Abstract:
In an air intake assembly, a portion of an inner peripheral wall of an intake funnel pipe is provided as a pivotally movable blocking body, so that when unthrottled, an inner wall surface of the blocking body is flush with the inner peripheral wall of the funnel pipe. The blocking body has a substantially trianglular outline shape, the apex of which is positioned on top when viewed along the axis of the support shaft. The support shaft is positioned at the apex of the blocking body, and allows pivotal movement of the blocking body, on the downstream side thereof, to allow adjustment of the rate of air flow through the funnel pipe. The blocking body within the funnel pipe of an air intake assembly allows a smooth flow of air therepast when actuated to throttle the air intake channel, and does not obstruct the air intake channel when inactive.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2003-341058, filed Sep. 30, 2003.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to vehicle intake systems. More particularly, the present invention relates to an air-intake routing and control structure for a motorcycle or similar vehicle.  
         [0004]     2. Description of the Background Art  
         [0005]     In the related art, an air-intake structure is known that includes an intake air control mechanism, for adjusting the amount of intake air passing through the air-intake channel connected to an engine. The adjustment is achieved using by a throttle valve, and an intake air flow control valve provided separately from the throttle valve. The known intake air flow control valve is positioned between a main body of the intake air control mechanism on which the throttle valve is provided, and an intake air-introducing member, such as a funnel pipe which constitutes part of the air-intake channel. The known intake air control valve varies the cross-sectional area of the air-intake channel by allowing part of the intake air control valve to project into the air-intake channel. An intake air control mechanism of this type is disclosed in Japanese Patent document JP-UM-A-63-60041.  
         [0006]     However, as disclosed in the arrangement described in Japanese Patent document JP-UM-A-63-60041, when the distance between the engine and the intake air-introducing member is small, it is difficult to provide a main body of the intake air control mechanism within this small space. Further, it is difficult to obtain an installation space for installing the main body having the throttle valve provided thereon and the intake air control valve together in the intake air control mechanism within the available space. Therefore, satisfactory arrangement of the intake air control valve is difficult to achieve.  
       SUMMARY OF THE INVENTION  
       [0007]     Throughout the present specification, the term “upstream side” designates a position upstream with respect to the direction of the airflow, and the term “downstream side” designates a position downstream with respect to the direction of the airflow, with respect to an air-intake component. In order to solve the above-described problem, the present invention is directed to an intake air control mechanism for connecting to an engine provided in a vehicle. The intake air control mechanism according to an embodiment of the present invention includes an air-intake channel, and controls the amount of intake air provided to the engine using a throttle valve positioned within an expanded portion, or blocking body chamber, formed in the air-intake channel. In addition, the expanded portion is provided in an intake air-introducing member, or funnel, provided within the intake air control mechanism separately from the main body having the throttle valve.  
         [0008]     A blocking body for varying the cross-sectional area of the air-intake channel is disposed in the expanded portion, or blocking body chamber. The blocking body chamber opens on the air-intake side of the intake air-introducing member, or funnel. The blocking body is driven by an actuator.  
         [0009]     A support shaft for pivotally supporting the blocking body is disposed on the upstream side of the blocking body. The support shaft is installed in the vicinity of the end of the opening of the intake air-introducing member. The support shaft is installed on the outside of the air-intake channel.  
         [0010]     Another embodiment of the present invention is directed to a vehicle&#39;s air-intake structure including an intake air control mechanism having a throttle valve connected to an engine provided on a vehicle, and an intake air-introducing member which is part of an air-intake channel of the intake air control mechanism. The vehicle&#39;s air-intake structure includes a blocking body for varying the cross-sectional area of the air-intake channel. The blocking body defines part of the inner peripheral wall of the intake air-introducing member. The inner peripheral surface of the blocking body that faces the inner portion of the intake air-introducing member is formed along the air-intake channel.  
         [0011]     The blocking body defines the end of the opening of the intake air-introducing member. The support shaft for pivotally supporting the blocking body is disposed on the upstream side of the blocking body. The support shaft is installed in the vicinity of the end of the opening of the intake air-introducing member. The blocking body is positioned outside the air-intake channel when the air-intake channel is unthrottled.  
