SK11202000A3 - Actuating piston for a hydraulically and mechanically actuated disk brake with partial brake lining - Google Patents

Abstract

The invention relates to an actuating piston (10) of a hydraulically and mechanically actuated disk brake with partial brake lining for motor vehicles. Said actuating piston is arranged in a cylinder boring of the disk brake in a sealing and displaceable manner and has a conical surface (18) capable of transmitting axial forces which cooperates with a corresponding conical surface of a mechanical actuating device of the disk brake. To provide an actuating piston (10) which saves weight while remaining strong, the part of the actuating piston (10) having the axial-force transmitting conical surface (18) is made of steel and the part of the actuating piston (10) which cooperates with the cylinder boring of the disk brake is made of a light metal or plastic material. The above components of the actuating piston (10) form a single-piece composite component.

Description

Control piston for hydraulically and mechanically controlled disc brake with split lining

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a control piston for hydraulically and mechanically actuable disc brakes for a split-lined motor vehicle, for a sealing and sliding arrangement in a cylindrical disc brake opening having a conical surface transmitting axial forces to interact with a corresponding conical surface .

BACKGROUND OF THE INVENTION

Disc brakes of this kind are normally operated hydraulically for service braking, for example by depressing the brake pedal of a vehicle's braking device, but may also serve as a parking brake or a so-called handbrake and be mechanically actuated for this purpose, such as a handbrake or a separate pedal for parking brake. Accordingly, in the case of disc brakes of the above-mentioned type, the piston referred to as the brake piston can often be pressed against the one or more brake linings by means of hydraulic pressure and on the other hand by means of a clean mechanical device in order to achieve the desired tightening force.

EP 0 403 635 B1 discloses such a disc brake in which, in use as a parking brake, the pulling force is transmitted via an adjusting mechanism used to compensate for wear of the brake lining to the actuating piston. A conical clutch, which is formed by the conical flange of the support part of the adjusting mechanism and a complementary conical surface formed on the actuating piston, is critical with respect to the load. In addition to axially distributing the tightening force from the actuating mechanism to the actuating piston, the tapered clutch should also prevent the two parts from turning relative to each other. Only when adjusting the lining wear by means of the adjusting mechanism should it be possible to easily twist the coupling surfaces against each other.

The object of the invention is to provide a control piston suitable for use in a brake of the type mentioned above, which is lighter than the control piston conventionally used. In particular, the proposed control piston is intended to transmit large axial forces at a lower weight, to have low radial expansion and to be able to cope with frictional wear of the conical surface transmitting axial forces.

SUMMARY OF THE INVENTION

Starting from a split-lined disc brake control piston, as known from EP 0 403 635 B1, this object according to the invention is achieved in that the part of the control piston comprising the conical surface transmitting axial forces consists of steel, and the part of the control piston cooperating with the cylindrical bore of the disc brake consists of a light metal or plastic, and that said parts of the control piston are formed as a one-piece component. The pairing of the steel / light metal or steel / plastic material according to the invention makes it possible, in conjunction with the design of the control piston as a one-piece unit, to transmit high axial forces in a two-ton size arrangement despite the significantly reduced control piston weight. Moreover, the design of the conical surface, which transmits axial forces, of steel resists very well the friction wear.

In one preferred embodiment of the control piston according to the invention, the hollow, and steel component, comprising a conical surface transmitting axial forces, is formed as a hollow cylindrical insert, held in the plastic or light metal component. This, in a weight-saving design, ensures good axial force distribution by means of the control piston.

