What is a Steering Gear Box, Function and its Types

The steering gear box allows the driver to control the direction of the vehicle either left or right and to balance the vehicle on the road. There is a Lever mechanism that enables a large force exerted on the road wheels and that with a minimum of driver’s effort.

Functions of a Steering Gear Box

The steering gear box has two basic functions which are given below:

• It redirects the input to the output axis of rotation through the right angle.
• Between the steering wheel and output arm

Types of Steering Gear Box

There are many types of steering gear box which are explained below:

• Worm and Roller type steering bear box
• Recirculating Ball rack and sector steering gear box
• Screw and nut steering gear mechanism
• Recirculating Ball nut and rocker lever steering gear box

Let us discuss all these steering gear boxes one by one:

Worm and Roller type steering bear box

• In the worm and roller type gear box , there is a worm sometimes also known as ‘Cam’ mountain between the two opposing taper roller bearings.
• There is a rolling element that engages with the worm so that driver effort would be less.
• The movement of the steering wheel turns the worm, which in turn drives the sector.
• The Drop arm is connected to the Sector by the arm shaft.
• Hence, the rotation of the wheel results in the linear motion of the drop shaft.

Screw and nut steering gear mechanism

• We know that screw is made by cutting the external spiral grooves on the cylindrical shaft while a nut is made by cutting the similar spiral groove on the internal surface of the hole in a solid block.
• The combination of the nut and screw mechanism increases the force and the moment ratio.
• When we apply a small input effort at the end of the scroll which is then capable of moving a much larger axial load along the screw.
• If the screw is prevented from moving longitudinally and once it was within the nut and advances or attracts an equal distance to the axis length of one complete spiral loop.
• This distance is known as lead or thread pitch.
• The friction is higher in this mechanism because of the larger surface area in contact between the male and female thread and it is difficult to maintain an adequate supply of lubricant between the mating faces.
• Thus the mechanical efficiency is slow and rate of where is very high

Recirculating Ball rack and sector steering gear box

• Recirculating ball Rack and sector are similar to the screw and nut steering gear box.
• It has helical grooves on the worm shaft and corresponding gross on the nut.
• There are small Steel balls between the worm gear and nut which helps to reduce the friction.
• These Steel balls are designed to run in and out of the system and recirculate in the loop.
• When the driver turns the steering wheel, the steering column terms the worm shaft which in turn rotates the steel balls and causes the linkage to move.
• It is an improved version of the worm and nut mechanism and has a mechanical efficiency of 90%.

Recirculating Ball nut and rocker lever steering gear box

• To improve the efficiency of the simple screw and nut gear box, is achieved by replacing the male and female screw Threads with a semicircular groove that is machined spirally onto the input shaft and inside of the half nut.
• There is a ring of steel balls between the internal and external grooves.
• The portion which is having the spiral groove of the shaft is known as the worm and the part which is having the internal spiral grooves is called half nut.
• The half nut has an extended tower that is made up of spigot pin and a conical seat.
• When these parts are assembled the conical seat engages with The rocker Lever and the roller on the nut engages guide slot machines in the top cover plate.
• When the worm shaft is rotated the roller prevents the turning of the nut and the movement of the nut long the worm will results in the axial displacement.

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