Abstract:
The invention relates to an electromechanical friction brake, for example in the form of a disc brake having an electromechanical actuation device. The electric motor of the actuation device presses a frictional brake lining against a brake disc by means of a reduction gearbox and a ball ramp mechanism. The actuation device is supported by a spring washer that is pretensioned so strongly that when the disc brake is released it acts on a segment with a falling spring characteristic; that is, a spring force exerted by the spring washer on the frictional brake lining increases with increasing tension of the disc brake.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2008/065589 filed on Nov. 14, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an electromechanical friction brake. The friction brake is intended in particular as a wheel brake for a motor vehicle. The term “electromechanical” means that it has an electromechanical actuating device, for instance with an electric motor and gear for its actuation, or in other words for pressing a friction brake lining against a brake body that is to be braked. The actuation of a brake is also called tightening. In the case of a disk brake, the brake body is a brake disk; in the case of a drum brake, the brake body is a brake drum. The invention is not limited to the disk or drum brake forms mentioned, but instead can be realized in principle in arbitrary forms of brakes. Although the invention is described below in terms of a disk brake, it is not limited to that type of brake. 
     2. Description of the Prior Art 
     From German Patent Disclosure DE 196 81 658 T1, one such friction brake is known, as a wheel brake for a motor vehicle. The known friction brake is embodied as a disk brake. As its actuating device, it selectively has an electromagnet or a linear motor, with which a friction brake lining can be pressed against a brake disk that forms a brake body to be braked. The actuating device is reinforced by a cup spring, which likewise acts on the friction brake lining in the direction of pressing against the brake body, or in other words in the direction of an actuation of the brake. Hence the actuating device needs to exert only a portion of the tightening force for pressing the friction brake lining against the brake body; the remainder of the tightening force is a spring force exerted by the cup spring. A smaller, lighter-weight and less-powerful electromechanical actuating device suffices. 
     The known friction brake does not have a normal cup spring but instead has a special cup spring, which has no linear characteristic spring curve; instead, its characteristic spring curve initially rises and then after a maximum drops again. After a minimum, which typically located near a zero spring force and may be positive or negative, the characteristic spring curve of the special cup spring typically rises again. If the minimum of the characteristic spring curve is negative, this means a negative spring force; that is, the direction of the spring force reverses itself. A special feature of the special cup spring is accordingly that its characteristic spring curve has a dropping portion. Conversely, in springs with a linear characteristic spring curve, the spring force, in the portion in which the characteristic spring curve drops, decreases with increasing deformation of the cup spring. In other words, the spring force of the cup spring rises with decreasing deformation, in the range in which its characteristic spring curve drops. The deformation, which can also be called deflection, means a flattening of the cup spring, which in the unloaded state is conical or curved. The deformation can continue to the point of a flat disk, or even beyond. The latter means that the cup spring is as it were inverted; that is, its curvature is reversed. 
     The known friction brake makes use of the special feature that the special cup spring used has a characteristic spring curve with a dropping portion. The cup spring is used in the region of its dropping characteristic spring curve; with the friction brake released, it is deformed to such an extent that its characteristic spring curve is in the range of the minimum. Upon actuation or tightening of the friction brake, the deformation of the cup spring decreases; the spring force increases, because of the characteristic spring curve that is dropping and that has moved in the negative direction. With increasing tightening of the friction brake, the spring force exerted by the cup spring on the friction brake lining thus increases, and as a result, a large proportion of the tightening force can be exerted by the cup spring. The proportion of the tightening force to be exerted by the actuating device is as a result low over the entire actuation and tightening force range. 
     The invention is not especially limited to a cup spring; instead, a spring element can in general be used whose characteristic spring curve drops at least over one portion. The spring element acts parallel to the actuating device; that is, the force of the actuating device and the force of the spring element are added together. 