If the actuating piston according to the invention is hollow, it often has a first section with a smaller inner diameter and a second section with a larger inner diameter. The steel component provided with a conical surface transmitting axial forces then extends along at least approximately the entire length of the second section, i.e. along the section with a larger inner diameter. In this way, it is achieved that the part of the piston housing which is most heavily loaded by the hydraulic pressure, which has, in addition, a smaller wall thickness than the remaining part of the piston housing, is effectively reinforced by the steel component. This counteracts radial expansion of the piston housing in said region, which may result in the actuating piston clamping in the cylinder or even tearing of the piston housing. Preferably, the steel component is tubular and is made by a sheet metal forming method, such as by deep drawing or extrusion. By extrusion is meant here that the tubular steel component is subjected to a rolling process on the counter-shaft.

According to a further embodiment of the hollow cylindrical and preferably tubular steel component which extends along a section with a larger inner diameter of the actuating piston, the steel component has at its end facing the first actuating piston section a radially directed annular flange which preferably projects radially outwardly . Such a radial annular flange reinforces the region of the steel component in which the conical surface transmitting axial forces is arranged.

In preferred embodiments of the control piston according to the invention, the steel component extends not only along the second section of the control piston having a larger internal diameter, but also extends inwardly into the first section of the control piston with a smaller internal diameter. For example, if the steel component is provided with a radially inwardly projecting annular flange that additionally reinforces the region of the steel component in which the tapered axial force transmitting surface is disposed, then the steel component preferably extends from the radial annular flange axially into the first section the diameter of the control piston. Particularly preferably, the transition region between the radial annular flange and the continuation of the steel component into the first section of the actuating piston is formed inwardly rounded in order to facilitate the insertion of sensitive components, such as a seal, without damage. The steel component may extend into the first section of the control piston only inwards, but may also extend over the entire length of the first section of the control piston.

According to yet another exemplary embodiment of a control piston according to the invention, the steel component is provided with a conical surface transmitting axial forces, formed as a substantially pot-shaped insert, held in a plastic or light metal component which forms part of the front surface of the control piston which faces brake disc. In the case of a slightly increased total weight compared to the above-mentioned embodiment, the latter embodiment has the advantage that, even with hydraulic actuation, almost all axial tightening forces are transmitted via the pot-lined brake lining, which results in a relieving of the mechanically less stable component. plastic or light metal actuating piston according to the invention.

Preferably, the steel control piston component according to the invention is provided with a conical surface transmitting axial forces if the control piston component cooperating with the cylindrical disc brake opening consists of a light metal, then cast into the light metal or light metal injection molded. If the component of the control piston interacting with the cylindrical bore of the disc brake consists of plastic, the steel component is preferably injection molded with plastic or is also embedded in the plastic. Injection or casting of the steel component into the plastic or light metal component results in an extremely tight and thus stable connection of the two components of the control piston according to the invention.

Depending on the plastic material used for the plastic component, it may be desirable to temper the plastic component to achieve the desired strength. Since many plastic materials shrink during the tempering process so that the plastic material changes in size, it may be advantageous to produce the component from plastic separately, temper it and then connect it to the steel component. In such a case, the plastic component is joined to the steel component, preferably by gluing or pressing into one piece of the connected component.

Regardless of whether the plastic component consists of a material that must be subjected to a tempering process and may collapse during the bonding process, gluing the steel component to the plastic or light metal component has the advantage that the adhesive layer can compensate for differences in expansion that may arise between the steel component and the plastic or light metal component. As a further advantage, when gluing a preferably tubular steel component into a preformed plastic or light metal component, aligning the central axis of the steel component in a simple manner with the central axis of the plastic or light metal component can be used, to equalize manufacturing tolerances between the steel component and the plastic or light metal component.

The adhesive may be applied to the steel component and / or the plastic or light metal component over the entire surface, but may also be provided in the form of an epoxy resin ring which is inserted between the steel component and the plastic or lightweight component. metal. Upon subsequent heating of the two components to approximately 150 ° C, the epoxy resin melts and glues the plastic or light metal component hydraulically tightly to the steel component.