         [0012]     According to one aspect of the invention, since the blocking body for varying the cross-sectional area of the air-intake channel is disposed in the expanded portion of the intake air control mechanism, the expanded portion can be used effectively for arranging the blocking body therewithin, and hence a space for arranging the blocking body can easily be ensured. In addition, since the expanded portion may be provided at a position apart from the engine, the blocking body may be disposed on the upstream side of, and apart from, the main body which immediately precedes the engine cylinders and has its own throttle valve.  
         [0013]     According to another aspect of the invention, since the expanded portion is provided in the intake air-introducing member and is formed separately from the main body which immediately precedes the engine cylinders and has its own throttle valve, the expanded portion can be provided easily and the separately provided intake air-introducing member can be utilized effectively for arranging the blocking body.  
         [0014]     According to another aspect of the invention, by arranging the blocking body in the air cleaner box, opening on the air-intake side of the intake air-introducing member, the required space for arranging the support shaft there is obtained. Also, the amount of operating sound produced by the movable blocking body is reduced by the air cleaner box, and the movable portion can is protected by splashing mud.  
         [0015]     According to another aspect of the invention, by disposing the blocking body apart from the engine, the actuator for driving the blocking body can be installed apart from the engine as well. Therefore, arrangement of members such as cable extending from the actuator is easily accomplished.  
         [0016]     According to another aspect of the invention, since the support shaft is disposed upstream of the blocking body at a distance from the engine, a space with respect to the engine is easily secured. Since the support shaft for pivotally supporting the blocking body is disposed on the upstream side of the blocking body, the blocking body can be throttled at a gentle angle with respect to the flow of intake air, and consequently, intake air can flow smoothly.  
         [0017]     According to another aspect of the invention, since the support shaft is installed in the vicinity of the end of the opening of the intake air-introducing member, it is disposed largely apart from the engine, and hence the space for arranging the support shaft is easily secured. In addition, since the support shaft is installed in the vicinity of the end of the opening of the intake air-introducing member, disturbance of intake air in the vicinity of the support shaft is reduced.  
         [0018]     According to another aspect of the invention, sine the support shaft is disposed outside the air-intake channel, the support shaft is prevented from disturbing the flow of intake air.  
         [0019]     According to another aspect of the invention, since the inner wall surface of the blocking body facing the intake air-introducing member is formed along the air-intake channel, intake air flows smoothly along the wall surface of the air-intake channel. In addition, since the blocking body defines the end of the opening of the intake air-introducing member, the flow of intake air is not easily disturbed when throttling the blocking body. Also, since it is not necessary to provide a notch to accommodate the blocking body range of motion, the air-intake channel is formed to be smooth.  
         [0020]     According to another aspect of the invention, since the blocking body is positioned outside the air-intake channel when the air-intake channel is unthrottled, intake air flows smoothly along the wall surface of the air-intake channel.  
         [0021]     For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is a side view of a motorcycle according to an embodiment of the present invention.  
         [0023]      FIG. 2  is a side view of a principal portion of a vehicle body showing an air-intake structure mounted to an engine.  
         [0024]      FIG. 3  is a drawing of an isolated air cleaner showing the actuation assembly mounted on the blocking body chamber.  
         [0025]      FIG. 4  is a front view of an intake-air introducing assembly according to the present invention showing the mechanisms which interconnects the left and right side support shafts.  
         [0026]      FIG. 5  is a plan view of the intake-air introducing assembly of  FIG. 4 .  
         [0027]      FIG. 6  is a perspective view of an isolated blocking body driving system.  
         [0028]      FIG. 7  is a cross-sectional view taken along the line  7 - 7  in  FIG. 4  showing the blocking body disposed within the blocking body chamber of the short air intake funnel.  
         [0029]      FIG. 8  is a cross-sectional view taken along the line  8 - 8  in  FIG. 4  showing the blocking body disposed within the blocking body chamber of the tall air intake funnel.  
