DE102008002538B4 - Brake caliper made of at least 2 components - Google Patents

Abstract

Brake caliper made of at least 2 components, at least one component being designed as a stiffening element (34a), characterized in that the at least one stiffening element (34a) is connected to at least one second component (35a) in a force-locking and / or form-locking manner, the at least one stiffening element (34a) is a base body with an infiltrated light metal alloy and the light metal infiltrated into the base body is an aluminum alloy AlSi12 or AlSi7Mg.

Description

State of the art

The invention relates in particular to a brake caliper of the type used in motor vehicles with disc brakes, as well as the production of such a brake caliper according to the preamble of the independent claims.

Brake units are always used in areas in which the movement of systems is to be reduced in a controlled manner or brought to a standstill. Known designs of brake units in e.g. Motor vehicles used in road traffic are, for example, shoe brakes, drum brakes and disc brakes. During the braking process, high braking forces act on the components of the braking unit, so that they have to withstand considerable static and dynamic loads. In the case of the disc brake, for example, the brake disc running on the wheel shaft is braked by the brake caliper which is fixed relative to it. The necessary braking force is applied by pressing brake linings against the brake disc in the bridge area of the brake caliper. Bridge areas in the brake caliper are therefore particularly heavily used areas.

aus. Infolge dessen weisen derartige Bremssättel insgesamt eine hohe Masse auf.The necessary rigidity of the brake calipers for the stresses occurring during braking is largely determined by the design and the choice of material. For this reason, in addition to an optimal structural design, materials are generally used that have the highest possible modulus of elasticity. Brake calipers are usually made of spheroidal graphite cast iron (GGG). The modulus of elasticity for the cast iron material GGG50, for example, is E _GGG50 = 170 GPa. However, the high density of cast iron has a disadvantage ${\mathrm{\varsigma }}_{\text{GGG}}$${50}_{}=7.1{\text{g / cm}}^3$

out. As a result, such brake calipers have a high overall mass.

eine deutlich geringere Dichte auf, als vergleichsweise Gusseisen mit Kugelgraphit. Somit kann die Bauteilmasse verringert werden. Dem gegenüber steht jedoch ein ungünstig niedriges Widerstandsvermögen der Leichtmetalle gegen Verformung infolge eines niedrigen E-Moduls. Zur Erreichung der notwendigen Bauteilsteifigkeit, vor allem in den besonders beanspruchten Bremssattelbereichen, wie zum Beispiel im Brückenbereich, sind diese Bereiche konstruktiv mit einer entsprechend größeren Dicke auszuführen. Diese Möglichkeit ist jedoch nicht immer gegeben, da vielfach der zur Verfügung stehende Bauraum für derartige Bremseinheiten, insbesondere bei Kraftfahrzeugen, begrenzt ist.To achieve a weight reduction, lightweight brake calipers are known in which the components are made of light metals, such as an aluminum alloy. The aluminum alloy ALSi has ₇ Mg ${\mathrm{\varsigma }}_{\text{AlSi}\mathrm{7th}\text{Mg}}=2.7\text{g / cm}3$

has a significantly lower density than comparatively spheroidal graphite cast iron. The component mass can thus be reduced. On the other hand, however, there is an unfavorably low resistance of light metals to deformation as a result of a low modulus of elasticity. In order to achieve the necessary component rigidity, especially in the particularly stressed brake caliper areas, such as in the bridge area, these areas must be designed with a correspondingly greater thickness. However, this possibility is not always given, since the space available for such brake units, in particular in motor vehicles, is often limited.

One possibility of keeping the required wall thicknesses low is the local stiffening of areas in lightweight brake calipers with a material with a higher modulus of elasticity. In this way, the overall weight of such brake calipers can still be reduced, while at the same time the wall thicknesses can be made smaller compared to the designs of the lightweight brake calipers without local stiffening. As a result, the available installation space can also be adhered to more easily.

In Scripture US 6,719,104 B1 describes a brake caliper for a brake unit for vehicles and the manufacture of such a device. The bridge area has local stiffening elements made of a composite material. The stiffening elements are implemented as insert components in different designs by encapsulating, for example, an aluminum alloy in the bridge area.

