Dishwasher Spray Arm Reversal Control for Obstacle Sensing
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Solution Overview
Problem
Dishwashing machines face challenges in efficiently rotating spray arms to ensure thorough cleaning without obstruction, as existing systems fail to effectively detect and adapt to loads exceeding predetermined limits, potentially leading to halted rotation or damage from obstacles.
Innovation Solution
A method involving a motor-actuated spray arm with a sensor system that monitors current draw to determine if the load exceeds a predetermined limit, generating a control signal to reverse the rotation and allow the spray arm to oscillate around obstacles, ensuring continuous cleaning coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the spray arm rotates continuously to ensure thorough cleaning, then cleaning coverage is improved, but the system may encounter obstacles causing halted rotation or damage
Solution Approach 1:
The motor controller monitors current draw from the motor and compares it to a threshold value. When the current exceeds the threshold, indicating an obstacle is detected, the controller reverses the motor rotation direction. This feedback mechanism allows the spray arm to adapt to obstacles while maintaining continuous cleaning operation.
Solution Approach 2:
The spray arm rotation system transitions from static continuous rotation to dynamic adaptive rotation. The system automatically adjusts rotation direction based on real-time load conditions, enabling the spray arm to oscillate around obstacles rather than halting completely, thus maintaining cleaning productivity.
2Reliability
If the spray arm encounters an obstacle and halts rotation, then damage from the obstacle is prevented, but cleaning coverage is reduced
Solution Approach 1:
Instead of halting rotation when an obstacle is detected, the system inverts the rotation direction by reversing the motor current polarity. This allows the spray arm to continue moving (in the opposite direction) around the obstacle rather than stopping, preventing damage while maintaining cleaning coverage.
Solution Approach 2:
The motor controller implements periodic reversal of rotation direction when obstacles are detected. The spray arm oscillates back and forth around the obstacle in a periodic manner, ensuring continuous cleaning action without sustained contact that could cause damage.
3Measurement precision
If a sensor system monitors current draw to detect obstacles, then obstacle detection accuracy is improved, but device complexity increases
Solution Approach 1:
The motor's own current draw serves as the sensing mechanism for obstacle detection. The existing motor controller monitors the current already being consumed by the motor during normal operation, eliminating the need for separate external sensors. This self-service approach provides accurate obstacle detection without adding device complexity.
Solution Approach 2:
The motor controller performs multiple functions: it drives the motor rotation, monitors current draw, detects obstacles, and controls rotation reversal. By making the controller multi-functional, the system achieves accurate obstacle detection without adding separate dedicated sensing components, thus avoiding increased device complexity.
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 enables the spray arm to adapt to obstacles by reversing rotation, ensuring thorough cleaning and preventing damage, thereby maintaining efficient operation and effective cleaning performance.
Implementation Method 1
rotating the spray arm by actuation of a motor operably coupled to the spray arm
Implementation Method 2
determining whether the load on the spray arm exceeds a predetermined limit by comparing current drawn by the motor to a predetermined limit
Data Source
AI summary
A method of controlling the rotation of a spray arm for a dishwasher having a washing chamber, in which the spray arm is located, by rotating the spray arm with of a motor operably coupled to the spray arm.