         [0030]      FIG. 9  is a cross-sectional view taken along the line  9 - 9  in  FIG. 4  showing the pulley assembly which actuates the blocking bodies.  
         [0031]      FIG. 10  is a cross-sectional view taken along the line  10 - 10  in  FIG. 9  showing the interconnections between the left and right side support shafts. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]     Referring to the drawings, an embodiment will be described below.  FIG. 1  is a side view of a motorcycle  100  according to the present embodiment. Motorcycle  100  is provided having a front wheel  1 , a front fork  2 , a head pipe  3 , a handle  4 , and a main frame  5 . The main frame  5  is an elongated square pipe formed of light weight alloy, that extends from the head pipe  3  and branches into left and right pipes which extend obliquely downward and rearward.  
         [0033]     On the lower portion of the main frame  5 , a parallel four-cylinder engine  6  is supported. The engine  6  is supported at a point  7  where the mid section of the main frame  5  and the upper end of the cylinder is connected. The engine  6  is also support at a point  9  where the rear end of the main frame  5  and the upper rear end of the mission case  8  of the engine  6  are connected.  
         [0034]     Air is taken into an air-intake port  10  of the engine  6  below an air cleaner  11 , which is an example of an air box, and which is supported by the main frame  5 . Reference numeral  12  designates an injector. The air cleaner  11  is stored in a recess formed on the underside of the front bottom surface of a fuel tank  13  formed so as to project upward.  
         [0035]     An exhaust pipe  16  extends forward from an exhaust port  15 , passes downwardly of the engine  6 , and then extends rearward. The exhaust pipe  16  is connected to a pair of left and right mufflers  17 . The left and right mufflers  17  are disposed on both sides of a rear wheel  18 . A radiator  19  is disposed forwardly of the engine  6 .  
         [0036]     A pair of left and right seat rails  20  are provided from the rear end of the main frame  5  obliquely upward toward the rear, a rear cowl  21  surrounds the seat rails  20 , and a seat  22  is provided thereon.  
         [0037]     At the vertical mid section of the rear end of the mission case  8  of the engine  6 , the front ends of rear swing arms  24  are supported by a pivot shaft  23  so as to be capable of swinging in the vertical direction. The rear wheel  18  is supported at the rear ends of the rear swing arms  24 .  
         [0038]     The motorcycle  100  also includes a rear cushion  25 , a step bracket  26 , and a foldable main step  27 . Pinion step holders  28  are provided so as to extend from the lower sides of the rear cowl  21  downward on left and right sides of the vehicle body. Pinion steps  29  are provided at the lower ends of the pinion step holders  28 . The lower ends of the pinion step holders  28  also support mufflers  17 . The motorcycle  100  has a side stand  30 , a main stand  31 , an output sprocket  32 , a chain  33 , and a driven sprocket  34 . Furthermore, a front cowl  35  covers the front of the vehicle to left and right sides of the vehicle body.  
         [0039]     As shown in  FIG. 1 , the front cowl  35  includes a lamp container  36  for a headlight or the like at the extremity of the front surface thereof. Ducts  37  are provided in the vicinity pf the lamp container  36  at a position slightly downward thereof on the left and right sides so as to open obliquely downward toward the front. The rear end portions of the ducts  37  extend inside the front cowl  35  obliquely upward toward the rear and open into the air cleaner  11 .  
         [0040]      FIG. 2  shows the structure of an air-intake system. An exit  38  at the rear end of the duct  37  is connected to the lower front surface of the air cleaner  11 .  
         [0041]     A throttle body  40  extends downward from the rear portion of the air cleaner  11 , and the lower end thereof is connected to the air-intake port  10  provided on the cylinder head of the engine  6 . The throttle body  40  is an example of the main body which immediately precedes the engine cylinders and has its own throttle valve (not shown) therein.  
         [0042]      FIG. 3  is an isolated side view of the air cleaner  11 . The front half of the air cleaner  11  is divided into a lower dirty room  42  and an upper front clean room  43  via a filter element  41 . The entire rear half constitutes a rear clean room  44 .  