     ADVANTAGES AND SUMMARY OF THE INVENTION 
     Like the known friction brake, the friction brake of the invention also has a spring element with a characteristic spring curve that (in some portions) drops and that acts parallel to an actuating device of the friction brake, or in other words urges the friction brake lining in the direction of a brake actuation. Because of the dropping characteristic spring curve, a spring force exerted by the spring element on the friction brake lining increases with increasing tightening of the friction brake. An electric motor and a gear are accordingly relieved. 
     The friction brake of the invention is electromechanical; it has an electromechanical actuating device with an electric motor. It can have a gear, in particular a step-down gear. For converting a rotating driving motion of the electric motor into a translational motion for pressing the friction brake lining against the brake body, the friction brake of the invention has a ramp mechanism. 
     Ball ramp mechanisms are known that have two coaxially disposed disks, between which balls—typically three balls, for the sake of static certainty—are distributed in the circumferential direction. One of the two disks can be driven to rotate. On or in facing end faces, the disks have ramps extending in the circumferential direction, which rises in one circumferential direction and in which the balls roll. The ramps are typically groovelike indentations, which become lower in one circumferential direction. 
     By rotation of the one disk, the balls roll in the rising direction of the ramps and force the disks apart, thereby generating the translational motion. In the opposite direction of rotation, the two disks approach one another. Instead of balls, still other roller bodies can be employed, such as cylindrical or conical rollers. These rollers can be supported rotatably on one disk, so that only the other disk has ramps on which the rollers or other roller bodies roll. A ramp mechanism without roller bodies is also conceivable, which has one or more circumferentially extending ramps that by rotation press down on a counterpart body and thereby generate a translational motion as in the known ball ramp mechanism. 
     Advantageously, but not necessarily, the ramp mechanism of the friction brake of the invention has roller bodies, such as balls or rollers as roller bodies, and forms a rolling, ball or roller ramp mechanism. The ramp mechanism, at least if it has roller bodies, has the advantage of low friction. A further advantage of the ramp mechanism is that the slope of the ramps can vary over their length. By means of an initially great slope, an air clearance, that is, a gap between the friction brake lining and the brake body with the friction brake released, can rapidly be overcome. By a decreasing slope, with increasing tightening of the friction brake, a greater force boost, and thus at limited drive torque great force, can be attained. A further advantage of a ramp mechanism is the possibility of a parking brake by means of an indentation in the ramps of the ramp mechanism after a rise. If the balls or roller bodies get into the indentation, the ramp mechanism remains on its own in that rotary position, and keeps the friction brake tightened when the electric motor is without current. 
     One aspect of the invention advantageously provides for a wear readjustment. To that end, the ramp mechanism has a rotary angle limitation in a direction of rotation that corresponds to the release direction of the friction brake. The rotary angle limitation may be formed by a stop on an end of the ramps. As a result, the ramp mechanism cannot be rotated in reverse any farther than up to the release of the friction brake. Moreover, the friction brake has a clutch, which in a rotary actuation direction transmits a torque that suffices to tighten the friction brake up to the maximum tightening force. In the opposed reverse or release direction of rotation, the torque transmitted by the clutch is limited. Examples of such a clutch are a slip clutch or a directionally switched clutch, that is, a so-called freewheel. The spring element of the friction brake can be a component of the slip clutch. For wear adjustment, the friction brake furthermore has a helical gear, which upon a rotation of the clutch inlet relative to the clutch outlet is adjusted in the direction of positioning the friction brake toward the brake body. The wear adjustment is effected because the ramp mechanism, with the friction brake released, is urged in the release direction by a torque. Because of the rotary angle limitation, the inlet and outlet of the ramp mechanism do not rotate counter to one another; instead, the clutch inlet and clutch outlet do so. As a result, the helical gear is adjusted, positioning of the friction brake toward the brake body is effected, and the spacing of the friction brake lining from the brake body, or in other words the air clearance, is reduced. 
     If a thickness of the friction brake lining is decreased by wear, then a spring travel decreases because of the elasticity of the friction brake lining. For compensation, another aspect of the invention contemplates a spring elasticity of the helical gear. If for wear compensation the helical gear is adjusted in the direction of a positioning of the friction brake lining toward the brake body, then a length of the helical gear increases, and thus its spring length or spring elasticity increases. The shortened spring travel resulting from wear of the friction brake lining is thus compensated for, and the compensation can be complete or partial, or overcompensation can take place. 
