270px, Typical starter ring gear A starter ring gear is a part attached to an

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal c ...

that is part of the assembly which transfers the torque from the starter motor to the engine's crankshaft, in order to start the engine. The starter ring gear is usually made from medium carbon steel. Starter ring gears are attached to either the flywheel or the flexplate of an engine. The teeth of the ring gear are driven by the smaller gear (known as the pinion) of the starter motor. The pinion engages the starter ring only during starting and once the engine is running the pinion withdraws.

Manufacture

The starter ring gear is most commonly made by forming a length of square or rectangular steel bar into a circle and welding the ends together. This ring is then

machined Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...

to create flat surfaces of the required inner and outer diameters. The gear teeth are then created using a hobbing tool, followed by processes to chamfer, deburr and clean the gear teeth. Induction hardening is used to increase the surface hardness of the teeth for abrasion resistance and also increase the core strength of the tooth to resist the bending forces applied to the tooth during starting. This heat-treatment is usually followed by tempering to reduce internal stresses and increase the toughness of the teeth. The hardness at pitch circle diameter is typically in the range 45-55 HRc.

Attachment

Starter ring gear attached to a flywheel In cars with a

manual transmission A manual transmission (MT), also known as manual gearbox, standard transmission (in Canada, the United Kingdom, and the United States), or stick shift (in the United States), is a multi-speed motor vehicle transmission system, where gear change ...

, the starter ring gear is fitted to the outer diameter of the

flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...

. The ring gear is usually fixed to the flywheel through use of an interference fit, which is achieved by heating the ring gear and so that thermal expansion allows it to be placed around the flywheel. In cars with an

automatic transmission An automatic transmission (sometimes abbreviated to auto or AT) is a multi-speed transmission used in internal combustion engine-based motor vehicles that does not require any input from the driver to change forward gears under normal driving ...

, the starter ring gear is usually welded to the outside of the

flexplate A flexplate (or flex plate) is a metal disk that connects the output from an engine to the input of a torque converter in a car equipped with an automatic transmission. It takes the place of the flywheel found in a conventional manual transmission s ...

References

{{DEFAULTSORT:Starter Ring Gear Automotive transmission technologies Engine components Gears

Manufacture

Attachment

See also

References