What is better than four-wheel drive or connected. What drive is better? Car drive: What to choose? What drive the most passable

The main and unchanging "acting person" of all full drive systems is transfer case: A special unit that gets torque from the gearbox and distributes it to the front and rear axles. But the method of distribution, as well as layout schemes, there are several.

Complete drive systems are made to three types:

Permanent four-wheel drive (Full-Time)

Pros:

• reliable "indelusive" design;
• the ability to drive with a full-wheel drive both off-road and on asphalt.

4Matic Permanent Dual Drive System (Mercedes-Benz)

Minuses:

• complexity compared to a rigidly connected drive;
• big mass;
• the complexity of the controlback setting;
• increased flow Fuel.

The first thing that comes to mind when there is a task to convey the torque into two axes, is to firmly connect them to the distribution of iron pipes. But here is not enough: when turning turns, the car's wheel pass different ways.

If you rigorously connect the axes, then some wheels will go, and some kind of slip. In the mud when the coating is soft, it is unstable. At the time of the Second World War, let's say, the legendary "jerseys" quietly went with rigidly connected axes, because they were exploited exclusively on off-road. But if the coating is solid, then these slips will generate the twist oscillations and slowly, but correctly destroy the transmission.

Therefore, in the transfer box of vehicles with constant full-wheel drive, the inter-sieve differential is located - the mechanism that distributes the power between the axes and allows them to rotate at different speeds. And if some wheel slows down, the turns of the other are increasing, but the torque falls on it.

All this is great while we are going on asphalt, and what to do, if we are stuck in the rear axle? On the front wheels, which will stand on a solid surface, will be the moment but there will be no revolutions, but the rear will rotate very quickly, but the moment on them will be small. Little will be the power on the rear wheel and exactly the same power of the differential will apply on the front. In this case, you can at least be a whole eternity - still do not shift.

For such cases, differential is supplied with lock - when it is turned on, the speed on all wheels is the same, and the moment depends only on the clutch of the wheels with the road.

Due to the presence of additional nodes (differential and lock), the entire system is obtained sufficiently heavy and complex. In addition, the permanent transmission of the moment on all the wheels increases energy loss, and therefore worsens the dynamics and increases fuel consumption.

Constant four-wheel drive In the automotive industry is still used, although recently this system gradually displaces four-wheel drive on demand, which will be on.

Hardly connected (part-time)

Pros:

• reliable mechanics;
• maximum simplicity at high passability.

Minuses:

• on the asphalt with a full drive can not ride.

From differential and locks, you can also refuse, provided that one of the axes will be temporarily disconnected. By such logic, the system has a rigidly connected full drive.

The axes are connected to each other without differential, and the moment is distributed in a strict ratio. As a result, high passability and minimum costs.

Part time today is almost extincted and used only on purely off-road cars. The modern driver is uncomfortable to use this system. Connect the axis only in a fixed state so as not to damage the mechanisms. Well, if after pokatushki in the forest, go on the highway and forget to turn off the four-wheel drive, that is, the risk to ruin the whole transmission.

Four-wheel drive with coupling

Pros:

• low cost and simplicity of the device;
• small mass;
• the ability to fine system settings.

Minuses:

• weak reliability and resistance to overload;
• instability characteristics.

The hard blocking of the differential is not bad on the off-road, but how to make the full drive system dose in the dynamics? There is always different sink degree ... The decision was found in the mid-50s.

Active Torque SPLIT AWD system for Mazda CX-7 with a multid-wide coupling instead inter-axis differential

An ordinary mechanical differential was supplemented viscous coupling (Viscounts). Viscussoft is a part in which rows of blades associated with input and output shafts rotate in special fluid. The input and output shafts are freely rotated relative to each other, but the secret of the coupling is in the filler, which, when increasing the temperature, increases its viscosity.

With ordinary movement, light turns or slipping of the clutch wheels does not interfere with the mutual movement of the blades, but as soon as the difference in the speed of rotation of the front and rear wheels grows, the fluid begins to mix intensively and heat. At the same time, it becomes viscous and blocks the movement of the blades relative to each other. The greater the difference, the higher the viscosity and the degree of blocking.

Today, couplings are used both in diagrams with constant full-wheel drive together with mechanical differentials and independently. They are connected to the leading shaft with a distribution, and the slave with an additional axis. If necessary, when one of the axes of the buxic, part of the moment through the coupling goes to it. What's next?

