Protective device for a brake disc

Abstract

The invention relates to a protective device (4) for a brake disc (2), characterized in that it comprises a plate (5) in the form of a ring portion, the plate being intended to extend along a friction surface of the brake disc, the plate comprising a set of reliefs (10) projecting in the opposite direction to the brake disc (2), each relief comprising a ventilation opening (8), each opening being oriented such that a flow of air leaving from a volume contained between the brake disc and the plate is oriented substantially parallel to the friction surface of the brake disc.

Description

[0001] DESCRIPTION

[0002] TITLE: Protective device for a brake disc

[0003] Technical field of the invention

[0004] The invention relates to a protective device for a brake disc. The invention also relates to a braking system comprising such a protective device. The invention further relates to a motor vehicle comprising such a braking system and / or such a protective device.

[0005] State of the prior art

[0006] Motor vehicle brake discs are generally equipped with a protective device that at least partially covers the brake disc to protect it from splashes. Such a protective device forms a barrier against splashes of solid and / or liquid particles that could hit the disc and thus damage it. They are generally in the form of a plate extending close to an inner face of the brake disc.

[0007] While such protective devices do protect the brake disc, they restrict airflow around the brake disc and therefore prevent it from cooling effectively. Brake discs equipped with such a protective device are therefore likely to reach higher temperatures, which leads to braking system malfunctions and ultimately, degraded braking performance.

[0008] To overcome these disadvantages, it is known to oversize the braking system, by providing brake discs with a larger diameter, however this results in a significant increase in production costs and the mass of the braking system. The use of perforated protective devices is also known: openings formed in the plate of the protective device allow air to pass through to cool the brake disc. The perforated protective devices known from the state of the art only slightly improve the capacity of the brake disc to cool and protect it less effectively against projections.

[0009] Presentation of the invention

[0010] The aim of the invention is to provide a protection device for a brake disc which overcomes the above drawbacks and improves the protection devices known from the prior art.

[0011] More specifically, a first object of the invention is a protection device allowing effective cooling of the brake disc while maintaining optimal protection of the brake disc.

[0012] Summary of the invention

[0013] The invention relates to a protective device for a brake disc, the protective device comprising a plate in the form of a crown portion, said plate being intended to extend along a friction surface of the brake disc, said plate comprising a set of reliefs projecting in the opposite direction from the brake disc, each relief comprising a ventilation opening, each opening being oriented so that an air flow exiting from a volume between the brake disc and said plate is oriented substantially parallel to the friction surface of the brake disc.

[0014] Each opening may be oriented such that an air flow exiting from the volume between the brake disc and said plate is oriented substantially parallel to a tangent of the brake disc, in the direction of rotation of the brake disc.

[0015] Each opening may be formed in a single side of a relief, said side extending along a radius of the crown portion.

[0016] The height of said reliefs can be between 2mm and 10mm inclusive.

[0017] Each opening can occupy a distinct angular sector of the crown portion.

[0018] Said crown may extend over an angular sector greater than or equal to 180°.

[0019] The said set of openings may include between eight and twenty openings inclusive.

[0020] The protection device may comprise at least one deflector arranged at one end of the crown portion, said deflector being configured to guide an incoming air flow between the protection device and the brake disc, in particular the protection device may comprise two deflectors each arranged at one end of the crown portion, each deflector being configured to guide an incoming air flow between the protection device and the brake disc.

[0021] The protective device may be formed as a single piece from a stamped sheet of metal.

[0022] The invention also relates to a braking system for a motor vehicle, comprising a brake disc, a brake caliper, and a protection device as defined previously, the brake caliper being positioned between two ends of the crown portion.

[0023] The invention also relates to a motor vehicle comprising a protection device as defined previously and / or a braking system as defined previously.

[0024] Presentation of figures

[0025] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment made without limitation in relation to the attached figures among which:

[0026] Figure 1 is a front view of a brake disc equipped with a protection device according to one embodiment of the invention.

[0027] Figure 2 is a perspective view of the protective device.

[0028] Figure 3 is a front view of the protective device.

[0029] Figure 4 is a first partial and perspective view of the protection device.

[0030] Figure 5 is a second partial perspective view of the protection device.

