Silicone is an inert synthetic compound that come in a variety of forms (oil, rubber, resin). Typically, heat-resistant and rubber-like, they are present in sealants, adhesives, lubricants, medical applications, cookware and insulation. Silicone is a polymer that contains silicon, combined with carbon, hydrogen and oxygen and, in some cases, other elements.
Silicone Properties
Silicone, due to its polysiloxane, provide several advantages:
Thermal stability (from -80°C to 250°C)
Resistance to natural ageing (oxidation, UV)
Resistance to fire, low emission of smoke and toxic fumes, self-protection, ceramization of ashes
Low surface energy
Good wetting on many substrates
Hydrophobia (beading effect)
Release or adhesion properties, according to need
Exceptional harmlessness for a wide range of applications
Biocompatibility, well-suited for food contact and medical applications
Safe and comfortable skin contact
Flexible chain of up to -100°C for enhanced lubrication and gas permeability performance
Easy processing, excellent spread and coating capabilities
Available in a variety of forms – fluids, liquid silicone elastomers (LSR) and high-consistency rubbers (HCR)
1. Torsen differential: The so-called Torsen differential is to use worm gear to achieve self-locking, which can work continuously like ordinary differentials, and has no delayed response, and does not interfere with the total torque The adjustment of the output, at this time, there is no loss of torque. Compared with the traction control and body stability control systems, it has a greater advantage in performance and is heavier in weight.
2. Helical gear differential: In fact, the principle is no different from the former, but the helical gear is parallel to the half shaft, and the helical gears are meshed with each other, which means that there will be a certain amount of wear and tear. But it will be slightly lighter in weight.
3. Mechanical differential: It mainly uses two sets of left and right pressure plate groups and clutch plates. The limited slip percentage function can be achieved by the arrangement and combination of clutch plates and pressure plates, and the response speed is very fast, but the difference between the differential oil The fluidity is relatively poor and the heat dissipation performance is not very good, so the durability is not very good.
4. Eaton differential: In fact, this differential is also a mechanical differential, but it is slightly simpler in structure than a mechanical differential. A flyweight is set in the differential housing. When the speed difference reaches When a certain value is reached, the flyweight will be locked, and the wheels on both sides will be connected linearly, so as to achieve the purpose of getting out of trouble.
The friction differential improves the locking coefficient of the differential by increasing the internal friction during differential rotation. There are roughly three practical structures: internal friction limited-slip differential, slider cam limited-slip differential and a worm gear limited-slip differential.
The internal friction differential increases the resistance torque of differential rotation by adding friction plates between the back of the axle shaft and the differential housing. It can be divided into two categories with spring preload and no spring preload: the differential resistance torque of the differential with spring preload is basically constant, which has nothing to do with the output torque of the drive axle, so the vehicle is under light load. When turning down, the traction force generated by the outer wheels is negative, which not only reduces the power of the vehicle, but also increases the loss of tires; the non-preloaded differential needs to stack multiple friction plates behind the half shafts to achieve the required locking compact coefficient, and its structure is not compact. This type of differential has special requirements for lubricating oil, and the different requirements for oil of hyperbolic gears and friction plates should be taken into account when selecting. Because its work is relatively stable and the technology is relatively mature, it is widely used in off-road vehicles, luxury cars and construction machinery abroad. The friction differential improves the locking coefficient of the differential by increasing the internal friction during differential rotation. There are roughly three practical structures: internal friction limited-slip differential, slider cam limited-slip differential and a worm gear limited-slip differential. The internal friction differential increases the resistance torque of differential rotation by adding friction plates between the back of the axle shaft and the differential housing. It can be divided into two categories with spring preload and no spring preload: the differential resistance torque of the differential with spring preload is basically constant, which has nothing to do with the output torque of the drive axle, so the vehicle is under light load. When turning down, the traction force generated by the outer wheels is negative, which not only reduces the power of the vehicle, but also increases the loss of tires; the non-preloaded differential needs to stack multiple friction plates behind the half shafts to achieve the required locking compact coefficient, and its structure is not compact. This type of differential has special requirements for lubricating oil, and the different requirements for oil of hyperbolic gears and friction plates should be taken into account when selecting. Because its work is relatively stable and the technology is relatively mature, it is widely used in off-road vehicles, luxury cars and construction machinery abroad.
