Components of Steering System and their Function
Layout of Steering System or Components of Steering System
Various components of the steering system are shown in Figure 4.1.
The following are the main components of steering system.
1. Steering wheel
2. Steering column or shaft.
3. Steering gear
4. Drop arm or pitman arm
5. Ball joints
6. Drag link
7. Steering arm
8. Stub axle
9. Left spindle and kingpin
10. Left tie rod arm
11. Track rod or tie-rod
12. Right tie rod arm, spindle and kingpin
13. Steering stops.
It is the control wheel to steer a vehicle by the driver. It contains traffic indicator switch, light switch, wiper switch etc.
2. Steering linkage:
The steering wheels are turned by the steering linkage. The steering linkage consists of pitman arm, ball joints, drag link, steering arm, spindle, tie rod and kingpin assembly.
Different forms of steering linkages are shown in Figure 4.3.
(a) Pitman arm:
It is also called drop arm which converts the output torque from the steering gear into force to the drag link. It is connected to the sector shaft of the steering gear by a split joint. Either full serrations or partial splines are used for transmitting the torque from the sector shaft to the pitman arm. The split arm is tightened around the sector shaft by a clamping bolt It is done for differentiating the male and female serrations or splines. The end of the pitman arm connected with the drag link has a tapered hole. The ball stud on the drag link is fixed into this hole.
(b) Ball joints:
These joints are connected at both ends of the drag link and tie rod. It performs the angular displacement, rotational movement of the drag link and the tie rod produced by the front wheel rotation and suspension articulation.
(c) Drag link:
It is connected between pitman arm and steering arm. It is a single prece forged component having a ball joint socket formed at the end in some other cases.
(d) Steering arm:
It is also a forged component which is connected to the steering knuckle. During turning, the drag link force is converted into a turning moment about the left kingpin. The steering arm is connected to the spindle through a keyway, locking taper and nut. The arm is extended either to the front or rear spindles according to package constraints. The end of the steering arm connects with the drag link and a tapered hole receives the ball stud.
(e) Left spindle and kingpin:
The torque obtained by the steering arm rotates the left spindle, wheel and tyre about the kingpin.
(f) Left tie rod arm:
The left tie rod arm is connected with the spindle in the same way as the steering arm. It converts the available torque to turn the right wheel into force in the tie rod. The tie rod has a tapered hole to receive the tie rod ball stud.
(g) Tie rod:
The tie rod is a tubular member. Both the left and right tie rod arms are connected by this tie rod. The force is transmitted between these two components. The tie rod ends have female threads. But the ball joint shafts have mating male threads. The threaded connections are held together firmly by locking clamps after setting the correct length. The length of the tie rod is an adjustable one to the specified amount.
In the direct cross type steering linkage. the pitman arm is directly connected to one tie rod which in turn is connected to another tie rod. The other end of the tie rod is connected to steering arms.
(h) Right tie rod arm, spindle and kingpin:
It converts the force from tie rod into a moment to turn through the knuckle arm, the right spindle wheel and the tyre about the kingpin. The right spindle and the kingpin assembly are merely similar assembly on the left side. But it has no steering arm connected to it.
(i) Steering stops:
Stops are used to limit the angular deflections of front wheels. It also avoids the rubbing of tyres against the frame produced by wear and tear of tyres. These steering stops are used at two different places. First, they are fixed’ in the path of motion of the steering arm or drop arm. Then, they are fixed in the path of motion of the steering knuckle.
3. Steering shaft:
The steering shaft is fitted inside the hollow steering column. When the steering wheel is turned, the steering shaft will also be rotated. Due to this, the motion is transmitted to the steering box.
4. Steering gear:
The pitman arm is splined to the steering gear box rocker arm at one end and the other end is connected to the drag link by a ball joint.
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