[0031] Detailed description

[0032] Figure 1 schematically illustrates a braking system 1 of a motor vehicle according to one embodiment of the invention. The motor vehicle may be, for example, a private vehicle, a utility vehicle, a truck or even a bus. The braking system 1 comprises a brake disc 2, a brake caliper 3, and a protection device 4 for the brake disc 2. The brake disc 2 is secured to a wheel of the vehicle, movable in rotation about an axis of rotation Y. The brake caliper 3 is a member provided with a jaw capable of clamping the brake disc 2 to brake the rotation of the wheel. In particular, the brake caliper 3 comprises a set of brake pads capable of being pressed against friction surfaces of the brake disc 2. The protection device 4 may be fixed directly or indirectly to a steering knuckle supporting an axis of rotation of the wheel.

[0033] According to the embodiment presented, the protective device 4 equips the brake disc 2 of a right front wheel of the vehicle. It covers an internal friction surface of the brake disc, that is to say a friction surface facing the vehicle. The brake caliper 3 is positioned on the front side of the brake disc, that is to say on the side of the brake disc 2 towards which the vehicle is moving forward. According to the point of view of figure 1, the front is located on the left of the figure and the rear is located on the right of the figure. According to this same point of view, the direction of rotation of the brake disc 2, when the vehicle is moving forward, corresponds to the counterclockwise direction and is represented by an arrow F1.

[0034] Of course, the protective device according to the invention could equip any other brake disc of the vehicle, in particular the brake disc of a left front wheel, and / or a left rear wheel, and / or a right rear wheel. Alternatively, the brake caliper 3 could also be positioned on the rear side of the brake disc. The protective device could also cover an external face of the brake disc.

[0035] The protective device 4 is illustrated in more detail in Figure 2. The protective device 4 is a member intended to protect the brake disc 2 from any type of projections which could damage it, in particular projections of solid particles such as gravel, pebbles, sand or mud or projections of liquid. For this purpose, the protective device 4 comprises a plate 5 covering at least part of a friction surface of the brake disc. This plate 5 extends generally in a plane P1 substantially perpendicular to the axis of rotation Y, along a friction surface of the brake disc 2.

[0036] The plate 5 has a crown portion shape whose center corresponds to the rotation axis Y. The outer diameter of the crown portion may be slightly larger than the outer diameter of the brake disc. The crown portion comprises two ends 6A, 6B: a first end 6A is positioned rather downwards, in a lower half of the protection device, and a second end 6B is positioned rather upwards, in an upper half of the protection device. As a note, the top and the bottom are defined in relation to a vertical axis and it is considered that the vehicle rests on horizontal ground. The brake caliper 3 is positioned between the two ends 6A and 6B of the crown portion. Preferably, the plate 5 extends over an angular sector greater than or equal to 180°.

[0037] Unlike the brake disc 2 which is rotatable, the protection device 4 is fixed relative to the vehicle. In particular, the protection device 4 can be fixed to a steering knuckle of the vehicle. For this purpose, it comprises three fixing holes 7 distributed at an internal contour of the crown. The plate 5 extends parallel to the brake disc without contact with the latter. The distance separating the plate 5 from the brake disc can be greater than or equal to 1 mm, preferably between 3 mm and 10 mm. The plate 5 can extend overall in a single plane P1, or alternatively, in several planes parallel to each other and connected to each other by connecting portions. The plate 5 can also possibly form a slight angle, for example of the order of 1 ° or 2 °, with the brake disc in order to avoid conflict with any other component of the vehicle located near the brake disc.The plate 5 may also include stiffening ribs and / or reliefs without openings. The plate 5 may thus include portions more or less close to the brake disc.

[0038] The plate 5 comprises a set of ventilation openings 8. These openings 8 are openings passing through the plate 5 and allow the establishment of an air flow which improves the cooling of the brake disc 2. In particular, the openings 8 allow the hot air contained between the brake disc 2 and the plate 5 to escape. Each opening 8 is formed in a relief 10 distinct from the plate 5, the relief projecting in the opposite direction from the brake disc 2. In other words, the plate 5 comprises a set of reliefs 10 projecting in the opposite direction from the brake disc 2, and each relief comprises a single ventilation opening 8. The contour 9 of each opening 8 comprises at least one segment extending along a radius of the crown portion.Each opening 8 is oriented so that an air flow exiting from the volume between the brake disc 2 and the plate 5 is mainly oriented parallel to a tangent of the brake disc, in other words parallel to a rotation speed vector of the brake disc 2. Such a direction is notably identified by the arrows F3 in FIG. 1.

[0039] As illustrated in all of the figures, each opening 8 is preferably oriented in the direction of rotation of the brake disc 2. That is to say, each opening 8 is oriented so that an air flow exiting from a volume between the brake disc 2 and the plate 5 is oriented in the direction of rotation of the brake disc, that is to say in the direction of the arrows F3. This provides optimal cooling of the brake disc. According to an alternative embodiment not shown, all or part of the openings 8 could be oriented so that an air flow exiting from a volume between the brake disc 2 and the plate 5 is oriented in the direction opposite to the direction of rotation of the brake disc, that is to say in the opposite direction relative to the orientation shown in the figures.

