Abstract:
In order to discharge air cleaned free from evaporated fuel vapor in a canister installed under the front seat floor, have none of the air coming inside a passenger room and inhibit water, dirt and dust from being absorbed in a drain pipe in a canister, the following drain pipe in a canister is invented. The drain pipe in canister is connected with a canister body installed under a front seat floor of a vehicle. The drain pipe in the canister comprises a first part extending from the canister body up to an upper portion of an engine room disposed on a front side of a passenger room, and a second part extending from the first part to a portion under a floor of the passenger room.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the foreign priority benefit under Title 35, United States Code, §119(a)-(c), of Japanese Patent Application No. 2006-05685 5 , filed on Mar. 2, 2006 with the Japanese Patent Office, the disclosure of which is herein incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a drain pipe connected with a canister system installed under the floor of a vehicle on which front seats are attached. 
         [0003]    Conventionally a vehicle is provided with a canister system to contain an active charcoal functioning as an absorbent to have fuel vapor adsorbed, as indicated, for instance, by such references as Japanese Utility Model Registration No. 2582688, Japanese Laid-open Patent Application No. H09-49460 and Japanese Laid-open Patent Application No. 2005-313667. 
         [0004]    There is a drain pipe attached to the canister body through which cleaned air after the fuel vapor is adsorbed and removed is to be discharged into the atmosphere and air in the atmosphere is to be taken in. Generally speaking the canister system for a vehicle is installed in either an engine room of a vehicle, under a rear seat floor of a vehicle or under a front seat floor of a vehicle as indicated, for instance, by such references as Japanese Utility Model Registration No. 2582688, Japanese Laid-open Patent Application No. H09-49460 and Japanese Laid-open Patent Application No. 2005-313667. 
         [0005]    In the case of a canister system installed in an engine room, the canister body is fixed on a vehicle body on the front side of the dash board, as indicated, for instance, by Japanese Utility Model Registration No. 2582688. A drain pipe with a lower end open, which communicates with the atmosphere, is attached to the lower part of the canister body. 
         [0006]    In the case of a canister system installed under a rear seat floor of a vehicle, a canister body is fixed on the front side of a rear fender, while a drain filter (filter box) connected through a drain pipe (drain passage) with the canister body and a discharge pipe are installed on the rear side of the rear fender. The cleaned air after the fuel vapor is adsorbed and removed is discharged into the atmosphere through this discharge pipe. 
         [0007]    In the case of the canister system indicated by Japanese Utility Model Registration No. 2582688 and Japanese Laid-open Patent Application No. HEI9-49460, no fuel vapor flows into a passenger room and no water comes into the canister body in case the vehicle floor is flooded with water because the canister body is located higher than the vehicle floor. 
         [0008]    The canister system disposed under the front seat floor of a vehicle is attached in a so called center tank vehicle in which the passenger room of the rear seats is made relatively spacious and the center of gravity is located relatively low, while a fuel tank is installed under the front seat floor, as indicated by Japanese Laid-open Patent Application No. 2005-313667. Especially in the case of the center tank vehicles equipped with On-board Refusing Vapor Recovery ( to be abbreviated as ORVR hereinafter) capable of recovering fuel vapor, a canister body is installed adjacent to and in the vicinity of the fuel tank and connected with a fuel tank through a vent pipe (communication pipe). Thanks to this configuration, the fuel vapor generated from inside the fuel tank is adsorbed on the adsorbent and the air communication resistance between the fuel tank and the canister body is reduced. Moreover a drain pipe is attached to the canister body to take in air from the atmosphere when purging the canister body to have the adsorbed fuel sent to an engine. 
         [0009]    However there is an drain opening located at a relatively low position under the vehicle floor in the case of the center tank vehicle equipped with ORVR, which is described in Japanese Laid-open Patent Application No. 2005-313667. Through this drain opening such water as from rainwater and dirt and dust are easily absorbed together with air from the atmosphere into a canister system. As a result, there is a problem with a drain filter being easily clogged. 
         [0010]    The present invention is to solve the aforementioned problem and intended to provide the drain pipe in the canister system which is installed under the front seat floor of a vehicle, prevent the air after fuel vapor is adsorbed and removed from flowing into a passenger room and inhibit water, dirt and dust being absorbed into a drain filter. 
       SUMMARY OF THE INVENTION 
       [0011]    A first aspect of the present invention provides a drain pipe in a canister system which is connected with a canister body and installed under a front seat floor of a vehicle, the drain pipe in the vehicle, comprising a first part extending from the canister body up to an upper space of an engine room disposed on a front side of a passenger room, and a second part extending from the first part to a space under the passenger room, which communicates with an atmosphere under the floor of the passenger room. 
