Patent Application
20050122681
The present invention is directed to bicycles and, more particularly, to a heat dissipating apparatus for a bicycle electronic component.
In recent years, bicycles have been equipped with many electronic components in order to provide various desirable functions. Such components are disclosed in Japanese Kokai Publication Nos. 9-213852 and 2002-83912. For example, bicycles may be equipped with motor drive circuits structured to operate a gearshift motor for a bicycle transmission and/or structured to operate a suspension control motor for a bicycle suspension. Bicycles also frequently are equipped with control circuits used to control the operation of headlights mounted to the bicycle. Circuits used to control such devices may include one or more high speed CPU's mounted to a control substrate. Some control circuits may include overvoltage protection circuits that stabilize voltage applied to the various circuits and devices from a power supply such as a battery or an alternating current generator that converts the rotation of a wheel to electrical energy. Overvoltage protection circuits are particularly useful to protect against excessive voltage that may be generated by an alternating current generator during high speed riding.
Many electronic components provided for bicycles comprise elements such as diodes, transistors, etc. that generate significant amounts of heat during operation. For example, voltage prevention circuits use Zener diodes and transistors to absorb a portion of the load placed on a headlight, and such electronic components generate large amounts of heat. In conventional bicycles, no measures are taken for dissipating the heat generated by such heat-generating elements. Thus, there is the danger that excessive heat generated by the heat-generating elements will alter the operating characteristics of the electronic components or destroy the electronic components altogether, thereby creating electronic component malfunctions and the like.
The present invention is directed to various features of a bicycle electronic component. In one embodiment, a heat dissipating apparatus for a bicycle electronic component comprises an electronic component that generates heat; a case having a thermally conductive portion, wherein the electronic component is supported by the case and the case includes a structure for mounting the case to a bicycle; and a thermally conductive member disposed between the electronic component and the case. Additional inventive features will become apparent from the description below, and such features alone or in combination with the above features may form the basis of further inventions as recited in the claims and their equivalents.
A saddle 16 is mounted to the upper middle part of frame body 2, a drive mechanism 5 is mounted to the lower part of frame body 2, a front wheel 6 having a hub dynamo 10 and possibly a roller brake is rotatably mounted to the bottom of front fork 3, and a rear wheel 7 is rotatably mounted to the rear of frame body 2. Hub dynamo 10 houses an alternating current generating dynamo 19 (
Drive mechanism 5 comprises a crank 27 rotatably mounted at the bottom bracket of frame body 2, front and rear transmissions 8 and 9, and a chain 29. Front transmission 8 comprises, for example, three front sprockets F1-F3 and front derailleur 26f. Front sprockets F1-F3 are mounted to crank 27, and front derailleur 26f is mounted on frame body 2. Rear transmission 9 comprises, for example, a multiple sprocket assembly 25 having eight rear sprockets R1-R8 and rear derailleur 26r. Multiple sprocket assembly 25 is mounted to rear wheel 7, and rear derailleur 26r is mounted at the back of frame body 2. Crank 27 comprises a right crank arm 27a and a left crank arm 27b, wherein front sprockets F1-F3 are mounted to right crank arm 27a. Chain 29 engages one of the front sprockets F1-F3 and one of the rear sprockets R1-R8.
Front sprockets F1-F3 are arranged in the order of an increasing number of teeth, wherein front sprocket F1 is the laterally innermost front sprocket having the least number of teeth, and front sprocket F3 is the laterally outermost front sprocket having the most number of teeth. Rear sprockets R1-R8 are arranged in the order of a decreasing number of teeth, wherein rear sprocket R1 is the laterally innermost rear sprocket having the most number of teeth, and rear sprocket R8 is the laterally outermost rear sprocket having the least number of teeth.
A rotation sensor (not shown) is provided for sensing the rotation of crank 27. The presence or absence of rotation of crank 27 ordinarily is used in part to control the operation of front and rear transmissions 8 and 9. For example, derailleurs cannot shift properly when crank 27 is stationary, so any requested operation of a derailleur may be delayed until crank 27 is rotating. A rotation sensor typically comprises a reed switch (not shown) mounted to frame body 2 and a plurality of (e.g., four) magnets (not shown) concentrically mounted to one of the crank arms 27a and 27b so that reed switch 23 provides four pulses for each revolution of crank 27.
A control box 11 containing various electronic components for controlling various components including front and rear transmissions 8 and 9, front and rear suspensions 13f and 13r and headlight 18 is mounted to frame body 2 between fork 3 and drive mechanism 5. More specifically, the components within control box 11 control front and rear transmissions 8 and 9 and front and rear suspensions 13f and 13r in response to the operation of gear switches and control switches (not shown) mounted to handlebar 15. The components within control box 11 also automatically control the operation of front and rear transmissions 8 and 9 in response to bicycle velocity. Headlight 18 is turned off and on in response to ambient light.
