JP5798830B2 - Supercritical cycle heat pump - Google Patents

Supercritical cycle heat pump Download PDF

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JP5798830B2
JP5798830B2 JP2011166353A JP2011166353A JP5798830B2 JP 5798830 B2 JP5798830 B2 JP 5798830B2 JP 2011166353 A JP2011166353 A JP 2011166353A JP 2011166353 A JP2011166353 A JP 2011166353A JP 5798830 B2 JP5798830 B2 JP 5798830B2
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pressure
oil
refrigerant
viscosity
expansion valve
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陽平 堀田
陽平 堀田
央幸 木全
央幸 木全
創 佐藤
創 佐藤
後藤　利行
利行 後藤
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Mitsubishi Heavy Industries Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/002—Lubrication
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/39—Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same evaporator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/13—Economisers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/23—Separators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00—Problems to be solved
    • F25B2500/16—Lubrication
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2513—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1931—Discharge pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1933—Suction pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21151—Temperatures of a compressor or the drive means therefor at the suction side of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the compressor

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)

Description

本発明は、ＣＯ２冷媒を用いた超臨界サイクル（ＣＯ２サイクル）ヒートポンプに関するものである。   The present invention relates to a supercritical cycle (CO2 cycle) heat pump using a CO2 refrigerant.

空調機や給湯機等に適用されているＣＯ２冷媒を用いた超臨界サイクルヒートポンプにおいては、圧縮機用の潤滑油（冷凍機油）として、ポリアルキレングリコール系油（ＰＡＧ油）やポリオールエステル系油（ＰＯＥ油）あるいはそれらの混合油を用いることが知られている（例えば、特許文献１，２参照）。また、その圧縮機として、低段側圧縮機構および高段側圧縮機構を備え、低段側圧縮機構で圧縮された中間圧冷媒ガスを密閉ハウジング内に吐出し、その冷媒ガスを高段側圧縮機構により吸入して高圧に２段圧縮する多段圧縮機を用いたものが知られている（例えば、特許文献３，４参照）。   In supercritical cycle heat pumps using CO2 refrigerant applied to air conditioners and water heaters, polyalkylene glycol-based oils (PAG oils) and polyol ester-based oils (refrigerating machine oils) It is known to use POE oil) or a mixed oil thereof (for example, see Patent Documents 1 and 2). The compressor also includes a low-stage compression mechanism and a high-stage compression mechanism. The intermediate-pressure refrigerant gas compressed by the low-stage compression mechanism is discharged into the hermetic housing, and the refrigerant gas is compressed at the high-stage side. One using a multi-stage compressor that sucks by a mechanism and compresses it to a high pressure in two stages is known (see, for example, Patent Documents 3 and 4).

さらに、特許文献３，４に示されるような多段圧縮機を用いたＣＯ２サイクルヒートポンプにおいて、放熱器と蒸発器間の冷媒回路中に、前後に第１電子膨張弁および第２電子膨張弁を設けて気液分離器を設置し、該気液分離器で分離された中間圧冷媒ガスを、多段圧縮機の中間圧雰囲気とされている密閉ハウジング内にインジェクションするインジェクション回路を設けたものが、例えば特許文献５，６等によって提案されている。   Further, in a CO2 cycle heat pump using a multistage compressor as disclosed in Patent Documents 3 and 4, a first electronic expansion valve and a second electronic expansion valve are provided before and after the refrigerant circuit between the radiator and the evaporator. A gas-liquid separator is installed, and an intermediate-pressure refrigerant gas separated by the gas-liquid separator is provided with an injection circuit that injects into a sealed housing that is an intermediate-pressure atmosphere of a multistage compressor. Patent Documents 5 and 6 propose this.

特開２００２−１７４４６２号公報JP 2002-174462 A 特開２００８−１８５２９０号公報JP 2008-185290 A 特開２００１−２７１７７６号公報Japanese Patent Laid-Open No. 2001-271776 特開２００５−２５７２４０号公報JP 2005-257240 A 特開２００８−１６３８９４号公報JP 2008-163894 A 特開２００８−１９０３７７号公報JP 2008-190377 A

ＣＯ２冷媒用の圧縮機では、どちらかと云えば、ポリアルキレングリコール系油（ＰＡＧ油）の使用が一般的とされている。しかし、ＰＡＧ油は、ＣＯ２冷媒に対する相溶性が低いことから、低温域において冷媒と分離し易く、システム側から圧縮機への油戻りが悪化し易いという課題を有している。特に、特許文献５，６に示されるように、インジェクション回路を設けたものでは、気液分離器内で油が分離し、低圧側冷媒回路からだけではなく、インジェクション回路からの油戻りも悪化し、圧縮機の潤滑性能に影響を及ぼしてしまう等の懸念があった。   In the compressor for CO2 refrigerant, it is generally used polyalkylene glycol oil (PAG oil). However, since the PAG oil has low compatibility with the CO 2 refrigerant, it has a problem that it is easily separated from the refrigerant in a low temperature range, and the oil return from the system side to the compressor is likely to deteriorate. In particular, as shown in Patent Documents 5 and 6, in the case where an injection circuit is provided, oil is separated in the gas-liquid separator, and not only from the low-pressure side refrigerant circuit, but also the oil return from the injection circuit deteriorates. There was a concern that it would affect the lubrication performance of the compressor.

一方、ポリオールエステル系油（ＰＯＥ油）は、冷媒に対する相溶性が高く、上記のような問題は生じ難いが、冷媒による希釈率の増大や油粘度の低下等が懸念される。この懸念は、密閉ハウジング内が中間圧とされる多段圧縮機を用いたものでは、中間圧ハウジング内の温度および圧力条件から、高圧ハウジングや低圧ハウジングとされた圧縮機に比べて低くなるものの、潤滑性能に影響を及ぼすことが考えられることから、何らかの制限をする必要があった。   On the other hand, polyol ester-based oil (POE oil) is highly compatible with the refrigerant and hardly causes the above problems, but there is a concern about an increase in the dilution rate due to the refrigerant and a decrease in the oil viscosity. This concern is low in the case of using a multistage compressor in which the inside of the hermetic housing has an intermediate pressure, because of the temperature and pressure conditions in the intermediate pressure housing, which is lower than that of a high-pressure housing or a low-pressure housing. Since it is considered that the lubrication performance is affected, it is necessary to make some restrictions.

本発明は、このような事情に鑑みてなされたものであって、圧縮機の潤滑油にＰＯＥ油を用いることで、インジェクション回路を設けたシステム側からの油戻り性を向上するともに、ＰＯＥ油を採用した場合の希釈率の増大や油粘度低下の懸念を解消することができる超臨界サイクルヒートポンプを提供することを目的とする。   The present invention has been made in view of such circumstances, and by using POE oil as the lubricating oil of the compressor, the oil return property from the system side provided with the injection circuit is improved and the POE oil is improved. It is an object of the present invention to provide a supercritical cycle heat pump that can eliminate the concern about an increase in dilution rate and a decrease in oil viscosity when adopting the above.

