Patent Publication Number: US-8123273-B2

Title: Screen for motorcycle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2008-024746 filed on Feb. 5, 2008 and Japanese Patent Application No. 2008-236185 filed on Sep. 16, 2008 the entire contents of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     A screen for a motorcycle which includes a wind screen having an adjustable inclination angle. 
     DESCRIPTION OF BACKGROUND ART 
     Motorcycle are known that include a movable wind screen having an adjustable height on a cowling which covers a front upper portion of a vehicle body. Some movable wind screens of this type have an inclination angle which is adjusted in an interlocked relationship with adjustment of the height. See, for example, Japanese Patent Laid-Open No. 2003-81160. 
     However, in the conventional configuration, if the wind screen is configured for adjustment to a higher position, at a higher position of the wind screen, the wind screen is spaced away from the cowling. In addition, the inclination angle thereof approaches the vertical direction. Although the air flow from between the cowling and the wind screen flows along the surface of the cowling, the probability occurs that the air flow may not sufficiently flow to the rear face of the wind screen. If the air flow does not sufficiently flow to the rear face of the wind screen, then the space between the wind screen and the driver is placed into a negative pressure state and the air flow is sucked toward the rear of the wind screen, resulting in a deterioration of the driving feeling of the driver. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     It is an object of an embodiment of the present invention to provide a screen for a motorcycle which allows air flow to flow appropriately along a rear face of a wind screen having an adjustable inclination angle. 
     According to an embodiment of the present invention, there is provided a screen for a motorcycle which includes a cowling for covering a front upper portion of a vehicle body and a movable wind screen disposed in an inclined relationship toward the rear direction of the vehicle body above the cowling and mounted such that the inclination angle thereof can be adjusted. A baffle plate, inclined toward the rear direction of the vehicle body, is provided between the cowling and the movable wind screen. The inclination angle of the baffle plate can be adjusted so that air flow from between the cowling and the movable wind screen flows along a rear face of the movable wind screen. 
     In an embodiment of the present invention, since the baffle plate, inclined toward the rear direction of the vehicle body, is provided between the cowling and the movable wind screen and the inclination angle of the baffle plate can be adjusted so that air flow from between the cowling and the movable wind screen flows along the rear face of the movable wind screen, the air flow can be let flow appropriately along the rear face of the movable wind screen. 
     In the configuration described above, preferably the inclination angle of the baffle plate is set to a large angle when the inclination angle of the movable wind screen is large, but when the inclination angle of the movable wind screen is small, the inclination angle of the baffle plate is set to a small angle. With this configuration, the inclination angle of the baffle plate and the inclination angle of the movable wind screen can be made substantially equal to each other, and the air flow can flow along the rear face of the movable wind screen. 
     In the configuration described above, the screen for a motorcycle may be configured such that the baffle plate is connected to the movable wind screen, and a connection mechanism which varies the inclination angle of the baffle plate in response to the inclination angle of the movable wind screen is provided. With this configuration, since the connection mechanism which connects the baffle plate to the movable wind screen varies the inclination angle of the baffle plate in response to the inclination angle of the movable wind screen, a configuration for causing the baffle plate to interlock with the movable wind screen can be simplified. 
     Further, in the configuration described above, the baffle plate may be connected for sliding movement to the cowling while a state wherein a lower end thereof is positioned in the proximity of the surface of the cowling is kept so that the air flow flowing along the surface of the cowling flows toward the rear direction of the vehicle body along a front face of the baffle plate. With this configuration, the air flow flowing along the surface of the cowling can be introduced efficiently to the front face of the baffle plate. 
     Further, in the configuration described above, the connection mechanism may include a connection member connected to the baffle plate to vary the inclination angle of the baffle plate in response to the inclination angle of the movable wind screen, the connection member being disposed below the baffle plate. With this configuration, since the connection member is disposed below the baffle plate, the connection member does not disturb flow of the air flow from between the movable wind screen and the baffle plate. Therefore, the air flow can flow more smoothly along the front face of the baffle plate. Thus, a reduction in the air resistance and a reduction of the wind noise can be achieved. 
     In this instance, the connection member may include a guide arm extending along the forward and backward direction below the baffle plate, the guide arm being rocked upwardly and downwardly in response to movement of a stay connected to the movable wind screen such that the inclination angle of the baffle plate is varied by the upward or downward rocking motion of the guide arm. With this configuration, since the guide arm extending along the forward and backward direction below the baffle plate is rocked upwardly or downwardly to vary the inclination angle of the baffle plate, the guide arm does not disturb the air flow from between the movable wind screen and the baffle plate. Thus, the air flow can flow smoothly along the front face of the baffle plate. 
     In an embodiment of the present invention, the baffle plate inclined toward the rear direction of the vehicle body is provided between the cowling and the movable wind screen and the inclination angle of the baffle plate can be adjusted so that air flow from between the cowling and the movable wind screen flows along the rear face of the movable wind screen. Therefore, the air flow can permit an flow appropriately along the rear face of the movable wind screen. 