         [0043]     A funnel pipe  45 , which is an example of the intake air-introducing member, is disposed vertically within the rear clean room  44 . The end  45   a  of the funnel pipe  45  on the upstream side of intake air is formed having a bellmouth-shape. The funnel pipe  45  has a substantially cylindrical shape, and provides an air-intake channel having a substantially circular cross section. The inner diameter thereof gradually increases toward the upstream end thereof, and hence it is almost entirely formed into an expanded portion. The funnel pipe  45  is formed separately from the main throttle body  40 , as is funnel tube  53 , described later. The structures of the funnel pipes  45 ,  53  are common, thus only funnel pipe  45  will be described.  
         [0044]     Clean air is introduced from the duct  37  into the dirty room  42 , and proceeds from the dirty room  42  through the filter element  41  to the front clean room  43 . Clean air enters into the funnel pipe  45  of the rear clean room  44 , and sucked from the throttle body  40  to the air-intake port  10 .  
         [0045]     A blocking body chamber  46  is provided upon the front side of the funnel pipe  45 , and a blocking body  60 , described later, provided therein is rotated by a pulley  47 . Blocking body  60  is provided on the side surface of the funnel pipe to vary the cross-sectional area of the air-intake channel. The blocking body chamber  46  is an expanded portion located on the upstream side of the throttle valve provided in the main throttle body  40 , where the air-intake channel is throttled by the blocking body.  
         [0046]     The pulley  47  is rotated in both directions by a pair of wire cables  48 ,  48 . One end of each of the wire cables  48 ,  48  is supported by a stay  49  on the side surface of the funnel pipe  45 . The other end thereof penetrates through the rear wall of the air cleaner  11  and extends to the outside of the air cleaner  11 , where it is connected to an actuator  50  ( FIG. 2 ). The pulley  47  is rotated in both directions by the actuator  50 . The actuator  50  is supported in the vicinity of the air cleaner  11  at a position rearwardly thereof so as to overlap the main frame  5  when viewed from the side, as shown in  FIG. 2 .  
         [0047]      FIG. 4  is a front view of an intake-air introducing assembly  51  in the air cleaner  11  shown from the front of the vehicle body. The intake-air introducing assembly  51  is divided into bases  52   a  and  52   b  on the left and the right at the widthwise midsection of the vehicle. Each base  52   a ,  52   b  is integrally formed with two types of funnel pipes formed of light-weight alloy or the like and having different heights. The two types of funnel pipes include the higher funnel pipe  45  positioned adjacent to the widthwise center of the vehicle, and the lower funnel pipe  53  positioned on the outer, or lateral, side thereof.  
         [0048]     The upper ends of the funnel pipes  45 ,  53  are different in height by an amount H. The funnel pipes  45 ,  53  are provided with blocking body chambers  46 ,  55 , respectively. The blocking body chambers  46  are formed to project slightly upward with respect to blocking body chambers  55 . The upper parts of the adjacent blocking body chambers  46 ,  46  of the base  52   a  and the base  52   b  are formed with bosses  56 ,  56  projecting upwards, which are connected integrally with a bolt  57  from the side.  
         [0049]     Between the adjacent blocking body chambers  46 ,  46 , the pulley  47  is rotatably attached to the side surface of the blocking body chamber  46  on the side of the base  52   a . A support shaft  58   a , which is a center axis of the rotation of the pulley  47 , extends through the blocking body chamber  46  and the blocking body chamber  55  of the base  52   a  widthwise of the vehicle, so that respective blocking bodies  60 ,  61  are rotated coaxially.  
         [0050]     The side of base  52   b  has the same structure. However, on this side, the pulley  47  is not provided, and instead a rotary plate  62  is rotatably and integrally provided on the shaft end of a support shaft  58   b  on the side of the base  52   b . A projecting strip  63  is formed at the lower end of the rotary plate  62  that extends toward the pulley  47 .  
