What is center differential?

1, Principle

automotive engine power through the clutch, transmission, drive shaft, and then finally to the drive axle to the left axle drive wheels assigned, in this transmission path Power on the drive axle assembly is the last one, it is the main component and a differential gear unit. Effect is deceleration torque-speed reducer, this function entirely by the engagement between the gear and the gears, which is easier to understand. The differential is more difficult to understand, what is differential, why should “differential”? Automotive differentials are the main pieces of drive axles. Car wheel when negotiating a curve trajectory of a circular arc, if the car turns left, the center point of the arc on the left, at the same time, to go right wheel camber length than the left wheel, in order to balance this difference , will slow down the left wheel and right wheel a little faster, with a different speed to compensate for the difference in the distance. If the rear axle made into a whole, can not be done on both sides of the wheel speed difference, that is, it can not automatically adjusted. To solve this problem, as early as a hundred years ago, the founder of the French car company Renault Louis Renault designed a differential on this stuff. Ordinary differential planetary gear, the planet wheel carrier (differential case), the side gears and other parts. The power of the engine through the shaft into the differential directly drives the planet gear carrier, and then drive the left and right by the two planetary gear axle, drive the left and right wheels. To meet design requirements 🙁 differential speed left axle) + (right axle speed) = 2 (the rotational speed of the planetary carrier). When the car straight, three frame right and left wheels in the planetary gear speed equal to the equilibrium state, and when the car is turning three equilibrium damaged, resulting in reduced speed of the inner wheel, the outer wheel speed increases. This adjustment is automatic, involved here, “the minimum energy principle”, that is, all objects on Earth tend minimal energy state. For example, to a bean into a bowl, beans will automatically remain in the bottom of the bowl and never stay in the bowl wall, because the bowl is the lowest potential energy (potential energy), which automatically selects the rest (minimum kinetic energy) without We will be in constant motion. Similarly, the wheel will automatically tend lowest energy state during turning, automatically adjust the speed of the left and right wheels according to the turning radius. When cornering, since the outer wheel slip has drag phenomenon, the inner wheel has a slip phenomenon at this time will have two wheels opposite directionsAdditional force, due to the “principle of minimum energy”, will inevitably lead to different rotational speeds of wheels on both sides, thereby destroying the balance of the three, and is reflected by the side gear to the axle, planetary gears or forcing the rotation, the outer axle speed speed up, slow down the speed of the inner axle, the wheel speed difference to achieve both sides. The differential is not only when the car turns to work, the car driving on uneven pavement also play a role. It can be said, as long as the left and right wheel speed is not the same in any case that the differential at work.

2. Category

different differential lockup mode used is different, now common differential lock, generally have the following lock-up mode: positive lock stop mode, the high-friction self-locking, jaw, and a viscous coupling type Torsen type. In which the jaw commonly used in heavy goods vehicles, this is not for details.

3, the lock mode

different differential lockup mode used is different, now common differential lock, the lock generally have the following ways: A locking force, high frictional self-locking, jaw, and a viscous coupling type Torsen type. In which the jaw commonly used in heavy goods vehicles, this is not for details. 1. A locking force

A locking force differential lock is provided on a conventional differential lock symmetrical bevel gear differential, the differential lock simple structure, easy manufacturing, high torque distribution ratio . However, quite inconvenient manipulation, generally need to stop; Further, if too early or too late connected off the differential lock, it will produce a series of problems when there is no differential, the torque distribution can not be changed. 2. High frictional self-locking

High frictional self-locking and friction-type slide cam plate like structure. -Disk friction torque produced by a relative slip between the friction plate to make the differential locking, this differential lock structure is simple, smooth, most common in cars and light vehicles; Ram Cam means of a slide between the cam blocks and largeTo make friction torque differential locking, which can be improved by the performance of the car is largely, but the complex structure, high processing requirements, the friction members wear, more costly. Two or more high-friction self-locking differential locks can be assigned within a range about both sides of the output torque of the wheel, and the access is automatically disengaged, and therefore widely used. 3. Torsen type

Torsen differential is a new inter-axle differential, in which the all-wheel drive car (including Audi A7) have a widely used. “Torsen” is the name are registered trademarks of Gleason Corporation, said, “torque sensitive differential.” It uses a basic principle of a worm gear having a self-locking feature. Compact Torsen differential, the transmission torque is large and the range of the adjustable variable, and therefore widely used in all-wheel drive car center differential and a rear wheel axle differential. However, due to its automatic locking effect at high rotational speed torque difference, generally it can not be used between the front wheel drive axle differential. 4. Viscous coupling type

It also uses the viscous coupling portion coupling four-wheel drive car is used as a differential. The new differential using silicone oil as a torque transfer medium. Silicone oil having a high coefficient of thermal expansion, when the rotational speed difference between the two axles is too large, a sharp rise in the temperature of the silicone oil, the volume continues to expand, pushing the friction blades closely silicone oil, which is viscous coupling ends directly into one of the drive shaft, i.e., the viscosity coupler lock. This phenomenon is called “hump phenomenon.” This occurs very quickly, suddenly differential lock, the vehicle broke down easily from the ground. Once criticize the oil is stopped, the temperature of the silicone oil gradually decreased until well after cooling, the hump phenomenon will disappear. In view of the viscous coupling soft smooth transmission of torque, a differential fast response, which is to promote the use of the inter-axle differential of the driving axle system, as the inter-axle differential, so that the all-wheel drive car greatly improve performance.

4, the drawbacks of

center differential lock (four-wheel drive) risk

in a four wheel drive vehicle center differential lock in the divisional when the four-wheel drive state, in a dry road surface tend to straight traveling of the vehicle, because at this time both right and left wheels withA large adhesion, so that the left and right driving wheels during cornering different from the rotational speed difference generated by the front and rear axles of the differential rotational speed difference before and after passing the drive shaft, the drive shaft back and forth at this time because there is no central differential will resolve out the difference in rotational speed, the differential force will limit the rotation of the wheel with the ground, thereby causing difficulties in steering, such as when the roll can lead to excessive speed. And on slippery surfaces, since the wheel speed difference can this force will relieve slide on the ground, it will not turn difficulties. Therefore four-wheel drive is only suitable for use on a small adhesion to sand, mud or snow road and the like, is used on a dry road surface, only straight running. After the issue front and rear locking differential

The above risk when it comes to four-wheel drive on the highway, and if we further lock the state in four-wheel drive front and rear axle differential, then turning vehicles on the road is almost impossible to achieve. In the normal course of running a sudden locking front and rear axle differential, will easily cause overturn of the vehicle. Damage to the locking differential four-wheel drive system

After locking the center differential and the front and rear axle differentials, power of the engine is likely to be concentrated from the slipping wheel to the wheel is still adhesion However, the design of the vehicle driveline torque of the engine is to allow equally to all four wheels, if only one or two wheels adhering force, a torque will be obtained which may exceed the driveline can bear. For example speaking, linked into a four-wheel drive and locking differentials front and rear axles of off-road vehicles, three-wheeled because the ground muddy and loss of adhesion, then the time 100 percent increase in engine power will have adhesion Flanagan axle wheels if the vehicle is traveling and adhesion resistance are large, the engine torque will be sufficient great broken wheel axle associated with this. Therefore, the use differential lock, control of the vehicle will become very important.