Abstract:
A vehicle step apparatus for a vehicle and a motor assembly thereof are provided. The vehicle step apparatus includes: a extending and retracting device including a mounting support, a vehicle step support and an arm assembly, the arm assembly being connected between the mounting support and the vehicle step support and configured to drive the vehicle step support to move between an extending position and a retraction position; a vehicle step disposed at the vehicle step support; a motor disposed at the mounting support and including a motor shaft coupled with the arm assembly; and an elastic element configured to take an elastic deformation to store energy when the motor drives the vehicle step support to move towards the extension position, and to release energy to assist the motor in driving the extending and retracting device when the motor drives the vehicle step support towards the retraction position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and benefits of Chinese Patent Application Serial No. 201510468824.6 and No. 201520576675.0, both filed with the State Intellectual Property Office of P. R. China on Aug. 4, 2015, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    Embodiments of the present invention generally relate to a vehicle technology field, and more particularly, to a vehicle step apparatus and a motor assembly thereof. 
       BACKGROUND 
       [0003]    A vehicle step apparatus mounted on a chassis of a vehicle is used to assist passengers to get on or off the vehicle. An extending and retracting device of a vehicle step apparatus is driven by a motor so as to drive the step to move between an extending position and a retracting position. 
         [0004]    Since a load of the vehicle step apparatus in the process of the extending and retracting device extending towards the extending position (i.e., an extending process) is different from that of the vehicle step apparatus in the process of the extending and retracting device retracting towards the retracting position (i.e., a retracting process), a current of the motor in an extending process is different from that of the motor in a retracting process, so that a working life of the motor is affected. 
       SUMMARY 
       [0005]    Embodiments of the present invention seek to solve at least one of the problems existing in the related art to at least some extent. Accordingly, an object of the present invention is to provide a motor assembly of a vehicle step apparatus, which has a long working life. 
         [0006]    Another object of the present invention is to provide a vehicle step apparatus, which includes the above motor assembly. 
         [0007]    Embodiments of a first aspect of the present invention provide a vehicle step apparatus, including: an extending and retracting device comprising a mounting bracket, a step bracket, and an arm assembly coupled between the mounting bracket and the step bracket and configured to drive the step bracket to move between an extending position and a retracting position; a step mounted on the step bracket; a motor mounted on the mounting bracket, and having a casing and a motor shaft coupled with the arm assembly to drive the arm assembly; and an elastic member configured to be elastically deformed so as to store energy when the motor drives the extending and retracting device to move towards the extending position, and to release energy so as to assist the motor to drive the extending and retracting device when the motor drives the extending and retracting device to move towards the retracting position. 
         [0008]    With the vehicle step apparatus according to embodiments of the first aspect of the present invention, the load of the motor in the processes of driving the step to retract is balanced with that of the motor in the processes of driving the step to extend. 
         [0009]    Embodiments of a second aspect of the present invention provide a motor assembly of a vehicle step apparatus, including: a motor comprising a motor shaft and a casing; a cover disposed on the casing to define a cavity; a connection plate disposed within the cavity and driven by the motor shaft to rotate; and an elastic element defining a first end connected to the cover and a second end connected to the connection plate, and configured to be elastically deformed to store energy when the motor shaft rotates in a first direction and to release energy to assist the motor shaft to rotate in a second direction opposite to the first direction when the motor shaft rotates in the second direction. 
         [0010]    Additional aspects and advantages of embodiments of present invention will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    These and other aspects and advantages of embodiments of the present invention will become apparent and more readily appreciated from the following descriptions made with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  is an exploded view of a vehicle step apparatus according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a schematic of an extending and retracting device of a vehicle step apparatus according to an embodiment of the present invention, wherein the extending and retracting device is a four-link mechanism; 
           [0014]      FIG. 3  is a schematic of an extending and retracting device of a vehicle step apparatus according to an embodiment of the present invention, wherein the extending and retracting device is a five-link mechanism; 
           [0015]      FIG. 4  is a schematic of an extending and retracting device of a vehicle step apparatus according to an embodiment of the present invention, wherein the extending and retracting device is a six-link mechanism; 
           [0016]      FIG. 5  is a schematic view of a vehicle step apparatus according to another embodiment of the present invention, wherein an extending and retracting device is in an extending position; 
           [0017]      FIG. 6  is a partial enlarged view of a scroll spring and the extending and retracting device in  FIG. 5 ; 
           [0018]      FIG. 7  is a schematic view of a vehicle step apparatus according to another embodiment of the present invention, wherein an extending and retracting device is in a retracting position; and 
           [0019]      FIG. 8  is an exploded view of a motor assembly of a vehicle step apparatus according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Reference will be made in detail to embodiments of the present invention. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present invention. The embodiments shall not be construed to limit the present invention. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. 
