Compared with spiral bevel gear drive, hyperbolic gear drive has the following advantages:
(1) In the working process, there is not only lateral sliding along the tooth height direction, but also longitudinal sliding along the tooth length direction. The longitudinal sliding can improve the running in process of gears and make them have higher running stability.
(2) Because of the offset, the β 1 of the driving gear is larger than the β 2 of the driven gear because of the hyperboloid gear pair. In this way, the number of teeth engaged at the same time is large, and the coincidence degree is large, which not only improves the transmission stability, but also improves the bending strength of the gear by about 30%.
(3) The diameter and helix angle of the driving gear in hyperbolic gear drive are larger, so the equivalent radius of curvature of the meshing gear is larger than that of the corresponding spiral bevel gear, which results in the improvement of the contact strength of the tooth surface.
(4) If the β 1 of hyperboloid driving gear becomes larger, the minimum number of teeth without undercutting can be reduced. Therefore, a smaller number of teeth can be selected to increase the transmission ratio.
(5) The driving gear driven by hyperboloid gear is large, and the distance between the cutter head and the cutter head is large, so the cutting edge life is long.
(6) The hyperboloid driving gear shaft is arranged above the driven gear center, which is convenient to realize the connection of multi axle drive axle and increase the height of the transmission shaft from the ground. Arranged under the center of driven gear can reduce the height of cardan drive shaft, help to reduce the height of car body, and reduce the height of raised channel in the middle of car floor.
Hyperbolic gear transmission also has the following disadvantages:
(1) The longitudinal sliding along the tooth length will increase the friction loss and reduce the transmission efficiency. The transmission efficiency of hyperboloid gear pair is about 96%, and that of spiral bevel gear pair is about 99%.
(2) The large pressure and friction work between tooth surfaces may lead to oil film damage and tooth surface sintering and seizure, that is to say, the anti scuffing ability is low.
(3) The hyperboloid driving gear has large axial force, which makes its bearing load increase.
(4) The special lubricating oil which can improve the oil film strength and anti scratch additive must be used for the hyperboloid gear transmission, and the common lubricating oil for the spiral bevel gear transmission can be used.
In general, when the transmission ratio is required to be greater than 4.5 and the profile size is limited, the hyperbolic gear transmission is more reasonable. This is because if the driving gear shaft diameter remains the same, the diameter of the double curved driven gear is smaller than that of the helical gear.
When the transmission ratio is less than 2, the hyperboloid driving gear is too large compared with the spiral bevel gear, occupying too much space. At this time, the spiral bevel gear transmission can be selected, because the spiral bevel gear transmission has a large differential available space.
For medium ratios, both gear drives are available.