To ensure resistance to seizure on the guiding face of a cage 10 and to reduce or prevent an abnormal noise, in a needle roller bearing for a gear inner 3 interposed in an annular space between a rotational shaft 1 fitted to a transmission and a transmission gear 2 externally fitted to the rotational shaft 1 opposed to each other.
The cage 10 is guided by the inner diameter face of the transmission gear 2, and a circumscribed circle X that is circumscribed with the outer diameter portion of the cage 10 is set so as to oppose to the inner diameter face of the transmission gear 2 through an appropriate gap h. This makes it easier to maintain the the situation where the cage 10 rotates in accompany with the transmission gear 2 with the needle roller 11 pressed against the transmission gear 2 side, even if the transmission gear 2 is relatively rotating with respect to the rotational shaft 1 at a rotational speed exceeding a certain speed range. As a result, the occurrence of the resonance phenomena of the transmission gear 2 is suppressed, and abnormal noise as in the conventional examples is reduced or prevented.
SATO TAKAHIKO
SATO HIROSHI
