Abstract:
A skateboard is constructed to provide a natural ride and good operability without adversely influencing a motor controller and batteries. The skateboard includes a board, wheels provided on a bottom side of the board at front and rear regions thereof, a motor controller for supplying the wheels with rotary power, a case provided on a bottom side of the board and housing the motor controller, and fixing bolts fixing an approximately central region of the case to the board, leaving front and rear end regions of the case free.

Description:
BACKGROUND OF THE INVENTON  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a skateboard, and more specifically, the present invention relates to a powered skateboard which includes a drive wheel supplied with rotary power by a drive motor.  
         [0003]     2. Description of the Related Art  
         [0004]     Conventionally, powered skateboards that are driven by a drive motor are known, an example of which is disclosed in JP-A 2000-140190, which is hereinafter referred to as Patent Document 1.  
         [0005]     According to the powered skateboard disclosed in Patent Document 1, the drive motor and the drive wheel supplied with rotary power by the drive motor are provided on a bottom side of the board. Further, a motor controller, which includes a controller for controlling the motor, a battery as a power source and so on, is attached to a bottom surface of the board.  
         [0006]     According to this technique, however, the controller and the battery are attached entirely and integrally with the board. Therefore, when the board is used and as the board is deformed by the rider&#39;s weight, the deformation load, for example, acts directly on the controller or the battery, potentially causing an adverse influence on the controller or the battery.  
         [0007]     In order to reduce the deformation of the board, the board may be made of a material which has a high strength/rigidity rather than a flexible structural material, or the board may be provided with a reinforcing member for enhanced strength/rigidity. However, superior strength/rigidity will lead to unnatural riding and operability.  
       SUMMARY OF THE INVENTION  
       [0008]     In order to overcome the problems described above, preferred embodiments of the present invention provide a skateboard that provides a natural ride and good operability without adversely influencing a drive power controller such as a controller and a battery.  
         [0009]     According to a preferred embodiment of the present invention, a skateboard includes a board, wheels provided on a bottom side of the board at front and rear regions thereof, a motor controller arranged to supply at least one of the wheels with rotary power, a case provided on a bottom side of the board and housing the motor controller, and a fixing element arranged to fix a center region of the case to the board, leaving front and rear end regions of the case free.  
         [0010]     According to a preferred embodiment of the present invention, an approximately central region of the case is fixed to the board by the fixing element, and the front and the rear ends of the case are free ends. Therefore, for example, when the rider applies a load onto the board, causing the approximately central region of the board to be displaced (flexed) in vertical directions on the front and the rear wheels serving as fulcrum points, the case does not deform so there is no adverse influence on the motor controller, which may include a controller and a battery. Further, since the board is not subject to a resisting force from the case against the deflection of the board, good operability by the rider&#39;s feet is obtained, and a natural comfortable ride can be assured due to suspension.  
         [0011]     According to another preferred embodiment of the present invention, a skateboard includes a board, wheels provided on a bottom side of the board at front and rear regions thereof, a motor controller arranged to supply at least one of the wheels with rotary power, a case provided on a bottom side of the board and housing the motor controller, and a support member arranged to support the case on the bottom side of the board, and move longitudinally relative to the board at least when a load is applied on the board.  
         [0012]     According to this preferred embodiment of the present invention, even if the rider applies a load onto the board and causes the generally central region of the board to be displaced (flexed) in vertical directions, the support member of the case moves in fore-and-aft directions (longitudinally of the board) in accordance with the amount of displacement, reducing the deformation load, vibration, force, etc. that is applied to the case. Use of the skateboard under such a condition does not deform the case, so there is no adverse influence on the motor controller, which may include, for example, a controller, a battery and other elements. Further, since the board is not subject to a resisting force from the case against the deflection of the board, good operability by the rider&#39;s feet is obtained, and a natural comfortable ride can be assured due to suspension.  
         [0013]     Preferably, the skateboard further includes a weight transfer detection sensor for detecting weight transfer of a rider riding on the board. The motor controller is preferably arranged to supply the wheel with the rotary force in accordance with a detection signal from the weight transfer detection sensor. In this case, good driving control of the wheel in accordance with the weight transfer of the rider can be achieved.  
         [0014]     Further, preferably, the board is made of a flexible structural material. In this case, the board flexes in vertical directions, making it possible to further improve operability by the rider&#39;s feet, further improve riding comfort due to suspension, and contribute to reduced weight.  
