WO2008095951A1

WO2008095951A1 - Friction brake having an annular friction surface

Info

Publication number: WO2008095951A1
Application number: PCT/EP2008/051437
Authority: WO
Inventors: Marcus Ziegler
Original assignee: Siemens Aktiengesellschaft
Priority date: 2007-02-07
Filing date: 2008-02-06
Publication date: 2008-08-14
Also published as: DE102007006163A1; DE102007006163B4

Abstract

The invention relates to a friction brake which can be used for a shaft and a bearing part that can be rotated in relation to each other about a rotational axis (3). The friction brake comprises two brake elements: the first brake element has a first friction surface (25) and has to be mechanically connected to the bearing part, and the second brake element has a second friction surface (24) and has to be mechanically connected to the shaft. The connectible and disconnectible magnetic effect of an activatable electromagnetic coil forces the two brake elements against each other during a braking action or stop in such a manner that the two friction surfaces (24, 25) rest one on the other and contact each other in the area of a contact surface. A magnetic flux passes through the contact surface. One of the friction surfaces (24) is in the shape of an annulus that is arranged concentrically to the rotational axis (3). The non-annular friction surface (25) is equal to the contact surface and has an edge with a radial direction component in relation to the rotational axis (3). The annular friction surface (24) is larger than the contact surface.

Description

description

Friction brake with an annular friction surface

The invention relates to a friction brake for a shaft and a receiving part, which are rotatable relative to each other about an axis of rotation, comprising two brake elements, of which the first brake element has a first friction surface and is mechanically connected to the receiving part and the second brake element has a second friction surface and is mechanically connected to the shaft, wherein an actuable electromagnetic coil is provided, whose magnetic force action can be switched on or off the two brake elements during a braking or holding operation against each other so that the two friction surfaces abut each other and touch each other in the region of a contact surface, a magnetic flux passes through the contact surface and one of the two friction surfaces has the shape of a concentric with the axis of rotation arranged annulus.

Such a friction brake is known for example from DE 100 46 903 C2. It is an emergency stop or holding brake of an electric drive. The opposing friction surfaces of this friction brake are the same size and both circular. They each form in their entirety the given during the braking / holding contact surface. On the one hand, the latter should not be too large in order to maximize the magnetic flux density that passes through here, and thus the achievable magnetic holding force. On the other hand, the largest possible area is desirable for heat dissipation. The always in practice in this regard compromise can lead to a heat accumulation at the friction surfaces, especially in strong or long braking operations. As a result of the resulting overheating, a reduced braking or holding effect may occur. The object of the invention is to provide a friction brake of the type described, which works reliably even during heavy or long braking.

This problem is solved by the features of independent claim 1. The friction brake according to the invention is characterized in that the non-annular friction surface is equal to the contact surface and has an edge with respect to the axis of rotation radial direction component and the annular friction surface is greater than the contact surface ,

In the friction brake according to the invention, the contact surface is advantageously always only a partial surface of the larger annular friction surface. The contact surface itself remains during the braking / holding process, in particular always the same size. It is preferably the same size as the other, that is, the non-annular friction surface. However, the contact surface changes with the relative movement of the two friction surfaces against each other in particular their position relative to the larger annular friction surface.

As a result, the resulting frictional heat is distributed over the larger annular friction surface compared to the contact surface. There results a lower energy density, so that the influence of temperature makes less noticeable. Especially in the case of short but strong braking processes, adiabatic conditions can occur in which the entire heat energy arising at the contact surface collects on the friction surfaces. The heat capacity of the involved components of the brake elements plays a minor role. On the other hand, the conditions on the friction surfaces are decisive.

Due to the larger available friction surface and, since in the friction brake according to the invention the contact surface moves together with the non-annular friction surface over the larger annular friction surface, it occurs neither at all or only at much stronger braking loads to the otherwise at a constant contact surface impending heat accumulation between the two friction surfaces. In the friction brake according to the invention, a larger area is involved in the friction process. This reduces the overall increase in temperature due to the frictional heat. The lower temperatures maintain a high braking force when using the currently common brake materials and also lead to less wear.

