DE10130395A1 - Friction material used in the production of friction elements for brakes and couplings in vehicles comprises a structural component and an infiltration component formed as a penetrating network - Google Patents

Abstract

Friction material (20) comprises a structural component (21) and an infiltration component (22) forming a composite accessible in three directions. The components are formed as a penetrating network. An Independent claim is also included for a process for the production of the friction material. Preferred Features: The structural component is formed as a particle structure having an open porosity or as a body with a sponge structure or honeycomb structure. The structural component is made of ceramic, especially Al2O3, SiC, glass, Fe, Cu, bronze, Ti, Al, brass, Kevlar, BN or carbon. The infiltration component is made of Cu, Al, Fe, soft metal, Cu with oxygen, intermetallic compounds, polymer, elastomer, glass, graphite, mica, coke powder, Al2O3, iron oxide, heavy spar, resin, rubber or silicon.

Description

The present invention relates to a friction material with two or more Material components, a friction element and a method for producing a Friction material.

Friction materials are used in many areas of technology, for example in vehicle technology for the production of frictional elements for brakes, Couplings and the like. The friction material is high Requirements because it is often exposed to very high loads. in the Operation mostly have high surface pressures on the friction material Temperatures and high speeds of friction. In general, friction materials have the longest possible service life and an even and low one Exhibit removal.

Conventional friction materials, which are used for example in automotive Serve friction clutches, can be roughly divided into the groups organic friction materials, Classify metallic sintered materials, CFC materials. Are friction materials, except for the latter, only multi-component systems.

Organic friction materials usually consist of an organic matrix Resin or rubber base, made of organic, metallic or ceramic fibers as well as numerous fillers of various types, which the friction and Influence wear behavior. A main application of organic. Clutch linings made of friction materials is the usual car or truck Special applications or increasingly come up with new high-torque concepts Linings made of organic friction materials are increasingly reaching their performance limits.

Metallic sintered friction materials or linings made of such materials usually have a continuous metallic matrix through a Sintering process occurs. These friction materials also contain fillers, which serve to optimize the coefficient of friction and wear. Unlike  organic friction materials, the selection of fillers is limited by the fact that the sintering temperature of the fillers required for the metallic matrix must be endured. Pads made of sintered friction materials are used wherever a high performance of the rubbers is required and material-related Losses in terms of comfort, noise and wear on counter friction surfaces must be accepted.

Friction materials based on CFC materials consist of a Carbon matrix and carbon fibers. Significant amounts of fillers are not included due to the complex manufacturing process. such Friction materials only develop good friction properties and at high temperatures are therefore due to the cost and the often high wear Special applications, for example in racing, limited.

The main distinguishing feature of the material groups mentioned is the Matrix material, namely resin / rubber, sintered metal structure or carbon. The Matrix forms a closed, three-dimensional network that Penetrating friction material. Would it be theoretically possible to make the remaining substances to remove the friction material, the matrix (in perforated form) would continue to unite form mechanical cohesion. The fillers and fibers themselves are in quasi-zero-dimensional or quasi-one-dimensional form, which means that it is either punctiform (particles) or expanded in one direction (fibers) extend. Fibers can also be present as a fabric (mat), which is one corresponds to two-dimensional expansion. The fillers or fibers form without the matrix, however, is not a mechanically stable bond.

DE 44 38 456 describes a friction unit for frictional engagement with a Counter body, in particular a brake or clutch body known that has at least one freely accessible friction surface. The friction surface is one carbon fiber reinforced, porous carbon body formed whose pores are at least partially filled with silicon carbide. To make one First, a carbon fiber-reinforced, porous carbon body becomes the friction surface provided, which is then infiltrated with liquid silicon.  

Another friction material is described in WO 98/50712, which is based on a similar one Way is made. The friction material consists of a metallic phase as well as a ceramic phase. During manufacture, either a porous one Ceramic body made, which is then infiltrated by the metal or one compresses green bodies that contain both metal and ceramic particles and that then undergoes further treatment steps.

However, the known friction materials described above have a number of disadvantages. This is the separation with regard to matrix with these friction materials and other substances are defined relatively firmly. The respective matrix materials can only can be varied conditionally. By designing the friction materials in the form of a Matrix made up of fillers and fibers that are in one-dimensional or expand two-dimensional direction, is interspersed with the fillers and Fibers distributed as independent "islands" within the matrix certain properties of the ingredients come to a limited extent or not at all to carry. For example, thermal properties such as storage capacity or conductivity cannot be fully used with one-dimensional fillers because the Heat can only be transported in and out through other substances. Also mechanical properties such as strength and toughness of a material are in the Composite is often not identical to the pure material as desired. For example, high fiber strength cannot be used if the No power transmission to the surrounding matrix due to weak interfaces given is. As a result, friction materials with the exception of the expensive CFC Materials whose disadvantages have already been explained above always Multi-material systems, in which only the large number of different elements and Connections guaranteed favorable properties.

Based on the prior art mentioned, the object of the invention Reason to create a friction material in which the previously described Disadvantages are avoided. In particular, a friction material is to be provided who have positive friction properties and withstand high loads, and which is also inexpensive and can be produced with little effort. Furthermore, a method for producing a friction material is to be specified  that can be carried out with little effort, causes low costs and leads to a friction material with good friction properties.

This object is achieved by the friction material according to claim 1 Friction element according to claim 19 and the method for producing a Friction material according to claim 20. Further advantageous features, aspects and details of the invention emerge from the dependent claims, the Description and the drawings.

