Patent Publication Number: US-11649854-B2

Title: Rotation induction device for vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2020-0107108, filed on Aug. 25, 2020, which is hereby incorporated by reference for all purposes as if set forth herein. 
     BACKGROUND 
     Field 
     Exemplary embodiments of the present disclosure relate to a rotation induction device for a vehicle, and more particularly, to a rotation induction device for a vehicle, which includes a bearing that is used for a suspension of a vehicle and made of synthetic resin, in order to improve operability. 
     Discussion of the Background 
     In general, a strut-type suspension is used for a front wheel of a four-wheel vehicle having a structure in which a coil spring is combined with a strut assembly having a hydraulic shock absorber embedded in an outer shell integrated with a main shaft. The strut-type suspension is divided into a suspension in which a piston rod of the strut assembly is rotated when the strut assembly is rotated with the coil spring during a steering operation, and a suspension in which the piston rod of the strut assembly is not rotated when the strut assembly is rotated with the coil spring during the steering operation. In order to smoothly allow the rotation of the strut assembly in any strut-type suspension, a bearing is used between a mounting member of a vehicle body and an upper spring support sheet of the coil spring. 
     As the bearing, a rolling bearing using a ball or needle is used. However, the rolling bearing has a problem in that fatigue fraction may occur in the ball or needle due to a vibration load or slight rolling, which makes it difficult to maintain a smooth steering operation. Therefore, there is a need for a device capable of solving the problem. 
     The related art of the present disclosure is disclosed in Korean Patent Application Publication No. 2020-0033219 published on Mar. 27, 2020 and entitled “Strut Bearing Assembly for Suspension”. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In one general aspect, a rotation induction device for a vehicle includes: an upper case having a piston rod disposed therethrough; a lower case disposed adjacent to the upper case and having the piston rod disposed therethrough; a center plate disposed between the upper case and the lower case such that the piston rod passes through the center plate, and configured to induce rotation of one or both of the upper case and the lower case; and a friction restraint part formed on one or both of the upper case and the lower case, and configured to restrain friction with the center plate. 
     The upper case may include: an upper cover part configured to cover a first surface of the center plate, and the upper cover part may define an upper hole through which the piston rod passes; and an upper blocking part disposed at a periphery of the upper cover part, and configured to block an inflow of foreign matters. 
     The lower case may include: a lower cover part configured to cover a second surface of the center plate, and the lower cover part may define a lower hole through which the piston rod passes; and a lower blocking part disposed at a periphery of the lower cover part, and configured to block an inflow of foreign matters. 
     The upper blocking part may include: an upper blocking hook part extended toward the lower case along the periphery of the upper cover part; and an upper blocking protrusion part protruding from the upper cover part toward the lower case, and disposed to face the upper blocking hook part across a space. 
     The lower blocking part may include: a lower blocking locking part disposed along the periphery of the lower cover part, and defining a groove into which the upper blocking hook part is configured to be locked and fixed; a lower blocking dropping part extended from the periphery of the lower cover part toward an end of the upper blocking hook part so as to drop foreign matters; and a lower blocking protrusion part protruding from the periphery of the lower cover part toward the upper case, and disposed in the space between the upper blocking hook part and the upper blocking protrusion part. 
     The upper blocking hook part may include an upper inclined surface formed thereon, and the lower blocking dropping part may include a lower inclined surface corresponding to the upper inclined surface. 
     The lower blocking protrusion part may overlap with the upper blocking protrusion part. 
     The friction restraint part may include: an upper restraint part formed on the upper case, and configured to be brought into line contact with the center plate; and a lower restraint part formed on the lower case, and configured to be brought into line contact with the center plate. 
     The upper restraint part and the lower restraint part may each have cycloid surfaces. 
     A lubricant may be stored in a space disposed between the cycloid surfaces. 
     One or more of the upper case, the lower case, and the center plate may be composed of a synthetic resin material. 
     The rotation induction device may include: an upper guide part protruding from the upper case toward the lower case and configured to support an inner periphery of the center plate; and a lower guide part protruding from the lower case toward the upper case and configured to support an outer periphery of the center plate. 