         [0012]    According to the first aspect of the present invention, the drain pipe has its one end connected with the canister body which is disposed under the front seat floor of the vehicle and extends to an upper portion of the engine room and further back to a portion under a floor of the passenger seat with the other end exposed to the atmosphere. 
         [0013]    As a result, fuel vapor in the upper portion in the fuel tank is adsorbed in the canister body and the air cleaned free from the fuel vapor is transported once to the engine room and then back to under the passenger seat floor and discharged into the atmosphere without coming inside the passenger room. Moreover dirt and dust are inhibited from coming inside the canister system. 
         [0014]    A second aspect of the present invention provides a drain pipe in a canister system according to the first aspect, further comprising a drain filter installed at or in a vicinity of a highest portion of the drain pipe in the canister system. 
         [0015]    According to the second aspect of the present invention, a drain filter is installed at a relatively high position in the drain pipe and kept a sufficiently long distance off the road surface where there remains dirt and dust, or water. As a result, dirt and dust, or water drops are prevented from coming up to the drain filter and the drain filter is not clogged. 
         [0016]    A third aspect of the present invention provides a drain pipe in a canister system according to the second aspect, further comprising a branch pipe which an auxiliary pipe branches from and is installed in a vicinity of the drain filter and on an atmosphere exposed side of the drain filter, wherein the branch pipe has a double concentric pipe structure. 
         [0017]    According to the third aspect of the present invention, the drain pipe is equipped with a branch pipe from which the branch pipe branches in the vicinity of the drain filter and on the atmosphere exposed side of the drain filter and the branch pipe has a double pipe structure. Due to this double pipe structure, air coming through the drain filter is inhibited from flowing into the auxiliary pipe while air flows to and from the auxiliary pipe when the flow resistance of the main drain pipe becomes high. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The object and features of the present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0019]      FIG. 1  is a side elevation view briefly illustrating a fuel tank system inclusive of a drain pipe in a canister system of the present invention; 
           [0020]      FIG. 2  is a plan view briefly illustrating a drain pipe in a canister system of the present invention; 
           [0021]      FIG. 3  is a perspective exploded view of essential parts of a drain pipe in a canister system of the present invention; 
           [0022]      FIG. 4  is a enlarged figure indicating a drain pipe in a canister system of the present invention seen from under a vehicle and the installation condition of a canister body; 
           [0023]      FIG. 5  is an enlarged cross sectional view illustrating the drain pipe in a canister system seen when cut along the X-X line in  FIG. 4 ; and 
           [0024]      FIG. 6  is an enlarged cross sectional view illustrating a drain pipe in a canister system of the present invention and an essential part of a drain pipe in a canister system. 
       
    
    
       [0025]    The same or corresponding elements or parts are designated with like references throughout the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    A drain pipe in a canister system on an embodiment of the present invention is to be explained hereinafter in detail referring to  FIG. 1  through  FIG. 6 .  FIG. 1  indicates an approximate side view of a drain pipe in a canister system on an embodiment of the present invention. 
         [0027]    Prior to explaining a drain pipe in a canister system on an embodiment of the present invention, a vehicle C in which a drain pipe D is installed, an explanation is made on a fuel tank T to be installed in the vehicle C, a fuel tank system A and a fuel vapor collecting unit. 
       Structure of the Vehicle 
       [0028]    As described in  FIG. 1 , the vehicle C in which the drain pipe D is installed is a so-called center tank vehicle in which a center of gravity is made relatively located low, a fuel tank T and a canister body  61  are installed under a floor of a front seat  1  (under a floor panel Cb) and a relatively large space is created on the back side of a passenger room R. In a vehicle like the vehicle C, a fuel replenishment inlet  3   a  is located on the back side of a rear seat  2  and a filler pipe  3  and a vapor return tube  4  both of which extend from the fuel replenishment inlet  3   a  to the fuel tank T are made relatively long. The floor panel Cb is located at so low a position that the rear seat  2  is folded flat to be flush with a luggage floor Ca. Therefore in order not to have the vapor return tube interfere with the floor panel Cb or others, there is a lowered portion  4   a  of the vapor return tube  4  between the middle of the fuel tank T and the rear wheel. On both ends of this lowered portion  4   a  the vapor return tube  4  is curved. 
