Oil seal

An oil seal constructed by a combination of a lip seal member which is fixed to an inner periphery of a shaft hole of a housing and a slinger which is fixed to a rotary shaft inserted to the shaft hole, and inhibiting a dust in an external side from entering into a machine inner side as well as inhibiting a sealed fluid in the machine inner side from leaking to the external side,

• wherein the slinger is integrally provided with a tubular portion that is fixed to the rotary shaft and a flange portion that extends in a direction away from the tubular portion, the flange portion being provided with a thread groove that carries out a pumping action, and
• wherein the lip seal member is an elastic body that includes:
• a main lip that is located directly adjacent the machine inner side, and that slidably contacts with the flange portion of the slinger so as to seal the sealed fluid;
• a dust lip that is located on an external side of the main lip and that includes a projection, the projection of the dust lip having an elongated prism-shape;
• and
• an intermediate lip that is arranged at an intermediate position between the main lip and the dust lip, the intermediate lip extending in a direction toward the main lip such that a lip end of the intermediate lip and a lip end of the main lip are oriented in an opposite direction in comparison to a lip end of the dust lip, and the lip end of the intermediate lip contacts an outer peripheral surface of the tubular portion of the slinger over an entire periphery thereof,
• wherein the intermediate lip is provided with an annular first projection having a first height and a circumferentially partial second projection having a second height greater than the first height on a surface of the intermediate lip that faces the outer peripheral surface of the tubular portion of the slinger, the first height and the second height being relative to the surface of the intermediate lip that faces the outer peripheral surface of the tubular portion of the slinger, and the second projection being arranged orthogonal to the first projection and having a ship-bottom shape such that the second height and a width of the second projection are greatest at a center portion in the longitudinal direction of the second projection,
• the first projection inhibits dust from passing the lip end of the intermediate lip while still allowing air to flow past the lip end of the intermediate lip by forming a micro gap relative to the outer peripheral surface of the tubular portion of the slinger without contacting the outer peripheral surface of the tubular portion of the slinger,
• the second projection maintains the micro gap when eccentricity is generated in the rotary shaft by having the second height that is greater than the first height of the first projection,
• the elongated prism-shape of the projection on the dust lip includes a length defined by a first pair of side sections that each extend in a circumferential direction of the dust lip and a width that defined by a second pair of side sections that each extend in a direction parallel with an axial length of the shaft, and
• the width of the second projection faces the first pair of side sections that each extend in the circumferential direction of the dust lip.