Patent Publication Number: US-2023142494-A1

Title: Apparatus for use in turning steerable vehicle wheels

Description:
TECHNICAL FIELD 
     The present invention relates to an apparatus for use in turning steerable vehicle wheels and, more specifically, to a power steering apparatus for use in turning steerable wheels of a vehicle. 
     BACKGROUND 
     A known steering apparatus includes a steering member which is rotatable to effect turning movement of steerable vehicle wheels. A ball nut is connected with an externally threaded portion of the steering member. The steering member is rotatable relative to the ball nut assembly to axially move the ball nut assembly relative to the housing. An electric motor is operable to apply a rotational force to the steering member to urge the steering member to rotate relative to the housing. The electric motor has an output shaft extending generally perpendicular to the axis of the steering member. 
     SUMMARY 
     An apparatus for use in turning at least one steerable vehicle wheel includes a steering member rotatably supported in a housing. The steering member rotates relative to the housing about a first axis to effect turning movement of the at least one steerable vehicle wheel. A ball nut is connected with an externally threaded portion of the steering member. The steering member is rotatable relative to the ball nut assembly to axially move the ball nut assembly relative to the housing. An electric motor is operable to apply a rotational force to the steering member to urge the steering member to rotate relative to the housing. The electric motor has an output shaft extending along a second axis extending generally parallel to the first axis. A first gear is rotatable about the second axis with the output shaft of the motor. A second gear in meshing engagement with the first gear is rotatable about a third axis extending transverse to the second axis. A third gear is rotatable with the second gear about the third axis. A fourth gear in meshing engagement with the third gear is rotatable with the steering member relative to the housing gear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding, reference may be made to the accompanying drawings, which are not to scale unless explicitly noted as such in the below description, and in which: 
         FIG.  1    is a schematic pictorial view of a steering apparatus constructed in accordance with the present invention; 
         FIG.  2    is a schematic pictorial view of the steering apparatus of  FIG.  1    with portions removed; and 
         FIG.  3    is a schematic sectional view of a portion of the steering apparatus of  FIG.  1   . 
     
    
    
     DESCRIPTION OF ASPECTS OF THE DISCLOSURE 
     An apparatus  10  for use in turning steerable vehicle wheels  12  constructed in accordance with the present invention is illustrated in  FIGS.  1 - 3   . The apparatus  10  ( FIG.  3   ) includes an input shaft  14  which may be operably connected to a steering wheel  16 . The input shaft  14  is supported by bearings  20  and  22  for rotation about an axis  24  of the input shaft relative to a housing  26 . Upon rotation of the steering wheel  16 , force is transmitted through the input shaft  14  to cause rotation of the input shaft relative to the housing  26 . Although the input shaft  14  is described as being connected to a steering wheel  16 , it is contemplated that the input shaft may be rotated relative to the housing  26  by a motor. 
     The input shaft  14  is connected to a first end of a torsion bar  30 . A second end of the torsion bar  30  is connected to an externally threaded steering member  32 . The externally threaded steering member  32  is coaxial with the input shaft  14  and supported by the bearings  22  and bearings  34  for rotation about the axis  24 . Therefore, rotation of the input shaft  14  is transferred to the steering member  32 . The torsion bar  30  permits relative rotation between the input shaft  14  and the steering member  32 . Although the apparatus  10  is described as including a torsion bar  30  that permits relative rotation between the input shaft  14  and the steering member  32 , it is contemplated that the steering member  32  may be directly connected to the input shaft  14 . 
     A ball nut  38  extends around an externally threaded portion of the rotatable steering member  32 . A plurality of balls  40  interconnects the externally threaded portion of the steering member  32  with an internally threaded portion of the ball nut  38 . The ball nut  38  is prevented from rotating relative to the housing  26  so that rotation of the steering member  32  causes axial movement of the ball nut relative to the housing and the steering member  32 . 
     A series of rack teeth  46  is formed on the periphery of the ball nut  38 . The rack teeth  46  mesh with teeth  48  formed on a sector gear  50  that is connected with the steerable vehicle wheels  12  by a steering linkage  52 . An output shaft  54  may interconnect the sector gear  50  and the steering linkage  52 . When the ball nut  38  moves axially, the rack teeth  46  interact with the teeth  48  of the sector gear  50  to rotate the sector gear and output shaft  54  and turn the steerable vehicle wheels  12  in a known manner. 
     A reversible electric motor  60  ( FIGS.  1 - 2   ) is operable to apply a rotational force to the steering member  32  to urge the steering member to rotate relative to the housing  26 . The electric motor  60  ( FIG.  2   ) has an output shaft  62  connected to a first gear  64 . The output shaft  62  of the motor  60  extends along an axis  66  so that the motor rotates the first gear  64  about the axis  66 . The axis  66  extends generally parallel to the axis  24  of the input shaft  14  and steering member  32 . The first gear  64  may be a miter gear. The first gear  64  is in meshing engagement with a second gear  70 . The second gear  70  is supported for rotation about an axis  72  that extends generally transverse to the axis  66 . It is contemplated that the axis  72  may extend perpendicular to the axis  66 . The second gear  70  may be a miter gear. 
     A third gear  78  may be connected to the second gear  70 . The third gear  78  rotates about the axis  72  with the second gear  70 . The third gear  78  may be a worm gear that is in meshing engagement with a fourth gear  82 , such as a worm wheel. The fourth gear  82  ( FIG.  3   ) may be connected to the steering member  32  and be supported for rotation about the axis  24  by the bearing  34 . The first gear  64 , second gear  70 , third gear  78  and fourth gear  82  transmit force to the steering member  32  to urge the steering member to rotate about the axis  24  during operation of the motor  60 . The first, second, third and fourth gears  64 ,  70 ,  78  and  82  permit the motor  60  to be located at any desired position around the axis  24  of the steering member  32  and the housing  26 . The motor  60  may be located with the axis  66  of the motor extending parallel to the axis  24  at any desired position about the axis  24  since the third gear  78  may be located around the axis  24 . 
     A gear box  90  ( FIG.  1   ) may interconnect the motor  60  and housing  26 . The gear box  90  may support the second and third gears  70 ,  78  for rotation about the axis  72 . A cover  92  may be connected to the gear box  90 . Although a specific gear box  90  is shown in  FIG.  1   , the gear box may have any desired construction for a desired location of the motor  60  relative to the housing  26 . 
     The apparatus  10  ( FIG.  1   ) may include vehicle condition sensors and an electronic control unit for controlling the motor  60  based on sensed vehicle conditions. The vehicle condition sensors may include a torque sensor and a position sensor electrically connected to the ECU. The torque sensor may sense the torque applied to the steering wheel  16  and generate a signal indicative of the torque. The position sensor may sense the rotational position of the steering wheel  16  and generate an electrical signal indicative of the steering wheel position. The electrical signals from the torque sensor and the position sensor are sent to the ECU. The ECU analyzes the output of the sensors and effects operation of the motor  60  as a function of the output of the sensors. In addition, the ECU may have inputs which vary as a function of sensed lateral acceleration of the vehicle or other vehicle operating conditions. The ECU receives the signals generated by the sensors and actuates the motor  60  in order to apply a rotational force to the steering member  32  to assist in turning of the steerable vehicle wheels  12 . 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.