Patent Publication Number: US-2007095597-A1

Title: Variable steering rack system

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0099161 filed in the Korean Intellectual Property Office on Oct. 20, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      (a) Field of the Invention  
      The present invention relates to a variable steering rack system. More particularly, the present invention relates to a variable steering rack system having less noise when the system is operating.  
      (b) Description of the Related Art  
      Generally, a variable steering rack system can regulate a maximum displacement of wheels of a vehicle when chains are mounted to tires of the vehicle.  
      Referring to  FIG. 1  and  FIG. 2 , according to the prior art, a steering system including a variable steering rack system includes a gear box  10 , a steering rack bar  19 , a stop knob  17 , a case  13 , a stopper  15 , a motor case  11 , a motor  21 , a motor gear  22 , and an intermediate gear  23 .  
      The motor case  11 , the stopper  15 , and the case  13  are orderly coupled to the gear box  10 , and a groove is formed on an interior circumference of the motor case  11 .  
      The stopper  15  is rotatable along the groove by the motor  21 .  
      The stop knob  17  is secured to the steering rack bar  19  and when the variable steering rack system is not operating, the stop knob  17  is inserted into an interior circumference of the stopper  15 .  
      When the variable steering rack system is operating, because the stopper  15  rotates corresponding to a movement of the steering rack bar  19 , the stop knob  17  is not inserted into the stopper  15 .  
      Therefore, the displacement of the steering rack bar  19  is restricted by as much as the thickness of the stopper  15 .  
      The motor  21  transmits a torque to an intermediate gear  23  and the intermediate gear  23  rotates the stopper  15 .  
      A stop protrusion  33  is formed in the groove of the interior circumference of the motor case  11  and a knob  31  is formed in the stopper  15 .  
      Therefore, as the stopper  15  rotates along the groove in the interior circumference of the case  11 , if the stop protrusion  33  contacts to the knob  31  of the stopper  15 , the stopper  15  stops rotating.  
      Generally, according to the prior art, because the motor  21  utilized in the variable steering rack system rotates at a high speed, a colliding sound is very loud when the stop protrusion  33  contacts with the knob  31  of the stopper  15 .  
      In addition, a moving range of the steering rack bar  19  can be controlled by as much as a displacement of the thickness of the stopper  15 .  
      The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.  
     SUMMARY OF THE INVENTION  
      The present invention has been made in an effort to provide a variable steering rack system having advantages of less noise and enhanced durability.  
      An exemplary variable steering rack system that can variably regulate a maximum displacement of a steering rack bar, according to a first embodiment of the present invention includes: a steering rack bar defining a stop protrusion at a predetermined position and moving by a power transmitted from a steering gear box; a case defining a first through-hole through which the steering rack bar penetrates; a stopper defining a second through-hole through which the steering rack bar penetrates, being engaged to an inner circumference of the first through-hole to be rotatable through a predetermined angle, and regulating a displacement of the steering rack bar as much as its thickness; a stopper housing connected to the case such that the stopper is disposed therebetween and defining a groove; an intermediate gear with a bar protruding therefrom that is inserted to the groove of the stopper, and rotating the stopper; and an operating portion operating the intermediate gear, wherein the groove of the stopper housing is configured to limit a movement of the bar such that the stopper rotates only as much as the predetermined angle.  
      A rubber layer is formed on at least a portion of an exterior circumference of the bar and is rotatable around the bar. A synthetic resin is coated on at least a portion of the surface of the stopper. The bar has a circular cross-section.  
      According to a second embodiment of the present invention, a variable steering rack system includes: a steering rack bar defining a stop protrusion and moving by a power transmitted from a steering gear box; a case defining a first through-hole through which the steering rack bar penetrates; a stopper defining a second penetration hole through which the steering rack bar penetrates, being engaged to an inner surface of the first penetration hole to be rotatable through a predetermined angle, and regulating a displacement of the steering rack bar as much as the predetermined thickness corresponding to the rotation thereof; a stopper housing connected to the case such that the stopper is disposed therebetween and defining a groove; an intermediate gear rotating the stopper; and an operating portion operating the intermediate gear.  
      The predetermined angle is preferably between 45° and 60°. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a steering system including a variable steering rack system according to the prior art.  
       FIG. 2  shows a variable steering rack system according to the prior art.  
       FIG. 3  shows a variable steering rack system according to a first exemplary embodiment of the present invention with the stopper housing removed for clarity.  
       FIG. 4  shows a variable steering rack system according to the first exemplary embodiment of the present invention.  
       FIG. 5  shows a steering rack bar and a stopper of the variable steering rack system according to embodiments of the present invention.  
       FIG. 6  shows a predetermined angle of a variable steering rack system according to a second exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.  
