Drive unit of an adjuster of a vehicle seat

In a drive unit (10) of an adjuster (80) of a vehicle seat, in particular of a motor vehicle seat, having at least an electronically commutated motor (12) and a gear stage (14) provided on the output side of the motor (12), wherein the motor (12) has a stator (16) and at least one rotor (22, 24) rotating around an axis (A) and interacting magnetically with the stator (16), two rotors (22, 24) are provided which rotate in different directions, wherein the gear stage (14) bears directly at least one rotor (22, 24).

BACKGROUND OF THE INVENTION

The present invention relates to a drive unit of an adjuster of a vehicle seat, in particular of a motor vehicle seat, having an electronically commutated motor and a gear stage provided on the output side of the motor, wherein the motor includes a stator and a rotor, with the rotor interacting magnetically with the stator and rotating around an axis.

Such drive units are used for motor-adjustable vehicle seats in order, by adjusting individual components relative to each other, to achieve an optimal seating position for the occupant. By means of the gear stage, the speed of rotation can be reduced and at the same time the torque delivered can be increased.

BRIEF SUMMARY OF SOME ASPECTS OF THE INVENTION

An aspect of the present invention is the provision of improvements to a drive unit of the type described above. In accordance with one aspect of the present invention, a drive unit of an adjuster of a vehicle seat, in particular of a motor vehicle seat, includes an electronically commutated motor and a gear stage provided on the output side of the motor. The electronically commutated motor includes a stator, a first rotor and a second rotor. The first rotor is configured for rotating in a first direction around an axis in response to the first rotor interacting magnetically with the stator. The second rotor is configured for rotating in a second direction in response to the second rotor interacting magnetically with the stator. The first direction is different from the second direction. At least one of the first and second rotors is directly borne by the gear stage.

Electronically commutated, brushless motors offer a high degree of electromechanical efficiency while at the same time taking up little space and generating very little noise. Several motors can be synchronized with each other with respect to the speed of rotation or position using the associated electronic systems without incurring any significant extra effort. The method of commutation offers the possibility of detecting a blocking state, of electrically defining a maximum permissible blocking force, and of monitoring temperature, and thus of achieving a higher energy density of the electromagnetic converter compared with brush motors, and this permits a significant reduction in installation space and weight. The integration of the control electronics into the motor offers advantages in recognizing blocking situations, evaluating existing sensors and achieving harmonization between the electronic function and the device being driven, for example when recording or programming parameters of the motor function.

Using two rotors (dual-rotor motor) rotating at different speeds of rotation and/or in different directions it is possible to generate a relative motion that is low compared with an absolute value for the speed of rotation and can be further reduced by the gear stage in order to increase the torque on the output side. The gear stage may be designed to be in a friction wheel configuration with hollow and/or solid rollers, or a gear wheel configuration is also possible. The friction wheel configuration is simpler to manufacture, and using hollow rollers reduces the weight. The gear stage can also form the bearing for the rotor. By bearing the rotor or preferably the rotors by the gear stage without any play, the running noises will be greatly reduced.

The different speed of rotation and/or the different direction of rotation of the rotors is achieved in a simple manner in design terms, preferably by ensuring that amongst themselves the rotors have a different number of poles, which in turn is preferably different from the number of stator poles, so that the speed of rotation of the rotors also deviates from the speed of rotation of the magnetic field of the stator.

A ratio of the stator poles to the poles of the rotor that is different from 2:3 and 3:2 permits differences in the speed and/or direction of rotation, as a result of which—for example when using two rotors—a small relative movement can be generated, which leads to a reduction in the speed of rotation while at the same time the output torque is increased.

In order to ensure low-noise or silent running of the motor, with low friction, low heat generation and low energy consumption, the stator is preferably electronically commutated, while the rotors preferably carry permanent magnets as poles. In the circumferential direction of the stator exactly every second stator pole preferably carries a coil in order to complete the magnetic flux circuit over the adjacent stator pole. The stator and rotors can be arranged in radial sequence or axial sequence (disc armature) with respect to the central axis. In order to generate the different speeds of rotation, the poles of the stator and the rotors may differ, for example, by two. In particular, using permanent magnets made of metals taken from the rare earth group, the type of winding, which also yields a relatively large torque even at low current, and the combination of the ratios of the numbers of poles in each case contribute to a further reduction in the amount of installation space required.

In order to block a torque force introduced by the output side it is possible, for example, to provide for the motor to drive an intermediate gear via a motor pinion, and the intermediate gear can be positively or frictionally blocked.