     The rotation induction device may include: a first lubricant retention part protruding from the lower case toward the upper case and covering an inner peripheral surface of the center plate to prevent lubricant from overflowing to an inside of the center plate; and a second lubricant retention part protruding from the lower case toward the upper case and covering an outer peripheral surface of the center plate to prevent lubricant from overflowing to the inside of the center plate. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram schematically illustrating that a rotation induction device for a vehicle in accordance with an embodiment of the present disclosure is installed. 
         FIG.  2    is a diagram schematically illustrating the rotation induction device for a vehicle in accordance with the embodiment of the present disclosure. 
         FIG.  3    is a diagram schematically illustrating an upper case and a lower case in accordance with an embodiment of the present disclosure. 
         FIG.  4    is a diagram schematically illustrating a friction restraint part in accordance with an embodiment of the present disclosure. 
         FIG.  5    is a diagram schematically illustrating a position guide part in accordance with an embodiment of the present disclosure. 
         FIG.  6    is a diagram schematically illustrating a lubricant retention part in accordance with an embodiment of the present disclosure. 
         FIG.  7    is a diagram schematically illustrating a center plate in accordance with an embodiment of the present disclosure. 
         FIG.  8    is a diagram schematically illustrating an installation space in accordance with an embodiment of the present disclosure. 
         FIG.  9    is a diagram schematically illustrating an inflow prevention part in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Hereinafter, a rotation induction device for a vehicle will be described below with reference to the accompanying drawings through various exemplary embodiments. It should be noted that the drawings are not to precise scale and may be exaggerated in thickness of lines or sizes of components for descriptive convenience and clarity only. Furthermore, the terms as used herein are defined by taking functions of the invention into account and can be changed according to the custom or intention of users or operators. Therefore, definition of the terms should be made according to the overall disclosures set forth herein. 
       FIG.  1    is a diagram schematically illustrating that a rotation induction device for a vehicle in accordance with an embodiment of the present disclosure is installed, and  FIG.  2    is a diagram schematically illustrating the rotation induction device for a vehicle in accordance with the embodiment of the present disclosure. Referring to  FIGS.  1  and  2   , the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure includes an upper case  10 , a lower case  20  and a center plate  30 . 
     The upper case  10  is made of a synthetic resin material, and has a piston rod  200  disposed therethrough. For example, the upper case  10  may have a hole formed in the center thereof such that a piston rod  200  passes through the hole, and an insulator  300  may be disposed above the upper case  10 . 
     The lower case  20  is made of a synthetic resin material, and disposed under the upper case  10  such that the piston rod  200  passes through the lower case  20 . For example, the lower case  20  may have a hole formed in the center thereof such that the piston rod  200  passes through the hole, and a sheet  500  to support the top of a spring  400  may be disposed under the lower case  10 . 
     The center plate  30  is made of a synthetic resin material, and disposed between the upper case  10  and the lower case  20  such that the piston rod  200  passes through the center plate  30 . Such a center plate  30  induces the rotation of any one of the upper and lower cases  10  and  20 . For example, the center plate  30  may retain the state in which the top surface thereof is contacted with the upper case  10  and the bottom surface thereof is contacted with the lower case  20 . The center plate  30  may induce the contact surfaces to slide, thereby inducing the rotation of the lower case  20 . 
       FIG.  3    is a diagram schematically illustrating the upper case and the lower case in accordance with an embodiment of the present disclosure. Referring to  FIGS.  2  and  3   , the upper case  10  includes an upper cover part  11  and an upper blocking part  12 , and the lower case  20  includes a lower cover part  21  and a lower blocking part  22 . 
     The upper cover part  11  has an upper hole  111  formed in the center thereof, such that the piston rod  200  passes through the upper hole  111 . The upper cover part  11  covers the top of the center plate  30 . For example, the upper cover part  11  may be formed in a ring shape through which the piston rod  200  can pass. 
     The upper blocking part  12  is formed at the edge of the upper cover part  11 , and serves to block the inflow of foreign matters. For example, the upper blocking part  12  may be integrated with the upper cover part  11 , and induce foreign matters to fall down while fluid introduced from the outside is moved upward and downward. 
     The lower cover part  21  has a lower hole  211  formed in the center thereof, such that the piston rod  200  passes through the lower cover part  21 . The lower cover part  21  covers the bottom of the center plate  30 . For example, the lower cover part  21  may be formed in a ring shape through which the piston rod  200  passes. 
