EP2429742B1

EP2429742B1 - Method for the manufacturing of a component for a braking system

Info

Publication number: EP2429742B1
Application number: EP09787729.4A
Authority: EP
Inventors: Giovanni Sana; Marcello BOSCHINI; Angelo Avellino; Renzo Moschini; Cristian Crippa; Paolo Cesani
Original assignee: Freni Brembo SpA
Current assignee: Brembo SpA
Priority date: 2009-05-13
Filing date: 2009-05-13
Publication date: 2018-05-30
Anticipated expiration: 2029-05-13
Also published as: WO2010131273A1; EP2429742A1

Description

The present invention relates to a method for the manufacturing of a component for a braking system. In particular, the present invention relates to a method for the manufacturing or implementation of a component for braking system which provides for the implementation of inserts with structural functions, adapted to be introduced into the body of the component for a braking system.
By the term "structural functions" is meant the property of the insert of receiving, partially or completely, the stresses that are present in the body of the component in which the insert is introduced, which stress is determined by the load applied to the component.
The use of inserts having structural functions introduced within a metal matrix is per se known in the vehicle field. For example, in US 4 468 272 and US 3 547 180 implementation methods of bodies are described, in which inserts with structural functions are drowned.
Although they are satisfying under many points of view, however, such solutions do not provide completely satisfying results, since the implementation of a suitable bond, or bonding, between the insert and the metal matrix of the component body results to be extremely troublesome, which bonding is capable of ensuring the mechanical continuity and, in particular, the transfer of the stresses within the component body from the metal matrix thereof to the insert.
In the case where the inserts are manufactured with metal materials, it is also known to use productive processes that provide, following the implementation of the insert, for the creation of an intermediate metal phase which establishes a bonding of the metallurgic type between the insert material and that of the matrix. Also known are techniques that provide for the coating of the insert with a facing material in virtue of plasma deposition techniques, so as to increase the anchoring of the metal matrix on the insert surface.
All these solutions, although being advantageous under some points of view, have anyhow shown particular drawbacks. Particularly, the metallurgic metal phases expected at the interface between the insert and the metal matrix constitute brittleness areas, from which cracks frequently originate, which cracks determine a structural discontinuity, therefore do not allowing particular processing operations and hardening and tempering thermal treatments on the body of the component comprising the insert.
In the case where inserts of ceramic material are used, the above-described integration difficulties between the metal matrix and the insert are considerably marked in that the ceramic material results to be not wettable by many metals, among which aluminum, forcing to complex and costly techniques for the facing of a metal material which is compatible both with the ceramic insert and the aluminum matrix.
These problems are especially felt for components of brakes such as the calipers. It is widely known that a disc brake is schematically composed of a caliper, extending astride a braking disc, provided with seats to house pads that are opposite and intended to act on friction surfaces of the disc, as well as piston - cylinder assemblies adapted to urge said pads against the friction surfaces of the disc.
Particularly, the pads are formed by a portion on which the piston directly acts, called plate, and a portion facing the disc called friction gasket, or simply gasket. Both the caliper and the plate are usually manufactured in a metal material, such as, for example, steel for the plates of the pads and aluminum alloys for the calipers, while the gasket is in friction material, such as, for example, sinterized metal powders. In such calipers, the body is urged by the action exerted by the pistons against the braking surfaces. These stresses can cause deformations in the caliper body moving away from the disc, which cause considerable problems upon braking of the vehicles.
In order to obviate these drawbacks, one is obligated to use not only particular geometries for the caliper body, but above all to use caliper bodies having large dimensions which, inter alia, result to be especially bulky and above all heavy. The weight of the caliper body affects particularly the non-overhanging mass of the vehicle, which, as it is known, has to be desirably minimized, while maintaining the structural characteristics of the caliper in order to not deteriorate the braking performance for the vehicle. The document DE102006051200 discloses a method for producing a body of metal-ceramic composites, including the steps of producing a ceramic preform by sintering using a starting powder containing ceramic particles at an aspect ratio of 1-10, in such a way that the obtained preform has a porous structure with pore diameters of 0.5-10 mum and an overall porosity of 15-60% , and of introducing molten metal of a pure metal or an alloy into the thus produced ceramic preform having a porous structure.
The problem underlying the present invention is to provide a method for the implementation of a component for a braking system, a component for braking system, and in particular a caliper for disc brakes which overcomes the above-listed drawbacks relative to the state of the art.
Such problem is solved by a method as recited in the annexed claims, as well as by a component for a braking system and a caliper as described in the annexed claims.
Further characteristics and advantages of the invention will result from the description reported below of some preferred exemplary embodiments thereof, given by way of indicative, non-limiting example, with reference to the annexed Figures, in which:

