Self-locking differential ST/RS (p. 6)

Purpose

So, what is this mechanism for? The simplest differential is capable of distributing power or torque between two wheels equally, evenly. If one wheel slips and cannot grip the road surface, then the torque on the second wheel will be zero. Improved models, and the vast majority of them are differentials with a self-locking mechanism, are equipped with a system that blocks the suspended axle shaft. Then the torque is distributed so that the maximum power is on the wheel that maintains good grip.

The Thorsen differential is the most optimal solution for an all-wheel drive vehicle, which is operated mostly in difficult conditions. “Thorsen” is not the name of the developer, but an abbreviation. This stands for Torque Sensing.

Device and main components

Diagram of a Torsen differential in an Audi Quattro car transmission

Let's look at what basic elements Thorsen consists of:

To engage the locker you simply move the gear lever to the locked position and to disengage the locker you move it back to the unlocked position. The switch has a spring-loaded positive engagement collar and has a knob that can also be turned to lock it in place. On a differential, the shift cable moves a shift yoke, which slides on the inside of the mesh on one of the side gears to lock it into the carrier.

When the shift moves back to the open position, the collar moves back to allow the differential gears to move freely. It only comes into play when one wheel loses traction, that is, the difference in wheel speed. Strengthens traction control because it multiplies the bias load created by the traction control braking effect. Does not require special oils. Does not require adjustment, as the gears compensate for any wear that occurs. With 24 spline gears only.

Fully automatic, no driver input required.
Completely transparent on the road, meaning no unwanted side effects.

They often failed due to this high load destroying the worm gears.

Housing (other name: “differential cup”). It transmits torque from the main gear to the side gears through the satellites. The driven gear of the main gear is mounted on it. Inside the differential cup there are axles on which the satellites are mounted.
Right and left side gears (other name: “sun gears”). They transmit torque to the axles/half shafts through a spline connection.
Satellites of the right and left semi-axial gears. The differential cup and side gears are connected. Thorsen has four satellites in its design.
Output shafts.

Note that this type of self-locking differential has the most advanced design.

An important factor is the fact that these helical gears are mounted in "pockets" in the center support, so any radial load on the helical gears causes them to be pressed against the side of the pocket, creating friction. In some cases additional parts may be required and will be charged in addition to the above charges.

Costs for this are £175 for the front differential and £150 for the rear. Note that these costs assume you already have 24 spline axes. If you are upgrading from 10 to 24 splines, you will need additional parts and these prices will be incorrect. Please contact us for more information if you would like to upgrade your axle.

Device

This mechanism is made of familiar elements - the device is similar to any planetary unit. You can highlight the main parts - this is the body, worm gears, satellites.

As for the general concept, there are not many differences here when compared with ordinary mechanisms. The housing is rigidly mounted on the drive unit of the transmission. Satellites are installed inside the case. They are fixed on special axes. The satellites are in rigid engagement with the axle gears. The gears of the axle shafts are mounted on shafts, to which torque is transmitted.

And now regarding the Thorsen mechanism itself. In this unit, the axle gear has helical teeth. This is nothing more than a traditional worm shaft.

The satellites are a pair of helical gears. One element of this pair forms a worm pair with the axle gear. A pair of satellite gears can also interact with each other due to spur gearing. The design has as many as three satellites, each of which represents a pair of gears.

Self-locking differential Torsen

Differentials are an integral part of a car's transmission. Designers have developed many of these units, which can be divided into three large groups - free, with forced locking and self-locking. The latter option is increasingly gaining popularity, and automakers are using this type of differential both between axles on all-wheel drive vehicles and as cross-axle differentials.

One of the representatives of self-locking differentials is Torsen. It belongs to high-friction units and is triggered when a difference in torque occurs.

One of the main advantages of Torsen is that to activate the lock, which prevents the entire torque from being transferred to only one of the wheels (the bridge), no additional mechanism is used; its operation is based on the friction forces arising from the difference in torques.

Torsen is a planetary gearbox, but differs from the classic unit design in the use of worm gears.

