Abstract:
An electro mechanical or pneumatically actuated disk brake, in particular for a utility vehicle, includes a brake caliper or saddle and a brake disk. The brake saddle overlaps the brake disk at least in sections of the outer periphery thereof. The disk brake also includes a tensioning device which is entirely or partially inserted into the brake saddle. The tensioning device is used to produce a tensioning movement between the brake linings and the brake disk. The disk brake further includes at least one, and preferably several, adjusting devices. The brake disk and/or the brake saddle are arranged on a stop with elastic pre-tension when the brake is in a release state. Braking is determined by a control method in a sensor-free manner during adjustment.

Description:
[0001]     This application is a continuation of international application no. PCT/EP2004/014009, filed Dec. 9, 2004, the entire disclosure of which is incorporated herein by reference.  
         [0002]     This application also claims the priority of German application 103 57 374.7, filed Dec. 9, 2003. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION  
       [0003]     The present invention relates to a pneumatically actuated disk brake with electromotively driven adjusting devices and a method for controlling the disk brake.  
         [0004]     In known compressed-air-actuated disk brakes, a braking operation is effected by an actuation of the brake application device, for example by movement of a piston rod of a pneumatically operating brake cylinder, by which movement a connected brake pad is pressed against the brake disk. Depending on whether the disk brake is designed as a fixed-caliper brake or as a sliding-caliper or hinged-caliper brake (or as a combination of these brake types), the brake disk is pushed toward the further brake pad on the other side of the brake disk and/or this further brake pad is pushed toward the brake disk.  
         [0005]     In the case of fixed-caliper brakes—see, for example, international publication WO 02/14708—the brake disk, which is axially movable, yet is mounted in a torque-transmitting manner on a wheel hub or another component, is forced by axial displacement, and while surmounting play, against the further brake pad, which is preferably fixed relative to the fixed caliper.  
         [0006]     Following ending of the braking operation, a defined release of the brake pad from the brake disk friction surface often does not takes place, at least on the side facing away from the brake application. Instead, the brake pads adhere to the brake disk with a residual pressure force due to the acting friction forces produced by a pad mounting and, where applicable, from the sliding resistance of the brake caliper. The contact between brake disk and brake pad is released by the vibrations which are usually generated during driving, or due to a so-called wobble of the brake disk, which is undesirable per se.  
         [0007]     The further contact between the brake pads and the brake disk following the release of the brake application device gives rise to an additional wear of both the brake disk and the brake pads, which results in a reduced service life for the wearing parts, with the corresponding cost disadvantages in terms of spare parts procurement and installation and removal.  
         [0008]     As a result of a somewhat longer contact of the brake pads against the brake disk, the brake temperatures are somewhat increased, which can likewise have an adverse effect on service life. Moreover, the increased running resistance which is generated due to the friction of the corresponding components in the unbraked setting can lead to a certain additional fuel consumption, which should be avoided.  
         [0009]     Apart from the absence of forced lifting, i.e. the reliable release of the brake pads from the brake disk following completion of the braking operation, a further design problem of fixed-caliper disk brakes is that the operational micromobility of the brake disk and/or of the brake caliper, in the event of severe vibration stress, as occurs when driving on poor roads, leads to heavy wear, particularly on engaging elements such as splines, with which the axially displaceable brake disk is held in a torsionally secure manner against an axle flange or against a comparable vehicle-side component.  
         [0010]     The enormous stress which is generated upon the engaging parts calls for a wear-conditioned premature exchange of the corresponding components, with the consequent costs.  
         [0011]     One object of the present invention is therefore to refine a disk brake of the type mentioned such that, with constructively simple means, the wear of the brake disk and of the brake shoes is minimized, the operating reliability is improved, and the service life, overall, is increased.  
         [0012]     In addition thereto, it is intended to provide a particularly advantageous method for controlling the electromotively driven adjusting devices which can be used for a disk brake of the type mentioned and also for the disk brake according to the invention.  
         [0013]     The object mentioned is achieved by a disk brake having a stop, against which, in the released state of the brake, the brake disk and/or the brake caliper bear(s) under elastic pretensioning. Preferably, the elastic pretensioning forces are dimensioned such that, when the disk brake is applied—i.e. upon a movement of the brake disk and/or of the brake caliper—they are readily surmounted by the brake application forces, and the movable brake disk and/or the movable brake caliper, during play adjustment operations or during travel in the period between brakings and/or play operations, are held in a sufficiently fixed position relative to the vehicle-side component, with the result that the brake pads do not begin to rub.  