         [0051]     The projecting strip  63  is adapted allow common rotation of the pulley  47  and the rotary plate  62  by being superimposed on, and connected by the adjustment screw  65  with, a projecting strip  64  that extends from the pulley  47  toward the rotary plate  62 . Thus, the support shaft  58   a  on the side of the base  52   a  and the support shaft  58   b  on the side of the base  52   b  rotate synchronously.  
         [0052]     The support shaft  58   b  has the same structure as the support shaft  58   a  except for the difference between the pulley  47  and the rotary plate  62 . The structure of the blocking body chambers  46  and the blocking body chambers  55  is the same. A bolt  66  projects from the side of the blocking body chamber  46  for mounting the boss  56  to the side of the funnel  45  with a nut  67 . Bolts  69 ,  69  are used to mount the blocking body chamber covers  46   a ,  55   a , respectively of the blocking body chambers  46  and the blocking body chambers  55 .  
         [0053]      FIG. 5  is a plan view of the intake-air introducing assembly  51 , in which reference numerals  70   a ,  70   b  designate mounting holes for mounting the base  52   a  and the base  52   b  to the bottom of the air cleaner  11 . The support shaft  58   a  is supported at both ends thereof by bearings  71 ,  72 , and connected at the outer ends thereof to end plates  73 . The end plates  73  are urged outward by springs  74 .  
         [0054]     The rear sides of the base  52   a  and the base  52   b  are provided with bosses  75   a ,  75   b  projecting from the tops of the adjacent blocking body chambers  46 ,  46  respectively, and are connected from the side by a bolt  76  and a nut  77 . At this time, the cable stay  49  is secured to the boss  75   b  together with the bolt  76 .  
         [0055]      FIG. 6  is a perspective view showing a driving system of the blocking body. The front ends of the cables  48  extend from the actuator  50  and are disposed outside the air cleaner  11 . The front ends of the cables  48  are supported by a stay  49  provided on the side wall of the funnel pipe  45 , and from there, the wire portions protrude and are connected to the pulley  47 .  
         [0056]      FIG. 7  is a cross-sectional view taken along the line  7 - 7  in  FIG. 4 , showing structures of the blocking body chamber  55  and the funnel pipe  53 . The blocking body chamber  55  is formed so that the front wall is protruding forward, and is covered with the blocking body chamber cover  55   a . The lower portion of the blocking body chamber cover  55   a  is formed into a tapered portion  55   b  protruding obliquely forward, and the lower portion of the blocking body  61 , which rotates forward when unthrottled, is projected outward of the air-intake channel.  
         [0057]     The upper end of the funnel tube  53  is formed into a bellmouth portion  53   a  spreading outward in a flange shape. The inner peripheral wall  53   b  defines an air-intake channel having a substantially circular cross-section. The inner peripheral wall  53   b  comprises continuous notches  53   c ,  53   d  that accommodate the blocking body  61 , formed by cutting off part of the side surface thereof. The upper notch  53   c  reaches the upper end of the funnel pipe  53 . The notch  53   d , located downwardly of the upper notch  53   c , extends substantially in parallel with the axis of the funnel pipe  53 . The upper notch  53   c  is significantly shorter than the lower notch  53   d.    
         [0058]     The blocking body  61  is formed into a substantially triangular shape when viewed in the direction of the axis of the support shaft  58   a , and the upper part, which corresponds to the apex portion, swings about the support shaft  58   a . The support shaft  58   a  is located adjacent to the upper end of the funnel pipe  53 . An inner wall surface  80  of the blocking body  61 , which faces the air-intake channel of the funnel pipe  53 , is formed into a concaved surface having the same curvature as that of the inner peripheral wall  53   b  of the funnel pipe  53 . Therefore, when not throttled, as shown in the figure by a solid line, the inner wall surface  80  is flush with the inner peripheral surface  53   b  of the funnel pipe  53 , which defines part of the side wall of the funnel pipe  53 . A bellmouth cross-sectional portion  80   b  is also formed integrally with the upper end of the inner wall surface  80 .  