Fig. 1 represents an enlargement of a granulometric material in which, between the granules, a volumetric filling material is interposed, which is adapted to mutually space the granules apart;
Fig. 2 represents an enlargement of the granulometric material of Fig. 1 after a sinterization step in which the filling material is volatilized, thereby leaving porosities;
Fig. 3 represents the sinterized granulometric material of Fig. 2 in which the porosities have been infiltrated with metal material;
Fig. 4 illustrates in sectional view an enlargement of an insert portion for a component of a braking system comprising a core in "full density" sinterized material, a first layer in porous sinterized material infiltrated by a metal matrix, and a second layer comprising the material of the metal matrix;
Figs. 5a, 5b, and 5c represent sections of steps of a productive method in which the components for the implementation of an insert or parts of an insert are mixed in different amounts, and the deposition thereof in a mold, by themselves or according to a preset order;
Figs. 6a, 6b, 6c, and 6d show in sectional view further steps of an implementation method of a insert in which an axial constipation (constipated) or axial packing (packed) of the insert material or a portion of the insert material at a predefined pressure is expected;
Fig. 7 illustrates in sectional view a sinterization oven adapted to the heating of an insert for the vaporization of the volumetric filling material and the insert sinterization;
Fig. 8 illustrates a step of the implementation method of a component for braking system in which a die is provided for, in which an insert adapted to the injection of metal into the die cavity is introduced;
Fig. 9a illustrates a further step of the implementation method of a component for braking system in which the metal has been injected within the cavity so as to fill in the die cavity and infiltrate in the porosities of the insert surface layer;
Fig. 9b represents a crucible in which a third material, for example, a metallic material in a molten state and a stirrer are present;
Fig. 9c represents the crucible of Fig. 9b in which the third material is cooled and stirred so as to form solidification grains and to distribute them in an even manner;
Fig. 9d illustrates the crucible of Fig. 9b and 9c, in which the process of partial cooling and stirring is completed, and partially solidified material is present, with evenly distributed solidification grains;
Fig. 9e represents a further embodiment of the injection and successive compression of the third semi-solidified material within a die in which an insert is provided;
Fig. 10 illustrates an insert provided with porous surface layers and bracket means for the positioning thereof within the die cavity for the injection of the metal matrix;
Fig. 11 illustrates an insert provided with further bracket means for the positioning thereof within a die cavity for the injection of the metal matrix of the braking system component;
Fig. 12 represents in an axonometric view a body of a caliper of the fixed type, represented partially in phantom lines to show therein reinforcing inserts drowned arranged at bridges of the caliper body, and for the reinforcement of the extended portions thereof, at the wheel side and hub side;
Fig. 13 illustrates in an axonometric view a caliper body of the floating type represented partially in phantom lines to show therein an insert drowned in the caliper body;
Fig. 14 represents in an axonometric view, stub axle side, the caliper of Fig. 13;
Fig. 15 represents a detail of a caliper with fixed body seen in an axonometric view in which an end bridge is partially sectioned, showing therein an insert drowned therein for the reinforcement of the bridge;
Fig. 16 represents a further detail with a partially sectioned portion to show the insert of the caliper of Fig. 15;
Fig. 17 represents a further caliper of the fixed type in a detail thereof in axonometric view, with a partially sectioned portion to highlight the presence of inserts drowned in the bridges and the extended members;
Fig. 18 shows a detail in axonometric view of a caliper of the fixed type, in which a detail partially in section is shown, which illustrates the presence of an insert drowned in an extended member.

