Variable particle size chip

Abstract

Brake pad (10) comprising a sole (1) and a friction lining (2), the lining (2) being delimited by a friction surface (26) intended to come into contact with a brake rotor, a fixing surface to the sole, a rear edge (21) and a front edge, the lining (2) comprising: a brake particle collection groove (3), the groove (3) being open on the friction surface (26) and being suitable for fluidic communication with a vacuum source, the collection groove (3) having a trailing edge (32); a first friction material, having a first grain size, and occupying a first volume (V1) of the friction lining (2);and a second friction material, having a second grain size larger than the first grain size, and occupying a second volume (V2) of the friction lining (2) distinct from the first volume (V1), the second volume (V2) extending at least from the trailing edge (32) of the groove (3) to the rear edge (21) of the friction lining (2). Figure of the abstract: Figure 3;

Description

Title of the invention: Variable particle size plate technical field

[0001] This disclosure relates to the field of friction brakes and, in particular, the linings used in such brakes. These brakes find applications in road vehicles (cars, buses, trucks) and railway vehicles (trains, trams, subways). Previous technique

[0002] Document FR 3 087 238 A1 describes a friction lining for disc or drum brakes, equipped with a groove for collecting brake particles. The groove is connected to a vacuum source whose function is to draw in and collect the particles in order to limit their spread into the environment. An air inlet hole, sized to obtain sufficient vacuum levels and flow rates, is provided in the lining. The vacuum level and flow rate are therefore kept constant (at the same suction power) throughout the life of the brake pad.

[0003] In application FR2212695, filed on 02.12.2022 and entitled "Inclined air inlet drilling", the hole is arranged at an angle to maximize the speed of the airflow at the level of the disc and also to encourage an airflow in the opposite direction to the direction of movement of the disc.

[0004] The Applicant is concerned with constantly improving suction performance to maximize particle capture while limiting the energy expended to generate suction. Summary

[0005] Thus, the present disclosure contributes to the improvement of suction performance.

[0006] A brake pad is proposed comprising a backing plate and a friction lining, the lining being delimited by a friction surface intended to come into contact with a brake rotor, a mounting surface to the backing plate, a rear edge and a front edge, the lining comprising: a groove for collecting brake particles, the groove being open to the friction surface and being adapted to be made fluidic with a vacuum source, the collection groove having a trailing edge; a first friction material, having a first grain size, and occupying a first volume of the friction lining; and a second friction material, having a second grain size larger than the first grain size, and occupying a second volume of the friction lining, distinct from the first volume, the second volume extending at least from the trailing edge of the groove to the edge rear of the friction lining.

[0007] The inventors have indeed demonstrated that when a brake pad has manufacturing imperfections, there is no seal at the trailing edge of the groove, between the pad and the disc. This lack of a seal surprisingly led to improved suction performance. However, since these manufacturing imperfections diminish as the pad wears, the airtight contact between the disc and the pad is quickly restored, thus negating the benefit of the imperfections on suction performance.The inventors have shown that using a larger grain size on a rear area of ​​the pad makes it possible to reproduce the effects obtained with a manufacturing imperfection on improving suction performance, and this over a greater part of the pad's life: the larger grains form a profile irregularity and therefore a non-adherence of the trailing edge of the groove to the disc, regardless of the pad's wear condition.

[0008] By definition, the terms "front" and "back" refer to the direction of movement of the rotor: a given point of the rotor sees, during its movement, first a "front" edge, then the "back" edge.

[0009] By “trailing edge”, it is appropriate to understand the internal surface of the groove located on the rear side of the groove.

[0010] By "grain size", we mean the usual definition of grain size in the study of the particle size distribution of the material. It can be, in a cross-sectional plane of the material, an arithmetic mean of the equivalent diameters (the diameter that a circular grain of identical cross-section would have) of a statistically relevant number of grains.

