Patent ID: 8505889

Claim:
A vibration-isolating bush comprising: a shaft member; an outer cylinder enclosing the shaft member axially in parallel; a rubbery elastic member interposed between the shaft member and the outer cylinder; and an intermediate cylinder interposed between the shaft member and the outer cylinder axially in parallel, the intermediate cylinder surrounding an outer circumference of the shaft member, wherein the shaft member has an axially central portion including a first bulging portion of a spherical zone shape bulging transversely outward, the intermediate cylinder encloses the first bulging portion and has an axially central portion including a second bulging portion of a spherical zone shape bulging transversely outward, the second bulging portion having an inner circumference with a first spherical recess corresponding to a first spherical bulge of the first bulging portion, the outer cylinder encloses the second bulging portion and has a second spherical recess corresponding to a second spherical bulge of an outer circumference of the second bulging portion, the rubbery elastic member includes an inner elastic portion adhered respectively to the outer circumference of the shaft member containing the first spherical bulge and to the inner circumference of the intermediate cylinder containing the first spherical recess, and an outer elastic portion adhered respectively to the outer circumference of the intermediate cylinder containing the second spherical bulge and to an inner circumference of the outer cylinder containing the second spherical recess, the outer elastic portion being compressed in the transverse direction and the inner elastic portion being uncompressed in the transverse direction, with the inner elastic portion having an axial size measured across a center of thickness of the inner elastic portion being larger than an axial size of the outer elastic portion measured across a center of thickness of the outer elastic portion, to bring a spring constant of the outer elastic portion in the transverse direction closer to a spring constant of the inner elastic portion in the transverse direction, said thickness of the inner elastic portion being measured from the inner elastic portion adhered to the outer circumference of the shaft member to the inner circumference of the intermediate cylinder and said thickness of the outer elastic portion being measured from the outer elastic portion adhered to the outer circumference of the intermediate cylinder to the inner circumference of the outer cylinder, and the inner elastic portion and the outer elastic portion each having annular hollow portions depressed in an axially inward direction to end at the axial end faces of the inner elastic portion and the outer elastic portion.