Filter element

1. A filter element having a hollow shape and for removing dust and a liquid mixed in compressed air, the filter element comprising:

a filter assembly that has a hollow shape;

an upper end cap that is attached to an upper end of the filter assembly, which is one of ends of the filter assembly in an axial direction; and

a lower end cap that is attached to a lower end of the filter assembly that is opposite to the upper end of the filter assembly,

wherein the filter assembly includes

a central space portion into which compressed air is introduced,

a hollow inner-core member that has a porous structure and that surrounds the central space portion,

a hollow inner-filter member that surrounds an outer periphery of the inner-core member,

a hollow outer-core member that has a porous structure and that surrounds an outer periphery of the inner-filter member, and

a hollow outer-filter member that surrounds an outer periphery of the outer-core member,

wherein the upper end cap includes

a hollow inner peripheral wall that is fitted into an upper end portion of a central space portion,

an intermediate wall that surrounds an outer periphery of an upper end portion of the outer-core member, and

an outer peripheral wall that surrounds an outer periphery of an upper end portion of the outer-filter member, an inner peripheral wall, the intermediate wall, and the outer peripheral wall being arranged in this order in a direction from the center of the upper end cap toward an outer periphery of the upper end cap,

wherein a height of the intermediate wall is smaller than a height of the outer peripheral wall and a height of the inner peripheral wall,

wherein the inside of the upper end cap is filled with an adhesive having a depth that enables the intermediate wall to be embedded in the adhesive, and

wherein the filter assembly and the upper end cap are bonded to each other by the adhesive in a state where an upper end portion of the filter assembly is inserted in the adhesive and the intermediate wall enters into the outer-filter member around the outer-core member.

2. The filter element according to claim 1 ,

wherein the intermediate wall is formed at a position between the outer peripheral wall and an intermediate position between the inner peripheral wall and the outer peripheral wall.

3. The filter element according to claim 1 ,

wherein the height of the intermediate wall is half of the height of the outer peripheral wall or smaller.

4. The filter element according to claim 1 ,

wherein a lower end portion of the intermediate wall is located at a position lower than at least an upper end portion of the inner-core member, an upper end portion of the inner-filter member, and the upper end portion of the outer-core member among the inner-core member, the inner-filter member, the outer-core member, and the outer-filter member of the filter assembly.

5. The filter element according to claim 1 ,

wherein the inner-filter member is folded in a pleated manner.

6. The filter element according to claim 1 ,

wherein the intermediate wall is continuous along a whole periphery.

7. The filter element according to claim 1 ,

wherein the intermediate wall is formed in a discontinuous state by arranging a plurality of wall portions such that the plurality of wall portions are spaced apart from one another.

8. The filter element according to claim 1 ,

wherein the intermediate wall is formed of a plurality of annular walls having different diameters so as to have a multiple structure.