Patent Publication Number: US-2023151866-A1

Title: Mechanical wear gauge

Description:
FIELD 
     The invention relates to a mechanical wear gauge for detecting a brake liner wear and a brake disc wear of a disc brake for vehicles, in particular for utility vehicles. 
     BACKGROUND 
     Brake liners and brake discs are subjected to a wear such that the brake liner thickness and the brake disc thickness decrease with an increasing period of use. A main cause of the brake liner wear and the brake disc wear are deposits in the form of particles of dirt on the brake disc and the brake liner, which lead to undesirable brake noises and an inadequate brake power. At the latest when reaching a wear limit, a replacement of the said components is required. Otherwise, the braking action of the vehicle decreases significantly and emergency braking is no longer possible. In order to establish the brake liner wear, brake liner wear sensors, which notify the driver via an output in the driver’s cab as soon as the wear limit is reached, are mainly used. The wear on brake discs can, inter alia, be detected by way of optical sensors. In disc brakes which have no sensor system for measuring the brake liner wear and for identifying the brake disc wear, the measurement must be carried out mechanically. For a mechanical wear measurement of the brake disc and the brake liners, the wheel must be removed from the vehicle axle because the disc brake is arranged at the rim side behind the wheel. Such a mechanical measuring device for a brake disc is disclosed in EP1447587A1. The brake disc has on the outer circumference and on the inner circumference thereof a wear marking in the form of a step-like shoulder. The measuring device is in the form of a bridge and performs the function of a depth gauge by the measuring device being placed in the step-like shoulders. In the event of a non-uniform wear, the measuring device is not arranged parallel with the brake disc. The wear is determined by way of a separate sensor which is guided on the bridge of the measuring device. 
     KR20130093933 discloses a mechanical wear gauge for the brake liners. The measuring device is in the form of a screwdriver. A wear scale is arranged in the handle. A measuring needle which is guided by way of springs is arranged partially in the handle and a receiving member which is connected to the handle. In order to measure the brake liner wear, the receiving member is supported on the edge of a recess of the liner carrier. Afterwards, the measuring needle is guided through the recess of the brake liner until it strikes the brake disc. Via the measurement scale, the thickness of the brake liner can subsequently be read. 
     A measurement of the wear limits during travel operation is possible only in an adequate manner without time being spent in a workshop. Even in a workshop, the verification of the wear limits of the brake liners and the brake disc without installed wear sensors requires a considerable amount of time since each wheel has to be disassembled and assembled again. 
     SUMMARY 
     An object of the present disclosure is to provide a mechanical measuring device that, with a minimal amount of time being taken and without the disassembly of a vehicle wheel, can measure a brake liner wear and a brake disc wear. 
     The object is achieved in that the mechanical wear gauge has an element for detecting a brake liner wear and an element for detecting a brake disc wear. The mechanical measuring device measures, one after the other, the brake disc thickness and the brake liner thickness, wherein the brake liner thickness is measured indirectly by way of the brake caliper. That is to say that the brake liner thickness is measured via the displacement of the brake caliper in the direction of the brake disc as occurs from the wear-related reaction-side brake liner. The brake liner facing the rim of the wheel is defined as the reaction-side brake liner. The brake liner facing away from the rim of the wheel is defined as a brake-application-side brake liner. The advantage of the mechanical measuring device according to the invention is that it requires only a mechanical tool by way of which in one working step, on a vehicle, the brake liner thickness and the brake disc thickness can be measured. 
     In another advantageous embodiment, it has been found that the wear measurement of the brake liner thickness and the wear measurement of the brake disc thickness can be carried out without disassembly of a wheel from a vehicle axle. With the mechanical measuring device, without any time being spent in a workshop, the wear measurements which mentioned herein can be carried out by the driver or another person. The mechanical wear gauge is guided for wear measurement from the rim side between the brake carrier and the brake caliper on the brake disc. 
     In another embodiment, the mechanical wear gauge includes a base member and two sliding members which are arranged parallel on the base member and which can be moved axially along a longitudinal axis of the base member. The base member is constructed to be square. However, it may have any other geometric shape. Furthermore, the base member performs a plurality of tasks. The base member acts as a handle for the user of the mechanical wear gauge. Furthermore, the base member performs the task of the output device for reading the brake liner thickness in the actual state and the brake disc thickness in the actual state. In addition, the base member has receiving locations for fixing the movable sliding members. The sliding members may be replaced in the event of wear or a breakage. A complete replacement of the mechanical wear gauge is not required. Furthermore, the base member and the movable sliding members form a compact space-saving construction because the base member combines three functions in one component. 
