DE19831838A1 - Vehicle disc brake equipment - Google Patents

Abstract

An electric motor drives a threaded spindle (2) to press the brake lining plate (39) against the brake disc. The drive force is transferred through a linkage system (45, 48, 50, 55) which is independent of the spindle. Alternatively the recirculating ball nut and the spindle forming the drive system can be matched in respect of their stiffness so that the load is spread evenly over several threads.

Description

The invention relates to a braking device for a Vehicle, with a brake disc, with one rotating part to be braked is connected, a brake pad plate having a brake pad, the arranged with their brake lining facing the brake disc is, an actuator that actuates an electric motor has a threaded spindle to counter the brake pad plate to press the brake disc.

Such a braking device is from DE 40 21 572 A1 known. This braking device has a hollow piston in which a rotary shaft is mounted, the rotary shaft is designed as a ball screw with which a Rotational movement in a sliding movement of the piston can be converted. The rotating shaft is over a Worm gear driven by an electric motor.

The outside of the piston is flattened on two sides and on these surfaces by means of plain bearings on the housing, so that it is secured against twisting. In addition, the  Piston mounted on the housing by means of linear ball bearings, which the Minimize frictional forces when moving the piston should.

Basically applies to braking devices that they for Generate sufficient braking power with a short Actuation path a high actuation force for pressing a Brake pad must be transferred against a brake disc. For an electromechanical braking device means that a considerable moment of force in the conversion of the Electric motor generated rotary motion in a translational Movement to generate the clamping force provided must become.

When using a ball screw, the maximum is transferable clamping force due to geometrical dimensions and Limited number of supporting balls. At electromechanical braking devices is therefore a Roller screw drive instead of a ball screw drive used because the roller screw drive with the same installation space can transmit a significantly greater clamping force. Of the Efficiency of a roller screw drive with feedback is however much lower than that of one Ball screw drive. Electromechanical braking devices are therefore either with a roller screw and a correspondingly large electric motor to compensate for the trained low efficiency and can  Provide the required clamping force, or have one Ball screw drive and a correspondingly small one Electric motor, but then often can not provide the required clamping force. There is therefore a considerable need for a braking device with high Clamping force and high efficiency, that means after one compact braking device with a relatively small electric motor, the desired clamping force is nevertheless generated should be able to.

Furthermore, the one hand during a braking operation Brake pad plates taken a bit, on the other hand widened the brake disc overlapping fist, causing shear forces on the Threaded spindle are transmitted. This leads to a Deterioration of the mechanical efficiency of the Geared screw.

There are also electromechanical braking devices have been developed in which the brake pad plate by means of a pressure piece and a bellows with the spindle connected is. Through the bellows and the pressure piece that keeps the bending moment away from the spindle. Of the Bellows means a restriction in the selection of the gear for converting the rotary movement of the Electric motor in a translational movement of the spindle Actuation of the brake pad plate in that the slope  the spindle must not exceed a certain dimension, thus the bellows with the maximum occurring Spindle torque is not overloaded.

The invention is based on the object at the outset called braking device for a vehicle so on form that they are still high in a compact design Can provide clamping force.

The task is performed by a braking device with the Features of claim 1 and a braking device with the Features of claim 12 solved. Beneficial Embodiments of the invention are in the subclaims specified.

The solution according to claim 1 provides means for managing the Brake pad plate before, the means for guiding the Brake pad plate independent of the threaded spindle are formed so that during a braking operation the transverse loads occurring on the threaded spindle are reduced become. By reducing the cross loads, the Efficiency for converting a rotary movement of the Electric motor in a translational movement of the thread spindle increased, so that a compact electric motor for Generation of the necessary clamping force is sufficient. This allows again a compact design of the braking device, with all mechanical requirements regarding the clamping force  and the response behavior can be met.

