The worm shaft is a key component in many manual steering gearboxes (such as worm-and-sector, worm-and-roller, and recirculating ball types). It connects the steering wheel to the steering mechanism.
Construction and Connection
- The worm shaft is directly attached to the steering wheel hub.
- It has a worm gear profile (like a screw thread) cut along its length.
- The shaft is supported inside the steering gearbox housing using bearings, allowing smooth rotation.
Function
- Driver Turns the Steering Wheel
When you rotate the steering wheel, the worm shaft rotates along with it. - Rotary-to-Linear Motion Conversion
The rotation of the worm shaft causes the mating component (sector gear, roller, or nut) to move.- In worm-and-sector, the sector gear rotates.
- In worm-and-roller, the roller follows the worm’s threads.
- In recirculating-ball, the nut moves linearly along the worm shaft.
- Transmitting Torque
The worm shaft acts as a torque multiplier, allowing the driver to turn the road wheels with less effort.
Advantages of Using a Worm Shaft
- Provides mechanical advantage (reduces steering effort).
- Smoothly converts rotary motion into controlled angular motion.
- Ensures safety by isolating road shocks from reaching the steering wheel directly.
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