         [0059]     A lower portion  81  of the blocking body  61  is formed into an arcuate shape extending outward, and is formed with an air hole  82  adjacent to the inner wall surface  80 . The outer extremity of the lower portion  81  and the upper end of the inner wall surface  80  are connected by a tapered surface  83 . The tapered surface  83  serves as a stopper surface which comes into abutment with the tapered portion  55   b  when unthrottled. The outer side of the inner wall surface  80  is formed with a thinned recess  84 .  
         [0060]     The blocking body  61  is formed with a step  85  at the upper portion thereof, and the support shaft  58   a  is superimposed thereon. Support shaft  58   a  is connected to the blocking body  61  by a bolt  86 , so that the blocking body  61  rotates together with the support shaft  58   a . Part of the bellmouth cross-sectional portion  80   b  is notched for mounting the bolt  86 . The blocking body chamber  55  is open at the top, and the support shaft  58   a  and the bolt  86  are exposed.  
         [0061]     Along the circumference of the funnel pipe  53 , the end of the blocking body  61  includes an upper cut surface  87  that is substantially arcuate in shape at the upper end portion thereof with respect to the centerline of the funnel pipe  53 , and a lower cut surface  88  that is substantially parallel with the centerline on the lower side thereof. The upper cut surface  87  and the lower cut surface  88  of the blocking body  61  substantially coincide with the upper notch  53   c  and the lower notch  53   d  when the blocking body  61  is unthrottled.  
         [0062]     The imaginary line in  FIG. 7  represents the position of the blocking body  61  when throttled, and the inner wall surface  80  protrudes obliquely into the air-intake channel in the funnel pipe  53 . In this situation, the lower end of the blocking body  61  protrudes more toward the center than the upper end of the blocking body  61  since the support shaft  58   a  serves as the fulcrum of the rotation. As a result, the cross-sectional area of the air-intake channel decreases. Since the fulcrum of the rotation is located on the upper portion of the blocking body  61 , and the lower portion  81 , which rotates by the largest extent, is located on the lower portion of the blocking body  61 , the cross-sectional area of the air-intake channel varies continuously such that the throttled extent is largest on the lower side when the blocking body  61  is rotated.  
         [0063]      FIG. 8  is a cross-sectional view taken along the line  8 - 8  in  FIG. 4 , showing the structures of the blocking body chamber  46  and the funnel pipe  45 . The elements common to the blocking body chamber  55  and the funnel pipe  53  are represented by common reference numerals and the redundant description is omitted. The blocking body chamber  46  is formed by providing the front wall of the funnel pipe  45  with a protrusion that extends toward the front, and includes a blocking body chamber cover  46   a , and a tapered portion  46   b . The blocking body chamber  46  is also open on top.  
         [0064]     The position of the support shaft  58   a  is at the mid-height section of the funnel pipe  45 . Support shaft  58   a  is connected to the blocking body  60  along the side of lower portion  81  of the blocking body  60 . The lower portion  81  of the blocking body  60  swings outwardly and inwardly of the funnel pipe  45  about the support shaft  58   a . The support shaft  58   a  is secured to the blocking body  60  by the bolt  86 . In other words, the fulcrum of the rotation is positioned on the upper side of the funnel pipe  45 , and the side of the lower portion  81 , which is moved by the largest extent, is positioned on the lower side of the funnel pipe  45 , so that the lower portion  81  of the blocking body  60 , which rotates forward when unthrottled, is moved outwardly of the air-intake channel.  
         [0065]     The blocking body  60  is formed with a substantially triangular outline shape when viewed in the direction of the axis of the support shaft  58   a . The upper portion of the blocking body  60 , which corresponds to the apex portion, swings about the support shaft  58   a . The blocking body  60  includes the inner wall surface  80 , the lower portion  81 , the air hole  82 , the tapered surface  83 , the thinned recess  84 , and a shoulder  85  as described above with respect to funnel pipe  53 . The inner wall surface  80  defines an extending portion  80   a  extending upwardly of the position of the support shaft  58   a , reaches a bellmouth portion  45   a  of the funnel pipe  45  to define part of the side wall, and the bellmouth cross-sectional portion  80   b  is also formed integrally therewith.  
