DE112004002908B4 - Locking arrangement with adjustment by magnetorheological fluid - Google Patents

Abstract

The invention relates to a locking clutch for coupling a first coupling part 3 with a second coupling part 4 rotating relative thereto. The locking coupling comprises a gear arrangement 14 for transmitting torque between the first coupling part 3 and the second coupling part 4, a chamber 18 sealed to the outside, in which the toothing arrangement 14 is disposed and which is at least partially filled with a magnetorheological fluid, and a controllable magnetic coil 25 which is adjacent to the chamber 18 and can generate a magnetic flux through the chamber 18. By activating the solenoid coil 25, the viscosity of the magnetorheological fluid can be changed, so that the transmission of a torque between the first clutch part 3 and the second clutch part 4 can be controlled. The invention further relates to a locking differential 52 which is controllable by magnetizing magnetorheological fluid.

Description

The The invention relates to a barrier arrangement, in particular for use in the drive train of a motor vehicle, in the form of a lock-up clutch or a locking differential may be formed. blocking clutches usually include at least two coupling elements with each other for transmission a torque can be coupled. Locking differentials usually include an input part as well as two output parts which are together for transmission a torque are drivingly connected, wherein a balancing effect can be generated between the output parts.

In multi-axle vehicles, locking clutches are often used in the drive train to a driven only as needed drive axle in use. To operate such clutches various solutions have been proposed. An example of a lockup clutch with an electric motor driven Rampenscheibenpaar is found in the DE 38 15 225 C2 , In this case, two ramp discs are provided which have oppositely extending ball grooves with variable depth, between which balls are held. Upon rotation of one of the discs relative to the other, their axial distance from one another changed, so that the disc pack of the lock-up clutch is acted upon.

From the DE 198 47 405 C1 is a lock-up clutch with two coupling elements known which are positively coupled with each other. In this case, the first of the two coupling elements is axially supported, while the second of the coupling elements is axially displaceable for this purpose. For axially fixing the second coupling element, a cavity system is provided which is filled with a magnetorheological fluid and bounded by a displacement body connected to the second coupling element. By means of an electromagnet magnetorheological fluid can be magnetized to form solidification, so that the two coupling elements are firmly coupled together.

The DE 103 04 140 B3 shows a friction clutch with two relatively rotatable coupling elements which are rotatably coupled to each other by means of a disk set. Axially adjacent to the disk set an annular chamber is formed, which is bounded on the one hand by a piston for actuating the disk pack and on the other hand by a lid and is filled with a magnetorheological fluid. In the annular chamber, a rotor disc is arranged, which is rotatably connected to one of the coupling elements. By exciting a magnetic coil adjacent the cover, the viscosity in the magnetorheological fluid is increased so that the rotor disc in the annular chamber generates a pressure which displaces the piston against the disc pack. In this way, the two coupling elements are coupled together.

The US Pat. No. 6,585,616 B1 shows a differential gear with two adjustable multi-plate clutches. The differential gear is in the form of a bevel gear differential and includes two side-shaft gears that are driven by differential gears encircling the differential cage. To lock the balancing effect between the side shaft gears, the multi-plate clutches are provided, which are filled with magnetorheological fluid. By activating solenoids located radially outward of the multi-plate clutches, the viscosity of the magneto-rheological fluid changes, thereby achieving a locking action between the differential carrier and the side-shaft gears.

It is still out of the EP 466 863 B1 a controllable clutch for connecting a drive train in a motor vehicle with multiple drive trains known. Such arrangements serve, in a normally driven only on the axis of the first drive train vehicle with insufficient traction zuzuschalten also the axis of the second drive train.

From the JP 63025142 A a differential gear arrangement is known, wherein the gear housing is filled with an electrorheological fluid. When current is applied to the differential gear assembly, the electrorheological fluid solidifies. As a result, a relative movement of the differential wheels is prevented relative to the side gears, whereby a blocking effect is achieved.

From the US Pat. No. 6,745,879 B1 is a hydromechanical coupling with piston-cylinder unit and magnetorheological clutch actuator known. The hydromechanical coupling comprises, in addition to the magnetorheological actuator, a gerotor pump, which promotes magnetorheological fluid in a circuit at a speed difference between an input part and an output part. When a magnetic coil disposed on the circuit is actuated, the magnetorheological fluid solidifies. In this way, the pressure in a pressure chamber of the piston-cylinder unit increases, so that the piston acts on the plate pack of the clutch.

The present invention has for its object to provide a lock assembly with a simple structure, which has a high power density, good controllability and short activation times. Such a locking arrangement may be in the form of a lock-up clutch or a Sperrdifferenti be designed as.

A first solution of the problem consists in a blocking coupling for coupling a first coupling part with a second coupling part rotatable relative thereto
a gear arrangement for torque transmission between the first coupling part and the second coupling part,
a sealed to the outside chamber, in which the toothing arrangement is arranged and which is at least partially filled with a magnetorheological fluid, as well as
a controllable magnetic coil disposed adjacent to the chamber and capable of generating a magnetic flux across the chamber, the viscosity of the magnetorheological fluid being varied;
wherein the toothing arrangement is designed in the manner of a planetary gear and a non-rotatably connected to the first coupling member ring gear, rotatably connected to the second coupling member sun gear and a plurality of ring gear on the one hand and the sun gear meshing planetary gears, wherein between the ring gear and the sun gear with magnetorheological fluid filled chamber is formed. By changing the viscosity from the liquid state to the plastic state, the deformation work also changes, so that teeth of the tooth arrangement can no longer mesh freely with each other and torque is transmitted between the first and second coupling parts.

Of the Advantage of this lock-up clutch is that it is simple and has a high power density. The magnetic coil becomes electric controlled, so that the Strength the magnetic field by appropriate choice of the current or the Voltage can be set arbitrarily. This results a high coupling accuracy and short activation times, so that fast changing driving conditions can be reacted. The configuration of solenoid, chamber and gear arrangement is coordinated so that when energized the magnetic coil as uniform as possible magnetic field is generated in the region of the chamber, so that a uniform viscosity of the liquid can be adjusted. In this case, the magnetic field in particular in the field of rolling Gearing interventions of the gear arrangement generated.

at the gearing arrangement are the gaps or gearing games between the gears from the chamber. By activating the solenoid coil is a running through the chamber Magnetic field generated, so that the Viscosity of magnetorheological fluid is changed. The bigger the Strength the magnetic field is bigger viscosity the magnetorheological fluid and the greater the blocking effect of the lock-up clutch.

