Patent Publication Number: US-7717093-B2

Title: Canister arrangement in power generating apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is based on and claims priority under 35 U.S.C. 119 to Japanese Patent Application No. 2007-047481, filed on Feb. 27, 2007, the entire contents of which is hereby incorporated by reference and should be considered part of this specification. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a canister arrangement in a power generating apparatus and more particularly to an arrangement of a canister containing an adsorbent for adsorbing fuel that evaporates from an engine fuel tank. 
   2. Description of the Related Art 
   Japanese Publication No. JP 7-34985 describes a conventional device having a canister containing an evaporative fuel adsorbent. The device described in JP 7-34985 includes an engine, a fuel tank for storing fuel to be supplied to the engine, and a canister containing an adsorbent for adsorbing fuel that evaporates from the fuel tank. The canister includes a communicating tube, which places the canister in communication with the atmosphere. The canister is also in communication with an intake system of the engine. 
   The engine is driven by fuel supplied from the fuel tank and outputs a driving force of a predetermined magnitude. During this operation, the adsorbent and the canister containing the adsorbent therein generally work as follows. Fuel vapor is roughly constantly produced in the fuel tank. During a period in which the engine is stopped or in a low-speed range as in idling, most of the fuel vapor is adsorbed by the adsorbent, thereby preventing the fuel vapor from being released into the atmosphere. 
   When the engine is in a medium-speed or high-speed operating range, a negative pressure builds up inside the intake system of the engine. The negative pressure causes atmospheric air to be sucked into the canister through the communicating tube of the canister. The fuel vapor that has been adsorbed onto the adsorbent is purged from the adsorbent by said sucked air and flows along with the air into the intake system, where it is supplied to the engine and subjected to combustion. 
   When the adsorbent is left unused for a long period of time with the fuel vapor adsorbed thereonto, or when the fuel vapor is repeatedly adsorbed onto and purged from the adsorbent a number of times, the capability (e.g., usable life) of the adsorbent decreases, and a purge rate (purge characteristics) on the fuel vapor decreases. 
   SUMMARY OF THE INVENTION 
   In view of the circumstances noted above, one aspect of the present invention is to improve the purge characteristics of an adsorbent in a power generating apparatus that adsorbs fuel that evaporates from a fuel tank so as to prevent release of the fuel vapor into the atmosphere, thereby increasing a usable life of the adsorbent. 
   In accordance with one aspect of the present invention, a power generating apparatus is provided. The power generating apparatus comprises an engine comprising an intake system and an exhaust system, a generator driven at least in part by the engine, and a fuel tank configured to store fuel to be supplied to the engine. The power generating apparatus also comprises a canister containing an adsorbent material for adsorbing fuel that evaporates from the fuel tank, the canister comprising a communicating tube that communicates the canister with the atmosphere, the canister being in communication with the intake system, the canister being positioned proximate the exhaust system. 
   In accordance with another aspect of the present invention, a method of operating a power generating apparatus having a canister arrangement is provided. The method comprises adsorbing fuel vapor from a fuel tank with an adsorbent material to inhibit release of the fuel vapor into the atmosphere, suctioning air from the atmosphere into the adsorbent material to thereby purge said adsorbed fuel vapor from the adsorbent material, said suctioned air and purged fuel vapor directed to an intake system of an engine and combusted therein, and heating the adsorbent material so as to accelerate the purging of fuel vapor adsorbed on the adsorbent material, thereby increasing the adsorbing rate of the adsorbent material. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention will now be described in connection with preferred embodiments of the invention, in reference to the accompanying drawings. The illustrated embodiments, however, are merely examples and are not intended to limit the invention. The drawings include the following 4 figures. 
       FIG. 1  is a schematic top plan view of one embodiment of a power generating apparatus. 
       FIG. 2  is a block diagram of the power generating apparatus. 
       FIG. 3  is a schematic side view of the power generating apparatus. 
       FIG. 4  is an enlarged schematic cross-sectional view taken along line IV-IV of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference numeral  1  in the drawings denotes a portable power generating apparatus. For clarity, in the following descriptions, a direction indicated by arrow Fr in the drawings is a forward direction of the apparatus  1 . 
   The power generating apparatus  1  can be placed on a working surface such as the ground or a floor, and is provided with a cart  2  that allows the apparatus to move on the working surface. The cart  2  includes a chassis  3 , front and rear wheels  4  supporting the chassis  3  on the working surface, and a pair of front and rear handles  5  supported by front and rear ends of the chassis  3 , respectively. 
