Patent Publication Number: US-8970356-B2

Title: Vehicle approach notification apparatus for electric motorcycle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(a) to Application No. 2010-221600, filed in Japan on Sep. 30, 2010. The entirety of the above-identified application is expressly incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vehicle approach notification apparatus for an electric motorcycle. More particularly, the present invention relates to a vehicle approach notification control apparatus for an electric motorcycle, which issues a notification sound for notifying a walker or the like of approach of an electric motorcycle. 
     2. Description of Background Art 
     In recent years, in an electric vehicle or a hybrid vehicle whose development is proceeding, since the driving sound when the vehicle is driven to run by an electric motor is weak in comparison with the driving sound of an engine driven vehicle, a walker or the like is less likely to recognize approach of the vehicle. Thus, an appropriate countermeasure against this fact is demanded. 
     In Japanese Patent Laid-Open No. 2008-195137, a vehicle approach notification apparatus is disclosed wherein, when it is detected that the vehicle speed of a hybrid four-wheeled car, which runs, principally upon low speed running, with the driving force of an electric motor, is lower than a predetermined value and the brake is being operated, a notification sound is outputted from a speaker disposed on the inner side of a bumper at a front portion of a vehicle body, so that approach of the vehicle is let known to a walker or the like. A control apparatus for outputting a predetermined notification sound to the speaker is disposed in an engine room at a front portion. 
     SUMMARY OF THE INVENTION 
     In application of such a vehicle approach notification apparatus as described above, since the possibility that the requirement for a system, a function and so forth may vary in mixed traffic with engine vehicles is high, the vehicle approach notification apparatus is preferably configured such that system changes such as specification changes or the like of the control apparatus can be carried out readily. Further, in motorcycles which are poor in surplus space in comparison with four-wheeled cars, it is demanded to implement an incorporation structure which can cope also with such system changes as described above while assuring a disposition space for a control apparatus, which is a comparatively large piece of equipment. 
     It is an object of the present invention to provide a vehicle approach notification apparatus for an electric motorcycle which solves the subject of the background art described above and optimizes an attachment structure of a control apparatus, which carries out output control of notification sound, to a vehicle body. 
     In order to achieve the object described above, according to a first aspect of the present invention, a vehicle approach notification apparatus for an electric motorcycle ( 1 ), which outputs a notification sound for notifying a walker or the like of approach of a vehicle from a speaker ( 60 ) attached to a vehicle body, is configured such that the vehicle approach notification apparatus includes a control unit ( 80 ) for controlling the notification sound, the control unit ( 80 ) is attached to a position, displaced rather forwardly of the vehicle body, of a bottom face in an accommodating box ( 49 ) disposed below a seat ( 24 ) of the electric motorcycle ( 1 ), and a cover plate ( 148 ) which configures part of the bottom of the accommodating box ( 49 ) is removably disposed above the control unit ( 80 ). 
     Further, according to a second aspect of the present invention, a low voltage battery ( 51 ), as a power supply for auxiliaries, is accommodated on the bottom of the accommodating box ( 49 ) displaced rather rearwardly of the vehicle body from the control unit ( 80 ), and the cover plate ( 148 ) is disposed so as to cover an upper portion of the low voltage battery ( 51 ) in flush with an upper face of the control unit ( 80 ). 
     Further, according to a third aspect of the present invention, the low voltage battery ( 51 ) is disposed in a battery accommodating recessed portion ( 50   a ) provided on the rear side of the vehicle body with respect to the accommodating box ( 49 ), the control unit ( 80 ) is disposed in a control unit accommodating recessed portion ( 50   b ) provided on the front side of the vehicle body with respect to the battery accommodating recessed portion ( 50   a ), the bottom face of the battery accommodating recessed portion ( 50   a ) is formed at a position lower than that of the bottom face of the control unit accommodating recessed portion ( 50   b ), and a cross pipe ( 59 ) which connects a pair of left and right rear frames ( 40 ) of a vehicle body frame ( 34 ) in a vehicle widthwise direction to each other is disposed below the bottom of the control unit accommodating recessed portion ( 50   b ). 
     Further, according to a fourth aspect of the present invention, the low voltage battery ( 51 ) is disposed such that a positive side terminal ( 155 ) and a negative side terminal ( 156 ) are disposed in the vehicle widthwise direction and both terminals ( 155 ,  156 ) are positioned on the rear side of the vehicle body and on the upper side of the vehicle body. 
     Further, according to a fifth aspect of the present invention, the control unit ( 80 ) and the low voltage battery ( 51 ) are disposed in an offset relationship to one side in the widthwise direction with respect to a vehicle body center line (C) as viewed in top plan of the vehicle body, and a fuse box ( 159 ) is disposed at a position opposite to the offset direction below the cover plate ( 148 ). 
     Further, according to a sixth aspect of the present invention, the offset direction is the opposite side to the side on which an electric motor (M) of the electric motorcycle ( 1 ) is disposed. 
     Further, according to a seventh aspect of the present invention, the control unit ( 80 ) includes a coupler ( 81 ) for being connected to a control unit connecting cable ( 83 ) extending from the low voltage battery ( 51 ), the coupler ( 81 ) is disposed on the front side of the vehicle body with respect to the control unit ( 80 ), the control unit connecting cable ( 83 ) disposed forwardly of the vehicle body from the positive side terminal ( 155 ) side of the low voltage battery ( 51 ) is connected to the coupler ( 81 ), and a connection cable ( 82 ) which connects the coupler ( 81 ) and the control unit ( 80 ) to each other is connected to the coupler ( 81 ) from the negative side terminal ( 156 ) side of the low voltage battery ( 51 ) with respect to the control unit connecting cable ( 83 ) as viewed in top plan of the vehicle body. 
     According to the first aspect of the present invention, the vehicle approach notification apparatus includes the control unit for controlling the notification sound and the control unit is attached to the position, displaced rather forwardly of the vehicle body, of the bottom face in the accommodating box disposed below the seat of the electric motorcycle and besides the cover plate, which configures part of the bottom of the accommodating box, is removably disposed above the control unit. Therefore, the accommodating box below the seat of the motorcycle can be accessed simply by opening and closing of the seat, and from a point of view of a waterproof structure and that the accommodating box is locked and managed, it is possible to dispose the control unit in the accommodating box to cope readily with application or change of the system. Further, if a partition plate is disposed above the control unit, then no influence is had on an accommodation item of a user. Further, since a front portion of the accommodating box is frequently formed in a forwardly tapering state similarly to the shape of the seat, also the cover plate can be formed with a necessary but minimized size. 
     According to the second aspect of the present invention, the low voltage battery as a power supply for auxiliaries is accommodated on the bottom of the accommodating box displaced rather rearwardly of the vehicle body from the control unit, and the cover plate is disposed so as to cover the upper portion of the low voltage battery in flush with the upper face of the control unit. Therefore, if the control unit and the low voltage battery, which is a maintenance part similar to the control unit, are disposed in a concentrated manner, and they are covered at an upper portion thereof with the same cover plate, then separate and independent cover plates for the individual parts become unnecessary. Besides, since the cover plate is in flush above the control unit and the low voltage battery, it is possible to stably retain an accommodated article in the accommodating box. 
     According to the third aspect of the present invention, the low voltage battery is disposed in the battery accommodating recessed portion provided on the rear side of the vehicle body with respect to the accommodating box, and the control unit is disposed in the control unit accommodating recessed portion provided on the front side of the vehicle body with respect to the battery accommodating recessed portion. Further, the bottom face of the battery accommodating recessed portion is formed at the position lower than that of the bottom face of the control unit accommodating recessed portion, and the cross pipe which, connects the left and right rear frames in pair of the vehicle body frame in the vehicle widthwise direction to each other, is disposed below the bottom of the control unit accommodating recessed portion. The accommodating box below the seat is frequently supported by the cross pipe of the vehicle body frame which is directed in the vehicle widthwise direction, and, from between the control unit and the auxiliary battery which are disposed on the bottom face of the accommodating box, the control unit is smaller in terms of the dimension in the heightwise direction. Therefore, the cross pipe can be laid on a shouldered portion formed on the bottom face of the control unit accommodating recessed portion thereby to achieve effective utilization of the space. 
     According to the fourth aspect of the present invention, the low voltage battery is disposed such that the positive side terminal and the negative side terminal are disposed in the vehicle widthwise direction and both terminals are positioned on the rear side of the vehicle body and on the upper side of the vehicle body. Therefore, it is possible to set the height of the low voltage battery in the upward and downward direction to a necessary but minimum height such that no influence is had on any member below the accommodating box while the seat height is maintained. Further, it is possible to facilitate wiring or maintenance of the battery. Furthermore, the terminals of the low voltage battery are disposed in a spaced relationship from the control unit, and also the necessity to pay attention to interference of the low voltage battery with the control unit upon maintenance of the low voltage battery can be reduced. 
