Source: {"pile_set_name": "USPTO Backgrounds"}

1. Field of the Invention
The present invention relates to an electromagnetic actuator by which a mover is driven in relation to a stator by energization to a coil, and to an active vibration damper and a fluid-filled active vibration damping device using the same.
2. Description of the Related Art
From the past, an electromagnetic actuator has been known as one type of vibration damping actuator used for actively controlling the vibration damping characteristics of a vibration damping device by applying active oscillation force to a member subject to vibration damping. With the electromagnetic actuator, the mover is attached so as to be displaceable relative to the stator, and by energization to a coil member attached on one of either the stator or the mover, the mover is driven in relation to the stator.
However, as shown in Japanese Patent No. JP-B-4852030, with the electromagnetic actuator, the stator and the mover are linked to each other by a plate spring, and by elastic deformation of the plate spring in the thickness direction, displacement of the mover in relation to the stator is allowed, and the mover and stator are aligned to each other in the radial direction of the plate spring.
Also, with JP-B-4852030, so that sufficient displacement is allowed of the mover in the thickness direction of the plate spring, a plurality of lightening holes are formed on the plate spring, and the plate spring has a constitution with which a center attachment part attached to the mover and an outer circumference attachment part attached to the stator are integrally linked to each other by a plurality of connection arm parts. This connection arm part extends in the radial direction while being inclined in the circumferential direction, with one end being integrally connected to the center attachment part, and the other end being integrally connected to the outer circumference attachment part.
Furthermore, with the electromagnetic actuator, as with JP-B-4852030, there are cases when a plurality of plate springs are used overlapping. In this case, the plate spring material, thickness dimension and the like can be set individually according to the required spring characteristics or the like, so with a plurality of plate springs, there are cases when these will be different from each other.
However, when palate springs with different materials, thickness dimensions and the like are used overlapping, due to differences in deformation volume in relation to ambient temperature changes, there can be mutual differences in the shape of the plate springs with a thickness direction view (particularly the shape of the connection arm part), and by local stress concentration occurring at the connection arm part, there is the risk of a decrease in durability of the plate springs.