The further evolution of the total drive systems, apparently, will be associated with electric motors. The first electric car with the engine on each wheel shown at the World Exhibition in Paris 1900 Ferdinand Porsche. Then it was, as if said, "non-viable concept car". Motors were too heavy, and the design is expensive. Now this scheme is clearly more prospects.

There is potential and a hybrid scheme, where one axis is driven by the engine internal combustion, and the second is an electric motor. However, if we talk about the real SUVs, then no power and friction couplings until they replace cheap, simple and hardy mechanics.

What we continue to talk about the car drives, today we have a global topic, namely what is better and what to choose a front or four-wheel drive for a wagenik or crossover? As we know there, it is not completely honest with you, that is, not permanent and often does not have a hard blocking of differential, that is, you cannot manually block it, it connects only after the front axle starts to buck. And now there is a completely fair question - "Does it be necessary or the front axle is enough for the eyes?". Here everything is not definitely, let's understand ...

Well, to speak at all - that the four-wheel drive is bad, I will not! Yet, I think - that is exactly the opposite, it is even good! There are large and heavy cars, where it works constantly, which is much improved by the permeability. There are not very big cars, middle class "C", sometimes "D", where it is also constant or strictly plugged (which improves both the permeability and controllability under certain conditions), but here are the parquets or crossovers, it is completely different. The four-wheel drive in them, unfortunately, has now become the property of marketers and Deltsov, that is, you are trying to prove that they are four wheels "digging" and in the end it turns out completely all wrong. In this article I will try to debunk all myths, but for a better understanding you need to tell about each type, and I think it is worth starting with the front.

As we already said -, about this topic, too, a lot of "copies broke", but there is the principle of conversation another, yet one driven axis or in front, or behind, today the essence of the question is different.

The front-wheel drive is very simple in the structure, and it is almost brought to perfection now, that is, it can walk very and very long without any breakdown.

Device :

• Engine
• Attached to the engine gearbox with differential, often in one case
• From the box (differential) there are two axes with. On each side two shrusses (internal and external)
• These shoes are suitable for front wheels through special hubs.

The torque is transmitted from the engine - transmissions - axes - wheels. This is how the front-wheel drive car is given.

It is worth noting that transmission fluids There is not much here, in the box itself, that's all, as a rule, the rest of the connections are dry (well, or almost dry, still under the anthers in the shurts there are lubricant, but it does not change it there. This tells us that you can do not follow this design at all. Of course, I still advise you, because if they break down, it will soon fail and the hinge, but believe me the next 70s - 80,000 km it can not be done. If the manufacturer is serious, then anthers can walk 150-200,000 km.

The rear suspension in the front drive do not carry any semantic load, that is, it is a banal "support for the wheels", there is practically no weight, it is a light (either beam, or a "multi-dimension"). And what is important, rear end practically does not require maintenance, well, if only brake pads change.

Four-wheel drive

Even the connected four-wheel drive through the Viscuft, has a much complex structure (I'm already silent about constant). Here are more parts that are spinning (most of the time) in idle, there are already two bridges, and not one, also the cardan shaft and the rear axle are no longer secondary.

Device :

• Engine
• Transmission, which can be combined with front differential. However, the front differential can be made separately
• Front axis with shurtles on the front wheels
• The inter-axis differential, it can also be in one case with a box, but maybe separately (it all depends on the design)
• Transfer case.
• Rear Cardan to transfer torque Back Bridge
• Viscounts or an electrospata (hydromechanical) for automatic rear axle connection
• Rear axle. Can be made in a cast case from which two semi-axes come out rear wheels. But now there are also two axes with shruses, by analogy with the front axle, are often often followed from the rear differential.

As you can see, the building is much more complicated! Here there are two more differentials, inter-axis and rear, there is also a transfer box, viscous coupling and so on. All this adds in weight a car at least 100 kg, and possibly more. There are also many parts here, which are "spinning" in oil, and they really need to follow them. Some manufacturers recommend changing them transmission oil. If any glare flows, a whole node can fail. I think all this understands, but again everyone thinks I have a four-wheel drive, then I'm on some PARKTNER or crossover, on RAV4 or the same DUSTER, just becoming a conqueror of off-road - "What I am, I myself like a UAZ" ! But is it really so?

