The XDRIVE full drive system is the development of the BMW concern and refers to a permanent full drive system. The system provides stepless, continuous and variable distribution of torque between the front and rear axle depending on the conditions of movement. Currently, the XDRIVE system is installed on sports SUVs ( SAV, Sports Activity Vehicle) X1, x3, x5, x6 and passenger cars 3rd, 5th and 7th episodes.
The history of the development of a full drive from BMW includes four generations:
Generation |
Characteristic |
1 generation Since 1985. |
the distribution of torque between the axes at normal motion in the ratio of 37:63 (37% - on the front axis, 63% - on rear axle), inter-axis differential blocking, rear inter-track differential with viscous coupling (Viscounts) |
2 generation Since 1991 |
the distribution of the torque between the axes at normal motion in the ratio of 36:64, blocking the inter-axis differential using a multi-voltage coupling with electromagnetic control, blocking the rear inter-track differential using a multid-wide coupling with electro-hydraulic control, the ability to redistribute torque between axes (wheels) ranging from 0 up to 100% |
3 generation Since 1999. |
the distribution of the torque between the axes at normal motion in the ratio of 38:62, the inter-axis and inter-track differentials of free type, electronic blocking of intercheses differentials, interaction with the system of dynamic control rate stability |
4 generation Since 2003. |
the distribution of the torque between the axes at normal motion in the ratio of 40:60, the function of the inter-axis differential performs multi-disc friction clutch from electronically control, the ability to redistribute torque between axes ranging from 0 to 100%, electronic blocking of interstole differentials, interaction with the system of dynamic control rate stability |
The XDrive Full Drive System is based on the rear-wheel drive transmission scheme for the BMW. The distribution of torque between the axes is carried out using dispensing boxwhich is a gear transmission of the front axle drive, controlled by a friction clutch. In the transmission of sports SUVs instead seamless transmission The chain transmission is used.
The XDRIVE system is integrated with DSC Stability Dynamic Control System (Dynamic Stability Control). In addition to the electronic blocking of the differential, the DSC system combines the DTC thrust control system (Dynamic Traction Control), the HILL DESCENT CONTROL (Hill Descent Control), etc.
The interaction of XDrive and DSC systems is carried out using an integral control system. chassis ICM (INTEGRATED CHASSIS MANAGEMENT). The ICM system also provides connections with AFS active steering system (Active Front Steering).
Principle of operation of the system
In the operation of the XDRIVE drive system, several characteristic modes determined by the surveillance algorithm of the friction clutch can be distinguished:
- touching from place;
- passing turns with excess turning;
- passing turns with insufficient turning;
- movement on slippery coating;
- parking.
When starting from place in normal conditions, the friction clutch is closed, the torque is distributed across the axes in the ratio of 40:60, which reached the maximum thrust when overclocking. When the speed is reached 20km / h, the distribution of the torque between the axes is carried out depending on the road conditions.
When turning turns with excess turning (the rear axis is entering the outside of the rotation), the friction clutch closes with greater force, and a greater torque is directed to the front axle. If necessary, the DSC system is included in the operation, which stabilizing the movement of the car by braking the wheels.
When turning turns with insufficient turning (the front axle is demolished to the outer side of the rotation), the friction clutch opens, and up to 100% torque is directed to the rear axle. If necessary, the DSC system is turned on.
When moving on a slippery coating (ice, snow, water), the slip of individual wheels is prevented by blocking the friction clutch and, if necessary, the electrain interlocking blocking of the DSC system.
During parking, the friction clutch completely opens, the car becomes rear-wheel drive, which reaches the reduction of loads in the transmission and steering control.
Modern BMW acquired a full drive back in 1985. It was long before the appearance of crossovers, so the Bavarians were optionally equipped with such a transmission of only the 3rd and 5th series, which received additional beaks x in the index. Distribution with an inter-axis differential was adjusted to the gearbox, from which drives on the front and rear axles were. In the systems of the first two generations (1985 and 1991), the various coupling structures were blocked by inter-axis and rear inter-track differentials.