     Further, the inclination angle of the baffle plate is set to a large angle when the inclination angle of the movable wind screen is large, but when the inclination angle of the movable wind screen is small, the inclination angle of the baffle plate is set to a small angle. Therefore, the inclination angle of the baffle plate and the inclination angle of the movable wind screen can be made substantially equal to each other such that the air flow can be let flow along the rear face of the movable wind screen. 
     Further, the connection mechanism which connects the baffle plate to the movable wind screen varies the inclination angle of the baffle plate in response to the inclination angle of the movable wind screen. Therefore, a configuration for causing the baffle plate to interlock with the movable wind screen can be simplified. 
     Further, the baffle plate is connected for sliding movement to the cowling while a state wherein a lower end thereof is positioned in the proximity of the surface of the cowling is kept so that the air flow flowing along the surface of the cowling permits the flow toward the rear direction of the vehicle body along the front face of the baffle plate. Therefore, the air flow flowing along the surface of the cowling can be introduced efficiently to the front face of the baffle plate. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       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 perspective view showing a front portion of a motorcycle according to a first embodiment of the present invention; 
         FIG. 2  is a perspective view showing a wind screen moved to a Hi position; 
         FIG. 3  is a side elevational view showing the wind screen together with a moving mechanism; 
         FIG. 4(   a ) is a view showing a mechanism section when the wind screen is at a Lo position, and  FIG. 4(   b ) is a view showing the mechanism section when the wind screen is at the Hi position; 
         FIG. 5  is an exploded perspective view showing a sub screen together with peripheral elements; 
         FIG. 6  is a view illustrating movement of the wind screen and the sub screen; 
         FIG. 7  is an exploded perspective view illustrating a screen for a motorcycle according to a second embodiment; 
         FIG. 8  is an exploded perspective view showing a connection structure of a wind screen; 
         FIG. 9  is an exploded perspective view showing a sub screen holder together with peripheral elements; 
         FIG. 10  is a view illustrating movement of the wind screen and the sub screen; 
         FIG. 11  is an exploded perspective view showing a screen for a motorcycle according to a third embodiment together with peripheral elements; 
         FIG. 12  is a side elevational sectional view of a screen for a motorcycle; and 
         FIG. 13  is a sectional view taken along line XIII-XIII of  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present invention are described with reference to the accompanying drawings. It is to be noted that indications regarding the direction such as forward, backward, leftward, rightward, upward and downward directions are given in accordance with directions as viewed from the driver who drives the vehicle body. 
       FIG. 1  is a perspective view showing a front portion of a motorcycle according to a first embodiment of the present invention. 
     The motorcycle includes an upper cowling  41  which covers a front upper portion of a vehicle body, and a headlamp  50  disposed at a front portion of the upper cowling  41 . A wind screen  51  is formed from a transparent resin material and is disposed at a front upper portion of the upper cowling  41 . 
     The upper cowling  41  is formed in a streamlined shape wherein it expands smoothly in a vehicle widthwise direction and an upward and downward direction toward the rear direction of the vehicle body such that air flow from forwardly of the vehicle body is rectified and flows around the driver without directly coming to the driver, and the wind screen  51  is formed in a substantially to be trapezoidal shape wherein the width thereof decreases toward the upward direction. This wind screen  51  is formed as a movable wind screen whose height and inclination angle can be adjusted by a moving mechanism  90  hereinafter described.  FIG. 1  shows the wind screen  51  in a state wherein it is moved to a low position (Lo position) and  FIG. 2  shows the wind screen  51  in another state wherein it is moved to a high position (Hi position). 
     Where the wind screen  51  is moved to the Hi position as shown in  FIG. 2 , it can exhibit a high wind protection effect suitable for high speed traveling (effect of reducing the wind pressure to the driver and wind noise and rectifying flows of air). On the other hand, where the wind screen  51  is moved to the Lo position as seen in  FIG. 1 , the effect can be adjusted to the wind protection effect that the driver feels an appropriate wind pressure suitable for middle or low speed traveling, and the agreeability upon traveling can be enhanced. 
       FIG. 3  is a side elevational view showing the wind screen  51  together with the moving mechanism  90 , and the wind screen  51  at the Lo position is indicated by solid lines, and the wind screen  51  at the Hi position (wind screen  51 ′ and so forth) is indicated by alternate long and two short dashes lines. 
     Meanwhile,  FIG. 4(   a ) is a view showing the mechanism section when the wind screen  51  is at the Lo position, and  FIG. 4(   b ) is a view showing the mechanism section when the wind screen  51  at the Hi position. It is to be noted that, in  FIGS. 4(   a ) and  4 ( b ), a sub screen  20  hereinafter described is omitted. 
     As shown in  FIG. 3 , the wind screen  51  is disposed in an inclined relationship toward the rear direction of the vehicle body and is disposed for upward and downward movement while the inclination angle thereof is varied along the direction of an arrow mark y in which it is swollen a little toward the rear direction of the vehicle body as viewed in side elevation by the moving mechanism  90 . 