上記した課題を解決するために、本発明の超臨界サイクルヒートポンプは、以下の手段を採用する。
すなわち、本発明にかかる超臨界サイクルヒートポンプは、低段側圧縮機構および高段側圧縮機構を備え、前記低段側圧縮機構で圧縮した中間圧の冷媒ガスを密閉ハウジング内に吐き出し、その冷媒ガスを前記高段側圧縮機構により吸入して高圧に圧縮する多段圧縮機、放熱器、第１電子膨張弁、気液分離器、第２電子膨張弁および蒸発器をこの順に接続して冷凍サイクルを構成し、前記気液分離器で分離された中間圧冷媒ガスを前記多段圧縮機の前記密閉ハウジング内に注入するインジェクション回路を設け、作動媒体としてＣＯ２冷媒を用いた超臨界サイクルヒートポンプであって、前記多段圧縮機の潤滑油として、ポリオールエステル系油またはその混合油を用いるとともに、前記中間圧冷媒の圧力および温度下での前記油の前記ＣＯ２冷媒に対する溶解度に基づいて、該溶解度と温度とから前記油の粘度を求め、該油の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁を介して前記中間圧冷媒の圧力を制御し、その圧力を予め設定されている使用制限範囲に制御する制御部を備えていることを特徴とする。 In order to solve the above problems, the supercritical cycle heat pump of the present invention employs the following means.
That is, the supercritical cycle heat pump according to the present invention includes a low-stage compression mechanism and a high-stage compression mechanism, and discharges the intermediate-pressure refrigerant gas compressed by the low-stage compression mechanism into the sealed housing. A refrigeration cycle by connecting a multi-stage compressor, a radiator, a first electronic expansion valve, a gas-liquid separator, a second electronic expansion valve, and an evaporator in this order, which are sucked by the high-stage compression mechanism and compressed to a high pressure A supercritical cycle heat pump comprising an injection circuit configured to inject an intermediate pressure refrigerant gas separated by the gas-liquid separator into the sealed housing of the multistage compressor, and using CO2 refrigerant as a working medium, As the lubricating oil of the multistage compressor, a polyol ester oil or a mixed oil thereof is used, and the CO of the oil under the pressure and temperature of the intermediate pressure refrigerant is used. Based on the solubility in the refrigerant, the viscosity of the oil is determined from the solubility and temperature, and the pressure of the intermediate pressure refrigerant is set via the first electronic expansion valve in order to keep the viscosity of the oil above a certain viscosity zone. It has a control part which controls and controls the pressure to the use restriction range set up beforehand.

本発明によれば、多段圧縮機の中間圧とされる密閉ハウジング内に、気液分離器で分離された中間圧冷媒ガスを注入するインジェクション回路を備え、作動媒体としてＣＯ２冷媒を用いた超臨界サイクルヒートポンプにあって、多段圧縮機の潤滑油に、ポリオールエステル系油またはその混合油を用いるとともに、該油の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁を介して中間圧冷媒の圧力を制御し、その圧力を予め設定されている使用制限範囲に制御する制御部を備えているため、ＣＯ２冷媒に対して相溶性が高いポリオールエステル系油またはその混合油（ＰＯＥ油）を用いることにより、システム側から多段圧縮機への油戻り性を向上することができるとともに、中間圧冷媒の圧力を予め設定されている使用制限範囲に制御して該油の粘度を一定の粘度ゾーン以上にキープすることで、冷媒の圧力や温度によって左右される油の希釈率の増大や油粘度の低下を防止することができる。従って、多段圧縮機内の潤滑油不足や油の希釈率の増大、粘度の低下等による潤滑性能の低下を解消し、その信頼性を確保することができる。   According to the present invention, the supercritical using the CO2 refrigerant as the working medium is provided with the injection circuit for injecting the intermediate pressure refrigerant gas separated by the gas-liquid separator into the hermetic housing which is the intermediate pressure of the multistage compressor. In a cycle heat pump, a polyol ester-based oil or a mixed oil thereof is used as a lubricating oil for a multi-stage compressor, and an intermediate is provided via a first electronic expansion valve in order to keep the viscosity of the oil above a certain viscosity zone. Since a control unit that controls the pressure of the pressure refrigerant and controls the pressure within a preset use restriction range is provided, a polyol ester oil or a mixed oil (POE oil) having high compatibility with the CO 2 refrigerant ) Can improve the oil return from the system side to the multistage compressor, and the pressure of the intermediate pressure refrigerant is set in a preset use restriction range. Controlled to be to keep the viscosity of the oil over a certain viscosity zones, it is possible to prevent a reduction in increase and oil viscosity dilution of oil depends on the pressure and temperature of the refrigerant. Accordingly, it is possible to eliminate the deterioration of the lubricating performance due to the shortage of lubricating oil in the multistage compressor, the increase in the dilution ratio of the oil, the decrease in the viscosity, and the like, and the reliability can be ensured.

さらに、本発明の超臨界サイクルヒートポンプは、上記の超臨界サイクルヒートポンプにおいて、前記制御部は、前記インジェクション回路より注入される中間圧冷媒および前記多段圧縮機の吸入冷媒の圧力および温度を検出し、それぞれの冷媒過熱度を前記第１電子膨張弁および前記第２電子膨張弁により目標過熱度に制御するとともに、前記油の粘度を一定の粘度ゾーン以上にキープすべく、前記第１電子膨張弁を介して前記中間圧冷媒の圧力を制御し、その圧力を予め設定されている使用制限範囲に制御する構成とされていることを特徴とする。   Furthermore, the supercritical cycle heat pump of the present invention is the above supercritical cycle heat pump, wherein the control unit detects the pressure and temperature of the intermediate pressure refrigerant injected from the injection circuit and the intake refrigerant of the multistage compressor, Each refrigerant superheat degree is controlled to a target superheat degree by the first electronic expansion valve and the second electronic expansion valve, and the first electronic expansion valve is set to keep the viscosity of the oil above a certain viscosity zone. The pressure of the intermediate-pressure refrigerant is controlled via a pressure, and the pressure is controlled within a preset use restriction range.

本発明によれば、制御部が、インジェクション回路より注入される中間圧冷媒および多段圧縮機の吸入冷媒の圧力および温度を検出し、それぞれの冷媒過熱度を第１電子膨張弁および第２電子膨張弁により目標過熱度に制御するとともに、油の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁を介して中間圧冷媒の圧力を制御し、その圧力を予め設定されている使用制限範囲に制御する構成とされているため、インジェクション回路が接続されている気液分離器の前後に設けられている既設の第１電子膨張弁および第２電子膨張弁を制御することによって、新たな機器を追加設置することなく、制御部のソフト変更のみでＰＯＥ油の粘度を一定の粘度ゾーン以上にキープし、油の希釈率の増大や油粘度の低下を防止することができる。従って、ハード構成の複雑化を避けつつ、相溶性の高いＰＯＥ油を用いて簡易に潤滑性能の改善を図ることができる。   According to the present invention, the control unit detects the pressure and temperature of the intermediate pressure refrigerant injected from the injection circuit and the suction refrigerant of the multistage compressor, and determines the respective superheat degrees of the first electronic expansion valve and the second electronic expansion. Use the valve to control the pressure of the intermediate pressure refrigerant through the first electronic expansion valve to control the target superheat degree by the valve and keep the oil viscosity above a certain viscosity zone, and use that pressure in advance Since it is configured to be controlled within the limit range, a new electronic expansion valve is provided by controlling the existing first electronic expansion valve and the second electronic expansion valve provided before and after the gas-liquid separator to which the injection circuit is connected. No additional equipment is required, and the viscosity of the POE oil can be kept above a certain viscosity zone only by changing the software of the control unit, preventing an increase in the oil dilution rate and a decrease in the oil viscosity. That. Therefore, it is possible to easily improve the lubrication performance by using a highly compatible POE oil while avoiding complicated hardware configuration.

