xDrive all-wheel drive from BMW. Definitely all-wheel drive How the system works

"Favorite" blah blah from BMW - the fable "xDrive works faster than a regular permanent 4WD." How can pluggable clutch work faster always on(!) drive - a question for BMW fans and marketers.

BMW 4WD options

Often there is a thesis that the history of xDrive originates from the very 1988 (1985) year that there are 4 generations xDrive systems and other similar nonsense. In fact, the official history of BMW, although it includes the “evolution of xDrive”, hinting at some kind of continuity (de facto there is none), clearly captures two facts:

1. xDrive system was first applied in 2003 on the new BMW X3 and facelifted BMW 3 Series (E46);
2. xDrive system constructively and fundamentally is not a descendant of earlier systems and is "absolutely new system”, “revolutionary turn”, “the only one before today intelligent 4WD system” and other blah blah blah.

So let's list BMW's 4WD options, counting xDrive as just one of those options. Note that BMW has always professed a rear-wheel drive ideology. And only rally and commercial successes Audi Quattro in the early 80s they pushed BMW engineers to develop their own all-wheel drive transmission.

To uncover...

The debut of 4WD from BMW. The transmission was developed in collaboration with FFD in accordance with the "Ferguson formula" (central differential with "soft", tolerant blocking, it is also "free differentials must be independently blocked if necessary, and four-wheel drive— to be a means of increasing stability and manageability”). The series included coupe, sedan and station wagon bodies.

Permanent four-wheel drive:

• Asymmetric (37/63, according to others 38/62 front / rear) planetary type central differential. Blocking with viscous coupling (up to 90% of thrust on any axle).
• The front differential is open.
• The rear differential is blocked by a viscous coupling.

Basic rear wheel drive model - differential rear axle connected directly with cardan shaft. Drive to the front axle by means of a power take-off mechanism via a toothed chain and a shaft leading to the differential. Differentials with viscous couplings were less durable than the worm Torsen on Audi.

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To uncover...

Permanent four-wheel drive with asymmetrical center differential (36/64). Electronic system differential locks based on wheel slip information with ABS sensors, positions throttle valve engine and brake condition.

First generation, April 1991 - September 1993: control of a separate ESD unit - BMW 33 19 1139133 (SIEMENS 5WK3 230).

• The front differential is free.
• Electro-hydraulic wet clutch (clutch) for locking the rear differential.

Second generation, October 1993 and prior to discontinued: ABS/ASC+T control (center) and simulated rear differential lock (ABD) via slipper rear wheel braking and engine speed limiting.

• Semi-dry electromagnetic clutch for central differential lock.
• Front and rear differentials are free.

The model is basic rear-wheel drive - the rear axle differential is attached directly using the cardan shaft. Drive to the front axle by means of a power take-off mechanism via a toothed chain and a shaft leading to the differential.

The semi-dry electromagnetic clutch is located in the transfer case and is a multi-plate electromagnetic clutch.

Both clutches (electromagnetic and electro-hydraulic) provided stepless blocking from 0 to 100% in a fraction of a second.

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To uncover...

Permanent single ended (38/62) 4WD with loose differentials. Imitation of differential lock due to the electronic traction control system ADB-X (Automatic Differential Brake).

The series included sedan and station wagon bodies.

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To uncover...

Permanent asymmetric (32/68) 4WD with free differentials (center - planetary). Imitation of differential lock due to the electronic traction control system ADB-X (Automatic Differential Brake). Speed ​​control system at steep descent(HDC).

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xDrive

To uncover...

It is currently used on the entire range of BMW vehicles with several variations:

• 1 episode (2012-)
• 2 series (2015-)
• 3 series E90 X models (2000-)
• Episode 4 (2014-)
• 5 series E60/E61 (2004-)
• Episode 6 (2012-)
• Episode 7 (2010-)
• separately - vehicles with V8 engines: BMW 750i xDrive (F01, 2010), 550i Gran Turismo xDrive (F07, 2010), BMW 550i xDrive (F10, 2011)
• X1 (2009-2015 for base RWD and 2015 for base FWD)
• X3 (2003-)
• X4 (2014-)
• X5 (2004-)
• X6 (2008-)
• M series - X5 M and X6 M (2010-)

The xDrive system does not have a center differential and therefore cannot be called "permanent" 4WD. One axle (rear, on the BMW X1 since 2015 - front) is permanently connected, the other is connected through an electronically controlled multi-plate clutch (the clutch pack drive is lever from an electric servomotor). At the command of the electronics, the clutch can change the degree of blocking from 50/50 in 0.1 seconds (according to other sources - in 0.08 seconds) tractive effort(fully closed) to 0/100 (fully open), transmitting up to 1500 Nm of torque. For comparison: the delay between pressing the gas pedal and the response of the motor is 0.2 seconds, i.e. xDrive is ahead of the engine in its work. The transmission of torque is carried out using a cardan shaft with chain drive(on "parquet" models of the X series) or gear train(on conventional all-wheel drive models).