In addition, if the steel component is to be glued into the plastic or light metal component, the steel component together with the brake adjuster arranged therein can be pre-assembled as a structural unit. This structural unit of the adjusting mechanism and the steel structural unit is then glued into the structural unit of plastic or light metal. The temperature resulting from the gluing process is so low that the adjusting mechanism seals are not damaged in any way.

The term "connected component" as used herein also includes those embodiments of the control piston according to the invention in which there is a minimum gap between the plastic or light metal component and the steel component. In order to achieve a hydraulically tight connection between the plastic or light metal component and the steel component despite such a gap, seals, for example O-ring seals, may be provided between the two components. Such exemplary embodiments of the control piston according to the invention also make it possible first to pre-assemble the steel component together with the adjusting mechanism as a structural unit before connecting it to a plastic or light metal component.

In order to further increase the stability of the connection of the steel component to the plastic or light metal component, according to a varied embodiment of the control piston according to the invention, the steel component is provided on the outer circumferential surface with projections which form a positive connection between the steel component and the component made of plastic or light metal. These protrusions can, for example, be designed as circumferential axial toothing. However, other types of projections are also suitable, for example, cross-grooving the outer peripheral surface of the steel component.

In preferred embodiments of the control piston according to the invention, the steel component has at least one generously dimensioned, radially annular surface on the side lying axially opposite to the conical surface transmitting axial forces. The stress on the material, in particular the compression of the material, of the plastic or light metal component, resulting from the transmission of a high axial force at the transition between the steel component and the plastic or light metal component is considerably reduced in this way.

In addition to the actuating piston according to the invention, the invention also relates to a disc brake for split-lined motor vehicles equipped with such an actuating piston whose weight is reduced by the use of the actuating piston according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described and explained in more detail below with reference to the accompanying drawings, in which: FIG. 1 shows a first embodiment of a control piston according to the invention in longitudinal section, FIG. 2 shows a modified, second embodiment of the control piston according to the invention, also in longitudinal section, FIG. 3 shows a third embodiment of the control piston according to the invention in longitudinal section, FIG. 4 shows an embodiment of the control piston according to the invention also in longitudinal section, slightly modified from FIG. 3, FIG. 5 shows an embodiment of the control piston according to the invention, modified once again from FIG. 3 and FIG. 4, and FIG. 6 shows the actuating piston shown in FIG. 5 together with the essential parts of the disc brake adjusting mechanism.

DETAILED DESCRIPTION OF THE INVENTION

The control piston 10 of the disc brake not shown below for a split-lined motor vehicle shown in FIG. 1, has a housing 12 through which the control piston 10 is sealed and axially slidably guided in the cylindrical bore of the disc brake.

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The control surface 10 abuts the actuating piston 10 on the brake pad of the disc brake so that it can press the disc brake against the brake disc. This can be done both by hydraulic pressure and by pure mechanical pressure of the actuating piston 10. Usually, for disc brakes that allow both hydraulic and pure mechanical pressure of the actuating piston 10. The actuating piston 10 is hydraulically operated under normal service braking and used as the parking brake is mechanically moved in the direction of the brake disc or is pressed against the brake lining support plate. The precise function of such disc brakes is well known to those skilled in the art and is therefore not explained in detail herein. Reference is made to EP 0 403 635 B1, which describes in detail the function of a disc brake in which the actuating piston can be moved hydraulically and clean mechanically.

The internal cavity 16 of the actuating piston 10 retains at least one part of the adjusting mechanism, see also FIG. 6, which serves to compensate for wear on the disc brake pads, by adjusting the control piston 10 according to the occurring wear of the brake pads in the direction of the brake disc, so that when the disc brake is used as a parking brake the tightening despite the more and more worn friction linings is essentially the same.