         [0021]    In the specification, unless specified or limited otherwise, relative terms such as “central”, “longitudinal”, “lateral”, “front”, “rear”, “right”, “left”, “inner”, “outer”, “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “top”, “bottom” as well as derivative thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the present invention be constructed or operated in a particular orientation. 
         [0022]    Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. In addition, terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance. 
         [0023]    In the description of the present invention, a structure in which a first feature is “on” a second feature may include an embodiment in which the first feature directly contacts the second feature, and may also include an embodiment in which an additional feature is formed between the first feature and the second feature so that the first feature does not directly contact the second feature, unless specified otherwise. Furthermore, a first feature “on,” “above,” or “on top of” a second feature may include an embodiment in which the first feature is right “on,” “above,” or “on top of” the second feature, and may also include an embodiment in which the first feature is not right “on,” “above,” or “on top of” the second feature, or just means that the first feature is at a height higher than that of the second feature. While a first feature “beneath,” “below,” or “on bottom of” a second feature may include an embodiment in which the first feature is right “beneath,” “below,” or “on bottom of” the second feature, and may also include an embodiment in which the first feature is not right “beneath,” “below,” or “on bottom of” the second feature, or just means that the first feature is at a height lower than that of the second feature. 
         [0024]    A vehicle step apparatus  100  according to embodiments of the present invention will be described in the following with reference to drawings. The vehicle step apparatus  100  according to embodiments of the present invention includes an extending and retracting device  10 , a step  20 , an electric motor  30  and an elastic element  40 . 
         [0025]    The extending and retracting device  10  includes a mounting bracket  11 , a step bracket  12  and an arm assembly  13 . The arm assembly  13  is coupled between the mounting bracket  11  and the step bracket  12  and configured to drive the step bracket  12  to move between an extending position and a retracting position. 
         [0026]    The step  20  is mounted to the step bracket  12 . The motor  30  is mounted on the mounting bracket  11  and includes a motor shaft  32  and a casing  31 . The motor shaft  32  is coupled with the arm assembly  13  so as to drive the arm assembly  13 . The elastic element  40  is configured to be elastically deformed so as to store energy when the motor  30  drives the extending and retracting device  10  to move towards the extending position, and to release energy to assist the motor  30  to drive the extending and retracting device  10  when the motor  30  drives the extending and retracting device  10  to move towards the retracting position. 
         [0027]    With the vehicle step apparatus according to embodiments of the present invention, the motor  30  drives the arm assembly  13  of the extending and retracting device  10  to move, so as to drive the step bracket  12  coupled with the arm assembly  13  to move, and finally a driving force of the motor  30  is transmitted to the step  20  coupled with the step bracket  12  so as to drive the step  20  to extend and retract. 
         [0028]    It may be understood that, the load of the motor  30  in the process of driving the step  20  to retract is bigger than that of the motor  30  in the process of driving the step  101  to extend so that the working current of the motor  30  in the process of driving the step  20  to retract is larger than that of the motor  30  in the process of driving the step  20  to extend. 
         [0029]    With the vehicle step apparatus  100  according to embodiments of the present invention, when the step  20  is extended, the motor shaft  32  drives the elastic element  40  to move and makes the elastic element  40  be elastically deformed so as to store energy. 
         [0030]    When the step  20  is retracted, the elastic element  40  releases energy to assist the motor  30  in driving the extending and retracting device  10 , so that the load and the working current of the motor  30  are decreased in the process of driving the step  20  to retract. Thus, the working current of the motor  30  in the processes of driving the step  20  to retract is generally consistent with that of the motor  30  in the processes of driving the step  20  to extend, the motor  30  is protected effectively and the working life of the more  30  is prolonged. 
         [0031]    The vehicle step apparatus  100  according to embodiments of the present invention will be described in the following with reference to  FIGS. 1 to 6 . 
         [0032]      FIG. 1  is an exploded view of the vehicle step apparatus  100  according to an embodiment of the present invention. As shown in  FIG. 1 , the vehicle step apparatus  100  includes the extending and retracting device  10 , the vehicle step  20 , the motor  30  and the elastic element  40 . 
