Patent Publication Number: US-2007121335-A1

Title: Headlamp for bicycle

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a headlamp for a bicycle, and more particularly, to a headlamp for a bicycle having a vibration detection unit detecting vibration.  
      2. Description of the Background Art  
      Conventionally, a headlamp for a bicycle having a solar battery and a secondary battery has been known (for example in Japanese Registered Utility Model No. 02-026089).  
      Further, a lighting display apparatus having a solar battery and a polyacene battery in combination is described in Japanese Patent Laying-Open No. 2003-303501.  
      Furthermore, a solar battery apparatus having a solar battery and an electric double layer capacitor in combination is described in Japanese Patent Laying-Open No. 07-177683.  
      The headlamp for a bicycle disclosed in Japanese Registered Utility Model No. 02-026089 is provided with a vibration sensor for detecting vibration and automatically switching on or off the headlamp.  
      From the viewpoint of manufacturing an inexpensive and small-sized headlamp, it is preferable to use a vibration sensor having a coil spring and a conductive wire provided therethrough (that is, a helical spring type vibration sensor).  
      A helical spring type vibration sensor, however, may not be capable of accurately detecting vibration caused when a bicycle is moving, depending on the state of installation. As a result, it may not be capable of switching on or off the headlamp in an appropriate manner.  
     SUMMARY OF THE INVENTION  
      One object of the present invention is to provide a headlamp for a bicycle capable of lighting on or blinking when the bicycle is moving and lighting off when the bicycle is not moving in an appropriate manner.  
      A headlamp for a bicycle in accordance with one aspect of the present invention includes a light emitting element, a power supply unit supplying electric power to the light emitting element, a vibration detection unit detecting vibration, and a switch mechanism providing ON-OFF control of electrical connection between the light emitting element and the power supply unit in response to a result detected by the vibration detection unit. The vibration detection unit has a coil spring and a conductive wire passing through the coil spring, and the coil spring and the conductive wire are disposed to extend in a direction obliquely intersecting with a horizontal direction and a vertical direction when the headlamp is attached to the bicycle.  
      With the above structure, the vibration detection unit extends in an oblique direction, and thus vibration detection sensitivity in the vertical direction is improved. Consequently, the headlamp can light on or blink when the bicycle is moving and light off when the bicycle is not moving in an appropriate manner.  
      Preferably, in the headlamp for a bicycle described above, when the headlamp is attached to the bicycle, the vibration detection unit is disposed to extend in a direction along a bar on which the headlamp is attached, when projected on a horizontal plane.  
      When the headlamp is attached on the bar, the headlamp can be attached stably at a predetermined angle about an axis in a direction orthogonal to the bar. Consequently, with the above structure, the direction of the vibration detection unit can stably be set at an oblique direction.  
      A headlamp for a bicycle in accordance with another aspect of the present invention includes a light emitting element, a power supply unit supplying electric power to the light emitting element, a vibration detection unit detecting vibration, a switch mechanism providing ON-OFF control of electrical connection between the light emitting element and the power supply unit in response to a result detected by the vibration detection unit, and a circuit board on which the vibration detection unit is mounted. The vibration detection unit has a coil spring and a conductive wire passing through the coil spring, and the coil spring and the conductive wire are disposed to extend in a direction obliquely intersecting with a direction in which the circuit board extends and a direction orthogonal to the circuit board.  
      Also in this aspect, the vibration detection unit extends in an oblique direction, and thus vibration detection sensitivity in a direction vertical to the circuit board is improved.  
      Preferably, in the headlamp for a bicycle described above, the power supply unit includes a solar battery and an electrical storage mechanism, and the solar battery is mounted on the circuit board.  
      From the viewpoint of efficiently obtaining electromotive force generated by the solar battery, the circuit board is disposed to be directed in the horizontal direction when the headlamp is attached to the bicycle. Consequently, with the above structure, vibration detection sensitivity in the vertical direction can reliably be improved.  
