Abstract:
The invention relates to a A disk brake apparatus with a readily—releasable wear adjuster, including equipped with a brake caliper ( 1 ), which overlaps a brake disk, with a tensioning device for tensioning brake pads and with an adjusting system for compensating for brake pad wear, where the adjusting system includes. Said disk brake eomprises at least one adjusting rotating device with an electric motor drive for adjusting the brake pad clearance ( 5 ). A and a release device that assists in releasing the adjusting rotating device is used in addition to when the electric motor drive retracts the brake pads to for adjusting the specified air clearance.

Description:
[0001]    The present application is a continuation of International Patent Application No. PCT/EP02/04037, filed Apr. 11, 2002, designating the United States of America and published in German as WO 02/088562, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Federal Republic of Germany Patent Application No. 101 20 327.5, filed Apr. 26, 2001. 
     
    
     
       BACKGROUND AND SUMMARY OF THE INVENTION  
         [0002]    The invention relates to a disk brake for commercial vehicles, and particularly to a wear-adjusting system for such disk brakes, as well as to a method for controlling such an adjusting system.  
           [0003]    Application devices for disk brakes are known, in the case of which a wear adjusting device, which is independent of the brake application, is driven electromechanically.  
           [0004]    Thus, distance sensors can, for example, be utilized for adjusting the release play, whose signals are used for controlling the actuating drive of the adjusting device.  
           [0005]    However, controls of this type require high expenditures for the sensing and electronic controlling and are also susceptible to disturbances. Systems of this type are described, for example, in European Patent Document EP 0 995 921 A1, in European Patent Document EP 0 995 923 A2 and in International Patent Document PCT/WO 99/08018.  
           [0006]    A clearly simpler and, in addition, reliable operating mode of the wear adjusting system operated by means of an electromechanical drive is possible if, when the brake is not operated, the rotating device causes the brake shoes to briefly come in contact with the brake disk and then, starting from this position, restores them by a predetermined amount which corresponds to the desired release play. Such a method of operation is described in German Patent Document DE 197 31 696 A1. Controls of this type have been successful per se. However, with respect to a special operating case, they require further improvements.  
           [0007]    If, specifically at the moment at which the adjusting system applies the brakes shoes to the brake disk for adjusting the release play, another braking is initiated and if, in addition, the brake shoes and the brake disk noticeably heat up because of the resulting heat development, as a result of the expansion, the brake may remain applied after the termination of the braking operation such that, because of the frictional resistance occurring as a result of the interaction in the self-lockingly designed adjusting threads between the adjusting nut and the adjusting spindle, the relatively small dimensioned driving motor of the wear adjusting system can no longer turn back the adjusting system. Because of these effects, the release play at the brake cannot be restored. As a result of this effect, the brake will grind during the drive which causes a further high braking temperature and an extremely high wear.  
           [0008]    It is therefore an object of the invention to further develop the disk brake of the above-mentioned type such that, with respect to the method and the construction, a reliable release play is ensured in a simple manner.  
           [0009]    According to the idea of the invention, it is provided that, in addition to the electric-motor drive, the adjusting system has a release device which promotes the release of the adjusting rotating device.  
           [0010]    If, during the operation of the disk brake, an operating situation occurs in which the electric-motor drive, because of the application of the brake, can no longer correctly adjust the release play, the additional release device will promote this release process. As a result of the joint effect of the electric-motor drive and the supplementary release device, the release play remains precisely adjustable despite the application of the brake.  
           [0011]    It is one solution to design the release device to be purely mechanical. As an alternative, it is conceivable to use electromechanically or electronically operated systems for supporting the release effect. Piezo elements can, for example, be used here which, when energized, can eliminate the application of the brake.  
           [0012]    According to a preferred embodiment of the invention, it is provided that the adjusting rotating device has an adjusting nut into which a rotating spindle is screwed which, on one of its ends, has a thrust piece acting upon the brake pad, in which case the release device acts upon the adjusting nut or the rotating spindle.  