         [0029]      FIG. 2  shows a rough plan view illustrating a drain pipe in a canister system of an embodiment of the present invention. 
       Fuel Tank Structure 
       [0030]    The fuel tank T shown in  FIG. 1  and  FIG. 2  is intended for storing fuel and a filler pipe  3 , one of whose end is connected with a fuel replenishment inlet  3   a , is connected to the fuel tank T through an inlet valve V 1  and a fuel neck tube  3   b  on the rear end side of the fuel tank T. Above the fuel tank T the vapor return tube  4 , one of whose end is connected with the filler pipe  3  in the vicinity of the fuel replenishment inlet  3   a  which is located at a relatively high position, is installed along the filler pipe  3 . 
         [0031]    The vapor return tube  4  is meant for circulating a part of the air in the upper part of the inside of the fuel tank T into the filler pipe  3  in the vicinity of the fuel replenishment inlet  3   a . This vapor return tube  4  has also a function of reducing the amount of the air coming from the atmosphere into the fuel tank T through the fuel replenishment inlet  3   a  and the filler pipe  3 . 
         [0032]    As indicated in  FIG. 1  and  FIG. 2  there is a canister body  61  which is installed in parallel with the fuel tank T and connected with the fuel tank T through a vent pipe  14 . On the front side of the canister body  61  a drain pipe D is attached and extends through a vent shut valve V 4  to a drain filter  62  installed at an upper space in an engine room ER located on the front side of the passenger room R. The drain pipe D further extends back to the space under the floor of the passenger room R from the drain filter  62  and has the end opened and exposed to the atmosphere. The fuel tank T is installed on a lower side of the floor panel Cb under the front seats and fixed on the floor panel Cb with a couple of tank bands  12  ( see  FIG. 4 ). 
         [0033]    As indicated in  FIG. 2  a pump module P, a vapor return float valve  5 , a fuel replenishment float valve  7  are installed on the upper surface of the fuel tank T. The main part of the pump module P is inside the fuel tank T. Each of the fuel replenishment float and the fuel replenishment float has a float valve which is to be closed when the fuel tank is full of fuel. 
       Structure of Fuel Tank System 
       [0034]    As indicated in  FIG. 2  a fuel tank system A is composed of the fuel tank T, the filler pipe  3 , the vapor return tube  4 , an intake manifold  15 , a fuel vapor collecting system B and a damage detection unit O. In the fuel vapor collecting unit B the fuel vapor generated in the upper portion of the inside of the fuel tank is transported to the canister system  6  not to have the fuel vapor come out to the outside while the fuel tank replenishment is under way. A damage detection unit O detects a hole in the pipes for the fuel tank replenishment if there is. The intake manifold  15  makes the pressure in the pipes inclusive of the fuel tank T, the filler pipe  3  and the vapor return tube  4  negative with respect to the atmosphere. 
         [0035]      FIG. 3  shows an exploded perspective view illustrating an essential part of a drain pipe in a canister system of the present invention. 
         [0036]    The pump module P illustrated in  FIG. 3  is equipped with a suction filter not shown, a fuel pump to transport the fuel to an injector  8  shown in  FIG. 2  through the fuel pipe  9 , a fuel level meter not shown to detect the fuel level in the fuel tank T and a cut valve V 3  connected with the canister body  61  through a fuel replenishment float valve  7 , a vent relief valve V 2  and a vent pipe  14 , which constitutes a whole venting line. The pump module P includes these apparatuses and its main part is installed inside the fuel tank T. 
         [0037]    The vent relief valve V 2  is a differential pressure valve to be opened if the fuel vapor pressure increases inside the fuel tank T. The vapor return float valve  5  is to be closed not to have the fuel tank over-replenished and the fuel come into the vapor return tube  4  when the fuel tank is being replenished. The fuel replenishment float valve  7  is closed when the fuel tank T is full of the fuel and the fuel is prevented from coming into the canister body  61 . 
       Structure of Fuel Vapor Collecting Unit 
       [0038]    As is indicated in  FIG. 3  the fuel vapor collecting unit B is intended to circulate the fuel vapor inside the fuel tank T through the vapor return tube  4 , inhibit fuel vapor being generated from being discharged into the atmosphere by having the fuel vapor adsorbed in the canister system  6 . This fuel vapor collecting unit B is composed mainly of the vapor return tube  4 , the canister system  6 , the vent pipe  14  connecting between the canister body  61  and the fuel tank T, a drain pipe D connected with the canister system  61  and a purge pipe  19  connected from the canister system  6  to the injector  8  (See  FIG. 1  and  FIG. 2 ) through a purge regulating electro-magnetic valve V 5 . 
