Flow rate control device, flow rate control method, and chiller

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Solution Overview

Problem

Existing flow rate control systems using impeller-type flowmeters and CPUs experience instability due to detection leakage and increased processing load, leading to high costs and complexity in hardware resources, particularly when performing PID control.

Innovation Solution

A flow rate control device utilizing a flowmeter that generates pulse signals with inverse pulse width proportional to fluid flow, an FV converter for frequency-voltage conversion, and a controller that adjusts motor drive input voltage based on flow rate differences, enabling reliable flow rate control with simple hardware and software processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a CPU samples pulse signals from an impeller-type flowmeter, then flow rate control can be implemented, but detection leakage occurs and control becomes unstable

Engineering Contradiction:

Improveflow rate control stabilityVSAvoidpulse signal detection leakage

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent replaces the mechanical CPU sampling process with an FV converter that continuously converts pulse signals to voltage signals. This substitution eliminates the intermittent sampling nature of CPU-based systems, providing continuous flow rate information without detection leakage while maintaining control stability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The FV converter acts as an intermediary between the flowmeter and the control system. It continuously transforms pulse signals into proportional voltage signals, ensuring that flow rate information is always available to the controller without the interruption and detection leakage inherent in direct CPU sampling.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a CPU with high processing capacity or multiple CPUs is used to eliminate detection leakage, then flow rate control stability improves, but hardware cost and complexity increase

Engineering Contradiction:

Improveflow rate control stabilityVSAvoidhardware resource complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of upgrading to more complex CPU systems (dual-core, multi-CPU), the patent substitutes a simple FV converter that performs continuous frequency-to-voltage conversion. This analog approach achieves stable flow rate control without requiring complex digital processing hardware.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The FV converter is a simple, low-cost component that provides continuous signal conversion. Rather than investing in expensive, complex CPU systems, the patent uses an inexpensive converter that continuously generates reliable flow rate information, achieving stability without hardware complexity.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If PID control is implemented on a CPU, then flow rate control precision improves, but processing load increases and responsiveness decreases

Engineering Contradiction:

Improveflow rate control precisionVSAvoidcontrol responsiveness

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent replaces CPU-based PID control with a simpler feedback mechanism that uses the continuous voltage signal from the FV converter. The controller adjusts motor frequency based on the voltage signal without requiring complex PID calculations, achieving precise control with faster responsiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The FV converter continuously provides accurate flow rate information in the form of a proportional voltage signal, enabling the controller to automatically adjust motor frequency without complex control algorithms. The system self-regulates based on the continuous feedback signal, achieving precision control without the processing burden of PID.

Inventive Principle:

Principle #25Self-service

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 solution effectively suppresses detection leakage and simplifies hardware resources while maintaining responsiveness, allowing for stable flow rate control without complex logic operations.

Implementation Method 1

an FV converter that makes frequency-voltage conversion of the pulse signal and generates a voltage value corresponding to the pulse signal

Methodology Applied

Scientific EffectFrequency-voltage conversion:

Data Source

PatentUS12372984B2Flow rate control device, flow rate control method, and chiller

Publication Date: 2025.07.29 SHINWA CONTROLS

AI summary

A flow rate control device according to one embodiment includes: a flowmeter that repeatedly generates a pulse signal based on flow of a fluid discharged from a fluid machine driven by a brushless motor or AC motor, such that a pulse width of the pulse signal is inversely proportional to a flow rate of the fluid; an FV converter that makes frequency-voltage conversion of the pulse signal and generates a voltage value corresponding to the pulse signal; and a controller that changes a frequency of a drive input voltage for driving the brushless motor or AC motor based on a difference between a converted flow rate of the fluid converted based on the voltage value generated by the FV converter and a preset target flow rate.