           [0013]    This simple constructive implementation of the adjusting rotating device with an adjusting nut and a rotating spindle, which are in each case driven by an electric motor, permits the providing of a separate adjusting rotating device with an electric-motor drive on each side of the disk brake. This can be used, for example, in the case of disk brakes which are constructed as fixed calipers or as a caliper with a very small displacement or swiveling path.  
           [0014]    As an alternative, it is conceivable that the adjuster rotating device has a rotating spindle onto which an adjusting nut is screwed which, on one of its ends, has a thrust piece acting on the brake pad, in which case the release device acts upon the adjusting nut or the rotating spindle.  
           [0015]    Many different mechanical implementations are conceivable with respect to the release device for an adjusting rotating device with an adjusting nut and rotating spindle.  
           [0016]    Expediently, the ramp profile is molded, particularly impressed, directly into the face of the adjusting nut or rotating spindle.  
           [0017]    The caliper or an element of the application unit is expediently the supporting element. In this case, an opposite ramp profile can be molded directly into the caliper or the element of the application unit.  
           [0018]    Advantageously—since it is easy to manufacture—the ramp profile is molded into a ramp disk which is non-rotatably disposed on the face of the adjusting nut or the rotating spindle.  
           [0019]    A particularly cost-effective variant is distinguished in that the release device is constructed in such a manner that the pressure supporting surface of the adjusting nut is equipped with a ramp profile, in which case a supporting disk with an opposite ramp profile rests on the pressure supporting surface, and in which case the flat back side of the supporting disk rests against a supporting surface of a supporting element.  
           [0020]    This supporting element may, for example, be the caliper or, on the side of the application device, a brake lever, or an additional force transmission element placed between the brake lever and the rotating spindle or adjusting nut.  
           [0021]    The release device is preferably arranged only on the side of the brake situated opposite the application device. For releasing or adjusting the brake release play in the initially described special case of the applied brake, it is sufficient for the brake to be released from its application at least on one side. Because of the supporting of the rotating spindles on the caliper, the corresponding release device can be arranged between the caliper and the thrust piece. Naturally, a variant with a release device on both sides of the brake disk or on the side of the application device is also conceivable.  
           [0022]    The invention makes it possible in a simple manner to displace the brake lever and/or the piston unit by a defined amount during each activation of the adjusting system in the direction of the brake disk by means of a mechanism which, also when the brake is applied, can be released again by the adjusting device or releases automatically, after previously the electric-motor actuating drive, with the assistance of the release device, has moved the thrust pieces so far away from the brake disk that, in the event of a possibly unacceptably small brake release play, because of a heating and application of the brake, at least the amount of the desired brake release play is reached.  
           [0023]    In this case, the wear adjusting device is operated until the brake shoes have contact with the brake disk. Subsequently, by releasing the brake release play securing mechanism, the desired brake release play is restored in that the brake lever and/or the piston unit are moved by means of the actuating drive or automatically again by the defined amount away from the brake disk.  
           [0024]    This method facilitates also the adjusting of the brake release play per se because the desired brake release play is defined by the amount of the advancing stroke of the brake release play securing mechanism or of the release mechanism as a fixed construction characteristic and does not have to be adjusted by an electronically controlled restoring of the adjusting spindles.  
           [0025]    As an alternative to the described ramp system, it is also possible to provide a type of clamping roller free wheel or a clamping body free wheel as the release device. These two variants of the release device can also be constructively implemented in a cost-effective manner and can also be mounted particularly compactly between the adjusting nut and the caliper or another supporting element. Thus, it is possible to provide indentations on the face of the adjusting nut or in a ring placed thereon, which indentations receive the clamping bodies. In the case of a clamping roller system, these indentations are preferably ramp-shaped. In the case of a clamping body system, they are preferably constructed parallel to the supporting surface.  
