Dynamic pressure gas bearing device

A dynamic pressure assembly comprising:

• a body;
• a solid fixed shaft without a bore therethrough fixed to said body and having a free end;
• a rotational member including a sleeve portion surrounding said fixed shaft with a radial clearance and a bottom portion having an internal surface opposed to an end surface of the free end of the fixed shaft, the rotational member being shiftable relative to the fixed shaft;
• a pressure chamber being formed between the internal surface of said bottom portion and the end surface of said free end;
• means for rotating said rotational member, said rotating means including a rotor fixed to said rotational member at an axial position thereof and a stator opposed to the rotor and fixed to said body;
• means for generating dynamic pressure in said radial clearance and supplying it to said pressure chamber through said radial clearance, the dynamic pressure generating means being formed between the shaft and the sleeve portion of the rotational member;
• and
• pressure regulating means including a restricted flow passage which has an opening in the center of said internal surface to vent a pressurized flow from the pressure chamber, thereby regulating dynamic pressure therein, the rim of said opening defining an annular seat for engagement by a portion of the end surface for closing the opening;
• the arrangement being such that said portion of the end surface of said shaft contacts said annular seat of the rotational member and closes the opening and thereby closes the passage when there is no relative rotation between the shaft and the sleeve or when such relative rotation is only at a low speed insufficient to develop in said pressure chamber a sufficiently high hydrodynamic pressure to axially displace the shaft relative to said sleeve by the hydrodynamic pressure established in said pressure chamber and opens the opening to said pressure chamber and thereby opens the passage when the rotation of the rotational member is at a high speed sufficient to develop a sufficiently high hydrodynamic pressure in said pressure chamber.

A dynamic pressure assembly comprising as members within a closed housing:

• a body;
• a solid fixed shaft without a bore therethrough fixed to said body and having a free end;
• a rotational member including a sleeve portion surrounding said fixed shaft with a radial clearance and a bottom portion having an internal surface opposed to an end surface of the free end of the fixed shaft, the rotational member being shiftable relative to the fixed shaft;
• a pressure chamber formed between the internal surface of said bottom portion and the end surface of said free end;
• means for rotating said rotational member, said rotating means including a rotor fixed to said rotational member at an axial position thereof and a stator opposed to the rotor and fixed to said body;
• a load member secured to said rotational member at a second axial position axially distant from said first position;
• means for generating dynamic pressure in said radial clearance and supplying it to said pressure chamber through said radial clearance, the dynamic pressure generating means being formed between the shaft and the sleeve portion of the rotational member;
• and
• pressure regulating means including a restricted flow passage which has an opening in the center of said internal surface to vent a pressurized flow from the pressure chamber, therby regulating dynamic pressure therein, the rim of said opening defining an annular seat for engagement by a portion of the end surface for closing the opening;
• the arrangement being such that said portion of the end surface of said shaft contacts said annular seat of the rotational member and closes the opening and thereby closes the passage when there is no relative rotation between the shaft and the sleeve or when such relative rotation is only at a low speed insufficient to develop in said pressure chamber a sufficiently high hydrodynamic pressure to axially displace the shaft relative to said sleeve by the hydrodynamic pressure established in said pressure chamber and opens the opening to said pressure chamber and thereby opens the passage when the rotation of the rotational member is at a high speed sufficient to develop a sufficiently high hydrodynamic pressure in said pressure chamber.