VENTILATED BRAKE DISC

Description

Technical field of the invention

[0001] The invention relates to a ventilated brake disc comprising a particular arrangement of connecting studs between two annular plates of the brake disc, as described in documents WO 0129442 A1, or US5542503A. The invention also relates to a motor vehicle comprising such a ventilated brake disc. Prior art

[0002] The brake discs of motor vehicles are prone to overheating under certain operating conditions, such as during a prolonged descent. Excessive brake disc temperature can lead to braking system malfunction. To improve brake disc cooling, ventilated brake discs are commonly used. Such brake discs consist of two separate annular plates centered on the same axis of rotation. Each of the two annular plates has a friction surface designed to interact with a brake pad in a brake caliper. The two annular plates are spaced apart along their axis of rotation and are connected by a series of connecting studs. This creates a free space between the two annular plates, allowing air to circulate.Such a brake disc thus comprises large heat exchange surfaces and can cool itself relatively efficiently. However, the cooling capacity of ventilated brake discs known from the prior art is still insufficient. The difficulty in effectively cooling brake discs is particularly evident when they are used in combination with low-porosity rims, which reduces airflow around the brake discs. Presentation of the invention

[0003] The aim of the invention is to provide a brake disc that remedies the above disadvantages and improves upon known brake discs of the prior art.

[0004] More specifically, an object of the invention is a brake disc capable of cooling itself more efficiently. Summary of the invention

[0005] The invention relates to a ventilated brake disc comprising two annular plates, each comprising a friction surface, the two plates being centered on the same axis and spaced apart along this axis, the two plates being connected to each other by a set of connecting studs, the set of connecting studs comprising: a first row of connecting studs distributed along a first circle centered on said axis, at least a plurality of the connecting studs of the first row comprising a pear-shaped section in a plane orthogonal to said axis, radially elongated and tapering in a centrifugal direction, a second row of connecting studs distributed along a second circle centered on said axis, the connecting studs of the second row comprising a circular section in a plane orthogonal to said axis, the diameter of the first circle being strictly less than the diameter of the second circle.

[0006] The first row comprises connecting blocks having a circular cross-section in a plane orthogonal to said axis.

[0007] The first row is formed by the repetition of a pattern comprising: a first connecting block with a pear-shaped cross-section, a second connecting block with a pear-shaped cross-section, the second connecting block being adjacent to the first connecting block, a third connecting block with a circular cross-section, the third connecting block being adjacent to the second connecting block.

[0008] The ventilated brake disc may include an annular mounting interface centered on said axis and connected to at least one of the two plates by a set of connecting tabs, each connecting tab being positioned radially opposite a connecting stud of circular section of said first row.

[0009] The set of connecting studs may include a third row of connecting studs distributed along a third circle centered on said axis, the connecting studs of the third row comprising a pear-shaped section in a plane orthogonal to said axis, elongated radially and thinning in a centrifugal direction, the diameter of the first circle being strictly greater than the diameter of the third circle.

[0010] The said connecting legs can extend radially up to a sixth circle centered on said axis, the sixth circle intersecting the connecting studs of the third row.

[0011] Each plate may include an internal surface opposite the other plate, the internal surface of each plate comprising a set of bosses, the set of bosses comprising a fourth row of bosses distributed along a fourth circle centered on said axis.

[0012] The set of bosses may include a fifth row of bosses distributed along a fifth circle centered on said axis, the diameter of the first circle being strictly less than the diameter of the fourth circle, and / or strictly greater than the diameter of the fifth circle.

[0013] The diameter of the second circle can be strictly greater than the diameter of the fourth circle, and / or the diameter of the third circle can be strictly less than the diameter of the fifth circle.

[0014] The invention also relates to a motor vehicle, comprising a ventilated brake disc as defined above. Presentation of the figures

[0015] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which: There figure 1is a perspective view of a brake disc according to one embodiment of the invention. figure 2 is a cross-sectional view of the brake disc, taken at an angle perpendicular to the brake disc's axis of revolution. figure 3 This is a cross-sectional view, perpendicular to the axis of revolution of the brake disc, of a portion of the brake disc. figure 4 This is a cross-sectional view of a portion of the brake disc, along a section parallel to the axis of revolution of the brake disc. figure 5 illustrates a simulation result of the velocity distribution of an airflow passing through the brake disc according to an embodiment of the invention. figure 6 illustrates a simulation result of the velocity distribution of an airflow passing through a first brake disc different from the invention. figure 7 illustrates a simulation result of a velocity distribution of an airflow passing through a second brake disc different from the invention. Detailed description