     The moving mechanism  90  for moving the wind screen  51  along the direction of the arrow mark y includes a guide element (also called adjust rail)  91  mounted on the upper cowling  41  and extending in the direction of the arrow mark y, a movable element  92  supported for movement on the guide element  91 , and a connection element  94  for connecting the wind screen  51  and the movable element  92  to each other. 
     A pair of guide elements  91  are provided and are supported on the inner side of the upper cowling  41 , and the movable element  92  supported for sliding movement on the guide elements  91  is connected to an electric motor not shown disposed in the inner side of the upper cowling  41  through a push cable  96  such that it is moved in the upward and downward directions under the guidance of the guide elements  91  by driving of the electric motor. 
     The connection element  94  which connects the wind screen  51  and the movable element  92  to each other has a movable element fixing side stay (movable element fixing side member)  97  fixed to the movable element  92  and extending substantially in the direction indicated by the arrow mark y (inclined direction), and a screen fixing side stay (screen fixing side member)  98  fixed to the wind screen  51 . 
     The movable element fixing side stay  97  of a substantially long plate-like shape includes a hole portion  99  and a cutaway portion  100  formed at a lower end side (vehicle body front side) and fixed to the movable element  92  by a fastening member such as a screw as seen in  FIGS. 4(   a ) and  4 ( b ), and a first projection (fixing portion)  101  and a second projection (fixing portion)  102  provided at predetermined distances in the longitudinal direction of the movable element fixing side stay  97 . Of the projections, the first projection  101  is formed at a substantially central portion in the longitudinal direction of the movable element fixing side stay  97 , and the second projection  102  is formed on an upper end side (vehicle body rear side) of the movable element fixing side stay  97 . Since the movable element fixing side stay  97  is secured to the movable element  92  through the hole portion  99  and the cutaway portion  100 , it moves together with movement of the movable element  92 . 
     Meanwhile, the screen fixing side stay  98  has a first face  103  formed on a plate-like member of a substantially L shape as viewed on a section and connecting to the movable element fixing side stay  97 , and a second face  104  connecting to the wind screen  51 . On the first face  103  of the screen fixing side stay  98 , an elongated hole portion  105  provided from a central portion in the longitudinal direction to the lower end side, a first recessed portion  106  cut away at a central portion of an end edge of the first face  103  and a second recessed portion  107  cut away on the end edge upper end side (vehicle body rear side) of the first face  103  are formed. 
     Meanwhile, the first recessed portion  106  and the second recessed portion  107  have locking portions  106 A and  107 A cut out toward the upper end side, respectively. And, the first and second recessed portions  106  and  107  having the locking portions  106 A and  107 A are engageable with the first and second projections  101  and  102  of the movable element fixing side stay  97 , respectively. Further, the elongated hole portion  105  of the screen fixing side stay  98  is engageable with the first and second projections  101  and  102  of the movable element fixing side stay  97 . 
     Meanwhile, on the second face  104  of the screen fixing side stay  98 , an elongated hole portion  108  formed substantially at a central portion in the longitudinal direction and a plurality of (totaling three) hole portions  109  formed on the opposite sides of the elongated hole portion  108 . Then, if the second face  104  of the screen fixing side stay  98  and the wind screen  51  are brought into contact with each other and the screen fixing side stay  98  and the wind screen  51  are connected to each other using fastening members  110  such as a screw through the elongated hole portion  108  and the hole portions  109  formed on the second face  104  of the screen fixing side stay  98  as shown in  FIG. 3 , then the screen fixing side stay  98  and the wind screen  51  are fixed to each other. 
     Here, as seen in  FIGS. 4(   a ) and  4 ( b ), the screen fixing side stay  98  can be fixed at two different positions in the longitudinal direction (direction of the arrow mark y, inclination direction) to the movable element fixing side stay  97 . In order to fix the screen fixing side stay  98  at the Lo position (refer to  FIG. 4(A) ) to the movable element fixing side stay  97 , the first projection  101  of the movable element fixing side stay  97  is engaged with the upper end side of the elongated hole portion  105  of the screen fixing side stay  98  and the second projection  102  of the movable element fixing side stay  97  is engaged with the locking portion  107 A of the second recessed portion  107  of the screen fixing side stay  98 . At this time, the first recessed portion  106  of the screen fixing side stay  98  does not engage with anything. 
     On the other hand, in order to fix the screen fixing side stay  98  at the Hi position (refer to  FIG. 4(B) ) to the movable element fixing side stay  97 , the first projection  101  of the movable element fixing side stay  97  is engaged with the lower end side of the elongated hole portion  105  of the screen fixing side stay  97  and the second projection  102  of the movable element fixing side stay  97  is engaged with the locking portion  106 A of the first recessed portion  106  of the screen fixing side stay  98 . At this time, the second recessed portion  107  of the screen fixing side stay  98  does not engage with anything. 
