Abstract:
This approaching vehicle notification sound speaker device is equipped with a voice coil for conducting an electrical signal, a cylindrical voice coil bobbin on which the voice coil is wound, an insulating sheet, and a cap. The sheet is wound on the voice coil bobbin at a position closer to the sound-emitting side than the voice coil, the cap is disposed closer to the sound-emitting side than the voice coil bobbin, the voice coil bobbin and the cap are made of an aluminum-containing material, and the sheet is formed with the inclusion of an aramid-based nonwoven fabric.

Description:
TECHNICAL FIELD 
     The present invention relates to an approaching vehicle warning speaker device. 
     BACKGROUND ART 
     Pedestrians, such as a walking person, may not notice an approaching hybrid vehicle or an electric vehicle, which moves very quietly. Various types of approaching vehicle warning speaker devices are proposed to be mounted on a vehicle, such as a hybrid vehicle, to generate a warning sound to notice pedestrians of an approaching vehicle, such as a hybrid vehicle. Manufacturers independently determine specifications of such approaching vehicle warning speaker devices. So that, approaching vehicle warning speaker devices are not designed based on unified standards specifying, for example, thermal resistance or environmental resistance. 
     The trend in recent years has shown that the method of mounting the approaching vehicle warning speaker device and the specification of the approaching vehicle warning speaker device are to be legislated. Furthermore, the approaching vehicle warning speaker device, which is mounted near an engine or a motor in a hybrid vehicle or the like, is required to have environmental resistance, such as the reproduced sound pressure, thermal resistance, moisture resistance, and water resistance for each frequency band. 
     One of objects of the present invention is to raise the high reproduced sound pressure and to improve environmental resistance such as thermal resistance, moisture resistance, and water resistance. 
     SUMMARY OF INVENTION 
     Solution to Problem 
     An approaching vehicle warning speaker device according to present invention includes a voice coil conductive of electric signals, a sleeve-shaped voice coil bobbin around which the voice coil is wound, an insulating sheet, and a cap. The sheet is wrapped around the voice coil bobbin at a location further in the sound-emission side than the voice coil. The cap is provided further in the sound-emission side than the voice coil bobbin. The voice coil bobbin and the cap are made of material containing aluminum. The sheet includes non-woven fabric containing aramid. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an approaching vehicle warning speaker device according to a first embodiment of the present invention with a portion cut out to show a cross section; 
         FIG. 2  is a perspective view illustrating the approaching vehicle warning speaker device in  FIG. 1  viewed from the opposite side; 
         FIG. 3  is a schematic figure illustrating a sectional view of the approaching vehicle warning speaker device in  FIG. 1  taken along line III-III; 
         FIG. 4  is a schematic figure illustrating an essential portion of the approaching vehicle warning speaker device in  FIG. 1  taken along the line III-III; and 
         FIG. 5  is a schematic view of an essential portion of an approaching vehicle warning speaker device according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An approaching vehicle warning speaker device according to one embodiment of the present invention will be described. The approaching vehicle warning speaker device according to one embodiment includes a voice coil conductive of electric signals, a sleeve-shaped voice coil bobbin around which the voice coil is wound, an insulating sheet, and a cap. The sheet is wrapped around the voice coil bobbin at a location further in the sound-emission side than the voice coil. The cap is provided further in the sound-emission side than the voice coil bobbin. The voice coil bobbin and the cap are made of material containing aluminum. The sheet includes non-woven fabric containing aramid. 
     The voice coil bobbin and the cap made of material containing aluminum offer preferable heat dissipating properties that improve thermal resistance. The components are made light in weight, providing high reproduced sound pressures. 
     The voice coil is preferably made of a covered wire coated with polyamide-imide or polyimide. The voice coil thus configured offers improved thermal resistance. 
     The thickness of the cap is preferably equal to or smaller than the thickness of the voice coil bobbin. The cap thus formed further reduces the weight of the approaching vehicle warning speaker device to improve the reproduced sound pressure. 
