Page 35 - Understanding Automotive Electronics

2735 | CH 1 Page 22 Tuesday, March 10, 1998 10:52 AM

1 AUTOMOTIVE FUNDAMENTALS

Figure 1.15
Shock Absorber
Assembly

FPO

The shock absorber consists of a cylinder and piston assembly. The
cylinder is filled with a viscous oil. There are small oil passages through the
piston through which the oil can flow. As the wheel assembly moves up and
down, the piston moves identically through the cylinder. The oil (which is
essentially incompressible) flows through the oil passages. A force is developed
in response to the piston motion that is proportional to the piston velocity
relative to the cylinder. This force acts in combination with the spring force to
provide a damping force. The magnitude of this force for any given piston
velocity varies inversely with the aperture of the oil passages. This aperture is
the primary shock absorber parameter determining the damping effect and
influencing the car’s ride and handling. In Chapter 2, the influence of the shock
absorber damping on wheel motion is explained. In Chapter 8, the mechanism
for varying the shock absorber characteristics under electronic control to
provide for variable ride and handling is explained.

22 UNDERSTANDING AUTOMOTIVE ELECTRONICS