[0040] The openings 8 may be of the "louver" type. This type of opening is also sometimes called "louver" from the Anglicism. These are openings substantially inclined relative to the axis perpendicular to the plane P1 in which the plate 5 extends. With reference to Figure 4, the orientation of an opening 8 may be defined as the orientation of a vector V, perpendicular to a plane P2 in which the contour 9 of the opening extends. The vector V forms a non-zero angle A1 with the Y axis. This angle A1 may be, for example, between 20° and 90°, in particular between 45° and 90°. The angle A1 may be, for example, between 30° and 80°. As a note, the contour 9 preferably extends in a plane, however, in the event that the contour 9 of the opening 8 does not extend perfectly in a plane, the plane P2 can be defined mathematically as the plane for which the average distance of the points of the contour 9 from said plane P is minimal.

[0041] With reference to Figure 3, for each opening 8, a Frenet reference frame can be defined comprising a radial axis R and a tangential axis T. The radial axis R is parallel to a radius of the crown and oriented towards the outside of the crown (centrifugal orientation). The tangential axis T is parallel to a velocity vector of the brake disc passing at the level of this opening. The axes R and T are perpendicular to each other and both perpendicular to the axis of rotation Y. The axes Y, R and T form an orthogonal reference frame. The vector V, defining the orientation of the opening, extends in a plane parallel to the axes Y and T. In other words, the vector V comprises only a tangential component and a component parallel to the axis of rotation Y. It therefore does not comprise a radial component. The tangential component is non-zero. The vector V is oriented in the direction of an outgoing flow from a volume defined between the brake disc 2 and the plate 5.In other words, the vector V is oriented so as to move away from the brake disc. The component of the velocity vector along the tangential axis T is oriented in the same direction as the velocity vector of the brake disc at this opening.

[0042] The reliefs 10 may have a substantially rectangular or trapezoidal shape, or even more generally any polygonal shape, the sides of the polygonal shape being connected or not by rounded edges. Each relief 10 may comprise a single side 11 extending along a radius of the crown portion and in which one of the openings 8 is formed. The other sides of the relief 10 may be devoid of openings. The reliefs 10 also comprise a flat surface 12 parallel to the plane P1 but offset relative to the latter. The flat surface 12 is connected by walls 13 to the plane P1. The walls 13 may form folds at approximately 45° with the flat surface 12 and with the plane P1. The contour 9 of each opening 8 comprises at least one segment belonging to the flat surface 12 and one segment belonging to the plane P1. In addition, the walls 13 connecting the flat surface 12 to the plate 5 also border the opening 8.

[0043] The distance along the Y axis separating the flat surface 12 from the P1 defines the height of the reliefs. This height can be, for example, between 2 mm and 10 mm inclusive. This height range constitutes a good compromise between an increase in the size of the protection device and the improvement of the ventilation of the brake disc 2.

[0044] The protective device 4 is preferably a metal part. It can be formed entirely by stamping, that is to say by a manufacturing process consisting of bending and cutting a sheet of metal. The protective device is simple to manufacture. It does not require more material than the protective devices known from the prior art. Advantageously, the shapes of the openings 8 and the reliefs 10 are shapes compatible with manufacturing by stamping. Advantageously, the reliefs 10 also increase the rigidity of the protective device 4.

[0045] Preferably, each opening 8 occupies a distinct angular sector of the crown portion. For example, the crown portion can be divided into sectors of approximately 15° each, each sector comprising an opening 8. Advantageously, the protection device can comprise a number of openings 8 greater than or equal to eight, for example between eight and twenty. The openings 8 can be regularly spaced. The length L1 of the openings 8 along the radial axis R can be at least equal to 30% of the width L2 of the crown, preferably at least equal to 70% of the width L2 of the crown.

[0046] The plate 5 may comprise an area 14 without an opening 8, which makes it possible to avoid a conflict between the protection device and another component of the vehicle. In this case, the plate 5 is without an opening in a lower area due to the proximity of the protection device to a lower suspension ball joint.