           [0026]    According to the method of the invention, first, for adjusting the brake release play by one controlling of the driving motor, a restoring of the rotating adjusting spindles can take place for securing the minimum brake release play. Subsequently, another controlling takes place in the sense of an advancing movement of the adjusting rotating spindles, while simultaneously the advancing movement of the brake release play securing device is triggered. After a sufficiently dimensioned waiting time, which is designed such that the brake shoes can be placed against the brake disk, by means of the actuating drive, a reversely rotating release pulse for securing the brake release play is initiated in order to secure the desired brake release play in this manner. In this manner, a very reliably operating electromechanical wear adjusting device is implemented by very simple means and low sensing and controlling expenditures.  
           [0027]    As an alternative to observing a waiting period, the end of the rotating movement of the motor can be determined by a sensing (stop detection), or the stopping point in time of the actuating drive can be determined by means of an excess current sensor.  
           [0028]    Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a sectional view of a part of a disk brake having an adjusting system for adjusting the brake pad wear in accordance with an embodiment of the present invention;  
         [0030]    FIGS.  2  to  4  are sectional views of elements of different variants of release devices for wear adjusting systems in accordance with various alternative embodiments of the present invention;  
         [0031]    [0031]FIGS. 5, 6 are sectional views of elements of adjusting rotating devices in accordance with various alternative embodiments of the present invention;  
         [0032]    [0032]FIG. 7 is an exploded view of an adjusting nut with a ramp disk and a view of the assembled elements in accordance an embodiment of the present invention; and  
         [0033]    [0033]FIG. 8 is a sectional view of a disk brake. 
     
    
     DETAILED DESCRIPTION  
       [0034]    [0034]FIG. 1 will be described first. FIG. 1 essentially illustrates an adjusting module for a disk brake which has a caliper  1 .  
         [0035]    The area of the brake situated opposite the application device is illustrated here.  
         [0036]    The application device can be constructed, for example, in the manner of the initially mentioned patent document.  
         [0037]    However, the present construction also relates to a fixed-caliper disk brake or a disk brake with only a very slight displacement or swivelling path of the caliper, in which case an adjusting of the brake pad wear preferably also has to take place on the side of the brake disk situated opposite the application device (see FIG. 8).  
         [0038]    An adjusting module  2  is arranged in a recess of the caliper  1 . This adjusting module  2  comprises a first mounting plate  3  and a second mounting plate  4  attached to the first mounting plate  3 . Here, an electric motor  5  is arranged on the mounting plate  3 , which electric motor  5  drives a chain  9  by means of a transmission  6  with gear wheels  7  and  8 , which chain is guided around two mutually parallel arranged adjusting rotating devices  10 ,  11 , which each have a rotating spindle  12 ,  13  screwed into adjusting nuts  14 ,  15 , onto which gear wheels  16 ,  17  are respectively placed with which the chain  9  meshes. It is also conceivable to arrange the electric motor on the outside on the caliper and to connect it with the transmission by way of a shaft penetrating the caliper (not shown).  
         [0039]    At its end facing away from the brake disk, that is, situated toward the caliper, the adjusting rotating device is supported on the caliper  1 . At their end facing the brake disk, the adjusting rotating spindles  12 ,  13  each have thrust pieces  18 ,  19  which act upon the brake pads which are not shown here.  
         [0040]    For adjusting the brake, the adjusting nuts are rotated by means of the electric motor  3  and the transmission as well as the gear wheels  7 ,  8  and the chain  9 , so that the rotating spindles  12 ,  13  are displaced in the direction of the brake disk.  
         [0041]    Between the adjusting nuts  14 ,  15  and the caliper  1 —purely as an example—different elements are in each case arranged at the left adjusting nut and the right adjusting nut  14  in order to explain the invention in detail on two different variants. In practice, the release devices  20 ,  21  have an identical design.  
         [0042]    According to the invention, the releasing of the rotating spindles from brake pads and the releasing of the brake pads from the brake disk respectively is facilitated by mechanically operating release devices  20 ,  21 . This means that the effect of the electric motor  5  is assisted during the release of the adjusting device  10 ,  11 .  