The Magnetic coil is arranged according to a preferred embodiment such the existence torusfömiges Magnetic field is generated by at least some of the gearing interventions the toothing arrangement runs. In this case, the magnetic coil according to a first embodiment be arranged axially adjacent to the toothing arrangement. The way formed locking clutch has a small radial size. According to an alternative embodiment, the magnetic coil also radially outside be arranged the toothing arrangement. This is especially cheap if the axial space of the lock-up clutch is limited. For training an optimal magnetic field are at least the ring gear, the planet gears and the sun wheel made of ferromagnetic material. This ensures that that the Magnetic circuit between one of the poles of the magnetic coil, over the Ring gear, the planet gears and the sun gear is closed to the second pole of the solenoid. Thus, especially in the field of gearing interventions an accurate Adjustability of the viscosity of the magnetorheological fluid.

Especially in the latter embodiment with radial magnetic coil, it is advantageous that two groups of planetary gears axially are arranged adjacent to each other. This way can be between the axially opposite poles of the magnetic coil a torusfömiges magnetic field generated passing through both groups of planetary gears. By Actuate the magnet coil becomes the viscosity of the magnetorheological liquid increased in the teeth of both groups of planet gears, so that transmit a torque can be. Preferably, axially between both groups of planetary gears Insulating of paramagnetic material provided. These ensure that the Magnetic flux circular through both Groups of planet wheels runs.

The gears between the ring gear and the planet gears and between the planet gears and the sun gear may be straight or helical gears. When using helical gears an axial force component is generated, which leads to greater friction losses. In this case, the reason caused by friction Grundsperrmoment an active locking torque is superimposed, which arises due to the work of deformation of the magnetorheological fluid. The deformation work is composed of squeezing, pumping and shearing work. According to a preferred embodiment, the teeth between the ring gear and the planetary gears are each designed axially shorter than the teeth between the planetary gears and the sun gear. In this way results a very homogeneous magnetic field. In the chamber, a chamber volume reducing filler can be provided, in which the planet gears are rotatably supported. So only a small amount of magnetorheological fluid is required.

The planetary gears are preferably in a cage rotatably held. In this case, the cage has at least one disc on, which arranged on the side facing away from the magnetic coil of the planetary gears is. Alternatively, the cage may also comprise two discs, where the planetary gears arranged axially between them and rotatably mounted on pins are. Preferably, the magnet coil is remotely located Washer made of ferromagnetic material, so that when activating the magnetic coil is attracted by this. In a preferred embodiment, the planetary gears in the cage held so that they are limitedly movable in the circumferential direction. For this purpose points the cage for example, in the circumferential direction extending slots, in which the planetary gears are attached. The cage comprises continuing axial breakthroughs, the with the gearing between the planetary gears and aligned with the ring gear or the sun gear. This way - can not activated state, d. H. switched off electromagnet - magnetorheological Fluid from the areas of the teeth interventions by the openings of the cage get into the reservoir. In activated state, d. H. when turned on Elekromagneten, due to the increased viscosity of the magnetorheological Fluid deformation work done between the gearing interventions. By the additional Shearing forces the cage twisted in the circumferential direction, so that the breakthroughs now no longer aligned with the gearing interventions. The chamber is thus encapsulated frontally, so that the deformation work additional Pumping and shearing superimposed becomes. This embodiment thus causes a better ratio between the maximum achievable torque and the drag torque in not activated state.

To A preferred development is with the first coupling part a support disk firmly connected, which limits the chamber towards the solenoid and against which the planet gears support axially can. There are sealing means between the support disk and a cylindrical portion provided the sun gear. These prevent magnetorheological fluid when rolling the gears is squeezed out of the chamber. The support disk is preferably paramagnetic, so that - viewed in longitudinal section - a circular magnetic field around the magnetic coil is generated.

The filled with magnetorheological fluid chamber is after a preferred development associated with a reservoir. this has preferably a variable one Volume, hence due to temperature changes in the magnetorheological Fluid resulting volume changes can be compensated. The reservoir is bounded by a piston, which via spring means is charged. The piston and the spring means are preferably in a tubular shape Section of the second coupling part arranged and against a Cover axially supported. Likewise, the reservoir can also be arranged in the first coupling part be. According to an alternative approach, the chamber except the magnetorheological fluid contain a small proportion of a gas volume, the compressibility of the volume compensation manufactures.

To a preferred embodiment, a housing is provided, in which the Gear arrangement and the magnetic coil are arranged. The case is preferably cup-shaped designed and has an outer wall portion and a coaxial inner wall section on. It can the first coupling part rotatably in the outer wall portion and the second coupling part rotatably on the inner wall portion be stored. It is further contemplated that the first coupling part connecting means for non-rotatable connection to a longitudinal drive shaft of a motor vehicle, and the second coupling part connecting means for non-rotatable connection having an axle differential. The second connection means are preferably designed in the form of a longitudinal toothing, in which can engage a journal for torque transmission.

The Locking clutch according to the invention is versatile. After a first use is the Locking clutch arranged in the drive train of a motor vehicle, that is a permanently driven first axle and if necessary switchable second axis, wherein the lock-up clutch for Connecting or disconnecting the second axis is used. Depending on the driving condition of the motor vehicle, the lock-up clutch via a vehicle dynamics controller controlled as needed. In this case, the torque to be transmitted by the appropriate strength of the magnetic field, d. H. by appropriate choice of the current or the voltage can be set arbitrarily. This results a high coupling accuracy and short activation times, so that fast changing driving conditions can be reacted.

After a second use, the lock-up clutch is arranged in the drive train of a motor vehicle with a permanently driven first axle and a second axle which can be engaged as required, wherein the lock-up clutch precedes a speed-sensing further clutch is and used to turn on or off this speed-sensing further coupling. When switched on, the switchable second axle is coupled, wherein a maximum torque capacity is available, while the second axle is decoupled from the drive train in the off state. This application has the advantage that can be dispensed with a complex control of the additional clutch and that the decoupling of the speed-sensing further clutch the powertrain ESP compatible. ESP-compatible in this context means that interventions in the driving dynamics of the motor vehicle can be done easily by means of a driving dynamics controller. The speed-sensing further clutch is usually designed in the form of a viscous coupling.

