automobile differential is a device composed of left and right side gears, two planetary gears and a gear carrier.
The differential is installed to adjust the speed difference between the left and right wheels. In four-wheel drive, in order to drive the four wheels, all the wheels must be connected. If the four wheels are mechanically connected together, the car cannot rotate at the same speed when driving in a curve. In order to allow the car to drive in a curve, The rotation speed is basically consistent. At this time, a middle differential needs to be added to adjust the speed difference between the front and rear wheels.
Four-wheel drive vehicles will have many problems while driving, such as braking in sharp turns, interference in the front and rear drive wheels, etc. Since the differential can absorb the difference in rotational speed of the front wheels, after adding a middle differential, the rotational speeds of the front and rear drive shafts can be different. The automobile differential is mainly used to eliminate the mechanical interference caused by the inconsistent left and right wheel speeds when the car is turning. Without a differential, mechanical damage will be caused by the inconsistent left and right wheel speeds.
Types of differentials
Open differential
The open differential can work normally when the car is turning, and the planetary gear set does not have any locking device. However, during off-road use, the open differential will weaken the ability to get out of trouble on non-paved roads.
Multi-plate clutch differential
Multi-plate friction limited-slip differential relies on a wet multi-plate clutch to generate differential torque . This system is mostly used as the center differential of the timely four-wheel drive system .
There are two sets of friction discs inside, one is the driving disc and the other is the driven disc. The driving disc is connected to the front axle, and the driven disc is connected to and the rear axle . The two sets of discs are soaked in special oil, and the combination and separation of the two are controlled by an electronic system. When driving in a straight line, the discs separate and the vehicle is basically in a front-wheel drive or rear-wheel drive state. During the turning process, a speed difference occurs between the front and rear axles, and a speed difference between the main and driven discs. If the speed difference between the inner and outer wheels of the vehicle does not meet the preset requirements of the electronic system, the two sets of discs will still remain separated. The vehicle steering is not affected.
When the current speed difference of the rear axle exceeds a certain limit, the electronic control system will control the hydraulic mechanism to tighten the multi-plate clutch. At this time, the driving plate and the driven plate begin to contact, similar to the combination of the clutch, the torque is transmitted from the driving plate to the driven plate. to achieve four-wheel drive. The
multi-plate friction limited-slip differential reacts quickly and can be combined instantly and can be combined through the vehicle's electronic control system. However, only up to 50% of the power can be transmitted to the rear wheels, and it is easy to overheat when working under high loads.
Torsen differential
The core of the Torsen differential is the worm gear. From the structural view of the Torsen differential, you can see the double worm gear and worm structure, which provides mutual meshing interlocking and unidirectional torque transfer from the worm gear. The structure of transmitted to the worm gear realizes the differential locking function. Simply put, the Torsen differential is a fully automatic purely mechanical differential, that is, a limited-slip differential that does not require human control + is 100% reliable + direct transmission.
When driving normally in a curve, the front and rear differentials function as traditional differentials. The worm gear does not affect the difference in the output speed of the half shaft. For example, when the car turns left, the right wheel is faster than the differential, and the right wheel is faster than the differential. The left side has a low speed and the left and right worm gears with different speeds can closely match the synchronous meshing gears. At this time, the worm gear is not locked because the torque is from the worm gear to the worm gear. When one wheel slips, the worm gear assembly comes into play, automatically adjusting power distribution extremely quickly through a Torsen differential or hydraulic multi-disc clutch. The core device of
is the central torque-sensing self-locking differential, which can continuously change the power output between the front and rear axles at a ratio of 25:75 to 75:25 according to the driving state. The response is very fast and is supported by the electronic stability program, which can improve the initiative of power distribution.
The Torsen differential can instantly provide feedback to the resistance difference between the drive wheels, thereby distributing the torque output and being able to adjust it within a wide torque output range.However, there is no two-wheel drive state and the differential limited slip capability is limited, so power cannot be completely transmitted to a certain wheel.
Viscous coupling differential
Viscous coupling differential is a clever device that automatically distributes power on all-wheel drive vehicles. Usually installed on all-wheel drive vehicles based on front-wheel drive. This kind of car usually drives in front-wheel drive mode. The biggest feature of the viscous coupling is that it can automatically distribute power to the rear drive axle as needed without driver control.
During normal driving, there is no speed difference between the front and rear wheels, the viscous coupling does not work, the power is not distributed to the rear wheels, and the car is still equivalent to a front-wheel drive car. When the car is driving on a non-paved road, the front wheels will slip and spin, and there will be a large speed difference between the front and rear wheels. The silicone oil between the inner and outer plates of the viscous coupling is stirred and begins to expand due to heat, producing a great viscous resistance, preventing the relative movement between the inner and outer plates, and generating a large torque. Power is automatically sent to the rear wheels, converting the car into an all-wheel drive vehicle.
When the car turns, the viscous coupling can also absorb the difference in rotation speed of the front and rear wheels due to the difference in the inner wheels, and function as a front and rear differential. When the car brakes , it can also prevent the rear wheels from locking first.
