Patent ID: 8864591

Claim:
A propeller shaft comprising: an inner cylindrical member having a center through bore, the center through bore having a splined cylindrical inner wall with which a splined cylindrical outer wall of a shaft is engaged; an outer cylindrical member disposed around the inner cylindrical member; a torque transmitting unit installed between the inner and outer cylindrical members to transmit a torque between the inner and outer cylindrical members; a sleeve member coaxially connected to the center through bore of the inner cylindrical member, the sleeve member permitting passage of the splined cylindrical outer wall of the shaft therethrough before effecting the engagement between the splined cylindrical outer wall of the shaft and the splined cylindrical inner wall of the inner cylindrical member; a boot unit having one end fixed to the outer cylindrical member and the other end fixed to the sleeve member thereby to hermetically close one open side of an interior of the outer cylindrical member, the interior containing therein a grease; and a positioning mechanism that effects a relative axial positioning between the shaft and the inner cylindrical member when the splined cylindrical outer wall of the shaft is inserted through the sleeve member into a given position of the center through bore of the inner cylindrical member leaving a cylindrical clearance between an inner cylindrical wall of the sleeve member and the shaft, the cylindrical clearance being closed by a seal ring for suppressing entry of foreign matter into the center through bore of the inner cylindrical member, wherein the positioning mechanism is arranged between the center through bore of the inner cylindrical member and the shaft, and comprises: a first annular groove formed on the splined cylindrical inner wall of the inner cylindrical member; and a second annular groove formed on the splined cylindrical outer wall of the shaft, the second annular groove receiving therein a snap ring, the snap ring being engageable with the first annular groove when the splined cylindrical outer wall of the shaft is inserted into the given position of the center through bore of the inner cylindrical member; and wherein the sleeve member is formed with a smoothed inner cylindrical wall, and in which the seal ring is compressed between the smoothed inner cylindrical wall of the sleeve member and a cylindrical outer wall of the shaft.