Seal device of the non-contact type

In a seal device of the non-contact type, comprising:

• a casing;
• a rotating shaft extending through the casing;
• a seal ring arranged between the outer circumference of the rotating shaft and the inner circumference of the casing and rotated together with the rotating shaft;
• a stationary ring arranged between the outer circumference of the rotating shaft and the inner circumference of the casing and held by the casing;
• and seal faces formed by those end faces of the rotating seal ring and the stationary ring which are opposed to each other and which are perpendicular to the axes of the rotating seal ring and the stationary ring, respectively, wherein dynamic pressure generating grooves are formed in one of the seal faces at a certain interval, extending from the outer circumferential rim of the seal face in the radial direction thereof, said seal device being characterized in that said grooves each have:
• a first spiral shaped portion extending from said outer circumferential rim, thereby presenting a leading edge with respect to the direction of rotation;
• a second terminal portion continuous with said first spiral shaped portion and extending from said leading edge in the direction of rotation, said second terminal portion having a closed end so that it does not extend about the entire circumference of the sealing face;
• said second terminal portion being tapered in the direction of rotation, becoming narrower as it comes nearer to its closed end;
• the ratio of the radial width of the dynamic pressure generating grooves to the radial width of the entire seal face is 0.5-0.7;
• and
• the ratio of the radial width of the second terminal portions to the radial width of the entire pressure generating grooves is 0.6-0.7.