The peculiarity of the worm gearbox is that it transmits rotation in only one direction, and its change leads to the so-called “wedging” or self-braking. That is, in such a transmission, only one element can be the leading element - the worm, while the gear is always the driven one. Attempts to apply torque to the gear (to make it drive) lead to jamming of the transmission due to high friction forces. The operating principle of Torsen is based on the self-braking effect of the worm gear.

Main components of a node

Torsen consists of the same components as any planetary node and includes:

body (cup);
worm gears;
satellites.

Torsen T2 layout

The overall concept of the Torsen is also no different from a conventional differential. The housing of the unit is rigidly fixed to the drive element of the transmission. Inside this cup there are satellites mounted on the axles and having gearing with semi-axial gears mounted on the shafts to which rotation is transmitted.

Now about the features of Torsen. The teeth of the semi-axial gear are helical, that is, this element acts as a worm (drive element of the transmission).

Torsen satellites are presented in the form of pairs of helical gears. One element of such a pair forms a worm pair with its drive gear (semi-axial). In this case, a pair of satellite gears also interacts with each other through spur gearing. In total, the differential design uses three satellites, each of which consists of two gears.

Torsen T1 device

Operating principle

Let's look at the essence of Torsen's work using an example where the unit is inter-wheel. When moving in a straight line, the drive wheels encounter the same resistance, so the unit evenly redistributes the torque between the wheels. During this movement, the satellites do not rotate and directly transfer force from the cup to the semi-axial gears (hard transmission).

When entering a turn, the wheel running along the inner radius encounters more resistance and slows down. As a result, the worm pair of this wheel is put into action - the semi-axial gear begins to rotate its satellite gear. That, in turn, transmits force to the second satellite gear, which additionally turns its side gear, increasing the torque on the wheel moving along the outer radius. Since the difference in moments on the axes is small, the friction force in the second worm pair is low and self-braking does not occur.

When one of the wheels hits a slippery surface, the resistance on it drops and the torque tends to this wheel. The side gear begins to spin its satellite gear, which then transmits force to the second satellite, and this is where the self-braking effect occurs. The satellite gear cannot act as a driving element and rotate the semi-axial gear due to the nature of the worm gear. Therefore, this worm pair jams. When jammed, it slows down the rotation of the second worm pair and the moment on the axle shafts is equalized.

The principle of operation of the differential between the axles

If we consider the whole principle of operation briefly, then Torsen can operate in three modes, depending on the resistance on the wheels. With the same resistance, the differential distributes torque evenly (the worm pairs are immobilized, and the differential appears to be locked).

When the resistance on one wheel increases, its worm pair is activated and forces the second to rotate, despite the appearance of a small resistance force in it, which leads to a redistribution of the moment in the desired ratio (one wheel slows down, and the second rotates faster).

The loss of resistance on one of the wheels is accompanied by jamming of the worm pair (due to high friction forces), which immediately slows down the second pair, so the torque on both wheels is equalized. In this case, Torsen begins to work in the same mode as during straight-line movement.

Kinds

The designers have developed three types of Torsen differentials, which are designated by the letter index “T” with a digital prefix. The differences between them come down to the layout of the unit and the shape of the working elements, which in turn affects the performance indicators.

Types of Torsen designs

The first type is Torsen T1. Its distinctive features are the arrangement of satellite pairs perpendicular to the axle axes and the use of helical teeth on both axle gears and satellites. The satellites of the pair interact with each other using spur gearing. The operating principle described above is discussed using the T1 version as an example. Has a high degree of “natural” friction.

Torsen T2 is the second generation of this limited-slip differential. It differs from the first type by the parallel arrangement of the satellites. It has helical teeth only on the satellites, but the semi-axial gears are helical. The engagement of the satellites with each other is also carried out by screw teeth, which participate in the blocking process (they can also wedge).

This generation has a lower degree of "natural" friction, early setting with less locking compared to T1. It has become widespread on civilian cars. But there is a modification called T2R, which can withstand high torque and is used exclusively on powerful cars such as the Ford Mustang. In design, it differs only in that it uses a splined coupling with helical teeth, through which it engages with the sun gear. In such a design, the characteristics of “natural” friction can change depending on driving conditions.