     In one aspect of the present disclosure, a fixed measuring arm, which is configured to measure the brake disc thickness, is arranged on the base member axially in the overlap region of the movable sliding member. The measuring arm and the base member form one component. The movable sliding member is arranged radially below the measuring arm. The measuring arm and the movable sliding member together form a measuring device which is also referred to as a sliding measurement member. The movable sliding member, which is arranged in the overlap region of the measuring arm, has a projection which is configured for the movable sliding measurement member to be guided axially along the longitudinal axis of the base member by the user. 
     In one aspect of the disclosure, the measuring arm has a pincer leg which is arranged at the end of the measuring arm opposite the base member. The sliding member which is arranged in the overlap region of the measuring arm has, parallel with the first pincer leg, a second pincer leg, wherein the first pincer leg and the second pincer leg are constructed to receive a brake disc in the axial direction thereof and to surround the brake disc during the wear measurement operation. The brake disc is clamped by way of the pincer legs and a precise measurement of the wear of the brake disc is enabled because the mechanical wear gauge cannot slide on the base member during the reading of the wear, that is to say, the wear gauge remains in position. 
     It has further been shown that the sliding member for measuring the brake liner thickness can be fixed to the base member by means of two fixing screws. The measuring arm has, for each fixing screw, an opening in the form of an elongate hole, through which the two fixing screws are inserted and can lock the movable sliding member against an axial displacement of the measuring arm in the longitudinal direction thereof when the fixing screws are tightened. The number of fixing screws is not limited and may vary depending on the size of the base member and depending on the size of the movable sliding member. The fixing of the movable sliding member by way of the fixing screws ensures precise reading of the brake disc wear, because the movable sliding member cannot axially slide after the fixing screws are tightened. In particular, knurled screws are suitable as fixing screws. 
     In another embodiment, the base member has a brake disc wear indicator having a brake disc wear scale which is configured for readability of the brake disc wear by the user. The brake disc wear indicator is in the form of an elongate hole in the base member and arranged in the overlap region of the movable sliding member in order to measure the brake disc thickness. For better readability, the base member is colored a different color from the movable sliding member arranged in the overlap region of the measuring arm and in the overlap region of the base member. The brake disc wear scale is formed along the brake disc wear indicator and indicates the range from the maximum brake disc thickness to the minimum brake disc thickness. On the movable sliding member, a marking is placed in the visible region of the brake disc wear indicator. The marking shows in combination with the brake disc wear scale the spacing between the pincer legs or in other words the width of the brake disc. A more cost-intensive digital output device is not required. 
     In another aspect of the disclosure, the base member has a brake liner wear indicator having a brake liner wear scale which is configured for reading the brake liner wear by the user. The brake liner wear indicator is arranged with respect to the longitudinal axis of the base member at the side of the base member opposite the brake disc wear indicator. The brake liner wear indicator is in the form of an elongate hole. The maximum wear rate of the brake liner is greater than the maximum wear rate of the brake disc, for which reason the elongate hole which is in the form of a brake liner wear indicator is greater in the longitudinal direction than the elongate hole of the brake disc wear indicator. A marking applied inside the brake liner wear indicator on the movable sliding member in order to measure the brake liner wear shows, in combination with the brake liner wear scale, the current brake liner wear. A more cost-intensive digital output device is not required. In addition, the brake liner wear indicator and the brake disc wear indicator are non-sensitive to dirt and easy to clean because the movable sliding members can be removed from the base member having the brake liner wear indicator and the brake disc wear indicator. 
     In an advantageous aspect of the disclosure, the end of the movable sliding member opposite the base member for measuring the brake disc wear is in the form of a hook. The movable sliding member is a punched component and the hook is flattened in the direction of the bolt cover of the disc brake. 
