Patent Publication Number: US-2021163062-A1

Title: Steer-by-wire type steering apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2017-0174865, filed on Dec. 19, 2017, and Korean Patent Application No. 10-2018-0039044, filed on Apr. 4, 2018, which are hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Technical Field 
     Some embodiments of the present disclosure may relate to a steer-by-wire type steering apparatus. More particularly, certain exemplary embodiments of present disclosure may relate to a steer-by-wire type steering apparatus that is capable of preventing rotation of a steering shaft when a driver generates a larger steering torque than a reaction torque of a reaction motor in the steering shaft. 
     2. Description of Related Art 
     In general, in a steering apparatus of a vehicle, power steering has been developed and applied to provide convenience of a driving operation by assisting in an operation force of a driver&#39;s steering wheel, and examples of power steering include hydraulic type power steering using a hydraulic pressure, electrically-powered hydraulic type power steering that simultaneously uses the hydraulic pressure and an electrical power of a motor, and electrically-powered type power steering using only an electrical power of the motor. 
     Recently, a steer-by-wire (SBW) type steering apparatus in which steering of the vehicle is performed using an electric motor such as a motor, by which a mechanical connection apparatus, such as a steering column, between the steering wheel and a wheel, a universal joint, or a pinion shaft is removed instead, has been developed and applied. 
     However, because there is no mechanical connection between a steering shaft and the wheel in such a steer-by-wire type steering apparatus, rotation of the driver&#39;s steering wheel is unlimited so that the driver&#39;s steering sense may be degraded. 
     That is, when rotation of the wheels reaches a maximum point (when, in a steering apparatus according to the related art, the steering wheel or wheels are in a full-turn state) or when the wheels collide with a curbstone of a road and cannot be rotated any more, the necessity for not rotating the steering shaft any more and providing such information to the driver has emerged. 
     SUMMARY 
     In this background, the present disclosure is to provide a steer-by-wire type steering apparatus that is capable of preventing rotation of a steering shaft when a driver generates a larger steering torque than a reaction torque of a reaction motor in the steering shaft. 
     It should be noted that objects of the present disclosure are not limited to the above-mentioned object, and other objects of the present disclosure will be understood by those skilled in the art from the following description. 
     To solve the foregoing problem, an embodiment provides a steer-by-wire type steering apparatus including a first pulley coupled to a steering shaft, a second pulley connected to the first pulley via a belt and coupled to a shaft of a reaction motor, an engaging member coupled to the shaft of the reaction motor and having engaging grooves formed in an outer circumferential surface thereof, a pair of rotation-preventing members each having one end coupled to a housing, in which the first pulley and the second pulley are embedded, via a hinge shaft to rotate and the other end having engaging protrusions supported in the engaging grooves, the pair of rotation-preventing members supported in engaging grooves of one side and the other side of the outer circumferential surface of the engaging member, and a cam member disposed between one ends of the pair of rotation-preventing members, being rotated while being coupled to a shaft of a driving motor and rotating each of the rotation-preventing members around the hinge shaft. 
     An embodiment provides a steer-by-wire type steering apparatus including a first member coupled to one side of a steering shaft and a shaft of a reaction motor and having fixing grooves formed in an outer circumferential surface of one side end thereof in an axial direction, a second member having fixing protrusions corresponding to the fixing grooves, coupled to an outside of the first member and having first support grooves formed in one side end of the second member in a circumferential direction and spaced apart from one another, a third member coupled to the other side of the steering shaft and the shaft of the reaction motor and having second support grooves at positions corresponding to the first support grooves, a ball member supported and inserted in the first support grooves and the second support grooves, and a rotation-preventing member formed in a ring form that is fixed to a housing in which the steering shaft is embedded, having engaging grooves formed in an inner circumferential surface thereof in the axial direction and coupled to outer circumferential surfaces of the second member and the third member. 
