Abstract:
A non-contact type torque and angle of rotation sensing device consisting of a magnetic member, sensing members and a computing unit for measuring a torque being applied to rotate a transmission member and the angle of rotation of said transmission member in a first axial direction is disclosed. The magnetic member defines a first center, and is mounted on and rotatable with the transmission member. The magnetic member deflects relative to the transmission member in a nonparallel manner relative to the first axial direction when rotating with the transmission member. Sensing members induce a magnetic field variation to output respective electrical signals that exhibit a phase difference there between. The computing unit receives and calculates the electrical signals of the sensing member to obtain the amplitude and to further translate the amplitude into torque value and angle of rotation.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to torque sensing technology and more particularly, to a non-contact type torque and angle of rotation sensing device for use in any torque transmission device to measure the torque on the torque transmission device and the angle of rotation of the torque transmission device in a non-contact manner. The invention relates also to a torque and angle of rotation measurement method using the non-contact type torque and angle of rotation sensing device. 
         [0003]    2. Description of the Related Art 
         [0004]    In line with the worldwide trend of environmental protection and energy saving, the utilization rate and popularity of electric bicycles keeps growing. Except the mechanisms used in a regular bicycle, an electric bicycle further comprises a battery, a drive motor, a controller, a torque sensor and other electronic control components. When riding an electric bicycle, the torque sensor of the electric bicycle will measure the rider&#39;s pedaling force and provide a corresponding signal to the controller, enabling the controller to control the drive motor output power to the bicycle subject to the detected torque. The greater the rider&#39;s pedaling force is, the higher the output power of the drive motor will be. Thus, manpower needed in order to save riding. Thus, an auxiliary power can be automatically provided to drive the electric bicycle, enabling the rider to ride the electric bicycle with less effort. 
         [0005]    Many different kinds of torque sensing devices have been created for electric bicycle applications. For example, a strain gauge may be installed in a pedal crank of an electronic bicycle to measure the deflection of the pedal crank, thereby providing an electrical signal indicative of the torque. Alternatively, a strain gauge can be installed in a transmission component of an electronic bicycle to detect tiny deflection of the transmission component during torque transmission, thereby estimating the torque. 
         [0006]    U.S. Pat. No. 6,644,135 discloses a torque sensor, entitled “Torque sensor for a bicycle bottom bracket assembly”, which comprises an axle supporting member for supporting the axle for rotation around a support axis, and four pressure sensors mounted on the axle supporting member. During rotation of the bottom bracket axle, the torque is directly transmitted to the axle supporting member, causing each pressure sensor to generate a corresponding pressure. The generated pressure is then converted into torque. 
         [0007]    The aforesaid conventional torque sensing devices commonly use a strain gage or pressure sensor in direct contact with the mounting location to convert the deflection rate of the structure of the mounting location into torque. However, the structural deflection state of the mounting location varies with the composition of the material of the structure of the mounting location and its manufacturing process, causing the strain gage unable to accurately measure the actual torque value. Furthermore, conventional torque sensing devices commonly have a complicated structure, or will be directly exposed to the outside open air after installation. Therefore, conventional torque sensing devices cannot take into account the installation requirements of simplicity and sense of beauty. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to prove a non-contact type torque and angle of rotation sensing device, which can accurately measure the torque and is easy to install. 
         [0009]    To achieve this and other objects of the present invention, a non-contact type torque and angle of rotation sensing device is provided for measuring a torque being applied to rotate a transmission member and the angle of rotation of the transmission member in a first axial direction. The non-contact type torque and angle of rotation sensing device comprises a magnetic member, a plurality of sensing members and a computing unit. The magnetic member is mounted on the transmission member and rotatable with the transmission member by the torque being applied to the transmission member. The magnetic member comprises a first center. Further, the magnetic member is deflectable relative to the transmission member in a predetermined direction in a nonparallel manner relative to the first axial direction to create an amount of deflection between the first center of the magnetic member and the first axial direction of the transmission member during rotation of the transmission member by the applied torque. The sensing members are adapted to commonly detect a magnetic field variation created and to output a respective electrical signal during rotation of the magnetic member. The electrical signals outputted by each two sensing members exhibit a phase difference. The amplitude of each electrical signal is directly proportional to the amount of deflection of the magnetic member. The computing unit is adapted to receive the electrical signals outputted by the sensing members and to compute the amplitudes of the electrical signals, thereby obtaining the value of the torque being applied to the transmission member and the angle of rotation of the transmission member. 
         [0010]    In other words, when the applied torque rotates the transmission member, the magnetic member is caused to produce an amount of deflection that is directly proportional to the applied torque, and at the same time, a variation of the magnetic field created by the magnetic member occurs subject to the angle of rotation of the magnetic member. Subject to eccentric rotation of the magnetic member, each sensing member senses the approach of a sine wave to induce an electrical signal (the transverse coordinate of the sine wave is the angle of rotation). Although the electrical signals of the sensing members change subject to the angle of rotation, the amplitude of the sine wave can be accurately estimated at any angle due to the phase difference relationship among the electrical signals provided by the sensing members, and therefore the applied torque can be further estimated. 