[0016] There figure 1 The figure illustrates a brake disc 1 according to an embodiment of the invention. The brake disc 1 comprises two annular plates 2 and 3, distinct from one another, and centered on the same axis X. The axis X corresponds to the axis of rotation of the wheel to which the brake disc 1 is intended to be fixed. Each of the two plates 2 and 3 comprises a friction surface 4 intended to cooperate with a brake pad of a brake caliper (not shown). The friction surfaces 4 are flat surfaces extending orthogonally to the axis X. The plates 2 and 3 have an overall cylindrical shape. The axis X corresponds to an axis of revolution of this cylindrical shape.

[0017] The two plates 2 and 3 are spaced apart along the X-axis and connected by a set of connecting studs 5, or fins 5. A free volume in which air can circulate is thus formed between the two plates 2 and 3. The friction surface 4 of each plate faces outwards from the brake disc. Each plate also includes an internal surface 7, opposite the friction surface 4, and facing the other plate. In other words, the internal surfaces 7 of each plate 2 and 3 are opposite each other. The connecting studs 5 therefore extend between the internal surfaces 7 of each plate 2 and 3.

[0018] The brake disc 1 further includes a mounting interface 8 configured for attaching the brake disc 1 to a wheel of a motor vehicle. For this purpose, the mounting interface 8 includes an annular portion 9 centered on the X-axis and connected by connecting lugs 10 to the plates 2 and 3. The annular portion 9 further includes mounting holes 11 for cooperating with mounting screws for attaching the brake disc 1.

[0019] The connecting tabs 10 extend radially and connect an outer periphery of the annular part 9 to an inner periphery of the two plates 2 and 3. One end 12 (more clearly visible on the figures 2 And 3 ) connecting tabs 10 extend between the two plates 2 and 3 and are in contact with the internal surfaces 7 of these two plates. The end 12 of the connecting tabs may in particular have a rounded shape.

[0020] The annular part 9 includes a flat face 13, extending orthogonally to the X axis, and offset along the X axis with respect to the friction surfaces 4 of the plate 2. In particular, the plane in which the flat face 13 of the annular part 9 extends is not interposed between the plane in which the friction surface 4 of the plate 2 extends and the plane in which the friction surface 4 of the plate 3 extends.

[0021] The two plates 2, 3 and the connecting studs 5 form a single unit, that is, a unit made of a single piece of material. In particular, the brake disc can be made of metal and obtained by casting. Preferably, the two plates 2, 3, the connecting studs 5 and the mounting interface 8 form a single unit, but alternatively, the mounting interface 8 could be fixed, for example by screwing, to the assembly formed by the two plates 2, 3 and the connecting studs 5.

[0022] The outer diameter of the plates 2 and 3 can be, for example, between 200 mm and 350 mm inclusive, preferably between 240 mm and 300 mm inclusive, and in particular approximately 280 mm. The inner diameter of the plates 2 and 3 can be, for example, between 100 mm and 250 mm inclusive, preferably between 120 mm and 200 mm inclusive, and in particular approximately 160 mm. The width L1 separating the friction surfaces 4 of the two plates 2 and 3 along the X-axis can be between 20 mm and 30 mm, for example approximately 24 mm. The width L2 separating the inner surfaces 7 of the two plates 2 and 3 along the X-axis can be between 5 mm and 15 mm, and in particular between 8 mm and 10 mm.

[0023] The set of connecting studs 5 is distributed over several circular rows. In particular, the set of connecting studs comprises a first row of connecting studs distributed along a first circle C1, a second row of connecting studs distributed along a second circle C2, and a third row of connecting studs distributed along a third circle C3. The three circles C1, C2, and C3 are concentric and centered on the axis X1. The diameter of the first circle C1 is strictly smaller than the diameter of the second circle C2 and strictly larger than the diameter of the third circle C3. According to one embodiment of the invention, the set of connecting studs comprises only these three rows of connecting studs. According to an alternative embodiment, the set of connecting studs 5 may not include said third row of connecting studs.According to another embodiment, the set of connecting studs could comprise more than three rows of connecting studs, for example four rows of connecting studs, or even five rows of connecting studs. These additional rows could each be arranged on a separate circle concentric with circles C1, C2, and C3.

