Motor Control and Lighting Synchronization in Image Forming Apparatus
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the timing mismatch between light emission and detection by a sensor can lead to unnecessary exposure of the photosensitive member due to incorrect rotational frequency detection using a BD signal, especially when the rotational frequency changes.
Innovation Solution
An image forming apparatus with a controller that adjusts the lighting control and rotational frequency control of the motor based on both position and light receiving signals, implementing a non-lighting period that is shorter than the deflection period but longer than the exposure period, and switching control methods based on rotational frequency changes to ensure accurate exposure and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the light source is continuously emitted until the motor reaches target rotational frequency, then the motor can reach the target frequency, but the photosensitive member is unnecessarily exposed to the light beam
Solution Approach 1:
The patent applies preliminary action by determining and executing a non-lighting period before the motor reaches its target rotational frequency. The controller calculates the required non-lighting period based on the deflection period at the target frequency and the exposure period, then suppresses light emission during this calculated period in advance, preventing unnecessary exposure before the motor is ready.
Solution Approach 2:
The patent applies dynamics by making the lighting control adaptive to the motor's rotational frequency. The controller dynamically adjusts the lighting state based on the relationship between the non-lighting period, deflection period, and exposure period, switching from continuous lighting to interrupted lighting with a calculated non-lighting period inserted, thereby optimizing both motor acceleration and photosensitive member protection.
2Object-affected harmful factors
If a non-lighting period is inserted to suppress unnecessary exposure, then photosensitive member exposure is controlled, but the light receiving signal may not be obtained timely
Solution Approach 1:
The patent applies parameter changes by precisely calculating the non-lighting period based on the deflection period and exposure period parameters. The controller determines the non-lighting period as the difference between the deflection period and exposure period, ensuring that the light beam is suppressed only for the exact duration needed to prevent unnecessary exposure while maintaining proper timing for light receiving signal detection.
3Speed
If the rotational frequency changes from a higher frequency to a lower frequency, then the motor speed is reduced, but the timing synchronization between light emission and detection becomes more difficult
Solution Approach 1:
The patent applies feedback by continuously monitoring the motor's rotational frequency and using this information to adjust the lighting control. The controller receives feedback about the rotational frequency change from the motor driver, recalculates the appropriate non-lighting period based on the new target frequency, and adjusts the lighting suppression timing accordingly to maintain synchronization between light emission and detection.
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 solution effectively suppresses unnecessary exposure of the photosensitive member while maintaining accurate rotation control, ensuring timely light receiving signal reception and preventing deterioration in motor control accuracy.
Implementation Method 1
a polygon mirror 61, which deflects the light beam; an optical sensor 71, which receives the light beam reflected by the polygon mirror 61 and generates a BD signal
Implementation Method 2
a laser diode 63, which emits a light beam under the control of the control circuit 83
Data Source
AI summary
An image forming apparatus includes a controller, wherein the controller execute first control of controlling a rotational frequency of the motor based on a light receiving signal, wherein, when the target rotational frequency changes from a first rotational frequency to a second rotational frequency that is lower than the first rotational frequency, the controller executes speed change control of: stopping execution of the first control; and changing a rotational frequency of the motor, and non-lighting period change control of changing the non-lighting period in the lighting control from a first non-lighting period corresponding to the first rotational frequency to a second non-lighting period corresponding to the second rotational frequency, and the controller starts the first control in response to satisfying a condition where the deflection period of the mirror obtained based on a position signal of a rotor of the motor is longer than the second non-lighting period.