Abstract:
A disassembled and assembled power module includes: a wheel shaft; a power module; a central shaft, arranged in the power module and passing through the wheel shaft; and an engaging unit, capable of fastening the central shaft to the wheel shaft. In an embodiment when the detachable power module is applied in an electric driven wheelchair, it enables the weight of the wheelchair to be reduced by simply detach and remove the detachable power from the wheelchair so that the electric driven wheelchair without the heavy power module can be carry and transport easily, and also the moving range of the electric driven wheelchair can be increased as its power module can be easily detached and replaced with another fully charged power module so that the range anxiety of the disabled person using the same or the assistant can be relieved.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application also claims priority to Taiwan Patent Application No. 101150541 filed in the Taiwan Patent Office on Dec. 27, 2012, the entire content of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The technical field relates to a detachable power module. 
       BACKGROUND 
       [0003]    Assisting tools for disabled people help them to move freely as normal people in some degree. The wheel chair is a representative among the assisting tools. 
         [0004]    Conventional wheel chairs are driven manually, which consumes physical energy. For a disabled person or an assistant thereof, sometimes the physical burden becomes unbearable. 
         [0005]    In view of the inconvenience of the conventional wheel chairs, electric driven wheel chairs are produced in the industry. Though the electric wheel chair reduces the physical energy consumption of the disabled person or the assistant thereof, the electric wheel chair still has criticized defects. Devices such as a transmission device, a motor, a control circuit and a battery need to be installed on an electric wheel chair, so the electric wheel chair has a considerable weight, making it difficult to carry or transport the electric wheel chair. As a result, the disabled people are unable to travel freely to areas where they want to arrive. Therefore, it is worth discussing how to reduce the weight of the wheel chair. 
       SUMMARY 
       [0006]    In an embodiment, the technical means of the disclosure is directed to a detachable power module, which includes: 
         [0007]    a wheel shaft; 
         [0008]    a power module; 
         [0009]    a central shaft, arranged in the power module and passing through the wheel shaft; and 
         [0010]    an engaging unit, capable of fastening the central shaft to the wheel shaft. 
         [0011]    In an embodiment, the technical means of the disclosure is directed to a detachable power module, which includes: 
         [0012]    a wheel shaft; 
         [0013]    a power module; 
         [0014]    a central shaft, arranged in the power module and passing through the wheel shaft; 
         [0015]    an engaging unit, capable of fastening the central shaft to the wheel shaft; and 
         [0016]    a releasing unit, arranged in the power module, the releasing unit being coupled to the engaging unit. 
         [0017]    In an embodiment, the technical means of the disclosure is directed to a detachable power module, which includes: 
         [0018]    a wheel shaft; 
         [0019]    a power module; 
         [0020]    a central shaft, arranged in the power module and passing through the wheel shaft; 
         [0021]    an engaging unit, capable of fastening the central shaft to the wheel shaft; 
         [0022]    a releasing unit, arranged in the power module, the releasing unit being coupled to the engaging unit; and 
         [0023]    a wheel shaft adapter, coupled to the wheel shaft. 
         [0024]    In an embodiment, the technical means of the disclosure is directed to a detachable power module, which includes: 
         [0025]    a power module; and 
         [0026]    a releasing unit, arranged in the power module. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0027]      FIG. 1  is a schematic partial exploded three-dimensional view of a detachable power module according to a first embodiment of the disclosure; 
           [0028]      FIG. 2  is a schematic three-dimensional view of a power module according to the disclosure; 
           [0029]      FIG. 3  is a schematic sectional view of a detachable power module according to a first embodiment of the disclosure; 
           [0030]      FIG. 4  is a schematic sectional view of a detachable power module according to a second embodiment of the disclosure; 
           [0031]      FIG. 5  is a schematic sectional view of a detachable power module according to a third embodiment of the disclosure; 
           [0032]      FIG. 6  is a schematic sectional view of a detachable power module according to a fourth embodiment of the disclosure; 
           [0033]      FIG. 7  is a schematic sectional view of a detachable power module according to a fifth embodiment of the disclosure; and 
           [0034]      FIG. 8  is a schematic sectional view of a detachable power module according to a sixth embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Below, implementation manners of the disclosure are illustrated through specific embodiments. Persons having ordinary knowledge in the art can easily understand the disclosure according to the content disclosed in the specification. 
