Vibration damping device

1. A vibration damping device comprising:

a tubular metal bracket which is connected to any one of a vibration generating portion and a vibration receiving portion;

a first attachment member which is connected to the other of the vibration generating portion and the vibration receiving portion;

a tubular second attachment member which is inserted into the metal bracket;

an elastic body which connects the first attachment member and the second attachment member to each other;

a partition member which partitions a liquid chamber in the second attachment member into a main liquid chamber having the elastic body as a portion of a partition wall and an auxiliary liquid chamber; and

a diaphragm which constitutes a portion of a partition wall of the auxiliary liquid chamber,

wherein one of end opening portions of the second attachment member in an axial direction is closed by the elastic body and the other thereof is closed by the diaphragm,

wherein a fixing portion which fixes the second attachment member is formed on the metal bracket,

wherein a fixed portion which is fixed to the fixing portion of the metal bracket is formed on the second attachment member,

wherein a gap is provided between a portion of an outer circumferential surface of the second attachment member, and a portion of an inner circumferential surface of the metal bracket,

wherein a second seal portion is provided between the fixed portion and the fixing portion, and

wherein the diaphragm includes a lower tubular portion extending from an outer circumferential edge portion of the lower surface of the diaphragm to the inner surface of the metal bracket such that an air chamber is formed by the inner surface of the lower tubular portion of the diaphragm, the lower surface of the diaphragm, and the inner surface of the metal bracket.

2. The vibration damping device according to claim 1 ,

wherein a rigid portion having a higher hardness than that of a heat insulating member which is the second seal portion is further provided between the fixed portion and the fixing portion, and

wherein a plurality of the rigid portions are provided at intervals in a circumferential direction.

3. The vibration damping device according to claim 1 ,

wherein the gap is a vacuum sealed space.

4. The vibration damping device according to claim 1 ,

wherein the diaphragm includes a diaphragm ring which is fitted into the other end portion of the second attachment member in the axial direction and an elastically deformable diaphragm main body which closes an inside of the diaphragm ring,

wherein a first seal portion which continuously extends over the entire circumference of the diaphragm ring and abuts against the metal bracket protrudes from the diaphragm ring,

wherein the one end portion of the second attachment member in the axial direction is fitted into the metal bracket via the second seal portion, and

wherein between the outer circumferential surface of the second attachment member and the inner circumferential surface of the metal bracket, a portion positioned between the first seal portion and the second seal portion is a vacuum sealed space.

5. The vibration damping device according to claim 4 ,

wherein the metal bracket is formed in a tubular shape with a bottom and the first seal portion abuts against an inner surface of the metal bracket.

6. The vibration damping device according to claim 4 ,

wherein an outer surface of the diaphragm main body is exposed to a gas having a higher pressure than a pressure in the sealed space.

7. The vibration damping device according to claim 1 ,

wherein the gap is a vacuum state and the air chamber is filled with an air of atmospheric pressure.

8. The vibration damping device according to claim 7 , further including a tubular diaphragm ring fitted into the lower end portion of the second attachment member,

wherein the outer circumferential portion of the diaphragm is vulcanization-bonded to an inner circumferential surface of the diaphragm ring,

wherein the lower end portion of the second attachment member is caulked radially inward, and thus, the tubular diaphragm ring is fixed, and

wherein the lower end opening portion of the second attachment member is hermetically sealed by the diaphragm.

9. The vibration damping device according to claim 2 ,

wherein the second attachment member further includes:

a main body tubular portion which is formed in a tubular shape coaxially with the center axis,

an inclination tubular portion which extends upward as going radially outward from an upper end opening edge of the main body tubular portion,

an annular upper flange which extends radially outward from an upper end portion of the inclination tubular portion,

an upper tubular portion which extends downward from an outer circumferential edge portion of the upper flange, and

a lower flange which extends radially inward from a lower end opening edge of the upper tubular portion,

wherein the fixed portion includes the upper flange, the upper tubular portion, and the lower flange, and

wherein the fixing portion and the rigid portions of the metal bracket are axially interposed between the upper flange and the lower flange so that the fixed portion is fixed to the fixing portion.