     Another aspect of the invention, contemplates a second spring element with a characteristic spring curve that drops (in some portions) and counteracts the spring element hereinafter also called the first spring element. As the second spring element, once again in principle any spring element with a characteristic spring curve that drops at least in some portions can be employed, and in particular again a special cup spring. The first spring element urges the friction brake lining directly or indirectly in the direction of an actuation of the friction brake; it is more prestressed when the friction brake is released than when the friction brake is actuated. Because of the dropping characteristic spring curve, the spring force of the first spring element rises upon actuation of the friction brake. The second spring element acts counter to the first spring element, or in other words in the direction of a release of the friction brake. With the friction brake released, the second spring element is not prestressed as much as with the friction brake actuated; because of the dropping characteristic spring curve, the spring force of the second spring element drops upon actuation of the friction brake. The two spring elements are designed in such a way, and overall the disposition of the spring elements is designed in such a way, that with the friction brake released, the resultant spring force of the two spring elements is virtually zero; a low, negative resultant spring force, that is, a spring force acting in the direction of a release of the friction brake by itself, that is, without the action of its actuating device, keeps the released friction brake in the released position and therefore preferred. When the friction brake is actuated, the resultant spring force of both spring elements is positive; that is, the actuation of the friction brake is reinforced by the two spring elements. Depending on the design of the two spring elements and the structural design of the friction brake, the resultant spring force can be approximately constant, or it can increase. By means of a resultant spring force that increases with increasing tightening, a major proportion of the tightening force is exerted by both spring elements even at a high tightening force. In principle, a decreasing spring force is also possible, although this might not be practical. By the inventive combination of two spring elements with a dropping characteristic spring curve, the resultant characteristic spring curve of the two spring elements and the resultant spring force acting on the friction brake lining can be varied. Moreover, a resultant spring force that is negative when the friction brake is released, or in other words that acts in the direction of a release of the friction brake, is possible, which exerts an initial tension on moving parts of the friction brake and avoids flapping when the friction brake is released. A spring element with a dropping characteristic spring curve should be understood to be a spring element with a characteristic spring curve that drops at least in some portions and that is used in the portion of its dropping characteristic spring curve. 
     In order to step a spring travel of the spring element that has the dropping characteristic spring curve up or down, one embodiment of the invention contemplates a gear by way of which the spring element with the dropping characteristic spring curve engages the friction brake lining. In a refinement in accordance to the invention, the gear has a varying gear ratio. Examples of such gears are lever mechanisms, in particular toggle lever mechanisms, or a ramp mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics of the invention will become apparent from the ensuing description of embodiments of the invention in conjunction with the drawings, in which 
         FIG. 1  shows a first exemplary embodiment of a friction brake of the invention, in the form of a disk brake, looking radially from outside onto a brake disk in section along a secant plane to the brake disk; 
         FIG. 2  shows a slope of a ramp of a ramp mechanism of the friction brake of  FIG. 1 ; 
         FIG. 3  shows a characteristic spring curve of a spring element of the friction brake of  FIG. 1 ; and 
         FIG. 4  shows a detail indicated by the arrow IV in  FIG. 1  of a modified embodiment of the invention. 
     
    
    
     The drawings are to be understood as simplified, schematic illustrations, not to scale, for the sake of comprehension and explanation of the invention. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The friction brake according to the invention, shown in  FIG. 1 , is embodied as a disk brake  1 . It has a brake caliper  2 , in which two friction brake linings  4 ,  5  are disposed, one on either side of a brake disk  3 . One of the two friction brake linings  4  is disposed fixedly in the brake caliper  2 ; the other friction brake lining  5  can be pressed for actuation, that is for tightening the disk brake  1 , against the brake disk  3  by an electromechanical actuating device  6 . The actuating device  6  is disposed on the same side of the brake disk  3  as the movable friction brake lining  5 . Both friction brake linings  4 ,  5  are braced in the circumferential direction of the brake disk  3  in a manner known per se in a brake holder, which is not shown here for the sake of clarity in the drawing. The brake holder, in a manner known per se, guides the brake caliper  2  transversely displaceably to the brake disk  3  on guide bolts  7 . When the movable friction brake lining  5  is pressed against the brake disk  3 , the brake caliper  2  is displaced transversely to the brake disk  3  and presses the fixed friction brake lining  4  against the other side of the brake disk  3 , which is braked as a result. This is known per se. The brake disk  3  forms a brake body that is to be braked. 