Features and advantages that result from the description of the friction material, also apply to the described method and the friction element, as well Advantages and features that result from the process, also for the Friction material and the friction element apply.

According to the first aspect of the invention, a friction material having two or more Material components provided, characterized according to the invention is that at least two material components are each one in three Form spatial directions continuous and that this Material components in the friction material in the form of each other penetrating networks are formed.

Due to the friction material according to the invention, it is possible with regard to to avoid the disadvantages described in the prior art. It is an essential one Aspect of the friction material according to the invention that this is now a structure has a few material components (at least two Material components) perform all important friction functions. This includes above all the functions "keep the coefficient of friction up", "stabilize the coefficient of friction", "Minimize wear", "conduct and store heat" and the like.

According to the invention, at least two of the material components of the Friction material as interpenetrating networks. That means, that the material components are available in a connected form. Would it would be possible to isolate them from each other non-destructively, so they would be geometrical represent defined, self-supporting structures.  

In contrast to the friction materials known from the prior art, at the friction material according to the invention the distinction between matrix and others Fabrics no longer make sense. The well-known definition that a matrix in three Spatial directions are continuously connected, where friction material according to the invention for at least two material components.

In contrast to the friction materials known from the prior art thus no longer a single material a continuous composite (in the stand technology, this was the matrix material). Rather, at least now forms a further material component that in the known from the prior art Friction materials formed a filler or fibers, a really continuous one Composite. This allows the respective properties of this way existing material components can be used in full. To this This way, it becomes possible to produce friction materials, for example only two Material components are formed, these material components are sufficient to meet all requirements for an optimal friction function fulfill. The manufacture of such friction materials is relatively simple and inexpensive.

This is because now those properties of the related referred to as fillers or fibers with the prior art Material components of the friction material are fully effective, which are not continuous form can not be used or only insufficiently. To include mechanical strength (a particle or an interrupted one) Fibers have hardly any macroscopically effective strength), the thermal conductivity (With insulated particles, the thermal conductivity only comes from the internal one Forwarding to carry, between the particles determines the matrix Conductivity), as well as the modulus of elasticity and in particular the compressive strength.

Another specific advantage of interpenetrating networks is that the combination creates new, favorable properties can, which do not occur in this form in conventional compounds. in this connection it is for example increased strength or the like.  

The friction material can advantageously be produced by means of an infiltration process his. Some advantageous, non-exclusive examples of suitable ones Infiltration procedures are described below in connection with the described method according to the invention.

At least one of the material components can preferably be selected such that that it has a wetting effect on at least one other material component. Such a wetting effect is present when the high The wetting effect material component the other Material component penetrates particularly easily. This makes it easy very high degree of mutual penetration of the networks of the respective material components.

At least one of the material components, one in three, can be advantageous Compound penetrating spatial directions forms as a scaffold component be trained. Such a scaffold component is particularly advantageous if if at least one further material component using a Infiltration procedure should be introduced. The scaffold component then forms a kind of basic body into which the infiltrating material, which then the forms another continuous composite, can penetrate.

Likewise, at least one of the material components, one in three Continuous spatial formation forms an infiltration component be trained. When using an infiltration process, it is the Infiltration component around a material component that is in another Material component, for example a scaffold component, infiltrates or is infiltrated.

Some non-exclusive examples of suitable designs or suitable materials for the framework component and Infiltration components will become closer as the description proceeds explained.  

The infiltration component can preferably be selected such that it has a wetting effect on the framework component.

At least one material component, preferably that, can advantageously be used Framework component, be designed as a particle framework with open porosity. How a scaffold component designed in this way is produced particularly advantageously can be in more detail in connection with the inventive method explained.

The individual components of a friction material configured in this way can are present in such a way that an initially produced particle structure, for example a sintered particle structure, with open porosity with a liquid material, at which in this case is the infiltration component, filled (infiltrated) which then solidifies. In this embodiment, the Framework component made of connected particles. With full filling of the Scaffold component is each of the material components completely in itself connected, which means that no isolated areas of the Infiltration components are more present.

In a further embodiment, at least one material component, preferably the framework component, as a body with a sponge structure or Honeycomb structure can be formed, the pores of which are interconnected Surface elements of the material component are formed. This body can then infiltrated with the infiltration component in the manner described above become. An example of how such a scaffold component is manufactured can be in connection with the inventive method in described in greater detail. In contrast to the previously described Embodiment, the scaffold body does not consist of connected particles, but from connected thin surface elements that form the pores of the framework component form.

In another embodiment, the at least one material component, preferably the framework component, as a continuous, long fiber or as Be fiber composite. When using a long fiber this can  for example, tangled and wrapped with at least one second material component be infiltrated. In contrast to conventional, from the prior art Known fiber composites, no fibers are finite in such a composite Length more available. The continuous, long fiber enables a better one Removal of heat, an improved internal heat transfer between two Material components and increases mechanical strength since there is no There are more interruptions in the grain.

In yet another embodiment, the at least one material component, in particular the framework component, produced by means of a burn-out process his. An example of such a method is related to the The method according to the invention explained in more detail.

When to produce the friction material according to the invention Infiltration process is used, at least one as a scaffold component trained material component of at least one infiltration component infiltrated. Once this has been done, it must be ensured that the Infiltration component forms a continuous network in three spatial directions. This can be done, for example, by adding the infiltration component solidifies the entry into the framework component, which means that a temperature-related change in the physical state of the infiltration components from liquid to solid occurs. It is also conceivable that the infiltration component hardens, whereby chemical cross-linking reactions lead to solidification. The way in which the infiltration component integrates the whole forms depends on the type of materials used.

