Abstract:
A rotary damper for a vehicle, for damping relative movements between vehicle wheels and the vehicle body. The damper has at least one gear assembly that converts the relative movement into rotation movement and is connected to at least one electric machine ( 2 ) in such manner so that actively controllable damping of the relative movement is possible.

Description:
[0001]    This application is a National Stage completion of PCT/EP2014/052004 filed Feb. 3, 2014, which claims priority from German patent application serial no. 10 2013 203 431.8 filed Feb. 28, 2013. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention concerns a rotary damper for a vehicle, for damping relative movements. 
       BACKGROUND OF THE INVENTION 
       [0003]    From automotive technology linear dampers are known, for the damping of linear movements. Furthermore, from the document DE 10 2008 042 389 A, a rotary damper is also known, which consists of an inner, fixed part and an outer part that can rotate relative to the inner part, the outer part being connected to a lever for producing the rotation. Between the inner part and the outer part there is arranged a frictional clutch in the form of a disk clutch, whose disks are connected fixed, in alternation, to the two parts. In the area of the lever, the outer part is fixed to a first component of a spindle gear, which can move in rotation on balls over a second component and during this, undergoes axial movement that is guided by a ramp on the second component. Accordingly, rotational movement of the outer part produced by the spindle drive is converted to axial movement of the first component and thus also of the outer part, in order to bring the friction surfaces of the clutch into contact. This brings about a coupling of the inner and outer parts, which brakes the outer part and therefore damps the rotational movement. 
       SUMMARY OF THE INVENTION 
       [0004]    The purpose of the present invention is to propose a rotary damper with as compact a structure as possible. 
         [0005]    According to the invention, that objective is achieved by virtue of the characteristics and advantageous design features that emerge from the description and the drawings. 
         [0006]    For a compact structure a rotary damper is proposed, preferably fitting in a vehicle in order to damp relative movements between vehicle wheels and the vehicle body, the damper comprising at least one gear assembly, that converts the relative movement into rotational movement, and at least one electric machine, which are functionally connected with one another in such manner that damping of the relative movement can be actively controlled. 
         [0007]    In this way the relative movement, after being converted to rotational movement, can be damped as desired by means of the electric machine connected to the gear assembly. To further improve the braking action, in the context of the present invention it can be provided that at least one dynamic brake is used. Dynamic brakes are those whose braking force is speed-dependent. With the dynamic brake the electric machine and so also the gear assembly can be braked appropriately in order to obtain a desired damping of the relative movement. As the dynamic brake, preferably at least one eddy current brake, a hydrodynamic brake or the like can be used. 
         [0008]    In a preferred embodiment variant of the invention it can be provided that when an eddy current brake is used, this is connected or arranged relative to the connection between the at least one gear assembly and the electric machine, in parallel, in series or in a power-branched configuration. 
         [0009]    To produce a particularly space-saving arrangement of the eddy current brake in the proposed rotary damper, it can be provided that the eddy current brake has for example a drum-shaped structure, arranged for example coaxially with the rotor of the electric machine. It is also conceivable for the eddy current brake to have for example a disk-shaped structure such that the disk-shaped plates can each be associated with a respective end side of the electric machine. 
         [0010]    The magnetic flux for producing the eddy currents can be produced by the stator of the electric machine. For this, as an example the stator plate or a similar component of the electric machine can for example have grooves or recesses which are rectangular, V-shaped or shaped in some other way, in order to produce a stray field on the outside. Alternatively, the stator can also be made longer than the rotor, and the drum of the eddy current brake can project into the stator of the electric machine. If the eddy current brake is designed with a disk shape or a plate shape, then, for example, to produce the required stray field an extension of the stator or of the pole-pieces of the electric machine can be provided so that magnetic flux is generated in the disks or plates of the eddy current brake. 
         [0011]    Beside the disk-shaped or drum-shaped designs, conical or similarly designed embodiments or combinations thereof can be used as eddy current brakes, which project at least in part into the stator or which surround it. Furthermore, to produce the eddy currents permanent magnets or the like can be used, which can be attached preferably on the housing of the rotary damper in the area of the outside of the stator or, for example, on the drum or the plates themselves. Instead of permanent magnets external excitation by means of a coil arrangement or the like is also conceivable, wherein for cost reasons it is preferable to use a coil arrangement with claw poles analogous to a claw pole generator or the like. 