     The actuating device  6  has an electric motor  8  which, via a step-down gear  9  and a ramp mechanism  10  that is to be explained further hereinafter, presses the movable friction brake lining  5  against the brake disk  3 . In the exemplary embodiment shown, the step-down gear  9  is a two-stage gear train with spur gears. 
     The ramp mechanism  10  has two coaxially disposed, essentially circular disks  11 ,  12 , which are rotatable counter to one another. One disk  11  has a set of teeth  32  on its outer circumference; thus it simultaneously forms both a face edge and last gear wheel of the gear train of the step-down gear  9 . Instead of a spur gearing, the disk  11  may also be embodied as a plate wheel or cone wheel (not shown), so that the last stage of the step-down gear  9  forms a right-angle gear (not shown). As a result, a disposition of the electric motor  8  parallel to the brake disk  3  is possible, instead of with an axis perpendicular to the brake disk  3  as shown in the exemplary embodiment. This makes a more-compact structure of the brake caliper  2  possible. Also by means of a worm gear, whose worm engages the set of teeth  32  on the circumference of the disk  11  of the ramp mechanism  10 , a disposition of the electric motor  8  parallel to the brake disk  3  is possible (not shown). 
     The disk  11  will hereinafter also be called the driving disk or in short the drive of the ball ramp mechanism  10  and is always identified by the same reference numeral  11 . The other disk  12  of the ramp mechanism  10  will hereinafter also be called the driven disk or the power takeoff of the ball ramp mechanism  10  and always has the reference numeral  12 . Both disks  11 ,  12 , on their facing end faces, have grooves that extend over a limited angle in the circumferential direction. The grooves form ball races or ramps  15 , in which balls  13 , as roller bodies, roll. Thus the ramp mechanism  10  is a ball ramp mechanism. Instead of balls  13 , the ramp mechanism may also have other roller bodies, such as cylindrical or conical rollers, or it may be embodied as a sliding mechanism (not shown) instead of as a rolling mechanism. A depth of the grooves that form the ball races decreases in one circumferential direction of the disks  11 ,  12 ; that is, the ball races have a slope in a circumferential direction of the disks  11 ,  12 . Three ball races distributed over the circumference are provided, so that the disks  11 ,  12  are braced with three balls  13  and thus in a statically certain manner. By means of a rotation of the driving disk  11  relative to the driven disk  12 , the balls  13  roll in the ball races and, because of the slope of the ball races, force the disks  11 ,  12  apart. By rotation of the driving disk  11 , the driven disk  12  is displaced translationally in the axial direction. Via a helical gear  14 , to be described hereinafter, the driven disk  12  of the ramp mechanism  10  presses the movable friction brake lining  5  against the brake disk  3 . 
     The slope of the ball races, hereinafter also called ramps  15 , in the disks  11 ,  12  of the ramp mechanism  10  is not constant; instead, it has the course shown in  FIG. 2 . At the beginning, the ramps  15  have a great slope over a short portion  16 , so that an air clearance, that is, a gap between the friction brake linings  4 ,  5  and the brake disk  3 , is rapidly overcome. Next, the ball races  15  have a portion  17  of decreasing slope. In this portion  17 , the friction brake linings  4 ,  5  contact the brake disk  3 , and the tightening and braking force is increased by rotation of the driving disk  11  in the tightening direction. The decreasing slope in the portion  17  of the ramps  15  brings about an increase in the force boost, so that a high tightening and braking force can be achieved. The tightening force is the force with which the movable friction brake lining  5  is pressed against the brake disk  3 . 
