Patent Publication Number: US-8529676-B2

Title: Fuel vapor adsorption canister

Description:
This application claims priority to Japanese Patent Application Serial Number 2010-085779, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to canisters trapping fuel vapor vaporized in a fuel tank. 
     2. Description of the Related Art 
     A gas vehicle such as automobile is provided with a canister as fuel vapor processor for treating fuel vapor (for example, gasoline vapor) vaporized in a fuel tank. The canister has generally a casing shaped as hollow container, and adsorbents housed in the casing. The casing has a fuel introducing port configured to introduce the fuel vapor vaporized in the fuel tank into the canister, an air communicating port configured to introduce ambient air into the canister, and an exhaust port connected to an air intake pipe for an internal combustion engine. The adsorbents are composed of activated carbon or the like, which can adsorb and desorb the fuel vapor. Thus, the fuel vapor vaporized in the fuel tank flows into the casing through the fuel introducing port and adsorbs onto the adsorbents during parking, etc. Then, ambient air is introduced into the casing through the air communicating port such that the fuel vapor is desorbed from the adsorbents and then is introduced into the engine via the exhaust port together with the air. 
     When a gas containing the fuel vapor is introduced into an adsorption chamber defined in the casing through the fuel introducing port, the fuel vapor is trapped by the adsorbents in the adsorption chamber. Then, the gas substantially consisting of the air is released into the atmosphere through the air communicating port. However, when a large amount of the fuel vapor flows into the canister during refueling, etc., a portion of the fuel vapor may not adsorb onto the adsorbent and may flow through the canister and into the atmosphere. 
     Japanese Laid-Open Patent Publication No. 2001-323845 discloses a canister having a plate in a chamber filled with adsorbents. The plate has one or more holes at its upper section for preventing the fuel vapor from passing through the canister and from flowing into the atmosphere. The plate increases airflow resistance in the adsorption chamber so that the fuel vapor remains in the adsorption chamber for a longer time. Accordingly, it is able to increase an adsorption efficiency of the fuel vapor by the adsorbent, resulting in decrease in the fuel vapor released into the atmosphere. However, because some of the adsorbents are disposed between the plate and an air communicating port, the fuel vapor desorbing from such adsorbent may flow into the atmosphere. Therefore, there has been a need in the art for an improved canister. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present teachings, a canister for trapping a fuel vapor vaporized in a fuel tank has a casing defining an adsorption chamber therein, an adsorbent capable of adsorbing the fuel vapor and filled in the adsorption chamber and a flow regulation plate disposed in the casing. The casing has a fuel introducing port configured to introduce the fuel vapor from the fuel tank into the adsorption chamber, and an air communicating port communicating the adsorption chamber with the atmosphere. The air communicating port is formed on a side surface of the casing extending in a direction of gravitational force. The flow regulation plate disposed at an end of the adsorption chamber near the air communicating port and has an opening configured to communicate the adsorption chamber with the air communicating port. The opening is positioned above the air communicating port in the direction of gravitational force. 
     In accordance with this aspect, the fuel vapor in the adsorption chamber must move upwardly in the direction of gravitational force against its own weight for flowing into the atmosphere via the air communicating port, so that it is able to substantially prevent the fuel vapor in the adsorption chamber from flowing into the atmosphere. In addition, because the flow regulation plate increases a flow resistance in the adsorption chamber, the fuel vapor remains in the adsorption chamber for a longer time. Thus, it is able to improve adsorption efficiency of the fuel vapor. Furthermore, the flow regulation plate guide the fuel vapor upwardly toward its opening, so that it is able to increase area where the fuel vapor flows through. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a horizontal cross-sectional view of a canister of a first embodiment; 
         FIG. 2  is a vertical cross-sectional view of the canister of the first embodiment; 
         FIG. 3  is a perspective view of a flow regulation unit of the first embodiment; 
         FIG. 4  is a vertical cross-sectional view of the canister of a second embodiment; and 
         FIG. 5  is a vertical cross-sectional view of the canister of a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved canisters. Representative examples of the present invention, which examples utilized many of these additional features and teachings both separately and in conjunction with one another, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skilled in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples and the dependent claims may be combined in ways that are not specifically enumerated in order to provide additional useful embodiments of the present teachings. 
     A first embodiment of this disclosure will be described with reference to accompanying drawings. A canister described below corresponds to a fuel vapor processor mounted on a gas vehicle or the like and is configured to temporarily trap fuel vapor (such as gasoline vapor) vaporized in a fuel tank. Here, when directions are not defined specifically, terms “upward” and “downward” intend to mean “upward” direction and “downward direction” in the direction of gravitational force, respectively. In addition, flow directions “upstream” and “downstream” are defined based on a flow of the fuel vapor flowing through a fuel introducing port, one or more adsorption chambers and an air communicating port of a canister. 