         [0015]     The present invention is advantageous when the motor controller includes a controller or a battery which is susceptible to bending.  
         [0016]     Further, preferred embodiments of the present invention are advantageous when the controller includes a plurality of batteries which are electrically connected with each other. Since each battery is heavy, the electrical connection between the batteries is likely to be cut by applied stress. However, according to preferred embodiments of the present invention, the case does not deform, and thus does not exert stress on the batteries, preventing such a problem.  
         [0017]     The term “skateboard” used in the description of preferred embodiments of the present invention means a mobile body which includes a plurality of wheels and a board disposed thereon, for a rider to ride on an upper surface of the board to transport.  
         [0018]     Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a perspective view showing a preferred embodiment of the present invention.  
         [0020]      FIG. 2  is a side view showing a skateboard without an intermediate portion.  
         [0021]      FIG. 3  is a schematic diagram of a section, showing how a front wheel which serves as a free wheel is attached.  
         [0022]      FIG. 4  is a conceptual diagram of a section, showing a construction of a rear wheel which serves as a drive wheel, and how it is attached.  
         [0023]      FIG. 5  is a conceptual diagram of a section, showing the inside of a case and how the case is attached.  
         [0024]      FIG. 6  is a conceptual diagram as a plan view, showing an inside of the case.  
         [0025]      FIG. 7  is a controller block diagram of the skateboard.  
         [0026]      FIG. 8  is a conceptual diagram showing how the case is supported when no load is applied in the preferred embodiment in  FIG. 1 .  
         [0027]      FIG. 9  is a conceptual diagram showing how the case is supported when a load is applied in the preferred embodiment in  FIG. 1 .  
         [0028]     FIGS.  10 ( a ) and  10 ( b ) illustrate a primary portion of another preferred embodiment of the present invention, wherein  FIG. 10 ( a ) is a conceptual diagram as a side view, and  FIG. 10 ( b ) is a conceptual diagram as a bottom view.  
         [0029]      FIG. 11  is a perspective view of the case used in the preferred embodiment shown in FIGS.  10 ( a ) and  10 ( b ).  
         [0030]      FIG. 12  is a conceptual diagram showing how the case is supported when no load is applied in the preferred embodiment shown in FIGS.  10 ( a ) and  10 ( b ).  
         [0031]      FIG. 13  is a conceptual diagram showing how the case is supported when a load is applied in the preferred embodiment shown in FIGS.  10 ( a ) and  10 ( b ).  
         [0032]     FIGS.  14 ( a )- 14 ( c ) illustrate another preferred embodiment of the present invention in which  FIG. 14 ( a ) is a conceptual diagram as a plan view,  FIG. 14 ( b ) is a conceptual diagram showing how the case is supported when no load is applied, and  FIG. 14 ( c ) is a conceptual diagram as a bottom view.  
         [0033]      FIG. 15 ( a ) is a conceptual diagram showing how the case is supported when a load is applied in the preferred embodiment of FIGS.  14 ( a )- 14 ( c ), and  FIG. 15 ( b ) is a conceptual diagram as a bottom view.  
         [0034]      FIG. 16  is a conceptual diagram of a section, showing a case housing two controllers. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0035]     Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.  
         [0036]     Referring to  FIG. 1 , a skateboard  1  according to a preferred embodiment of the present invention includes a board (deck)  3 . In front and rear regions on a bottom side of the board  3 , wheels  5  and  7  are provided, respectively. At a generally central region of a bottom surface of the board  3 , a case is supported as shown in  FIG. 5  and  FIG. 6 , which houses a motor controller  12  which preferably includes a drive motor controller (control circuit board)  9  and a battery  11  which defines a power source of the controller  9 . The controller  9  and the battery  11  are preferably fixed on a bottom surface of the case  13 . The battery  11  includes, for example, a plurality (for example, sixteen in the present preferred embodiment) of cells  11   a  which are electrically connected in series, for example, by welding. The cells  11   a  are defined by Ni—Cd battery cells, for example. Note that in  FIG. 5  and  FIG. 6 , reference numeral “ 11   b ” indicates a connection portion, such as a weld joint, for example, at which mutually adjacent cells  11   a  are connected with each other.  
