Abstract:
An air cleaner for use in combination with a fuel system of an engine, includes an air cleaning element housed within a casing. Air introduced from an air inlet, defined in the casing, follows an air flow path from the air inlet passing through the air cleaning element. The air flow path includes a direction change of approximately ninety degrees. This direction change transpires over a curved guide surface formed in the casing to reduce the likelihood of vortexes which reduce the air ram pressure. The curved guide surface may include a detachable panel. Also, the panel may include an air path to an air branch chamber. When two air inlets are used, it is advantageous to include a partitioning wall separating the two air flow paths prior to the air cleaning element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to air cleaners used in conjunction with engines. More particularly, the present invention concerns air cleaners which utilize ram air pressure. 
     2. Description of the Related Art 
     Japanese Patent Laid-open No. 9-96261 entitled “Air cleaner for vehicles” discloses an air cleaner of the type which utilizes ram air pressure. Such types of air cleaners are well known. With reference to FIGS. 8-10, ram air is introduced into an intake passage  206  and the air having passed through the intake passage  206  enters into a lower case  210  through an inlet  209 . The air then passes from the lower case  210  through an element  207 . The clean air that has passed through the element  207  is guided into an upper case  208 , and introduced into a carburetor  202  connected to a lower portion of the upper case  208 . The ram air is utilized to produce a ram pressure higher than the atmospheric pressure. The ram pressure is applied to the carburetor  202  to supply a high-density air-fuel mixture into an engine  201  for thereby increasing the air-fuel mixture charging efficiency of the engine  201  to increase the output power thereof when the vehicle runs at a high speed. 
     As shown in FIG. 10, the lower case  210  has left and right inlets  209  with respective intake passages  206  connected thereto. The structure of the lower case  210  and the intake passages  206 , as shown in FIG. 8, is of a general nature. With the above structure, air flows introduced from the inlets  209  collide with each other in the center of the lower case  210 . Though the ram pressure, higher than the atmospheric pressure, is generated utilizing the ram air, a sufficient ram pressure may not be applied to the carburetor  202 . Furthermore, the air flows introduced from the inlets  209  develop vortex flows at the bottom or sides of the lower case  210  (As will be discussed in relation to FIG. 7 a , hereinafter). When a vortex flow loss is caused, the ram air cannot effectively be introduced into the carburetor  202  because the resistance in the flow passages is increased. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an air cleaner which is arranged to improve air flows such that sufficient ram pressure is applied to a carburetor. 
     According to the present invention, there is provided an air cleaner of the type wherein an air cleaner element is housed in an air cleaner case. Air, introduced from an air inlet defined in the air cleaner case, is passed through an air cleaner element after the direction of flow of the air is changed 90 degrees or substantially 90 degrees. The air cleaner is characterized in that the air cleaner case has a curved guide surface for smoothly guiding the air introduced from the air inlet toward the air cleaner element. The curved guide surface smoothly guides the air introduced from the air inlet toward the air cleaner element, and thereby reduces vortex flows generated by the air introduced from the air inlet. 
     The air cleaner may also have the curved guide surface formed as a detachable piece. A reverse side of the detached piece and the air cleaner case may define an air branch chamber. A filter is disposed in the air branch chamber and held by a filter presser extending from the detachable piece. The air branch chamber allows part of the air introduced from the air inlet can be led out of the air cleaner case via the detachable piece, through the filter. Preferably, a filter presser extending from the detachable piece holds the filter, so that the number of parts used can be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein: 
     FIG. 1 is a side view of a motorcycle incorporating an air cleaner according to the present invention; 
     FIG. 2 is a side view of an air intake system according to the present invention; 
     FIG. 3 is a perspective view of the air intake system of FIG. 2; 
     FIG. 4 is an exploded perspective view of the air cleaner of FIG. 1; 
     FIG. 5 is a cross-sectional view of the air cleaner; 
     FIG. 6 a  is a view illustrating a first operation of the air cleaner; 
     FIG. 6 b  is a further view illustrating the first operation of the air cleaner; 
     FIG. 7 a  is a view illustrating a second operation of an air cleaner, in accordance with the background art; 
     FIG. 7 b  is a view illustrating a second operation of the air cleaner, according to the present invention; 
     FIG. 8 is a side view of an air intake system according to the background art; 
     FIG. 9 is a cross-sectional view of an air cleaner of the air intake system of FIG. 8; and 
     FIG. 10 is a cross-sectional view of a lower portion of the air cleaner of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will now be described with reference to the accompanying drawings. The terms “front”, “rear”, “left”, “right”, “upper”, “lower,” and similar directional terms used herein, refer to directions as viewed from the rider of a motorcycle. Fr, Rr, L, R represent front, rear, left, and right sides, respectively. The FIGS. shall be viewed in accordance with the orientation of the reference characters. 