In accordance with a general embodiment, a method for the implementation of a component for a braking system comprises the following steps.
A first material 2 of the granular type is provided, of a type adapted to the sinterization. This material 2 is capable of high structural performance once it has been sinterized.
For example, a ceramic material is selected, with particles having a controlled particle size. This particle size is achieved, in accordance with an embodiment, from powders by means of processes such as, for example, atomization, which is capable of conferring to the particles a spheroidal, or substantially spheroidal morphology, especially useful for the forming and sinterization processes.
For example, ceramic techniques will be able to be used, ceramics having particular structural characteristics or ability to receive structural loads, such as, for example, alumina and, alternatively and/or in combination silicon nitride, and alternatively and/or in combination silicon carbide. Such materials will be selected, as well as for their cost, also for their ability to resist the thermal stress, or thermal shock, as well as for their high elastic module.
In accordance with an embodiment, to the above-described materials it is possible to replace or use, in combination, a composite material, for example, a ceramic composite, a metal-ceramic composite.
In particular, the ceramic composite material is selected from a material obtained from a porous agglomerate of carbon fibres obtained by pirolysis, and infiltrated with silicon in which, during the infiltration step, silicon carbides are formed, while leaving free silicon and carbon fibres (C/SiCSi), or a material obtained from a porous agglomerate of silicon carbides infiltrated with silicon (SiSiC), or alumina (Al2O3). Advantageously, such material is also SiSiC.
Advantageously, the metal-ceramic composite material is selected from a material obtained from a porous structure of boron carbides infiltrable with aluminium (AIBC), or a material obtained from a porous structure of silicon carbides infiltrable with aluminium (AlSiC), or a material obtained from a porous structure of titanium carbides infiltrable with aluminium (AITiC), or oxysilicon nitride and aluminium (SiAlON).
All the composite materials cited above can be reinforced both with particles and filaments, according to the thermo-mechanical needs.
In a further step of the method, a second material 3 is provided, which constitutes a binder or volumetric filler. In particular, this material is capable of at least partially separating the particles of the first sinterization granular material 2 one from the other. This second material is selected so as to be easily evacuated, when the formed insert is heated to a temperature, for example, also of few hundreds Celsius degrees.
For example, this second material 3 is volatilized during the first steps of the sinterization.
This material is selected, for example, from polyester and/or waxes, and/or simple wood shavings.
In a successive step of the method, the first sinterization material 2 and the second volumetric filling material 3 are mixed in pre-established parts.
In accordance with an embodiment, a mixing from 20% to 50% of the material total volume is provided for and preferably 30% to 40% of the material total volume, of said second volatile material 3 with said first sinterization material 2. The percentage of the second material 3 is selected so as to ensure, as a function of the type and shape of the particles of the first sinterization material 2, that, following the volatilization of the second material 3 and the sinterization of the first material 2, this portion of the body has the desired porosity, while maintaining a good structural stability. For example, in accordance with an embodiment, the final porosity following the mixture constipation and sinterization results to be ranging between 10% and 25% of the total volume of the porous portion and preferably between 15% and 20% of the total volume of the porous portion (Fig. 1).
Advantageously, the mixing of the first 2 and the second 3 materials is carried out under dry conditions.
In accordance with an embodiment, such mixture is used to form at least one surface portion 13 of the insert 4 formed with a core 12 thereof of first constipated or full density sinterization material 2. By "full density", a first sinterization material 2 is intended to be particularly meant, which is not mixed with other volatile material, when it is constipated and sinterized. For example, by "full density" is meant a sinterization material 2 that, following constipation and sinterization, has a porosity below 5% of the volume thereof, and preferably a porosity ranging between 1% and 2% of the volume thereof.
In accordance with an embodiment, a container or mold 14 is provided, having a cavity defining the geometry of the insert to be used within the braking system component. This mold 14 cavity is, for example, initially filled in with a first mixture layer in pre-established parts of a predefined amount of mixture of the first 2 and the second 3 materials, for example, 30% - 40% of the first material 2, and 70% - 60% of the second material 3, advantageously suitably mixed one to the other so as to get an even distribution of the second material in the first material. For example, this layer will constitute at least one surface portion of the insert 4 (in Fig. 5a, the first material 2 adapted to the sinterization is indicated with the letter A, and the second filling material 3 and adapted to volatilize at lower temperatures that those for the sinterization of the first material 2 is indicated with the letter B).
Then, the insert 12 core is arranged on this layer by placing a predefined amount of the first sinterization granular material 2.