Most expensive models are equipped with additional overdrive (“thruster”) gears in the rear wheel drive (DPC system), similar to or Nissan Juke.

The key difference between the xDrive system and earlier versions of BMW 4WD is the much higher resistance to piloting errors with worse adequacy due to the fully electronic control of the torque transfer. On the other hand, xDrive is technically much simpler, more reliable, smarter, and changing parameters in software is much cheaper and faster than setting up real differentials.

The xDrive system works in conjunction with other vehicle systems and changes the degree of clutch lock based on their data:

• ICM(integral control system undercarriage) how the top-level system synchronizes the work of xDrive and other systems.
• DSC(Dynamic Stability Control - system dynamic stabilization). If the vehicle shows signs of understeer (front wheel drift outside turn), the clutch opens and the thrust is transferred to the rear axle. In case of oversteer (skidding), the clutch closes completely, distributing traction between the axles equally and thereby helping to level the machine. If the effect is insufficient, the DSC system selectively brakes the spinning wheels. This allows the open axle differentials to automatically distribute torque to the unbraked wheels and helps to straighten the car when skidding or drifting into a corner. A typical situation is braking at the beginning of the drift of the front axle of the rear wheel closest to the center of rotation, compensating for the loss of traction by redistributing it.
• Also, the link between xDrive and DSC additionally provides a cross lock function. If a wheel spins without power transmission, it is braked electronically by the DSC system.
• Dynamic control system exchange rate stability(DSC) via ICM is also linked to the AFS active steering system, which allows the AFS system to stabilize the vehicle when braking with different coefficients of friction on different wheels(μ-Split braking).
• It also interacts with traction control systems DTC and descent assistance HDC.

In general, xDrive uses in its work the data of the engine management system, the position of the gas pedal, the angle of the steering wheel, the speed of the wheels (and the speed of the car, respectively), the angular and lateral acceleration of the car. All this allows the xDrive system to control the clutch proactively (similar to the Nissan), and not on the fact of drive slippage.

Separately, it is worth describing the system DPC(Dynamic performance control), which allows you to redistribute the moment between the rear wheels, realizing the effect of "steering" (even when releasing gas and idling).

Technically, the DPC is two combined devices located in the final drive of the rear axle and consisting of a planetary gear with three satellites, a multi-disc brake driven by an electric motor, and a ball ramp. The DPC system provides a drive torque difference between the rear wheels of up to 1800 Nm.

The DPC steer effect improves steering response and lateral stability car. When driving in corners, the torque in the still stable driving mode is mainly directed to the rear axle in order to increase the vehicle's maneuverability and prevent understeer.

• If oversteer is anticipated, xDrive increases torque on the front axle, and DPC reduces torque on the outer rear wheel relative to the turn (takes torque from the heavily loaded outer rear wheel due to centrifugal force and redirects it to the inner rear wheel).
• If understeer is expected, xDrive reduces torque on the outer front wheel, while the DPC simultaneously shifts drive torque to the rear wheel farthest from the center of rotation.

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General logic of xDrive

To uncover...

Such logic causes comments from drivers, because. xDrive cannot, for example, climb an icy curb when parking (because the clutch is open in parking mode). Or, for example:

• xDrive allows the rear wheels to slip, throwing rear axle into a skid, and only then the front axle is connected. The car begins to skid, the first reaction is to release the gas (as it should be with rear-wheel drive), but in fact it turns out you need to press even more with the thought that a miracle will happen now and the front will stretch the butt. And even when skidding, it is supposed to turn the steering wheel in the direction of skidding, and when connecting front wheel drive, the car abruptly breaks off in the same direction with the front wheels. I am a little disappointed with the car's behavior on slippery roads.
• In a recent snowfall, I decided to start on the floor on an empty road with a crossover and the back threw very much to the side, I would have been in the stream, it hit a neighboring car. So it turns out that xDrive is good for tracks and beautifully shot clips, and in city traffic you need to take into account that the rear-wheel drive is the most offensive.

Tellingly, the pre-styling X5 with permanent 4WD has no such problems:

... rows confidently constantly with 4 wheels. when slipping / skidding, DSC is activated and brakes the desired wheel(s).

The logic of work also implies the ability to use the stabilization system with a sharp blow to the brake pedal when the car is “lost”. Even if the DSC stabilization system is disabled, this will be a signal for it to start action - it will “wake up” for a short time and help stabilize the car. In a similar way, for example, the EBD system is configured on the right-hand drive "Galant" Mitsubishi 1996-2003.