     According to the fifth aspect of the present invention, the control unit and the low voltage battery are disposed in an offset relationship to one side in the widthwise direction with respect to the vehicle body center line as viewed in top plan of the vehicle body, and the fuse box is disposed at the position opposite to the offset direction below the cover plate. Therefore, the fuse box can be disposed in the proximity of the low voltage battery, and while the length of a high voltage wiring line from the low voltage battery can be reduced, the disposition space for the fuse box can be provided efficiently. 
     According to the sixth aspect of the present invention, the offset direction is the opposite side to the side on which an electric motor of the electric motorcycle is disposed. Therefore, one-sidedness of the position of the center of gravity by the offset disposition of the electric motor in the vehicle widthwise direction with respect to the vehicle body center line can be corrected by the weight of the control unit and the low voltage battery. 
     According to the seventh aspect of the present invention, the control unit includes the coupler for being connected to the control unit connecting cable extending from the low voltage battery, and the coupler is disposed on the front side of the vehicle body with respect to the control unit. Further, the control unit connecting cable disposed forwardly of the vehicle body from the positive side terminal side of the low voltage battery is connected to the coupler, and the connecting cable which connects the coupler and the control unit to each other is connected to the coupler from the negative side terminal side of the low voltage battery with respect to the control unit connecting cable as viewed in top plan of the vehicle body. Therefore, the connection direction of the coupler can be directed to the vehicle widthwise direction. Further, the remaining space after the control unit and the auxiliary battery are disposed in the forward and rearward direction of the vehicle body can be effectively utilized to dispose the coupler, and besides optimum wiring can be implemented. 
     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 side elevational view of an electric motorcycle, which includes a vehicle approach notification control apparatus according to an embodiment of the present invention; 
         FIG. 2  is a see-through side elevational view of the electric motorcycle; 
         FIG. 3  is a side elevational view of a vehicle body frame; 
         FIG. 4  is a perspective view of the vehicle body frame; 
         FIG. 5  is an exploded perspective view of a front portion of a head pipe; 
         FIG. 6  is a front elevational view of a vehicle body in a state in which a front cover and so forth are removed; 
         FIG. 7(   a ) is a front elevational view and  FIG. 7(   b ) is a sectional view of a cover member according to a modification to a cover member shown in  FIG. 5 ; 
         FIG. 8(   a ) is a front elevational view and  FIG. 8(   b ) is a sectional view of a cover member according to a second modification to the cover member shown in  FIG. 5 ; 
         FIG. 9  is an enlarged front elevational view showing a structure around a front stay; 
         FIG. 10  is a partial sectional side elevational view showing a structure around the head pipe; 
         FIG. 11  is a perspective view illustrating an attached state of a speaker; 
         FIG. 12  is a perspective view showing a structure around a steering handle member; 
         FIG. 13  is a partial sectional side elevational view showing a configuration around an accommodation box; 
         FIG. 14  is a top plan view showing a configuration around the accommodation box; 
         FIG. 15  is a side elevational view of an electric motorcycle to which an approach notification control apparatus according to a second embodiment of the present invention is applied; 
         FIG. 16  is an enlarged front elevational view around a front stay according to the second embodiment of the present invention; 
         FIG. 17  is a partial sectional side elevational view showing a configuration around an accommodation box according to the second embodiment of the present invention; 
         FIG. 18  is a partial sectional side elevational view showing a configuration around the accommodation box according to the second embodiment of the present invention; 
         FIG. 19  is a top plan view showing a configuration around the accommodation box according to the second embodiment of the present invention; 
         FIG. 20  is a partial sectional front elevational view showing a configuration around a battery case according to the second embodiment of the present invention; 
         FIG. 21  is a partial sectional top plan view of a control unit; 
         FIG. 22  is a sectional view taken along line B-B of  FIG. 19   
         FIG. 23  is a top plan view showing a configuration of a vehicle body of an electric motorcycle 
         FIG. 24  is a sectional view of a swing arm as viewed from above the vehicle body 
         FIG. 25  is a block diagram showing a configuration of the control unit 
         FIG. 26  is a graph illustrating a relationship between the vehicle speed and running sound of various vehicles; and 
         FIG. 27  is a flow chart illustrating a procedure of approach notification sound output control. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views. 
       FIG. 1  is a side elevational view of an electric motorcycle  1 , which includes a vehicle approach notification control apparatus according to an embodiment of the present invention.  FIG. 2  is a see-through side elevational view of the electric motorcycle  1 . The electric motorcycle  1  is a saddle type electric vehicle of the scooter type having a low floor  15 . A rear wheel WR supported for rotation on an axle  23  is driven to rotate by rotating power exhibited by an electric motor M built in a swing arm  21 . 
     A vehicle body frame  34  of the electric motorcycle  1  includes a head pipe  36  inclined rearwardly upwards and supporting a front fork  2  for supporting a front wheel WF for rotation thereon and a steering handle member  9  in the form of a bar connected to an upper portion of the front fork  2  for steering movement. A main frame  35  extends rearwardly downwards from the head pipe  36 . A pair of left and right under frames  39  are connected to a lower portion of the main frame  35  through curved portions  38  and extend rearwardly. A pair of left and right rear frames  40  integrally connect to a rear end of the under frames  39  and extend rearwardly upwards. The head pipe  36  supports a steering stem  37  for rotation thereon. The steering handle member  9  is secured to an upper end of the steering stem  37 . An under bracket  68  for supporting an upper end portion of the front fork  2  is secured to a lower end portion of the steering stem  37 . 
     On a pivot plate  19  provided at a front portion of the rear frames  40  of the vehicle body frame  34 , a side stand  20  for keeping the vehicle body in an erected state inclined to the left side is mounted for pivotal motion. The swing arm  21  is supported at a front portion thereof for rocking motion through a pivot shaft  58 . A rear cushion unit  31  is provided between a rear portion of the left side rear frame  40  and a rear portion of the swing arm  21 . Further, a main stand  22  for erecting the vehicle body uprightly is attached to a lower portion of the swing arm  21 . The swing arm  21  is of the cantilever type for supporting the rear wheel WR for rotation only by means of an arm on the left side in the vehicle widthwise direction. A PDU (power drive unit)  52  for controlling output power of the electric motor M is disposed at a position immediately rearwardly of the pivot shaft  58  forwardly of the cantilever arm. 
     The electric motorcycle  1  includes a front cover  7  for covering the head pipe  36  from the front. A leg shield  10  extends from rearwardly of the head pipe  36  to the front cover  7  in such a manner as to cover the legs of a rider seated on a seat  24  from forwardly. The low floor  15  connects to a lower portion of the leg shield  10  such that the feet of the rider seated on the seat  24  are placed thereon and covering a battery case  47  from above. A pair of left and right floor side covers  17  depend from the opposite sides of the low floor  15  in such a manner as to cover the opposite sides of the under frames  39 . An undercover  18  interconnects lower edges of the floor side covers  17 . A seat lower front cover  16  extends upwardly from a rear end of the low floor  15  in such a manner as to cover a lower portion of the seat  24  from the front. A pair of left and right side covers  25  connect to the opposite sides of the seat lower front cover  16  in such a manner as to cover a lower portion of the seat  24  from the opposite sides. A rear cover  28  connects to the side covers  25  and covers the rear wheel WR from above. 
     The battery case  47  is covered with the low floor  15 , the floor side covers  17 , the under cover  18 , the seat lower front cover  16  and the side covers  25 . A headlamp  4  is disposed at a front end of the front cover  7  in such a manner that it is supported by a front stay  33  secured to the head pipe  36 . A tail lamp  30  is attached to the rear frame  40 . A rear fender  32  is disposed below the tail lamp  30 . 
     Direction indicators  5  are disposed on the left and right of the headlamp  4  in the vehicle widthwise direction. A horn  69  for issuing an alarm is disposed rearwardly of the headlamp  4 . A front fender  3  disposed below the front cover  7  is attached to the front fork  2  in such a manner as to cover the rear wheel WR from above while a sub fender  26  for covering the rear wheel WR from obliquely forwardly upwardly is attached to an upper portion of the swing arm  21 . 
     The steering handle member  9  is covered at a middle portion thereof in the vehicle widthwise direction with a handle cover  8 . A front carrier  6  disposed forwardly of the front cover  7  is supported on the front stay  33 . A load basket  66  or the like can be attached to the front carrier  6 . A luggage carrier  27  is provided at an upper portion of the rear cover  28  rearwardly of the seat  24 . A rear carrier  29  disposed above the luggage carrier  27  is removably attached to the rear frame  40 . 