The slider cam type limited slip differential has a wide range of applications, and the main components include the differential case, the slider, and the inner and outer cams. According to the different installation direction of the slider, it can be divided into radial slider type and axial slider type; according to the different number of slider installation rows, it can be divided into single row slider type and double row slider type. When the adhesion coefficients of the left and right wheels and the road surface are different, and the ratio of the two does not exceed the locking coefficient, the slider cam differential can ensure that the wheels with poor adhesion coefficients do not slip. When the adhesion of the left and right wheels to the road surface is good, the left and right wheels can roll normally according to the motion requirements and maintain good steering performance. However, the structure of this type of differential is relatively complex, and the requirements for molding, materials, chemical treatment, heat treatment, etc. are relatively high, so the cost is also relatively high.
Worm gear limited-slip differentials are mainly used in trucks, off-road vehicles and road tractors, and can cope with various complex road conditions. Currently, the most widely used is the Torsen differential. The Torsen differential was developed by Gleason Company in the United States. [3] It makes full use of the self-locking and high-friction characteristics of the worm gear, so that the locking coefficient of the differential has been greatly improved. Torsen differentials have reliable performance and compact structure. They can not only automatically prevent slippage, but also automatically adjust the locking coefficient according to the different turning radius and road driving conditions. However, when the torque difference is large, this type of differential will automatically lock, which affects the normal differential function. Therefore, this type of differential is generally not used as a wheel on the steering drive axle. Differential used.
Frition Plate Limited Slip Differential(LSD) essentially consists of an ordinary bevel gear differential combined with friction plates which can (partially) engage the side gears to the differential cage. The larger the torque, the greater the locking effect.
The friction plates usually have a spline connection with the side gears. The outer plates are usually connected with a sliding connection to the differential cage. The outer plates will always have the same speed as the differential cage, and the friction plates have the same speed as the side gears and drive shafts.
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LSD can also be divided into different types of locking rates. The way of distinguishing can also be distinguished from the shape of the cam hole. The higher the angle is, the higher the locking rate is. At this time, the initial torque of the LSD operation is lower, that is, there is a slight difference in wheel speed between the two wheels. It will be locked to make the two wheels rotate synchronously; on the contrary, the lower the locking rate, the higher the allowable value of LSD for the difference in wheel speed between the left and right wheels. The locking rate can be from 15 degrees to 65 degrees. It is recommended to use a setting of 15~35 degrees for a tail-swing car and a street car. This is because if a general street car uses an LSD with a high locking rate, when turning at a low speed or reversing into the garage, the left and right tires will be easily locked. There is a difference in the rotation speed, and the driver needs to constantly replenish the oil to make the inner wheel make a idling sound of “brushing, brushing, brushing”, so that the vehicle can turn smoothly, making driving more difficult, losing the convenience of daily use, and accelerating tire wear. Speed, so unless you really love self-challenging mountain roads, or even a tail flick, don’t try LSD with a high lock rate easily.
Regarding the principle and application skills of mechanical LSD, it is not comparable to the advancement of drive technology. Take Audi Quattro four-wheel drive system as an example. Through high-speed computing computer, rudder angle/G value/wheel speed sensor, and electronic hydraulic pressure Drive friction disc type LSD, there is no so-called difference in way or locking rate, you can lock how you want to lock。
This kind of mechanical LSD, which is widely used in modification and competition, can be divided into one-way 1-way and two-way 2-way according to different working times. The so-called one-way and two-way refers to the time of the LSD action. Only when the accelerator is opened and the left and right wheels produce slip, the limited-slip effect is 1 Way (one-way LSD); regardless of whether the accelerator is on or off, as long as The left and right drive tires that can generate slippage are continuously locked, which is called 2way (two-way LSD); and when the accelerator is opened, if it can have a half effect in the closed state, it is called 1.5 Way LSD (two-way LSD). .
In addition to the working timing, LSD can also be divided into different types of locking rates. The higher the angle of the cam hole, the higher the locking rate. The locking rate can be from 15 degrees to 65 degrees. The higher the value, the more suitable for racing cars, such as drift cars. A setting of 15~35 degrees is better.