In Scripture U.S. 5,433,300 A a brake caliper with a bridge area is also described which has an inserted insert component as a stiffening element. The insert component consists of a ceramic material with a porous honeycomb structure. To manufacture the brake caliper, the insert component is positioned in a mold. The ceramic stiffening element is then completely encased with a light metal. As a result of the die-casting process used, the light metal also penetrates the insert component and fills the honeycomb structure. Here, too, the components are connected to one another by a material bond.

In the post-published registration DE 10 2006 051 200 A1 describes the production of a body from a metal-ceramic composite material and its use as an insert component for stiffening lightweight components, particularly in motor vehicle construction. The insert component is introduced into the mold for a lightweight component, with the lightweight component being manufactured in the subsequent casting process.

In Scripture WO 2004/018 718 A1 discloses an insert made of a fiber composite material as a stiffening element in the bridge area of a brake caliper. This insert consists of an aluminum alloy and is criss-crossed with continuous ceramic fibers. The insert is then placed in a mold in the bridge area and sealed with an aluminum alloy cast a caliper. To improve the connection between the insert and the light metal surrounding it, an additional adhesive coating made of Ni is applied to the surface of the insert.

With all previously known brake calipers with completely encapsulated stiffening elements, there is in principle the risk that casting errors, incorrect positioning of the inserts within the casting mold and insufficient connection of the stiffening element to the casting material of the brake caliper can occur. This can lead to an increase in the susceptibility of the brake caliper to damage during operation. In addition, when the light metal melt is poured around it, and also during a subsequent heat treatment to harden the light metal, the inserted and encapsulated insert components are exposed to high temperatures. Temperature-related defects can occur in the stiffening element, which reduce the load-bearing capacity of the brake calipers.
It is often necessary to provide the stiffening element with an adhesive coating in order to achieve a sufficient connection to the cast material. This is an additional process step that causes additional manufacturing costs. Furthermore, due to the manufacturing process, in the case of brake calipers with encapsulated stiffening element, the cast material must always be provided with a corresponding thickness on the outer surfaces of the stiffening element. Thus, the entire cross section in this area cannot be used for a stiffening effect with the material provided for this with a higher modulus of elasticity. In the case of brake calipers, which are also completely cast using the die-casting process, the design rules for the entire brake caliper must be observed. Since essentially only slides and no cores can be used in die casting, the structural design is limited by a configuration that is as symmetrical as possible.

Advantages of the invention

The brake caliper according to the invention provides that at least one component of the brake caliper designed as a stiffening element is non-positively and / or positively connected to at least one second component of the brake caliper. This has the advantage over the prior art that there is no material connection between a stiffening element and the other components of the brake caliper. Such a non-positive and / or positive connection makes it possible overall to increase the error tolerance in the manufacture of the brake caliper in comparison with previous cohesive methods.

The brake caliper according to the invention also has advantages over the prior art with regard to the stiffness that can be achieved in the particularly stressed areas of the brake caliper. The brake caliper of the present invention has a cross section in these areas that consists exclusively of a material with a high modulus of elasticity. In comparison to previous brake calipers, a higher rigidity can be achieved with the same cross section or a smaller cross section can be selected with the same rigidity. This has the consequence that a reduction in installation space can be achieved. Alternatively, the space saved can also be used, e.g. with a disc brake for the use of brake discs with a larger disc diameter.

In addition, it is advantageous in the brake caliper according to the invention that the optimal structural design of the individual components is only slightly restricted by a non-positive and / or positive connection of at least one stiffening element with at least one further component of the brake caliper. According to the invention, the initially separate saddle components result in component components that are simpler in themselves. These can each be optimized for the existing loads and the available installation space. The more complex shape of the overall saddle results only through the subsequent non-positive and / or positive connection.

Another advantage is the very simple and inexpensive manufacturing process for the brake caliper according to the invention. A non-positive and / or positive connection only requires machining of the joints. This can be done for example by mechanical methods. Since the stiffening element as an independent component and the other components of the brake caliper are each manufactured separately from one another, the result is simplified logistics up to the final assembly of the components.