      Preferably, in the headlamp for a bicycle described above, the electrical storage mechanism includes an electric double layer capacitor or a polyacene capacitor.  
      Thereby, an electric storage mechanism having a capacity sufficient for a headlamp for a bicycle can be achieved.  
      Preferably, the headlamp for a bicycle described above further includes an illuminance detection unit detecting ambient illuminance, and the switch mechanism provides ON-OFF control of electrical connection between the light emitting element and the power supply unit in response to a result detected by the vibration detection unit and a result detected by the illuminance detection unit. Thereby, a headlamp automatically lighting off when the ambient illuminance is high can be achieved.  
      Preferably, in the headlamp for a bicycle described above, the switch mechanism establishes electrical connection between the light emitting element and the power supply unit in response to the vibration detection unit detecting that the vibration continues for a predetermined period of time and the illuminance detection unit detecting that the ambient illuminance is not more than a predetermined illuminance. Thereby, automatic switching between lighting on or blinking and lighting off of the headlamp can be performed in an appropriate manner.  
      According to the present invention, a headlamp for a bicycle capable of lighting on or blinking when the bicycle is moving and lighting off when the bicycle is not moving in an appropriate manner as described above can be provided.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a view showing a structure of a headlamp for a bicycle in accordance with a first embodiment of the present invention.  
       FIG. 2  is a side view of the headlamp for a bicycle in accordance with the first embodiment of the present invention.  
       FIG. 3  is a view of the headlamp for a bicycle shown in  FIG. 2  seen from a direction indicated by an arrow III.  
       FIG. 4  is a view of the headlamp for a bicycle shown in  FIG. 2  seen from a direction indicated by an arrow IV.  
       FIG. 5  is a view of the headlamp for a bicycle shown in  FIG. 2  seen from a direction indicated by an arrow V  
       FIG. 6  is a cross sectional view taken along a line VI-VI in  FIG. 3 .  
       FIG. 7  is a cross sectional view taken along a line VII-VII in  FIG. 4 .  
       FIG. 8  is a cross sectional view taken along a line VIII-VIII in  FIG. 4 .  
       FIG. 9  is a cross sectional view taken along a line IX-IX in  FIG. 2 .  
       FIG. 10  is a cross sectional view taken along a line X-X in  FIG. 9 .  
       FIG. 11  is a cross sectional view showing a vibration sensor mounted in the headlamp for a bicycle shown in FIGS.  1  to  10 .  
      FIGS.  12  to  14  are views showing a circuit board and components mounted on the circuit board in the headlamp for a bicycle shown in FIGS.  1  to  10 .  
       FIG. 15  is a view showing a structure of a headlamp for a bicycle in accordance with a second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, embodiments of a headlamp for a bicycle in accordance with the present invention will be described. It is to be noted that identical or corresponding parts will be designated by the same reference numerals, and the description thereof may not be repeated.  
     First Embodiment  
       FIG. 1  is a view showing a structure of a headlamp for a bicycle in accordance with a first embodiment of the present invention. Referring to  FIG. 1 , a headlamp  1  for a bicycle in accordance with the present embodiment includes an LED element  10 , a power supply device  20  supplying electric power to LED element  10 , a vibration sensor  30  detecting vibration, an illuminance detector  40  detecting ambient illuminance, a switching device  50 , an ON/OFF switch  60 , and a current backflow preventing diode  70 .  
      LED element  10  is connected to power supply device  20  via ON/OFF switch  60  and current backflow preventing diode  70 . Power supply device  20  includes a solar battery  21  and an electrical storage mechanism  22 . Solar battery  21  converts solar energy into electrical energy by utilizing photovoltaic effect of a semiconductor. Electrical storage mechanism  22  stores electric power generated by solar battery  21 . Examples of electrical storage mechanism  22  include a secondary battery, and a high-capacity capacitor such as an electric double layer capacitor or a polyacene capacitor.  