A second solution The above object is in a limited slip differential used in the drive train of a motor vehicle, comprising an input part, which is rotationally driven; a first output part and a second one Output part, each over differential gears are drivingly connected to the input part; an externally sealed chamber, in the differential gears are arranged and at least partially with a magnetorheological Fluid filled is; and a controllable magnetic coil adjacent to the chamber is arranged and can generate a magnetic flux across the chamber, where the viscosity the magnetorheological fluid is changed; where the locking differential is designed in the form of a planetary differential and a ring gear, a sun gear, several differential wheels, with the ring gear on the one hand and the sun gear on the other hand are in meshing engagement, as well a web assembly for supporting the differential gears, wherein between the ring gear and the sun gear filled with magnetorheological fluid te chamber is formed. By change the viscosity from the liquid changed to the plastic state the strain work, So that the differential gears no longer combing freely can and transmit torque between the first and second coupling parts becomes.

Of the Advantage of this locking differential is the simple structure and in a high power density. The magnetic coil becomes electric controlled, so that the Strength of the magnetic field by appropriate choice of the current or the voltage can be set arbitrarily. This results a high switching accuracy and short activation times, so that fast changing driving conditions can be reacted. The configuration of solenoid, chamber and differential wheels is coordinated so that when energized the solenoid one possible uniform Magnetic field is generated in the region of the chamber, so that a uniform viscosity of the liquid can be adjusted. In this case, the magnetic field in particular in the field of rolling Gearing interventions of the differential wheels generated.

The Gaps or gearing between the differential gears and the gears are thus in meshing engagement from the chamber. The limited slip differential can be arbitrary in the drive train of a motor vehicle be connected. For example, the ring gear as a torque input serve, so that the Sun gear and the bridge arrangement serve as torque outputs. In this embodiment the limited slip differential works as a center differential with a fixed one basic translation between two driven axles. By activating the magnetic coil the differential is locked, so that a torque compensation between the exits is prevented.

The Magnetic coil is arranged according to a preferred embodiment such the existence torusfömiges Magnetic field is generated by at least some of the gearing interventions the planetary differential runs. The magnet coil is preferably axially adjacent to the toothing arrangement arranged. To form an optimal magnetic field are at least the ring gear, the differential wheels and the sun wheel made of ferromagnetic material. This ensures that that the Magnetic circle between one of the poles of the magnetic coil, over the Ring gear, the planet gears and the sun gear is closed to the second pole of the solenoid. Thus, in particular in the field of gearing interventions an accurate adjustability the viscosity of the magnetorheological fluid. The locking differential according to the invention but can also be designed in the form of an axle differential.

The Gears between the ring gear and the planet gears as well between the planet wheels and the sun wheel Straight or helical gears be. When using helical teeth wheels an axial force component is generated which leads to greater friction losses. To a preferred development, the teeth between the Ring gear and the planet wheels each axially shorter designed as the teeth between the planetary gears and the sun gear. This creates a particularly homogeneous magnetic field. In the chamber can a filling volume reducing the chamber volume can be provided, in which the differential wheels are held rotatably. So only a small amount of the magnetorheological Fluids required.

Preferably, the web arrangement comprises at least one flange which is arranged on the side facing away from the magnetic coil of the differential wheels. According to a preferred embodiment, a support disk is fixedly connected to the ring gear, which limits the chamber in the direction of the magnetic coil. There are Sealant provided between the support disk and a cylindrical portion of the sun gear. These prevent magnetorheological fluid from being squeezed out of the chamber as the gears roll. The support disk and / or the web arrangement are preferably paramagnetic, so that - viewed in longitudinal section - a circular magnetic field is generated around the magnetic coil.

The filled with magnetorheological fluid chamber is after a preferred development associated with a reservoir. this has preferably a variable one Volume, hence due to temperature changes in the magnetorheological Fluid resulting volume changes can be compensated. The reservoir is bounded by a piston, which via spring means is charged. The piston and the spring means are preferably in a tubular shape Section of the second output part arranged and against a lid axially supported. According to an alternative approach, the chamber except the magnetorheological fluid contain a small proportion of a gas volume whose compressibility makes the volume compensation.

To In a preferred embodiment, the locking differential is in one casing rotatably mounted. The housing is preferably pot-shaped designed and has an annular space for receiving the solenoid on. In this case, the first output part is rotatable in a cylindrical Bearing section stored while the second output part radially in the first output part coaxial with Is mounted axis of rotation.

preferred embodiments will be explained below with reference to the drawing. Hereby shows:

• a) im Längsschnitt;
• b) im Querschnitt gemäß Schnittlinie I-I aus 1a);

1 a first embodiment of a lock clutch according to the invention

• a) in longitudinal section;
• b) in cross section according to section line II 1a );

2 a second embodiment of a locking coupling according to the invention with connecting flange;

3 A third embodiment of a lock clutch according to the invention with a shortened toothing;

4 A fourth embodiment of a lock clutch according to the invention with optimized seal;

• a) mit einfachen Käfig für die Planetenräder im Längsschnitt;
• b) einen Querschnitt durch die Käfigebene gemäß 5a);

5 A fifth embodiment of a lock clutch according to the invention

• a) with simple cage for the planet gears in longitudinal section;
• b) a cross section through the cage plane according to 5a );

6 A sixth embodiment of a locking clutch according to the invention with double cage for the planetary gears;

• a) im Längsschnitt;
• b) im Querschnitt gemäß Schnittlinie VII-VII aus 7a);
• c) im Längsschnitt mit Darstellung der Magnetfeldlinien

7 a seventh embodiment of a locking clutch according to the invention with a compact hub

• a) in longitudinal section;
• b) in cross-section according to section line VII-VII 7a );
• c) in longitudinal section showing the magnetic field lines

8th a seventh embodiment of a locking clutch according to the invention with a compact hub;

• a) im Längsschnitt;
• b) das Prinzip der Planetenanordnung im Querschnitt;
• c) im Längsschnitt mit Darstellung der Magnetfeldlinien;

9 an eighth embodiment of a lock clutch according to the invention with two groups of planetary gears

• a) in longitudinal section;
• b) the principle of the planetary arrangement in cross section;
• c) in longitudinal section showing the magnetic field lines;

10 a motor vehicle with inventive locking clutch in the longitudinal drive train;

11 a motor vehicle with inventive locking clutch and downstream Viscocoupplung in the drive train;

• a) im Längsschnitt;
• b) im Querschnitt.

12 an inventive locking differential

• a) in longitudinal section;
• b) in cross-section.