     According to the present embodiments, in a steer-by-wire type steering apparatus, when a driver generates a larger steering torque than a reaction torque of a reaction motor in a steering shaft, rotation of the steering shaft can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a view for schematically illustrating a steer-by-wire type steering apparatus according to the present embodiments; 
         FIG. 2  is a perspective view of a part of the steer-by-wire type steering apparatus according to the present embodiments; 
         FIGS. 3 through 7  are front views of a part of the steer-by-wire type steering apparatus according to the present embodiments; 
         FIG. 8  is a view for schematically illustrating a steer-by-wire type steering apparatus according to other embodiments; 
         FIG. 9  is a perspective view of a part of the steer-by-wire type steering apparatus according to other embodiments; 
         FIG. 10  is an exploded perspective view of a part of the steer-by-wire type steering apparatus according to other embodiments; 
         FIG. 11  is a cross-sectional view of a part of the steer-by-wire type steering apparatus according to other embodiments; and 
         FIGS. 12 through 14  are front views of a part of the steer-by-wire type steering apparatus according to other embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In adding reference numerals to elements in each drawing, the same elements will be designated by the same reference numerals, if possible, although the elements are shown in different drawings. Further, in the following description of the present disclosure, a detailed description of known functions and configurations incorporated herein will be omitted when it is determined that the description may make the subject matter of the present disclosure rather unclear. 
     In addition, when describing elements of the present embodiments, the terms, such as first, second, A, B, (a), and (b), may be used. These terms are only used to distinguish one element from another element, and the essence, order, or sequence of a corresponding element is not limited by these terms. When it is described that an element is “connected to,” “coupled to,” or “joined to” another element, it will be understood that the element may be directly connected to or jointed to another element, but still another element may also be “connected,” “coupled,” or “jointed” between the two elements. 
     First, referring to  FIGS. 1 through 7 , a steer-by-wire type steering apparatus according to the present embodiments includes a first pulley  131  coupled to a steering shaft  103 , a second pulley  135  connected to the first pulley  131  via a belt  133  and coupled to a shaft  120   a  of a reaction motor  120 , an engaging member  140  coupled to the shaft  120   a  of the reaction motor  120  and having engaging grooves  140   a  formed in an outer circumferential surface thereof, a pair of rotation-preventing members  141   a  and  141   b  each having one end fixed to a housing  127 , in which the first pulley  131  and the second pulley  135  are embedded, via a hinge shaft  149  to rotate and the other end in which engaging protrusions  141   c  supported in the engaging grooves  140   a  are formed, the pair of rotation-preventing members  141   a  and  141   b  being supported in the engaging grooves  140   a  at each of one side and the other side of the outer circumferential surface of the engaging member  140 , and a cam member  143  disposed between one ends of the rotation-preventing members  141   a  and  141   b , being rotated while being coupled to a shaft  125   a  of a driving motor  125  and rotating each of the rotation-preventing members  141   a  and  141   b  around the hinge shaft  149 . 
     In the steer-by-wire type steering apparatus according to the present embodiments, an angle sensor  105  and a torque sensor  107  are coupled to one side of the steering shaft  103  connected to a steering wheel  101 , and when a driver operates the steering wheel  101 , the angle sensor  105  and the torque sensor  107  that sense the driver&#39;s operation transmit electrical signals to an electronic control unit (ECU)  110  so that the reaction motor  120  and a pinion shaft motor  130  may operate. 
     The ECU  110  controls the reaction motor  120  and the pinion shaft motor  130  based on electrical signals transmitted from the angle sensor  105  and the torque sensor  107  and electrical signals transmitted from several sensors mounted on a car. 
     The pinion shaft motor  130  slides a rack bar  111  connected to a pinion shaft  113  to perform steering of both-side wheels  119  using a tie rod  115  and a knuckle arm  117 , and the reaction motor  120  generates a steering reaction sense in an opposite direction when the driver operates the steering wheel  101 , or performs steering of the steering shaft  103  when autonomous driving is performed. 
     However, in the drawings of the present embodiments, for convenience of explanation, the angle sensor  105  and the torque sensor  107  are provided in the steering shaft  103 . However, a motor position sensor, a variety of radar, and a camera image sensor for transmitting steering information to the ECU  110  may be provided, obviously, and hereinafter, a detailed description thereof will be omitted. 
     Because, in the steer-by-wire type steering apparatus, the steering shaft  103  and the pinion shaft  113  are not mechanically connected to each other, the driver&#39;s rotation of the steering wheel  101  is unlimited so that mechanical limitations in which rotation is stopped at an arbitrary angle, are required. 
     That is, when rotation of the wheels  119  reaches a maximum point (when, in a steering apparatus according to the related art, the steering wheel  101  or the wheels  119  are in a full-turn state) or when the wheels  119  collide with a curbstone of a road and cannot be rotated any more, a reaction torque is output from the reaction motor  120  to the maximum. Thus, the steering shaft  103  is not rotated any more so that rotation of the steering shaft  103  is prevented to give this information to the driver. 