      Vibration sensor  30  detects vibration of a bicycle to determine whether or not the bicycle is moving. Illuminance detector  40  detects ambient illuminance. In the present embodiment, ambient illuminance is detected by measuring the magnitude of electromotive force generated by solar battery  21 .  
      Switching device  50  includes an NOR element  51 , a bipolar transistor  52 , and a monostable multivibrator  53 . NOR element  51  has an input terminal connected to vibration sensor  30  and an input terminal connected to illuminance detector  40 . Further, NOR element  51  has an output terminal connected to the base of bipolar transistor  52  via monostable multivibrator  53 . Bipolar transistor  52  is disposed between LED element  10  and power supply device  20 . Current flows between the collector and the emitter of bipolar transistor  52  only when vibration sensor  30  detects vibration and illuminance detector  40  detects that ambient illuminance is not more than a predetermined illuminance. Thereby, electric power is supplied from power supply device  20  to LED element  10 , and thus LED element  10  lights on. In the manner described above, LED element  10  can automatically light on only when the bicycle is moving and the ambient illuminance is low.  
      When the headlamp is being used, ON/OFF switch  60  is always in an ON state. It is possible to stop using the headlamp by turning off ON/OFF switch  60 .  
       FIG. 2  is a side view of headlamp  1  for a bicycle. Further, FIGS.  3  to  5  are views of headlamp  1  for a bicycle seen from directions indicated by an arrow III, an arrow IV, and an arrow V in  FIG. 2 , respectively. Furthermore, FIGS.  6  to  10  are cross sectional views taken along a line VI-VI in  FIG. 3 , a line VII-VII in  FIG. 4 , a line VIII-VIII in  FIG. 4 , a line IX-IX in  FIG. 2 , and a line X-X in  FIG. 9 , respectively.  
      In FIGS.  6  to  10 , a direction indicated by an arrow DR 1  corresponds to a “forward direction” when headlamp  1  for a bicycle is attached on a handle bar at an intended angle. Similarly, a direction indicated by an arrow DR 2 , a direction indicated by an arrow DR 3 , and a direction indicated by an arrow DR 4  correspond to a “backward direction”, an “upward direction”, and a “downward direction”, respectively, when headlamp  1  for a bicycle is attached on the handle bar at an intended angle.  
      Referring to FIGS.  2  to  10 , headlamp  1  for a bicycle includes a main body  2  and a bracket  3  as a “securing tool”. To attach headlamp  1  for a bicycle on a handle bar  100  of the bicycle, handle bar  100  is passed through bracket  3 . Solar battery  21  is disposed on an upper surface of a printed circuit board (PCB)  21 A. PCB  21 A is disposed to extend in a horizontal direction when headlamp  1  for a bicycle is attached on handle bar  100  at an intended angle. On a lower surface of PCB  21 A, LED element  11 , electrical storage mechanism  22 , vibration sensor  30 , and ON/OFF switch  60  are mounted. In this manner, headlamp  1  for a bicycle is provided in a compact structure.  
       FIG. 11  is a cross sectional view showing vibration sensor  30 . Referring to  FIG. 11 , vibration sensor  30  includes a helical spring  31  made of an elastic metal conductive wire  31 A, a central metal conductive wire  32 , a resin base  33 , a resin exterior portion  34 , and a resin lid  35 . Resin base  33 , resin exterior portion  34 , and resin lid  35  constitute a “casing” for accommodating helical spring  31  and central metal conductive wire  32 . When the bicycle is moving, helical spring  31  and central metal conductive wire  32  come into contact with each other as a result of vibration, and electrical connection is established therebetween. Thereby, the vibration is detected. Helical spring  31  is made for example of phosphor bronze having a diameter of about 0.15 mm. Central metal conductive wire  32  is made for example of bronze having a diameter of about 0.5 mm. Examples of such vibration sensor  30  include “SW-18010P” manufactured by Yusan Electric Co., Ltd.  
      A one-shot circuit for removing noise is connected to vibration sensor  30 . Thereby, only vibration continuing for a predetermined period of time (for example, not less than about 45 seconds) is detected, and thus whether or not the bicycle is moving can be determined in an appropriate manner.  
