SEALING DEVICE

PROBLEM TO BE SOLVED: To provide a sealing device including a function that seals foreign objects so as to prevent the foreign objects at the exterior of a housing from intruding into the housing and a function that releases a pressure in the housing to the exterior of the housing when the pressure exceeds a predetermined value and having a structure which makes the external foreign objects, such as a scale, less likely to be caught by a slide part and prevents wear of the slide part from accelerating.SOLUTION: A sealing device includes: first and second seal lips which slidably contact with a rotary member in a tight manner thereby sealing foreign objects; and a check lip which opens and closes a pressure release passage formed in the sealing device. When a pressure exceeds a predetermined value, the check lip and any one of the first and second seal lips are opened to release the pressure to the exterior of a housing. At that time, the other of the first and second seal lips is kept slidably contacted with the rotary member in the tight manner. 【課題】ハウジング外部の異物がハウジング内部へ侵入しないように異物をシールする機能およびハウジング内部の圧力が所定値を上回ったときに圧力をハウジング外部へ開放する機能を備える密封装置において、スケール等の外部異物が摺動部に噛み込みにくく、もって摺動部の摩耗が促進されにくい構造の密封装置を提供する。【解決手段】回転部材に摺動可能に密接することにより異物をシールする第１および第２シールリップと、当該密封装置の内部に形成した圧力開放流路を開閉するチェックリップとを有する。圧力が所定値を上回ったときにチェックリップならびに第１および第２シールリップのうちの何れか一方のシールリップが開弁することにより圧力をハウジング外部へ開放し、このとき第１および第２シールリップのうちの他方のシールリップは回転部材に摺動可能に密接した状態を維持する。【選択図】図２