      Referring to  FIG. 3  to  FIG. 5 , embodiments of the variable steering rack system include a steering rack bar  301 , case  303 , a stopper  305 , a stopper housing  501 , an intermediate gear  307 , and an operating portion  309 .  
      The steering rack bar  301  defines a stop protrusion  403  at a predetermined position and moves by a power transmitted from a steering gear box  401 .  
      The case  303  defines a first through-hole  311  through which the steering rack bar  301  penetrates. The case  303  can be integrally formed with the gear box  401 . The stopper  305  defines a second through-hole  313  through which the steering rack bar  301  penetrates.  
      In addition, the stopper  305  is engaged to an inner circumference of the first through-hole  311  to be rotatable through a predetermined angle, and regulates a displacement of the steering rack bar  301  as much as the thickness of the stopper.  
      The stopper housing  501  is connected to the case  303  such that the stopper  305  is disposed therebetween. The stopper housing  501  defines a groove  503 .  
      The intermediate gear  307  is configured such that a bar  315 , perpendicularly formed thereto, is inserted to the groove  503  of the stopper housing  501  and rotates the stopper  305 . The operating portion  309  operates the intermediate gear  307 .  
      The groove  503  of the stopper housing  501  limits a movement of the bar  315  such that the stopper  305  rotates only as much as the predetermined angle.  
      As shown in  FIG. 5 , the steering rack bar  301  is movably connected to the gear box  401  and moves in an up and down direction in  FIG. 5  by a power transmitted from the gear box  401 .  
      The stopper  305  is rotatably connected to the interior circumference of the first penetration hole  311 , rotatable through the predetermined angle, and the stop protrusion  403  of the steering rack bar  301  may be inserted to the second penetration hole  313 .  
      That is, when the stop protrusion  403  is inserted to the second through-hole  313 , the range of motion of the steering rack bar  301  widens. If the stop protrusion  403  is not inserted to the stopper  305  so that the stopper  305  rotates as much as the predetermined angle, the range of motion of the steering rack bar  301  is limited by the thickness of the stopper  305 .  
      According to an exemplary embodiment of the present invention, the operating portion  309  may be a motor, and the operating portion  309  operates the intermediate gear  307 .  
      If the operating portion  309  rotates the intermediate gear  307 , the intermediate gear  307  rotates the stopper  305  by as much as the predetermined angle.  
      That is, the stop protrusion  403  of the steering rack bar  301  may be selectively inserted to the second through-hole  313  corresponding to the rotation of the stopper  305 .  
      Referring to  FIG. 3  and  FIG. 4 , the bar  315  is formed on the intermediate gear  307  and is coupled to the groove  503  of the stopper housing  501 . That is, the movement of the bar  315  is limited by the groove  503 . A detailed description of the groove  503  is provided later.  
      A rubber layer  317  is formed on at least a portion of an exterior circumference of the bar  315  such that the rubber layer  317  can rotate along the exterior circumference. More particularly, the rubber layer  317  is formed at a surface of the bar  315  which the groove  503  contacts. When the intermediate gear  307  rotates, the rubber layer  317  rotates along the groove  503 . Therefore, when the movement of the bar  315  is limited by the groove  503 , noise is prevented by the rubber layer  317 .  
      A synthetic resin  510  coats a surface of the stopper  305  where the stopper  305  contacts the stop protrusion  403  or the case  303 . Therefore, when the stop protrusion  403  of the steering rack bar  301  contacts the stopper  305  or the stopper  305  rotates through the predetermined angle, noise is reduced.  
      The bar  315  has a circular cross-section so that it can move more easily within the groove  503 .  
      Referring to  FIG. 6 , a variable steering rack system of a second exemplary embodiment of the present invention does not include the bar  315 , the rubber layer  317 , or the coated synthetic resin  5   10 .  
      In the second exemplary embodiment of the present invention, the stopper  305  stops in the same method as shown in  FIG. 2 ; that is, stopper  305  comprises a knob  31  (not shown in  FIG. 6 ) that contacts stop protrusion  33  (not shown in  FIG. 6 ) to stop the stopper  305  from rotating. However, the stopper  305  of the second exemplary embodiment of the present invention moves through an angle of between 45° and 60°. Because the angle that the stopper  305  rotates is small, the impact force when the knob  31  of the stopper  305  collides to the stop protrusion  33  is reduced. Therefore, noise of the impact force is reduced.  
      According to a result of an experiment, if the stopper  305  rotates 45°, about 27% of the noise is reduced and if the stopper  305  rotates 60°, about 10% of the noise is reduced.  
      According to the first exemplary embodiment of the present invention, when the variable steering rack system operates, the noise is reduced by the rubber layer and the synthetic resin coating. According to the second exemplary embodiment of the present invention, the noise is reduced by a decrease in the impact force of the stopper due to the small rotating angle of the stopper. Therefore, durability of the variable steering rack system may be enhanced.  
      While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.