Brake disc with assembly inserts made of polymer material interposed between its central hub and its peripheral rim

Abstract

The invention relates to a vehicle brake disc (1) comprising a peripheral annular ring (100) having two friction faces, and a central fixing bowl (200) integral with said ring, said central bowl comprising an annular flange (210), an annular ring (220) extending in the direction of said ring from the outer peripheral edge of said flange, and a peripheral rim (230) projecting radially from the outer side from the distal end of said ring opposite said flange; said brake disc further comprising several assembly inserts (300) made of polymer material, fitted onto corresponding notches formed on the outer periphery of said rim, and further comprising holes through which the threaded rods of screws (V) also pass through respective holes formed in said ring and screwed onto nuts so as to ensure the clamping of said central bowl to said ring.Figure to be published with the abbreviation: Fig. 1.

Description

Title of the invention: Brake disc with assembly inserts made of polymer material interposed between its central hub and its peripheral rim. Technical field

[0001] The present invention relates to a brake disc intended to cooperate with a braking device of a vehicle. The invention finds particularly advantageous applications in the field of motor vehicles but could be applied to all vehicles equipped with disc brakes such as motorcycles. Previous technique

[0002] Motor vehicles generally include a braking system comprising a brake pedal acting on a master cylinder, to transmit, via hydraulic circuits, fluid pressure to braking devices which act on each wheel of the vehicle.

[0003] Braking devices, commonly called disc braking systems, are known, which allow a wheel of a vehicle to be braked using a brake disc comprising a peripheral annular ring having two friction faces, as well as a central fixing bowl attached to this peripheral ring and comprising an annular flange in which holes are provided allowing the central bowl to be tightened by screwing between a rim and the bearing hub of this wheel.

[0004] The braking action is performed by two brake pads belonging to a caliper and arranged on either side of the peripheral annular ring. The caliper includes at least one means for actuating the pads, enabling them to move against the two friction faces of the rotating brake disc. The friction of these brake pads against these friction faces transforms the mechanical energy of the brake disc's rotation into heat energy and slows the vehicle's wheel.

[0005] The peripheral annular ring is generally made of cast iron, which is a suitable material thanks to an appropriate coefficient of friction and good thermal conductivity.

[0006] To reduce the mass of the brake, brake discs are known in particular whose peripheral annular cast iron ring is overmolded onto a central fixing bowl formed in another lighter material, for example in sheet steel or aluminium.

[0007] Document FR 2 988 450 Al thus discloses a brake disc whose central fixing bowl in sheet steel includes an annular ring extending towards the peripheral annular ring from the external peripheral edge of the annular flange, as well as a peripheral rim extending radially from the external side from the distal end of said ring opposite said flange, and whose peripheral cast iron ring is overmolded on this peripheral rim.

[0008] The constituent materials of the central fixing bowl and the peripheral ring having different coefficients of thermal expansion, high mechanical stresses may be exerted between the central fixing bowl and the peripheral annular ring in the event of significant heating of the brake disc, which may affect its braking performance.

[0009] In order to overcome this drawback, document DE 19843399 Al discloses a brake disc whose central fixing bowl in aluminium alloy has radial arms which connect it to the peripheral annular ring in cast iron, in order to allow thermal expansions without generating high mechanical stresses.

[0010] However, this type of central mounting bowl, which includes machining, is not simple to manufacture and is relatively expensive. In particular, the connection with the ring comprising internal radial cooling fins is complex. Description of the invention

[0011] The present invention aims to improve the situation.