In addition, the medium surrounding the friction brake, e.g. Air, the areas of the annular friction surface cool, just do not form the contact surface. This also contributes to the comparatively low operating temperatures. The areas of the annular friction surface currently not involved in the braking process are in particular freely accessible and are thus cooled. At another time, however, these areas also contribute to the braking process again. During a relative rotation through 360 ° between the two friction surfaces, each region of the larger annular friction surface is preferably at least once part of the contact surface.

On the other hand, the larger annular friction surface that is particularly favorable in terms of temperature does not lead to a deterioration of the magnetic flux relationships and the achievable magnetic holding force, since in this respect the entire larger friction surface does not depend on the contact surface. The latter can be designed by appropriate dimensioning of the smaller non-annular friction surface so that magnetic saturation occurs and thus the magnetic flux density passing through the contact surface is particularly high.

Due to the provided on the non-annular friction surface edge with the radial direction component, a certain self-cleaning effect is achieved in two congruent annular friction surfaces according to the state the technology is impossible. Dirt and / or wear particles are carried away by the edge with the radial direction component of the area of the friction surfaces.

With the friction brake according to the invention can be in

Circumferentially reach substantially constant braking torque. This applies in particular if the contact surface is arranged symmetrically or evenly distributed on the annular larger friction surface in a direction tangential to the axis of rotation (= circumferential direction).

The friction brake according to the invention can be used in various applications, for example, in an electric drive. In addition to the actuatable electromagnetic coil, it may preferably also comprise other magnetic components, such as e.g. a permanent magnet integrated in particular in one of the two brake elements.

Advantageous embodiments of the friction brake according to the invention will become apparent from the features of the dependent claims of claim 1.

A variant in which at least one of the two friction surfaces is composed of a plurality of mutually separate partial friction surfaces is favorable. This favors the self-cleaning additionally.

Furthermore, the non-annular friction surface can preferably be composed of a plurality of strip-shaped partial friction surfaces distributed uniformly in a circumferential direction relative to the axis of rotation. This geometry shape is simple. It can be easily manufactured.

According to another preferred variant, the strip-shaped partial friction surfaces are each directed radially outward, resulting in a particularly good ventilation and cooling of the friction surface (s). This effect is further increased by the strip-shaped partial friction surfaces are in particular each inclined relative to the radial direction. In addition, this also has a favorable effect on self-cleaning. Dirt particles are then removed from the friction surfaces particularly effectively.

Preferably, in addition, the strip-shaped partial friction surfaces are each bent, in particular as circular ring segments. So you have, for example, the cross-sectional shape of a fan or grand piano. This results in further advantages in terms of cooling.

In a further advantageous embodiment, the non-annular friction surface on a closed strip shape, which results from a superposition of a circular function with a sine function. It then has e.g. the shape of a rounded polygon or a circular ring with symmetrically distributed indentations and indentations. In particular, it is possible for three bulges and indentations to be distributed in alternating sequence over the circumference of the circumference.

Also favorable is a variant in which the first brake element has a first and a second magnetic pole which are formed by mutually separate partial friction surfaces of the multi-part first friction surface. In particular, the magnetic circuit of a permanently excited and electromagnetically operated friction brake can be realized particularly easily.

Advantageously, it is also provided that each magnetic pole at least two Teilreibflächen are assigned and alternate the two magnetic poles respectively associated Teilreibflächen in the circumferential direction. The magnetic flux between adjacent partial friction surfaces, which are each assigned to a different magnetic pole, then closes in particular tangentially over the larger annular friction surface of the other friction element. The river only has the NEN gap formed between the adjacent partial friction, for which during the braking / holding operation also the pressed-on other friction element is available. Another gap as in the prior art is eliminated.