[0011] Friction materials intended for use in brake pad linings generally comprise a friction modifier to enhance the coefficient of friction (this includes one or more abrasive materials and / or one or more solid lubricants), a fibrous material for reinforcement, a filler to provide consistency to the material, and a binder. Friction modifiers may include inorganic friction modifiers, for example, alumina, silica, magnesia, zirconia, chromium oxide, quartz, etc., and organic friction modifiers, for example, synthetic rubber, cashew resin, etc. Friction modifiers may also include solid lubricants such as graphite, molybdenum disulfide, etc. The fibrous material may include metallic fibers, inorganic fibers, and / or organic fibers.The filler material may include barium sulfate, calcium carbonate, metal powder, vermiculite, mica, and similar materials. The filler is thus mineral and / or metallic.

[0012] According to one aspect, the first material comprises a first metallic filler and the second material comprises a second metallic filler distinct from the first metallic filler, and the difference in grain size between the first and second materials is conferred by a difference in grain size of their metallic fillers. According to another aspect, the first material comprises a first mineral filler and the second material comprises a second mineral filler distinct from the first mineral filler, and the difference in grain size between the first and second materials is conferred by a difference in grain size of their mineral fillers.

[0013] According to another aspect, the second grain size is at least three times larger than the first grain size. Optionally, the second grain size is at least 5 times, or at least 10 times, or even at least 15 times larger than the first grain size. Optionally, the second grain size is less than 50 times, or less than 20 times, or less than 15 times, or less than 10 times the size of the first grain.

[0014] According to another aspect, the groove has a leading edge and the second volume includes the leading edge. According to this variant, the entire groove is contained within the second volume, allowing for significant air intake at the interface between the groove and the disc.

[0015] According to another aspect, the first volume is at least three times larger than the second volume. Indeed, it can be advantageous for the material with the smaller grains to remain the major component of the overall lining composition in order to provide a large contact surface between the lining and the disc (on a microscopic scale).

[0016] According to another aspect, the second volume extends from the friction surface to the fixation surface. This configuration makes it possible to retain the benefits of using a coarse-grained material throughout the entire lifespan of the insert.

[0017] According to another aspect, a sub-layer separates the fixing surface from the first and second volumes. The material forming the sub-layer may have a different hardness than the first and second friction materials.

[0018] According to another aspect, the groove is a first groove, the trim comprising a second groove in front of the first groove, the second groove having a second trailing edge, the first material occupying a third volume extending from the second trailing edge to the first groove.

[0019] According to another aspect, the packing includes a conduit extending from the groove to a free end, aligned with the inner or outer edge of the packing, or the mounting surface. This conduit can, synergistically, amplify the improvement in suction performance obtained by incorporating the coarse-grained material into the garnish.

[0020] The invention also relates to a method for manufacturing a brake pad comprising: placing a first friction material, of a first grain size, in a first volume of a mold; placing a second friction material, of a second grain size larger than the first grain size, in a second volume of the mold, the second volume being distinct from the first volume and extending to a rear side of the mold; sintering the friction materials onto a base plate; and creating a groove for collecting brake particles by molding or machining, the groove being at least partially located in the second volume. The groove can, in particular, be obtained during the sintering of the friction materials. Brief description of the drawings

[0021] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0022] [Fig-1] The [Fig. 1] is a perspective view of a brake pad.

[0023] [Fig.2] [Fig.2] is a cross-sectional view of the plate of [Fig.1], along line II- II identified on the [Fig.1].

[0024] [Fig.3] illustrates a brake pad.

[0025] [Fig.4] illustrates a brake pad.

[0026] [Fig.5] illustrates a brake pad.

[0027] [Fig.6] illustrates a brake pad. Description of the implementation methods

[0028] The figures represent different elements schematically. They are not necessarily drawn to scale. The cylindrical coordinate system is used: the axial direction corresponds to the axis of rotation of the rotor (disc or drum), the radial direction is perpendicular to the axial direction, and the tangential or circumferential direction is perpendicular to the radial direction.

[0029] As illustrated in Figures 1 and 2, a brake pad 10 comprises a backing plate 1, also called a base plate. The backing plate 1 is, for example, made of metallic material. The backing plate 1 is a flat plate of substantially constant thickness (for example, between 3 and 5 mm) whose general shape in its principal plane is trapezoidal with straight or curved edges. It may include tabs for guiding it in a caliper or bracket. The backing plate 1 comprises an inner face 13 to which a lining 2 is fixed, and an outer face 14 which is opposite and parallel to the inner face 13. These two faces are joined by a lateral edge 11.