さらに、本発明の超臨界サイクルヒートポンプは、上述のいずれかの超臨界サイクルヒートポンプにおいて、前記制御部は、低圧と中間圧および中間圧と高圧の関係により予め設定されている低段側使用制限範囲および高段側使用制限範囲内において、前記密閉ハウジング内の前記油の粘度に応じて使用制限範囲を変化させ、該油の粘度が規定値に満たない場合でも、該規定値よりも低い第２の規定値を満たしておれば、一部の制限された圧力範囲での運転を可能としていることを特徴とする。   Furthermore, the supercritical cycle heat pump of the present invention is the above-described supercritical cycle heat pump, wherein the control unit has a low-stage side use restriction range set in advance according to the relationship between low pressure and intermediate pressure and intermediate pressure and high pressure. And within the upper stage use restriction range, the use restriction range is changed according to the viscosity of the oil in the hermetic housing, and even if the oil viscosity is less than the prescribed value, the second lower than the prescribed value. If the specified value is satisfied, it is possible to operate in a limited pressure range.

さらに、本発明によれば、制御部が、低段側の低圧と中間圧および高段側の中間圧と高圧の関係により予め設定されている低段側使用制限範囲および高段側使用制限範囲内において、密閉ハウジング内の油の粘度に応じて使用制限範囲を変化させ、該油の粘度が規定値に満たない場合でも、該規定値よりも低い第２の規定値を満たしておれば、一部の制限された圧力範囲での運転を可能としているため、密閉ハウジング内のＰＯＥ油の粘度が規定値を満たしていない場合であっても、第２の規定値を満たしておれば、上記使用制限範囲内の一部の制限された圧力範囲（例えば、図２に示す制限線Ｌよりも下側の圧力範囲）で運転することができる。従って、油温の上昇によるＰＯＥ油１７の粘度低下による潤滑性能の低下を確実に阻止することができるともに、システム側の運転の自由度を確保することができる。   Furthermore, according to the present invention, the control unit has a low-stage side use restriction range and a high-stage side use restriction range that are set in advance according to the relationship between the low-stage low pressure and intermediate pressure and the high-stage intermediate pressure and high pressure. Inside, the use restriction range is changed according to the viscosity of the oil in the sealed housing, and even when the viscosity of the oil is less than the specified value, if the second specified value lower than the specified value is satisfied, Since operation within a limited pressure range is possible, even if the viscosity of the POE oil in the hermetic housing does not satisfy the specified value, the above may be satisfied if the second specified value is satisfied. It is possible to operate in a partly limited pressure range within the use limit range (for example, a pressure range below the limit line L shown in FIG. 2). Accordingly, it is possible to reliably prevent a decrease in lubrication performance due to a decrease in the viscosity of the POE oil 17 due to an increase in the oil temperature, and it is possible to ensure a degree of freedom of operation on the system side.

本発明によると、ＣＯ２冷媒に対して相溶性が高いポリオールエステル系油またはその混合油（ＰＯＥ油）を用いることにより、システム側から多段圧縮機への油戻り性を向上することができるとともに、中間圧冷媒の圧力を予め設定されている使用制限範囲に制御して該油の粘度を一定の粘度ゾーン以上にキープすることで、冷媒の圧力や温度によって左右される油の希釈率の増大や油粘度の低下を防止することができるため、多段圧縮機内の潤滑油不足や油の希釈率の増大、粘度の低下等による潤滑性能の低下を解消し、その信頼性を確保することができる。   According to the present invention, by using a polyol ester-based oil or a mixed oil thereof (POE oil) that is highly compatible with a CO2 refrigerant, oil return from the system side to the multistage compressor can be improved, By controlling the pressure of the intermediate pressure refrigerant within a preset use restriction range and keeping the viscosity of the oil above a certain viscosity zone, an increase in the dilution ratio of the oil, which depends on the pressure and temperature of the refrigerant, Since it is possible to prevent a decrease in oil viscosity, it is possible to eliminate a decrease in lubrication performance due to a shortage of lubricating oil in the multistage compressor, an increase in the dilution ratio of oil, a decrease in viscosity, and the like, and to ensure its reliability.

本発明の一実施形態に係る超臨界サイクルヒートポンプの冷凍サイクル図である。It is a refrigerating cycle figure of the supercritical cycle heat pump concerning one embodiment of the present invention. 図１に示す超臨界サイクルヒートポンプの多段圧縮機に充填したＰＯＥ油における圧力の使用制限範囲を示すマップである。It is a map which shows the use restriction | limiting range of the pressure in the POE oil with which the multistage compressor of the supercritical cycle heat pump shown in FIG. 1 was filled. ＣＯ２冷媒とＰＯＥ油との温度をパラメータとした圧力−溶解度特性図である。It is a pressure-solubility characteristic figure which made the temperature of CO2 refrigerant and POE oil the parameter. ＣＯ２冷媒とＰＯＥ油との溶解度をパラメータとした温度−粘度特性図である。It is a temperature-viscosity characteristic figure which made solubility the CO2 refrigerant and POE oil a parameter.

以下に、本発明の一実施形態について、図１ないし図４を参照して説明する。
図１には、本発明の一実施形態に係るＣＯ２冷媒を用いた超臨界サイクルヒートポンプの冷凍サイクル図が示されている。
超臨界サイクルヒートポンプ（ＣＯ２サイクルヒートポンプ）１は、多段圧縮機２を備えており、この多段圧縮機２、オイルセパレータ３、放熱器４、第１電子膨張弁５、気液分離器６、第２電子膨張弁７および蒸発器８をこの順に順次冷媒配管９を介して接続することにより、閉サイクルの冷媒回路（冷凍サイクル）１０を構成している。 Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 4.
FIG. 1 shows a refrigeration cycle diagram of a supercritical cycle heat pump using a CO 2 refrigerant according to an embodiment of the present invention.
A supercritical cycle heat pump (CO2 cycle heat pump) 1 includes a multistage compressor 2, and this multistage compressor 2, oil separator 3, radiator 4, first electronic expansion valve 5, gas-liquid separator 6, second By connecting the electronic expansion valve 7 and the evaporator 8 sequentially in this order via the refrigerant pipe 9, a closed cycle refrigerant circuit (refrigeration cycle) 10 is configured.

さらに、上記冷媒回路（冷凍サイクル）１０には、気液分離器６で分離された中間圧の冷媒ガスを多段圧縮機２の中間圧とされる密閉ハウジング１４内に注入するインジェクション回路１１が設けられているとともに、オイルセパレータ３内で冷媒ガスから分離された潤滑油を、インジェクション回路１１中に設けられている熱交換器１２を介して中間圧冷媒ガスと熱交換させた後、多段圧縮機２の吸入冷媒配管９Ａ中に戻す油戻し回路１３が設けられている。   Further, the refrigerant circuit (refrigeration cycle) 10 is provided with an injection circuit 11 for injecting the intermediate-pressure refrigerant gas separated by the gas-liquid separator 6 into the hermetic housing 14 which is the intermediate pressure of the multistage compressor 2. In addition, after the lubricating oil separated from the refrigerant gas in the oil separator 3 is heat-exchanged with the intermediate-pressure refrigerant gas via the heat exchanger 12 provided in the injection circuit 11, the multistage compressor An oil return circuit 13 is provided for returning to the second suction refrigerant pipe 9A.

