Page 266 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CH AP TER 9 .1 Steering

Fig. 9.1-18 Electro-hydraulic power steering system of the Opel Astra (1997). The individual components are:
1 electrically operated power-steering pump with integrated reserve tank (‘power pack’)
2 pump–steering valve hydraulic lines
3 rack and pinion steering gear with external drive, attached to auxiliary frame
4 steering valve.

Servo boost is also guaranteed by the electrical be adjusted by the control electronics individually for
pressure supply even when the engine is not the particular vehicle.
running.
Pressure-controlled systems generate only the 9.1.4.3 Electrical power steering
amount of oil required for a particular driving situa- systems
tion. Compared with standard power steering sys-
tems, energy consumption is reduced to as little The bypass of the hydraulic circuit and direct steering
as 20%. boost with the aid of an electric motor has additional
The steering characteristics (nature and amount of advantages in terms of weight and engine bay space
steering boost, sensitivity, speed dependency) can compared with electro-hydraulic steering, because of

Fig. 9.1-19 Open-centre control system from ZF. The pressure supply unit designed as a modular unit can be fitted with different
3
electric motors (DC motor with or without brushes) and pump fuel feed volumes (1.25–1.75 cm per rpm) depending on its particular
function. Oil tanks for horizontal or vertical installation are also available. Operating pressure is up to 120 bar, with a maximum power
consumption of 80 A.

268