What Is a Hypoid Gear?

Hypoid gear (hypoid gear) is also called "altitude gear". The conical surface is used as the indexing curved surface, which approximately replaces the falling wheel on the hyperbolic body at the end of the frustum curved surface.

Hypoid gear refers to a bevel gear with an offset axis. It is customarily called a "hyperbolic gear", and it is also called a "hypoid gear" or a "hypoid gear".

The importance of hypoid gears in the development of automobile rear axle assemblies has been paid more and more attention by developers, and the requirements for gear weight, transmission stability, load carrying capacity, and life have become higher and higher.

Hypoid gears, because the tooth surface is a complex curved surface, it is difficult to obtain a more accurate geometric model and a more accurate finite element model by conventional methods, and to more accurately simulate and analyze this complex surface contact process, The requirements for the accuracy of the finite element model are very high. The more accurate finite element model is the hexahedral finite element model.

1.Axis offset

Hypoid gears are used for the transmission between two axes with different axes, see the figure below. The distance between the axis of the small wheel and the axis of the large wheel is called the offset distance, which is represented by E.

1.The main names and definitions of the gear teeth

The code of the main name of each part of the gear is shown in the figure below.

(1) Tooth height h: the distance measured from the top circle to the root circle along the dorsal cone generatrix.

(2) Tooth height h _a : The distance between the tooth top circle and the index circle measured along the back cone generatrix.

(3) Tooth root height h _f : the distance between the index circle and the tooth root circle measured along the back cone generatrix.

(4) Working tooth height h ': When a pair of bevel gears mesh with each other, the top circle of the two teeth and the back cone generatrix each have an intersection point, and the shortest distance between the two intersection points is measured along the common generatrix.

(5) Top clearance c: The distance measured between the top circle of the tooth and its matching gear tooth root circle along the common generatrix of the two back cones.

(6) Pitch P: the arc length on the index circle of the tooth profile on the same side of two adjacent teeth.

(7) Tooth thickness s: The indexing arc length between the two sides of a tooth.

(8) Cogging width: On a bevel gear, the indexing arc length between the tooth surfaces on both sides of a cogging is long.

(9) Backlash j: Backlash is the amount of tooth groove width on the working pitch circle that is greater than the tooth thickness of the meshing gear teeth.

Main names of gear teeth

Tooth line

The tooth length curve refers to the intersection of the tooth surface and the pitch cone. Generally, the tooth length curve of an imaginary plane gear is used as the basis of the characteristics of the bevel gear and its classification.

Several common tooth length curves include straight lines, oblique lines, and long trochoidal lines. See the figure below.

Tooth line

In addition, there are quasi-involutes processed with tapered hobs, but they are rarely used.

Among the curved tooth lines, arcs and long cycloids are most widely used, and arcs are mostly used. Arc teeth are easy to grind, can achieve high precision, and can be used for high-speed transmission. The long trochoidal teeth are of the same height and use continuous cutting without intermittent tooth splitting. ^[2]