5.4.4.b Hypoid transmission
In addition to the bevel main gear transmission, in which the axes intersect mutually, a hypoid transmission is used in passenger cars (shown in Figure 5.34). In this transmission, the teeth have a special profile, and the axis of the drive gear is offset downward relative to the center of the driven wheel by a certain distance (S). This makes it possible to position the cardan shaft lower and reduce the height of the convex upper part of the tunnel in order to accommodate the shaft in the floor of the body, as a result of which a more convenient placement of passengers in the body is achieved. In addition, it is possible to slightly lower the center of gravity of the vehicle and increase its driving stability. Hypoid gear has smoother operation, higher tooth strength and wear resistance.
Note
However, the hypoid gear has one unpleasant feature: the jamming threshold during the back stroke. The calculations of this gear, of course, exclude such a possibility, but it is always worth remembering that this drive gear can jam when the design speed is exceeded (when rotating in the opposite direction). Thus, be careful when shifting to a reverse gear.
For hypoid transmission, it is necessary to use special grades of lubricant due to the high pressure between the teeth during operation and high speeds of relative sliding between the teeth. In addition, higher gear mounting accuracy is required.
Figure 5.34 Drive gear elements. Tapered and hypoid gears.
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