Preferably several motors are combined to form a multimotor that can meet various performance requirements, depending on the situation, and at the same time is compact and ergonomically advantageous. For example, the motors are arranged in a structurally simple way in parallel slots of a common motor carrier, with one common intermediate gear wheel forming the output of the multimotor. The possibility of modular power definition also enables extremely high power outputs to be called up for short periods of time. While, for example, the motors of the multimotor are normally connected in series, they may also be connected in parallel in a special situation, in order to deliver a higher performance on the basis of the higher voltage. Such a situation could be, for example, a crash or an imminent crash of a vehicle.

The motor can be used in combination with a gear stage that can be selected from several types of gear stages, and it is also possible to connect several gear stages one behind the other. Accordingly, a modular system is available that, with just a few modules, creates a large number of drive units to meet the various requirements.

Designing the gear stage as a differential gear, which by making use of two different speeds and/or directions of rotation causes a movement of an output around an axis, makes it possible to generate particularly small relative movements which permit a low speed of rotation at the output. The two different speeds and/or directions of rotation can be input into the gear stage by the motor or can be generated by the gear stage itself and, by locking one component with such a speed of rotation, can be picked off as output at the other component.

In addition to the electromechanical efficiency of the motor, the efficiency of the gear stage is also important for the overall efficiency of the drive unit, which is why preference is given to coaxial, fully symmetrical gear constructions having the smallest possible number of individual bearings, in particular in the friction wheel configuration, without any additional bearings, and instead having their own bearing function.

The gear stage may be designed as a single-stage planetary differential gear having a sun gear, a set of planet rollers or gears and a hollow gear, with the sun gear and the hollow gear each being rotationally fixedly connected to a rotor in the motor, while a planetary carrier bearing the planet rollers or gears serves as the output.

The gear stage can also, however, be designed as a multi-stage (i.e. at least two-stage) planetary differential gear having one or more sun gears, one or more sets of inner planet rollers, one or more sets of outer planet rollers and one or more outer rings, arranged concentrically to the central axis, with the sun gears or the outer rings being axially adjacently arranged with respect to the axis. Different outer diameters of the two sun gears or different inner diameters of the two outer rings (or respectively different elasticities) result in slight differences in the speed of rotation.

The gear stage can also be designed as a single-stage planetary differential gear having one or more sun gears, a set of preferably unstepped planet rollers and one or more hollow gears, arranged concentrically to the central axis, with the sun gears or hollow gears being axially adjacently arranged with respect to the axis. Different elasticities and different outer diameters of the two sun gears or different inner diameters of the two hollow gears result in slight differences in the speeds of rotation.

The differences in the speed of rotation can be picked off, for example, if one of the two adjacent gear elements having different diameters is attached to the housing and one of them is connected with the output. In the configuration having two outer rings, the one that is attached to the housing is connected to the stator, while the sun gear, which acts as the drive element, is rotationally fixedly connected to a rotor in the motor.

In order, on the one hand, to apply pretension to hold together and center the gear stage, and, on the other hand, to compensate for tolerances, the hollow gear or the outer ring preferably possess an elastic metal ring and an elastomer bed in which the metal ring is set. A support that accepts the elastomer bed together with the metal ring and secures them axially is preferably joined to a bell-shaped part of the output which is designed as a hollow shaft.

The direction of rotation of the output can be optionally selected by means of a switch gear without having to change the direction of rotation of the motor. This considerably simplifies the electronics needed for the motor. Switching is accomplished in an easy-to-manufacture design by providing preferably an electromagnet defined by a switching coil. The electromagnet interacts with two mutually repulsing permanent holding magnets which are coupled geometrically with two adjacent, similar gear elements in order to lock these by frictional or positive means. Using a switch gear it is also possible to select between two different gear ratios.

The drive unit preferably drives an adjuster within the vehicle seat. Thereby, the drive unit is preferably integrated into the load-bearing gear of the adjuster, wherein the load-bearing gear preferably directly bears a rotor. The adjuster designed like this has the advantage that separate transmission elements, for example a low-efficiency worm gear or the like, as well as separate bearing elements for the rotor, are not needed between the drive unit and the load-bearing gear. If, in addition, the rotor is borne without any play continuously, via the gear stage to the load-bearing gear, the running noises will be greatly reduced.

