Pump Motor Monitoring for Dishwasher Liquor Level Control
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Solution Overview
Problem
Household appliances like dishwashers face inefficiencies due to inadequate liquor levels leading to air suction, foaming, and potential pump blockages, which affect cleaning efficacy and motor safety, and existing solutions like flow meters are costly and unreliable.
Innovation Solution
A monitoring device that detects motor rotational speed and power deviations to identify disturbances, controlling an inlet valve to adjust liquor levels and prevent foaming, while also protecting the motor from damage by detecting blockages and faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a flow meter is installed in the inlet pipe to monitor water amount and shut off the valve, then the water quantity can be controlled, but the device becomes costly and space-consuming
Solution Approach 1:
The patent replaces the mechanical flow meter with an electrical monitoring system that uses the motor's existing electrical parameters (current, power, rotational speed) to detect fluid flow conditions. This substitutes a complex mechanical measurement device with a simpler electrical sensing approach based on motor performance characteristics.
Solution Approach 2:
The motor itself serves as the sensing element by providing self-diagnostic information through its electrical parameters. The monitoring device utilizes the motor's own operational data (current consumption, rotational speed, power) to detect flow disturbances, eliminating the need for separate flow measurement instruments.
2Reliability
If the liquor level is kept high to prevent air suction, then adequate cleaning pressure is maintained, but water consumption and heating energy increase unnecessarily
Solution Approach 1:
The patent implements a feedback control system where the monitoring device continuously detects motor electrical parameters and compares them against stored reference values. When deviations indicating air suction or foaming are detected, the system automatically adjusts the inlet valve to restore proper liquor levels, creating a closed-loop control that optimizes water usage while maintaining cleaning pressure.
Solution Approach 2:
The system dynamically adjusts the liquor level based on real-time detection of pump operating conditions rather than maintaining a fixed high level. The inlet valve is controlled adaptively to match the actual water needs of the cleaning process, allowing the system to respond to changing contamination levels and pump performance.
3Reliability
If the liquor level is kept high to counteract foaming, then sufficient cleaning pressure is achieved, but water consumption increases
Solution Approach 1:
The monitoring device provides continuous feedback on pump performance by analyzing motor electrical parameters. When foaming is detected through characteristic deviations in current or power consumption, the system responds by adjusting the inlet valve to maintain adequate liquor levels only when necessary, rather than continuously maintaining high water levels.
Solution Approach 2:
The system applies water supplementation selectively and partially - only when and where needed to counteract detected foaming or air suction conditions. Rather than continuously adding water to prevent any possibility of pressure loss, the system intervenes only when actual disturbances are detected, minimizing unnecessary water consumption.
4Power
If the motor power is increased to handle blockages, then the pump can overcome higher resistance, but the motor may be damaged by excessive heat from converted electrical power
Solution Approach 1:
The monitoring device performs preliminary detection of blockage conditions by analyzing motor electrical parameters before the motor can be damaged. When characteristic deviations indicating increased resistance or blockage are detected, the system can take preventive action by interrupting operation or alerting the user, preventing the motor from operating in a damaging high-power state for extended periods.
Solution Approach 2:
The patent converts the potentially harmful effect of increased motor power during blockages into a useful diagnostic signal. The very increase in power consumption that could lead to motor damage also provides the monitoring device with detectable changes in electrical parameters, allowing the system to identify blockage conditions and respond appropriately to prevent damage.
Data Source
AI summary
An electric household appliance has a chamber that is at least partially filled with liquid during operation of the appliance. A motor drives a pump for drawing liquid from the chamber. A monitoring device detects the rotational speed and the power of the motor, compares detected values for the rotational speed and power to a predefined characteristic, and signals an exceptional state if the comparison indicates that the detected values deviate significantly from the characteristic.