     A driving motor  125  mechanically connected to the steering shaft  103  is provided so as to prevent rotation of the steering shaft  103 . When a steering torque that is greater than or equal to a maximum reaction torque of the reaction motor  120  is generated, the rotation-preventing members  141   a  and  141   b  operate so that the rotation of the steering shaft  103  is stopped. 
     First, the steering shaft  103  coupled to the steering wheel  101  is provided in a steering column  123  fixed to a body of the car, and the reaction motor  120  for providing a steering reaction sense to the steering shaft  103 , and the driving motor  125  that operates to stop rotation of the steering shaft  103  when a steering torque that is greater than or equal to the maximum reaction torque of the reaction motor  120  is generated in the steering shaft  103 , are provided at both sides of the steering column  123  via the housing  127 . 
     The first pulley  131  is coupled to the steering shaft  103 , and the second pulley  135  is coupled to the shaft  120   a  of the reaction motor  120 , and the first pulley  131  and the second pulley  135  are connected to each other via the belt  133 . 
     Thus, when the driver operates the steering wheel  101 , the ECU  110  operates the reaction motor  120  based on signal values detected by the torque sensor  107  and the angle sensor  105  so as to generate a reaction torque in an opposite direction to a rotation direction of the steering shaft  103 . 
     Also, the engaging member  140  in which the engaging grooves  140   a  are consecutively formed in the outer circumferential surface thereof, is coupled to the shaft  120   a  of the reaction motor  120  and is rotated together with the shaft  120   a  of the reaction motor  120 , and the pair of rotation-preventing members  141   a  and  141   b  that limit rotation of the engaging member  140  are provided. 
     Here, one ends of the rotation-preventing members  141   a  and  141   b  are coupled to the housing  127  in which the first pulley  131  and the second pulley  135  are embedded, via the hinge shaft  149 , and the engaging protrusions  141   c  supported in the engaging grooves  140   a  of the engaging member  140  are formed in the other ends of the rotation-preventing members  141   a  and  141   b.    
     Also, the other ends of the rotation-preventing members  141   a  and  141   b  are supported in the engaging grooves  140   a  of one side and the other side of the outer circumferential surface of the engaging member  140 , respectively. 
     The cam member  143  for rotating each of the rotation-preventing members  141   a  and  141   b  based on each hinge shaft  149  is disposed at one end of each of the rotation-preventing members  141   a  and  141   b . The cam member  143  is coupled to the shaft  125   a  of the driving motor  125  and is rotated. 
     Also, an elastic member  145  for elastically supporting the rotation-preventing members  141   a  and  141   b  using the engaging member  140  is coupled to an inner circumferential surface of the housing  127 . Thus, as long as the cam member  143  does not spread the rotation-preventing members  141   a  and  141   b  bilaterally, the cam member  143  is supported inward based on the hinge shaft  149 . 
     Support grooves  147  in which the elastic member  145  is inserted and supported, are formed in the inner circumferential surface of the housing  127 . The support grooves  147  may be formed in a protruding end  148  that protrudes from the inner circumferential surface of the housing  127 . 
     The cam member  143  may be formed in a trapezoidal form having a predetermined thickness, and when both ends of a long side  143   a  of two facing and parallel sides of the trapezoidal form are supported in one end of each of the rotation-preventing members  141   a  and  141   b , each of the rotation-preventing members  141   a  and  141   b  is spread bilaterally based on the hinge shaft  149 . In this case, the elastic member  145  is compressed, and the engaging protrusions  141   c  are moved to positions deviated from the engaging grooves  140   a.    
     Also, when a short side  143   b  of two facing and parallel sides of the cam member  143  is placed at one end of each of the rotation-preventing members  141   a  and  141   b , as shown in  FIG. 5 , the elastic member  145  is restored, and the engaging protrusions  141   c  are moved to positions at which the engaging protrusions are inserted into the engaging grooves  140   a.    
     That is, when both sides of the long side  143   a  of the cam member  143  are supported by the rotation-preventing members  141   a  and  141   b , the elastic member  145  is compressed, and the engaging protrusions  141   c  are moved to positions deviated from the engaging grooves  140   a , and when both sides of the long side  143   a  of the cam member  143  are not supported by the rotation-preventing members  141   a  and  141   b , the elastic member  145  is restored, and the engaging protrusions  141   c  are inserted into the engaging grooves  140   a.    
     Thus, when the engaging protrusions  141   c  are supported in the engaging grooves  140   a , rotation of the steering shaft  103  is prevented, and when the engaging protrusions  141   c  are moved to positions deviated from the engaging grooves  140   a , the rotation of the steering shaft  103  is possible. 