[0012] To this end, it proposes a vehicle brake disc comprising: - a peripheral annular ring having two friction surfaces designed to receive the braking forces applied by brake pads, and - a central fixing bowl integral with said peripheral annular ring and comprising an annular flange in which holes are provided allowing tightening by screwing this central bowl between a rim and the bearing hub of a wheel of said vehicle, said central bowl also comprising an annular ring extending towards said peripheral crown from the outer peripheral edge of said annular flange, as well as a peripheral rim projecting radially from the outer side from the distal end of said ring opposite said flange; characterized in that it further comprises several assembly inserts made of polymer material, fitted onto corresponding notches formed on the outer perimeter of said peripheral rim, and further having holes through which threaded rods of screws also pass through respective holes formed in said peripheral annular ring and screwed onto nuts so as to ensure the fixing by tightening of said central fixing bowl to said peripheral annular ring.

[0013] These assembly inserts interposed between the peripheral annular ring and the central fixing bowl allow the differences in thermal expansion between these two elements when the latter are made of two different materials (such as, for example, cast iron for the peripheral annular ring and a lighter material like steel or aluminum for the central fixing bowl), so as to avoid the generation of high mechanical stresses between these two elements in the event of significant heating of the brake disc.

[0014] Moreover, the invention has the advantage of being relatively inexpensive to implement since the central fixing bowl can be made simply by stamping from a sheet of metal.

[0015] According to preferred characteristics of said brake disc according to the invention: - said assembly inserts are made of polybenzimidazole (PBI); - each of said inserts comprises a central sleeve having a cross-section complementary to the profile of said notches and of the same thickness as that of said peripheral rim, each said insert also comprising two stop shoulders extending on either side of said central sleeve from which they protrude radially, sandwiching the perimeter of a corresponding said notch so as to ensure the axial locking of this insert vis-à-vis said central fixing bowl; - said notches are distributed angularly and uniformly around the circumference of said peripheral rim; - said peripheral annular ring comprises axially within its thickness two coaxial solid annular discs of the same external diameter and connected to each other by a plurality of radial internal fins; - one of said annular discs includes an annular portion projecting radially on the inner side opposite the other disc and in which said orifices are provided; - said screws and nuts are made of high-strength steel; - the tightening torque of said screws is greater than or equal to 100 Nm; and / or - said central fixing bowl is made of an aluminum alloy.

[0016] The invention also relates, in a second aspect, to a motor vehicle comprising a braking system equipped with such brake discs. Brief description of the drawings

[0017] The description of the invention will now be continued by a detailed description of an exemplary embodiment, given below by way of illustration but not limitation, with reference to the accompanying drawings, on which: - [Fig. 1] represents a perspective view of a brake disc for a motor vehicle according to the invention; and - [Fig.2] is a perspective view of the peripheral annular ring of the brake disc of [Fig.1]; - [Fig.3] represents a perspective view of the central mounting bowl of the brake disc of [Fig.1]; - [Fig.4] is a perspective view of one of the brake disc assembly inserts of [Fig.1]; and - [Fig.5] represents a cross-sectional view taken along a diametrical plane of the brake disc of [Fig.1]. Description of the implementation methods

[0018] Fig. 1 represents a brake disc 1 according to the invention intended to be fixed between a bearing hub of a motor vehicle and the rim of a corresponding wheel of that vehicle.

[0019] This brake disc 1 has overall rotational symmetry about an axis A. In the following description, the terms "external" and "internal" will be used to define the relative position of an element with reference to this axis of revolution A. The element closest to this axis A will thus be described as internal as opposed to the other element further away from this same axis A which will be described as external.

[0020] The brake disc 1 includes a peripheral annular ring 100 intended to receive the braking forces applied by brake pads, as well as a central fixing bowl 200 integral with this peripheral ring 100.

[0021] Represented alone on [Fig.2], the peripheral annular ring 100 is advantageously made of cast iron due to its suitable coefficient of friction and its good thermal conductivity, and preferably in one piece by a casting process.

[0022] It comprises axially within its thickness two coaxial solid annular disks 110, 120 of the same external diameter and connected to each other by a plurality of radial internal fins 130 distributed angularly in a uniform manner around their circumference.

[0023] Such a conformation of the peripheral annular ring 100 ensures air circulation between the two discs 110, 120, which optimizes the dissipation of thermal energy generated during braking and thus guarantees constant performance even under intense braking conditions while extending the life of the brake disc 1 and the brake pads cooperating with it.