     In this manner, the movable element fixing side stay  97  has the first projection  101  and the second projection  102  which can fix the screen fixing side stay  98  at two different positions substantially in the inclination direction to the movable element fixing side stay  97 . 
     It is to be noted that this wind screen  51  is moved upwardly and downwardly in response to an operation of an operation switch (not shown) provided on the handle bar or the like of the motorcycle. In the present embodiment, as seen in  FIGS. 3 ,  4 ( a ) and  4 ( b ), since the guide elements  91  is formed in a bow shape in which it is swollen a little toward the rear direction of the vehicle body, the wind screen  51  moved upwardly does not move in a direction in which it coincides fully with the inclination direction, but moves such that the upper end thereof is directed a little to the forward direction (that is, so that an upwardly erected state may be established) together with the upward movement, and the wind screen  51  moved downwardly is inclined toward the rear direction of the vehicle body together with the downward movement. 
     In the present configuration, a sub screen (baffle plate)  20  which is inclined toward the rear direction of the vehicle body is disposed between the upper cowling  41  and the wind screen  51  as seen in  FIGS. 1 and 2 . This sub screen  20  is formed such that the vertical length thereof is smaller than that of the wind screen  51  and the width thereof is greater than a maximum width of the wind screen  51  so that the wind pressure to the shoulder portions of the driver may be reduced. Further, the sub screen  20  is entirely formed as a unitary member from a transparent resin material in order to assure the forward sight. 
       FIG. 5  is an exploded perspective view showing the sub screen  20  together with peripheral elements. 
     The sub screen  20  includes a pair of left and right shaft fitting portions  21 A,  21 A provided at a lower end central portion  21  thereof so as to project to the rear face side, and the shaft fitting portions  21 A,  21 A are inserted into a pair of left and right hole portions  25 A,  25 A provided on a visor  25  which forms a lid for a recessed portion  41 A formed at a front upper portion of the upper cowling  41 . This visor  25  is fitted in the upper cowling  41  to form part of a surface member of the upper cowling  41 , and a pair of left and right bearing portions  25 B,  25 B having holes communicating with holes of the shaft fitting portions  21 A,  21 A project on the reverse side of the visor  25 . A single shaft  26  is fitted in the holes and the shaft  26  is prevented from coming off and connect the sub screen  20  and the visor  25  to each other. It is to be noted that, a locking portion locks the visor  25  to the upper cowling  41 . 
     According to this connection structure, since a portion near to a lower end of the sub screen  20  is connected for sliding movement to the upper cowling  41  by means of a shaft, the sub screen  20  is connected for rocking motion to the upper cowling  41  while it keeps a state wherein the lower end thereof is positioned in the proximity of the surface of the upper cowling  41 . Therefore, air flow flowing along the surface of the upper cowling  41  can be guided efficiently to the front face of the sub screen  20  and can flow to the rear direction of the vehicle body along the front face of the sub screen  20 . 
     On the left and right sides of the lower end central portion  21  of the sub screen  20 , escape portions  21 B,  21 B which form gaps with respect to the upper cowling  41  are formed as seen in  FIG. 5 . Those escape portions  21 B,  21 B are provided to introduce part of the air flow flowing along the surface of the upper cowling  41  to the rear of the sub screen  20 . Therefore, part of the air flow can flow toward the driver on the rear side of the upper cowling  41 , and the amount of the air flow flowing along the front face of the sub screen  20  can be adjusted appropriately. 
     The left and right end portions  20 L,  20 R of the sub screen  20  are curved a little toward a front upper portion of the vehicle body such that air flow from a forward direction of the vehicle body can flow to the obliquely upward side toward the rear direction of the vehicle body by the left and right end portions  20 L,  20 R of the sub screen  20 . Therefore, in comparison with an alternative configuration wherein the left and right end portions  20 L,  20 R of the sub screen  20  are not curved, part of the air flow can be introduced toward the upward direction above the shoulders of the driver to appropriately reduce the wind pressure to the shoulder portions of the driver. 
     Further, in the present configuration, a connection mechanism  30  which forms the connection element  94  for connecting the sub screen  20  to the wind screen  51  is provided. This connection mechanism  30  functions also as an inclination angle variation mechanism for varying the inclination angle of the sub screen  20  in response to the inclination angle of the wind screen  51 . 
     More particularly, the connection mechanism  30  has a pair of left and right sub screen connecting stays (baffle plate connecting stays)  31  for connecting the movable element fixing side stay  97 , which connects the wind screen  51  and the movable element  92  to each other, and the sub screen  20  to each other. 
     Each of the sub screen connecting stays  31  includes a stay body  31 A having an elongated hole portion  31 C extending substantially obliquely upwards toward the rear direction of the vehicle body, and a bent plate portion  31 B bent from a lower edge of the stay body  31 A. The bent plate portion  31 B is fixed to the sub screen  20  by means of a fastening member such as a screw to fix the stay body  31 A in an uprightly erected state from the sub screen  20 . 