     In one aspect, the flattened portion is in the form of a contact face. The contact face of the hook is used for abutment against the bolt cover. The movable sliding member cannot slide counter to a localized abutment as a result of the contact face of the hook on the bolt cover, and the movable sliding member remains in position inside the wear measurement member. 
     In another embodiment, the base member has a resilient connection at the side opposite the measuring arm, wherein the sliding member for measuring the brake liner wear is fixed to the base member by way of the resilient connection. The resilient connection has two or more resilient elements which are formed by the base member. The resilient elements have a radial pretensioning and press the sliding member for measuring the brake liner wear against the base member. The pretensioning of the resilient elements is only so strong that the sliding member for measuring the brake liner wear remains axially movable in the longitudinal direction thereof. The resilient connection is inexpensive and requires no additional components. In addition, the movable sliding member for measuring the brake liner wear can be easily replaced by the sliding member being pressed counter to the pretensioning force, that is to say, counter to the direction of the base member, and removed. 
     In one aspect, the mechanical wear gauge is produced from metal or plastics material depending on requirements. The base member having the measuring arm and the sliding members may be produced from a metal sheet, that is to say, from a flat rolled metal. Metal sheets have the advantage that they can be produced with different thicknesses and can be readily processed. The sliding members and the base member having the measuring arm may, for example, be produced by way of punching from the metal sheet. It is also conceivable for the mechanical wear gauge to be produced from plastics material by means of an injection-molding method. The fixing screws can also be produced by means of injection-molding methods. The mechanical wear adjustment device made of plastics material is particularly light and has no sharp edges which could damage another component. 
     In one aspect, the mechanical wear gauge has an overall thickness between 5 mm and 15 mm, preferably between 5 mm and 10 mm, and can be easily transported or, for example, stored in a space-saving manner in a tool compartment of a vehicle. In addition, as a result of its small overall thickness, the mechanical wear gauge can be moved along the vehicle axle and brake disc components into the starting position thereof in order to measure the brake liner wear or to measure the liner thickness of the brake disc without having to disassemble components of the vehicle axle or the brake disc. 
     In another embodiment according to the present disclosure, a vehicle has a vehicle axle and a wheel which is arranged on the vehicle axle, wherein the wheel has a disc brake, two brake liners, and a brake disc which is arranged between the brake liners, and the wear of the brake liners or the brake disc is measured by way of a mechanical wear gauge. The mechanical wear adjustment device is constructed in accordance with the description below and the preceding described embodiments. The vehicle is preferably a heavy or light utility vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Selected embodiments of the invention will be explained below with reference to the appended Figures. 
       In the drawings: 
         FIG.  1    shows a mechanical wear gauge according to the invention in a laterally rotated plan view, 
         FIG.  2    shows a mechanical wear gauge during a measurement operation on a sectioned disc brake of a wheel. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows the mechanical wear gauge  1  according to the invention in an initial state thereof, that is to say, prior to the measurement operation. The mechanical wear gauge  1  is formed from a metal sheet and has a base member  2  having a measuring arm  3  which is formed on the base member  2 . The measuring arm  3  extends along a longitudinal axis A of the base member  2  and has at the end of the measuring arm  3  opposite the base member  2  a pincer leg  3   a . The pincer leg  3   a  is arranged with respect to the measuring arm  3  coaxially on the measuring arm  3 . Furthermore, a sliding member  5 , referred to also as a first sliding member  5 , for measuring a brake disc wear DW shown in  FIG.  2    is arranged in an overlap region OV of the measuring arm  3 . The sliding member  5  further comprises a second pincer leg  5   a  of the mechanical wear gauge  1 . The pincer leg  5   a  of the sliding member  5  is arranged opposite the pincer leg  3   a  of the measuring arm  3 . Together, the pincer legs  3   a ,  5   a  form a set of pincers which can engage around a brake disc  22  (see  FIG.  2   ) in terms of the width or the thickness thereof. The sliding member  5  is axially movable in the longitudinal direction thereof. That is to say, the pincer leg  5   a  is also axially movable and the mechanical wear gauge  1  can be adapted to the thickness of the brake disc  22 . The pincer leg  3   a  of the measuring arm  3  is rigid, therefore non-movable. The measuring arm  3  has a clamp  9  by way of which the sliding member  5  is secured to the measuring arm  3 . Both the measuring arm  3  and the sliding member  5  partially have a curvature. The curvature is constructed and provided to allow for measure of the brake disc thickness without a bolt  26  having to be disassembled. At the end of the sliding member  5  facing the base member  2 , a first auxiliary sliding member  14  in the form of a lateral formation is formed, by way of which the user can adjust the sliding member  5 . There is arranged on the measuring arm  3 , at the side opposite the first auxiliary sliding member  14 , a second auxiliary sliding member  13 , to which the user can apply a force which is directed counter to the first auxiliary sliding member  14  and fixes the mechanical wear gauge in position. 