   An engine  9  for driving an alternating-current generator  8  can be mounted on the chassis  3 . In one embodiment, the engine  9  is a four-cycle engine. However, the engine  9  can be other suitable engine-types. The engine  9  includes an engine body  10  that outputs a driving force, an intake system  14  for supplying an air-fuel mixture  13 , which is a mixture of air  11  and fuel  12 , to the engine body  10 , and an exhaust system  16  for exhausting combustion gas, which is a resultant product of the combustion of the air-fuel mixture  13  in the engine body  10 , to the atmosphere. 
   The engine body  10  includes a crankcase  20  supporting a crankshaft  19 , a cylinder  21  in the crankcase  20  (e.g., in an upright orientation), a piston  22  axially slidably inserted into the cylinder  21 , an interlocking rod  23  for interlocking between the crankshaft  19  and the piston  22 , an intake valve  26  and an exhaust valve  27  for selectively closing and opening a first intake passage  24  and a first exhaust passage  25  formed in a projecting end of the cylinder  21 , respectively, and a valve actuating mechanism (not shown) for selectively closing the intake and exhaust valves  26  and  27  housed in a valve actuating chamber  28  defined in the projecting end of the cylinder  21 . The engine body  10  also includes a spark plug  31  with a discharging unit thereof facing a combustion chamber  30  inside the cylinder  21 . Though the illustrated embodiment shows one cylinder  21  and the corresponding piston  22  and intake/exhaust valves  26 ,  27 , one of ordinary skill in the art will recognize that the engine  9  can have multiple cylinders, each having a corresponding piston and intake/exhaust valves. 
   The intake system  14  can include a carburetor  35 , an intake pipe  36 , and an air cleaner  37 , connected in series with the first intake passage  24 . A space inside the carburetor  35 , the intake pipe  36 , and the air cleaner  37  is defined as a second intake passage  38 , which is in communication with the first intake passage  24 . The carburetor  35  can include a throttle valve  40  for adjusting an opening of the second intake passage  38 , an actuator  41  (e.g., a step motor or other suitable motor type) for actuating the throttle valve  40 , a choke valve  42  for adjusting an opening of the second intake passage  38  at a position upstream of the throttle valve  40 , and an actuator  43  (e.g., a step motor or other suitable motor type) for actuating the choke valve  42 . 
   The exhaust system  16  can include an exhaust pipe  45  and a muffler  46 , connected in series with the first exhaust passage  25 . A space inside the exhaust pipe  45  and the muffler  46  is defined as a second exhaust passage  47 , which is in communication with the first exhaust passage  25 . 
   A fuel tank  50  for storing fuel  12  to be supplied to the engine  9  through the carburetor  35  can be provided, for example, above the engine  9 . An adsorbent  52  for adsorbing thereonto fuel vapor  51  originating from the fuel  12  in the fuel tank  50 , and a canister  53  containing the adsorbent  52  therein are provided. In the illustrated embodiment, the adsorbent  52  is activated carbon. However, other suitable adsorbent materials can be used in other embodiments. The canister  53  can include, in its bottom, a communicating tube  54  which places the canister  53  in communication with the atmosphere. 
   A first communicating passage  57 , through which an upper end of the fuel tank  50  is in communication with an upper end of the canister  53 , is provided. A second communicating passage  58 , through which the upper end of the canister  53  is in communication with the air cleaner  37  of the intake system  14 , is also provided. A blow-by gas passage  59 , through which the valve actuating chamber  28  is in communication with the air cleaner  37  of the intake system  14 , is also provided. Each of the passages  57  to  59  can be formed of an elastic rubber hose. However, the passages  57 - 59  can be formed of other suitable materials, and need not all be of the same material. 
   A soundproof cover  61 , which in one embodiment can be a resin cover, that releasably covers at least a portion of the generator  8 , the engine  9 , the fuel tank  50 , the canister  53 , and the passages  57  and  59  as a unit can be provided. 
   In the illustrated embodiment, the canister  53  is positioned proximate and laterally spaced from the muffler  46  of the exhaust system  16 . The canister  53  can be positioned near an inner surface of a portion  62  of the soundproof cover  61 , as well as between the muffler  46  and the portion  62  of the soundproof cover  61 . Referring to the side view ( FIG. 3 ) of the power generating apparatus  1 , in one embodiment the entire canister  53  can overlap with each of the muffler  46  and the portion  62  of the soundproof cover  61 . 
   The power generating apparatus  1  can include a starter motor  65  for starting the engine  9 , an ignition unit  66  for causing the spark plug  31  to electrically discharge as required, a temperature sensor  67  for detecting a temperature of the engine body  10 , and an engine speed sensor  68  for detecting the number of revolutions of the crankshaft  19  in the engine body  10 . 