     The lower blocking part  22  is formed at the edge of the lower cover part  21 , and serves to block the inflow of foreign matters. For example, the lower blocking part  22  may be integrated with the lower cover part  21 , and serve to induce the coupling with the upper blocking part  12 . Furthermore, the lower blocking part  22  may be spaced apart from the upper blocking part  12 , and thus drop foreign matters while guiding fluid. 
     More specifically, the upper blocking part  12  includes an upper blocking hook part  121  and an upper blocking protrusion part  122 . 
     The upper blocking hook part  121  is extended downward from the edge of the upper cover part  11 . For example, the upper blocking hook part  121  may have a lower end formed in a hook shape so as to be hooked to the lower case  20 . 
     The upper blocking protrusion part  122  protrudes downward from the upper cover part  11  so as to face the upper blocking hook part  121 . For example, the upper blocking protrusion part  122  may have an outer diameter smaller than that of the upper blocking hook part  121 . 
     The lower blocking part  22  includes a lower blocking locking part  221 , a lower blocking dropping part  222  and a lower blocking protrusion part  223 . 
     The lower blocking locking part  221  is formed at the edge of the lower cover part  21 , and has a groove to which the upper blocking hook part  121  is hooked and fixed. For example, the lower blocking locking part  221  may be formed at the outer circumferential surface of the lower case  20 , and the upper blocking hook part  121  may be inserted into the lower blocking locking part  221  and then hooked and fixed thereto. Thus, fluid introduced between the upper blocking hook part  121  and the lower blocking locking part  221  may flow backward due to the shapes of the upper blocking hook part  121  and the lower blocking locking part  221 , which makes it possible to suppress the inflow of foreign matters. 
     The lower blocking dropping part  222  is extended from the edge of the lower cover part  21  toward the bottom of the upper blocking hook part  121 , in order to drop foreign matters. For example, the lower blocking dropping part  222  may be extended from the outer lower end of the lower cover part  21 , and the upper blocking hook part  121  may be disposed above the lower blocking dropping part  222 . 
     At this time, the upper blocking hook part  121  has an upper inclined surface  125  formed thereon, and the lower blocking dropping part  222  has a lower inclined surface  225  formed to face the upper inclined surface  125 . The space between the upper inclined surface  125  and the lower inclined surface  225  may be so narrow as to suppress the inflow of foreign matters into the lower blocking locking part  221 . Since the upper inclined surface  125  is formed on the outer lower end of the upper blocking hook part  121 , foreign matters contained in the air introduced between the upper blocking hook part  121  and the lower blocking dropping part  222  may flow downward so as to be discharged to the outside. 
     The lower blocking protrusion part  223  protrudes upward from the edge of the lower cover part  21  so as to be disposed between the upper blocking hook part  121  and the upper blocking protrusion part  122 . For example, the lower blocking protrusion part  223  may be extended upward from the top surface of the edge of the lower cover part  21 . The top of the lower blocking protrusion part  223  may be located at a higher level than the bottom of the upper blocking protrusion part  122 . Therefore, the movement of fluid having passed through the lower blocking protrusion part  223  may be restricted by the upper blocking protrusion part  122 , such that foreign matters are dropped. 
     Therefore, the inflow of foreign matters between the upper blocking part  12  and the lower blocking part  22  may be suppressed, and the foreign matters may be rapidly dropped through the upper inclined surface  125  and the lower inclined surface  225 , which makes it possible to prevent rotational friction or damage caused by the accumulation of foreign matters. Furthermore, although fine foreign matters pass through the space between the upper blocking hook part  121  and the lower blocking locking part  221 , the foreign matters may be caught by the upper blocking protrusion part  122  and dropped down to the top of the lower cover part  21 . At this time, when the pair of lower blocking protrusion parts  223  are formed so that the upper blocking protrusion part  122  is disposed between the lower blocking protrusion parts  223 , it is possible to prevent an increase in rotational friction and part damage caused by the inflow of foreign matters into the center plate  30 . 
