Sheet Conveyance Control for Collision Avoidance in Image Formers
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Solution Overview
Problem
In image forming apparatuses, the risk of collision or overlap between successive sheets due to conveyance accuracy errors leads to delays in positioning the following sheet for image formation, especially when conveyed at a lower velocity than the preceding sheet.
Innovation Solution
An image recording apparatus with a conveyance controlling device, a supply controlling device, and a judging device that intermittently conveys sheets at varying velocities to prevent collisions, allowing the following sheet to be rapidly positioned by predicting and inhibiting conveyances that would cause the trailing end of the preceding sheet to pass a reference position, enabling high-velocity conveyance once the preceding sheet has passed this position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the following sheet is conveyed at a lower velocity than the preceding sheet to avoid collision, then the risk of collision or overlap is reduced, but the distance between the following sheet and the trailing end of the preceding sheet increases, causing delay in positioning
Solution Approach 1:
The patent applies dynamic velocity adjustment by switching between a first conveying velocity (higher) and a second conveying velocity (lower) based on real-time position detection. The sheet conveying mechanism dynamically changes its operation mode: using higher velocity when safe and lower velocity when approaching the reference position, thereby optimizing both throughput and collision avoidance.
Solution Approach 2:
The patent employs feedback control through a sensor that detects the position of the trailing end of the preceding sheet. This position information is fed back to the control device, which then adjusts the conveying velocity of the following sheet accordingly. The feedback loop enables adaptive velocity control that responds to actual sheet positions rather than using fixed velocity settings.
2Productivity
If the following sheet is conveyed at the same distance as the preceding sheet during successive intermittent conveyances, then positioning efficiency is improved, but conveyance accuracy errors cause collision or overlap
Solution Approach 1:
The patent changes the conveying parameter (velocity) based on the detected position relationship between sheets. Instead of maintaining a constant conveying distance that could lead to collisions due to accuracy errors, the system adjusts the conveying velocity parameter dynamically. When the trailing end of the preceding sheet approaches the reference position, the velocity is reduced to compensate for potential accuracy deviations.
Solution Approach 2:
The system transitions from static equal-distance conveyance to dynamic differential conveyance. The following sheet is conveyed at different velocities depending on the position of the preceding sheet, allowing the system to adapt to conveyance accuracy variations and prevent collisions while maintaining efficient positioning.
3Productivity
If high-velocity conveyance is used continuously for the following sheet, then throughput is maximized, but the risk of collision with the preceding sheet increases
Solution Approach 1:
The patent implements periodic velocity modulation where the following sheet is conveyed at high velocity during safe periods and switches to low velocity during critical periods when the trailing end of the preceding sheet is near the reference position. This periodic action pattern maximizes throughput during safe intervals while ensuring collision avoidance during critical intervals.
Data Source
AI summary
An image recording apparatus including: (i) a first controlling portion configured to intermittently convey a following sheet at a second velocity together with intermittent conveyance of a preceding sheet at a first velocity higher than the second velocity; (ii) a predicting portion configured to predict one of the successive intermittent conveyances of the following sheet which is performed together with one of the successive intermittent conveyances of the preceding sheet which causes the trailing end of the preceding sheet to pass a reference position; and (iii) a second controlling portion configured to inhibit the predicted one of the successive intermittent conveyances of the following sheet, and configured to convey the following sheet at a third conveying velocity higher than the second conveying velocity, from a point of time at which the trailing end of the preceding sheet passes the reference position, such that conveyance of the following sheet at the third conveying velocity is stopped without a leading end of the following sheet being brought into contact with the trailing end of the preceding sheet.