In many cases the fitting parts which form the load-bearing gear—or at least one of them—are movable around or relative to a center, for example, a gear wheel engaging with a toothed rack being movable around the center of the wheel, or two interlocking fitting parts of an eccentric planetary gear being movable around the eccentric. The drive unit (motor plus gear stage), whose dimensions can be kept very small, that is integrated into the load-bearing gear, is preferably—at least more or less (e.g., at least about)—arranged at this center, i.e. approximately in the same plane (or more precisely layer) in which the fitting part or parts move. The drive unit arranged at the center of the load-bearing gear is preferably smaller in diameter than, or at the most has the same diameter as, the toothing for the gear connection between the fitting parts. By such an integration of the drive unit, the required installation space is kept small, in particular in the axial direction defined by the axis of the motor, which is arranged preferably perpendicular to the plane in which the fitting part or parts move. The amount of installation space gained compared with a known solution can be used for improving the load absorption in the event of a crash.

In order to keep the manufacturing costs of the adjuster to a minimum, the aim is to use, on the one hand, inexpensive motors with low power consumption and low torque and, on the other hand, gear stages with a very high speed reduction, with preference being given to electronic controls and couplings over mechanical solutions, for example also when coupling and synchronizing two single adjusters on different sides of a vehicle seat.

Other aspects and advantages of the present invention will become apparent from the following.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT

A drive unit10comprises a motor12and a gear stage14. The gear stage14is provided on the output side of the motor12. The motor12is an electronically commutated motor having a stator16whose stator poles18are arranged in a star-shape around an axis A. The axis A running perpendicular to the plane of the drawing inFIG. 2defines the following directional data in cylindrical coordinates. A coil20is wrapped around every second one of the altogether twelve stator poles18. In order to generate a spatially rotating magnetic field, the coils20are periodically and at staggered intervals in relation to each other energized by a DC-fed electronic unit (not depicted in detail) that is integrated into the motor12.

The motor12is a dual-rotor motor (“dual motor”) with an inner rotor22and an outer rotor24. The inner rotor22and the outer rotor24rotate about the axis A and carry permanent magnets26along the circumferential surface facing the stator16, with the magnets being alternately poled in the circumferential direction. All the permanent magnets26used in the present application exhibit preferably a high degree of permeability, for example by containing metals from the rare earth group. An inner flux ring28, which is assigned to the inner rotor22, and an outer flux ring30, which is assigned to the outer rotor24, complete the magnetic flux circuit. The two flux rings28and30may, if necessary, at the same time act as carriers of the permanent magnets26. The outer rotor24provides a larger amount of torque due to the magnetic forces active over a larger radius (compared with the inner rotor22). The motor is preferably of hollow-shaft design, i.e. the area around the axis A is left open.

The number of permanent magnets26is selected in such a manner that their ratio to the number of stator poles18is unequal to 2:3 or 3:2, as a result of which the rotation of the inner rotor22or the outer rotor24deviates from the rotation of the magnetic field in the stator16. In the present case, the inner rotor22comprises ten permanent magnets26and the outer rotor24comprises fourteen permanent magnets26. In keeping with the different number of permanent magnets26, in the third motor variant (dual motor) the inner rotor22and the outer rotor24rotate in the present case at different speeds of rotation (5:7) and also in opposite directions of rotation, as indicated by arrows in the drawing.

Instead of having a radial structure, the motor may also have an axial configuration, i.e. the rotors (disc armature) and the stator are arranged axially one behind the other.

The purpose of the gear stage14is to reduce the rotational speed delivered by the motor12while at the same time transmitting the torque delivered by the motor12. The gear stage14is designed as a differential gear system, various types of which are described below. Each type exists either as a toothed wheel planetary differential gear having flat, toothed planet gears, or also as a preferred configuration in the form of a friction wheel planetary differential gear having cylindrical, smooth planet rollers which—just like the sun wheel—may be hollow or solid. A hollow-shaft design of the gear stage14, in which the area round the central axis remains free, is preferred.

The first type of gear stage is a single-stage planetary differential gear which will be described first in its friction wheel configuration. The gear stage14is aligned with the central axis A of the motor12. A sun gear32is arranged around the axis A and three planet rollers34, which in turn are enclosed by a hollow gear36, run along the circumferential surface of the sun gear. The hollow gear36provides for radial pretensioning and thus for good rolling of the planet rollers34without any slip occurring. An annular planetary carrier38bears the planet rollers34on axial pins.

With the exception of the surface characteristics of the components, the toothed wheel configuration is identical to the friction wheel configuration, and for that reason an apostrophe has been added to the reference numbers of the corresponding components. The sun gear32′, planet gears34′ and hollow gear36′ are in each case toothed, but are coupled in the same way with the motor12and execute the same relative movements, and the planetary carrier38is again used as the output.