         [0033]    The extending and retracting device  10  includes the mounting bracket  11 , the step bracket  12  and the arm assembly  13 . The arm assembly  13  is coupled between the mounting bracket  11  and the step bracket  12 , and configured to drive the step bracket  12  to move between the extending position and the retracting position. 
         [0034]    The step  20  is disposed on the step bracket  12 . The motor  30  is disposed on the mounting bracket  11  and includes the motor shaft  32  and the casing  31 . The motor shaft  32  is coupled with the arm assembly  13  so as to drive the arm assembly  13 . The elastic element  40  is configured to be elastically deformed to store energy when the motor  30  drives the step bracket  12  to move towards the extending position, and to release energy to assist the motor  30  in driving the extending and retracting device  10  when the motor  30  drives the step bracket  12  towards the retracting position. 
         [0035]    When the vehicle step apparatus  100  is used, the mounting bracket  11  is fixed to a vehicle, for example the mounting bracket  11  is fixed to a chassis of the vehicle. At least one arm of the arm assembly  13  is pivotally coupled with the mounting bracket  11 , and the motor shaft  32  is coupled with an arm of the arm assembly  13  so as to drive the arm assembly  13  to move, further to drive the step bracket  12  coupled with the arm assembly  13  to move. Thus, the motor  30  rotates clockwise to drive the extending and retracting device  10  to extend and rotates counterclockwise to drive the extending and retracting device  10  to retract. 
         [0036]    In an embodiment of the present invention, the elastic element  40  is a scroll spring, and the scroll spring defines a first end and a second end. The first end  41  of the scroll spring is fixed, and the second end  42  of the scroll spring is driven by the motor shaft  32  to twist. 
         [0037]    Specifically, as shown in  FIG. 1 , an end of the outermost ring of the scroll spring is bent outwards to form the first end  41 , and an end of an innermost ring of the scroll spring is bent inwards to form the second end  42 . The first end  41  includes the end of the outermost ring of the scroll spring and a portion of the outermost ring coupled with the end of the outermost ring, and correspondingly, the second end  42  includes the end of the innermost ring of the scroll spring and a portion of the innermost ring coupled with the end of the innermost ring. 
         [0038]    When the extending and retracting device  10  (i.e., the step  20 ) is extended, the first end  41  of the scroll spring is fixed, and the second end  42  of the scroll spring rotates along with the motor shaft  32  and is twisted tightly to store energy. 
         [0039]    When the extending and retracting device  10  (i.e., the step  20 ) is retracted, the first end  41  of the scroll spring is fixed, and the second end  42  of the scroll spring rotates along with the motor shaft  32  and releases energy so as to assist the motor  30  to drive the extending and retracting device  10  to retract. In addition, the elastic element  40  is configured as the scroll spring, and the scroll spring has a simple and compact structure and is easy to be mounted. 
         [0040]    However, the present invention is not limited to this, and the elastic element  40  may be a spring leaf, a belleyille spring or other units or parts easy to be deformed elastically. Those skilled in the related art may choose a scroll spring in a suitable size according to a difference between the load of the motor  30  in the process of driving the step  20  to extend and that of the motor  30  in the process of driving the step  20  to extend, so that the scroll spring can better balance the load of the motor  30  in the process of driving the step  20  to extend with that of the motor  30  in the process of driving the step  20  to extend. 
         [0041]    In some embodiments, as shown in  FIG. 1 , the vehicle step apparatus  100  further includes a first connection plate  50  and a first cover  60 . A first recess is formed in a casing  31  of the motor  30 , and the first recess is covered by the first cover  60  to define a cavity. The first connection plate  50  is mounted in the cavity and driven by the motor shaft  32  to rotate. The scroll spring is mounted within the cavity, the first end  41  of the scroll spring is fixed in the first cover  60  and the second end  42  of the scroll spring is coupled with the first connection plate  50 . 
         [0042]    Furthermore, the first cover  60  is detachably fastened to the casing  31 . A limitation notch  61  is formed in the first cover  60 , a limiting column  111  is formed on the mounting bracket  11 , and the limiting column  111  is fitted within the limiting notch  61  to mount the first cover  60  on the mounting bracket  11 , and the first end  41  of the scroll spring is fitted over the limiting column  111 . 
         [0043]    With reference to  FIG. 1 , the first recess is formed in a side of the casing  31  facing the mounting bracket  11 , and the first cover  60  includes a cover body and a flange coupled with an edge of the cover body. A stepped positioning surface is formed on an inner wall of the flange, and the first cover  60  covers the first recess via the stepped positioning surface. The limiting notch  61  extends inwards from an edge of the first cover  60 . 