Four-wheel drive through the viscous coupling (electrical unit, hydromechanical clutch)

Well, what did we come to the most interesting, for whom the four-wheel drive of such crossovers, where can it be used? For many, this means - that you can immediately go to the forest on the mushrooms and berries, which is possible to strike such a off-road, what they say "on the door"! Guys stop, on crossovers and parquets Four-wheel drive very conditional, I would even say "urban" it is not intended for serious roadless tests.

Why? Yes, it is simply not designed for this. Often on many crossovers, it connects through the Viscouft or an electrofit

• Viscounts We have already spoken about it (you can detail). Transmits torque by means of a special fluid concluded in the Viscounts Corps. When one axis begins to stop, the liquid quickly hardens, thereby closing the rear axle and connecting it. Cons of such a drive that it is practically not possible to turn on or block the rear differential to work. Only after slipping. Therefore, the effectiveness of such a full drive is low enough.

• How it becomes clear, the work happens a little differently. There is no special fluid here, but there are electromagnets that are closed or disconnected when the voltage is applied to them, thereby connecting or turns off the four-wheel drive. This coupling is dry, there are no oils in it, it is good and bad. It is good that you do not need to follow the flow of the glands and change the liquid. Bad - this clutch is quickly overheated. Connecting a full drive occurs after front-wheel drive Draw, usually after the second rotation front wheel. In some cars equipped with such a node there is a forced blocking, that is, you can physically lock the rear axle. It seems to be a solution to it, the control is much better than the Viscouft, however, there is a large spoon of tar. Such a drive is very quickly overheated and disconnected if you can buck on the Viscounts for a long time, then the electromagnetic clutch will turn off after 3 - 5 minutes of slipping. Also, they are faster due to large temperatures, as specialists say - just burn.

• Hydromechanical coupling. Very similar design with an electromagnetic option. However, here disks are closed due to oil pressure. Inside there is a pump that creates pressure for compressing or connecting. Pumps now can also be with an electrically driven, used to be mechanical.

Actually, such structures are applied on a large number of crossovers or parkelors, here another find - very and very difficult.

Full or front?

As you can see to call such complete drives - full, as the language does not turn! For which they are sharpened. You know, somehow talked with the "Mother" mechanic about such automatic connections, And that's what he told me - "To see even (middle dirt) on such cars will be obligated, they are simply not designed for this off-road, do not think that you have bought a car for Pateuries Similar with our UAZ, these are different classes! Especially if you have automatic box gear, because it can also quickly overheat (with mechanics everything is a bit better). These cars are designed to make a maximum of fighting the snowy courtyard in the city of winter, well, or with a couple of shallow puddles on the road to the country "

Do you know how the shovel is in your trunk or a neighbor passenger - what do I mean? On the front-wheel drive car you will need to clear ahead ahead (with the help of a shovel), well, or ask the neighbor-passenger so that he pushed you a little. But such a plugged all-wheel drive car can get out of himself. Okay? Of course yes! But is it worth overpaying for it?

If you disassemble the front and complete options, you should think, and where and how are you moving? It is also worth considering that all-wheel drive car:

• Costs more.
• Completed with full drive are at least "medium" and "top", that is, you will not find it in the "standard".
• The car weighs more
• More vibrations. Because more nodes spinning.
• Service is more expensive
• More torque elements, which reduces the resource
• Fuel consumption
• Modest possibilities of this all-wheel drive car

Actually, if you are 100% urban resident, the snow in the cities are cleaned, go to the cottage where there are not quite comfortable a few meters of dirt - then take such a four-wheel drive, as I think this is overpaying, and he does not need it!

If you are a resident of the countryside, the asphalt you saw only on TV, and the snow wounds so that it's hard to move on the tractor - it will not help you! Here you need to look more brutal technique, perhaps on the frame. Yes, at least the same UAZ, it will be more practical.

Four-wheel drive from crossovers and parcktails, it's not exactly what you expect - believe me. It is rather a trick of marketers, and not the all-wheel drive car in the understanding of the "offender of the off-road". Of course, the benefit of it is (for example, you live near the city, in the winter it seems to be cleaning the roads but not always), but it is not so significant that it is more than 100,000 rubles more, as I think it is meaningless. Yes, and maintain such a car more expensive! If you consider everything plus and cons, I personally would not bought it! Although you may have other thoughts, write in the comments.