         [0011]    Further, the transmission member comprises a disc-like holder block. The disc-like holder block comprises an elongated guide portion. The magnetic member comprises a coupling groove accommodating the elongated guide portion. The coupling groove has a width greater than the length of the elongated guide portion. 
         [0012]    The non-contact type torque and angle of rotation sensing device further comprises a driving member mounted on the transmission member, comprising a push portion detachably abutted against the magnetic member. 
         [0013]    Further, the sensing members are arranged on one same plane and spaced from one another at a predetermined interval. 
         [0014]    Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is an exploded view of a non-contact type torque and angle of rotation sensing device in accordance with the present invention. 
           [0016]      FIG. 2  is a sectional assembly view of the non-contact type torque and angle of rotation sensing device in accordance with the present invention. 
           [0017]      FIG. 3  is a front view of the non-contact type torque and angle of rotation sensing device in accordance with the present invention before rotation of the magnetic member. 
           [0018]      FIG. 4  is a rear side view of  FIG. 3  where only the magnetic member and the transmission member are shown. 
           [0019]      FIG. 5  is similar to  FIG. 3 , illustrating the magnetic member deflected relative to the transmission member. 
           [0020]      FIG. 6  is a rear side view of  FIG. 5  where only the magnetic member and the transmission member are shown. 
           [0021]      FIGS. 7-10  are schematic drawings illustrating eccentric rotation of the magnetic member. 
           [0022]      FIG. 11  is a magnetic field variation curve chart obtained from the magnetic member of the non-contact type torque and angle of rotation sensing device in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring to  FIGS. 1-4 , a non-contact type torque and angle of rotation sensing device  10  in accordance with the present invention is shown mountable on a transmission member  20  that is rotatable by a torque. The transmission member  20  can be a transmission axle of a vehicle, sports equipment or any of a variety of other mechanical mechanisms. In this embodiment, the transmission member  20  is a bottom bracket axle of an electric bicycle that can be rotated around a support axis in a first axial direction  22  when a rider pedals the pedals of the electric bicycle. The transmission member  20  is inserted through a disc-like holder block  24  that has an elongated guide portion  26  protruded from its one side. 
         [0024]    The non-contact type torque and angle of rotation sensing device  10  comprises a magnetic member  30  and a plurality of sensing members  40 . The magnetic member  30  is ring magnet having a center hole  32  defining a first center  34 , an accommodation space  36  radially extended from the center hole  32 , and an elongated groove  38  located on one side thereof and facing toward the disc-like holder block  24 . The elongated groove  38  has a width greater than the length of the elongated guide portion  26 . Alternatively, the elongated groove  38  can be made in the form of a slot cut through the two opposite sides of the magnetic member  30 . 
         [0025]    The transmission member  20  is inserted through the center hole  32  of the magnetic member  30  and attached with its one side to the disc-like holder block  24  to have the elongated guide portion  26  be accommodated in the elongated groove  38 . Further, a driving member  50  is mounted on the transmission member  20  at the other side of the magnetic member  30 . 
         [0026]    The driving member  50  comprises a coupling ring  52  sleeved onto one end of the transmission member  20 , an extension portion  54  extended from the outer perimeter of the coupling ring  52  and suspending in the accommodation space  36 , and a push portion  56  located on the distal end of the extension portion  54  and stopped against the peripheral wall of the accommodation space  36 . Further, two flexible connection rods  58  are inserted through the center hole  32  and connected between the coupling ring  52  and the disc-like holder block  24 . 
         [0027]    Thus, the driving member  50  and the corresponding one end of the transmission member  20  are rotated by a torque produced during pedaling of the bicycle rider, the other end of the transmission member  20  can then be forced to rotate the chain wheel (not shown). As illustrated in  FIGS. 5 and 6 , the push portion  56  of the driving member  50  is stopped against the magnetic member  30  and the flexible connection rods  58  are connected between the driving member  50  and the disc-like holder block  24 , and therefore the magnetic member  30  and the disc-like holder block  24  are simultaneously rotated during rotation of the transmission member  20 . Under the effect of the torque, the driving member  50  and the disc-like holder block  24  twist the two flexible connection rods  58 , causing a deflection between the driving member  50  and the disc-like holder block  24 . At this time, the magnetic member  30  rotates with the transmission member  20  and deflects relative to the transmission member  20  in a direction along the elongated guide portion  26  in a nonparallel manner relative to the first axial direction  22 . According to this embodiment, the magnetic member  30  moves a direction perpendicular to the first axial direction  22 , resulting in an amount of deflection D between the first center  34  of the magnetic member  30  and the first axial direction  22  of the transmission member  20 . This amount of deflection D is directly proportional to the torque. 