         [0036]    Referring to  FIG. 1 ,  FIG. 2 , and  FIG. 3 , a detachable power module according to an embodiment of the disclosure is applied to a wheel chair or a wheel-type vehicle. In the following, a wheel chair is taken as an example for illustration. 
         [0037]    A diagram is showing separate rotation unit  11  and power module A in  FIG. 1 , and a schematic sectional view of the power module A in  FIG. 2  are shown in  FIG. 3 . When the power module A and the rotation unit  11  need to be combined, a central shaft  20  of the power module A is inserted into a wheel shaft  10 ; three engaging units  26  on the central shaft  20  are respectively snapped into three holes of the wheel shaft  10 ; and an input gear  23   a  of a deceleration unit on the central shaft  20  is engaged with a planetary gear of the rotation unit  11 . Six embodiments of the combined power module A and rotation unit  11  are described in detail with reference to  FIG. 3  to  FIG. 8 . 
         [0038]    The wheel chair has at least one rotation unit  11  and a power supply unit. 
         [0039]    Each rotation unit  11  has a hand wheel  110  and a road wheel  111 . The hand wheel  110  is arranged at a side of the road wheel  111 . A hub receiving space  112  exists between the hand wheel  110  and the road wheel  111 . 
         [0040]    If the wheel-type vehicle has at least one rotation unit, the rotation unit has the foregoing hub receiving space  112 . 
         [0041]    The power supply unit may be an energy storage unit, for example, a battery. 
         [0042]    The detachable power module has a central shaft  20 , a power module A, a pushing unit  25 , an engaging unit  26  and at least one central shaft push-out unit  29 . 
         [0043]    The power module A has a motor unit  21 , a control unit  22 , a deceleration unit  23 , an electrical contact unit  27  and at least one central shaft  20  engaging on the wheel shaft  10 . 
         [0044]    The wheel shaft  10  is arranged at the rotation unit  11  through a wheel shaft bearing  28 ; the wheel shaft  10  has at least one fixing hole  100 . In this embodiment, the number of the fixing holes  100  is more than one, and the fixing holes  100  are distributed in an equiangular manner. 
         [0045]    The wheel shaft  10  is arranged in the rotation unit  11  through the wheel shaft bearing  28 ; the wheel shaft bearing  28  enables the rotation unit  11  to rotate at a periphery of the wheel shaft  10 . A locking interface  101  exists between the wheel shaft  10  and the central shaft  20 . The locking interface  101  may be a spline, a quadrate groove or a key groove. The locking interface  101  prevents the central shaft  20  from rotating. The road wheel  111  rotates through a wheel shaft bearing  28 . When the road wheel  111  rotates, the wheel shaft  10  maintains a static state. In an example, the wheel shaft  10  is fixed on the wheel chair. If the disclosure is applied to a wheel-type vehicle, the wheel shaft  10  should be arranged at the rotation unit  11  of the wheel-type vehicle through a wheel shaft bearing  28 . 
         [0046]    The motor unit  21  is arranged in the hub receiving space  112 . In an example, the motor unit  21  is an axial flux motor, a radial flux motor or an external rotation motor. 
         [0047]    The control unit  22  is arranged in the hub receiving space  112 , and is electrically coupled to the motor unit  21 . 
         [0048]    The deceleration unit  23  is arranged in the hub receiving space  112 , and is coupled to the motor unit  21 . The deceleration unit  23  is further integrated with the road wheel  111 , so as to drive the road wheel  111 . In an example, the deceleration unit  23  is a planetary gear set, and the planetary gear is integrated with the rotation unit  11 . However, if the deceleration unit  23  is set selectively, the power output of the motor unit  21  is coupled to the rotation unit  11 . 
         [0049]    The electrical contact unit  27  is arranged in the central shaft  20 , and extends towards the wheel chair. The electrical contact unit  27  is electrically coupled to the control unit  22 . In an example, the electrical contact unit  27  is a plug or a socket. 
         [0050]    The central shaft  20  is arranged in the hub receiving space  112 . The central shaft  20  is fixed at a stator set of the motor unit  21  of the power module A, and passes through the wheel shaft  10 . The central shaft  20  has at least one receiving hole  200 . In an example, the number of the receiving holes  200  is more than one, and the receiving holes  200  are distributed in an equiangular manner. 