多段圧縮機２は、単一の密閉ハウジング１４内に図示省略の電動モータが内蔵されるとともに、該電動モータを介して駆動される低段側圧縮機構１５および高段側圧縮機構１６の２つの圧縮機構が設置されたものである。この多段圧縮機２は、低段側圧縮機構１５により蒸発器８で蒸発された低圧の冷媒ガスを吸込み、それを中間圧まで圧縮して密閉ハウジング１４内に吐出し、その中間圧冷媒ガスを高段側圧縮機構１６により吸入して高圧に２段圧縮し、該高圧冷媒ガスを多段圧縮機２に接続されているオイルセパレータ３に吐出する構成とされている。なお、低段側圧縮機構１５および高段側圧縮機構１６には、ロータリ式、スクロール式、その他の様々な形式の圧縮機構を単一もしくは混在させて使用することができる。   The multi-stage compressor 2 includes an electric motor (not shown) in a single hermetic housing 14, and includes a low-stage compression mechanism 15 and a high-stage compression mechanism 16 that are driven via the electric motor. A compression mechanism is installed. The multistage compressor 2 sucks the low-pressure refrigerant gas evaporated by the evaporator 8 by the low-stage compression mechanism 15, compresses the refrigerant gas to an intermediate pressure, and discharges the compressed gas into the hermetic housing 14. The high-stage side compression mechanism 16 sucks and compresses the high-pressure refrigerant into two stages, and discharges the high-pressure refrigerant gas to the oil separator 3 connected to the multistage compressor 2. The low-stage side compression mechanism 15 and the high-stage side compression mechanism 16 can use a rotary type, a scroll type, and other various types of compression mechanisms, either singly or in combination.

多段圧縮機２の中間圧とされる密閉ハウジング１４内の底部には、低段側圧縮機構１５および高段側圧縮機構１６の摺動部位を潤滑するための潤滑油（冷凍機油）１７が一定量充填されており、給油ポンプを介して摺動部位に強制給油されるようになっている。本実施形態では、この潤滑油１７として、ＣＯ２冷媒に対して相溶性が高いとされているポリオールエステル系油（ＰＯＥ油）またはその混合油（以下、単にＰＯＥ油と称する。）が用いられている。   Lubricating oil (refrigeration machine oil) 17 for lubricating the sliding parts of the low-stage side compression mechanism 15 and the high-stage side compression mechanism 16 is constant at the bottom in the hermetic housing 14 that is set to an intermediate pressure of the multistage compressor 2. The amount is filled, and the sliding part is forcibly lubricated via an oil pump. In the present embodiment, a polyol ester oil (POE oil) or a mixed oil thereof (hereinafter simply referred to as a POE oil) that is considered to be highly compatible with the CO 2 refrigerant is used as the lubricating oil 17. Yes.

オイルセパレータ３は、多段圧縮機２から吐出されたＣＯ２冷媒中に含まれている潤滑油１７を分離し、油戻し回路１３を介して多段圧縮機２の吸入冷媒配管９Ａに戻すものである。放熱器４は、高温高圧の冷媒ガスと冷却媒体とを熱交換し、冷媒ガスを放熱させて超臨界状態もしくは凝縮液化状態とすることにより、その冷媒を第１電子膨張弁５へと流出させるものである。第１電子膨張弁５は、高圧の冷媒を中間圧に減圧し、気液分離器６に供給するものである。この第１電子膨張弁５は、ヒートポンプ１の性能、能力が最大化されるとともに、後述のように潤滑油１７として用いられるＰＯＥ油の粘度が一定の粘度ゾーン以上をキープするように、中間圧冷媒の圧力および温度を計測し、その過熱度を目標値に制御するものである。   The oil separator 3 separates the lubricating oil 17 contained in the CO2 refrigerant discharged from the multistage compressor 2 and returns it to the suction refrigerant pipe 9 </ b> A of the multistage compressor 2 via the oil return circuit 13. The radiator 4 exchanges heat between the high-temperature and high-pressure refrigerant gas and the cooling medium, and releases the refrigerant to the first electronic expansion valve 5 by releasing the refrigerant gas to a supercritical state or a condensed liquefied state. Is. The first electronic expansion valve 5 reduces the high-pressure refrigerant to an intermediate pressure and supplies it to the gas-liquid separator 6. The first electronic expansion valve 5 has an intermediate pressure so that the performance and capacity of the heat pump 1 are maximized and the viscosity of the POE oil used as the lubricating oil 17 is kept above a certain viscosity zone as will be described later. The pressure and temperature of the refrigerant are measured, and the degree of superheat is controlled to a target value.

気液分離器６は、中間圧に減圧された気液二相のＣＯ２冷媒を気液分離し、ガス冷媒を気液分離器６からインジェクション回路１１を経て多段圧縮機２の密閉ハウジング１４内にインジェクションするとともに、液冷媒を第２電子膨張弁７に向って流出させるものである。第２電子膨張弁７は、中間圧の液冷媒を減圧し、低圧低温の気液二相冷媒として蒸発器８に供給するものであり、多段圧縮機２に吸入される低圧冷媒ガスの圧力および温度を計測し、蒸発器８出口の冷媒過熱度を目標値に制御するものである。   The gas-liquid separator 6 gas-liquid separates the gas-liquid two-phase CO2 refrigerant reduced to an intermediate pressure, and the gas refrigerant passes from the gas-liquid separator 6 through the injection circuit 11 into the hermetic housing 14 of the multistage compressor 2. In addition to the injection, the liquid refrigerant flows out toward the second electronic expansion valve 7. The second electronic expansion valve 7 decompresses the intermediate-pressure liquid refrigerant and supplies it to the evaporator 8 as a low-pressure low-temperature gas-liquid two-phase refrigerant, and the pressure of the low-pressure refrigerant gas sucked into the multistage compressor 2 and The temperature is measured and the refrigerant superheat degree at the outlet of the evaporator 8 is controlled to a target value.

蒸発器８は、第２電子膨張弁７からの気液二相冷媒を被冷却媒体と熱交換させ、被冷却媒体から吸熱して気液二相冷媒を蒸発させることにより、低温低圧のガス冷媒として多段圧縮機２に吸入させるものである。以上によって、多段圧縮機２の中間圧雰囲気とされている密閉ハウジング１４内に、気液分離器６からの中間圧冷媒ガスをインジェクションするインジェクション回路１１を備えた超臨界サイクルヒートポンプ１が構成されている。   The evaporator 8 exchanges heat between the gas-liquid two-phase refrigerant from the second electronic expansion valve 7 and the medium to be cooled, absorbs heat from the medium to be cooled, and evaporates the gas-liquid two-phase refrigerant, whereby a low-temperature and low-pressure gas refrigerant is obtained. As shown in FIG. As described above, the supercritical cycle heat pump 1 including the injection circuit 11 for injecting the intermediate pressure refrigerant gas from the gas-liquid separator 6 is configured in the hermetic housing 14 that is an intermediate pressure atmosphere of the multistage compressor 2. Yes.