Now a small video.

Very often car enthusiasts argue about what type of drive is better. Let's look at the advantages and disadvantages of each type separately.

Rear drive

Let's start with the rear drive, which is considered classic, it is due to the fact that there were cars for a very long time rear drive And the front engine is located on the front.

Disadvantages of the rear drive:
1. High rise in production, which is reflected in the final price of the car.
2. Cars with rear-type drive is harder, they are usually always located in the center of the body tunnel, eating a useful volume of the cabin, and a reducing comfort of the rear passengers.
3. Patency in the conditions of snow and dirt is worse than the front or all-wheel drive machines.
4. Next to the rear axle car.

Front type drive

The engine is installed transversely relative to the axis of the car.

Advantages of the front drive:
1. The cheapest in production.
2. Due to the lack of a cardan shaft, as a rule, there is no central tunnel (but is present in case the car has an all-wheel drive version).
3. High passability In the snow and dirt, congenital good term stability.
4. Lower vehicle mass.

Disadvantages of the front type drive:
1. Vibration from the motor due to the rigid attachment is transmitted to the body.
2. The steering wheel with intensive acceleration transmits reactive efforts (expressed by the shaks). Therefore, front-wheel drive cars with a capacity of more than 250 hp As a rule, they are not issued due to the inability to realize the potential of the engine.
3. Ply sharp start There is a redistribution of weight back, the front axle is unloaded, and leading wheels have a tendency to slip.
4. demolition of the front of the car.

Full type of drive

The leading are all the wheels, which ensures good course stability and permeability. There are several types of full drive permanent or connected.

Permanent full drive

When the car is equipped with a system of constant full drive torque continuously transmitted to all wheels. The car has a permanent readiness for complex road situations, the lacks can be considered the highest fuel consumption and the structure complex in technical plan.

Connected full drive

This type of drive assumes movement in conventional modes in the monolvodny (more often by-contained) mode with the connection of the full drive system only as needed. The advantage is low fuel consumption, a higher level of comfort, disadvantage - increased transmission wear and poor handling when the full drive system is enabled, since the front and rear axles will move with different angular velocities and the effort is not compensated.

Connected automatically all-wheel drive by type - thrust on demand

The type of drive when the automation connects the second axis when the sink is first by blocking the inter-seed clutch. There are two types of connected drive - with a Viscouft that is cheaper, but does not provide timely connection of the axis, that is, the car can get stuck or leave the trajectory, or with a multidisk coupling, which is more expensive, but provides a more efficient connection of the second axis as It closes much faster and allows you to accurately distribute traction over the axes in real time.

An example is the XDrive system installed on bMW cars, which constantly redistributes the torque, taking into account the readings of the set of sensors. For movement in off-road conditions, such systems are equipped with differential locks, when activated which the traction is divided by 50 * 50 axes. The advantage of this system is the low fuel consumption, a more enduring technical component, the disadvantage can be considered the cost and complexity in production.

Advantages of a full drive:
1. High term stability.
2. Best car handling.
3. The best among all types of driving permeability.
4. The most efficient start from the place, especially in low tire clutch conditions with expensive.

Disadvantages of the full type of drive:
1. The most expensive in production, repair and maintenance.
2. Elevated level Noise due to two cardanov.
3. The central tunnel creates the same shortcomings and inconvenience that at the rear drive.
4. High mass and increased fuel consumption.
5. In the event of a critical situation on the road, the car slides all four wheels, which markedly complicates his return to the driver.

At first glance, the principle of operation of the transmission of the all-wheel drive car is simple: torque from power aggregate It is distributed between four leading wheels. Such a car is very convenient due to its pronounced pluses associated with unpretentiousness to the quality of the coating under wheels. On the primer, in the ice, on the wet seeming terrain or on the highway in a strong shower, the all-wheel drive car will show itself on top. Plus, it can not be afraid to move from asphalt coating and cross the area with a lack of even hint on the roads, and on the asphalt four-wheel drive makes itself felt a good start and acceleration, almost without slipping.

But sometimes there are also cases that seem to be difficult to explain due to the advantages that all-wheel drive cars possess. It happens that the driver sits behind the wheel of an SUV with an impressive clearance, and the car was stuck in the "Cashe" and Loe on the belly.