     FIG. 1 is a side view of a motorcycle having an air cleaner according to the present invention. The motorcycle  1  comprises a vehicle body frame  2 . A head pipe  3  is mounted on a front portion of the vehicle body frame  2 . A front fork  4  is rotatably mounted on the head pipe  3 . A handle  5  is mounted on an upper portion of the front fork  4 . 
     A front wheel  6  is rotatably mounted on a lower portion of the front fork  4 . A front fender  7  covers the front wheel  6 . A fuel tank  8  is mounted on the vehicle body frame  2 , rearwardly of the bead pipe  3 . A seat  9  is disposed rearwardly of the fuel tank  8 . A power unit  11  is disposed downwardly of the fuel tank  8  and the seat  9 . The power unit  11  comprises an engine and a transmission. 
     A swing arm  12  is swingably mounted on the vehicle body frame  2 , rearwardly of the power unit  11 . A rear wheel  13  is rotatably mounted on a rear end of the swing arm  12  and drivable by the power unit  11 . A rear fender  14  is disposed upwardly of the rear wheel  13 . The motorcycle  1  also includes a front cowl  15 , a seat cowl  16 , a rear suspension  17 , an exhaust pipe  18 , a muffler  19 , a main stand  21 , a duct cover  22 , a cowl stay  23 , and a carburetor  27 . 
     An air intake system  30  will now be described with reference to FIG.  2 . FIG. 2 is a side view of components of air intake system  30 , according to the present invention. The air intake system  30  includes left and right inlet ducts  31 ,  32  (the far inlet duct  32  is illustrated in FIG. 3) for introducing ram air. The air intake system  30  also includes an air cleaner  50  for being supplied with the air introduced from the ducts  31 ,  32 , and a group of auxiliary tubes  33  for sending the air supplied to the air cleaner  50  for feedback. 
     The left and right inlet ducts  31 ,  32  have ends positioned at a front face of the front cowl  15  and other ends connected to the air cleaner  50 . The left and right inlet ducts  31 ,  32  have respective retainers  34   b ,  37   b  (the far retainer  37   b  is illustrated in FIG. 3) secured to the cowl stay  23 . The carburetor  27  includes a float chamber  27   a , a diaphragm  27   b , and a chamber  27   c  below the diaphragm  27   b.    
     FIG. 3 is a perspective view of the components of the air intake system  30 . The left inlet duct  31  comprises a duct body  34  and a cover duct  36  covering the duct body  34  with a grill  35  interposed therebetween. The left inlet duct  31  has an opening  31   a . The duct body  34  has an expansion chamber  34   a  disposed in an intermediate portion of the duct  34  close to the cover duct  36 . A retainer  34   b  to be secured to the cowl stay  23  (see FIG. 2) is disposed on an outer side of the expansion chamber  34   a.    
     The right inlet duct  32  is of a shape symmetrical to the left inlet duct  31  with respect to the longitudinal direction of the motorcycle. The right inlet duct  32  includes a duct body  37 , an expansion chamber  37   a  of the duct body  37 , a retainer  37   b  of the duct body  37 , a grill  38 , and a cover duct  39 . 
     The group of auxiliary tubes  33  (indicated by the two-dot-and-dash lines) includes a left tube  41  and a right tube  42  joined to the left tube  41 . A directional control valve  44  is connected to the tubes  41 ,  42 . A cleaner tube  45  interconnects the directional control valve  44  and the air cleaner  50 . A float chamber tube  46  interconnects the directional control valve  44  and the directional float chamber  27   a  (see FIG.  2 ). A carburetor tube  47  interconnects the air cleaner  50  and the chamber  27   c  (see FIG. 2) below the diaphragm  27   b . As described hereinafter, the group of auxiliary tubes  44  changes pressures applied to the carburetor  27  depending on the vehicle speed, thereby promoting efficient fuel atomization. 