         [0014]     According to the invention, in a constructively simple manner, when the brake application device is released, i.e. when the braking operation is ended, free play between the brake shoes or their brake pads and the brake disk is produced, so that these components come into contact only during the braking and afterwards detach from one another again. The free play here corresponds to the play set by the adjusting device, i.e. to the distance between the brake disk and the brake shoe.  
         [0015]     In this way, brakings are not impeded and yet the rubbing effects which arise during travel, resulting in higher wear and fuel consumption, are minimized and the prospect of “intelligent” adjustment of the play, including “intelligent” play function, is optimized. As a result of the prospect of minimizing the fuel consumption, this disk brake will inevitably in future be the brake of choice, in particular in an additionally space-saving design as a fixed-caliper brake with intelligent, since electrically driven and electronically—for example via a brake-integrated control unit or an “upgraded” EBS control unit—controllable and adjustable adjusting function.  
         [0016]     The elastic pretensioning of the movable element—brake caliper and/or brake disk—against the stop on the vehicle-side component is especially advantageous, since the adjusting devices have on one or both sides of the brake disk at least one or more electromechanical drives—electric motors—and can be controlled by means of an electronics system.  
         [0017]     According to the invention, at least one or more of the adjusting devices is or are disposed on each side of the brake disk, which, without exception, are electromechanically driven, to be precise by means of independent motors for the brake application side and the reaction side of the brake disk, so that the mobility of the brake disk can be limited to a “microdisplacement path”—the path which has to be bridged when the brake is applied.  
         [0018]     According to one embodiment, the brake caliper is configured such that it is immovable relative to a vehicle-side component such as an axle flange or the like, in particular as a fixed caliper. It presents itself as constructively simple, in this case, if the brake disk is mounted in an axially displaceable, yet non-rotatable manner on the vehicle-side component.  
         [0019]     In design terms, it is advantageous if the stop is formed against the vehicle-side component and the elastic pretensioning is realized by pressure elements, which are likewise supported against the vehicle-side component. Each pressure element can here simply consist of a contact element, bearing against the brake disk, and a compression spring.  
         [0020]     According to an advantageous refinement of the invention, the axially displaceably mounted brake disk can be forced against the stop by the resiliently held pressure element.  
         [0021]     The spring forces are preferably applied by steel springs or a similar spring material, which rest in a corresponding receptacle of the brake caliper, the axle flange or the like and against which the respective pressure element is supported.  
         [0022]     The spring forces are here dimensioned such that the forces of, for example, 1-2 kN which are generated within the force application zone of the brake disk during a touching operation in play adjustment operations, and the axially acting inertial forces of, for example, 2-4 kN which are generated substantially at the center of gravity of the brake disk, provoke no or only a negligibly small axial movement of the brake disk, and these forces, which are directed counter to the necessary relative mobility of the brake disk, grow only slightly in the course of a braking operation.  
         [0023]     The axially acting inertial forces generated at the center of gravity of the brake disk, which appear as vibration stress and which, by way of compensation, demand corresponding retention forces to be applied by the resilient force elements, on the one hand, and the half as high contact forces in respect of the touching, which require correspondingly lower retention forces of the resilient pressure elements, can be reconciled by the fact that, when the brake disks are adjusted by adjusting or actuating pistons of the brake, due to the unilateral application of force to the friction surface of the brake disk, initially only a small tilting movement of the brake disk is performed. In this case, only a component force of the resilient pressure elements which lie further inward in the radial direction has to be surmounted.  
         [0024]     Since the inertial forces act substantially at the center of gravity of the brake disk, these inertial forces are opposed by the full contact force of the pressure elements.  
         [0025]     Through a suitable choice of the position of the brake-actuating pistons and the position of the pressure elements, which can both be chosen within certain limits, the ratio between the actuating resistance and the retention forces in connection with vibration effect can likewise be freely chosen within certain limits.  
         [0026]     In principle, the pressure element can consist of a compression spring, which bears against the end face of the brake disk and/or the brake caliper. Particularly advantageous, however, is a configuration of the pressure elements in which the contact region comprises a non-resilient contact element, so that the spring itself is not in direct contact with the brake disk. The sometimes high contact temperatures, which might otherwise lead to a reduction in the spring tension force, are hence not transmitted to the spring itself. The contact element and the adjoining spring can be configured as a single component, but can also consist of two interacting components.  