         [0044]    The limiting column  111  is formed on a side of the mounting bracket  11  opposing to the motor  30 , and a catch groove fitted with the limitation notch  61  is formed in the limitation column  111 . The first cover  60  bears against the casing  31  via bottom surfaces of the catch grooves of two limitation columns  111  so as to limit the first cover  60  in the axial direction. Side surfaces of the catch grooves of two limitation column  111  limit the first cover  60  in both the radial direction and the circumferential direction. The second end  42  of the scroll spring is passed through the limiting notch  61  and fitted over the limiting column  111 . 
         [0045]    Therefore, the first cover  60 , the casing  31  and the mounting bracket  11  are fixed with one another so as to provide a suitable position for fixing the second end  42  of the scroll spring. 
         [0046]    Specially, the first connection plate  50  is configured as a substantially circular plate. The first connection plate  50  is disposed within the cavity, and the first connection plate  50  defines a first surface opposing to the first recess and a second surface opposing to the first cover  60 . The first connection plate  50  is coupled with the motor shaft  32  directly or indirectly, so that the first connection plate  50  can rotate under the drive of the motor shaft  32 . The scroll spring is fitted over the first connection plate  50 , and the second end  42  of the scroll spring is connected to the first connection plate  50  and rotates along with the first connection plate  50  in a same direction. 
         [0047]    Therefore, the scroll spring can be integrated in the motor  30  so as to decrease transmission loss and make the structure of the vehicle step apparatus  100  more compactly. 
         [0048]    It may be understood by those skilled in the related that, the first connection plate  50 , the first cover  60  and the first recess may have a circular shape or an oval shape. A number of each of the limiting notch  61  and the limiting column  111  is not limited to two, and when there are more than two limiting notches  61 , the limiting notches  61  are provided and evenly spaced apart from each other along a circumferential direction of the first cover  60 . 
         [0049]    In some embodiments, a first catch groove  51  is formed in an outer circumferential surface of the first connection plate  50 , and the second end  42  of the scroll spring is inserted into and fitted within the first catch groove  51 . The motor shaft  32  is coupled with the arm assembly  13  via a first connection shaft  80 . The first connection shaft  80  is coupled with the motor shaft  32  via spline coupling, and the first connection plate  50  is fitted over the first connection shaft  80  and coupled with the first connection shaft  80  via spline coupling. 
         [0050]    Specifically, as shown in  FIG. 1 , the first catch groove  51  is extended inwards from the outer edge of the first connection plate  50 , and the first catch groove  51  extends along the radial direction of the first connecting plate  50 . A center of the first connection plate  50  has a first spline hole, and a center of the motor shaft  32  has a second spline hole. The first connection shaft  80  has an external spline, and the first connection shaft  80  is coupled with one arm of the arm assembly  13  and passed through the mounting bracket  11 . 
         [0051]    Therefore, the motor shaft  32  drives the first connection shaft  80  and the first connection plate  50  to rotate, and the second end  42  of the scroll spring fixed on the first connection plate  50  rotates along with the first connection plate  50 , so that the scroll spring is gradually rolled up tightly, thus resulting in a simple and compact structure. In addition, the first connection shaft  80  is coupled with the motor shaft  32  and the first connecting plate  50  via spline connection so as to ensure driving force transmission and make installation and disassembly to be easy. 
         [0052]    In some embodiments, a mounting hole  311  is formed in the casing  31 , and the limitation column  111  is passed through the mounting hole  311 . A threaded hole  111   a  is formed in the limitation column  111 , and the motor  30  is mounted on the mounting bracket  11  via a bolt  15  fitted within the threaded hole  111   a.    
         [0053]    Specifically, the limitation column  111  is passed through the limitation notch  61  and bears against the casing  31 . The mounting hole  311  of the casing  31  is opposite to the threaded hole  111   a  of the limitation column  111 , and the bolt  15  is passed through the mounting hole  311  and is fitted within the threaded hole  111   a  so as to mount the casing  31  to the mounting bracket  11 . Thus, the motor  30 , the first connecting plate  50  and the mounting bracket  11  are mounted together via the bolt  15 , and it is easy to change and maintain the scroll spring. 
         [0054]    However, the present invention is not limited to this. The casing  31 , the first connection plate  50  and the mounting bracket  11  may be fixed with one another by welding or other means. 