It is also very advantageous that the at least one existing stiffening element is not exposed to any temperature treatments due to the manufacturing method according to the invention for the brake caliper. In the brake caliper according to the invention, the stiffening element on the one hand and the at least one further component of the brake caliper can be manufactured completely separately, for example from light metal. As a result, only the at least one further component of the brake caliper can be subjected to a hardening process that is intended and optimized for it.

Figure list

• 1 einen grundsätzlichen Aufbau einer Scheibenbremse in einer perspektivischen Darstellung,
• 2 einen Bremssattel gemäß Stand der Technik im Zusammenbau mit angrenzenden Bauteilen in einer perspektivischen Darstellung,
• 3 einen erfindungsgemäßen Bremssattel in perspektivischer Darstellung,
• 4 eine beispielhafte Ausführung einer Verbindung in einem erfindungsgemäßen Bremssattel zwischen einem Versteifungselement und mindestens einer weiteren Komponente des Bremssattels

Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the description below. Show it

• 1 a basic structure of a disc brake in a perspective view,
• 2 a brake caliper according to the state of the art in assembly with adjacent components in a perspective view,
• 3 a brake caliper according to the invention in a perspective view,
• 4th an exemplary embodiment of a connection in a brake caliper according to the invention between a stiffening element and at least one further component of the brake caliper

Description of the exemplary embodiments

In 1 and 2 the basic structure of a disc brake as it is used in particular in motor vehicles is explained in general. There is a brake disc 10 over several screw connections 15th connected to a rotatable wheel axle. The brake disc emerges at one point on its circumference 10 in some areas in an almost U-shaped brake caliper encompassing them 50 one. 2 shows the caliper 50 with adjacent components.

The caliper 50 is about attachment points 22nd and 52 frictionally with a saddle housing 20th connected. The saddle housing 20th is designed like a frame and has additional screwing points 24 on. About these screw connections 24 is the composite of the brake caliper 50 and saddle housing 20th overall relative to the rotatable brake disc 10 firmly connected to a vehicle body. The caliper 50 is almost U-shaped when seen in cross section, with between the two legs 58 and 59 the brake disc 10 is arranged. Both legs 58 and 59 thus point inwards towards the center of the brake disc 10 . The leg facing the vehicle body 58 of the caliper 50 is made longer and more massive, at the end of the leg 58 the attachment points 52 to the saddle housing 20th are trained. The massive inner area of the thigh 58 has two cup-like recesses lying parallel to one another on the same plane 56 on. These cutouts 56 each accommodate a hydraulic or pneumatic piston cylinder. Between a side surface of the brake disc 10 and their thighs facing each other 58 or 59 of the caliper 50 is a brake pad each 40 arranged. The size of the brake pads 40 roughly corresponds to that in the caliper 50 immersed surface area of the end faces of the brake disc 10 . When the brake is not applied 100 are the brake pads 40 just so far from the end faces of the brake disc 10 at a distance that, when a vehicle is in motion, the brake disc then rotates with the wheel axle 10 can rotate without touching a brake component. The brake is used to brake the vehicle 100 actuated. They drive in the thigh 58 of the caliper 50 located two piston cylinders. At the same time, the brake pads are removed on both sides 40 on the respective face of the brake disc 10 pressed on. The resulting frictional force between the brake pads 40 and the brake disc 10 acts as a braking force and reduces vehicle movement. The brake caliper is during the braking process 50 braced against the force-applying piston cylinder. This leads to strong mechanical stresses, which is caused by the temperature rise within the brake caliper generated as a result of the frictional forces 50 is additionally increased.

3 shows a brake caliper according to the invention in a perspective view 50a . The basic installation, for example in a brake unit, and the assembly with adjacent components, when the brake unit is designed as a disc brake, essentially correspond to the descriptions according to FIG 1 and 2 . The same applies to the functioning of a brake caliper according to the invention 50a . The difference in the structure of a brake caliper on which the invention is based 50a is primarily to be found at the points that are in operation of the brake unit 100 are subject to particularly high mechanical loads due to the loads that occur. Depending on the design of the brake caliper 50a these ranges can vary. All these versions have in common that the brake caliper 50a usually at least one component as a stiffening element in particularly highly stressed areas 34a This has at least one stiffening element 34a is then at least with a second component 35a of the caliper 50a non-positively and / or positively connected.

