Convex Shrink-Fit Joint Assembly for Higher Torque Transmission
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Solution Overview
Problem
Existing shrink-fit joints for rotational parts are not capable of resisting high torques, limiting their application in transmission and drive units.
Innovation Solution
A method involving precise turning and grinding to create convex surfaces on two rotational parts, where the external component is heated to expand its inner diameter, allowing for a precise shrink-fit assembly that maximizes torque transmission when cooled to room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional shrink-fit joints are used to connect rotational parts, then the joint can be assembled, but the torque transmission capability is insufficient
Solution Approach 1:
The patent applies curvature to the contact surfaces by machining convex shapes on both the inner and outer components. The outer component has a convex outermost surface and the inner component has a convex innermost surface that mate together. This curved surface geometry increases the contact area and distributes stress more effectively compared to conventional flat or straight surfaces, thereby enhancing torque transmission capability and joint reliability
Solution Approach 2:
The patent utilizes thermal expansion parameter changes to enable assembly. The outer component is heated to expand its inner diameter, allowing it to be placed over the inner component. Upon cooling, the outer component contracts to create a tight interference fit. This thermal parameter change enables precise control of the fit characteristics and maximizes torque transmission while avoiding assembly damage
2Strength
If precise turning and grinding methods are applied to create convex surfaces, then the torque transmission is maximized, but the manufacturing complexity increases
Solution Approach 1:
The patent employs precise turning and grinding operations to create convex surfaces on both components. The outer component is turned to form a convex outermost surface, and the inner component is ground to form a convex innermost surface. These curved surfaces are then heat-treated to achieve the final precise geometry. While this increases manufacturing complexity compared to flat surfaces, it maximizes torque transmission by optimizing the contact area and stress distribution
Solution Approach 2:
The patent replaces conventional mechanical machining alone with a combination of thermal processing and precision machining. By heating the outer component to expand it, the assembly process becomes easier, and the subsequent cooling creates the tight fit. This substitution of mechanical assembly with thermal expansion/contraction reduces the complexity of achieving precise interference fits without compromising torque transmission
3Ease of manufacture
If the outer component is heated to expand its inner diameter, then the assembly process is facilitated, but the heating process adds time and energy consumption
Solution Approach 1:
The patent applies thermal expansion to the outer component by heating it to a controlled temperature. This expansion increases the inner diameter of the outer component, allowing it to be easily placed over the inner component. After assembly, the outer component is allowed to cool and contract, creating a tight interference fit. This thermal expansion principle significantly facilitates the assembly process compared to cold fitting, while the heating and cooling time is managed through controlled thermal processing
Solution Approach 2:
The patent utilizes the phase transition concept in thermal processing, where the outer component transitions from a heated expanded state to a cooled contracted state. This phase transition in thermal state enables the assembly to be performed with reduced force and then locked in place upon cooling, achieving both ease of manufacture and strong joint formation while managing the time investment through efficient thermal cycle control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in a torque-transmitting assembly capable of transmitting higher torques compared to conventional shrink-fit joints, with a 16% increase in torque transmission compared to joints with straight surfaces.
Implementation Method 1
heating the innermost surface of the external component to expand a size of the innermost surface after machining the innermost surface of the external component
Implementation Method 2
holding the inner component and the external component in place until an interface between the innermost surface of the external component and the outermost surface of the inner component reaches the room temperature after placing the heated external component onto the inner component to complete a shrink-fit joint
Data Source
AI summary
A method for manufacturing a torque-transmitting assembly includes turning an inner component and machining an outermost surface of the inner component such that the outermost surface of the inner component has a continuous convex shape. The method further includes turning an external component and machining an innermost surface of the external component such that the innermost surface of the external component has a continuous convex shape. The method also includes heating the innermost surface of the external component to expand a size of the innermost surface after machining the innermost surface of the external component and placing the heated external component onto the inner component while the inner component is maintained at room temperature.