     The voice coil bobbin may have a thickness of 50 μm to 80 μm. Although a thinner voice coil bobbin is preferable, the voice coil bobbin thinner than 50 μm can hardly keep its initial shape when the temperature of the voice coil bobbin is high. Meanwhile, the voice coil bobbin thicker than 80 μm cannot offer a desired frequency characteristic because of its heavy weight. 
     The cap may have a thickness of 30 μm to 50 μm. Although a thinner cap is preferable, the cap thinner than 30 μm cannot offer sufficient strength. Meanwhile, the cap thicker than 50 μm cannot offer a desired frequency characteristic because of its heavy weight. 
     Preferably, a damper is bonded to the sheet in a manner encircling the sheet. The damper is more firmly bonded to the sheet than to the voice coil bobbin containing aluminum. This improves environmental resistance. 
     Preferably, the voice coil is joined to a tinsel wire, the tinsel wire is led out from the voice coil bobbin, at a location further in the sound-emission side than the damper, further in the sound-emission side toward the outer edge of the damper, the tinsel wire inflecting at an inflection point in the sound-emission side to be directed to the side opposite the sound-emission side, and the terminal of the tinsel wire is joined to the outer edge of the damper. 
     Configured in such a manner, the length of the portion of the tinsel wire running above the damper can be reduced. This reduces the force acting on the tinsel wire generated by vibration of the voice coil and thus reduces the force acting on a joint between the tinsel wire and the voice coil bobbin. Therefore, the volume of reinforcement (e.g., modified polyamide) applied to the joint between the tinsel wire and the voice coil can be minimized or eliminated. 
     The tinsel wire is preferably provided approximately line symmetric about the line extending from the inflection point along the sound-emission direction. 
     With the tinsel wire thus provided, the damage to the joint between the voice coil bobbin and the tinsel wire due to, for example, excessive load on the tinsel wire caused by resonation of the tinsel wire by vibration of the voice coil bobbin is suppressed, and thus the environmental resistance can be improved. 
     An adhesive bonds together the sheet and the damper. An adhesive containing one or more components selected from a group of acrylic resin, silicone resin, and epoxy resin can be used. 
     Preferably, a diaphragm that generates sound is provided, and the diaphragm is bonded to the sheet. In this configuration, the sheet comprising non-woven fabric made of aramid is provided between the voice coil bobbin and the diaphragm to bond together the voice coil bobbin and the diaphragm. The diaphragm and the voice coil bobbin containing aluminum are more firmly bonded together via the sheet than bonding the diaphragm directly to the voice coil bobbin. Thus, the shock resistance can be improved. 
     Preferably, the sheet and the diaphragm are bonded together using the adhesive, and an annular member is joined to the voice coil bobbin at a location further in the side opposite the sound-emission side than the diaphragm. 
     With such a configuration, the annular member dams the adhesive that bonds the diaphragm, so that the adhesive will not spread beyond the area to be bonded. This reduces the amount of the adhesive that is used. Therefore, the approaching vehicle warning speaker device can be made light in weight, thereby raising the reproduced sound pressure. 
     EMBODIMENTS 
     Embodiments of an approaching vehicle warning speaker device according to the present invention will now be described with reference to  FIGS. 1 to 5 . 
     First Embodiment 
     An approaching vehicle warning speaker device  100  according to a first embodiment of the present invention will now be described with reference to  FIGS. 1 to 4 . The approaching vehicle warning speaker device  100  according to the first embodiments is used as, for example, an approaching vehicle warning speaker device mounted on a hybrid vehicle.  FIG. 1  is a perspective view illustrating the approaching vehicle warning speaker device  100  with a portion cutout.  FIG. 2  is a perspective view of the approaching vehicle warning speaker device  100  in  FIG. 1  viewing from the opposite side. In  FIG. 1 , sound is emitted in the direction indicated by arrow A. Arrow B in  FIGS. 3 to 5  indicates the outward side of the approaching vehicle warning speaker device  100 . The approaching vehicle warning speaker device  1  according to the first embodiment is mounted not only on a hybrid vehicle but may also be mounted in an electric vehicle. 