The last type is T3. Structurally, it is in many ways similar to the T2 version (parallel arrangement of satellites with helical teeth, helical semi-axial gears), but its layout was somewhat revised and a planetary structure was used in its design. This made it possible not only to reduce the overall parameters of the unit, but also to provide the ability to set the torque distribution ratio along the axes. Because of this feature, Torsen T3 is used only as a center differential, while T1 and T2 are used both between axles and as a cross-axle differential.

Positive and negative qualities

Torsen is one of the best options for self-locking differentials and this is due to its following advantages:

Operation in fully automatic mode without third-party intervention (there are no manual or electronic control mechanisms);
Instant speed of blocking;
Silence;
Possibility of use both between axles and between wheels;
Smooth operation;
Maintenance of the unit comes down to timely replacement of lubricant.

But at the same time, this unit also has many disadvantages. The entire operating principle of Torsen is based on the frictional force generated in worm gears under certain conditions. And this leads to a decrease in the overall efficiency of the unit and accelerated wear of working elements.

Another weak point that all worm differentials have is diagonal hanging, with which they become absolutely helpless.

In addition, Torsen is an expensive unit due to the complexity of manufacturing and the need to use high-strength materials.

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Operating principle

Let's see how the Thorsen differential works. Let's look at this using the example of an interwheel unit. When a pair of drive wheels moves in a straight line, they both encounter the same resistance. Therefore, the mechanism distributes torque evenly between both wheels. When driving straight, the satellites are not engaged, and the force is transmitted directly from the cup to the side gears.

When the car enters a turn, the inside wheel experiences more resistance and its speed decreases. The worm pair of the inner wheel begins to work. The axle gear rotates the planet gear. The latter transmits torque to the second gear of the axle shaft. This increases the force on the outer wheel. Since the difference in torque on the two sides is small, the friction in the second worm pair is also low. In this case, self-locking will not occur. This is what the principle of the Thorsen differential is based on.

When one of the driving wheels of the car is on a slippery area, its resistance decreases. The torque tends to this wheel. The axle shaft spins the satellite gear, and it transmits torque to the second satellite. In this case there will be self-braking. The satellite gear is not capable of acting as a driving element and cannot rotate the side gear due to certain features of worm gears. Therefore, the worm pair jams. And if it jams, it will slow down the rotation of the second pair, and the torque on each of the axles will be equalized.

Limited slip differential

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Home » About Rally » Equipment » Limited slip differential

Today I want to talk about one interesting and useful device that can combine the following machines:

So what do these machines have in common? All of these vehicles have locking differential(s). Why this is needed and what options there are, I will tell you below.

Plus I’ll show you which option will be used in Rally Club cars.

Let's start with the basics. A differential is a mechanism that allows the wheels of a car to rotate at different speeds relative to each other, this is necessary for the tires to roll without slipping when cornering. Moreover, if the differential is installed between the wheel drives (half-axles), it is called inter-axle, and if between different axles - inter-axle. An example of how a free differential works is perfectly illustrated in this video:

Imagine this situation: one of the wheels of the drive axle has hit a surface with a low coefficient of adhesion (ice, dry dust or a puddle, or maybe a hole with clay), and the other is standing on clean asphalt (soil). What happens in the case of a conventional, so-called free differential? That's right, a wheel with less grip will slip, while a wheel that clings securely to the road is at rest, not transmitting any torque. Exactly the same situation will be observed when cornering, where the inner wheel can slip due to unloading.