   The power generating apparatus  1  can further include a controller  69 , a battery  70 , a main switch  71 , and a starter switch  72 . The controller  69  can electronically control the actuators  41 ,  43  and the ignition unit  66  based on detection signals supplied from the temperature sensor  67  and the engine speed sensor  68 . The battery  70  can be charged with a portion of the electric power generated by the generator  8  through the controller  69 , and can supply electric power to the actuators  41 ,  43 , the ignition unit  66 , and the like. The main switch  71  can switch on and off power supply from the battery  70  to the starter motor  65 , the controller  69 , and the like. The starter switch  72  can switch on and off power supply from the battery  70  to the starter motor  65  through the main switch  71 . The controller  69  can include an outlet  74  through which the other portion of the electric power generated by the generator  8  can be output to an outside load  73 . 
   When the engine  9  is driven under control of the controller  69 , outside air  11  is sucked through the intake system  14  into the engine  9 . The carburetor  35  mixes the fuel  12  with said sucked air  11  to produce the air-fuel mixture  13 . The air-fuel mixture  13  is subjected to combustion in the engine  9 . Through combustion, the engine  9  can drive the generator  8  to generate electric power, which can be output to the load  73  through the outlet  74 . Combustion gas, which is a resultant product of the combustion in the engine  9 , is released as exhaust  15  through the exhaust system  16  into the atmosphere. 
   During the above operation, the adsorbent  52  and the canister  53  work as follows. Fuel vapor  51  is roughly constantly produced in the fuel tank  51 . When the engine  9  is stopped or in a low-speed range (e.g., idling), most of the fuel vapor  51  is adsorbed by the adsorbent  52  through the first communicating passage  57 , thereby preventing the fuel vapor  51  from being released into the atmosphere. 
   When the engine  9  is in a medium-speed or high-speed range, a negative pressure builds up inside the intake system  14 . The negative pressure causes air  76  to be sucked into the canister  53  from the outside through the communicating tube  54  of the canister  53 . The fuel vapor  51  that has been adsorbed onto the adsorbent  52  material is purged from the adsorbent  52  by the sucked air  76  and flows along with the air  76  through the second communicating passage  58  into the air cleaner  37  of the intake system  14  and supplied to the engine  9  therefrom, where it is subjected to combustion. 
   During a period in which the engine  9  is driving, blow-by gas  77  generated in the valve actuating chamber  28  is sucked into the air cleaner  37  of the intake system  14  and supplied to the engine  9  therefrom, then subjected to combustion. 
   According to one embodiment, the canister  53  can be positioned proximate the exhaust system  16  of the engine  9 . 
   Hence, when, in a state in which the engine  9  is stopped or in the low-speed range (e.g., idling) with the fuel vapor  51  adsorbed by the canister  53 , the engine  9  is then shifted to the medium-speed or high-speed range, the muffler  46  of the exhaust system  16  is heated by the exhaust  15  from the engine  9  that passes through the muffler  46 . Radiant heat liberated from the thus-heated muffler  46  heats the adsorbent  52  in the canister  53 , which accelerates purging of the fuel vapor  51  adsorbed onto the adsorbent  52 . 
   Accordingly, a purge rate of the fuel vapor  51  from the adsorbent  52  increases. That is, the purge characteristics of the adsorbent  52  are improved, which improves an adsorbing rate. Consequently, an increase of a usable life of the adsorbent  52  can be attained. 
   The improvement in the purge characteristics of the adsorbent  52  allows for the reduction of the amount of the adsorbent  52  used and the reduction in size of the canister  53 . The smaller size of the canister  53  that can be achieved is significantly beneficial for the power generating apparatus  1 , which has small surplus space due to a strong desire to reduce the size of the apparatus  1 . 
   As described above, the soundproof cover  61  for releasably covering at least a portion of the generator  8 , the engine  9 , the fuel tank  50 , and the canister  53  is provided. The canister  53  can be positioned near the inner surface of the portion  62  of the soundproof cover  61  as well as between the exhaust system  16  and the portion  62  of the soundproof cover  61 . 
   Accordingly, the portion  62  of the soundproof cover  61  inhibits the radiant heat liberated from the exhaust system  16  toward the canister  53  from being wasted. As a result, the adsorbent  52  in the canister  53  is efficiently heated by the radiant heat, thereby further improving the purge characteristics thereof. 
   Meanwhile, the communicating tube  54  can be provided in the bottom of the canister  53 . 
   The communicating tube  54  allows water  78  accumulated inside the canister  53  to be effectively drained out of the canister  53 . As a result, the purge characteristics of the adsorbent  52  can be improved without being inhibited by the accumulation of the water  78 . 
   In another embodiment, the canister  53  can be positioned proximate the exhaust pipe  45  of the exhaust system  16 . 
   Although these inventions have been disclosed in the context of a certain preferred embodiments and examples, it will be understood by those skilled in the art that the present inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the inventions and obvious modifications and equivalents thereof. In addition, while a number of variations of the inventions have been shown and described in detail, other modifications, which are within the scope of the inventions, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within one or more of the inventions. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combine with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above.