     After the portion  17  having the decreasing slope, the ramps  15  have an indentation  18 . If the disk brake  1  is tightened so much that the balls  13  get into the indentations  18  of the ramps  15 , then the ramp mechanism  10  automatically remains in that position; the disk brake  1  remains tightened without the aid of the electric motor  8 . This is the so-called parking brake position of the disk brake  1 , in which the disk brake  1  maintains the braking force without being supplied with current. 
     Over a portion  19  adjoining the indentation  18 , the ramps  15  rise again. The tightening and braking force can be further increased as a result. This portion  19  is provided for wheel brakes of a rear axle of a motor vehicle to enable increasing the braking force even more while the vehicle is driven in reverse. The reason for this is that with braking while driving in reverse, there is an additional load on the rear axle, and thus a greater braking force is possible and may be necessary. Otherwise, the ramps  15  may also end with the indentation  18 . In the event that no parking brake function is desired, the indentation  18  may be omitted. The portion  17  in which the slope of the ball races  15  decreases is utilized for typical service braking operations. 
     In the release direction, a rotary angle of the disks  11 ,  12  of the ramp mechanism  10  is limited. The rotary angle limitation is effected by means of a stop  20 , which is formed by the depth and shape of the grooves, forming the ramps  15 , at the beginning of the ramps  15  in the disks  11 ,  12 . The stop that limits the rotary angle of the disks  11 ,  12  in the release direction can also be realized in some other way; for instance, both disks  11 ,  12  may have lugs that abut one another (not shown) upon reverse rotation of the disks  11 ,  12 . Thus in the reverse direction of rotation, that is, in the release direction of the disk brake  1 , the disks  11 ,  12  can rotate back counter to one another only as far as their outset position. 
     The driven disk  12  of the ramp mechanism  10  is urged by a cup spring  21  in the direction of the brake disk  3 , or in other words in the direction of tightening of the disk brake  1 . The cup spring  21  is braced in a housing  22  of the brake caliper  2  in which the step-down gear  9  and the ramp mechanism  10  are accommodated as well. It is a special cup spring  21 , which has no linear characteristic spring curve; its characteristic spring curve  23  is shown in a graph in  FIG. 3 . The relative spring force F/F 0  is plotted on the ordinate; on the abscissa, the deformation s of the cup spring is plotted in relation to the height h 0  of the cup spring  21  when it is undeformed. The characteristic spring curve rises up to a maximum and then drops to a minimum, from which point it rises again. At the minimum of the characteristic spring curve, the spring force is approximately zero. At the minimum, the characteristic spring curve of the cup spring  21  can have a low positive or negative value. Negative means that the spring force is operative in the opposite direction. The deformation s of the cup spring  21  means that the spring becomes increasingly flattened. It reaches a flat disk shape on the dropping portion of the characteristic spring curve  23  somewhat before the minimum. Upon further deformation, the cup spring  21  is as it were inverted and curves in the opposite direction. 
     In the disk brake  1  of the invention, when the disk brake  1  is released the cup spring  21  is prestressed such that it is located approximately at the minimum of the characteristic spring curve  23 . Upon tightening of the disk brake  1 , the deformation of the cup spring  21  decreases; that is, it curves more markedly in the direction of its relaxed state. Upon maximal tightening of the disk brake  1 , the deformation of the cup spring  21  decreases until it is in the range of the maximum of the characteristic spring curve  23 . Thus the cup spring  21  is used in the portion of its characteristic curve  23  in which the characteristic curve  23  drops. In the graph in  FIG. 3 , the portion used of the characteristic spring curve is drawn with a solid line; outside the portion used, the characteristic spring curve is drawn with dashed lines. Upon tightening, the characteristic spring curve is drawn through from minimum to maximum, or from right to left in the graph. The deformation, which can also be called deflection, decreases, which means that with the disk brake  1  released, the nearly flattened cup spring  21  upon tightening curves in the direction of its relaxed shape. That also means that the spring force exerted by the cup spring  21  on the movable friction brake lining  5  rises with increasing tightening of the disk brake  1 , instead of decreasing as in spring elements with a rising characteristic spring curve. With increasing tightening of the disk brake  1 , the portion of the tightening force exerted by the cup spring  21  with which the movable brake lining  5  is pressed against the brake disk  3  thus rises. The electromechanical actuating device  6 , including the step-down gear  9  and the ramp mechanism  10 , are correspondingly less loaded; the electric motor  8  needs to exert only a portion of the tightening force necessary for brake actuation and can accordingly be made smaller, lighter in weight, and less powerful. The step-down gear  9  too can be designed for a suitably lesser torque. Overall, the cup spring  21 , which according to the invention is used in the dropping portion of its characteristic spring curve  23 , can be conceived of as a spring element with a characteristic spring curve that (in some portions) drops. 
