Patent Publication Number: US-2011053695-A1

Title: Shudderless inboard constant velocity joint

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to low-friction inboard constant velocity joints and, more particularly, to a low-friction inboard constant velocity joint, which can reduce the friction and joint axial force generated during operation, thus realizing improved anti-NVH (Noise, Vibration and Harshness) performance. 
     2. Description of the Related Art 
     Generally, as shown in  FIG. 1 , a tripod CV (Constant Velocity) joint comprises an outer race  10  integrally connected to a stub shaft  11 , a trunnion  18  inserted into an inner track of the outer race  10  and spline-coupled to a half shaft, thus transmitting power to the half shaft, and a roller assembly  13  fitted over each of three journals  20  of the trunnion  13  and absorbing relative movement generated between an associated track  12  of the outer race  10  and the journal  20  of the trunnion  18 . 
     When the half shaft is inclined relative to the stub shaft  11  during operation of the tripod CV joint, relative movement is generated between the track  12  of the outer race  10 , the trunnion  18  and the roller assemblies  13 , thus generating a friction force between them. The friction force generates an axial force in an axial direction of the half shaft. The axial force has three peak values per one revolution of the tripod CV joint. 
     When a high load acts on the CV joint, for example, due to a quick start of a vehicle or when the joint angle formed between the stub shaft and the half shaft is at a high angle, the axial force is increased and causes the vehicle to shudder in a transverse direction. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art and the present invention is intended to propose a shudderless inboard CV joint, which has both oil storage chambers formed around an upper portion of each track of an outer race and around a journal of a trunnion and an oil groove formed along a circumference of an outer ring of each roller assembly, wherein oil is supplied both to the oil storage chambers and to the oil grooves, thus reducing the frictional resistance formed between the track and the outer ring and between an inner ring and the trunnion journal. 
     According to one aspect of the present invention, there is provided a shudderless inboard CV joint, comprising: an outer race connected to a first shaft and having a plurality of tracks therein; a trunnion connected to a second shaft and having a plurality of journals protruding in radial directions; and a roller assembly having both an inner ring fitted over each of the journals of the trunnion and an outer ring engaging with each of the tracks of the outer race so as to move in an axial direction of the track, the inner and outer rings being arranged concentrically, wherein an oil storage chamber is formed around an upper portion of each of the tracks and oil is supplied to the oil storage chamber, thus reducing a friction formed between the track and the outer ring. 
     The shudderless inboard CV joint, according to the present invention, has the following advantages. 
     1. Due to the oil storage chamber formed around the upper portion of each track of the outer race, oil can easily flow in the frictional contact junction between the tract and the outer ring, thus realizing maximum lubrication effects. 
     2. Round surface parts formed in the outer circumferential surface of the outer ring come into two-point contact with the track, thus stably maintaining horizontality of the rollers during the rolling of the rollers. 
     3. The oil groove formed along the circumference of the outer ring can reduce the frictional resistance formed between the outer ring and the track. 
     4. Each of the trunnion journals has wide angle portions and narrow angle portions, so that the shudderless inboard CV joint can maintain the stable situation of the roller assembly under a high load. 
     5. Due to the oil storage chamber formed around each of the trunnion journals, the shudderless inboard CV joint can reduce the frictional resistance formed between the inner ring and the journal. 
     Therefore, the shudderless inboard CV joint of the present invention can reduce both the frictional resistance and the axial force formed by relative movement between the trunnion journals, the inner rings, the outer rings and the tracks, thus realizing improved anti-NVH (Noise, Vibration and Harshness) performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view illustrating an assembly of an outer race and a trunnion of a shudderless inboard CV joint according to an embodiment of the present invention; 
         FIG. 2  is a perspective view of the assembly of  FIG. 1  after being assembled; 
         FIG. 3  is a sectional view illustrating an action of the shudderless inboard CV joint of  FIG. 2  when shafts joined to the joint are inclined to each other; 
         FIG. 4  is a view of the shudderless inboard CV joint of  FIG. 2 , viewed in a front view and in a partially enlarged view; 
         FIG. 5  is a perspective view of the trunnion shown in  FIG. 1 ; 
         FIG. 6  is a front view of  FIG. 5 ; 
         FIG. 7  is a partially enlarged view of one trunnion journal shown in  FIG. 6 ; 
         FIG. 8  is a sectional view taken along line Y-Y of  FIG. 7 ; 
         FIG. 9  is a sectional view taken along line X-X of  FIG. 1 ; 
         FIG. 10  is a partially sectioned view of a roller assembly shown in  FIG. 1 ; and 
         FIG. 11  is a partially enlarged view of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinbelow, a shudderless inboard CV joint according to an embodiment of the invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view illustrating an assembly of an outer race and a trunnion of a shudderless inboard CV joint according to an embodiment of the present invention.  FIG. 2  is a perspective view of the assembly of  FIG. 1  after being assembled.  FIG. 3  is a sectional view illustrating an action of the shudderless inboard CV joint of  FIG. 2  when shafts joined to the joint are inclined to each other.  FIG. 4  is a view of the shudderless inboard CV joint of  FIG. 2 , viewed in a front view and in a partially enlarged view.  FIG. 5  is a perspective view of the trunnion shown in  FIG. 1 .  FIG. 6  is a front view of  FIG. 5 .  FIG. 7  is a partially enlarged view of one trunnion journal shown in  FIG. 6 .  FIG. 8  is a sectional view taken along line Y-Y of  FIG. 7 .  FIG. 9  is a sectional view taken along line X-X of  FIG. 1 .  FIG. 10  is a partially sectioned view of a roller assembly shown in  FIG. 1 .  FIG. 11  is a partially enlarged view of  FIG. 4 . 
