Patent Publication Number: US-2007116395-A1

Title: Ball bearing

Description:
BACKGROUND OF THE INVENTION  
      This invention relates to a ball bearing such as a deep groove ball bearing or an angular ball bearing.  
      A wide variety of retainers are used in ball bearings such as deep groove ball bearings and angular ball bearings. Such retainers include a crown-shaped one having a plurality of bridges extending from an annular portion in one axial direction of the bearing and defining pockets therebetween, one having a pair of annular portions on its both sides which are connected to each other by a plurality of bridges defining pockets therebetween, and one formed by a pair of annular members each comprising hemispherical pockets and connecting portions provided between the adjacent hemispherical pockets, and connected together at the connecting portions. Many of such retainers have circular pockets (with a discontinuous portion for crown-shaped retainers). Equal spaces are provided between such pockets and the balls in the rotational and axial directions of the bearing.  
      Some retainers include elliptical pockets, defining smaller and larger spaces in the axial and rotational directions of the bearing, respectively, between the pockets and the balls, so as to increase the contact area between the balls and the pockets, thereby reducing the contact pressure therebetween (for example, see Japanese patent publication 58-180839).  
      In a ball bearing which supports a rotary shaft which is frequently subjected to acceleration and deceleration, such as a speed change shaft mounted in an automotive transmission, the balls in the pockets rotate alternately faster and slower than the retainer at short intervals. Thus, if the retainer has circular pockets, the balls tend to repeatedly collide against the retainer. This may damage the retainer.  
      As a countermeasure against the above-mentioned problem, the retainer may have elliptical pockets to define larger spaces in the rotational direction as disclosed in Japanese patent publication 58-180839. However, in this case, if the spaces in the rotational direction are not large enough, the frequency of collisions might not decrease sufficiently.  
      If the spaces in the rotational direction are too large, the pockets account for a larger part of the retainer in the rotational direction. This reduces the sectional area of the bridges defined between the pockets (if such bridges are actually defined between the pockets) and thus the stiffness thereof. In the case of a retainer formed by two annular members including hemispherical pockets and connecting portions provided between the adjacent hemispherical pockets and connected together at the connecting portions, the connecting spaces at the connecting portions tend to be insufficient. The number of pockets may be decreased to prevent such a problem. However, in this case, the number of balls and thus the load capacity of the bearing also decrease.  
      An object of the present invention is to reduce collisions between the retainer and the balls even though the balls rotate alternately faster and slower than the retainer at short intervals, without decreasing the stiffness of the bridges of the retainer or the connecting spaces at the connecting portions.  
     SUMMARY OF THE INVENTION  
      According to the present invention, there is provided a ball bearing comprising an inner ring having a raceway groove, an outer ring having a raceway groove, a plurality of balls disposed between the raceway grooves, and a retainer retaining the balls in pockets formed in the retainer, wherein the pockets of the retainer are elliptical pockets with or without a discontinuous portion, whereby spaces in the rotational direction of the ball bearing are defined between the pockets and the balls, the spaces being 4-10% of the diameter of the balls.  
      More specifically, the ball bearing according to the present invention comprises the retainer having the pockets which are elliptical or elliptical with a discontinuous portion to receive the balls, and the spaces are provided between the pockets and the balls in the rotational direction of the bearing, the spaces being designed to account for 4-10%, preferably 6-10%, of the diameter of the balls, so as to reduce collisions between the retainer and the balls even though the balls rotate alternately faster and slower than the retainer at short intervals, without reducing the stiffness of the bridges of the retainer or the connecting spaces at the connecting portions.  
      The pockets in the rotational direction account for not less than 4%, preferably not less than 6%, of the diameter of the balls, based on a calculation result which has shown that the maximum distance by which the balls rotate relative to the retainer was 4-6% of the diameter of the balls when a speed change shaft of an automotive transmission supported by the ball bearing was accelerated and decelerated. The spaces in the rotational direction defined between the pockets and the balls are determined not to exceed 10% of the diameter of the balls, because otherwise the sectional area of the bridges and thus their stiffness decrease if the retainer has such bridges between the pockets, and if the retainer comprises a pair of annular members having hemispherical pockets and connecting portions provided between the adjacent pockets, and connected together at the connecting portions, the connecting spaces at the connecting portions tend to be insufficient.  
      The retainer may be formed by pressing a metal sheet.  
      Alternatively, the retainer may be formed by injection molding of resin.  
      Further alternatively, the retainer may be formed by cutting a metal material or a resin material.  
      The ball bearing according to the present invention is preferably used to support a speed change shaft mounted in an automotive transmission.  