     What is hereinafter called the first cup spring  21  acts counter to a second cup spring  24 , which engages the opposite side of the driven plate  12  of the ramp mechanism  10  and which is likewise braced in the housing  22  of the brake caliper  2 . The second cup spring  24  is likewise a special cup spring  24 , with a characteristic spring curve corresponding to  FIG. 3  with a dropping portion, and which is used in the dropping portion of its characteristic spring curve. Since the second cup spring  24  is disposed conversely to the first cup spring  21 , the second cup spring  24  becomes more severely deformed upon tightening of the disk brake  1 ; it traverses the characteristic spring curve from maximum to minimum, or in other words from left to right, whereupon its spring force decreases. While the spring force of the first cup spring  21  increases upon tightening of the disk brake  1 , the contrary spring force of the second cup spring  24  decreases upon tightening of the disk brake  1 . With the disk brake  1  released, the second cup spring  24  compensates for the spring force of the first cup spring  21 , which with the disk brake  1  released is in the range of its minimal spring force. As a result, without the action of the actuating device  6  or in other words with the electric motor  8  currentless, the disk brake  1  remains in the released position. With the disk brake  1  released, the spring force of the second cup spring  24 , which acts in the direction of release of the disk brake  1 , can also be somewhat greater than the spring force of the first cup spring  21 , which acts in the direction of tightening of the disk brake  1 . As a result, the two cup springs  21 ,  24  keep the disk brake  1  released with little prestressing, and they avoid flapping noises. With the disk brake  1  actuated, the spring force of the first cup spring  21  is greater than the contrary spring force of the second cup spring  24 , so that there is a resultant spring force which exerts the desired, described tightening force on the movable friction brake lining  5 . Since the first cup spring  21  and the resultant spring force of the two cup springs  21 ,  24  bring to bear a portion of the tightening force of the disk brake  1 , the actuating device  6  is corresponding relieved. Depending on the design, the resultant spring force of the two cup springs  21 ,  24  may make up a large proportion of the tightening force of the disk brake  1 . In the parking brake position of the disk brake  1 , in which the balls  13  of the ramp mechanism  10  are located in the indentations  18  in the ramps  15 , the step-down gear  9  is load-free. Its gear wheels and/or the set of teeth  32  of the disk  11  can therefore be made of plastic. 
     As already noted, the driven disk  12  of the ramp mechanism  10  acts on the movable friction brake lining  5  via the helical gear  14 . A spindle  25  and a nut  26  of the helical gear  14  are sleeve-shaped and thin-walled and as a result have a spring elasticity. 
     A tubular nut  26 , on the face end of which the friction brake lining  5  is disposed, is engagement with the spindle  25 . The helical gear  14  serves the purpose of wear readjustment upon wear of the friction brake linings  4 ,  5 . It is adjusted in the direction of a positioning of the friction brake lining  5  toward the brake disk  3 , in order to compensate for wear of the brake linings  4 ,  5 . Upon this adjustment, a free length, protruding from the nut  26 , of the spindle  25  becomes greater, and as a result a spring travel increases because of the spring elasticity of the sleevelike and undulating spindle  25 . As a result, at least partial compensation is provided for the fact that a spring elasticity of the friction brake linings  4 ,  5  becomes less when the thickness decreases from wear. 
