Transfer Nip Sheet Posture Control Using Torque-Sensed Belt Speed
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Solution Overview
Problem
Existing image forming apparatuses face instability in sheet posture due to differences in conveyance speeds between the registration roller pair and the transfer portion, particularly with low-stiffness sheets, leading to potential image defects despite torque control adjustments.
Innovation Solution
The apparatus incorporates a guide member with a convex portion and a torque sensor to stabilize sheet posture by controlling the rotational speed of the conveyance roller pair, ensuring the sheet is conveyed faster through the transfer nip than by the registration roller pair, and adjusting torque detection to maintain optimal sheet alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotational speed of the registration roller pair is controlled to match the conveyance speed of the transfer portion, then the torque deviation becomes zero, but the sheet posture becomes unstable especially with low-stiffness sheets
Solution Approach 1:
The guide member with convex portion is positioned upstream before the transfer nip to preliminarily guide and align the sheet. This preliminary guidance action occurs before the sheet reaches the transfer portion, ensuring proper sheet posture is established in advance, which is particularly effective for low-stiffness sheets that need external guidance to maintain stable posture.
Solution Approach 2:
The guide member acts as an intermediary element between the registration roller pair and the transfer portion. It mediates the sheet conveyance by providing physical guidance through its convex portion, bridging the gap between the two conveyance systems and ensuring smooth transition while maintaining sheet stability.
2Speed
If the conveyance speed of the sheet by the registration roller pair is increased to match the transfer portion speed, then speed difference is reduced, but the sheet is pushed into the transfer portion causing loop formation
Solution Approach 1:
The guide member with convex portion is positioned upstream to preliminarily guide the sheet before it enters the transfer nip. This preliminary guidance prevents the sheet from being pushed into the transfer portion by providing early directional control, avoiding loop formation while maintaining speed synchronization.
Solution Approach 2:
The guide member serves as an intermediary that buffers the interaction between the registration roller pair and the transfer portion. It mediates the sheet flow by providing gradual guidance rather than abrupt direction changes, preventing sheet deformation and loop formation during the transition.
3Measurement precision
If a torque sensor is added to detect belt drive motor torque, then conveyance speed control precision is improved, but device complexity increases
Solution Approach 1:
The torque sensor leverages the existing belt drive motor system and its natural torque characteristics. Rather than adding complex measurement infrastructure, the system uses the motor's inherent torque output as the measurement basis, allowing the existing motor control system to serve the dual purpose of drive and measurement.
Solution Approach 2:
The torque sensor enables the belt drive motor system to perform multiple functions: both driving the intermediate transfer belt and providing precise torque measurement for conveyance speed control. This multi-functionality reduces the need for separate measurement systems and integrates control capabilities into the existing drive mechanism.
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 approach stabilizes the sheet posture upstream of the transfer nip, preventing image defects and ensuring consistent image quality even with low-stiffness sheets.
Implementation Method 1
a torque sensor configured to detect a torque of the belt drive motor
Implementation Method 2
a belt drive motor configured to drive the belt
Implementation Method 3
a conveyance roller pair configured to convey a sheet toward the transfer nip
Data Source
AI summary
An image forming apparatus includes an image bearing member, a belt, an outer roller, an inner roller, a tension roller, a conveyance roller pair, a guide member including a convex portion, a belt drive motor configured to drive the belt, a torque sensor configured to detect a torque of the belt drive motor, and a control unit configured to execute, after the sheet has reached the transfer nip, a conveyance control of controlling a rotational speed of the conveyance roller pair such that a first conveyance speed of the sheet conveyed by the transfer nip becomes faster than a second conveyance speed of the sheet conveyed by the conveyance roller pair based on a detection result of the torque sensor.