     Firstly, a canister  10  will be described in reference to  FIG. 1 .  FIG. 1  is a horizontal cross-sectional view of the canister  10 . The canister  10  is configured to temporarily trap fuel vapor vaporized in a fuel tank. The canister  10  has a casing  20  having an opening and a lid  21  configured to close the opening. 
     The casing  20  is shaped as a hollow container as shown in  FIG. 1 . The casing  20  has three ports each communicating inside and outside of the casing  20 . One of the ports is a fuel introducing port  22  for introducing the fuel vapor vaporized in the fuel tank into the canister  10 . The fuel introducing port  22  is communicated with the fuel tank via a pipe. Another one of the ports is an exhaust port  23  for discharging the fuel vapor from the canister  10 . The fuel introducing port  22  and the exhaust port  23  are formed alongside on one wall portion of the casing  20 . The exhaust port  23  is communicated with an air intake pipe of an engine or the like via a pipe. The other of the ports is an air communicating port  24  for releasing air after removing the fuel vapor and for introducing ambient air into the canister  10 . The air communicating port  24  is communicated with a fresh air inlet (not shown) for introducing ambient air. 
     The casing  20  has a partition wall  25  dividing an inner space of the casing  20  into a first adsorption chamber  11  and a second adsorption chamber  12 . The partition wall  25  is formed integrally with the casing  20 . The first adsorption chamber  11  is communicated with the fuel introducing port  22  and the exhaust port  23  via a filter  26 . On the other hand, the second adsorption chamber  12  is communicated with the air communicating port  24  via a filter  27 . The first adsorption chamber  11  and the second adsorption chamber  12  are communicated with each other via a communicating chamber  13 , which is defined on the side opposite to the fuel introducing port  22 , the exhaust port  23  and the air communicating port  24 . 
     The casing  20  has a partition  28  protruding from the wall portion toward a center of the first adsorption chamber  11  such that the partition  28  divides the first adsorption chamber  11  into a first section near and directly communicating with the fuel introducing port  22  and a second section near and directly communicating with the exhaust port  23 . The partition  28  is formed integrally with the casing  20 . 
     The first adsorption chamber  11  and the second adsorption chamber  12  are filled with adsorbents  14  capable of adsorbing and desorbing the fuel vapor. The filter  26  and the filter  27 , which are disposed in the first adsorption chamber  11  and the second adsorption chamber  12 , respectively, are porous and have a large number of pores smaller than a diameter of the adsorbents  14 . Thus, it is able to hold the adsorbents  14  in the first adsorption chamber  11  and the second adsorption chamber  12 . 
     The first adsorption chamber  11  of the casing  20  has an opening side opposite to the fuel introducing port  22  and the exhaust port  23 . And, the opening side is closed with an inner lid  29 . Here, an opening side of the second adsorption chamber  12  is also closed with another inner lid  29 . Because configurations of the inner lids  29  for the first adsorption chamber  11  and the second adsorption chamber  12  are substantially same, the inner lid  29  for the first adsorption chamber  11  will be described, whereas the inner lid  29  for the second adsorption chamber  12  will not be described. 
     The inner lid  29  is composed of a filter  30  and a porous plate  31  and allows air to pass therethrough. And, the inner lid  29  holds the adsorbents  14  in the first adsorption chamber  11 . The inner lid  29  is configured to move slidably along an inner surface of the canister  20  while closing the opening side of the first adsorption chamber  11 . Between the inner lid  29  and the lid  21  a coil spring  32  is provided such that one end of the coil spring  32  is connected to the inner lid  29  and the other end of the coil spring  32  is connected to the lid  21 . Accordingly, when the opening of the casing  20  is closed with the lid  21 , the inner lid  29  is pressed toward the first adsorption chamber  11  by the coil spring  32 . Therefore, it is able to prevent generation of unnecessary space between particles of the adsorbents  14  in order to keep the flow resistance constant in the first adsorption chamber  11 . 
     For trapping the fuel vapor in the canister  10 , the fuel vapor is introduced into the casing  20  via the fuel introducing port  22 , and is flowed through the first adsorption chamber  11 , the communicating chamber  13  and the second adsorption chamber  12 , and then is discharged from the canister  20  via the air communicating port  24 . The partition  28  prevent the fuel vapor introduced into the first adsorption chamber  11  through the fuel introducing port  22  from flowing out through the exhaust port  23 . On the other hand, for removing the fuel vapor from the canister  20 , air (ambient air) is introduced into the casing  20  through the air communicating port  24 , and is flowed through the second adsorption chamber  12 , the communicating chamber  13  and the first adsorption chamber  11 , and then is discharged through the exhaust port  23 . That is, this canister  10  has a U-shaped flow pathway. In addition, the canister  20  is mounted horizontally on a bottom surface of a vehicle body. Thus, when the fuel vapor flows from the fuel introducing port  22  to the air communicating port  24 , the fuel vapor flows in a substantially horizontal direction. 