         [0037]     The board  3  is preferably made of flexible structural material such as plywood, so that it is generally horizontal as shown in  FIG. 8  under no load, but flexes in vertical directions under a load as shown in  FIG. 9 , bringing a center portion into a downwardly recessed curve on a front and a rear wheels  5 ,  7  serving as fulcrums. Since the flexible structural material flexes in vertical directions, it provides improved operability by a rider&#39;s feet, providing suspension which improves riding comfort, as well as contributing to reduced weight. The flexible structural material should preferably have a spring coefficient between about 15 kg/cm and about 30 kg/cm. In the present preferred embodiment, a flexible structural material having an approximately 20 kg/cm spring coefficient (sagging about 1 cm under an approximately 20 kg load) is preferably used. The flexible structural material is also called flexibly bendable material.  
         [0038]     Each of the wheels  5 ,  7  is preferably a single wheel. The wheel  5  in the front preferably serves as a free wheel whereas the wheel  7  at the rear preferably serves as a drive wheel which incorporates a drive motor  15 .  
         [0039]     Referring to  FIG. 2  and  FIG. 3 , the free wheel or the wheel  5  is rotatably supported by a supporting arm  17 . The supporting arm  17  is preferably formed in a downward facing U, and includes an upper arm portion  17   a,  and right and left arm portions  17   b.  The upper arm portion  17   a  is supported pivotably freely in a range of 360 degrees by a fixed frame  21  via an arm shaft  19 . As shown in  FIG. 1 , the fixed frame  21  is integrally fixed to and supported on a bottom surface of the board  3  by a plurality of fastening bolts  23 , for example.  
         [0040]     Each of the right and the left arm portions  17   b  has a long hole  25  which extends in forward and rearward directions. The long hole  25  is provided with a wheel attaching shaft  27  which rotatably supports the wheel  5 . Therefore, the attaching location of the front wheel or the wheel  5  is adjustable within the long hole  25  by moving the wheel in the forward or rearward direction for a desired turning characteristic of the skateboard  1 .  
         [0041]     Referring to  FIG. 2  and  FIG. 4 , a hollow fixed sleeve  29  is provided inside the drive wheel or the wheel  7 , and the drive motor  15  is fixed within the fixed sleeve  29 . A bearing  31  is provided on each side of the fixed sleeve  29 . The bearings  31  rotatably support the wheel  7 . The fixed sleeve  29  has two side portions  29   a,  each integrally fixed to and supported by a supporting arm  35  via a wheel attaching shaft  33 .  
         [0042]     The supporting arm  35  is preferably formed in a downward facing U, and includes an upper arm portion  35   a,  and right and left arm portions  35   b  which provides a fixed support to the side portions  29   a  of the fixed sleeve  29 . The upper arm portion  35   a  is pivotable freely in a range of 360 degrees around an arm shaft  37 , and is supported by a fixed frame  39 . The fixed frame  39  is integrally fixed to and supported on a bottom surface of the board  3  by a plurality of fastening bolts  41 , for example.  
         [0043]     The drive motor  15  is controlled based on signals supplied from the controller  9 , which is powered by a battery  11 . A drive gear  45  is inserted around the motor shaft  43 . The drive gear  45  engages with a middle gear  47 , and the middle gear  47  engages with an internal gear  49  which is provided inside the wheel  7 , whereby a rotating force after speed reduction in accordance with gear ratios between the gears is transmitted to the wheel  7 .  
         [0044]     As shown in  FIG. 1  and  FIG. 5 , the controller  9  and the battery  11  are housed in a case  13 , an approximately central region of which is fixed to and supported on the bottom surface of the board  3 , with a fixing element such as fixing bolts  51 , for example. Thus, front and rear ends of the case  13  are free ends. The fixing bolts  51  are preferably round-head bolts as shown in  FIG. 5 . Alternatively, flat-head bolts may be used so the heads will not protrude from the board  3 . Many other fixing elements and materials may be used to fix the case  13  to the board  3 .  
         [0045]     A fixed support via the fixing bolt  51  may be a single-point support at the approximate central region or a multi-point support. If the multi-point support is used, preferably as shown in  FIG. 1 , the fixing bolts  51  are preferably arranged to be aligned along Line X which crosses the board  3 , i.e., substantially perpendicularly to the longitudinal directions of the board  3 .  
         [0046]     The controller  9  is supplied with detection signals from a weight transfer detection sensor  53  located closer to the fore foot and a weight transfer detection sensor  55  placed closer to the rear foot as shown in  FIG. 2 . The weight transfer detection sensor  53  for the fore foot is attached to the fixed frame  21  which supports the wheel  5  whereas the weight transfer detection sensor  55  for the rear foot is attached to the fixed frame  39  which supports the wheel  7 .  
