Steering GearBox and Types of steering gearbox – Studymaterial

Automobile

Steering gear box

• The case which holds the steering gear is called as steering gearbox.

• The Rotary movement of the steering wheel is converted into reciprocating motion of the steering linkage.

The driver easily turns the stub axle either left or right side with the help of steering gear box.

Types of steering gear box

Based on the construction and working principle the steering gear box are classified into the following types

1. Worm and sector type
2. Worm and Roller type
3. Worm and Nut type
4. Worm and wheel type
5. Recirculating Ball type steering
gearbox
6. Cam and Peg Steering Gear Box
7. Cam and Roller type
8. Rack and Pinion Steering Gear Box

Rack and pinion steering gear box

Construction

• In this type of steering gearbox, in place of cam or worm, the pinion gear is attached to the steering shaft through universal joints.

• The pinion is meshed with rake gear.The circular input motion of the pinion is converted into a linear rack output movement.

• The tie rod at each end of the rack is connected to the steering arm by means of ball joint.

Working Principle

• When the drive turns the steering wheel, the pinion at the end of steering wheels rotates at its own axis.

Based on the direction of rotation of the pinion, the rack moves towards the left or right.

This rack movement, make the tie rod to push the steering arm on one side and to pull the steering arm on other side.

• This turn the stub axle at its pivot point. The wheel attached in the stub axle is also turned and thus the steering movement is achieved.

Cam and Peg Steering Gear Box

Construction

• This type of steering box, in place of worm, a cylindrical shaft, supported by two roller bearing in the housing.

• The cylindrical shaft carried a deep spiral groove, usually a variable pitch on its surface between its bearing and this shaft is known as a cam.

• An integral rocker arm and shaft is placed half-way along the cam. At the free end of the rocker arm a conical peg is fitted which engages the groove.

Working Principle

When the steering wheel and shaft rotate the camshaft, one side of the spiral groove screws the peg axially forward or backwards depending upon the direction of turning of the cam.This forces the rocker arm to pivot about its shaft axis and as a result a similar angular motion is transferred to the drop arm, which is attached to the shaft’s outer end. Thus the road wheels are turns either left or right

Worm and Sector Steering Gearbox

Construction

• The worm is firmly connected to the inner column of the steering shaft.

• Worm shaft is mounted on the housings with the help of two taper roller bearing makes the rotation of shaft easily.

• The sector gear is meshed with worm.
• The sector gears form a part of the rocker shaft in the steering gear box.

Working principle

• When the driver turns the steering wheel, the worm will turn and turns the sector gear. The rotary motion of the steering wheel is converted into angular motion of the sector gear.

The drop arm attached to the sector is also oscillated and through the steering linkages, the wheel is turned to the required degrees in the required direction.

Recirculating ball type steering gear box

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It consists of a worm at the end of a steering rod. A nut is mounted on the worm with two sets of balls in the grooves of the worm, in between the nut and the worm.

The balls reduce the friction during the movement of the nut on the worm. The nut has a number of teeth on the outside,which mesh with the teeth on a worm wheel sector, on which is further mounted the drop arm. When the steering wheel is turned, the balls in the worm roll in the grooves and cause the nut to travel along the length of the worm.

The balls, which are in 2 sets, are recirculated through the guides.The movement of the nut causes the wheel sector to turn at an angle and actuate the link rod through the drop arm, resulting
in the desired steering of the wheels.

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