Gears have been used by mankind for a long time, this method of communicating rotational energy is the most common in mechanics.
These mechanisms transmit movement from one shaft to another, usually with a change in the frequency of revolutions per unit time. Means of engagement and direct elements of the message of motion are either wheels or racks with grooves and protrusions of a special shape cut on their working surfaces.
Of the two round elements interacting in the transmission, one, of a larger diameter, is called a wheel, and the second is called a gear, although, in essence, they are both gears.
Depending on whether the task of the gearbox is to increase the speed of rotation or, conversely, to decrease, the drive can be either a wheel or a gear.
Modern structural materials allow you to create gears that can successfully transform power up to 36 million watts.
The requirements for the mechanisms are different, so the variety of gear shapes is very large. The axis of rotation can be parallel, intersecting or intersecting, depending on this there are cylindrical, helical, worm or bevel gears. A feature of the latter is the ability to communicate rotation to a shaft located at right angles to the drive axis. This feature is often needed in a wide variety of mechanisms, for example, the transmission of mechanical energy from a cardan shaft of a car to drive wheels is carried out precisely according to such a kinematic scheme.
Most often, a bevel gear has straight teeth of radial cutting (tangential). If the driving and driven axes do not intersect, then such a gearbox is called hypoid. The use of such mechanisms in the design of the rear axle is caused by the desire of developers to lower the overall center of gravity of the car to give it greater stability.
In addition to spur gears, other gears are also used, for example with spiral cutting.
In addition, bevel gears enable rotation messages not only at a straight line, but also at almost any other angle, blunt or sharp.
The manufacturing technology of bevel gears is approximately the same as cylindrical gears, but the workpiece has a rather complex shape. It consists of two truncated cones with a common large base on one axis. The generators of the cones are at right angles. The tooth profile is clearly visible from the non-working side of the bevel wheel, while the width of the tooth decreases from the periphery to the center. The material of manufacture is special steel, resistant to wear and very hard.
The cutting profile is a line of involute, this form provides the most smooth rotation, uniform wear and maximum distribution of mechanical stress at the moment of contact of the teeth.
Gears with a variable profile length along the profile are difficult to manufacture, and machine tools with program control are used to obtain them.