"Braking band of a disc for disc brake of the ventilated type"

[0001] . Field of the invention

[0002] . The present invention relates to a braking band and to a ventilated disc for disc brake, particularly, but not exclusively, for applications in the automobile field.

[0003] . Background art

[0004] . The brake caliper in a disc brake is generally arranged straddling the outer peripheral edge of a brake disc, adapted to rotate about a rotation axis (A-A) defining an axial direction (X- X) . Moreover, in a disc brake there is defined a radial direction (R-R) which is substantially orthogonal to said axial direction (X- X) , and a tangential (C-C) or circumferential direction (C-C) , orthogonal both to said axial direction (X-X) and to said radial direction (R-R) .

[0005] . As is known, discs for disc brake comprise a bell adapted to associate the disc with a hub of a vehicle, from which an annular portion extends called a braking band, which is intended to cooperate with pads of a caliper. In the case of discs of the ventilated type, the braking band is made by means of two plates facing and connected to each other by means of connecting elements, respectively, for example in the shape of pillars or fins. The outer surfaces of the two plates define opposite braking surfaces while the inner surfaces, together with the pillars or fins, delimit ventilation channels for cooling the disc, which channels the air flows through according to a centrifugal direction during the rotary motion of the disc itself.

[0006] . Said braking band is intended to cooperate with disc brake calipers adapted to exert a braking action on the vehicle by exerting, by means of pads, friction on opposite surfaces of the two plates, said braking surfaces.

[0007] . It is known that during the operation of the brakes, the friction between the brake caliper pads and the braking surfaces of the braking band generates an increased quantity of heat which requires being disposed of.

[0008] . The heat generated indeed causes several undesired phenomena, such as for example, the deformation of the braking band, the formation of cracks on the braking surfaces or localized transformations of state of the material forming the braking band which in turn result in the deterioration of the braking band itself .

[0009] . In the applications on high performance motor vehicles with an increased braking efficiency in particular, there is much energy to be disposed of and the aforesaid need to dispose of the heat generated during the braking action is even more felt.

[0010] . Ventilated discs of the type mentioned above have undergone a continuous evolution over time, in particular concerning the number and shape of the so-called ventilation channels, thus defining the gap formed by the two plates axially facing each other.

[0011] . Among said known ventilated discs, the so-called "pillar discs" have shown to be particularly efficient in terms of heat disposal performance, i.e. cooling in which discs the ventilation channels are limited internally by particular column connecting elements, having limited comparable radial and circumferential extension with respect to the axial extension thereof, defined as "pillars" which transversely connect the two plates .

[0012] . For example, "pillar" ventilated discs are known from EP 1 373 751 Bl, in which the pillars geometrically are arranged along three concentric circumferences which are coaxial to the disc and have a different radius, to form three "lines"; if cross-sectioned in a plane which is parallel to the two plates and is median with respect thereto, the pillars have different types of cross sections (for example, "rhomboidal" cross-sectioned pillars in the intermediate and outer lines; "drop-shaped" pillars in the inner line) .

[0013] . Other ventilated discs with "pillar" structures are known for example from WO 2004/102028 and from US 5,542,503.

[0014] . The so-called "fin" or "wing" discs are known among ventilated discs, in which the ventilation channels are limited internally by particular connecting elements elongated along a prevalent direction, for example directed according to a direction parallel to the radial direction (R-R) , or spiral connecting elements, and which transversely connect the two plates.

[0015] . It is also known that the braking action carried out by the pads against the braking surfaces of the disc generates heat, accordingly an increase of temperature of the disc up to making the disc itself incandescent in the case of particularly burdensome performance. The disc is deformed and the contact between the pads and the braking surfaces deteriorates due to the increased temperature reached by the disc during the braking. Moreover, the friction material of the pads undergoes a kind of vitrification and polluting by the disc material.

[0016] . It has also been detected that the higher temperature is reached at a middle annular portion of the braking surfaces, i.e. at a middle annular portion of the outer surfaces of the respective plates. Such an area is easily subject to the formation of cracks over the course of the life of the disc.

[0017] . To obviate the above-disclosed drawbacks, the need in the field is particularly felt on the one hand to increase the efficiency of the dispersion of the heat generated by the braking so as to contain the temperatures reached by the disc during and following the braking, and the need on the other hand to increase the mechanical resistance of these middle portions of the braking band .