上記超臨界サイクルヒートポンプ１の冷媒回路（冷凍サイクル）１０には、多段圧縮機２からの吐出配管に、吐出冷媒ガスの圧力および温度を検出する吐出圧力センサ１８および温度センサ１９が設けられ、多段圧縮機２の吸入冷媒配管９Ａに、吸入冷媒ガスの圧力および温度を検出する吸入圧力センサ２０および温度センサ２１が設けられ、更にインジェクション回路１１に、中間圧冷媒の圧力および温度を検出する中間圧力センサ２２および温度センサ２３が設けられている。また、多段圧縮機２における密閉ハウジング１４の底部に、潤滑油１７の油温を検出する油温センサ２４が設けられている。   The refrigerant circuit (refrigeration cycle) 10 of the supercritical cycle heat pump 1 is provided with a discharge pressure sensor 18 and a temperature sensor 19 for detecting the pressure and temperature of the discharged refrigerant gas in the discharge pipe from the multistage compressor 2. The suction refrigerant pipe 9A of the compressor 2 is provided with a suction pressure sensor 20 and a temperature sensor 21 for detecting the pressure and temperature of the suction refrigerant gas. Further, the injection circuit 11 has an intermediate pressure for detecting the pressure and temperature of the intermediate pressure refrigerant. A sensor 22 and a temperature sensor 23 are provided. An oil temperature sensor 24 that detects the oil temperature of the lubricating oil 17 is provided at the bottom of the hermetic housing 14 in the multistage compressor 2.

吐出圧力センサ１８および温度センサ１９の検出値は、高圧保護、吐出温度制御あるいは吐出過熱度制御等に用いられ、吸入圧力センサ２０および温度センサ２１は、低圧保護および第２電子膨張弁７による吸入過熱度制御に用いられるものである。更に、中間圧力センサ２２、温度センサ２３および油温センサ２４の検出値は、潤滑油１７として用いられるＰＯＥ油の粘度を一定の粘度ゾーンにキープするための以下の制御に用いられるものである。   The detection values of the discharge pressure sensor 18 and the temperature sensor 19 are used for high pressure protection, discharge temperature control or discharge superheat control, etc., and the suction pressure sensor 20 and the temperature sensor 21 are low pressure protection and suction by the second electronic expansion valve 7. It is used for superheat degree control. Furthermore, the detected values of the intermediate pressure sensor 22, the temperature sensor 23, and the oil temperature sensor 24 are used for the following control for keeping the viscosity of the POE oil used as the lubricating oil 17 in a certain viscosity zone.

ＰＯＥ油１７の粘度は、制御部２５を介して以下の通り制御されるようになっている。
ＰＯＥ油１７の粘度は、圧力および温度によって決まるＣＯ２冷媒に対する溶解度に依存している。ＰＯＥ油１７のＣＯ２冷媒に対する溶解度は、図３に示される温度をパラメータとした圧力−溶解度特性図から明らかな通り、温度が同じであれば、圧力が高くなる程、溶解度が大きくなり、また、圧力が同じであれば、温度が低くなる程、溶解度が大きくなる特性を有しており、例えば、圧力が５．４ＭＰａの場合、温度が６０℃であれば、溶解度は２０ｗｔ％となる。 The viscosity of the POE oil 17 is controlled through the control unit 25 as follows.
The viscosity of the POE oil 17 depends on the solubility in the CO 2 refrigerant determined by the pressure and temperature. As is apparent from the pressure-solubility characteristic diagram with the temperature shown in FIG. 3 as a parameter, the solubility of the POE oil 17 with respect to the CO 2 refrigerant increases as the pressure increases as the temperature is the same. If the pressure is the same, the lower the temperature, the higher the solubility. For example, when the pressure is 5.4 MPa, the solubility is 20 wt% when the temperature is 60 ° C.

一方、ＰＯＥ油１７のＣＯ２冷媒溶解時の粘度は、図４に示される溶解度をパラメータとした温度−粘度特性図から明らかな通り、温度が同じであれば、溶解度が高い程、粘度が低くなり、また、溶解度が同じであれば、温度が高くなる程、粘度が低くなる特性を有しており、例えば、溶解度が上記の如く２０ｗｔ％の場合、温度が４０℃であれば、粘度は５．０ｍＰａ．ｓとなる。このように、中間圧とされる多段圧縮機２の密閉ハウジング１４内に充填されているＰＯＥ油１７の粘度は、中間圧冷媒の圧力、温度を計測することにより把握でき、このことは、中間圧冷媒の圧力、温度を制御することにより、ＰＯＥ油１７の粘度をコントロールできることを意味する。   On the other hand, as is apparent from the temperature-viscosity characteristic diagram using the solubility shown in FIG. 4 as a parameter, the viscosity when the POE oil 17 is dissolved in the CO2 refrigerant is lower as the solubility is higher if the temperature is the same. In addition, if the solubility is the same, the higher the temperature, the lower the viscosity. For example, when the solubility is 20 wt% as described above, the viscosity is 5 when the temperature is 40 ° C. .0 mPa. s. As described above, the viscosity of the POE oil 17 filled in the hermetic housing 14 of the multistage compressor 2 having an intermediate pressure can be grasped by measuring the pressure and temperature of the intermediate pressure refrigerant. It means that the viscosity of the POE oil 17 can be controlled by controlling the pressure and temperature of the pressurized refrigerant.

そこで、ＣＯ２冷媒に対して相溶性が高いＰＯＥ油１７に冷媒が溶け込んで希釈率が増大したり、それによって油の粘度が低下したりしないように、ＰＯＥ油１７の粘度が一定の粘度ゾーン以上をキープするように制御部２５により、第１電子膨張弁５を介して中間圧冷媒の圧力および温度を制御している。つまり、中間圧冷媒の圧力および温度を中間圧力センサ２２および温度センサ２３で計測し、その圧力および温度下でのＰＯＥ油１７のＣＯ２冷媒に対する溶解度を図３から求め、該溶解度と温度とから図４によりＰＯＥ油１７の粘度を求める。そして、その粘度を一定の粘度ゾーン以上にキープすべく、制御部２５により第１電子膨張弁５を介して中間圧冷媒の圧力および温度を制御し、その圧力を予め設定されている使用制限範囲に制御することで、ＰＯＥ油１７の粘度を一定の粘度ゾーン以上としている。   Therefore, the viscosity of the POE oil 17 is equal to or higher than a certain viscosity zone so that the refrigerant does not dissolve in the POE oil 17 having high compatibility with the CO2 refrigerant and the dilution rate is increased and the viscosity of the oil is not reduced thereby. The pressure and temperature of the intermediate-pressure refrigerant are controlled by the control unit 25 via the first electronic expansion valve 5 so as to keep That is, the pressure and temperature of the intermediate pressure refrigerant are measured by the intermediate pressure sensor 22 and the temperature sensor 23, and the solubility of the POE oil 17 in the CO2 refrigerant under the pressure and temperature is obtained from FIG. 4 to determine the viscosity of the POE oil 17. The controller 25 controls the pressure and temperature of the intermediate pressure refrigerant through the first electronic expansion valve 5 in order to keep the viscosity above a certain viscosity zone, and the pressure is set in a preset use restriction range. By controlling this, the viscosity of the POE oil 17 is set to a certain viscosity zone or more.

