Ceramic bearing construction

#The present invention relates to construction between a rotating metal shaft and an inner race of a ceramic bearing to be used in aircraft engines and other industrial rotary machines.

#In the fields of aircraft engines and other industrial rotary machines, ceramic bearings have been proposed for use under high temperature and high-velocity severe operating conditions.

#FIG. 1 shows one example of conventional ceramic bearings. A ceramic bearing d comprises an inner race b, an outer race c and a plurality of balls a interposed between the races b and c and is mounted to a metal shaft e. Metal taper rings f are interposed between the ceramic inner race b and the metal shaft e so as to absorb difference in thermal expansion between assembling and operation of the ceramic bearing to thereby prevent cracking of the latter.

#FIG. 1 is a sectional side view of a conventional ceramic bearing;

#FIG. 2 is a sectional side view of a preferred embodiment of the present invention;

#FIG. 3 is a sectional view taken along line III--III in FIG. 2;

#Referring to FIGS. 2 and 3, a preferred embodiment of the present invention will be described. A ceramic bearing 4 comprises a ceramic inner race 2, a ceramic outer race 3 and a plurality of balls 1 interposed therebetween and is shrinkage-fitted over a metal shaft 5 to be securely held in position. More specifically, for prevention of the ceramic inner race 2 from being separated away from the metal shaft 5 during assembling or operation, the outer diameter of the metal shaft 5 is selected to be slightly greater than the inner diameter of the ceramic inner race 2 and they are assembled to each other by heating the ceramic bearing 4 and then fitting the same over the metal shaft 5.

#In this case, a plurality of equidistantly spaced-apart grooves 6 are previously machined in parallel with the axis of the metal shaft 5 on the outer periphery of the metal shaft 5 and/or on the inner periphery of the ceramic inner race 2 and then the ceramic bearing 4 is shrinkage-fitted over the metal shaft 5.

#The grooves 6 may be in the form of serrations, knurls, teeth, screw threads, cross stripes and the like. FIGS. 4(A) and 4(B) show the cases where the grooves 6 in the form of screw threads are formed on the outer periphery of the metal shaft 5 and on the inner surface of the ceramic inner race 2, respectively. FIGS. 5(A) and 5(B) show the cases where the grooves 6 in the form of cross stripes are formed on the outer periphery of the metal shaft 5 and on the inner periphery of the ceramic inner race 2, respectively.