Steering Rack and Power steering pump!

POWER STEERING RACK

Rack and pinion steering is quickly becoming the most common type of steering on cars, small trucks and SUVs. It is actually a pretty simple mechanism. A rack and pinion gear set is enclosed in a metal tube, with each end of the rack protruding from the tube. A rod, called a tie rod, connects to each end of the rack.

The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle 

The rack-and-pinion gear set 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.

On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock from far left to far right.

Part of the rack contains a cylinder with a piston in the middle. The piston is connected to the rack. There are two fluid ports, one on either side of the piston. Supplying higher-pressure fluid to one side of the piston forces the piston to move, which in turn moves the rack, providing the power assist.

POWER STEERING PUMP

Describe a Trunion and where it is found?

In older cars, the trunnion is part of the suspension and either allows free movement of the rear wheel hub in relation to the chassis or allows the front wheel hub to rotate with the steering. On many cars the trunnion is machined from a brass or bronze casting and is prone to failure if not greased properly, American motors used moulded rubber "Cleve bloc" bushings on the upper trunnion to seal out dirt and retain silicone lubricant for the life of the car

ABS

Anti lock braking system (ABS) is an vehicles system that allows the wheels on a vehicle to maintain contact with the road surface according to driver inputs while braking preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding.

Typically ABS includes a central electronic control unit (ECU), four wheel speed sensors and at least two hydraulic valves within the brake hydraulics. The ECU constantly monitors the rotational speed of each wheel, if it detects a wheel rotating significantly slower than the others, the wheel speed sensor sends a signal to the ECU. It actuates the valves to reduce hydraulic pressure to the brake at the affected wheel, therefore reducing the braking force on that wheel, the wheel then turns faster. Conversely, if the ECU detects a wheel turning significantly faster than the others, brake hydraulic pressure to the wheel is increased so the braking force is reapplied, slowing down the wheel. 

Main Components

Speed sensors

The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information.

Valves

There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions, In position one, the valve is open; pressure from the master cylinder is passed right through to the brake. In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder. In position three, the valve releases some of the pressure from the brake.

Pump

Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up.

Controller

The controller is an ECU type unit in the car which receives information from each individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to the controller, the controller will then limit the brake force (EBD) and activate the ABS modulator which actuates the braking valves on and off.