     The battery case  47  in which a high voltage battery  48  of, for example, 72 V for supplying power to the electric motor M is built is disposed between the left and right under frames  39  in such a manner that it is supported by the under frames  39 . Further, a cross member  44  extending across a substantially central portion of the battery case  47  is provided between the left and right under frames  39 . The low floor  15  is supported by the cross member  44 . 
     At a front portion of the under frames  39 , a front protective member  41  for protecting a front side lower portion of the battery case  47  from forwardly is provided in such a manner that a central portion thereof is connected to a lower end of the main frame  35 . Further, at a rear portion of the under frames  39 , a rear protective member  43  for protecting a rear lower portion of the battery case  47  from rearwardly is provided. A plurality of lower protective members  42  extending in the forward and backward direction of the vehicle body is provided between the front and rear protective members  41  and  43  in such a manner that they project the battery case  47  from below. 
     A pair of left and right cooling air introduction ducts  45  are connected at a downstream end portion thereof to a front portion of the battery case  47  through a connecting pipe  46 . The cooling air introduction ducts  45  extend along the main frame  35  in such a manner as to sandwich the main frame  35  from the opposite sides in the leg shield  10 . A recess  11  concave in the forward direction of the vehicle body is formed at a position of the leg shield  10  corresponding to the connecting portion between the main frame  35  and the head pipe  36 . A lid  12 , which covers an upper portion of the recess,  11  is attached to the leg shield  10 . An air inlet port  13  is formed between a lower edge of the lid  12  and the recess  11 . The cooling air introduction ducts  45  are connected on an upper end side thereof to the leg shield  10  in a communicating relationship with the air inlet port  13 . 
     A cooling fan  53  is attached to an upper face of a rear portion of the battery case  47  such that air taken in from the air inlet port  13  by operation of the cooling fan  53  is introduced into the battery case  47  through the cooling air introduction ducts  45  and the connecting pipe  46  thereby to cool the high voltage battery  48  in the battery case  47 . 
     An accommodating box  49  made of synthetic resin and disposed below the seat  24  above the swing arm  21  is disposed between the left and right rear frames  40  in such a manner that it is supported by the rear frames  40 . The accommodating box  49  is covered from above with the openable and closable seat  24 . An accommodating recess  50  for accommodating therein a low voltage battery  51 , for example, of 12 V for supplying power to auxiliaries such as the headlamp  4  and the tail lamp  30  is formed integrally at a lower portion of the rear side of the accommodating box  49  in such a manner that it projects downwardly. 
     The vehicle approach notification control apparatus according to the present invention outputs predetermined notification sound from the speaker as sound generation means attached to the self vehicle to notify a walker and so forth of approach of the self vehicle. In the electric motorcycle  1  according to the present embodiment, a speaker  60  for emitting notification sound is provided at a position higher than the head pipe  36  on the inner side with respect to the front cover  7  and a control unit  80  for controlling the output of the speaker  60  is disposed forwardly of the low voltage battery  51  in the accommodating box  49 . 
     Further, it is possible to provide a plurality of speakers for emitting notification sound on the vehicle body, and in the present embodiment, a second speaker  70  is disposed on a front end face of the accommodating box  49  centrally in the vehicle widthwise direction. With the second speaker  70 , outputted notification sound is reflected by the leg shield  10  and so forth so that the notification sound can be recognized also from the left, right and rear of the vehicle body. 
       FIGS. 3 and 4  are a side elevational view and a perspective view of the vehicle body frame  34 , respectively. A gusset  57 , which increases the coupling strength between the head pipe  36  and the main frame  35  and functions as an attaching stay for various auxiliaries, is provided at a joining portion of the head pipe  36  and the main frame  35 . The main frame  35  extends linearly in a rearwardly downward direction from the head pipe  36  and is connected to the front protective member  41 , which extends in the vehicle widthwise direction. The cooling air introduction ducts  45  extend along the main frame  35  in such a manner that they sandwich the main frame  35  from the opposite sides in the leg shield  10 . The under frames  39  are formed integrally with the curved portions  38  connected to the left and right in the vehicle widthwise direction of the main frame  35  below the gusset  57 . The front protective member  41  is jointed at left and right end portions thereof in the vehicle widthwise direction to the curved portions  38 . Further, a first cross pipe  59  extending in the vehicle widthwise direction is disposed between the left and right rear frames  40  rearwardly upwardly of the battery case  37 . 
     It is to be noted that the attaching position of the second speaker can be changed in various manners, and for example, also it is possible to attach the second speaker, for example, between left and right portions of the front protective member  41  at a lower end portion of the main frame  35 . 
     The battery case  47  in which the high voltage battery  48  is accommodated is configured from a case main body  47   b  of a bottomed box shape, and a lid  47   a  which covers an opening at an upper portion of the case main body  47   b . A flange portion  56  is formed around a joining plane between the case main body  47   b  and the lid  47   a.    
     A side bracket  54  is secured by welding to an upper face of each of the under frames  39 . The cross member  44  and the flange portion  56  of the battery case  47  are secured to this side bracket  54 . The flange portion  56  is formed bypassing the cross member  44  and is secured to an upper face of the side bracket  54  by bolts  55 . The lower protective members  42  for protecting the battery case  47  are provided between the front protective member  41  and the rear protective member  43  and connect the front and rear protective members  41  and  43  to each other. 
       FIG. 5  is an exploded perspective view of a front portion of the head pipe  36 . Like reference characters to those described hereinabove denote like or equivalent elements. The headlamp  4  and the direction indicators  5  are formed as a unit. The front stay  33  which supports this lamp unit is formed from an upright frame portion  104  disposed so as to have a space in the leftward and rightward direction and disposed forwardly of the head pipe  36  by being formed by bending of a single round pipe material, and an upper side connecting plate  105  and a lower side connecting plate  107  which connect liner portions of the upright frame portion  104  on the left and right to each other. The front stay  33  is secured to the head pipe  36  by a pipe material (not shown) coupled to the rear face side of the upper and lower connecting plates  105  and  107 . 
     A pair of left and right support bases  108  are provided forwardly of a lower portion of the upright frame portion  104 , and weld nuts  109  are welded to a lower face of each of the support bases  108 . Further, two weld nuts  106  are welded also at two places of the upper side connecting plate  105  spaced from each other on the left and the right. Lower side carrier securing holes  103  are formed at a portion of the front cover  7 , which corresponds to the weld nuts  109  of the support bases  108 , while upper side carrier securing holes  102  are formed at a portion of the front cover  7 , which corresponds to the weld nuts  106  of the upper side connecting plate  105 . 
     The front carrier  6  is secured to the front stay  33  by co-fastening using fastening members fitted in the carrier securing holes  102  and  103 . To forward downward portions of the front stay  33  between the left and right support bases  108 , headlamp stay  119  for securing the headlamp  4  using a pair of left and right weld nuts  116  are attached. 
     The electric motorcycle  1  is configured such that a throttle operation is carried out by turning motion of a throttle grip attached to a right side end portion of the steering handle member  9 . In the present embodiment, a sensor main body  67  of a throttle opening sensor for detecting this throttle operation is disposed at a position forwardly of the head pipe  36 . A throttle wire  111  connected to the throttle grip is connected at the other end portion thereof to an outer peripheral end portion of a pulley  110  attached for rotation to the sensor main body  67 . Consequently, an operation state of the throttle grip can be detected based on the rotational state of the rotary shaft of the pulley  110 . The pulley  110  is normally biased in a direction in which the throttle is returned by a torsion coil spring not shown. 
     A throttle cable  114  including the throttle wire  111  coated with an outer tube is laid from the right side to the left side in the vehicle widthwise direction forwardly of the head pipe  36  and is, while being curved, laid back to the right side and then is secured to a predetermined position by an attaching stay  113 . A protective hood  112  for preventing the pulley  110  from contacting with any other part or the like is provided above the pulley  110 . 
     A circular cover member  90  in which two through-slits  90   a  are formed at a portion of an upper portion of the upper side carrier securing hole  102  which corresponds to a position of the speaker  60 , which notifies a walker or the like of approach of the electric motorcycle  1 , forwardly of the vehicle body, and which is displaced leftwardly in the vehicle widthwise direction of the front cover  7 . The cover member  90  is removably mounted on the front cover  7 . 