         [0066]     The wall of the funnel pipe  45  on the side of the blocking body chamber  46  is formed with a notch  45   d , and the notch  45   d  linearly extends in substantially parallel with the axis of the funnel pipe  45  upward in the drawing and reaches the bellmouth portion  45   a . Along the circumference of the funnel pipe  45 , the end  88  of the blocking body  60  is adapted to coincide substantially with the notch  45   d  when unthrottled. The inner peripheral surface  45   b  of the funnel pipe  45  defines an air intake channel.  
         [0067]     In this arrangement, since the side wall  80  is extends until it reaches the opening at the upper end of the funnel pipe  45 , even when the support shaft  58   a  is located at a low position with respect to the height of the funnel pipe  45 , it is not necessary to form notches which may appear as concavity and convexity on the inner wall  45   b  of the funnel pipe  45  when unthrottled. In this way, the flow of intake air is smooth.  
         [0068]      FIG. 9  is a cross sectional view taken along the line  9 - 9  in  FIG. 4 . The lower portion of the projecting strip  64  extending downward from the pulley  47  engages an adjusting screw  65 . The adjusting screw  65  penetrates the projecting strip  63 , and engages a nut  65   a . An adjust spring  65   b  is interposed between the projecting strip  63  and the projecting strip  64 , and the distance between the projecting strip  63  and the projecting strip  64  can be adjusted by the nut  65   a.    
         [0069]      FIG. 10  is a cross-sectional view taken along the line  10 - 10  in  FIG. 9 . The pulley  47  is secured to a threaded portion formed at the end of the support shaft  58   a  with a nut  78   a . The projecting strip  64  integrally formed with the pulley  47  is formed with a U-shaped groove  64   a  at the lower end thereof, which engages the outer peripheral portion of the adjusting screw  65 .  
         [0070]     On the other hand, the rotary plate  62  is also secured to a threaded portion formed at the end of the support shaft  58   b  with a nut  78   b . The support shaft  58   a  and the support shaft  58   b  are coaxially disposed. The projecting strip  63  formed at the lower end of the rotary plate  62  is formed with a through hole  63   a , through which the adjusting screw  65  is passed. When the projecting strip  63  and the projecting strip  64  are superimposed by the U-shaped groove  64   a , the displacement with respect to the thorough hole  63   a  can be adjusted.  
         [0071]     The operation of the present embodiment will now be described. Although the description will be made mainly with respect to the base  52   a , it will be understood that the base  52   b  also operates in the same manner. Referring now to  FIG. 7  and  FIG. 8 , when the blocking body  60  and the blocking body  61  rotate in the direction indicated by an arrow A when unthrottled, the air-intake channel is brought into the fully opened state. On the other hand, when it is rotated in the direction indicated by an arrow B, the blocking body  60  and the blocking body  61  protrude into the air-intake channel, thereby throttling the cross-sectional area of the air-intake channel.  
         [0072]     Each of the blocking bodies  60 ,  61  is substantially triangle when viewed in the direction of the axis of the support shaft  58   a . When the upper portion of the blocking bodies  60 ,  61 , which corresponds to the apex thereof, swings about the support shaft  58   a , the blocking bodies  60 ,  61  act to throttle such that the cross-sectional area of the air-intake channel is reduced. Therefore, the inner wall surface  80 , which projects into the air-intake channel when throttled, forms a continuous inclined surface varying so as to protrude more into the air-intake channel on the lower side. The flow of intake air flows more smoothly when compared with a conventional slide-type valve wherein the blocking body slides in the radial direction of the funnel pipe, causing turbulence in the flow of air.  
         [0073]     Also, since the blocking bodies  60 ,  61  are disposed on the funnel pipes  45 ,  53 , and since the funnel pipes  45 ,  53  are intake air-introducing members located at a distance from the engine, space for arranging the blocking bodies  60 ,  61  is easily secured. In addition, since the blocking bodies  60 ,  61  are disposed at the positions distant from the engine, members such as the cables  48 ,  48  and the like extending from the actuator  50  for driving the same can be prevented from interfering with the engine, and hence they are easily arranged.  