         [0051]    The pushing unit  25  is arranged in the central shaft  20 , and extends towards the wheel shaft  10 . A reset piece  250  is arranged on the pushing unit  25 . An end of the reset piece  250  pushes against the pushing unit  25 , and the pushing unit  25  penetrates through the reset piece  250 . Another end of the reset piece  250  pushes against a part of stator sets of motor unit  21 . In an example, the pushing unit  25  is a push rod, and the reset piece  250  is a spring. 
         [0052]    The engaging unit  26  has at least one reset piece  260 , at least one engaging piece  261  and at least one linkage piece  262 . The reset piece  260  and the engaging piece  261  are arranged in the receiving hole  200 . An end of the reset piece  260  pushes against the engaging piece  261 , and another end of the reset piece  261  pushes against the receiving hole  200 . The engaging piece  261  passes out of the receiving hole  200 , and is selectively engaged at the fixing hole  100 . An end of the linkage piece  262  is coupled to the pushing unit  25 , and another end of the linkage piece  262  is coupled to the engaging piece  261 . In an example, the linkage piece  262  is a steel wire, the engaging piece  261  is a cylinder, and the reset piece  260  is a spring. 
         [0053]    The central shaft push-out unit  29  is arranged between the central shaft  20  and the wheel shaft  10 , and is located at a side of the central shaft  20 . The central shaft push-out unit  29  is an elastic piece. An end of the central shaft push-out unit  29  pushes against the central shaft  20 , and another end of the central shaft push-out unit  29  pushes against the wheel shaft  10 . 
         [0054]    Referring to  FIG. 3 , the electrical contact unit  27  may be electrically coupled to a power supply unit and a control unit disposed on the wheel chair. In an example, the power supply unit is a battery such a lithium battery, a storage battery, a lead acid battery, a nickel-metal hydride battery, a lithium ion battery, a solar cell or a fuel cell. 
         [0055]    The power supply unit supplies power to the control unit  22  and the motor unit  21  through the electrical contact unit  27 . The control unit  22  controls the motor unit  21 . The power output of the motor unit  21  drives the deceleration unit  23 , and the deceleration unit  23  drives the rotation unit  11 , so as to drive the wheel chair having the disclosure installed. 
         [0056]    The hand wheel  110  is rotated, so as to output a signal to the control unit  22 . After receiving the signal, the control unit  22  further controls the power output of the motor unit  21 . Alternatively, a rotation actuating unit sends a signal to the control unit  22 , so as to further control the output of the motor unit  21 . 
         [0057]    When the wheel chair needs to be transported to some place and the weight thereof needs to be reduced, the pushing unit  25  is pushed and pressed, and the pushing unit  25  compresses the reset piece  250 . The pushing unit  25  pulls the linkage piece  262 , so that the engaging piece  261  is no longer engaged at the fixing hole  100 . The engaging piece  261  compresses the reset piece  260 . An electrical coupling state between the electrical contact unit  27  and the power supply unit is then released, so as to remove the power module A from the hub receiving space  112 . The power module A is the foregoing motor unit  21 , control unit  22 , a part of the deceleration unit  23  and a part of the electrical contact unit  27 . After the power module A is removed, the pushing unit  25  is released, so that the reset piece  260  restores the engaging piece  261  to an initial position, and the reset piece  250  restores the pushing unit  25  to an initial position. 
         [0058]    When the engaging state is released, the central shaft push-out unit  29  applies a pushing force to the central shaft  20 , so as to push a part of the central shaft  20  away from the wheel shaft  10 , and to push a part of the power module A out of the hub receiving space  112 . Hence, the power module A is easily removed from the hub receiving space  112 . 
         [0059]    If the power module A needs to be assembled on the hub receiving space  112 , the engaging piece  261  needs to be engaged at the fixing hole  100  again, so that the power module A is fixed at the hub receiving space  112 . 
         [0060]    When the power module A is assembled in the hub receiving space  112  again, the central shaft push-out unit  29  is squeezed by the central shaft  20  and the wheel shaft  10 . Therefore, when the engaging state is released again, the squeezed central shaft push-out unit  29  is capable of applying a pushing force to the central shaft  20  again. 