     To the elongated hole portion  31 C of the stay body  31 A, a collar body  33  having a large diameter portion on one end side and a receiving member  34  which forms a large diameter portion on the other end side, which form a cylindrical collar  32  having large diameter portions for preventing the removal at the opposite ends thereof are inserted from the opposite left and right sides of and connected to the elongated hole portion  31 C. The cylindrical collar  32  is mounted for sliding movement along the elongated hole portion  31 C. In the cylindrical collar  32 , a pin  97 A which projects to the inner side of the vehicle body from the movable element fixing side stay  97  is fitted, and a nut  35  is fastened to the end portion of the pin  97 A projecting from the cylindrical collar  32  to prevent the removal of the pin  97 A. Since the pin  97 A is mounted for sliding movement in the elongated hole portion  31 C of the stay body  31 A through the cylindrical collar  32 , the sliding resistance can be reduced low by using a material having a low coefficient of friction for the cylindrical collar  32 . 
     According to this configuration, when the wind screen  51  moves from the Lo position (indicated by solid lines in  FIG. 6 ) to the Hi position (indicated by alternate long and two short dashes lines in  FIG. 6 ) as seen in  FIG. 6 , the pin  97 A of the movable element fixing side stay  97  moves in the rearwardly obliquely upward direction (rearward direction along the direction indicated by the arrow mark y) integrally with the wind screen  51  ( 97 ′,  97 A′ in  FIG. 6 ). Therefore, while the pin  97 A moves to the rear side of the vehicle body within the elongated hole portion  31 C of the sub screen connecting stay  31 , it erects the sub screen connecting stay  31  uprightly around the center of rocking motion (corresponding to the axis of the shaft  26  (refer to  FIG. 5 )) ( 31 ′ in  FIG. 6 ). Together with the upright erection of the sub screen connecting stay  31 , also the sub screen  20  to which the sub screen connecting stay  31  is fixed is erected uprightly ( 20 ′ in  FIG. 6 ) and the inclination angle of the sub screen  20  increases (indicated by alternate long and two short dashes lines in  FIG. 6 ). In other words, the inclination angle of the sub screen  20  is adjusted to a large angle when the inclination angle of the wind screen  51  is large. It is to be noted that a meter unit  55  is disposed in a space rearwardly of the upper cowling  41 . 
     On the other hand, where the wind screen  51  moves from the Hi position (indicated by alternate long and two short dashes lines in  FIG. 6 ) to the Lo position (indicated by solid lines in  FIG. 6 ), since the pin  97 A of the movable element fixing side stay  97  moves in the forwardly obliquely downward direction (forward direction along the direction indicated by the arrow mark y) as seen in  FIG. 1 , while the pin  97 A moves to the front side in the elongated hole portion  31 C of the sub screen connecting stay  31 , it lays the sub screen connecting stay  31  down to decrease the inclination angle of the sub screen  20  to which the sub screen connecting stay  31  is fixed (indicated by solid lines in  FIG. 6 ). In other words, when the inclination angle of the wind screen  51  is small, the inclination angle of the sub screen  20  is adjusted to a small angle. 
     The connection mechanism  30  described above automatically changes the inclination angle of the sub screen  20  in an interlocking relationship with the inclination angle of the wind screen  51  in this manner. Further, in the present configuration, the connection mechanism  30  is configured such that the inclination angle of the sub screen  20  is adjusted to an angle which substantially coincides with the inclination angle of the wind screen  51  as seen in  FIG. 6 . 
     Therefore, at whichever one of the Lo position and the Hi position the wind screen  51  is positioned, or even if the wind screen  51  is positioned at an intermediate position between them, air flow from between the upper cowling  41  and the wind screen  51  can be let flow along the rear face of the wind screen  51  by the sub screen  20 . Accordingly, the space between the wind screen  51  and the driver is prevented from being placed into a negative pressure state. 
     As described above, according to the present embodiment, since the sub screen  20  which is inclined toward the rear direction of the vehicle body is provided between the upper cowling  41  and the wind screen  51  and the sub screen  20  is configured such that the inclination angle thereof can be adjusted so that air flow from between the upper cowling  41  and the wind screen  51  can flow along the rear face of the wind screen  51  by the sub screen  20 , even if the inclination angle of the wind screen  51  is changed, the air flow can always flow along the rear face of the wind screen  51 . 
     Consequently, the situation wherein the space between the wind screen  51  and the driver is placed into a negative pressure state can be prevented without limiting the inclination angle or the height of the wind screen  51  of the movable type. Thus, for example, a specification change such as to configure the wind screen  51  for adjustment to a higher position can be readily carried out. 
     Since the connection mechanism  30  which connects the sub screen  20  and the wind screen  51  to each other varies the inclination angle of the sub screen  20  in response to the inclination angle of the wind screen  51 , in comparison with an alternative case wherein the individual inclination angles of the wind screen  51  and the sub screen  20  are varied by separate mechanisms, simplification of the configuration such as a reduction in the number of parts is possible. In addition, it is possible to readily adjust the inclination angle of the sub screen  20  to the inclination angle of the wind screen  51 . 