DTC mode, Dynamic Traction Control (not available on all versions) - a kind of "intermediate" stage between the enabled and disabled DSC system. A short press on the DSC button is enough - and the car will allow you to slip a little, set a small skid angle, and spin all four wheels. As the situation progresses to a really dangerous difficult skid, DSC will gently intervene and straighten the car.

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xDrive device

To uncover...

Handout xdrive box developed jointly with the Austrian company Magna Steyr and designed for engines with a torque of up to 650 Nm. moment on front axle is selected by a package of clutches, the compression ratio of which smoothly changes in the range of 0-100% using a lever mechanism driven by an electric servomotor. The lubricant is a special synthetic oil Shell with a service life of 190 thousand km.

Below is a variant with gear transmission ("regular" models).

For comparison - xDrive with a chain drive ("parquet" models):

Full xDrive drive from now on, it is also available to buyers of powerful BMW fives. Amazing. And to state this positive fact, it was not at all necessary to go to Finland and ride on the ice of a frozen lake in a BMW 530xi.

But I went. Ride. And I realized that the electronically controlled xDrive is perhaps even more interesting system than the Torsen on the Audi quattro...

Spaghetti, pasta are bad food for racers, Rauno Aaltonen categorically declares at dinner. - Spaghetti makes a person softer. And meat and potatoes are stronger! Well, more salad. That's what I eat. And look, I'm 67 years old and still lead my own snowmobile tours in Finland. Three days, eight hundred kilometers across virgin lands. And there is no one to trust: the youth can not stand it!

Rauno Aaltonen, together with his son Tino, is invited by the BMW people as a "racing taxi driver". Fantastic uncle! He has an opinion on everything. Sometimes undisputed, but their own. And it's worth listening to. After all, Rauno Aaltonen is the man who in the late 60s, together with Paddy Hopkirk and Timo Mäkinen, raced and won the Mini on the slippery serpentines of Monte Carlo. Behind Aaltonen - podiums in rally, in motorcycle racing, in the ring "body" championships, years of methodical work at school driving skills BMW... No wonder sports historians consider it the most versatile of all the great "flying Finns".

Do you know why Finland leads by a huge margin in the number of motorsport world champions? It's genetic. After all, Finnish men are hunters. The lives of their families depended on their speed, endurance, accuracy and composure for centuries!

Aaltonen does not mention the famous Finnish roads: this is obvious. Ice-covered dirt tracks in winter, wide frozen lakes where you can train all winter without any problems - this is what turned the former cold-blooded hunters into the fastest and most versatile racers on the planet. And now around Rovaniemi - endless white expanses. There is where to roam!

Especially in full drive.

The event organized by the Germans from BMW in subpolar Finland was called the xDrive experience. This is a demonstration of the capabilities of the new proprietary xDrive system, which is now equipped with all BMW all-wheel drive vehicles. Arranged xdrive transmission very simple - the rear-wheel drive remains constant, as in any BMW, and the front wheels are connected automatically using a simple mechanism. When you look at him, you even take aback - he is so simple. A tiny electric motor that develops only 1 newton meter - even a mixer cannot be turned like this. Behind the motor are two reduction gears, a worm gear and a planetary gear. Then - an eccentric, which, turning, displaces a long lever. And he, in turn, clamps the clutch pack, connecting the drive to the front wheels.

Brilliantly crafted! Energy costs are minimal, the effect is maximum. Why hasn't anyone thought of this before? However, the Valvetronic throttleless intake with its engineering elegance was also first introduced on BMW...

But here's what's not clear. Initially, any BMW car with the xDrive system is rear-wheel drive. The front-wheel drive is connected electronically without any participation of the driver. For example, during parking maneuvers, the X-drive clutch is completely turned off - the car is strictly rear-wheel drive, since it is not necessary to connect the front now and even harmful. But the “strictly rear” drive mode is activated not only when the car is maneuvering in the yard with low speed and large steering angles, but also after 180 km/h!

On high speed you do not need all-wheel drive, the Bavarians assure. - However, if you "lost" the car on such a move, then if necessary, xDrive will connect the front wheels. But it probably won't help...

What a striking contrast with the ideology of Audi! In Ingolstadt, they have long professed a diametrically opposed religion - four-wheel drive must be permanent and symmetrical. Subaru and Mitsubishi are built according to the same scheme, and that's it. rally cars WRC. And now the Munichers are coming - and turning the world upside down?

Indeed, all 530s with xi nameplates were delivered to Rovaniemi straight from the Swedish BMW winter training ground in Arjeplog. Outside - the usual "fives". Unless the body is planted a little higher, only 15 mm. But ground clearance remained unchanged. In the cabin - excellent leather seats with active sidewalls, the familiar smell of expensive plastic. And, alas, the same “symmetrical” furniture design of the front panel that annoys me. God, when will all this bangle stuff end...