         [0043]    In the case of the operating principle of the release device  20  illustrated in the left area of the drawing as well as in FIG. 2, the supporting surface of the adjusting nut  15  is equipped with a ramp profile  22  (see FIG. 2), which interacts with a corresponding ramp profile  23  of a supporting disk  24  axially adjoining the adjusting nut  15  and being supported on the caliper  1  with its surface facing away from the adjusting nut. The flat back side of the supporting disk  24  ensures the transmission of the reaction force from the piston system in this form on the caliper.  
         [0044]    During an operation of the brake, the reaction force resulting from the application force of the brake is deflected from the thrust piece  19  by way of the adjusting thread between the rotating spindle  13  and the adjusting nut  15  to the adjusting nut  15  and, by way of its face away from the brake disk and provided with the ramp profile, to the supporting disk  24  and, from there, to the supporting surface at the caliper  1 .  
         [0045]    This facilitates the release of the adjusting rotating device in a simple mechanical manner.  
         [0046]    The ramp profile can be impressed directly into the corresponding face of the adjusting nut  15  or can be entered there in a different manner. The ramp profile may also be contained in an additional ramp disk which rests on the face of the adjusting nut (not shown here).  
         [0047]    During a brake release play adjusting operation by means of the electromechanical drive  5 , a rotation of the adjusting nut  15  first takes place in the sense of a rotating-out of the thrust piece  19  connected with the adjusting thread bolt or the rotating spindle  13  or constructed in one piece.  
         [0048]    At the start of the adjusting movement, the adjusting nut  15  first rotates against the ramp disk  24  by a predetermined rotating angle until a stop has been reached. Then, corresponding to the slope of the ramp profile, the adjusting nut  15  is displaced by a predetermined amount, together with the screwed-in thrust piece  19 , against the brake disk.  
         [0049]    The amount of this displacement corresponds to the constructively defined desired brake release play.  
         [0050]    During this first, limited part of the adjusting movement, an adjustment of the thrust piece  19  relative to the adjusting nut  15  can already take place by way of the adjusting thread. In this case, the desired brake release play is obtained from the sum of the axial adjusting movements of the adjusting nut  15  relative to the caliper  1  and to the thrust piece  19  relative to the adjusting nut  15 .  
         [0051]    It is also possible to avoid the adjustment of the thrust piece  24  relative to the adjusting nut  15  in the area of the rotation of the adjusting nut  15  provided for securing the brake release play, in that the protection against rotation of the thrust piece  15  and of the adjusting thread bolt (rotating spindle  13 ) respectively is provided with a swivel play, whose amount corresponds to the rotating angle of the adjusting nut  15  required for securing the brake release play.  
         [0052]    For ensuring the operability of the release device, it is advantageous for the rotating inhibition of the supporting disk  24  against the supporting surface on the caliper  1  in each operating condition to be greater than the rotating inhibition between the adjusting nut  15  and the supporting disk  24 .  
         [0053]    This means that, at the start of the rotating movement of the adjusting nut  15 , the supporting disk with the ramp profile  23  during the displacement of the adjusting nut  15  is to adhere to the supporting surface of the caliper without any rotation and, only after the rotating stop has been reached, is to continue to rotate in the sense of the actual adjusting movement of the pressure piece  19  with the adjusting nut  15 .  
         [0054]    Such a rotating inhibition of the ramp disk can be implemented in a simple manner.  
         [0055]    Thus, for example, a friction-increasing coating can be provided on the supporting surface of the ramp disk  24 . As an alternative or in addition, it is also possible to provide a friction-reducing coating on the side of the ramp profile  22 ,  23 .  
         [0056]    For example, by means of a diamond dust coating, a friction increase can be obtained up to coefficients of friction of 0.5. A friction reduction can be implemented in a simple manner by means of a sliding lacquer coating.  