         [0061]    Referring to  FIG. 4 , a detachable power module according to a second embodiment of the disclosure is applied to a wheel chair. The wheel chair has at least one rotation unit  31 . Alternatively, the disclosure is applied to a wheel-type vehicle, the wheel-type vehicle has a frame, and the frame has at least one rotation unit. 
         [0062]    Each rotation unit  31  has a hand wheel  310  and a road wheel  311 . The hand wheel  310  is arranged at a side of the road wheel  311 . A hub receiving space  312  exists between the hand wheel  310  and the road wheel  311 . The hub receiving space  312  further has a receiving groove  313 . 
         [0063]    If the wheel-type vehicle has the rotation unit, the rotation unit has the foregoing hub receiving space  312 . 
         [0064]    The detachable power module has a central shaft  44 , a power module B, a pulling unit  45 , an engaging unit  46 , a releasing unit  47  and at least a wheel shaft  30 . 
         [0065]    The wheel shaft  30  is arranged in the rotation unit  31  through a wheel shaft bearing  28 , and the wheel shaft  30  is coupled to a wheel chair. 
         [0066]    In the case of the wheel-type vehicle, the wheel shaft  30  is arranged at a rotation unit of the wheel-type vehicle. 
         [0067]    The power module B has a motor unit  41 , a control unit  42 , a deceleration unit  43  and an electrical contact unit  49 . 
         [0068]    The motor unit  41  is arranged in the hub receiving space  312 . 
         [0069]    The control unit  42  is arranged in the hub receiving space  312 , and is electrically coupled to the motor unit  41 . 
         [0070]    The deceleration unit  43  is arranged in the hub receiving space  312 , and is coupled to the power output of the motor unit  41 . In an example, the deceleration unit  43  is a planetary gear set, and the planetary gear set is integrated with the rotation unit  41 . 
         [0071]    The electrical contact unit  49  is arranged in the central shaft  44 . The electrical contact unit  49  is electrically coupled to the control unit  42 . In an example, the electrical contact unit  49  is a plug or a socket. The electrical contact unit  49  is further electrically coupled to a power supply unit, and the power supply unit is capable of being arranged at a non-rotating part of the wheel chair or the power module B. 
         [0072]    The central shaft  44  is arranged in the hub receiving space  312 . The central shaft  44  is fixed at a stator set of the motor unit  41  of the power module B, and passes through the wheel shaft  30 . The central shaft  44  has a receiving hole  440  at a position corresponding to the fixing hole  300 . The number of the receiving holes  440  is three, and the receiving holes  440  are distributed in an equiangular manner. 
         [0073]    The pulling unit  45  is arranged in the central shaft  44  and extends towards the wheel shaft  30 . The pulling unit  45  has a reset piece  450 . An end of the reset piece  450  pushes against the pulling unit  45 . The pulling unit  45  passes through the reset piece  450 . Another end of the reset piece  450  pushes against the central shaft  44 . In an example, the pulling unit  45  is a pulling rod, and the reset piece  450  is a spring. 
         [0074]    The engaging unit  46  has at least one reset piece  460 , at least one engaging piece  461  and at least one linkage piece  462 . The reset piece  460  and the engaging piece  461  are arranged in the receiving hole  440 . The engaging piece  461  passes through the reset piece  460 , passes out of the receiving hole  440 , and is selectively engaged at the fixing hole  300 . An end of the linkage piece  462  is coupled to the pulling unit  45 , and another end of the linkage piece  462  is coupled to the engaging piece  461 . In an example, the linkage piece  462  is a steel wire, the engaging piece  461  is a cylinder, and the reset piece  460  is a spring. 
         [0075]    The releasing unit  47  has a reset piece  470 , a pushing piece  471  and a connection piece  472 . The reset piece  470  and the pushing piece  471  are arranged in the receiving groove  313 . An end of the connection piece  472  is coupled to the pushing piece  471 , and another end of the connection piece  472  is coupled to the pulling unit  45 . In an example, the reset piece  470  is a spring, the pushing piece  471  is a button, and the connection piece  472  is a steel wire. 
         [0076]    If the power module B needs to be removed from the hub receiving space  312 , the pushing piece  471  is pressed. The pushing piece  471  compresses the reset piece  470 . The connection piece  472  is pulled by the pushing piece  471 . The connection piece  472  further pulls the pulling unit  45 , and the pulling unit  45  compresses the reset piece  450 . The pulling unit  45  pulls the linkage piece  462 , so that the engaging piece  461  is no longer engaged at the fixing hole  300 . The engaging piece  461  compresses the reset piece  460 , so that the power module B is free from a fixed state, and the power module B can be removed from the hub receiving space  312 . 