[0024] Representing approximately one third of the total thickness of this peripheral annular ring 100, each of the annular discs 110, 120 has an outer friction face intended to cooperate with a respective brake pad of a caliper.

[0025] As can be clearly seen in [Fig.2], one 110 of these annular discs 110, 120 has an internal diameter smaller than that of the other disc 120, so that it has an internal annular portion 111 projecting radially from the internal side opposite this other disc 120 and in which are provided a plurality of through holes 112 distributed angularly in a uniform manner around its circumference.

[0026] Shown alone in [Fig. 3], the central fixing bowl 200 is made of a lighter material than that constituting the peripheral annular ring 100, and preferably by stamping from a sheet of metal. Advantageously, this central fixing bowl 200 will be made of a reinforced aluminum alloy of type 7075 offering excellent mechanical strength and increased durability. In order to protect it against the risk of corrosion, surface anodizing may also be carried out.

[0027] This central fixing bowl 200 includes a radial annular flange 210 intended to be interposed between a bearing hub of the motor vehicle and the rim of a corresponding wheel of this vehicle.

[0028] The annular flange 210 has a plurality of circular holes 211 (in this case, five) distributed angularly in a uniform manner around its circumference and intended to be passed through by screws which have previously passed through a said rim and then screwed onto a said bearing hub so as to ensure the tightening of the central bowl 200 between this rim and this hub.

[0029] This annular flange 210 also has an orifice 212 intended to allow pre-mounting by screwing the brake disc 1 onto said bearing hub using a screw not shown, this orifice 212 having a countersink 212A made on its outward edge to house the conical head of this screw so as to prevent it from protruding axially from this flange 210.

[0030] The holes 211 and the orifice 212 can be made by machining, or by punching during the stamping of the sheet metal.

[0031] The central fixing bowl 200 also includes a frustoconical annular ring 220 extending, gradually flaring out, towards the peripheral annular ring 100 from the outer peripheral edge of this annular flange 210.

[0032] This central fixing bowl 200 further comprises a peripheral rim 230 extending radially on the external side from the distal end of said ring 220 opposite the flange 210.

[0033] As can be clearly seen in [Fig.3], this peripheral rim 230 has, on its outer edge, a plurality of U-shaped notches 231 distributed angularly uniformly around its circumference and whose number is identical to that of the through holes 112 made on the disc 110 of the peripheral annular ring 100.

[0034] The brake disc 1 further comprises several assembly inserts made of polymer material 300, each fitted onto a corresponding notch 231 of the annular peripheral rim 230 of the central fixing bowl 200.

[0035] Each of the inserts 300, one example of which is shown alone in [Fig.4], comprises a central sleeve 310 having a U-shaped cross-section complementary to the profile of the notches 231 and of the same thickness as that of the peripheral rim of the annular collar 230 of the central fixing bowl 200.

[0036] Each assembly insert 300 also includes two stop shoulders 320, 330, in this case of substantially semicircular shape, extending axially on either side of the central sleeve 310 from which they project radially, sandwiching the perimeter of a corresponding notch 230, as illustrated by figures 1 and 5, so as to ensure the axial locking of this insert 300 vis-à-vis the central fixing bowl 200.

[0037] With reference to these figures 4 and 5, these assembly inserts 300 further each have a through hole 340 oriented axially (i.e. parallel to the axis of revolution A of this disc 1) through which passes the threaded rod of a corresponding screw V also through a respective orifice 112 of the peripheral annular ring 100 and screwed onto a nut E so as to ensure the fixing, as illustrated by [Fig.5], of the central fixing bowl 200 to this peripheral annular ring 100.

[0038] The screws V and the nuts E are advantageously manufactured from high-strength steel, capable of withstanding the mechanical forces generated during braking.

[0039] In order to ensure a secure and durable fixing, the tightening torque of the screws V is advantageously greater than or equal to 100 Nm.

