Advantages of hypoid gears
Hypoid gears have high strength and smooth motion and are suitable for transmissions with relatively high speeds.
- The axis of the pinion gear is offset, which increases the helix angle of the pinion gear, resulting in a significant increase in the diameter of the pinion gear, which can enhance the strength and rigidity of the pinion gear; and under the same conditions, it can achieve a larger transmission ratio than the spiral bevel gear.
- There is relative lubrication along the tooth length and height direction, so the tooth surface wears evenly. After heat treatment, it is also easy to grind, improve the contact area, improve the tooth surface finish and reduce noise.
- The axis is offset so that the drive’s layout in space has a greater degree of freedom. For example, the lower bias can be used to lower the car’s center of gravity and increase stability, and it can also be used to increase the body’s height and the off-road performance of the car.
- The axes are offset and can be crossed, and a stable straddle can support the two gears.
- The helix angle of the Pinion gear is increased, the strength is significantly improved, and it is suitable for a larger transmission ratio.
- Good lubricating conditions and high transmission efficiency.
The disadvantage of hypoid gears
Hypoid gear transmissions also have some disadvantages compared to other types of crossed-shaft transmissions:
- The calculation and design are far more complicated than other gear pairs. According to Gleason’s method, taking geometric calculation as an example, there are as many as 150 basic formulas, including three iteration calculations (usually three iterations, sometimes more )
- Compared with general orthogonal spiral bevel gears, the calculation of tooth cutting adjustment is more complicated, and the matching cutting of contact area is also more difficult.
- Lubricating conditions are high, requiring special hypoid gear lubricating oil.
- The longitudinal slip between the tooth surfaces of hypoid gears is far more than that of cylindrical gears and spiral bevel gears. This slip significantly impacts the load capacity and tooth surface wear. In most cases, mechanical wear or tooth surface gluing occurs, and the second failure mode is fatigue pitting.
- To avoid gluing or pitting on the tooth surface, the tooth surface needs sufficient hardness, and the contact area must have appropriate shape, size, and location requirements.
- Tooth surface lubrication requires a special anti-wear lubricant (called “hypoid gear oil”). The lubrication problem is critical to the operation of hypoid gears, which determines the load-carrying capacity of a heavily loaded hypoid gear pair.
- Under the above conditions, especially after using special lubricating oil, the hypoid gear’s bearing capacity is only limited by the bending strength at the maximum recheck and offset.