The solution according to claim 12 provides a special sphere nut to actuate the ball screw, the on the load entry side has a lower rigidity than in remaining area. This will put the load on distributed multiple threads, making the one of such trained ball screw also generated clamping force very high requirements of braking devices heavier Vehicles are enough.

The invention is illustrated below by way of example attached drawings explained in more detail. Show it:

Fig. 1 shows a portion of a brake device according to the invention with regardless of a threaded spindle for actuating a brake lining plate formed guide means in a perspective view;

Fig. 2a schematically shows a horizontal section through the braking device of Fig. 1,

Fig. 2b schematically shows a vertical section through the braking device of Fig. 1,

Fig. 3, the brake pad plate of the brake device according to Fig. 1 in front view, along with guide pins,

Fig. 4 shows another embodiment of the braking device according to the invention with trained independently by the threaded spindle guide means,

Fig. 5 shows a further brake device according to the invention with trained independently by the threaded spindle guide means,

FIG. 6a, the pressure plate of the brake device of Fig. 1 together with two guide pins and a threaded spindle,

Fig. 6b a section through the pressure plate along the line AA in Fig. 6a,

Fig. 7 shows a further brake device according to the invention with trained independently by the threaded spindle guide means,

Fig. 8 is a vertical section through a braking device,

Fig. 9, the braking device shown in Fig. 8 in side view,

Fig. 10 shows schematically a plan view of the brake device shown in Fig. 8,

Fig. 11 schematically shows a conventional ball screw in longitudinal section together with a graphical representation of the load distribution,

Fig. 12 is a ball screw according to the invention in longitudinal section along with a graphical representation of the load distribution,

Fig. 13a and 13b each show a section through a conventional ball screw, and

Fig. 14a and 14b each show a section through an inventive ball screw.

The braking device according to the invention has a housing 1 , in which an electromechanical converter device (actuator) for actuating a ball screw 2 is provided ( FIGS. 1, 8). A fist 6 consisting of a bridge 4 and a clamping arm 5 is arranged on the housing and engages around the edge region of a brake disk 8 . The housing 1 and the fist 6 are connected to one another by means of a flexurally and torsionally rigid, thin-walled sheet metal ring 7 .

The electromechanical converter device or the actuator has an electric motor which is formed from a winding 10 , which forms the stator, and from a rotor 12 . The rotor is tubular, the armature 11 being attached to its outer surface. The tubular rotor is arranged within the magnet 10 , a needle bearing or a ball bearing 13 being provided at both ends of the armature 11 between the rotor and the stator formed from the magnet 10 and the housing 1 , so that between the rotor and the stator a predetermined air gap 14 is always maintained. The tubular base body 12 is bent outwards at its end facing away from the brake disc 8 , the offset being designed as a toothed wheel 15 . The gear wheel 15 is in engagement with the drive side of a planetary gear 17 arranged on the housing 1 . The planetary gear 17 is designed as a one or two-stage reduction gear. The output side of the planetary gear 17 forms an annular disk 18 which is connected to a tubular rotating body 21 via a bellows 19 . The bellows 19 is flexible, but torsionally rigid, so that it transmits the rotational movement of the annular disc 18 directly to the tubular rotating body 21 .

The tubular rotating body 21 is connected with its end facing the brake disc 8 in a rotationally fixed manner to a ball nut 23 . The ball nut 23 is cranked radially outwards at its front edge area facing the brake disc 8 . This offset 24 is gripped by a rotary body of the fist 6 which extends in a step-like manner in cross section into the region between the tubular rotary body 21 and the base body 12 of the rotor. This rotary body has a ring segment 25 arranged on the side of the crank 24 of the ball nut that faces away from the brake disc, an axial ball bearing 27 between this ring segment 25 and the crank 24 and a radial one between the inwardly facing end face of the ring segment 25 and the main body of the ball nut 23 Fixing ball bearings 28 are arranged. The radial fixing ball bearing 28 is preferably located in the area of the longitudinal center of the ball nut 23 . The ball nut 23 sits on the ball screw 2 with a set of balls 30 .