      When the bicycle is moving, vibration in an upward and downward direction of the bicycle is stably and continuously caused, as compared to vibration in a forward and backward direction and in a width direction of the bicycle. Accordingly, by detecting the vibration in the upward and downward direction with high accuracy, whether or not the bicycle is moving can be determined more accurately, and ON/OFF control of headlamp  1  for the bicycle can be performed in an appropriate manner.  
      It has conventionally been known that vibration sensor  30  of the helical spring type described above is most insensitive to vibration in its longitudinal direction (a direction indicated by an arrow DR 5 ). On the other hand, the direction of vibration to which vibration sensor  30  is most sensitive has conventionally been unknown. The inventors of the present invention have studied the matter and found that vibration sensor  30  of the helical spring type is most sensitive to vibration in a direction obliquely intersecting with its longitudinal direction and width direction.  
      FIGS.  12  to  14  are views showing PCB  21 A and components mounted on the PCB.  FIG. 12  shows PCB  21 A seen from below,  FIG. 13  shows PCB  21 A seen from the side, and  FIG. 14  shows PCB  21 A seen from the back.  
      Referring to FIGS.  12  to  14 , when projected on the lower surface of PCB  21 A, vibration sensor  30  is disposed in a direction along handle bar  100  on which headlamp  1  for the bicycle is attached (a right and left direction in  FIGS. 12 and 14 ). Further, vibration sensor  30  is disposed to extend in a direction (indicated by arrow DR 5 ) obliquely intersecting with a direction of a main surface of PCB  21 A. Specifically, vibration sensor  30  is disposed to extend in a direction (indicated by arrow DR 5 ) obliquely intersecting with a horizontal direction and a vertical direction when headlamp  1  for the bicycle is attached on handle bar  100  at an intended angle.  
      With this manner, the upward and downward direction obliquely intersects with the direction in which vibration sensor  30  extends (the direction indicated by arrow DR 5 ). Accordingly, vibration in the upward and downward direction can be detected with high sensitivity. As a result, whether or not the bicycle is moving can be determined in an appropriate manner.  
      The inventors of the present invention have confirmed the effect described above by performing a process described below.  
      Firstly, PCB  21 A shown in FIGS.  12  to  14  is placed on a vibration test apparatus to be vibrated in the upward and downward direction (the direction indicated by arrows DR 3  and DR 4 ). Six PCBs are tested, each vibrated with varying vibration intensities, and the vibration intensity (vibrational acceleration) at which LED element  10  starts lighting on is measured with an angle θ for mounting vibration sensor  30  changed (at 0°, 5°, 10°, and 15°). Table 1 shows the result obtained through the process described above.  
               TABLE 1                          Acceleration when the LED element starts lighting on (Unit: G)                             Angle (θ) for Mounting Sensor                                         0°   5°   10°   15°                                                         Sample   1   1.07   1.12   0.78   0.74           No.   2   1.76   1.64   1.62   1.54               3   2.73   2.20   2.00   1.97               4   1.14   1.03   1.02   1.00               5   1.38   1.48   1.30   1.19               6   2.28   2.00   1.84   1.76                                         Average   1.73   1.58   1.43   1.37                      
 
      As shown in Table 1, LED element  10  lit on at the smallest acceleration when θ=15° has been found that vibration sensor  30  is more sensitive to the vibration in the upward and downward direction vertical to the ground when 0=150. Consequently, in headlamp  1  for the bicycle in accordance with the present embodiment, angle θ is set at 15°. When there is a change in the specifications of vibration sensor  30 , angle θ for mounting the sensor is altered as appropriate.  