Interesting to know! In 1883, the American farmer Emmett Bandell was patented design similar to the current system of full drive.

Of course, the reasons for this can be a lot, the most common of which drivers with experience, "gasket between the wheel and seat" are expressed. But it also happens that the transmission of "all-terrain" does not intend to cope with the tests. And here there are reasonable questions: "Why not cope?", "What can I handle?". We will talk about this further in the material provided.

Manually connected four-wheel drive (Part-time)

This type of transmission can be rightfully called the "primient" among full drives. The principle of its action lies in the rigid connection of the front axle. Thus, all wheels are rotated at the same speed, and the inter-axis differential is not provided. The torque is distributed equally between all the wheels. Anything in this case, so that the axes are rotating at different speeds, will not come out, except to be implemented in the "purge" of the car and build a new differential.

In the meantime, it is not recommended to dissect in a car stream with a connected front axle. If you move even on low transmission straightforwardly to short distances, nothing terrible will occur, but if you need to turn around, the emerging difference occurs in the length of the bridge paths. Since the distribution goes 50/50% between axes, then the power surplus is released only by slipping the wheels of one of the axes.

On the sand, gravel or in the dirt wheels can slip if necessary, and nothing will interfere, since the clutch with surfaces is weak. But if the weather is dry, and you are moving on an asphalt road, then the power will have nowhere to go as on the off-road. Thus, the transmission is subjected to high loads, rubber is faster, the controllability deteriorates and term stability at high speeds is lost.

If the car is operated more often on off-road or generally purchased only for cruising by crossed, then the full drive system with the forced connection of the front bridge will fully meet your expectations. The bridge is connected immediately and hard, so nothing blocks and not have to. The design is very simple and reliable, there are no locks and differentials, no drives no electric, nor mechanical type, there is no excess hydraulics and pneumatics.

But if you are the urban "dandy", appreciate the time and do not want to bother about the weather conditions and alternating areas of the city with its loose and slippery road surfaces, cunning deep puddles, then the option of this all-wheel drive system is absolutely not suitable for you. If you move with always forcedly connected front axle, then this is fraught with the subsequent damage, it is not entirely convenient to manipulate it, and in general you can not have time to connect it.

Cars with PART-TIME: Suzuki Vitara., Toyota. Land Cruiser. 70, Great Wall Hover, Nissan Patrol, Ford Ranger., Nissan Navara, Suzuki Jimni, Mazda BT-50, Nissan NP300, Jeep Wrangler, UAZ.

Permanent four-wheel drive (Full-Time)

The disadvantages of the plug-in full drive became the root cause of creating a new invention - a permanent full drive, which is deprived of all the problems that Part-Time had. This is the most uncompromising "4WD", which is deprived of all sorts of "And if": all the wheels are presenters, between the axes are free differential, which releases accumulating excess power due to the scrolling of one of the gear satellites, which contributes to the movement of the car with a constant full-wheel drive. The main nuance of cars with such a type of full drive is to slip. If the car begins to buck by one axis, the second is automatically turned off.

Now the car has become furniture or in the house, as you wish, in general, in real estate. How does it happen? If one wheel starts, the interclass differential turns off the second, and the second axis also turns off the differential on the machine, but already the inter-axis. Of course, in reality, the stop does not happen so quickly. Movement is a dynamic process, therefore, there is a stroke reserve, inertial force. The wheel is turned off, moves along the inertia a couple-triple meters and turns on again.

But in this case, the car is sooner or later somewhere stroop. Therefore, in order to maintain all the off-road qualities of the "passing", such cars, as a rule, establish one or two forced blockages of the inter-axis differential. In the front differential, it is very rare to meet the factory blocking. If desired it is installed separately.

But the system of constant full drive is as far from the ideal of driving qualities on asphalt roads. Such cars ruling, let's say, I would like better. In critical situations, the SUV pulls out the turn and it does not immediately react to infant and podium. Drivers of such cars require special skills and an excellent feeling of the vehicle.

To improve controllability, they began to establish inter-axis self-locking differentials with a forced lock system. Different automakers used various solutions: some differential type Torsen, someone viscous coupling, but the task for all one is to improve the controllability of the car, and for this you need a partial blocking of the differential.

If one of the axes begins, the self-locking mechanism works, and the differential does not affect the second axis, which torque continues to flow. A number of cars have been equipped with another mechanism for self-locking the rear axle differential, which has a positive effect on the acute control.