On top of the panel is an additional display with two linear scales. You don’t have to look at the top: this is a hypothetical “degree of all-wheel drive”. But at the bottom, the actual degree of blocking of the clutch that connects the front is displayed. While I do not touch the gas pedal, the bar at the bottom is empty - the clutch is open. But the very first press on the pedal - and the display instantly comes to life. Electronics proactively, without waiting for starting off, "clamps" xDrive - judging by the display, by about 60% of the maximum, "hard" state. That is, when starting from a standstill, the current BMW 530xi will be similar to previous all-wheel drive Bavarian cars, in which the front wheels were always supplied with less torque than the rear ones.

For what? For the "rear-wheel drive" that is so familiar to BMW drivers!

I turn off the stabilization system by long pressing the DSC button - and with the very first press on the gas I make the "five" in a rear-wheel drive dashingly twist around its axis. Great! Here is the first difference from the "permanent all-wheel drive" Audi, Subaru and Mitsubishi. Those in response to the first addition of gas always first respond as front-wheel drive - they tend to slip out, going into demolition. A BMW with "X-drive" on a slippery surface behaves the other way around. The first impulse of the all-wheel drive "five" to add gas is to go into a skid!

But xDrive instantly reacts to the start of a skid - the bar on the display immediately goes dark in its entirety, the clutch is completely blocked, and the BMW momentarily turns into a car with hard all-wheel drive. Here is the second difference from Audi. After all, the Ingolstadt Torsen is not blocked completely, but by 70%, no more. And the X-drive clutch is able to clamp the transmission tightly. Its carrying capacity allows you to apply to the front wheels up to 1500 Nm of torque. Moreover, xDrive is “clamped” completely very quickly, in just one tenth of a second.

I did not expect such a pleasant and predictable behavior from an “automatically-connected-all-wheel drive” car. Processes in the "x-drive" are generally imperceptible. Electronics constantly monitors the situation, flexibly “playing” with the degree of connection of the front end, the column on the display dances all the time, reflecting the activity of the electric motor - somewhere there, under the floor, it rotates wildly back and forth, clamping and loosening the grip of the clutches. But this does not affect the behavior of the car in any way - BMW behaves like a real all-wheel drive. You confidently throw the "five" into wide slides, make it go sideways in an arc under the pull ... And it does everything you want!

Of course, we will still force you to fight in a face-to-face fight on ice bmw 530xi and Audi A6 3.0 quattro. But the correspondence difference of the all-wheel drive “five”, as it seemed to me, is a more unambiguous behavior. There is no such first phase when the Audi quattro, under traction with the wheels turned, first slides into a drift - and only then goes into a skid, the direction and angle of which can be controlled by the steering wheel. And in the case of BMW, the demolition phase on ice is simply absent! Immediately - only skidding. Which is no less convenient to manage than on an Audi.

And if the car is turned sideways, if a U-turn seems inevitable, then...

If you feel that you are "losing" the car, slow down! - Rauno Aaltonen in a funny fur hat makes an energetic gesture with his hand. - Only abruptly, by hitting the pedal. For what? Even if the DSC stabilization system is disabled, this will be a signal for it to start action - it will “wake up” for a short time and help stabilize the car. And be sure to try the DTC mode, it's a wonderful thing!

DTC mode, Dynamic Traction Control - this is a kind of "intermediate" stage between the enabled and disabled stabilization system. A short press on the DSC button is enough - and the “five” allows you to slip a little, set a small skid angle, spin all four wheels ... And then, as the situation moves into the phase when only a well-trained person can cope with a skid the driver will gently intervene - and straighten the car.

Moreover, the all-wheel drive "five" is good even with the DSC system turned on - the electronic "collar" here is relatively loose. By the way, the electronics of the xDrive and DSC systems are closely related to each other - the all-wheel drive receives information from all sensors of the stabilization system, which play the role of the "vestibular apparatus". Moreover, according to BMW engineers, the X-drive software was developed by them independently, it significantly exceeds engine control algorithms in complexity - and is hardly amenable to chip tuning ...

Electronics! It was she who became the catalyst that helped complete the development of the "rear-wheel drive" concept of BMW. Indeed, since the beginning of the 80s, when they began to work on a transmission for the all-wheel drive BMW 325iX in Munich, BMW engineers wanted to “marry” the advantages of rear and all-wheel drive. But testing all the early all-wheel drive "treshki" with their asymmetric transmission (38% of the moment to the front wheels and 62% to the rear), we always noted - yes, the car is perfectly controlled, but it does not forgive mistakes in driving. And BMW with "x-drive" - ​​forgives!