[0040] In use, these assembly inserts 300 interposed between the fixing bowl 200 and the peripheral annular ring 100 allow the differences in thermal expansion between the two materials constituting these two elements 200, 100 to be absorbed, so as to avoid the generation of high mechanical stresses between them in the event of significant heating of the brake disc 1.

[0041] These assembly inserts 300 made of polymer material also allow the fixing bowl 200 to be thermally insulated from the peripheral annular ring 100, so as to limit its heating and expansion.

[0042] Even more advantageously, the assembly inserts 300 are made of a thermoplastic polymer with high thermal resistance, such as in particular polybenzimidazole (PBI) capable of continuously withstanding temperatures up to 310°C and more briefly temperatures exceeding 500°C.

[0043] According to alternative embodiments not shown, recesses can for example be made in the annular ring of the central fixing bowl in order to further reduce the mass of the brake disc 1.

[0044] Numerous other variants are conceivable, and it should be noted in this regard that the present invention is not limited to the embodiments described and illustrated, but also encompasses all variants of execution within the grasp of a person skilled in the art.

Claims

Demands

1. Brake disc (1) for a vehicle comprising: - a peripheral annular ring (100) having two friction faces intended to receive the braking forces applied by brake pads, and - a central fixing bowl (200) integral with said peripheral annular ring (100) and comprising an annular flange (210) in which holes (211) are provided for tightening by screwing this central bowl (200) between a rim and the bearing hub of a wheel of said vehicle, said central bowl (200) also comprising an annular ring (220) extending in the direction of said peripheral ring (100) from the outer peripheral edge of said annular flange (210), as well as a peripheral rim (230) projecting radially on the outer side from the distal end of said ring (220) opposite said flange (210);characterized in that it further comprises several assembly inserts (300) made of polymer material, fitted onto corresponding notches (231) formed on the outer perimeter of said peripheral rim (230), and further having holes (340) through which threaded screw rods (V) also pass through respective holes (112) formed in said peripheral annular ring (100) and screwed onto nuts (E) so as to ensure the fixing by tightening of said central fixing bowl (200) to said peripheral annular ring (100).;

2. Brake disc (1) according to claim 1, characterized in that said assembly inserts (300) are made of polybenzimidazole (PBI).

3. Brake disc (1) according to claim 1 or 2, characterized in that each of said inserts (300) comprises a central sleeve (310) having a cross-section complementary to the profile of said notches (231) and of the same thickness as that of said peripheral rim (230), each said insert (300) also comprising two stop shoulders (320, 330) extending on either side of said central sleeve (310), from which they project radially, sandwiching the periphery of a corresponding said notch (231) of so as to ensure the axial locking of this insert (300) vis-à-vis said central fixing bowl (200).

4. Brake disc (1) according to any one of claims 1 to 3, characterized in that said notches (231) are distributed angularly in a uniform manner around the circumference of said peripheral rim (230).

5. Brake disc (1) according to any one of claims 1 to 4, characterized in that said peripheral annular ring (100) has axially within its thickness two coaxial solid annular discs (110, 120) of the same external diameter and connected to each other by a plurality of radial internal fins (130).

6. Brake disc (1) according to claim 5, characterized in that one (110) of said annular discs (110, 120) comprises an annular portion (111) projecting radially from the inner side opposite the other disc (120) and in which said orifices (112) are provided.

7. Brake disc (1) according to any one of claims 1 to 6, characterized in that said screws (V) and said nuts (E) are made of high-strength steel.

8. Brake disc (1) according to any one of claims 1 to 7, characterized in that the tightening torque of said screws (V) is greater than or equal to 100 Nm.

9. Brake disc (1) according to any one of claims 1 to 8, characterized in that said central fixing bowl (200) is made of an aluminum alloy.

10. Motor vehicle comprising a braking system equipped with brake discs (1) according to any one of claims 1 to 9.

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