また、制御部２５は、インジェクション回路１１より密閉ハウジング１４内に注入される中間圧冷媒および多段圧縮機２への吸入冷媒の圧力および温度を中間圧力センサ２２および温度センサ２３、吸入圧力センサ２０および温度センサ２１により検出し、それぞれの冷媒過熱度を第１電子膨張弁および第２電子膨張弁により目標過熱度（例えば、中間圧力飽和温度＋αｄｅｇおよび吸入圧力飽和温度＋αｄｅｇ）に制御するとともに、ＰＯＥ油１７の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁５を介して中間圧冷媒の圧力および温度を制御し、その圧力を予め設定されている使用制限範囲に制御している。   The control unit 25 determines the pressure and temperature of the intermediate pressure refrigerant injected into the sealed housing 14 from the injection circuit 11 and the suction refrigerant to the multistage compressor 2, the intermediate pressure sensor 22, the temperature sensor 23, the suction pressure sensor 20, and The refrigerant is detected by the temperature sensor 21, and the respective superheat degrees of the refrigerant are controlled to the target superheat degrees (for example, the intermediate pressure saturation temperature + αdeg and the suction pressure saturation temperature + αdeg) by the first electronic expansion valve and the second electronic expansion valve, and the POE oil In order to keep the viscosity of 17 above a certain viscosity zone, the pressure and temperature of the intermediate pressure refrigerant are controlled via the first electronic expansion valve 5, and the pressure is controlled within a preset use restriction range. .

さらに、本実施形態では、超臨界サイクルヒートポンプ１の多段圧縮機２が２段圧縮機とされていることから、それが運転可能な圧力範囲として、上述の点を考慮の上、図２に示されるように、低段側の低圧と中間圧および高段側の中間圧と高圧の関係を基に、低段側使用制限範囲および高段側使用制限範囲を予め設定している。そして、例えば、ＰＯＥ油１７の粘度の規定値（第１の閾値）を５．０ｍＰａ．ｓとした場合、該ＰＯＥ油１７の粘度が、この規定値以上の粘度であれば、上記使用制限範囲の全ての領域において超臨界サイクルヒートポンプ１（多段圧縮機２）が運転可能とされている。   Furthermore, in this embodiment, since the multistage compressor 2 of the supercritical cycle heat pump 1 is a two-stage compressor, it is shown in FIG. As described above, the low-stage use restriction range and the high-stage use restriction range are set in advance based on the relationship between the low pressure and intermediate pressure on the low stage side and the intermediate pressure and high pressure on the high stage side. For example, the specified value (first threshold value) of the viscosity of the POE oil 17 is 5.0 mPa.s. If the viscosity of the POE oil 17 is equal to or higher than this specified value, the supercritical cycle heat pump 1 (multistage compressor 2) can be operated in the entire range of the use restriction range. .

加えて、本実施形態においては、密閉ハウジング１４内のＰＯＥ油１７の粘度が、上記規定値（第１の閾値）を満たしていない場合であっても、一部の領域で運転が可能とされている。すなわち、密閉ハウジング１４内のＰＯＥ油１７の粘度が、上記の規定値５．０ｍＰａ．ｓよりも低い第２の規定値（第２の閾値）である、例えば３．０ｍＰａ．ｓを満たしておれば（例えば、４．０ｍＰａ．ｓの場合）、上記の使用制限範囲において、制限線Ｌよりも下側の圧力範囲でのみ運転可能とされている。これは、制限線Ｌよりも下側の範囲では、軸受の負荷が減少するため、必要とする粘度も小さくなることに由来する。これによって、油温の上昇によるＰＯＥ油１７の粘度低下による潤滑性能の低下を確実に阻止することができるともに、超臨界サイクルヒートポンプ１側の運転の自由度を確保することが可能となる。   In addition, in the present embodiment, even in a case where the viscosity of the POE oil 17 in the sealed housing 14 does not satisfy the specified value (first threshold value), it is possible to operate in a partial region. ing. That is, the viscosity of the POE oil 17 in the hermetically sealed housing 14 is the specified value of 5.0 mPa.s. is a second specified value (second threshold value) lower than s, for example, 3.0 mPa.s. If s is satisfied (for example, in the case of 4.0 mPa.s), it is possible to operate only in the pressure range below the limit line L in the use limit range. This is because, in the range below the limit line L, the bearing load decreases, so that the required viscosity is reduced. As a result, it is possible to reliably prevent a decrease in the lubrication performance due to a decrease in the viscosity of the POE oil 17 due to an increase in the oil temperature, and it is possible to ensure the degree of freedom of operation on the supercritical cycle heat pump 1 side.

以上に説明の構成により、本実施形態によれば、以下の作用効果を奏する。
上記の超臨界サイクルヒートポンプ１において、多段圧縮機２の低段側圧縮機構１５で中間圧に圧縮されたＣＯ２冷媒は、密閉ハウジング１４内に吐き出され、インジェクション回路１１より密閉ハウジング１４内に注入される中間圧の冷媒ガスと共に高段側圧縮機構１６に吸入される。この冷媒は、高段側圧縮機構１６で高圧に２段圧縮され、冷媒回路（冷凍サイクル）１０側へと吐出され、オイルセパレータ３で冷媒ガス中の潤滑油１７が分離された後、放熱器４に導入される。 With the configuration described above, according to the present embodiment, the following operational effects can be obtained.
In the supercritical cycle heat pump 1, the CO 2 refrigerant compressed to the intermediate pressure by the low-stage compression mechanism 15 of the multistage compressor 2 is discharged into the sealed housing 14 and injected into the sealed housing 14 from the injection circuit 11. Together with the intermediate-pressure refrigerant gas. This refrigerant is compressed in two stages to a high pressure by the high-stage compression mechanism 16 and discharged to the refrigerant circuit (refrigeration cycle) 10 side. After the lubricating oil 17 in the refrigerant gas is separated by the oil separator 3, the radiator 4 is introduced.

放熱器４に導入された冷媒は、冷却媒体に放熱することにより超臨界状態もしくは凝縮液化状態とされ、第１電子膨張弁５で中間圧に減圧されることにより気液二相状態となって気液分離器６に至り、そこで中間圧液冷媒と中間圧ガス冷媒とに分離される。分離された中間圧ガス冷媒は、インジェクション回路１１を介して上記の如く多段圧縮機２の密閉ハウジング３内にインジェクションされる。一方、中間圧液冷媒は、第２電子膨張弁７で再度減圧されることにより、低温低圧の気液二相冷媒となって蒸発器８に供給される。   The refrigerant introduced into the radiator 4 is brought into a supercritical state or a condensed liquefied state by radiating heat to the cooling medium, and becomes a gas-liquid two-phase state by being reduced to an intermediate pressure by the first electronic expansion valve 5. The gas-liquid separator 6 is reached, where it is separated into an intermediate-pressure liquid refrigerant and an intermediate-pressure gas refrigerant. The separated intermediate-pressure gas refrigerant is injected into the sealed housing 3 of the multistage compressor 2 through the injection circuit 11 as described above. On the other hand, the intermediate-pressure liquid refrigerant is decompressed again by the second electronic expansion valve 7, thereby becoming a low-temperature and low-pressure gas-liquid two-phase refrigerant and supplied to the evaporator 8.