         [0055]    In some embodiments of the present invention, the extending and retracting device  10  may be one of a four-link mechanism  10   a,  a five-link mechanism  10   b  and a six-link mechanism  10   c.    
         [0056]    In an embodiment shown in  FIG. 2 , the extending and retracting device  10  is a four-link mechanism  10   a,  and the extending and retracting device  10  comprises the mounting bracket  11 , the step bracket  12  and the arm assembly  13 . The arm assembly  13  is coupled between the mounting bracket  11  and the step bracket  12 . 
         [0057]    The arm assembly  13  comprises a first arm  131  and a second arm  132 . An upper end of the first arm  131  is pivotally coupled with the mounting bracket  11  via a first connection pin  136 , and a lower end of the first arm  131  is pivotally coupled with the step bracket  12  via a second connection pin  137 . An upper end of the second arm  132  is pivotally coupled with the mounting bracket  11  via a third connection pin  138 , and a lower end of the second arm  132  is pivotally coupled with the step bracket  12  via a fourth connection pin  139 . 
         [0058]    In an embodiment shown in  FIG. 3 , the extending and retracting device  10  is a five-link mechanism  10   b,  and the extending and retracting device  10  comprises the mounting bracket  11 , the step bracket  12  and the arm assembly  13 . The arm assembly  13  is coupled between the mounting bracket  11  and the step bracket  12 . The arm assembly  13  comprises a first arm  131 , a third arm  133  and a fourth arm  134 . 
         [0059]    An upper end of the first arm  131  is pivotally coupled with the mounting bracket  11  via a first connection pin  136 , and a lower end of the first arm  131  is pivotally coupled with the step bracket  12  via a second connection pin  137 . An upper end of the third arm  133  is pivotally coupled with the mounting bracket  11  via a third connection pin  138 , and a lower end of the third arm  133  is pivotally coupled with an upper end of the fourth arm  134  via a fifth connection pin  140 . A lower end of the fourth arm  134  is pivotally coupled with the step bracket  12  via a fourth connection pin  139 . 
         [0060]    In an embodiment shown in  FIG. 4 , the extending and retracting device  10  is a six-link mechanism  10   c,  and the extending and retracting device  10  comprises the mounting bracket  11 , the step bracket  12  and the arm assembly  13 . The arm assembly  13  is coupled between the mounting bracket  11  and the step bracket  12 . The arm assembly  13  comprises a first arm  131 , a third arm  133 , a fourth arm  134  and a fifth arm  135 . 
         [0061]    An upper end of the first arm  131  is pivotally coupled with the mounting bracket  11  via a first connection pin  136 , and a lower end of the first arm  131  is pivotally coupled with the step bracket  12  via a second connection pin  137 . An upper end of the third arm  133  is pivotally coupled with the mounting bracket  11  via a third connection pin  138 , and a lower end of the third arm  133  and an upper end of the fourth arm  134  are pivotally coupled with a first end of the fifth arm  135  via a fifth connection pin  140 . The second end of the fifth arm  135  is pivotally coupled with a middle portion of the first arm  131  by a sixth connection pin  141 . A lower end of the fourth arm  134  is pivotally coupled with the step bracket  12  via a fourth connection pin  139 . In the embodiments of the above-mentioned extending and retracting device  10 , the motor shaft  32  of the motor  30  is coupled with the first arm  131  or the second arm  132  via the first connection shaft  80  so as to drive it to rotate, and then the driving force of the motor  30  is finally transmitted to the step bracket  12  so as to drive the step bracket  12  to extend and retract. 
         [0062]    In an embodiment of the present invention, the extending and retracting device  10  includes a first extending and retracting device  10   d  and a second extending and retracting device  10   e,  and the motor  30  includes a first motor  30   a  and a second motor. The step  20  is mounted to the step brackets  12  of the first extending and retracting device  10   d  and the second extending and retracting device  10   e.  The first motor  30   a  is coupled with the arm assembly  13  of the first extending and retracting device  10   d,  and the second motor is coupled with the arm assembly  13  of the second extending and retracting device  10   e.    
         [0063]    Specifically, the scroll spring is coupled between at least one of the first motor  30   a  and the second motor and the corresponding mounting bracket  11 , and the motor shaft  32  of each motor  30  is coupled with one arm of the corresponding arm assembly  13 . Therefore, when the step  20  has a large length dimension, the motion stability of the step  20  can be improved by driving the step  20  with the first motor  30   a  and second motor, and the first and second extending and retracting devices  10   d,    10   e  connected with the step  20 . 
