Patent Application
20240376944
The invention relates to a disc brake for a utility vehicle.
The brake caliper of a disc brake of the type in question is held movably on a vehicle-mounted brake carrier, for which purpose guide bars are provided, said guide bars each consisting of a guide bushing and a screw, which is guided therein and is screwed into a threaded hole in the stationary, i.e. vehicle-mounted, brake carrier, usually into a brake carrier horn.
The respective guide bushing rests by means of an end face against the associated surface of the brake carrier, wherein a high-tensile screw that presses the guide bar against the brake carrier under a preload is used as a screw.
In many cases, use is made of brake carriers whose surface facing the guide bushings is provided with a coating that reduces the friction coefficient, e.g. made of zinc phosphate.
However, owing to the reduced frictional engagement between the guide bushing and the brake carrier, this increases the risk that the guide bushing will be twisted, and this can lead to a loss of the preloading force of the screw and ultimately to its loosening.
This results in a restriction to the operational and functional safety of the disc brake overall since the ultimate effect of the loosening of the screw fastening is a total failure of the brake. A disc brake is a component relevant to safety, and therefore this hazard presents an unacceptable situation.
To provide a remedy, DE 10 2013 109 673 A1 proposes to arrange a retention element in the form of two wedge lock washers between the guide bushing and the brake carrier, the circumferential wedge surfaces of the washers engaging in one another in the manner of toothing.
Although security against rotation is achieved by means of this design, it is only by the provision of additional components, namely said wedge lock washers, the procurement of which is associated with additional costs, something that runs counter to the constant effort to optimize costs.
The object on which the invention is based is to further develop a disc brake of the type in question in such a way that its functional and operational safety is improved with a low outlay in terms of design and manufacture.
This object is achieved by a disc brake having the features of the independent claims.
Fundamentally, the solution according to the invention of the object consists in increasing the surface pressure in the region of contact of the guide bushing with the brake carrier, that is to say with the associated brake carrier horn, resulting in an increase in the friction coefficient which prevents twisting of the guide bushing in an effective manner as long as the screw produces a corresponding contact pressure.
This frictional engagement is also present if the surface of the brake carrier is provided in the contact region with a coating, e.g. in the form of zinc phosphate, which, as described in the prior art, reduces the friction coefficient.
According to an advantageous development of the invention, the guide bushing, or at least the projection according to the invention, consists of a harder material than the brake carrier, wherein either the guide bushing as a whole is manufactured from a harder steel or the projection is harder due to appropriate treatment.
It is contemplated to provide the contact region between the guide bushing and the brake carrier with, for example, a paste that increases the friction coefficient or with a coating that hardens, the latter in the contact region of the projection, optionally also in the adjoining region-which forms a contact surface-of the end face of the guide bushing. As another alternative to increasing the friction coefficient, an insert that increases the friction coefficient can be provided on the end face of the guide bushing.
In respect of its cross section, the projection itself can take different configurations, e.g. as a sharp-edged ridge with a triangular cross section or as a projection with a flat surface. In either case, the higher surface pressure leads to this projection, as it were, digging into the brake carrier.
The arrangement of the projection can likewise differ. A known way of centering the guide bushing is to provide it at the end with an integrally formed collar which is fitted into a recess in the threaded hole of the brake carrier, while the annular contact surface, adjacent to the collar, of the guide bushing rests against the adjacent outer side of the brake carrier. The projection according to the invention is formed on the annular contact surface, either on the outer edge region or approximately in the middle of the contact surface.
Where the projection is designed as a ridge, i.e. with an encircling sharp edge, this ridge can be designed as an isosceles triangle in cross section or merely with a bevel. Here, the ridge, in conjunction with the screw preloading force, gives rise to a stress concentration radially on the outside, i.e. at the contact surface of the guide bushing and, by way of a lever arm with a maximum effect, a significant increase in the resistance torque in the direction of torsion with respect to a torque acting externally on the guide bar.
An increase in the resistance torque, similar to that in the taper seat of a drill chuck, is also obtained if the projection is designed as a sharp-edged ridge which plastically deforms the surface of the brake carrier by virtue of the screw preloading force.
It may furthermore be regarded as a particular advantage of the invention that the guide bushing can be implemented with a low outlay in terms of manufacture, and this is significant insofar as disc brakes are produced in large numbers as series-produced parts. The invention therefore meets the requirements for cost optimization to a high degree.
Among the contributing factors to this is the fact that the guide bushing according to the invention can be installed retroactively in already assembled brake carriers, and therefore a corresponding disc brake can be retrofitted, especially since no special machining of the brake carrier is required for this purpose.
The elimination of separate retention means, e.g. the wedge lock washers described with reference to the prior art, which is now possible, also leads to minimization of costs.
Further advantageous embodiments of the invention are characterized in the dependent claims.
Exemplary embodiments of the invention are described below with reference to the attached drawings.
Guide bars 2 are secured on two brake carrier horns 5 situated opposite one another in alignment, for which purpose a screw 4 is passed through a cylindrical guide bushing 3 of the guide bar 2 and screwed into a threaded hole 8 (
Mounted in an axially movable manner on these guide bars 2 is a brake caliper (not shown), which is also known as a sliding caliper.
The screw 4 used is preferably a hexagon socket screw, the head of which lies in a recess in the guide bushing 3.
On its end face facing the brake carrier 1, the guide bushing 3 has, as can be seen very clearly in
The end face of the guide bushing 3 facing the brake carrier horn 5, namely a contact surface 9 starting radially from the collar 6, has an encircling projection 10, designed as a ridge in the example, which is arranged in the radial end region of the contact surface 9 associated with the circumferential surface of the guide bushing 3.
In
The example of the projection 10 shown in
In
Another variant of the projection 10 can be seen in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 123 775.5 | Sep 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/072278 | 8/8/2022 | WO |