At the end, a further predefined amount of mixture of the first 2 and the second 3 materials is arranged on top of the insert 4 core 12, for example, 30% - 40% of the first material 2, and 70% - 60% of the second material 3, advantageously suitably mixed one to the other so as to get an even distribution of the second material in the first material, to establish a further coating layer, or portion or surface layer of the insert.
The thus-filled mold is constipated by means of a packing, for example, an axial packing, which is performed, in accordance with an embodiment, at room temperature. For example, such axial packing is performed by means of hydraulic presses 110 (Fig. 6a).
In accordance with an embodiment, the packing is exerted with pressures ranging between 1000 bars and 1500 bars and, preferably, with constipation times of the order of a few seconds.
In accordance with an embodiment, for example, when the insert has geometries with a particular spatial complexity, the method provides for the arrangement of a first amount of the first sinterization granular material 2 adapted to costitute the core of an insert 4 in a first mold 5 (Fig. 5b). Subsequently, this material 2 is constipated with a predefined pressure, for example, through a packing at a pressure ranging between 1000 bars and 1500 bars at room temperature (Fig. 6b).
Then, a predefined amount of mixture 6 of the first and second materials 2, 3, advantageously suitably mixed one to the other so as to get an even distribution of the second material in the first material (Fig. 5c) is placed in a second mold 7. Said second mold 7 being, for example, adapted to constitute at least one portion of the insert surface layer. Such mold 7 is then pressed so as to constipate the material 13 (Fig. 6c). For example, this constipation occurs by packing at a pressure ranging between 1000 bars and 1500 bars, and it is performed at room temperature.
Once the surface layer 13 has been withdrawn from the mold 7 thereof, and the insert core 12 has been withdrawn from the mold 5 thereof, these can be introduced directly within a mold for their sinterization, or they can be introduced in a further mold 14, so as to suitably couple them, and to subject them to a further constipation action, for example, by packing, preferably at a pressure of 1000 bars - 1500 bars at room temperature (Fig. 6d).
In virtue of the above-described mixture 6, a porous layer is obtained following forming and sinterization, having a porosity 8 formed by mutually communicating chambers (Fig. 2). In accordance with an embodiment, these communications are obtained also in virtue of the shape of the particles to be sinterized, which preferably are of a substantially spheroidal type.
For example, the particles of the first material have a substantially spheroidal shape, with a diameter of 10-100 micrometers, preferably 50 micrometers.
In accordance with an embodiment, during the forming of the core 12 of the insert 4, and particularly during constipation, the pressure brings into contact the particles of the material to be sinterized 2, which, by the successive sinterization, allows creating bonding points, or bridges, and subsequently, in practice eliminating, or drastically reduce, the spaces between the particles. For example, the porosity achieved by the insert core 12 will be limited to 1% - 5% of the insert core volume.
In accordance with an embodiment, the porous layer 13 initially has a second material 3 which volatilizes at low temperatures, for example, in the first steps of the sinterization (Fig. 1). In this layer, the particles of the first material 2 will have, following the forming and the first sinterization, or first heating adapted to volatilize the second material 3, more spaced contact points compared to the insert core 12, thanks to the spaces left by the dimensions that the second material 3 had before volatilizing, evenly mixed between the particles of the first material 2. When this surface layer 13 sinterizes, the mutually spaced particles thereof do not manage to fill all the interspaces which are present therebetween, thus leaving areas that will be not able to be completely joined, since they were spaced apart by the second material as a filler which allowed a high-pressure constipation of the mixture, then, upon vaporizing, leaving interspaces having such dimensions as to be not completely filled during sinterization (Fig. 2).
The selection of the percentage at which the second material is to be mixed to the first one, and the even distribution thereof, allow creating, during the sinterization of the mixture layer, small bridges between the particles of the first material 2 which are sufficient to achieve a rigid and stable structure.
The thus-obtained insert 4, both in the case of a forming in a single mold 14 and of a coupling of several portions obtained with distinct molds 5, 7, is introduced in a sinterization oven 20. As the temperature of the insulated chamber 113 of the oven 20 rises, for example, that obtained by actuating power supplies 112, for example of the controlled type, which supply heating means 111, the second volumetric filling material 3 volatilizes, while the sinterization of the first material 2 is started, thus generating porosities 8 where the second material 3 was (Fig. 7).
For example, the second material 3 at a temperature of some hundreds degrees volatilizes and it is withdrawn from the oven 20, for example, by special suction systems 21, thus escaping through the porosities 8 left by the granulometric particles of the first material 2, which are suitably spaced apart thanks to the presence of the second volumetric filling material 3.
In accordance with an embodiment, the mixture 6 of the insert 4 surface layer 13, during the sinterization steps, beside vaporizing the second material 3, creates linking small bridges between the various particles, however leaving a suitable porosity 8 which allows communicating the outer surface of the insert with the internal part of this porous surface layer, generating infiltration passages for the third material 10.