[0030] According to this disclosure, the lining 2 is made of at least two distinct friction materials. The lining 2 is delimited by a friction surface 26 (friction surface), a fixing surface 20 opposite the friction surface 26 and fixed to the sole 1, an inner edge 23, an outer edge 24, a rear edge 21 and a front edge 22. The outer edge 24, rear edge 21, and front edge 22 are convex or straight, the inner edge 23 is concave or straight.

[0031] The thickness of the lining 2 (measured vertically in [Fig. 1], perpendicular to plane H) decreases during the wear of the pad. The friction surface 26 therefore gradually approaches the pad 1 as the lining 2 wears. During operation, the lining 2 (and the rotor, not shown) release particles due to friction between the lining 2 and the rotor. The path of the particles 28 along the friction surface 26 is shown as a dashed line in [Fig. 1].

[0032] The lining 2 is provided with at least one collection groove 3 open on the friction surface 26, and which is located near the rear edge 21. The groove 3 may be at a distance from the rear edge 21 of less than 20% of the circumferential width of the lining 2. For example, the portion of the friction surface 26 which is located between the rear edge 21 and the groove 3 may be less than 10% of the total friction surface 26.

[0033] The depth of the groove(s) 3 may be less than the height of the lining 2 (measured perpendicular to the plane of the friction face 26), i.e., there may remain some lining material 2 between the bottom of each groove 3 and the inner face 13 of the sole 1. The distance between the bottom of each groove 3 and the inner face 13 (measured perpendicular to this inner face 13) is called the "residual height" and is, for example, equal to at least 1%, or at least 5%, or at least 10%, or at least 20% of the initial height (before wear) of the lining 2.

[0034] Alternatively, the depth of the groove or grooves 3 is equal to the height of the trim 2, that is to say that the bottom of the groove or grooves 3 coincides with the inner face 13 of the sole 1.

[0035] The collection groove 3, or at least one of the collection grooves 3, extends at least partly along the rear edge 21, and is straight or follows the curvature of the rear edge 21. The smallest dimension of the groove 3 is its width, measured in the plane H of the plate 10, substantially in the tangential direction T.

[0036] The trim 2 is for example provided with a single continuous groove, substantially straight or having one or more bends between two or more substantially straight portions.

[0037] Alternatively, the lining 2 is provided with a plurality of collection grooves 3 which are disjoint in pairs. By disjoint grooves, it should be understood that the grooves do not communicate with each other except, possibly, through a channel internal to the lining.

[0038] In the illustrated example, the groove 3 has a blind end 31 which does not open onto the outer surface 24. On the inner surface 23 side, the groove has a hole, one end 91 of which opens onto the inner surface 23.

[0039] Various examples of holes can be envisaged, perpendicular to the sole or to the inner edge, or inclined, according to all the configurations described by means of the angles [3, ô and 0 in application FR2212695, filed on 02.12.2022 and not published.

[0040] One of these examples is illustrated in [Fig.2], which is a cross-sectional view of the plate 10 along the direction marked II:II in [Fig.1]. The leading edge 33 of the groove 3 is shown there, that is to say, the internal surface of the groove which is first "seen" by a point on the disk during its rotation.

[0041] An airflow is generated in the collection groove 3 by a vacuum source (suction system), connected to the groove by means of a conduit 40. At the blind end 31, the base 1 has a through suction hole 17 which opens into the groove 3. Thus, the particles 28 sucked into the groove 3 pass into the suction hole 17 and then into the conduit 40.

[0042] The hole 90 opens at one of its ends outside the friction face 26, either onto a peripheral surface 21, 22, 23, 24, or through the sole 1, or into another groove. In the illustrated example, one end 91 of the hole 90 opens onto the internal surface 23, and the other end 92 opens into the collection groove 3. This hole provides additional suction. Indeed, thanks to a sudden increase in cross-section at the end 92, a vacuum exists, during operation, between the end 91 and the collection groove 3. The hole 90 is inclined at an angle [3] in a vertical plane.

[0043] This configuration is given as an example, other inclinations being possible as described in the unpublished document FR2212695.

[0044] Figure 3 shows (in part) a plate 10 comprising a friction lining 2 fixed to a base plate 1. A particle collection groove 3 is adjacent to a rear edge 21 of the lining. The groove 3 comprises one or more blind ends 31, a leading edge 33 and a trailing edge 32.