The ball screw 2 has on its end facing the brake disc a central, elongated recess 32 in which a bolt-shaped pressure piece 33 is loosely inserted, which is rounded at both end regions and plate 35 is clamped between the bottom of the recess 32 and a pressure. In the peripheral region of the brake disc 8 facing end face of the ball screw 2, the ball screw 2 is elastically bendable with the pressure plate 35, but torsionally connected by a further bellows 37th The pressure piece 33 holds the pressure plate 35 and the ball screw 2 at a predetermined distance, the pressure plate 35 being able to be pivoted about the loosely inserted pressure piece 33 .

The pressure plate 35 is preferably designed as a so-called point load / uniform distance load converter plate (PGKP), that is to say that the shape is designed in such a way that the pressure force exerted by the pressure piece 33 on the pressure plate 35 and applied at one point evenly points to a pressure point toward the brake disc 8 Printing area 36 is transferred. The shape of the pressure plate 35 is determined by means of a finite element calculation, a shape with a concave curvature rising from the outside toward the center generally resulting on the side facing away from the brake disc 8 and a dent formed in the center of the pressure plate 35 is in which the pressure piece 33 is stored. A brake pad plate or brake pad back plate 39 is releasably attached to the pressure surface 36 , on which a brake pad 40 is fastened. In a pressure plate 35 formed out as a PGKP, a thin brake pad plate 39 can be used. The brake pad plate 39 is a wear part to be replaced together with the respective brake pad 40 , which is why considerable costs can be saved with a thin brake pad plate.

A further brake pad plate 39 'with a brake pad 40 ' facing the brake disk 8 is attached to the clamping arm 5 of the fist 6 and is fastened, for example, by means of a screw 42 .

By providing the bellows 19 between the annular disk 18 and the rotating body 19 , the actuator containing the electric motor is decoupled from the structural deformation that occurs during braking. In the long run, this allows the electric motor to function precisely and, in particular, to maintain a permanently narrow air gap between the rotor and the stator.

In Fig. 1 is a perspective view of the housing and the sliding mechanism of the housing-side brake lining is shown. On the outside of the housing 1 , two guide grooves 45 are formed, each of which is delimited by two wall strips 46 projecting outwards from the housing. The guide grooves 45 run parallel to the ball screw and are arranged approximately at the same height as the ball screw 2 . Two guide bolts 48 are formed on the end face of the housing 1 facing the brake lining 40 . The guide bolts 48 are in turn arranged parallel to the ball screw. They are formed on the housing adjacent to the guide grooves 45 , with their height position of the middle between the two conversion strips 46 corresponding to the guide grooves 45 .

The brake pad plate is provided with two guide brackets 50 which are arranged at the level of the guide grooves 45 and are connected to the brake pad plate 39 at a right angle. The guide brackets 50 essentially consist of a strip-shaped wall part which is angled at a distance from the brake lining plate 39 in two steps in a right angle. The guide bracket 50 thus has a short connection section 52 , which is directly connected to the brake lining plate 39 at a right angle, a short tangential guide section 53 adjoining it at a right angle, and a long radial guide section 54 . At the tangential guide section 53 , a guide hole 55 is made through which one of the guide bolts 48 extends. The radial guide section 54 is located at least in some areas in one of the guide grooves 45 and preferably has nipples which project upwards or downwards along its longitudinal edges and bear directly against the wall strips 46 of the guide groove 45 . These nipples 56 prevent the guide brackets from becoming stuck in the guide grooves 45 in the event of corrosion.

The guide bracket 50 are thus slidably supported by the radial guide portions 54 in the guide grooves 45 , wherein they can not move up or down with respect to the housing 1 . This means that the brake pad plate 39 and thus the brake pad 40 is guided in the horizontal direction, so that the position of the brake pad 40 in the radial direction with respect to the brake disc 8 is clearly defined. With the Radialführungsab cut 54 , the radial position of the brake pad 40 with respect to the brake disc 8 is thus determined.