To avoid this effect, various options for inter-wheel locks are used. There are quite a few options for implementing differential locking. Basically, locks are divided into two large groups: differentials that are locked rigidly, 100% (so-called lockers, from the English locker - “lock”), and limited slip differentials (in the English version - “limited slip”, or LSD - Limited Slip Differential). Each of these options has its own advantages and disadvantages. The main disadvantage of “hard” differential locks is their amazing ability to destroy the transmission, gearbox and tire wear. Also, when driving on hard surfaces with good grip, the car will behave quite well due to the same speed (and as a result, the path) of the wheels in a turn. For professional sports, these disadvantages are rather features. For everyday use, such locks are difficult to apply. Therefore, I want to dwell in more detail on limited slip differentials. Their representatives are: 1. MULTI-DISC DIFFERENTIAL. Symmetrical differentials with spring-loaded friction disc packs in their design. They have a static preload (actuation torque) from 2 to 12 kg/m. Used in motorsports, they wear out quickly and require intervention to restore performance after each race.

2. Viscous coupling. A completely sealed unit, with friction discs, one of which has a rigid kinematic connection with the body, the other with the shaft. The discs have holes and channels to increase fluid friction. All this inside is filled with silicone liquid, which has a high viscosity and fills the body by 80-90%. The unit cannot be repaired, since the quantity and viscosity of the fluid determine the characteristics of the viscous coupling. If there is a fluid leak, the coupling must be replaced.

3. Torsen. From English “TORQUE” - torque and “SENSING” - sensitive, that is, sensitive to torque. The satellites are located in the housing perpendicular to its axis, connected to each other in pairs using spur gearing, and connected to the semi-axial gears by a worm gear. During a turn, the axle gear connected to the lagging wheel turns the satellite engaged with it, which, in turn, rotates the second satellite and the axle gear. Such a rigid kinematic connection allows the wheels of the car to rotate at different speeds. The friction forces arising in the worm gear from the difference in torque on the wheels lock the differential. The disadvantage of the design is the complexity of manufacturing, assembling the unit as a whole and repairing it.

4. “Quaife” This design was developed in 1965 by the English and refers to cylindrical self-locking limited slip differentials (or, as they are called abroad, limited slip differentials) or simply a self-locking differential lock. The indisputable advantage of the Quaife self-locking differential is its simplicity. Two housing parts, two side gears, ten satellite gears (cylindrical gears), a cage - and that’s it! When the car moves in a straight line without wheel slipping, the Quif lock works like a regular differential. The side gears rotate at the same speeds, and the satellites only transmit torque equally to both wheels, rotating with the housing and side gears as one unit. And in a turn, when there is a mismatch in wheel speeds, the differential lock begins to work - the satellites rotate between the body and the semi-axial gears, allowing the outer wheel to run forward. A self-locking differential can better utilize engine torque on slippery surfaces or when there is excess traction. Differentials of this design are produced by many companies, and the most famous is, of course, Quaife. In Russia, blockers with a similar design are produced by VAL-Raicing, Lada Special Transmission and a number of lesser-known companies.

At the moment, the Rally Club has at its disposal a lock from the Lada Special Transmission company, specially designed for Ford ib5 gearboxes. Soon it will be installed on a combat vehicle, but for now we have the opportunity to look at the insides of this useful device.

Components

Excellent and visual material on differentials can be found here: wiki.24subaru.ru/index.php/LSD

Follow the updates on VKontakte , on Drive and on our YouTube .

Three operating modes

If we consider the full operating principle of the Thorsen differential, we must say that the system can operate in three different modes. The specific mode depends on the level of resistance on the wheel. When it is the same, the torque is distributed evenly.

If the resistance on one of the wheels increases, then the worm pair is switched on, and thus the second pair is activated, despite the slight resistance on it. This leads to the redistribution of torque as needed. In this case, one wheel will slow down. The second one will spin faster.

If one of the tires completely loses resistance, then this will be accompanied by blocking or jamming of the worm pair due to high friction. Then the second pair immediately slows down. The torque is leveled out. The operation of the Thorsen differential in this mode is similar to straight-line movement.

Differential "Thorsen": principle of operation

“Thorsen” is one of the types of self-locking differentials. This mechanism exists on both domestic cars and foreign cars. The principle of operation of the Thorsen differential is based on changing friction of mechanical parts, which leads to the distribution of torque between the wheel pair.

