Selectively operable rotary drive means

An alternator cooling fan drive includes a radial bearing, the outer race of which mounts the fan within the magnetic field produced by the alternator under load. The bearing has pathways with a curvature close enough to the balls that the races will self-center and transmit a minimum torque to the fan when the magnetic field is weak. The pathway and ball configurations are sufficiently divergent that when the magnetic field pulls in on the fan, the races can misalign and wedge the balls more tightly between the races to transmit more torque to the fan. The fan drive is thus more directly responsive to the need for cooling.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A selectively operable drive means for driving an at least partially ferrous metal cooling fan by a rotary axial shaft of a power source that has the characteristic of producing waste heat proportional to the strength of a magnetic field produced by the power source, comprising,

a rolling element bearing having an outer race mounting the cooling fan within the magnetic field, whereby the magnetic field may act on the cooling fan to pull said portion and the outer race axially toward the power source, an inner race mounted to rotate with the shaft, and a complement of rolling elements disposed between pathways of the races, said rolling elements and pathways engaging one another with a relative configuration that is sufficiently conforming that the races will, when the magnetic field is relatively weak, axially align relative to one another as the pathways seek to center on the rolling elements to a relatively low cooling position with reduced friction between the rolling elements and the pathways and consequent slippage of the fan and outer race relative to the shaft when less heat is generated,

said relative configuration of the rolling elements and pathways also being sufficiently divergent that the races will axially misalign to a relatively high cooling position when a relatively stronger magnetic field acts on the ferrous portion of the fan to, in turn, wedge the rolling elements more tightly between the pathways to transmit more turning force from the inner race, through the rolling elements, and to the outer race and cooling fan to give consequently less slippage, and consequently greater fan speed and cooling, when more waste heat is generated.

2. A selectively operable drive means for driving an at least partially ferrous metal cooling fan by a rotary axial shaft of a power source that has the characteristic of producing waste heat proportional to the strength of a magnetic field produced by the power source, comprising,

a rolling element bearing having an outer race mounting the cooling fan within the magnetic field, whereby the magnetic field may act on the cooling fan to pull said portion and the outer race axially toward the power source, an inner race mounted to rotate with the shaft, and a complement of curved rolling elements disposed between curved pathways of the races, said rolling elements having a radius of curvature smaller than the radius of curvature of the pathways with at least one of said pathways having a radius of curvature sufficiently close to the radius of curvature of the rolling elements that the races will, when the magnetic field is relatively weak, axially align relative to one another as the pathways seek to center on the rolling elements to a relatively low cooling position with reduced friction between the rolling elements and the pathways and consequent slippage of the fan and outer race relative to the shaft when less heat is generated,

at least one of said pathways having a radius of curvature sufficiently larger than the radius of curvature of the rolling elements that the races will axially misalign to a relatively high cooling position when a relatively stronger magnetic field acts on the ferrous portion of the fan to, in turn, wedge the rolling elements more tightly between the pathways to transmit more turning force from the inner race, through the rolling elements, and to the outer race and cooling fan to give consequently less slippage, and consequently greater fan speed and cooling, when more waste heat is generated.

3. A selectively operable drive means for driving at least partially ferrous metal cooling fan by a rotary axial shaft of a power source that has the characteristic of producing waste heat proportional to the strength of a magnetic field produced by the power source, comprising,

a radial ball bearing having an outer race mounting the cooling fan within the magnetic field, whereby the magnetic field may act on the cooling fan to pull said portion and the outer race axially toward the power source, an inner race mounted to rotate with the shaft, and a complement of bearing balls disposed between curved pathways of the races, said bearing balls having a radius smaller than the radius of curvature of the pathways with at least one of said pathways having a radius of curvature sufficiently close to the radius of the bearing balls that the races will, when the magnetic field is relatively weak, axially align relative to one another as the pathways seek to center on the bearing balls to a relatively low cooling position with reduced friction between the bearing balls and the pathways and consequent slippage of the fan and outer race relative to the shaft when less heat is generated,

at least one of said pathways having a radius of curvature sufficiently larger than the radius of the bearing balls that the races will axially misalign to a relatively high cooling position when a relatively stronger magnetic field acts on the ferrous portion of the fan to, in turn, wedge the bearing balls more tightly between the pathways to transmit more turning force from the inner race, through the bearing balls, and to the outer race and cooling fan to give consequently less slippage, and consequently greater fan speed and cooling, when more waste heat is generated.