Brake mechanism and a method of controlling force amplification

Abstract

The present invention concerns a brake mechanism of a disc brake received in a caliper ( 16 ) and a method for controlling the force amplification for the brake mechanism. The brake mechanism comprises a lever ( 26, 31 ) actuated by a brake actuator. The lever is acting on a cross bar ( 34, 37 ) by means of an intermediate part ( 27 ). The lever ( 26, 31 ) and the intermediate part ( 27 ) have a line of contact moving along a circular arc during an application stroke of the brake mechanism. The cross bar ( 34, 37 ) of the brake mechanism is closely guided and is only moveable in the thrust direction and in the tangential direction of the brake disc. The force amplification of the brake mechanism is adapted to the force characteristics of the brake actuator.

1 . A brake mechanism of a disc brake received in a brake caliper ( 16 ) reaching over a brake disc, which brake mechanism comprises a lever ( 26 ,  31 ) actuated by a brake actuator, characterized in that the lever ( 26 ,  31 ) is acting on a cross bar ( 34 ,  37 ) of the brake mechanism by means of an intermediate part ( 27 ), which lever ( 26 ,  31 ) and intermediate part ( 27 ) have a line of contact moving along a cam profile during an application stroke of the brake mechanism, and that the caliper ( 16 ) receives the cross bar ( 34 ,  37 ) in such a way that it is movable in the thrust direction and in the tangential direction of the brake disc but hindered to move in a direction perpendicular to the above directions.  
     
     
         2 . The brake mechanism of  claim 1 , characterized in that the intermediate part is a rocker ( 29 ) received in a groove ( 35 ) of the cross bar ( 34 ,  37 ) and that the rocker ( 29 ) is movable between the inner walls of the groove ( 35 ).  
     
     
         3 . The brake mechanism of  claim 1 , characterized in that the intermediate part is a stud ( 28 ).  
     
     
         4 . The brake mechanism of any of the previous claims, characterized in that the lever ( 26 ,  31 ) rotates in relation to a first point of rotation ( 1 ) and that the intermediate part rotates in relation to a second point of rotation ( 2 ).  
     
     
         5 . The brake mechanism of  claim 4 , characterized in that the surfaces of the lever ( 26 ,  31 ) and the intermediate part ( 27 ) in contact move along a cam profile having a distance (R 1 ) from the point of rotation ( 1 ) for the lever ( 26 ,  31 ) and a radius (R 2 ) from the point of rotation ( 2 ) for the intermediate part ( 27 ), respectively.  
     
     
         6 . The brake mechanism of  claim 5 , characterized in that the distance (R 1 ) from the point of rotation ( 1 ) for the lever ( 26 ) varies depending on the position of the lever ( 26 ).  
     
     
         7 . The brake mechanism of  claim 5 , characterized in that the cam profile is a circular arc.  
     
     
         8 . The brake mechanism of any of the  claims 5  to  7 , characterized in that the points of rotation ( 1 , 2 ) for the lever ( 26 ,  31 ) and the intermediate part ( 27 ) are offset from each other with a distance (D) in the plane of the lever (L).  
     
     
         9 . The brake mechanism of any of the  claims 4  to  8 , characterized in that the lever ( 26 ,  31 ) has an active length (L) between the point of rotation ( 1 ) of the lever ( 26 ,  31 ) and a position ( 3 ) in which the actuator goes into contact with the lever ( 26 ,  31 ).  
     
     
         10 . The brake mechanism of any of the previous claims, characterized in that the brake mechanism comprises a bearing bracket ( 22 ,  30 ) received in an opening ( 17 ) of the caliper ( 16 ) in the wall furthest from the brake disc and that the lever ( 26 ,  31 ) is received in the bearing bracket ( 22 ,  30 ) by means of a bearing ( 33 ).  
     
     
         11 . The brake mechanism of  claim 10 , characterized in that the lever ( 26 ,  31 ), the bearing bracket ( 22 ,  30 ) and/or the intermediate part ( 27 ) are exchangeable in order to alter the force amplification of the brake mechanism.  
     
     
         12 . A method for controlling the force amplification from a brake actuator to brake pads acting on a brake disc, for a brake mechanism according to any of the previous claims, characterized in that the force amplification of the brake mechanism is adapted to the force characteristics of the brake actuator.  
     
     
         13 . The method of  claim 12 , characterized in that the force amplification characteristics of the brake mechanism is controlled by amending the radius (R 2 ) of the circular arc followed by a line of contact between the lever ( 26 ,  31 ) and the intermediate part ( 27 ), the offset distance (D) between the points of rotation ( 1 , 2 ) of the lever ( 26 ,  31 ) and the intermediate part ( 27 ), respectively, the form of the outer surface of the lever ( 26 ,  31 ) in contact with the intermediate part ( 27 ) and/or the active length (L) of the lever ( 26 ,  31 ).  
     
     
         14 . The method of  claim 13 , characterized in that the radius (R 2 ), the offset distance (D), the form of the outer surface of the lever and/or the active length (L) of the lever ( 26 ,  31 ) is controlled to give constant break force independent of the stroke length for the brake actuator acting on the lever ( 26 ,  31 ).  
     
     
         15 . The method of  claim 14 , characterized in that the brake actuator is a pneumatic cylinder.