Dishwasher Filling Sequence Using Pump Concentricity Feedback
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Solution Overview
Problem
Commercial dishwashers face challenges in accurately metering the amount of washing liquid filled during the wash cycle, often resulting in undesirable noise due to air being sucked in by the circulating pump, especially when the liquid level is low.
Innovation Solution
A dishwasher control device manages a filling sequence with a primary and secondary phase, where the inlet valve is open for a preset time to ensure the circulating pump operates at its rated speed, and a concentricity check monitors the pump's operation to determine if the target liquid quantity is reached, continuing filling if necessary to prevent noise and ensure sufficient liquid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inlet valve is opened for a preset time to fill washing liquid, then the filling process is quick and simple, but the amount of liquid filled cannot be metered exactly
Solution Approach 1:
The control device monitors the circulating pump's operation during and after the primary filling phase. If the pump does not run smoothly (indicating insufficient liquid), the system provides feedback to continue the filling sequence until the pump operates correctly, ensuring accurate liquid quantity without complex metering hardware.
Solution Approach 2:
The circulating pump itself serves as the measurement indicator. By monitoring whether the pump runs smoothly at rated speed, the system uses the pump's own operational characteristics to determine if sufficient liquid has been filled, eliminating the need for separate liquid level sensors or flow meters.
2Power
If the circulating pump runs at rated speed during filling, then the pump operates efficiently, but noise is generated when liquid level is low causing air to be sucked in
Solution Approach 1:
The system performs a preliminary primary filling phase for a preset time to quickly fill the washing chamber with liquid before the pump is expected to run smoothly. This preliminary action ensures sufficient liquid is present before the pump operates at rated speed, preventing air suction and noise.
Solution Approach 2:
The patent accepts temporary noise during the transition phase as an acceptable trade-off. Rather than continuously monitoring liquid levels to prevent noise, the system allows brief periods where the pump may run at rated speed with potential noise, but ensures proper liquid levels are established through the primary filling phase and run-out monitoring.
3Productivity
If the filling sequence is terminated when the pump runs smoothly, then the process is efficient, but premature termination may occur due to incomplete liquid filling
Solution Approach 1:
The control device continuously monitors the circulating pump's operation during the filling sequence. The feedback from the pump's operational status (whether it runs smoothly at rated speed) is used to determine when to terminate filling, ensuring both efficiency and reliability by confirming actual liquid sufficiency rather than relying solely on timer-based termination.
Solution Approach 2:
The primary filling phase fills the chamber preliminarily to a level that should be sufficient for smooth pump operation. This preliminary filling action, combined with subsequent monitoring, ensures that termination occurs only when both time and operational criteria are met, preventing premature termination.
Data Source
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AI summary
In the case of a dishwasher, in particular a domestic dishwasher (1), having a control device (2) for implementing a dishwashing cycle (SG) for the cleaning of washware, having a dishwashing chamber (7) for accommodating the washware during the dishwashing cycle (SG), having an inflow valve (18) which can be operated by the control device (2) and is intended for introducing dishwashing liquid (S) into the dishwashing chamber (7), and having a circulating pump (22), which can be adjusted, in particular controlled or regulated, by the control device (2) and is intended for circulating the dishwashing liquid (S) located in the dishwashing chamber (7), the dishwashing cycle (SG) comprises at least one filling sequence (F, F1, F2, F3), in the case of which the inflow valve (18) is open during a primary filling phase (PF), the duration of which is dependent on a time setting (DT) which corresponds to a desired quantity (FMS) of dishwashing liquid (S) which is to be introduced into the dishwashing chamber (7) and is sufficient for concentricity of the circulating pump (22) running at a nominal speed (NN), and in the case of which use is made of a concentricity-monitoring unit (25), at the end of the primary filling phase (PF), to carry out a concentricity check (RP) to ascertain whether the circulating pump (22) running at the nominal speed (NN) is operating concentrically, wherein the filling sequence (F1) is terminated if the circulating pump (22) is operating concentrically, and the filling sequence (F2, F3) is continued if the circulating pump (22) is not operating concentrically.