Brushless Motor Speed Control Switching for Image Formers
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Solution Overview
Problem
In electrophotographic image forming apparatuses with brushless motors, rotation speed control based on induced voltage accuracy decreases at high speeds, and using BD signals at low speeds risks damaging photosensitive members.
Innovation Solution
Implementing a controller that switches between power supply and interruption to the motor coils, detecting induced voltage values during power interruption, and performing phase switching based on a reference value to switch from induced voltage control to BD signal control within a specific range where regeneration current does not interfere with detection, ensuring stable rotation speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rotation speed control based on induced voltage is used, then control is simple and does not require additional sensors, but detection accuracy decreases as rotation speed increases
Solution Approach 1:
The patent dynamically switches between two control methods based on rotation speed: using induced voltage control at low speeds and BD signal control at high speeds. This dynamic adaptation resolves the contradiction by selecting the appropriate control method for each operating condition, maintaining both simplicity and accuracy across the full speed range.
Solution Approach 2:
The patent changes the control parameter based on rotation speed. At low speeds, it uses induced voltage as the control parameter; at high speeds, it switches to BD signal timing. This parameter change allows the system to maintain detection accuracy while preserving control simplicity through selective parameter usage.
2Measurement precision
If rotation speed control based on BD signal is used from low speed, then high speed control accuracy is maintained, but photosensitive member damage is feared due to light beam movement
Solution Approach 1:
The patent dynamically selects the control method based on rotation speed thresholds. BD signal control is enabled only when rotation speed exceeds a predetermined threshold, ensuring that the light beam does not move on the photosensitive member during low-speed operation. This dynamic switching resolves the contradiction by enabling high-accuracy control only when safe to do so.
Solution Approach 2:
The patent introduces a speed threshold as an intermediary condition that mediates between the two control methods. This threshold acts as a safety gate, allowing BD signal control (high accuracy) only when rotation speed is sufficient to prevent photosensitive member damage, while using induced voltage control (safe but less accurate) below this threshold.
3Measurement precision
If phase switching is performed during power interruption period, then control precision is improved, but regeneration current causes detection failure during part of the interruption period
Solution Approach 1:
The patent segments the power interruption period into two parts: a first period for phase switching and a second period for induced voltage detection. By dividing the interruption period, the system can perform phase switching without interfering with induced voltage detection, resolving the contradiction between control precision and detection reliability.
Solution Approach 2:
The patent performs phase switching in advance during the first part of the power interruption period, before induced voltage detection begins in the second part. This preliminary action ensures that phase switching is completed before detection starts, eliminating interference and maintaining both precision and reliability.
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 stabilizes rotation speed control by minimizing the impact of regeneration current interference and reduces the risk of photosensitive member damage, maintaining accuracy and preventing damage at varying rotation speeds.
Implementation Method 1
detect a value related to an induced voltage which is generated in at least one of the plurality of coils
Data Source
AI summary
An image forming apparatus includes: a light source; a polygon mirror; a brushless motor rotating a rotary polygon mirror; a light receiver configured to receive the light beam reflected by the polygon mirror; and a controller configured to perform driving control; detect a value related to an induced voltage; and perform a phase switching process. In a start-up period, the controller performs a control switching process of performing switching from rotation speed control based on the induced voltage to rotation speed control based on the light receiving timing of the light beam in a specific range in which a length from a start timing of an interruption period of the power to a timing when the detected value reaches the reference value does not become shorter than a length of a reference-disabled period.