Motor-driven position adjustment apparatus for steering wheel
In a motor-driven steering wheel position adjustment apparatus, a nut 17 being a driven member is mounted such that it can be detached from an inner column of a steering column, based on a shock load applied at the time of a secondary collision, and therefore a threaded rod of a feed screw mechanism does not have resistance with respect to displacement of the inner column in the forward direction at that time. Improvement in the protection of a driver at the time of a collision can thus be achieved, and, since an integrated member can be used for the threaded rod, silence during the position adjustment of a steering wheel by the feed screw mechanism can be ensured.
1. A motor-driven position adjustment apparatus for a steering wheel comprising: a steering column with a steering shaft rotatably supported inside; a driven member joined to a part of the steering column; a push-pull rod which is arranged in the axial direction of the steering column in a state where one end is joined to the driven member; a driving member that is rotatably supported on the periphery of a part toward the other end of the push-pull rod, and that displaces the push-pull rod in the axial direction of the steering column as it rotates; and an electric motor for rotating and driving the driving member, and the steering column being displaced based on a relative displacement of the driving member and the push-pull rod based on a current supplied to the electric motor to adjust a position of a steering wheel supported on an end of the steering shaft,
wherein at least either one of a joined part between the push-pull rod and the driven member, and a joined part between the driven member and the steering column, can be separated based on a shock load applied at the time of a collision, and
wherein the separable joined part includes a pair of members to be joined, which are fitted via an elastic deformable spacer.
2. A motor-driven position adjustment apparatus for a steering wheel according to claim 1 , wherein the spacer has a high coefficient of friction.
3. A motor-driven position adjustment apparatus for a steering wheel according to claim 1 , wherein a spacer is interposed between an outer peripheral surface of the push-pull rod, and an inner peripheral surface of a retainer sleeve arranged on the periphery of the push-pull rod, and the retainer sleeve is joined to a driven member such that it can be displaced freely together with the driven member at the time of a collision.
4. A motor-driven position adjustment apparatus for a steering wheel according to claim 1 , wherein an outer diameter of a part of the push-pull rod that is positioned on an inner diameter side of the spacer at a normal time, is made larger than an outer diameter of a part of the same that enters the inner diameter side of the spacer when a collision occurs.
5. A motor-driven position adjustment apparatus for a steering wheel according to claim 4 , wherein the push-pull rod has a first part and a second part of smaller outer diameter than the first part, two spacers whose inner diameters are different in a free state are provided at two positions in the axial direction on the periphery of the push-pull rod, and at normal times, the first part of the push-pull rod is located inside of the spacer whose inner diameter is larger in the free state, and the second part of the push-pull rod is located inside of the spacer whose inner diameter is small in the free state.
6. A motor-driven position adjustment apparatus for a steering wheel according to claim 1 , wherein the separable joined part is constructed by joining a pair of members to be joined, using a joining member that breaks based on a shock load.
7. A motor-driven position adjustment apparatus for a steering wheel according to claim 1 , wherein the spacer comprises a metallic spring.
8. A motor-driven position adjustment apparatus for a steering wheel according to claim 1 , wherein the spacer comprises a non-metallic elastic material.