       Canister Structure 
       [0039]    The canister system  6  is to temporarily collect and store the fuel vapor in the fuel tank T, to supply the intake manifold with the stored fuel vapor by having the stored fuel vapor freed with the air suctioned by the negative pressure of a engine E with respect to the atmosphere (negative pressure refers to lower pressure than the atmosphere hereinafter) as well as to prevent the fuel vapor from being discharged into the atmosphere. 
         [0040]    The canister system  6  consists mainly of the canister body  61 , the drain filter  62 , the drain pipe D and a vent shut valve V 4 . The canister body  61  contains adsorbent. On this adsorbent adsorbs the fuel vapor which is pressurized in the upper portion the fuel tank T by the replenished fuel and transported therefrom during the fuel replenishment. The drain filter is intended for removing dirt and dust contained in the air introduced from the atmosphere during purging. The drain pipe is to connect between the canister body  61  and the drain filter  62  to supply air to the canister body  61 . The vent shut valve V 4  is installed in the drain pipe D between the canister body  61  and the drain filter  62 . 
         [0041]    As indicated in  FIG. 2  the stored fuel vapor in the canister body  61  is purged while the engine is running and suctioned into the intake manifold  15  through the purge regulating electro-magnetic valve V 5  together with air suctioned due to the negative pressure in the intake manifold  15 . ECU not shown which is connected with the purge regulating electro-magnetic valve V 5  controls the opening time of the purge regulating electromagnetic valve V 5  based on several sensor outputs and the amount of the fuel vapor to be suctioned. 
         [0042]    The intake manifold is an air suctioning passage for the engine E, through which the cleaned air with an air cleaner is supplied to the engine E through a throttle valve not shown. 
       Structure of Canister Body 
       [0043]      FIG. 4  is an enlarged view of a canister system seen from its underneath which is attached to a vehicle, indicating how the canister system is attached to a vehicle.  FIG. 5  is an enlarged view of a cross section of the canister body cut along the X-X line in  FIG. 4 . 
         [0044]    As indicated in  FIG. 4  and  FIG. 5  the canister body  61  is installed adjacent to the fuel tank T and is connected with the fuel tank T through a vent pipe which is relatively thick and short in shape and has a small flowing resistance. The canister body  61  is attached through a rubber sheet to a bracket  63  made of a sheet of steel which is fixed on a lower side of the floor panel Cb. An attachment portion extending from the canister body  61  is not so robust as the canister body  61 . As a result, in case the vehicle undergoes a collision and the floor panel Cb is deformed, the collision shock on the canister body  61  is absorbed by the deformation of the attachment portion and the rubber and the canister body  61  is prevented from breaking. 
         [0045]    As seen in  FIG. 5  the canister body  61  is covered with a protective plate made of plastic which is fixed on the lower side of the floor panel Cb. The canister body  61  is connected with the intake manifold  15  through a purge pipe  19  in which the purge regulating electromagnetic valve V 5  is installed (See  FIG. 1  to  FIG. 3 ). There is an inner pressure sensor S attached to the canister body  61  and a sensor pipe  18  is attached to the inner pressure sensor S with its end opened. 
       Structure of Drain Filter 
       [0046]    A drain filter  62  as indicated in  FIG. 2  is intended for removing dirt and dust contained in the air suctioned from the atmosphere and is a container containing a paper filter, for instance. 
         [0047]    The drain filter  62  is installed at the highest position of or in its vicinity of the drain pipe D in the engine room ER. This drain filter  62  is attached to the front side of the separating wall with the dash board which forms an inner wall of the engine room ER and is fixed on the separating wall with a bolt tightened onto a bracket fixed in the upper part of the engine room ER. 
       Structure of Drain Pipe 
       [0048]    As seen in  FIG. 1  to  FIG. 3  the canister system  6  is equipped with the drain pipe D. This drain pipe D consists of a connecting pipe D 1 , an exhaust pipe D 2 , an auxiliary pipe D 3  and a branch pipe D 4 . The connection pipe D 1  connects between the canister body  61  and the drain filter  62 , and extends to an upper portion of the engine room ER. There is a vent-shut valve V 4  in this connection pipe D 1 , which is electrically connected with and controlled by ECU not shown. This vent-shut valve V 4  is closed only when the pressure of the fuel tank T is made negative. 
         [0049]    Through the drain pipe D 2  is discharged into the atmosphere the cleaned air which comes through the drain filter  62  and fuel vapor from the fuel tank T is removed from. 
