Heater Current Control via Saturation Time Detection
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Solution Overview
Problem
Existing image forming apparatuses face challenges in precisely controlling the current supplied to heaters to prevent excessive current flow, which can lead to inefficiencies and potential damage.
Innovation Solution
The apparatus incorporates a current sensor and a controller that execute phase control by determining a saturation time and calculating a new phase angle based on the current sensor's signals, allowing for precise control of current supply to the heater, switching from phase control to wave-number control when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If phase control is executed using a current sensor to prevent excessive current flow, then heater temperature control is improved, but the ability to precisely determine low current levels deteriorates
Solution Approach 1:
The patent dynamically adjusts the threshold value used for determining current levels based on the operating conditions and heater temperature. The controller adapts the threshold dynamically rather than using a fixed value, allowing accurate detection of low current levels while maintaining effective prevention of excessive current flow. This dynamic adjustment resolves the contradiction by making the measurement system adaptable to different operating states.
Solution Approach 2:
The patent changes the parameter being measured by using the saturation time of the current sensor output signal as an indirect measure of current level. Instead of directly measuring absolute current values, the system measures the time it takes for the sensor output to reach saturation, which provides precise information about low current levels while maintaining the ability to prevent excessive currents through the same measurement mechanism.
2Manufacturing precision
If a current sensor is used to detect current flow in the heater, then current control precision is improved, but the complexity of the control system increases
Solution Approach 1:
The current sensor is configured to self-saturate at a predetermined level, and the system uses the saturation time of the sensor's own output signal as the measurement parameter. This self-service approach eliminates the need for additional measurement circuits or complex signal processing, as the sensor's inherent saturation characteristic provides the measurement information directly, reducing overall system complexity while maintaining precision.
Solution Approach 2:
The patent introduces the saturation time as an intermediary parameter that bridges the gap between simple sensor output and precise current measurement. By measuring the time it takes for the sensor output to reach saturation rather than directly measuring current magnitude, the system achieves high precision control without requiring complex measurement electronics, thus reducing control system complexity while improving precision.
3Speed
If the current sensor output signal is used directly for control, then the response time is improved, but the precision in determining current levels deteriorates
Solution Approach 1:
The system performs preliminary action by allowing the current sensor output signal to naturally rise and saturate before taking the measurement. By measuring the saturation time - the time it takes for the signal to reach its maximum level - the system captures complete information about the current level during the natural response process, maintaining fast response while achieving high precision through the time-based measurement approach.
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
This configuration enables precise determination of low current levels, effectively increasing heater temperatures while reducing excessive current flow and potentially lowering the cost of current sensors.
Implementation Method 1
a current sensor configured to output a signal corresponding to a value of current flowing in the current sensor
Implementation Method 2
a heater, and a switching circuit connected to the heater... provide alternating current to the heater
Data Source
AI summary
A heating system includes a heater, a switching circuit providing alternating current to the heater, and a current sensor. The heating system also includes a controller that controls operation of the switching circuit. At a predetermined time during a half cycle, the controller outputs an activation signal to the switching circuit. Based on an elapsed time from outputting the activation signal that a current signal is at least at a predetermined level, the controller calculates a second time from which a current level does not exceed a threshold level during the half cycle, and outputs an activation signal to the switching circuit at the second time. The heating system is useable within an image forming apparatus.