         [0027]     It is also conceivable for the brake caliper to be configured so as to be movable relative to a vehicle-side component, such as an axle flange or the like, in particular as a sliding caliper, and for the brake caliper to be supported under elastic pretensioning against the stop on the vehicle-side component (brake caliper). In one embodiment of the disk brake as a sliding or hinged-caliper brake with fixed brake disk and movable brake caliper, an elastic “restoring and retention force” can also act in this way, by which the brake caliper is held in the stop position, counter to the forces acting in the play adjustment, and which, once again, is dimensioned such that, when the brake is actuated, the movement of the brake caliper which is then necessary is opposed only by a minor resistance which does not impede the braking.  
         [0028]     The invention also provides a method for adjusting the play of a pneumatically actuated disk brake having electromotively driven adjusting devices on both sides of the movable brake disk, wherein, during the adjustment of the play, commencing or already initiated brakings are easily detected by “sensorless” means from the turning behavior of the motors M 1  and M 2  of the adjusting devices. A brake-internal control unit can herewith easily detect a braking virtually “autarkically”, without connection to a master control system.  
         [0029]     It is here beneficial, on safety grounds, if the method for adjusting the play, using the sensorless determination of brakings, is repeated at predefined intervals of, for example, 0.5 to 3 min.  
         [0030]     It is further expedient if the method for adjusting the play is interrupted following the recognition of an initiated braking and is then repeated after a predefined—only a few seconds long—time interval.  
         [0031]     Preferably, the position of the brake disk or of the brake caliper against a resilient stop is used as a reference point in a controlling of the disk brake.  
         [0032]     In the following, motor  1  denotes the at least one or more brake-application-side motors, together with associated adjusting devices on one side of the brake disk, and motor  2  denotes the at least one or more reaction-side motors, together with associated adjusting devices on the other side of the brake disk.  
         [0033]     According to a particularly preferred embodiment, in the event of a play adjustment, initially by means of the one motor M 1 , the at least one brake-application-side adjusting device is moved to a predefined minimum play distance between brake shoe and brake disk of, for example, 300 micrometers. The reaction-side adjusting device is then moved by means of the motor M 2  in the direction of the brake disk, until a stationary position is reached, which is registered. The reaction-side adjusting device is subsequently moved again in the direction of the brake disk and an attempt is simultaneously made to open the brake-application-side motor M 1 , whereupon, should this not be possible, a braking is then inferred. If no braking is in progress, the reaction-side motor M 2 , starting from the determined zero position, is then opened into its correct minimum play setting.  
         [0034]     In addition, preferably, following the adjustment of the minimum play at the reaction-side motor M 2 , the brake-application-side motor M 1  is moved, in the direction of the brake disk, until it reaches a stationary position, which is registered. Stop and stationary positions in the direction of greater wear in relation to a minimum play setting are adopted as the stationary position, whereas stop and stationary positions in the opposite direction are rejected. The brake-application-side motor M 1 , starting from the determined stationary position against the brake disk, is then moved to its minimum play.  
         [0035]     In this way it is easily possible, without sensors, to infer initiated brakings from motor standstill during opening movement of the adjusting devices from the stop.  
         [0036]     In addition, the invention also provides a method for controlling a disk brake in which the position of the brake disk or of the brake caliper on the stop is used as a reference point in controlling the adjusting motors of the disk brake.  
         [0037]     This is extremely advantageous since, in a simple manner, the zero point which is necessary for all manner of controls (play adjustment, cleaning of the disk, etc.) can in this way easily be precisely determined over and over again. In order to avoid momentarily excessively high current consumption, the adjustment can also be made sequentially one after the other to the various brakes of a vehicle. As a result of the stop, the movements of disk and/or pads in all manner of play adjustments and functions can also be realized in a virtually “force-free” manner and without excessive opposing friction forces or the like, and can thus be performed in a particularly precise and reliable manner. Prior art methods are known from European document EP 0 703 133 B1 and German document DE 44 33 377 A1.  
         [0038]     According to a further, independent embodiment, following braking, a supplementary active release of the brake pads from the brake disk is effected by means of the adjusting devices.  
         [0039]     Further advantageous configurations of the invention are described below with reference to the appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]      FIG. 1  shows a disk brake in a diagrammatic side sectional view.  
