A braking device capable of generating a larger braking force is provided. The present invention provides a braking device including a housing ( 10 ) having a peripheral wall ( 11 ), a coil holding unit ( 20 ) provided inside the housing ( 10 ), a coil ( 30 ) held by the coil holding unit ( 20 ), a first activation chamber ( 40 ) formed between an inner peripheral surface of the peripheral wall ( 11 ) of the housing ( 10 ) and an outer peripheral surface of the coil holding unit ( 20 )arranged in parallel with the inner peripheral surface, a rotor ( 60 ) provided inside of the first activation chamber ( 40 ), and a magnetorheological fluid ( 80 ) filling an inside of the first activation chamber ( 40 ), wherein the inner peripheral surface of the peripheral wall ( 11 ) of the housing ( 10 ) is at a position farthest from the center of rotation of the rotor ( 60 ) in a radial direction in the inside of the housing ( 10 ), wherein the rotor ( 60 ) is in a cylindrical shape including an outer peripheral surface having a gap between the outer peripheral surface of the rotor ( 60 ) and the inner peripheral surface of the peripheral wall ( 11 ) of the housing ( 10 ) and an inner peripheral surface having a gap between the inner peripheral surface of the rotor ( 60 ) and the outer peripheral surface of the coil holding unit ( 20 ), and wherein a shearing stress of the magnetorheological fluid ( 80 ) acts on the inner peripheral surface and the outer peripheral surface of the rotor ( 60 ).
1. A braking device comprising:
a housing having a peripheral wall and an end wall;
a coil holding unit provided inside the housing;
a coil held by the coil holding unit;
a first activation chamber formed between an inner peripheral surface of the peripheral wall and an outer peripheral surface of the coil holding unit arranged in parallel with the inner peripheral surface;
a second activation chamber formed between the end wall and the coil holding unit;
a rotor provided inside of the first activation chamber;
a plate provided inside of the second activation chamber, wherein the plate rotates together with the rotor; and
a magnetorheological fluid filling an inside of the first and second activation chambers,
wherein the inner peripheral surface of the peripheral wall is at a position farthest from a center of rotation of the rotor in a radial direction in the inside of the housing,
wherein the rotor is in a cylindrical shape including an outer peripheral surface having a gap between the outer peripheral surface of the rotor and the inner peripheral surface of the peripheral wall and an inner peripheral surface having a gap between the inner peripheral surface of the rotor and the outer peripheral surface of the coil holding unit,
wherein the peripheral wall, the end wall, the rotor and the plate are a soft magnetic material respectively, and
wherein a shearing stress of the magnetorheological fluid acts on the inner peripheral surface and the outer peripheral surface of the rotor and both surfaces of the plate.
2. The braking device according to claim 1 , wherein the coil holding unit and the peripheral wall are made of steel-based sintered metal having a density equal to or more than 7 g/cm 3 .