According to a further advantageous embodiment, the part friction surfaces are arranged at the same distance from the axis of rotation. There is then only an effective radius for the resulting brake torque, so that always the same conditions are guaranteed. In addition, in this embodiment, the magnetic flux between adjacent Teilreibflächen closes tangentially.

Preferably, it is also possible for each magnetic pole to have a claw which surrounds its associated partial friction surfaces and for the two claws to engage in contact with one another in the region of the partial friction surfaces. Each of the claws creates a mechanical and also magnetic connection between the partial friction surfaces belonging to the respective magnetic pole, in particular beyond the plane of the partial friction surfaces. As a result, despite the various partial friction surfaces, only a very small number of required individual components results. The assembly is thus simplified.

Further features, advantages and details of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing. It shows:

1 and 2 show two embodiments of friction brakes with a formed between two friction surfaces

Contact surface and with one or two contacting magnetic poles,

3 shows two different sized one-piece friction surfaces of a friction brake with a contacting magnetic pole,

4 and 5 an annular larger friction surface and a multi-part smaller friction surface of a friction exercise brake with a contacting magnetic pole,

6 shows an annular larger friction surface and a two-part smaller friction surface of a friction brake with two contacting magnetic poles,

7 and 8 two different sized each multipart

9 shows a brake element with a multi-part friction surface of a friction brake with two contacting within a common circumferential zone magnetic poles and

FIGS. 10 and 11 show two exemplary embodiments of the arrangement of the two magnetic poles of the braking element according to FIG. 9, which are distributed in the peripheral zone and which are formed by partial friction surfaces.

Corresponding parts are provided in FIGS. 1 to 11 with the same reference numerals.

1 shows an embodiment of a permanently magnetically excited and electromagnetically actuated friction brake 1 for an electric drive 2 in the form of an electric motor. The drive 2 comprises one around a

Rotary axis 3 rotatably driven shaft 4, which is rotatably supported by means of a bearing 5 in a stator 6 of the drive 2 shown only schematically and partially.

The friction brake 1 consists essentially of two

Brake elements 7 and 8 together, of which the first brake element 7 comprises a Außenpol body 9, a permanent magnet 10, an inner pole body 11 and arranged between the Außenpol- body 9 and the inner pole body 11 electrically switched on and off solenoid 12 , The outer pole body 9 and the inner pole body 11 each have, as the main component, a cylinder arranged concentrically with the axis of rotation 3, wherein a radius R2 of the cylinder of the outer pole body pers 9 is greater than a radius Rl of the cylinder of the Innenpol body 11. The first brake element 7 is mechanically fixed by means of a mounting or connecting flange of the inner pole body 11 with the stator 6 and thus also with the bearing 5. At axial end faces of Außenpol- body 9 and the inner pole body 11 each have a Teilreibfläche 13 and 14, which together form the friction surface 15 of the first brake element 7.

The second brake element 8 is designed as an anchor plate or yoke. It is by means of a spring mechanism 16 and a holding body 17 only shown schematically against rotation with the shaft 4 and thus also connected to a rotor of the electric drive 2 not shown in detail. This connection permits axial movement in the direction of the axis of rotation 3 and relative to the shaft 4. The spring mechanism 16 is designed, for example, as a flat spring. At the front side facing the first brake element 7, the second brake element 8 has an annular friction surface 18.

The operation of the friction brake 1 will be described below.

The permanent magnet 10 generates a magnetic field which emerges perpendicularly from the outer pole body 9 or inner pole body 11 at the partial friction surfaces 13 and 14. Magnetic poles are thus formed on the partial friction surfaces 13 and 14. The magnetic field exiting here causes magnetic attraction forces acting in the axial direction on the yoke of the second brake element 8. When the solenoid 12 is de-energized, the yoke of the second brake element 8 is pressed with its friction surface 18 against the partial friction surfaces 13 and 14 of the first brake element 7 because of these attractive forces.

Between the two brake elements 7 and 8 then arise in FIG 1 unspecified contact surfaces, the same size and location of the Teilreibflächen 13 and 14. In the friction brake 1, the contact between the participating Ligten friction surfaces 15 and 18 so instead of exactly at the location of the two formed by the Teilreibflächen 13 and 14 magnetic poles.