In mechanical tightening, the axial force is applied to the actuating piston 10 via the conical surface 18. As can be seen from FIG. 1, this conical surface 18 transmitting axial forces is formed on a hollow cylindrical steel component 20 which is embedded in a component 22 consisting of plastic or light metal, which forms the remaining part of the control piston 10 and in particular the part of the control piston 10 cooperating with cylindrical bore of disc brake. The steel component 20 is sealed or glued into the light metal or plastic component 22 so that the two components 20 and 22 form a one-piece component. Alternatively, when the component 22 is made of plastic, the steel component 20 may also be injection molded with the plastic component 22.

Due to the material saving transmission of the axial forces introduced into the control piston 10 via the conical surface 18. the steel component 20 has a generously dimensioned radial annular surface 24 as well as a slightly less dimensioned radial annular surface 26 on the side axially opposite to the conical surface 18. Almost all circumferential edges of the steel component 20 that are present in the plastic or light metal component 22 are designed to be strongly rounded to avoid any notch effect.

When the component 22 consists of a light metal, X12CrNiS 18.8 steel, material number 1.4305, with a thermal coefficient of expansion of 17 to 18 x 10'6 m / (mx K), is preferably used as the material for the steel component 20 light metal component 22 alloy AIS17, material number 3.2581 having a coefficient of thermal expansion of 24 or 21 x

10.6 m / (m x K). When using said materials, the different thermal expansion in the temperature range under consideration, based on the relatively closely adjacent thermal expansion coefficients of the two materials, plays only a minor role. Of course, when the component 22 is made of plastic, other steels may also be used for the steel component 20.

Fig. 2 shows a second embodiment of the actuating piston 10 which differs from the first embodiment in that the steel component 20 is not hollow cylindrical but pot-shaped and extends to the face 14 of the actuating piston 10. Transmission of axial forces by the actuating piston 10 on the brake lining not shown here is even more advantageous in the second embodiment, since the axial force applied through the conical surface 18 can be transmitted to the brake lining almost exclusively directly by the steel component 20. The light metal or plastic component 22 is thereby relieved.

For an even more stable connection between the steel component 20 and the light metal or plastic component 22, according to FIG. 2, a plurality of protrusions 28 are arranged on the peripheral surface of the steel component 20, which lead to a positive connection between the steel component 20 and the plastic or light metal component 22. The protrusions 28 may be formed, for example, in the form of an axial toothing arranged on the outer circumferential surface of the steel component 20.

Fig. 3 shows a further embodiment of the actuating piston 10 in which the steel component 20 is tubular and of substantially the same wall thickness. The hollow actuating piston 10 has a first section 30 and a second section 32, wherein the inner diameter of the first section 30 is smaller than the inner diameter of the second section 32. The steel component 20, which is provided with a conical surface 18 transmitting axial forces extends along at least approximately its entire length. of the second section 32 in the actuating piston 10 so as to reinforce the actuating piston 10 in this region in which the wall thickness of the plastic or light metal component 22 is relatively small, thereby counteracting radial expansion of the actuating piston 10. To reinforce the steel section component

20, in which the conical surface 18 transmitting axial forces is present, the steel component 20 is provided with a radially inwardly projecting annular flange 34, which in the embodiment shown in FIG. 3 is located at the end of the steel component 20 facing the first section 30 of the control piston 10.

According to FIG. 4, which shows an exemplary embodiment of a control piston 10 similar to FIG. 3, the steel component 20 extends not only along the second section 32 of the actuating piston 10, but also inwards in its first section 30. The transition region between the annular flange 34 and the smaller diameter portion of the steel component 20 is rounded to facilitate insertion of the adjuster gasket, see fig. 6, into the first section 30 and to avoid damaging the seal.

According to FIG. 5, which shows a modified embodiment of the control piston 10, similar to FIG. 3 and FIG. 4, the tubular steel component 20 extends further inwardly into the first section 30 of the actuating piston 10. In this way, it is ensured that the seal 36 of the adjusting mechanism shown in FIG. 6, during its overall axial translational movement, is always in contact with the inner surface of the steel component 20, which is for this purpose finely machined in this region, i.e. along the first section 30. FIG.