       FIG. 6  is a front elevational view of the vehicle body in a state in which the front cover  7  and so forth are removed. Like reference characters to those described hereinabove denote like or equivalent elements. The speaker  60  is disposed in an offset relationship to the vehicle body left side with respect to the head pipe  36  at the center in the vehicle widthwise direction on the face of the leg shield  10  on the vehicle body front side. On the right side in the vehicle widthwise direction across the head pipe  36 , a key cylinder  115  of a main switch is disposed. A keyhole into which a main key (not shown) is to be inserted is formed at one end portion of the key cylinder  115 , and this keyhole is exposed to the vehicle body rear side from a through-hole provided in the leg shield  10  (refer to  FIG. 12 ). The speaker  60  and the key cylinder  115  are advantageous in weight balance, threading of a cable or the like and so forth since it is disposed at a substantially equal distance in the vehicle widthwise direction and at a substantially same height with respect to the center of the vehicle body (head pipe center C). 
     The speaker  60  is disposed so as to be directed forwardly of the vehicle body from an upper portion of the upper side connecting plate  105  of the front stay  33 . Since also the front carrier  6  (refer to  FIG. 2 ) attached to the front stay  33  is formed in conformity with the height of the front stay  33 , notification sound outputted from the speaker  60  is not disturbed by the front carrier  6  and so forth. Also when the load basket  66  of a large size (refer to  FIG. 2 ) or the like is attached to the front carrier  6 , since the speaker  60  is disposed at a position rather near to an upper portion of the load basket  66 , even if a baggage is placed in the load basket  66 , the possibility that generated sound may be disturbed is reduced. 
     The pulley  110  of the throttle opening sensor is disposed below the key cylinder  115  on the right side in the vehicle widthwise direction, and the throttle cable  114  is laid from forwardly of the head pipe  36  past the left side in the vehicle widthwise direction and then to the right side of the vehicle body past the rear of the head pipe  36 . 
       FIG. 7(   a ) is a front elevational view and  FIG. 7(   b ) is a sectional view of a cover member  91  according to a modification to the cover member  90  shown in  FIG. 5 . Three through-slits  91   a  through which notification sound passes are disposed in the cover member  91 . Flanges  92  are provided on an outer peripheral portion of the cover member  91  such that the cover member  91  can be secured to the front cover  7  by screws  94  using bosses  93  provided on the rear face side of the front cover  7 . Since the cover member  91  is configured for removable mounting on the front cover  7 , for example, it is possible to fit with cover members of other various shapes in order to carry out sound volume adjustment of notification sound or design change or to fit, in a vehicle which does not include the speaker  60 , with a lid member having no through-slit. 
       FIG. 8(   a ) is a front elevational view and  FIG. 8(   b ) is a sectional view of a cover member  95  according to a second modification to the cover member  90  shown in  FIG. 5 . The sectional view in  FIG. 8(   b ) is a sectional view taken along line A-A of the front elevational view in  FIG. 8(   a ). The cover member  95  is formed from a base member  96  in which window portions  96   a  of a substantially sectoral shape are formed, and a rotatable plate  97  for closing up the window portions  96   a . The rotatable plate  97  is configured for engaging at an outer circumferential end face  99  thereof with an inner circumferential groove of the base member  96  so as to be rotatable. Consequently, by gripping an operating projection  100  to rotate the rotatable plate  97 , the opening area of the window portions  96   a  can be changed arbitrarily. Flanges  98  are provided on an outer circumferential portion of the cover member  95 , and are secured to the front cover  7  by means of screws  122  using bosses  101  provided on the rear face side of the front cover  7 . 
       FIG. 9  is an enlarged front elevational view showing a structure around the front stay  33 . Like reference characters to those described hereinabove denote like or equivalent elements. The protective hood  112  which covers the pulley  110  from above is inclined such that it assumes a lower position toward the outer side in the vehicle widthwise direction and is disposed at a front end portion thereof forwardly of the vehicle body with respect to the center potion of the pulley  110 . The sensor main body  67  (refer to  FIG. 5 ) and the pulley  110  are disposed adjacent the head pipe  36  and rearwardly with respect to the position of a lower end portion of the head pipe  36  as viewed in side elevation of the vehicle body. Further, as viewed in front elevation of the vehicle body, the sensor main body  67  and the pulley  110  are disposed in an offset relationship to the right side in the vehicle widthwise direction from the head pipe  36 . 
     Since the sensor main body  67  and the pulley  110  of the throttle opening sensor are disposed between the upright frame portion  104  of the front stay  33  and the head pipe  36  as viewed in side elevation, even if external force is applied to the front cover  7 , the possibility that the sensor main body  67  or the pulley  110  may be influenced by the external force is reduced. 
     Further, also the taking out direction of the rotary shaft of the pulley  110  or the throttle wire  111  is inclined with respect to the axial direction of the head pipe  36  in conformity with the throttle cable  114  which is disposed in a curved stage forwardly of the head pipe  36 . Consequently, the possibility that a turning operation of the steering handle member  9  may have an influence on the sensor output is reduced. While the throttle cable  114  is curved arcuately and passes between the head pipe  36  and the speaker  60 , it is guided to the front of the head pipe  36  and is connected to the pulley  110  supported for rotation on the sensor main body  67  of the throttle opening sensor. 
     Further, with the protective hood  112  provided above the pulley  110 , even if a screw or a bolt drops from a fastening location above the head pipe  36  upon assembly, it is possible for the protective hood  112  to receive the dropping article so that it may not have an influence on the rotating operation of the pulley  110 . Since the protective hood  112  is inclined outwardly downwardly in the vehicle widthwise direction, the screw, bolt or the like dropping from above can be dropped outwardly in the vehicle widthwise direction, that is, in a direction toward a position at which a smaller number of attachment members exist and water and so forth can be prevented from being accumulated at an upper portion of the protective hood  112 . 
     Further, on a side face portion of the upright frame portion  104  on the right side in the vehicle widthwise direction, a recessed portion  104   a  for preventing interference between the upright frame portion  104  and the pulley  110  even if the upright frame potion  104  should be moved rearwardly by an action of external force from forwardly is formed. 
       FIG. 10  is a partial sectional side elevational view showing a structure around the head pipe  36 . The front carrier  6  is secured to the front stay  33  through round pipe stays  6   a  and  6   b . The front carrier  6  can be configured from frame portions which are disposed in a spaced relationship from each other in the leftward and rightward direction by being formed, for example, by bending working of a single round pipe material, and a plate-like member which connects liner portions of the frame portions to each other. 
     As described hereinabove, the speaker  60  which outputs notification sound is disposed rearwardly upwardly of the front stay  33  on the left side in the vehicle widthwise direction of the head pipe  36 . In the present embodiment, a notification sound switch for selecting whether or not notification sound should be outputted is provided integrally with a rear portion of the speaker  60 . A notification sound switch  118  is an on/off switch of the projectable/retractable type which is slidably operated in the forward and backward directions of the vehicle body with respect to a retaining member  117  secured to a wall face of the leg shield  10 . An operating element of the notification sound switch  118  is exposed to a face of the leg shield  10  on the vehicle body rear side. The key cylinder  115  and the speaker  60  are disposed forwardly upwardly of the head pipe  36  in an overlapping relationship with each other as viewed in side elevation of the vehicle body. 
       FIG. 11  is a perspective view illustrating an attached state of the speaker  60 . In the speaker  60 , a functioning part such as cone paper, a magnet or the like is accommodated between a rear side case  61  and a front side cover  63 . The speaker  60  is secured by fastening two flanges  61   a  formed on the rear side case  61  to bosses  62  formed on the front face of the leg shield  10  by fastening members  62   a  such as screws. 
     A harness  170  is laid on the left side in the vehicle widthwise direction of the head pipe  36  such that it extends along the throttle cable  114  which is laid to the front side of the vehicle body past the left side in the vehicle widthwise direction forwardly of the head pipe  36 . A front brake cable  170   a  is laid sidewardly of the harness  170 . A damping grommet  106   b  made of rubber is attached to a position of the upper side connecting plate  105  of the front stay  33  which corresponds to a threaded hole  106   a  of a weld nut  106  (refer to  FIG. 5 ). It is to be noted that a damping grommet is attached not only to the portion corresponding to the weld nut  106  on the right side in the vehicle widthwise direction but also to a portion corresponding to the weld nuts  109  of the support bases  108  (refer to  FIG. 5 ) of the front stay  33 . 
       FIG. 12  is a perspective view showing a structure around the steering handle member  9 . This figure corresponds to a state which is overlooked from a point of view of the rider. The steering handle member  9  is formed from a handle pipe  135  fixed to an upper end portion of the steering stem  37  supported for pivotal motion on the head pipe  36 , and handle grips  9   a  secured to the opposite end portions of the handle pipe  135 . The handle grip  9   a  on the right side in the vehicle widthwise direction is supported for rotation with respect to the handle pipe  135  and functions as a throttle apparatus connected to the throttle cable  114 . 