         [0077]    After the power module B is removed from the rotation unit  31 , the pushing piece  471  is no longer pressed. The reset piece  470  restores the pushing piece  471  to an initial position, the reset piece  460  restores the engaging piece  461  to an initial position, and the reset piece  450  restores the pulling unit  45  to an initial position. 
         [0078]    If the power module B needs to be assembled on the rotation unit  31  again, as long as the engaging piece  461  is engaged at the fixing hole  300 , the power module B is fixed at the rotation unit  31 . 
         [0079]    Referring to  FIG. 5 ,  FIG. 5  shows a third embodiment of the disclosure. This embodiment is derived from the foregoing second embodiment. Therefore, the actions for assembling and disassembling the power module are the same as those in the second embodiment. Moreover, most components in this embodiment are similar to those in the foregoing embodiment, so in this embodiment, the part being the same as the foregoing embodiment is not described herein again. 
         [0080]    The wheel shaft  30 , the rotation unit  31 , the central shaft  44 , the power module B, the pulling unit  45 , the engaging unit  46  and the releasing unit  47  are the same as those in the second embodiment. 
         [0081]    If the wheel chair is a conventional one without any power system and none of the wheel shafts in the foregoing two embodiments is applicable to the wheel chair, this embodiment further provides a wheel shaft adapter  32 . An end of the wheel shaft adapter  32  is coupled to the wheel chair, and another end of the shaft joint  32  is coupled to the wheel shaft  30 . The coupling can be implemented by means of a fixing piece. 
         [0082]    In addition, if none of the wheel shafts in the foregoing two embodiments is applicable to a frame of a wheel-type vehicle, an end of the wheel shaft adapter  32  is coupled to the frame, and another end of the wheel shaft adapter  32  is coupled to the wheel shaft  30 . 
         [0083]    This embodiment further comprises a power supply unit  48 . The power supply unit  48  is arranged in the hub receiving space  312 . The power supply unit  48  is electrically coupled to the control unit  42 . In an example, the power supply unit  48  is a battery such as a lithium battery, a storage battery, a lead acid battery, a nickel-metal hydride battery, a lithium ion battery, a solar cell or a fuel cell. 
         [0084]    Referring to  FIG. 5 , the power supply unit  48  supplies power to the control unit  42 , so as to drive the motor unit  41 , and further drive the deceleration unit  43 , thereby driving the rotation unit  31 . 
         [0085]    Referring to  FIG. 6 ,  FIG. 6  shows a fourth embodiment of the disclosure, being applied to a wheel chair. The wheel chair has at least one rotation unit  51 . Alternatively, the disclosure is applied to a wheel-type vehicle, the wheel-type vehicle has a frame, and the frame has at least one rotation unit. 
         [0086]    Each rotation unit  51  has a hand wheel  510  and a road wheel  511 . The hand wheel  510  is arranged at a side of the road wheel  511 . The hand wheel  510  has at least one engaging hole  513 . In this embodiment, the number of the engaging holes  513  is more than one, and the engaging holes  513  are arranged in an equiangular manner. A hub receiving space  512  exists between the hand wheel  510  and the road wheel  511 . The hub receiving space  512  has receiving holes  514  at positions corresponding to the engaging holes  513 . 
         [0087]    If the rotation unit is arranged at the wheel-type vehicle, the rotation unit has the hub receiving space  512 . 
         [0088]    The detachable power module has a power module C, a releasing unit  63  and at least one shaft  50 . 
         [0089]    The power module C has a motor unit  61 , a control unit  62  and a power supply unit  64 . 
         [0090]    The motor unit  61  is arranged in the hub receiving space  512 . 
         [0091]    The control unit  62  is arranged in the hub receiving space  512 , and is electrically coupled to the motor unit  61 . 
         [0092]    The power supply unit  64  is arranged in the hub receiving space  512 , and is electrically coupled to the control unit  62 . In an example, the power supply unit  64  is a battery such as a lithium battery, a storage battery, a lead acid battery, a nickel-metal hydride battery, a lithium ion battery, a solar cell or a fuel cell. 