       FIG.  4    is a diagram schematically illustrating a friction restraint part in accordance with an embodiment of the present disclosure. Referring to  FIG.  4   , the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure may further include a friction restraint part  40 . The friction restraint part  40  is formed on any one or more of the upper and lower cases  10  and  20 , and serves to restrain friction with the center plate  30 . 
     More specifically, the friction restraint part  40  includes an upper restraint part  41  and a lower restraint part  42 . 
     The upper restraint part  41  is formed on the upper case  10 , and brought into line contact with the center plate  30 . For example, the upper restraint part  41  may be brought into line contact with the top surface of the center plate  30  so as to reduce frictional resistance. 
     The lower restraint part  42  is formed on the lower case  20 , and brought into line contact with the center plate  30 . For example, the lower restraint part  42  may be brought into line contact with the bottom surface of the center plate  30  so as to reduce frictional resistance. 
     The upper restraint part  41  and the lower restraint part  42  each have cycloid surfaces. When the upper and lower restraint parts  41  and  42  each have the cycloid surfaces, stress concentrated by a vertical load may be distributed. The space formed between the cycloid surfaces may have a lubricant stored therein. That is, the connection point between the adjacent cycloid surfaces may correspond to the bottoms of the cycloid surfaces, such that a recess is formed therebetween, and a lubricant such as grease may be stored in such a recess. 
       FIG.  5    is a diagram schematically illustrating a position guide part in accordance with an embodiment of the present disclosure. Referring to  FIG.  5   , the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure may further include a position guide part  50 . The position guide part  50  is formed on any one or more of the upper and lower cases  10  and  20 , and serves to guide the position of the center plate  30 . 
     More specifically, the position guide part  50  includes an upper guide part  51  and a lower guide part  52 . 
     The upper guide part  51  protrudes downward from the upper case  10  and supports the inner circumferential surface of the center plate  30 . For example, the upper guide part  51  may protrude downward from the bottom surface of the upper cover part  11 , have a circular belt shape, and be disposed to face the upper blocking protrusion part  122 . 
     The lower guide part  52  protrudes upward from the lower case  20  and supports the outer circumferential surface of the center plate  30 . For example, the lower guide part  52  may protrude upward from the top surface of the lower cover part  21 , have a circular belt shape, and be disposed to face the lower blocking protrusion part  223 . At this time, the upper blocking protrusion part  122  may be disposed between the lower blocking protrusion part  223  and the lower guide part  52 . 
       FIG.  6    is a diagram schematically illustrating a lubricant retention part in accordance with an embodiment of the present disclosure. Referring to  FIG.  6   , the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure may further include a lubricant retention part  60 . The lubricant retention part  60  may be formed on the lower case  20  so as to form a barrier wall for storing a lubricant. 
     More specifically, the lubricant retention part  60  includes a first lubricant retention part  61  and a second lubricant retention part  62 . 
     The first lubricant retention part  61  protrudes upward from the lower case  20  and covers the inner circumferential surface of the center plate  30 . For example, the first lubricant retention part  61  may be extended upward from the top surface of the lower cover part  21  so as to directly support the inner circumferential surface of the center plate  30 , or disposed adjacent to the upper guide part  51  so as to prevent a lubricant from overflowing to the inside of the center plate  30 . 
     The second lubricant retention part  62  protrudes upward from the lower case  20  and covers the outer circumferential surface of the center plate  30 . For example, the second lubricant retention part  62  may be extended upward from the top surface of the lower cover part  21 , directly support the outer circumferential surface of the center plate  30 , and prevent a lubricant from overflowing to the outside of the center plate  30 . The second lubricant retention part  62  may be separately formed or replaced with the lower guide part  52 . 
     At this time, the height (a) of the lubricant retention part  60  may be set in the range of 50% to 60% of the height (b) of the center plate  30 . That is, when the first and second lubricant retention parts  61  and  62  have the same height, the height (a) of the lubricant retention part  60  may be defined as expressed by Equation 1 below.
 
0.5 b≤a≤ 0.9 b   [Equation 1]
 
     Through the regulation of the ratio of the height of the lubricant retention part  60 , the lower case  20  may serve as a lubricant pocket of the center plate  30 , and the lubricant retention part  60  may serve as a barrier wall for preventing a lubricant leak, which makes it possible to maximize the lubrication performance of the lubricant and to reduce torque. 