The guide bolts 48 sit with little play with respect to the tangential direction of the brake disc 8 in the guide holes 55 of the guide bracket 50 ( FIG. 3), so that the lining is pulled up to a circumferential force which corresponds to a deceleration of z = 0.2 the guide bracket 50 is supported only when this circumferential force is exceeded on the respective guide bolts 48 opposite in the circumferential direction.

The tangential guide section 53 is arranged with respect to the brake lining plate 39 offset in the direction of the housing 1 . This offset corresponds at least to the thickness of an unused brake pad 40 and ensures that when the brake device is readjusted due to the pad wear, the engagement between the guide pin 48 and the guide holes 55 is ensured even with heavily worn brake pads.

In the braking device according to the invention, the brake pad plate 39 and the brake pad 40 attached to it are guided independently of the ball screw 2 by the guide bracket 50 in both the tangential and radial directions with respect to the brake disc 8 . As a result, the transverse forces occurring during braking are not transmitted to the ball screw 2 or at least greatly reduced. As these lateral forces are kept away from the ball screw 2, the formed of the ball screw 2, the ball nut 23 and the interposed balls 30 ball screw drive always operates in the ideal efficiency range, sufficient whereby a relatively small drive unit, in order to provide a sufficient clamping force is available.

FIG. 4 shows a further embodiment of the brake device according to the invention, which in turn has two guide brackets 50 , which, however, are not formed on a brake pad plate but on the pressure plate. This is advantageous because if the brake lining wears, only the brake lining 40 has to be replaced together with the brake lining plate 39 , the guide brackets 50 remaining in their arrangement on the braking device.

A further embodiment in which the guide means are arranged directly on the pressure plate 35 is shown in FIG. 5. The guide means in this case have guide bolts 60 , each of which is fastened at one end to the pressure plate 35 and at its other end in a guide bush 61 formed on the housing 1 . The guide bushing is lined with a sliding coating 62 , such as a Teflon layer, to reduce the frictional resistance between the guide pin 60 and the guide bushing 61 .

To prevent distortion of the two guide bolts 60 due to manufacturing tolerances or in the event of temperature expansion of the pressure plate 35 , the outlet-side guide bushing can be formed with a hole which is elongated in cross section, so that the guide bolt is supported with play therein. An alternative embodiment to this is shown in FIGS. 6a and 6b, in which the outlet-side guide pin 60 is seated in an elongated hole 63 of the guide plate 35 . The elongated hole 63 extends in the width direction of the guide plate and has narrow inwardly projecting webs 64 on its two lateral edges, which are undercut on the brake lining side. The superimposed in this long hole 63 guide bolt 60 is provided at its end portion with the groove-shaped recesses 65, in which engage the inwardly projecting ridges 64 of the elongated hole, so that the bolt 60 is mounted in the longitudinal direction of the long hole with play and perpendicular to the printing surface 36 substantially is fixed without play. This movement of the bolt 60 in the pressure plate 35 allows compensation of the distance between the two guide bolts 60 so that they can be freely supported in the two bushings 61 without any constraining forces.

The brake pad plate 39 is connected to the pressure plate 35 via a clamping spring (not shown). The clamping spring allows a radial movement of the brake lining plate 39 with respect to the pressure plate 35 , so that there is an interface between the brake lining plate 39 and the pressure plate 35 with an axial positive guidance and a radial degree of freedom. The brake pad plate 39 can shift force in relation to the pressure plate 35 when the circumference occurs and is supported on a holder (not shown). To reduce the friction between the brake pad plate 39 and the pressure plate 35 and thus to reduce the bolt load, the brake pad plate 39 and the pressure plate 35 can be formed from a material or with a surface treatment with a low coefficient of friction.