Purpose

The Thorsen differential first appeared in 1958. The design and principle of operation were developed by the American engineer V. Glizman. The patent for mass production of this self-locking mechanism was received by the Thorsen company, whose name became the name for the device.

Device

This mechanism is made of familiar elements - the device is similar to any planetary unit. You can highlight the main parts - this is the body, worm gears, satellites.

And now regarding the Thorsen mechanism itself. In this unit, the axle gear has helical teeth. This is nothing more than a traditional worm shaft.

Three operating modes

Three types of “Torsen”

In the first option, gears of the driving axle shafts, as well as satellites, are used as worm pairs. Each axle axis has its own satellites, connected in pairs with those on the opposite axis. This connection is carried out using spur gearing. The axes of the satellites are perpendicular to the semi-axes. This version of the Thorsen differential is recognized as the most powerful among all similar designs. It is capable of operating over a very wide torque range.

The second option differs in that the axes of the satellites are parallel to the axle axes. The satellites in this case are installed differently. They are located in special seats of the cup. The paired satellites are connected by a helical gearing, which, when wedging, participates in blocking.

The third option is the only one among the entire series where the design is planetary. It is used as a center differential in all-wheel drive vehicles. The axes of the satellites and the drive gears are also parallel to each other here. Due to this, the unit is very compact. Thanks to the design, it is initially possible to distribute the load between two bridges in a ratio of 40:60. If partial blocking is triggered, the proportion may deviate by 20%.

Advantages of differentials of this design

This design has many advantages. This mechanism is installed because the accuracy of its operation is extremely high, while the device operates very smoothly and quietly. Power is distributed between the wheels and axles automatically - no driver intervention is required. Redistribution of torque does not affect braking in any way. If the differential is operated correctly, then there is no need to service it - the driver is only required to check and periodically change the oil.

This is why many drivers install the Thorsen differential on the Niva. It also uses a permanent all-wheel drive system and no electronics, so extreme sports enthusiasts often replace the standard differential with this unit.

Flaws

There are also disadvantages. This is a high price, because the structure inside is quite complex. Since the differential operates on the thorn principle, this increases fuel consumption. Despite all the advantages, the efficiency is quite low when compared with similar systems of another type. The mechanism is highly prone to jamming, and the wear of internal elements is quite intense. Special products are needed for lubrication, since a lot of heat is generated when the unit operates. If different wheels are installed on the same axle, the parts wear out even more intensively.

Application

The unit is used as an interwheel and interaxle mechanism to redistribute torque. A unit of this type is installed on many foreign cars, but it is most widely known on the Audi Quatro. Manufacturers of all-wheel drive cars very often prefer this particular design. The “Thorsen” differential is installed on VAZ for its comparative simplicity and instantaneous operation.

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Three types of “Torsen”

Application

Torsen self-locking differentials are used both as inter-wheel and inter-axle torque distribution devices. The Torsen Audi Quattro differential is widely known. In modern all-wheel drive vehicles, this mechanical device is installed quite often. Note that the Torsen center differential is used on almost all Hummer cars.

So here's how to do it and what names are usually associated with the systems. Typically carried out with a carrying box after transfer in case of longitudinal installations. You can avoid this when the surface you're riding on allows for some level of slipping, rather than on high grip surfaces. This is typically done by physically locking the shafts together using a toothed clamp operated electronically, hydraulically, or manually using a lever.

This is usually a user activated system, but can also be automatic. Low range can be found in these systems, but not always. Pros: Cheap and simple, strong, consistent torque transfer when engaged. Cons: Cannot be used on road, with high wear resistance when used on high traction surfaces.

The popularity of the Thorsen torque vectoring device is due to the lack of communication with any electronics or clutches. This transmission element is a relatively simple mechanism, characterized by instantaneous operation and the absence of a negative impact on the braking process. That is why leading automakers use this type of differential in their cars.