The second type of gear stage is a multi-stage planetary differential gear which again is described in its radially layered friction wheel configuration, but it can also exist as a toothed wheel design. Again, solid and/or hollow components may be used. A sun gear32is again arranged around the axis A, and on the circumferential surface of the sun gear is arranged a set of inner planet rollers34. A first outer planet roller40and a second outer planet roller42, arranged axially one behind the other, are inserted into each gap. Each of the outer planet rollers40and42is axially about half as long as an inner planet roller34, and the second outer planet roller42is slightly smaller in diameter compared with the first outer planet roller40, something which is easily achieved, for example, by using cylindrical rollers having metric dimensions, on the one hand, or inch-based dimensions, on the other hand. Instead of the cylindrical shape, another shape may also be used for the roll bodies.

A first outer ring44is radially outside of, and encloses the first outer planet rollers40. A second outer ring46is radially outside of, and encloses the second outer planet rollers42. Each of the outer rings44,46serves as a hollow gear. The outer rings44,46pretension the planet rollers40,42and34at all contact points simultaneously towards the sun gear32. This pretensioning of the two radially layered rows of rollers ensures that all the rollers bear each other and a concentric radially symmetrical slip-free arrangement is obtained, which results in a high degree of efficiency of the gear stage14. A planetary carrier, and thus an internal bearing of the planet rollers, is not necessary but nor is it excluded. At its end face, the sun gear32can be provided with radially outward projecting rims in order to hold the planet rollers in place in the axial direction. This can also be done in the case of the other types of gear stage.

The two outer rings44and46are in principle constructed in the same way so that in the following only the first outer ring44will be described. The first outer ring44comprises an elastic metal ring48made of steel. The radially inward facing surface of the first outer ring44is in contact with the first outer planet rollers40. The first outer ring44has a smaller internal diameter than is needed by the geometrical arrangement of the enclosed rollers in order to apply the pretensioning. On the radially outward-facing side and at both axial faces, the metal ring48is located in an elastomer bed50of the first outer ring44. The metal ring48and the elastomer bed50made of plastic together ensure that very uniform pressure is applied. In addition, the elastomer bed50insulates the running noises and reduces moment impacts. The two-part design of the first outer ring44described here can also be incorporated in the hollow gear36or36′ of the first type of gear stage. A support52is provided in order to axially secure the first outer ring44with its metal ring48and its elastomer bed50, and this feature may also be incorporated in the two other types of gear stage. For the purposes of assembly, the support52is of two-part construction and engages the elastomer bed50radially on the outside and with two flanges at the face ends.

For the sake of rotational symmetry, which helps avoiding running noises, the metal ring48and the elastomer bed50are preferably of continuous design in the circumferential direction, but they may also be slotted or divided, in particular they may have arrow-shaped slots, for example when they are to be connected to the support52in a rotationally fixed manner. In order to dissipate heat generated in the gear stage14, the elastomer bed50preferably possesses good thermal conductivity, which is achieved for example by embedding metallic or other heat-conducting fibers or by filling hollow spaces and recesses with a thermally conducting material. A thermally conducting paste may also be provided between the metal ring48and the elastomer bed50.

The small difference in diameter between the first outer planet rollers40and the second outer planet rollers42and, as a result, between the inner diameter of the first outer ring44and the second outer ring46causes the two outer rings44and46to rotate at different speeds. This small difference in the speed of rotation is made use of to achieve a great speed reduction (e.g. 200) in gear stage14when it is connected to the motor12.

In the combination of this second type of gear stage with the motor12, the first outer ring44, more precisely its support52, is for example attached to the housing, i.e. to the stator16. The sun gear32, which acts as the drive wheel, is connected to the inner rotor22(or the outer rotor24or a planetary carrier38), while the second outer ring46acts as the output54. In this case, the output shaft, which for example may be a hollow shaft, is attached by means of a bell-shaped end piece to the second outer ring46, more precisely to the support52thereof. In the present case, the second outer ring46rotates in the same direction as the sun gear32. The configuration selected for the second type of gear stage makes it unnecessary to provide a separate bearing for the sun gear32and thus for the inner rotor22(and the outer rotor24) and for the second outer ring46, i.e. for the output54, but it does not exclude the possibility. However, bearing of the inner rotor22(and the outer rotor24) in the gear stage14has the advantage that there is no play, and thus the inner rotor22(and the outer rotor24) run noiselessly.