[0047] Furthermore, the protection device 4 comprises two deflectors 15A, 15B arranged at the ends 6A, 6B of the crown portion. Each deflector 15A, 15B is configured to guide an incoming air flow between the protection disc 4 and the brake disc 2. For this purpose, each deflector 15A, 15B extends obliquely on the side opposite the brake disc. Consequently, each deflector 15A, 15B extends in a plane P3 forming with the plane P1 a non-zero angle, for example an angle of between 10° and 60°. Alternatively, the protection device could not comprise such deflectors or comprise only one of the two deflectors. When the vehicle moves forward, a flow of fresh air, identified by arrow F2 in Figure 1, rushes between the brake disc and the protection device, passing at end 6A.The incoming air flow is generally uniform and enters between the brake disc and the protection device from the front of the vehicle. The deflector 15A deflects the incident air flow towards the volume between the brake disc 2 and the protection device 4. The flow of fresh air in contact with the brake discs is thus increased. This fresh air heats up by cooling the brake discs and then escapes from the volume defined between the brake disc 2 and the protection device 4 through the openings 8. The orientation of the openings 8 in the direction of rotation of the brake disc facilitates the evacuation of the hot air. Indeed, the air heated in contact with the brake disc is also set in rotation by the latter. This outgoing air flow is represented by the arrows F3 in Figure 1. The outgoing air flow is therefore generally circular.The air exiting through the openings positioned at the top of the protection device is directed generally from the rear to the front of the vehicle. Surprisingly, the protection device achieves excellent cooling performance for the brake disc.

[0048] The performance of the protective device could be quantified by simulation. When a brake disc is without a protective device, it achieves a cooling capacity of 41 W / m2K, i.e. a cooling time constant of 285s. This same brake disc equipped with a protective device according to the state of the art would see its cooling capacity reduced to 21W / m2K, i.e. a cooling time constant of 340s. The protective device according to the invention makes it possible to achieve a cooling capacity of 36W / m2K, i.e. a cooling time constant of 296s. The protective device according to the invention makes it possible to achieve cooling performances very close to those achieved in the absence of any protective device.

[0049] Furthermore, openings 8 provide better protection against projections than other openwork protective devices known from the prior art. The openings form baffles that make it less likely that particles will intrude between the protective device and the brake disc. In particular, the protective device provides excellent protection against projections incident parallel to the Y axis of rotation. Indeed, the openings 8 have a zero or otherwise very small surface area when viewed in projection along the Y axis.

Claims

DEMANDS 1. Protective device (4) for a brake disc (2), characterized in that it comprises a plate (5) in the shape of a portion of a crown, said plate being intended to extend along a friction surface of the brake disc, said plate comprising a set of reliefs (10) projecting in the opposite direction to the brake disc (2), each relief comprising a ventilation opening (8), each opening being oriented so that an airflow exiting from a volume between the brake disc and said plate is oriented substantially parallel to the friction surface of the brake disc.

2. Protective device (4) according to the preceding claim, characterized in that each opening is oriented so that an airflow exiting from the volume between the brake disc and said plate is oriented substantially parallel to a tangent of the brake disc, in the direction of rotation of the brake disc.

3. Protective device (4) according to any one of the preceding claims, characterized in that each opening (8) is formed in a single side (11) of a relief, said side extending along a radius of the portion of the crown.

4. Protective device (4) according to any one of the preceding claims, characterized in that the height of said reliefs (10) is between 2mm and 10mm inclusive.

5. Protective device (4) according to any one of the preceding claims, characterized in that each opening (8) occupies a distinct angular sector of the portion of the crown.

6. Protective device (4) according to any one of the preceding claims, characterized in that said crown extends over an angular sector greater than or equal to 180°.

7. Protective device (4) according to any one of the preceding claims, characterized in that said set of openings (8) comprises between eight and twenty openings inclusive.

8. Protective device (4) according to any one of the preceding claims, characterized in that it comprises at least one deflector (15A, 15B) arranged at one end of the portion of the crown, said deflector being configured to guide an incoming airflow between the protective device (4) and the brake disc (2), in particular in that it comprises two deflectors (15A, 15B) each arranged at one end of the portion of the crown, each deflector being configured to guide an incoming airflow between the protective device (4) and the brake disc (2).

9. Protective device (4) according to any one of the preceding claims, characterized in that it is formed from a single piece of stamped metal sheet.

10. Braking system (1) for a motor vehicle, characterized in that it comprises a brake disc (2), a brake caliper (3), and a protective device (4) according to any one of the preceding claims, the brake caliper (3) being positioned between two ends (6A, 6B) of the portion of the crown.

11. Motor vehicle, characterized in that it comprises a protective device (4) according to any one of claims 1 to 9 and / or a braking system (1) according to the preceding claim.

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