Bevel gears are used for transmission between two intersecting shafts, and are most commonly used for transmission between vertical shafts. The straight bevel gear reducer is a bevel gear similar to the straight bevel gear, which is meshed and driven in a similar way. This kind of gear is very sensitive to assembly error, because the distance between the two gears and the intersection point of the axis must be ensured. Straight bevel gears are difficult to manufacture accurately, and can only be calibrated on the transmission error device, so they are never used in situations requiring high speed and precision transmission.
Helical bevel gear is a bevel gear similar to cylindrical helical gear. Although it is still relatively "rough", it can provide a more stable transmission than straight bevel gear. The further development of hypoid bevel gear used in automobiles is due to the need to reduce the center of the transmission shaft, thus reducing the channel height of rear-wheel drive vehicles. The hypoid bevel gear shaft is 90 degrees apart, but it is specially offset by 50mm, which improves the position of the rear axle, at the cost of increasing the sliding speed of the contact point.
The geometry of hypoid bevel gears is extremely complex. The specially manufactured gear is extremely expensive due to its high installation cost. Unless the standardized rear axle transmission device can be used, the design of right-angle transmission must be avoided. Standardized devices are produced in large quantities, and therefore adopt well-developed professional technology, which is extremely cheap and amazingly accurate. For example, a well-manufactured rear axle can transmit 100kw power at 5000r/min, and the transmission accuracy at gear tooth frequency can be within 5mm. Except for the grinded parallel shaft helical gear, it is as accurate as all other gears.