     The steer-by-wire type steering apparatus according to the present embodiments may further include a torque sensor  107  for measuring a steering torque value generated in the steering shaft  103  and an electronic control device (ECU)  110  that calculates a reaction torque value of the steering shaft  103  based on the steering torque value measured by the torque sensor  107 , traits the calculated reaction torque value to the reaction motor  120 , and compares the steering torque value with a set maximum reaction torque value to determine whether to operate the driving motor  125 . 
     Here, when the steering torque value is smaller than the set maximum reaction torque value, the ECU  110  operates the driving motor  125  so that both ends of the long side  143   a  of two facing and parallel sides of the cam member  143  are supported by one end of each of the rotation-preventing members  141   a  and  141   b  and the engaging protrusions  141   c  are moved to positions deviated from the engaging grooves  140   a.    
     Also, when the steering torque value is greater than the set maximum reaction torque value, the ECU  110  operates the driving motor  125  so that one end of the long side  143   a  of two facing and parallel sides of the cam member  143  is supported by one end of the rotation-preventing member  141   b  (see  FIG. 6 ) and  141   a  (see  FIG. 7 ) for supporting in a direction toward a reaction torque and thus only the rotation-preventing members  141   b  (see  FIG. 6 ) and  141   a  ( FIG. 7 ) for supporting the direction toward the reaction torque may be moved to positions deviated from the engaging grooves  140   a.    
     That is, when the steering torque value in one direction, for example, in a left-turn direction is greater than the maximum reaction torque value, only rotation of the steering shaft  103  in the left-turn direction is prevented, and rotation of the steering shaft  103  in a right-turn direction that is opposite to the left-turn direction is possible. 
     This will be described based on  FIGS. 6 and 7 . First,  FIG. 6  illustrates the case where the steering torque value in the left-turn direction is greater than the maximum reaction torque value, and the case means that left-turn of the engaging member  140  that is a counterclockwise direction in the drawings is not possible and right-turn of the engaging member  140  that is a clockwise direction in the drawings is possible. Here, the left-turn of the engaging member  140  which is impossible means that left-turn of the steering shaft  103  connected to the shaft  120   a  of the reaction motor  120  via the first pulley  131  and the second pulley  135  is not possible, either. 
     That is, because  FIG. 6  illustrates the case where the driver generates a steering torque in the left-turn direction, the reaction torque is generated in the right-turn direction that is the clockwise direction in the drawings, and only the rotation-preventing member  141   b  (see  FIG. 6 ) for supporting a reaction torque direction so that the right-turn of the engaging member  140  is possible, is moved to a position deviated from the engaging grooves  140   a.    
     Contrary to this, because  FIG. 7  illustrates the case where the steering torque value in a right-turn direction is greater than the maximum reaction torque value, right-turn of the engaging member  140  that is a clockwise direction in the drawings is not possible, and left-turn of the engaging member  140  that is a counterclockwise direction in the drawings is possible. Here, the right-turn of the engaging member  140  which is impossible means that right-turn of the steering shaft  103  connected to the shaft  120   a  of the reaction motor  120  via the first pulley  131  and the second pulley  135  is not possible, either. 
     Here, because  FIG. 7  illustrates the case where the driver generates a steering torque in the right-turn direction, the reaction torque is generated in the left-turn direction that is the counterclockwise direction in the drawings, and only the rotation-preventing member  141   a  (see  FIG. 7 ) for supporting the reaction torque direction so that the left-turn of the engaging member  140  is possible, is moved to a position deviated from the engaging grooves  140   a.    
     That is, only rotation of the steering shaft  103  in one side direction is not possible depending on whether the ECU  110  operates the driving motor  125  to rotate the cam member  143  in which direction. 
     Meanwhile, referring to  FIGS. 8 through 14 , a steer-by-wire type steering apparatus according to the present embodiments includes a first member  241  coupled to one side of a steering shaft  203  and a shaft  223  of a reaction motor and having fixing grooves  241   a  formed in an outer circumferential surface of one side end thereof in an axial direction, a second member  243  having fixing protrusions  243   a  corresponding to the fixing grooves  241   a  therein, coupled to an outside of the first member  241  and having first support grooves  243   b  formed in one side end of the second member  243  in a circumferential direction and spaced apart from one another, a third member  245  coupled to the other side of the steering shaft  203  and the shaft  223  of the reaction motor and having second support grooves  245   b  at positions corresponding to the first support grooves  243   b , a ball member  251  supported and inserted in the first support grooves  243   b  and the second support grooves  245   b , and a rotation-preventing member  247  formed in a ring form that is fixed to a housing in which the steering shaft  203  is embedded, having engaging grooves  247   a  formed in an inner circumferential surface thereof in the axial direction and coupled to outer circumferential surfaces of the second member  243  and the third member  245 . 
