Brake Pad for Braking Systems, In Particular for Disc Brakes

Abstract

Brake pad for braking systems, in particular for disc brakes, consisting of friction portion ( 10 ), tribologically active, and mechanical support portion ( 20 ) which is intended to cooperate with the actuating means of a braking system. At least friction portion ( 10 ) is made from a ceramic matrix material obtained with a method comprising the following operational steps: —preparing a mixture of at least one siliconic type ceramic precursor, of particles of hard materials suitable as abrasives, of particles of substances suitable as lubricants and particles of metal materials;—hot-pressing the mixture to obtain a preformed body;—submitting the preformed body to a process of pyrolysis in order to obtain ceramisation of the preceramic binder, thus obtaining the ceramic matrix material. The mixture comprises a catalyst suitable for favouring reticulation of said ceramic precursor during the hot-pressing step and the pyrolysis process is carried out a temperatures below 8000° C. The mechanical support portion ( 20 ) may be made in ceramic matrix material as one piece with the friction portion or it may consist of a support plate provided with lightening apertures.

1 - 37 . (canceled) 
     
     
         38 . Brake pad for braking systems, in particular for disc brakes, comprising a friction portion tribologically active and a mechanical support portion intended to cooperate with actuating means of a braking system, at least said friction portion being made from a ceramic matrix material obtained through a process comprising the following operational steps:
 preparing a mixture of at least one siliconic type ceramic precursor, of particles of hard materials suitable as abrasives, of particles of substances suitable as lubricants and particles of metal materials;   hot-pressing the mixture to obtain a preformed body;   submitting said preformed body to a process of pyrolysis in order to achieve ceramisation of the preceramic binder, thus obtaining said ceramic matrix material;   said mixture comprising a catalyst suitable for favouring reticulation of said ceramic precursor during said hot-pressing step and said pyrolysis step being carried out at temperatures below 800° C.   
     
     
         39 . Brake pad according to  claim 38 , wherein said pyrolysis process is carried out reaching at maximum temperatures between 400 and 600° C. 
     
     
         40 . Brake pad according to  claim 38 , wherein said pressing step is carried out at temperatures between 120° C. and 150° C. 
     
     
         41 . Brake pad according to  claim 38 , wherein said pressing step is carried out at pressures between 250 and 500 Kg/cm 2 . 
     
     
         42 . Brake pad according to  claim 38 , wherein said mechanical support portion is made from said ceramic matrix material. 
     
     
         43 . Brake pad according to  claim 42 , wherein said mechanical support portion is made as one piece with said friction portion. 
     
     
         44 . Brake pad according to  claim 42 , comprising a reinforcing element with lightening apertures, incorporated in said mechanical support portion or arranged on the external surface of this portion. 
     
     
         45 . Brake pad according to  claim 44 , wherein said reinforcing element is associated with said mechanical support portion for co-pressing during said hot-pressing step. 
     
     
         46 . Brake pad according to  claim 38 , wherein said mechanical support portion consists of a support plate, provided with one or more lightening apertures and associated with said friction portion. 
     
     
         47 . Brake pad according to  claim 46 , wherein said one or more lightening apertures are made in the portion of said support plate intended to be coupled with said friction portion. 
     
     
         48 . Brake pad according to  claim 46 , wherein said support plate comprises a perimetric frame that internally delimits an empty space. 
     
     
         49 . Brake pad according to  claim 48 , wherein said support plate comprises a plate-like element suitable for closing the empty space of said perimetric frame and in correspondence to which said lightening apertures are made. 
     
     
         50 . Brake pad according to  claim 46 , wherein said support plate is provided with stiffening elements in correspondence to the points on which the actuating means of said braking system are intended to act. 
     
     
         51 . Brake pad according to  claim 46 , wherein said support plate is in metal. 
     
     
         52 . Brake pad according to  claim 46 , wherein said support plate is in non-metallic material. 
     
     
         53 . Brake pad according to  claim 38 , wherein said mechanical support portion consists of a support plate in non-metallic material, associated with said friction portion. 
     
     
         54 . Brake pad according to  claim 38 , wherein said mechanical support portion consists of a support plate, said friction portion associated with said support plate by co-pressing during said hot-pressing step. 
     
     
         55 . Brake pad according to  claim 38 , wherein said mechanical support portion consists of a support plate, said support plate associated with said friction portion in ceramic matrix material subsequently to said pyrolysis step. 
     
     
         56 . Brake pad according to  claim 38 , wherein said mixture comprises between 5% and 10% in weight of ceramic precursor and catalyst, between 20% and 30% of abrasives, less than 60% of metal materials and less than 50% of lubricants. 
     
     
         57 . Brake pad according to  claim 38 , wherein said at least one ceramic precursor is selected from the polysiloxanes. 
     
     
         58 . Brake pad according to  claim 38 , wherein said catalyst is selected from organic coordination compounds with metals selected from the group consisting of zinc, copper, aluminium, iron, zirconium, vanadium, chromium, manganese, cobalt, nickel and titanium and mixtures thereof. 
     
     
         59 . Brake pad according to  claim 38 , wherein said abrasive particles are powders selected from the group consisting of silicium carbide, boron carbide, silicium, zircon, zirconium oxide, periclase, corundum or spinel and mixtures thereof. 
     
     
         60 . Brake pad according to  claim 59 , wherein said abrasive particles are present as powders of two different particle sizes, the ratio of the average diameters of the two powders being between 9 and 11. 
     
     
         61 . Brake pad according to  claim 60 , wherein the weight ratio between the abrasive powder of greater particle size and the powder of lesser particle size is between 0.8 and 1.8. 
     
     
         62 . Brake pad according to  claim 38 , wherein said metal particles comprise particles selected from the group consisting of iron, iron alloy, copper, brass, silicium and mixtures thereof. 
     
     
         63 . Brake pad according to  claim 38 , wherein said lubricant particles comprise graphite in powder, coke powders, powders of tin sulphide and/or tin powders. 
     
     
         64 . Brake pad according to  claim 63 , wherein graphite is present in a percentage between 9% and 13% in weight of said mixture. 
     
     
         65 . Brake pad according to  claim 63 , wherein coke powder is present in a percentage lower than 35% in weight of said mixture. 
     
     
         66 . Brake pad according to  claim 63 , wherein tin sulphide powder is present in a percentage lower than 10% in weight of said mixture. 
     
     
         67 . Brake pad according to  claim 63 , wherein tin powder is present in a percentage less than 5%.