     The position of the sliding member  5  can be adjusted in a variable manner by means of a fixing screw  6  on the base member  2  and by means of a fixing screw  6   a  on the measuring arm  3 . The fixing screws  6 ,  6   a  are guided through elongate holes  15 ,  15   a  of the base member  2  and the measuring arm  3  and are each locked by way of a counter-nut which is not shown. Between the fixing screws  6 ,  6   a , in the base member  2 , a brake disc wear indicator  7  in the form of an elongate hole is formed, so that the sliding member  5  is visible with a marking  17 . In addition, there is arranged on the base member  2 , at the side of the brake disc wear indicator  7 , a brake disc wear scale  7   a  by way of which the actual brake disc wear can be read by way of the marking  17  of the sliding member  5 . At the side of the base member  2  opposite the sliding member  5  for measuring the brake disc wear, a sliding member  4 , referred to also as a second sliding member  4 , for measuring a brake liner wear (PW) shown in  FIG.  2    is arranged. The sliding member  4  is secured to the base member  2  by way of a resilient connection  12 . The resilient connection  12  is formed from the base member  2  and comprises two U-shaped receiving members  12   a ,  12   b  in which the second sliding member  4  rests. Between the U-shaped receiving members  12   a ,  12   b , the second sliding member  4  is clamped with tensioning by the base member  2  and prevents the second sliding member  4  from radially falling out of the base member  2  of the mechanical wear gauge  1 . The second sliding member  4  extends along the longitudinal axis A of the base member  2 . The end of the second sliding member  4  opposite the base member  2  is in the form of a hook  10 . The hook  10  serves to increase a contact face  11  of the second sliding member  4 . In order to read the brake liner wear, a brake liner wear indicator  8  having a brake liner wear scale  8   a  is arranged centrally between the U-shaped receiving members  12   a ,  12   b  of the resilient connection  12  on the base member  2 . The brake liner wear indicator  8  is in the form of an elongate hole. In the region of the brake liner wear indicator  8 , there is arranged on the second sliding member  4  a marking  18  by way of which the user can measure the actual brake liner wear state using the brake liner wear scale  8   a . The base member  2  of the sliding member  5 , for measuring the brake liner wear PW, and the sliding members  4 , for measuring the brake disc wear DW, can be displaced relative to each other. 
       FIG.  2    illustrates the mechanical wear gauge  1  according to  FIG.  1    during a measurement operation on a brake disc  20  of a wheel  30 . The wheel  30  is arranged on a vehicle axle  40  of a vehicle  50 . The measurement operation of the brake liner wear measurement and the measurement operation of the brake disc wear measurement will be explained in greater detail below. Firstly, the mechanical wear gauge  1  is guided between a brake liner carrier  24  of the disc brake  20  and a caliper  25  of the disc brake  20 . The pincer leg  3   a  of the measuring arm  3   a  is placed on the brake disc  22  and the sliding member  5  for measuring the brake disc wear DW is displaced axially in the direction of the brake disc  22  until the pincer leg  5   a  of the sliding member  5  abuts the brake disc  22 , so that the brake disc  22  is enclosed between the pincer leg  5   a  of the sliding member  5  and the pincer leg  3   a  of the measuring arm  3 . Subsequently, the fixing screws  6 ,  6   a  are tightened, wherein the mechanical wear gauge  1  is centered on the brake disc  22 . The second sliding member  4  for measuring the brake liner wear PW is pushed out with the contact face  11  thereof until the contact face  11  comes into contact with a bolt cover  23  in the direction of the longitudinal axis A of the base member  2 . Via the displacement of the caliper  25  relative to the brake disc  22  in the event of a brake liner wear PW of a reaction-side brake liner  21 , this brake liner wear PW can be measured. Field tests have shown that the brake liner wear PW of a brake-application-side brake liner  21   a  has substantially identical brake liner wear values to the reaction-side brake liner  21 . Finally, during the measurement operation, the brake liner wear PW of the reaction-side brake liner  21  is read via the brake liner wear scale  8   a  and the brake disc wear DW of the reaction-side brake liner  21  is read via the brake disc wear scale  7   a . The reading of the brake liner wear scale  8   a  and the reading of the brake disc wear scale  7   a  can also be carried out by removing the mechanical wear gauge  1  with tightened fixing screws  6 ,  6   a .  
     