         [0012]    Alternatively to or in combination with the eddy current brake, a hydrodynamic brake or clutch can be used, As the medium for this, aside from oil it is also possible for example to use a magneto-rheological or electro-rheological fluid, whose viscosity can be adjusted by means of the magnetic or electric field, respectively. 
         [0013]    As an alternative to the electric machine designed as an internal-rotor machine, in the proposed rotary damper it is also possible to use an external-rotor electric machine. For example, a metallic cylinder, forming an external rotor arrangement of the external-rotor machine, can at the same time form the eddy current brake, which, by virtue of a further stator or a permanent magnet, is located in a magnetic flux for producing the eddy currents. Optionally, the magnetic flux can also be produced in the rotor of the external-rotor machine by a multi-component rotor arrangement or the like, such that between the components of the multi-component rotor arrangement a minimal air-gap is provided. The metallic portion of the rotor arrangement can for example consist of a metallic cylinder and the magnetic portion of the rotor arrangement for example of a cylindrical, non-magnetic holding arrangement for the magnets or suchlike. The magnet holding arrangement and the metallic cylinder are coupled to the gear assembly, for example in the form of a planetary gear assembly, in such manner that the magnet holding arrangement and the metallic cylinder move in opposite directions, Regardless of the design of the rotor arrangement of the electric machine the eddy current brake is, as it were, integrated in the rotor arrangement or contained therein. Other possible arrangements too are conceivable. 
         [0014]    The proposed rotary damper can preferably be used for damping relative movements between vehicle wheels and a vehicle body. However other uses, for example in other vehicles are also possible, 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Below, the present invention is explained in more detail with reference to the drawings, which show: 
           [0016]      FIG. 1 : A schematic view of a possible embodiment variant of a rotary damper with an electric machine and an eddy current brake connected in parallel upstream from a planetary gear assembly; 
           [0017]      FIG. 2 : A schematic view of a possible embodiment variant of a rotary damper with an alternative design of the eddy current brake arranged in parallel; 
           [0018]      FIG. 3 : A schematic view of a related embodiment variant of the rotary damper, with two planetary gear assemblies connected upstream from an electric machine and an eddy current brake arranged in series; 
           [0019]      FIG. 4 : A schematic view of a related embodiment variant of the rotary damper, with two planetary gear assemblies connected upstream from an electric machine and an eddy current brake arranged in a power-branched manner; 
           [0020]      FIG. 5 : A schematic view of another embodiment variant of the rotary damper, with two planetary gear assemblies connected upstream from an electric machine and an eddy current brake arranged in a power-branched manner; 
           [0021]      FIG. 6 : A schematic view of a further embodiment variant of the rotary damper, with an electric machine designed as an external-rotor machine; 
           [0022]      FIG. 7 : A schematic view of an alternative design of the rotary damper shown in  FIG. 6 ; 
           [0023]      FIG. 8 : A cross-sectional view of a stator plate of the electric machine, with radial grooves arranged on the outer circumference; and 
           [0024]      FIG. 9 : An enlarged view of the stator plate in the area of a groove, showing the stray flux produced. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]      FIG. 1  is a possible embodiment variant of the rotary damper according to the invention, having a first planetary gearset  1  as the gear assembly and, connected downstream therefrom, an electric machine  2  with a parallel eddy current brake  3  in a drum-shaped configuration. A lever that transmits the relative movement is connected to a ring gear  4  of the planetary gearset  1 , such that in a known way the ring gear  4  engages with planetary gearwheels mounted on a planetary carrier  8 , the gearwheels in turn engage with a sun gear  5 . For the parallel arrangement, the sun gear  5  is connected to a rotor  6  of the electric machine  2  and a drum  7  of the eddy current brake  3 . The planetary carrier  8  is connected to a housing  9  of the rotary damper. 
         [0026]    In this way the relative movement to be damped between two bodies or masses, particularly in a vehicle between a wheel and the vehicle body, is transmitted by way of a deflection lever as rotational movement to the planetary gear assembly  1  which, for example, increases the rotation speedal and reduces the torque introduced. The electric machine  2  is connected in parallel with the eddy current brake  3  on a common shaft. For example, the electric machine  2 , designed as an electric motor or generator, drives the planetary gearwheels of the positionally fixed planetary carrier  8  by way of the sun gear  5 , whereas in turn the planetary gearwheels mesh with the ring gear  4 , 
         [0027]      FIG. 2  shows an alternative design of the eddy current brake  3  in a disk or plate configuration. In this version, the eddy current brake  3  has for example two disk-shaped plates  10 ,  10 A, each associated with an end side of the electric machine  2 . The magnetic flux for producing the eddy currents of the eddy current brake  3  is created by an axially extended structure of the stator of the electric machine  2 , wherein approximately ring disk shaped, angled portions  11 ,  11 A are provided, which are directed approximately parallel to the disk-shaped plates  10 ,  10 A of the eddy current brake  3 . The angled portions  11 ,  11 A can, for example, be in the form of extended pole-pieces of the stator of the electric machine  2 . 
