# US 10,502,446 B2 · Air conditioning device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,446 B2 - Document ID: US10502446B2 - Status: Granted - Kind: B2 - Application number: 15/543,655 - Filed: 2015-12-17 - Published: 2018-01-25 - Granted: 2019-12-10 - Earliest claimed: 2015-01-30 - Assignees: Daikin Industries, Ltd. - Applicants: Daikin Industries, Ltd. - Inventors: Ryuuta Ohura; Yuusuke Oka; Junya Minami - Web page: https://patentgrep.com/patent/US10502446B2 ## CPC - F24F 11/89: Arrangement or mounting of control or safety devices - F25B 13/00: Compression machines, plants or systems, with reversible cycle (defrosting cycles F25B47/02) - F25B 43/02: for separating lubricants from the refrigerant - F25B 49/02: for compression type machines, plants or systems - F25B 2313/0314: Temperature sensors near the indoor heat exchanger - F25B 2313/0315: Temperature sensors near the outdoor heat exchanger - F25B 2400/19: Pumping down refrigerant from one part of the cycle to another part of the cycle, e.g. when the cycle is changed from cooling to heating, or before a defrost cycle is started - F25B 2700/13: Mass flow of refrigerants - F25B 2700/1931: Discharge pressures - F25B 2700/1933: Suction pressures - F25B 2700/21151: at the suction side of the compressor - F25B 2700/21152: at the discharge side of the compressor - F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02) - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS ## Abstract In an air conditioning device (10) to which an outdoor unit (20) and indoor units (40) are connected, when a flow rate of a gaseous refrigerant in a gas main pipe (72a) is lower than a lower limit flow rate in main pipe, an amount of refrigerating machine oil accumulated in the gas main pipe (72a) is calculated. When gas branch pipes (72b) include a gas branch pipe (72b) having a flow rate lower than a lower limit flow rate in branch pipe even though the flow rate of the gaseous refrigerant in the gas main pipe (72a) is higher than the lower limit flow rate in main pipe, an amount of the machine oil accumulated in the gas branch pipe (72b) is calculated. When the amounts are integrated and the integrated value exceeds a set amount, oil collecting operation is performed. ## Claims ### Claim 1 An air conditioning device comprising: a refrigerant circuit including an outdoor unit and a plurality of indoor units, the outdoor unit being connected to the plurality of indoor units via an interconnecting pipe; an oil collection controller; and an operation controller controlling an operation of the refrigerant circuit, wherein the interconnecting pipe includes: a liquid interconnecting pipe including a liquid main pipe connected to the outdoor unit, and a plurality of liquid branch pipes branching off from the liquid main pipe, each of the plurality of liquid branch pipes connected to a corresponding one of the indoor units; and a gas interconnecting pipe including a gas main pipe connected to the outdoor unit, and a plurality of gas branch pipes branching off from the gas main pipe, each of the plurality of gas branch pipes connected to a corresponding one of the indoor units, wherein the operation controller is configured to calculate, at predetermined time intervals, an amount of refrigerating machine oil accumulated in the gas interconnecting pipe during operation of the air conditioning device using the oil collection controller, integrate the amount calculated for each predetermined time interval, and perform, when a value of the integration exceeds a set amount, an oil collecting operation for collecting the refrigerating machine oil in the refrigerant circuit into the compressor; the oil collection controller includes an oil accumulation amount calculator configured to, at each predetermined time interval, (i) determine that, when a flow rate of a gaseous refrigerant in the gas main pipe is lower than a preset lower limit flow rate in the gas main pipe, the refrigerating machine oil is accumulated in the gas main pipe, and calculate an amount of the refrigerating machine oil accumulated in the gas main pipe as the amount of oil accumulated in the gas interconnecting pipe, and (ii) determine that, when the flow rate of the gaseous refrigerant in the gas main pipe is higher than the preset lower limit flow rate in the gas main pipe and the plurality of gas branch pipes are determined to include a gas branch pipe having a flow rate of the gaseous refrigerant higher than a preset lower limit flow rate in the plurality of gas branch pipes and a gas branch pipe having a flow rate of the gaseous refrigerant lower than the preset lower limit flow rate in the plurality of gas branch pipes, the refrigerating machine oil is accumulated in the gas branch pipe having the flow rate of the gaseous refrigerant lower than the preset set lower limit flow rate in the plurality of gas branch pipes, and calculate an amount of the refrigerating machine oil accumulated in the gas branch pipe having the lower flow rate in the plurality of gas branch pipes as the amount of oil accumulated in the gas interconnecting pipe. ### Claim 2 (depends on 1) The air conditioning device of claim 1, wherein the oil collection controller includes a reference value storage storing, as a reference value for determining the flow rate of the gaseous refrigerant, a refrigerant state value indicating a state of the refrigerant corresponding to the preset lower limit flow rate determined for each of the plurality of gas branch pipes, and when calculating the amount of oil accumulated in a gas branch pipe, the oil accumulation amount calculator compares, for each of the plurality