Variable Reduction Ratio Power Transmission for Fixing Roller Heating
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Solution Overview
Problem
The existing fixing devices in image forming apparatuses require a longer time for the fixing roller to heat up before image formation due to the need for a high-torque motor when using a shared motor for both the fixing roller and switching mechanism, which increases the size and cost of the device.
Innovation Solution
A power transmission mechanism with two paths is used, where a first path with a higher reduction ratio is selected for separating the pressing member from the heating rotating body, and a second path with a lower reduction ratio is selected for pressing, allowing the motor to rotate the cam quickly to complete the pressing operation and begin image formation rapidly, while minimizing the motor's size and torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared motor is used for both the fixing roller and switching mechanism, then the number of motors is reduced and cost is lowered, but the motor size and torque requirements increase, causing longer heating time
Solution Approach 1:
The patent applies dynamics by making the reduction ratio variable through selection. Two different reduction ratios are provided in the power transmission mechanism, allowing the system to dynamically switch between them based on operational requirements. This enables the motor to operate with appropriate torque characteristics for each phase (separation vs. pressing) without requiring excessive torque capacity throughout, thus reducing motor size and heating time while maintaining the shared motor configuration.
2Power
If a high reduction ratio is used in the power transmission mechanism, then the motor torque requirement is reduced and size is minimized, but the switching speed becomes slow and heating time increases
Solution Approach 1:
The patent resolves this contradiction by providing a power transmission mechanism with selectable reduction ratios. The control unit dynamically selects between a first reduction ratio (higher, for torque) and a second reduction ratio (lower, for speed) based on the operational phase. During separation when high torque is needed, the higher reduction ratio is selected; during pressing when speed is critical for heating, the lower reduction ratio is selected. This dynamic adjustment allows the system to optimize both torque and speed without compromise.
Solution Approach 2:
The patent changes the transmission parameter (reduction ratio) based on operational requirements. By providing multiple reduction ratio options and selectively engaging them through the power transmission mechanism, the system adapts its mechanical characteristics to match the needs of different operational phases. This parameter change allows high torque during separation and high speed during pressing, resolving the contradiction between motor size and switching speed.
3Reliability
If the pressing roller is continuously pressed against the fixing roller, then the fixing nip is maintained, but the elastic layer does not return to original shape and recording sheet transport becomes problematic
Solution Approach 1:
The patent applies periodic action by implementing a switching mechanism that alternates the pressing roller between contact and separation states. Instead of continuous pressing, the system periodically engages and disengages the pressing roller based on operational requirements. This periodic separation allows the elastic layer to recover its original shape, preventing deformation accumulation and ensuring smooth recording sheet transport, while still maintaining the fixing nip during actual fixing operations.
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 solution reduces the time required for the fixing roller to heat up and enables efficient operation with a single motor, maintaining a compact size and reducing costs by optimizing the power transmission paths based on the operational needs of pressing and separating the rollers.
Implementation Method 1
a compression spring (84) that acts as a biasing unit
Implementation Method 2
a motor (106) that acts as a drive source; a power transmission mechanism (110-148) that transmits rotational power of the motor (106)
Implementation Method 3
a plate cam (100) that acts as a switching unit; As the plate cam rotates, the pressing roller is separated from the fixing roller
Implementation Method 4
a fixing belt (54) that acts as a heating rotating body; in order to evenly heat the entire fixing roller
Data Source
AI summary
A fixing device includes a heating rotating body driven by a motor, a pressing member, a biasing unit, a switching unit that receives rotational power of the motor in order to either separate the pressing member and the heating rotating body or to allow the biasing unit to press the pressing member and the heating rotating body together, a power transmission mechanism that transmits the rotational power of the motor to the switching unit over a first path or a second path, the first path having a larger reduction ratio, and a power transmission targeting unit that switches the target of transmission of rotational power of the motor between the heating rotating body and the switching unit depending on the rotational direction of the motor and that includes a path selection unit that selects the first path during separation and the second path during pressing by the switching unit.