This is for example the bridge area of the brake caliper 50 , 50a a mechanically highly stressed area. The bridge area is usually that part of the brake calliper 50 , 50a considered the pliers-like in the caliper 50 , 50a submerged brake disc 10 encloses The leg in particular 59 and at least one of the brake disc 10 facing part of the thigh 58 to understand, as well as both legs 58 , 59 connecting bridge floor 55 .

According to one embodiment of the brake caliper according to the invention 50a in 3 is a Part of the bridge area as a stiffening element 34a educated. The stiffening element 34a includes the thigh 59 and the bridge floor 55 of the caliper 50a . The stiffening element 34a is mainly used as a load-bearing component of the caliper 50a designed and optimized. Within a connection area 60 is the stiffening element 34a with a bridge base 35a Arranged non-positively and / or positively connected So the bridge base 35a for example with the help of screws 54 non-positive via screw connection points 53a with the stiffening element 34a be screwed.

The bridge base 35a is for example compared to the stiffening element 34a preferably the less stressed component of the brake caliper 50a . Thus the bridge base can 35a consist of a material which, in contrast to the stiffening element 34a does not make great demands on strength and rigidity. Such a component is advantageously made of a material with a low density. This allows the total mass of the caliper 50a be reduced. Light metal alloys come into question for such components, especially those that can be cast and hardened in series production. Hardenable aluminum alloys, such as AlSi ₇ Mg, are well suited.

The stiffening element 34a is designed to be very stiff for optimal load absorption. In addition to the structural design, a material with a high modulus of elasticity is chosen to achieve high rigidity. This also allows the wall thicknesses of the stiffening element 34a be made narrow. In the case of non-positive connections, threads are used directly in the stiffening elements 34a provided, materials such as various steel alloys or molybdenum can be used. If, on the other hand, the selected material still has a low density, the mass of the brake caliper can 50a are also reduced overall. Both properties are ideally achieved by a stiffening element 34a from a composite material fulfilled Cast-metal matrix composites (Cast-MMC) already show an increased modulus of elasticity, although not very pronounced. The use of metal-ceramic composite materials is more advantageous. These composite materials very often have a modulus of elasticity> 150MPa.

A proven design is a stiffening element 34a of a ceramic base body with an infiltrated light metal, in particular an aluminum alloy such as AlSi ₁₂ or AlSi ₇ Mg. The base body advantageously has the geometry of the finished stiffening element even before it is infiltrated with a light metal 34a on.

The subsequent infiltration of the base body with a light metal melt is made easier if the base body has a porous base structure. It is therefore proposed as a possibility to design the base body as a sintered component. The base body consists essentially of identical or different sintered ceramic particles and / or fibers made of oxides such as Al ₂ O ₃ or TiO ₂ , carbides such as SiC or nitrides such as Si ₃ N ₄ or AlN. For example, Al ₂ O ₃ particles with a length / width ratio of 1 to 5 are conceivable. Regardless of the manufacturing process of the base body, it is advantageous for its optimal infiltrability with a light metal if its pore structure has a total porosity of 15% to 60%, preferably of 25% to 50%. The pore diameter is ideally in the range between 0.5 µm and 10 µm, preferably in the range between 1 µm and 5 µm.

Aluminum-based metal-ceramic composite materials with a ceramic content of up to 70% show very good material values. In tests it can be shown that stiffening elements made of 55-70% by volume Al ₂ O ₃ and 30-45% by volume made of AlSi ₇ Mg have a modulus of elasticity of up to 242GPA and a strength of up to 600MPa. Such in the caliper 50a used stiffening elements 34a , for example in the bridge area, not only have a high level of rigidity, but also meet the load requirements in the component.

In addition to the described execution of a stiffening element 34a in at least part of the bridge area, other components or areas of the brake caliper are also quite conceivable 50a with one or more stiffening elements 34a execute. Also in these cases is in the connection area 60 at least one stiffening element 34a non-positively and / or positively with at least one further component 35a of the caliper 50a connected. The non-positive and / or positive connection can be made, for example, by wedging, clamping, pinning or screwing.

