STEERING GEARBOX

Presented by

VENGATAPATHI K

Functions of Steering Wheel

The rotary motion of the steering wheel is converted into straight line motion of the linkage by the steering gears. The gear which is used for steering arrangement is WORM gear.

Types of Steering Gears The types of steering gears are

1. The Pitman-arm type and 2. The Rack-and-Pinion type.

Types of Steering Gearbox 1. Worm and Roller 6.Screw and Nut 2. Worm and Sector 7.Recirculationg Ball 3. Cam and Roller 8.Worm and Ball 4.Cam and Peg 9.Rack and Pinion 5.Cam and Turn lever

Cam and Roller

Cam and Roller Construction• The cam and roller steering boxes are very efficient.

• The cam is carried by the steering shaft connected with rollers.

• The drop arm spindle carries the vee shaped roller.

• This spindle is carried by ball bearings in the casing.

• The meshing member contains the spiral grooves. The centre position of the pin supports the roller.

Cam and Roller Working• By moving the steering wheel and steering shaft, the cam is rotated.• Due to this rotation, the roller is constrained to follow the helix of the groove.• When the cam rotates, the roller is followed the cam and made the rocker shaft to rotate.• The contour of the cam is properly designed to match with our aim.

Reciprocating Ball Type

Reciprocating Ball Type Construction This type of gear was the most widely used steering gear at one time in Tata and Standard 20 vehicles. It consists of a worm at the end of steering rod, half nut and transfer tube containing the balls. The balls are fed back to the nut connected by half nut with the transfer tube. A worm and nut are placed at the end of the steering shaft. Steel balls are loaded between the sets of groove of worm and nut for recirculation. The nut has teeth on its circumference. These teeth are to be meshed with a toothed wheel.

Reciprocating Ball Type WorkingWhen the driver turns the steering wheel, the two steel ball races will roll in the grooves and make the nut to travel along the length of the worm.The motion from the nut is transmitted to the wheel sector.

Advantage•These balls reduce the friction and increase the efficiency of the mechanism to 90%.

Rack and Pinion Type

Rack and Pinion Type Construction This type of steering gear is mainly used in cars having independent front suspension. The pinion is mounted at the end of the steering shaft. A universal joint is connected at the bottom end of the steering shaft to mount the steering box centrally. A rack is engaged with the pinion. The rack reciprocates sideways to give lateral movement to the front wheels. Spring pads connected with the rack reduce the backlash between gears to a minimum.

Rack and Pinion Type Working

The driver effort is transmitted to the front wheel through the steering wheel, to steering shaft and finally to the steering knuckle. The rack having ball joints at each end for allowing the rise and fall of the wheel is engaged with the pinion mounted at the end of the steering shaft. A rack is engaged with the pinion. The rack reciprocates sideways to give lateral movement to the front wheels. The backlash in rack is reduced to a minimum due to spring pads are placed below the rack.

Rack and Pinion Type Advantages The rack and pinion steering provides sufficiently a low gear reduction. It is also made suitable for heavier motor vehicles by power assisting.

Cam and Lever Type

Cam and Lever Type The cam is mounted at the lower end of the steering shaft. It consists of variable pitch worm. A twin lever carrying studs meshes in the groove of the cam. This arrangement provides minimum of friction when the contact is made between cam and a small stud. When the cam turns, the studs will also move in an arc. The cam is cylindrical in shape.

Worm and Roller Gear

Worm and Roller Gear

Worm and roller gear have two-toothed roller which are fastened to the cross shaft called as roller shaft or sector shaft. The threads of the worm gear are meshed with roller shaft at the end of the steering tube. When the worm shaft is turned by the steering tube, the roller will also be moved in an arc for rotating the roller shaft. The bearings are designed to resist both radial and end thrust. This system is used in Ford cars and American passenger cars.

Screw and Nut Gear

Screw and Nut Gear Construction

These types of steering boxes are commonly used. Screw and nut gear has a phosphor-bronze of steel nut which is screwed on to a multi-start Acme thread. A single ball race provided at the top end of the rocker shaft carries the axial thrust of the column. At that time, the nut sliding in the housing supports the lower end. The screw is made to rotate freely on bearings.

Screw and Nut Gear Working A shaft connects the screw with the steering wheel. Therefore, as the screw is turned by rotating the steering wheel. The spindle is mounted on ball bearings. The drop arm is taken by this spindle at its outer end. The two arms of the spindle are attached to the nut by bronze pads. These pads are placed and made to rotate in the cylindrical recesses provided in the sides of the nut.

Screw and Nut Gear Working Also these pads have parallel grooves to receive the arms of the spindle. The bronze pads cause the arms of the two armed spindles moving in circular path.

Cam and Peg Type

Cam and Peg Type The steering gear has a tapered peg in the rocker arm engaged with a special cam provided on the inner column. The peg is moved along the groove for rotating the rocker shaft by rotating the cam. An adjusting screw on the side cover is connected for governing the backlash and end float of the rocker shaft. The rocker arm is rotated with high efficiency cam and peg gear rotates by a peg in the bearings.

Worm and Ball Bearing

Worm and Ball Bearing In worm and ball bearing, the principle of transmitting the movement from the steering tube is worm and ball nut. A worm is connected at the lower end of the steering shaft whereas a ball nut is connected with worm. Steel balls are circulated for obtaining frictionless drive between the worm and nut. If the steering shaft is turned to left, the ball nut is moved downward by rolling action. The teeth of the ball bearing nut moving up or down the shaft will be moved on the sector teeth to force the cross shaft and rotate.

Worm and Sector Type

Worm and Sector Type Worm and sector are based on the principle of transmitting the motion from the steering tube to the Pitman arm. The worm is attached with the inner column of the bearing block. The box is connected to the level of the plug with normal gear oil for lubrication of the steering gear. The worm at the end of the steering shaft meshes with a sector mounted on a sector shaft. When the steering wheel is rotates, then the worm will rotates.

Worm and Sector Type Then the sector will also be rotating the section shaft. So, the motion is transmitted to the wheel through the linkage.

Our ULTIMATE AIM is to transmit the power from steering linkage to wheel

QUESTIONS

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