Worm-Driven Nip Pressure Control Without Clutch
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Solution Overview
Problem
Existing image heating apparatuses face increased size and cost due to the need for a clutch to prevent reaction force transmission from a cam to the driving source, which complicates the drive transmission device.
Innovation Solution
The apparatus employs a changing mechanism with a motor, worm, worm wheel, and cam to adjust the pressing force at the nip portion by displacing the second rotary member relative to the first, using a displacement mechanism to change the position of the pressure roller with respect to the heating roller, thereby controlling the pressure applied to the recording material without the need for a clutch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clutch is provided to prevent reaction force transmission from cam to driving source, then reaction force transmission is prevented, but device size and costs increase
Solution Approach 1:
The patent extracts the harmful reaction force transmission path by providing a gap between the cam and the pressure roller. This gap allows the cam to rotate freely on its shaft without transmitting reaction forces to the driving source, effectively removing the need for a clutch while preventing the harmful effect.
Solution Approach 2:
The cam shaft acts as an intermediary element that decouples the cam from the driving source. By allowing the cam to rotate independently on the cam shaft without transmitting reaction forces, the system mediates between the need for cam-driven pressure application and the need to prevent reaction force transmission to the motor.
2Reliability
If a clutch is provided to block reaction force transmission, then driving source protection is achieved, but manufacturing cost increases
Solution Approach 1:
The patent removes the expensive clutch component by extracting the reaction force transmission path through a simple gap design. The cam rotates freely on its shaft without contacting the pressure roller during certain phases, preventing reaction force transmission to the driving source without requiring any additional protective components.
Solution Approach 2:
The patent replaces the expensive clutch with a simple geometric gap in the cam mechanism. This gap is a passive, cost-free design feature that achieves the same protective function as an active clutch mechanism, significantly reducing manufacturing costs.
3Reliability
If a clutch is provided in the drive transmission device, then reaction force blocking is achieved, but device size increases
Solution Approach 1:
The patent extracts the reaction force blocking function from a separate clutch component and integrates it into the cam mechanism itself. The gap between the cam and pressure roller prevents reaction force transmission without requiring any additional space for a clutch, thereby reducing device size.
Solution Approach 2:
The patent merges the reaction force blocking function with the cam mechanism by designing the cam to rotate freely on its shaft without transmitting reaction forces to the driving source. This integration eliminates the need for a separate clutch component, reducing overall device size.
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 allows for adjustable pressure application to various recording materials while preventing reaction force transmission to the driving source, reducing the device's size and cost while maintaining efficient energy use and durability.
Implementation Method 1
a worm having both ends supported rotatably, a second drive transmission member that is attached to a first end of the worm in a rotational axis direction of the worm and to which a driving force from the first drive transmission member is transmitted, a worm wheel that is meshed with the worm
Data Source
AI summary
An image heating apparatus includes a first rotary member and a second rotary member that form a nip portion, and, a changing mechanism configured to change a pressing force applied at the nip portion. The changing mechanism includes a worm having both ends supported rotatably, a worm wheel that is meshed with the worm and to which a driving force from the worm is transmitted, a rotatable shaft to which the worm wheel is attached, a cam that is attached to the shaft, and, a displacement mechanism that is abutted against the cam and that is configured to displace the second rotary member with respect to the first rotary member along with a rotation of the cam.