In 1999, the market was released bMW crossover X5, equipped with all-wheel drive transmissions of the third generation. Its fundamental differences: all couplings are abolished, the blocking of inter-wheeled differentials mimic the brake mechanisms under the control of electronics, inter-seed differential And at all free.
And in 2003 on compact crossover X3 appeared xDrive, which was subsequently pressed on all all-wheel drive BMW. The system has undergone several modernization, but its basis and the principle of operation remained the same.
Fundamental basis
With all innovations, the current XDRIVE retained the principal architecture of predecessors. It is more efficient to distribute the moment between the axes, the frictional coupling with an electronically controlled, which, in fact, replaced the inter-axis differential and blocking it. In addition, in the arsenal " x-Drive"There are happening from the first x5 electronic system, imitating the blocking of interstole differentials (ADB-X): She grabs brake mechanisms Stripping wheel, allowing you to realize a larger torque on the other.
The redistribution of the moment between the axes depends on the compression force of the clutch friction teams: they are compressed or diverged by the electronics team - depending on the situation. Spraying frictional controls servomotor. The tricky lever (shown in the diagram below, position 2) converts the rotational movement of the electric motor shaft into its axial movement, which presses or sprinkles the friction.
When the coupling is blocked, part of the torque is removed from the rear axle and is transmitted forward - through a handout box with a chain or gear drive. Differences in the design are due to the layout of the central tunnel. In Mésta crossovers, therefore an aggregate with a chain is used, and on cars - more compact option with gears.
BMW Lukuvit, calling XDrive transmissia by constant full-wheel drive. In conventional modes, the moment is distributed in the ratio of 40:60 in favor of the rear axle. At the same time, the coupling is almost completely clamped (with full blocking, a rigid connection is provided between the axes, the moment is divided equally). If the coupling is dissolved, then the entire moment goes to the rear axle. That is, in fact, we are constant rear drive With automatically connected front axle.
But another advertising trick. The manufacturer claims that the coupling can cross forward up to 100% traction. This will happen if with a completely blocked coupling (both axes are rigidly connected) rear wheels will hang in the air or turn out to be absolutely slipping ice, and under the front will be dry asphalt. Then on the front axle, you can really implement 100% torque, because the rear wheels do not have a clutch with an expensive, that is, the torque on them is zero. But there is no magic in this - the balls of physics rule the ball, and not a unique coupling design. This task is on the shoulder of any differential with rigid lock. In addition, the situation described under normal conditions is unreal: even if the rear wheels will be on mirror ice, clutch tires with a coated, let it be very insignificant, it will still be, and with it there will be a minor fraction of the transmitted torque. Therefore, 100% for the front axle xDrive can not be able to transfer.
And yet XDrive is really effective and at the same time constructively simple. It perfectly complements the Electronic DSC Stability System, which allows you to realize all the advantages of the full drive: it improves the dynamics and controllability, while it takes care of the safety and does not infringe on the driver's ambitions.
Planned upgrades
With the advent of the second generation of the X5 crossover in 2006, a little updated XDrive. Restricted to the revision of the control electronics, having endowed the course stability system even greater rights.
Before constructive changes, the case has come two years later. At the X6 model in the "X-Drive" scheme introduced an active rear differential with DPC electronic control (DYNAMIC PERFORMANCE CONTROL). He is able to redistribute the moment between the rear wheels - it eliminates the car from insufficient turning and allows him to pass turns with greater speed, remaining on a given trajectory driver.
DPC provides stepless blocking, up to 100%. It is constructively implemented by adding two planetary gears and a pair of multi-disc friction couplings that drive electric drives. For the first time, a similar scheme also demonstrated Mitsubishi Lancer Evolution VII. BMW is available only on h5 and x6 crossovers. For junior models, its simplified electronic analogue was added as an option - Performance Control. This feature is built into the course stability system: in turn it will slow down internal rear wheelTo add moment on the outside.
