Method for determining the wear of brake pads of a disc brake, and a disc brake having a measuring device for carrying out the method

Abstract

The invention relates to a method for determining the wear of brake pads (4) of a disc brake that comprises a brake calliper (1) which engages around a brake disc (3) and is axially displaceably held, with respect to the brake disc (3), on a vehicle-side backing plate (2), wherein, by means of a brake-application device, during braking, the brake pads (4), which are mounted in the backing plate (2) and each have a pad-carrier plate (5) and a friction pad (6) fastened thereon, can be pressed against the brake disc (3), and each brake pad (4) is mounted in a pad shaft of the backing plate (2), which, when viewed in the rotational direction of the brake disc (3), is delimited by opposing backing-plate horns (7) against which the pad-carrier plate (5) displaceably rests. The method is designed such that, using a measuring device, a distance (X), which changes owing to wear of the friction pad (6), between the pad-carrier plate (5) and a backing-plate horn (7) is determined and, when a predefined minimum thickness of the friction pad (6) is reached, an optical and / or acoustic indication is given.

Description

[0001] Method for determining the wear of brake pads of a disc brake and a disc brake with a measuring device for carrying out the method

[0002] DESCRIPTION

[0003] The invention relates to a method for determining the wear of brake pads of a disc brake according to the preamble of claim 1 and to a disc brake with a measuring device for carrying out the method.

[0004] For safety reasons in particular, it is necessary to monitor the wear of the brake pads and to enable the necessary replacement of the respective brake pad at the best possible time, for which the wear condition of the brake pads should be determined as accurately as possible.

[0005] For economic reasons in particular, there is a demand for an optimal time for replacing brake pads, with the aim of only replacing them when the friction lining has worn down to a permissible minimum thickness. This means that an earlier replacement counteracts the optimization of operating costs, while a late replacement, i.e., when the specified minimum thickness is not met, impairs the functional reliability of the disc brake.

[0006] Various methods are known for determining the wear condition of brake pads. For example, disc brake pads use a conductive cable that is routed through the pad carrier plate. When the wear limit is reached, this cable is abraded by the brake disc contacting the friction pad, thereby transmitting an electrical signal to an evaluation unit in the vehicle's electrical system.

[0007] For continuous wear detection of the friction linings, several such cables must be inserted into the friction lining, which, however, is only possible with considerable manufacturing effort.

[0008] In another design variant, continuous pad wear detection is achieved through a cumulative wear measurement, which determines friction pad and brake disc wear based on the position of the brake caliper adjustment. However, this does not provide any information about uneven wear on the action-side brake pad compared to the reaction-side.

[0009] In order to exclude an inadmissible degree of wear of the brake pads, possible uneven wear must be taken into account in the wear signal sent to the evaluation unit, which reduces the maximum usable friction lining thickness.

[0010] Furthermore, the influence of tolerances is so great that it cannot be guaranteed that the individual brake pad will reach its permissible remaining thickness, which is, for example, 2 mm. In fact, the total wear indicator is often displayed when the brake pads still have more than 5 mm of remaining thickness.

[0011] The invention is based on the object of further developing a method of the generic type in such a way that the wear path is recorded independently of the movement of the brake pads and the brake disc.

[0012] This object is achieved by a method having the features of claim 1.

[0013] The method according to the invention makes it possible to detect the wear path independently of the movement of the force-transmitting components, in particular the brake disc.

[0014] According to the invention, the overlap of the pad carrier plate with the brake carrier horn is measured directly at its pad contact surface. The pad carrier plate rests with its narrow edge against the corresponding contact surface of the brake carrier horn, perpendicular to the direction of displacement of the brake caliper.

[0015] This ensures that the specified minimum overlap is maintained and that the brake pad cannot be pushed out of the pad slot of the brake carrier.

[0016] The side of the corresponding brake carrier flange facing the brake disc serves as the reference surface, since the brake carrier is fixed to the vehicle. This means that the brake pad is displaced axially relative to the brake disc relative to the brake carrier flange.

[0017] Since the method according to the invention is applied to each of the two brake pads, wear is determined separately for each brake pad. This means that a targeted replacement of a brake pad identified as worn is now possible.

[0018] If necessary, the continuous individual pad measurement can be carried out as a total wear sensing, i.e. taking into account the wear of the brake disc, the total brake disc wear as well as a delta unequal wear of the two brake pads can be determined from the evaluated measurement parameters.

[0019] A disc brake having a brake calliper which spans a brake disc and is held axially displaceably relative to the brake disc on guide bars connected to a vehicle-side brake carrier, wherein by means of an application device the brake pads mounted in the brake carrier, each having a pad carrier plate and a friction pad fastened thereon, can be pressed against the brake disc during braking, and each brake pad is mounted in a pad shaft of the brake carrier which is delimited by opposing brake carrier horns against which the pad carrier plate bears displaceably, is characterized by at least one measuring device for carrying out the method according to the invention.

[0020] Preferably, such a measuring device is assigned to each brake pad. Such a measuring device can be provided as a laser displacement sensor mounted on the brake caliper, with which the position of the respective pad carrier plate can be determined in relation to the reference surface of the brake carrier flange.

[0021] As a further design variant of the measuring device, a linear potentiometer can be provided. This potentiometer is connected to a reference surface on the brake carrier horn, for example, in a bore. The position of the pad carrier plate can be determined by the changing resistance of the sliding contacts via a voltage change. Alternatively, the measuring device can also be designed as a cable-operated sensor. In any case, the measuring device should be calibrated in the installed state to compensate for any existing brake disc center offset during installation. If not calibrated, the permissible residual pad wear increases by the maximum permissible disc center offset.

