Sensorless Electric Water Pump Back-EMF Flow Control
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Solution Overview
Problem
Conventional electric water pumps face challenges in maintaining closed-loop control and low power consumption during very low flow conditions, often requiring expensive sensors and leading to higher power consumption when operating in open-loop arrangements.
Innovation Solution
An electric water pump design with a controller that continuously monitors the impeller's rotational speed and adjusts its direction to maintain closed-loop control, allowing for high flow rates at maximum speed and low flow rates at reduced speeds, utilizing a centrifugal pump with a stator and rotor, and an impeller that rotates in both clockwise and counterclockwise directions to manage flow rates efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensorless control is used to reduce cost, then the pump cannot maintain closed-loop control at very low speeds, but using sensors increases cost
Solution Approach 1:
The patent inverts the conventional approach by using the back-EMF signal not for its traditional purpose of rotor position detection, but as a flow rate sensor. The back-EMF magnitude correlates with coolant flow rate, allowing the system to maintain closed-loop control at very low speeds without requiring additional position sensors, thus resolving the contradiction between cost and control capability
Solution Approach 2:
The system uses its own inherent back-EMF signal, which is already present during motor operation, to provide flow rate feedback. This self-service approach eliminates the need for external flow sensors or position sensors, maintaining closed-loop control capability while avoiding additional hardware costs
2Productivity
If the pump operates in open-loop arrangement to achieve very low flow rates, then power consumption increases and diagnostic capability is lost, but closed-loop control maintains diagnostic capability and lower power consumption
Solution Approach 1:
The patent implements feedback by using the back-EMF signal to sense coolant flow rate and feed this information back to the controller. This allows the controller to adjust motor operation to achieve very low flow rates (3-5 L/min) while maintaining closed-loop control, thereby avoiding the increased power consumption and loss of diagnostic capability associated with open-loop operation
3Productivity
If the pump operates in open-loop arrangement to achieve very low flow rates, then diagnostic capability is lost, but closed-loop control maintains diagnostic capability
Solution Approach 1:
The back-EMF signal provides continuous feedback about motor operation and coolant flow rate to the controller. This feedback mechanism maintains diagnostic capability even at very low flow rates, as the controller can monitor the back-EMF signal to verify operational accuracy and detect potential issues, thereby preventing information loss
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
Enables low power consumption and diagnostic feedback during low flow conditions, avoiding the need for sensors while maintaining effective coolant flow management across varying operational speeds, with the ability to produce low flow rates of 3-5 L/min at reduced power usage.
Implementation Method 1
an electric motor disposed within the motor chamber, with the electric motor including a stator and a rotor
Implementation Method 2
the position of the rotor relative to the stator is determined by reading the back electromotive force (EMF) generated by the magnets in the rotor passing the coils in the stator
Implementation Method 3
an impeller is fixed to the rotor shaft for rotation in the fluid chamber, with the impeller being operable to pump coolant from the fluid inlet to the fluid outlet
Data Source
Figure 1~3
Figure 2
Figure 4
AI summary
An electric fluid pump (16) and method of regulating flow of liquid therethrough is provided. The pump has an electric motor (10) including a stator (38) and a rotor (40), wherein the rotor is supported for rotation to drive an impeller (46) that is fixed thereto for rotation to pump coolant from a fluid inlet (18) to a fluid outlet (24). A controller (48) is in operable, closed loop communication with the electric motor, and the impeller is operable to rotate in a first rotary pumping direction (CW) and an opposite second rotary pumping direction (CCW) in response to a signal (54) from the controller. The first rotary pumping direction produces a first positive flow rate of coolant (22) outwardly from the fluid outlet and the second rotary pumping direction produces a second positive flow rate of coolant (28) outwardly from the fluid outlet, with the first positive flow rate being greater than the second positive flow rate.