The process, in accordance with an embodiment, provides that the sinterization suitably bonds the insert 12 core, reaching the desired compaction and bonding of the particles of the first material 2, which exhibits the suitable mechanic characteristics that are desired for the insert.
In accordance with an embodiment, the particles of the first material 2 that are present in the surface layer 13 and in the insert core 12 bond one to another, causing a strong cohesion between the core and the at least one porous layer.
For example, in the case alumina is used as the first sinterization material 2, the temperatures of the sinterization oven reach 1600 °C - 1700 °C, and are maintained for a period of time not below one hour. In virtue of this treatment, the alumina reaches an elastic module mechanic characteristic equal to or above 330 GPa.
Once the sinterization has been completed, the insert, having at least one surface portion 13 thereof which is porous, is withdrawn from the oven, and is introduced into a cavity 18 of a die 19 adapted to the injection and compaction under pressure of the third material 10, which material constitutes the metal matrix of the braking system component body 1 (Figures 8 to 9e).
The arrangement of the insert within the die cavity occurs, for example, by using a special bracket system, which allows arranging the insert within the cavity, where it will be suitably embedded by the third material injected in the cavity, so that the insert result to be in those regions of the component where it has to carry on the structural characteristics thereof.
In order tb promote this bracket system, during the forming thereof, the insert can be connected to special brackets 22, which remain embedded in the insert during the forming and sinterization thereof (Fig. 10).
In accordance with a further embodiment, it is possible to use brackets 23 which geometrically couple with the insert mold following the forming and sinterization thereof, and which represent the suitable supports adapted to position the insert into the die 19 cavity 18 (Fig. 11).
Once the insert has been arranged within the die 19 cavity 18, a predefined amount of a third material 10 is injected at a pre-established temperature and pressure to form the body 11 of the braking system component 1. In accordance with an embodiment, a compaction of the material injected follows the injection, so as to at least partially embed said insert 4 in the body 11 and to allow the third material 10 to infiltrate, or continue infiltrating, into the porosities 8 of the at least one surface layer 13 of the insert 4, thus firmly anchoring said insert 4 to said body 11, without thereby noticeably alter the properties of the sinterized material 2 (Figures 3, 4, and 9a).
The injection step of the third material 10 occurs at a predefined and preferably controlled rate. For example, the material is injected into the die 19 cavity 18 at a rate ranging between 0.1 m/sec and 5 m/sec, and preferably 0.15 m/sec - 0.30 m/s.
For example, in accordance with a particular embodiment, the third material is aluminum, advantageously comprising the alloy A357. This alloy is preferably injected at 0.2 m/s, which can be defined as the advancing rate of the third semi- or partially solid material with evenly distributed grains in the die at a temperature below 610 °C. In accordance with an embodiment, the material is compacted at a pressure above 1000 bars. In accordance with an embodiment, the compaction occurs only after the end of the injection.
In virtue of these pressures and temperatures, it is possible not to alter the structural characteristics of the insert 2 material.
Furthermore, these compaction temperature and pressures following the injection of the metal material of the matrix 3 allow obtaining lower shrinkages or contractions in the component body 1 during the solidification and, consequently, a higher compaction of the jet and integration of the insert.
The component body obtained according to this method, unlike the jets obtained by die-casting, is free from air bubbles embedded in the jet, and ensures a better embedding of the insert in the matrix, also avoiding that air bubbles arrange themselves between insert and metal matrix, generating structural discontinuities.
This aspect, besides considerably reducing the shrinkage cavity, allows performing quenching operations on the jet.
Furthermore, in virtue of a lower temperature of the third material during the injection and a high compaction pressure, a solidification rate of the component is obtained, which is higher that the solidification that would be possibly obtained by a gravity casting process.
In virtue of the proposed method, a component body is obtained with a fine microstructure and a high or very high mechanic performance compared to the same work pieces, but obtained by the gravity casting.
In virtue of the proposed method, a thermal exchange between jet or injected and compressed piece and die or iron mold is obtained of about 10,000 W/m2 °C.
In the proposed method, in virtue of the higher solidification rates compared to those of a gravity casting, it is possible to further improve the mechanic characteristics of the component body.
In accordance with a particular embodiment, said third material 10 is brought to the molten state, and then it is gradually cooled and concomitantly stirred, so as to form solidification grains evenly distributed and forming a solid part ranging from 5% to 20% by volume of the material, preferably 10% to 20% by volume of the material (Figures 9b to 9d).
From tests, it has been found how the provision of a partially solidified third material with a solid fraction equal to 10%-20% by volume of the material, so that the solid part is formed into evenly distributed grains in the liquid portion, allows an injection or advancing of the semi-solid material in the die cavity at a rate of 0.15 m/sec - 0.3 m/sec, thereby ensuring the complete removal of air bubbles in the component and the embedding of the insert in the metal matrix, so that the metal matrix of the third material penetrates or infiltrates in the insert porosities.
