Radial roller bearing, rotary machine including radial roller bearing, and method for designing radial roller bearing
The properties of lubricating oil are utilized to avoid excessive quality in terms of the circularity of roller members while reducing the noise from a radial roller bearing alone during rotation and thereby reducing the noise from a rotary machine. The radial roller bearing includes an outer ring member ( 30 A), a plurality of roller members ( 30 B), and a retainer, and a lubricating oil (O) is supplied between the outer ring member ( 30 A) or a rotating shaft and the roller members ( 30 B). The circularity (ΔR) of the roller members ( 30 B) in a cross section perpendicular to a centerline (CL) thereof is set to be lower than or equal to the minimum oil film thickness (h min ) of an oil film formed by the lubricating oil (O).
1. A radial roller bearing comprising:
an outer ring member;
a plurality of roller members that roll on an inner surface of the outer ring member; and
a retainer,
a lubricating oil being supplied between the outer ring member or a rotating shaft and the roller members,
wherein the circularity of the roller members in a cross section perpendicular to a centerline thereof is set to be lower than or equal to the minimum oil film thickness of an oil film formed by the lubricating oil.
2. The radial roller bearing according to claim 1 , wherein the minimum oil film thickness h min is calculated from the following equation:
h min =R* 2.65 G 0.54 *U 0.7 *W −0.13
wherein R is the relative radius of curvature, G is a material parameter of the lubricating oil, U is a speed parameter of the roller members, and W is a load parameter of the roller members.
3. The radial roller bearing according to claim 2 , wherein the speed parameter U is calculated from a lower limit of a normal-use rotational speed range of a rotary machine with which the radial roller bearing is used.
4. The radial roller bearing according to claim 1 , wherein each of the roller members has an outer surface whose generatrix in an axial direction is curved such that the outer diameter of the roller member decreases slightly in a direction from the center toward an end thereof in the axial direction to avoid stress concentration in a contact area between a portion of the outer surface of the roller member near the end thereof and the inner surface of the outer ring member or an outer surface of the rotating shaft, and the precision of the circularity of the roller members in a cross section perpendicular to the centerline thereof decreases in the direction from the center toward the end thereof in the axial direction.
5. The radial roller bearing according to claim 1 , wherein the circularity is set to 0.8 μm or less if the radial roller bearing is used in an electric compressor for a car air conditioner such that the rotational speed of the roller members is 12,000 to 43,000 rpm.
6. A rotary machine comprising the radial roller bearing according to claim 1 as a bearing part.
7. A method for designing a radial roller bearing provided with
an outer ring member,
a plurality of roller members that roll on an inner surface of the outer ring member, and
a retainer,
a lubricating oil being supplied between the outer ring member and the roller members,
the method comprising:
setting the circularity of the roller members in a cross section perpendicular to a centerline thereof to be lower than or equal to the minimum oil film thickness of an oil film formed by the lubricating oil.
8. The method for designing a radial roller bearing according to claim 7 , wherein the minimum oil film thickness h min is calculated from the following equation:
h min =R* 2.65 G 0.54 *U 0.7 *W −0.13
wherein R is the relative radius of curvature, G is a material parameter of the lubricating oil, U is a speed parameter of the roller members, and W is a load parameter of the roller members.
9. The method for designing a radial roller bearing according to claim 8 , wherein the speed parameter U is calculated from a lower limit of a normal-use rotational speed range of a rotary machine with which the radial roller bearing is used.
10. The method for designing a radial roller bearing according to claim 7 , wherein each of the roller members has an outer surface whose generatrix in an axial direction is curved such that the outer diameter of the roller member decreases slightly in a direction from the center toward an end thereof in the axial direction to avoid stress concentration in a contact area between a portion of the outer surface of the roller member near the end thereof and the inner surface of the outer ring member or an outer surface of a rotating shaft, and the precision of the circularity of the roller members in a cross section perpendicular to the centerline thereof decreases in the direction from the center toward the end thereof in the axial direction.
11. The method for designing a radial roller bearing according to claim 7 , wherein the circularity is set to 0.8 μm or less if the radial roller bearing is used in an electric compressor for a car air conditioner such that the rotational speed of the roller members is 12,000 to 43,000 rpm.