Recording Head Heater Protection Through Current-Time Cutoff
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Solution Overview
Problem
In inkjet-type image forming apparatuses, abnormal temperature rise of the recording head occurs due to malfunctions in the temperature sensor, switching element, or controller, leading to continuous power supply to the heater.
Innovation Solution
The apparatus includes a current detection unit to monitor current flow in the power line and a system-side switching element to cut off the current if the continuous flow exceeds a predetermined value, controlled by a main controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a temperature sensor, switching element, and controller are installed in the recording head to control temperature, then temperature management capability is improved, but the risk of abnormal temperature rise due to malfunction increases
Solution Approach 1:
A current detection unit is introduced as an intermediary component between the power supply and the heater. This unit monitors current flow and provides information to the main controller, which then controls the system-side switching element to cut off power when necessary. This intermediary monitoring mechanism prevents abnormal temperature rise even when the original temperature control system malfunctions.
Solution Approach 2:
The current detection unit continuously monitors the current flowing to the heater and feeds this information back to the main controller. The main controller uses this feedback to determine whether to maintain or cut off power supply, creating a closed-loop safety mechanism that prevents runaway heating conditions.
2Measurement precision
If the controller continuously monitors and adjusts temperature using the temperature sensor, then temperature precision is improved, but the complexity of the control system increases
Solution Approach 1:
The control system is segmented into two independent parts: (1) the original temperature control loop (temperature sensor, controller, switching element) and (2) the safety monitoring loop (current detection unit, main controller, system-side switching element). This segmentation allows the temperature control function to operate with high precision while the safety mechanism operates independently, reducing overall system complexity through functional separation.
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
Prevents abnormal temperature rise of the recording head by forcibly stopping the current flow to the heater, even in the event of malfunctions in the power supply control system.
Implementation Method 1
a current detection unit configured to detect a current that flows in the power line
Implementation Method 2
a heater installed in a recording head, and temperature management of ink ejection nozzles is performed using the heater
Data Source
Figure 1
Figure 2
AI summary
An image forming apparatus (10) includes a recording head (1a-1d) and a host control system (61). The recording head eject inks. The host control system controls the recording head. The recording head includes a heater (41), a temperature sensor (42), a switching element (43) on a power line to the heater, and a controller (44) configured to control the switching element on the basis of a measurement temperature of the temperature sensor and thereby control temperature of the recording head. Further, the host control system includes a current detection unit (72) configured to detect a current that flows in the power line, a system-side switching element (73) arranged on upstream side of the power line from the switching element, and a main controller (71) configured to cut off the current using the system-side switching element if a continuous current flow time of the current detected by the current detection unit exceeds a predetermined value.