In accordance with a particular embodiment, this third material 10, before being injected, is heated in a vessel 24 so as to completely bring it to the liquid state or molten state. Subsequently, the material is cooled while it is concomitantly stirred, so as to form solidification grains, preferably with globular morphology and, further preferably, evenly distributed within the vessel and, advantageously, avoiding that gas is entrapped within the material. Subsequently, this partially solidified material is injected into the die 19 comprising the insert 4.
In accordance with an embodiment, when the material reaches a temperature below the "liquidus" temperature, for example, for the alloy A357, the temperature of 618 °C, so as to obtain a solid part ranging between 5% and 20%, the material is then injected into the die at a temperature ranging between 615 °C and 580 °C.
In accordance with an embodiment, with a solid fraction of 10%, the material is injected into the die at a temperature of 610 °C.
In particular, it has been found that, by injecting the material at 610°C, this has a solid fraction of 10%.
Preferably, subsequently, a successive compaction pressure or incremental pressure is provided, which allows the complete infiltration of the third material in the insert porous layer. For example, a pressure ranging between 800 bars - 1500 bars, preferably above 1000 bars, is applied to the third material injected into the die.
In accordance with an alternative embodiment, a method provides that a predefined amount of the first sinterization granular material 2 adapted to constitute the insert 4 core is arranged in a mold 14 for insert 4, and that a predefined amount of the mixture 6 of the first and second materials is arranged in the same mold 14, so that at least one portion of the insert 4 surface results to be composed of said mixture adapted to interface with the third material 10. Then, said predefined amount of the first material 2 and the mixture 6 is concomitantly constipated at a predefined pressure.
In accordance with an embodiment alternative to what has been described before, a predefined amount of the first sinterization granular material 2 adapted to constitute the insert 4 core is placed in a first mold 5 for insert 4. Then, said predefined amount of the first material 2 is constipated at a predefined pressure, thus forming the insert 4 core 12. A predefined amount of the mixture 6 of the first and second materials is placed in a second mold 7, so as to form with this mixing at least one portion of the insert 4 surface adapted to interface with the third material 10. Subsequently, said predefined amount of the mixture 6 is constipated at a predefined pressure, thus forming a surface layer 13 of said insert 4. In accordance with an embodiment, said insert 4 core 12 is placed in a third mold 14 together with the surface layer 13, thus forming the insert 4.
Advantageously, said first material 2 adapted to the sinterization comprises particles with controlled particle size obtained from powders, for example, by atomization, so as to confer a substantially spheroidal shape to the particles.
In accordance with an embodiment, said first material 2 comprises alumina and/or silicon carbides having predefined thermal shock resistance and predefined elastic module.
In accordance with an embodiment, said second material 3 constitutes a binder and comprises volumetric fillers capable of maintaining suitably and at least partially spaced apart the particles of the first material 2 one from the other during the forming process. This second material 3 is capable of being evacuated, for example by volatilization, at temperatures below the sinterization temperatures of the first material.
In accordance with an embodiment, said second material 3 comprises polyester and/or waxes and/or shavings.
In accordance with an embodiment, said first and/or second material is formed with an axial packing that is performed at a pressure ranging between 1000 bars and 1500 bars, preferably at room temperature, for a preset period of time, for example, a few seconds.
In accordance with an embodiment, following the forming, said second material 3 is volatilized during sinterization, preferably in the first steps of the sinterization, for example, upon reaching a temperature of some hundreds degrees.
Advantageously, said first material 2, when it is sinterized, allows obtaining a material with an elastic module of at least 330 GPa.
In accordance with an embodiment, said insert 4 is sinterized at a temperature ranging between 1600 °C and 1700 °C, preferably for a treatment time not below 1 hour.
In accordance with an embodiment, the insert 4 is introduced in a die.
In accordance with an embodiment, the third material 10 is injected into the die at a pressure above 1000 bars. In accordance with an embodiment, the third material comprises an aluminum alloy, for example, comprising "A357".
In accordance with a still further embodiment, a method provides that a predefined amount of first sinterization granular material 2 adapted to constitute the insert 4 body is arranged in a mold 14 for insert 4.
In accordance with an embodiment, said first material is formed with an axial packing that is performed at a predefined pressure, for example, ranging between 1000 bars and 1500 bars, preferably at room temperature, for a preset period of time, for example, a few seconds.
In accordance with an embodiment, said insert 4 is sinterized at a temperature ranging between 1600 °C and 1700 °C, preferably for a predefined treatment time so as to get a predefined porosity.
Then, said insert 4 is introduced in a die in a predefined position.