of gas branch pipes, a current value of the refrigerant state value with the reference value, and calculates the integrated value based on the amount of the refrigerating machine oil accumulated in the gas branch pipe determined to have the flow rate of the gaseous refrigerant lower than the preset set lower limit flow rate. ### Claim 3 (depends on 1) The air conditioning device of claim 1, wherein the oil collection controller includes a reference value storage storing, as a reference value for determining the flow rate of the gaseous refrigerant, a refrigerant state value indicating, for one or more air volume levels to be set for each of the indoor units, a state of the refrigerant corresponding to the preset lower limit flow rate for each of the indoor units, and when calculating the amount of oil accumulated in a gas branch pipe, the oil accumulation amount calculator compares, for each of the plurality of gas branch pipes, the reference value with a current value of the refrigerant state value of each of the plurality of gas branch pipes, and calculates the integrated value based on the amount of the refrigerating machine oil accumulated in the gas branch pipe determined to have the flow rate of the gaseous refrigerant lower than the preset set lower limit flow rate. ### Claim 4 (depends on 2) The air conditioning device of claim 2, wherein the reference value storage has the reference value for one or more air volume levels to be set for each of the indoor units, and the oil accumulation amount calculator compares, for each indoor unit, the reference value corresponding to the one or more air volume levels with the current value of the refrigerant state value of the plurality of gas branch pipes, and calculates the integrated value based on the amount of the refrigerating machine oil accumulated in the gas branch pipe determined to have the flow rate of the gaseous refrigerant lower than the preset set lower limit flow rate in branch pipe. ### Claim 5 (depends on 2) The air conditioning device of claim 2, wherein the controller performs control in which an evaporation temperature is maintained at a target value in cooling operation, the reference value storage stores a set value of the evaporation temperature as the reference value, and the oil accumulation amount calculator calculates the integrated value based on the amount of the refrigerating machine oil accumulated in a gas branch pipe in which a current value of the evaporation temperature is higher than the set value, the gas branch pipe being included in the plurality of gas branch pipes. ### Claim 6 (depends on 2) The air conditioning device of claim 2, wherein the controller performs control in which a condensing temperature is maintained at a target value in heating operation, the reference value storage stores a set value of the condensing temperature as the reference value, and the oil accumulation amount calculator calculates the integrated value based on the amount of the refrigerating machine oil accumulated in a gas branch pipe in which a current value of the condensing temperature is lower than the set value, the gas branch pipe being included in the plurality of gas branch pipes. ### Claim 7 (depends on 3) The air conditioning device of claim 3, wherein the controller performs control in which an evaporation temperature is maintained at a target value in cooling operation, the reference value storage stores a set value of the evaporation temperature as the reference value, and the oil accumulation amount calculator calculates the integrated value based on the amount of the refrigerating machine oil accumulated in a gas branch pipe in which a current value of the evaporation temperature is higher than the set value, the gas branch pipe being included in the plurality of gas branch pipes. ### Claim 8 (depends on 3) The air conditioning device of claim 3, wherein the controller performs control in which a condensing temperature is maintained at a target value in heating operation, the reference value storage stores a set value of the condensing temperature as the reference value, and the oil accumulation amount calculator calculates the integrated value based on the amount of the refrigerating machine oil accumulated in a gas branch pipe in which a current value of the condensing temperature is lower than the set value, the gas branch pipe being included in the plurality of gas branch pipes. ### Claim 9 (depends on 4) The air conditioning device of claim 4, wherein the controller performs control in which an evaporation temperature is maintained at a target value in cooling operation, the reference value storage stores a set value of the evaporation temperature as the reference value, and the oil accumulation amount calculator calculates the integrated value based on the amount of the refrigerating machine oil accumulated in a gas branch pipe in which a current value of the evaporation temperature is higher than the set value, the gas branch pipe being included in the plurality of gas branch pipes. ### Claim 10 (depends on 4) The air conditioning device of claim 4, wherein the controller performs control in which a condensing temperature is maintained at a target value in heating operation, the reference value storage stores a set value of the condensing temperature as the reference value, and the oil accumulation amount calculator calculates the integrated value based on the amount of the refrigerating machine oil accumulated in a gas branch pipe in which a current value of the condensing temperature is lower than the set value, the gas branch pipe being included in the plurality of gas branch pipes.