A simplified embodiment of the braking device according to the invention is shown in FIG. 7, which essentially corresponds to that from FIG. 1, but with the radial guide section of the guide bracket 50 and the corresponding guide groove 45 being omitted. The guide brackets 50 only have the connection section 52 and the tangential guide section 53 , which are provided with the guide holes 55 through which the guide bolts 48 extend. This simplified embodiment can be designed to provide a radial guide with guide bushings (not shown) which are inserted in the guide holes 55 and are extended in the longitudinal direction of the guide pins 48 so that they prevent the guide bracket 50 from tilting relative to the guide pins 48 .

Another solution according to the invention for increasing the application force by increasing the load rating of the ball screw drive of a braking device is explained below with reference to FIGS. 8 to 14b.

Fig. 11 shows schematically in cross section a conventional ball screw with a ball nut 68, a ball screw 69 and a plurality of balls 70 arranged therebetween. The ball nut 68 is supported at one end on an axial bearing 71 . A clamping force F is applied to the spindle 69 on the axial bearing 71 side. The load generated by the clamping force F is largely absorbed by the first three rotations 72 on the load entry side of the threads of the ball screw 69 and the ball nut 68 , so that the other rotations contribute only slightly to the load transmission. Because of the small number of rotations that take over the major part of the load, the clamping force generated on the ball drive is limited.

The reason for this is that the axial load on the ball drive causes compression of the ball screw and elongation of the ball nut so that the opposite grooves of the respective rotations, which are removed from the load entry side, do not exactly match and are offset from one another. The grooves on the load input side of the revolutions are offset slightly more than the other revolutions, so that they have to take over the essential part of the load ( FIGS. 13a, 13b).

According to the invention, therefore, a ball drive is provided, the ball nut 23 of which has a lower rigidity on the load input side than in the remaining area of the ball nut. The easiest way to achieve this is by means of a ball nut 23 which has a smaller wall thickness on the load entry side than in the rest of the area.

FIG. 12 shows a two-part ball nut 23 which has an inner bearing bush 74 and an outer cylindrical nut housing 75 . In cross section, the bearing bush has a profile that increases from the load entry side to the load discharge side, with a radially outwardly projecting ring projection 76 being formed on the load discharge side. The annular projection 76 engages behind the nut housing 75 by a corresponding annular segment 75 miles. On the load entry side, the nut housing is bent radially outward in order to provide a contact surface 79 for an axial bearing 80 . Due to this two-part design of the ball nut 23 , the bearing bush 74 loaded under pressure is preloaded by the nut housing 75 loaded under tension, the body engaging with the ball screw 2 , namely the bearing bush 74 , being designed with a stiffness distribution according to the invention and nevertheless being a ball bearing nut under tension 23 is created. As can be seen from the diagram shown in FIG. 12, the individual load of the respective round trips is significantly lower than in the conventional embodiment and is at most about 17%, so that the total load is distributed more evenly over the individual round trips. This makes it possible to transmit higher forces with the ball drive according to the invention and thus to provide a higher clamping force.

Alternative embodiments of the recirculating ball nut 23 according to the invention are shown in FIGS. 14a and 14b. The embodiment according to FIG. 14a has a pressure-loaded nut in which the wall thickness increases substantially continuously from the load entry side to the load discharge side.

The embodiment according to FIG. 14b has a tension-loaded nut, the spindle load being deflected by means of a spindle sleeve 82 , so that it is introduced on the side of the ball nut which is remote from the axial bearing 71 .

A preferred, one-piece embodiment of the ball nut 23 is shown in FIG. 8. This ball nut 23 already described above is provided with the offset 24 , so that it can be loaded from the outside to train. In the area of the bend 24 , a slot is introduced into the tubular body of the ball nut 23 surrounding the ball screw 2 , so that the area of the ball nut facing the brake disk 8 has a smaller wall thickness than the area removed from the brake disk. Since the load entry side is on the side of the brake disc or the pressure plate 35 , this ball nut has a lower rigidity on the load entry side than on the load discharge side, whereby the effect according to the invention of uniform distribution of the load of the individual rotations is achieved.