     FIG. 4 is an exploded perspective view of the air cleaner  50 , according to the present invention. The air cleaner  50  comprises an air cleaner case  51  and an air cleaner element  52  (hereinafter referred to as an “element  52 ”) housed in the air cleaner case  51 . The element  52  has a frame  52   a.    
     The air cleaner case  51  comprises a case body  53  and a cover  58  covering the case body  53 . The case body  53  houses left and right filters  54 ,  55  therein, and has left and right auxiliary guide members  56 ,  57  as curved guide surfaces for holding the filters  54 ,  55 , respectively. The case body  53  has a plurality of through holes  53   a  to which the carburetor  27  (see FIG. 2) is attached. The case body  53  also has left and right attachments  53   b ,  53   c  formed as air inlets to which the left and right inlet ducts  31 ,  32  (see FIG. 3) are attached. 
     The case body  53  also has a partition wall  53   f  on which the element  52  is placed, and left and right curved guide surfaces  61 ,  62  for guiding air smoothly toward the element  52 . A separation wall  53   g  divides the left and right curved guide surfaces  61 ,  62  from each other. Left and right branch chambers  63 ,  64  are formed as air branch chambers in a lower portion of the case body  53 . The case body  52  also includes an edge  53   h  to which a cover  58  is attached. 
     The left branch chamber  63  has a branch port  63   a , and the right branch chamber  64  has a branch port  64   a . The cover  58  has a dome  58   a  serving as a passage for an air flow, and an edge  58   b  extending around the dome  58   a  for mating engagement with the case body  53 . 
     The left auxiliary guide member  56  is housed in the left branch chamber  63  and has a guide surface  56   a  serving as a curved guide surface that lies flush with the left curved guide surface  61  when the left auxiliary guide member  56  is mounted in the case body  53 . A filter presser  56   b  extends from the guide surface  56   a , and the guide surface  56   a  has an air inlet  56 c. The guide surface  56   a  has retainers  56   d  to be secured to the case body  53  by attachment screws  65 . 
     The right auxiliary guide member  57  is housed in the right branch chamber  64 . The right auxiliary guide member  57  is of a shape that is symmetrical to the left auxiliary guide member  56  with respect to the longitudinal direction of the motorcycle  1 . The right auxiliary guide member  57  has a guide surface  57   a , a filter presser  57   b , an air inlet  57   c , and retainers  57   d . Similarly, the left filter  54  and the right filter  55  are symmetrical with respect to the longitudinal direction of the motorcycle  1 . 
     FIG. 5 is a cross-sectional view of the air cleaner  50  illustrating the air cleaner  50  in an assembled form. The element  52  has its frame  52   a  placed on the partition wall  53   f  of the case body  53 . The left inlet duct  31  is connected to the left attachment  53   b  of the case body  53 , and the right inlet duct  32  is connected to the right attachment  53   c  of the case body  53 . 
     The left curved guide surface  61  and the guide surface  56   a  of the left auxiliary guide member  56  lie flush with each other when they are installed in place. Likewise, the right curved guide surface  62  and the guide surface  57   a  of the right auxiliary guide member  57  lie flush with each other when they are installed in place. 
     The left filter  54  is held in place by the filter presser  56   b  of the left auxiliary guide member  56 . The right filter  55  is held in place by the filter presser  57   b  of the right auxiliary guide member  57 . In other words, the left and right curved guide surfaces  61 ,  62  have respective portions serving as the left and right auxiliary guide members  56 ,  57 , which are detachable, and the left and right filters  54 ,  55  are held in place respectively by the filter pressers  56   b ,  57   b  extending from the left and right auxiliary guide members  56 ,  57 . Therefore, since no separate parts are used for securing the left and right filters  54 ,  55 , the number of parts used can be reduced. 
     The cleaner tube  45  has an end connected to the branch port  63   a  of the left branch chamber  63 , and an opposite end connected to the directional control valve  44 , as shown in FIG.  3 . The carburetor tube  47  has an end connected to the branch port  64   a  of the right branch chamber  64 , and an opposite end connected to the chamber  27   c  (see FIG. 2) below the diaphragm  27   b.    
