Variable grain brake pad

Abstract

A brake pad (10) comprising a back plate (1) and a friction lining (2), wherein the lining (2) is delimited by a friction surface (26) intended to be in contact with a brake rotor, a surface for anchoring to the back plate, a rear edge (21) and a front edge, wherein the lining (2) comprises: a brake particle collection groove (3), wherein the groove (3) is open on the friction surface (26) and can be brought into fluid connection with a low pressure source, wherein the collection groove (3) has a rear edge (32); a first friction material having a first grain size and occupying a first friction lining (2) volume (V1); and a second friction material having a second grain size greater than said first grain size and occupying a second volume (V2) of the friction lining (2), different from the first volume (V1), wherein the second volume (V2) extends at least from the rear edge (32) of the groove (3) to the rear edge (21) of the friction lining (2).

Description

Technical Field

[0001] This disclosure relates to the field of friction brakes, and more particularly to pads used in such brakes. These brakes are used especially in road vehicles (e.g., automobiles, buses, trucks) and rail vehicles (e.g., trains, trams, subways). Background Technology

[0002] Document FR 3 087 238 A1 describes a friction liner for disc or drum brakes, the friction liner having grooves for collecting brake particles. These grooves are connected to a low-pressure source and function to draw in and collect the particles to limit their diffusion into the environment. Air inlets are arranged in the liner, sized to achieve sufficient low-pressure levels and flow rates. Therefore, the low-pressure level and flow rate remain constant throughout the liner's lifespan (assuming equal suction power).

[0003] In FR 2212695, filed on December 2, 2022, entitled "Angled Inlet Hole", the hole is arranged at an angle to maximize the airflow velocity near the disc and to encourage an airflow direction opposite to the displacement direction of the disc.

[0004] The applicant focuses on continuously improving suction performance to maximize particle capture while limiting the energy required to generate suction. Summary of the Invention

[0005] Therefore, this disclosure helps to improve suction performance.

[0006] A brake pad is proposed, comprising a backing plate and a friction pad, wherein the pad is defined by a friction surface intended to contact a brake rotor for anchoring to a surface of the backing plate, a rear edge, and a front edge, wherein the pad includes: a brake particle collecting groove, wherein the groove is open on the friction surface and can be brought into fluid communication with a low-pressure source, wherein the collecting groove has a rear edge; a first friction material having a first particle size and occupying a first friction pad volume; and a second friction material having a second particle size greater than the first particle size and occupying a second volume of the friction pad, the second volume being different from the first volume, wherein the second volume extends at least from the rear edge of the groove to the rear edge of the friction pad.

[0007] The inventors have demonstrated that when the liner has manufacturing defects, there is no seal between the liner and the disk near the trailing edge of the groove. This lack of seal unexpectedly leads to improved suction performance. However, because these manufacturing defects lessen with liner wear, the sealing contact between the disk and the liner is quickly restored, causing the suction performance benefits derived from the defects to disappear. The inventors have demonstrated that using larger particle sizes in the rear region of the liner to reproduce the effect gained from utilizing manufacturing defects improves suction performance, and thus, for a larger portion of the liner's life: the largest particles form profile irregularities, thus preventing adhesion between the trailing edge of the groove and the disk, regardless of the liner's wear condition.

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

[0009] "Rear edge" should be understood as the inner surface of the groove located on the rear side of the groove.

[0010] "Particle size" is understood as the common definition of particle size in material particle size analysis studies. It may involve the arithmetic mean of the equivalent diameters (the diameters that circular particles with the same cross-section would have) of a statistically relevant number of particles in a cross-section of a material.