This reduces the load on the individual circulation device and the load can be distributed over several cycles become. With conventional ball drives, the essential Load of two or three rounds added, whereas in the ball drive according to the invention the load up to can be distributed to 8 or more rounds. This allows with a high-efficiency ball forces are transmitted as previously only by Roller screw drives is known. It becomes a transmission created that with a high degree of efficiency for the Brake device can transmit necessary application forces which makes it possible to have relatively small drive units to provide and the entire braking device compact from form.  

In the embodiments described above fiction According to ball drives, the ball nuts have areas with different wall thickness. For the invention it is essential that the rigidity of the recirculating ball nut that of the ball screw is adapted. This can also in a similar way by forming a hollow ball circulating spindle, which has a correspondingly variable wall thickness owns, or by providing different materials on the ball screw or on the ball nut will create.

Furthermore, in an advantageous embodiment ( FIGS. 9, 10), the housing, in which the linings are supported in the circumferential direction, is supported by means of lugs 85 attached to holding arms 84 . The lugs 85 are arranged above the center of the brake disc and in the line of action of z = 0.2 circumferential force resultant and are made of a hard, wear-resistant material. This minimizes or eliminates the tangential inclination of the fist to the brake disc, since the frictional forces act on lever arms of the same length on both sides of the brake disc. This special arrangement is advantageously provided on both the entry and exit sides in order to ensure this function when driving forwards and backwards.

In the axial direction, that is, in the direction of movement of the Ge threaded spindle 2 , the housing 1 is mounted by means of axially extending housing pins 87 in cylindrical rubber bushes 88 so that the housing pins 87 can be moved in the rubber bushings 88 for axial wear adjustment and are fixed against tumbling . As shown in Fig. 10 shows ge, the housing is designed such that it is predominantly loaded on train, whereby radial deformations are reduced and the radial oblique wear is reduced.

Claims (20)

1. Braking device for a vehicle, with

• - a brake disc ( 8 ) which is connected to a rotating part to be braked,
• - A brake pad ( 40 ) having a brake pad plate ( 39 ) which is arranged with its brake pad ( 40 ) of the brake disc ( 8 ) opposite,
• - An actuator which has an electric motor for actuating a threaded spindle ( 2 ) to press the brake pad plate ( 39 ) against the brake disc ( 8 ), characterized by means ( 45 , 48 , 50 , 55 ; 60 , 61 ) for guidance the brake lining plate (39), wherein the means for guiding the brake lining plate (39) independent of the threaded spindle (2) are designed so that the operation during a braking cross occurring at the threaded spindle (2) are reduced loads.