One of the material components, preferably the Scaffold component, one or more of the following materials: Ceramic, in particular aluminum oxide, SiC, glass, metal, in particular sinterable Metals, Fe, Cu, bronze, Ti, Al, brass, Kevlar, BN, carbon.

In a further embodiment, one of the material components, preferably the infiltration component, can have one or more of the following materials: metal, in particular Cu, Al, Fe, soft metal, Cu with oxygen, intermetallic compound, polymer, elastomer, glass, graphite, mica, coke powder, Al ₂ O ₃ , iron oxide, heavy spar, resin, rubber, silicon.

The material groups for individual material components described above represent exemplary, non-exhaustive lists, so that Of course, other materials are also used for the material components can be. The individual materials of the respective material components can be available individually or in any combination.

The friction material can advantageously have three or more material components. Such a third material component can be, for example, a act reactively generated phase. Additionally or alternatively to the formation of new ones According to the present invention, phases are also possible, third or even to introduce additional material components into the friction material. You can do this For example, materials either form their own composite, or else Be part of an existing network. It is conceivable that each of the Additional materials added to the material components present in the friction material become.

For example, it is conceivable that the framework component and / or the Infiltration component has one or more additives, the latter can be added, for example. Almost all of them can be used as additives known friction and wear modifiers are used, for example Oxides, graphite, carbon, sulfides, ceramics, intermetallic compounds and like.

The friction material can advantageously be a ceramic material component and a have metallic material components. The metallic material component can be chosen so that it is compared to the ceramic Material component has a wetting effect. According to the invention are the metallic Material component and the ceramic material component in the Friction material in the form of interpenetrating networks educated. This makes it a friction material or composite friction material created in which the positive rubbing properties of metals and ceramics  are realized so that it withstands high loads. The friction material has a high temperature resistance, for example higher than that of pure sintered metal coverings.

The combination of materials via penetrating networks means that the respective properties of the ceramic and the metallic material in come into play in a special way. For example, the metallic increases Network not only the heat conduction, but also the fracture toughness and thus the Strength of the bond. On the other hand, the ceramic network means that compared to a purely metallic alloy, higher hardness, rigidity, Wear resistance and creep resistance are present. Thermal conductivity is in Tribological processes are almost always desirable because of the rapid heat dissipation reduces the thermal load on the friction surface. The increased strength of the ceramic material component is due to the crack-resistant property of caused metallic material component. The metal fiber is still there under tension, resulting from a higher shrinkage when cooling results. The tensile stress creates a compressive stress in the ceramic Material component, which makes this tensile stress-sensitive material group is relieved according to the material.

Such a configuration of the friction material can at the interfaces structures formed between the metallic and the ceramic phases be the mechanical properties of the composite over the Significantly influence the interfacial strength and the material created in this way give the positive properties and thus its suitability as a friction material.

The metallic material component can preferably also be non-metals include.

The ceramic material component is advantageously a framework component as described above, while the metallic material component advantageously forms an infiltration component. In the solid state, the metallic material component advantageously comprises copper and copper oxide. The metallic material component can comprise copper in the liquid state and oxygen dissolved in copper. The oxygen fraction can advantageously be at 3 at%. This makes the melt particularly good wetting. The ceramic material component preferably comprises aluminum oxide (Al ₂ O ₃ ). These materials and in particular their combination lead to particularly good friction properties of the metal-ceramic friction material. For example, copper with dissolved oxygen has a very strong wetting effect on the ceramic, so that the metal penetrates the ceramic particularly easily during manufacture, which results in an easy to manufacture very high degree of mutual penetration of the networks of the two material components.

The metallic component can be in place of the copper oxide or additionally Titanium and / or chrome included. The composition and strength of the Interface is made by adding titanium, chromium and / or oxygen and by suitable annealing treatment, in particular under the control of temperature and / or Partial pressure of oxygen, significantly influenced. This is especially true in particular also advantageous for the copper / aluminum oxide system.

The oxygen partial pressure pO ₂ ≧ 7.2.10 ^-8 bar and the temperature can be substantially around or exactly 1,000 ° C. This creates CuAlO ₂ at the interface of the aluminum, which favorably increases the interface adhesion.

The friction material is advantageously made from a powder by adding metallic material to a powder or a ceramic friction body Material that is present as a green body or can already be sintered, and one Has residual porosity, produced, the metallic material in molten state compared to the ceramic material a wetting Property. In this case, for example, an initial Starting powder mixture made of ceramic and metal, or it will first the ceramic powder is pressed and optionally sintered and then the wetting metallic powder, or the wetting metallic Powder mixture, applied.  

The friction material can be, for example, uniaxial and / or isostatic Presses made of ceramic powder.

The metallic powder, or the powder mixture, for example Cu / CuO, Cu / Ti or Cu / Cr or the like, caused by its wetting Property that it has in the liquid state compared to the ceramic that it is in liquid state penetrates into the ceramic body without external pressure (infiltrated) and wets the interfaces, resulting in a soldering effect. This is under otherwise in particular if the oxygen content in the melt ≧ 3 at%.

According to a second aspect of the invention, a friction element, the one Has carrier body provided, the friction element according to the invention is characterized in that on at least one side of the carrier body provided as described above friction material according to the invention or is appropriate.

If a friction material with a ceramic material component and a metallic material component is to be connected to a carrier body, can, for example, an interface between the friction material and the Carrier body wetted by the metallic material component or to be soldered. Due to the wetting property of the metallic material or powder (infiltration component) compared to the ceramic (Scaffold component) and the carrier body when the liquid penetrates or metal melt (infiltration) in the ceramic body also the Interface between the actual friction material and the carrier body wetted, and there is also a soldering effect here. This results in a particularly high strength of the connection without exerting pressure from the outside must become.