         [0041]      FIGS. 2   a ,  2   b ,  3   a , and  3   b  show details of various illustrative embodiments, likewise in diagrammatic side views, respectively together with an associated force-distance diagram.  
         [0042]      FIG. 4  shows a flow chart for the controlling method according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0043]     In  FIG. 1 , a brake disk for commercial vehicles, which is here configured, by way of example, as a fixed-caliper brake, is represented, which has a brake caliper  2  which is configured as a fixed caliper and reaches over a brake disk  3 , which is disposed in an axially displaceable and torsionally secure manner on a vehicle part configured as an axle flange  1 . The fixed caliper  2  is fixed immovably on the axle flange  1 .  
         [0044]     In the fixed caliper  2  there is disposed a brake application device  16 , actuable by a piston rod of a brake cylinder and having an eccentrically mounted swivel lever  17 , which brake application device is designed and constructed such that, when the swivel lever  17  is pivoted, pressure pieces (here not recognizable in detail) on this side of the brake disk  3  (referred to as the brake application side) are displaced parallel to the brake disk axis and press a brake shoe  4  disposed on the brake application side against the brake disk  3 , which latter, if the brake application movement proceeds further, is displaced axially in the direction of the further brake shoe  5  on the other side of the brake disk (reaction side) until it comes into contact there and the actual braking action between the brake disk  3  and the brake shoes or pads  4 ,  5  commences. As a result of the frictional contact between the two brake shoes  4 ,  5 , the brake disk  3  and, with it, the wheel hub  1  or a connected wheel (not represented) are braked. For the operation of an exemplary brake application device, reference should additionally be made to international publication WO 02/14708.  
         [0045]     To the two brake shoes  4 ,  5  there are respectively assigned, on the brake application side and the reaction side, at least one, and in particular two, adjusting devices  7 ,  8 , with which an operational wearing of the brake shoes  4 ,  5  can be compensated. For example, after each braking operation, or after a plurality of braking operation, the brake shoes  4 ,  5  are advanced in the direction of the brake disk  3  by the thickness of the abrasion. The adjusting devices are electromechanically driven, in which case on each side of the brake disk there is respectively provided an electric motor  6 , of which the brake-application-side electric motor  6  can here be recognized. The electric motor acts via a drive connection on rotary spindles or the like, which, when turned, alter the axial position of the pressure pieces relative to the brake disk  3 . The advantage of these adjusting operations lies, inter alia, in the prospect of using “intelligent” play functions which extend far beyond a mere adjustment of the brake.  
         [0046]     In order to ensure that the brake disk  3 , following ending of the braking operation, is pushed back into its original position, so that a sufficient free play is created between the outer brake shoe  5  and the brake disk  3 , according to the invention, in the direction of displacement of the brake disk  3 , resilient spring elements  9  are provided, against which the brake disk  3  bears.  
         [0047]     According to one embodiment (which cannot here be seen), a plurality of, in the peripheral direction, evenly distributed pressure elements  9  are provided, which preferably come to bear in the region of the axial inner rim of the brake disk  3 .  
         [0048]     The displacement of the brake disk  3  which is conditioned by the pressure elements  9  is limited by stops  12 , which can be seen particularly clearly in  FIGS. 2 and 3 .  
         [0049]     The fixed stops  12  are held by screws  13 , which are screwed into the end face of the axle flange  1 .  
         [0050]     According to  FIG. 1 , the pressure element  9 , by way of example, is configured in compact arrangement in two parts. It comprises a contact element  11 , which bears against the brake disk  3 , and a compression spring  10 , configured as a helical spring, for generating the elastic pretensioning between the stop  12  and the brake disk  3 .  
         [0051]     As a result of the two-part configuration, frictional heat which is generated during braking is effectively prevented from being transmitted from the heated brake disk  3  to the compression spring  10 .  
         [0052]     The pressure elements  9  are respectively inserted in an axially extending recess  15  of the axle flange  1 .  
         [0053]     The stop  12  here is located on the brake application side, so that, following a braking, the brake disk is moved back from the reaction side in the direction of the brake application side.  
         [0054]     In  FIGS. 2 and 3 , there is respectively represented a part-detail of the disk brake in the contact region of a pressure element  9  against the brake disk  3 .  