     A meter apparatus  130  for displaying various kinds of information such as a vehicle speed, an accumulated distance and a battery remaining amount is disposed centrally in the vehicle widthwise direction of the handle cover  8 . The meter apparatus may be composed of various displays such as liquid crystal display. An operation button  134  for carrying out a changing over operation between an odometer and a trip meter displayed on the meter apparatus  130  and resetting of a trip meter is disposed on the right side in the vehicle width direction. 
     An optical axis changeover switch  131  for the headlamp  4 , an activating switch  132  for the direction indicators  5  and an activating switch  133  for the horn  69  are disposed in order from above on the handle cover  8  in the proximity of the handle grip  9   a  on the left side in the vehicle widthwise direction. 
     It is to be noted that, on an ordinary engine driven vehicle, an engine starter button is disposed in the proximity of the handle grip  9   a  on the right side. However, on the electric motorcycle  1  according to the present embodiment, a starter button is not required and therefore is not provided, and a free space corresponding to the starter button is provided. A control unit  80   a  for controlling the output of the speaker  60  may be disposed, utilizing the free space, in the inside of the handle cover  8  below the handle pipe  135  on the right side. 
     The key cylinder  115  is attached to a stay  136  secured to the right side in the vehicle widthwise direction of the head pipe  36 , and a keyhole into which a main key is to be inserted is disposed rearwardly upwards from a through-hole formed in the leg shield  10 . The notification sound switch  118  for the speaker  60  is disposed on the left side in the vehicle widthwise direction across the head pipe  36 . It is to be noted that also it is possible to output approach notification sound using the horn  69  for generating alarming sound or conversely to output alarming sound using the speaker  60  to reduce the number of parts. 
       FIG. 13  is a partial sectional side elevational view showing a configuration around the accommodating box  49 . A support shaft  137  directed in the vehicle widthwise direction is disposed at an upper portion of the front end of the accommodating box  49  supported by the pair of left and right rear frames  40  of the vehicle body frame  34 . A supported plate  141  is securely mounted on a lower face of a front portion of a bottom plate  24   a  of the seat  24  by a pair of bolts  142 . A supporting member  138  disposed below the supported plate  141  is supported for pivotal motion on the accommodating box  49  through the support shaft  137 . A pair of left and right cylindrical members  140  are secured at an upper end thereof to the supported plate  141  by pins  151 , and are fitted at a lower portion thereof for upward and downward sliding movement in the supporting member  138 . Coiled springs  139  which surround the cylindrical members  140  are interposed between the supporting member  138  and the supported member  141 . A buffering stop mechanism when the seat  24  is opened fully is configured from a slide mechanism which uses the springs  139 . 
     The accommodating recess  50  projecting downwardly is formed on the bottom of the accommodating box  49 . The accommodating recess  50  is formed from a battery accommodating recessed portion  50   a  for principally accommodating the low voltage battery  51  therein, and a control unit accommodating recessed portion  50   b  for principally accommodating the control unit  80  therein. The low voltage battery  51  disposed in the battery accommodating recessed portion  50   a  is secured to the accommodating box  49  by causing engaging pieces  144  on the opposite ends of a band  143  suspended on an upper face of the low voltage battery  51  to be engaged with hooks  145  fixedly provided on the bottom portion of the accommodating box  49  forwardly and rearwardly of the battery accommodating recessed portion  50   a . The low voltage battery  51  is disposed such that a terminal section thereof is positioned upwardly and rearwardly of the vehicle body. 
     The control unit  80  and the low voltage battery  51  are covered from above with a cover plate  148  removably attached to an upper face of the bottom portion of the accommodating box  49 . The cover plate  148  is fastened at four places around the control unit  80  by screw members  149 . 
     The accommodating box  49  is disposed such that it partly overlaps with the rear frame  40  as viewed in side elevation of the vehicle body. The first cross pipe  59  which interconnects the two rear frames  40  in the vehicle widthwise direction is disposed at a height between a lowermost portion of the accommodating recess  50  and the cover plate  148 . The control unit  80  is disposed such that it partly overlaps with the rear frame  40  as viewed in side elevation of the vehicle body and overlaps with the first cross pipe  59  as viewed in top plan of the vehicle body. Further, the cover plate  148  is configured such that it covers an upper face of the low voltage battery  51  and the control unit  80  substantially in level with the same. Consequently, a separate independent cover plate for each part becomes unnecessary and besides an accommodation article in the accommodating box can be retained stably. 
     Stays  150  are securely mounted at two locations of the first cross pipe  59  spaced leftwardly and rightwardly from each other. Weld nuts are securely mounted on a lower face of the stays  150 . By screwing bolts into the weld nuts from the bottom face side of the control unit accommodating recessed portion  50   b , the accommodating box  49  is secured on the front side thereof to the first cross pipe  59 . Further, a second cross pipe  40   a  for connecting the rear frames  40  to each other is disposed rearwardly upwardly of the first cross pipe  59 . A stepped engaging portion for engaging with the second cross pipe  40   a  from above is formed on a rear wall of the accommodating box  49 . A clip  146  for securing a main harness  147  is provided on a rear wall of the battery accommodating recessed portion  50   a.    
     A coupler  81  for connecting the harness extending from the control unit  80  to the harness on the vehicle body side is disposed in the neighborhood on the vehicle body front side of the control unit  80  in the control unit accommodating recessed portion  50   b.    
     The second speaker  70  described hereinabove is secured to the vehicle body front side of the accommodating box  49 . The second speaker  70  is secured to a central position in the vehicle widthwise direction by fastening members  72  such as bolts using bosses  71  provided on a wall face  49   a  on the vehicle body front side of the accommodating box  49 . Notification sound outputted from the second speaker  70  is outputted first toward the front side of the vehicle body and then reflected leftwardly and rightwardly in the vehicle widthwise directions and rearwardly of the vehicle body by a face of the leg shield  10  on the vehicle body rear side. Further, since the second speaker  70  is attached to the accommodating box  49 , an attaching member for exclusive use for the speaker is unnecessary, and besides the accommodating box  49  serves also as an echo member of the second speaker  70  and a desired sound pressure can be assured by a speaker of a small size. 
       FIG. 14  is a top plan view showing a configuration around the accommodating box  49 . Like reference characters to those described hereinabove denote like or equivalent elements. The low voltage battery  51  accommodated in the battery accommodating recessed portion  50   a  is disposed such that a positive side terminal  155  and a negative side terminal  156  are positioned rearwardly upwardly of the vehicle body. A power supply line led out from the positive side terminal  155  is taken in the main harness  147  and is laid on one side thereof to the front side of the vehicle body. The other side of the main harness  147  is led out to the outside of the accommodating box  49  from an exit hole  152   a  formed in the bottom on the right side in the vehicle widthwise direction of the battery accommodating recessed portion  50   a  in order to supply power to various accessories. Also a ground line led out from the negative side terminal  156  is taken in the main harness  147 . 
     A fuse box  159  is disposed on the left side in the vehicle widthwise direction of the battery accommodating recessed portion  50   a . The fuse box  159  is disposed at a position between the bottom of the battery accommodating recessed portion  50   a  and the bottom of the control unit accommodating recessed portion  50   b . A control unit connecting harness  83  led out from the main harness  147  is laid on the front side of the vehicle body in such a manner that it is sandwiched between the fuse box  159  and the cover plate  148  in the upward and downward direction. 
     A partition plate  158  erected upwardly of the vehicle body is formed between the low voltage battery  51  and the fuse box  159 . The fuse box  159  is secured in such a manner that it is sandwiched between the partition plate  158  and a side wall on the left side in the vehicle widthwise direction of the battery accommodating recessed portion  50   a . With the partition plate  158 , it is made possible to dispose the fuse box  159  in the proximity of the low voltage battery  51  thereby to enhance the maintenance performance and facilitate an operation of mounting and removing the low voltage battery  51  while the fuse box  159  is retained. 
     A seal face  160  which contacts in face with the cover plate  148  to exhibit a waterproof property and so forth is provided around a threaded hole  149   a  into which a screw member  149  for securing the cover plate  148  is to be screwed. At a portion of the seal face  160  on the vehicle body front side of the fuse box  159 , a recessed portion  161  for passing the control unit connecting harness  83  therethrough is formed. 
     A first drain hole  191  for discharging water admitted in the inside of the battery accommodating recessed portion  50   a  is provided at a position of the bottom of the battery accommodating recessed portion  50   a  displaced leftwardly in the vehicle widthwise direction and forwardly. Further, a second drain hole  192  is provided also in the bottom between the fuse box  159  and the partition plate  158 . Consequently, even if water or the like should enter the control unit accommodating recessed portion  50   b , it is discharged rapidly through the first drain hole  191  of the battery accommodating recessed portion  50   a  formed continuously with the control unit accommodating recessed portion  50   b  at a position lower than the control unit accommodating recessed portion  50   b . Further, if water enters the attachment bottom of the fuse box  159 , then it can be discharged from the second drain hole  192 . It is to be noted that, in the case where the side stand  20  is attached to the right side in the vehicle widthwise direction, the first drain hole  191  can be provided rather near to the right side in the vehicle widthwise direction. 
