Installation structure for lip type seal

1. An installation structure which is installed to an inner periphery of a shaft hole provided in a housing, comprising:

a lip seal slidably in close contact with a peripheral surface of a shaft inserted to said shaft hole; and

a cartridge arranged on an outer peripheral side of said lip seal,

wherein said lip seal includes a first lip seal member, a second lip seal member, a backup ring, and a retaining ring;

said first lip seal member having:

an integrally formed cylinder portion;

an annular radial portion integrally formed from an end portion of said cylinder portion, said annular radial portion being at a sealed fluid side of said lip seal and being located toward an inner side of said cylinder portion in a radial direction of said first lip seal member; and

a first seal lip portion integrally formed on an inner peripheral end portion of said radial portion, said first seal lip portion extending toward said sealed fluid side, and

said second lip seal member having:

an annular flat surface portion; and

a second seal lip portion integrally formed on an inner peripheral end portion of said annular flat surface portion so as to slope toward said sealed fluid side,

said backup ring having an annular flat shape and being arranged further toward an atmospheric air side of said lip seal than said second lip seal member so as to back up said second lip seal member, and

said retaining ring having:

an integrally formed tubular portion;

a fold-back portion provided continuously to a sealed fluid side end portion of said tubular portion;

an inward flange portion provided continuously to said fold-back portion; and

a caulking portion provided on an atmospheric air side end portion of said tubular portion,

said cylinder portion of said first lip seal member being arranged at an outer peripheral side of said tubular portion of said retaining ring, and said second seal lip member and said backup ring being caulked and fixed between said inward flange portion and said caulking portion of said retaining ring, and

said cartridge having:

a small-diameter tube portion;

an annular step portion integrally formed on a sealed fluid side end portion of said small-diameter tube portion toward an outer side of said small-diameter tube portion in a radial direction;

a large-diameter tube portion integrally formed on an outer peripheral end portion of said annular step portion toward said sealed fluid side, said annular step portion having an S-shaped cross sectional shape, or an approximately S-shaped cross sectional shape, so that said small-diameter tube portion and said large-diameter tube portion partly overlap in an axial direction of said cartridge, and

said cartridge being fitted to an inner peripheral surface of said shaft hole at an outer peripheral surface of said large-diameter tube portion, while said lip seal is fitted to an inner peripheral surface of said small-diameter tube portion.

2. An installation structure as claimed in claim 1 , wherein the cartridge integrally has an outward flange shaped engagement portion for defining an insertion depth when the cartridge is inserted to the shaft hole on an end portion in an axial direction of the large-diameter tube portion, and said cartridge integrally has an inward flange shaped engagement portion for defining an insertion depth when the lip seal is inserted to the cartridge on an end portion in an axial direction of the small-diameter tube portion, and a gap in a radial direction is set between the outer peripheral surface of the small-diameter tube portion and the inner peripheral surface of the shaft hole when the cartridge is fitted to the inner peripheral surface of the shaft hole by the outer peripheral surface of the large-diameter tube portion.

3. An installation structure as claimed in claim 1 , wherein the cartridge has an outer peripheral seal constructed by an elastic membrane interposed between the cartridge and the inner periphery of the shaft hole to serve for a sealing operation, on the outer peripheral surface of the large-diameter tube portion.

4. An installation structure as claimed in claim 2 , wherein the cartridge has an outer peripheral seal constructed by an elastic membrane interposed between the cartridge and the inner periphery of the shaft hole to serve for a sealing operation, on the outer peripheral surface of the large-diameter tube portion.