1 shows a lock-up clutch with a housing 2 and a rotatably arranged for this first coupling part 3 and a second coupling part which can be coupled therewith in a rotationally fixed manner 4 , The first coupling part 3 has first connection means 5 , which serve to introduce a torque, for example from a longitudinal drive shaft of a motor vehicle, in the lock-up clutch. The second coupling part 4 has second connection means 6 , which are designed in the form of a longitudinal toothing and for non-rotatable insertion of a connecting shaft, not shown here, for example, for driving an axle differential serve. The first coupling part 3 and the second coupling part 4 are each rotatable in the housing on a common axis of rotation 2 stored. This is between the first coupling part 3 and the housing 2 a rolling bearing 7 intended. The second coupling part 4 can if necessary opposite to the housing 2 be stored sliding.

The housing 2 is designed substantially pot-shaped and has a cylindrical outer wall portion 9 and a coaxial thereto arranged cylindrical inner wall portion 10 as well as one of these two connecting ground 12 , Between the outer wall section 9 , the inner wall section 10 and the floor 12 is an annulus 13 formed in which a gearing arrangement 14 and a magnetic coil 25 is arranged. The gear arrangement 14 is designed in the form of a planetary gear and includes a rotationally fixed to the first coupling part 3 connected ring gear 15 , one with the second hitch be part 4 rotatably connected sun gear 16 and a plurality of planetary gears 17 , which in each case with the ring gear 15 and the sun wheel 16 comb. In this case, the number of planet gears 17 be chosen arbitrarily, the minimum number is three. The planet wheels 17 be in the embodiments according to the 1 to 4 such as 7 and 8th floating between the ring gear 15 and the sun wheel 16 held. It is between the ring gear 15 and the sun wheel 16 a sealed chamber 18 formed in the axial direction on the one hand by a flange 19 and on the other hand by a support disk 20 of the first coupling part 3 is limited. The support disk 20 wears a sealing ring 22 which seals the chamber to the outside. The chamber 18 is at least largely filled with a magnetorheological fluid from one in the housing 2 arranged magnetic coil 25 can be magnetized.

The operation of the lock-up clutch is as follows. In the non-activated state rotate the first coupling part 3 , the planetary gear 14 and the second coupling part 4 together with the same speed about the axis of rotation A. occur different speeds between the first coupling part 3 and the second coupling part 4 , For example, due to changing driving conditions between the front and the rear axle of the motor vehicle, there is a difference in rotational speed between the ring gear 15 and the sun wheel 16 , The planet wheels 17 roll against the ring gear 15 and the sun wheel 16 off, taking in the chamber 18 located magnetorheological fluid is displaced by each successive rolling tooth flanks. By this pumping action, the magnetorheological fluid becomes the speed difference between the ring gear 15 and sun gear 16 in the chamber 18 promoted in a circle. This results in a low drag torque, which leads to a certain heat loss. To compensate for the resulting increase in volume of the magnetorheological fluid is a reservoir 24 intended. This is located in a tubular portion of the second coupling part 4 in which a piston 26 axially slidably seated. Here is the piston 26 by spring means 27 acted upon axially, in turn, with respect to a tight-fitting in the pipe section lid 29 are axially supported.

To close the lockup clutch is the solenoid 25 turned on, so that the resulting magnetic field, the magnetorheological fluid in a highly viscous or a plastic state. In this way, the planetary gears 17 prevented from the ring gear 15 or the sun gear 16 free to roll, so that a torque from the ring gear 15 on the sun wheel 16 is transmitted. By magnetizing the magnetorheological fluid increases its viscosity, so that a rolling movement between the planetary gears 17 and the ring gear 15 or the sun gear 16 is slowed down. By choosing the teeth between the planetary gears 17 and the ring gear 15 or the sun gear 16 the drag torque can be varied. This arises - even with deactivated magnetic coil - by the displacement of the magnetorheological fluid While the drag torque is relatively small in the case of spur gears, helical gears cause an axial force component, resulting in greater frictional forces.

For a particularly favorable magnetic flux are the housing 2 , the ring gear 15 , the sun wheel 16 and the planet wheels 17 made of ferromagnetic material. For this example, non-austenitic steels come into question. The between the planetary gears 17 and the magnetic coil 25 arranged support disk 20 is preferably made of a non-magnetic material, for which austenitic steels or aluminum are preferably suitable. The configuration of magnetic coils, chamber and planetary gear is coordinated so that upon excitation of the magnetic coil as uniform a magnetic field is generated in the chamber, so that a uniform viscosity of the liquid can be adjusted.

1b shows a cross section through the lock-up clutch. It is the ring gear 15 , the sun wheel 16 as well as meshing with both wheels planetary gears 17 seen. In this embodiment, eight circumferentially regularly distributed planet gears are provided, the number of which can be varied depending on the torque to be transmitted.

2 shows a second embodiment of the lock-up clutch, which in terms of their construction substantially from that 1 equivalent. On the description too 1 In this respect, reference is made to the same components with the same Bezugszei Chen and different components are provided with subscripted by the number 2 reference numerals. Unlike the lockup clutch after 1 has the first coupling part 3 ₂ a pin 30 with a spline 32 for introducing a torque. For this purpose, a connection flange 33 with a corresponding counter-toothing on the pin 30 attached and axially by means of a locking ring 34 secured. For storage of the assembly consisting of connection flange 33 and first coupling part 3 ₂ in the case 2 is a rolling bearing 7 ₂ provided, which with a bearing outer ring in a cover part 35 and with a bearing inner ring on a bearing section 36 of the connecting flange 33 is arranged. The advantage of this embodiment is that the rolling bearing 7 ₂ has a small diameter and thus is inexpensive to produce. In addition, generates the smaller bearings 7 ₂ only small drag moments.

3 shows a third embodiment of the lock-up clutch, which in terms of their construction substantially from that 1 equivalent. On the description too 1 In this respect, reference is made, wherein the same components with the same reference numerals and different components are provided with subscripted by the numeral 3 reference numerals. The present embodiment is different from that 1 in that the toothing of the ring gear 15 ₃ axially shorter than the teeth of the planetary gears 17 , In this way, can be activated upon activation of the solenoid 25 achieve a particularly strong magnetic field, because the density of the magnetic flux is greater. This creates between the sun gear 16 and the ring gear 15 ₃ a particularly homogeneous magnetic field in the magnetorheological fluid, so that the viscosity over the radial extent is constant. The housing 2 and the second coupling part 4 with integral sun gear 16 , the planetary gears 17 and the ring gear 15 ₃ are made of magnetic material, while the flange 19 and the support disk 20 of the first coupling part 3 are non-magnetic. In this way, a good magnetic flux through the filled with magnetorheological fluid chamber 18 guaranteed.

