24-08-2013, 04:52 PM
Power Steering
Power Steering[.ppt (Size: 2.37 MB / Downloads: 97)
STEERING SYSTEM
The steering system allows the operator to guide the vehicle along the road and turn left or right as desired. The system includes the steering wheel, which the operator controls, the steering mechanism, which changes the rotary motion of the steering wheel into straight-line motion, and the steering linkage. Most systems were manual until a few years ago. Then power steering became popular. It is now installed in most vehicles manufactured today.
The steering system must perform some important functions like –
Provide precise control of front-wheel direction.
Maintain the correct amount of effort needed to turn the front wheels.
STEERING LINKAGE
Steering linkage is a series or arms, rods, and ball sockets that connect the steering mechanism to the steering knuckles. The steering linkage used with most manual and power steering mechanisms typically includes a pitman arm, center link, idler arm, and two tie-rod assemblies.
Turning the Car
For a car to turn smoothly, each wheel must follow a different circle. Since the inside wheel is following a circle with a smaller radius, it is actually making a tighter turn than the outside wheel. If we draw a line perpendicular to each wheel, the lines will intersect at the center point of the turn. The geometry of the steering linkage makes the inside wheel turn more than the outside wheel.
STEERING RATIO
The steering ratio is a number of degrees that the steering wheel must be turned to pivot the front wheels 1 degree. The higher the steering ratio, the easier it is to steer the vehicle, all other things being equal. However, higher the steering ratio, the more the steering wheel has to be turned to achieve steering. With a 30: 1 steering ratio, the steering wheel must turn 30 degrees to pivot the front wheels 1 degree.
Variable steering ratio
"Variable steering ratio" means that the ratio is larger at one position than another. Therefore the wheels are turned faster at certain positions than at others. At the center or straight-ahead position, the steering gear ratio is high, giving more steering control. However, as the wheels are turned, the ratio decreases so that the steering action is much more rapid. This design is very helpful for parking and maneuvering the vehicle.
Rack and Pinion
As the steering wheel is rotated, the pinion gear on the end of the steering shaft rotates. The pinion gear moves the rack from one side to the other. This action pushes or pulls on the tie rods, forcing the steering knuckles or wheel spindles to pivot on their ball joints. This turns the wheels to one side or the other so the vehicle can be steered.
The rack-and-pinion gearset does two things:
It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.
It provides a gear reduction, making it easier to turn the wheels.
Rack-assist type:
The power assist unit is attached to the steering gear rack.
The power assist unit can be located freely on the rack, allowing great flexibility in layout design.
The power assist units’ high reduction gear ratio enables very low inertia and superior driving feel.
Electric power steering rack assist is a scalable system, suitable for midsize cars to full-size trucks.
Power Steering[.ppt (Size: 2.37 MB / Downloads: 97)
STEERING SYSTEM
The steering system allows the operator to guide the vehicle along the road and turn left or right as desired. The system includes the steering wheel, which the operator controls, the steering mechanism, which changes the rotary motion of the steering wheel into straight-line motion, and the steering linkage. Most systems were manual until a few years ago. Then power steering became popular. It is now installed in most vehicles manufactured today.
The steering system must perform some important functions like –
Provide precise control of front-wheel direction.
Maintain the correct amount of effort needed to turn the front wheels.
STEERING LINKAGE
Steering linkage is a series or arms, rods, and ball sockets that connect the steering mechanism to the steering knuckles. The steering linkage used with most manual and power steering mechanisms typically includes a pitman arm, center link, idler arm, and two tie-rod assemblies.
Turning the Car
For a car to turn smoothly, each wheel must follow a different circle. Since the inside wheel is following a circle with a smaller radius, it is actually making a tighter turn than the outside wheel. If we draw a line perpendicular to each wheel, the lines will intersect at the center point of the turn. The geometry of the steering linkage makes the inside wheel turn more than the outside wheel.
STEERING RATIO
The steering ratio is a number of degrees that the steering wheel must be turned to pivot the front wheels 1 degree. The higher the steering ratio, the easier it is to steer the vehicle, all other things being equal. However, higher the steering ratio, the more the steering wheel has to be turned to achieve steering. With a 30: 1 steering ratio, the steering wheel must turn 30 degrees to pivot the front wheels 1 degree.
Variable steering ratio
"Variable steering ratio" means that the ratio is larger at one position than another. Therefore the wheels are turned faster at certain positions than at others. At the center or straight-ahead position, the steering gear ratio is high, giving more steering control. However, as the wheels are turned, the ratio decreases so that the steering action is much more rapid. This design is very helpful for parking and maneuvering the vehicle.
Rack and Pinion
As the steering wheel is rotated, the pinion gear on the end of the steering shaft rotates. The pinion gear moves the rack from one side to the other. This action pushes or pulls on the tie rods, forcing the steering knuckles or wheel spindles to pivot on their ball joints. This turns the wheels to one side or the other so the vehicle can be steered.
The rack-and-pinion gearset does two things:
It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.
It provides a gear reduction, making it easier to turn the wheels.
Rack-assist type:
The power assist unit is attached to the steering gear rack.
The power assist unit can be located freely on the rack, allowing great flexibility in layout design.
The power assist units’ high reduction gear ratio enables very low inertia and superior driving feel.
Electric power steering rack assist is a scalable system, suitable for midsize cars to full-size trucks.