Capacitance detection device

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Solution Overview

Problem

Detecting the state of oil and refrigerant inside a compressor is challenging due to the compressor's high-pressure environment and electrical noise interference, making it difficult to accurately measure the minute electrostatic capacitance.

Innovation Solution

An electrostatic capacitance detection device is implemented, comprising an electrode pair, a capacitor connected in series, and an inverter with a power line connected to the series-connected electrode pair and capacitor, allowing for accurate detection by applying an AC voltage from the inverter power lines and using a voltage detecting unit to measure the voltage between the electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If electrodes are provided to detect electrostatic capacitance for measuring oil level and refrigerant concentration, then detection capability is improved, but measurement precision deteriorates due to electrical noise from the motor and high-pressure environment

Engineering Contradiction:

Improvedetection capabilityVSAvoidelectrostatic capacitance measurement precision

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent introduces a capacitor as an intermediary component connected in series with the electrodes. This capacitor acts as a mediator that blocks high-frequency electrical noise from the motor while allowing the measurement of electrostatic capacitance related to oil level and refrigerant concentration. The capacitor filters out the harmful electrical interference, enabling precise measurements in the noisy compressor environment.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical parameters of the detection circuit by introducing a capacitor with specific capacitance value. This parameter change modifies the frequency response of the electrode circuit, allowing it to pass low-frequency signals (related to oil/refrigerant capacitance) while blocking high-frequency noise from the motor, thereby improving measurement precision.

Inventive Principle:

Principle #35Parameter changes

2Power

If the compressor operates as a high-pressure vessel to compress refrigerant, then compression function is improved, but detection difficulty increases due to the high-pressure environment interfering with electrode measurements

Engineering Contradiction:

Improvecompression powerVSAvoiddetection difficulty

Core Design Contradiction:

PowerVSDifficulty of detecting and measuring

Solution Approach 1:

The capacitor serves as an intermediary that isolates the detection circuit from the high-pressure environment's electrical interference. By placing the capacitor in series with the electrodes, it creates an electrical barrier that allows the high-pressure compression function to operate normally while protecting the measurement circuit from noise and interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If the motor rotates to generate electrical energy for compression, then power generation is improved, but harmful factors increase due to electrical noise interfering with capacitance detection

Engineering Contradiction:

Improveelectrical power generationVSAvoidelectrical noise

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful electrical noise from the motor into a beneficial filtering effect. By introducing a capacitor in series with the electrodes, the circuit naturally filters out the high-frequency noise while passing the low-frequency capacitance signals. The capacitor transforms the noisy electrical environment into a usable measurement signal, turning the motor's electrical interference from a harmful factor into a manageable condition.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

This configuration enables accurate detection of electrostatic capacitance without being affected by noise, allowing for reliable oil level, oil depletion, and refrigerant concentration monitoring within the compressor.

Implementation Method 1

an electrostatic capacitance detection device, comprising an electrode pair, a capacitor connected in series, and an inverter with a power line connected to the series-connected electrode pair and capacitor, allowing for accurate detection by applying an AC voltage from the inverter power lines and using a voltage detecting unit to measure the voltage between the electrodes

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Data Source

PatentEP3505920B1Capacitance detection device

Publication Date: 2021.03.03 MITSUBISHI ELECTRIC CORP

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AI summary

Provided is an electrostatic capacitance detection device including: an electrode pair including a pair of electrodes, the electrode pair being arranged inside a compressor configured to compress refrigerant; a capacitor being connected in series to the electrode pair; an inverter having one of power lines connected to one end of series-connected electrode pair and capacitor, and is configured to drive the compressor, the power lines being used for driving the compressor; and a voltage detecting unit configured to measure a voltage between the pair of electrodes of the electrode pair.