Abstract:
A torque detection device for detecting a torque applied to a bicycle for controlling power output of a motor applied to the bicycle in helping moving the bicycle is disclosed. The torque detection device includes a shaft coupled to a driving chain wheel and pedals of the bicycle. A circuit including strain gauge based elements is embedded in the shaft for converting a torsional deformation caused by the torque applied to the shaft by a rider via the pedals into an electrical signal. The electrical signal, after being properly processed, is applied to a motor power controller which in turns controls the power output of the motor whereby the torque from the motor is determined based on the torque applied by the rider to the bicycle. Thus, as the rider applies a great torque to the pedals, the motor correspondingly supplies a large output of power to the bicycle for helping moving the bicycle. No additional manual control of the motor is needed.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a torque detection device for a motor assisted bicycle, and in particular to a device for detection of the torque applied to a bicycle by a rider for controlling the torque output of a motor for assisting moving the bicycle in a controlled manner. 
     BACKGROUND OF THE INVENTION 
     In the trend of environmental protection, bicycles are widely used as personal transportation means. To help bicycle riders in difficult situations, such as moving uphill, an electrical motor may be mounted to the bicycle to generate additional torque to the bicycle wheels. The motor is usually powered by a battery set which has a limited power supply. Thus, the power of the battery set must be conserved and consumed in an efficient way. A manual control may be mounted in the frame and operated by the rider in order to selectively turn on/off the motor. The manual control cannot responds automatically to different riding situations by changing power output of the motor and thus may cause waste of the power of the battery set. Furthermore, manually controlling the motor while watching the traffic condition may be difficult for some riders and accidents may result therefrom. 
     Taiwan Patent Application No. 84215538 discloses a device for controlling the motor of the bicycle. Such a device is in general ineffective in controlling the motor. U.S. Pat. No. 5,900,703 also discloses a device to control the motor. The device cannot control the output power of the motor and thus may still cause waste of power. 
     Thus, it is desired to provide a torque detection device that allows a motor of a power-assisted bicycle to be controlled based on torque applied by a rider to the bicycle for overcoming the above problems. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a torque detection device for detecting torque applied to a bicycle by a rider and generating a signal corresponding to the torque for controlling power output of a motor of the bicycle whereby the power output of the motor is determined based on the torque applied by the rider for efficient use of power of a battery set of the bicycle. 
     Another object of the present invention is to provide a device which automatically controls power output of a motor of a power-assisted bicycle for eliminating manual control of the motor. 
     To achieve the above object, in accordance with the present invention, there is provided a torque detection device for detecting a torque applied to a bicycle for controlling power output of a motor applied to the bicycle in helping moving the bicycle. The torque detection device comprises a shaft coupled to a driving chain wheel and pedals of the bicycle. A circuit comprising strain gauge based elements is embedded in the shaft for converting a torsional deformation caused by the torque applied to the shaft by a rider via the pedals into an electrical signal. The electrical signal, after being properly processed, is applied to a motor power controller which in turn controls the power output of the motor whereby the torque from the motor is determined based on the torque applied by the rider to the bicycle. Thus, as the rider applies a great torque to the pedals, the motor correspondingly supplies a large output of power to the bicycle for helping moving the bicycle. No additional manual control of the motor is needed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the accompanying drawings, in which: 
     FIG. 1 is an exploded view of a torque detection device constructed in accordance with a first embodiment of the present invention to be mounted to a bicycle frame; 
     FIG. 2 is an exploded view of a connector of the torque detection device of the present invention; 
     FIG. 3 is cross-sectional view of the torque detection device of the present invention; 
     FIG. 4 is circuit diagram of a signal amplification circuit of the torque detection device of the present invention; 
     FIG. 5 is an exploded view of a torque detection device constructed in accordance with a second embodiment of the present invention to be mounted to a bicycle frame; 
     FIG. 6 is a perspective view of a torque detector of the torque detection device of FIG. 5 mounted to a driving chain wheel of the bicycle; 
     FIG. 7 is an exploded view of FIG. 6; 
     FIG. 8 is a front view of FIG. 6; and 
     FIG. 9 is a side elevational view of a bicycle to which the torque detection device of the present invention is mounted. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings and in particular to FIGS. 1-3, a torque detection device constructed in accordance with the present invention comprises a torque sensing shaft  1 . In a preferred embodiment of the present invention, the torque sensing shaft  1  comprises means, such as strain gauges, that generates an electrical signal corresponding to torsional deformation of the shaft  1  for detecting torque applying thereto. The shaft  1  serves as a pedal axle of a bicycle A (see FIG. 9) rotatably received in a five-branch tube  2 A of a frame  1 A of the bicycle A. A plurality of conductive rings  11  is mounted around the shaft  1  and spaced from each other by insulative rings  111  to serve as electrical contacts. A direction sensing element  12  is also mounted on the shaft  1 . The direction sensing element  12  may comprise a magnet element or an infrared sensor embedded in the shaft  1 . Signal amplification means  13  (see FIG. 4) is mounted in the shaft  1  and comprises a circuit connected to the contacts  11  for generating the electrical signal representing the torque applied to the shaft  1 . The signal is output through the corresponding contact  11 . 