In a modified design of the second type of gear stage, the (smaller) second outer ring46is attached to the housing and the (larger) first outer ring44is the output, which results in counter-rotation of the sun gear32and the first outer ring44. By optionally attaching the outer rings44and46to the housing, which results in a change in the output, for example by means of two pawl systems or a circuit which is described in more detail below, it is possible to reverse the direction of rotation of the output while the direction of rotation of the sun gear32remains the same. The design of the electronic system needed for the motor12can then be greatly simplified, which also simplifies the manufacture of the motor12.

The second type of gear stage can be further modified by providing a different number of roller sets. In general, it is possible to provide one or more sun gears arranged axially behind each other, an equal number of appropriately axially arranged inner planet rollers, possibly a set of intermediate planet rollers for synchronization purposes, one or more sets of outer rollers arranged axially behind each other, and an equal number of appropriately axially arranged outer rings. The small difference in rotational speeds is taken off in the manner described between two adjacent gear elements. Instead of a sun gear plus a set of inner planet rollers, it is also conceivable to use just a sun gear of suitably large diameter which rolls directly on the next outer set of planet rollers, and/or instead of a set of outer planet rollers plus an outer ring it is conceivable to use just an outer ring of suitably small diameter which rolls directly on the next inner set of planet rollers.

The third type of gear stage is again a single-stage planetary differential gear which is again described as a radially layered frictional wheel configuration, although a toothed wheel configuration is also possible. The gear stage14is aligned with the central axis A of the motor12. A sun gear32is arranged around the axis A and three planet rollers34roll along its circumferential surface. About halfway along their axial length, the unstepped planet rollers34are enclosed by an annular first hollow gear36that has low elasticity, i.e. is relatively stiff. Along the other half of their axial length the planet rollers34are enclosed by a second hollow gear56. The second hollow gear56has a higher degree of elasticity and a smaller inner circumference than the first hollow gear36. Both factors, together with the second hollow gear56being the contact with the planet rollers34, results in the second hollow gear56having a shape that deviates from a circular shape, more specifically the second hollow gear56has a slightly triangular shape. This triangular shape of the second hollow gear56is slightly exaggerated in the drawings, and it changes dynamically while in operation. The differences in elasticity are attained by selecting suitable materials.

Both hollow gears36and56provide radial pretensioning with a high pressure force, thereby ensuring good rolling of the planet rollers34without any slip, and the sun gear32compensates the radial forces. With drive input via the sun gear32instead of via a planetary carrier, the ratio of the inner circumferences of the hollow gears does not have to be 200/199 for a gear ratio of 200, but instead a more generous ratio and thus one that is less sensitive to tolerance can be selected. In addition to, or instead of, the sun gear32, a planetary carrier bearing the planet rollers can be used as the input drive, similar to the design of the first type of gear stage, or a bearing cage locating the planet rollers may be provided. In a modified embodiment, two sun gears of different elasticity arranged axially one behind the other may also be provided in combination with a hollow gear, or other combinations of continuous or split sun gears and hollow gears of different elasticity may be provided. The planet rollers may also be stepped.

In order to transmit the deformation of the second hollow gear56to a rigid shaft for the output54or alternatively to bear it on the housing, the second hollow gear56is mounted in an elastomer bed50, for example a rubber ring, which encloses it radially on the outside, and this ring is in turn radially arranged within a support52. The elastomer bed50may also be regarded as a further component of the hollow gear56which comprises a metal ring. Instead of the elastomer bed50, elastic spokes for the second hollow gear56or an axial or radial power pick-off may be provided, possibly with the interposition of a cup with deformable walls or a perforated disc comprising damper elements. The slightly non-uniform movement of the hollow gear56is preferably not or only slightly compensated.

In a combination of this third type of gear stage with the motor12, the first hollow gear36is, for example, attached to the housing, i.e. to the stator16. The sun gear32acts as the drive, while the second hollow gear56acts as the output54. In this case, the power-output shaft, which for example may be a hollow shaft, is attached by means of a bell-shaped end piece to the second hollow gear56, more precisely to the support52thereof. The respective diameters must always be in the same orders of magnitude so that further ratios are possible through the choice of diameters. The axial lengths of the sun gear32, planet rollers34and hollow gear36are preferably large enough that the inner rotor22and the outer rotor24can be positioned relative to the stator16by means of the gear stage14. The configuration selected for the third type of gear stage also makes it unnecessary to provide separate bearing of the sun gear32and thus of the inner rotor22and the outer rotor24as well as of the second hollow gear56, i.e. of the output54, but it does not exclude this possibility.