2. Braking device according to claim 1, characterized in that the means ( 45 , 48 , 50 , 55 ; 60 , 61 ) for guiding the brake pad plate ( 39 ) directly on the brake pad plate ( 39 ) or act on it. 3. Braking device according to claim 1, characterized in that the means ( 45 , 48 , 50 , 55 ; 60 , 61 ) for guiding the brake pad plate ( 39 ) directly on one between the brake pad plate ( 39 ) and the spindle ( 2 ) attack arranged pressure plate ( 35 ) or are formed on this. 4. Braking device according to one of claims 1 to 3, characterized in that the means for guiding the brake lining plate ( 39 ) have radial guide means ( 45 , 50 ; 60 , 61 ). 5. Braking device according to claim 4, characterized in that the radial guide means have at least one Füh approximately element ( 50 ; 60 ) which is movable in the direction of movement of the threaded spindle ( 2 ) and is mounted in the radial direction of the rotating part substantially free of play. 6. Braking device according to claim 5, characterized in that two guide brackets ( 50 ) are provided as guide elements, which are mounted on a threaded spindle around the closing housing ( 1 ), the Ge threaded spindle ( 2 ) approximately approximately between the two Füh approximately ( 50 ) is arranged. 7. Braking device according to one of claims 1 to 6, characterized in that the means for guiding the brake lining plate ( 39 ) have tangential guide means ( 48 , 50 ; 60 , 61 ). 8. Braking device according to claim 7, characterized in that the tangential guide means have at least one guide element ( 50 ) which in the direction of movement of the threaded spindle ( 2 ) is displaceable and in the tangential direction of the rotating part is substantially free or with little play. 9. Braking device according to claim 8, characterized in that the guide elements are two guide brackets ( 50 ), each having a guide hole ( 55 ) through which a guide pin ( 48 ) extends, which on a housing enclosing the threaded spindle ( 1 ) is fastened, the threaded spindle ( 2 ) being arranged approximately centrally between the two guide bolts ( 48 ). 10. Braking device according to one of claims 2 to 9, characterized in that the pressure plate has (35) has two holes into each of which a guide bolt (60) is arranged with one end, wherein the guide pin (60) approximately parallel to the threaded spindle ( 2 ) are arranged on and on the housing ( 1 ) in the direction of movement of the threaded spindle. 11. Braking device according to claim 10, characterized in that the outlet-side hole in the pressure plate is designed as an elongated hole in which the guide pin ( 60 ) are mounted with play in the longitudinal direction of the elongated hole. 12. Braking device for a vehicle, in particular according to one of claims 1 to 11, with

• - A brake disc ( 8 ) which is connected to a rotating part to be braked,
• - A brake pad ( 40 ) having a brake pad ( 39 ) which is arranged with its brake pad ( 40 ) opposite the brake disc ( 39 ),
• - which, like operates an actuator having an electric motor for Actuate the gene of a ball nut (23) derum a ball screw (2) for applying the brake lining plate (39) having a brake pad plate (39) against the brake disc (8) urging pressure force, wherein the ball nut ( 23 ) and the threaded spindle ( 2 ) have a corresponding thread, in which balls ( 30 ) are arranged, characterized in that the ball nut ( 23 ) and the ball screw ( 2 ) are matched to one another with their rigidity, that the load is distributed as evenly as possible over several revolutions of the thread.

13. Braking device according to claim 12, characterized in that the ball nut ( 23 ) has a lower stiffness on the La steintragsseite than in the rest of the ball nut ( 23 ). 14. Braking device according to claim 13, characterized in that the ball nut ( 23 ) on the load entry side has a smaller wall thickness than in the rest of the area. 15. Braking device according to claim 13, characterized in that the ball screw ( 2 ) in the with the Ku gelumlaufmutter ( 23 ) in engagement area la stone bearing side has a higher rigidity than lastaus bearing side. 16. Braking device according to one of claims 1 to 15, characterized in that the actuator is formed from the electric motor and a gear ( 17 ) and is arranged in a housing ( 1 ), the housing ( 1 ) having a sheet metal ring ( 7 ) is coupled to a brake disc ( 8 ) overlapping fist ( 6 ) and the gear is coupled with a bellows ( 19 ) to the ball screw ge, so that the actuator is decoupled from deformation of the fist ( 6 ). 17. Braking device according to claim 16, characterized in that the ball nut ( 23 ) with an axial roller bearing ( 27 ) and a radial fixing ball bearing ( 28 ) is mounted on the fist ( 6 ), the radial fixing ball bearing in the region of the longitudinal center of the Ball nut ( 23 ) is arranged. 18. Braking device according to claim 16 or 17, characterized in that the electric motor has a rotor and egg NEN stator, at least one ball bearing ( 13 ) being provided between the rotor and the stator, so that a predetermined air gap ( 14 ) between the Rotor and the stator is formed. 19. Braking device according to one of claims 16 or 18, characterized in that the transmission ( 17 ) is a Pla neten transmission. 20. Braking device according to one of claims 1 to 19, characterized in that between the ball screw ( 2 ) and the brake pad plate ( 39 ) a point load / constant load converter plate is arranged as a pressure plate ( 35 ).