         [0055]     Whereas in  FIG. 2 , the stop  12  which limits the return path of the brake disk  3  is fixedly positioned, in the embodiment illustrated in  FIG. 3 , the stop is mounted resiliently in the direction of displacement of the brake disk  3 , for which purpose a pressure element  14  in the form of a helical spring is provided, which is supported, on the one hand, against the head of the screw  13  and, on the other hand, against the stop  12 .  
         [0056]     Through an appropriate dimensioning of the spring forces of the pressure elements  9 ,  14 , an axial mounting of the brake disk is obtained. In extreme cornering maneuvers and the enormous deformations of the axle components to which this gives rise, this axial mounting allows the brake disk to be displaced beyond the stationary position. For full functionality, the spring force of the pressure element  14  must, of course, be greater than that of the pressure element  9  which forms a counterforce (see respectively  FIGS. 2   b  and  3   b ).  
         [0057]     Moreover, the use of the two pressure elements  9 ,  14  means that the brake disk  3  is held in its position even in the event of considerable operational vibrations.  
         [0058]     The spring force, preferably resulting from a compression spring, is dimensioned, in particular, in such a way that, when the brake is actuated, the necessary relative movement between the brake disk and the brake caliper is enabled without an elevated spring resistance. On the other hand, the spring force should be such that, if a sliding caliper, for example, is in an undefined position, for example as a result of inertial forces generated, for example, in a cornering maneuver, a unilateral rubbing of the brake is prevented, i.e. the spring force must be sufficient to be able to absorb the generated inertial forces. This applies equally to the brake disk, acting as a sliding disk, of a fixed-caliper brake.  
         [0059]     The contact force applied by the resilient pressure element should also be dimensioned such that the forces and moments of inertia which are generated during a normal journey cannot move the brake disk and/or the brake caliper permanently out of the contact position. The contact-pressure forces of the resilient pressure element(s) should, on the other hand, be kept sufficiently small that, when the brake is actuated, only a least possible resistance has to be surmounted, since this might otherwise lead to unequal braking forces on the two sides of the brake disk and hence to unequal brake pad wear.  
         [0060]     The disk brake having the electromechanical or electromotively driven adjusting devices  7 ,  8  on each side of the brake disk  3 , in particular in conjunction with the stop  12  against which the brake disk  3  and/or the brake caliper  2 , in the released state of the brake, bear under elastic pretensioning, also allows a particularly advantageous configuration of the braking method for the play adjustment, which method is necessary in order to adjust and reset wear-conditioned changes in play between the brake pads and the brake disk, as well as changes occurring for the first time after resumption of use following a pad change or upon initial usage.  
         [0061]     This method is described in greater detail below with reference to  FIG. 4 . Here the method steps are not limited to the described procedure. It is conceivable, for example, to broadly change round the sequence of processes with respect to the method steps on the reaction-side and on the brake-application-side brake pad, insofar as this is possible.  
         [0062]     One object of the play adjustment is to set an optimal distance between the brake disk  3  and the brake pads or brake shoes  4  and  5 , and in this way to compensate for wear and thermal expansions over the working life.  
         [0063]     It is here necessary to permanently guarantee a minimum clearance or a minimum play between the brake shoes  4 ,  5  and the brake disk  3 .  
         [0064]     The minimum play is made up of the sum of the individual plays on both sides of the brake disk  3  between the brake shoes  4  and  5  and the brake disk  3 .  
         [0065]     Without an adequate minimum play, there is the danger of hot running if, in such a state, braking is performed for too long or too intensely and the brake pairing is thermally restrained such that it can no longer be released.  
         [0066]     Especially in combination with the aforementioned brake disk  3  which is virtually fixed and bears resiliently against a defined stop and which is designed such that it cannot be displaced by adjuster force or by braking force or thermal retraining force, it should be possible for the brake disk  3 , in the event of unilateral thermal restraint (unilateral play), to be able to escape to the other side and for the remaining unilateral restraint then still to be releasable by the electromechanical motors of the adjusting device  7 ,  8 . A unilateral minimum play should also be available to the other side of the brake disk.  
         [0067]     A supplementary necessity in all play adjustment effected by means of the electromotive adjusting devices  7 ,  8  is the necessity to be able to recognize brakings easily at all times.  
         [0068]     Admittedly, this is readily possible in theory, by a brake signal being used, for example, by a control unit (ABS, ESP, or the like) for also recognizing braking at the disk brake, to control the adjusting devices respectively only when no braking is initiated.  
