| 摘要 |
A homokinetic universal joint has an outer ring (1) formed in its inner periphery with three axially extending cylindrical track grooves (2) and a tripod member (3) mounted in the outer ring (1) and having three trunnions (4) extending radially so as to be inserted in the track grooves (2). A guide roller (5) is mounted on each trunnion (4) through needle rollers (8) so as to be engaged in each track groove (2). Each needle roller (8) or each guide roller (5) is formed with minute recesses arranged at random so that an RMS(L) IRMS(C) ratio will not be more than 1.0 wherein RMS(L) and RMS(C) are surface roughness values in the longitudinal and circumferential directions, respectively. An SK value, another surface roughness parameter, is set to be not more than -1.5. Each minute recess should have an average area of 35 to 150 square microns, the area ratio of the minute recesses to the entire surface being 10 to 40%. <IMAGE>
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