     Further, since the sub screen  20  is connected for rocking motion to the upper cowling  41  while a state wherein the lower end thereof is positioned in the proximity of the surface of the upper cowling  41  is maintained, a quantity of air flow flowing along the surface of the upper cowling  41  can be introduced efficiently to the front face of the sub screen  20 , and sufficient air flow can flow readily along the rear face of the wind screen  51 . 
     Further, since the sub screen  20  is formed with a width greater than that of the wind screen  51 , rectification of the air flow and reduction of the wind pressure to the driver can be carried out by both of the wind screen  51  and the sub screen  20 . Therefore, the rectification effect and the windbreak effect can be improved. Even in the case where the specifications change such as to configure the wind screen  51  to be decreased in width, the rectification effect and the windbreak effect can be secured sufficiently by the sub screen  20 , and also the degree of freedom in planning and the degree of freedom in design of the wind screen  51  can be improved. 
       FIGS. 7 to 10  show a screen for a motorcycle according to a second embodiment. 
     In the second embodiment, the connection mechanism  30  which connects the sub screen  20  to the wind screen  51  includes a pair of left and right sub screen holders (hereinafter referred to as holders)  150  provided on the wind screen  51  side, and the sub screen  20  is connected to the wind screen  51  through the holders  150  as seen in  FIG. 7 . 
     More particularly, a pair of left and right movable element fixing side stays  97  are attached to the wind screen  51  as shown in  FIG. 7 . Boss portions  97 B which project from the inner side faces are provided individually on the movable element fixing side stays  97 , and the holders  150  are fitted on the boss portions  97 B and screws  151  are tightened. In this instance, the holders  150  are supported for pivotal motion (for tilting motion) around the boss portions  97 B respectively. 
     Support plates  153  of a substantially L-shaped section are secured to the pair of left and right movable element fixing side stays  97  through first projections  101  and second projections  102  by nuts  101 A and  102 B, respectively as seen in  FIG. 8 . The wind screen  51  is fixed to the pair of left and right support plates  153  by means of a plurality of bolts  155 , and the wind screen  51  and the movable element fixing side stays  97  are connected integrally thereby. It is to be noted that the connection structure is same as that in the first embodiment. 
       FIG. 9  is an exploded perspective view showing the holder  150  together with peripheral elements. The holder  150  is formed from a pair of left and right holder elements  161  and  162  connected to each other by bolts  153 . A groove portion  165  into and from which a pair of left and right sub screen connecting stays  31  provided on the sub screen  20  can be advanced and retracted is provided between the holder elements  161  and  162 . A plurality of (three in the present example) rolling members  171 ,  172  and  173  are supported for rotation on the inner side of the groove portion  165 . It is to be noted that, in  FIG. 9 , a bearing portion  161 A is provided for supporting the boss portions  97 B of the movable element fixing side stays  97  for pivotal motion, and a hole portion  162 A is provided in which an end portion of the bearing portion  161 A is fitted. 
     The rolling members  171  to  173  include a plurality of (two in the example) first rolling members  171  and  172  fitted in the elongated hole portion  31 C formed in the sub screen connecting stay  31 , and a second rolling member  173  which contacts with an upper face  31 D of the sub screen connecting stay  31 . The first rolling members  171  and  172  are supported for rotation on shaft portions  166  and  167  which project from the holder element  161 , and the second rolling member  173  is supported for rotation on the holder element  161  through a biasing member  175 . 
     Where the holder  150  is mounted on the sub screen connecting stay  31 , the pair of left and right holder elements  161  and  162  are connected in such a manner as to sandwich the sub screen connecting stay  31  from the left and right. In this instance, the first rolling members  171  and  172  are inserted in the elongated hole portion  31 C extending along the longitudinal direction of the sub screen connecting stay  31  and connect the holder  150  and the sub screen connecting stay  31  through the first rolling members  171  and  172 . 
     The biasing member  175  biases the second rolling member  173  such that, when the holder  150  and the sub screen connecting stay  31  are connected to each other, the second rolling member  173  is pressed against the upper face  31 D which extends in the longitudinal direction of the sub screen connecting stay  31 , and is formed by bending a spring wire member in such a manner as seen in  FIG. 9 . 
     By the biasing member  175 , the second rolling member  173  is pressed against the upper face  31 D of the sub screen connecting stay  31 , and by this reactive force, the first rolling members  171  and  172  are pressed against an upper side inner face  31 E of the elongated hole portion  31 C of the sub screen connecting stay  31 . In particular, the sub screen connecting stay  31  is sandwiched from above and below by the first rolling members  171  and  172  and the second rolling member  173  as shown in  FIG. 10 . Therefore, the connection strength between the holder  150  and the sub screen connecting stay  31  is assured sufficiently, and the holder  150  can be slidably moved along the sub screen connecting stay  31  through the rolling members  171  to  173 . Upon such sliding movement, since the rolling members  171  to  173  roll, the sliding resistance can be reduced. 
