Sheet Conveying Device with Dynamic Nip Pressure Control
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Solution Overview
Problem
Existing sheet conveying devices in image forming apparatuses face challenges in efficiently conveying sheets of varying thickness and strength, particularly in maintaining stable nip pressure to prevent sheet tearing during jam removal and ensuring reliable conveyance.
Innovation Solution
A sheet conveying device with a pair of rollers, a biasing member, a guide member, a biasing support, and a biasing force changer, where the biasing force is adjusted based on the type of sheet being conveyed, using a pressure spring and a cam mechanism to change the nip pressure dynamically, and a guide unit to stabilize the position of the biasing support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed biasing force is applied to the pressure roller, then the structure is simple, but the sheet conveying reliability deteriorates for sheets of varying thickness and strength
Solution Approach 1:
The biasing force is made dynamically adjustable through a cam mechanism that changes the pressing force between the pressure roller and drive roller based on sheet type. The cam mechanism allows the biasing support to move along a guide member, changing the biasing force from a fixed value to a variable value that adapts to different sheet conditions, thereby improving conveying reliability without requiring multiple separate mechanisms.
Solution Approach 2:
The physical parameter of biasing force is changed from constant to variable by introducing a cam mechanism. The cam profile is designed to provide different pressing forces for different sheet types (e.g., thin sheets vs. thick sheets), allowing the system to optimize conveying reliability for each sheet type by changing the force parameter dynamically during operation.
2Reliability
If high nip pressure is applied to prevent sheet tearing, then sheet handling reliability improves, but the risk of sheet damage increases for weak sheets
Solution Approach 1:
The nip pressure parameter is made variable through the cam mechanism, allowing the system to adjust the pressing force according to sheet strength characteristics. For weak sheets, the cam provides lower pressing force to prevent damage, while for strong sheets, higher pressing force ensures reliable conveying, thus resolving the contradiction between reliability and damage prevention.
Solution Approach 2:
Different pressing forces are applied locally to different sheet types based on their specific properties. The cam mechanism enables the system to provide customized pressing force levels for different sheet categories (thin, thick, weak, strong), ensuring each sheet receives the appropriate force level needed for reliable handling without excessive damage risk.
3Adaptability or versatility
If the biasing support position is fixed, then the mechanism is simple, but the ability to adapt to different sheet types deteriorates
Solution Approach 1:
The biasing support is transformed from a fixed component to a movable one that can change position along the guide member. This dynamic positioning capability, enabled by the cam mechanism, allows the system to adapt to different sheet types by adjusting the biasing support position, which in turn adjusts the biasing force, providing versatility without requiring multiple complete mechanisms.
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 solution ensures stable and efficient sheet conveyance by adjusting nip pressure according to sheet type, preventing tearing during jam removal and enhancing workability, while maintaining consistent sheet handling across different sheet strengths.
Implementation Method 1
A pressure spring (biasing member) is provided, and the pressure spring is configured to bias the bearing 37a of the relay driven roller 42b toward the relay drive roller 42a
Implementation Method 2
a biasing force changer configured to change a biasing force of the biasing member along with movement of the biasing support
Data Source
AI summary
A sheet conveying device includes a pair of rollers, a biasing member, a guide member, a biasing support, and a biasing force changer. The pair of rollers includes a first roller and a second roller disposed in contact with the first roller. The pair of rollers is configured to hold a sheet between the first roller and the second roller. The biasing member is configured to bias the first roller toward the second roller. The biasing support is configured to support the biasing member and has a guide target member configured to slide along the guide member to move the biasing support. The biasing force changer is configured to change a biasing force of the biasing member along with movement of the biasing support. The guide target member has a portion projecting into a sheet conveyance passage through which the sheet is conveyed by the pair of rollers.