Steering Column

Assembly and intermediate shaft The steering column central shaft comprises of two shafts, the upper shaft is splined to accept the steering wheel and located in bearings in the column tube. A universal joint is located on the bottom of the upper shaft, the joint allows for angular movement between the upper and lower shafts. The lower shaft is made in two parts, the top section of the lower shaft is located outside of the lower section. The two sections of the lower shaft are connected by two nylon injection molded shear pins. The lower shaft goes through a lower bearing attached to the bulkhead, the lower shaft is connected by a universal joint to the intermediate shaft in the engine compartment.

An upper column tube provides for the location of the steering lock and ignition switch and also the steering switch gear and a rotary coupler. The rotary coupler provides the electrical connection for the steering wheel mounted airbag, switches and horn. The upper mounting bracket has two slots, a slotted metal bracket is held in each slot by four resin shear pins.

The column is mounted on four captive studs which are located on a column mounting bracket. The captive studs pass through the metal brackets, locknuts secure the steering column to the bulkhead. The two lower mountings are fixed and cannot move when loads are applied to them. The upper mounting is designed to disengage or deform when a load is applied, allowing the column to collapse in the event of an accident. The steering column must be replaced as a complete assembly if necessary.

When an axial load is applied to the upper column tube, energy absorption is achieved by the following mechanism:

• The mounting bracket deforms.
• The resin shear pins holding the slotted metal brackets shear.
• The top mounting bracket slides out of the slotted metal brackets.

The slotted metal brackets remain on the captive studs on the bulkhead. If the column mounting moves, injection molded shear pins retaining the two sections of the lower column shaft will shear. This allows the two sections of the lower shaft to "telescope" together.

In the event of a collision where the steering box itself moves, two universal joints in the column allow the intermediate shaft to articulate, minimizing movement of the column towards the driver. If movement continues energy absorption is achieved by the following mechanism:

• The de-couple joint in the intermediate shaft will disengage.
• The lower section of the steering column shaft will move through the lower bearing.
• The injection molded shear pins retaining the two sections of the lower column shaft will shear.

This allows the two sections of the lower shaft to "telescope" together reducing further column intrusion. Protection to the drivers face and upper torso is provided by an SRS airbag module located in the center of the steering wheel.