal wall  126  to the purge orifice  116 , which is arranged above the grille  128  along the length of the casing, thereby ensuring communication with the activated-carbon chamber  122 . 
     The activated-carbon filter shown in  FIG. 2  works as follows: 
     During the charging phases, the fumes move from the input orifice  114  filling the storage chamber  124 , then enter the activated-carbon chamber  122  via the left-hand side of the grille  128 , and pass through the entire length of this activated-carbon chamber  122  as far as the breather orifice  118  (flow represented by a broken-line arrow). 
     During the purge phases (solid-line arrow), the fumes move in the opposite direction and pass through the entire length of the activated-carbon chamber  122  from the breather orifice  118  to the purge orifice  116 . 
       FIG. 3  shows an embodiment very similar to the embodiment shown in  FIG. 2 . As a result, the same reference signs have been used to indicate the same elements. 
     The only difference with the embodiment shown in  FIG. 2  is that the breather orifice  118  leads to a chamber  134  separated from the activated-carbon chamber  122  by a gas-impermeable wall  136 . This gas-impermeable wall  136  extends along most of the length of the casing. One extremity of this chamber  134  is therefore connected to the activated-carbon chamber via the breather orifice  118 , while the other extremity of this chamber  134  communicates with the atmosphere, on the upper side of the casing  112  close to the purge orifice  116 . 
     The carbon filter shown in  FIG. 3  works identically to the one shown in  FIG. 2 . 
       FIGS. 4 and 5  show an activated-carbon filter  210  comprising a casing  212  fitted with an input orifice  214 , a purge orifice  216  and a breather orifice  218  on the upper extremity thereof. 
     A gas-impermeable internal wall  220  extends along the length of the casing  212  as far as a gas-permeable transverse internal wall  221  extending along the entire width of the casing  212 . 
     The internal wall  220  separates the upper part of the casing into two activated-carbon chambers  222 ,  223 . 
     The transverse internal wall  221  separates these two activated-carbon chambers  222 ,  223  from a storage chamber  224  occupying the lower volume of the casing  212 . The breather orifice  218  leads to the upper part of one of the activated-carbon chambers  222 , the input orifice  214  and the purge orifice  216  leading to the upper part of the other carbon chamber  223 . 
     Two transverse grilles  228  separate the activated carbon contained in each activated-carbon chamber  222 ,  223  from the orifices leading thereto. 
     The transverse internal wall  221  also supports the activated carbon contained in the activated-carbon chambers  222 ,  223 . For this purpose, retaining elements  234 , such as springs, located between a cover  232  and this internal wall  221  hold the latter against the internal wall  220 . 
     In this example, the volume of the storage chamber  224  represents substantially half of the volume of the two activated-carbon chambers  222 ,  223 . 
     The activated-carbon filter  210  shown in  FIGS. 4 and 5  works as follows: 
     During the charging phases (broken-line arrow), the fumes move from the input orifice  214  via an activated-carbon chamber  223 , then pass through the internal wall  221  and fill the storage chamber  224  before penetrating the other activated-carbon chamber  224  as far as the breather orifice  218 . 
     During the purge phases (solid-line arrow), the fumes move in the opposite direction from the breather orifice  218  to the purge orifice  216 . 
     All types of activated carbon can be placed in the activated-carbon chambers of the filter according to the invention.