         [0028]    In other respects, in the embodiment variant shown in  FIG. 2 , as in that of  FIG. 1  the electric machine  2  is shown with a parallel eddy current brake  3 , in both cases coupled to the sun gear  5  of the planetary gear assembly  1 , with the ring gear  4  in turn connected to the lever (not shown) for transmitting the relative movement. 
         [0029]      FIG. 3  shows another embodiment variant of the rotary damper, in which the electric machine  2  and the eddy current brake  3  are arranged in series. The relative movement is again transmitted by a lever to the ring gear  4  of the first planetary gear assembly  1 , whereas for the series arrangement the sun gear  5  of the first planetary gear assembly  1  is connected to the rotor  6  of the electric machine  2  and to a ring gear  12  of a second planetary gear assembly  13 , the second planetary gear assembly  13  being connected downstream from the first planetary gear assembly  12 . A sun gear  14  of the second planetary gear assembly  13  is connected to the drum  7  of the eddy current brake  3 . The planetary carrier  8  of the first planetary gear assembly  1  and the planetary carrier  15  of the second planetary gear assembly  13  are connected to the housing  9 . In this series arrangement the second planetary gear assembly  13  is connected downstream from the first planetary gear assembly  1  provided for the electric machine  2 , and the second planetary gear assembly  13  is functionally connected to the eddy current brake  3 . In contrast to the previous embodiment variants, the magnetic flux for producing the eddy currents for the eddy current brake  3  is produced by permanent magnets  16  attached to the housing  9 . 
         [0030]      FIG. 4  shows a further embodiment variant of the rotary damper, in which the electric machine  2  is arranged with a power-branched eddy current brake  3 . The ring gear  4  of the first planetary gear assembly  1  is again connected to the lever that transmits the relative movement, whereas for the power-branched arrangement the sun gear  5  of the first planetary gear assembly  1  is connected to the ring gear  12  of the second planetary gear assembly  13 . The sun gear  14  of the second planetary gear assembly  13  is connected to the drum  7  of the eddy current brake  3 . The planetary carrier  8  of the first planetary gear assembly  1  is connected to the housing  9 , whereas the planetary carrier  15  of the second planetary gear assembly  13  is connected to the rotor  6  of the electric machine  2 . 
         [0031]    In this type of power-branched arrangement of the electric machine  2  and the eddy current brake  3 , depending on the transmission ratio of the gear assembly the power-branching serves as overload protection for the electric machine  2 . Due to the inertia of the rotor  6  and the planetary gear assemblies  1  and  13  connected upstream from the electric machine  2 , externally introduced accelerations for example in the form of direction changes can block the branch driven by electric motor, so that in such a case the rotary movement is mostly damped by the eddy current brake  3 . 
         [0032]    A further variant of the power-branching is shown in  FIG. 5 . In this embodiment variant of the rotary damper the lever transmitting the relative movement is connected to the ring gear  4  of the first planetary gear assembly  1  and for the power-branched arrangement the sun gear  5  of the first planetary gear assembly  1  is connected to the ring gear  12  of the second planetary gear assembly  13 . The sun gear  14  of the second planetary gear assembly  13  is connected to the drum  7  of the eddy current brake  3 , whereas the planetary carrier or web  8  of the first planetary gear assembly  1  and the planetary carrier or web  15  of the second planetary gear assembly  13  are both connected to the housing  9 . In contrast to the previous embodiment variants, the second planetary gear assembly  13  comprises a double planetary set, wherein the first planetary gearwheels  17  of the double planetary set engage, on the one hand, with the sun gear  14  of the second planetary gear assembly  13  and, on the other hand, with the ring gear  12  of the second planetary gear assembly  13 . The second planetary gearwheels  18  of the double planetary set engage with the rotor  6  of the electric machine  2  which is designed as a ring gear. 