[0024] For example, if brake disc 1 has an outer circumference diameter of 280 mm and an inner circumference diameter of 180 mm, the diameter of the first circle C1 can be between 210 mm and 250 mm inclusive. The diameter of the second circle C2 can be between 255 mm and 275 mm inclusive. The diameter of the third circle C3 can be between 185 mm and 205 mm inclusive. If brake disc 1 has a different outer circumference diameter, these dimensions can be adjusted proportionally.

[0025] There figure 2 and the figure 3are cross-sectional views along a plane P orthogonal to the X axis and passing equidistant from the internal surfaces 7 of the two plates 2, 3. These figures therefore allow observation of a section orthogonal to the X axis of the different connecting studs 5. The position of a connecting stud can be precisely defined by the position of a barycenter of the section along the plane P of the brake disc 1. For example, in the particular case where this section has a circular shape, then the barycenter corresponds to the center of this circle.

[0026] The first row of connecting studs comprises connecting studs of two kinds, differentiated by the references 21 and 22. The connecting studs 21 form a first part of the connecting studs of the first row and the connecting studs 22 form a second part of the connecting studs of the first row.

[0027] The connecting pads 21 comprise a cross-section in plane P that is radially elongated and tapers in a centrifugal direction, i.e., radially towards the outer edge of the plates 2, 3. In particular, the cross-section of the connecting pads 21 is pear-shaped, meaning it resembles a droplet falling by gravity towards the X-axis. This pear-shaped cross-section is characterized by two opposite sides 23 forming an angle A1 between 20° and 60°, preferably between 30° and 50°. The two opposite sides 23 are connected by semicircular rounded edges 24, 25. A first rounded edge 24, on the side of the outer edge of the plates 2, 3, may have a radius between 1 mm and 5 mm inclusive, for example, approximately 2 mm. A second rounding 25, on the side of the inner perimeter of the plates 2, 3 can have a radius strictly greater than the radius of the first rounding 24, in particular a radius between 2mm and 6mm inclusive, for example about 3mm.

[0028] The connecting studs 22 of the first row include a circular cross-section in plane P. This circular shape may have a radius substantially equal to the radius of the second rounded end 24, in particular a radius between 2 mm and 6 mm inclusive, for example approximately 3 mm. Alternatively, the first row could include only the connecting studs 21.

[0029] The connecting studs 26 in the second row also include a circular cross-section in plane P. This cross-section may have a radius between 2 mm and 6 mm inclusive, for example, approximately 3 mm. This circular shape may, in particular, be identical to the circular shape of the connecting studs 22 in the first row. Alternatively, all or part of the connecting studs in the second row could have a pear-shaped cross-section.

[0030] The connecting studs 27 of the third row also include a pear-shaped cross-section in plane P, that is, a cross-section that is radially elongated and tapers in a centrifugal direction. This shape, known as a teardrop shape, may, in particular, be identical to the shape of the connecting studs 21 of the first row. Alternatively, all or part of the connecting studs of the third row could have a circular cross-section.

[0031] The first row is formed by the repetition of a pattern comprising a first connecting block 21, a second connecting block 21, and a third connecting block 22. The second connecting block is adjacent to the first connecting block (that is, directly next to the first connecting block), and the third connecting block is adjacent to the second connecting block. It is therefore understood that each pattern comprises two pear-shaped connecting blocks and one circular connecting block. Consequently, the first row contains twice as many pear-shaped connecting blocks as circular connecting blocks. The distance between the different connecting blocks in the first row can be constant.

[0032] As can be seen on the figure 2The first row comprises 18 such patterns, consisting of 36 pear-shaped connecting studs and 18 circular connecting studs. Brake disc 1 thus exhibits a rotational symmetry of 10°, at least in the arrangement of the connecting studs. Alternatively, the number of pattern repetitions could be different, for example, between 10 and 30 inclusive.

[0033] Advantageously, the first row comprises a number of circular studs equal to the number of connecting tabs 10. Consequently, the number of pattern repetitions is also equal to the number of connecting tabs 10. Each connecting tab 10 is positioned radially opposite a connecting stud 22, that is, opposite a circular stud. Furthermore, the total number of connecting studs in the first row (in this case, 54) is equal to the number of connecting studs 26 in the second row. Each connecting stud 21 or 22 in the first row is positioned radially opposite a connecting stud 26 in the second row. The resulting configuration allows for better airflow between the connecting studs and therefore better cooling of the brake disc.

