| 摘要 |
<p>A controllable brake, such as a magnetorheological (MR) fluid brake (20) including a rotor (28) which is preferably disc-like and rotatably supported by a shaft (30) which is rotatably supported by bushings (42) received within a housing (22). A coil assembly (48) is electrically energized to create a changeable magnetic field within a pole piece (32), which is preferably manufactured from a powdered metal material, which most preferably has a density of between about 6.8 and about 7.0 gm/cm3. A magnetically-soft medium, such as an MR fluid (23) which preferably includes magnetically-soft particles disbursed in a carrier liquid is contained within first and second gaps (86 and 88) located between the pole piece (32) and rotor (28). The MR fluid's (23) rheology is controlled by the generated magnetic field to vary the operating torque of the MR brake (20). In one aspect, the brake (20) includes a magnetic saturation zone (25) to reduce the propensity of magnetizing the shaft (30). In another aspect, the pole piece halves (24 and 26) are received in radially spaced pole pockets (37) formed in the housing (22) and preferably include an axial bias spring (70) to ensure intimate contact therebetween. In another aspect, a lip projection (76) traps MR fluid (23) between the lip projection (76) and shaft (30) and minimizes fluid exposure to the shaft seal (44). In another aspect, cooling fins (55) or a projection (53) restrains rotation of the housing (22). In yet another aspect, a spring (46) centers the rotor (28) relative to the housing (22).</p> |
