Brushless DC Motor Commutation for Laser Printer Noise Reduction
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Solution Overview
Problem
Laser printers face noise issues due to motors operating at frequencies within the audible range, causing hearing annoyance, and existing solutions like increasing motor poles or using non-square wave commutation are complex and expensive.
Innovation Solution
A brushless DC motor commutation scheme that extrapolates motor position between discrete sensor signals and updates it when actual signals are received, using an ASIC controller with PID logic and commutator logic to produce pulse width modulation for motor windings, effectively smoothing motor commutation with standard components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If motor poles are increased to reduce noise, then the fundamental frequency and harmonics are shifted to a higher value, but the hearing annoyance remains because the frequency is still in the audible range
Solution Approach 1:
The patent changes the commutation waveform parameter from square wave to sinusoidal wave. This parameter change transforms the current waveform shape, eliminating the abrupt transitions that generate harmonics in the audible range, thereby reducing motor noise without increasing motor complexity
Solution Approach 2:
The patent replaces the traditional mechanical commutation approach (increasing motor poles) with an electrical control solution (sinusoidal commutation waveform generation). This substitution achieves noise reduction through waveform control rather than mechanical modification, avoiding increased device complexity
2Object-affected harmful factors
If non-square wave commutation is used to reduce noise, then motor noise is reduced, but more than three feedback sensor signals are required and the system becomes complex and expensive
Solution Approach 1:
The patent enables the motor control system to generate sinusoidal commutation waveforms using its existing three hall-effect sensors and standard microcontroller resources. The system serves itself by utilizing available components to create the desired waveform without requiring additional expensive sensors or complex external circuitry
Solution Approach 2:
The patent makes the existing three hall-effect sensors serve multiple functions: they provide both position feedback for commutation and enable sinusoidal waveform generation through software processing. This multi-functionality eliminates the need for additional dedicated sensors, reducing system complexity and cost
3Device complexity
If standard motors are used to reduce cost, then device complexity is reduced, but motor noise in the audible range causes hearing annoyance
Solution Approach 1:
The patent replaces mechanical noise reduction approaches (modifying motor construction) with an electrical control approach (sinusoidal commutation). This allows standard off-the-shelf motors to be used while achieving noise reduction through software-based waveform control, maintaining both simplicity and low noise
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 reduces motor noise by generating sinusoidal current waveforms, eliminating harmonics in the audible range, resulting in a quieter operating laser printer with reduced complexity and cost.
Implementation Method 1
The PID logic produces a pulse width modulation (PWM), in duty cycle, for application to any winding of the motor
Implementation Method 2
The commutator logic includes a lookup table with a multiplier for the PWM. High and low switches are provided per each winding of the three windings and are cumulatively switched according to the extrapolated motor position PWM and the multiplier
Implementation Method 3
an ASIC controller with a PID (proportional, integral, derivative) controller and commutator logic
Data Source
AI summary
In a laser printer, methods and apparatus include commutating a brushless dc motor having three windings. A controller receives discrete motor position signals, such as from hall-effect or FG sensors, and extrapolates motor position between the signals. It commutates the motor based on the extrapolated motor position and updates motor position whenever an actual discrete signal is received. Drive signals from the controller to the motor are such that a current flowing in any of the three windings follows a generally sinusoidal waveform. High and low switches are provided per each winding of the three windings and are cumulatively switched according to an extrapolated motor position based multiplier applied to a pulse width modulation duty cycle. In this regard, lookup tables, counters, registers and the like are provided. An engine card of the printer includes an ASIC with a power driver for use with generally off-the-shelf brushless dc motors.