When the early automobiles came into existence, the main challenge with the manufacturers was to achieve the operational efficiency. The proper and reliable operation of the automobile was a challenge in itself and very less attention was put on areas like safety and convenience. Steering of car was one of the areas less focused on during the primitive designing of the car. Hence a rack and pinion steering was used that used primarily physical force to change the direction of motion of the car. It can still be seen in heavy duty vehicles like tractors where still physical rack and pinion steering is used. It involves a lot of physical force.
With time, the operational obstacle in cars was overcome and focus shifted towards convenience. Here came the era of power steering. Power steering uses hydraulic or electric motor actuator systems to sense the amount of force applied and magnification of force is done to achieve steering action. Consequently, steering action could be obtained by the use of minimal force.
Working of a traditional rack and pinion steering
A rack and pinion steering is the traditional and most widely used steering in cars and other automotive. This mechanism consists of a rod that has tie rods connected on both ends. A rack is provided on the rod and a pinion gear is mounted on the rack. This pinion gear connects the rack with the steering wheel. This arrangement is enclosed in a cylindrical tube on the rod. Deliberately, the rack is provided near one of the tires so that uniform turning of both the wheels alike does not happen. This is in all relation with the physics of automobile turning. Both the wheels of the vehicle should turn at different angles. The inner wheel is expected to take a smaller circle than the outer wheel for a smooth steer. When the driver rotates the steering wheel, the pinion gear on the rack turns which moves the rack rod in horizontal linear motions. The tie rod connecting the rack rod moves a steering arm on the spindle which turns the wheel for a steering action. The gear arrangement on the rack and pinion can be arranged for necessary ease and degree of motion required. This is how a rack and pinion steering mechanism works.
Working of power steering
Power steering is basically amplifier device that multiplies the manual force input of the driver to give necessary force to the rack and pinion arrangement for required amount of steering action. These amplifiers can be in the form of mechanical or electrical devices.
Hydraulic power steering
When we talk of mechanical amplifiers these are essentially hydraulic mechanisms. The power to reduce the human effort is derived from the engine power. When the steering is in neutral mode, fluid pressure on both sides of the piston will be equal and no movement will be there. During turning of the steering wheel on either side, the control valve operates which closes the fluid passage towards one side of the piston. This creates change in the forces and the gear arrangement over the rack and pinion moves as per the applied force giving the steering action.
Electrical power steering
In case of an electrical steering, a sensor senses the applied amount of force on the steering wheel and an electrical actuator activates an electrical motor that rotates the rack and pinion arrangement accordingly.
Future of power steering
Though power steering gives much relief to humans in terms of force that has to be applied, it affects the fuel economy as the power to turn the pinion arrangement is drawn from the engine power. In case of electrical power steering, the batteries that rotate the motors are charged with the engine power only. The future of the steering lies in electronic steering that will completely eliminate the mechanical connections of the steering wheel. We may expect joystick kind of electronic steering in the future that will actuate motor systems to obtain the steering actions.