The friction material can be on one side or on both sides of the carrier body to be appropriate.  

A friction element according to the invention as described above can For example, be part of a clutch or a brake, which in any way of vehicles, for example land, water and aircraft can. Such friction elements are particularly advantageous in automobiles or Aircraft used.

According to a third aspect of the invention, a method for producing a Friction material, comprising two or more material components, in which at least one infiltratable as a scaffold component Material component in the form of a continuous in three spatial directions Composite is produced, in which the scaffolding component is then from at least one second forming an infiltration component Material component is infiltrated such that the second material component forms a continuous structure in three spatial directions, so that the two, a continuous composite, material components upon completion of the process in the friction material in the form of mutually penetrating Networks.

The inventive method can be simple and inexpensive How to produce a friction material, which is related to the friction function Requirements met in an optimal way. The method for Production of a friction material according to the invention as described above be used. According to the method of the invention Production of a friction material the infiltration of at least one Material component with at least a second material component central aspect.

The infiltration component can, for example, by means of self-infiltration, infiltrate reactive infiltration or pressure infiltration or be infiltrated. The first two infiltration methods are processes that through the capillary effect (self-infiltration) or through new formation of Phases (reactive infiltration) take place without external pressure. The pressure infiltration on the other hand, requires an external pressure to be applied in terms of process technology the infiltration component, which is preferably a liquid  acts against the capillary repulsion in the pores of the framework component to force.

A particle structure with an open one can advantageously be used as the structure component Porosity can be produced. This scaffold component is then from the Infiltration component infiltrates, which then solidifies or hardens. The type and How the infiltration component is converted depends on the material used.

Such a scaffold component can be manufactured, for example, by this is initially produced in the form of a green body. This can be done, for example Pressing a powder mixture or by a conventional slip process be accomplished. In a slip process, a mass is generally used first mixed in a solution and then poured into a mold. The green body can advantageously consist of a ceramic mass. The The green body is then - preferably in a suitable oven sintered that an open residual porosity remains. Then the sintered Green body, for example a sintered ceramic, with the infiltration component brought into contact, which is, for example, a heated infiltrating Material can act. This removes the scaffolding component from the Infiltration component infiltrates.

Preferably, the infiltrating material is chosen so that it automatically means without external pressure, penetrates into the scaffolding component. This is it advantageous if the combination scaffold component / infiltration component has a wetting effect. The capillary effect in this case pulls the Infiltration component in the open porosity. Of course it is also possible under non-wetting conditions to produce the structure of the invention. For this the infiltration component must be pressurized so that the If the infiltration-inhibiting capillary effect is overcome by the external pressure becomes.

In a further embodiment, a body can initially be used as the scaffolding component Sponge structure or honeycomb structure are made, the pores of the  Scaffolding component that consists of interconnected surface elements of the Framework components are formed, from which the infiltration component is infiltrated, which then solidifies or hardens. The infiltration is carried out analogously to that in relation in the manner described on the particle structure with open porosity.

In another embodiment, a continuous, long fiber or a fiber composite are produced, the fiber or the Fiber composite is infiltrated by the infiltration component, which subsequently solidifies or hardens.

In a further embodiment, the scaffold component can be manufactured by the infiltrable material component around one or more core element (s) is arranged that the at least one core element is then removed and that in the thus created porosity of the framework component Infiltration component is infiltrated or infiltrated, which then solidifies or hardened.

The production of a friction material described in this way can be done, for example, by a Burnout process can be realized, which is based on a concrete Example is to be explained without the invention to this example restrict. The framework component can be manufactured, for example, by a metal in a vacuum or in a reducing atmosphere by one or more Core element (s) - for example one or more carbon sponges / Carbon sponges - is poured. This sponge can after solidification of the metal are burned out in an oxidizing atmosphere. In the so generated open porosity can now be another material component, such as the Infiltration component, infiltrated in the manner already described above become. It goes without saying that the second to be infiltrated Material component must have a lower melting point than the first Material component that forms the porous structure.

In a further embodiment, a ceramic can initially be used as the framework component Powder are pressed into a friction body, the ceramic powder before Pressing and / or the friction body after pressing and optionally after  a sintering process with a metallic powder as an infiltration component provided and then to a temperature above the melting point of the metallic powder is heated so that the metallic powder liquefies and the scaffold component is infiltrated by the liquid infiltration component. The Process results in less effort and leads to a stable, durable friction body, with improved friction properties.

According to yet another aspect of the invention, one is as above Described method according to the invention for producing a friction material and provided for its connection to a support body, in which the Scaffold component is brought into contact with the support body and heated, wherein the scaffold component is provided with the infiltration component and at Heating the support body with the framework component through the Infiltration component is connected. The scaffolding component consist, for example, of a green body pressed from ceramic powder, while the infiltration component is a molten metallic Powder can trade. In such a case, the connection between Friction material and carrier body take place in such a way that when the metallic powder of the carrier body with the friction material through the molten metallic powder is soldered. Instead of a green body, also use an already sintered ceramic body with residual porosity.

In the case of such a method for production and connection, there is no need for previously known manufacturing and connection processes one operation. So that is the effort is reduced, which is why the manufacturing costs for the one Carrier body connected friction material, or for a corresponding Friction element, are reducible. Nevertheless, the process leads to one with one Friction material connected carrier body or friction element, the high Withstands loads and has excellent friction properties. On separate attachment of the carrier body to the friction material is no longer necessary.