[0011] Friction materials intended for use in brake pads and linings typically include friction modifiers to enhance the coefficient of friction (which may include one or more abrasives and / or one or more solid lubricants), fibrous materials for reinforcement, fillers to impart material consistency, and binders. Friction modifiers may include inorganic friction modifiers such as alumina, silica, magnesium oxide, zirconium oxide, chromium oxide, and quartz, as well as organic friction modifiers such as synthetic rubber and cashew resin. Friction modifiers may also include solid lubricants such as graphite and molybdenum disulfide. Fiber materials may include metal fibers, inorganic fibers, and / or organic fibers. Filler materials may include barium sulfate, calcium carbonate, metal powders, vermiculite, mica, etc. Therefore, fillers are minerals and / or metals.

[0012] According to one aspect, the first material includes a first metallic filler and the second material includes a second metallic filler different from the first metallic filler, and the particle size difference between the first material and the second material is given by the particle size difference of their metallic fillers. According to another aspect, the first material includes a first mineral filler and the second material includes a second mineral filler different from the first mineral filler, and the particle size difference between the first material and the second material is given by the particle size difference of their mineral fillers.

[0013] According to another aspect, the second granularity is at least three times the first granularity. Optionally, the second granularity is at least five times, at least 10 times, or even at least 15 times the first granularity. Optionally, the second granularity is less than 50 times, or less than 20 times, or less than 15 times, or less than 10 times the first granularity.

[0014] According to another embodiment, the groove includes a leading edge, and the second volume also includes the leading edge. According to this variation, the entire groove is contained within the second volume. This leaves a significant possibility of air being drawn in at the interface between the groove and the disk.

[0015] According to another perspective, the first volume is at least three times the size of the second volume. In fact, it is advantageous that the material with the smallest particles remains dominant in the overall composition of the liner in order to provide a large contact surface (at the microscale) between the liner and the disk.

[0016] On the other hand, the second volume extends from the friction surface to the anchoring surface. This configuration is designed to maintain the benefits of utilizing large-particle material throughout the entire lifespan of the liner.

[0017] On the other hand, the sublayer separates the anchoring surface from the first and second volumes. The material forming the sublayer may have a different hardness than the first and second friction materials.

[0018] According to another aspect, the groove is a first groove, wherein the liner includes a second groove before the first groove, wherein the second groove has a second trailing edge, and wherein the first material occupies a third volume extending from the second trailing edge to the first groove.

[0019] According to another embodiment, the liner includes a channel extending from the groove to the free end, on the right side of the inner or outer edge of the liner, or on the anchoring surface. This channel can synergistically multiply the improved suction performance resulting from the integration of large-particle material into the liner.

[0020] The present invention also relates to a method for manufacturing a brake pad, comprising: placing a first friction material having a first particle size in a first volume of a mold; placing a second friction material having a second particle size larger than the first particle size in a second volume of the mold, wherein the second volume is different from the first volume and extends to the rear side of the mold; sintering the friction material on a backing plate; and implementing brake particle collecting grooves by molding or machining, wherein the grooves are at least partially located in the second volume. The grooves may be obtained, particularly during the sintering of the friction material. Attached Figure Description

[0021] Other features, details, and advantages will become apparent upon reading the following detailed description and analyzing the accompanying drawings, which are shown in the drawings: Figure 1 This is a perspective view of the brake pads; Figure 2 It is along Figure 1 The line II-II marked in the middle is from Figure 1 Cross-sectional view of the obtained liner block; Figure 3 The brake pads are shown.

[0022] Figure 4 The brake pads are shown.

[0023] Figure 5 The brake pads are shown.

[0024] Figure 6 The brake pads are shown. Detailed Implementation

[0025] The accompanying drawings schematically represent various components. They are not necessarily drawn to scale. A cylindrical reference frame 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.

[0026] like Figure 1 and Figure 2 As shown, the brake pad 10 includes a backplate 1, also referred to as a base. The backplate 1 is made of metal, for example. The backplate 1 is a flat plate with a generally constant thickness (e.g., between 3 mm and 5 mm), and its overall shape in the main plane is a trapezoid with straight or curved edges. The backplate may include ears designed to guide it in a caliper or bracket. The backplate 1 includes an inner surface 13 on which the friction pad 2 is anchored, and an outer surface 14 opposite to and parallel to the inner surface 13. The two surfaces are connected by side edges 11.