4 shows a fourth embodiment of the lock-up clutch, which in terms of their construction substantially from that 1 equivalent. On the description too 1 In this respect reference is made, wherein the same components with the same reference numerals and different components are provided with subscripted by the numeral 4 reference numerals. The embodiment according to 4 is characterized in that the support disk 20 ₄ that with the first coupling part 3 ₄ firmly connected and the chamber 18 towards the magnetic coil 25 ₄ axially limited, radially inward to an outer cylindrical portion of the sun gear 16 zoom ranges. In this way, the pump pressure of the magnetorheological fluid generated by the rolling movement of the gears does not act directly on the sealing ring 22 but presses against the support disk 20 ₄ , It is particularly favorable when the annular gap between the cylindrical portion of the sun gear 16 and the support disk 20 ₄ is displaced radially outward, that the sealing surface outside the alignment of the toothing between the sun gear 16 and the planet wheels 17 lies. Thus, it would also be ensured that the pressure generated by the magnetorheological fluid in the toothing region is not directly on the sealing ring 22 acts.

5 shows a fifth embodiment of the lock-up clutch, which in terms of their construction substantially from that 1 equivalent. On the description too 1 In this respect, reference is made, wherein the same components with the same reference numerals and different components are provided with subscripted by the numeral 5 reference numerals. The special feature of this embodiment is that the planet gears 17 ₅ from a disc-shaped cage 37 are held in the circumferential direction to each other. This will be the planetary gears 17 each with the cage 37 fastened bolts 38 rotatably held. The cage 37 has in the range between two planet wheels 17 Circumferentially distributed openings for the passage of the magnetorheological fluid into the reservoir 24 , The advantage of this embodiment is that the tolerances between the ring gear 15 , the planet wheels 17 and the sun wheel 16 can be kept rough, which has a positive effect on the manufacturing cost. In addition, the coarse tolerances reduce the drag torque in the non-activated state of the solenoid coil 25 so that the friction losses are minimized. The disk-shaped cage 37 consists of ferromagnetic material and is located on the magnetic coil 25 opposite side of the planet gears 17 , This is how the cage works 37 as an armature disc and is activated by the magnetic field together with the planetary gears 17 in the direction of the magnetic coil 25 dressed. This leads to additional friction and to reduce the axial gap dimensions of the planetary gear set in the chamber 18 so as to increase the barrier effect produced by the plasticization of the magnetorheological fluid. By this measure, the power density of the lock-up clutch is particularly large.

In 5b ) is the particular of the cage 5a ), to the description of which reference is made. It can be seen that the planet gears 17 in the cage 37 ₅ held so that they are limited in the circumferential direction movable. For this purpose, the cage 37 ₅ in the circumferential direction extending slots 28 on where the planetary gears 17 are attached. For fastening the bolts 38 in the oblong holes 28 one, being between the bolts 28 and the elongated holes in the circumferential direction bounding wall spring elements 50 are provided. These allow a limited relative rotation of the cage 37 ₅ to the planet wheels 17 , The bolts wander 38 on which the planetary gears 17 are rotatably supported in the circumferential direction in the slots 28 , The cage 37 ₅ further comprises axial openings 31 . 31 ' that with the gearing between the planetary gears 17 and the ring gear 15 or the sun gear 16 aligned. In this way - in the non-activated state, ie when the electromagnet is switched off - magnetorheological fluid from the areas of the teeth interventions by the openings 31 . 31 ' of the cage into the reservoir. In the activated state, ie when the electromagnet is switched on, deformation work is performed between the gear meshes due to the increased viscosity of the magnetorheological fluid. The additional shear forces the cage 37 ₅ twisted in the circumferential direction, so that the openings 31 . 31 ' now no longer aligned with the gearing interventions. The chamber 18 is thus encapsulated on the front side, so that the deformation work additional pumping and shearing work is superimposed. This embodiment thus causes a more favorable ratio between the maximum achievable torque and the drag torque in the non-activated state.

Another embodiment shows 6 which are essentially those of 5 corresponds to whose description in this respect reference is made. In contrast to different from the lock-up clutch 5 is a cage in the present lock-up clutch 37 ₆ provided, the two coupled discs 39 . 40 between which are the planet gears 17 are held rotatably. In the left pane 40 are in the circumferential direction between the planetary gears 17 Breakthroughs provided for the passage of electromagnetic fluid into the reservoir 24 serve. It is envisaged that the magnetic coil 25 removed disc 40 made of magnetic material, while the magnetic coil 25 adjacent disc 39 is non-magnetic. That way, the disc can 40 act as an anchor disc, so that the planetary gears 17 when generating a magnetic field in the direction of the magnetic coil 25 be drawn what the in the description too 5 has described benefits.

7 shows a seventh embodiment of the lock-up clutch, which in terms of their construction substantially from that 1 equivalent. In this respect, reference is made to the corresponding description, wherein the same components with the same reference numerals and different components are provided with subscripted by the numeral 7 reference numerals. The second coupling part 4 ₇ is integral with the sun gear in the present embodiment 16 ₇ designed and constructed substantially tubular. An inner paragraph 41 serves as a contact surface for the lid 29 , The present embodiment has the advantage that the second coupling part 4 ₇ can be made easier, so that manufacturing costs are saved. For a good magnetic flux is provided that the second coupling part 4 ₇ , the planetary gears 17 , the ring gear 15 ₇ as well as the ground 12 of the housing 2 made of ferromagnetic material. In contrast, the flange portion 19 ₇ of the first coupling part 3 ₇ and the outer wall portion 9 ₇ of the housing 2 not magnetic. The flange section 19 ₇ is with the ring gear 15 ₇ firmly connected, for which any connection means, such as welding, a screw or a spline with axial securing means come into question. The ring gear 15 ₇ has a cylindrical section 42 that's up to the ground 12 of the housing 2 reaches to close the magnetic circuit. The floor 12 can with the outer wall section 9 ₇ of the housing 2 be firmly connected in any way. For this purpose, for example, a screw or a welded connection in question. In 7c ) is the magnetic flux through a similar lock-up clutch, as in 7a ) is shown. On the description of the lock clutch after 7a ) is referred to insofar. The only difference is that in the present embodiment, the magnetic field through the outer wall portion 9 ₇ of the housing 2 which is ferromagnetic in the present case. This embodiment has the advantage that a larger radial annular space for the solenoid coil 25 is available, which can thus also be larger.