As for how to distinguish the working characteristics of the limited slip differential, it can be identified from the shape of the cam hole on the pressure ring. The shape of the 1Way cam hole on the deceleration side is flat, and the 1.5 Way cam hole is slightly angled, but compared with the acceleration side. It is still slightly smooth, and the angle of the acceleration and deceleration side of 2Way is the same. Because the limited-slip force of the limited-slip differential has a direct relationship with the opening width of the cam top-opening pressure ring (the tighter the clutch plate is, the stronger the force), so the 1Way cam can only be pushed up during acceleration. Open the pressure loop, so it only works during acceleration; although the 1.5 Way can also open the pressure loop during deceleration, but because the angle is smaller than the acceleration side, the force is also smaller; as for the 2Way, the acceleration and deceleration side angles are the same, so The force during acceleration and deceleration is also the same. That is to say, because the working characteristics of LSD are determined by the design angle of the cam hole, the workability of mechanical LSD can be changed. One-way and two-way adjustment is a very thoughtful design.
For applicable models, 1Way’s LSD is more suitable for use in front-wheel drive vehicles that attach importance to the grip of the front wheels, because as long as you continue to accelerate when cornering, the front wheels can maintain a certain driving force. There is no obvious understeer problem due to the locking of the left and right wheels. However, it is worth noting that since the 1Way LSD presents two completely different characteristics during acceleration and deceleration, when the brakes are applied heavily in high-speed corners, the tracking performance of the driving wheels is easily affected.
Rally cars are also one of the heavily used LSD models. Without the assistance of LSD, it is not only impossible to make four-wheel lateral movements, but once the tires get stuck in the mud or snow, it is also difficult to get out of trouble.
As for the 2Way LSD, it is more suitable for rear-drive vehicles. In addition to obtaining sufficient driving force during acceleration, the tracking performance of the driving wheel will not change much when the brake is applied heavily, so the tires can be kept to a certain extent. Grip. But in contrast, under the condition of acceleration and deceleration, the understeer characteristics will also tend to be obvious, unless the corners are turned with a little tail flick. In addition, the 1.5 Way LSD can obtain enough driving force when accelerating, and once the accelerator is released, it will not become difficult to get used to because of the instantaneous loss of the limited slip effect. The 1.5Way LSD is therefore ideal for vehicle installations in all drive modes.
As for the LSD selection of four-wheel drive models, it is recommended that the front wheels can use 1Way, and the rear wheels can use 1.5Way or 2Way LSD, which is more suitable for beginners. In addition, there is also a central differential on the four-wheel drive car to adjust the front and rear. If you are not a serious player, it is recommended to keep the original design of the axle speed. Some high-performance four-wheel drive vehicles have an electronic mid-difference, which can actively adjust the torque of the front and rear wheels. It is a pity to replace them. The reason why the friction plate type LSD needs to use special gear oil, in addition to increasing the heat dissipation efficiency and lubricating effect, through the assistance of the special oil, the friction plate can be moderately idling and slipping when the friction plate is close to the limit, without serious wear and tear, which can be effectively extended. The service life of the friction plate. The reason why the friction plate type LSD needs to use special gear oil, in addition to increasing the heat dissipation efficiency and lubricating effect, through the assistance of the special oil, the friction plate can be moderately idling and slipping when the friction plate is close to the limit, without serious wear and tear, which can be effectively extended. The service life of the friction plate.
The reason why the friction plate type LSD needs to use special gear oil, in addition to increasing the heat dissipation efficiency and lubricating effect, through the assistance of the special oil, the friction plate can be moderately idling and slipping when the friction plate is close to the limit, without serious wear and tear, which can be effectively extended. The service life of the friction plate.
In short, regarding the selection of LSD working characteristics, it can be basically concluded that people who attach importance to handling, it is best to choose one-way LSD, because on mountain roads or racing tracks with many continuous small curves, the accelerator needs to be turned on and off frequently. , It is easy to cause difficulty in turning under the continuous limitation of differential during oil recovery. At this time, if a one-way LSD is used, the LSD can be stopped when the accelerator is closed, so it can reduce the blind spot of operation and the unsmooth turning caused by stepping on the accelerator, especially for those who are not familiar with the driving route or braking point. Beginner. On the contrary, the two-way LSD is more suitable for vehicles that need to drift frequently. It can play the feature of locking at any time, so that the rear wheels can be easily thrown out like a go-kart, and the response at the moment of opening the accelerator is also very sensitive. , so even in corners, the driving force can be provided instantaneously.
