Page 34 - Understanding Automotive Electronics

2735 | CH 1 Page 21 Tuesday, March 10, 1998 10:52 AM

AUTOMOTIVE FUNDAMENTALS 1

Figure 1.14
Major Components of
a Suspension System

FPO

a strut), which is in effect a viscous damping device. There is a similar assembly
at each wheel, although normally there are differences in the detailed
configuration between front and rear wheels.
The mass of the car body is called the sprung mass, that is, the mass that is
supported by springs. The mass of the wheel assemblies at the other end of the
springs is called unsprung mass.
All springs have the property that the deflection of the spring is
proportional to the applied axial force. The proportionality constant is known
as the spring rate. The springs are selected for each car such that the car body
height is as desired for the unloaded car. Typically, the weight on the front
wheels is greater than on the rear wheels, therefore, the front springs normally
have a higher spring rate than the rear.
Similar to the springs, the shock absorbers (struts) also produce a force
that acts to support the weight of the car. However, unlike the springs, the
shock absorbers produce a force in response to the motion of the wheel
assembly relative to the car body. Figure 1.15 is an illustration of a typical shock
absorber.

UNDERSTANDING AUTOMOTIVE ELECTRONICS 21