Among the cars with constant full-wheel drive can be allocated Toyota Land. Cruiser 100, 105, Land Cruiser Prado, Land Rover. Discovery, Land Rover Defender, Lada 4x4.

Automatically plug-in Torque on-Demand (AWD)

Time and Involve Melting Omns of Automotive Engineers have made their work by developing a full drive system into something new with the introduction of electronic-managed systems with a redistribution and transfer of torque. As a result, stabilization systems appeared and currency stability, anti-slip systems, as well as systems that distribute torque. All of them are implemented using the electronics involved. Than more expensive The car and modern it is stuffing, the more complex schemes are applied to it.

This is a tracking of the angle of steering, body rolls and speeds, up to how often the wheels are fluctuated during a certain distance of the path. The car carries out the most complete collection of information about its behavior while driving. The computer processes it and regulates the transmission of torque between the axes by means of an electron-controlled coupling, which changed the differential. On modern sports cars This invention has become very worthy of attention.

To date, electronic systems can be called almost perfect in their behavior. It is worth adding several new sensors and parameters to manufacturers, thanks to which the system runs on ahead.

But here there are nuances of use: this type All-wheel drive transmission is suitable for use only on asphalt tracks with rare enclosures of symbolic off-road, primer, for example. Basically, electronic clutches during slipping on off-road start greatly and fail. And for this you do not need to push the tank ruts for hours, and there are enough ten minutes of drums on the ice. And if it is systematically overheated, then breakdowns cannot be avoided as expensive repair.

Than "cooler" system, the more subjected to breakdowns. So you need to choose a car with the mind, having determined for myself whose tracks you will roll it. Do not go into extremes: if the SUV, then only in the forest and to the village, and if the car, then only in the city. There are plenty of cars from this segment that are universal in their driving characteristics. But without fanaticism too. On the light car You can, of course, go to personal roadBut on which one and what is the other question.

If wiring breaks on one of the ABS sensors, then the entire system will fail and will not receive information from the outside. Or gasoline poured not better quality - And everything, the reduced gear does not turn on, ahead of the trip to the car service. And it can happen that the electronics will supply the car into the service mode, completely disabling all the systems of its livelihoods.

Among these cars it is worth highlighting Kia Sportage. (after 2004), Cadillac Escalade., Nissan Murano, Nissan X-Trail, Ford Explorer, Toyota RAV4 (after 2006, Land), Land Rover Freelander., Mitsubishi Outlander. XL.

Multi-mode (Selectable 4WD)

This system is perhaps the most multifunctional in relation to the full drive with its various manipulations: it can be used manually or automatically, and also forcibly disable the rear or front bridges. Using the Selectable 4WD system does not increase the fuel consumption. The leader in the fuel receipter is the cars mentioned in our early cars with part-time.

The mansion is some cars with a selective transmission, which can be called a constant full-wheel drive, with the ability to force the front axle to turn off the front axle. On such cars, the transmission combines part-time and full-time. Among them Mitsubishi Pajero., Nissan Pathfinder., Jeep Grand. Cherooke.

In "Padzherik", for example, you can choose one of several transmission modes: 2WD, 4WD with automatic locking of the central differential, 4WD with a rigid differential lock or reduced transmission. As you can see, here you can find references to all the above-mentioned systems of the full drive.

Some front-wheel drive cars can have a leading rear axle. A small electromotor is mounted in the main transmission housing, which is connected at the request of the driver - the E-4WD system. The electric motor is powered by OT automobile generator. Such a system improves the controllability of the machine on the highway in the shower, and also helps with confidence to pass snow-covered, iced and dirty sections of the path. Bright representative Car with this system is the latest BMW models.

If another one and a half dozen years ago, the owner of the all-wheel drive car was considered a practically unconditional conqueror of the roads, then recently, arguing on the topic of a full drive of the car, car enthusiasts, as a rule, use a clarifying formulation, speaking of "full-fledged full-wheel drive."

