Gear reducer
Apparatus and methods relate to a gear reducer, which may be used downhole to reduce rotational speed output from a downhole motor, such as a turbine motor, to a slower speed desired for rotation of a drill bit. The gear reducer includes a planetary gear arrangement coupled to receive rotational input from the downhole motor and a cycloidal gear arrangement driven by rotation resulting from the planetary gear arrangement. An output shaft couples to the cycloidal gear arrangement and rotates during operation slower than the rotational input from the downhole motor.
1 . A gear reducer for a downhole motor in a well, comprising:
a planetary gear arrangement coupled to receive rotational input from the downhole motor;
a cycloidal gear arrangement coupled to be driven by rotation resulting from the planetary gear arrangement; and
an output shaft coupled to the cycloidal gear arrangement, wherein during operation the output shaft rotates slower than the rotational input from the downhole motor;
wherein during operation the rotational input from the downhole motor is at a first revolutions per minute (RPM) and crankshafts of the planetary gear arrangement individually rotate during operation at a second RPM greater than the first RPM.
2 . The gear reducer of claim 1 , wherein the planetary gear arrangement comprises:
a ring gear coupled to rotate with a powered rotor of the downhole motor;
a first planetary gear meshed with the ring gear and disposed on a first crankshaft; and
a second planetary gear meshed with the ring gear and disposed on a second crankshaft.
3 . The gear reducer of claim 1 , wherein the cycloidal gear arrangement comprises:
a first cycloidal rotor partially meshed with teeth inside a cycloidal stator, wherein a first offset cam of a first crankshaft passes through the first cycloidal rotor and a second offset cam of a second crankshaft passes through the first cycloidal rotor; and
a second cycloidal rotor partially meshed with the teeth inside the cycloidal stator, wherein a third offset cam of the first crankshaft passes through the second cycloidal rotor and a fourth offset cam of the second crankshaft passes through the second cycloidal rotor.
4 . The gear reducer of claim 3 , wherein the output shaft has a top end with first and second bores to respectively receive bottom ends of the first and second crankshafts that are rotated together about a center rotational axis of the output shaft by the first and second cycloidal rotors.
5 . The gear reducer of claim 1 , wherein the output shaft rotates slower than the rotational input from the downhole motor due to increasing revolutions per minute (RPM) with the planetary gear arrangement and then decreasing RPM with the cycloidal gear arrangement.
6 . The gear reducer of claim 1 , wherein during operation the rotational input from the downhole motor is lefthand rotation opposite of righthand rotation of the output shaft.
7 . A gear reducer for a downhole motor in a well, comprising:
a planetary gear arrangement coupled to receive rotational input from the downhole motor;
a cycloidal gear arrangement coupled to be driven by rotation resulting from the planetary gear arrangement; and
an output shaft coupled to the cycloidal gear arrangement, wherein during operation the output shaft rotates slower than the rotational input from the downhole motor;
wherein the output shaft rotates slower than the rotational input from the downhole motor due to increasing revolutions per minute (RPM) with the planetary gear arrangement and then decreasing RPM with the cycloidal gear arrangement.
8 . The gear reducer of claim 7 , wherein the planetary gear arrangement comprises:
a ring gear coupled to rotate with a powered rotor of the downhole motor;
a first planetary gear meshed with the ring gear and disposed on a first crankshaft; and
a second planetary gear meshed with the ring gear and disposed on a second crankshaft.
9 . The gear reducer of claim 7 , wherein the cycloidal gear arrangement comprises:
a first cycloidal rotor partially meshed with teeth inside a cycloidal stator, wherein a first offset cam of a first crankshaft passes through the first cycloidal rotor and a second offset cam of a second crankshaft passes through the first cycloidal rotor; and
a second cycloidal rotor partially meshed with the teeth inside the cycloidal stator, wherein a third offset cam of the first crankshaft passes through the second cycloidal rotor and a fourth offset cam of the second crankshaft passes through the second cycloidal rotor.
10 . The gear reducer of claim 9 , wherein the output shaft has a top end with first and second bores to respectively receive bottom ends of the first and second crankshafts that are rotated together about a center rotational axis of the output shaft by the first and second cycloidal rotors.
11 . The gear reducer of claim 7 , wherein during operation the rotational input from the downhole motor is at a first revolutions per minute (RPM) and crankshafts of the planetary gear arrangement individually rotate during operation at a second RPM greater than the first RPM.
12 . The gear reducer of claim 7 , wherein during operation the rotational input from the downhole motor is lefthand rotation opposite of righthand rotation of the output shaft.
13 . The gear reducer of claim 7 , further comprising a positive pressure lubricant supply to the planetary and cycloidal gear arrangements, wherein the positive pressure lubricant supply includes a piston acted on by drilling fluid taken at least one stage up along a turbine motor that is the downhole motor.
14 . A gear reducer for a downhole motor in a well, comprising:
a planetary gear arrangement coupled to receive rotational input from the downhole motor;
a cycloidal gear arrangement coupled to be driven by rotation resulting from the planetary gear arrangement; and
an output shaft coupled to the cycloidal gear arrangement, wherein during operation the output shaft rotates slower than the rotational input from the downhole motor;
wherein during operation the rotational input from the downhole motor is lefthand rotation opposite of righthand rotation of the output shaft and,
wherein the planetary gear arrangement comprises:
a ring gear coupled to rotate with a powered rotor of the downhole motor;
a first planetary gear meshed with the ring gear and disposed on a first crankshaft; and
a second planetary gear meshed with the ring gear and disposed on a second crankshaft.
15 . A gear reducer for a downhole motor in a well, comprising:
a planetary gear arrangement coupled to receive rotational input from the downhole motor;
a cycloidal gear arrangement coupled to be driven by rotation resulting from the planetary gear arrangement; and
an output shaft coupled to the cycloidal gear arrangement, wherein during operation the output shaft rotates slower than the rotational input from the downhole motor;
wherein during operation the rotational input from the downhole motor is lefthand rotation opposite of righthand rotation of the output shaft and, wherein during operation the rotational input from the downhole motor is at a first revolutions per minute (RPM) and crankshafts of the planetary gear arrangement individually rotate during operation at a second RPM greater than the first RPM.
16 . A gear reducer for a downhole motor in a well, comprising:
a planetary gear arrangement coupled to receive rotational input from the downhole motor;
a cycloidal gear arrangement coupled to be driven by rotation resulting from the planetary gear arrangement, and
an output shaft coupled to the cycloidal gear arrangement, wherein during operation the output shaft rotates slower than the rotational input from the downhole motor;
wherein during operation the rotational input from the downhole motor is lefthand rotation opposite of righthand rotation of the output shaft and wherein the output shaft rotates slower than the rotational input from the downhole motor due to increasing revolutions per minute (RPM) with the planetary gear arrangement and then decreasing RPM with the cycloidal gear arrangement.