Moreover, it seemed to me that the all-wheel drive electronics on the “fives” are already more perfect than on the BMW X3 with a similar xDrive system. Anyway, BMW X3 3.0 on the same Finnish ice was less pleasant and obedient in management. For example, on the “x-third” there is no DTC mode, and with the stabilization system turned off, the electronics still sometimes intervened and “bited” the brakes - this was an imitation of differential locks. Yes, and the front-wheel drive was connected not as quickly as on the “fives”.

Of course, these are just first impressions. On the gravel wet pavement BMW xi fifth series may behave differently. Yes, and on ice ... After all, I drove experimental cars - work on debugging the X-drive control has not yet been completed.

In a good way, several programs are needed for such a system, Rauno Aaltonen believes. - For asphalt and ice, for studded and for friction winter tires... But for a production car, this is, of course, impossible. And colleagues from BMW are now just looking for a single compromise control program for all occasions ...

Yes, now it all depends on the algorithm that will be put into xDrive. So let's wait for serial all-wheel drive sedans and station wagons BMW 525xi and 530xi, which will come to Russia at the end of spring. In Europe, by the way, xDrive will also be installed on diesel version 530xi, but that's not for us.

And by the end of the year, the turn of the third series will come - versions of the BMW 325xi and 330xi, which will have exactly the same xDrive as on the "fives". It is a pity, of course, that all-wheel drive is the prerogative only expensive cars With powerful motors. Moreover, in Russia we have a price difference between rear wheel drive sedans and their all-wheel drive versions will be more than the €2,500 xDrive surcharge announced in Europe. The reason is simple - if the usual BMW 525i and 530i sedans are assembled in Kaliningrad, then all-wheel drive cars are made only at the "parent" Bavarian plant in Dingolfingen. And the Russian localization of the assembly all-wheel drive vehicles BMW will not be engaged - it is unprofitable, the volumes are not the same. After all, Russia is not America, where half of all BMW all-wheel drive cars are sold ...

background

BMW has always professed a rear-wheel drive ideology. And only the rally and commercial successes of the Audi Quattro in the early 80s prompted BMW engineers to develop their own all-wheel drive transmission ...

"Treshka" BMW 325iX series E30 appeared in 1985. Its transmission was developed in collaboration with the famous FFD company in accordance with the "Ferguson formula" and differed from the quattro conceptually - the moment from the engine was divided along the axes using the center differential not equally, but in a ratio of 38/62 in favor of the rear wheels. The center and rear differentials were self-locking, with built-in viscous couplings that automatically worked when slipping. All-wheel drive "treshki" were well controlled, but they were noticeably more expensive than usual and did not achieve sports success - differentials with viscous couplings were less durable than the worm Torsen on Audi.

Further all-wheel drive versions alternated. The new “treshka” of the 1991 model (E36) did not have an all-wheel drive version, but in the same 1991, the BMW 525iX sedans and station wagons of the then E34 series picked up the baton. The transmission on the "fives" was also asymmetric (36/64), but much more complex - the locks of the center differential (with an electromagnetic drive) and the rear (with an electro-hydraulic drive) were in charge of the electronics. From 1991 to 1996, a little less than 10 thousand all-wheel drive "fives" were produced.

The next change in the lineup brought castling again: the new “five” with the E39 body (1995-2003) did without all-wheel drive, but the previous “three-ruble note” E46 had two all-wheel drive versions - 330Xi and 325Xi. The transmission was also asymmetric (38/62), but this time all the differentials were “open”, and the role of the lock was partially played by the brakes, triggered by the electronics command. Exactly the same all-wheel drive system before restyling in 2003 had BMW crossover x5.

And now all BMW all-wheel drive cars have switched to xDrive - a system without a center differential, but with an automatically connected front end. For the first time, xDrive debuted on the X3 crossover, then migrated to the X5, and now it will be equipped with fives and new threes with the xi nameplate.

xdrive- original system intelligent all-wheel drive developed by BMW. Although this system refers to permanent all-wheel drive, at its core it retains the classic rear-wheel drive transmission scheme for BMW, i.e. at normal conditions movement and condition pavement the car behaves predominantly as a rear-wheel drive. But if necessary, part of the torque is instantly transferred to the front wheels. In this way, the system constantly monitors the state of the car's movement, continuously distributing power between the axles in an optimal ratio. As a result, the xDrive system provides exceptional handling and dynamics when cornering and driving on slippery roads.

History of creation and development of the system

Proprietary all-wheel drive system BMW xDrive was officially introduced in 2003. Up to this point, its predecessor was a scheme with a constant distribution of torque between the axles in a fixed ratio. Initially, all-wheel drive was offered as an option for the rear-wheel drive models of the BMW 3 and 5 series of the 80s. The history of the development and improvement of BMW all-wheel drive systems has four generations.

All-wheel drive BMW model iX325 1985

1st generation

1985 - All-wheel drive system that distributes torque constantly in a ratio of 37:63 for the front and rear axles, respectively. The rear and center differentials were rigidly blocked when slipping by viscous couplings, the front differential was of a free type. Used on the 325iX model.