A possible embodiment of a non-positive and positive connection is shown in 4th shown. Within a connection area 60 are a stiffening element 34a (for example part of the bridge area as in 3 ) with another component (for example the bridge base 35a out 3 ) connected. For this purpose are on the stiffening element 34a and on the at least one further component 35a of the caliper 50a in the connection area 60 mounting heels at their respective ends 36 , 38 formed, the top and bottom each stepped to the rest of the component body 34a , 35a are discontinued. The top and bottom of the mounting heels 36 , 38 close in the connection area 60 preferably each flush from each other. On the mounting heels 36 , 38 are on the top and bottom, preferably in the shoulder of the respective remaining component body 34a , 35a , Longitudinal grooves 37 , 39 brought in. A positive connection of the stiffening element 34a and the at least one further component 35a is made using at least two steel plates 70 realized, each on the top and bottom of the mounting heels 38 , 39 are arranged lying on top. Each grip on the side of the steel plates 70 complementary to the grooves 37 , 39 trained longitudinal webs 47 , 49 form-fit in the respective grooves 37 , 39 one. This will hold the steel plates 70 the stiffening element 34a and the at least one further component 35a of the caliper 50a in position to each other. Due to the existing form fit, forces can also be absorbed. Preferably the outwardly facing surfaces of the steel plates close 70 . flush with the adjacent outer surfaces of the stiffening element 34a or the at least one further component 35a of the caliper 50a from.

In addition, a non-positive connection is proposed. This is in the area of the mounting heels 36 and 38 introduced at least one through hole. Countersunk bores in the steel plates are also at least approximately axially centered to the respective through bore 70 introduced, the countersinks each facing the outside of the steel plates 70 are directed. The non-positive connection of the stiffening element 34a with the at least one further component 35a is thus implemented as a push-through screw connection. Countersunk screws are used for this 54 used, whose screw head is preferably within the countersink of one steel plate 70 is arranged. Likewise are those on the thread of the countersunk screws 54 screwed threaded nuts 75 preferably within the depression of the then opposite steel plate 70 arranged. The push-through connection described clamps the steel plates on the outside 70 against the mounting heels in between 36 , 38 . This advantageously enables the cutting of a thread into, for example, the stiffening element made of composite material 34a omitted. The existing frictional connection can cause loads on the brake caliper 50a act, be absorbed.

It is also possible to use the complete brake caliper 50a itself as a stiffening element 34a execute. Accordingly, areas of the brake caliper that are not particularly stressed then exist 50a made of a composite material, even if no high rigidity is required in these areas. As a result, for example, the number of components and the one-piece brake caliper can be reduced 50a for example directly with the saddle housing 20th be screwed.

The exemplary embodiments described only show possible structural configurations of a brake caliper according to the invention by way of example 50a . It goes without saying that there are also other advantageous embodiments of the brake caliper that are not listed in detail 50a possible according to the category of the independent claims without deviating from the basic idea of the invention. Such is the brake caliper of the invention 50a also only described for example in a disc brake. In principle, its use in brake units in a different design applies in the same way.

For the production of the brake caliper according to the invention 50a of at least two components, a first component is used as a stiffening element 34a educated. As a load-absorbing component, it generally has a higher modulus of elasticity than the at least second component. This is done for a stiffening element 34a Advantageously, a composite material, in particular a metal-ceramic composite material, is used as the material.
One possibility to manufacture the stiffening element 34a is a starting powder made of ceramic particles and / or fibers to form a green body with the geometry of the finished stiffening element 34a to press. Similar or mixed particles and / or fibers made of oxides such as Al ₂ O ₃ or TiO ₂ , carbides such as SiC or nitrides such as Si ₃ N ₄ or AlN are used as the starting powder. The green compact is then made into a ceramic Base body sintered. This base body is then infiltrated with a light metal melt, for example an aluminum alloy, in particular AlSi ₁₂ , with pressure support and becomes the finished stiffening element 34a cooled down.

To improve the infiltration of the light metal into the base body, pore formers can be added to the ceramic starting powder before the sintering process. Elongated, easily burn-out materials, such as e.g. Cellulose flakes proposed. These are present in the starting powder in a mixing ratio of 1% by volume to 30% by volume, preferably 2% by volume to 20% by volume. These pore formers burn out during the sintering process, so that a pronounced pore channel structure is created.