      The ball bearing according to the present invention comprises the retainer having the pockets which are elliptical or elliptical with a discontinuous portion to receive the balls, and the spaces are provided between the pockets and the balls in the rotational direction of the bearing, the spaces being 4-10%, preferably 6-10%, of the diameter of the balls. With this arrangement, it is possible to reduce collisions between the balls and the retainer, without reducing the stiffness of the bridges of the retainer or the connecting spaces at the connecting portions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a vertical sectional view of a ball bearing according to a first embodiment of the present invention;  
       FIG. 1B  is a partial developed plan view of a retainer of the ball bearing of  FIG. 1A ;  
       FIG. 2  is a vertical sectional schematic view of an automotive transmission in which the ball bearing shown in  FIG. 1A  is used;  
       FIG. 3A  is a vertical sectional view of a ball bearing according to a second embodiment of the present invention;  
       FIG. 3B  is a partial developed plan view of a retainer of the ball bearing of  FIG. 3A ;  
       FIG. 4A  is a vertical sectional view of a ball bearing according to a third embodiment of the present invention;  
       FIG. 4B  is a partial developed plan view of a retainer of the ball bearing of  FIG. 4A ;  
       FIG. 5A  is a vertical sectional view of a ball bearing according to a fourth embodiment of the present invention; and  
       FIG. 5B  is a partial developed plan view of a retainer shown in  5 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Now referring to the drawings,  FIGS. 1A and 1B  show a ball bearing according to the first embodiment of this invention. It is an angular ball bearing  1  comprising an inner ring  2  having a raceway groove  2   a , an inner ring  3  having a raceway groove  3   a , a plurality of balls  4  disposed between the raceway grooves  2   a  and  3   a , and a retainer  5  retaining the balls  4 . A countersink  3   b  is formed in the outer ring  3  on one side of the raceway groove  3   a.    
      The retainer  5  is an annular member formed by pressing a metal sheet and has pockets  5   a  formed by punching. The balls  4  are each received in one of the pockets  5   a . The retainer  5  includes annular portions formed on both sides of the pockets  5   a  and connected to each other by bridges  5   b  defined between the adjacent pockets. A flange  5   c  is provided on one of the annular portions for reinforcement. The pockets  5   a  of the retainer  5  are elliptical ones with their major axis extending in the rotational direction of the bearing. Spaces δ are defined in the rotational direction between the pockets  5  and the balls  4 . The spaces δ are 6-10% of the diameter D of the balls  4 .  
       FIG. 2  shows a transmission  21  for an automobile in which angular ball bearings  1  of the first embodiment are used. The transmission  21  comprises a first speed change shaft  23  to which the power of an engine  22  is transmitted through a clutch, and a second speed change shaft  24  which transmits the engine power to the wheels. The speed change shafts  23  and  24 , to which a plurality of transmission gears  23   a  and  24   a  are respectively mounted, have both ends thereof supported by the angular ball bearings  1 .  
       FIGS. 3A and 3B  show the second embodiment of this invention. The ball bearing  1  of this embodiment is an angular ball bearing as with the first embodiment, and includes a retainer  5 . The retainer  5  is formed by injection molding of resin, and includes annular portions on both sides of elliptical pockets  5   a  and connected to each other by bridges  5   b  defined between the adjacent pockets. As with the first embodiment, spaces δ in the rotational direction defined between the elliptical pockets  5   a  and balls  4  are 6-10% of the diameter of the balls  4 .  
       FIGS. 4A and 4B  show the third embodiment of this invention. The ball bearing  1  of this embodiment is a deep groove ball bearing and includes a retainer  5 . The retainer  5  retains a plurality of balls  4  disposed between a raceway groove  2   a  of an inner ring  2  and a raceway groove  3   a  of an outer ring  3 . The retainer  5  comprises a pair of annular members. Each annular member is formed by pressing a metal sheet, and includes hemispherical recesses  5   d  and connecting portions  5   e  provided between the adjacent recesses  5   d . The respective hemispherical recesses  5   d  of one annular member face their counterparts of the other annular member so as to define pockets  5   a . The two annular members are connected to each other by studs  5   f  at the connecting portions  5   e . The pockets  5   a  defined by the recesses  5   d  are elliptical, and spaces δ in the rotational direction of the bearing are provided between the pockets  5   a  and the balls  4 . The spaces δ are 6-10% of the diameter of the balls  4  as with the first embodiment.  
       FIGS. 5A and 5B  show the fourth embodiment of this invention. The ball bearing of this embodiment is a deep groove ball bearing as with the third embodiment, and includes a retainer  5  formed by cutting a metal material. The retainer  5  comprises an annular portion and a plurality of bridges  5   b  extending from the annular portion in one axial direction of the bearing. Pockets  5   a  are defined between the adjacent bridges  5   b . Thus, the retainer  5  is crown-shaped as a whole. The pockets  5   a  are elliptical with a discontinuous portion. Spaces δ in the rotational direction of the bearing are defined between the pockets  5  and the balls  4 . The spaces δ are 6-10% of the diameter of the balls  4  as with the first embodiment.  
      In each of the above-mentioned embodiments, the spaces δ in the rotational direction of the bearing disposed between the pockets and the balls are 6-10% of the diameter D of the balls  4 . Alternatively, the spaces δ may account for 4-6% of the diameter D of the balls  4 .