Magnetorheological fluid damper
A magnetorheological fluid damper using magnetorheological fluid, whose viscosity changes according to an intensity of a magnetizing field, as working fluid includes a cylinder in which magnetorheological fluid is sealed, a piston which is slidably arranged in the cylinder, a first fluid chamber and a second fluid chamber which are partitioned by the piston, a main flow passage which is open on opposite end surfaces of the piston and allows communication between the first and second fluid chambers, an electromagnetic coil which generates a magnetizing field to be applied to the magnetorheological fluid flowing in the main flow passage, a bypass flow passage which is formed at a position less affected by the magnetizing field generated by the electromagnetic coil than the main flow passage, and a bypass branching portion which branches the bypass flow passage from the main flow passage.
1. A magnetorheological fluid damper using magnetorheological fluid, whose viscosity changes according to an intensity of a magnetizing field, as working fluid, comprising:
a cylinder in which the magnetorheological fluid is sealed;
a piston which is slidably arranged in the cylinder;
a first fluid chamber and a second fluid chamber which are partitioned by the piston;
a main flow passage which is open on opposite end surfaces of the piston and allows communication between the first and second fluid chambers;
an electromagnetic coil which generates a magnetizing field to be applied to a portion of the magnetorheological fluid which is flowing in the main flow passage;
a bypass flow passage which is formed at a position less affected by the magnetizing field generated by the electromagnetic coil than a position of the main flow passage; and
a bypass branching portion which branches the bypass flow passage from the main flow passage,
the piston including:
a piston core, the bypass flow passage being disposed in the piston core; and
a piston plate which defines the bypass branching portion as an annular space between the piston core and the piston plate.
2. The magnetorheological fluid damper according to claim 1 , wherein:
the piston includes a flux ring which is provided on an outer periphery of the piston core and forms the main flow passage between the piston core and the flux ring;
the piston plate is fixed to the piston core and supports an end part of the flux ring; and
the bypass branching portion is defined between a step portion formed on the piston core and the piston plate.
3. The magnetorheological fluid damper according to claim 2 , wherein:
the piston plate is provided on one end of the flux ring;
one end of the bypass flow passage is open on the bypass branching portion; and
another end of the bypass flow passage is open to either one of the first and second fluid chambers.
4. The magnetorheological fluid damper according to claim 2 , wherein:
the piston plate is provided on two opposite ends of the flux ring; and
two opposite ends of the bypass flow passage are open to the main flow passage.