Hypoid

Hypoid refers to a type of gear arrangement and the corresponding tooth geometry in which the axes of the driving pinion and the driven gear do not intersect and are offset from each other. Hypoid gears are a form of spiral bevel gear, but their pitch surfaces are generated on a hyperboloid of revolution, allowing the gears to mesh smoothly despite the offset. The resulting tooth form enables spiral contact along a length of the gear face.

In contrast to bevel gear sets with intersecting axes, hypoid gear sets have nonconcurrent axes, which allows for a larger pinion diameter relative to the ring gear. This arrangement provides higher torque capacity, a lower gear ratio, and space for components such as a drive shaft to pass beneath the ring gear. The offset also contributes to quieter operation and improved load distribution, though it requires more complex manufacturing and profiling.

Manufacture and maintenance: Hypoid gears are produced using specialized tooling and cutting methods that account for the hyperboloid pitch surface. Precision in gear geometry, backlash, and alignment is important to control noise, wear, and efficiency. Lubrication plays a significant role due to the sliding action between the gears, and proper sealing is often necessary to prevent contamination and maintain performance.

Applications and variants: The most common use of hypoid gears is in automotive differentials, where the offset allows the driveshaft to run lower under the vehicle. They are also used in some industrial gearboxes, marine transmissions, and certain heavy machinery. Hypoid gears are typically more expensive to manufacture than simple bevel gears, but offer advantages in torque capacity, packaging, and smoothness.