Then, a third material 10 is provided.
This third material 10, before being injected into the die, is heated in a vessel 24 so as to completely bring it to the liquid state or molten state. Subsequently, the material is cooled while it is concomitantly stirred, so as to form solidification grains, preferably with globular morphology and, further preferably, evenly distributed within the vessel and, advantageously, avoiding that gas is entrapped within the material. Subsequently, this partially solidified material is injected in the die 19 comprising the insert 4.
In accordance with an embodiment, when the material is cooled at a temperature below the "liquidus" temperature, for example, for the alloy A357, a temperature of 618 °C, so as to obtain a solid part ranging between 5% and 20%, the material is then injected into the die at a temperature ranging between 615 °C and 580 °C.
In accordance with an embodiment, with a solid fraction of 10%, the material is injected into the die at a temperature of 610 °C.
Preferably, subsequently, a successive compaction pressure or incremental pressure is provided, which allows at least one partial infiltration of the third material in the insert porosities. For example, a pressure ranging between 800 bars - 1500 bars, preferably above 1000 bars, is applied to the third material injected into the die.
In virtue of any one of the above-described methods, it is possible to implement the body of a braking system component 1 having high structural performance. The component 1 for a braking system comprises an insert 4 in a first sinterized granular material 2 capable of high structural performance, having at least one porous surface portion 13, initially comprising a predefined mixture of said first material 2 and a second binder material 3 constituting a volumetric filler capable of at least partially separating the granular particles of the first material 2 one from the other. Said second material 3, by volatilizing before or as the first material 2 is sinterized, determines where the porosity 8 was. Said insert is at least partially drowned in a body obtained by injecting a third material 10 at a pre-established temperature and pressure to form said body 11 of the braking system component 1. Said insert 4 results to be at least partially embedded in said body, so that the third material 10 results to be infiltrated in said porosity 8 of the insert 4, thus firmly anchoring said insert 4 to said body 11, without thereby noticeably altering the properties of the sinterized material 2. By the above-described method, caliper bodies of the fixed type or, alternatively of the floating type are implemented. The caliper body 1 may comprise a hub side extended body portion 15, a wheel side extended body 16, and at least one bridge 17. Said insert 4 constitutes a reinforcing member of at least one bridge 17, reducing the flexural deformation of the bridge when the caliper is urged away from the opposite extended members 15, 17 thereof by the braking action. The caliper body 1 comprises a hub side extended body portion 15, a wheel side extended body 16, and at least one bridge 17, and said insert constitutes a reinforcing member of at least one extended member 15, 16, avoiding undue deformations when these are urged by the action of the pistons housed therein.
In virtue of the above-described method, and particularly of the provision of the metal matrix that infiltrates in the porosities of at least one surface layer of the insert creating a co-penetration of the material of the braking system component body with the insert material with high structural characteristics, it is possible to have a continuous and progressive transfer of the stresses from the caliper body to the insert body maximizing the structural stress degree which the insert comprising material capable of a high stress resistance passes through, fully taking advantage of the structural characteristics thereof.
For example, in the case where the insert is used in a caliper body for disc brake, the possibility of transferring the stresses from the caliper body to that of the insert allows stiffening the caliper body, thereby allowing a higher mechanic strength, consequently a higher performance or, better, the possibility of exerting a still higher braking action without deformation of the caliper body, which deformation would prevent the required transfer of the braking action to the disc brake. Alternatively, the braking performance being kept constant, in virtue of the provision of the inserts at least partially drowned and firmly anchored to the caliper metal matrix, it is possible to obtain a considerable reduction of the caliper weight and/or a reduction of the caliper dimensions.
Advantageously, it is possible to use these inserts, for example, comprising a ceramic material which is highly resistant to the high temperatures, arranged in the caliper body facing the braking disc where the highest temperatures due to the braking action are generated.
Further advantages which derive from the previous description are, firstly, the fact that the caliper body, or anyhow the body of the braking system component, will have a considerably reduced weight compared to the calipers made of cast iron or also with a body completely made of aluminum.
Furthermore, the material used for the implementation of the inserts is provided with mechanic resistance and, in some example of chemical inertia against oxidative phenomena, such as not to require treatments and to allow a virtually infinite duration for the caliper.
Furthermore, the considerable lightness achieved by the braking system component, which in no way compromises the structural characteristics of the body, is particularly relevant. In fact, the material, for example, the ceramic material adopted for the insert, is provided with a high rigidity, which allows not undergoing considerable deformations not even when it is subjected to high stresses.

