Four-wheel drive technology of the Audi Quattro articles

"Rally to see the four-wheel drive, four-wheel drive to see Quattro" I believe that this is a new way of thinking of the left from the early eighties, Audi With this set, then in the Rally arena can be described as invincible, so many Rally fans obsessionand pay homage to the Quattro system in the end why so magical?

Figure: 1980 Audi Quattro, can be regarded as the first stage this set of four-wheel drive system. Its use is the first generation Quattro system.
To learn Quattro, you must first understand its core components: Torsen differential. As shown above, the hollow shaft and differential housing 3 through spline first company, composed of three pairs of worm gear Vice worm 5,9 and 3 worm gear 8. Two spur gears at both ends of each worm gear, through the middle of the worm shaft 7 installed in series with the differential housing. Worm gear meshing with the front and rear axle worm meshed with each other through the spur gear front axle worm and the front differential gear shaft 1, 4 each integral the rear axle worm and differential gear shaft. If you want an analogy with ordinary differential Torsen differential, the worm equivalent of the side gears, worm shaft is equivalent to a planetary gear shaft, equivalent spur gear planetary gear.

Differential gear shaft before power goes to the front axle, the differential gear shaft power transmission subsequent bridge, in order to achieve the front and rear drive traction role. The Torsen differential work process can be divided into the following three conditions:
① When the car is traveling straight on a dry pavement with good adhesion coefficient, since the the two worm shaft speed is the same, and therefore between the worm and worm-free relative rotation of the differential housing with two worm shafts are rotated synchronously around the worm screw axis, torque distributed evenly between the front and rear axles.
② if the vehicle on slippery roads, the operations such as turning or accelerating, in this case, if the front wheel speed is faster, the front axle worm driven engagement therewith a worm wheel is rotated simultaneously worm spur gear driven engagement therewith after the shaft worm spur gear reverse rotation. Spur gear by the torque of the internal friction due to the worm gear pair transmission inverse efficiency is very low, corresponding to the rear axle worm block, thereby limiting the increase in speed of the rear wheels to achieve a differential action (only in the two-shaft speed Poor little difference to differential).
③ If the car in bad road slip, for example, the front wheel idling case ② similar, but this time around the shaft worm speed difference is too large by a great deal of internal friction torque, making the rear axle worm spur gear also limits the front axle worm straight spur gears rotate, all the torque distribution to the rear axle worm, the equivalent differential locked, can not afford the differential action.
In fact, Audi is only used in the shaft between the Torsen differential, front and rear axle differentials are ordinary differential. Then the reader will ask slip slip available to the Torsen differential between the axis between the shafts, wheel slip Torsen differential is not useless this? Do not worry, Audi specifically for this problem is designed EDL (electronically controlled differential lock), wheel spin, EDL its braking torque output reached the other side of the little wheel. Longitudinal engine layout installed Torsen differential transmission line layout is simple and the weight concentrated in the axis better maneuverability Torsen differential is mounted in a longitudinal engine models. No two sharp needles, an increase of certain vehicle weight, high manufacturing costs, is too sensitive to the slipping wheel makes driving fun little flaws are Quattro certain loss.