     The control unit connecting harness  83  laid to the front side of the vehicle body past an upper portion of the fuse box  159  and the connection harness  82  led out from the control unit  80  are connected to each other by the coupler  81  positioned on the vehicle body front side of the control unit  80 . The coupler  81  is covered with a coupler cover  190  made of rubber. In particular, the coupler  81  is disposed in the proximity of the face on the vehicle body front side of the control unit  80 , and the control unit connecting harness  83  connected by the connector provided on one end of the connection harness  82  and extending rearwardly past sidewardly of the low voltage battery  51  is led out to the outside of the accommodating box  49  together with a wiring line connecting to the low voltage battery  51 . Therefore, the control unit connecting harness  83  can be wired collectively in a high space efficiency in the accommodating box  49 . 
     With such a control box accommodation structure as described above, since the control unit  80  is accommodated in the control unit accommodating recessed portion  50   b  provided on the bottom of the accommodating box  49 , the control unit  80  can be protected effectively against an impact from the outside while an influence of rain and so forth is prevented from being had on the control unit  80 . Further, since the control unit  80  is covered from above by a cover plate  84  in the accommodating box  49 , placement of some other accommodation article from and into the accommodating box  49  is facilitated, and interference of some other accommodation article with the control unit  80  can be prevented advantageously. 
     Further, since the low voltage battery  51  is accommodated in the battery accommodating recessed portion  50   a  connecting to the control unit accommodating recessed portion  50   b , the low voltage battery  51  is disposed in the proximity of the control unit  80 , and consequently, assurance of the power supply is facilitated and it is made possible to directly connect the control unit  80  to the low voltage battery  51  to achieve enhancement of the wiring efficiency. Further, since the low voltage battery  51  is disposed such that the terminals  155  and  156  are positioned at an upper portion thereof, even if water or the like should flow into the battery accommodating recessed portion  50   a , an influence of the water or the like upon the terminals  155  and  156  can be avoided. 
     Furthermore, since part of the rear frame  40  and the control unit accommodating recessed portion  50   b  are disposed in an overlapping relationship with each other as viewed in side elevation and the first cross pipe  59  disposed between a lowermost portion of the battery accommodating recessed portion  50   a  and the cover plate  148  in the upward and downward direction is provided to extend between the rear frames  40 , the control unit accommodating recessed portion  50   b  is surrounded by the rear frames  40  and the first cross pipe  59 . Consequently, an influence from the outside can be further suppressed from being had on the control unit  80 . 
     As seen in the figure, the accommodating box  49  is disposed so as to be positioned at the center of the vehicle body center line C. On the other hand, the control unit  80  and the low voltage battery  51  are disposed in an offset relationship to the right side in the vehicle widthwise direction with respect to the vehicle body center line C in order to correct the position of the center of gravity, which is displaced to the left side of the vehicle body, because the electric motor M and so forth are built in the arm portion of the swing arm  21  of the cantilever type. Details of the relationship between the dispositional position of the control unit  80  and the low voltage battery  51  and the position of the center of gravity of the vehicle body are hereinafter described. 
       FIG. 15  is a side elevational view of an electric motorcycle  1   a  to which an approach notification control apparatus according to a second embodiment of the present invention is applied. Like reference characters to those described hereinabove denote like or equivalent elements. The present embodiment is characterized in that the disposition of the second speaker and the control unit is different. Since  FIG. 15  is similar to  FIG. 1  except the disposition of the second speaker and the control unit, description of similar portions is omitted. 
     The second speaker  70   a  is disposed at a lower portion of the accommodating recess  50  projecting downwardly from the accommodating box  49  such that the sound emitting direction is directed downwardly. In this instance, a sound guiding duct  154  for introducing notification sound outputted from the second speaker  70   a  to a sideward direction of the vehicle body is provided. Notification sound introduced by the sound guiding duct  154  is emitted leftwardly and rightwardly in the vehicle widthwise direction from through-holes  25   a  formed in the left and right side covers  25  in the vehicle widthwise direction. 
     Further, as a modification to the dispositional position, the second speaker  70   b  can be disposed on a lower face of the battery case  47  of the high voltage battery  48  disposed below the low floor  15  such that the sound emitting direction thereof is directed downwardly. In this instance, a sound guiding duct  177  of a megaphone shape or a horn shape for diffusing notification sound outputted from the second speaker  70   b  is provided. The sound guiding duct  177  is configured such that the lower face thereof is positioned substantially in flush with the lower face of an undercover  42   a.    
     The control unit  80   a  can be disposed in the inside of the handle cover  8  below the right side handle pipe  135  utilizing a free space assured because a starter button for an engine becomes unnecessary. Further, the control unit  80   b  can be disposed at a position on the rear face side of the front stay  33  below the speaker  60 . 
       FIG. 16  is an enlarged front elevational view around the front stay  33  according to the second embodiment of the present invention. Like reference characters to those described hereinabove denote like or equivalent elements. This figure shows an attachment structure of the control unit  80   b  disposed at a position on the rear face side of the front stay  33  below the speaker  60 . Since  FIG. 16  is similar to  FIG. 9  except the attachment structure of the control unit  80   b , description of similar portions is omitted. 
     The control unit  80   b  can be secured to the upright frame portion  104  on the right side in the vehicle widthwise direction of the front stay  33  utilizing flanges  199  formed at upper and lower end portions thereof. According to such an attachment structure as just described, also when external force is applied to the front carrier  6  or the like, the external force can be prevented from having an influence on the control unit  80   b . Further, since the speaker  60  and the control unit  80   b  are disposed in the proximity of each other, in the case where the approach notification control apparatus is set as an optional part, an attaching operation of the approach notification control apparatus to the vehicle body can be carried out at a time only by removing the front cover  7 . Further, with this disposition, also it is possible to form the speaker  60  and the control unit  80   b  as a unitary part to further simplify the attaching operation of the approach control notification apparatus. 
       FIG. 17  is a partial sectional side elevational view showing a configuration around the accommodating box  49  according to the second embodiment of the present invention. Like reference characters to those described hereinabove denote like or equivalent elements. This figure shows an attachment structure of the second speaker  70   a  disposed at a lower portion of the accommodating recess  50  projecting downwardly from the accommodating box  49  such that the sound emitting direction thereof is directed downwardly. Since  FIG. 17  is similar to  FIG. 13  except the attaching structure of the second speaker  70   a , description of similar portions is omitted. 
     In the present embodiment, the second speaker  70   a  is attached using bosses  152  formed on a lower face of the battery accommodating recessed portion  50   a  and screw members  153  such that the sound emitting direction thereof is directed downwardly of the vehicle body. The second speaker  70   a  is disposed at the center in the vehicle widthwise direction, and the sound guiding duct  154  for guiding notification sound outputted from the second speaker  70   a  to a sideward direction of the vehicle body is provided. 
       FIGS. 18 and 19  are a partial sectional front elevational view and a top plan view, respectively, showing a configuration around the accommodating box  49  according to the second embodiment of the present invention. Like reference characters to those described hereinabove denote like or equivalent elements. The second speaker  70   a  is attached to a lower face of the battery accommodating recessed portion  50   a.    
     The sound guiding duct  154  formed from a pipe-like member is provided around the second speaker  70   a , and notification sound outputted from the second speaker  70   a  is introduced in the leftward and rightward directions of the vehicle though the sound guiding duct  154  and emitted sidewardly of the vehicle body from a through-hole  25   a  formed in each of a pair of left and right side covers  25  disposed at a lower portion of the seat  24 . A flange  25   d  is formed at each of end portions of the sound guiding duct  154 , and the flanges  25   d  and the side covers  25  are secured to each other using bosses  25   b  formed on the rear face side of the side covers  25  and screw members  25   c.    
     With such an attachment structure for the second speaker  70   a  as described above, the second speaker  70   a  is attached making use of a dead space which is a lower portion of the battery accommodating recessed portion  50   a  and it is possible to emit notification sound from the second speaker  70   a  in the leftward and rightward directions of the vehicle body. Further, with such a sound guiding duct  157  as described above, since the sound emitting direction of the second speaker  70   a  can be changed arbitrarily, the degree of freedom in disposition of the second speaker is enhanced. 