The absence of other changes in the XDRIVE transmission design indicates the reliability of the system. Representatives of BMW argue that for all the time of their existence, she did not deliver serious problems. According to statistics, not counting the glands and anthep drives, the carrier controller is most often due to the system. But it happens closer to 300,000 km of run, and so much rolls only every third, and even the fourth owner. In addition, the location of the node outside the dispensing box simplifies the replacement procedure, and the price of the motor is low.
Mountain anniversary
In BMW, decided to celebrate the 15th anniversary of their line of crossovers big mileage In winter roads Montenegro. The route did not provide for off-road, but abounded by mining serpentines. Actually, in such conditions the ability of the XDRIVE system and should be disclosed in all its glory.
Before me, the entire line of crossovers except the younger X1. Machines shoves in winter unwanted tires. The temperature difference between the flat and mountain parts of the route is from a small minus to +15 ºС.
The limiters in the speed of driving through serpents were only common sense and instinct of self-preservation. Not everywhere the width of the road allows you to freely dispense with the oncoming cars, and most turns are blind.
I will say honestly: a long time to go on the limit of coupling properties of tires was scary and physically difficult. But in these conditions, XDrive never made it take an open, and sometimes pleasantly surprised. The older brothers X5 and X6 with the active rear differential zadorly screwed into the hairpins. In sports mode, the stabilization system allowed a bit to lose weight and under the addition of gas to outlet sideways. And in rare running and open turns, the older "Xers" with an increase in speed confidently relied with external wheels, as if the turn turned into a profiled.
More reserved x3 and x4 have been less provoked to active ride. But X3 was still able to please in one potentially dangerous situation.
In front of the long-awaited open turn of the asphalt in the braking zone was covered with anter. The brake pedal is desperately vibrated, and the speed fell frighteningly slowly. But the emergency measures did not have to take: x3 with a margin fit into turn, without losing sustainability. Well, thanks xDrive!
Freedom fee
Free (open) symmetric differential has a serious disadvantage. He always divides the torque equally. When one wheel loses the clutch with the road, the other stops. For example: if we possess only one wheel on the all-wheel drive car with three free differentials in the transmission, it will rotate helplessly, and the car does not move from the place. And so that the car go, use different blocking of differentials to pass part of the moment on the wheel (or wheels) with best clutch: These are self-locking differentials, various coupling or their electronic simulators that work under the control of the system of exchange rate stability.
German concern BMW has developed its own full system permanent drive XDrive is still in the last century, but the system is constantly improving and to date is established for many models of the concern. Maximum effectively optimize the control of the car and at the same time keep all the indicators under control, it is entrusted with this system. Today, the XDRIVE XDrive system is installed on the BMW new generation SUV:
- Sports Activity Vehicle x 6.
In addition, this development system is also installed on passenger models BMW, on the 3rd, 5th and 7th series. The system has proven itself in twenty-five years of its existence and therefore the concern does not plan to abandon its use.
The main characteristics of the system
The Intelligent XDrive Drive System controls the action of all forces in the car, both external ones and its own. Traction and dynamics are distributed perfectly in new due to the action of this development. In order to be clear, some of the characteristics of the system should be given:
- It provides a variable distribution of the torque of a stepless character. Due to this, the torque is distributed evenly between the rear and front wheels, increasing their speed repeatedly;
- The system on the intellectual level recognizes the change in the situation and, if necessary, the torque is incredibly redistributed quickly;
- xDrive provides incredibly sensitive steering, so the driver does not have to take any effort when driving by car;
- The system doses very accurately and regulates braking, so that the operation of the concern car has become even more secure;
- The system includes elastic shock absorbers and elements that, due to its sensitivity, optimize and control vertical and longitudinal dynamic strengths;
- The system provides incredible stability and dynamic movement on any road surface.
