The so-called torque-sensitive limited-slip differential means that the limited-slip torque of the differential is closely related to the input torque of the differential housing, which is called torque-limited differential for short. The so-called speed-sensitive limited slip differential means that the limited slip torque of the differential is closely related to the speed difference between the left and right half shafts of the differential, which is called speed-limited differential for short. The so-called active control differential refers to the limited slip differential which can realize the limited slip by electronic device or electro-hydraulic control device and make the driving wheels on both sides get better driving attachment effect in real time, which is called active limited slip differential for short.
Torque limited slip differential is favored by the market for its superior performance and moderate price. However, the speed limited slip differential generally realizes the perception of differential speed by means of the viscous friction characteristics of liquid or special tooth profile. With the development of science and technology and the breakthrough of electronic technology, the active control limited slip differential will have a better development space.
1. Torque limited sliding differential
(1) Torsten limited slip differential. Is Tolson torque? The abbreviation of sensing, which means torque sensitivity. This type of differential is the most typical gear tooth limited slip differential. Its earliest model T- 1 has been widely used in four-wheel drive vehicles. It uses the irreversible principle of worm gear transmission and the high friction condition of tooth surface to make the differential automatically lock or unlock according to its internal differential torque (internal friction torque of the differential), that is, it plays a differential role when the differential torque is small, and automatically locks the differential to a certain extent when it is too large, which effectively improves the passability of the automobile.
(2) Friction plate limited slip differential. Friction plate limited slip differential is developed on the basis of symmetrical bevel gear differential. It is the earliest structure form of limited slip differential, which is widely used, and it is also a torque limited slip differential with high market share at present. The main idea of this limited slip differential is to increase the internal friction torque of the differential and realize the "limitation" of the differential action. In order to increase the friction torque in the differential, a driving friction plate and a driven friction plate are usually installed between the half-shaft gear and the differential case. The cross shaft consists of two mutually perpendicular planetary gear shafts, and the ends of the planetary gear shafts are made into convex V-shaped wedge grooves, which match with the concave V-shaped wedge grooves on the holes of the differential case, and the V-shaped surfaces of the two planetary gear shafts are installed in opposite directions. In addition to Torsten type and friction plate type, torque limited slip differential also has cone plate type and slider cam type.
2. Speed-limited sliding differential
The most typical speed limited slip differential is viscous differential, which uses the viscous friction characteristics of liquid to limit slip, and its function of limiting slip depends on the speed difference between the front and rear axles (inter-axle differential) or the left and right wheels (inter-wheel differential). Viscous differential has two working states: shear state and hump state.
3. Active limited slip differential
Torque-type limited-slip differential and speed-type limited-slip differential realize the function of limited-slip differential according to the perception of torque difference and speed difference when working, which has the functions of automatic adaptation and self-adjustment, and the driver cannot actively control it. Therefore, in some cars and off-road vehicles, the active control limited slip differential is adopted. At present, there are three structural forms of active control limited slip differential-electromagnetic, electro-hydraulic and motor. The first two are introduced below.
(1) electromagnetism. The electromagnetic active limited slip differential is mostly based on friction plate differential, and the active control of limited slip performance is realized by electromagnetic force. In general, the relevant sensors will collect information such as vehicle running conditions and road conditions, and transmit them to the electronic control unit. The electronic control unit analyzes, judges and processes these information, and then adjusts and controls the electromagnetic force of the electromagnetic device according to the built-in control program. The electromagnetic force is amplified by actuators such as cams, and a pressing force is formed on the friction element, thereby generating an internal friction torque and forming a slip-limiting function. Because the electromagnetic force of the electromagnetic device can be actively adjusted according to the working conditions, the internal friction torque can be changed, that is, the locking coefficient can be dynamically changed to realize real-time active control, thus better meeting the needs of automobile use.
(2) Electro-hydraulic type. The electro-hydraulic active limited slip differential is also based on friction plate differential, which is generally similar to the hydraulic pump differential, except that the oil pressure in the hydraulic pump differential is passively generated, while the oil pressure in the electro-hydraulic active limited slip differential is actively adjusted. After analyzing, judging and processing the information such as vehicle working conditions and road working conditions, the electronic control unit controls the electronic control hydraulic valve according to the control program, so as to realize the active adjustment of oil pressure and change its internal friction torque, thus dynamically changing its locking coefficient and realizing real-time active control.