[0034] The connecting studs 27 of the third row each extend between two adjacent connecting tabs 10. The number of connecting studs 27 in the third row is therefore identical to the number of connecting tabs 10 (i.e., 18 connecting studs 27 in this case). Each connecting stud 27 of the third row is positioned radially opposite a space formed between two adjacent pear-shaped connecting studs of the first row.

[0035] The connecting lugs 10 extend radially to a sixth circle C6 centered on the X-axis. This sixth circle C6 intersects the connecting studs 27 of the third row; in other words, circle C6 cuts the section in plane P of the connecting studs 27. Advantageously, the third circle C3 and the sixth circle C6 can be separated by a distance less than or equal to 10 mm, in particular less than or equal to 5 mm. According to an alternative embodiment, the third circle C3 and the sixth circle C6 could coincide.

[0036] With reference to the figure 4It can be observed that the connecting studs 5 have a variable cross-section depending on the cutting plane considered. Each connecting stud 5 is narrowest at plane P and gradually widens towards the internal surfaces 7 of plates 2 and 3. In particular, fillets 29 are formed at the interface between the connecting studs 5 and the internal surfaces 7. Plane P can form a plane of symmetry for the assembly formed by the internal surfaces 7 of plates 2 and 3 and the connecting studs 5. A cross-section of the connecting studs along a plane orthogonal to the X-axis and different from plane P can be homothetic to the cross-section of the connecting studs along plane P.

[0037] Furthermore, the internal surface 7 of each plate 2, 3 also includes a set of bosses 30. The bosses 30 (clearly visible on the figure 4The bosses 30 are raised reliefs projecting from the internal surface 7 of each platform 2, 3. They are generally rounded and without edges. They may include a cross-section orthogonal to the X-axis, which is substantially circular. The bosses 30 are arranged in pairs, each boss 30 of the first platform 2 being positioned opposite a boss 30 of the second platform 3 along the X-axis, without being in contact with each other. Each boss can rise to a height roughly equal to one-quarter of the width L2 separating the internal surfaces 7. The pairs of bosses 30 thus form local narrowings in the space separating the internal surfaces 7.

[0038] The entire set of bosses comprises a fourth row of bosses distributed along a fourth circle C4 and a fifth row of bosses distributed along a fifth circle C5. The fourth circle C4 and the fifth circle C5 are centered on the X-axis. Alternatively, the brake disc could have no bosses, only the fourth row, or only the fifth row of bosses. The bosses could also be distributed over a larger number of circles, for example, three or four circles.

[0039] The diameter of the fourth circle C4 is strictly greater than the diameter of the first circle C1 and strictly less than the diameter of the second circle C2. Therefore, the fourth row of bosses 30 is radially intercalated between the first row of connecting studs 21, 22 and the second row of connecting studs 26. The fourth circle C4 can be positioned approximately equidistant from circles C1 and C2. The diameter of the fifth circle C5 is strictly less than the diameter of the first circle C1 and strictly greater than the diameter of the third circle C3. Therefore, the fifth row of bosses 30 is radially intercalated between the first row of connecting studs 21, 22 and the third row of connecting studs 27. The fifth circle C5 can be positioned approximately equidistant from circles C1 and C3.

[0040] During operation, the brake disc 1 is fixed to the vehicle's wheel and rotates around the X-axis. A centrifugal airflow is established between the two discs 2 and 3 due to a pressure difference between the outer and inner edges of the discs. The air therefore flows into the space defined between the two inner surfaces 7, passing between the various connecting lugs 10. The airflow is guided in this space by the various connecting studs 5. Air turbulence is likely to form depending on the shape and position of these connecting studs 5. Advantageously, the specific position and shape of the connecting studs allow for a uniform airflow within the space defined between the two inner surfaces 7. In particular, the teardrop shape of the connecting studs minimizes air turbulence and offers low resistance to the airflow. This further improves airflow.

[0041] There figure 5 This illustrates, in particular, the airflow velocity distribution in the space formed between the two plates 2 and 3. This velocity distribution is remarkably homogeneous, meaning there are no areas where the airflow is very fast and others where it is much slower. With a brake disc according to the invention rotating at 800 revolutions per minute around the X-axis, the velocity difference between the areas where the air flows fastest and the areas where it flows slowest is only on the order of 20 m / s. This homogeneity is also characterized by a very small pressure difference between the different areas of the space formed between the two internal surfaces 7. Under the aforementioned operating conditions, this pressure difference is less than or equal to 1.5 mbar, specifically on the order of 1.3 mbar.

