Skew Correction Roller Nipping Force Control
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Solution Overview
Problem
Conventional skew correcting devices in image forming apparatuses are inadequate in correcting skew for sheets with varying basis weights, as they either fail to form a loop in thick paper due to high rigidity or apply insufficient force to thin paper, leading to defective image formation.
Innovation Solution
A skew correcting device with a first and second roller pair, a contact portion, and a switching mechanism controlled by a control unit based on sheet information to adjust the nipping force, allowing for effective skew correction across different types of sheets by altering the inter-roller distance and nipping force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed nipping force is used by the upstream roller pair, then the device structure is simple, but it cannot form a loop of desired size in both thick and thin paper
Solution Approach 1:
The patent applies the dynamics principle by making the nipping force of the upstream roller pair variable rather than fixed. The nipping force is dynamically adjusted based on sheet information (such as basis weight) before the leading edge contacts the contact portion. This allows the system to adapt to different sheet types and form loops of desired size in both thick and thin paper, resolving the contradiction between simple structure and precise skew correction.
2Reliability
If the upstream roller pair applies strong nipping force, then thick paper can be conveyed, but thin paper cannot form a loop of desired size due to excessive force
Solution Approach 1:
The patent applies parameter changes by adjusting the nipping force parameter of the upstream roller pair based on sheet characteristics. Before the leading edge contacts the contact portion, the nipping force is changed according to sheet information (e.g., basis weight). This ensures that thick paper receives sufficient nipping force for reliable conveyance while thin paper receives appropriate force to form a loop of desired size, resolving the contradiction between conveyance reliability and loop formation precision.
3Manufacturing precision
If the upstream roller pair applies weak nipping force, then thin paper can form a loop, but thick paper slips at the nip and cannot form a loop of desired size
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the nipping force parameter before the leading edge contacts the contact portion. The nipping force is set differently based on sheet information: stronger force for thick paper to prevent slipping and ensure reliable conveyance, and appropriate force for thin paper to enable loop formation. This resolves the contradiction between loop formation precision and conveyance reliability.
4Adaptability or versatility
If a single nipping force setting is used for all sheet types, then the device operation is simple, but skew correction performance is insufficient for various sheet types
Solution Approach 1:
The patent applies self-service by having the system automatically adjust the nipping force based on sheet information without requiring manual intervention. The control unit automatically determines the appropriate nipping force setting before the leading edge contacts the contact portion, based on detected sheet characteristics. This maintains operational simplicity while achieving high adaptability for skew correction across various sheet types.
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 enables precise skew correction for various sheet types, ensuring accurate image formation by forming appropriate loops regardless of sheet thickness, thereby improving skew correcting performance and preventing image defects.
Implementation Method 1
a first roller pair (115a, 115b) that nips and conveys a sheet S
Implementation Method 2
a switching mechanism (140) that changes a nipping force of the first roller pair (115a, 115b) before the leading edge of the conveyed sheet comes into contact with the contact portion to form a loop in the sheet
Implementation Method 3
a control unit that makes a determination on the basis of sheet information as to whether the nipping force of the first roller pair is to be changed, the control unit being configured to control the switching mechanism on the basis of the determination
Implementation Method 4
the upstream roller pair brings the leading edge of the sheet into contact with a contact portion of the rollers or shutters to correct skew of the leading edge of the sheet
Implementation Method 5
a second roller pair disposed upstream of the first roller pair and configured to nip and convey the sheet
Data Source
AI summary
A skew correcting device includes a first roller pair configured to nip and convey a sheet, a second roller pair disposed upstream of the first roller pair and configured to nip and convey the sheet, a contact portion disposed downstream of the first roller pair, the contact portion being a portion that the leading edge of the conveyed sheet comes into contact to correct skew of the sheet, a switching mechanism configured to change a nipping force of the first roller pair before the leading edge of the conveyed sheet comes into contact with the contact portion to form a loop in the sheet, and a control unit configured to make a determination on the basis of sheet information as to whether the nipping force of the first roller pair is to be changed, the control unit being configured to control the switching mechanism on the basis of the determination.