Due to the contact pressure between the friction surfaces 15 and 18 of the two brake elements 7 and 8 results in frictional forces, which in dependence on the location of your point of attack, ie in particular approximately at a distance Rl and R2 from the rotation axis 3, cause a braking torque.

In contrast, if current flows through the magnetic coil 12, a coil magnetic field which counteracts the magnetic field of the permanent magnet 10 is generated. The two magnetic fields essentially cancel each other out. The spring force of the spring mechanism 16 then pulls the yoke of the second brake element 8 away from the first brake element 7, so that an axial gap 19 is created between the friction surfaces 15 and 18 and no braking effect is given.

A further embodiment shown in FIG. 2 of a permanent magnetically excited and electromagnetically actuated friction brake 20 has a similar structure to the friction brake 1. An essential difference is that the yoke of the second brake element 8 only has the partial friction surface 13 of the outer pole body 9 during the braking process , so only one magnetic pole, contacted. The friction brake 20 thus has at its first brake element 7 only a one-piece friction surface 21, which is formed exclusively by the Teilreibfläche 13. The latter again determines the contact surface to the yoke of the second brake element 8 during the braking process.

The first brake element 7 has a slightly modified inner pole body 22, whose cylinder is slightly longer than in the friction brake 1 and extends into a central recess of the yoke of the second brake element 8. Between the cylinder end extending into the recess and the yoke of the second brake element 8 is a radial gap 23 is provided, which is to be bridged by the magnetic flux in both the braked and unbraked state.

On the other hand, the brake torque behavior improves because instead of the two effective radii Rl and R2 only the outer radius R2 is decisive. As a result, fluctuations in the brake torque, which otherwise occur due to a different removal of material at the surfaces defined by the two radii R1 and R2, that is to say at the partial friction surfaces 13 and 14, can be avoided.

In Figures 1 and 2, the friction surfaces 15, 18 and 21 and the Teilreibflächen 13 and 14 are indicated only schematically. They can take different forms. Exemplary embodiments of this are shown in FIGS. 3 to 8.

In the embodiments shown in Figures 3 to 8 for combinations of friction surfaces of the first and second brake element 7 and 8, the two friction surfaces are always different in size. So you have a different total area. The larger friction surface is in particular circular. At the same time, the smaller friction surface is shaped such that a contact surface formed between the two friction surfaces during the braking operation covers all areas of the larger friction surface when the two friction surfaces are rotated once around the rotation axis 3 relative to one another. For this purpose, the smaller friction surface has an edge or at least one edge region with a radial direction component which differs from zero relative to the rotation axis 3.

With such friction surfaces results in a very favorable temperature behavior, since the areas of the larger friction surface, which just do not contribute to contacting the smaller friction surface, can radiate heat. Due to this cooling, the temperature is kept at a lower level. This is advantageous for the braking effect. Here, a friction surface is understood as meaning an area of the first or the second friction element 7 or 8, which may in principle be involved in the friction during a braking operation. This may be a single contiguous surface or a plurality of partial surfaces separated from one another at least in the friction plane. Beyond the friction plane, however, the areas forming the partial surfaces can also be connected to one another mechanically. By contrast, the instantaneous intersection of the friction surfaces of the first or second friction element 7 or 8 is understood as the contact surface. While the friction surfaces are given by the chosen design and also remain unchanged, the contact surface generally changes its position relative to the larger annular friction surface during a braking operation. The contact surface is always equal to the smaller friction surface in the embodiments shown in Figures 3 to 8.

The size of the contact surface of the respective friction brake results from the requirements of the contact force between the two brake elements 7 and 8. To increase the heat dissipation, the larger annular friction surface can be further increased, while at the same time the contact surface and thus the contact pressure and the braking effect to change.