         [0028]    The sensing members  40  can be Hall sensors or giant magnetoresistive (GMR) sensors. As shown in  FIG. 2  and  FIGS. 7-10 , two sensing members  40  are arranged adjacent to the magnetic member  30 . According to the present preferred embodiment, these two sensing members  40  are mounted on the inside wall of the bottom bracket axle of an electric bicycle on one same plane at a predetermined interval, for example, the these two sensing members  40  are kept apart at 30°, 45°, 60° or 90° angle. These two sensing members  40  are adapted to sense the magnetic field variation during rotation of the magnetic member  30  with the transmission member  20  and to output a respective electrical signal indicative of the sensed magnetic field variation to a computing unit  60 . The aforesaid magnetic field variation is directly proportional to the amount of deflection D, i.e., directly proportional to the torque being applied to the transmission member  20 . Upon receipt of the electrical signals from the sensing members  40 , the computing unit  60  converts the electrical signals into digitals by means of a formula built therein, and then composes the digitals thus obtained into a waveform curve. 
         [0029]    As stated above, when the magnetic member  30  is being forced by a torque to produce an amount of deflection D that is directly proportional to the applied torque, the magnetic member  30  is rotated with the transmission member  20  in an eccentric manner. Because the two sensing members  40  are immovable, the distance between the magnetic member  30  and each sensing member  40  will be alternatively increased and reduced subject to change of the angle of rotation during rotary motion of the magnetic member  30  on the first axial direction  22 . Thus, as shown in  FIG. 11 , the electrical signals provided by the two sensing members  40  subject to the variation of the magnetic field created by the magnetic member  30  can be converted into near-sinusoidal waveforms of curve A and curve B with a predetermined phase difference therebetween. If the magnetization of the magnetic member  30  is more symmetrical, the curves A;B shown in  FIG. 11  will be more closer to sine waves. The amplitude of the sine waves is directly proportional to the amount of deflection of the magnetic member  30 . The greater the amount of eccentricity is, the greater the amplitude will be. If the amount of deflection is zero, the amplitude will also be zero. 
         [0030]    The invention mainly uses two sensing members  40  to detect the variation of the magnetic field created by the magnetic member  30  and then to create two sine wave curves A;B that have a phase difference therebetween. Subject to the amplitude of these two curves A;B, the torque value is calculated. In one example of the present invention where the two sensing members  40  are kept apart at 90° angle, the torque value τ of the transmission member  20  can be calculated subject to the following Formula (I). In Formula (I), a represents electrical signal mean value that is the mean value obtained through one run (360°) of rotation of the transmission member  20  and can be obtained in the pre-calibration; the constant of proportionality k can be obtained by applying a predetermined torque to the transmission member and then measuring the sine wave amplitude. 
         [0000]      τ= kx=k √{square root over (( s   1   −a ) 2 +( s   2   −a ) 2 )}{square root over (( s   1   −a ) 2 +( s   2   −a ) 2 )}  (I)
       τ: Torque   k: Constant of proportionality   x: Amplitude   s 1 , s 2 : Electrical signal value of each sensing member   a: Electrical signal mean value       
 
         [0036]    Subject to the aforesaid technical features, the transmission member  20  and the magnetic member  30  are both to withstand the applied torque and the sensing members  40  do not touch the transmission member  20 , and therefore, the amount of deflection of the magnetic member  30  is directly related to the amount of the applied torque without causing any change subject to the material properties of the transmission member  20  or the other related components. Thus, the measurement result of the present invention is direct and more sensitive than prior art techniques. Further, by means of using at least two sensing members  40  to detect the magnetic field variation of the magnetic member  30  and to create two sine wave curves A;B that have a phase difference therebetween, and then putting the amplitude of each of the two sine wave curves A;B into the aforesaid trigonometric functions of the aforesaid Formula (I) to calculate the amount of deflection of the magnetic member in a complementary manner and to further estimate the actual torque value, the invention accurately estimates the applied torque. 
         [0037]    Further, the structural design and mounting arrangement of the magnetic member  30  and the sensing member  40  can be changed to fit different application requirements. Even for use in a narrow space inside a bottom bracket axle of a bicycle, or for application to fit the outer appearance of a product or to match with the positioning of a power source, the non-contact type torque and angle of rotation sensing device of the present invention can be conveniently adjusted and installed for high-performance sensing application. 
         [0038]    Further, when four sensing members are equiangularly arranged around the magnetic member, the measurement result will be more accurate. Further, except for the purpose of torque measurement, the invention can also measure the angle and speed of rotation of the transmission member. For this application, two sensing members are used to detect the magnetic field variation of the eccentric rotation of the transmission member and to provide a respective sine wave signal, and then to calculate the turning angle θ of the transmission member using the following Formula (II). 
         [0000]      θ=tan −1 ( s   1   −a )/( s   2   −a )  (II)
 
         [0039]    Thus, using the technical features of the aforesaid magnetic member and sensing members, the objects of the invention can thus be achieved. 
         [0040]    Further, it is to be understood that the components and applications disclosed above are simply examples for easy understanding of the spirit and scope of the invention but not intended to limit the scope of the invention. Various modifications and enhancements can be made thereunto without departing from the spirit and scope of the invention. For example, the invention can also be used in electric vehicles or electric tools. Accordingly, the invention is not to be limited except as by the appended claims.