次に、図４〜５は、本発明の実施の形態の第２例を示している。本例の場合、保持器２０ａの各凸部２６ａ、２６ａの円周方向に亙る断面形状を、略Ｖ字状に形成している。即ち、これら各凸部２６ａ、２６ａの内周面に、軸２１の円筒面と摺接する上記凸部２６ａ、２６ａの先端部から円周方向一端側（図４〜５の反時計方向側）に向かってこの円筒面から緩やかに離れていく緩斜面部２８、２８と、同じく上記先端部から円周方向他端側（図４〜５の反時計方向側）に向かってこの円筒面から急に離れていく急斜面部２９、２９とを、それぞれ形成している。この為、図４に示す様に、外輪１８ａに対して軸２１が反時計方向に相対回転してロック状態になる際に、上記急斜面部２９、２９が上記軸２１の円筒面からの力を受け易い。従って、上記保持器２０ａが上記軸２１に確実に追従し、ロック状態を実現できる。一方、図５に示す様に、外輪１８ａに対して軸２１が時計方向に相対回転するオーバラン状態の際には、上記緩斜面部２８、２８と上記軸２１の円筒面とのくさび効果により、グリースその他の潤滑油等の潤滑剤を上記保持器２０ａと上記軸２１との間に効率よく取り込める。この為、オーバラン時に、上記各凸部２６ａ、２６ａと軸２１の外周面との間に作用する摩擦力を低減できる。その他の構造及び作用は、前述した第一例の場合と同様である。
Next, FIGS. 4 to 5 show a second example of the embodiment of the present invention. In the case of this example, the cross-sectional shape of each of the convex portions 26a and 26a of the cage 20a in the circumferential direction is formed in a substantially V shape. That is, on the inner peripheral surfaces of the convex portions 26a, 26a, from the tip end portions of the convex portions 26a, 26a, which are in sliding contact with the cylindrical surface of the shaft 21, to one end side in the circumferential direction (counterclockwise side in FIGS. 4 to 5). The gentle slopes 28, 28 that gradually move away from the cylindrical surface, and the other end side in the circumferential direction (counterclockwise side in FIGS. 4 to 5) from the tip end suddenly from this cylindrical surface. The steep slopes 29 and 29 that are separated from each other are formed, respectively. Therefore, as shown in FIG. 4, when the shaft 21 rotates relative to the outer ring 18a in the counterclockwise direction and becomes locked, the steep slope portions 29 and 29 exert a force from the cylindrical surface of the shaft 21. Easy to receive. Therefore, the cage 20a can surely follow the shaft 21 and the locked state can be realized. On the other hand, as shown in FIG. 5, in an overrun state in which the shaft 21 rotates relative to the outer ring 18a in the clockwise direction, the wedge effect between the gentle slope portions 28, 28 and the cylindrical surface of the shaft 21 causes. Lubricants such as grease and other lubricating oils can be efficiently taken in between the cage 20a and the shaft 21. Therefore, it is possible to reduce the frictional force acting between the convex portions 26a and 26a and the outer peripheral surface of the shaft 21 at the time of overrun. Other structures and operations are the same as in the case of the first example described above.