         [0033]      FIGS. 6 and 7  show two embodiment variants of the rotary damper, in which the electric machine  2  is in the form of an external-rotor machine. This type of electric machine  2  has the advantage that the eddy current brake  3  is contained within the rotor arrangement of the electric machine  2 . The stator of the electric machine  2  is arranged on the inside of the rotor  6 . 
         [0034]    In  FIG. 6 , as its rotor  6  and eddy current brake  3 , the electric machine  2  comprises a metallic cylinder, the inside of the cylinder that faces toward the stator being provided with a magnet arrangement and the outside of the cylinder facing toward a magnet arrangement fixed to the housing for producing the eddy currents. In this way the metallic cylinder of the external rotor  6  at the same time forms the eddy current brake  3 , which is located in a magnetic flux by virtue of the magnet arrangement, for example in the form of a permanent magnet  16 , fixed on the housing  9 . 
         [0035]    As in the previous embodiment variants, the lever that transmits the relative movement is connected to the ring gear  4  of the first planetary gear assembly  1 . The sun gear  5  of the first planetary gear assembly  1  is connected to the rotor  6  of the electric machine  6 , whereas the planetary carrier  8  of the first planetary gear assembly  1  is connected to the housing  9 . 
         [0036]    In  FIG. 7  the electric machine  2  and the eddy current brake  3  constitute a multi-component rotor arrangement. The rotor arrangement comprises a metal cylinder  21  and a cylindrical magnet holding arrangement  22 , arranged coaxially with one another with an air-gap between them. The magnetic flux in the rotor arrangement is produced by the metal cylinder  21 , since the metal cylinder  21  and the cylindrical magnet holding arrangement  22  move in opposite directions. 
         [0037]    As with the previous embodiment variants the lever that transmits the relative movement is connected to the ring gear  4  of the first planetary gear assembly  1 , whereas the sun gear  5  of the planetary gear assembly  1  is coupled by way of a rotational-direction-reversing intermediate stage to the metal cylinder  21 . Furthermore, the planetary carrier  8  of the planetary gear assembly  1  is connected to the housing  9 . Since the sun gear  5  is connected to the metal cylinder  21  by way of an intermediate stage, the rotational directions of the metal cylinder  21  and the magnet holding arrangement  22  are different. 
         [0038]    For example, the intermediate stage can be formed by providing a further spur gear on the magnet holding arrangement  22 , which is connected to the sun gear  5  in a rotationally fixed manner. The spur gear  23  engages with an intermediate gearwheel or planetary gear  24  mounted to rotate on the planetary gear shaft. In turn, the intermediate gearwheel  24  meshes with a ring gear  25  provided on the metal cylinder  21 . 
         [0039]      FIG. 8  shows as an example, a cross-section of a stator plate  19  of an eddy current brake  3  with a drum configuration. Around the outer circumference coaxially extending grooves  20  are provided, by which a desired stray flux for the eddy current brake  3  is produced. In the version shown the grooves  20  have for example a V-shaped cross-section. 
         [0040]      FIG. 9  illustrates the physical principle for producing the stray flux by means of the grooves  20  provided, As can be seen from that figure, the magnetic field is correspondingly distorted by each groove  20 . By virtue of the surrounding grooves  20  in the stator sheet  19  the stray flux is produced, since at the edges of each groove  20  north and south poles are formed. 
       INDEXES  
       [0000]    
       
           1  First planetary gear assembly 
           2  Electric machine 
           3  Eddy current brake 
           4  Ring gear of the first planetary gear assembly 
           5  Sun gear of the first planetary gear assembly 
           6  Rotor of the electric machine 
           7  Drum of the eddy current brake 
           8  Planetary carrier of the first planetary gear assembly 
           9  Housing of the rotary damper 
           10 ,  10 A Disk-shaped plates of the eddy current brake 
           11 ,  11 A Ring-disk shaped angled portions 
           12  Ring gear of a second planetary gear assembly 
           13  Second planetary gear assembly 
           14  Sun gear of the second planetary gear assembly 
           15  Planetary carrier of the second planetary gear assembly 
           16  Permanent magnet 
           17  First planetary gearwheels 
           18  Second planetary gearwheels 
           19  Stator plate 
           20  Groove 
           21  Metal cylinder 
           22  Magnet holding arrangement 
           23  Spur gear 
           24  Intermediate gearwheel 
           25  Ring gear 
         N North pole 
         S South pole