         [0093]    If no power supply unit is configured, an electrical contact unit may be arranged at the central shaft as described in the foregoing embodiment. The central shaft passes through the shaft, and the electrical contact unit is electrically coupled to the control unit  62 . 
         [0094]    The releasing unit  63  has a knob  630 , at least one linkage piece  631 , at least one reset piece  632  and at least one engaging piece  633 . The knob  630  is arranged in the power module C. The reset piece  632  and the engaging piece  633  are arranged in the receiving hole  514 . An end of the reset piece  632  pushes against the engaging piece  633 , and another end of the reset piece  632  pushes against the receiving hole  514 . An end of the engaging piece  633  passes out of the receiving hole  514 , and is selectively engaged at the engaging hole  513 . An end of the linkage piece  631  is coupled to the knob  630 , and another end of the linkage piece  631  is coupled to the engaging piece  633 . In an example, the linkage piece  631  is a steel wire, the reset piece  632  is a spring, and the engaging piece  633  is a cylinder. 
         [0095]    As shown in  FIG. 6 , the power supply unit  64  supplies power to the control unit  62 . The control unit  62  drives the motor unit  61 , and the motor unit  61  drives the rotation unit  51 , so as to drive the wheel chair. 
         [0096]    When the power module C needs to be removed from the rotation unit  51 , the knob  630  is rotated. The knob  630  is linked with the linkage piece  631 , and the linkage piece  631  further pulls the engaging piece  633 , so that the engaging piece  633  is no longer engaged at the engaging hole  513 . The engaging piece  633  compresses the reset piece  632 , so that the power module C can be removed from the rotation unit  31 . After the power module C is removed, the knob  630  is released, and the reset piece  632  restores the engaging piece  633  to an initial position. 
         [0097]    If the power module C needs to be assembled on the rotation unit  51  again, as long as the engaging piece  633  is engaged at the engaging hole  513  again, the detachable power module C of the disclosure can be fixed at the rotation unit  51 . 
         [0098]    Referring to  FIG. 7 ,  FIG. 7  shows a fifth embodiment of the disclosure. In this embodiment, the shaft  70 , the rotation unit  71 , the power module  72  and the central shaft  73  are set in the same manner as the foregoing embodiments. 
         [0099]    In this embodiment, the central shaft  73  further has a locking interface  730  and at least one clamping groove  731 . The locking interface  730  is, for example, at least a surface, a spline, a quadrate groove or a key groove. The clamping groove  731  is a V-shaped groove. 
         [0100]    The at least one receiving groove  700  is arranged at the shaft  70  or in the hub receiving space  710 . The receiving groove  700  is located at a position corresponding to the clamping groove  731 . 
         [0101]    An engaging unit  74  is arranged between the central shaft  73  and the shaft  70 . The engaging unit  74  has at least one reset piece  740  and at least one engaging piece  741 . The reset piece  740  and the engaging piece  741  are arranged in the receiving groove  700 . An end of the reset piece  740  pushes against the receiving groove  700 , and another end of the reset piece  740  pushes against the engaging piece  741 . The engaging piece  741  is selectively engaged at the clamping groove  731 . The reset piece  740  is an elastic component, and the engaging piece  741  is a ball. 
         [0102]    Further referring to  FIG. 7 , if the power module  72  needs to be disassembled from the rotation unit  71 , the power module  72  can be extracted directly. When power module  72  is extracted, the engaging piece  741  is under the effect of an external force, rolls along the clamping groove  730 , and retracts into the receiving groove  700 . The reset piece  740  is compressed, and an engaging state between the engaging piece  741  and the clamping groove  731  is released, so that the power module  72  can be detached from the rotation unit  71 . 
         [0103]    After the power module  72  is detached from the rotation unit  71 , the engaging piece  741  is pushed out of the receiving groove  700  by the reset piece  740 . 
         [0104]    When the power module  72  needs to be assembled on the rotation unit  71  again, the power module  72  is directly pushed into the rotation unit  71 . Being positioned by the locking interface  730 , the engaging piece  741  corresponds to the position of the clamping groove  731 . When the engaging piece  741  is pushed to the position of the clamping groove  731 , the engaging piece  741  rolls along the clamping groove  731 . The reset piece  740  pushes the engaging piece  741  into the clamping groove  731 , so that the engaging state between the engaging piece  741  and the clamping groove  731  is restored, thereby fixing the power module  72  at the rotation unit  71 . 