      To summarize the above, headlamp  1  for a bicycle in accordance with the present embodiment includes LED element  10  as a “light emitting element”, power supply device  20  as a “power supply unit” supplying electric power to LED element  10 , vibration sensor  30  as a “vibration detection unit” detecting vibration, illuminance detector  40  as a “illuminance detection unit” detecting ambient illuminance, and switching device  50  as a “switch mechanism” providing ON-OFF control of electrical connection between LED element  10  and power supply device  20 . Vibration sensor  30  includes helical spring  31  as a “coil spring”, and central metal conductive wire  32  as a “conductive wire” passing through helical spring  31 . Helical spring  31  and central metal conductive wire  32  are disposed to extend in a direction (indicated by arrow DR 5 ) obliquely intersecting with the horizontal direction and the vertical direction when the headlamp is attached to the bicycle.  
      In other words, helical spring  31  and central metal conductive wire  32  are disposed to extend in a direction (indicated by arrow DR 5 ) obliquely intersecting with a direction in which PCB  21 A as a “circuit board” on which vibration sensor  30  is mounted extends and a direction orthogonal to PCB  21 A.  
      Switching device  50  establishes electrical connection between LED element  10  and power supply device  20 , more specifically, in response to vibration sensor  30  detecting that vibration continues for a predetermined period of time and illuminance detector  40  detecting that ambient illuminance is not more than a predetermined illuminance.  
      With the above structure, vibration sensor  30  extends in an oblique direction, and thus vibration detection sensitivity is improved. Consequently, the headlamp can light on or blink when the bicycle is moving and light off when the bicycle is not moving in an appropriate manner.  
      It is to be noted that the operation of switching device  50  is not limited to that described above. For example, illuminance detector  40  may not be mounted, and switching device  50  may establish electrical connection between LED element  10  and power supply device  20  only in response to vibration sensor  30  detecting that vibration continues for a predetermined period of time.  
      In headlamp  1  for the bicycle, when the headlamp is attached to the bicycle, vibration sensor  30  is disposed to extend in a direction along handle bar  100  when projected on a horizontal plane.  
      When headlamp  1  is attached on handle bar  100 , headlamp  1  can be attached stably at a predetermined angle about an axis in a direction orthogonal to handle bar  100 . Consequently, with the above structure, the direction of vibration sensor  30  can stably be set at an oblique direction.  
      The direction in which vibration sensor  30  is mounted is not limited to that described above. For example, when the headlamp is attached, vibration sensor  30  may be disposed to extend in the forward and backward direction of the bicycle when projected on a horizontal plane.  
      Power supply device  20  includes solar battery  21  and electrical storage mechanism  22 . Solar battery  21  is mounted on PCB  21 A.  
      From the viewpoint of efficiently obtaining electromotive force generated by solar battery  21 , PCB  21 A is disposed to be directed in the horizontal direction when the headlamp is attached to the bicycle. Consequently, with the above structure, vibration detection sensitivity can reliably be improved.  
      The “bicycle” on which the headlamp in accordance with the present embodiment is attached is typically a two-wheeler, and it may for example be a tricycle. Further, the headlamp may be attached on handle bar  100  as described above, and may be attached on a shaft.  
     Second Embodiment  
       FIG. 15  is a view showing a structure of a headlamp for a bicycle in accordance with a second embodiment. Referring to  FIG. 15 , the headlamp for a bicycle in accordance with the present embodiment is a modification of the headlamp for a bicycle in accordance with the first embodiment, and it includes LED element  10 , power supply device  20 , vibration sensor  30 , illuminance detector  40 , switching device  50 , ON/OFF switch  60 , and current backflow preventing diode  70 , as in the first embodiment.  
      In the present embodiment, in switching device  50 , monostable multivibrator  53  and a multivibrator  54  are disposed between NOR element  51  and bipolar transistor  52 . This allows LED element  10  to automatically blink (instead of lighting on in the first embodiment) only when the bicycle is moving and the ambient illuminance is low. To let people in a surrounding area notice the presence of the moving bicycle, blinking seems to be preferable to lighting on.  
      Although the embodiments of the present invention have been described, it is intended from the beginning to combine features of each embodiment described above as appropriate.  
      Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.