     A configuration of the approaching vehicle warning speaker device  100  will now be described. The approaching vehicle warning speaker device  100  includes a voice coil  101  conductive of electric signals, a sleeve-like voice coil bobbin  102  around which the voice coil is wound, an insulating sheet  103 , a diaphragm  104  that generates sound, a cap  105 , a damper  106 , a tinsel wire  107 , and an annular member  108 . 
     The voice coil bobbin  102  and the cap  105  are made of aluminum. The cap  105  is joined to the diaphragm  104 . The cap  105  may be joined to the edge of the voice coil bobbin  102  in the sound-emission side. 
     The voice coil bobbin and the cap made of aluminum offer preferable heat dissipating property and improved thermal resistance. Moreover, the reduced weight provides a high reproduced sound pressure. 
     The sheet  103  comprising aramid non-woven fabric is wrapped around the voice coil bobbin  102  further in the sound-emission side (further to the side indicated by arrow A) than the voice coil  101 . The diaphragm  104  and the damper  106  are bonded to the sheet  103  in a manner encircling the sheet  103 . The diaphragm  104  is provided further in the sound-emission side than the damper  106 . The diaphragm  104  and the damper  106  may be bonded to the voice coil bobbin  102 . 
     With the diaphragm  104  bonded to the sheet  103  in a manner encircling the sheet  103 , the diaphragm  104  is more firmly bonded to the voice coil bobbin  102  made of aluminum than the diaphragm directly bonded to the voice coil bobbin  102 . The environmental resistance of the approaching vehicle warning speaker device  100  is thus improved. 
     With the damper  106  bonded to the sheet  103  in a manner encircling the sheet  103 , the damper  106  is more firmly bonded to the voice coil bobbin  102  made of aluminum than the damper  106  directly bonded to the voice coil bobbin  102 . The environmental resistance of the approaching vehicle warning speaker device  100  is thus improved. 
     The voice coil  101  is made of a covered wire coated with polyamide-imide. The voice coil  101  thus provided offers improved thermal resistance. The covered wire is not necessarily coated with polyamide-imide but may be coated with polyimide. 
     The cap  105  is made thinner than the voice coil bobbin  102 . In the first embodiment, the voice coil bobbin  102  is made of an aluminum plate having a thickness of 50 μm, and the cap  105  is made of an aluminum plate having a thickness of 30 μm. With such thicknesses provided, the approaching vehicle warning speaker device  100  can be made light in weight, thereby offering a high reproduced sound pressure. 
     Thicknesses of the voice coil bobbin  102  and the cap  105  are not respectively limited to 50 μm and 30 μm. The voice coil bobbin  102  may have a thickness of 50 μm to 80 μm, and the cap  105  may have a thickness of 30 μm to 50 μm. 
     Using standard aluminum plates having thicknesses of 30 μm, 50 μm, and 80 μm as materials of the voice coil bobbin  102  and the cap  105 , for example, manufacturing cost can be reduced. 
     As illustrated in  FIG. 3 , the tinsel wire  107  is joined to a lead wire  110  of the voice coil  101  and led out from the voice coil bobbin  102 , at a location further in the sound-emission side than the damper  106 , further in the sound-emission side (indicted by the arrow A) toward the outer edge  161  of the damper  106  (indicated by the arrow B). The tinsel wire  107  inflects at an inflection point  171  in the sound-emission side to be directed to the side opposite the sound-emission side and extends toward the direction opposite the sound-emission side toward the outer edge  161 . The tinsel wire  107  is joined to the outer edge  161  of the damper  106  at a joint  172 . 
     With such a configuration, the length of the portion of the tinsel wire  107  running above the damper  106  is reduced. This reduces the force acting on the tinsel wire  107  generated by vibration of the voice coil bobbin  102  and thus reduces the force acting on joints between the tinsel wire  107  and the voice coil bobbin  102 . Therefore, the volume of reinforcement (e.g., modified polyamide) applied to the joint between the tinsel wire  107  and the voice coil  101  can be minimized or eliminated. The weight of the vibrating portion of the approaching vehicle warning speaker device  100  can thus be reduced. 
