Sensorless Motor Excitation Control for Stable Image Forming Speed
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Solution Overview
Problem
Sensorless motors used in image forming apparatuses face challenges in maintaining consistent rotation speed due to load variations, which can affect image quality, as existing vector control methods struggle to efficiently manage excitation and torque currents.
Innovation Solution
A motor control apparatus that dynamically adjusts the target value of the excitation current based on predefined periods, setting it to a higher value during load variation periods to minimize speed deviations and prevent increased coil temperature and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the excitation current is increased to suppress rotation speed variation during load changes, then the motor speed stability is improved, but the power consumption and coil temperature increase
Solution Approach 1:
The patent applies dynamics by making the excitation current target value adjustable based on operational conditions. The control unit dynamically switches between a first target value (during constant speed operation) and a second target value (during load variation periods), allowing the system to optimize between speed stability and power consumption based on real-time needs
Solution Approach 2:
The patent changes the parameter of excitation current target value based on operational phase. By detecting load variation periods and switching the excitation current target value between two different levels, the system achieves better speed response during disturbances while maintaining lower power consumption during normal operation
2Loss of time
If the excitation current is increased to improve speed response during load variation, then the time to return to target speed is reduced, but the coil temperature increases
Solution Approach 1:
The patent applies periodic action by implementing time-based control phases: a first period for constant speed operation with lower excitation current, and a second period for load variation recovery with higher excitation current. This periodic switching optimizes both response time and thermal management
Solution Approach 2:
The system dynamically adjusts excitation current based on the operational period, using higher current only when needed for speed recovery after load disturbances, thereby minimizing both response time and overall thermal accumulation
3Productivity
If vector control is used to drive the motor, then the motor can drive the photosensitive member, but load variations cause rotation speed changes that affect image quality
Solution Approach 1:
The patent uses feedback by detecting rotation speed changes and identifying load variation periods based on deviations from target speed. This feedback mechanism triggers appropriate control responses (switching to higher excitation current) to maintain speed accuracy and ensure consistent image quality
Solution Approach 2:
The system changes the excitation current parameter in response to detected load variations, adjusting the motor's electromagnetic characteristics to maintain precise speed control during image formation operations
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 approach effectively shortens the time for the motor to return to target speed, maintains image quality, and reduces power consumption and coil temperature fluctuations.
Implementation Method 1
a current supply unit configured to supply a coil current to a plurality of coils of a motor by controlling a voltage applied to the plurality of coils
Data Source
AI summary
A motor control apparatus includes a current supply unit and a control unit. The current supply unit supplies a coil current to a plurality of coils of a motor by controlling a voltage applied to the plurality of coils based on a target value of an excitation current and a target value of a torque current. The control unit sets the target value of the excitation current to a first target value in a first period within a period in which a rotation speed of the motor is controlled to be a target speed, and sets the target value of the excitation current to a second target value larger than the first target value in a second period different from the first period.