Bearing assembly for downhole motor
View Patent ↗A downhole motor for drilling and servicing of wells has an elongated outer housing and an elongated mandrel rotatably disposed within the housing. A primary thrust bearing is disposed between the lower end of the housing and the mandrel, and transfers axial loads downward from the housing to the mandrel, and then to the drill bit or other tool mounted on the lowermost end of the mandrel. The placement of the primary thrust bearing permits it to extend radially to the outer diameter of the housing. One preferred embodiment of the primary thrust bearing comprises bearing surfaces of polycrystalline diamond compact (“PDC”) material.
1. A downhole motor, comprising:
an elongated housing having a longitudinal bore therethrough and a lower end comprising an end section;
an elongated mandrel rotatably disposed within said bore of said housing and extending beyond said lower end of said housing;
a primary thrust bearing disposed between said lower end of said elongated housing end section and said elongated mandrel, whereby downward axial loads can be transferred from said elongated housing to said elongated mandrel;
one or more radial bearings disposed within said housing, between said mandrel and said housing; and
a secondary thrust bearing assembly disposed between said housing and said mandrel, said secondary thrust bearing assembly comprising:
a plurality of vertically stacked ball bearings with races disposed between said ball bearings, said ball bearings having a diameter substantially equal to a distance between said housing and said mandrel, whereby radial forces can be transferred between said housing and said mandrel,
said races having a radial dimension less than said diameter of said ball bearings, whereby said races do not contact said mandrel or said housing,
wherein at least one of said radial bearings comprises a sleeve assembly positioned between said secondary thrust bearing assembly and said primary thrust bearing with a sleeve fixed to said housing, a lower end of said secondary thrust bearing assembly bearing against said sleeve, and
wherein said mandrel comprises a downwardly facing shoulder bearing against a top end of said secondary thrust bearing assembly, whereby upward axial loads can be transferred from said mandrel, through said secondary thrust bearing assembly, to said sleeve, and thence to said housing.
2. A downhole motor, comprising:
an elongated housing having a longitudinal bore therethrough and a lower end comprising an end section;
an elongated mandrel rotatably disposed within said bore of said housing and extending beyond said lower end of said housing;
a primary thrust bearing disposed between said lower end of said elongated housing end section and said elongated mandrel, whereby downward axial loads can be transferred from said elongated housing to said elongated mandrel;
a secondary thrust bearing assembly disposed between said housing and said mandrel, said secondary thrust bearing assembly comprising upper and lower cylinders having opposing faces and a bearing surface between said faces, said upper cylinder bearing against a shoulder on said mandrel and said lower cylinder bearing against a shoulder in said housing, whereby forces are transferred from said mandrel to said housing; and
one or more radial bearings disposed within said housing, radially between said mandrel and said housing, said one or more radial bearings positioned outboard of said primary and secondary thrust bearings.
3. The downhole motor of claim 2 , wherein said one or more radial bearings are positioned above said primary and secondary thrust bearings.
4. The downhole motor of claim 3 , wherein said one or more radial bearings comprise sleeve type bearings.
5. The downhole motor of claim 2 , wherein said bearing surface between said cylinders comprises polycrystalline diamond compact buttons mounted on said faces.
6. The downhole motor of claim 2 , wherein said one or more radial bearings comprise carbide bearing surfaces.