The mechanical limited slip differential (lsd) can have the same effect as the Torsen differential, and it is more widely used. l There are quite a lot of models and the price difference is also big, which can be found on the Internet. One disadvantage of the Torsen differential is that it cannot be 100% locked, only about 80% of the torque can be locked at a maximum.
“Mechanical limited-slip differential” is only to distinguish the assembly of electronic limited-slip differential. This limited-slip differential does not require the intervention of electronic equipment, and works entirely on mechanical principles, so the response speed and reliability are Better than an electronic limited-slip differential.
Torsen differential (torsendifferential), also known as Torsen self-locking differential, uses the irreversibility principle of worm gear transmission and the high friction condition of the tooth surface to make the differential according to its internal differential torque ( That is, the size of the internal friction torque of the differential) will automatically lock or loosen, that is, when the differential torque in the differential is small, it will act as a differential, and when the differential torque in the differential is too large It will be automatically locked, which can effectively improve the passing ability of the car.
When a vehicle is driving on the road, the wheels perform two motions relative to the ground, namely sliding and rolling. In order to reduce friction, tire wear and power consumption when the vehicle is running, the wheels should be rolled as much as possible to reduce slippage. However, when the car turns or drives on an uneven road, the wheels on both sides move at different distances. If the two wheels are connected by a rigid shaft, slippage will inevitably occur during driving, which will reduce the driving performance of the vehicle. Therefore, the wheels on both sides of the same drive axle need to be driven by two half shafts respectively, so that the left and right wheels can rotate at different speeds, so as to ensure the pure rolling of the wheels as much as possible. Off-road vehicles need to drive on bumpy, muddy, slippery, soft and other road surfaces or even no roads, and these ground adhesion coefficients are small. When one wheel is located on the ground with a small adhesion coefficient, although the adhesion coefficient between the other wheel and the ground is good, the traction force that the car can achieve cannot be effectively utilized, resulting in the car not driving normally.
To solve the above problems that may occur in off-road vehicles, it is necessary to use a differential device with anti-skid function. Common methods include differential locks and limited-slip differentials. The differential lock is locked together with the axle shaft of the car through the differential housing, which can stop the differential action. increase to the maximum. However, the differential lock needs to be manually locked when entering a difficult road section. If it is not released in time in a good road section, the car may cause an accident due to the lack of differential action. Therefore, most modern off-road vehicles do not use differential locks. A limited slip differential is used instead.
The Torsen differential achieves slip-limiting by cleverly using a pair of worm gears and a worm gear. Its characteristic is that the driving torque is transmitted from the worm gear to the worm gear, and cannot be transmitted in the reverse direction. It will lock up. It is through this feature that limited slip is achieved. In normal cornering, that is, all tires do not slip, the Torsen differential behaves like a normal differential. The additional worm drive and worm gear do not A speed difference is affected between the output shafts. For example, if the car is turning left, the drive shaft of the right wheel rotates faster than the differential housing, and the drive shaft of the left wheel rotates slower than the differential housing. The speed difference between the left and right worm gears can be exactly matched in a synchronized gear drive . Note that the worm gear and worm drive are not locked because torque is transferred from the worm gear to the worm drive. Assuming that if the right wheel loses its grip and slips, it will have an effect on the worm gear and worm drive. In the moment when there is no effect, it is necessary to know that the ordinary differential principle is that the torque will not be sent to the left wheel that has the ability to grip all. The torque of the worm is sent to the slipping and idling right wheel. In this way, the fast rotating right worm wheel drives its worm drive, which drives the left worm drive through the synchronous gear. Remember the characteristics of the worm/worm drive mentioned earlier? When the worm drive drives the worm gear, they lock up. As a result, the worm drive on the left and the worm drive on the right lock together, so that the left and right wheels rotate at the same speed to restore the car’s grip.
Torsen differential. Costs a lot. However, there are many advantages to using Torsen’s 4WD. First, its purely mechanical differential intervenes almost as soon as the tires slip. Second, its locking is linear. That is, it is strictly a full-time four-wheel drive. Under normal conditions, the torque distribution between the front and rear wheels is 50:50 (other distribution ratios are also possible, depending on the gears of the worm drive). Pros: Fast response, permanent 4WD Cons: High cost, torque distribution cannot be changed.