The ceramic powder may comprise Al ₂ O ₃ and the metallic powder may comprise Cu with CuO and / or titanium and / or chromium. This achieves particularly high strengths and ensures good wetting.

The pressing can be uniaxial or in one direction, and / or isostatic, depending on the requirements of the respective application.

An annealing treatment is advantageously carried out in the method. In particular, the oxygen partial pressure and / or the temperature controlled or controlled.

The method preferably involves simultaneous sintering and infiltration of the Infiltration component in the scaffolding component and soldering with one Carrier body. This means that only one work step is required for these functions.

The friction body is advantageously used during the sintered infiltration soldering process pressed to the carrier body. This ensures a particularly high plane parallelism of the Surfaces achieved. The friction body or green body can be one-sided or be attached to the carrier body or covering carrier on both sides. The friction body or green body can also directly on the carrier body or the carrier plate are pressed on.

For example, when using a ceramic-metal starting powder mixture the separate application or pouring of the metal powder onto the Friction or green body. This further reduces the effort.

Other special annealing processes can also be carried out in the process the structure of the framework component and / or the boundary layer between to change the friction body and the carrier body. Depending on the requirements the structure of the scaffold component is preserved in this way or the boundary layer the optimal structure. These special annealing processes can, for example, after the application of the friction body or Rub blocks on the carrier body or lining carrier.

Furthermore, several parameter changes can be made in the method, that is, parameters such as the sintering time, the Sintering temperature, the pressing conditions, the composition of the  Infiltration component, the composition of the framework component, the shape and size of the manufactured friction bodies and the like can be changed. Also through these measures, the friction body or friction element additional, possibly required for certain applications advantageous properties are conferred.

The invention is explained below using exemplary embodiments Reference to the accompanying drawings explained in more detail. Show it:

Fig. 1 shows a schematic representation of a first embodiment of a friction material according to the invention;

FIG. 2 shows various schematic representation of sequences of an infiltration process;

Fig. 3 is a schematic view of a further embodiment of the friction material of the present invention;

Fig. 4 shows another embodiment of a friction material according to the invention;

FIG. 5 is still another embodiment of a friction material according to the invention; and

Fig. 6 schematically shows the process steps for the production of the friction material, according to a preferred embodiment of the invention.

In Fig. 1, an inventive friction material 20 is shown which is formed from at least two material components. In the present exemplary embodiment, a total of two such material components are shown, with a first material component being a framework component 21 and a second component being an infiltration component 22 . The material components of the friction material 20 according to FIG. 1 are such that, for example, a sintered particle framework, which is the framework component 21, is filled (infiltrated) with a liquid material, which is the infiltration component 22 , which then solidifies or hardens. In this embodiment, the framework component 21 consists of interconnected particles 25 , each of which includes corresponding cavities 26 . In this way, a connection is created that is continuous in three spatial directions. In the left part of FIG. 1, the framework component 21 is shown before the infiltration with the infiltration component 22 .

When the framework component 21 is completely filled with the infiltration component 22 , as can be seen from the right part of FIG. 1, each of the material components is completely self-contained, that is to say that there are no isolated, independent regions of the framework component 21 or the infiltration component 22 occurrence. The structure of the finished friction material 20 can be characterized approximately as follows according to FIG. 1. While the initial structure of the framework component 21 is approximately the same as a spherical network or particle network, in which the individual particles 25 are predominantly curved, the infiltration component 22 , which according to the invention occupies the cavities 26 of the framework component 21 , is predominantly concave in these areas.

For example, aluminum oxide or another ceramic, a sinterable metal, such as iron, copper, bronze or the like, can be used as the material for the framework component 21 . For the infiltration component, for example copper, aluminum, iron, an intermetallic compound, a polymer, an elastomer or the like can be used. The material of the framework component 21 and / or in particular the infiltration component 22 can optionally be provided with one or more additives in each case.

A friction material 20 as shown in FIG. 1 can be produced, for example, in the manner described below. It is assumed that the framework component 21 is made of a ceramic material and the infiltration component 22 is made of a metal.

A ceramic green body is produced by pressing a powder mixture or by a conventional slip process known per se. This ceramic green body is sintered in an oven in such a way that an open residual porosity remains. Subsequently, the sintered ceramic, which is now the framework component 21, is brought into contact with the heated, infiltrating material, in the present case the metallic infiltration components 22 . This can be done in different ways, two options being described below.

Preferably, the infiltrating material is chosen so that it automatically means without external pressure, penetrates into the ceramic. For this it is necessary that the Combination of porous material infiltrating material has a wetting effect. The one in this If there is a capillary effect, the liquid is drawn into the open porosity.

For a composite material made of copper and aluminum oxide, for example, the following method is proposed, with which the desired positive friction properties of the friction material 20 can be achieved. First, an Al ₂ O ₃ powder mixture is cold isostatically pressed, a uniaxial pre-pressing process optionally being used here in advance. The powder can have a particle size of 1 to 7 μm, preferably 5 to 7 μm. The baling pressure is advantageously set to 2,500 bar. The resulting green body is then sintered, so that an open porosity of between 5 and 40%, preferably between 30 and 40%, remains. The sintering temperature is preferably set to 1,000 ° C, the holding time is 30 minutes. The heating rate and the cooling rate are 8 K / minute. The green body is then heated and the metallic infiltration component is melted, which can take place at about 1,100 ° C. The metallic phase corresponds essentially to that described on page 2, lines 20-31. The molten metal is finally poured into the framework component 21, preferably under a non-oxidizing atmosphere.

