Inkjet Head Sheet Lifting Detection Threshold Control
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Solution Overview
Problem
Conventional inkjet image forming apparatuses face challenges in accurately determining sheet lifting in real time, especially when handling sheets of varying thicknesses, due to the need for precise control of the rotation angle of glass to adjust laser light height, which is difficult to achieve.
Innovation Solution
A liquid ejection apparatus with a first control unit that adjusts the threshold for detecting sheet lifting based on the thickness of the recording medium, using a light projection and reception unit to emit and receive a detection beam, allowing for real-time determination of sheet lifting and preventing head attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between the inkjet head and the recording medium is set close to about 1 mm to achieve high image quality, then image quality is improved, but the risk of head attack increases when the sheet is lifted
Solution Approach 1:
The sheet lifting sensor detects sheet lifting before the sheet reaches the inkjet head position. By performing detection in advance at an upstream position, the system can identify potential head attack risks before they occur, allowing for preventive action to be taken
2Reliability
If a sheet lifting detection mechanism using optical sensors is provided upstream of the inkjet head, then head attack is prevented, but the device complexity increases
Solution Approach 1:
The optical sensor system serves multiple functions: it detects sheet lifting to prevent head attacks, and it can also be used to detect sheet thickness variations. By making the detection system multi-functional, the need for separate dedicated mechanisms is reduced, thereby lowering overall device complexity
3Measurement precision
If the rotation angle of glass is controlled accurately to adjust laser light height for different sheet thicknesses, then detection accuracy is improved, but the ease of operation deteriorates
Solution Approach 1:
The system automatically adjusts the detection threshold based on the detected sheet thickness without requiring manual intervention. The control unit autonomously modifies the threshold value to match the sheet thickness, eliminating the need for operators to manually control glass rotation angles or perform complex adjustments
Solution Approach 2:
The detection threshold parameter is dynamically changed based on sheet thickness measurements. The control unit automatically adjusts the threshold parameter to correspond to different sheet thicknesses, maintaining detection accuracy across varying conditions without requiring manual parameter adjustment
4Measurement precision
If the laser light height is adjusted according to sheet thickness to maintain accurate lifting detection, then detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The system uses a feedback mechanism where the detected sheet thickness information is fed back to the control unit, which then automatically adjusts the detection threshold. This closed-loop feedback system maintains detection accuracy for different sheet thicknesses without requiring complex mechanical adjustment mechanisms
Solution Approach 2:
The patent replaces mechanical adjustment mechanisms (such as glass rotation) with an electronic/software-based threshold adjustment system. The control unit modifies detection parameters through electronic control rather than mechanical movement, simplifying the overall device structure while maintaining detection accuracy
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 accurate and real-time detection of sheet lifting across different sheet thicknesses, ensuring the distance between the inkjet head and the sheet is maintained, preventing damage and ensuring high image quality.
Implementation Method 1
the laser light is blocked if the sheet is lifted, whereby the intensity of the light received by the light reception unit varies
Data Source
AI summary
A liquid ejection apparatus includes a first control unit, a light projection unit, a light reception unit, a determination unit, and a liquid ejection head. The first control unit is configured to change a threshold for determining a lifting of a recording medium conveyed along a conveyance path according to thickness of the recording medium. The light projection unit is configured to emit a detection beam for detecting the lifting of the recording medium. The light reception unit is configured to receive the detection beam. The determination unit is configured to determine the lifting of the recording medium, when the recording medium is detected with a height greater than the threshold by the detection beam. The liquid ejection head is configured to eject liquid to the recording medium.