8th shows a further alternative embodiment, wherein the second coupling part 4 ₈ according to the embodiment according to 7 is constructed. Reference is made to the description thereof, wherein the same components are provided with the same and different components with subscripted by the number 8 reference numerals. The lockup clutch according to 8th has different from those of 7 a ferromagnetic housing 2 ₈ , The circular magnetic flux is thereby over the ground 12 axially, one axially to the ground 12 approaching cylindrical section of the sun gear 16 ₈ , the planetary gears 17 , the ring gear 15 ₈ and the cylindrical wall section 9 ₈ of the housing 2 produced. The first coupling part 3 ₈ including flange 19 ₈ and the support disk 20 ₈ are made of non-magnetic material.

9 shows a further embodiment of the lock-up clutch, which corresponds in terms of their operation to the preceding lock-up clutches. In this respect, reference is made to the corresponding description, wherein the same components with the same reference numerals and different Components are provided with subscripted by the numeral 9 reference numerals. In the present embodiment, the solenoid is 25 ₉ radially outside the gear arrangement 14 ₉ arranged and in a carrier element 43 held. In this case, the carrier element is in an annular space 13 ₉ between the case 2 and the ring gear 15 ₉ on the inside of the case 2 appropriate. The gear arrangement is like a planetary gear 14 designed and includes a ring gear 15 ₉ , a sun wheel 16 ₉ and two groups of axially adjacent planetary gears 17 ₉ 17 ₉ ' that with the ring gear 15 ₉ on the one hand and with the sun wheel 16 ₉ on the other hand comb. Here are the planet gears - as in particular 9b ) - loose, that is without a carrier, between the ring gear 15 ₉ and the sun wheel 16 ₉ kept combing. The number of planet gears 17 ₉ . 17 ₉ ' is arbitrary and depends on the height of the torque to be transmitted. The ring gear 15 ₉ is with the first coupling part 3 ₉ firmly connected and in the housing 2 on the one hand and on the output shaft 44 on the other hand by means of rolling bearings 7 . 45 rotatably mounted. The ring gear 15 ₉ is designed such that a closed chamber 18 ₉ is formed, in which the sun wheel 16 ₉ is rotatably arranged. The chamber 18 ₉ is partially filled with magnetorheological fluid, between a cranked shoulder of the ring gear 15 ₉ and a hub 46 of the second coupling part 4 ₉ a sealing ring 22 is provided, the leakage of the magnetorheological fluid from the chamber 18 ₉ prevented. Except the magnetorheological fluid is in the chamber 18 ₉ contain a gas volume whose compressibility makes the volume compensation. The two groups of planet wheels 17 ₉ . 17 ₉ ' are arranged axially spaced from each other, wherein in each case between two lying in a sectional plane planet gears insulating 47 are provided. The insulating agent 47 hold the planet wheels 17 ₉ . 17 ₉ ' in their position and cause a - viewed in cross section - circular magnetic flux around the magnetic coil 25 ₉ around, which of the support element 43 via a first ferromagnetic section 48 of the ring gear 15 ₉ , the first group of planet wheels 17 ₉ , the sun wheel 16 ₉ , the second group of planet wheels 17 ₉ ' , a second ferromagnetic section 48 ' of the ring gear 15 ₉ back to the carrier element 43 runs. The magnetic flux is through the annular lines in 9c ). To ensure a good magnetic flux, the planetary gears 17 ₉ . 17 ₉ ' , the sections 48 . 48 ' of the ring gear 15 ₉ and the sun wheel 16 ₉ made of ferromagnetic material, while in particular the middle section 49 of the ring gear 15 ₉ and the insulating agent 47 paramagnetic.

10 shows a four-wheel drive motor vehicle 80 whose engine 81 via a manual transmission 82 and a transfer case (angle drive) with front axle differential 83 and front drive shafts 84 with the driven front wheels 85 connected is. In addition, it has a longitudinal shaft 86 the drive to the rear axle of the transfer case (angle drive) with front axle differential 83 diverted. In the longitudinal shaft 86 is a lockup clutch according to the invention 1 interposed, the torque across the rear differential 88 and the drive shafts 89 on the rear wheels 90 can transfer. The lockup clutch serves to connect or disconnect the rear axle driven by the differential gear. Depending on the driving condition of the motor vehicle, the lockup clutch 1 controlled as required via a vehicle dynamics controller. In this case, the torque to be transmitted by the corresponding strength of the magnetic field, that can be set arbitrarily by appropriate choice of the current or the voltage.

11 shows a similar motor vehicle 80 as in 10 , to the description of which reference is made. The same components are provided with the same reference numbers. In contrast to the above embodiment, the lock-up clutch according to the invention 1 in this case, a viscous coupling 87 for example, as in the DE 198 10 940 A1 is shown, downstream. The viscous coupling serves as needed for driving the rear wheels 90 over the the rear differential gear 88 and the drive shafts 89 , When a difference in rotational speed occurs between the front and rear axles, the viscous coupling automatically transitions to a state in which the torque is transmitted between the axles. In normal operation is the lock-up clutch 1 closed, so that a torque is transmitted to the rear axle. In order to avoid that a braking torque is transmitted to the rear axle when decelerating the motor vehicle via the viscous coupling, which would lead to increased slip on the rear axle and reduced lateral stability of the motor vehicle, the viscous coupling 87 if necessary by means of the lock-up clutch 1 decoupled from the drive train. In this way, the lock-up clutch acts 1 as a disconnect clutch when engaging in the driving dynamics of the motor vehicle, for example when engaging an anti-lock braking system or an electronic stability program.

12 shows an inventive locking differential with a housing 52 and an input part rotatably arranged therefor 53 and a drive-connected first output part 54 and a second output part 61 , where the two output parts 54 . 61 have a balancing effect among each other. The locking differential is designed in the form of a planetary differential and includes a with the input part 53 rotatably connected ring gear 65 , one with the first output part 54 firmly connected sun gear 66 as well as several with the ring gear 65 on the one hand and with the sun wheel 66 on the other hand meshing planet gears 67 , The planetary gears 67 are on a jetty arrangement 58 rotatably held, fixed to the second output part 61 connected is.