[0027] According to this disclosure, the liner 2 is made of at least two different friction materials. The liner 2 is defined by a friction surface 26 ("friction" surface), an anchoring surface 20 opposite to the friction surface 26 and anchored to the backing plate 1, an inner edge 23 and an outer edge 24, a rear edge 21 and a front edge 22. The outer edge 24, the rear edge 21 and the front edge 22 are convex or straight, and the inner edge 23 is concave or straight.

[0028] The thickness of liner 2 (in) Figure 1 The friction surface 26 (perpendicular to plane H) decreases with wear of the liner. Therefore, as the liner 2 wears, the friction surface 26 gradually approaches the back plate 1. During operation, the liner 2 (and the rotor, not shown) releases particles due to friction between the liner 2 and the rotor. The particles 28 travel along the trajectory of the friction surface 26. Figure 1 The above is shown as a dotted line.

[0029] The liner 2 is provided with at least one collecting groove 3, which is open on the friction surface 26 and located near the rear edge 21. The groove 3 may be less than 20% of the circumferential width of the liner 2 from the rear edge 21. For example, the portion of the friction surface 26 located between the rear edge 21 and the groove 3 may be less than 10% of the total friction surface 26.

[0030] The depth of one or more grooves 3 may be less than the height of the liner 2 (measured perpendicular to the plane of friction surface 26), meaning that some liner 2 material may remain between the bottom of each groove 3 and the inner surface 13 of the backing plate 1. The distance between the bottom of each groove 3 and the inner surface 13 (measured perpendicular to the inner surface 13) is called the "residual height" and is, for example, equal to at least 1%, at least 5%, at least 10%, or at least 20% of the initial height of the liner 2 (before wear).

[0031] Alternatively, the depth of one or more grooves 3 is equal to the height of the liner 2, meaning that the bottom of one or more grooves 3 coincides with the inner surface 13 of the back plate 1.

[0032] The collection groove 3, or at least one of the collection grooves 3, extends at least partially along the rear edge 21 and is straight or follows the curve of the rear edge 21. The minimum dimension of the groove 3 is its width, measured in the plane H of the liner 10, approximately in the circumferential direction T.

[0033] The liner 2 may have a single continuous groove, which is generally straight or has one or more bends between one or more generally straight portions.

[0034] Alternatively, the liner 2 is provided with a plurality of collection grooves 3, which are paired and do not intersect. The non-intersecting grooves mean that the grooves are not connected to each other, possibly except through channels inside the liner.

[0035] In the example shown, the groove 3 has a blind end 31 that is not open on the outer surface 24. On the inner surface side 23, the groove has a hole that includes an end 91 that is open on the inner surface 23.

[0036] Examples of various holes are conceivable, perpendicular to the back plate or inner edge, or inclined, according to any configuration described by angles β, δ and θ in application FR 2212695 filed on December 2, 2022 and not yet published.

[0037] One of these examples is shown in Figure 2 In the middle, the diagram is along Figure 1 A cross-sectional view of the liner 10 in the II-II direction marked in the middle. There, the leading edge 33 of the groove 3 can be seen, which means the inner surface of the groove, which is "first seen" by a point on the disk during disk rotation.

[0038] An airflow is generated in the collection tank 3 via a channel 40 connected to a low-pressure source (suction system). Near the blind end 31, the back plate 1 includes a through suction hole 17 leading to the groove 3. Therefore, particles 28 suctioned in the groove 3 enter the suction hole 17 and then the channel 40.

[0039] The orifice 90 opens at one end to the exterior of the friction surface 26, or on one of the peripheral surfaces 21, 22, 23, 24, or through the back plate 1, or into another groove. In the example shown, one end 91 of the orifice 90 is open on the inner surface 23 and the other end 92 opens to the collection groove 3. This orifice provides supplemental suction. In fact, by utilizing the sudden increase in cross-section at end 92, a reduced pressure exists between end 91 and the collection groove 3 during operation. The orifice 90 is inclined at an angle β in the vertical plane.

