Page 258 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CH AP TER 9 .1 Steering

Mercedes E and S Class, plus almost all new light van
designs with independent front wheel suspension. The
advantages over manual recirculating ball steering sys-
tems are (see also Section 9.1.3.1):
simple construction;
economical and uncomplicated to manufacture;
easy to operate due to good degree of efficiency;
contact between steering rack and pinion is free of
play and even internal damping is maintained
(Fig. 9.1-10);
tie rods can be joined directly to the steering rack;
minimal steering elasticity compliance;
compact (the reason why this type of steering is fitted
in all European and Japanese front-wheel-drive
vehicles);
the idler arm (including bearing) and the intermedi-
ate rod are no longer needed;
Fig. 9.1-6 Side view of a rigid front axle showing the movement
directions 9 and 7 of the drag link and axle housing during easy to limit steering rack travel and therefore the
bump and rebound-travel. The path of point 7 is determined by steering angle.
the front half of the leaf spring and can be calculated on a spring-
balance by measuring the change in length when a load is
added to and removed from the spring. The main disadvantages are:

otherwise there is a danger of the wheels experiencing greater sensitivity to impacts;
a parallel toe-in alteration when the suspension reaches greater stress in the case of tie rod angular forces;
full travel, i.e. both being turned in the same direction disturbance of the steering wheel is easier to feel
(Fig. 9.1-7). If a rigid axle is laterally controlled by (particularly in front-wheel drivers);
a panhard rod, the steering rod must be parallel to it. tie rod length sometimes too short where it is
Its construction is similar to that of the intermediate connected at the ends of the rack (side take-off
rod of the steering linkage shown in Fig. 9.1-13; length design;
adjustment and ball joints on both sides are necessary. size of the steering angle dependent on steering rack
travel;
9.1.2 Rack and pinion steering this sometimes requires short steering arms 3
(Fig. 9.1-4) resulting in higher forces in the entire
9.1.2.1 Advantages and disadvantages steering system;
decrease in steering ratio over the steer angle associ-
This steering gear with a shift movement is used not only ated with heavy steering during parking if the vehicle
on small and medium-sized passenger cars, but also on does not have power-assisted steering;
heavier and faster vehicles, such as the Audi A8 and cannot be used on rigid axles.

Fig. 9.1-7 If the movement curve 7 of the axle housing and curve 9 of the rear steering rod joint do not match when the body bottoms out,
the wheels can turn and therefore an unwanted self-steering effect can occur.

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