Brushless Motor Current Detection Timing for Stable Image Forming
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Solution Overview
Problem
The existing image forming apparatuses using sensorless DC brushless motors face issues with motor rotation unevenness due to current detection errors during switching noise, leading to instability and the need for high-duty voltage constraints, which results in costly motor specifications to handle temporary high loads.
Innovation Solution
Implementing a control mechanism that alternates between two settling times for current detection: a first settling time during image formation to stabilize motor rotation and a second settling time during non-image formation to allow higher duty voltage application, thereby optimizing motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a settling time is provided to wait for switching noise to subside before AD converter read, then current detection precision is improved, but motor drive voltage cannot be applied at high duty due to time loss
Solution Approach 1:
The patent applies dynamics by making the settling time adjustable rather than fixed. The control装置 dynamically changes the settling time duration based on operational conditions: using a first (longer) settling time during image formation to ensure precision, and a second (shorter) settling time during non-image formation to maximize motor drive efficiency and allow higher duty voltage application.
Solution Approach 2:
The patent changes the parameter of settling time duration based on operational mode. By switching between different settling time values (first settling time during image formation, second settling time during non-image formation), the system optimizes both current detection precision and motor drive efficiency for different operational contexts.
2Measurement precision
If all low-side switching elements are turned on simultaneously for current detection in all phases, then current detection accuracy is improved, but high-side switching elements must be turned off causing voltage application constraints
Solution Approach 1:
The patent applies dynamics by making the settling time adjustable rather than fixed. The control装置 dynamically changes the settling time duration based on operational conditions: using a first (longer) settling time during image formation to ensure precision, and a second (shorter) settling time during non-image formation to maximize motor drive efficiency and allow higher duty voltage application.
Solution Approach 2:
The patent changes the parameter of settling time duration based on operational mode. By switching between different settling time values (first settling time during image formation, second settling time during non-image formation), the system optimizes both current detection precision and motor drive efficiency for different operational contexts.
3Ease of operation
If a maximum duty value of 88% is constrained due to current detection time, then current detection can be performed, but sufficient voltage cannot be applied during high loads such as startup
Solution Approach 1:
The patent applies dynamics by making the settling time adjustable rather than fixed. The control装置 dynamically changes the settling time duration based on operational conditions: using a first (longer) settling time during image formation to ensure precision, and a second (shorter) settling time during non-image formation to maximize motor drive efficiency and allow higher duty voltage application.
Solution Approach 2:
The patent changes the parameter of settling time duration based on operational mode. By switching between different settling time values (first settling time during image formation, second settling time during non-image formation), the system optimizes both current detection precision and motor drive efficiency for different operational contexts.
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 image forming operations while enabling higher duty motor drive voltage, allowing the use of smaller and less costly motors by reducing rotation unevenness and increasing PWM voltage on-duty to nearly 100%.
Implementation Method 1
an amount of electrification to each coil is determined by PWM voltage control using an inverter
Implementation Method 2
after an AD converter or the like quantizes analog information of the current value, obtained by a shunt resistor
Implementation Method 3
after an AD converter or the like quantizes analog information of the current value, obtained by a shunt resistor, into digital information
Implementation Method 4
a motor such as a stepping motor, a brush motor, or a brushless motor may be used as a drive source
Data Source
AI summary
An image forming apparatus, including: a motor which includes a plurality of coils for driving an image forming portion; an inverter which applies a voltage to the plurality of coils; a current detecting portion which detects a current flowing in the plurality of coils; and a control portion which controls the inverter, based on a detection result of the current detecting portion, wherein the control portion controls the inverter so as to stop the application of the voltage during a current detection period for the current detecting portion to detect the current, and wherein the current detecting portion is capable of executing, in the current detection period, a first current detection operation of starting detection of the current after a predetermined settling time elapses and a second current detection operation of starting the detection at an earlier timing than the lapse of the predetermined settling time.