[0040] This configuration is given as an example because other tilts, as described in the unpublished document FR 2212695, are possible.

[0041] Figure 3 The diagram shows (partially) a pad 10 including a friction pad 2 anchored to a backing plate 1. A particle collection groove 3 is located adjacent to the rear edge 21 of the pad. The groove 3 includes one or more blind ends 31, a leading edge 33, and a trailing edge 32.

[0042] The friction pad 2 is formed of two different materials, one with a smaller particle size than the other. Therefore, the first material occupies volume V1, and the second material, with a larger particle size than the first material, occupies a second volume V2. The dotted 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 the second volume is entirely occupied by the second material.

[0043] Volume V2 extends at least between the trailing edge 32 and the trailing edge 21. Therefore, when particles tear and detach in the region between the trailing edge 32 and the trailing edge 21 of the friction surface 26, roughness is created, which allows air leakage to occur at the interface between the disk and the friction surface 26 during suction. Thus, the suction capacity of the groove and therefore the suction performance of the device can be increased in the same manner as the optional orifice 90 described above.

[0044] exist Figure 3 In the example, the leading edge 33 of the groove 3 is located in the volume V1 and is therefore formed of a first material with smaller particles.

[0045] like Figure 4 The groove 3 can, however, be completely contained within the volume V2. The roughness near the leading edge has the same effect as that formed on the trailing edge, and similarly increases suction performance.

[0046] Figure 4End 91 of the aperture 90 is also shown. This end 91 can lead to either the first volume or the second volume. In the version shown herein, the aperture 90 is completely contained within the second volume V2.

[0047] If in Figure 3 and Figure 4 In the example, volume V2 extends from friction surface 26 to back plate 1, then Figure 5 A variation is shown in which the interface (dotted line) between the two materials is sloping and does not extend to the backing plate. The figure also shows a substrate 27 that can be provided beneath the two materials. This substrate may be formed of a third material, specifically having a different hardness than the first and second materials.

[0048] Volumes V1 and V2 can together form the entirety of liner 2.

[0049] Volume V1 can be at least three times the volume V2, preferably at least five times the volume V2. This ensures that the friction surface 26 (regardless of wear condition) has a large contact area with the disc. An excessively small volume V1 will reduce braking performance and increase wear due to excessive particle size coverage on the friction surface. The article "The effect of the size of zirconia particles in brake pads on the composition and size distribution of particulate matter emitted" (Park et al., Tribology International, March 2021, DOI 10.1016 / j.triboint.2021.106995) describes the detrimental effects of friction materials with excessively large particle sizes.

[0050] Apart from their particle size, the first and second materials can be substantially the same. The first material may differ from the second material in terms of the particle size of the filler (mineral or metal) and / or the size of the abrasive element, but the rest of the composition of the two materials is the same.

[0051] The following shows two examples of the first and second materials (mass percentage of each element).

[0052]

[0053] These materials are to be understood as examples, and those skilled in the art will know how to modify the composition of each of these materials to obtain the desired particle size. A third example may be given for illustration, wherein the first material has small zirconia particles and small mica particles, and wherein the second material has large zirconia particles and large mica particles.

[0054] The particle size of the second material may be between three and fifteen times that of the particle size of the first material. In absolute terms, the particles of the first material may have a size between 60 μm and 120 μm, preferably between 90 μm and 110 μm, and more preferably about 100 μm. The particles of the second material may have a size between 300 μm and 800 μm, preferably between 350 μm and 600 μm, and more preferably about 400 μm. These orders of magnitude correspond to Example 2. In a variation that may correspond to Example 1, the particles of the first material may have a size between 0.5 μm and 20 μm, preferably between 1 μm and 15 μm, and more preferably about 2 μm. The particles of the second material may have a size between 25 μm and 150 μm, preferably between 30 μm and 120 μm, and more preferably about 100 μm.