Any car enthusiast will say that for the assault on the courtyard littered with snow, or when overcoming the blurred primer, the car with a wheel formula 4x4 will be the perfect option. Yes, and when driving on an asphalt road to slippery rainy autumn, a driver who droves the all-wheel drive car will feel much more confident. However, after a few meters after the snow-covered area of \u200b\u200bthe road is overcome, or the car will be chosen with a broken primer on the asphalt road, the additional leading axis will be only the cause of serious fuel overpower.

pros all-wheel drive cars Obvious - such machines are less sensitive and whimsical to the quality of the coating under the wheels, when Congress from the road with a solid coating, a four-wheel-drive car will be able to confidently deliver the driver and passengers to the destination, and on a wet or ice highway such a car will save decent dynamics and handling.

Trying to keep the advantages of a full drive without the deterioration of the car's fuel efficiency, most of the modern automakers resort to the help of electronic systems working with multi-disc clutches capable of connecting the second wheel axis in automatic mode only in case of the need.

Classification of full drive systems

Among the specialists it is customary to distinguish between three varieties of full drive systems:

1. Unconnected permanent (Full-Time or 4WD);
2. Connected by electronics (Torque On-Demand or AWD);
3. In addition, there are all-wheel drive systems with manual connection (Part-time).

All-wheel drive transmission, which was the first to become massively installed on mass-produced machines, the Part-Time system is considered. Such a system is a device that is rigidly connecting the front axle. As a result, the wheels of both axes are forced to rotate at the same speed. Naturally, the installation of the mid-sieve differential in this case does not matter.

Differential - what is it?

Considering such a device as a differential, it should be borne in mind that this is a special mechanical device that takes craving from the drive shaft and distributing it in the required proportion on the drive wheels. In this case, the difference in the rotational speed of the wheels is compensated automatically. Thus, by means of differential, the torque direction takes place to the drive wheels, and at the same time the wheels themselves will have different (differentiated) angular velocity.

Differentials can be used for both bridges of a vehicle equipped with all-wheel drive transmission. Separate models are equipped with a differential, which is mounted in - such a solution to the full drive is made classified as the "Full-Time" systems.

To understand why a car is needed differential, it is worth understanding the principle of its work. The thing is that the wheels of any car have the same speed of rotation only when it moves in the forward direction. As soon as the car begins to enter the turn, each of the four wheels acquires an individual speed, while both axes begin to "compete" in speed. An explanation of this phenomenon will be the emergence of its trajectory for each of the wheels - those that are inside the turn passing a smaller path compared to the outer wheel.

Thus, do not be differential, in turning the inner wheel would be turned on the spot, to compensate for the rotation of the outer wheel. In such conditions, it would have been impossible to ride at high speed, it would not have to talk about the control of the car. The presence of differential enables the axes in the desired way to "overtake" each other when the speed difference occurs.

The device of the interstole differential - when entering the rotation, it allows the inner wheel to spin slowly

PART-TIME system

The PART-TIME system is designed without installing the inter-axis differential. Such a device involves the transmission of torque from the operating motor on both axes in the same amount - thus, both axes are spinning with equal speed. Obviously, cars equipped with part-time drive system, moving on roads with a good asphalt or concrete coating contraindicated, because trying to make a turn, the driver provokes the emergence of the above-described difference in the length of the bridges path.

Since the moment on the axes is transmitted in a ratio of 50 to 50, when the steering wheel turns, slipping wheels of any of the axes will occur. If under the wheels of the car snow, dirt or sand (which often happens when traveling to the cottage, picnic or fishing), then a small grip of wheels and road surface will not cause any harm to the car. But in case of maneuvering on a dry and solid surface of the road, the emerging slipping has a negative effect on the functioning of the transmission, causes accelerated wear Tires, and also reduces the quality of the car charter.

Thus, cars equipped with a system of connected full drive are good for regular operation in conditions of bad roads or to conquer off-road. In this case, as a rule, blockages are not required, since one bridge will initially be strictly connected.

Other pluses of all-wheel drive solutions part-time are related to the relative reliability and simplicity of the entire design: there are no electrical or mechanical drives, the locks are not used, differentials are not used. It simplifies the system and the fact that there are no additional hydraulic or pneumatic elements in it. However, for everyday use, such a system is inconvenient. The use of the constantly turned on the axis of the front wheels is fraught with a vehicle breakdown, and constantly turn on and off the bridge is simply inconvenient. The list of models of machines, the design of which involves the use of part-time, includes the following stamps and models vehicle: Nissan Patrol First Generations, Pickup, Nissan NP300, Jeep Wrangler and Domestic.