[0022] Further advantageous embodiments of the invention are characterized in the subclaims.

[0023] Embodiments of the invention are described below with reference to the accompanying drawings.

[0024] They show:

[0025] Figures 1 to 3 each show a disc brake provided with at least one measuring device for carrying out the method according to the invention in a perspective view and in a plan view.

[0026] The figures show a disc brake for a commercial vehicle, which has a brake calliper 1 which overlaps a brake disc 3 and which, with respect to the brake disc 3, is mounted so as to be axially displaceable on guide bars (not shown) which are connected to a vehicle-side brake carrier 2.

[0027] By means of an application device, of which only two brake pistons 12 are shown in the figures, the brake pads 4, which are mounted in the brake carrier 2 and each have a pad carrier plate 5 and a friction pad 6 fastened thereon, can be pressed against the brake disc 3 during braking.

[0028] Each of the two brake pads 4 is mounted in a pad shaft of the brake carrier 2, which is delimited by opposing brake carrier horns 7, seen transversely to the direction of displacement of the brake calliper, against which the pad carrier plate 5 rests displaceably on the edge side.

[0029] Two measuring devices are attached to the brake caliper 1, with which the method according to the invention for determining the wear of brake pads 4 can be carried out. The measuring device determines a distance X between the pad carrier plate 5 and a brake carrier horn 7, which changes in the axial direction due to wear of the friction lining. When the minimum thickness of at least one brake pad 4 is reached, a visual or acoustic indication is given to replace the brake pad(s) 4.

[0030] In Figure 1, lasers 9 are provided as measuring devices with which a laser measurement can be carried out, wherein for measuring the change in distance X in the axial direction of the pad carrier plate 5 to the brake carrier horn 7, a rear side facing away from the friction lining 6 of the brake pad 4 in the case of the brake pad on the application side serves as the reference surface 8, while in the case of the opposite brake pad 4, the side of the pad carrier plate 5 facing the friction lining 6 serves as the reference surface.

[0031] Another example of a measuring device is shown in Figure 2. Here, the measuring devices are each designed as linear potentiometers 10, which are connected to a reference surface of an associated brake carrier horn 7, whereby here, too, each brake pad 4 is assigned a linear potentiometer 10.

[0032] Functionally, the position of the respective lining carrier plate 5 is determined by the changing resistance of sliding contacts of the linear potentiometer 10 by means of voltage change.

[0033] A further embodiment of the invention can be seen in Figure 3.

[0034] Here, the position of the pad carrier plates 5 is determined by a cable sensor 11, whereby the rear side of the pad carrier plate 5 of the brake pad 4 on the application side, facing away from the friction lining 6, forms a reference surface, while the other end or a cable pulley of the cable sensor 11 is attached to the brake caliper 1. The cable is connected to the reaction-side brake pad 4 on the side of the brake pad 4 facing the friction lining 6. List of reference symbols

[0035] 1 brake caliper

[0036] 2 brake carrier 3 brake disc

[0037] 4 brake pad

[0038] 5 Pad carrier plate

[0039] 6 Friction lining

[0040] 7 Brake carrier horn 8 Reference surface

[0041] 9 lasers

[0042] 10 linear potentiometers

[0043] 11 wire-actuated encoders

[0044] 12 brake pistons

Claims

Claims 1. A method for determining the wear of brake pads (4) of a disc brake, which has a brake calliper (1) which engages over a brake disc (3) and is held axially displaceably relative to the brake disc (3) on a vehicle-mounted brake carrier (2), wherein, by means of an application device, the brake pads (4) mounted in the brake carrier (2), each having a pad carrier plate (5) and a friction pad (6) fastened thereon, can be pressed against the brake disc (3) during braking, and each brake pad (4) is mounted in a pad shaft of the brake carrier (2), which is delimited by brake carrier horns (7) which are opposite one another, viewed in the direction of rotation of the brake disc (3), and against which the pad carrier plate (5) bears displaceably, characterized in thatthat a measuring device determines a distance (X) between the lining carrier plate (5) and a brake carrier horn (7) which changes in the axial direction due to wear of the friction lining (6) and an optical and / or acoustic indication is given when a predetermined minimum thickness of the friction lining (6) is reached.

2. Method according to claim 1, characterized in that the measuring device corresponds to a reference surface (8) of the lining carrier plate (5).

3. A disc brake having a brake calliper (1) which engages over a brake disc (3) and is held axially displaceably relative to the brake disc (3) on a vehicle-mounted brake carrier (2), wherein, by means of an application device, the brake pads (4) mounted in the brake carrier (2), each having a pad carrier plate (5) and a friction pad (6) fastened thereto, can be pressed against the brake disc (3) during braking, and each brake pad (4) is mounted in a pad shaft of the brake carrier (2), which is delimited by brake carrier horns (7) which are opposite one another, viewed in the direction of rotation of the brake disc (3), and against which the pad carrier plate (5) bears displaceably, characterized by at least one measuring device for carrying out the method according to claim 1.

4. Disc brake according to claim 3, characterized in that each pad carrier plate (5) is assigned a measuring device.

5. Disc brake according to claim 3 or 4, characterized in that a broad side of the respective pad carrier plate (5) forms a reference surface (8) for the measuring device.

6. Disc brake according to one of claims 3-5, characterized in that the respective measuring device is attached to the brake calliper (1) or to the brake carrier (2).

7. Disc brake according to one of claims 3-6, characterized in that the measuring device is designed as a laser displacement sensor (9).

8. Disc brake according to one of claims 3-7, characterized in that the measuring device is designed as a linear potentiometer (10).

9. Disc brake according to one of claims 3-8, characterized in that the measuring device is designed as a cable pull sensor (11).

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