         [0069]     However, it is also desirable to provide a method for adjusting the play, in which brakings are detected at the brake itself by its own electronics preferably integrated in the brake. According to the insight of the invention, this is readily possible only through skillful controlling of the adjusting devices, provided that the brake electronics system is designed at least to recognize a standstill of the adjusting devices.  
         [0070]     Since the brake disk  3 , under elastic pretensioning during a braking operation, is displaced from the brake-application-side pad or from the brake-application-side brake shoe in the direction of the brake pad  5  located on the rear side of the caliper or on the away-facing side of the brake disk, both brake pads  4 ,  5  are blocked during a braking operation.  
         [0071]     Without a brake recognition, the adjuster electronics assumes, in this case falsely, two pads bearing against the brake disk, which, following the braking, is no longer the case. The subsequently adjusted play would then be too large.  
         [0072]     For the surveying of the brake disk positions on both sides and for the simultaneous recognition of the braking, two adjusting motors, which can be moved independently from one another, are necessary on both sides of the brake disk.  
         [0073]     The electronics, as well as the software for controlling the adjusting motors, must therefore permit an independent movement of the adjuster motors on both sides of the brake disk  3 .  
         [0074]     For this purpose, each brake can boast a dedicated electronic control unit, or a corresponding control electronics can be centrally provided for a plurality of brakes, thus, for instance, on an overlapping EBS control unit, which controls and/or regulates each side separately.  
         [0075]     More specifically, a play adjustment, as can be seen from  FIG. 4 , is made up of a sequential scanning of the brake pad positions of both brake disk sides, and a subsequent repositioning of the brake shoes or brake pads  4 ,  5  relative to the brake disk.  
         [0076]     Thus, the program according to  FIG. 4  starts with a brake disk stop recognition on one side of the brake disk and then performs the brake disk stop recognition on the other side of the brake disk. Next, the new pad positions are adjusted on both sides of the brake disk by means of movement of the brake shoes by the electromechanical adjusting device, and the method for controlling the play is halted.  
         [0077]     Below, by way of example, the process of a particularly advantageous illustrative embodiment of the play adjustment method is described. More specifically, the process of play adjustment is as follows:  
         [0000]     Step 1  
         [0078]     First of all, in a play adjustment, the brake-application-side motor M 1  (and hence the associated rotary adjusting device(s)) is driven to a minimum play distance of, for example, 300 micrometers.  
         [0000]     Step 2  
         [0079]     The reaction-side motor M 2  (and hence the associated rotary adjusting device(s)) moves subsequently or at the same time in the direction of the brake disk, until it reaches a stationary position. This is registered (for example, via changes in the current and/or voltage characteristics for the powering of the motor).  
         [0000]     Step 3  
         [0080]     The motor M 2  subsequently moves back in the direction of the brake disk, until it again reaches a stationary position. At the same time, an attempt is made to open the motor M 1 . If this is not possible, it is clear that a braking has been initiated. Otherwise, the disk contact setting (i.e. a zero position for the play adjustment) of the motor M 2  against the brake disk has been correctly registered.  
         [0000]     Step 4  
         [0081]     Preferably only at the end of both touching operations, both brake shoes are moved to their optimal positions relative to the brake disk, since, for the time in which the motor  1  touches the brake disk, the minimum play (the sum of both sides) is unilaterally provided. The raising of the motor  2  to the minimum play, which has now been provisionally adjusted on one side, is step 4.  
         [0000]     Step 5  
         [0082]     As soon as the motor M 2  reaches its play setting, the motor M 1  (and hence the associated rotary adjusting device(s)) is moved in the direction of the brake disk until it reaches a stationary position.  
         [0083]     The stationary position is registered (for example, via changes in the current and/or voltage characteristics for the powering of the motor). A brake recognition is preferably not conducted on this side, since the undefined position of the swivel lever could at low pressures falsify the play determination.  
         [0084]     Stop and stationary positions in the direction of greater wear are adopted as the position. Stop and stationary positions in the opposite direction are rejected, on the other hand.  
         [0085]     With this, the motor M 1 , too, is adjusted to a correct play (for example, 300 micrometers or more), with the result that now the entire play on both sides of the brake disk is correctly set.  
         [0086]     If the play is unable to be set correctly, because, for example, a braking has been recognized, the play adjustment can be repeatedly attempted at predefined intervals.  
         [0087]     A motor standstill in the directions of opening here indicates brakings.  
         [0088]     After each braking or as long as no correct play has been set, or alternatively at a regular interval of, for example, 1 min. or respectively a few seconds after a brake actuation, a renewed play adjustment can be performed.  