Claims

A method for the implementation of a component (1) for a braking system, in which
- a first granular material (2) is provided, which comprises granules and is adapted to the sinterization, capable of high structural performance;

- a second binder material (3) is provided, constituting a volumetric filler capable of partially separating the granules of the first sinterization granular material (2) one from the other;

- a predefined amount of the first sinterization granular material (2) adapted to constitute the core of an insert (4) is placed in a mold (5; 14);

- the first sinterization material (2) is mixed in pre-established parts to the second volumetric filling material (3), thus forming a mixture (6);

- a predefined amount of the mixture (6) of the first and second materials is placed in a mold (7; 14) for said insert (4);

- the first sinterization material (2) is constipated with a predefined pressure;

- the mixture (6) of the first and second materials is constipated with a predefined pressure;

- the second volumetric filling material is volatilized, thus generating porosities (8) where the second material was;

- the insert (4) is sinterized;

- said insert (4) is introduced in a die (9) for the implementation of the braking system component;

- a predefined amount of a third material (10) is injected at a pre-established temperature and rate in said die (9) to form the body (11) of the braking system component by embedding said insert (4) in the body (11);

- said third material (10) is compacted so that the third material (10) infiltrates in said porosity (8) of the insert (4), thus firmly anchoring said insert (4) to said body (11), without noticeably altering the properties of the sinterized material (2).
The method according to claim 1, wherein:
- a predefined amount of the first sinterization granular material adapted to constitute the insert (4) core is placed in a mold (14) for insert (4), and

- a predefined amount of the mixture (6) of the first and second materials is placed in the same mold (14), so that at least one portion of the insert (4) surface adapted to interface with the third material (10) results;

- said predefined amount of the first material and the mixture are concomitantly constipated at a predefined pressure.
The method according to claim 1, wherein:
- a predefined amount of the first sinterization granular material adapted to constitute the insert (4) core is placed in a first mold (5) for insert (4);

- said predefined amount of the first material is constipated at a predefined pressure, thus forming the insert (12) core;

- a predefined amount of the mixture (6) of the first and second materials is placed in a second mold (7), so as to form at least one portion of the insert (4) surface adapted to interface with the third material (10);

- said predefined amount of the mixture is constipated at a predefined pressure, thus forming a surface layer (13) of said insert.
The method according to claim 3, wherein:
- said insert core (12) is placed in a third mold (14) together with the surface layer (13), thus forming the insert (4).
The method according to any one of the claims 1 to 4, wherein:
- said first material (2) adapted to the sinterization comprises particles of a controlled particle size obtained from powders, for example, by atomization, so as to confer a spheroidal shape.
The method according to any one of the claims 1 to 5, wherein:
- said first material comprises alumina and/or silicon carbides of a predefined thermal shock resistance and elastic module.
The method according to any one of the claims 1 to 6, wherein:
- said second binder material (3) comprises volumetric fillers capable of maintaining the particles of the first material (2) suitably spaced apart during the forming process, and capable of being evacuated, for example, volatilizing, at lower temperatures than the sinterization temperatures of the first material.
The method according to any one of the claims 1 to 7, wherein:
- said second material comprises polyester and/or waxes and/or shavings.
The method according to any one of the claims 1 to 8, wherein:
- said first and/or second material is formed with an axial packing performed at a pressure ranging between 1000 bars and 1500 bars, preferably at room temperature, for a preset period of time, for example, a few seconds.
The method according to any one of the claims 1 to 9, wherein:
- following forming, said second material (3) is volatilized during the sinterization upon reaching a temperature of some hundreds degrees.
The method according to any one of the claims 1 to 10, wherein:
- said first material (2), when it is sinterized, allows obtaining an elastic module of at least 330 GPa.
The method according to any one of the claims 1 to 11, wherein:
- said insert (4) is sinterized at a temperature ranging between 1600 °C and 1700 °C.
The method according to any one of the claims 1 to 12, wherein:
- the third material comprises an aluminum alloy, for example, comprising A367.
The method according to any one of the claims 1 to 13, wherein:
- the third material (10) is injected into the die at a temperature below 610 °C, and compacted at a pressure above 1000 bars.
The method according to any one of the claims 1 to 14, wherein:
- said third material (10) is heated in a vessel so as to completely bring it to a liquid state;

- said third liquid material is cooled under stirring so as to form evenly distributed solidification grains, avoiding that gas is entrapped within the material;

- said material is injected into the die comprising the insert (4) and infiltrated in the insert porosities (8).
The method according to any one of the claims 1 to 15, wherein said third material, before being injected into the die, has a solid fraction thereof of 10% by volume and, for example, in the case of the aluminum alloy, it is injected into the die at a temperature of 610 °C.
The method according to any one of the claims 1 to 16, wherein said third material (10) is injected into the die (19) at a predefined rate, for example, ranging between 0.1 m/sec and 5 m/sec, and preferably 0.15 m/sec to 0.30 m/sec.
The method according to any one of the claims 1 to 17, wherein said insert has a porosity, following constipation and sinterization, ranging from 10% to 25% of the total volume of the body portion which is desired to be porous, and preferably from 15% to 20% of the total volume of the body portion which is desired to be porous.