     As shown in  FIG. 1  and  FIG. 2 , a first flow regulation plate  40  is disposed in the second adsorption chamber  12  along the filter  27 . The first flow regulation plate  40  has an elongated opening  42  extending in a horizontal direction and positioned near an upper end of the flow regulation plate  40  such that spaces at each side of the first flow regulation plate  40  are communicated with each other via the opening  42 . The first flow regulation plate  40  regulates a flow of the fuel vapor toward the air communicating port  24  in the second adsorption chamber  12 . Thus, the fuel vapor remains in the second adsorption chamber  12  for a longer time, and diffuses in a larger area of the second adsorption chamber  12 , so that it is able to efficiently adsorb the fuel vapor onto the adsorbents  14 . The first flow regulation plate  40  is positioned at one end space of the second adsorption chamber  12  near the air communicating port  24  and along the filter  27 . The opening  42  is formed on an upper portion of the first flow regulation plate  40  in the direction of gravitational force. Accordingly, the fuel vapor flowing into the second adsorption chamber  12  must move upwardly against its own weight to the opening  42  positioned above the air communicating port  24  in order to flow out through the air communicating port  24 . This upward moving distance is increased due to provision of the first flow regulation plate  40 , so that it is more difficult for the fuel vapor to flow into the atmosphere from the second adsorption chamber  12  than a case without the first flow regulation plate  40 . In addition, because the first flow regulation plate  40  makes the fuel vapor flow upwardly, the fuel vapor can reach areas, which the fuel vapor cannot reach without any flow regulator such as the first flow regulation plate  40 . Therefore, because a larger amount of the adsorbents  14  can adsorb the fuel vapor, the canister  10  can trap the fuel vapor more efficiently. 
     In a case that adsorbents are disposed between the first flow regulation plate  40  and the air communicating port  24 , the fuel vapor can flow through the air communicating port  24  and into the atmosphere just after desorbing from such adsorbents. However, in this embodiment, the first flow regulation plate  40  is disposed at the end space of the second adsorption chamber  12 , and thus is disposed between the air communicating port  24  and the adsorbents  14  filled in the second adsorption chamber  12 . Accordingly, the fuel vapor desorbing from the adsorbents  14  in the second adsorption chamber  12  must move upwardly to the opening  42  in the second adsorption chamber  12 , and most of the fuel vapor may adsorb onto the adsorbents  14  again in the second adsorption chamber  12  during upward movement. Therefore, it is able to decrease the fuel vapor flowing out of the air communicating port  24 . 
     In the second adsorption chamber  12 , a second flow regulation plate  41  is disposed upstream from the first flow regulation plate  40 . The first flow regulation plate  40  has the opening  42  above the air communicating port  24  in the direction of gravitational force, whereas the second flow regulation plate  41  has an opening  42  below the air communicating port  24  in the direction of gravitational force. Accordingly, the fuel vapor flows through both of the openings  42  in the second adsorption chamber  12 , so that the moving distance of the fuel vapor in the second adsorption chamber  12  is increased due to provision of the first and the second fuel regulation plates  40  and  41 . Therefore, the fuel vapor contacts with a larger amount of the adsorbents  14 , so that it is able to efficiently adsorb the fuel vapor onto the adsorbents  14 . 
     In this embodiment, the first flow regulation plate  40  and the second flow regulation plate  41  are connected each other by connection portions  43  and are integrally constructed of a resin as a flow regulation unit  44 . Thus, it is able to easily place the first and the second flow regulation plates  40  and  41  in the second adsorption chamber  12  and to adequately keep a distance between the first and the second flow regulation plates  40  and  41  at a predetermined distance. In addition, the flow regulation unit  44  has a seal member  45  such as O-ring along an outer circumference of the flow regulation unit  44 . When the flow regulation unit  44  is disposed in the second adsorption chamber  12 , the seal member  45  sealingly contacts with both an inner surface of the casing  20  and the partition wall  25 . Thus, it is able to prevent the fuel vapor from flowing between the outer circumference of the flow regulation unit  44  and either the inner surface of the casing  20  or the partition wall  25 . 