蒸発器８に流入した低圧低温の気液二相冷媒は、蒸発器８を流通する間に被冷却媒体と熱交換され、被冷却媒体から吸熱することにより蒸発される。この低圧冷媒ガスは、吸入冷媒配管９Ａを介して油戻し回路１３からの油と合流して多段圧縮機２の低段側圧縮機構１５に吸入され、再び圧縮される。以上のサイクルが繰り返される間、放熱器４での放熱を利用することにより、暖房、加熱あるいは給湯等に供することができ、一方、蒸発器８での吸熱作用を利用することにより、冷房あるいは冷却に供することができる。   The low-pressure and low-temperature gas-liquid two-phase refrigerant that has flowed into the evaporator 8 exchanges heat with the medium to be cooled while flowing through the evaporator 8 and is evaporated by absorbing heat from the medium to be cooled. This low-pressure refrigerant gas merges with the oil from the oil return circuit 13 via the intake refrigerant pipe 9A, is sucked into the low-stage compression mechanism 15 of the multistage compressor 2, and is compressed again. While the above cycle is repeated, the heat dissipation in the radiator 4 can be used for heating, heating, hot water supply, or the like, while the heat absorption in the evaporator 8 can be used for cooling or cooling. Can be used.

この間、放熱器４からの放熱を暖房、加熱、給湯等に利用する場合においては、放熱器４を流れる冷媒に、インジェクションによる中間圧冷媒が加わるため、冷媒循環量が増大され、その分暖房、加熱、給湯能力を向上することができる。また、蒸発器８での吸熱を冷房、冷却等に利用する場合においては、エンタルピが増大され、蒸発器８で蒸発される冷媒の熱量が増加されるため、その分冷房、冷却能力を向上することができる。   During this time, in the case where the heat radiation from the radiator 4 is used for heating, heating, hot water supply, etc., the refrigerant circulating through the radiator 4 is added to the refrigerant flowing through the radiator 4, so that the refrigerant circulation amount is increased. Heating and hot water supply capacity can be improved. Further, when the heat absorption in the evaporator 8 is used for cooling, cooling, etc., the enthalpy is increased and the amount of heat of the refrigerant evaporated in the evaporator 8 is increased, so that the cooling and cooling capacity is improved accordingly. be able to.

また、本実施形態においては、多段圧縮機２の密閉ハウジング１４内に充填する潤滑油（冷凍機油）１７として、ＣＯ２冷媒に対して相溶性が高いとされているＰＯＥ油を用いている。このため、気液分離器６を設けた気液分離方式のインジェクション回路１１を備えている超臨界サイクルヒートポンプ１であっても、気液分離器６で油が分離され、油戻り性が悪化して多段圧縮機２内の潤滑油が不足する等の事態を招く虞がなく、多段圧縮機２での潤滑性能を確実に確保し、その信頼性を向上することができる。   In the present embodiment, POE oil that is highly compatible with the CO 2 refrigerant is used as the lubricating oil (refrigerating machine oil) 17 filled in the sealed housing 14 of the multistage compressor 2. For this reason, even in the supercritical cycle heat pump 1 including the gas-liquid separation type injection circuit 11 provided with the gas-liquid separator 6, the oil is separated by the gas-liquid separator 6 and the oil return property is deteriorated. Thus, there is no possibility of causing a situation such as a shortage of lubricating oil in the multistage compressor 2, and the lubricating performance in the multistage compressor 2 can be reliably ensured and the reliability can be improved.

さらに、ＰＯＥ油１７は、ＣＯ２冷媒に対して相溶性が高いことから、冷媒による希釈率の増大や粘度の低下が懸念されているが、中間圧冷媒の圧力および温度下でのＰＯＥ油１７のＣＯ２冷媒に対する溶解度に基づいて、その溶解度と温度とからＰＯＥ油１７の粘度を求め、該ＰＯＥ油１７の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁５を介して中間圧冷媒の圧力および温度を制御し、その圧力を予め設定されている使用制限範囲に制御する制御部２５を備えており、これによって、中間圧冷媒の圧力を予め設定されている使用制限範囲に制御してＰＯＥ油１７の粘度を一定の粘度ゾーン以上にキープし、冷媒の圧力や温度によって左右されるＰＯＥ油１７の希釈率の増大や粘度の低下を防止している。このため、多段圧縮機２内のＰＯＥ油１７の希釈率の増大、粘度の低下等による潤滑性能の低下を解消し、その信頼性を確保することができる。   Furthermore, since the POE oil 17 is highly compatible with the CO 2 refrigerant, there is a concern about an increase in dilution rate and a decrease in viscosity due to the refrigerant. However, the POE oil 17 under the pressure and temperature of the intermediate pressure refrigerant is concerned. Based on the solubility with respect to the CO2 refrigerant, the viscosity of the POE oil 17 is obtained from the solubility and temperature, and the intermediate pressure is set via the first electronic expansion valve 5 in order to keep the viscosity of the POE oil 17 above a certain viscosity zone. A control unit 25 is provided for controlling the pressure and temperature of the refrigerant and controlling the pressure within a preset use restriction range, whereby the pressure of the intermediate pressure refrigerant is controlled within a preset use restriction range. Thus, the viscosity of the POE oil 17 is kept above a certain viscosity zone, and an increase in the dilution rate of the POE oil 17 and a decrease in the viscosity, which are influenced by the pressure and temperature of the refrigerant, are prevented. For this reason, the deterioration of the lubrication performance due to the increase in the dilution rate of the POE oil 17 in the multistage compressor 2 and the decrease in the viscosity can be eliminated, and the reliability can be ensured.

また、上記制御部２５は、インジェクション回路１１を介して多段圧縮機２の密閉ハウジング１４内に注入される中間圧冷媒ガスおよび多段圧縮機２に吸入される冷媒ガスの圧力および温度を検出し、それぞれの冷媒過熱度を第１電子膨張弁５および第２電子膨張弁７により目標過熱度（例えば、中間圧力飽和温度＋αｄｅｇおよび吸入圧力飽和温度＋αｄｅｇ）に制御するとともに、ＰＯＥ油１７の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁５を介して中間圧冷媒の圧力および温度を制御し、その圧力を予め設定されている使用制限範囲に制御するように構成されている。   The control unit 25 detects the pressure and temperature of the intermediate pressure refrigerant gas injected into the sealed housing 14 of the multistage compressor 2 and the refrigerant gas sucked into the multistage compressor 2 through the injection circuit 11, Each refrigerant superheat degree is controlled to a target superheat degree (for example, intermediate pressure saturation temperature + α deg and suction pressure saturation temperature + α deg) by the first electronic expansion valve 5 and the second electronic expansion valve 7, and the viscosity of the POE oil 17 is constant. The pressure and temperature of the intermediate-pressure refrigerant are controlled via the first electronic expansion valve 5 so as to keep the above viscosity zone or more, and the pressure is controlled within a preset use restriction range.

このため、インジェクション回路１１が接続されている気液分離器６の前後に設けられている既設の第１電子膨張弁５および第２電子膨張弁６を制御することにより、新たな機器を追加設置することなく、制御部２５のソフト変更のみでＰＯＥ油１７の粘度を一定の粘度ゾーン以上にキープし、ＰＯＥ油１７の希釈率の増大や粘度の低下を防止することができる。従って、ハード構成の複雑化を避けつつ、相溶性の高いＰＯＥ油１７を用いて簡易に潤滑性能の改善を図ることができる。   For this reason, new equipment is additionally installed by controlling the existing first electronic expansion valve 5 and second electronic expansion valve 6 provided before and after the gas-liquid separator 6 to which the injection circuit 11 is connected. Without doing so, the viscosity of the POE oil 17 can be kept above a certain viscosity zone only by changing the software of the control unit 25, and an increase in the dilution rate of the POE oil 17 and a decrease in the viscosity can be prevented. Therefore, it is possible to easily improve the lubrication performance by using the highly compatible POE oil 17 while avoiding the complicated hardware configuration.