     The torque sensing shaft  1  has two ends  14 ,  15  coupled to a driving chain wheel  3 A and pedals  4 A,  5 A of the bicycle A. A rider drives the pedals  4 A,  5 A to move the bicycle A causing a torque to act on the shaft  1 . The torque is detected and a corresponding signal generated by the torque detection device of the present invention. 
     A connector  2  defines a plurality of holes  21  for receiving bolts  6 A that fixes the connector  2  in a cavity  2 A′ defined in an underside of the five-branch tube  2 A, as shown in FIG.  3 . The connector  2  comprises a plurality of contact bars  22  and a direction detecting member  23  respectively corresponding to the contacts  11  and the direction sensing element  12  of the shaft  1 . The contact bars  22  are resiliently supported and extend beyond the cavity  2 A′ for engaging with the corresponding contacts  11  of the shaft  1  to transmit signal and power therebetween. The signal generated in the signal amplification means  13  is transmitted to a motor power controller  8 A of the bicycle A via the corresponding contact bar  11  and a cable assembly  7 A connected to output terminnals  24  of the signal detector  2  for controlling the output of the motor  9 A (FIG.  9 ). 
     The direction detecting member  23  may comprise a Hall IC or reed switch (corresponding to the magnet element of the direction sensing element  12 ) or an infrared transmitter (corresponding to the infrared sensor of the direction sensing element  12 ) for cooperating with the direction sensing element  12  of the shaft  1  to detect the rotation direction thereof. Different direction signals will be generated corresponding to clockwise and counterclockwise rotations of the shaft  1 . The direction signal is sent through the output terminals  24  to the motor power controller  8 A. 
     The connector  2  is housed in an insulative casing  3 . A plurality of holes  31  is defined in the casing  3  corresponding to the holes  21  of the connector  2  for receiving the bolts  6 A. 
     With reference to FIG. 4 which shows a circuit diagram of the signal amplification means  13 , the signal amplification means  13  is powered by a power source VS which is constituted by electrical power supplied from the motor power controller  8 A via the contacts  11 . In other words, at least two of the contacts  11  are used as the power input contacts of the signal amplification means  13 . The signal amplification means  13  comprises two variable resistors  131 ,  132  which may be in the form of thin plates made of a material that changes electrical properties thereof, such as resistance, when elongated or deformed whereby the resistance thereof varies with the torque applied to the shaft  1 . An example is strain gauge. 
     The variable resistors  131 ,  132  form an electrical bridge with two fixed resistors R 1 , R 2 . Electrical potential at intermediate points B 1 , B 2  between the variable resistors  131 ,  132  and the corresponding fixed resistors RI, R 2  is taken as the output signal. The output signal is amplified by a differential amplification circuit comprising an operational amplifier U 1  and corresponding resistors R 3 , R 4 , R 5 , R 6 . The amplified output signal taken at output U 1 ′ of the differential amplification circuit represents the magnitude of torque applied to the shaft  1  by the rider and the signal is applied to the motor power controller  8 A. 
     The direction detecting member  23  is also included in the circuit diagram of FIG.  4 . The direction signal from the direction detecting member  23  is applied to the motor power controller  8 A. Therefore, the input of the motor power controller  8 A includes, at least, the magnitude of the torque applied to the shaft I and the rotational direction of the shaft  1  and based on such inputs, the motor power controller  8 A controls the output of the motor  9 A of the bicycle A that is applied to the bicycle for helping moving the bicycle A. 
     With reference to FIGS. 5-8 which show a second embodiment of the torque detection device of the present invention, the second embodiment comprises a torque sensing shaft  1 ′ that is different from the torque sensing shaft  1  of the first embodiment. The torque sensing shaft  1 ′ comprises no strain gauge and instead, a torque detector  5  is used to detect the torque applied to the bicycle A by the rider. The signal amplification means  13  that is for amplification of the signal from the strain gauge is thus eliminated. However, the contact rings  11 , the insulative rings  111  separating the contact rings  11  and the direction sensing element  12  are retained on the shaft  1 ′. A slot  16  is defined in surface of the shaft  1 ′ for receiving and retaining a wire  17  therein. The wire  17  has a first end connected to the corresponding contact  11  of the torque sensing shaft  1 ′ and a second end connected to a sensing device  4  for transmitting the electrical signal from the sensing device  4  to the contact  11 . The signal is then transmitted to the connector  2  via the engagement between the contact  11  and the corresponding contact bar  22  of the connector  2 . 