         [0105]    Referring to  FIG. 8 ,  FIG. 8  shows a sixth embodiment of the disclosure. All components in this embodiment are the same as those in the foregoing embodiments except that the position of the engaging unit is changed. Therefore, the following description is focused on the engaging unit, and other components are not described again. 
         [0106]    A shaft  90  is fixed in a frame  91 . An engaging unit  80  is located between the shaft  90  and a central shaft  93 . The frame  91  is a component of a wheel chair or a component of a wheel-type vehicle. 
         [0107]    The central shaft  93  has at least one first receiving space  930 . The first receiving space  930  is a slot or a via hole. The number of the first receiving spaces  930  is more than one, and the first receiving spaces  930  are distributed in an equiangular manner. The first receiving space  930  is located at an end of the central shaft  93 , that is, the first receiving space  930  is adjacent to the frame  91 . 
         [0108]    The shaft  90  has at least one second receiving space  900 . The second receiving space  900  is a slot or a via hole. If the number of the second receiving spaces  900  is more than one, the second receiving spaces  900  are distributed in an equiangular manner. The second receiving space  900  is opposite the first receiving space  930 . 
         [0109]    The engaging unit  80  has at least one engaging piece  800 , at least one reset piece  801  and at least one optional connection piece  802 . 
         [0110]    The reset piece  801  is, for example, an elastic component. The reset piece  801  is arranged in the second receiving space  900 . An end of the reset piece  801  pushes against the second receiving space  900 , and another end of the reset piece  801  pushes against the engaging piece  800 , so that the engaging piece  800  is selectively engaged at the first receiving space  930 . Based on the above embodiments, the engaging direction in this embodiment is opposite or different from that in the foregoing embodiments. 
         [0111]    The connection piece  802  is, for example, a steel wire. An end of the connection piece  802  passes through the reset piece  801 , and is coupled to the engaging piece  800 . Another end of the connection piece  802  is coupled to a pulling unit that is not shown in the figure. The pulling unit is, for example, a pushing unit, a pulling unit or a releasing unit described in the foregoing embodiments, or a pulling rod having a resilience force. The pulling unit is arranged at the wheel chair or the frame. 
         [0112]    As described in the previous embodiment, if no connection piece  802  is set in this embodiment, the first receiving space  930  is a V-shaped slot. When the power module  94  is pulled away from the rotation unit  92 , the effect of the external force forces the engaging piece  800  to be released from an engaging state with the first receiving space  930 , and the engaging piece  800  compresses the reset piece  801 , so that the power module  94  can be detached from the wheel chair or the frame. 
         [0113]    If the power module  94  needs to be combined with the wheel chair again, the power module  94  can be pushed into the rotation unit  92  or the frame of the wheel chair, so that the engaging piece  800  is engaged at the first receiving space  930 . 
         [0114]    If the connection piece  802  is set in this embodiment, when the pulling unit is pulled, the connection piece  802  enables the engaging piece  800  to be released from the engaging state with the first receiving space  930 , so that the power module  94  can be detached from the wheel chair or the frame. 
         [0115]    Similarly, if the power module  94  needs to be combined with the rotation unit  92  or the frame again, the pulling unit is pulled again, and the power module  94  is pushed into the rotation unit  92  or the frame of the wheel chair. Subsequently, the pulling unit is released, so that the engaging piece  800  is engaged at the first receiving space  930 . 
         [0116]    To sum up, the embodiments of the disclosure are used for illustrating that the power module can be easily assembled to or disassembled from the rotation unit, thereby reducing the weight of the electric wheel chair or frame, so that the electric wheel chair or frame with the reduced weight can be transported to any place. 
         [0117]    Further, if the disclosure is applied to a conventional wheel chair, the disclosure can be combined with the conventional wheel chair through a shaft joint without changing the structure of the original wheel chair. 
         [0118]    Based on the above, the shaft joint enables the disclosure to be combined with a frame. 
         [0119]    The specific embodiments described above are merely used to illustrate the disclosure exemplarily, and are not intended to limit the application scope of the disclosure. Any equivalent alteration and modification made using the content disclosed herein and without departing from the spirit and technical scope of the disclosure shall fall within the scope of the appended claims.