       FIG.  7    is a diagram schematically illustrating the center plate in accordance with the embodiment of the present disclosure. Referring to  FIG.  7   , the center plate  30  in accordance with the embodiment of the present disclosure is brought into line contact with the upper case  10  and the lower case  20 , in order to induce rotation. 
     More specifically, the center plate  30  includes a center disk part  31 , a center inner circumferential part  32 , a center outer circumferential part  33 , a center upper curved part  34  and a center lower curved part  35 . 
     The center disk part  31  is disposed between the upper cover part  11  and the lower cover part  21 . For example, the center disk part  31  may be formed in a disk shape with a hole formed in the center thereof. The center disk part  31  may be disposed between the upper guide part  51  and the lower guide part  52 . 
     The center inner circumferential part  32  is formed on the inner circumferential surface of the center disk part  31 . For example, the center inner circumferential part  32  may be designed in such a manner that the top thereof is located at a higher level than the top surface of the center disk part  31  and the bottom thereof is located at a lower level than the bottom surface of the center disk part  31 . The center inner circumferential part  32  may be supported by the upper guide part  51  such that the position of the center inner circumferential part  32  is maintained. 
     The center outer circumferential part  33  is formed on the outer circumferential surface of the center disk part  31 . For example, the center outer circumferential part  33  may be designed in such a manner that the top thereof is located at a higher level than the top surface of the center disk part  31 , and the bottom thereof is located at a lower level than the bottom surface of the center disk part  31 . The center outer circumferential part  33  and the center inner circumferential part  32  may correspond to each other. The center outer circumferential part  33  and the center inner circumferential part  32  may be supported by the lower guide part  52  such that the positions thereof are maintained. 
     The center upper curved part  34  is formed at the top of the center disk part  31 , and brought into line contact with the upper case  10 . For example, the center upper curved part  34  may have a plurality of curved surfaces, each of which is designed so that the top thereof is located at a higher level than the center inner circumferential part  32  and the center outer circumferential part  33 . Thus, the center upper curved part  34  may be brought into line contact with the upper cover part  11 . 
     The center lower curved part  35  is formed at the bottom of the center disk part  31 , and brought into line contact with the lower case  20 . For example, the center lower curved part  35  may have a plurality of curved surfaces, each of which is designed so that the bottom thereof is located at a lower level than the center inner circumferential part  32  and the center outer circumferential part  33 . Thus, the center lower curved part  35  may be brought into line contact with the lower cover part  21 . 
     At this time, the center upper curved part  34  and the center lower curved part  35  each have one or more cycloid surfaces. When the center upper and lower curved parts  34  and  35  each have the cycloid surfaces, stress concentrated by a vertical load may be distributed. 
     A curved storage part  36  formed between the cycloid surfaces may store a lubricant therein. That is, the connection point between the adjacent cycloid surfaces may correspond to the bottoms of the cycloid surfaces, such that a recess is formed therebetween, and a lubricant such as grease is stored in such a recess. 
     At this time, the height (c) of the cycloid surface from bottom to top may be set in the range of 10% to 50% of the height (d) of the center plate  30 . The height (d) of the center plate  30  may indicate the distance between the top of the center upper curved part  34  and the bottom of the center lower curved part  35 , and the height (c) of the center upper curved part  34  or the center lower curved part  35  from bottom to top may be defined as expressed by Equation 2 below.
 
0.1 d≤c≤ 0.5 d   [Equation 2]
 
     Through the ratio regulation of the heights of the center upper and lower curved parts  34  and  35  from bottom to top, two or more center upper curved parts  34  and two or more center lower curved parts  35  may be formed on the center disk part  31 , and the plurality of curved storage parts  36  formed as grooves at the intersections between the respective curved surfaces may be filled with a lubricant. The lubricant stored in the curved storage part  36  can improve the lubrication effect to lower torque. 
       FIG.  8    is a diagram schematically illustrating an installation space in accordance with an embodiment of the present disclosure. Referring to  FIG.  8   , the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure may further include an installation space  70 . The installation space  70  may be formed between the upper case  10  and the lower case  20 , and formed as a ring-shaped space into which the center plate  30  is to be inserted. 