     Now, with reference to FIGS. 6 a  and  6   b , a first operation of the air cleaner  50  will be described. An air flow from the inlet duct  31  ( 32 ) to the air cleaner  50  will first be described. FIG. 6 a  shows an air flow at the time the speed of the motorcycle  1  is 20 kn/h or lower, and FIG. 6 b  shows an air flow at the time the speed of the motorcycle  1  is 20 km/h or higher. Hollow arrows indicate a main airflow, and solid arrows indicate auxiliary airflows. 
     In FIG. 6 a , as indicated by the hollow arrows, air supplied from the inlet duct  31  ( 32 ) is introduced into the air cleaner case  51  while part of the air is passing through the expansion chamber  34   a  ( 37   a ). The air that has passed through the element  52  is introduced into the carburetor  27 . 
     Air introduced from the left and right tubes  41 ,  42  is introduced via the directional control valve  44  and the float chamber tube  46  into the float chamber  27   a  (see FIG.  2 ), as indicated by the solid arrows al. As indicated by the solid arrow a 2 , the air in the air cleaner case  51  is delivered from the right branch chamber  64  via the carburetor tube  47  to the chamber  27   c  (see FIG. 2) below the diaphragm  27   b , at all times. 
     In FIG. 6 b , when the speed of the motorcycle  1  reaches 20 kmn/h, the directional control valve  44  is operated by a controller (not shown). The directional control valve  44  causes a switch from the left and right tubes  41 ,  42  to the cleaner tube  45  for introducing air in the air cleaner  50  from the left branch chamber  63  into the float chamber  27   a , as shown by the solid arrows b 1 . 
     In practice, ram air is utilized to supply a ram pressure higher than the atmospheric pressure from the left and right inlet ducts  31 ,  32  to the air cleaner  50  when the speed of the motorcycle  1  is increased. A ram pressure which is substantially the same as the pressure in the left and right inlet ducts  31 ,  32  is applied to the float chamber  27   a  for promoting efficient fuel atomization. 
     Air flows in the air cleaner  50  will be described below in conjunction with a comparative example. FIGS. 7 a  and  7   b  illustrate a second operation of the air cleaner. FIG. 7 a  shows a comparative example, and FIG. 7 b  shows an embodiment in accordance with the present invention. 
     In FIG. 7 a , air flows from a left inlet duct  101  into an air cleaner  100  are indicated by the arrow ( 1 ) while air flows from a right inlet duct  102  into the air cleaner  100  are indicated by the arrow ( 2 ). The introduced air flows collide with each other in the center of an air cleaner case  103 , and suffer a large pressure loss until they pass through an air filter  104 , as indicated by the arrows ( 3 ). Therefore, ram air cannot effectively be introduced into a carburetor (not shown). At a bottom  103   a  of the air cleaner case  103 , the introduced air develops vortex flows as indicated by the arrows ( 4 ) and the arrows ( 5 ), and cannot effectively be introduced into the carburetor (not shown). 
     In FIG. 7 b , the air cleaner  50 , according to the present invention, has the separation wall  53   a  contiguous to the left and right curved guide surfaces  61 ,  62 . Therefore, air introduced from the left inlet duct  31  as indicated by the arrow ( 6 ), and air introduced from the right inlet duct  32  as indicated by the arrow ( 7 ) do not collide with each other, and can pass smoothly through the element  52 . 
     The air cleaner  50  also has the left and right curved guide surfaces  61 ,  62  in the case body  53  of the air cleaner case  51 . Air introduced from the left and right inlet ducts  31 ,  32  flows toward the element as indicated by the arrows ( 8 ), ( 9 ). As a result, the generation of vortexes of air in the air cleaner case  51  can be reduced. 
     In this embodiment, as shown in FIG. 4, the left auxiliary guide member  56  is separated from the left curved guide surface  61 , and the right auxiliary guide member  57  is separated from the right curved guide surface  62 . However, the left curved guide surface  61  and the left auxiliary guide member  56  may be integrally formed with each other, and likewise, the right curved guide surface  62  and the right auxiliary guide member  57  may be integrally formed with each other. 
     According to the present invention, the above arrangement offers many advantages. Since the air cleaner case has the curved guide surface, air introduced from the air inlet can smoothly be led to the air cleaner element. Therefore, the generation of vortexes of air introduced from the air inlet can be reduced. The curved guide surface has a portion as a detachable piece, and a filter is held by a filter presser extending from the detachable piece. Therefore, the number of parts used can be reduced. Since no separate parts are required to secure the filter, the cost of the air cleaner can be reduced. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.