Hypoid gearboxes can be categorized as bevel gearboxes. A special feature of hypoid gearboxes is that the axes cross on two parallel planes. Hypoid gearboxes therefore have an axis offset, unlike other bevel gearboxes. The direction of rotation of the input shaft and the output shaft can be the same or opposing, depending on the installation conditions of the bevel gears.
Hypoid bevel gears are an example among the spiral bevel gears. A main advantage of hypoid gearing is that the bevel pinion can be realized with a greater spiral angle because of the axis offset. This increases the overall coverage of the tooth. For this reason, hypoid gearboxes are capable of transmitting more torque than single helical tooth. Because of the greater overall coverage, higher ratios can also be reached.
Hypoid gearboxes are characterized by being extremely quiet. However, they are not suitable for extremely fast speeds. On the one hand, the axis offset leads to additional sliding of the tooth in the longitudinal direction, which means that special lubricating oils have to be used, and on the other hand the reaction force of the tooth is so high that tapered roller bearings are used in order to ensure that the bearing has a sufficient service life at the usual drive speeds.
Because of the power loss that occurs because of mounting and sealing, hypoid gearing is more suitable for the output stage in multi-stage gearboxes. The speeds that are required are lower here, and the torques are appropriately higher. Single-stage hypoid gearboxes are already possible with bevel gear stage ratios of 3:1 to 10:1. In order to reach higher transmission ratios, the hypoid gearbox can be combined with a planetary gear. Because of the large plate diameter, hypoid gearboxes are particularly suitable for realizing hollow shafts if the input shaft needs to be used to lead through lines or use clamping sets. Torque division is possible by means of an input shaft with two outputs.
The advantages of hypoid gearboxes:
- Use when installation space is limited
- High torques
- Compact design
- Can be combined with other types of gearbox
- A hollow shaft is possible on the input shaft
The disadvantages of hypoid gearboxes:
- Complex design
- Lower efficiency level than planetary gearbox
- Not suitable for fast speeds