     Referring to  FIG. 19 , on the side covers  25  on the left side in the vehicle widthwise direction, a key cylinder  115  for unlocking the seat  24  by a turning operation of a main key  174  is disposed. A lock mechanism  172  provided at a rear end of the accommodating box  49  is configured such that, if the main key  174  is turned, then the lock mechanism  172  releases a hook (not shown) secured to a lower face of the seat  24 . This figure illustrates a state in which the cover plate  148  attached to an upper portion of the low voltage battery  51  is removed. Around each of screw members  171  for securing the accommodating box  49  to the first cross pipe  59  (refer to  FIG. 17 ), a portion around the threaded hole  149   a  for attaching the cover plate  148  is formed in a flat shape so that it can contact closely with the cover plate  148  thereby to exhibit a sealing property. 
       FIG. 20  is a partial sectional front elevational view showing a configuration around a battery case  47  according to a modification to the second embodiment of the present invention. Like reference characters to those described hereinabove denote like or equivalent elements. This figure shows a section of the battery case  47  as viewed from forwardly of the vehicle body. A fitting rib  56   a  is formed on a circumferential edge of an upper opening of the case main body  47   b . A fitting groove  56   b  is formed on an opening edge of the lid  47   a . By fitting them with each other, water immersion from the joining portion between the case main body  47   b  and the lid  47   a  is prevented thereby to assure a watertight property. It is to be noted that the flange portion  56  formed on the circumferential edge of the opening of the case main body  47   b  is secured to the side bracket  54  by bolts  55 . 
     In the present modification, the second speaker  70   b  is attached using bosses  175  formed on the bottom face of the case main body  47   b  and screw members  176  such that the sound emitting direction thereof is directed downwardly of the vehicle body. The second speaker  70   b  is disposed substantially centrally in the vehicle widthwise direction at a position near to the road surface G. The sound guiding duct  177  of a megaphone shape or a horn shape is disposed around the second speaker  70   b . The sound guiding duct  177  is formed from a tubular member  178  secured to the bottom face of the case main body  47   b  by screw members  179  and formed such that the opening area thereof increases toward a downward direction. A net plate  180  for reducing the influence of sand and so forth upon the second speaker  70   b.    
     With the disposition of the second speaker  70   b  described above, the second speaker  70   b  can be attached making effective use of a dead space which is a lower portion of the battery case  47 . Further, since the sound guiding duct  177  of a horn shape is used, sound emitted toward the ground face can be diffused widely together with reflection by the road surface. Furthermore, the battery case  47  having a wide bottom face serves as a good plane of vibration, and a sufficient sound emitting function can be obtained even by a small-sized speaker. 
       FIG. 21  is a partial sectional top plan view of the control unit  80 . The control unit  80  is configured such that a wiring board  185  is attached to a case  182 , in which a control board  183  is accommodated, through a waterproof grommet  184 . The connection harness  82  connected to the control board  183  extends through the wiring board  185 . The connection harness  82  is formed from a first wiring line  186  to which a first coupler  187  is connected, and a second wiring line  188  to which a second coupler  189  is connected. 
       FIG. 22  is a sectional view taken along line B-B of  FIG. 19 . The first coupler  187  and the second coupler  189  are disposed such that they overlap with each other in the upward and downward direction at a position forwardly of the vehicle body with respect to the control unit  80 . And, the first coupler  187  and the second coupler  189  are covered with the single coupler cover  190 . It is to be noted that, in the present embodiment, a two-pin type part is used for the first coupler  187  and a four-pin type part is used for the second coupler  189 . 
       FIG. 23  is a top plan view showing a vehicle body configuration of the electric motorcycle  1 . Like reference characters to those described hereinabove denote like or equivalent elements. The leg shield  10  extends forwardly of the head pipe  36  in such a manner as to cover the head pipe  36  from sidewardly. The opposite side edges of the leg shield  10  are provided contiguously to the opposite side edges of the front cover  7  at left and right positions in the vehicle body widthwise direction of the front stay  33 . By such a configuration as just described, miniaturization of the front cover  7  can be achieved. The speaker  60  is disposed on the left side in the vehicle widthwise direction of the head pipe  36 , and the key cylinder  115  is disposed on the right side in the vehicle widthwise direction across the head pipe  36 . 
     The swing arm  21  according to the present embodiment is of the cantilever type which supports the rear wheel WR only by the arm on the left side of the vehicle body. Then, since the electric motor M, a speed reduction mechanism and so forth are built in the inside of the cantilever arm, the position of the center of gravity of a rear portion of the vehicle body is likely to be displaced to the left side of the vehicle body. Therefore, in the present embodiment, not only the PDU  52  disposed in the proximity of the pivot shaft  58  is disposed in an offset relationship to the right side of the vehicle body with respect to the vehicle body center line C but also the low voltage battery  51  and the control unit  80  are disposed in an offset relationship to the right side of the vehicle body so that a balance of the position of the center of gravity in the leftward and rightward direction can be established. Further, also where the control unit  80   a  is disposed in the proximity of the steering handle member  9  on the right side as shown in  FIG. 12 , an effect of achieving a left and right balance of the position of the center of gravity can be obtained. 
       FIG. 24  is a sectional view of the swing arm  21  as viewed from above the vehicle body. Like reference characters to those described hereinabove denote like or equivalent elements. The swing arm  21  is supported for rocking motion on a pair of left and right pivot plates  19  through the swing arm pivot  58  (pivot shaft). The pivot shaft  58  is an elongated bolt having a screw head  202  and is fitted in a cylindrical collar  204  supported by bosses  200  on the swing arm  21  side through bushes  201  and secured by a nut  203  on the right side in the vehicle widthwise direction. It is to be noted that the bushes  201  are thermally secured to the cylindrical collar  204 , and a collar member of a small thickness is thermally secured to the outer periphery side of each of the bushes  201 . Then, the collar members and the bushes  201  are force fitted into through-holes of the bosses  200  to define the position of the swing arm  21  in the vehicle widthwise direction. 
     The PDU  52  is accommodated in a large width case section forwardly of the rear wheel WR. Consequently, the PDU  52  is disposed rather forwardly of the swing arm  21  in such a manner as to cross the vehicle body center line C, which passes the front and rear wheels of the electric motorcycle  1 , in the vehicle widthwise direction. As described hereinabove, in the electric motorcycle  1 , one-sidedness of the weight balance in the vehicle widthwise direction by offset disposition of the electric motor M to the left side in the vehicle widthwise direction is corrected by figuring out the disposition of the PDU  52  as described hereinabove. As seen in the figure, the position G 1  of the center of gravity of the PDU  52  is positioned on the right side in the vehicle widthwise direction with respect to the vehicle body center line C. 
     The swing arm  21  according to the present embodiment is of the cantilever type, which supports the rear wheel WR for rotation only by the arm section on the left side. The electric motor M, a centrifugal clutch  216  as a clutching mechanism for rotational driving force, and a speed reducing mechanism  221  are disposed in a concentrated manner at a position on the vehicle body rear side of the arm section. 
     The electric motor M is of the inner rotor type which is formed from a stator  208  secured to an inner wall of the swing arm  21  and having a stator coil, and a rotor  209  secured to a motor driving shaft  212 . The centrifugal clutch  216  is configured from a drive plate  214  on which a clutch shoe  215  is provided, and a clutch outer  211  for being driven by frictional resisting force of the clutch shoe  215 . The drive plate  214  is secured to a left side end portion in the figure of the motor driving shaft  212 , and the motor driving shaft  212  is secured to an output power shaft  218  which is fitted rotatably with the motor driving shaft  212 . It is to be noted that the motor driving shaft  212  and the output power shaft  218  are configured for rotation relative to each other by a needle roller bearing  217  and a ball bearing  210 . 
     Then, the centrifugal clutch  216  is configured such that, if the speed of rotation of the motor driving shaft  212  becomes higher than a predetermined speed, that is, if the speed of rotation of the drive plate  214  becomes higher than a predetermined speed, then the clutch shoe  215  moves to the outer side in a diametrical direction to generate frictional resisting force so that the clutch outer  211  is driven to rotate. Consequently, the rotational driving force of the electric motor M is transmitted to the output power shaft  218 . It is to be noted that a left side end portion in the vehicle widthwise direction of the output power shaft  218  is supported for rotation by a bearing  213  fitted in a swing arm cover  205 . The right side in the vehicle widthwise direction of the output power shaft  218  is supported for rotation by a bearing  219  fitted in a driving case  237  and a bearing  223  fitted in a reduction gear case  220 . At a vehicle body rear end portion of the driving case  237 , a supporting hole  238  for the rear cushion unit  31  is formed. An output wiring line  206  for the electric motor M and a connector  207  for a motor speed sensor (not shown) are disposed on the vehicle body front side of the electric motor M in a swing arm cover  205 . 
