Patent ID: 9726246
Date: 2017-08-08
CPC Classifications: F16F

Claim:
1. An antivibration device comprising: a first bush; a second bush; and a coupling member that couples the first bush and the second bush to each other, wherein each of the first bush and the second bush has an inner attachment portion that is attached to a member on a vehicle, an outer attachment portion coupled to the coupling member, and an antivibration base made of rubber-like elastic material that is provided between an outer circumferential side of the inner attachment portion and an inner circumferential side of the outer attachment portion, wherein the inner attachment portion of the first bush has a convex portion protruding from an intermediate position of the inner attachment portion of the first bush, wherein the antivibration base of the first bush includes a stopper portion attached to the inner circumferential side of the outer attachment portion, wherein the antivibration base of the second bush includes a hollow portion, a protruding portion that protrudes from the outer circumferential side of the inner attachment portion into the hollow portion, and a viscous fluid that is enclosed in the hollow portion and that is agitated by the protruding portion to generate resistance due to relative displacement between the inner attachment portion and the outer attachment portion of the second bush, wherein when a load input in an axial direction of the coupling member is a predetermined value or smaller, the stopper portion of the first bush has a preliminary compression pressing on the outer circumferential side of the convex portion of the inner attachment portion of the first bush in the axial direction of the coupling member away from the coupling member and the protruding portion of the second bush remains in the hollow portion thereby creating a dynamic spring constant of the first bush that is larger than that of the second bush, and a loss factor of the second bush that is larger than that of the first bush, and wherein when the load input in the axial direction of the coupling member exceeds the predetermined value, the stopper portion of the first bush is released from pressing on the convex portion of the inner attachment portion of the first bush in the axial direction of the coupling member and the protruding portion of the second bush is pressed against the inner circumferential side of the outer attachment portion of the second bush in the axial direction of the coupling member towards the coupling member thereby creating the dynamic spring constant of the first bush that is smaller than that of the second bush.