[0045] The friction lining 2 is formed of two distinct materials, one having a smaller grain size than the other. Thus, a first material occupies a volume V1 and a second material, with a larger grain size than the first material, occupies a volume V2. A dashed line describes the interface between the two materials. In this disclosure, it is understood that the first volume V1 is entirely occupied by the first material and that the second volume is entirely occupied by the second material.

[0046] The volume V2 extends minimally between the trailing edge 32 and the rear edge 21. Thus, during the removal of particles in the area of ​​the friction surface 26 between the trailing edge 32 and rear edge 21, an asperity is formed which allows, during suction, to create an air leak at the interface between the disc and the friction surface 26. It is thus possible, in the same way as with the optional hole 90 discussed above, to increase the suction capacity of the groove and thus increase the suction performance of the device.

[0047] In the example of [Fig.3], the leading edge 33 of the groove 3 is located in volume VI and is therefore formed from the first material, with smaller grains.

[0048] As described in [Fig.4], the groove 3 can however be fully included in the volume V2. Asperities at the leading edge have the same effect as those formed on the trailing edge and increase the suction performance accordingly.

[0049] Figure 4 also illustrates end 91 of hole 90. This end 91 can to open into the first or second volume. In the version illustrated here, hole 90 is entirely contained within the second volume V2.

[0050] In the examples of Figures 3 and 4, the volume V2 extends from the friction surface 26 to the sole 1. Figure 5 shows a variant in which the interface between the two materials (dotted line) is inclined and does not reach the sole. This figure also shows that a sub-layer 27 can be provided beneath the two materials. The sub-layer can be formed of a third material, in particular one having a different hardness than the first and second materials.

[0051] Volumes VI and V2 can together form the entirety of the trim 2.

[0052] The volume V1 can be at least three times, preferably at least five times, larger than the volume V2. This ensures that the friction surface 26 (regardless of its wear state) provides a large contact area with the disc. A volume V1 that is too small would reduce braking performance and increase wear due to a grain size that is generally too large over too much of the friction surface. The article “Size effect of zircon particles in brake pads on the composition and size distribution of emitted particulate matter” (Park et al., Tribology International, 03 / 2021, DOI 10.1016 / j.triboint.202L106995) describes the detrimental effects of a friction material with an excessively large grain size.

[0053] Apart from their grain size, the first and second materials may be substantially identical. A The first material may differ from the second material in the grain size of the filler, mineral or metallic, and / or in the size of the abrasive elements, the rest of the composition of the two materials being identical.

[0054] The following table presents two examples of first material and second material (mass percentages of each element). Example 1 Example 2 Elements First Second First Second Material Material Material Material Phenolic resin 15.30 15.30 Glass fibers 13.60 13.60 Rock wool 5.95 5.95 Steel wool 5.95 5.95 Trifer tetroxide 1.70 1.70 Friction dust 5.95 5.95 Graphite 8.50 8.50 Rubber 11.90 11.90 Cashew nuts 4.25 4.25 Quartz 8.50 8.50 Zircon small grains 1.70 1.70 1.70 Zircon large grains 1.70 Calcium carbonate 1.70 1.70 Mica small grains 15 15 15 Mica large grains 15

[0055] It is understood that these materials are given by way of example and that a person skilled in the art would know how to vary the composition of each of these materials to obtain a desired grain size. A third example may be given by way of illustration, in which the first material has small zircon grains and small mica grains, and in which the second material has large zircon grains and large mica grains.

[0056] The grain size of the second material can be between three and fifteen times the grain size of the first material. In absolute terms, the grains of the first material can have a size between 60 µm and 120 µm, preferably between 90 µm and 110 µm, and more preferably around 100 µm. The grains of the second material can have a size between 300 µm and 800 µm, preferably between 350 µm and 600 µm, and more preferably around 400 µm. These orders of magnitude can be seen in Example 2. In a variant that can Corresponding to example 1, the grains of the first material can have a size between 0.5 pm and 20 pm, preferably between 1 pm and 15 pm, more preferably around 2 pm. The grains of the second material can have a size between 25 pm and 150 pm, preferably between 30 pm and 120 pm, more preferably around 100 pm.