How does this make me a better driver? The center differential will allow a speed difference between the front and rear axle. Like a regular differential, it's an easy way to handle speed bias, but not torque bias, since this system will always send 50% of the torque to both sides, and they can't bias torque. The displacement rate, but not the torque, means that the power will always go to the wheel with less traction. The good news for us is that very few cars use this type of center, distinguished by the fact that they usually have mechanical locking or very good traction control systems.

Today in the automotive world there are three types of all-wheel drive devices:

Classic transmission with all-wheel drive (denoted by the term full-time), which has three differentials. This determines that such a car has all-wheel drive on all wheels in any driving mode. But, as mentioned above, if at least one of the wheels loses traction, such a car will stand still. That is, in such a car, partial or complete differential locking is mandatory. Today, the most popular solution on traditional SUVs is a rigid mechanical locking of the center differential. In this case, the moment is distributed along the axles in proportions of 50 to 50. Thanks to this, the car becomes more passable, but is not able to drive on paved roads at speeds exceeding 30-40 km/h (higher speeds will have a detrimental effect on the differentials and can lead to their breakdown). As an option on off-road models, an additional rear differential lock can be provided.

Pros: Cheap, simple, purely mechanical, instant translation, smooth and controllable. In practice this gives you a maximum of 2 wheel drives without torque. Without traction control, completely open systems are only marginally better than nothing for traction. The viscous connector is usually mated to the open differential or integrated into the differential and acts as a torque converter, it has an input shaft connected that is completely disconnected from the output shaft, and the torque transmission medium is a fluid.

At the same time, such a direction as mechanically connected all-wheel drive - part-time - arose. In its design there is no center differential at all, instead of which there is a special mechanism that connects the second axle. This type of transmission is usually used on pickup trucks and low-price SUVs. On hard road surfaces, such a car can only drive using one axle drive (in most cases, the rear one). And in order to overcome off-road areas, the driver must manually engage all-wheel drive, rigidly locking the front and rear axles together. As a result, it turns out that the moment is supplied to both axes at once. However, the free differentials on the axles continue to remain, so the car may not move if the wheels are hung diagonally. This problem can be solved: you just need to lock one of the cross-axle differentials - usually the rear one first. That is why some models have a limited slip differential on the rear axle.

The gerotor is a pump, like most oil pumps, and they are very efficient pumps for high pressure, low displacement fluids. Fully automatic and providing varying degrees of locking, this system has been replaced by electronic clutches. Cons: Reactive, durability may be an issue, not full lock, no torque vectoring.

Pros: Torque activated rather than speed activated, safe, can be locked with brake, two-position setting. Cons: Expensive and not mechanically locked. The friction clutch method is very popular because with advances in electronics, very high variability in performance, smoothness and drive ability, and extended torque vectoring can be achieved. The simplest way to explain it is that it acts like an open differential with clutches on the input shaft, output shaft, or both to vary the friction within the carrier housing from fully open to fully locked.

All-wheel drive, connected automatically. Today this is the most popular and universal solution. It is most often designated AWD (A-AWD) - automatic all-wheel drive. The design of such a system is very similar to part-time, where there is no center differential, but in order to connect the second axle, an electromagnetic or hydraulic clutch is used. The clutch is blocked electronically, and two functioning mechanisms are used for this - reactive and preventive, which will be discussed a little below.

It is necessary to understand well that in order to obtain the maximum effect from all-wheel drive (and from any - both full-time and awd), a variable differential lock between the axles is required, depending on driving conditions. This is done using various methods and devices. These include a self-locking gear differential, viscous clutch, and electronically controlled locking.

The simplest of them is to use a viscous clutch (the differential with it is called VLSD (viscous limited-slip differential), but it is ineffective. The operating principle of this simple device is that it transmits torque using a viscous fluid. When the rotation speed begins to differ input and output shafts of the coupling, the viscosity of the liquid inside it increases, up to the point of transition to a solid state. In this simple way, the coupling is blocked and the torque is evenly distributed between the axes. The viscous coupling has disadvantages. Firstly, it is its large inertia, which eliminates the possibility of its use off-road, limiting it to hard road surfaces. And secondly, it has a very limited service life - until the car runs approximately 100 thousand kilometers, after which the viscous clutch stops functioning and the differential is released. Still, today such clutches are sometimes used - to block the rear cross-axle differential of SUVs or the center differential in Subaru cars with manual transmission. In the recent past, a viscous coupling was used to connect a second axle to automatic all-wheel drive systems in Toyota cars, but this practice was later abandoned due to low efficiency.