II generation

1991 - permanent drive with a power ratio between the axles of 36:64, with the possibility of redistribution to any axle up to 100% of the torque. was carried out using an electromagnetic multi-plate clutch, the rear differential was blocked by a clutch with an electro-hydraulic drive, the front one was free. In its work, the system took into account the readings of the wheel speed sensors, the current engine speed and the position of the brake pedal. Used on the 525iX model.

III generation

1999 - four-wheel drive with a constant power distribution in the ratio of 38:62, all differentials are free with electronic locking. The system functioned in conjunction with the dynamic stability control system. This all-wheel drive scheme was used on the first generation X5 crossover and showed excellent results both when driving on asphalt and in lung conditions off-road.

IV generation

2003 – intelligent system xDrive all-wheel drive was introduced as part of standard equipment the new model X3 and the updated model of the 3rd series E46. To date, xDrive is installed on all models of the X series, optionally - for all other BMW models, except for the 2nd series.

System elements

• in a housing with a multi-plate clutch that performs the function of an interaxle differential.

• Cardan gears (front and rear).

• Cross-axle differentials (front and rear).

Multi-plate friction clutch

The function of power distribution between the axles is performed by a transfer box driven by a servomotor. Depending on the model BMW car chain or gear drive type can be used driveline front axle. The clutch is activated by the command of the control unit and in a fraction of a second changes the ratio of torque transmission along the axes.

How the system works

At its core, the xDrive system uses a rear-wheel drive transmission scheme. Driving in normal mode provides for a torque distribution in the ratio of 40:60 (for front and rear axles). If necessary, on the axis with better grip with the road surface, the full power potential can be transmitted. xDrive works in harmony with all integrated systems active safety, including Active Steering and Vehicle Stability Control.

System operating modes

• Start of movement : differential locked, power between the axles is distributed in an optimal ratio of 40:60, at speeds above 20 km / h, the torque ratio is determined by the system based on current driving conditions and the road surface.
• Oversteer: when the xDrive system detects that the rear axle is moving outward from the pivot point more power redirected to the front axle; connected if necessary dynamic system directional stability, braking right wheels and leveling the car.
• Understeer: When the steering system registers the front axle away from the center of rotation, up to 100% of the torque is applied to the rear axle, and the stability control system helps to stabilize the vehicle if necessary.
• Driving on a slippery road: The torque is distributed electronically to the axle with the best grip, preventing slippage.
• car parking: all power is redirected to the rear axle, making it easier for the driver to control and reducing the load on the transmission elements.

Based on the readings of numerous sensors, the control electronics are able to accurately recognize the tendency of the car to drift when cornering or the imminent loss of traction of the wheels with the road surface. The system also takes into account the current parameters of the engine, the speed of the car, the speed of the wheels, the angle of their rotation and the lateral acceleration of the car. This allows you to proactively calculate and change the balance of power distributed between the axles in a fraction of a second. The stabilization of the car occurs on the verge of losing control, while maintaining traction and dynamics. The stability control system is activated at the last moment in the event that the intelligent all-wheel drive has not coped with the task.

The basis of safe and enjoyable driving is the most complete control of the forces acting on the car. Management security is the most important aspect, taken into account during the creation process running system, as well as the drive of BMW cars.

The influence of dynamic forces (whether vertical, transverse or longitudinal) can be tamed in various ways, which include:

• skillful steering;
• gentle braking;
• speed and sensitivity of actuation of shock absorbers and a system of elastic elements.

Following all of the above factors allows you to maximize driving safety and get maximum satisfaction even from sports driving on disgusting road surfaces.

Why do you need all-wheel drive?

Initially all-wheel drive BMW versions were calculated to determine the most acceptable parameters of the traction force and the ability to maintain the original state under various influences characteristic of the movement. Only 25 years later, the engineered BMW xDrive all-wheel drive system was able to make this mission a reality, and on a scale that is unparalleled anywhere in the world. This intelligent system, due to its fast response, variability and accuracy, has the ability to adjust the force in cases where it is converted into motion dynamics. This technology was developed in such a way as to apply to the maximum all the advantages of the distribution of force among the four wheels and get rid of or at least reduce the characteristic disadvantages.

In the ingrained understanding, the all-wheel drive system is aimed at improving traction when driving on country roads or slippery roads. At the same time, one has to face some flaws arising from the inefficient distribution of efforts, which can be expressed in: unsatisfactory qualities of the running gear; in limiting the susceptibility of the steering wheel to turns when driving at high speeds; in the lack of comfort when performing various maneuvers. All these shortcomings draw attention to themselves very much, especially when compared with the rear-wheel drive system characteristic of BMW.