     The adjustment of the helical gear  14  is effected in that the drive plate  11  of the ramp mechanism  10  is urged in the release direction by the electric motor  8 , when the disk brake  1  is released. The stop  20  of the ramps  15  that forms the rotary angle limitation prevents a rotation of the two disks  11 ,  12  of the ramp mechanism  10  counter to one another. The driven disk  12  moves in the release direction along with the drive disk  11 , whereupon the spindle  25  rotates in the nut  26  of the helical gear  14 , and the helical gear  14  is adjusted as described in the direction of a positioning of the friction brake lining  5  toward the brake disk  3 . As a result, the compensation for wear is accomplished. 
     The two cup springs  21 ,  24 , located in the housing  22  of the brake caliper  2  and contacting the driven disk  12  of the ramp mechanism  10  form a slip coupling, which allow the described rotation of the driven disk  12  of the ramp mechanism  10  past the release position in the release direction. In the tightening direction, and when the two disks  11 ,  12  of the ramp mechanism  10  are not resting on their rotary angle limitation  20 , the two cup springs  21 ,  24  that form the slip coupling keep the driven plate  12  fixed against relative rotation. 
     In the modified embodiment in  FIG. 4 , the drive disk  11  of the ramp mechanism  10  also has ramps  27  on its face end remote from the driven plate  12 , and roller bodies, in the exemplary embodiment conical rollers  28 , roll on these ramps. On the side of the drive disk  11  remote from the driven disk  12 , a plate, here called a pressure plate  29 , is disposed which also has ramps  30 , on which the conical rollers  28  roll. Thus the modification according to  FIG. 4  has a second ramp mechanism  31 . The pressure plate  29  is rotatable with an axial bearing  33  and is supported axially fixedly in the housing  22  of the brake caliper  2 . The first cup spring  21  does not engage the driven plate  12  but instead engages the pressure plate  29 . For actuation of the disk brake  1 , as in  FIG. 1 , the drive disk  11  of the first ramp mechanism  10  is driven to rotate by the electromechanical actuating device  6 . In the process, the drive disk, supported rotatably and axially fixedly in the housing  22  of the brake caliper  2 , does not move axially but instead, via the second ramp mechanism  31 , it moves the pressure plate  29  in the axial direction. In that process, the pressure plate  29 , depending on the direction of the slope of the second ramp mechanism  31 , either tightens or loosens the first cup spring  21  engaging it. Via the second ramp mechanism  31 , the first cup spring  21  exerts a moment on the drive disk  11 , which acts in the direction of tightening of the disk brake  1  and reinforces the tightening of the disk brake  1  as described in conjunction with  FIG. 1 . The first cup spring  21  can be used in  FIG. 4  in the rising portion of its characteristic spring curve. If it is used as in  FIG. 1  in the dropping portion of its characteristic spring curve, the slope of the second ramp mechanism  31  is reversed, so that the pressure plate  29 , on tightening of the disk brake  1 , is displaced axially in the direction toward the brake disk. In every case, the spring force of the first cup spring  21  increases upon tightening of the disk brake  1 . The second ramp mechanism  31  forms a gear by way of which the first cup spring  21  subjects the drive plate  11  to a moment and acts indirectly on the friction brake lining  5  via the first ramp mechanism  10 . With the first ramp mechanism  31 , a step-up or step-down of a spring travel and of the spring force of the first cup spring  21  is achieved, so that an adaptation of the spring properties of the cup spring  21 , which is used in the portion of its dropping characteristic spring curve, to the given conditions and requirements of the disk brake  1  is possible. Since the ramps  27 ,  30  of the second ramp mechanism  31  can have a slope that varies over the length of the ramps  27 ,  30 , it is possible with the second ramp mechanism  31  to realize a gear of varying gear ratio. As a result, manifold possibilities for adaptation of the properties of the first cup spring  21  to the given conditions and requirements of the disk brake  1  are possible. 
     The foregoing relates to the preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.