Dishwasher Circulation Pump Control to Prevent Dry Running Damage
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Solution Overview
Problem
Dishwashers face impaired washing and rinsing performance due to insufficient water recirculation, leading to potential pump damage from dry running conditions, and existing control methods are complex and inadequate for restoring optimal conditions.
Innovation Solution
A dishwasher control method that includes increasing the circulation pump's RPM, resetting the valve position, and drawing additional water into the hydraulic circuit upon detecting dry running conditions, with a restoring cycle that repeats until optimal functioning is restored or a maximum number of attempts is reached, accompanied by an alarm if issues persist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the circulation pump operates under normal conditions, then water recirculation maintains washing performance, but the pump may encounter dry running conditions causing damage
Solution Approach 1:
The control unit proactively detects insufficient water levels in the sump before the pump operates, and preemptively opens the water intake valve to replenish water. This preliminary action prevents dry running conditions from occurring in the first place, protecting the pump from damage while maintaining reliable operation.
Solution Approach 2:
The control unit continuously monitors water level conditions and pump operation status, using this feedback to dynamically control the water intake valve. When the sensor detects low water levels or the control unit identifies insufficient recirculation, it automatically opens the valve to restore proper water levels, creating a closed-loop feedback system that prevents pump damage.
2Productivity
If the circulation pump recirculates insufficient water, then washing performance is impaired, but increasing pump RPM alone is insufficient to restore optimal conditions
Solution Approach 1:
The restoration process is segmented into distinct sequential steps: first replenishing water to the sump, then resetting the diversion valve to its initial position, and finally increasing pump RPM. This segmentation ensures that each condition is properly established before moving to the next step, comprehensively restoring optimal washing performance rather than attempting a single inadequate adjustment.
Solution Approach 2:
The control unit systematically changes multiple operating parameters to restore optimal conditions: it modifies the water intake valve position to replenish water, adjusts the diversion valve position to ensure proper flow distribution, and increases the pump RPM to achieve nominal recirculation rates. These coordinated parameter changes comprehensively address the insufficiencies causing poor washing performance.
3Reliability
If the control method monitors and adjusts pump conditions, then pump damage is prevented, but the control method becomes particularly complex
Solution Approach 1:
The control unit performs multiple functions within a single integrated system: it monitors water levels via sensors, controls the water intake valve, manages the diversion valve position, regulates pump RPM, and coordinates the sequential restoration steps. This multi-functional approach consolidates what could be separate complex systems into one unified control unit, preventing pump damage while minimizing overall control complexity.
Solution Approach 2:
The control system is self-regulating, automatically detecting insufficient water conditions and initiating the restoration sequence without external intervention. The control unit autonomously coordinates the water intake valve, diversion valve, and pump RPM adjustments, and continuously monitors until optimal conditions are restored, reducing the need for complex external control mechanisms.
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
Effectively restores optimal water recirculation, preventing pump damage and improving washing performance while informing the user of persistent issues.
Implementation Method 1
the circulation pump which draws water from the sump, arranged in the lower section of the wash tub, to turn it back to the wash tub
Data Source
Figure 1
Figure 2
AI summary
A dishwasher (1) comprising: - a wash tub (2) in which the dishes to be washed are placed; - a hydraulic circuit (3) for circulating washing liquid through the wash tub (2), connectable to an external source of water and having at least a first rotatable spray arm (4) and a second rotatable spray arm (5) arranged in the wash tub (2) to spray the dishes with the washing liquid, a sump (8) which is arranged in the lower section of the wash tub (2) to collect the washing liquid that has been sprayed on the dishes during washing operation, a filter (9) preventing the dirt from getting into the circulation during washing, and a duct (10) for conveying the filtered washing liquid from the sump (8) to the first spray arm (4) and the second spray arm (5); - a circulation pump (11) arranged on the hydraulic circuit (3) downward of the sump (8) to draw the washing liquid from the sump (8) toward the first and second spray arms (4, 5) through the duct (10); - a valve (12) arranged on the hydraulic circuit (3) downward of the circulation pump (11) for allowing to selectively deliver the washing liquid to the first spray arm (4) or to the second spray arm (5); and - a control unit (13) connected to the hydraulic circuit (3), to the circulation pump (11) and to the valve (12), for controlling their functioning during washing operation. It is an object of the present invention also a control method of the dishwasher (1) as above specified.