From these characteristics it becomes clear that BMW did everything that the all-wheel drive car was fully safe and brought pleasure to the driver. The machine provided by the XDrive system has a huge power, but it shows incredibly intellectual obedience to control. Years of work and continuous improvement of technologies The concern achieved the fact that the car equipped with the XDrive system gained incredible variability and accuracy of the reaction to sending control. The system in any conditions converts drive forces, optimally adapting them to the situation, and effectively improves the movement dynamics.
If we talk simple wordsthen the XDRIVE system intellectually adapts all-wheel drive car Under the needs of the driver.
Four-wheel drive
Many manufacturers are equipped with a full drive, but the XDRIVE system is only at BMW. Traditionally, the four-wheel drive is directed mainly to minimize the inconvenience of the roads delivered by the coating, irregularities, soil or ice. But if efforts are distributed over the axes uneven or inefficiently, then the four-wheel drive will not bring pleasure from driving. Characteristic for such an ineffective distribution will be next shortcomings Management:
- Limited sensitivity to steering turns;
- There are insufficient challenges;
- Straight movement becomes unstable;
- Comfort is lost when maneuver.
BUT B. concern BMW. To the issue of creating a full drive of a new generation, quite differently approached. The manufacturers took the proven and well-proven rear-wheel drive of the concern car. Optimizing and improving its characteristics, they were distributed to all four wheels.
And now a quarter of a century four-wheel drive BMW shows incredible dynamics and complete safety on the roads around the world.
What is the efficiency of the system
As mentioned above, the main principle of the XDrive system is to uniform distribution of torque on both automotive axes. Such an efficient and accurate distribution becomes possible using a handouting box, it has a type of gear transmission of the front axle. The box is managed when the friction clutch is operational. If the XDRIVE system is installed on a BMW sports SUV, then in the transmission, the transmission of the toothed type is replaced with the chain.
In addition, significantly increase the efficiency of the system and additional optionswhich are introduced into the transmission along with it:
- Dynamic coursework control system;
- Electronic blocking of the differential moment;
- Control system traction;
- Help system on descent;
- System of integral control of the chassis department;
- Active steering system;
- Basic principles of system operation.
Intellectual bMW system has its own characteristic modes that determines the clutch of the friction nature:
- Smooth start from place;
- Overcoming turns with a purity of redundant type;
- Overcoming turns with insufficient type rotation;
- Movement in slippery coating;
- Optimized parking.
When the car begins in conditions of normal location and high-quality road indicators of the friction nature clutch has a closed look and torque in this case has a distribution over the axes of 40:60, this leads to the most efficient thrust during acceleration. After the car is gaining a speed of 20 km / h, the torque is redistributed depending on the coating of the canvas and the control moments.
Passage of turning points
During the implementation of maneuvers on turns with the reverse axis turning car BMW. can bring to the outer part of the turn. To avoid a frictional clutch, it takes a closure with more power, while the front axle takes on a torque. If the machine passes a very cool turn of the angle, which is not standard, then the system of dynamic control comes to the rescue and stabilizes the movement with some brazing of the wheels.
If the car passes a turn with a turning of insufficient nature, when the front axle can be adjusted to the outer part of the rotation, the clutch of the friction nature makes opening. In this situation, one hundred percent of the torque is distributed to the rear axle. If arose non-standard situationThe process of movement stabilization system is entering the process.
When the car passes a turn with a non-standard rotation, the front axle of the machine is closed to the outer part of the turn. In this case, the clutch of the friction type conducts opening and 100% torque is distributed to the rear axle. If the car is not aligned, then the system of course stability is entering.
When a car moves on a slippery road leaf, covered with water, people or snow can slip individual wheels and drive the car. That this does not happen the friction clutch is blocked and if the situation does not come to stability, then auxiliary system installation of a dynamic resistance is included in the work.
Car parking equipped with a XDrive system concept occurs with a full blurring of friction-type clutch. In this case, the car completely goes into the rear-wheel drive state and thereby effectively decreases a transmission load on the steering control. The reasonable and intellectual intervention of the auxiliary systems during the control of the car creates optimally comfortable driving conditions and improves the security of the control repeatedly.
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