         [0057]    As an alternative, it is also possible to provide a type of braking mechanism on the ramp disk  34  for increasing the rotating inhibition. This can be implemented, for example, by a frictional force on the circumference of the ramp disk  24 , preferably by means of a sliding spring element in the manner of a tolerance ring (not shown).  
         [0058]    As an alternative, it is also possible to use, in the manner of FIG. 2 and  3 , instead of a ramp system, a release device  21  in the manner of a clamping roller free wheel or a clamping body free wheel for the axial adjustment.  
         [0059]    As illustrated in the right part of FIG. 1 as well as in FIGS. 3 and 4, in the case of an implementation as a clamping roller free wheel as well as in the case of an implementation as a clamping body free wheel, recesses  25  are provided on the face of the adjusting nut  14  or—illustrated here—in a ring  26  arranged between the adjusting nut and the supporting disk  24 , which recesses  25  accommodate the clamping bodies  27  or the clamping rollers  28 .  
         [0060]    In the case of a clamping roller system (FIG. 3), these indentations  26  are provided with a ramp shape. In contrast, in the case of the clamping body system (FIG. 2), they extend parallel to the supporting surface.  
         [0061]    In the case of the clamping body system, because of their free-wheeling clamping effect, the clamping bodies  27  swivel when the adjusting movement begins. The resulting height difference of the clamping bodies causes the axial adjustment of the adjusting nut  14 .  
         [0062]    In contrast, in the case of the clamping roller system of FIG. 4, when the adjusting movement starts, the free-wheel-type locking effect of the clamping roller  28  engages. Since, because of the rotating inhibition of the upper, in this case, flat supporting disk  24 , the latter cannot be moved, the clamping rollers  28  roll upward on the ramp planes and, in the process, cause the axial adjustment of the adjusting nut  14 .  
         [0063]    The further course of the brake release play adjustment preferably takes place such that, by way of a continued rotation of the adjusting nut  14 , the thrust piece  18  is screwed out so far that the brake shoe or the brake pad comes in contact with the brake disk. As a result of the now acting frictional forces in the force transmission path (thrust piece contact surface, adjusting thread, ramp disk supporting surface), the further adjusting movement is stopped. After the detection of this condition, for example, by way of the current consumption of the electric motor or after a sufficiently dimensioned stopping time in this condition, the adjusting nut  14  is rotated back by the rotating angle required for releasing the brake release play.  
         [0064]    In the critical case that, specifically at the moment at which, during a brake release play adjusting operation, the brake shoes are placed against the brake disk, another braking is initiated, the adjusting nut  14  can now be rotated back by the electrical adjusting mechanism, also when the brake is applied, in a simple manner into its initial position restoring the brake release play. This can be achieved because the rotating resistance in the clamping body, the ball ramp or sliding ramp mechanism in the releasing direction is so low because of the selected geometries on the ramp system or in the clamping system that the releasing becomes possible at very low expenditures of force or takes place almost automatically.  
         [0065]    Thus, it is, for example, in the case of the ramp system of FIGS. 1 and 2, to select the ramp angle with approximately 10° such that, under the given frictional conditions (steel on steel, hardened), a freedom from self-locking occurs anyhow.  
         [0066]    In the case of the brake release play adjusting operation, when the brake shoes are applied, the resulting reaction force has to be compensated proportionately by corresponding adjusting forces of the adjusting rotating device because a reverse rotating force is generated by way of the sliding ramp which has no self-locking.  
         [0067]    When now a service braking takes place at a high force, the adjusting force of the adjusting rotary drive is overcome and the adjusting nut  14 ,  15  is automatically rotated back into its initial position securing the brake release play. When a ball ramp or clamping body system is used, this process takes place in an equivalent form.  
