170 Auto Suspension and Steering
uncoils as the steering wheel is turned. Using a clockspring
ensures that there is always a complete electrical circuit
between the air bag squib and the rest of the air bag
system, regardless of the position of the steering wheel.
Steering Columns and Shafts
The steering shaft is installed in the steering column.
Bearings are generally used to hold the shaft in position.
The shaft and column assembly is usually removed and
replaced as a unit. However, individual parts are often
replaced without removing the shaft or column. In this
section, we will discuss the individual parts that make up
the steering column and shaft assembly.
Shaft Design
Modern steering shafts are made of two sections of
steel rod. One section is hollow and the other is solid. The
solid section slides into the hollow section. See Figure 9-6.
Air bag
Air bag warning
light
Front
impact
sensor
Clockspring
assembly
Air bag control module
Front impact
sensor
Figure 9-3. Typical air bag system. Note the location of the impact sensors, the air bag control module, and the clockspring
assembly. (Toyota)
Power
source
Ignition
control &
drive circuit
Front
impact
sensors
Safing
sensors
Squib
Gas
generant
Inflator
Air bag
Impact Collision
Air bag system diagram
Figure 9-4. Air bag activation sequence. At least one front impact sensor and the safing sensor must be triggered to cause
deployment. (Toyota)
Clockspring
Air bag lead
Figure 9-5. Cutaway of an air bag clockspring. This type of
clockspring is common. (Toyota)