     According to this configuration, when the wind screen  51  is at the Lo position (indicated by solid lines in  FIG. 10 ), the holder  150  is positioned on the front side of the sub screen connecting stay  31  as seen in  FIG. 10 , and at this position, the sub screen  20  is kept in a state wherein the inclination angle is small similarly to the wind screen  51 . 
     On the other hand, if the wind screen  51  moves from the Lo position to the Hi position (indicated by alternate long and two short dashes lines in  FIG. 10 ), then the holder  150  ( 150 ′ in  FIG. 10 ) moves to the rearwardly obliquely upward direction (direction in which the guide elements  91  extends) of the vehicle body integrally with the wind screen  51  ( 51 ′ in  FIG. 10 ). Therefore, while the holder  150  moves toward the rear side of the vehicle body within the elongated hole portion  31 C of the sub screen connecting stay  31  ( 31 ′ in  FIG. 10 ), it uprightly erects the sub screen connecting stay  31  around the center of rocking motion (corresponding to the axis of the shaft  26  (refer to  FIG. 7 )). Together with the upright erection of the sub screen connecting stay  31 , also the sub screen  20  ( 20 ′ in  FIG. 10 ) to which the sub screen connecting stay  31  is fixed is erected uprightly and the inclination angle of the sub screen  20  increases. By this, the inclination angle of the wind screen  51  and the inclination angle of the sub screen  20  can be normally kept to the same angle similarly as in the first embodiment. 
     According to the present embodiment, the connection mechanism  30  includes the sub screen connecting stay  31  provided on the sub screen  20  and extending in the forward and backward direction of the vehicle body and further includes the sub screen holder  150  provided on the wind screen  51  and holding the stay  31  for sliding movement along the sub screen connecting stay  31 . Therefore, in comparison with an alternative case wherein the inclination angles of the wind screen  51  and the sub screen  20  are changed by separate mechanisms from each other, the inclination angles of the wind screen  51  and the sub screen  20  can be normally kept to the same angle by a simple configuration. 
     Further, in the present embodiment, since the sub screen holder  150  slidably moves on the sub screen connecting stay  31  through the plurality of rolling members  171  to  173 , the sliding resistance can be reduced. 
       FIGS. 11 to 13  show a screen of a motorcycle according to a third embodiment. Here,  FIG. 11  is an exploded perspective view showing the screen together with peripheral elements,  FIG. 12  is a side sectional view of the screen, and  FIG. 13  is a sectional view taken along line XIII-XIII of  FIG. 12 . 
     In the third embodiment, as shown in  FIGS. 1I and 12 , a pair of left and right guide arms  181 ,  181  extending along the forward and backward direction below the sub screen  20  are provided, and a mechanism for varying the inclination angle of the sub screen  20  in response to movement of the wind screen  51 , that is, the connection mechanism  30  for connecting the sub screen  20  to the wind screen  51 , is formed from the guide arms  181 ,  181 . 
     More particularly, the pair of left and right guide arms  181 ,  181  are formed from plate-formed members of a substantially L-shaped sectional shape wherein vertical plate portions  181 A,  181 A mounted at end portions thereof for pivotal motion on side faces of the pair of left and right guide elements  91 ,  91  and extending rearwardly and bent plate portions  181 B,  181 B bent to the inner side along lower edges of the vertical plate portions  181 A,  181 A are provided integrally. It is to be noted that the bent plate portion  181 B is not formed at a front end and a rear end of the vertical plate portion  181 A but is formed only between the front and the rear end. 
     The front ends of the vertical plate portions  181 A,  181 A are mounted for pivotal motion on side faces of the pair of left and right guide elements  91 ,  91  through bolts  191  and collars  192  respectively. Consequently, the left and right guide arms  181 ,  181  are supported for pivotal motion around an axis of the bolts  191  extending in the vehicle widthwise direction on the guide elements  91 ,  91 . Here, the collars  192  are formed from a low friction material and are disposed between the guide arms  181  and the guide elements  91  to reduce the sliding resistance upon pivotal motion of the guide arms  181 . 
     Meanwhile, the vertical plate portions  181 A,  181 A are connected at the rear end thereof to a pair of left and right downward projections  22 A,  22 A of the sub screen  20  through a pair of left and right arms  193 ,  193 . More particularly, the pair of left and right arms  193 ,  193  are connected at one end (lower end) thereof to the rear ends of the vertical plate portions  181 A,  181 A individually by pins  194 ,  194 , and are connected at the other end (upper end) thereof to the downward projections  22 A,  22 A of the sub screen  20  individually by pins  195 ,  195 . It is to be noted that, in  FIGS. 11 and 12  a snap ring  196  is provided (for example, E-shaped snap ring (so-called E ring)) for fastening the pins  194 ,  195  used for pin-connection of the arms  193 . 