The gear stage14may be designed as a switch gear by means of which it is possible to select between two different directions of rotation of the output54while retaining one sole permanent direction of rotation of the motor12, which is described in more detail in the following on the basis of the second type of gear stage. As explained with the second type of gear stage, a set of inner planet rollers34sits on the sun gear32, and a set of first planet rollers40is in turn arranged on top of the planet rollers34and is held in place under pretension by a first outer ring44. Axially offset from the first planet rollers40and the first outer ring44, a set of second planet rollers42is held in place under pretension by a second outer ring46. The second outer ring46forms part of the output54. The axial length of the inner planet rollers34is selected such that a third outer ring58is arranged axially alongside the first outer ring44on the side facing away from the second outer ring46. The third outer ring58is under pretension and directly encircles the inner planet rollers34. The outer diameters of the first outer ring44and of the third outer ring58coincide at least approximately.

The middle of a wound spring60is attached to the housing; otherwise some of the windings of the spring are wrapped around the first outer ring44, and the rest of its windings are wrapped around the third outer ring58. In each case a permanent magnet is arranged as a holding magnet61at both free ends of the wound spring60, and the mutually facing poles of the two holding magnets61repel each other. The holding magnets61preferably possess high permeability, for example because they contain metals from the rare earth group. A soft iron core62is arranged between the two holding magnets61. A switching coil63, which can be energized with optional polarity, is wrapped around the soft iron core62.

With the switching coil63in the non-energized state, both holding magnets61are in contact with the core62, which locally completes the magnetic flux circuit. Both outer rings44and58and thus the gear stage14are as a result held in place. When the coils20of the stator16are energized, the switching coil63is also energized. Depending on the direction of the current, one of the two holding magnets61continues to be attracted while the other is repulsed. As a result, the latter opens up this side of the wound spring60, thereby releasing the corresponding outer ring44or58. Due to the small differences in diameter of the outer rings44and58, which normally cause differences in the speeds of rotation, the direction of rotation of the second outer ring46and thus of the output54is defined according to which outer ring44or58is blocked, while the direction of rotation of the motor12and thus of the sun gear32remains constant (unidirectional motor), with the two possible directions of rotation of the output being opposite to each other.

Apart from the switch gear described above, which has a friction-type locking device, in a modification of the design it is also conceivable to employ a switch gear with a positive-acting locking solution. As shown inFIG. 12, the holding magnets61may, for example, be arranged on toothed pawls64which respectively switchably lock the toothed outer rings. The function is the same as described above.

The locking device can also be used to block torque forces which are introduced by the output54in the idle state. Such blocking action does not have to occur inside the gear stage14but may also be applied between the motor12and the gear stage14.

As shown inFIG. 13A, the output shaft of the motor12is, for example, provided on the one hand with a motor pinion66which engages in an intermediate gear67connected to the sun gear32and, on the other hand, it is connected frictionally with a disc cam68having two cam projections68′. In the idle state, two spring-loaded toothed pawls64engage at least approximately positively in the intermediate gear67, blocking the latter in particular against the torque forces introduced on the output side. Once the motor12starts to rotate, the disc cam68rotates with it and the cam projections68′ come into contact with control contours64′ of the toothed pawls64, thereby lifting the toothed pawls64out of engagement with the intermediate gear67, as illustrated inFIG. 13B. The intermediate gear67can now be driven without any hindrance, wherein the frictional contact with the disc cam68is preferably eliminated. In a preferred variant of the embodiment, the disc cam68is not borne in frictional contact with a rotating axis but is connected in rotationally fixed manner to the non-rotating part of the motor, and this in turn is rotatably borne through a small angular range relative to the housing. Because of the torque exerted between the motor pinion66and the disc cam68borne in this manner, the latter now rotates automatically when the motor12is switched on and thus automatically causes the toothed pawls to disengage. The type of motor commutation is of no importance for this locking device. The locking action may also occur frictionally.

The drive unit10provided according to the invention is not limited to a combination of a single motor12with a single gear stage14. For certain performance requirements it may be sensible to combine several motors12, for example in order to meet temporally different requirements. A motor carrier70contains several motor slots71which are arranged around a central bearing for a common intermediate gear67. The motors12inserted into the motor slots—for example, three motors—then engage with motor pinions66in this intermediate gear which—as described above—can be locked against any torque force introduced on the output side. The multimotor72created in this way is then coupled to a gear stage14by means of the intermediate gear67, for example it may be coupled to a sun gear32of one of the types of gear stage described above. The type of motor commutation is of no significance in this connection.

