Friction brake system for a vehicle

Abstract

The present application relates to a friction brake system (1) for a vehicle. The friction brake system (1) comprises a braking member (12) connectable to at least one brake pad and configured for pressing the brake pad against a friction surface. The system (1) further comprises a transmission unit (2) configured for converting a rotary motion generated by an electric motor (30) into a braking motion of the braking member (12). The transmission unit (2) comprises a ball-in-ramp assembly (3) having a first plate (9) with at least one groove (23), a second plate (10) with at least one groove (22) facing the groove (23) of the first plate (9), and at least one ball (11) arranged between the first plate (9) and the second plate (10). The ball (11) is retained by the groove (23) of the first plate (9) and the groove (22) of the second plate (10). Further, the ball-in-ramp (3) assembly is configured to convert a rotary motion of the first plate (9) into a translational motion of the second plate (10) with respect to the first plate (9). The first plate (9) is configured to be rotated by the electric motor (30). Further, at least one of the first plate (9) and the second plate (10) is mechanically coupled with the braking member (12) such that a rotation of the first plate (9) causes the braking motion of the braking member (12). A depth of the groove (23, 24) of at least one of the first plate (9) and the second plate (10) increases between a first portion (24) and a second portion (25) of the groove (23, 24) in a non-linear manner such that a path defined by the groove (23, 24) is steeper in the first portion (24) than in the second portion (25).

1 . A friction brake system ( 1 ) for a vehicle, comprising
 a braking member ( 12 ) connectable to at least one brake pad and configured for pressing the brake pad against a friction surface, and   a transmission unit ( 2 ) configured for converting a rotary motion generated by an electric motor ( 30 ) into a braking motion of the braking member ( 12 ),   characterized in that the transmission unit ( 2 ) comprises a ball-in-ramp assembly ( 3 ) having:   a first plate ( 9 ) with at least one groove ( 24 ),   a second plate ( 10 ) with at least one groove ( 23 ) facing the groove ( 24 ) of the first plate ( 9 ), and   at least one ball ( 11 ) arranged between the first plate ( 9 ) and the second plate ( 10 ), wherein the ball ( 11 ) is retained by the groove ( 23 ) of the first plate ( 9 ) and the groove ( 22 ) of the second plate ( 10 );   wherein the ball-in-ramp assembly ( 3 ) is configured to convert a rotary motion of the first plate ( 9 ) into a translational motion of the second plate ( 10 ) with respect to the first plate ( 9 ),   wherein the first plate ( 9 ) is configured to be rotated by the electric motor ( 30 ) and at least one of the first plate ( 9 ) and the second plate ( 10 ) is mechanically coupled with the braking member ( 12 ) such that a rotation of the first plate ( 9 ) causes the braking motion of the braking member ( 12 ),   wherein a depth of the groove ( 22 ,  23 ) of at least one of the first plate ( 9 ) and the second plate ( 10 ) increases between a first portion ( 24 ) and a second portion ( 25 ) of the groove ( 22 ,  23 ) in a non-linear manner such that a path ( 27 ,  28 ) defined by the groove ( 24 ) is steeper in the first portion ( 24 ) than in the second portion ( 25 ).   
     
     
         2 . The friction brake system ( 1 ) of  claim 1 , characterized in that the groove ( 23 ) of the first plate ( 9 ) and the groove ( 22 ) of the second plate ( 10 ) each define a path ( 27 ,  28 ) having a radial component, wherein the ball ( 11 ) is held at an intersection point ( 29 ) of the path ( 27 ) defined by the groove ( 23 ) of the first plate ( 9 ) with the path ( 28 ) defined by the groove ( 22 ) of the second plate ( 10 ). 
     
     
         3 . The friction brake system ( 1 ) of  claim 2 , characterized in that neighbouring grooves ( 23 ,  23 ′) of the first plate ( 9 ) overlap at a circumferential position. 
     
     
         4 . The friction brake system ( 1 ) of  claim 1 , characterized in that the grooves ( 23 ) of the first plate ( 9 ) and the grooves ( 22 ) of the second plate ( 10 ) have an identical shape at least in sections. 
     
     
         5 . The friction brake system ( 1 ) of  claim 1 , characterized by a planetary gear ( 4 ), wherein the first plate ( 9 ) is configured to be rotated by the electric motor ( 30 ) via the planetary gear ( 4 ). 
     
     
         6 . The friction brake system ( 1 ) of  claim 1 , characterized in that the ball-in-ramp assembly ( 3 ) comprises at least three grooves ( 23 ,  23 ′) of the first plate ( 9 ), at least three grooves ( 22 ,  22 ′) of the second plate ( 10 ), and at least three balls ( 11 ,  11 ′) retained by pairs of the grooves of the first and second plates ( 9 ,  10 ). 
     
     
         7 . The friction brake system ( 1 ) of  claim 1 , characterized in that the ball-in-ramp assembly ( 3 ) comprises at least five grooves ( 23 ,  23 ′) of the first plate ( 9 ), at least five grooves ( 22 ,  22 ′) of the second plate ( 10 ), and at least five balls ( 11 ,  11 ′) retained by pairs of the grooves of the first and second plates. 
     
     
         8 . The friction brake system ( 1 ) of  claim 1 , characterized by a housing ( 18 ), wherein the second plate ( 10 ) is held such that it is not rotatable with respect to the housing ( 18 ). 
     
     
         9 . The friction brake system ( 1 ) of  claim 1 , characterized in that the braking member ( 12 ) comprises a caliper housing ( 33 ) connectable to a first brake pad and a braking bolt ( 13 ) connectable to a second brake pad, wherein the caliper housing ( 33 ) and the braking bolt ( 13 ) are each coupled with one of the first plate ( 9 ) and the second plate ( 10 ) such that the caliper housing ( 33 ) and the braking bolt ( 13 ) are configured to press the first and second brake pads against opposing surfaces of a brake disc when the braking member ( 12 ) executes the braking motion. 
     
     
         10 . The friction brake system ( 1 ) of  claim 1 , characterized by a housing ( 18 ), wherein the caliper housing ( 33 ) and the braking bolt ( 13 ) are held such that they execute a translational motion with respect to the housing ( 18 ) when the braking member ( 12 ) executes the braking motion. 
     
     
         11 . The friction brake system ( 1 ) of  claim 9 , characterized in that the first plate ( 9 ) is coupled with the caliper housing ( 33 ) and the second plate ( 10 ) is coupled with the braking bolt ( 13 ) and/or characterized in that the first plate ( 9 ) is coupled with the braking bolt ( 13 ) and the second plate ( 10 ) is coupled with the caliper housing ( 33 ). 
     
     
         12 . The friction brake system ( 1 ) of  claim 1 , characterized by an axial needle bearing ( 17 ), which supports the first plate ( 9 ). 
     
     
         13 . A parking brake for a vehicle comprising the friction brake system ( 1 ) of  claim 1 , wherein the friction brake system ( 1 ) is configured to keep the vehicle motionless when parked by pushing the brake pad against the friction surface. 
     
     
         14 . A service brake for a vehicle, comprising the friction brake system ( 1 ) of  claim 1 , wherein the friction brake system ( 1 ) is configured to reduce a rotational speed of a wheel by pushing the brake pad against the friction surface.