Permanent full drive

The listed features and disadvantages of the system of the connected full drive led to the development of a constantly connected all-wheel drive system, eliminated from such problems. As a result, the light saw cars with a 4WD drive, in which all the existing wheels perform the role of the leading, and there is also a free inter-axis differential, which allows to produce "unnecessary" power due to slipping of one of the reducer satellites. Thus, the car always moves with all the leading wheels.

The nuance of the 4WD mechanism is the following feature. When slipping of any wheel, an inter-wheeled differential disables the second wheel of this axis. Similarly, the second pair of wheels is also working. It is quite possible that the car with the 4WD drive system, which at the same time with the wheels of both axes are completely immobilized. To minimize the fall of off-road properties of all-wheel drive vehicles with a 4WD system, developers install at least one blocking of forced type. As a rule, the inter-axis differential is forcibly blocked.

As an additional option, it is often offered to install the blocking of the front differential. SUVs with 4WD models include SUVs such as: Land Cruiser 100 Prado and Land Cruiser 100, and. But perhaps the most famous modelequipped with a 4WD drive, is.

Despite all its advantages, the system of a constantly connected full drive, unfortunately, has certain disadvantages. So, in terms of controllability on asphalt and other solid roads, SUVs with both leading axes are quite far from ideal. In critical situations, such a car will try to slip out of turn, without reacting to the rotation of the steering wheel and pressing the gase pedal properly.

Connected four-wheel drive (automatic)

The modern format of crossovers, regardless of the size of the car, assumes the possibility of a quick and short-term connection of an additional pair of leading wheels. Naturally, such connections should be carried out in automatic mode, without the driver's participation. To implement such solutions, automotive designers began to apply special multi-disc clutches, if necessary, connecting the wheels of the rear axle in addition to the constantly rotating front wheels.

The all-wheel drive system implemented in this way is much simpler classic off-road structures. There is no dispensing box, and only a pair of gears for the extraction of power and the output shaft are provided near the front differential.

Subsequently, the developers came up with the use of airline differentials, equipped in addition to the forced blocking by also self-locking mechanisms. Using various solutions (Viscounts or differential Torsen), the developers sought a single common goal - to partially block the inter-axis differential in order to increase the controllability of the car - in the event of a slip of any of the axes, the triggered blocking did not allow the differential to turn off the second pair of wheels and the moment from the engine continued To do it. Cars with a presented variant of the full drive are marked with AWD abbreviation.

Differential Torsen

However, among themselves couplings also differ significantly regardless of the similarity of the principle of connecting the wheels of the second axis. One of the first couplings began to apply engineers concern Volkswagen. For their Hatchbacks Golf. We are talking about the signature transmission of Syncro, where the installed friction panels are not compressed, but operated in silicone fluid, thick in conditions of improving the load and capable of independently transmitting rotation. The introduced Viscouft was unmanaged and was not capable of transmitting all 100% of the moment to the rear axle. In addition, even with rather non-long slippers, Silicone boils, which led to overheating and subsequent coupling coupling.

Viscounts (viscous coupling)

A more advanced design was used in the early models Ford. Escape. Couplings compressing through the work of wedge-shaped slots and balls have already been used here. These clutches, although they worked much more clearly, they could cause very sharp and sensitive blows at the moment of turn.

Haldex coupling

A peculiar revolution among couplings used in full drive systems are called the first generation of the Haldex coupling in the late 90s of the last century. In such a device, the discs were compressed using a hydraulic cylinder with a pump to generate oil pressure. The pump was mounted on one of the half of the coupling, the drive to him came from another half. Now, in the event of a difference in the speed of rotation of the wheels of the front and rear axes, the compression pressure increased, and the coupling was blocked. In comparison with the previously installed couplings, Haldex worked very gently and gained a serious success.

It should be borne in mind that modern technologies and materials used have made it possible to make a truly high-tech coupling that can be kept in a partially connected state without concerns overheating. Thus, manufacturers managed to distribute torque transmitted to pairs of wheels in favor of the rear axle, providing a car "classic" handling and all-wheel drive capabilities. Taking into account the flexibility of the working algorithms used and a very deep degree of development of the design of the multi-disc couplings used, in the modern period of time this is the most popular decision of the organization of a all-wheel drive transmission, which is unlikely to replace something in the next few years.