1. The four-wheel drive
The so-called four-wheel drive, also known as all-wheel drive, front and rear wheels means the car has power. According to the state of the road surface with the engine output torque in different proportions distributed on all the front and rear wheels, in order to improve the car’s driving ability. General use 4X4 or 4WD be said that if you see a car marked with the above words, it means that the vehicle has four-wheel drive capabilities.
Characteristics of the driving means profile
in the past only with 4-wheel drive off-road vehicles, off-road vehicles in general, downstream of the transmission with the manual component device, a front and rear axles each mounted It referred to the drive axle components. Torque transmission output shaft through the component and, respectively, transmitted to the drive axle on the front and rear axles, then the torque is transmitted to the wheels through a drive axle. Now some cars also were using 4-wheel drive system, such as the Audi A4quattro, Q7, Outlander 4WD version. Now horsepower than the larger car, shifted the center of gravity during acceleration, the weight of the entire vehicle will move to the rear axle, causing the front axle buoyant. Front-wheel drive car will slip even on a good road, four-wheel drive can prevent this from happening.
Interior Design
The 4-wheel drive means
is a constant mesh car, increasing the viscous coupling, eliminating the need for manual component force, a torque by automatically to be allocated on the front and rear wheels. In normal road surface, the drive means 92 the percentage of four engine output torque distribution to the front wheels to the rear wheels 8 percentage distribution; on the slippery road surface, will be at least 40 percent machine engine output torque to the rear wheels; front wheel start to slip, front and rear wheel speed difference causes coupler immediately thickened mucus and lock coupler, such that the propeller shaft transmitting torque to the rear wheels only, until the front, the rear wheel rotation speed difference disappears automatically reply to the original drive form.
HEV-drive
Currently, four wheel drive cars have been introduced computerControl system, when the front wheel or rear-wheel drive car at any time before and after power distribution feedback wheel road surface conditions, driving becomes four. 4-wheel drive can be broken down into 4 driving modes: full-time drive (Full-Time), driver (Part-Time) when and timely drive (Real-Time) and the time and / timely mixed driving.
When a drive full
Full drive (Full-Time): the vehicle is always maintained before and after the 4-wheel drive mode, the engine output torque when driving 50:50 set on the front and rear wheels. Full-time drivers with good driving control and tracking of travel, the disadvantage is more waste oil, the economy is bad.
and the drive (Part-Time): by the driver according to the road conditions, by turning on or off the splitter to change two or four-wheel drive driving mode, which is typically 4WD SUV or SUV most common drive mode. The advantage is driving modes can be selected according to the actual situation, more economical; drawback is its relatively complicated mechanical structure, the driver should have some experience to master the switching timing.
timely driven
timely drive (Real-Time): using timely driven (Real-Time) of the vehicle, which driving mode which is selected by the computer control, normal Pavement general rear-wheel drive, or if the bad-road driving wheel slip, the computer will automatically detected and the engine output torque is immediately assigned to the other two, the state is switched to the 4-wheel drive, simple operation. The disadvantage is that the computer immediate reaction is slow, the lack of driving pleasure.
system class
four-wheel drive system is divided into two categories: active and passive, but nothing more than only one purpose, that is, the power slip from idle wheels removed, then reassigned to grip the larger wheels, wheel slip is like, we use wood and other things stuffed in stone wheels slipping below, the reason is very simple.
to prevent wheel spin
When two (front or rear) wheel spin drive vehicle slip occurs, only a remedy, the engine is reduced the driving force, and the driverOnly through oil revenues in order to achieve this goal, the trip computer or the control received a small throttle. The four-wheel drive car is different, you can let your liking playing foot refueling, power is automatically assigned to each wheel through an electronic system that can more effectively prevent wheel slippage occurs.
four-wheel drive car will be more to strengthen contact with the road
A lot of people might think four-wheel drive car will be more to strengthen contact with the road, in fact, they stick to the concept of performance to confuse, four-wheel drive vehicles and two-wheel drive car is the biggest difference is that: FF models because of idle wheels and understeer, a departure from the corners, and FR models will drift, the four-wheel drive power distribution because each wheel is automatic, there would not be on top of this problem, this is a problem related to the tracking performance of the car, but not contact with the road.
and the two wheel drive version
Conversely, a car with four-wheel drive and two plate version, often two versions of acceleration and affixed version of the performance better than four, the best example is the Audi A4, because the four-wheel drive car than the two-wheel drive in terms of weight and friction is greater. Passive four-wheel drive system, uses a mechanical transfer means such as a gear type differential torque sensing – Audi’s Quattro, or hydraulic actuator sub – Porsche 911 Turbo, the system is after idling wheel occur before intervention. And the active four-wheel drive system, through the multi-disc clutch is controlled by the computer to intervene, for example, the public 4 Motion, the computer will continue to collect the tire speed and the size of the data such as the accelerator, put before the tire generating idle good torque distribution.