Sheet Transport Timing Control for Image Displacement in Printers
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in maintaining image precision when handling sheets of varying sizes and thicknesses due to differences in sheet transport speed and nipping forces, leading to image displacement and reduced transport efficiency.
Innovation Solution
An image forming apparatus with a control system that adjusts the sheet transport operation and image formation timing based on the length of the sheet in the transport direction, ensuring accurate image placement without increasing costs by modifying the sheet re-feed timing and deceleration timing to compensate for sheet thickness and size variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separation/feeding part nips the sheet during transport by the registration roller pair, then the sheet can be fed reliably, but the actual sheet transport speed differs from the desired speed causing image displacement
Solution Approach 1:
The patent applies preliminary action by stopping the separation/feeding part before the sheet is fully received by the transport roller pair. This prevents the separation/feeding part from imposing load on the registration roller pair during transport, thereby eliminating the cause of transport speed deviation and image displacement while maintaining reliable sheet feeding
2Productivity
If the transport speed is increased to meet higher speed demands, then productivity improves, but the load from the separation/feeding part causes greater image displacement
Solution Approach 1:
By stopping the separation/feeding part in advance before the sheet is received by the transport roller pair, the patent eliminates the load that would otherwise increase with higher transport speeds. This allows high productivity to be achieved without the detrimental effect of image displacement that would normally accompany increased speed
3Productivity
If the roller pressure of the registration roller pair is increased to prevent transport efficiency degradation, then transport efficiency improves, but impressions are made on the sheets
Solution Approach 1:
The patent eliminates the need for increased roller pressure by stopping the separation/feeding part before the sheet is received by the transport roller pair. This removes the root cause of transport efficiency degradation, allowing normal roller pressure to maintain high transport efficiency without causing impressions on the sheets
Data Source
AI summary
An image forming apparatus has an image bearing member bearing a toner image, a transfer part transferring the toner image from the image bearing member onto a sheet, a separation/feeding part separating and feeding sheets stacked on a sheet stacking member, and a transport part transporting the sheet fed by the separation/feeding part to the transfer part, in which a transporting operation of the transport part is changed according to a length of the sheet to be transported in a transport direction of the sheet. A control is configured to control so that a timing to decelerate to the transfer speed by the transport part with respect to a start of image formation is changed according to a length of the transported sheet in a transport direction of the sheet.