         [0089]     It is particularly advantageous that a brake recognition during the play adjustment is possible even without evaluation of a braking-indicating signal, for example by a control unit or the like (ABS, EBS, ESP, or the like), so that, also at the brake, a braking can be autarkically directly recognized via an electronics system present on the brake, in order to prevent overheatings and the like.  
         [0090]     The necessity of a further play adjustment could be deduced, in combination with an EBS system, also by the fact that the rendered braking energy is observed on the basis of braking pressures and braking times, which would lead to a further reduction in adjuster activity. To this extent, there still remain, therefore, a number of conceivable triggers for an adjustment. There does not have to be a fixed time frame, therefore.  
         [0091]     A further particular advantage of the method according to the invention consists in the fact that the adjuster drive motors can be driven with a predefined controlling sequence, which largely prevents an overlapping of the electrical power absorption of the same. In addition, a play adjustment in the nature of a brake-disk-touching method is possible, without a feedback to the adjusting device situated opposite the brake disk  3  being given.  
         [0092]     Particularly advantageously, the adjusting motors are realized as sensorless-operated, electronically commutating direct-current motors (EC motors, sensorless-operated). In these motors, the constant registration of the rotor position which is necessary to the operation of the same is effected by an analysis of the electrical parameters which, in the coils of the winding, are variable on a position-dependent basis. The advantage is the extreme simplification of the mechanical and electromechanical structure of the motors and the associated maximum possible robustness of the same. In this connection, however, a somewhat higher or a relatively high computer capacity in the electronic control unit is required, which in practice does not pose a problem.  
         [0093]     In order to obtain an adequate vibration resistance, the magnitude of the elastic contact of the brake disk  3  against the wheel hub has to be dimensioned such that even forces and moments of inertia which are generated at the brake disk under the most severe driving conditions on poor stretches of road cannot surmount this contact force through vibration stresses.  
         [0094]     The relative mobility between brake disk  3  and brake caliper is designed such that, in the case of those forces which, in the play adjustment operation, are provoked by a touching and under the forces and moments of inertia which act in driving operation even on poor stretches of road, no or only a very small relative movement occurs and, when the brake is actuated, the brake-actuating forces are opposed by a merely small resistance for the execution of the relative movement which is then necessary.  
         [0095]     In practice, the elastic forces are preferably applied by steel springs or a comparable spring material. They are dimensioned, in particular, such that the forces of, for example, 1 to 2 kN which are generated within the force application zone of the brake actuation during the touching operation, as well as the fundamental axially acting forces of about 3 to 4 kN which are generated at the center of gravity of the brake disk  3 , still provoke no or only a negligibly small axial movement of the brake disk  3 , and such that these forces, which are directed counter to the necessary relative mobility of the brake disk  3 , grow only slightly in the course of a braking operation.  
         [0096]     The apparent conflict between relatively small contact forces during the touching operation and twice as high retention forces against vibration stress is resolved in the brake disk  3  according to the invention by the fact that, when the brake disk  3  is adjusted by the adjusting or actuating pistons of the brake, due to the unilateral force action upon the friction surface of the brake disk  3 , initially only a small tilting movement of the brake disk  3  is performed, in which case only a component force of the pressure springs which lie further inward in the radial direction has to be surmounted. Due to the rotation of the brake disk  3 , this continues screwing only in the axial direction. Since the inertial forces, however, act substantially at the center of gravity of the brake disk  3 , these inertial forces are opposed by the full contact force.  
         [0097]     Through suitable choice of the position of the brake-actuating pistons and the position of the contact springs or compression springs, which can both be freely chosen within certain limits, the ratio between actuating resistance and retention forces in connection with vibration effect can likewise be freely chosen within certain limits.  
         [0098]     The pressure elements acting upon the brake disk  3  are here advantageously configured such that the resilient effect is not generated in the region of the springs which is in direct contact with the brake disk  3 , since, as a result of the where applicable, high contact temperatures, the spring tension force is able to be reduced.  
         [0099]     The pretensioning springs of the pressure elements comprise a non-resilient contact region, via which the spring forces are transmitted to the brake disk  3 , and the region generating the spring tension force, which is disposed outside the heat influence zone of the brake disk  3 . The contact region and the spring tension force region can be configured as a single component or can also consist of two naturally paired components.  
         [0100]     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.