[0018] . Solutions are known from WO 2004/102028 and also from WO 2002/064992, US7066306, US7267210, US 2006 0243546, US 2004 0124047, US6367599, US5542503 and US4865167. Although they are satisfactory from various viewpoints, these known solutions do not allow a compromise to be reached between the desired mechanical resistance in the middle annular area of the braking band and the contrasting need to maximize, in the same area, the airflow capable of removing the significant localized increase of temperature caused by the braking action.

[0019] . However, it is worth noting that ventilated discs of the type mentioned do not in themselves provide a solution to a further problem arising simultaneously to the problem mentioned above and which is to be resolved at the same time, a problem which may affect the disc brakes, in particular the disc brakes with ventilated discs, a problem briefly described hereinbelow.

[0020] . As is known, during the operation of the brakes, the disc and the braking bands in particular may mechanically vibrate at various frequencies correlated with various vibration manners of the dis itself. Such disc vibrations may result for example from resonances triggered by vibrations of objects mechanically coupled to the disc which are stressed in the braking step should the vibration frequencies of such objects be coincident with or sufficiently close to the vibration frequencies of the disc.

[0021] . It is also known that the above vibrations cause an audible noise, in particular in the shape of disturbing squealing noises, when the resonance frequencies are in the audible range (for example, between 2 and 9 KHz, with subsequent more or less shrill squealing noises) .

[0022] . Accordingly, the need arises to devise solutions for reducing or eliminating such squealing noises by means of construction contrivances which "move" the vibration frequencies of the disc to different values from the excited ones.

[0023] . Certain solutions are known for discs with structures which are different from the mentioned "pillar" structures.

[0024] . For example, IT 1 273 754 has braking bands with projections protruding into the inner part of the plates, towards the gap between the two plates, in particular positions and with masses which were specifically identified in order to reduce the vibrations arising and the subsequent noise.

[0025] . Other ventilated discs with structures adapted to reduce disturbing vibrating phenomena are known for example, from US 4 523

666.

[0026] . Document US3,983,973 of Knorr-Bremse GmbH shows a brake disc comprising a pair of friction plates spaced apart from each other to form a ventilation channel. A braking force may be applied against said plates by means of a braking gasket of brake pads. The two plates are interconnected by a plurality of flow guide ribs or fins so as to define ventilation passages between the friction plates. Strips of anti-vibrating material are positioned in radial grooves formed in the opposite surfaces of the friction plates. These inserts consist of metal elements which damp the vibrations and have a greater expansion coefficient than that of the ferrous material with which the friction plates are made, such as lead, bronze or copper.

[0027]. A similar solution is known from US2009035598.

[0028] . It is known from document US2012111692 to couple passive dampers of the Squawk type with the braking device to reduce the vibrations .

[0029] . From solutions US6131707, W02016020820, WO2017153902 ,

W02017153873, EP0318687, WO2011058594 , W02006105131, US2006219500,

US6145636, US2010122880, US6325185, US4523666, US5004078, it is known to provide connections between the braking band plates circumferentially distributed in non-uniform manner in order to reduce the vibrations excited by the braking action.

[0030] . However, under certain conditions of the braking action, these distributions of the connecting elements of the plates create structural non-uniformities capable of generating completely undesired stresses concentrated in the braking band.

[0031] . Therefore, the need has arisen for new structures of ventilated discs which simultaneously offer both particular cooling efficiency performance and properties of minimizing the vibrations and noise in the braking step, and while avoiding to cause concentrated stresses in the braking band which could compromise the integrity and duration thereof.

[0032] . The aforesaid known examples of ventilated discs and related braking bands are not capable of adequately meeting all the strongly desired requirements mentioned.

[0033] . It is thus the problem at the basis of the present invention to devise a braking band and a disc for disc brake, which have structural and functional features such as to meet the aforesaid needs while obviating the drawbacks mentioned with reference to the known art.

[0034] . Solution

[0035] . It is object of the present invention to provide a braking device in which the tendency to create these waves and subsequent squealing noises is reduced.

[0036] . This and other objects and advantages are achieved by a braking band according to claim 1, and also by a disc of disc brake according to claim 9, and also by a vehicle according to claim 10.

[0037] . Certain advantageous embodiments are the subject of the dependent claims .