An operating switch 28, a liquid crystal display (LCD) 24 and an optical sensor 36 are connected to gearshift controller 23. Operating switch 28 is used for requesting various operations of gearshift controller 23, LCD 24 is used for displaying various operating information, and optical sensor 36 serves as an ambient light sensor for controlling the operation of headlight 18.
A dynamo waveform shaping circuit 34 receives the alternating current signal from dynamo 19 and provides speed indicating signals to gearshift controller 23. More specifically, dynamo waveform shaping circuit 34 may perform half-period sampling of the alternating current sine wave signals, pass the sampled signals through an appropriate waveform shaping circuit such as a Schmitt circuit, and generate a pulsed signal corresponding to the speed of the bicycle.
A charging and rectifying circuit 33 also receives the alternating current signal from dynamo 19, coverts the alternating current signal to a direct current signal, and provides the direct current signal to an electricity storing device 32. Charging and rectifying circuit 33 may comprise a half-wave rectifying circuit that rectifies the alternating current from dynamo 19 into direct current and supplies the direct current to the electricity-storing device 32.
Electricity storing device 32 provides operating power to gearshift controller 23, charging and rectifying circuit 33, overvoltage prevention circuit 52a and motor driver 52b. Approximately 1 mA of electric current is supplied to gearshift controller 23, motor driver 52b and charging and rectifying circuit 33. Approximately 1 A of electric current is supplied directly to motor driver 52b. Electricity storing device 32 may comprise, for example, a high capacity capacitor. Electricity-storing device 32 also may comprise a secondary battery, such as a nickel-cadmium battery, lithium-ion battery, nickel-hydride battery, etc., instead of a capacitor.
Overvoltage prevention circuit 52a is used to prevent excessive voltage generated by dynamo 19 from being applied to headlight 18. Overvoltage prevention circuit 52a accomplishes this by converting a portion of a high voltage generated by dynamo 19 to thermal energy while bicycle 1 is traveling at high speed. Overvoltage prevention circuit 52a comprises a Zener diode and various transistors. As shown in
Motor unit 30 comprises a gear shifting motor 45 and an operating position sensor 47. Motor 45 moves one of the front derailleur 26f or rear derailleur 26r. Operating position sensor 47 senses the operating position of the relevant front derailleur 26f or rear derailleur 26r, and this operating position information is provided to gearshift controller 23. Of course, motor unit 30 could be used to operate one of front suspension 13f or 13r, in which case motor 45 would be a suspension control motor.
Motor driver 52b performs positioning control for gear-shifting motor 45. Motor driver 52b comprises various transistors, such as an FET and the like. As shown in
In this embodiment, thermally conductive sheet 60 is a relatively soft, thin and flexible member formed using copper or aluminum to facilitate contact with heat generating elements 53 and lid 11a of control box 11 over a relatively large area. Since thermally conductive sheet 60 makes contact with both the heat-generating elements 53 comprising the electronic components 52 (i.e., the Zener diode of overvoltage prevention circuit 52a, the transistors in motor driver 52b and CPU 52c , etc.) and lid 11a of control box 11 through a large area, the heat generated inside the electronic components 52 can be efficiently dissipated. As a result, fluctuations in operating characteristics of the electronic components or heat destruction of the electronic components can be avoided. Heat dissipation is further enhanced by the fact that control box 11 is mounted in a location on bicycle 1 as shown in
While the above is a description of various embodiments of inventive features, further modifications may be employed without departing from the spirit and scope of the present invention. For example, while electronic components 52 such as overvoltage prevention circuit 52a, motor driver 52b and high speed CPU 52c shown in FIGS. 5(A)-5(C) were provided as examples of electronic components that generate heat, the teachings herein could be applied to any heat generating components.
While control box 11 was mounted to frame body 2 of bicycle 1, control box 11 could be mounted most anywhere on bicycle 1. For example, control box 11 also could be mounted to handlebar 15 or to a basket mounted somewhere on bicycle 1. While control box 11 was made of an aluminum alloy in the described embodiment, copper or some other metal with a high coefficient of thermal conductivity also could be used to form at least the heat dissipating part of control box 11.
While bicycle 1 was described as a trekking bike, clearly the teachings herein could be applied to any type of bicycle, such as a mountain bike, sport bike or some other bicycle.
The size, shape, location or orientation of the various components may be changed as desired. Components that are shown directly connected or contacting each other may have intermediate structures disposed between them. The functions of one element may be performed by two, and vice versa. The structures and functions of one embodiment may be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the scope of the invention should not be limited by the specific structures disclosed or the apparent initial focus or emphasis on a particular structure or feature.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-408969 | Dec 2003 | JP | national |