     The present invention provides a CV (Constant Velocity) joint which can transmit a rotational force at a constant velocity regardless of a joint angle between shafts. Particularly, the present invention provides a shudderless inboard CV joint which can realize improved anti-NVH (Noise, Vibration and Harshness) performance. 
     The shudderless inboard CV joint (sometimes so-called “LSJ (Least Shudder Joint)”) is a CV joint which can reduce both the friction and a joint axial force generated by relative movement formed between an outer race  10  and a trunnion assembly, thus minimizing the transverse shudder of a vehicle. 
     The shudderless inboard CV joint (LSJ) according to an embodiment of the present invention comprises an outer race  10  and a trunnion assembly and transmits a rotational force of a first shaft to a second shaft at a constant velocity regardless of the joint angle formed between the two shafts. 
     The outer race  10  is integrated with a stub shaft  11  (first shaft) such that the outer race  10  can rotate along with the stub shaft  11  at the same time. Three tracks  12  are axially formed in the outer race  10  at angularly spaced locations such that respective roller assemblies  13  of the trunnion assembly seated in the tracks  12  can rotatably move in axial directions of the tracks  12 . 
     Describing in detail the structure of each track  12 , as shown in  FIG. 4  and  FIG. 11 , the three tracks  12  are angularly spaced apart from each other in the outer race  10  at angles of 120°. Each of the tracks  12  comprises a curved portion S formed in each side surface of the track  12  and having both a predetermined radius R of curvature and a predetermined height, and a rectilineal portion T extending from an upper end of the curved portion S in a direction tangent to the curved portion S at a predetermined angle. 
     Here, the curved portion S is brought into curved-surface contact with an outer ring  14  of a roller assembly  13  which will be described later herein. The rectilineal portion T forms an oil storage chamber  22  around the upper portion of the track  12 , thus supplying oil to the upper portion of the track  12  and reducing the friction force generated by relative movement between the track  12  and the outer ring  14 . 
     The trunnion assembly is inserted into the outer race  10  and functions to transmit a rotational force, and comprises a trunnion  18  and a roller assembly  13 . 
     The trunnion  18  is spline-coupled to a half shaft  21 , so that, when the half shaft  21  rotates, the trunnion  18  is rotated in the same direction. 
     The trunnion  18  comprises a retaining ring  19  for receiving the half shaft  21  therein and three journals  20 , which protrude outwards from the circumference of the retaining ring  19  in radial directions. The retaining ring  19  has a shaft hole therein to be spline-coupled to the half shaft  21 . 
     Each of the journals  20  of the trunnion  18  comprises round-shaped wide angle portions  20   a  formed on the left and right ends of the journal  20  at locations placed on torque transmission axes, as shown in  FIG. 7 , round-shaped narrow angle portions  20   b  formed on the front and rear ends of the journal  20  at locations perpendicular to the torque transmission axes, as shown in  FIG. 8 , and recess portions  20   c  extending between the wide angle portions  20   a  and the narrow angle portions  20   b.    
     The wide angle portions  20   a  have respective curved surfaces, which have a width W and a radius Ra of curvature based on respective centers offset by a predetermined distance from a central axis of the journal  20  in opposite directions. The maximum distance A between ends of the wide angle portions  20   a  is defined along the major axis of an ellipse formed by the two offset centers. The wide angle portions  20   a  coincide with the curve of the ellipse. 
     Here, the ratio of Ra to A/2 is expressed by the equation Ra=(0.982˜0.998)A/2. 
     The narrow angle portions  20   b  form the ellipse in cooperation with the wide angle portions  20   a  and has a width N (N&lt;W). The narrow angle portions  20   b  coincide with the curve of the ellipse. The maximum distance B between ends of the narrow angle portions  20   b  is defined along the minor axis of the ellipse. 
     The major axis of the ellipse is aligned with the torque transmission axes, while the minor axis of the ellipse is perpendicular to the torque transmission axes. The length difference A−B between the major axis A and the minor axis B of the ellipse is 0.02˜0.05 mm. 
     As described above, both the wide angle portions  20   a  and the narrow angle portions  20   b  of the journal  20  have respective round shapes, so that, when the journal  20  is in contact with an inner ring  16  of the roller assembly  13  which will be described later herein, the round portions  20   a  and  20   b  can stably maintain horizontality of the roller assembly  13  (see  FIG. 3 ). 