     In the steer-by-wire type steering apparatus according to the present embodiments, an angle sensor  205  and a torque sensor  207  are coupled to one side of the steering shaft  203  connected to a steering wheel  201 , and when a driver operates the steering wheel  201 , the angle sensor  205  and the torque sensor  207  that sense the driver&#39;s operation transmits electrical signals to an ECU  210  so that a reaction motor  220  and a pinion shaft motor  230  may operate. 
     The ECU  210  controls the reaction motor  220  and the pinion shaft motor  230  based on the electrical signals transmitted from the angle sensor  205  and the torque sensor  207  and electrical signals transmitted from several sensors mounted on the car. 
     The pinion shaft motor  230  slides a rack bar  211  connected to a pinion shaft  213  to perform steering of both-side wheels  219  using a tie rod  215  and a knuckle arm  217 . The reaction motor  220  generates a steering reaction sense in an opposite direction when the driver operates the steering wheel  201 , or performs steering of the steering shaft  203  when autonomous driving is performed, and the shaft  223  of the reaction motor is coaxially connected to the steering shaft  203 . 
     The first member  241  is coupled to one side of the steering shaft  203  and the shaft  223  of the reaction motor so as to prevent rotation of the steering shaft  203 , and the third member  245  is coupled to the other side thereof, and the second member  243  and the ball member  251  are coupled between the first member  241  and the third member  245 . When a steering shaft torque that is greater than or equal to a reaction torque is generated in the shaft  223  of the reaction motor, the ball member  251  is supported in the engaging grooves  247   a  of the rotation-preventing member  247  so that rotation of the steering shaft  203  is stopped. 
     However, for convenience of explanation, an example, in which the first member  241  is coupled to the steering shaft  203  and the third member  245  is coupled to the shaft  223  of the reaction motor, is illustrated to be described. 
     The fixing grooves  241   a  formed in the axial direction are formed in an outer circumferential surface of one side end of the first member  241  coupled to the steering shaft  203 , and the fixing protrusions  243   a  of the second member  243  are coupled to the fixing grooves  241   a  so that the first member  241  and the second member  243  may be rotated as a single body. 
     The second member  243  is formed in a ring form, and the fixing protrusions  243   a  corresponding to the fixing grooves  241   a  of the first member  241  are axially formed in an inner circumferential surface of the second member  243  and coupled to the outside of the first member  241 , and the first support grooves  243   b  are formed in one side end of the second member  243  and are spaced apart from one another in the circumferential direction. 
     The second support grooves  245   b  are formed in positions of the third member  245  coupled to the shaft  223  of the reaction motor, which correspond to positions of the first support grooves  243   b  of the second member  243 . 
     Here, the first support grooves  243   b  are formed in a conical shape that is circularly in line contact with the ball member  251 , as shown in  FIGS. 10 and 11 . 
     Both sides of the second support grooves  245   b  are inclined so that widths thereof gradually increase from a surface facing one side end of the second member  243  to a radial outer circumferential surface of the second member  243 , and the ball member  251  is supported and inserted in the first support grooves  243   b  of the second member  243  and the second support grooves  245   b  of the third member  245 . 
     The rotation-preventing member  247  formed in a ring form and having the engaging grooves  247   a  formed in the inner circumferential surface thereof in the axial direction, is coupled to the outer circumferential surfaces of the second member  243  and the third member  245 . 
     Here, although not shown in the drawings, the rotation-preventing member  247  is fixed to the housing in which the steering shaft  203  is embedded, or a body of the car and is not rotated regardless of rotation of the first member  241 , the second member  243 , and the third member  245  and is fixed. 
     The first member  241  has an extension part  241   b  that is formed at one side end of the fixing grooves  241   a  based on a center part in which the fixing grooves  241   a  are formed, and extends in the axial direction, and a large-diameter part  241   c  formed at the other side end of the fixing grooves  241   a  and having an enlarged diameter. 
     An elastic member  249  is provided between the large-diameter part  241   c  of the first member  241  and the second member  243  and applies an elastic force in the axial direction so as to support the ball member  251  using the elastic force of the elastic member  249 . 