The mechanically parallel-connected motors12are normally, in electrical terms, operated in series. InFIG. 16this is demonstrated using two motors12and the principle can be extended in known manner to include several motors. One or more relays74, which can also be understood as electronic equivalent circuits, are provided between the motors12. Normally, because of the series connection, the operating voltage is distributed at least approximately uniformly among the existing motors12.

In certain, special situations, it may be desirable for the drive unit10to put out a higher rotational speed and/or a higher torque. In the case where the drive unit10is used in a vehicle, such a situation would be a crash. The devices driven by drive unit10are then intended to assume as quickly as possible certain settings in order to increase the protection of the vehicle occupants. In this case it is accepted that the drive unit10might subsequently be unusable. Another special situation would be the rapid setting of one or more adjusters of a vehicle seat over a large range, for example folding the backrest forward (swing free) combined with a longitudinal adjustment in order to facilitate access to a rear set of seats (easy entry).

A mechanical solution for the rapid adjustment could be achieved using the second and third type of gear stage, configured as a switch gear unit with selectable gear ratios, if the difference in the geometries of the outer rings44and46or in the elasticities of the hollow gears36and56is sufficiently large. Using the locking device provided in the switch gear unit, which when alternatingly switched accurately locks either an outer ring44or46or a hollow gear36or56, it is possible to generate different speeds and thus different gear ratios at the output. If the direction of rotation of the motor12remains constant the direction of rotation of the output changes, a state which corresponds to the situation described above for the unidirectional motor. A constant direction of rotation of the output can be generated—apart from by switching the locking device—also by changing the direction of rotation of the motor12.

In the present embodiment of the multimotor72, the existing relays74are actuated in the special situation by a vehicle electronic system which is not shown in further detail, which occurs in such a manner that the series connection is cancelled and the motors12are connected in parallel. Increasing the applied voltage increases the power uptake of the single motors12and of the multimotor72as a whole, at least for a short while and preferably until the driven devices have attained the desired settings. Because of the short actuation times, thermodynamic effects can be ignored here. If the application is for a crash situation, the relays74can be triggered before the actual crash occurs, when the crash sensors provided in the vehicle's electronic system provide the signals for an impending crash. The solution is thus presave-capable.

If the motor12or multimotor72is operated with the coils20in a star-connected circuit, it is possible in the special situation, as indicated inFIG. 17, to switch the operation to a star-connected system with a central tap in order to reduce the effective resistance and also to increase the performance for a short time.

Using a star-connected circuit to energize the motors is also a particularly good solution for a combination involving the dual-rotor motor and a locking device. When the special situation occurs, one of the two rotors of the dual-rotor motor is mechanically blocked by the locking device. The downstream gear stage14then acts as a differential gear with a higher gear ratio (less reduction). After the switch is made to the middle tap, the other rotor runs with a higher power uptake due to the lower resistance, and this ultimately produces the desired increase in power at the output54.

The drive unit10provided according to the invention is used in the present case to drive the adjuster80in a vehicle, although the drive unit10may also be used elsewhere. Generally, the adjuster80comprises two components which are movable relative to each other, between which the drive unit10operates with its output54. The low speed of rotation of the output54produces a large amount of torque. Means can be provided to convert the rotational movement of the output54into linear motion in the adjuster80. A separate drive unit may also be provided for each adjustment direction of the adjuster80. Examples of how the adjuster80might be used are in the case of vehicle seats a backrest inclination adjuster, especially in the form of a self-locking geared fitting, a seat height adjuster acting between two gear elements of a four-bar mechanism, a seat inclination adjuster pivoting the front edge of a seat cushion, or a longitudinal seat adjuster that moves the vehicle seat on rails in a longitudinal direction.

In several applications, two similar single adjusters80act together in order to jointly move a component. For example, as a rule, in vehicle seats the same single adjusters80are present on both sides of the seat and, in a known manner, they are coupled and synchronized in pairs by means of a rotatable transmission rod. Using the drive unit10according to the invention, which takes up very little installation space, it is possible to provide each single adjuster80in a pair with its own drive unit10. These drive units are synchronized by, for example, the electronic system used for electronic commutation of the motor12or—in the case of a vehicle seat—via the stiffness of the structure of the vehicle seat.