     The tinsel wire  107  is provided approximately line symmetric about the line extending from the inflection point  171  along the sound-emission direction (indicated by S in the figure). 
     With the tinsel wire  107  thus provided, the damage to the joint between the voice coil bobbin  102  and the tinsel wire  107  due to, for example, excessive load on the tinsel wire  107  caused by resonation of the tinsel wire  107  by vibration of the voice coil bobbin  102  is suppressed, and thus the environmental resistance is improved. An adhesive or the like may be applied to the tinsel wire  107  as required to enhance strength. 
     An adhesive bonds together the sheet  103  and the damper  106 . For example, an adhesive containing one or more components selected from a group of acrylic resin, silicone resin, and epoxy resin can be used. 
     As illustrated in  FIG. 4 , an adhesive  111  is used to bond together the sheet  103  and the diaphragm  104 . The annular member  108  is joined to the voice coil bobbin  102  at a location further in the side opposite the sound-emission side than the diaphragm  104  (that is, further in the side to the voice coil  101  and the damper  106 ). The annular member  108  according to the first embodiment is a paper strip that is wound a plurality of times around the voice coil bobbin  102 . The thickness of the annular member  108  wound around the voice coil bobbin  102  is, for example, 0.4 to 0.6 mm. 
     The annular member  108  thus provided dams the adhesive for bonding the diaphragm  104 , so that the adhesive will not spread beyond the area to be bonded. This allows only the required amount of adhesive for bonding the diaphragm  104  to be applied and thus reduces the amount of adhesive that is used. The weight of the vibrating portion of the approaching vehicle warning speaker device  100  can thus be reduced, thereby raising the reproduced sound pressure. 
     Second Embodiment 
     An approaching vehicle warning speaker device  200  according to a second embodiment of the present invention will now be described with reference to  FIG. 5 . The approaching vehicle warning speaker device  200  has the same configuration as the approaching vehicle warning speaker device  100  according to the first embodiment except that the annular member  108  is replaced with an annular member  208 . 
     The annular member  208  is a member made of paper. The annular member  208  includes an annular portion  281  provided on the circumference of the voice coil bobbin  102  and an angled portion  282  an edge of which continues from the sound-emission side edge of the annular portion  281 . The angled portion  282  extends from the annular portion  281  in the sound-emission side (indicated by the arrow A) toward the outer edge  161  of the damper  106  (indicated by the arrow B). The other edge of the angled portion  282  is further in the sound-emission side than the edge of the diaphragm  104 , which edge being in the side to the voice coil  101 . The projecting distance of the annular member  208  from the voice coil bobbin  102  along the direction indicated by the arrow B may be, for example, 1 mm. 
     The angled portion  282  of the annular member  208  thus provided dams the adhesive  111  for bonding the diaphragm  104 , so that the adhesive  111  will not spread further into the area to the voice coil  101 . This allows only the required amount of adhesive for bonding the diaphragm.  104  to be applied and thus further reduces the amount of adhesive that is used. The weight of the vibrating portion of the approaching vehicle warning speaker device  200  can thus be reduced, thereby raising the reproduced sound pressure. 
     The best mode, such as a configuration and a method, to carryout the present invention is not limited to those described above. Although description and illustration on the present invention are presented mainly for a particular embodiment, various modifications regarding the shape, material, the number of parts, and other structural details can be made for the embodiment by those skilled in the art without departing from the technical idea and the scope of the present invention. 
     Definitive descriptions used to describe shapes and materials are given by way of illustration to promote understanding of the present invention, not byway of limiting the scope of the present invention. Therefore, a component referred to as a name not including the above definitive description or a portion thereof falls within the scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
         
           
               100 ,  200  approaching vehicle warning speaker device 
               101  voice coil 
               102  voice coil bobbin 
               103  sheet 
               104  diaphragm 
               105  cap 
               106  damper 
               107  tinsel wire 
               108 ,  208  annular member 
               111  adhesive