Mud Motor Coupling Tooth Geometry for Torque and Wear Resistance
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Solution Overview
Problem
Couplings in mud motors used for directional drilling face challenges with high torque and hostile environments, leading to reduced torque transfer capacity, seal breakdown, and imbalance due to internal constriction, resulting in costly transmission failures.
Innovation Solution
A coupling design featuring a pair of mated hubs with irregularly shaped teeth that have a broader base than top, providing enhanced torsional strength, fatigue resistance, and wear resistance, with an 'S' curved side and slanted side to distribute stress effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal structure is disposed between the coupling hub member and female coupling member to protect from corrosive mud and reduce friction, then protection and friction reduction are improved, but the torque transfer capacity is reduced due to reduced radius of the coupling hub member
Solution Approach 1:
The coupling is divided into separate male and female coupling members that mate together, allowing the seal to be positioned in the gap between them rather than reducing the hub radius. This segmentation enables the seal to protect the interface without compromising the torque transfer capacity of the individual coupling members.
Solution Approach 2:
The seal structure acts as an intermediary element positioned between the male and female coupling members. It mediates the interaction between these components by providing protection and friction reduction at the interface, while the torque transfer occurs through the larger-radius coupling members themselves, not through the seal.
2Ease of manufacture
If regular shaped teeth are used in the coupling design, then manufacturing is simpler, but torsional strength and fatigue resistance are reduced under high torque conditions
Solution Approach 1:
The tooth design incorporates varying cross-sectional dimensions along its length, with a larger base cross-section and a smaller top cross-section. This local variation in geometry provides enhanced torsional strength and fatigue resistance at the base where stresses are highest, while maintaining manufacturability through standard machining processes.
3Adaptability or versatility
If the coupling hub member radius is reduced to accommodate the seal structure, then the seal can be installed, but the torque transfer capacity is reduced
Solution Approach 1:
By segmenting the coupling into separate male and female members with a gap between them, the seal can be installed in this gap without requiring reduction of the coupling member radii. The torque transfer path remains intact through the full-radius coupling members.
Solution Approach 2:
The seal is positioned in the axial dimension between the coupling members rather than radially within the hub, allowing the radial dimensions to remain large for torque transfer while accommodating the seal in the axial direction.
Data Source
AI summary
Coupling for transmission of torque, speed, and hydraulic thrust from a power section of a motor to a drive or output shaft. The coupling has a pair of mated hubs each with cantilevered teeth extending therefrom. The teeth are irregular in shape with an “S” curved driver side, a slanted unloaded surface, and a tooth base broader that the tooth top, which provide improved torsional and fatigue strength and wear resistance to the coupling. The coupling has utility in single and double articulation as a transmission in a mud motor for downhole directional drilling of subterranean formations. The coupling also has utility in other drilling operations employing motors requiring couplings of or for single or double articulation for minerals, geothermals, and HDD associated underground utilities. The invention further has utility with coiled tubing drilling and any power transmission equipment either with angular misalignment or direct drive.