In the following, as an example of a preferred application of the drive unit10according to the invention, a description is given of its integration into an adjuster80having a load-bearing gear, designed as a self-locking geared fitting and used, for example, to adjust the inclination of the backrest of a vehicle seat. The adjuster80comprises a first fitting part81with a toothed rim81adesigned like a hollow gear, and a second fitting part82, having a gear wheel82a, in geared connection with the first fitting part81. The fitting parts81and82together form the load-bearing gear. The diameter of the tip circle of the gear wheel82ais about one tooth height less than the diameter of the root circle of the toothed rim81a, and the number of teeth on the gear wheel82ais smaller than the number of teeth on the toothed rim81a. When driven by the drive unit in a manner described below, relative rolling movement of the gear wheel82aon the toothed rim81ais possible, and this is exhibited as the relative rotation of the two fitting parts81and82with a superimposed tumbling motion.

For bearing purposes, a first collar81bis formed on the first fitting part81concentrically to the toothed rim81a, thereby defining a secondary axis B, and a second collar82bis formed on the second fitting part82(or instead a sleeve is pressed in place) concentrically to the gear wheel82a, thereby defining the central axis A. The diameter of the second collar82bis larger than that of the first collar81b.

The drive unit10according to the invention which here is made up of a slightly modified motor12and a gear stage14of the second gear stage type with friction wheels, as described above (although any other combination may be put together), is arranged with optimized space in the center of the load-bearing gear and integrated into the second fitting part82, more accurately into the second collar82b. The stator16, with its outer flux ring30, is pressed into the second collar82in the half facing axially away from the first fitting part81, with the electronic unit, which is not depicted in more detail here, being arranged also within the second collar82bon the side facing axially away from the first fitting part81.

The shown inner rotor22and the outer rotor24(not shown inFIG. 18) are arranged inside the collar82b, with the hollow sun gear32being borne by the gear stage14, in the present case continuously without any play up to the second fitting part82. The inner planet rollers34are arranged radially in a row on the sun gear32, while the first outer planet rollers40and the second outer planet rollers42are arranged in rows on the inner planet rollers34. The first outer ring44and the second outer ring46hold the planet rollers together under tension and at the same time ensure that the inner rotor22is borne without any play. The first outer ring44is also pressed into the second collar82b, i.e. like the stator16it is attached to the housing, or the second collar82bitself forms the first outer ring44.

With its smaller diameter, the second outer ring46, which at the same time serves as the output54of the drive unit10, is rotatable within the second collar82b. The second collar82bis formed as a slide bearing bush or such a bush is pressed into the end of the second collar82bfacing axially towards the first fitting part81. An axially projecting drive segment85extending over about one quarter of the circumference is formed on the second outer ring46. The drive segment85may also be arranged on a separately formed ring attached in rotationally fixed manner to the second outer ring46. In the same plane as the drive segment85there are two curved wedge segments86arranged on the first collar81a, while the drive segment85engages with play between the narrow sides of the wedge segments86. A spring87engaging between the broad ends of the wedge segments86, which face each other, forces the wedge segments86apart in the circumferential direction. Together, the drive segment85and the wedge segments86define an eccentric88.

The drive unit10rotates the eccentric88, and the speed of rotation is greatly reduced compared with the frequency of the magnetic field of the stator16, and the torque is greatly increased. For each full rotation of the eccentric88, which slides along the second fitting part82, the toothed rim81aof the first fitting part81is rotated further by one tooth on the gear wheel82aof the second fitting part82, and the secondary axis B moves slowly to the same extent around axis A. This results in the relative rotation with the superimposed tumbling motion described above which represents the adjusting movement. Fluctuations in torque due to the tumbling motion can be compensated by the electronics used to commutate the motor12, e.g. by means of a speed of rotation dependent on the angle of rotation and/or time.

Despite the integration of the drive unit10into the load-bearing gear of the adjuster80, the drive unit10is designed as a hollow-shaft drive, i.e. both in the motor12and in the gear stage14the central area around the axis A remains free so that, if necessary, a transmission rod or the like can still be installed.

The large mass of the adjuster80offers acoustical advantages. Because of the fixed, tight and, in the pretensioned friction wheel configuration, also play-free connection of the small rotating mass of the inner rotor22to the large mass of the adjuster80, the solid-borne sound vibrations of the inner rotor22are well conducted, but because of the large mass to be accelerated they reach only low amplitudes. Through the contact between the stator16and the load-bearing gear, the large mass of the adjuster80also offers thermodynamic advantages.

It will be understood by those skilled in the art that while the present invention has been discussed above with reference to an exemplary embodiment, various additions, modifications and changes can be made thereto without departing from the spirit and scope of the invention as set forth in the following claims.