The entrance part 53 has first connection means 55 for introducing a torque into the limited slip differential, for example from an output shaft of a transmission. The first output part 54 has second connection means 56 , which are designed in the form of a longitudinal toothing and for non-rotatable insertion of a connecting shaft, not shown here, for example, for driving a first axis, are used. The second output part 61 also has a longitudinal toothing for connecting a connecting shaft, not shown here, which drives, for example, a second axis. The entrance part 53 and the two starting parts 54 . 61 are each rotatable in the housing on a common axis of rotation 52 stored. For this is between the entrance part 53 and the housing 52 a rolling bearing 57 intended. The first output part 54 is opposite the case 52 slidably mounted. The second output part 61 is coaxial within the first output part 54 by means of a needle bearing 60 rotatably mounted.

The housing 52 is designed substantially pot-shaped and has a cylindrical cylindrical wall portion 59 and a flange-shaped bottom 62 , Between the wall section 59 and a cranked approach on the ground 62 is an annulus 63 formed in which a magnetic coil 75 is arranged. Axially adjacent to the solenoid 75 is the planetary differential 64 arranged between the ring gear 65 and sun gear 76 or web arrangement 58 a sealed chamber 68 educated. This is in the axial direction on the one hand by the input part 53 and on the other hand by one in the ring gear 65 captive support disk 70 limited. The support disk 70 wears a sealing ring 72 that turns the annular gap to the sun gear 66 seals. Radial between the sun gear 66 and the bridge arrangement 58 is another sealing ring 71 provided the chamber 68 seals to the outside. The chamber 68 is at least largely filled with a magnetorheological fluid that of the housing 52 arranged magnetic coil 75 can be magnetized.

The operation of the locking differential corresponds to that of a conventional differential gear. In normal driving turn the input part 53 as well as the two starting parts 54 . 61 together with the same speed about the axis of rotation A. If different speeds occur between the first output part 54 and the second output part 61 on, for example, due to changing driving conditions between the front and the rear axle of the motor vehicle, so there is a difference in rotational speed between the sun gear 66 and the bridge arrangement 58 , The planet wheels 67 roll against the ring gear 65 and the sun wheel 66 off, taking in the chamber 68 located magnetorheological fluid is displaced by each successive rolling tooth flanks. By this work of deformation, the magnetorheological fluid becomes the speed difference in the chamber 68 promoted in a circle. This results in a low drag torque, which leads to a certain heat loss. To compensate for the resulting increase in volume of the magnetorheological fluid is a reservoir 74 intended. This is located in a tubular portion of the second output part 61 in which a piston 76 axially slidably seated. The piston 76 is by spring means 77 acted upon axially, in turn, with respect to a tight-fitting in the pipe section lid 79 are axially supported.

To close the locking differential is the solenoid 75 turned on, so that the resulting magnetic field, the magnetorheological fluid in a highly viscous or a plastic state. In this way, the planetary gears 67 prevented from being free from the ring gear 65 or the sun gear 66 roll off, so that a torque from the ring gear 65 on the sun wheel 66 and the bridge arrangement 58 is transmitted. By varying the current strength of the strength of the magnetic field generated and thus the viscosity of the magnetorheological fluid can be accurately adjusted, so that it is possible to meter precisely the blocking effect of the locking differential. For a particularly favorable magnetic flux are the ring gear 65 , the sun wheel 66 and the planet wheels 67 as well as the ground 62 of the housing 52 made of ferromagnetic material. For this example, non-austenitic steels come into question. The between the bridge arrangement 58 and the magnetic coil 75 arranged support disk 70 is preferably made of a non-magnetic material, for which preferably austenitic steels or Alumini come into question. The configuration of magnetic coils, chamber and planetary gear is coordinated so that upon excitation of the magnetic coil as uniform a magnetic field is generated in the chamber, so that a uniform viscosity of the liquid can be adjusted.

12b shows a cross section through the locking differential. It is the ring gear 65 , the sun wheel 66 that meshes with both wheels planet wheels 67 as well as the web arrangement 58 integral with the second output part 61 is connected, can be seen. In this embodiment, eight circumferentially regularly distributed planet gears are provided, the number of which can be varied depending on the torque to be transmitted.

1

lock-up clutch

2

casing

3

first coupling part

4

second coupling part

5

first connection means

6

second connection means

7

roller bearing

9

outer wall section

10

internal wall section

12

ground

13

annulus

14

Serration / planetary gear

15

ring gear

16

sun

17

Planetary gear / differential gear

18

chamber

19

flange

20

support disc

22

seal

23

radial gap

24

reservoir

25

solenoid

26

piston

27

spring means

29

cover

30

spigot

32

spline

33

flange

34

circlip

35

cover section

36

bearing section

37

Cage

38

bolt

39

disc

40

disc

41

paragraph

42

cylindrical section

43

support element

44

output shaft

45

roller bearing

46

hub

47

insulation

48

section

49

section

51

limited slip differential

52

casing

53

introductory

54

first output portion

55

first connection means

56

second connection means

57

roller bearing

58

web arrangement

59

wall section

60

needle roller bearings

61

second output portion

62

ground

63

annulus

64

planetary differential

65

ring gear

66

sun

67

Differential gear / planet

68

chamber

70

support disc

71

sealing ring

72

sealing ring

73

radial gap

74

reservoir

75

solenoid

76

piston

77

spring means

79

cover

80

motor vehicle

81

engine

82

manual transmission

83

Transfer Case with differential

84

drive shaft

85

front wheels

86

Propeller shaft

87

Viscokupplung

88

differential gear

89

drive shaft

90

rear wheels

A

axis of rotation

Claims (31)