         [0050]    In case the drain pipe D 2  is clogged, air can be discharged from the canister body  61  through the auxiliary pipe D 3  and suctioned through the auxiliary pipe D 3  and the drain filter  62  into the canister body  61  with the adsorbed fuel vapor freed in the canister body  61  and transported through the purge pipe  19  to the intake manifold  15 . 
         [0051]    The auxiliary pipe D 3  is branched from the branch pipe D 4  which is attached in the vicinity of the drain filter  62  on the side exposed to the atmosphere. 
         [0052]      FIG. 6  is a cross section view showing an inner structure of a drain pipe in a canister system of the present invention. 
         [0053]    As seen in  FIG. 6  the branch pipe D 3  has three joint portions, one joint portion connected with the drain filter  62 , one with the exhaust pipe D 2  and the other with the auxiliary pipe D 3 . The joint portion with the auxiliary pipe D 3  branches from the other part of the branch pipe D 3 . The branch pipe D 3  is a portion where both a flow passage from the exhaust pipe D 2  to the drain filter  62  and another flow passage from the auxiliary pipe D 3  to the drain filter  62  join. 
         [0054]    The branch pipe D 4  includes a small diameter concentric pipe D 5  and a large diameter concentric pipe D 6 . 
         [0055]    The large diameter concentric pipe D 6  is composed of a cylindrical member with a flange portion D 6   a  and a joint portion D 6   b  through which the auxiliary pipe D 3  is connected. The joint portion D 6   b  is branched from the outer surface the cylindrical member. 
         [0056]    The small diameter concentric pipe D 5  is composed of a cylindrical member with a flange portion D 5   a  and a joint portion D 5   c  through which the branch pipe D 4  is connected with the drain filter  62 . The flange portion D 5   a  is formed in agreement with the flange portion D 6   a  so that the flange portion D 5   a  is coupled with the flange portion D 6   a.    
         [0057]    Because the small diameter concentric pipe D 5  is sufficiently smaller in diameter than the large diameter concentric pipe D 6 , the small diameter concentric pipe D 5  is installed inside the large diameter concentric pipe D 6  with the flange portion D 5   a  and the flange portion D 6   a  in contact with each other and coupled together, which results in a double pipe structure. 
         [0058]    Inside the branch pipe D 4  there are formed a main flow passage D 4   a  and an auxiliary flow passage D 4   b . The main flow passage D 4   a  is formed by the small diameter pipe concentric pipe D 5  and the portion of the large diameter concentric pipe D 6  from the opening D 5   b  of the small diameter concentric pipe D 5  to the joint with the exhaust pipe D 2 . The auxiliary flow passage D 4   b  consists of a space formed between an inner surface of the large diameter concentric pipe D 6  and an outer surface of the small diameter concentric surface and a branched portion connected with the auxiliary pipe D 3 . 
         [0059]    Because the auxiliary flow passage D 4   b  in the drain pipe D includes the space formed between an inner surface of the large diameter concentric pipe D 6 , which is much narrower than the main flow passage D 4   a , there is a very small amount of air flowing toward the auxiliary pipe D 3  compared with the air flowing toward the exhaust pipe D 2  in the ordinary condition. In case the flow resistance in the exhaust pipe D 2  becomes higher than in the auxiliary pipe D 3 , there flows more air toward the auxiliary pipe D 3  according to the flow resistance in the exhaust pipe D 2 . 
         [0060]    For instance, if the vehicle is submerged in water under its floor panel Cb and the exhaust pipe D 2  filled with water and clogged, air can flow through the auxiliary flow passage D 4   b  and there does not occur a problem with the fuel tank T being unable to communicate with the atmosphere. 
       Structure of Damage Detection Unit 
       [0061]    The damage detection unit O is intended for detecting a hole on the fuel tank T and the pipes in the fuel tank system A if there is a hole generated, based on the inner pressure measured with an inner pressure sensor S (see  FIG. 3 ). The damage detection unit determines whether or not a negative pressure is kept in the pipes in the fuel tank system A or the pressure in the pipes in the fuel tank system A is as high as the atmosphere, when the pressure in the fuel tank T and the pipes in the fuel tank system A is to be negative due to a negative pressure in the intake manifold  15 , which is caused on ECU&#39;s request during engine&#39;s operation. 