[0038] . An analysis of this solution has shown how the solution proposed allows a much greater braking comfort to be achieved with respect to the solutions of the prior art, therefore a reduction of the vibrations and an absence of vibrations in particular resulting in squealing noises.

[0039] . Moreover, the solution proposed maintains a cooling efficiency of the disc which is very high and even improved in certain embodiments; for example, the efficiency is greatly improved due to the increased turbulence of the flow of air which flows through the gap of the braking band, turbulence caused by the specific shape of the projections in the plate (s) and arranged between the connecting elements and extending in circumferential direction .

[0040] . Drawings

[0041] . Further features and advantages of the device, the disc brake and the vehicle will become apparent from the description provided below of preferred embodiments thereof, given by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0042] . - figure 1 depicts an axonometric view of a disc of disc brake according to the present invention, partially cross-sectioned along a plane passing through the axial and radial directions;

[0043] . - figure 2 shows a plan view of the disc in figure 1, cross-sectioned along an average flow plane of the fluid flowing through the gap;

[0044] . - figure 3 depicts an axonometric view of a detail of the outer edge of the disc in figure 1, from the radial direction towards the inside of the disc;

[0045] . - figure 4 shows an axonometric view of a detail of the section in figure 2;

[0046] . - figure 5 depicts a side view of the edge in figure 3, along the radial direction;

[0047] . - figure 6 shows a plan view of a disc according to a further embodiment, cross-sectioned along an average flow plane of the fluid flowing through the gap;

[0048] . - figure 7 depicts an axonometric view of a detail of the outer edge of the disc in figure 6, from the radial direction towards the inside of the disc;

[0049] . - figure 8 shows an axonometric view of a detail of the section in figure 6;

[0050] . - figure 9 depicts an axonometric view of a detail of the disc in figure 6, partially cross-sectioned along a plane passing through an axial and radial direction;

[0051] . - figure 10 shows a plan view of a disc according to a further embodiment again, cross-sectioned along an average flow plane of the fluid flowing through the gap;

[0052] . - figure 11 depicts an axonometric view of a detail of the outer edge of the disc in figure 10, from the radial direction towards the inside of the disc; [0053] . - figure 12 shows an axonometric view of a detail of the section in figure 10;

[0054] . - figure 13 depicts an axonometric view of a detail of the disc in figure 10, partially cross-sectioned along a plane passing through an axial and radial direction.

[0055] . Description of some preferred embodiments

[0056] . According to a general embodiment, a braking band 1 of a disc for disc brake 2 of the ventilated type is provided.

[0057] . Said braking band 1 extends between an inner diameter Dl, close to a rotation axis X-X of the braking band 1, and an outer diameter D2, far from said rotation axis X-X. Said rotation axis defines an axial direction X-X.

[0058] . Said braking band 1 defines a radial direction R-R substantially orthogonal to said axial direction X-X, and a circumferential direction C-C orthogonal both to said axial direction X-X and to said radial direction R-R.

[0059] . Said braking band 1 comprises two plates 3, 4 facing each other .

[0060] . Said plates 3, 4 comprise inner surfaces 5, 6 directly or indirectly facing each other and delimiting a gap 7 which defines a ventilation duct for the braking band 1.

[0061] . Said plates 3, 4 comprise outer surfaces 8, 9.

[0062] . Said outer surfaces 8, 9 comprise opposite flat circumferential portions which form braking surfaces 10, 11. In other words, portions of the outer surfaces 8, 9 cooperate with brake pads housed in a brake caliper to exert a braking action when sandwiched against the braking band 1. The portion of the outer surfaces 8, 9 which is brushed or involved by the pads defines the braking surfaces 10, 11.

[0063] . Said plates 3, 4 comprise a plate body 12, 13 having an extension in axial direction X-X or thickness of plate 14, 15. In other words, when assessed in axial direction, each plate 3, 4 shows a thickness of plate 14, 15 which is given by the thickness in axial direction of the plate body 12 of plate 3, 4.

[0064] . Said plates 3, 4 are joined to each other by heat dissipation elements or connecting elements 16, 17, 18, 19 of the plates 3, 4.

[0065] . Said connecting elements 16, 17, 18, 19 are shaped as columns and/or ribs protruding from one plate towards the opposite plate in the shape of connecting bridges of the plates 3, 4.