     A pair of left and right movable element fixing side stays  97 ,  97  connected to the wind screen  51  are connected to movable elements  92 ,  92  disposed on the inner side of the pair of left and right guide elements  91  by a pair of front and rear bolts  197 ,  197 . In particular, movable element fixing side stays  97  and guide arms  181  are separately disposed on the inner side and the outer side of the guide elements  91  thereby to achieve a configuration which does not require a separate provision of mounting portions for the parts (movable element fixing side stays  97  and guide arms  181 ). 
     Holders (guide arm holders)  97 C,  97 C which extend to the outside in the vehicle widthwise direction of the stays  97 ,  97  for holding the pair of left and right guide arms  181 ,  181  are individually provided on the movable element fixing side stays  97 . As shown in  FIG. 13 , the holders  97 C,  97 C include plate-formed members on which stay fixing portions  97 D,  97 D fixed by welding to the movable element fixing side stays  97  and bent plate portions  97 E,  97 E bent in a substantially L shape from the movable element fixing side stays  97  are provided integrally. A pair of upper and lower sliders  201  and  202  for holding the guide arms  181 ,  181  from above and below are mounted on the bent plate portions  97 E,  97 E, and the sliding resistance with the guide arms  181 ,  181  is reduced by the sliders  201  and  202  to support the guide arms  181 ,  181  for sliding movement. 
     Since the left and right guide arms  181 ,  181  are supported for sliding movement on the holders  97 C,  97 C which move integrally with the left and right movable element fixing side stays  97 ,  97 , if the movable element fixing side stays  97 ,  97  are moved upwardly and downwardly along the guide elements  91 ,  91 , then the left and right guide arms  181 ,  181  supported on the holders  97 C,  97 C of the movable element fixing side stays  97 ,  97  are rocked upwardly and downwardly with reference to an end thereof (axis of the bolts  191 ). Therefore, the rear ends of the guide arms  181 ,  181  move upwardly and downwardly to move a rear portion of the sub screen  20  upwardly and downwardly through the arms  193 ,  193 , whereby the sub screen  20  can be tilted around the shaft  26  (refer to  FIG. 5  or  7 ) extending through the shaft fitting portions  21 A,  21 A provided at the front portion of the sub screen  20  to vary the inclination angle. 
     Accordingly, if the movable element fixing side stays  97  are moved to vary the inclination angle of the wind screen  51 , then the guide arms  181 ,  181  are rocked in response to the movement of the stays  97  to vary the inclination angle of the sub screen  20 , and the inclination angle of the wind screen  51  and the inclination angle of the sub screen  20  can be held at a substantially equal angle similarly as in the first embodiment. 
     As described above, according to the present embodiment, since the connection mechanism  30  which includes the guide arms  181 ,  181  extending along the forward and backward direction below the wind screen  51  and rocks the guide arms  181 ,  181  upwardly and downwardly in response to movement of the movable element fixing side stays  97  connected to the wind screen  51  to vary the inclination angle of the sub screen  20  by the upward and downward movement of the guide arms  181 ,  181  is configured, various parts which compose the connection mechanism  30  can be disposed below the sub screen  20 . 
     Accordingly, in addition to effects similar to those of the first and second embodiments, since there is no necessity to dispose the sub screen connecting stay  31  and so forth above the sub screen  20 , parts of the type described do not disturb the flow of the air from between the upper cowling  41  and the wind screen  51 , and the air flow can flow more smoothly along the front face of the sub screen  20 . Thus, a reduction of the air resistance and a reduction of wind noise can be achieved. 
     Further, in the connection mechanism  30  of the present configuration, the left and right guide arms  181 ,  181  are connected to the sub screen  20  through the arms  193 ,  193  thereby to configure a link mechanism for appropriately tilting the sub screen  20  in response to upward or downward movement of the guide arms  181 ,  181 . In other words, by adjusting the mounting position and the arm length of the guide arms  181 ,  181 , the relationship between the inclination angle of the wind screen  51  and the inclination angle of the sub screen  20  can be adjusted, and also a change of design is easy. 
     While the present invention is described above based on the embodiments, the present invention is not limited to them, but various changes of design can be carried out. For example, while, in the embodiments described above, the sub screen  20  is mounted for rocking motion on the upper cowling  41  through the visor  25 , the mounting is not limited to this, but the sub screen  20  may be mounted for rocking motion directly on the upper cowling  41 . In this instance, the sub screen  20  may be formed as part of the upper cowling  41 . 
     Further, since the sub screen  20  is smaller in size than the wind screen  51  and besides is supported for rocking motion on the upper cowling  41 , even if the sub screen  20  is formed from a non-transparent material, the visual observability of the driver can be assured sufficiently, and the degree of freedom in design of the sub screen  20  can be assured sufficiently. 
     Further, while, in the embodiments described above, the present invention is applied to a screen for a motorcycle wherein the wind screen  51  is driven by an electric motor, any other driving source than the electric motor may be used, or the present invention can be applied widely to a manual screen wherein the wind screen  51  is operated manually and so forth. 
     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.