     The adsorbents  14  filled in the first adsorption chamber  11  and the second adsorption chamber  12  are composed of activated carbon capable of adsorbing the fuel vapor, such as extruded activated carbon or granular activated carbon. Here, the granular activated carbon has smaller diameter than the extruded activated carbon. The extruded activated carbon combines powdered activated carbon with binder, which are generally extruded into a cylindrical shape. The diameter of the granular activated carbon is about 0.7-2.0 mm, whereas the diameter of the extruded activated carbon is about 2.0-2.5 mm. 
     In this embodiment, the first flow regulation plate  40  and the second flow regulation plate  41  increase the flow resistance in the second adsorption chamber  12 . Accordingly, the adsorbents  14  are composed of the extruded activated carbon having larger diameter in order to decrease the flow resistance such that it is able to prevent excessive retention of the fuel vapor in the casing  20 . In addition, in a case that the flow resistance in the second adsorption chamber  12  is excessively high, it is not able to introduce the fuel vapor into the canister  10  from the fuel tank adequately and an inner pressure of the fuel tank does not decrease adequately. As a result, it may be difficult to refuel the fuel tank due to the excessively elevated inner pressure of the fuel tank. However, use of the extruded activated carbon decreases the flow resistance in the second adsorption chamber  12 , and thus can resolve such problem. 
     The adsorbents  14  filled in the first adsorption chamber  11  and the second adsorption chamber  12  can be mixed with heat storage materials. Various materials can be used as the heat storage materials, for example phase-change heat storage materials capable of absorbing and releasing heat depending on changes in temperature. Furthermore, the heat storage materials can be constructed in a granular shape of a mixture of binders and microcapsules containing phase-change heat storage materials therein. 
     In a second embodiment, one flow regulation plate  46  is disposed in the second adsorption chamber  12  as shown in  FIG. 4 . The flow regulation plate  46  is positioned at an end near the air communicating port  24  in the second adsorption chamber  12 , i.e., at the most downstream position in the second adsorption chamber  12 . The flow regulation plate  46  has an opening  42  above the air communicating port  24  in the direction of gravitational force. Accordingly, the flow regulation chamber  46  can regulate a flow of the fuel vapor in the second adsorption chamber  12  and prevent the fuel vapor in the second adsorption chamber  12  from flowing into the atmosphere via the air communicating port  24  like the first flow regulation plate  40  of the first embodiment. Here, because other configurations of the second embodiment are same as or similar to those of the first embodiment, they are labeled with the same reference numbers as those of the first embodiment, respectively, and will not be described. 
     In a third embodiment, a flow regulation unit  48  having four flow regulation plates  47  parallel to each other is disposed in the second adsorption chamber  12  as shown in  FIG. 5 . Each of the first and the third flow regulation plates  47  along a flow direction of the fuel vapor in the canister  10  (in a direction from right to left in  FIG. 5 ) has an opening  42  at a lower portion, i.e., below the air communicating port  24  in the direction of gravitational force, on the other hand, each of the second and the fourth flow regulation plates  47  has an opening  42  at an upper portion, i.e., above the air communicating port in the direction of gravitational force. And, the opening  42  of the fourth flow regulation plate  47 , which is disposed at the most downstream in the flow direction, is positioned above the air communicating port  48 . Therefore, the openings  42  of the flow regulation plates  47  are positioned alternately at the upper portions and the lower portions, i.e., above and below the air communicating port  24 . Accordingly, the flow regulation unit  48  can regulate the flow of the fuel vapor in the second adsorption chamber  12  and prevent the fuel vapor desorbing from the adsorbents  14  from flowing into the atmosphere through the air communicating port  24 . In addition, the flow regulation unit  48  increases the moving distance of the fuel vapor in the second adsorption chamber  12 , so that it is able to adsorb the fuel vapor onto the adsorbents more efficiently. 
     In accordance with the canister  10  of this embodiment, a plurality of the flow regulation plates are formed integrally and used as a single unit, so that it is able to easily change the flow resistance in the adsorption chambers by exchanging the flow regulation unit without changing shape of the casing  20 . Thus, it is able to provide the canister  10  suitable performance depending on a type of a vehicle and usage environment by only change of the flow regulation unit. 
     In other embodiments, the number of the flow regulation plates is not limited to one, two or four, and can be increased or decreased. 
     The casing  20 , the flow regulation plates and the flow regulation unit can be formed integrally in order to decrease the number of parts and to simplify manufacturing process. 
     In the above-described embodiments, the opening  42  is formed in the elongated shape. However, the opening  42  can be formed in other shapes such as a plurality of bores. 
     In the above-described embodiments, the adsorbents  14  are composed of the extruded activated carbons. However, the granular activated carbon having smaller diameter can be filled in at least one of the first adsorption chamber  11  and the second adsorption chamber  12  instead of the extruded activated carbon in order to provide a preferred flow resistance.