| 主权项 |
1. A drive force transmission apparatus that transmits a drive force of an electric motor to a shaft of a driven subject, the drive force transmission apparatus comprising:
a first rotatable member that includes a gear tooth forming portion, which is configured into a tubular form and is engageable with a motor-side gear that is rotated upon receiving the drive force of the electric motor; a second rotatable member that couples between the shaft and the first rotatable member to enable integral rotation of the shaft and the first rotatable member; and a shock absorbing member that is made of a rubbery elastic material, wherein the shock absorbing member is placed between the first rotatable member and the second rotatable member and is elastically deformable in a twisting direction about a rotational axis of the first rotatable member and the second rotatable member, wherein: the first rotatable member includes:
a first shaft portion, which is configured into a tubular form and extends in a direction parallel to the rotational axis, wherein the first shaft portion is located on a radially inner side of the gear tooth forming portion; anda through-hole that extends through the first shaft portion to communicate between one end surface and another end surface of the first shaft portion in the direction parallel to the rotational axis; the second rotatable member includes a second shaft portion that is fitted into the through-hole from one end side to another end side of the through-hole in the direction parallel to the rotational axis; the second shaft portion includes a resilient projection that projects outwardly in a radial direction, which is perpendicular to the direction parallel to the rotational axis, from an outer peripheral surface of a peripheral wall part of the second shaft portion, which extends continuously all around the rotational axis and is located at another end side of the second shaft portion that is opposite from one end side of the second shaft portion where the one end side of the through-hole is placed; the resilient projection is axially spaced from a distal end of the second shaft portion toward the one end side of the through-hole; the resilient projection is resiliently inwardly deformed in the radial direction at least during movement of the resilient projection along the another end side of the through-hole at a time of fitting the second shaft portion into the through-hole; the resilient projection is entirely located on a radially outer side of the outer peripheral surface of the second shaft portion when the resilient projection is resiliently inwardly deformed in the radial direction; and the resilient projection is resiliently outwardly restored and is engaged to an opening end surface of the through-hole, which is formed at the another end side of the through-hole in the first shaft portion, immediately after passing through the through-hole at the time of fitting the second shaft portion into the through-hole. |