The condition for this process is that the liquid metal wets the ceramic, ie the wetting angle Θ is less than 90 °, as can be seen from the left side of FIG. 2. The smaller the angle is, the more favorable it is for infiltration because the wetting liquid, so the infiltration component 22 is drawn by the capillary action, which is shown by the arrow K in the pores 27 of the framework component 21st

Of course, it is also possible to produce the structure according to the invention under non-wetting conditions. For this purpose, the liquid must be pressurized so that the capillary action K, which in this case prevents infiltration, is overcome by the external pressure, as is shown in the right part of FIG. 2.

In terms of process engineering, such pressure infiltration takes place, for example, in an infiltration oven. Here, for example, the metal, for example aluminum, is heated in a crucible in a vacuum until it melts. Temperatures of more than 660 ° C are required for this. The ceramic green body is then immersed in the melt. An infiltration pressure is then generated in the furnace by a gas, for example nitrogen, which presses the melt into the pores of the immersed body. This pressure corresponds at least to the required infiltration pressure p, according to the Laplace formula

p = 2.γ.cos Θ / r

directly from the surface energy of the metal γ, the wetting angle Θ and the Pore radius r depends.

On cooling, the green body is, that is, the framework component 21, before the solidification of the metal, i.e. the infiltration components 22, drawn from the melt at still existing pressure. Only after the metal has solidified can the further cooling take place without pressure.

The manufacturing processes described so far can also be applied to the embodiments for the friction material 20 described below with only slight deviations.

FIG. 3 shows a friction material 20 in which the framework component 21 is in the form of a body 28 with a sponge structure or honeycomb structure. This sponge-like body 28 is filled with a further material, that is to say the infiltration component 22 , which then, as mentioned above, solidifies after production (temperature-related change in the state of matter) or hardens (chemical crosslinking reaction leads to solidification). In contrast to the exemplary embodiment according to FIG. 1 the framework component 21 does not consist of connected particles, but rather of interconnected thin surface elements which form the pores 29 of the framework component 21 .

In the exemplary embodiment according to FIG. 3, the framework component 21 can consist, for example, of a metal such as aluminum, titanium, iron or the like, while the infiltration component is made of a polymer, for example a thermoset or a thermoplastic, an elastomer, a soft metal, glass or the like can be. Again, the framework component 21 and / or the infiltration component 22 can each be optionally provided with one or more additives.

In comparison to FIG. 1, in which the framework component 21 was formed by a ceramic particle framework, the porous preform, that is to say the framework component 21 in the friction material 20 according to FIG. 3, now forms a metallic sponge framework. The infiltration of the metallic sponge structure 28 by means of the infiltration component 21 takes place analogously to the manner described in FIG. 1 with the difference that the temperatures now have to be matched to the new, infiltrating material. This means that the temperature during the pressureless or pressurized infiltration must be set above the melting temperature (for metals) or the glass transition temperature (for glass) or the processing temperature of polymers customary for injection molding and below the decomposition temperature (for polymers, elastomers).

Advantageously, the framework component 21 , that is to say the metallic sponge body 28 in the present example, is filled with an infiltration component 22 , for example a friction lining mixture, which consists, for example, of graphite, mica, coke powder, Al ₂ O ₃ , iron oxide, heavy spar, resin, rubber and the like consists.

For infiltration, the infiltration component 22 is in the state of the lowest possible viscosity, that is to say at the highest possible temperature, which depends on the particular mixture. By immersing the sponge body 28 in the liquid and applying pressure of approximately 50 bar, the pores 29 of the sponge body 28 are filled with the friction lining mixture.

In FIG. 4, an embodiment is shown for a friction material 20, wherein the scaffold component 21 is formed by fibers. Individual fibers are shown in the left part of FIG. 4, while a single long fiber is shown in the right part of FIG. 4. The arrows shown in Fig. 4 stand for the heat flow dQ / dt.

In the right part of FIG. 4, a long fiber is shown as scaffold component 21 , which is wound tangled and has been infiltrated with a second material, that is, the infiltration component. In contrast to conventional fiber composites, as are known from the prior art, there are no fibers of finite length in the composite according to FIG. 4. The continuous, long fiber enables better heat dissipation through the internal heat transfer between the different material components and increases the mechanical strength, since there are no interruptions in the fiber course. If a fiber felt is used as the starting material and infiltrated with another material, a quasi-continuous bond is created since the individual felt threads lie directly against each other.

The fiber material for the framework component 21 can be, for example, aluminum oxide, SiC, glass, a metal, such as copper, brass, Kevlar, BN or the like. The infiltration component can be formed, for example, from phenolic resin, rubber, soft metal, glass or the like. The framework component and / or the infiltration component can optionally in turn each be provided with one or more additives.

Finally, FIG. 5 shows a friction material 20 , with a framework component 21 , which is designed as a porous base 31 , an infiltration component 22 , which is shown as filling material 30 , and a third material component, which in the present case is a reaction phase 32 acts.

In carbon materials, where pyrolysis is used in the manufacturing process, the escape of the non-carbon components creates a connected, that is, open to the outside, porosity. If the porosity of the porous base 31 is increased by using low-carbon resins, by infiltration of less resin or by fewer infiltration steps, the desired structure of a second continuous network according to the invention can be achieved. First of all, this continuous network consists, for example, of elemental silicon (infiltration component 22 or filler material 30 ). When the silicon reacts with the carbon, SiC is formed. This reaction product (reaction phase 32 ) surrounds the elemental silicon and occurs as a third, interconnected network that completely or partially envelops the silicon network. Depending on the control of the reaction parameters, it is possible to largely convert the elemental silicon into SiC. In this case, carbon and SiC are present as interconnected networks.