         [0074]     In addition, since the funnel pipes  45 ,  53  are located apart from the engine, by positioning the support shaft  58   a  upstream of the funnel pipes  45 ,  53 , spacing of the support shaft with respect to the engine is easily secured. In this case, when the support shaft  58   a  is installed in the vicinity of the ends of the upper openings of the funnel pipes  45 ,  53 , the space with respect to the engine is secured even more easily.  
         [0075]     Also, since the funnel pipes  45  and  53  are disposed in the air cleaner  11 , the blocking bodies  60 ,  61  are also arranged in the air cleaner  11 . Therefore, the operating sound produced by the movable blocking bodies  60 ,  61  is reduced. In addition, since the pulley  47 , the support shaft  58   a , or the like, which are movable members of the blocking bodies  60 ,  61  are also accommodated within the air cleaner  11 , they are protected from splashing mud.  
         [0076]     Furthermore, when the blocking body  60  is unthrottled, the inner wall surface  80  facing the air-intake channel is formed into a curved surface so as to be flush with the inner peripheral wall  45   b  of the funnel pipe  45 . The lower portion  81  is positioned so as to be retracted out of the air-intake channel. Becuase the blocking body  60  is positioned outside the air-intake channel and does not project into the air-intake channel, intake air flows smoothly along the wall surface of the air-intake channel. This condition is the same for the blocking body  61 .  
         [0077]     Since the blocking bodies  60 ,  61  form part of the ends of the openings of the funnel pipes  43 ,  53 , it is not necessary to form recesses facing the air-intake channel within the movable ranges of the blocking bodies  60 ,  61  even when these bodies are in the unthrottled position. Therefore, the air-intake channel is smooth. Consequently, the flow of intake air is not easily disturbed when throttling using the blocking bodies  60 ,  61 .  
         [0078]     In addition, since the height of the support shaft  58   a  is the same for the funnel pipes  45  and  53 , which have different heights, the blocking bodies  60 ,  61  can be driven by the common support shaft  58   a . Hence a reduction in the number of components is achieved. In addition, since the support shaft  58   a  is disposed outside the funnel pipes  45 ,  53 , or in other words, since the support shaft  58   a  is disposed outside the air-intake channel, it does not project into the air-intake channel, and consequently, the flow of intake air may be prevented from being easily disturbed.  
         [0079]     The present invention is not limited to the one described above. For example the intake air-introducing member is not limited to the funnel pipe, and may be any member as long as it defines the air-intake channel. It may either be formed integrally with the throttle body or separately therefrom. Furthermore, the expanded portion is not necessarily required to be mounted on the separate intake air-introducing member. In addition, the height of the funnel, the position and the shape of the blocking body, and the height of the support shaft may be combined as needed, and the combinations shown below are conceivable.  
                           TABLE 1                               position &amp; shape   height of blocking       No.   Height of funnel   of blocking body   body shaft                   1   uneven (for example,     FIG. 7 , 8,   same           low at both ends and   depending on the           high on the   height of           inner portion   the funnel       2   same as 1     FIG. 7 , 8,   same               depending on the               height of the funnel       3   same as 1       use link or the like                   because they are not                   the same       4   high       same       5   same as 4       same       6   low       same                  
 
         [0080]     Note: Figure Nos. shown in the column of “position and shape of blocking body” indicate that the blocking bodies are to be formed into the shape and to be positioned at the position as shown in those drawings, and when a plurality of numbers of the drawings are shown, either one may be selected arbitrarily.  
         [0081]     Although the present invention has been described herein with respect to an illustrative embodiment, the foregoing description is intended to be illustrative, and not restrictive. Those skilled in the art will realize that many modifications of the embodiment could be made which would be operable. All such modifications which are within the scope of the claims are intended to be within the scope and spirit of the present invention.