Fluid brake device and variable valve timing apparatus

A fluid brake device comprising:

• a case defining a fluid chamber inside;
• magnetic viscosity fluid kept in the fluid chamber, the magnetic viscosity fluid having a viscosity variable in accordance with magnetic flux passing through;
• a control device which carries out variable control of the viscosity of the magnetic viscosity fluid by varying the magnetic flux;
• a rotor having a brake shaft penetrating the case to come into contact with the magnetic viscosity fluid so that the rotor receives a braking torque according to the viscosity of the magnetic viscosity fluid;
• and
• a sealing sleeve arranged in the case to surround the brake shaft along a rotation direction, a seal gap being defined between the sealing sleeve and the brake shaft and communicating with the fluid chamber, wherein
• the sealing sleeve has a flux guide that guides magnetic flux to the brake shaft through the seal gap,
• the brake shaft has
• a magnetic shaft extending in an axis direction,
• a regulation layer that regulates the magnetic flux by covering an outer circumference surface of the magnetic shaft, and
• an exposing part opposing to the flux guide, the brake shaft being exposed from the regulation layer through the exposing part.