Printing Apparatus Conveyance Control for Image Quality
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Solution Overview
Problem
Existing ink jet printing apparatuses face challenges in maintaining image quality after the rear end of the print medium leaves the conveyance roller pair, with configurations either resulting in significant blank spaces or image degradation due to direct contact with discharge rollers.
Innovation Solution
A printing apparatus and control method that alternates between normal and release conveyance operations, adjusting the conveyance roller rotation and suction force to ensure image quality up to the rear end of the print medium without degrading the image, even without a discharge roller pair, by precisely controlling the conveyance and suction mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a discharge roller pair is disposed downstream of the print head to enable printing up to the rear end of the print medium, then the blank space at the rear end of the image is reduced, but the image may be degraded due to direct contact between the discharge roller and the printed surface
Solution Approach 1:
A platen is introduced as an intermediary support surface between the print medium and the discharge roller. The platen provides a stable backing for the print medium during conveyance, allowing the discharge roller to contact only the platen surface rather than directly contacting the printed image, thereby preventing image degradation while maintaining the ability to print near the rear end of the medium
Solution Approach 2:
The mechanical contact-based discharge roller system is supplemented with a suction mechanism that uses aerodynamic forces (suction force) to hold and convey the print medium. This substitution allows for contactless or minimal-contact handling of the printed surface, eliminating the image degradation caused by mechanical roller contact
2Object-affected harmful factors
If no discharge roller pair is used to avoid image degradation, then the image quality is preserved, but a relatively large blank space is formed at the rear end of the image because print operations must stop after the rear end leaves the conveyance roller pair
Solution Approach 1:
The platen serves as a mediator that extends the printable area by providing continuous support to the print medium rear end. This allows the conveyance system to maintain control and registration of the print medium even after it leaves the conveyance roller pair, enabling print operations to continue closer to the actual rear end of the medium and reducing the necessary blank space
Solution Approach 2:
The suction mechanism replaces the need for mechanical discharge rollers to maintain print medium control. By using aerodynamic suction force applied through the platen, the system can precisely control the position and conveyance of the print medium rear end without mechanical contact, allowing print operations to extend to the very rear end of the medium
3Productivity
If the conveyance roller pair continuously nips the print medium to maintain registration, then printing can continue after the rear end leaves the conveyance roller pair, but the suction force may degrade the image on sensitive print mediums
Solution Approach 1:
The suction force is applied locally and selectively through the platen only in the regions where print medium support is needed, rather than uniformly across the entire print medium. This localized application allows the conveyance roller pair to maintain continuous nipping for registration control while the suction provides supplemental support only where necessary, avoiding excessive force that could degrade images on sensitive print mediums
Solution Approach 2:
The suction force is dynamically adjusted based on the print medium type and printing conditions. The system can vary the suction intensity and application area to match the specific requirements of different print mediums, allowing continuous conveyance for productivity while adapting the suction force to prevent image degradation on sensitive materials
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
Enables high-quality printing up to the vicinity of the rear end of the print medium without image degradation, maintaining efficient image formation and medium handling across various types and sizes of print media.
Implementation Method 1
adjusting the conveyance roller rotation and suction force to ensure image quality
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A printing apparatus (100) has a conveyance roller (1) and a driven roller (2) disposed upstream of a print head (3) in the first direction, a platen (6) facing the print head (3) and supporting the print medium (S), a producing unit (52) producing a holding force for holding the print medium (S) at the platen (6) A conveyance operation includes a first conveyance operation in which the print medium (S) is conveyed without any release from between the conveyance roller (1) and the driven roller (2) and a second conveyance operation in which the print medium (S) is released from between the conveyance roller (1) and the driven roller (2). A rotation amount of the conveyance roller (1) during the second conveyance operation is increased than that during the first conveyance operation.