     More specifically, the installation space  70  may indicate a space formed between the upper guide part  51  and the lower guide part  52 . That is, the installation space  70  may correspond to the ring-shaped space between the outer circumferential surface of the upper guide part  51  and the inner circumferential surface of the lower guide part  52 . 
     The volume (e) of the center plate  30  may be set in the range of 50% to 98% of the volume (f) of the installation space  70 . The volume (e) of the center plate  30  and the volume (f) of the installation space  70  may be defined as expressed by Equation 3 below.
 
0.5 f≤e≤ 0.98 f   [Equation 3]
 
     The ratio regulation of the volume (e) of the center plate  30  may regulate a change in position by a horizontal load so as to prevent a lubricant leak due to a change in position or shock which is caused by a horizontal load of the center plate  30 , which makes it possible to improve the durability and lubrication performance. 
       FIG.  9    is a diagram schematically illustrating an inflow prevention part in accordance with an embodiment of the present disclosure. Referring to  FIG.  9   , the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure may further include an inflow prevention part  80 . The inflow prevention part  80  is formed on any one or more of the upper and lower cases  10  and  20 , and serves to block the inflow of foreign matters through the piston rod  200 . For example, the inflow prevention part  80  may block foreign matters from flowing into the gap between the upper case  10  and the piston rod  200  and the gap between the lower case  20  and the piston rod  200 . 
     More specifically, the inflow prevention part  80  includes an upper prevention part  81 , a lower prevention part  82  and an inner prevention part  83 . 
     The upper prevention part  81  is extended downward from the inside of the upper case  10 , and covers the piston rod  200 . For example, the upper prevention part  81  may be integrated with the upper cover part  11 , and extended downward from the inner circumferential surface of the upper cover part  11 . The inner circumferential surface of the upper prevention part  81  may cover the piston rod  200 . The bottom of the upper prevention part  81  may be located at a lower level than the bottom of the upper guide part  51 . 
     The lower prevention part  82  is extended from the inside of the lower case  20  so as to cover the piston rod  200 , and disposed under the upper prevention part  81 . For example, the lower prevention part  82  may be integrated with the lower cover part  21 , and formed in the lower cover part  21 . The inner circumferential surface of the lower prevention part  82  may cover the piston rod  200 . The lower prevention part  82  and the upper prevention part  81  may be disposed on a straight line. The top surface of the lower prevention part  82  may be located at a lower level than the top surface of the lower cover part  21 . 
     The inner prevention part  83  is extended upward from the lower case  20 , and disposed to face the upper prevention part  81 . For example, the inner prevention part  83  may be integrated with the lower cover part  21 , and inserted between the upper prevention part  81  and the upper guide part  51  so as to form a labyrinth structure. At this time, the top of the inner prevention part  83  may be located at a high level than the bottoms of the upper prevention part  81  and the upper guide part  51 . 
     The distance (g) between the upper prevention part  81  and the lower prevention part  82  may be set in the range of 10% to 50% of a height (h) of the upper prevention part  81 . The height (i) of the upper case  10  may be equal to or larger than the height (h) of the upper prevention part  81 . 
     That is, the height (h) of the upper prevention part  81  may indicate the length of the upper prevention part  81  protruding from the bottom surface of the upper cover part  11 , and the height (i) of the upper case  10  may indicate the thickness of the upper cover part  11 . The heights (h) and (i) may be defined as expressed by Equation 4 below.
 
0.1 h≤g≤ 0.5 h, h≤i   [Equation 4]
 
     The regulation of the distance (g) between the upper prevention part  81  and the lower prevention part  82  and the height (h) of the upper prevention part  81  may block the contact between the upper prevention part  81  and the lower prevention part  82  and thus prevent reduction in torque. Furthermore, the inflow of foreign matters may be blocked through the labyrinth structure, which makes it possible to protect the equipment. Furthermore, the regulation of the height (i) of the upper case  10  may block reduction in stiffness of the upper cover part  11 . 
     In the rotation induction device  1  for a vehicle in accordance with the embodiment of the present disclosure, the friction restraint part  40  may be formed on the upper case  10  and the lower case  20  so as to restrain friction caused by the contact with the center plate  30 . 
     Although exemplary embodiments of the disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as defined in the accompanying claims. Thus, the true technical scope of the disclosure should be defined by the following claims.