         [0064]    In the process of driving the step  20  to extend, the elastic element  40  is compressed to store energy, and the two motor shafts  32  rotate in the same direction synchronously to drive the arms of the corresponding arm assemblies  13  to rotate, so that the arm assemblies  13  transmit the driving force to the step bracket  12 , and the step bracket  12  moves to the extending position in a predetermined track. 
         [0065]    In the process of driving the step  20  to retract, the elastic element  40  releases energy to assist the two motors  30 , and the two motor shafts  32  to rotate in the same reverse direction synchronously to drive the arms of the corresponding arm assemblies  13 , so that the arm assemblies  13  transmit the driving force to the step bracket  12 , and the step bracket  12  moves to the retracting position in a predetermined track. The working current of the motor  30  in the process of driving the step  20  to retract is decreased so as to balance the work current of the motor  30  in the process of driving the step  20  to retract with the work current of the motor  30  in the process of driving the step  20  to extend and to prolong work-life of the motor  30 . 
         [0066]    In another embodiment of the present invention, the extending and retracting device  10  includes a first extending and retracting device  10   d  and a second extending and retracting device  10   e,  and one motor  30  is provided. The step  20  is mounted to the step brackets  12  of the first extending and retracting device  10   d  and the second extending and retracting device  10   e.    
         [0067]    The motor  30  is coupled with the arm assembly  13  of the first extending and retracting device  10   d,  and the motor shaft  32  of the motor  30  is coupled with the arm assembly  13  of the second extending and retracting device  10   e  via a transmission shaft  70 . 
         [0068]    Specifically, the motor  30  is coupled with one arm of the arm assembly  13  of the first extending and retracting device  10   d,  and the motor shaft  32  of the motor  30  is coupled with one arm of the arm assembly  13  of the second extending and retracting device  10   e  via a transmission shaft  70 . In this way, one motor may be omitted, thus the manufacturing cost of the vehicle step apparatus  100  is decreased. In addition, it is easy to control a single motor. 
         [0069]    In another embodiment of the present invention, the extending and retracting device  10  includes a first extending and retracting device  10   d  and a second extending and retracting device  10   e,  and one motor  30  is provided. The step  20  is mounted to the step brackets  12  of the first extending and retracting device  10   d  and the second extending and retracting device  10   e.    
         [0070]    The motor  30  is coupled with the arm assembly  13  of the first extending and retracting device  10   d  via the first connection shaft  80 , and coupled with the arm assembly  13  of the second extending and retracting device  10   e  via a transmission shaft  70  and a second connection shaft  90 . 
         [0071]    The elastic element  40  includes a first scroll spring and a second scroll spring. The first scroll spring is coupled between the mounting bracket  11  of the first extending and retracting device  10   d  and the motor  30 , and the second scroll spring is disposed at an outside of the mounting bracket  11  of the second extending and retracting device  10   e  away from the mounting bracket  11  of the first extending and retracting device  10   d.  The amount of energy stored in the elastic element  40  is increased by increasing the number of the scroll springs, so as to assist the motor  30  and balance twisting forces at two sides of the transmission shaft  70 . 
         [0072]      FIG. 5  is a schematic view of the vehicle step apparatus  100  according to another embodiment of the present invention, in which the extending and retracting device  10  (i.e., the step  20  and the step bracket  12 ) is in the extending position. In the embodiment shown in  FIG. 5 , the extending and retracting device  10  includes a first extending and retracting device  10   d  and a second extending and retracting device  10   e,  and one motor  30  is provided. The step  20  is mounted on the step brackets  12  of the first extending and retracting device  10   d  and the second extending and retracting device  10   e.    
         [0073]    The motor  30  is coupled with the arm assembly  13  of the first extending and retracting device  10   d  via the first connection shaft  80 , and coupled with the arm assembly  13  of the second extending and retracting device  10   e  via a transmission shaft  70  and a second connection shaft  90 . 
         [0074]    The elastic element  40  is the scroll spring, and one scroll spring is provided. The one scroll spring is disposed at an outside of the mounting bracket  11  of the second extending and retracting device  10   e.  The first end  41  of the scroll spring is fixed, and the second end  42  of the scroll spring is driven by the motor shaft  32  to twist via the transmission shaft  70 . 