         [0062]    The ECU is electrically connected with such parts as the vent-shut valve V 4 , the purge regulating electromagnetic valve V 5  and temperature sensors. The ECU takes a control over the vent-shut valve V 4 , the purge regulating electromagnetic valve V 5  and other parts and gives an instruction to have the pipes in the fuel tank system A down to a negative pressure, have the canister body  61  purged and transport the fuel vapor adsorbed in the canister body  61  to the intake manifold  15 . 
       Work of Drain Pipe 
       [0063]    How the drain pipe D of the canister system  6  of the present invention works is to be explained with reference to  FIG. 1  to  FIG. 3 . 
         [0064]    To begin with, it is explained how the drain pipe D of the canister system  6  when the fuel tank T is replenished, with reference to  FIG. 1  and  FIG. 2 . 
         [0065]    For instance, when the fuel tank T is replenished after the engine E is switched off, fuel is poured into the fuel tank T from the fuel replenishment inlet  3   a through the filler pipe  3 . During this replenishment is transported into the canister system  6  through the vent pipe  14  fuel vapor remaining in the upper portion of the fuel tank T, whose volume amount is almost the same as the volume amount of the poured fuel into the fuel tank T. As a result the fuel replenishment is done smoothly. 
         [0066]    Since part of the fuel vapor remaining in the upper portion of the fuel tank T is transported through the vapor return tube  4  and the vicinity of the replenishment inlet  3   a  to the filler pipe  3 , the air from the atmosphere is inhibited from coming into the fuel tank T and it is possible to reduce the amount of the fuel vapor to be evaporated. 
         [0067]    The fuel vapor coming from fuel tank T into the canister system  6  through the vent pipe  14  is adsorbed on the absorbent and stored. The air, from which the fuel vapor is removed, is discharged under the passenger room floor into the atmosphere out of the exhaust pipe D 2  and does not flow inside the passenger room. 
         [0068]    The canister body  61  is installed adjacent to the fuel tank T and connected with the vent pipe  14  which is so short and thick that air easily flows from the fuel tank T to the canister body  61  because of small air flow resistance in-between. 
         [0069]    The fuel vapor flowing into the vapor return tube  4  flows toward the replenishment inlet  3   a  and circulates through the filler pipe  3  into the fuel tank T. As a result, an amount of air coming into the fuel tank T decreases, which results in reduction in an amount of fuel vapor generated. 
         [0070]    Replenishment of the fuel tank T stops as soon as float valves not shown which are installed in the vapor return valve  5  and the replenishment float  7  are closed due to the fuel level becoming high, which leads to the replenishment gun not shown working. 
         [0071]    Referring to  FIG. 1 , how the drain pipe of the present invention works while the canister system  6  being purged is explained. 
         [0072]    When the canister body  61  is purged while the engine E is in operation, the purge regulating electromagnetic valve V 5  is opened and fuel vapor adsorbed in the canister body  61  is transported into the intake manifold  15  of the engine E. 
         [0073]    Specifically speaking, when the purge regulating electro-magnetic valve V 5  is opened, air is suctioned from the atmosphere through the exhaust pipe D 2  and fuel vapor adsorbed on the adsorbent in the canister body  61  is suctioned into the intake manifold  15  through the connection pipe D 1 , the vent shut valve V 4 , the canister body  61 , the purge pipe  19  and the purge regulating electromagnetic valve V 5 . 
         [0074]    As a result the canister system  6  recovers its adsorbing capacity as fuel vapor adsorbed on the adsorbent is freed. 
         [0075]    Since the drain filter  62  is installed at the highest position in the drain pipe D, water drops, dirt and dust are prevented from coming into the canister body  61  and the drain filter  62  is not clogged. 
         [0076]    The branch pipe installed between the drain filter  62  and the auxiliary pipe D 3  has a double pipe structure in which a small diameter concentric pipe D 5  is disposed in a large diameter concentric D 6  and there is a space between the small diameter concentric pipe D 5  and the large diameter concentric pipe D 6 . Therefore an amount of air coming into and from the auxiliary pipe is restricted according to the flow resistance of the exhaust pipe D 2 . In case the exhaust pipe D 2  is clogged with dirt, the canister body  61  remains communicated with the atmosphere through the auxiliary pipe D 3 . 
         [0077]    The present invention does not have to be restricted in the embodiment above mentioned. Other modifications are also possible as long as they are within the scope of the present invention. 
         [0078]    For instance the drain filter  62  is described to be disposed at highest position in the drain pipe D, however the drain filter  62  does not have to be at the highest position and is disposed at a relatively high position in the drain pipe D, the same effect as is already mentioned is obtained.