Balanced bearing assembly
View Patent ↗An engine starter includes a motor housing having an inlet and an outlet for a motive fluid, a fluid-driven motor within the motor housing, the motor including a rotor and a stator, the stator directing a flow of fluid over the rotor, thereby inducing rotation of the rotor about an axis and exerting an axial force on the rotor and an output shaft operably coupled to the rotor such that rotation of the rotor drives rotation of the shaft about the axis. A front and a rear ball bearing assembly support the rotor. A front biasing member is pre-loaded to exert a first biasing load on the front ball bearing assembly and a rear biasing member is pre-loaded to exert a second biasing load on the rear ball bearing assembly in opposition of the axial force exerted on the rotor. The biasing members distribute the axial force between the two ball bearing assemblies.
1. A engine starter comprising:
a motor housing having an inlet for receiving a fluid and an outlet for exhausting the fluid;
a fluid-driven motor within the motor housing, the motor including a rotating mass and a stator, the stator directing a flow of fluid over a portion of the rotating mass, thereby inducing rotation of the rotating mass about an axis and exerting an axial force on the rotating mass;
a front ball bearing assembly supporting a front portion of the rotating mass about the axis and a rear ball bearing assembly supporting a rear portion of the rotating mass rotatably about the axis;
a front biasing member pre-loaded to exert a first biasing load on the front ball bearing assembly relative to the motor housing in opposition of the axial load exerted on the rotating mass; and
a rear biasing member pre-loaded to exert a second biasing load on the rear ball bearing assembly and the rotating mass relative to the motor housing in opposition of the axial force exerted on the rotating mass, the first biasing load being approximately one third of the axial force exerted on the rotor.
2. The engine starter of claim 1 , wherein the front and rear ball bearing assemblies are deep groove radial ball bearing assemblies.
3. The engine starter of claim 1 , wherein the front ball bearing assembly includes an outer race, an inner race and a ball press-fit between the outer race and the inner race, wherein the outer race is coupled to the stator and the inner race is coupled to the rotating mass.
4. The engine starter of claim 3 , wherein the outer race is precision slip fit between an outer retaining ring and the front biasing member.
5. The engine starter of claim 4 , wherein the outer retaining ring is mounted to a hub, the hub being mounted to the stator.
6. The engine starter of claim 1 , wherein the rotating mass includes an output shaft, wherein the rear ball bearing assembly includes an outer race, an inner race and a ball press-fit between the outer race and the inner race, and wherein the outer race is coupled to the motor housing and the inner race is coupled to the output shaft.
7. The engine starter of claim 1 , wherein the rotating mass includes a front output shaft coupled to a front face of a rotor and supported for rotation by the front ball bearing assembly and a rear output shaft coupled to a rear face of the rotor and supported for rotation by the rear ball bearing assembly.
8. The engine starter of claim 1 , wherein the front and rear biasing members are each one of a wave spring, a belleville washer or a coil spring.
9. The engine starter of claim 1 , wherein the rear bearing assembly absorbs the axial force less the first biasing load.
10. The engine starter of claim 1 , wherein the second biasing load is approximately 20 lbs.
11. The engine starter of claim 1 , wherein the front ball bearing assembly absorbs about 30% of the axial force and the rear ball bearing assembly absorbs about 70% of the axial force.
12. A engine starter comprising:
a motor housing having an inlet for receiving a fluid and an outlet for exhausting the fluid;
a fluid-driven motor within the motor housing, the motor including a rotating mass and a stator, the stator directing a flow of fluid over the rotating mass, thereby inducing rotation of the rotating mass about an axis and exerting an axial force on the rotating mass;
a front ball bearing assembly supporting a front portion of the rotating mass rotatably about the axis and a rear ball bearing assembly supporting a rear portion of the rotating mass rotatably about the axis;
a front biasing member pre-loaded to exert a first biasing load on the front ball bearing assembly relative to the motor housing in opposition of the axial load exerted on the rotating mass; and
a rear biasing member pre-loaded to exert a second biasing load on the rotating mass and the rear ball bearing assembly relative to the motor housing in opposition of the axial force exerted on the rotating mass, the second biasing load being about two thirds of the axial force exerted on the rotating mass.
13. A method of operating an engine starter, the method comprising:
directing a flow of fluid over a rotating mass, the flow of fluid inducing rotation of the rotating mass about an axis and exerting an axial force on the rotating mass;
supporting a front portion of the rotating mass shaft for rotation on a front ball bearing assembly and supporting a rear portion of the rotating mass for rotation on a rear ball bearing assembly;
pre-loading a front biasing member against the front ball bearing assembly to apply a load of about one third the axial force exerted by the flow of fluid on the rotating mass in opposition to the axial force; and
pre-loading a rear biasing member against the rear ball bearing assembly to apply a load of about two third the axial force exerted by the flow of fluid on the rotating mass in opposition to the axial force.
14. The method of claim 13 , wherein at least one of the biasing members is one of a wave spring, a belleville washer or a coil spring.
15. The method of claim 13 , wherein pre-loading the rear biasing member includes applying a load of about 20 lbs.