         [0075]    In other words, the first connection shaft  80  is coupled with one arm of the arm assembly  13  of the first extending and retracting device  10   d,  the second connection shaft  90  is coupled with one arm of the arm assembly  13  of the second extending and retracting device  10   e,  and the motor shaft  32  drives the corresponding arm assemblies  13  to move via the first connection shaft  80  and the second connection shaft  90  respectively. The scroll spring and the motor  30  are located outside the first and second extending and retracting devices  10   d,    10   e  respectively. 
         [0076]    Furthermore, as shown in  FIG. 6 , a second recess  112  is formed in an outside of the mounting bracket  11  of the second extending and retracting device  10   e  away from the mounting bracket  11  of the first extending and retracting device  10   d,  and the second recess  112  is covered by a second cover  62 . The second connection shaft  90  defines a first end coupled with the transmission shaft  70 , and a second end extended beyond the outside of the mounting bracket  11  of the second extending and retracting device  10   e  and coupled with a second connection plate  63  via splined coupling. That is to say, the second connection plate  63  is fitted over the second end of the second connection shaft  90  via splined coupling. 
         [0077]    A second catch groove  64  is formed in an outer peripheral surface of the second connection plate  63 . A catch column  113  is formed on the outside of the mounting bracket  11  of the second extending and retracting device  10   e,  and is disposed in the second recess  112 . The scroll spring is disposed in the second recession  112 , and the first end  41  of the scroll spring is fitted over the catch column  113  and the second end  42  of the scroll spring is inserted into the second catch groove  64  and fitted therein. 
         [0078]    Therefore, the motor shaft  32  rotates and drives the first connection shaft  80 , the transmission shaft  70 , the second connection shaft  90  and the second connection plate  63  to rotate together in the same direction, so that the scroll spring rotates and twists in the same direction. 
         [0079]    Operations of the vehicle step apparatus  100  according to embodiments of the present invention will be described in the following with reference to  FIGS. 5-7 . 
         [0080]    As shown in  FIGS. 5 and 6 , the motor shaft  32  rotates and drives the transmission shaft  70  and one arm of the arm assembly  13  coupled with the motor shaft  32  to rotate. The transmission shaft  70  drives one arm of the arm assembly  13  coupled with the transmission shaft  70 , so that the two arm assemblies  13  transmit the driving force to the step bracket  12 , and the step bracket  12  (i.e., the step  20 ) moves to the extending position in the predetermined track, in which the elastic element  40  is compressed to store energy. 
         [0081]    As shown in  FIG. 7 , the motor shaft  32  rotates in the reverse direction and drives the transmission shaft  70  and one arm of the arm assembly  13  coupled with the motor shaft  32 . The transmission shaft  70  drives one arm of the arm assembly  13  coupled with the transmission shaft  70 , so that the two arm assemblies  13  transmit the driving force to the step bracket  12 , and the step bracket  12  (i.e., the step  20 ) moves to the retracting position in the predetermined track, in which the elastic element  40  releases energy to reduce the load of the motor  30  in the process of driving the step  20  to retract, thus reducing the working current of the motor  30  in the process of driving the step  20  to retract. 
         [0082]    A motor assembly  200  of the vehicle step apparatus  100  according to embodiments of the present invention will be described in the following with reference to  FIG. 8 . 
         [0083]    As shown in  FIG. 8 , the motor assembly  200  of the vehicle step apparatus  100  according to embodiments of the present invention includes a motor  30 , a first cover  60 , a first connection plate  50  and an elastic element  40 . 
         [0084]    The motor  30  includes a motor shaft  32  and a casing  31 . The first cover  60  is disposed on the casing  31  so as to define a cavity. The connection plate is disposed within the cavity and driven by the motor shaft  32  to rotate. 
         [0085]    The elastic element  40  defines a first end coupled with the first cover  60  and a second end coupled with the first connection plate  50 . The elastic element  40  is configured to be elastically deformed to store energy when the motor shaft  32  rotates in a first direction, and to release energy to assist the motor shaft  32  in rotating in a second direction opposite to the first direction when the motor shaft  32  rotates in the second direction. In some embodiments, the elastic element  40  may be a scroll spring. It may be understood that the number of the scroll spring is not limited to one. 
         [0086]    With the motor assembly  200  according to embodiments of the present invention, when the motor shaft  32  rotates in the first direction, the motor shaft  32  drives the elastic element  40  to move, so that the elastic element  40  is deformed elastically to store energy. When the motor shaft  32  rotates in the second direction, the elastic element  40  releases energy to assist the motor  30  in driving the extending and retracting device  10  to retract, thus the load and working current of the motor  30  in the process of rotating in the second direction are decreased. Thus, the working current of the motor  30  in the process of driving the step  20  to retract is generally consistent with that of the motor  30  in the process of driving the step  20  to extend, so that the motor  30  is protected effectively and the working life of the motor assembly  200  is prolonged. 