In the process of creating the first all-wheel drive, the designers of BMW were able to perfectly combine the advantages of the already proven with better side rear-wheel drive and all-wheel drive system.

More dynamic cornering – more safety in winter

Of note is 1985, when the BMW 325iX was shown at the Frankfurt Motor Show (IAA). This model clearly shows main principle all-wheel drive: greater cornering dynamics means less danger in winter. The main distinguishing feature that distinguishes this car from others like it is the unusual distribution of force between the wheels. Instead of the usual equal distribution of weight, the German company proposed an option where, when driving, 63% of the torque falls on the rear axle, and 37% on the front axle. This made it possible to maintain the exact execution of turns.

The rear axle wheel drive contains viscous blocking elements, which, in the event of dynamic situations, have the ability to coordinate the power flow. This means that in case of need, for example, turning the rear wheels, the torque will be redirected to the front axle. Despite the fact that the regulation of the locks occurred automatically, the anti-lock mechanism was always in working order. In practice, this concept worked in conditions where the car could show all its advantages:

• when accelerating out of corners, the traction force was optimized;
• in the period of a jerk on a wet road surface, the transfer of force occurred without slipping;
• when moving on ice and snow, safe driving performance was ensured.

The need for electronic control of the distribution of efforts

The developed electronic control systems have opened up new possibilities for optimizing traction, dynamics and stability during the movement of all-wheel drive vehicles.

In 1991, the next BMW 525ix model was introduced, in which, when diagnosing the current condition, the electronic system took into account the wheel speed information received from the anti-lock mechanism, data on the position of the throttle valve of the engine and the state of the brake system.

The distribution of the drive torque during normal driving in the ratio of 36% to the front axle and 64% to the rear was provided by a multi-plate clutch, adjustable continuously variable and located in the transfer case. This electro-hydraulic clutch, in order to avoid situations with the rotation of each individual wheel, regulated the power flow that occurs in the final drive of the rear axle. The combination with the front axle was due to the power take-off device. With the help of a cardan shaft, the rear axle differential was attached.

The transfer case was blocked electromagnetically, so even in difficult conditions, driving stability was automatically ensured. For acceleration on both flat and unpaved roads, there was always enough traction due to the adjustable locks.

In 1999, the BMW X5 also introduced all-wheel drive, which led to an improvement in the distribution of forces through electronic control. This model was the first in the category sports cars SAV (Sports Activity Vehicle), in which the torque was distributed in the following ratio: 38% to the front wheels and 62% to the rear.

Free globally center differential controlled the power flow among the front and rear wheels. Brake control action (individual for each wheel) provided the necessary blocking for stability during movement and optimization of traction.

The BMW X5 also contained:

• auto brake mechanism(ADB-X);
• dynamic stability control (DSC);
• descent speed control (HDC).

The combination of all of the above characteristics made the car suitable not only for sports driving, but for driving on a road surface that is far from perfect.

BMW xDrive intelligent all-wheel drive: quick, precise, ahead

In 2003, the BMW X3 model was introduced, from which the use of a new generation began. all-wheel drive systems. In parallel with this car, all-wheel drive began to be used in the BMW X5. In this BMW xDrive system, the variable distribution of torque between the front and rear wheels has been preserved due to the electronic multi-plate clutch with longitudinal locking. This clutch function was provided by the Dynamic Stability Control (DSC) system, whereby the xDrive system defined new limits for the accuracy and speed of distribution of drive torques determined by the situation. In addition, this system confirmed the status of "intelligent all-wheel drive", as it became possible to pre-determine the risk of slipping of the drive wheels and counteract this through the distribution of forces.

The continuous development of xDrive has thus far optimized traction, driving stability in poor road conditions and cornering dynamics. This system is used with the same success for BMW 3, 5, 7 series models.

Improve agility and optimize cornering dynamics with new xDrive and DSC tuning methods

For vehicles with all-wheel drive, currently equipped with xDrive, it is possible to adjust the optimization of dynamics, which is especially noticeable, as a rule, when cornering. The turning force is mainly directed to the rear axle to improve maneuverability. When exiting a turn, in order to make the traction force as optimal as possible, the original percentage ratio between the front and rear axles, which is 40:60, is restored. The electronic driving dynamics control contributes to a gradual effect on the braking and also ensures the stabilization of the drive torque. Thanks to the same system, under various circumstances, resistance to understeer becomes possible and effective.

The xDrive and DSC control electronics, in the event of a strong outward protrusion of the front wheels, specifically brake the rear wheel located closest to the center of the turn. As a result, traction power is lost, but at the same time, this loss is compensated by an increase in drive power.

Dynamic Performance Control - the highest precision in the distribution of forces

Combination BMW systems xDrive and Dynamic Performance Control (driving dynamics management) significantly increase the ability to most effectively optimize the traction and driving stability of the car. Dynamic Performance Control is available on the BMW X6 , X5 M and X6 M because there is a differential power distribution between the right and left rear wheels.

