# differential gear

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differential gear
1. differential (def. 7).
2. any of various comparable arrangements of gears, as an epicyclic train.
[1885-90]

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In automotive mechanics, a gear arrangement that transmits power from the engine to a pair of driving wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or traversing an uneven road.

On a straight road the wheels rotate at the same speed; when turning a corner the outside wheel has farther to go and would turn faster than the inner wheel if unrestrained. The automobile differential was invented in 1827; originally used on steam-driven vehicles, it was well known when internal-combustion engines finally appeared.

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in automotive mechanics, gear arrangement that permits power from the engine to be transmitted to a pair of driving wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or traversing an uneven road. On a straight road the wheels rotate at the same speed; when turning a corner the outside wheel has farther to go and will turn faster than the inner wheel if unrestrained.

The conventional automobile differential was invented in 1827 by a Frenchman, Onésiphore Pecqueur. It was used first on steam-driven vehicles and was a well-known device when internal-combustion engines appeared at the end of the 19th century.

The elements of the Pecqueur differential are shown in the Figure—>. The power from the transmission is delivered to the bevel ring gear by the drive-shaft pinion, both of which are held in bearings (not shown) in the rear-axle housing. The case is an open boxlike structure that is bolted to the ring gear and contains bearings to support one or two pairs of diametrically opposite differential bevel pinions. Each wheel axle is attached to a differential side gear, which meshes with the differential pinions. On a straight road the wheels and the side gears rotate at the same speed, there is no relative motion between the differential side gears and pinions, and they all rotate as a unit with the case and ring gear. If the vehicle turns to the left, the right-hand wheel will be forced to rotate faster than the left-hand wheel, and the side gears and the pinions will rotate relative to one another. The ring gear rotates at a speed that is equal to the mean speed of the left and right wheels. If the wheels are jacked up with the transmission in neutral and one of the wheels is turned, the opposite wheel will turn in the opposite direction at the same speed.

The torque (turning moment) transmitted to the two wheels with the Pecqueur differential is the same. Consequently, if one wheel slips, as in ice or mud, the torque to the other wheel is reduced. This disadvantage can be overcome somewhat by the use of a limited-slip differential. In one version a clutch connects one of the axles and the ring gear. When one wheel encounters low traction, its tendency to spin is resisted by the clutch, thus providing greater torque for the other wheel.

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Universalium. 2010.

### Look at other dictionaries:

• differential gear — or differential gearing n. a certain arrangement of gears (epicyclic train) connecting two axles in the same line and dividing the driving force between them, but allowing one axle to turn faster than the other: it is used in the driving axles of …   English World dictionary

• differential gear — n technical an arrangement of ↑gears that allows one back wheel of a car to turn faster than the other when the car goes around a corner …   Dictionary of contemporary English

• differential gear — diferencialas statusas T sritis automatika atitikmenys: angl. differential gear vok. Differentialgetriebe, n rus. дифференциальная передача, f pranc. différentiel, m …   Automatikos terminų žodynas

• differential gear — gear that permits a different speed for two adjacent axles, differential …   English contemporary dictionary

• differential gear — noun a bevel gear that permits rotation of two shafts at different speeds; used on the rear axle of automobiles to allow wheels to rotate at different speeds on curves • Syn: ↑differential • Hypernyms: ↑bevel gear, ↑pinion and crown wheel,… …   Useful english dictionary

• differential gear — /ˌdɪfərɛnʃəl ˈgɪə/ (say .difuhrenshuhl gear) noun Machinery 1. → differential (def. 6). 2. any of various analogous arrangements of gears …   Australian English dictionary

• differential gear — noun Date: circa 1859 differential 3a …   New Collegiate Dictionary

• differential gear — See differential gears …   Dictionary of automotive terms

• differential gear — dif′feren′tial gear′ n. mac an epicyclic train of gears designed to permit two or more shafts to rotate at different speeds • Etymology: 1885–90 …   From formal English to slang

• differential gear — noun An arrangement of bevel gears permitting the rotation of two shafts at two different speeds whilst supplying the same torque; used on the rear axles of automobiles to aid cornering …   Wiktionary