         [0087]    In an embodiment of the present invention, the first cover  60  is detachably fastened to the casing  31 , and a limitation notch  61  is formed in the first cover  60 . A limiting column  111  is formed on the mounting bracket  11 , and the limiting column  111  is fitted within the limiting notch  61  to mount the first cover  60  on the mounting bracket  11 . 
         [0088]    It may be understood that, when the first direction is a forward rotation direction of the motor  30 , the second direction is a reverse rotation direction of the motor  30 , and at this time, a direction of rolling the scroll spring up tightly is consistent with the first direction. 
         [0089]    When the extending and retracting device  10  is extended, the first end  41  of the scroll spring is fixed, and the second end  42  of the scroll spring rotates along with the motor shaft  32  and is twisted tightly to store energy. When the extending and retracting device  10  is retracted, the first end  41  of the scroll spring is fixed, and the second end  42  of the scroll spring rotates to loose itself so as to release energy, thus providing power for driving the retracting the extending and retracting device  10  to retract. 
         [0090]    In the embodiment as shown in  FIG. 8 , a first catch groove  51  is formed in an outer peripheral surface of the first connection plate  20 , and a second end  42  of the scroll spring is inserted into the first catch groove  51  and fitted therein, and a first end  41  of the scroll spring is fitted over the limiting column  111 . The motor shaft  32  is coupled with the arm assembly  13  via a first connection shaft  80 . The first connection shaft  80  is coupled with the motor shaft  32  via spline coupling, and the first connection plate  50  is fitted over the first connection shaft  80  and coupled with the first connection shaft  80  via spline coupling. 
         [0091]    Therefore, the motor shaft  32  drives the first connection shaft  80  and the first connection plate  50  to rotate, and the second end  42  of the scroll spring fixed on the first connection plate  50  rotates along with the first connection plate  50 , so that the scroll spring is gradually rolled up tightly, thus resulting in a simple and compact structure. In addition, the first connection shaft  80  is coupled with the motor shaft  32  and the first connecting plate  50  via spline connection so as to ensure driving force transmission and make installation and disassembly to be easy. 
         [0092]    In some embodiments, a mounting hole  311  is formed in the casing  31 , and the limitation column  111  is passed through the mounting hole  311 . A threaded hole  111   a  is formed in the limitation column  111 , and the motor  30  is mounted on the mounting bracket  11  via a bolt  15  fitted within the threaded hole  111   a.  Thus, the motor  30 , the first connecting plate  50  and the mounting bracket  11  are mounted together via the bolt  15 , and it is easy to change and maintain the scroll spring. 
         [0093]    Operations of the arm assembly  200  of the vehicle step apparatus  20  according to embodiments of the present invention will be described in the following with reference to  FIG. 8 . 
         [0094]    In the process of driving the step  20  to extend, the elastic element  40  is compressed to store energy, and the motor shaft  32  rotates in the first direction to drive the first arm  131  of the arm assembly  13  to rotate, so that the arm assembly  13  transmits the driving force to the step bracket  12 , and the step bracket  12  moves to the extending position in a predetermined track. 
         [0095]    In the process of driving the step  20  to retract, the elastic element  40  releases energy to assist the motor  30 , and the motor shaft  32  to rotate in the second direction to drive the arm of the corresponding arm assembly  13  to rotate, so that the arm assembly  13  transmits the driving force to the step bracket  12 , and the step bracket  12  moves to the retracting position in a predetermined track. 
         [0096]    Since the elastic element  40  releases energy to decrease the load of the motor  30  in the process of driving the step  20  to retract, the working current of the motor  30  in the process of driving the step  20  to retract is decreased so as to balance the work current of the motor  30  in the process of driving the step  20  to retract with the work current of the motor  30  in the process of driving the step  20  to extend and to prolong work-life of the motor  30 . 
         [0097]    Reference throughout this specification to “an embodiment,” “some embodiments,” “one embodiment”, “another example,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment”, “in an embodiment”, “in another example,” “in an example,” “in a specific example,” or “in some examples,” in various places throughout this specification are not necessarily referring to the same embodiment or example of the present invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. 
         [0098]    Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present invention, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present invention.