# US 12,000,636 B2 · Liquid level detector and air conditioning apparatus including the liquid level detector

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- Number: US 12,000,636 B2
- Document ID: US12000636B2
- Status: Granted
- Kind: B2
- Application number: 17/634,682
- Filed: 2019-11-18
- Published: 2022-10-13
- Granted: 2024-06-04
- Earliest claimed: 2019-11-18
- Assignees: Mitsubishi Electric Corporation
- Applicants: Mitsubishi Electric Corporation
- Inventors: Hiroki Maruyama; Takuya Matsuda; Hiroyuki Okano; Naomichi Tamura
- Web page: https://patentgrep.com/patent/US12000636B2

## CPC

- F25B 49/02: for compression type machines, plants or systems
- F25B 49/022: {Compressor control arrangements}
- F25B 13/00: Compression machines, plants or systems, with reversible cycle (defrosting cycles F25B47/02)
- F25B 43/006: {Accumulators}
- G01F 23/0007: {for discrete indicating and measuring (G01F23/02 - G01F23/28 take precedence)}
- G01F 23/14: by measurement of pressure
- G01F 23/247: {for discrete levels}
- G01F 23/248: {Constructional details; Mounting of probes}
- F25B 2313/0293: related to the indoor fan, e.g. controlling speed
- F25B 2400/01: Heaters
- F25B 2500/19: Calculation of parameters
- F25B 2600/021: Inverters therefor
- F25B 2600/2513: Expansion valves
- F25B 2700/04: Refrigerant level
- F25B 2700/19: Pressures
- F25B 2700/1933: Suction pressures
- F25B 2700/2113: of a suction accumulator
- F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME

## Abstract

A liquid level detector includes: a vertically-mounted accumulator that stores refrigerant; a heater that heats the accumulator; a temperature detector that detects a surface temperature of the accumulator; a pressure detector that detects a pressure of the refrigerant in the accumulator; and a controller. The controller detects a position of a liquid surface of the refrigerant in the accumulator based on a surface temperature of the accumulator detected by the temperature detector when the accumulator is heated by the heater, and a pressure of the refrigerant in the accumulator detected by the pressure detector.

## Claims

### Claim 1

A liquid level detector, comprising:
a vertically-mounted accumulator provided on a suction side of a compressor and configured to store refrigerant;
a heater configured to heat the accumulator;
a temperature detector configured to detect a surface temperature of the accumulator;
a pressure detector configured to detect a pressure of the refrigerant in the accumulator; and
a controller configured to detect a position of the liquid surface of the refrigerant in the accumulator based on a surface temperature of the accumulator detected by the temperature detector when the accumulator is heated by the heater, and a pressure of the refrigerant in the accumulator detected by the pressure detector,
wherein the controller calculates a saturation temperature of the refrigerant from a pressure of the refrigerant detected by the pressure detector, and adds the preset threshold value to the calculated saturation temperature to thereby calculate a temperature sum,
determines the position of the liquid surface of the refrigerant in the accumulator based on a result of comparison of the calculated temperature sum and the surface temperature detected by the temperature detector, and
determines a frequency of the compressor based on the determined position of the liquid surface of the refrigerant in the accumulator.

### Claim 2 (depends on 1)

The liquid level detector of claim 1, further comprising a memory that stores information used to calculate a saturation temperature of the refrigerant from a pressure of the refrigerant detected by the pressure detector, and stores the threshold value.

### Claim 3 (depends on 1)

An air-conditioning apparatus comprising the compressor and the liquid level detector of claim 1.