However, other materials are also conceivable in which a third network is formed around the infiltrating component, for example in the copper-oxygen-aluminum oxide system. Here, oxygen-containing liquid copper is infiltrated into a sintered aluminum oxide network. The reactive fiber here is the copper aluminate CuAlO ₂ . In addition or as an alternative to the formation of new phases, it is also possible according to this invention to introduce third or further materials into the composite.

In FIG. 6, a method is finally shown how a friction material 20, in particular according to FIGS. 1 to 3 could be prepared. As shown in Fig. 6, a ceramic powder 10 is first pressed in a mold 11 uniaxially and / or isostatically. The ceramic powder 10 , which is, for example, Al ₂ O ₃ , is a ceramic material component of the friction material, for example a framework component. For pressing, the ceramic powder 10 is filled into the mold 11 and then a mold tool 12 is pressed vertically from above in the press direction P into the mold 11 . The shape is selected in accordance with the shape of the friction body 13 or friction lining to be produced, a change in volume during sintering having to be taken into account during later infiltration.

The pressure required during pressing is dependent on different parameters and is selected such that the pressing results in a friction block or friction body 13 with a fixed shape. The pressed friction body 13 forms a green body which is removed from the compression mold 12 after the pressing and is made available for further processing (step A).

In a next process step, the pressed green or friction body 13 is placed on a carrier body 14 . Before this, the green body can be sintered in such a way that a residual porosity remains. The carrier body 14 is, for example, a carrier plate which will later be firmly connected to the friction material. The support body 14 has on the one or more friction body 14 are disposed a planar surface 14 a. However, it is also possible to attach one or more friction blocks or friction bodies 13 to the rear side 14 b of the carrier body 14 (step B).

In the next process step, a metallic powder 15 or a metallic powder mixture is poured onto the friction body (s) 13 . The metallic powder 15 is a metallic material component of the friction material, for example an infiltration component. The metallic powder mixture or the metallic powder 15 , which is brought into contact with the friction body 13 , has a wetting property. This means that the composition of the powder 15 or the powder mixture in the molten state has a wetting property with respect to the ceramic or the green or friction body 13 and with respect to the carrier body 14 or the carrier plate, so that the liquid or melt - if possible without - at the appropriate temperature external pressure - in the friction body 13 made of ceramic or penetrates infiltrated, and the interface 14 a between the friction body 13, which forms a Reibbelang, and the carrier body 14 wetted. A soldering effect is thus produced, which brings about the firm connection between the friction body 13 and the carrier body 4 .

The metallic powder 15 is made, for example, of copper or copper oxide, the oxygen content being at 3 at%, or it comprises a mixture of copper and another metal, for example titanium. Chromium can also be added. In Fig. 6 the application of the wetting metallic powder 15 is shown as step C.

Now one of the powder mixture is in an oven, which is to receive the arrangement corresponding oxygen partial pressure set in the furnace atmosphere. This Step is optional or optional and is used to prevent oxygen loss to minimize the melt.

The arrangement of the friction body 13 , carrier body 14 and metal powder 15 is then heated in the furnace to a temperature which is above the melting temperature of the powder mixture or of the metallic powder 15 . The liquid made of metal penetrates into the ceramic friction body 13 (infiltration) and also wets the interface between the friction body 13 and the carrier body 14 . As a result, the components are soldered at the same time. So there is a simultaneous sintering, infiltration and soldering of the friction body 13 (step D).

The friction element produced in this way has a very firm connection between the friction body 13 and the carrier body 14 .

In addition to aluminum oxide and copper, combinations of other ceramics and Metals conceivable, with the wetting property of the liquid metal opposite the ceramic or the carrier body is decisive and the Materials can be selected under this criterion.

It is also possible to produce the friction body 13 without the carrier body 14 . The method described above is used analogously for this. It is essential that the metallic powder 15 is combined and processed with the ceramic powder or the friction body 13 pressed therefrom in the manner described above.

LIST OF REFERENCE NUMBERS

10

Ceramic powder or ceramic material component

11

mold

12

press die

13

friction body

14

support body

14

a surface of the carrier body

14

b Back of the carrier body

15

metallic powder or metallic material component

20

friction

21

framework component

22

infiltration component

25

particle

26

cavity

27

pore

28

Body with sponge structure

29

Pores (filled)

30

filling material

31

porous base

32

reaction phase
K direction of capillary action
P pressing direction
Θ wetting angle

Claims (34)