Locking coupling for coupling a first coupling part ( 3 ) with a relatively rotatable second coupling part ( 4 ) comprising a gearing arrangement ( 14 ) for torque transmission between the first coupling part ( 3 ) and the second coupling part ( 4 ); an externally sealed chamber ( 18 ), in which the toothing arrangement ( 14 ) and at least partially filled with a magnetorheological fluid; and a controllable magnetic coil ( 25 ) adjacent to the chamber ( 18 ) and can generate a magnetic flux across the chamber, wherein the viscosity of the magnetorheological fluid is changed; the toothing arrangement ( 14 ) is designed in the manner of a planetary gear and one with the first coupling part ( 3 ) rotatably connected ring gear ( 15 ), one with the second coupling part ( 4 rotatably connected sun gear ( 16 ) as well as several planet gears ( 17 ) which are in meshing engagement with the ring gear on the one hand and the sun gear on the other hand, wherein between the ring gear ( 15 ) and the sun wheel ( 16 ) the chamber filled with magnetorheological fluid ( 18 ) is formed. Locking coupling according to claim 1, characterized in that the magnetic coil ( 25 ) is arranged such that a toroidal magnetic field is generated, which by at least some of the meshing interventions of the tooth arrangement ( 14 ) runs. Locking coupling according to claim 2, characterized in that the magnetic coil ( 25 ) axially adjacent to or radially outside the gear arrangement ( 14 ) is arranged. Locking coupling according to one of claims 1 to 3, characterized in that two groups of planet gears ( 17 . 17 ' ) are arranged axially adjacent to each other, wherein the magnetic coil ( 25 ) radially outside the planet gears ( 14 ) is arranged. Locking coupling according to claim 4, characterized in that between the two groups of planetary gears ( 17 . 17 ' ) Insulating agent ( 47 ) are provided from paramagnetic material. Locking coupling according to one of claims 1 to 5, characterized in that at least the ring gear ( 15 ), the planet gears ( 17 ) and the sun wheel ( 16 ) are made of ferromagnetic material. Locking coupling according to one of claims 1 to 6, characterized in that the toothings between the ring gear ( 15 ) and the planetary gears ( 17 ) are each axially shorter than the teeth between the planetary gears ( 17 ) and the sun wheel ( 16 ). Locking coupling according to one of claims 1 to 7, characterized in that in the chamber ( 18 ) a chamber volume reducing filler body is seated, in which the planet gears ( 17 ) are rotatably held. Locking coupling according to one of claims 1 to 8, characterized in that the planet gears ( 17 ) in a cage ( 37 ) are rotatably held. Locking coupling according to claim 9, characterized in that the cage ( 37 ) at least one disc ( 39 . 40 ), which on the magnetic coil ( 25 ) facing away from the planetary gears ( 17 ) is arranged. Locking coupling according to claim 10, characterized in that the planet gears ( 17 ) in the cage ( 37 ) are held in such a way that they are in the circumferential direction relative to the cage ( 37 ) are limited in mobility. Locking coupling according to claim 10 or 11, characterized in that the magnetic coil ( 25 ) remotely located disc ( 37 . 40 ) is ferromagnetic. Locking coupling according to one of claims 1 to 12, characterized in that a support disk ( 20 ) with the first coupling part ( 3 ), which is the chamber ( 18 ) in the direction of the magnetic coil ( 25 ) and against which the planet gears ( 17 ) can support axially. Locking coupling according to claim 13, characterized in that sealing means ( 22 ) between the support disk ( 20 ) and the sun wheel ( 16 ) are provided. Locking coupling according to claim 13 or 14, characterized in that the support disk ( 20 ) is paramagnetic. Locking coupling according to one of claims 1 to 15, characterized in that the chamber ( 18 ) with a variable volume reservoir ( 24 ) is connected to receive magnetorheological fluid. Locking coupling according to claim 16, characterized in that the reservoir ( 24 ) by a piston ( 26 ) is limited by spring means ( 27 ) is acted upon. Locking coupling according to claim 17, characterized in that the piston ( 26 ) and the spring means ( 27 ) in a tubular portion of the second coupling part ( 4 ) and against a lid ( 29 ) are axially supported. Locking clutch according to one of claims 1 to 18, characterized in that this is arranged in the drive train of a motor vehicle, the one permanently driven first axle and a switchable as needed Having the second axis, wherein the lock-up clutch for coupling or uncoupling the switchable second axis is used. Locking clutch according to one of claims 1 to 19, characterized in that is arranged in the drive train of a motor vehicle, the one permanently driven first axle and a switchable as needed second axis, wherein the lock-up clutch of a speed-sensing clutch is upstream and to turn on or off the speed-sensing another coupling is used. Locking differential for use in the drive train of a motor vehicle, comprising an input part ( 53 ) which is rotatably drivable; a first output part ( 54 ) and a second output part ( 61 ), each via differential gears ( 67 ) with the input part ( 53 ) are drive-connected; an externally sealed chamber ( 68 ), in which the differential wheels ( 67 ) and which is at least partially filled with a magnetorheological fluid; and a controllable magnetic coil ( 75 ) adjacent to the chamber ( 68 ) is arranged and a magnetic flux through the chamber ( 68 ), wherein the viscosity of the magnetorheological Flu ids changed; wherein the limited slip differential is designed in the form of a planetary differential and a ring gear ( 65 ), a sun wheel ( 66 ), several differential wheels ( 67 ) connected to the ring gear ( 65 ) on the one hand and the sun gear ( 66 on the other hand are in toothing engagement, and a web arrangement ( 58 ) for carrying the differential wheels ( 67 ), wherein between the ring gear ( 65 ) and the sun wheel ( 66 ) the chamber filled with magnetorheological fluid ( 68 ) is formed. Locking differential according to claim 21, characterized in that the magnetic coil ( 75 ) is arranged such that a toroidal magnetic field is generated, which by at least some of the meshing interventions of the planetary differential ( 74 ) runs. Locking differential according to claim 21 or 22, characterized in that the input part ( 53 ) with the ring gear ( 65 ) is rotatably connected, that the first output part ( 54 ) with the sun wheel ( 66 ) is rotatably connected and that the second output part ( 61 ) with the web arrangement ( 58 ) is rotatably connected. Locking differential according to one of claims 21 to 23, characterized in that in the chamber ( 68 ) einitzt the chamber volume reducing filler. Locking differential according to one of claims 21 to 24, characterized in that the toothings between the ring gear ( 65 ) and the planetary gears ( 67 ) are each axially shorter than the teeth between the planetary gears ( 67 ) and the sun wheel ( 66 ). Locking differential according to claims 21 to 25, characterized in that the web arrangement ( 58 ) comprises at least one flange, which on the magnetic coil ( 75 ) far away side of the differential wheels ( 67 ) is arranged. Locking differential according to one of claims 21 to 26, characterized in that a support disk ( 70 ) with the ring gear ( 65 ), which is the chamber ( 68 ) in the direction of the magnetic coil ( 75 ) limited. Locking differential according to claim 26 or 27, characterized in that the web arrangement ( 58 ) and / or the supporting disk ( 70 ) are paramagnetic. Locking differential according to one of claims 21 to 28, characterized in that the ring gear ( 65 ), the differential wheels ( 67 ) and the sun wheel ( 66 ) are ferromagnetic. Locking differential according to one of claims 21 to 29, characterized in that the chamber ( 68 ) with a variable volume reservoir ( 74 ) is connected to receive magnetorheological fluid. Locking differential according to claim 30, characterized in that the reservoir ( 74 ) by a piston ( 76 ) is limited by spring means ( 77 ) is acted upon.