         [0047]     Referring to  FIG. 7 , the controller  7  includes a CPU  57  and a driver  59 . The CPU  57  is supplied with a voltage at a voltage dividing point P of a voltage divider circuit which includes a series connection of the fore-foot and rear-foot weight transfer detection sensors  53 ,  55 ; a voltage from a speed sensor S provided by an encoder indicating the speed of wheel  7 ; and a drive current of the drive motor  15  supplied from a feedback circuit F. The CPU  57  and the driver  59  are mounted on a substrate which is preferably made of a material such as glass-epoxy resin or other suitable material.  
         [0048]     The weight transfer detection sensors  53 ,  55  for the forward and the rearward feet preferably have the same resistance characteristic. When a load is applied from the fore foot, the resistance value of the fore foot weight transfer detection sensor  53  decreases in inverse proportion to the load. When a load is applied from the rear foot, the resistance value of the rear foot weight transfer detection sensor  55  decreases in inverse proportion to the load. Therefore, when there is no load or the same amount of load exerted on both of the detection sensors  53  and  55 , the voltage at the voltage dividing point P of the voltage divider circuit becomes one half of voltage divider circuit source voltage V. On the other hand, when the rider transfers his weight on the board  3 , to increase the load on the fore-foot weight transfer detection sensor  53  over the load on the rear-foot weight transfer detection sensor  55 , the voltage becomes higher than V*½, by an amount that is proportional to the difference between the loads detected by the two detection sensors. Likewise, when the rider makes a weight transfer to decrease the load on the fore-foot weight transfer detection sensor  53  to become smaller than the load on the rear-foot weight transfer detection sensor  55 , the voltage becomes lower than V*½, by an amount that is proportional to the difference between the loads detected by the two detection sensors.  
         [0049]     The CPU  57  generates a drive command signal (PWM: Pulse Width Modulation signal) whose pulse width represents the voltage at the voltage dividing point P of the voltage divider circuit, and sends the signal to the driver  59  at the next stage of the circuit. Based on the drive command signal from the CPU  57 , the driver  59  outputs a drive current to the drive motor  15 .  
         [0050]     According to the skateboard  1  as described above, when the rider on the board  3  transfers his weight to his fore foot, the CPU  57  sends to the driver  59  a drive command signal which has a pulse width representing the difference between the loads on the forward-foot side and the rearward-foot side. The drive motor  15  is supplied with a drive current corresponding to the pulse width, and begins to accelerate or to travel forward. On the other hand, when the rider transfers his weight to his rear foot, the CPU  57  sends to the driver  59  a drive command signal which has a pulse width representing the difference between the loads on the forward-foot side and the rearward-foot side (a drive command signal which has a reverse amplitude of the amplitude when the weight transfer is to the fore foot). The drive motor  15  is supplied with a drive current corresponding to the pulse width, and begins to decelerate or to travel rearward.  
         [0051]     According to the skateboard  1  as described above, the case  13  is fixed at its generally central region by the fixing bolts  51 , for example, thereby freeing up the front and rear ends of the case  13 . Therefore, even if the load from the rider is applied to the board  3  and a generally central region of the board  3  deflects in a downward direction on the fulcrums provided by the front and the rear wheels  5 ,  7  (e.g., even if a state change occurs from a state in  FIG. 8  to a state in  FIG. 9 ), the case  13  is not deformed, and there is no adverse influence on the motor controller  12  including the drive motor controller  9  and the battery  11  which are susceptible to deflection. Therefore, it becomes possible for example, to prevent a weld joint  11   b  from coming off the battery  11   a,  resulting in an electrically open circuit between the batteries  11   a.  Further, since the board  3  is not subject to a resisting force from the case  13  against the deflection of the board  3 , good operability by the rider&#39;s feet is obtained, and a natural comfortable ride can be assured due to suspension.  
         [0052]     Further, the motor controller  12  supplies the wheel  7  with a rotary power in accordance with detection signals from the weight transfer detection sensors  53 ,  55 . This makes possible to provide good control on the drive of the wheel  7  in accordance with the weight transfer of the rider.  
         [0053]     Next, FIGS.  10 ( a ) and ( b ) show another preferred embodiment in which a case  13  is supported on the bottom surface side of the board  3 .  
