Coupling Shaft Axial Movement for Thermal Expansion
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Solution Overview
Problem
The existing rotation shaft coupling structures in image forming apparatuses, such as those used in tandem-type digital color copiers, face issues with stability and fatigue due to thermal expansion differences between the drive roller and the roller drive shaft, leading to potential loosening or breakage of screws over time.
Innovation Solution
A rotation shaft coupling structure is designed with a coupling shaft of large length that extends through a hollow drive roller, featuring a threaded end that mates with an internal thread on the roller drive shaft, allowing for axial extension and contraction, and includes an inclined surface and shaft-peripheral contact surface to enhance stability and prevent backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rotation shaft coupling structure is used, then the structure is simple and easy to manufacture, but the coupling stability deteriorates due to thermal expansion differences causing screw loosening or breakage over time
Solution Approach 1:
The coupling shaft is designed with a free end that allows axial extension and contraction, transforming the rigid coupling structure into a dynamic one that can adapt to thermal expansion differences. This enables the coupling to maintain stability despite temperature changes without requiring complex additional components
Solution Approach 2:
The patent changes the physical state of the coupling shaft by allowing it to vary in length axially in response to thermal expansion. This parameter change enables the coupling to accommodate dimensional changes in the drive roller without causing screw loosening or breakage
2Ease of operation
If the coupling shaft is rigidly fixed at both ends, then the structural stability is high, but the operability deteriorates due to fatigue failure and screw loosening from thermal expansion
Solution Approach 1:
By making one end of the coupling shaft a free end that can move axially, the structure becomes dynamic rather than rigid. This improves operability by preventing fatigue failure while maintaining sufficient stability through the threaded portion at the other end
3Volume of stationary object
If the coupling shaft length is reduced, then the device size is minimized, but the stability deteriorates due to increased susceptibility to thermal expansion effects
Solution Approach 1:
The free end design allows the coupling shaft to accommodate thermal expansion dynamically, enabling a more compact overall structure without sacrificing stability. The axial movement capability compensates for the reduced length
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
This configuration maintains a secure coupled state over time, unaffected by temperature changes, and improves operability by reducing the likelihood of fatigue failure and screw loosening, while minimizing component count and size.
Implementation Method 1
a threaded portion at a first end portion of the coupling shaft in the axial direction, the threaded portion mating with the internal thread of the recessed portion
Implementation Method 2
thermal expansion differences between the drive roller and the roller drive shaft, leading to potential loosening or breakage of screws over time
Data Source
AI summary
A rotation shaft coupling structure includes a roller drive shaft including a recessed portion having an internal thread; a rotation roller including a coupling member housing the recessed portion of the roller drive shaft; and a coupling shaft extending through the rotation roller in the axial direction. The coupling shaft includes a threaded portion at a first end portion thereof, the threaded portion mating with the internal thread of the recessed portion, and the coupling shaft couples the roller drive shaft and the rotation roller to each other. The first end portion of the coupling shaft in the axial direction is joined to the roller drive shaft and the rotation roller in the coupling member of the rotation roller, and a second end portion of the coupling shaft in the axial direction is a free end that allows the coupling shaft to extend and contract in the axial direction.