     A torque detector  5  is fixed to the driving chain wheel  3 A by bolts  6 A. The torque detector  5  comprises two resiliently deformable elements  51  supported thereon. The resiliently deformable elements  51  are located at opposite positions with respect to a center of the driving chain wheel  3 A. In other words, the resiliently deformable elements  51  are spaced 180 degrees from each other. There can be more than two such resiliently deformable elements  51  and preferably, the resiliently deformable elements  51  are symmetrically arranged with respect to the center of the driving chain wheel  3 A. The resiliently deformable elements  51  may comprise springs, such as torsional springs or compression springs. Each element  51  is fixed to a mounting block  52  that is fixed to the driving chain wheel  3 A whereby a spring force acts upon the pedals  4 A,  5 A when the pedals  4 A,  5 A are driven by the rider and the elements  51  deform. The deformation of the elements  51  is substantially proportional to the torque applied to the torque sensing shaft  1 ′. 
     The torque detector  5  comprises a pair of arms  53 ,  54  which are opposite to and spaced from each other for defining a space  55  in which the sensing device  4  is arranged. A reference member  531 ,  541  is attached to a free end of each arm  53 ,  54 . The distance between each reference member  531 ,  541  and the sensing device  4  varies corresponding to the deformation of the resiliently deformable elements  51  whereby by sensing the variation of distances between the reference members  531 ,  541  and the sensing device  4 , the detonation of the elements  51  may be determined which in turn determines the torque applied to the shaft  1 ′. In the embodiment illustrated, the reference members  531 ,  541  comprise magnet elements which magnetically interacts with the sensing device  4  for inducing voltage signal in the sensing device  4 . The sensing device  4  may be comprised of Hall IC for interaction with the magnets of the reference numbers  531 ,  541  to induce the voltage signal. This signal is applied to the wire  17  and is transmitted to the motor power controller  8 A via the connector  2 . 
     When the rider applies a large torque to the shaft  1 ′ by forcibly depressing the pedals  4 A,  5 A, for example in the situation of riding uphill, the variation of distance between the reference members  531 ,  541  and the sensing device  4  is increased and the sensing device  4  outputs a high voltage signal via the corresponding contact  11  of the connector  2 . The high voltage signal is applied to the motor power controller  8 A and causes a great power output of the motor  9 A for facilitating moving the bicycle A uphill. 
     On the contrary, when the bicycle A is moving downhill or moving on a horizontal surface, the torque applied to the shaft  1 ′ is small or approaches zero whereby the variation of distance between the reference members  531 ,  541  and the sensing device  4  is little or even zero and the sensing device  4  outputs a lower voltage signal via the corresponding contact  11  of the connector  2  or even does not output any signal. The lower voltage signal is applied to the motor power controller  8 A and causes only a small power output of the motor  9 A. 
     The direction sensing element  12  and the direction detecting member  23  determine the rotational direction of the chain wheel of the bicycle A for facilitating the control and safety of use of the motor  9 A. 
     An adjustment block C is attached to the torque detector  5  by a bolt  2 C, preferably with a washer  1 C interposed therebetween. By adjusting the bolt  2 C, the resiliently deformable elements  51  may be pre-loaded to different extents thereby adjusting the output signal of the torque detector  5 . 
     With reference to FIG. 9, wherein a bicycle A is shown to which the torque detection device in accordance with the present invention is mounted, the torque detection device is mechanically coupled to the pedal axle that comprises the torque sensing shaft  1 ,  1 ′ whereby the forces that a rider applies to pedals  4 A,  5 A for riding the bicycle A are transmitted to the torque detection device and detected thereby. An electrical signal representing the magnitude of the torque is generated and transmitted to the motor power controller  8 A via the connector  2  whereby the motor power controller  8 A controls the power output of the motor  9 A in accordance with the actual requirement of torque. An effective control of the power from the motor  9 A applied to the bicycle A may thus be obtained. 
     Although the present invention has been described with respect to the preferred embodiments, it is contemplated that a variety of modifications, variations and substitutions may be done without departing from the scope of the present invention that is intended to be defined by the appended claims.