         [0054]     In the present preferred embodiment, as clearly understood from  FIG. 11 , the case  13  preferably includes four rod members  61  on its two longitudinal side surfaces, each of the rod members extending substantially perpendicularly to the side surface at a place closer to a longitudinal end of the side surface. On the other hand, the board  3  has a bottom surface provided with four guide rails  63 , each of which has a generally L-shaped section and serves as supports for the rod members  61 . As clearly understood from  FIG. 10 ( b ), each guide rail  63  is provided at a location corresponding to one of the rod members  61 , and supports the rod member  61 . Under this state, the center region of the case  13  is free.  
         [0055]     As shown in  FIG. 12 , the board  3  is upwardly curved under no load. The rod members  61  are non-slidingly supported by the guide rails  63 . On the other hand, the board  3  flexes to become flat under a load as shown in  FIG. 13 , and the rod members  61  in the case  13  becomes slidable in the fore-and-aft directions with respect to the guide rails  63 . Other arrangements are the same as in the previous preferred embodiment, so the description of these common features will not be repeated here.  
         [0056]     According to the present preferred embodiment, even when the rider applies a load onto the board  3 , causing a generally central region of the board  3  to be displaced (flexed) in the vertical directions, the guide rails  63  which support the case  13  moves in the fore-and-aft directions according to the amount of displacement, i.e. the front guide rails  63  move forward and the rear guide rails move rearward, reducing the deformation load, vibration and so on exerted on the case  13 . Use of the skateboard under such a condition does not deform the case  13  and so there is no adverse influence on the motor controller  12  including the controller  9 , the battery  11  and so on. Further, since the board  3  is not subject to a resisting force applied from the case  13  against the deflection of the board  3 , good operability by the rider&#39;s feet is obtained, and a natural comfortable ride can be assured due to suspension.  
         [0057]     Next, FIGS.  14 ( a )-( c ) and FIGS.  15 ( a ) and ( b ) show another preferred embodiment in which a case  13  is supported on the bottom surface side of a board  3 .  
         [0058]     In the present preferred embodiment, four sets of bolts  65  and nuts  67  are preferably used as supports, and the case  13  is provided with four long through holes  69  for insertion of the bolts  65 . The bolts  65  should preferably be flat-headed so that the heads of bolts  65  will not protrude on the upper surface of the board  3  but will become flush with it.  
         [0059]     Using the bolts  65  and the nuts  67  as described above, the case  13  is suspended on the bottom surface side of the board  3  spaced at a distance therefrom, as shown in  FIG. 14  under no load. Under a load, the board  3  flexes downward as shown in  FIG. 15 , and the bolts  65  move in the long holes  69  toward the center of the board  3 . Other arrangements are the same as in the previous preferred embodiments, so description of the common features will not be repeated here.  
         [0060]     According to the present preferred embodiment, even when the rider applies his load onto the board  3 , causing a generally central region of the board  3  to be displaced (flexed) in vertical directions, the bolts  65  and the nuts  67  which support the case  13  move in the directions indicated by Arrow A (in  FIG. 14  and  FIG. 15 ), according to the amount of displacement, reducing the deformation load, vibration and so on exerted on the case  13 . Use of the skateboard under such a condition does not deform the case  13  and so there is no adverse influence on the motor controller  12  including the controller  9 , the battery  11  and so on. Further, since the board  3  is not subject to a resisting force from the case  13  against the deflection of the board  3 , good operability by the rider&#39;s feet is obtained, and a natural comfortable ride can be assured due to suspension.  
         [0061]     It should be noted here that not only the rear wheel  7  but also the front wheel  5  may be a drive wheel. In this case, the wheel  5  is also provided with a drive motor  15 . When both of the wheels  5 ,  7  serve as the drive wheels, it is preferable as shown in  FIG. 16 , that two controllers  9   a  are used respectively for the wheels  5 ,  7 , and the controllers  9   a  should be housed in the case  13 .  
         [0062]     Further, the fixing element arranged to fix a generally central portion of the case  13  onto the bottom surface of the board  3  is not limited to the fixing bolt  51 , but may be constituted by other fixing elements or materials such as an adhesive.  
         [0063]     The board  3  is not limited to wood, but may be made of other flexible structural members such as a synthetic resin.  
         [0064]     The present invention being thus far described and illustrated in detail, it is obvious that these descriptions and drawings only represent examples of preferred embodiments of the present invention, and should not be interpreted as limiting the present invention. The spirit and scope of the present invention is only limited by words used in the following claims.