Centrifugal compressor having compound bearing assembly

A compressor comprising:

• a case;
• a rotatable impeller operable to compress a fluid within the case when rotated;
• a shaft that is fixed relative to the impeller and presents a rotational axis;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the shaft bearing being fixed relative to the shaft, said outer race of the case bearing being fixed relative to the case, and said outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• at least one of the bearings having a radial configuration, with the races of said at least one of the bearings presenting opposed ball-receiving grooves that are aligned along a radial line that projects at least substantially radially from the rotational axis,
• said at least one of the bearings having a ball pitch line velocity of at least about 5500 fpm during operation of the impeller.

A compressor comprising:

• a case;
• a rotatable impeller operable to compress a fluid within the case when rotated;
• a shaft fixed relative to the impeller;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the shaft bearing being fixed relative to the shaft, said outer race of the case bearing being fixed relative to the case, and said outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• said balls of each of the bearings being formed of steel,
• at least one of the bearings having a ball pitch line velocity of at least about 8000 fpm during operation of the impeller.

A compressor comprising:

• a case;
• a rotatable impeller operable to compress a fluid within the case when rotated;
• a shaft fixed relative to the impeller;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the shaft bearing being fixed relative to the shaft, said outer race of the case bearing being fixed relative to the case, and said outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• at least one of the cages including an annular wall that presents a plurality ball-receiving openings,
• said at least one of the cages further including a pair of radial projections extending at least substantially around the circumference of the wall, with the ball-receiving openings being located between the projections.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a radially innermost race fixed relative to the shaft, a radially outermost race fixed relative to the case, and an integrally formed common race assembly spaced radially between the innermost and outermost races,
• said common race assembly being moveable relative to the innermost and outermost races,
• said common race assembly presenting an inside race associated with the innermost race and an outside race associated with the outermost race,
• said innermost race weighing a first weight, and said common race assembly weighing a second weight that is equal to or less than about one and one-half times the first weight.

A method of rotatably mounting an impeller shaft of a centrifugal supercharger in a supercharger case, said method comprising the steps of:

• (a) providing a case bearing having an inner diameter;
• (b) providing a shaft bearing having an outer diameter that is greater than the inner diameter;
• (c) altering at least one of the bearings so that the outer diameter of the shaft bearing is smaller than the inner diameter of the case bearing, thereby permitting the shaft bearing to fit within the case bearing;
• (d) fixing an inner race of the case bearing to an outer race of the shaft bearing;
• (e) fixing an outer race of the case bearing to the case of the supercharger;
• and
• (f) fixing an inner race of the shaft bearing to the impeller shaft.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a radially outward case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, with the inner race of the shaft bearing being fixed relative to the shaft and the outer race of the case bearing being fixed relative to the case,
• said compound bearing assembly including a coupler located between and fixedly interconnecting the outer race of the shaft bearing and the inner race of the case bearing,
• said coupler having a first coefficient of thermal expansion, said outer race of the shaft bearing having a second coefficient of thermal expansion, and said inner race of the case bearing having a third coefficient of thermal expansion,
• said first coefficient of thermal expansion being greater than the second and third coefficients of thermal expansion,
• said coupler weighing less than each of the outer race of the shaft bearing and the inner race of the case bearing.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a radially outward case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the shaft bearing being fixed relative to the shaft, said outer race of the case bearing being fixed relative to the case, and said outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• said shaft bearing being a 300 Series bearing.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a pair of spaced apart bearing assemblies supporting the shaft on the case,
• a first one of the pair of bearing assemblies comprising a compound bearing assembly that includes a first shaft bearing and a radially outward first case bearing,
• a second one of the pair of bearing assemblies including a second shaft bearing,
• said bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the first shaft bearing being fixed relative to the shaft, said outer race of the first case bearing being fixed relative to the case, and said outer race of the first shaft bearing and inner race of the first case bearing being fixed relative to one another,
• said inner race of the second shaft bearing being fixed relative to the shaft,
• said second shaft bearing weighing less than the first shaft bearing.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a radially outward case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the shaft bearing being fixed relative to the shaft, said outer race of the case bearing being fixed relative to the case, and said outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• said case bearing presenting a case bearing weight,
• said compound bearing assembly being axially preloaded to a preload amount, wherein the preload amount is determined according to the equation:
• preload amount≦38×(case bearing weight)0.82.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a radially outward case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, with the inner race of the shaft bearing being fixed relative to the shaft, the outer race of the case bearing being fixed relative to the case, and the outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• said compound bearing assembly being under substantially no axial preload.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine
• said shaft presenting a cantilevered section, with the impeller being located on the cantilevered section;
• and
• a compound bearing assembly rotatably supporting the shaft on the case, said compound bearing assembly including a shaft bearing and a radially outward case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, with the inner race of the shaft bearing being fixed relative to the shaft, the outer race of the case bearing being fixed relative to the case, and the outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• said inner race of the shaft bearing presenting an inside shaft-engaging surface,
• said shaft-engaging surface being rotated at speeds of at least about 5500 fpm during operation of the impeller.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine,
• said shaft presenting a cantilevered section, with the impeller being located on the cantilevered section;
• and
• a compound bearing assembly rotatably supporting the shaft on the case,
• said compound bearing assembly including a shaft bearing and a radially outward case bearing,
• said shaft and case bearings each including relatively moveable inner and outer races, a cage, and a plurality of balls rotatably positioned within the cage between the races,
• said inner race of the shaft bearing being fixed relative to the shaft, said outer race of the case bearing being fixed relative to the case, and said outer race of the shaft bearing and inner race of the case bearing being fixed relative to one another,
• said balls of the shaft bearing presenting a first common diameter and said balls of the case bearing presenting a second common diameter, with the first common diameter being equal to or greater than the second common diameter.

A centrifugal supercharger for supercharging an engine of a vehicle, said supercharger comprising:

• a case;
• a rotatable impeller operable to compress induction fluid for the engine when rotated;
• a shaft fixed relative to the impeller and drivingly connectable to the engine;
• and
• a pair of spaced apart bearing assemblies supporting the shaft on the case,
• a first one of the pair of bearing assemblies comprising a compound bearing assembly that includes a first shaft bearing and a radially outward first case bearing,
• a second one of the pair of bearing assemblies including a second shaft bearing,
• said bearings each including relatively moveable inner and outer races,
• said inner race of the first shaft bearing being fixed relative to the shaft, said outer race of the first case bearing being fixed relative to the case, and said outer race of the first shaft bearing and inner race of the first case bearing being fixed relative to one another,
• said inner race of the second shaft bearing being fixed relative to the shaft, and said outer race of the second shaft bearing contacting the case.