In FIG. 3, a combination of an annular friction surface 24 of the yoke of the second brake element 8 with a closed, non-annular, smaller friction surface 25 of the outer pole body 9 is comparable to a friction brake as shown in FIG. In this example, therefore, only one magnetic pole is contacted during a braking / holding operation. The friction surface 25, which has a smaller strip width than the friction surface 24, is formed by a superposition of a circular ring shape with a sinusoidal shape. Distributed uniformly over the circumferential length, a total of three sine periods are provided. The three protrusions 26 of the friction surface 25 thus formed extend, in particular, as far as the outer circumference of the larger friction surface 24, whereas the indentations 27 extend in particular to the inner circumference of the friction surface 24. CKEN. The friction surface 25 in the embodiment has approximately the shape of a rounded triangle.

In FIGS. 4 and 5, combinations of the annular friction surface 24 with a multi-part friction surface 28 or 29 of the outer-pole body 9 are comparable to a friction brake as shown in FIG. The friction surfaces 28 and 29 are each composed of a plurality of (in the example six) strip-shaped partial friction surfaces 30 and 31 arranged uniformly distributed in the circumferential direction. The latter can be formed, for example, by axially projecting strip-shaped webs on the axial end face of the outer pole body 9.

In friction surface 28, partial friction surfaces 30 are straight, radially outwardly extending strip segments which cover the annular width of friction surface 24. The partial friction surfaces 30 are arranged in a star shape.

In the friction surface 29, the part friction surfaces 31 are also outwardly extending strip segments, which, however, have a convexity directed outward (i.e., toward the outer periphery of the friction surface 24) and an inclination with respect to the radial direction. They are shaped in the manner of a fan or wing cross-section. The partial friction surfaces 31 also cover the full annular width of the friction surface 24.

The subdivision of the friction surfaces 28 and 29 in the Teilreibflächen 30 and 31 causes a rotational movement of the yoke of the second brake element 8, an additional cooling of the friction surface 24. The special shape of Teilreibflächen 30 and 31 favors an additional air supply, as it also from a fan is caused.

In FIGS. 6 to 8, combinations of friction surfaces of a friction brake are comparable to those shown in FIG. During the braking / holding process, therefore, both the outer pole body 9 and the inner pole body 11 are involved in contacting the yoke of the second braking element 8. In the combination according to FIG. 6, in addition to the friction surface 24, a friction surface 32 assigned to the first brake element 7 is provided with two closed non-annular partial friction surfaces 33 and 34. The partial friction surfaces 33 and 34 each have a shape comparable to that of the friction surface 25 according to FIG. 3. The partial friction surface 34 of the inner pole body 11 is placed completely within the partial friction surface 33 of the outer pole body 9.

In the combination according to FIG. 7, both friction surfaces are segmented. This also applies in particular to the yoke of the second friction element 8, which has a segmented friction surface 35 with curved part friction surfaces 36 comparable to those of the friction surface 29 according to FIG. In this exemplary embodiment, the first brake element 7 has a two-part friction surface 37 with annular friction surfaces 38 and 39 provided on the outer pole body 9 and on the inner pole body 11. Here, therefore, the friction surface 37 of the first friction element 7 is larger than the friction surface 35 of the second friction element 8th.

The combination according to FIG. 8 is a mixed form of the combinations according to FIGS. 5 and 7. The outer pole body 9 and the inner pole body 11 are provided with a multi-part friction surface 40 with curved partial friction surfaces 41 and 42, respectively. The latter are each formed as subregions of the strip-shaped curved partial friction surfaces 31 according to FIG. Due to the embodiment with two magnetic poles, each of the partial friction surfaces 31 is divided into the outer partial friction surface 41 and the inner partial friction surface 42 by removing an intermediate region. A friction surface 43 of the yoke of the second brake element 8 is in the embodiment of FIG 8 also in two parts with two annular Teilreibflächen 44 and 45 executed. Alternatively, however, the single-part annular friction part 24 could just as well be used.