     Further, the recess portions  20   c  connect the wide angle portions  20   a  to the narrow angle portions  20   b  and four recess portions  20   c  are formed at four locations such that the recess portions  20   c  are not in contact with the inner ring  16  of the roller assembly  13 . Defined between the inner ring  16  and the recess portions  20   c  are oil storage chambers  23 . Lubrication oil is supplied to the oil storage chambers  23 , thus reducing the frictional resistance formed between the journal  20  and the inner ring  16  and realizing an increased lubrication performance of the shudderless inboard CV joint. 
     In the embodiment, each of the recess portions  20   c  has a rectilineal surface as shown in the drawings. However, it should be understood that the recess portions may be formed as curved surfaces without affecting the functioning of the present invention. 
     The roller assembly  13  functions to transmit a rotational force from the trunnion  18  to the outer race  10  and comprises an outer ring  14 , a needle bearing  15 , an inner ring  16  and a retainer  17 . 
     Described in detail, as shown in  FIG. 10 , the outer ring  14  has a round-shaped appearance and comprises round surface parts  14   b  having a radius r of curvature based on respective centers offset by a predetermined distance d/2 from the diametrical axis of the outer ring  14  in opposite directions, and a circumferential oil groove  14   a  formed along the circumference of the outer surface of the outer ring  14 , along which the round surface parts  14   b  meet together. 
     The roller assembly  13  transmits torque to the outer race  10  in a state in which round surface parts  14   b  formed in upper and lower portions of the outer circumferential surface of the outer ring  14  are in two-point contact with the track  12  of the outer race  10 , so that the CV joint of the present invention can stably maintain the horizontality of the outer ring  14  in a rolling direction and can reduce contact stress between the track  12  and the outer ring  14 . 
     Further, oil can be supplied to the oil groove  14   a  formed along the circumference of the outer surface of the outer ring  14 , thus reducing the frictional resistance formed between the outer ring  14  and the track  12  of the outer race  10  and realizing an increased lubrication performance of the shudderless inboard CV joint. 
     A needle bearing  15  is installed between the inner ring  16  and the outer ring  14  and is retained in a desired location inside the outer ring  14  by the retainer  17 , thus controlling relative movement between the inner ring  16  and the outer ring  14 . 
     The inner ring  16  is in contact with the journal  20  of the trunnion  18 . Described in detail, an inner rectilineal surface of the inner ring  16  is in contact with the round outer surface of the trunnion journal  20 , so that, even when the trunnion journal  20  is tilted in the track  12  at an angle, the roller assembly  13  can maintain horizontality thereof. 
     The operational effect of the shudderless inboard CV joint according to the embodiment of the present invention will be described hereinbelow. 
     When the half shaft  21  rotates, the trunnion  18  spline-coupled to the half shaft  21  rotates in the same direction. Thus, the roller assembly  13  assembled with the trunnion journal  20  rotates in a torque transmitting direction, so that the outer race  10  engaged with the roller assembly  13  rotates. Therefore, a stub shaft  11  integrally connected to the outer race  10  is rotated. 
     When the joint is angled, that is, when the half shaft  21  is inclined relative to the stub shaft  11  at an angle of inclination, the trunnion journal  20  is tilted from the inner ring  16  of the roller assembly  13  at a tilting angle. 
     Here, the roller assembly  13  transmits the torque to the outer race  10  in a state in which the round surface parts  14   b  of the outer ring  14  are in two-point contact with the track  12  of the outer race  10 , so that the roller assembly  13  can stably maintain horizontality thereof and can reduce contact stress during the rolling thereof in which the roller assembly  13  rolls and moves in an axial direction of the track  12 . 
     In the shudderless inboard CV joint, oil contained in the oil groove  14   a  formed along the circumference of the outer ring  14  can reduce the frictional resistance formed between the outer ring  14  and the track  12  of the outer race  10 , thus improving lubrication performance of the CV joint. 
     Further, oil contained in the four oil storage chambers  23  defined by the recess portions  20   c  of the trunnion journal  20  can reduce the frictional resistance formed between the inner ring  16  and the trunnion journal  20 , so that the lubrication performance of the CV joint can be further improved. 
     Further, oil contained in the oil storage chamber  22  defined by the rectilineal portion T of the track  12  can reduce the frictional resistance formed between the track  12  of the outer race  10  and the outer ring  14 , thus further improving lubrication performance of the CV joint. 
     Described again, the oil supplied both to the oil storage chamber  22  defined by the track  12  and to the oil groove  14   a  of the outer ring  14  can reduce the frictional resistance formed between the track  12  and the outer ring  14 , and the oil supplied to the oil storage chambers  23  defined by the trunnion journal  20  can reduce the frictional resistance formed between the inner ring  16  and the trunnion journal  20 . Thus, the shudderless inboard CV joint of the present invention can reduce the axial force of the half shaft  21  and the stub shaft  11 , thereby realizing improved anti-NVH performance. 
     Although preferred embodiments of the present invention have been described 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 invention as disclosed in the accompanying claims.