       
         
           
               
               
             
               
                 List of reference numerals as part of the description 
               
             
            
               
                 
                   1 
                 
                 Mechanical wear gauge 
               
               
                 
                   2 
                 
                 Base member 
               
               
                 
                   3 
                 
                 Measuring arm 
               
               
                 
                   3 
                   a 
                 
                 Pincer leg of the measuring arm  3 
 
               
               
                 
                   4 
                 
                 Second sliding member for measuring the brake liner wear (PW) 
               
               
                 
                   5 
                 
                 Sliding member for measuring the brake disc wear (DW) 
               
               
                 
                   5 
                   a 
                 
                 Pincer leg of the sliding member  5 
 
               
               
                   6 ,  6   a   
                 Fixing screws 
               
               
                 
                   7 
                 
                 Brake disc wear indicator of the base member  2 
 
               
               
                 
                   7 
                   a 
                 
                 Brake disc wear scale of the brake disc wear indicator  7 
 
               
               
                 
                   8 
                 
                 Brake liner wear indicator of the base member  2 
 
               
               
                 
                   8 
                   a 
                 
                 Brake liner wear scale of the brake liner wear indicator  8 
 
               
               
                 
                   9 
                 
                 Clamp 
               
               
                 
                   10 
                 
                 Hook of the second sliding member  4 
 
               
               
                 
                   11 
                 
                 Contact face of the second sliding member  4 
 
               
               
                 
                   12 
                 
                 Resilient connection of the base member  2 
 
               
               
                   12   a , b   
                 U-spaced receiving members of the resilient connection  12 
 
               
               
                 
                   13 
                 
                 Auxiliary sliding member of the measuring arm  3 
 
               
               
                 
                   14 
                 
                 Auxiliary sliding member of the sliding member  5 
 
               
               
                   15 ,  15   a   
                 Elongate hole 
               
               
                 
                   17 
                 
                 Marking of the sliding member  5 
 
               
               
                 
                   18 
                 
                 Marking of the second sliding member  4 
 
               
               
                 
                   20 
                 
                 Disc brake 
               
               
                 
                   21 
                 
                 Reaction-side brake liner 
               
               
                 
                   21 
                   a 
                 
                 Brake-application-side brake liner 
               
               
                 
                   22 
                 
                 Brake disc 
               
               
                 
                   23 
                 
                 Bolt cover 
               
               
                 
                   24 
                 
                 Brake liner carrier 
               
               
                 
                   25 
                 
                 Caliper 
               
               
                 
                   26 
                 
                 Bolt 
               
               
                 
                   30 
                 
                 Wheel of the vehicle axle  40 
 
               
               
                 
                   40 
                 
                 Vehicle axle of the vehicle  50 
 
               
               
                 
                   50 
                 
                 Vehicle 
               
               
                 A 
                 Longitudinal axis of the base member  2 
 
               
               
                 DW 
                 Brake disc wear 
               
               
                 PW 
                 Brake liner wear 
               
               
                 OV 
                 Overlap region of the measuring arm  3