The friction surfaces 25, 29, 32, 35 and 40 according to FIG 3, 5, 6, 7 and 8 differ in their shape from a purely radial or purely tangential shape. This favors a self-cleaning cleaning effect. Dirt particles are picked up during a rotational movement and conveyed to the outer edge and thus out of the area of the friction surfaces.

In FIG. 9, a section, namely a modified first brake element 47, is shown in a perspective view from a further exemplary embodiment of a friction brake 46. In addition, the friction brake 46 also contains a second brake element 8 in a yoke shape, not illustrated in FIG. 9, and in particular with an annular friction surface comparable to the friction surface 24.

In the case of the friction brake 46, two magnetic poles are involved in the friction contact during the braking process, these two magnetic poles, unlike the friction brake 1 according to FIG. 1, being arranged within a common circumferential zone 48. The distance of this peripheral zone 48 from the axis of rotation 3 is given by the radius R2.

In the case of the first brake element 47, the outer pole body is claw-shaped in the region of the one axial end side. It represents in the embodiment of FIG 9, a Außenpol- claw 49 with circumferentially uniformly distributed axially projecting annular segments 50, wherein between adjacent circular ring segments 50 each have a recess 51 is provided.

On the inner pole body 11, an inner pole claw 53 provided with claw arms 52 is placed on this axial end side. Each of the claw arms 52 extends into one of the recesses 51 without touching the outside pole claw 49. The inner pole claw 53 and the outer pole claw 49 thus engage with each other without contact. At the ends of the jaw arms 52 placed in the recesses 51, as well as on the circular ring segments 50, axially projecting webs are arranged within the peripheral zone 48. Their axial surfaces form a multipart friction surface 56 of the first brake element 47. The part friction surfaces 54 are assigned to the outer pole and the part friction surfaces 55 to the inner pole.

The part friction surfaces 54 and 55 at the same time determine the given during a braking / holding operation contact surface with the yoke of the second brake element 8, not shown in FIG 9.

The braking / holding forces thus arise only in the peripheral zone 48. So there is essentially only a single effective for the braking radius, namely the radius R2, before. This ensures a constant brake torque behavior over a longer period of operation.

During a braking / holding operation, a magnetic flux 57 between the inner pole and the outer pole terminates tangentially via the yoke of the second brake element 8 in the frictional brake 46. This differs from the exemplary embodiments according to FIGS. 1 to 8, in which this conclusion of FIG Magnet flux in the radial and / or axial direction takes place. The tangential termination 58 of the magnetic flux 57 within the

Yoke of the second braking element 8 is indicated in FIG 9 by a slightly stronger line thickness.

As a result of the gaps present in the tangential direction between the circular ring segments 50 and the ends of the claw arms 52 engaging in the recesses 51, the contact surface also changes in the case of the friction brake 46 with respect to the larger annular friction surface 24 (not shown in FIG. 9) during a braking operation. In the area of the tangential gap, the heat can then be dissipated so that an advantageous cooling of the friction surfaces 56 and 24 takes place.

In the exemplary embodiment according to FIG. 9, the webs forming the part friction surfaces 54 and 55 each have the shape of a circular ring segment. In principle, however, other forms are possible. Alternative embodiments are shown in FIGS. 10 and 11. In the embodiment according to FIG. 10, partial friction surfaces 59 assigned to the outer pole and partial friction surfaces 60 assigned to the inner pole are provided, which extend radially outward within the common circumferential zone 48 in each case as straight strip segments. The radial outer ends of the Teilreibflächen 59 and 60 are rounded.

In the embodiment according to FIG. 11, partial friction surfaces 61 assigned to the outer pole and partial friction surfaces 62 assigned to the inner pole are provided which extend outwardly within the common circumferential zone 48 as straight strip segments and inclined relative to the radial direction. The inclination favors self-cleaning of the involved friction surfaces of dirt particles.