1. Friction material, with two or more material components, characterized in that at least two material components ( 21 , 22 ) each form a continuous composite in three spatial directions, and that these material components ( 21 , 22 ) in the friction material ( 20 ) in the form of interpenetrating networks are formed. 2. Friction material according to claim 1, characterized in that this means an infiltration process is established. 3. Friction material according to claim 1 or 2, characterized in that at least one of the material components ( 22 ) is selected so that it has a wetting action against at least one other material component ( 21 ). 4. Friction material according to one of claims 1 to 3, characterized in that at least one of the material components, which forms a continuous in three spatial directions, is designed as a scaffold component ( 21 ). 5. Friction material according to one of claims 1 to 4, characterized in that at least one of the material components, which forms a continuous in three spatial directions, is designed as an infiltration component ( 22 ). 6. Friction material according to claim 5, characterized in that the infiltration component ( 22 ) is selected so that it has a wetting action with respect to the framework component ( 21 ). 7. Friction material according to one of claims 4 to 6, characterized in that at least one material component, preferably the framework component ( 21 ), is designed as a particle framework with open porosity. 8. Friction material according to one of claims 4 to 6, characterized in that at least one material component, preferably the framework component ( 21 ) as a body ( 28 ) is formed with a sponge or honeycomb structure and that its pores ( 29 ) are formed from interconnected surface elements of the material component are. 9. Friction material according to one of claims 4 to 6, characterized in that at least one material component, preferably the framework component ( 21 ), is designed as a continuous, long fiber or as a fiber composite. 10. Friction material according to one of claims 4 to 6, characterized in that at least one material component, preferably the framework component ( 21 ) is produced by means of a burnout process. 11. Friction material according to one of claims 1 to 10, characterized in that one of the material components, preferably the framework component ( 21 ), has one or more of the following materials: ceramic, in particular aluminum oxide, SiC, glass, metal, in particular sinterable metals, Fe , Copper, bronze, Ti, Al, brass, Kevlar, BN, carbon. 12. Friction material according to one of claims 1 to 11, characterized in that one of the material components, preferably the infiltration component ( 22 ) comprises one or more of the following materials: metal, in particular copper, aluminum, iron, soft metal, copper with oxygen, intermetaüische connections , Polymer, elastomer, glass, graphite, mica, coke powder, Al ₂ O ₃ , iron oxide, heavy spar, resin, rubber, silicon. 13. Friction material according to one of claims 1 to 12, characterized in that this has three or more material components. 14. Friction material according to one of claims 4 to 13, characterized in that the framework component ( 21 ) and / or the infiltration component ( 22 ) has one or more additives. 15. Friction material according to one of claims 1 to 14, characterized in that the friction material ( 20 ) has a ceramic material feature ( 10 ) and a metallic material component ( 15 ). 16. Friction material according to claim 15, characterized in that the metallic material component ( 15 ) is selected so that it has a wetting action with respect to the ceramic material component ( 10 ). 17. Friction material according to claim 15 or 16, characterized in that the metallic material component ( 15 ) comprises copper and copper oxide in the solid state. 18. Friction material according to one of claims 15 to 17, characterized in that the ceramic material component ( 15 ) comprises aluminum oxide. 19. Friction element with a carrier body ( 14 ), characterized in that a friction material ( 20 ) according to one of claims 1 to 18 is attached to at least one side of the carrier body ( 14 ). 20. A method of making a friction material comprising two or more Material components in which as a scaffold component at least one infiltrable material component in the form of one in three spatial directions continuous composite is produced, in which the scaffolding component then at least one forming an infiltration component second material component is infiltrated such that the second Material component a continuous in three spatial directions forms, so that the two, forming a continuous composite Material components in shape at the end of the process in the friction material of interpenetrating networks. 21. The method according to claim 20 for producing a friction material according to a of claims 1 to 18.   22. The method according to claim 20 or 21, characterized in that the Infiltration component by means of self-infiltration, reactive infiltration or Pressure infiltration is infiltrated or infiltrated into the scaffold component. 23. The method according to any one of claims 20 to 22, characterized in that as Framework component first created a particle framework with open porosity and that the scaffold component infiltrates from the infiltration component which then solidifies or hardens. 24. The method according to claim 23, characterized in that the Framework component is first made in the form of a green body that the Green body is sintered such that an open residual porosity remains that the Subsequently, the scaffold component comes into contact with the infiltration component is brought so that the infiltration component in the framework component is infiltrated or infiltrated. 25. The method according to any one of claims 20 to 22, characterized in that as Scaffold component first a body with a sponge structure or Honeycomb structure is made and that the pores of the framework component that from interconnected surface elements of the scaffolding component are formed, are infiltrated by the infiltration component, which subsequently solidifies or hardens. 26. The method according to any one of claims 20 to 22, characterized in that as Scaffolding component first a continuous, long fiber or a Fiber composite is produced and that the fiber or the fiber composite of the Infiltration components is infiltrated, which then solidifies or hardens. 27. The method according to any one of claims 20 to 22, characterized in that the scaffold component is made by the infiltrable Material component arranged around one or more core element (s) is that the at least one core element is subsequently removed and that the infiltration component into the porosity of the framework component thus generated infiltrated or infiltrated, which then solidifies or hardens.   28. The method according to any one of claims 20 to 25, in which as a framework component first a ceramic powder is pressed to a friction body, the ceramic powder before pressing and / or the friction body after pressing and optionally after a sintering process with a metallic powder Provide infiltration component and then, to a temperature is heated above the melting point of the metallic powder, so that the metallic powder liquefies and the framework component from the liquid Infiltration components is infiltrated. 29. A method for producing a friction material according to any one of claims 20 to 28 and for its connection to a carrier body in which the Framework component is brought into contact with the carrier body and heated, the framework component being provided with the infiltration component and when heating the support body with the framework components through the Infiltration component is connected. 30. The method according to claim 28 or 29, wherein the pressing uniaxially and / or isostatic. 31. The method according to any one of claims 20 to 30, wherein an annealing treatment undefined temperature is carried out at a defined oxygen partial pressure. 32. The method according to any one of claims 20 to 31, in which a simultaneous Sintering, infiltrating the infiltration component into the framework component and Soldering is carried out with a carrier body. 33. The method of claim 32, wherein the friction body during the sintering Infiltration soldering process is pressed onto the carrier body. 34. The method according to any one of claims 20 to 33, wherein one or more of the Parameters sintering time, sintering temperature, pressing conditions, composition of the infiltration components, composition of the framework components, shape and size of the friction body produced can be changed.