     Also, a coupling part  241   d  having a screw part therein is provided at an inner circumferential surface of the extension part  241   b  of the first member  241 , and the third member  245  has a through hole  245   a  in its inside so that a body part  248   b  of a fastening member  248  is coupled to the coupling part  241   d  of the first member  241  through the through hole  245   a.    
     Also, an engaging step  245   c  is formed at one side of the through hole  245   a  so that a head part  248   a  of the fastening member  248  is supported by the engaging step  245   c  and deviation of the fastening member  248  is prevented. 
     Because the fastening member  248  couples the first member  241  to the third member  245 , thereby adjusting a distance therebetween so that the elastic force of the elastic member  249  may be adjusted with a fastening amount of the fastening member  248 . 
     Thus, the first member  241 , the second member  243 , and the third member  245  are assembled to be operable on the same axis so that the elastic force of the elastic member  249  is set. 
     Here, two or more first support grooves  243   b  of the second member  243  and two or more second support grooves  245   b  of the third member  245  are spaced apart from one another in the circumferential direction. In the drawings, three first support grooves  243   b  and three second support grooves  245   b  are provided. In this case, the first support grooves  243   b  and the second support grooves  245   b  are disposed in the circumferential direction at equal intervals so that the ball member  251  is maintained in the axial direction with an equal support force. 
     In the steer-by-wire type steering apparatus according to the present embodiments, when rotation of the wheels  219  reaches a maximum point, or when the wheels  219  collide with a curbstone of a road and cannot be rotated any more, as described above, rotation of the steering shaft  203  is prevented. 
     That is, in a general steering condition, the elastic member  249  is maintained in a compressed state by a predetermined amount due to the fastening member  248 , and a rotation torque is transmitted from the steering shaft  203  to the shaft  223  of the reaction motor through the first member  241 , the second member  243 , and the third member  245 . 
     In this case, the ball member  251  is placed only in the first support grooves  243   b  and the second support grooves  245   b , as shown in  FIGS. 12 and 13 . When rotation of the steering shaft  203  should be prevented, as described above, i.e., when an excessive rotation torque that is greater than or equal to the reaction torque of the shaft  223  of the reaction motor is transmitted from the steering shaft  203 , due to a rotational force of the second member  243 , the ball member  251  is moved outward in a radial direction along both sides of the second support grooves  245   b  and is supported in the engaging grooves  247   a  of the rotation-preventing member  247  so that further rotation is limited. 
     That is, when the rotation torque transmitted from the steering shaft  203  to the second member  243  is excessive, the ball member  251  is moved outward in the radial direction along both inclined surfaces of the second support grooves  245   b  due to a component force of a force moving in the circumferential direction, and simultaneously, as the ball member  251  is moved from a center part of the first support grooves  243   b  outside, the second member  243  is moved in the axial direction by a difference in an axial movement amount of the ball member  251  and the elastic member  249  is further compressed. 
     Contrary to this, when the rotation torque is reduced, due to a restoration force of the elastic member  249 , the second member  243  is moved in the axial direction, and the ball member  251  is moved to the center part of the first support grooves  243   b  and simultaneously, the ball member  251  is moved to a position deviated from the engaging grooves  247   a  and is returned to the second support grooves  245   b.    
     Thus, when the elastic force of the elastic member  249  is set according to a design target value and a rotational force that is greater than or equal to a predetermined rotation torque value is transmitted, the second member  243  is rotated and is moved in the axial direction due to the elastic force of the elastic member  249  and radial movement of the ball member  251  is performed so that rotation of the steering shaft  203  may be prevented. 
     As described above, according to the present embodiments, when a driver generates a larger steering torque than a reaction torque of a reaction motor in a steering shaft in a steer-by-wire type steering apparatus, rotation of the steering shaft can be prevented. 
     As described above, although all elements that constitute the present embodiments are described as being coupled as one or operating while being coupled to one another, the present embodiments are not necessarily limited to these embodiments. That is, when all elements are within the scope of the purposes of the embodiments, all elements may also operate while being selectively coupled as one or more. 
     The above embodiments of the present disclosure have been described only for illustrative purposes, and those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the scope and spirit of the disclosure. Therefore, the embodiments of the present disclosure are not intended to limit, but are intended to illustrate the technical idea of the present disclosure, and the scope of the technical idea of the present disclosure is not limited to the embodiments. The scope of the present disclosure shall be construed on the basis of the accompanying claims in such a manner that all of the technical ideas included within the scope equivalent to the claims belong to the present disclosure.