What is a Thorsen differential and how does it work?

The next method of variable differential locking is a limited-slip gear differential. Today such a device is known called Torsen

. So, what is a Thorsen differential? The principle of its operation is the property of a worm gear to jam when a certain ratio of torque values occurs on the axes.

This method is used on many cars with all-wheel drive (for example, the entire range of Audi all-wheel drive), it has a technically complex design and, accordingly, high cost. But at the same time, it is effective both on hard roads and off-road. Among the disadvantages, it is worth noting that when there is no rotational resistance on any of the axles, the differential is unlocked, so the car will not be able to move. This is precisely the vulnerability of cars with a Torsen differential - when there is no traction on both wheels of one axle, the car will not move. In this regard, Audi uses a differential with ring gears and additional clutches on its new models.

Electronic differential lock control includes both conventional methods of adjusting the position of slipping wheels using the vehicle's braking system, as well as more complex electronic control devices with the degree of differential locking, depending on the situation on the road. Their advantage lies precisely in the presence of electronics, which instantly independently determines the need for each wheel of the car in torque and the required amount. There are many sensors designed for this - a rotation sensor, an accelerometer, which records the longitudinal and lateral acceleration of the car, and gas pedal sensors, as well as steering wheel position sensors. In contrast to such electronic devices, both the viscous clutch and the limited slip differential are completely mechanical devices that do not require interference from the electronic system. It is worth noting that the system, which simulates differential locking by using standard car brakes, most often does not work as effectively as compared to direct differential locking. Typically, such imitation is used as an alternative to inter-wheel locking. Today it is used even on machines with a single-axis drive. An example of electronically controlled locking is the VTD all-wheel drive transmission, which is installed on Subaru cars with a 5-speed automatic transmission. There is also a system called DCCD, which is used on the Subaru Impresa WRX STI and Mitsubishi Lancer Evolition, which has an active ACD center differential. And these transmissions, without exaggeration, can be considered the most advanced in the entire automotive world.

Advantages of differentials of this design

Principle of operation

Thorsen is a worm-type limited slip differential. This means that automatic differential locking occurs when there is a difference in torque on the body of the mechanical device and on the drive shaft. The differential itself consists of driven and driven worm gears, which are called “half-axial” and “satellite” gears, respectively. The worm gear has one feature: it does not rotate from other gears, but it can itself rotate other gears. This property (wedging) allows the differential to be partially blocked.

If the wheels of a car have good grip on the road surface and move smoothly, then the torque between the axles is distributed equally. With a sharp increase in torque, the drive worm gears try to start moving in the opposite direction. The driven gears are overloaded, the output shafts are blocked, and excess torque from the machine's engine is transferred to the other axle.

Flaws

Pros and cons of a Torsen differential

Among the main disadvantages of limited slip differentials, which include Torsen, are relatively low efficiency and increased fuel consumption due to high friction losses, as well as high wear of loaded parts and a tendency to jam. In addition, the significant heat generation of differentials of this type requires special measures for its cooling and special lubricants. The advantages of “torsens” include smoothness and high accuracy of operation, as well as a relatively low noise level. And, of course, the fact that the fight against road troubles does not require any special body movements from the driver - the distribution of engine power between the wheels occurs automatically.

Torsen differentials, as a rule, do not require maintenance when used correctly. For their reliable operation, it is enough to regularly change the transmission oil and monitor its level. If signs of wear appear (most often this is the characteristic noise of the gearbox), it is better to replace the entire assembly, since “amateur” replacement of individual parts can cause failure of the entire transmission. It is also necessary to remember that rapid wear of a differential with a worm pair can be caused by driving with different characteristics of wheels on the same axle - for example, using a “non-standard” spare wheel.