Fixing Device Variable Reduction Ratio Power Transmission
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Solution Overview
Problem
The existing fixing devices in image forming apparatuses face challenges in reducing the size and cost of the shared motor used for both the switching mechanism and the rotary drive motor, leading to increased motor size and longer startup times due to high torque requirements and high reduction ratios needed to separate the pressing roller from the fixing roller.
Innovation Solution
A fixing device with a power transmission mechanism that utilizes two distinct paths with different reduction ratios, allowing the motor to transmit power efficiently for both pressing and separating the pressing member and heating rotating body, using a first path with a higher reduction ratio for separation and a second path with a lower reduction ratio for pressing, controlled by a transmission control unit and path selection mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a high reduction ratio is used in the power transmission mechanism to reduce the load on the shared motor during pressing roller separation, then the motor size can be reduced, but the rotation speed of the cam slows down, causing an increase in the time necessary to return the pressing roller to the pressing state
Solution Approach 1:
The patent applies dynamics by making the reduction ratio variable rather than fixed. The power transmission mechanism switches between a first power transmission path with a first reduction ratio and a second power transmission path with a second reduction ratio based on the operational state. During pressing roller separation, the first path with higher reduction ratio is used to reduce motor load and size. During pressing roller return to pressing state, the second path with lower reduction ratio is used to maintain fast rotation speed, thus resolving the contradiction between motor size and time loss.
2Device complexity
If a shared motor is used for both the switching mechanism and the rotary drive motor, then the cost and device complexity are reduced, but the motor must bear both the load for compressing the compression spring and the load for rotary driving of the fixing roller, requiring a high torque motor that increases the size of the motor
Solution Approach 1:
The patent resolves this contradiction by dynamically selecting between two power transmission paths with different reduction ratios. The control unit switches the active path based on whether the pressing roller needs to be separated or returned to the pressing state, allowing the shared motor to operate at optimal torque and speed conditions for each operation, thereby avoiding the need for an oversized high-torque motor.
Solution Approach 2:
The patent changes the transmission parameters (reduction ratio) dynamically based on operational requirements. By having two distinct power transmission paths with different reduction ratios and selecting the appropriate one based on the current operation mode, the system allows the shared motor to deliver appropriate torque and speed without requiring excessive motor size.
3Stability of the object's composition
If the pressing roller is continually pressed against the fixing roller, then the fixing nip is maintained, but the portion of the elastic layer that elastically deforms may not fully return to its original shape if a long time passes without any images being formed, preventing smooth transport of recording sheets
Solution Approach 1:
The patent applies periodic action by implementing a switching mechanism that periodically separates the pressing roller from the fixing roller during non-printing periods. The control unit controls the switching unit to separate the pressing roller when no printing operation is performed and return it to the pressing state when printing is required. This periodic separation allows the elastic layer to fully recover its original shape, preventing permanent deformation and ensuring smooth recording sheet transport, while maintaining fixing nip stability during actual printing 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 allows for rapid switching between pressing and separating states, reducing the time before image forming begins and minimizing the motor's size by optimizing torque and rotation speed, thereby addressing the issues of motor size and startup time.
Implementation Method 1
a pressing roller, which acts as a pressing member, is pressed against the circumferential surface of a rotating fixing roller by the restorative force of an elastic member such as a compression spring
Implementation Method 2
the restorative force of an elastic member such as a compression spring
Implementation Method 3
A portion of the elastic layer elastically deforms in order to form the fixing nip
Implementation Method 4
a fixing device that uses a heat fixing method fixes toner to a recording sheet
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 transmission control unit that establishes and cuts off transmission of rotational power of the motor to the switching unit by the power transmission mechanism and that includes a path selection unit that selects the first path during separation and the second path during pressing by the switching unit.