In addition, the at least one stiffening element is separated 34a at least one second component 35a manufactured. A light metal is preferably used as the material. The at least second component is proposed as one possibility 35a Cast from a hardenable aluminum alloy, in particular from AlSi ₇ Mg. This can be done using conventional gravity casting. The cast material is then hardened through a defined temperature treatment.
At least one stiffening element 34a and at least the second component of the brake caliper 50a , are non-positively and / or positively connected. This connection can be done, for example, by wedging, clamping, pinning or screwing.

Claims (19)

Brake caliper made of at least 2 components, at least one component being designed as a stiffening element (34a), characterized in that the at least one stiffening element (34a) is connected to at least one second component (35a) in a force-locking and / or form-locking manner, the at least one stiffening element (34a) is a base body with an infiltrated light metal alloy and the light metal infiltrated into the base body is an aluminum alloy AlSi ₁₂ or AlSi ₇ Mg. Caliper after Claim 1 characterized in that the at least one stiffening element (34a) is made from a composite material. Brake caliper according to at least one of the preceding claims, characterized in that the at least one stiffening element (34a) is formed at least in part of the bridge area. Caliper after one of the Claims 1 to 3 characterized in that the base body consists of ceramic. Caliper after at least one of the Claims 1 to 4th characterized in that the base body is sintered essentially from ceramic particles and / or fibers, in particular from oxides (preferably Al ₂ O ₃ or TiO ₂ ), carbides (preferably SiC) or nitrides (preferably Si ₃ N ₄ or AlN). Caliper after Claim 5 characterized in that the Al ₂ O ₃ particles have a length / width ratio of 1 to 5. Caliper after at least one of the Claims 1 to 6th characterized in that the base body has a pore structure with a total porosity of 15% -60% (preferably 25% to 50%) and a pore diameter between 0.5 µm and 10 µm (preferably between 1 µm and 5 µm). Caliper after at least one of the Claims 1 to 7th characterized in that the at least one stiffening element (34a) consists proportionally between 55-70vol% of a ceramic base body made of Al ₂ O ₃ and proportionally between 30-45vol% of an aluminum alloy AlSi ₇ Mg infiltrated therein. Brake caliper according to at least one of the preceding claims, characterized in that the at least one stiffening element (34a) has an E-module> 150 GPa. Brake caliper according to at least one of the preceding claims, characterized in that at least one second component (35a) is made from a hardenable light metal alloy, in particular from an aluminum alloy. Method for producing a brake caliper consisting of at least two components, with the method steps that a) at least one first component is designed as a stiffening element (34a), that b) at least one second component (35a) is made from a light metal and that c) at least the first and at least the second component (34a, 35a) are non-positively and / or positively connected to one another, the at least one stiffening element (34a) being a base body with an infiltrated light metal alloy and the light metal infiltrated into the base body being an aluminum alloy AlSi ₁₂ or AlSi ₇ Mg is. Procedure according to Claim 11 characterized in that the at least one stiffening element (34a) is made from a composite material. Method according to at least one of the Claims 11 and 12 characterized in that a ceramic-metal composite material is used as the material for the at least one stiffening element (34a). Method according to at least one of the Claims 11 to 13 characterized in that, for the production of the at least one stiffening element (34a), a starting powder is pressed and sintered to form a base body, which is additionally infiltrated with a light metal melt, supported by pressure. Procedure according to Claim 11 characterized in that ceramic particles and / or fibers, in particular made of oxides (preferably Al ₂ O ₃ or TiO ₂ ), carbides (preferably SiC) or nitrides (preferably Si ₃ N ₄ or AlN) are used as the starting powder. Method according to one of the Claims 14 and 15th characterized in that 1vol% to 30vol% (preferably 2vol% to 20vol%) pore-forming agent is preferred to the starting powder before the sintering process elongated, easily burn-out substances, especially cellulose flakes, are added. Procedure according to Claim 16 characterized in that the pore formers present in the base body burn out during the sintering process, so that a pronounced pore channel structure is created. Method according to at least one of the Claims 11 to 17th characterized in that at least one second component (35a) is cast from a light metal, in particular from an aluminum alloy. Method according to at least one of the Claims 11 to 18th characterized in that at least one stiffening element (34a) is connected to an at least second component (35a) by wedging, clamping, pinning or screwing.

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