[0057] Figure 6 shows another example, in which more than one groove is provided. The first groove 3 is preceded by a second groove 4. A volume V3 between the two grooves is occupied by the first material. Variants with more than two grooves and more than two materials are also conceivable.

[0058] It is understood that the different aspects shown in Figures 3 to 6 can be combined: for example, an underlayer may be provided under the three materials of [Fig.6], or an interface between the two materials may not reach the sole in the example of [Fig.3] where this interface crosses the groove.

[0059] This disclosure also relates to a method for manufacturing a wafer 10. The method may comprise a number of steps. The method differs essentially from a conventional method by placing two separate materials in the mold to sinter the two materials at the base in such a way as to obtain a wafer with two separate volumes occupied by the two materials, as described in the examples above.

[0060] Thus, a first volume of the mold can correspond to the volume VI of the wafer and can be filled with a first material with small grains, and a second volume of the mold can correspond to the volume V2 of the wafer and can be filled with a material with larger grains.

[0061] After sintering, the wafer can undergo the usual operations of heat treatment, chamfer grinding, scorching, lacquering, quality controls, etc.

[0062] The method may include a machining step in which the particle collection groove is machined, for example by milling. In this case, the groove is machined such that the trailing edge of the groove lies within the second volume, i.e., the volume occupied by the coarse-grained material. In an alternative embodiment, the groove may be obtained by molding.

Claims

Demands

1. Brake pad (10) comprising a backing plate (1) and a friction lining (2), the lining (2) being delimited by a friction surface (26) intended to come into contact with a brake rotor, a fixing surface (20) to the backing plate, a rear edge (21) and a front edge (22), the lining (2) comprising: - a brake particle collection groove (3), the groove (3) being open on the friction surface (26) and being suitable for fluidic communication with a vacuum source, the collection groove (3) having a trailing edge (32); - a first friction material, having a first grain size, and occupying a first volume (VI) of the friction lining (2);and - a second friction material, having a second grain size greater than the first grain size, and occupying a second volume (V2) of the friction lining (2) distinct from the first volume (VI), the second volume (V2) extending at least from the trailing edge (32) of the groove (3) to the rear edge (21) of the friction lining (2).;

2. Plate according to claim 1, wherein the first material comprises a first metallic filler and the second material comprises a second metallic filler distinct from the first metallic filler, and the difference in grain size between the first and second materials is conferred by a difference in grain size of their metallic fillers.

3. Plate according to claim 1, wherein the first material comprises a first mineral filler and the second material comprises a second mineral filler distinct from the first mineral filler, and the difference in grain size between the first and second materials is conferred by a difference in grain size of their mineral fillers.

4. A plaque according to any one of the preceding claims, wherein the second grain size is at least three times greater than the first grain size.

5. Plate according to any one of the preceding claims, wherein the groove (3) has a leading edge (33) and the second volume (V2) includes the leading edge (33).

6. Plate according to any one of the preceding claims, wherein the first volume (VI) is at least three times larger than the second volume (V2).

7. Plate according to any one of the preceding claims, wherein the second volume (V2) extends from the friction surface (26) to the fixing surface (20).

8. Plate according to any one of claims 1 to 6, wherein a sub-layer (27) separates the fixing surface (20) from the first and second volumes (VI, V2).

9. Plate according to any one of the preceding claims, wherein the groove (3) is a first groove (3), the lining comprising a second groove (4) in front of the first groove (3), the second groove (4) having a second trailing edge (42), the first material occupying a third volume (V3) extending from the second trailing edge (42) to the first groove (3).

10. Plate according to any one of the preceding claims, wherein the trim (2) comprises a conduit (90) extending from the groove (3) to a free end (91), at the inner edge (23) or outer edge (24) of the trim (2), or of the fixing surface (20).

11. A method for manufacturing a brake pad (10) comprising: - placing a first friction material, of a first grain size, in a first volume of a mold; - placing a second friction material, of a second grain size larger than the first grain size, in a second volume of the mold, the second volume being distinct from the first volume and extending to a rear side of the mold; - sintering the friction materials on a base; and - creating a brake particle collection groove by molding or machining, the groove being at least partially located in the second volume.

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