         [0068]    In the case of a disk brake of the initially mentioned construction having a sliding caliper, it is also possible that, when a brake release play adjusting operation is initiated, the brake lever is advanced by a certain amount corresponding to a minimum brake release play in the sense of an application movement. The brake release adjustment then takes place in the manner described in German Patent Document DE 197 31 696 A1. After the brake shoes were applied, the lever is restored into its initial position and the brake release play is thereby adjusted. The advancing stroke of the brake lever securing the brake release play can take place by means of a separate adjusting device, but preferably by means of the electromechanical adjusting drive in that, by way of an element driven by the same actuating drive, such as an eccentric cam, the advancing stroke of the brake lever is generated at the beginning of the adjusting movement.  
         [0069]    In the case of the brake of the initially mentioned type, it is also possible to displace the traverse relative to the brake lever by the amount of the brake release play in the direction of the brake disk. Thus, for example, in the case of an adjusting synchronization shaft which extends through the eccentric axis and has bevel gears at the ends, when the adjusting system is operated, as a result of eccentric cams or radial cams connected with the synchronization shaft, the eccentric bolt is lifted off its seat in the traverse by the amount of the defined brake release play.  
         [0070]    According to FIG. 6, the adjuster rotating device  10  has the adjusting nut  14  into which the rotating spindle  12  is screwed, which, on one of its ends, has the thrust piece  18  acting upon the brake pad. The ramp profile is constructed, on the one side, in the caliper  1  and, on the other side, on the face of the adjusting nut  24 .  
         [0071]    In contrast, according to FIG. 5, the adjusting nut  14  has the thrust piece  18  (it is molded onto the adjusting nut  14  here), and the rotating spindle  12  with a screw-type head is supported at its axial end facing away from the adjusting nut—thus, in the area of its head—itself on the ramp disk  24  and, in the area of the face of the head, itself has a corresponding ramp profile.  
         [0072]    [0072]FIG. 7 is a perspective view of an adjusting nut  14  which has the ramp profile on its face. The ramp disk  24  can be placed on this face, which ramp disk  24  is surrounded by a friction spring  29  as a brake element increasing the rotating inhibition.  
         [0073]    For ensuring the release function, pins  30  at the ramp disk engage in appropriately dimensioned recesses  31  of the adjusting nut and are used for securing the rotating angle. At the right edge of FIG. 7, a unit is illustrated which is preassembled from elements illustrated in the left part of FIG. 7.  
         [0074]    [0074]FIG. 8 is a sectional view of a hinged-caliper disk brake, in which the elements illustrated in FIGS.  1  to  7  can be used.  
         [0075]    The application device comprises a rotary lever  32  which can be operated by a piston rod of a brake cylinder (not shown here) and is supported on the caliper  1  by bearing elements, such as balls, which are not visible here. On its side facing away from the caliper  1 , rotary lever  32  acts at one or two points upon an intermediate element  33 , which has a hemispherical projection  34  on one of its ends.  
         [0076]    When the rotary lever  32  is swiveled, the lower eccentric-type end (not visible here) of the rotary lever  32  causes an advancing of the intermediate element  33  in the direction of the brake disk  41 . The intermediate element  33 , in turn, presses an adjusting nut  14  toward the front, in which an adjusting spindle is screwed to the thrust piece which rests against a brake pad  35  and advances it during brakings.  
         [0077]    So that, with an increasing brake pad wear, the latter does not have to compensated by a correspondingly large swiveling movement of the caliper  1 , an adjusting device (one or two adjusting rotating drives) is also provided on the side of the brake disk  41  situated opposite the application device, the adjusting nuts  14  of the adjusting device here having been supported in each case on ramp disks  24  whose flat back sides are situated on the interior caliper surface.  
         [0078]    The caliper  1  must only bridge the working stroke during the application of the brake by means of a swiveling. This is implemented by a type of elastic spring  36 , which is arranged between the caliper  1  and a projection  37  fastened to a wheel axle, the swiveling angle of two stops  38 ,  39  being fastened between a lower projection  40  of the caliper and the wheel axle projection  37 .  
         [0079]    On the side of the brake disk situated opposite the application device, the ramp disks  24  are arranged between the caliper and the adjusting nut.  
         [0080]    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.