To support the cooling effect, the yoke of the second brake element 8 may have a fan wheel structure in all of the above exemplary embodiments on a side remote from the friction surface. In addition, the respective friction brake may preferably be arranged in the region of a winding head of an electrical winding provided in the stator 6 of the electric drive 2. Then, the cooling effect achieved on account of the special refinements of the friction brakes can at the same time also be used for cooling the otherwise usually uncooled winding head.

The brake according to the invention can also be used in automotive technology for braking trucks, cars and two-wheeled vehicles.

Claims

claims

A friction brake for a shaft (4) and a receiving part (5, 6) which are rotatable relative to one another about a rotation axis (3), comprising two brake elements (7, 8, 47), a) of which the first brake element (7 47) has a first friction surface (15; 21; 25; 28; 29; 32; 37; 40; 56) and is mechanically connected to the receiving part (5,6) and the second brake element (8) has a second friction surface (15). 18, 24, 35, 43) and is to be mechanically connected to the shaft (4), b) an actuatable electromagnetic coil (12) is provided whose magnetic force action can be switched on or off the two brake elements (7, 8; 47) during a braking or holding process pressed against each other so that the two

Friction surfaces (15, 18, 21, 24, 25, 28, 29, 32, 35, 37, 40, 43, 56) abut one another and touch each other in the area of a contact surface, c) a magnetic flux (57) through the contact surface - Passing through and d) one of the two friction surfaces (24, 37, 43) has the shape of a concentric with the axis of rotation (3) arranged circular ring, characterized in that e) the non-annular friction surface (25, 28, 29, 32, 35; 40; 56) is equal to the contact surface and has an edge with a radial direction component relative to the axis of rotation (3), and f) the annular friction surface (24; 37; 43) is larger than the contact surface.

2. Friction brake according to claim 1, characterized in that at least one of the two friction surfaces (15, 28, 29, 32, 35, 37, 40, 43, 56) consists of a plurality of mutually separate partial friction surfaces (13, 14, 30, 31; 33, 34, 36, 38, 39, 41, 42, 44, 45, 54, 55, 59, 60, 61, 62).

3. Friction brake according to claim 1, characterized in that the non-annular friction surface (28; 29; 35; 40; 56) comprises a plurality of strip-shaped partial friction surfaces (30; 31; 36; 41; 42; 54,55; 59,60; 61,62) distributed uniformly in a circumferential direction relative to the rotational axis (3) ).

4. friction brake according to claim 3, characterized in that the strip-shaped Teilreibflächen (30; 59,60) are each directed radially outward.

5. Friction brake according to claim 3, characterized in that the strip-shaped Teilreibflächen (31; 36; 41, 42; 61, 62) are each inclined relative to the radial direction.

6. Friction brake according to claim 3, characterized in that the strip-shaped partial friction surfaces (31; 36; 41, 42) are each bent, in particular as circular ring segments.

7. friction brake according to claim 1, characterized in that the non-annular friction surface (25; 33,34) has a closed strip shape, which results from a superimposition of a circular function with a sine function.

8. Friction brake according to claim 1, characterized in that the first brake element (7; 47) has a first and a second magnetic pole, which by separated Teilreibflächen (13, 14, 33, 34, 38, 39, 41, 42; , 55; 59, 60; 61, 62) of the multi-part first friction surface (15; 32; 37; 40; 56) are formed.

9. Friction brake according to claim 8, characterized in that each magnetic pole at least two Teilreib- surfaces (41, 42; 54, 55; 59, 60; 61, 62) are assigned and the two magnetic poles respectively associated Teilreibflächen (41, 42 54, 55, 59, 60, 61, 62) in the circumferential direction.

10. Friction brake according to claim 8, characterized in that the Teilreibflächen (54, 55; 59, 60; 61, 62) are arranged at the same distance from the axis of rotation (3).

11. Friction brake according to claim 8, characterized in that each magnetic pole has a part of its friction surfaces (54, 55; 59, 60; 61, 62) comprehensive claw (49,53) and the two claws (49,53) in the area the Teilreibflä ^¬ Chen (54, 55, 59, 60, 61, 62) contact each other without contact.