Abstract: A shock absorber (D1) comprises a ring-shaped seal member (3) supported by a cylinder (1) so as to cause a tip to contact the piston rod (2) resiliently. A ring-shaped actuator (4a) exerts an inward force on the outer circumference of the seal member (3). The actuator (4a) is constituted by a polymer material that varies its diameter upon impression of a direct-current voltage. By controlling the direct-current voltage depending on the relative displacement speed between the piston rod (2) and the cylinder (1), the frictional resistance which the seal member (3) exerts on the piston rod (2) is kept large when the relative displacement speed is in an extremely low operation speed region, and is decreased as the actuator (4) decreases the inward force when the relative displacement speed increases above the extremely low operation speed region.

Abstract: A shock absorber (D1) comprises a ring-shaped seal member (3) supported by a cylinder (1) so as to cause a tip to contact the piston rod (2) resiliently. A ring-shaped actuator (4a) exerts an inward force on the outer circumference of the seal member (3). The actuator (4a) is constituted by a polymer material that varies its diameter upon impression of a direct-current voltage. By controlling the direct-current voltage depending on the relative displacement speed between the piston rod (2) and the cylinder (1), the frictional resistance which the seal member (3) exerts on the piston rod (2) is kept large when the relative displacement speed is in an extremely low operation speed region, and is decreased as the actuator (4) decreases the inward force when the relative displacement speed increases above the extremely low operation speed region.

Abstract: According to the present invention there is provided a vehicular height adjusting device capable of diminishing a shock caused by a sudden change in pressure of an accumulator oil chamber at the time of adjusting the vehicular height to adjust the vehicular height in a gentle manner and capable of diminishing a beat noise of an opening/closing valve generated by the vehicular height adjusting operation, thereby improving the comfortableness.