Steel brake piston for a hydraulic brake

A cold-formed steel brake piston for a hydraulic disk brake, constructed as a pot which is open on one side comprising:

• a base, and
• a wall including an inner wall and an outer wall, having a directed substantially rotational symmetry with respect to a piston longitudinal axis (A) and with a wall thickness (s) varied in sections with a differently varied inner diameter (di),
• wherein the wall sections, which are formed in a directional manner by ironing substantially parallel to the piston longitudinal axis (A), adjoin the base configured orthogonally,
• wherein the outer wall has, on an end-side wall section, a radially inwardly groove which is open in a radially outward direction and which forms, radially at the inside, a groove bead projection,
• wherein the open side of the pot ends as a bearing for a friction pad backplate, and the bearing extends as a planar piston end surface orthogonally with respect to the piston longitudinal axis (A), and having integrated interfaces which serve a) for the fixing between friction pad and steel brake piston and b) as support bearing for spring mounting of the friction pad,
• wherein, proceeding from the piston end surface, a minimum piston inner diameter (dimin) is axially set back in the direction of the base by a multiple of a minimum piston wall thickness (smin), and the minimum piston inner diameter (dimin) is formed by the groove bead projection,
• wherein a quotient of a wall thickness (sb) of the base in relation to the minimum piston wall thickness (smin) of a base-side wall section, (sb/smin), is provided so as to have a value of 1.4-2.1, and
• wherein a diameter difference between the minimum inner diameter (dimin) and a maximum inner diameter (dimax) is at least approximately 2 mm.

A cold-formed steel brake piston for a hydraulic disk brake, constructed as a pot which is open on one side comprising:

• a base, and
• a wall including an inner wall and an outer wall, having a directed substantially rotational symmetry with respect to a piston longitudinal axis (A) and with a wall thickness (s) varied in sections with a differently varied inner diameter (di),
• wherein the wall sections, which are formed in a directional manner by ironing substantially parallel to the piston longitudinal axis (A), adjoin the base configured orthogonally,
• wherein the outer wall has, on an end-side wall section, a radially inwardly groove which is open in a radially outward direction and which forms, radially at the inside, a groove bead projection
• wherein the open side of the pot ends as a bearing for a friction pad backplate, and the bearing extends as a planar piston end surface orthogonally with respect to the piston longitudinal axis (A), and having integrated interfaces which serve a) for the fixing between friction pad and steel brake piston and b) as support bearing for spring mounting of the friction pad,
• wherein, proceeding from the piston end surface, a minimum piston inner diameter (dimin) is axially set back in the direction of the base by a multiple of a minimum piston wall thickness (smin), and the minimum piston inner diameter (dimin) is formed by the groove bead projection,
• wherein a quotient of a wall thickness (sb) of the base in relation to the minimum piston wall thickness (smin) of a base-side wall section, (sb/smin), is provided so as to have a value of 1.4-2.1, and
• wherein an elongated length of the end-side wall section amounts to at least approximately 5 mm.