System and method for detecting an elevated drain for a washing machine appliance
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Solution Overview
Problem
Conventional washing machine drain pump assemblies struggle to discharge all wash fluid to an elevated external drain due to loss of pump prime, leading to residual fluid in the drain hose that flows back into the sump, causing overfilling or sub-optimal wash fluid levels.
Innovation Solution
A washing machine with a water level detection system that includes a pressure sensor and controller to measure sump pressure, adjust fluid volumes, and determine if the external drain is elevated by comparing the difference between initial and subsequent fluid volumes, allowing for compensation to prevent overfilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the drain hose is made particularly lengthy or the external drain is elevated, then the drain pump cannot discharge all wash fluid to the external drain due to loss of pump prime, but this causes residual wash fluid to flow back into the sump resulting in overfilling
Solution Approach 1:
The system performs preliminary detection of elevated external drains by measuring the volume of wash fluid discharged during a test drain cycle. Based on this preliminary measurement, the controller预先 adjusts the fill volume in subsequent cycles to compensate for residual fluid that will flow back into the sump, preventing overfilling before it occurs.
Solution Approach 2:
The system uses feedback from the water level detection system to monitor the actual wash fluid level in the sump. When residual fluid flows back from the drain hose, the feedback mechanism detects the rising fluid level and triggers corrective action by reducing or stopping additional fluid intake, thereby maintaining proper fluid levels despite the drain hose length or external drain elevation.
2Quantity of substance
If the drain pump operates with a lengthy drain hose or elevated standpipe, then the pump loses prime and cannot discharge all wash fluid, but compensating for this requires detecting and measuring fluid volumes accurately
Solution Approach 1:
The system replaces direct mechanical measurement of fluid volume with a pressure-based detection method. The pressure sensor measures pressure variations in the sump, and the controller calculates fluid volume based on these pressure readings and known sump geometry, achieving accurate measurement without complex mechanical displacement sensors.
Solution Approach 2:
The system changes the measurement parameter from direct volume measurement to pressure measurement. By monitoring pressure changes in the sump during fill and drain cycles, the system infers fluid volume and detects elevated external drains, simplifying the measurement system while maintaining accuracy.
3Reliability
If the system detects and compensates for elevated external drains, then overfilling is prevented, but this requires additional detection systems and control logic
Solution Approach 1:
The pressure sensor serves multiple functions: it detects the water level in the sump, measures the volume of wash fluid discharged during drain cycles to identify elevated external drains, and provides feedback during operation to prevent overfilling. This multi-functionality eliminates the need for separate detection devices, reducing overall system complexity while maintaining reliable fluid level control.
Solution Approach 2:
The system uses its own operational data (pressure readings during normal fill and drain cycles) to automatically detect elevated external drains and adjust subsequent operation. No external calibration equipment or additional sensors are required - the system self-diagnoses and self-adjusts based on its own performance characteristics.
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
The system effectively prevents overfilling by accurately determining if the external drain is elevated and adjusting fluid levels, ensuring optimal wash fluid management and performance.
Implementation Method 1
A pressure sensor fluidly coupled to the sump measures a sump pressure
Data Source
AI summary
A washing machine appliance includes a sump for collecting wash fluid, a supply valve for supplying the wash fluid, a drain assembly for discharging the wash fluid from the sump, and a water level detection system for measuring sump pressures/fill levels. A controller is configured to perform an initial fill cycle and determine a first volume of wash fluid required to reach a target pressure. The drain assembly then drains the sump and the process is repeated to determine a second volume of wash fluid required to reach the target pressure. The difference between the first volume and the second volume is at least partially a result of wash fluid that the drain assembly could not discharge through the drain hose. The controller may determine that the external drain is elevated, and compensate accordingly, if a difference between the first volume and the second volume exceeds a predetermined threshold.