[0066] . Advantageously, at least one of the plates 3; 4 comprises at least one projection 20, 21, 22 projecting from said plate 3; 4 into said gap 7 without reaching the opposite plate 4; 3.

[0067] . Said projection 20, 21, 22 forms at least one localized narrowing of said gap 7. In other words, travelling said gap 7, when said projection 20, 21, 22 is reached, a reduction is encountered of the section in axial direction X-X of the size of gap 7.

[0068] . Said projection 20, 21, 22 forms at least a thickening of the plate body 12; 13, thus creating a localized increase of said thickness of plate 14; 15. In other words, considering the thickness of the body of a plate in axial direction X-X, thickness 14, 15 increases at said projection 20, 21, 22. [0069] . Said at least one projection 20, 21, 22 extends at least from a first connecting element 16, 17, 18, 19 to an adjacent connecting element 16, 17, 18, 19, thus connecting said connecting elements 16, 17, 18, 19 to one another.

[0070] . Said at least one projection 20, 21, 22 extends at least along said circumferential direction (C-C) connecting at least two adjacent connecting elements 16, 17, 18, 19 placed side-by-side in circumferential direction C-C.

[0071] . The group of each projection 20, 21, 22 extends circumferentially along a discontinuous annular path, avoiding a uniform distribution of the projections in circumferential direction .

[0072] . According to one embodiment, the group of each projection 20, 21, 22 extends circumferentially along discontinuous circular sectors, avoiding a closed annular path.

[0073]. According to one embodiment, said connecting elements 16, 17, 18, 19 are grouped into at least two rows or lines 23, 24, 25 arranged circumferentially.

[0074] . A first of said lines 23 is internally arranged in radial direction or towards said axis X-X close to said inner diameter Dl.

[0075] . A second of said lines 24 is arranged outermost radially far from said axis X-X close to said outer diameter D2.

[0076] . At least a third of said lines 24 is radially arranged between said first inner line 23 and said second outer line 24.

[0077] . According to one embodiment, at least two of said connecting elements 16, 17, 18, 19 are pillars 26 which have a circular-shaped section in a plane substantially parallel to the airflow along gap 7 or ventilation channels.

[0078] . According to one embodiment, at least two of said connecting elements 16, 17, 18, 19 are fins 27 or ribs which have an elongated-shaped section, for example in radial direction R-R, in a plane substantially parallel to the airflow along gap 7 or ventilation channels.

[0079] . According to one embodiment, at least two of said connecting elements 16, 17, 18, 19 have a rhombus or diamond-shaped section with four vertexes 28 joined by four sides 29 in a plane substantially parallel to the airflow along gap 7 or ventilation channels, in which said sides delimiting said section are substantially rectilinear-shaped .

[0080] . According to one embodiment, said at least one projection 20, 21, 22 projects into said gap 7 from only one of said plates 3;

4.

[0081] . According to one embodiment, said at least one projection 20, 21, 22 is at least two projections 20, 21, 22 and said at least two projections 20, 21, 22 project into said gap 7 from both said plates 3, 4.

[0082] . According to one embodiment, said at least one projection 20, 21, 22 is at least two projections 20, 21, 22 and said at least two projections 20, 21, 22 project into said gap 7 from both said plates 3, 4 and face each other.

[0083] . According to one embodiment, said at least one projection 20, 21, 22 is at least two projections 20, 21, 22 and said at least two projections 20, 21, 22 project into said gap 7 from both said plates 3, 4 and are at least partially offset from each other. In other words, no part, or only a portion, of a first projection 20, 21, 22 of a first plate 3; 4 faces a second projection arranged in the facing plate 4; 3 in axial direction X-X.

[0084] . According to one embodiment, said at least one projection 20, 21, 22 is a plurality of projections 20, 21, 22 which connect two-by-two the connecting elements 16, 17, 18, 19 of at least one circular sector 30.

[0085] . According to one embodiment, said at least one projection 20, 21, 22 is a plurality of projections 20, 21, 22 which connect two-by-two the connecting elements 16, 17, 18, 19 of non-adjacent circular sectors 30.

[0086] . According to one embodiment, said at least one projection 20, 21, 22 is a plurality of projections 20, 21, 22 which connect two-by-two the connecting elements 16, 17, 18, 19 of a plurality of non-adjacent circular sectors 30.

