1.  Field of the Invention
This invention relates to a waterproof connector having an annular packing mounted on an outer periphery of a fitting portion of a connector housing. 
2.  Description of the Related Art
There is known a waterproof connector of the type in which an annular packing is mounted on an outer periphery of a tubular fitting portion of a connector housing, and when a fitting portion of a mating connector is fitted to the tubular fitting portion, the annular packing forms a seal between the two fitting portions.  For example, in a female terminal connector 500 shown in FIG.  5 and disclosed in Patent Literature 1, a tubular fitting portion 505 for receiving female terminals 503 therein is formed within a tubular case member 501, and an annular packing 507 is mounted on an outer periphery of the tubular fitting portion 505.  A cap member 509 is fitted on a distal end portion of the tubular fitting portion 505, and the packing 507 is held between the cap member 509 and a support wall 511. 
As shown in FIG.  6, the packing 507 has a two-layer structure and therefore has two annular layers, that is, an outer peripheral layer 513 and an inner peripheral layer 515, adhesively bonded together as shown in FIG.  6.  Annular ridges 519 are formed on an outer peripheral surface 517 of the outer peripheral layer 513, so that this outer peripheral surface 517 has a concave-convex shape (that is, a corrugated shape).  Annular grooves 523 are formed in an inner peripheral surface 521 of the inner peripheral layer 515, so that this inner peripheral surface 521 has a shallow concave-convex shape. 
When the female terminal connector 500 is connected to a male terminal connector (mating connector) 525 as shown in FIG.  7, a fitting portion 527 of the male terminal connector 525 is fitted on the outer periphery of the cap member 509, and also a distal end portion of this fitting portion 527 is fitted on the outer periphery of the packing 507.  As a result, the ridges 519 of the packing 507 mounted on the tubular fitting portion 505 are elastically deformed to be held in intimate contact with an inner peripheral surface of the fitting portion 527, thereby forming a seal between the fitting portions 505 and 527 of the female and male terminal connectors 500 and 525, thus preventing the intrusion of water, dirt and dust. 
Patent Literature 1: JP-A-2002-151194
A water-tight and air-tight sealing performance of the packing 507 is obtained by suitably deforming the ridges 519. 
However, when the packing 507 was formed into the oilless type, the coefficient of friction increased, so that its sliding performance was lowered.  In this case, a distal end of an apex portion 519a of the ridge 519 was pulled or deformed in a direction (direction of arrow a) of fitting of the fitting portion 527, and an improperly-deformed portion 529, for example, of an overhanging shape was formed as shown in FIG.  8.  Such deformed portion 529 caused the catching, turning-up and buckling of the packing, and increased an inserting resistance, and also the strength of intimate contact of the packing with the inner peripheral surface of the fitting portion 527 was lowered, and as a result the inserting ability and the waterproof performance were lowered.