[0055] Figure 6 Another example is shown, in which more than one groove is provided. A second groove 4 is in front of a first groove 3. The volume V3 between the two grooves is occupied by a first material. Variations with more than two grooves and more than two materials are also conceivable.

[0056] Understand as Figures 3 to 6 The various aspects shown can be combined: for example, they can be combined with each other. Figure 6 The bottom layer is provided below the three materials, or the interface between two materials is in Figure 3 In one example, the backplate may not be reached; in this example, the interface passes through a groove.

[0057] This disclosure also relates to a method for producing the liner 10. This method may include several steps. The method differs substantially from typical methods in that two different materials are placed in a mold for sintering the two materials to a backing plate to obtain a liner having two different volumes occupied by the two materials, as described in the example above.

[0058] Therefore, the first volume of the mold can correspond to the volume V1 of the liner and can be filled with the first small particle material, and the second volume of the mold can correspond to the volume V2 of the liner and can be filled with the large particle material.

[0059] After sintering, the liner can undergo typical heat treatment, grinding and chamfering, ablation, painting, quality control and other operations.

[0060] The method may include a machining step during which the groove for collecting particles is machined, for example by milling. In this case, the groove is machined such that the trailing edge of the groove is located in a second volume, meaning the volume occupied by the large particle material. In a variant, the groove may be produced by molding.

Claims

1. A brake pad (10) comprising a backing plate (1) and a friction pad (2), wherein the pad (2) is defined by a friction surface (26) intended to contact a brake rotor for anchoring to a surface (20) of the backing plate, a rear edge (21) and a front edge (22), the pad (2) comprising: Braking particle collection groove (3), wherein the groove (3) is open on the friction surface (26) and can be brought into fluid connection with a low-pressure source, wherein the collection groove (3) has a trailing edge (32); A first friction material having a first particle size and occupying the volume (V1) of a first friction liner (2); as well as The second friction material has a second particle size larger than the first particle size and occupies a second volume (V2) of the friction liner (2), which is different from the first volume (V1), wherein the second volume (V2) extends at least from the rear edge (32) of the groove (3) to the rear edge (21) of the friction liner (2).

2. The brake pad according to claim 1, wherein the first material comprises a first metal filler and the second material comprises a second metal filler different from the first metal filler, and the particle size difference between the first material and the second material is given by the particle size difference of their metal fillers.

3. The brake pad according to claim 1, wherein the first material comprises a first mineral filler and the second material comprises a second mineral filler different from the first mineral filler, and the particle size difference between the first material and the second material is given by the particle size difference of their mineral fillers.

4. The brake pad according to any one of the preceding claims, wherein the second particle size is at least three times the first particle size.

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

6. The brake pad according to any one of the preceding claims, wherein the first volume (V1) is at least three times the second volume (V2).

7. The brake pad according to any one of the preceding claims, wherein the second volume (V2) extends from the friction surface (26) to the anchoring surface (20).

8. The brake pad according to any one of claims 1 to 6, wherein the bottom layer (27) separates the anchoring surface (20) from the first volume and the second volume (V1, V2).

9. The brake pad according to any one of the preceding claims, wherein the groove (3) is a first groove (3), the pad includes a second groove (4) preceding the first groove (3), the second groove (4) having a second trailing edge (42), and the first material occupies a third volume (V3) extending from the second trailing edge (42) to the first groove (3).

10. The brake pad according to any one of the preceding claims, wherein the pad (2) includes a channel (90) extending from the groove (3) to the free end (91), on the right side of the inner edge (23) or outer edge (24) of the pad (2), or on the anchoring surface (20).

11. A method for manufacturing a brake pad (10), comprising: A first friction material with a first particle size is placed in the first volume of the mold; A second friction material having a second particle size larger than the first particle size is placed in a second volume of the mold, wherein the second volume is different from the first volume and extends to the rear side of the mold; the friction material is sintered on the back plate; as well as The brake particle collection groove is implemented by molding or machining, wherein the groove is at least partially located in the second volume.

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