[0087] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C along a discontinuous annular path, for example along an arc of the circumference of the braking band 1.

[0088] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for a plurality of non- adjacent arcs of the circumference of the braking band 1.

[0089] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for 1/10 (one tenth) of the circumference of the braking band 1.

[0090] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for a plurality of non- adjacent stretches each extending 1/10 of the circumference of the braking band 1.

[0091] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for 1/8 (one eighth) of the circumference of the braking band 1, or extends circumferentially C- C for a plurality of non-adjacent stretches each extending 1/8 of the circumference of the braking band 1.

[0092] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for 1/6 (one sixth) of the circumference of the braking band 1, or extends circumferentially C- C for a plurality of non-adjacent stretches each extending 1/6 of the circumference of the braking band 1.

[0093] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for 1/4 (one quarter) of the circumference of the braking band 1, or extends circumferentially C-C for a plurality of non-adjacent stretches each extending 1/4 of the circumference of the braking band 1.

[0094] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for an even number of non- adjacent stretches.

[0095] . According to one embodiment, the group of said projections 20, 21, 22 extends circumferentially C-C for an odd number of non- adjacent stretches. [0096] . According to one embodiment, said at least one projection

20, 21, 22 is a single piece without discontinuity, or in a single piece, which extends for a circular sector 30 and from the proximity of the inner band diameter D1 to the proximity of the outer band diameter D2.

[0097] . According to one embodiment, said at least one projection 20, 21, 22 is at least a plurality of circumferentially non-adjacent projections, each being a single projection which extends for a circular sector 30 and from the proximity of the inner band diameter D1 to the proximity of the outer band diameter D2.

[0098] . According to one embodiment, said at least one projection 20, 21, 22 is at least a plurality of projections which connect the connecting elements 16, 17, 18, 19 of a same line 23; 24; 25.

[0099] . According to one embodiment, said at least one projection 20, 21, 22 is at least a plurality of projections which connect the connecting elements 16, 17, 18, 19 of a same line 23; 24; 25, which considered as a whole, extend limited to a circular sector.

[00100] . According to one embodiment, said at least one projection 20, 21, 22 is at least a plurality of projections which connect the connecting elements 16, 17, 18, 19 of a same line 23; 24; 25, which considered as a whole, extend limited to a plurality of circumferentially non-adjacent circular sectors.

[00101] . According to one embodiment, said at least one projection 20, 21, 22 connects all the connecting elements 16, 17, 18, 19 of all the lines 23; 24; 25, which considered as a whole, extend limited to a circular sector. [00102] . According to one embodiment, said at least one projection 20, 21, 22 connects all the connecting elements 16, 17, 18, 19 of all the lines 23; 24; 25, which considered as a whole, extend limited to a plurality of circumferentially non-adjacent circular sectors .

[00103] . The present invention also relates to a disc of disc brake 2 comprising a braking band 1 according to any one of the embodiments described above.

[00104] . The present invention also relates to a vehicle comprising a braking band 1 according to any one of the embodiments described above .

[00105] . Those skilled in the art may make many changes, adaptations and replacements to the embodiments described above or can replace elements with others which are functionally equivalent in order to meet contingent needs without however departing from the scope of the appended claims.

[00106] . The group of projections 20, 21, 22 arranged close to one another forms a group of projections 20, 21, 22 which is arranged circumferentially, thus creating a circumferential distribution having circumferential discontinuities capable of creating a non- uniform distribution of the group of projections, a distribution adapted to avoid the presence of modes of vibration of the braking band 1 which, if driven into resonance, create disturbing noises or squealing noises. [00107] . LIST OF REFERENCES

1 braking band

2 disc of disc brake

3 plate

4 plate

5 inner surface

6 inner surface

7 gap

8 outer surface

9 outer surface

10 braking surface

11 braking surface

12 plate body

13 plate body

14 plate thickness

15 plate thickness

16 connecting elements

17 connecting elements

18 connecting elements

19 connecting elements

20 projection

21 projection

22 projection

23 lines

24 lines

25 lines

26 pillars

27 fins or ribs

28 rhombus or diamond with four vertexes

29 rhombus sides

30 circular sector

X-X rotation axis and axial direction R-R radial direction C-C tangential direction D1 inner band diameter D2 outer band diameter