Seal for a servo medium of a torque transmission device

A seal for a servo medium of a torque transmission device comprising:

• a stationary member having a bore and a body rotating about a central longitudinal axis and extending in this bore with a part of an outer peripheral surface, a material of the body having a smaller coefficient of thermal expansion than that of the member,
• at least one passage for the servo medium opens into the bore of the member, while the body is intersected by one channel per passage of the member, an inlet of each channel being aligned to the respective passage, said inlet permitting a transfer of the servo medium from the member to the body at least in defined angular positions of the body and the member relative to each other,
• the part of the outer peripheral surface of the body extending in the bore is configured as a radial bearing surface of the body, which radial bearing surface has a diameter that is either equal to or, due to a groove-shaped recess, smaller than a diameter of the rest of the outer peripheral surface of the body,
• the radial bearing surface of the body is limited by an axial bearing of the body, which axial bearing is defined either by inner end faces of two annular extensions on the outer peripheral surface of the body or by side walls of the recess in the outer peripheral surface of the body, wherein:
• a sealing between the member and the body of the torque transmission device is effected exclusively through two annular sealing gaps formed between the axial bearing of the body and side faces of the member, and
• a gap width of the sealing gaps can be decimated with rising operational temperature of the servo medium with utilization of a greater coefficient of thermal expansion of the material of the member compared to that of the body, so that through all operational temperatures of the servo medium an almost same, low level of leakage of servo medium is achieved.