Fig. 6 illustrates the control piston 10 of FIG. 5 together with the essential parts of the adjustment mechanism 40 not explained in detail here, such as is known from EP 0 403 635 B1. FIG. 6 can be well recognized as the conical surface 18 on the steel component 20.

transmitting axial forces, cooperates with a respective conical surface which is formed on the adjusting nut 38 of the adjusting mechanism 40.

f y fiw -2000

Claims (14)

A control piston (10) of a hydraulically and mechanically actuable disc brake for motor vehicles with a split lining, for a sealing and sliding arrangement in a cylindrical disc brake opening having a conical surface (18) transmitting axial forces for interaction with a corresponding conical surface of a mechanical a disc brake actuating device, characterized in that the part of the control piston (10) comprising an axial force transmitting conical surface (18) consists of steel, and the part of the control piston (10) arranged to interact with the cylindrical bore of the disc brake a light metal or plastic, and that said components of the control piston (10) together form a unitary component. Actuating piston according to claim 1, characterized in that the actuating piston (10) is hollow, and the steel component (20) provided with a conical surface (18) transmitting axial forces is formed as a hollow cylindrical insert retained in the component (22) of plastic or light metal. Control piston according to claim 2, characterized in that the hollow control piston (10) has a first section (30) with a smaller inner diameter and a second section (32) with a larger inner diameter, and that the steel component (20) is provided with a conical cone. the axial force transmitting surface (18) extends along at least approximately the entire length of the second section (32). Control piston according to claim 3, characterized in that the steel component (20) provided with a conical surface (18) transmitting axial forces, at its end facing the first section (30) of the control piston (10) preferably radially inwards a protruding annular flange (34). Control piston according to claim 3 or 4, characterized in that the steel component (20) provided with a conical surface (18) transmitting axial forces also extends to the first section (30) of the control piston (10). Actuating piston according to claim 1 or 5, characterized in that the actuating piston (10) is a hollow and steel component (20) provided with a conical surface (18) transmitting axial forces, formed as a substantially pot-shaped insert, held in a a plastic or light metal component (22) that forms part of the front surface of the actuating piston (10) that faces the brake disc. Actuating piston according to one of the preceding claims, characterized in that the steel component (20) is embedded in light metal or plastic or is injection molded with light metal or plastic. Control piston according to any one of the preceding claims, characterized in that the steel component (20) is glued to the plastic or light metal component (22) or is pressed into the plastic or light metal component (22). Actuating piston according to one of the preceding claims, characterized in that the steel component (20) is provided on the outer circumferential surface with protrusions (28) which cause positive contact with the component (22) of plastic or light metal. Actuating piston according to one of the preceding claims, characterized in that the steel component (20) has at least one generously dimensioned, radially annular surface (24) on the side lying axially opposite the conical surface (18) transmitting axial forces. Control piston according to one of the preceding claims, characterized in that the component (22) is a light metal component and consists of an AlSi7 alloy to an AlSi12 alloy with a thermal expansion coefficient of 24 or 21 x 106 m / (mx K). and that the steel component (20) consists of X12CrNiS 18.8 steel with a coefficient of thermal expansion of 17 to 18 x 10 -6 m / (mx K). Method for manufacturing a control piston (10) according to any one of the preceding claims, characterized in that a structural unit (20) and an adjusting mechanism (40) are first formed from a steel component (20) and then connected to the component (20). 22) of plastic or light metal. Method for producing a control piston (10) according to any one of the preceding claims, characterized in that an epoxy resin ring, a steel component (20) is positioned between the steel component (20) and the plastic or light metal component (22). ) and the plastic or light metal component (22) with the epoxy resin ring disposed therebetween is heated until the epoxy resin is melted, and then the epoxy resin is allowed to solidify. Hydraulically and mechanically operable disc brake for split-lined motor vehicles, characterized by a control piston (10) according to any one of the preceding claims.