[0042] Conversely, with disc brakes known from the prior art and operating under the same conditions, the velocity difference between the areas where the air flows fastest and the areas where the air flows slowest reaches a value of 30 m / s, or even more. The pressure difference between the different zones of the space formed between the two internal surfaces 7 is greater than or equal to 5 mbar, and sometimes even greater than or equal to 10 mbar. For example, the figures 6 And 7 Figures 31 illustrate the airflow velocity distribution in the space between the two plates of two different brake discs of the invention, operating under the same conditions. Darker areas highlight that these velocity distributions are particularly heterogeneous. The cooling achieved with such brake discs is less efficient.

[0043] Furthermore, the bosses 30 increase the heat exchange surface area with the air, further improving cooling efficiency. The proposed arrangement of the connecting studs 5 and the bosses 30 thus makes it possible to achieve a heat exchange surface area greater than or equal to 900 cm² for a brake disc with an outer diameter of 280 mm. The invention therefore achieves an excellent compromise between the largest possible heat exchange surface area and the smallest possible pressure variation between the different zones of the space formed between the two internal surfaces 7. When the brake disc 1 heats up due to the friction of the brake pads against the friction surfaces 4, it efficiently dissipates the stored heat through an airflow between the two internal surfaces 7. Thus, the brake disc temperature remains moderate and the braking system's efficiency is maintained.

Claims

1. Ventilated brake disc (1) comprising two annular plates (2, 3) each comprising a friction surface (4), the two plates being centred on the same axis (X) and spaced apart from one another along this axis, the two plates being connected to one another by a set of connecting studs (5), comprising - a first row of connecting studs (21, 22) distributed along a first circle (C1) centred on said axis, at least a plurality of the connecting studs (21) of the first row comprising a pear-shaped cross section in a plane orthogonal to said axis, of radially elongate shape and tapering in a centrifugal direction, - a second row of connecting studs (26) distributed along a second circle (C2) centred on said axis, the connecting studs of the second row comprising a cross section of circular shape in a plane orthogonal to said axis, the diameter of the first circle being strictly smaller than the diameter of the second circle, the first row comprising connecting studs (22) having a cross section of circular shape in a plane orthogonal to said axis, characterized in that the first row is formed by the repetition of a pattern comprising a first connecting stud (21) of pear-shaped cross section, a second connecting stud (21) of pear-shaped cross section, the second connecting stud being adjacent to the first connecting stud, and a third connecting stud (22) of circular cross section, the third connecting stud being adjacent to the second connecting stud.

2. Ventilated brake disc (1) according to the preceding claim, characterized in that it comprises an annular fastening interface (8) centred on said axis (X) and connected to at least one of the two plates (2, 3) by a set of connecting tabs (10), each connecting tab being positioned radially opposite a connecting stud (22) of circular cross section of said first row.

3. Ventilated brake disc (1) according to either of the preceding claims, characterized in that the set of connecting studs comprises a third row of connecting studs (27) distributed along a third circle (C3) centred on said axis (X), the connecting studs of the third row comprising a pear-shaped cross section in a plane orthogonal to said axis, of radially elongate shape and tapering in a centrifugal direction, the diameter of the first circle being strictly greater than the diameter of the third circle.

4. Ventilated brake disc (1) according to Claims 2 and 3, characterized in that said connecting tabs (10) extend radially up to a sixth circle (C6) centred on said axis (X), the sixth circle intersecting the connecting studs (27) of the third row.

5. Ventilated brake disc (1) according to one of the preceding claims, characterized in that each plate (2, 3) comprises an inner surface (7) facing the other plate, the inner surface of each plate comprising a set of bosses (30), the set of bosses comprising a fourth row of bosses distributed along a fourth circle (C4) centred on said axis.

6. Ventilated brake disc (1) according to the preceding claim, characterized in that the set of bosses (30) comprises a fifth row of bosses distributed along a fifth circle (C5) centred on said axis (X), the diameter of the first circle (C1) being strictly smaller than the diameter of the fourth circle (C4), and / or strictly greater than the diameter of the fifth circle (C5).

7. Ventilated brake disc according to Claim 3 and according to Claim 6, characterized in that the diameter of the second circle (C2) is strictly greater than the diameter of the fourth circle (C4), and / or in that the diameter of the third circle (C3) is strictly smaller than the diameter of the fifth circle (C5).

8. Motor vehicle, characterized in that it comprises a ventilated brake disc (1) according to one of the preceding claims.