Thanks to this torque distribution, the entire speed range is accompanied by optimal steering response and lateral stability. When oversteering, xDrive redistributes effort, reducing drive torque by rear wheels, and Dynamic Performance Control reduces the force directed to the most loaded rear wheel by shifting it to the rear wheel located closer to the center of the turn. In the event of understeer, these systems operate in the opposite way.

The stabilizing effect of Dynamic Performance Control is evident even when the driver releases the accelerator while moving. Special devices located in the main gear of the rear axle contribute to the variable distribution of force both in a situation of a sharp change in load and in forced idling.

Video test drive all-wheel drive BMW e34

Now the “charged” sedan has been declassified officially. It is interesting that the car, although built on the basis, has an internal F90 index, referring to the Bavarian F-models of the previous generation. So what do we have?

Main - new sedan became the first passenger car with all-wheel drive. With the increase in power, the capabilities of the canonical rear-wheel drive began to be lacking, and in the BMW M division they nevertheless decided to switch to four-wheel drive. The M xDrive transmission is structurally the same as in the BMW civilian models with a longitudinal engine: constant rear drive and a multi-plate clutch for connecting the front wheels. However, all components are strengthened, an active rear M-differential is installed with electronic control, and also added a software option to disable front-wheel drive, like a sedan: in this mode, the car will retain its traditional rear-wheel drive character to the delight of enthusiasts and drift lovers.

By default, the emka has all-wheel drive, but when the stabilization system is switched to the tolerant M Dynamic Mode, which allows slips, the transmission also switches to the 4WD Sport setting with an emphasis on rear-wheel drive. If ESP is completely disabled, then you can choose one of three drive modes: standard 4WD, "relaxed" 4WD Sport and hooligan 2WD.

Other important changes include the traditional eight-speed "automatic", which replaced the preselective "robot". Improved compared to conventional models, the gearbox shifts quickly and smoothly, and the torque converter lock-up is disabled only during gear changes.

The BMW M5 retained the old V8 4.4 biturbo engine, but it has new turbochargers, increased injection pressure, modified lubrication and cooling systems. Lightweight exhaust system- with Helmholtz resonators, which allow you to put the desired "voice" on high revs. Engine power - 600 hp against 560-600 hp in the previous model (depending on the version), and the torque is 750 Nm instead of 680-700 Nm, with maximum traction already available from 1800 rpm.

Compared to the base “five”, the extreme sedan has an increased track, the kinematics of the suspension has been revised, the stabilizers have become thicker, and the rubber joints are tougher. M5 equipped with adaptive dampers with three modes of operation. The same number of settings and the steering mechanism. Base brakes are compound (cast iron discs with aluminum hubs): in front - six-piston with a fixed bracket, and in the back - simple single-piston with a floating bracket. For an extra charge - carbon-ceramic discs, which reduce unsprung weight by 23 kg from the car: such brakes have golden calipers instead of regular blue ones.

The old rear-wheel drive "emka" in running order weighed 1870 kg (without a driver), and the new all-wheel drive is 15 kg lighter. First of all, this was achieved thanks to the carbon fiber roof, which was previously used on the M3, M4 and M6 models. The front fenders, hood, doors and trunk lid are aluminum. And instead of a lead-acid battery, a more compact and lighter lithium-ion battery is installed in the trunk, and with a capacity of only 70 Ah versus 105 for the previous Emka.

What about dynamics? If the old sedan accelerated to 100 km / h in 4.4 seconds, and the most forced 600-horsepower version did it in 3.9 seconds, then the indicator of the new all-wheel drive vehicle- 3.4 s. The Mercedes-AMG E 63 S (612 hp) sedan has the same time, the model (608 hp) made on the basis of the civilian “five” does this exercise in 3.5 s, and wagon audi RS 6 performance (605 hp) - in 3.7 s. Up to 200 km / h BMW M5 accelerates in 11.1 s, maximum speed limited (250 km / h), but if you order the M "Driver" s Package, then the cut-off will be shifted to 305 km / h.

What else? Flared fenders, muscular bumpers, an advanced air intake system and 19 or 20 inch wheels are commonplace for such machines. Inside, there is an M-steering wheel with red spots on the M1 and M2 buttons, on which you can “hang” individual combinations of modes for all driving electronics. And the modified selector of the "machine" - with a two-armed key for changing settings on the top.

world premiere BMW sedan The M5 will take place in September at the Frankfurt Motor Show. Immediately after that, European dealers will start accepting orders. The price in Germany is already known: from 117,900 euros - 4,000 euros less than they ask for the Mercedes-AMG E 63 S. But deliveries of commercial vehicles will begin only next spring.