     Rotational driving force transmitted to the output power shaft  218  is transmitted to the final output power shaft (axle)  23  through the speed reducing mechanism  221 . More particularly, the rotational driving force is transmitted to the final output power shaft  23 , which is rotatably supported by a bearing  236  secured to a second speed reducing gear wheel  235  and fitted in the driving case  237  and another bearing  233  fitted in the reduction gear case  220 , through a first speed reducing gear wheel  228  which meshes with a speed reducing gear wheel  222  formed at a right side end portion in the figure of the output power shaft  218 , a first speed reducing shaft  224  rotatably supported by a bearing  225  secured to the first speed reducing gear wheel  228  and fitted in the reduction gear case  220  and another bearing  226  fitted with the driving case  237 , and a second speed reducing gear wheel  235  which meshes with a speed reduction gear wheel formed on the first speed reducing shaft  224 . 
     A wheel  227  of the rear wheel WR is secured to a right side end portion in the figure of the final output power shaft  23  with a collar  229  interposed therebetween. A brake drum having a liner  231  is formed on the inner diameter side of the wheel  227 . A pair of upper and lower brake shoes  230  which are driven by a brake cam  232  around an axis provided by an anchor pin (not shown) are accommodated in the inner side of the brake drum. It is to be noted that an oil seal  234  is disposed on the rear side in the figure of the bearing  233 . 
       FIG. 25  is a block diagram showing a configuration of the control unit  80 . The control unit  80  includes a REG (regulator) circuit  250 , an EEPROM  251  as pseudo engine sound volume storage means in which sound sources and sound volumes of engine sound and so forth of engine driven vehicles are recorded, a WDT (watch dog timer)  252  for maintaining normal operation of the system, an audio processor  255 , and an amplifier  256 . 
     To the control unit  80 , information from the PDU  52  is inputted through the first coupler  187 . Further, to the REG circuit  250  of the control unit  80 , the low voltage battery  51  is connected through the second coupler  189  of the two-pin type. Furthermore, to the amplifier  256  of the control unit  80 , the speaker  60  is connected through the second coupler  189 . To the audio processor  255 , output information of the EEPROM  251  and the WDT  252  and a motor speed Nm and a vehicle speed V inputted from the PDU  52  are inputted. 
     The audio processor  255  calls a predetermined sound source from the EEPROM  251  based on information of the motor speed Nm and the vehicle speed V and outputs notification sound with a predetermined sound volume from the speaker  60  (and various second speakers) through the amplifier  256 . 
     It is to be noted that, while, in this figure, an input portion from the low voltage battery  51  and an output portion from the amplifier  256  are shown separately from each other, both portions are collected to the second coupler  189  of the four-pin type. Further, to the audio processor  255 , output information from a raindrop sensor  257  and an illuminance sensor  258  can be inputted further. In this instance, this can be coped with, for example, by changing the second coupler  189  of the 4-pin type to that of the 6-pin type. 
     If it is detected by the raindrop sensor  257  that it is raining, then the audio processor  255  can increase the sound volume of notification sound from that in a normal state so that the perception effect of the notification sound may not be reduced by the sound of the rain. On the other hand, if it is detected by the illuminance sensor  258  that it is nighttime, then the audio processor  255  can set the sound volume of the notification sound so as to be lower than that in a normal state. Also it is possible to apply a noise sensor or the like such that the sound volume of the notification sound is set so as to increase when the environmental noise is high, for example, because the traffic amount is great. 
       FIG. 26  is a graph illustrating a relationship between the vehicle speed and the running sound in various vehicles. In this graph, A as an engine driven vehicle, B as an engine four-wheeled car, and C as a motorcycle without power are illustrated. In the case where the engine driven motorcycle and the engine four-wheeled car are compared with each other, the engine driven motorcycle which exhibits a high engine speed upon low speed running because the total engine displacement volume is small and wherein the engine is exposed outwardly of the vehicle body exhibits a generally high sound pressure level (sound volume). 
     The data of the motorcycle without power represented by C indicate a sound volume in the case where a vehicle for a test having no engine as a power source is driven. If attention is paid to the data of the motorcycle without power, running sound whose level a little exceeds that of the engine four-wheeled car immediately after starting thereof begins to indicate increase of the difference thereof after the vehicle speed exceeds 10 km/h. Then, at the vehicle speed of 20 km/h, the running sound comes to C20 which is a little lower than A20 of the engine driven motorcycle. In other words, the ratio in engine sound in the overall running sound decreases as the vehicle speed increases, and at the vehicle speed of 20 km/h, the influence of presence/absence of engine sound to be had on the running sound is small. 
     From the foregoing, in the approach notification control apparatus according to the present embodiment, the notification sound is set such that it is outputted from the speaker with such a sound volume that a slanting line portion representing the difference between the motorcycle without power of C and the engine driven motorcycle of A may be filled up in order to implement running sound equivalent to that of the engine driven motorcycle. Further, the notification sound from the speaker is set such that it is not outputted if the vehicle speed exceeds 20 km/h. 
       FIG. 27  is a flow chart illustrating a procedure of approach notification sound outputting control. At step S 1 , the motor speed Nm is detected based on information from the PDU  52 , and at step S 2 , the vehicle speed V is detected based on the information from the PDU  52 . At step S 3 , it is decided whether or not the motor speed Nm is equal to or lower than an upper limit value NL. This upper limit value NL is set to a connection speed of the centrifugal clutch  216  (refer to  FIG. 24 ) disposed on the output transmission route of the electric motor M. 
     At step S 4 , notification sound is outputted from the speaker  60  such that the sound volume thereof increases in response to the increase of the motor speed Nm. Then at step S 5 , it is decided whether or not the motor speed Nm exceeds the upper limit value NL, and if an affirmative decision is made, then the processing advances to step S 6 , but if a negative decision is made, then the processing returns to step S 4 . In other words, in a non-running state before the centrifugal clutch is connected, the notification sound is outputted such that it increases in response to the speed of rotation of the electric motor M. 
     At step S 6 , it is decided whether or not the vehicle speed V is equal to or lower than an upper limit value VL. In the present embodiment, the upper limit value VL is set to the vehicle speed of 20 km/h. If an affirmative decision is made at step S 6 , then the processing advances to step S 7 , at which the notification sound is outputted such that the difference of the sound volume thereof from a target sound volume may be filled up in response to increase of the vehicle speed V. In the present embodiment, as illustrated in the graph of  FIG. 26 , the notification sound is outputted such that the slanting line portion between the motorcycle without power of C and the engine driven motorcycle of A may be filled up. 
     Sound volumes of notification sound at individual predetermined vehicle speeds can be set in advance as sound volume data in accordance with individual vehicles by an experiment or the like, and the set data can be retained into the EEPROM  251  (refer to  FIG. 25 ) of the control unit  80 . In the present embodiment, the sound volume of notification sound is set such that running sound equivalent to that of a vehicle with a prime mover which incorporates a 50-cc engine corresponding to the automobile rank of the electric motorcycle  1  is outputted. However, for example, in the case where the automobile rank of an electric motorcycle corresponds to a motorcycle of a total engine displacement volume greater than 50 cc but smaller than 400 cc, running sound equivalent to that of a motorcycle which incorporates a 400-cc engine can be outputted. It is to be noted that, the relationship between the vehicle rank of an electric motorcycle and the sound volume of notification sound can be set arbitrarily in response to the vehicle category, the license category and so forth in the road traffic act. 
     Then, at step S 8 , it is decided whether or not the vehicle speed V exceeds the upper limit value VL, and if an affirmative decision is made, then the processing advances to step S 9 , at which the outputting of notification sound is stopped, thereby ending the series of controls. It is to be noted that, if a negative decision is made at step S 6 , then the processing advances to step S 9 , but if a negative decision is made at step S 8 , then the processing returns to step S 7 . 
     With such approach notification sound outputting control as described above, it is possible to output approach notification sound with a sound volume which conforms to running sound of an actual engine driven vehicle in comparison with such a controlling method that the sound volume is increased merely based on increase of the motor speed or the vehicle speed. In particular, the approach notification sound can be controlled such that running sound equivalent to that of an engine driven vehicle corresponding to the vehicle rank or the vehicle category of the electric motorcycle. Further, the tone of the approach notification sound may be selected from recorded sound data from an engine driven vehicle corresponding to the vehicle rank or the vehicle category of the electric motor or from among various tones of sound. 
     It is to be noted that the structure, disposition and so forth of the various speakers which output notification sound and the control unit which controls the speakers are not limited to those of the embodiments described above but can be altered in various manners. The approach notification control apparatus according to the present invention can be applied not only to an electric motorcycle but also to various electric vehicles such as three/four-wheeled vehicles of the saddle type 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.