さらに、本実施形態では、多段圧縮機２が２段圧縮機とされており、図２に示されるように、低段側の低圧と中間圧および高段側の中間圧と高圧の関係により予め設定されている低段側使用制限範囲および高段側使用制限範囲内において、密閉ハウジング１４内のＰＯＥ油１７の粘度に応じて使用制限範囲を変化させ、ＰＯＥ油１７の粘度が規定値（第１の閾値）に満たない場合でも、該規定値よりも低い第２の規定値（第２の閾値）を満たしておれば、一部の制限された圧力範囲での運転を可能としている。このため、密閉ハウジング１４内のＰＯＥ油１７の粘度が規定値を満たしていない場合であっても、第２の規定値を満たしておれば、使用制限範囲内の一部の制限された圧力範囲（例えば、図２に示す制限線Ｌよりも下側の圧力範囲）で運転することができる。従って、油温の上昇によるＰＯＥ油１７の粘度低下による潤滑性能の低下を確実に阻止することができるともに、超臨界サイクルヒートポンプ１側の運転の自由度を確保することができる。   Further, in the present embodiment, the multistage compressor 2 is a two-stage compressor, and as shown in FIG. 2, the low-stage low pressure and intermediate pressure and the high-stage intermediate pressure and high pressure are preliminarily set in advance. Within the set lower-stage use restriction range and the higher-stage use restriction range, the use restriction range is changed in accordance with the viscosity of the POE oil 17 in the hermetic housing 14, and the viscosity of the POE oil 17 is a specified value (first Even when the threshold value is less than (1 threshold value), if the second specified value (second threshold value) lower than the specified value is satisfied, operation within a limited pressure range is possible. For this reason, even if the viscosity of the POE oil 17 in the hermetic housing 14 does not satisfy the specified value, if the second specified value is satisfied, a part of the limited pressure range within the use limit range (For example, it is possible to operate in a pressure range below the limit line L shown in FIG. 2). Accordingly, it is possible to reliably prevent a decrease in lubrication performance due to a decrease in the viscosity of the POE oil 17 due to an increase in the oil temperature, and it is possible to ensure the degree of freedom of operation on the supercritical cycle heat pump 1 side.

なお、本発明は、上記実施形態にかかる発明に限定されるものではなく、その要旨を逸脱しない範囲において、適宜変形が可能である。例えば、上記実施形態では、オイルセパレータ３、熱交換器１２、油戻し回路１３が設けられている例について説明したが、これらは必須のものではなく、省略されてもよい。また、多段圧縮機２は、密閉ハウジング１４内に内蔵される電動モータ、低段側圧縮機構１５および高段側圧縮機構１６が、如何なる配置構成とされたものであってもよい。   In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, in the above embodiment, the example in which the oil separator 3, the heat exchanger 12, and the oil return circuit 13 are provided has been described, but these are not essential and may be omitted. The multistage compressor 2 may have any arrangement configuration of the electric motor, the low-stage side compression mechanism 15, and the high-stage side compression mechanism 16 incorporated in the hermetic housing 14.

さらに、本発明に係る超臨界サイクルヒートポンプ１は、空調機や給湯機等に限定されることなく、幅広い用途に適用可能であり、多段圧縮機２の吐出側と吸入側間に四方切換弁を設け、冷媒回路（冷凍サイクル）１０を加熱サイクルと冷却サイクルとに切換え可能としたものにも適用できることはもちろんである。   Furthermore, the supercritical cycle heat pump 1 according to the present invention is not limited to an air conditioner or a water heater, and can be applied to a wide range of applications. A four-way switching valve is provided between the discharge side and the suction side of the multistage compressor 2. Needless to say, the present invention can also be applied to a refrigerant circuit (refrigeration cycle) 10 that can be switched between a heating cycle and a cooling cycle.

１ 超臨界サイクルヒートポンプ
２ 多段圧縮機
４ 放熱器
５ 第１電子膨張弁
６ 気液分離器
７ 第２電子膨張弁
８ 蒸発器
１０ 冷媒回路（冷凍サイクル）
１１ インジェクション回路
１４ 密閉ハウジング
１５ 低段側圧縮機構
１６ 高段側圧縮機構
１７ 潤滑油（ＰＯＥ油）
１８ 吐出圧力センサ
１９，２１，２３ 温度センサ
２０ 吸入圧力センサ
２２ 中間圧力センサ
２４ 油温センサ
２５ 制御部
Ｌ 制限線
DESCRIPTION OF SYMBOLS 1 Supercritical cycle heat pump 2 Multistage compressor 4 Radiator 5 1st electronic expansion valve 6 Gas-liquid separator 7 2nd electronic expansion valve 8 Evaporator 10 Refrigerant circuit (refrigeration cycle)
11 Injection circuit 14 Sealed housing 15 Low stage compression mechanism 16 High stage compression mechanism 17 Lubricating oil (POE oil)
18 Discharge pressure sensor 19, 21, 23 Temperature sensor 20 Suction pressure sensor 22 Intermediate pressure sensor 24 Oil temperature sensor 25 Control part L Limit line

Claims (3)

低段側圧縮機構および高段側圧縮機構を備え、前記低段側圧縮機構で圧縮した中間圧の冷媒ガスを密閉ハウジング内に吐き出し、その冷媒ガスを前記高段側圧縮機構により吸入して高圧に圧縮する多段圧縮機、放熱器、第１電子膨張弁、気液分離器、第２電子膨張弁および蒸発器をこの順に接続して冷凍サイクルを構成し、前記気液分離器で分離された中間圧冷媒ガスを前記多段圧縮機の前記密閉ハウジング内に注入するインジェクション回路を設け、作動媒体としてＣＯ２冷媒を用いた超臨界サイクルヒートポンプであって、
前記多段圧縮機の潤滑油をポリオールエステル系油またはその混合油とするとともに、
前記中間圧冷媒の圧力および温度下での前記油の前記ＣＯ２冷媒に対する溶解度に基づいて、該溶解度と温度とから前記油の粘度を求め、該油の粘度を一定の粘度ゾーン以上にキープすべく、第１電子膨張弁を介して前記中間圧冷媒の圧力を制御し、その圧力を予め設定されている使用制限範囲に制御する制御部を備えていることを特徴とする超臨界サイクルヒートポンプ。 A low-stage side compression mechanism and a high-stage side compression mechanism are provided. The intermediate-pressure refrigerant gas compressed by the low-stage side compression mechanism is discharged into the hermetic housing, and the refrigerant gas is sucked by the high-stage side compression mechanism and is pressurized. The refrigeration cycle was configured by connecting the multistage compressor, the radiator, the first electronic expansion valve, the gas-liquid separator, the second electronic expansion valve, and the evaporator in this order, and separated by the gas-liquid separator. A supercritical cycle heat pump provided with an injection circuit for injecting intermediate pressure refrigerant gas into the hermetic housing of the multistage compressor, using CO2 refrigerant as a working medium,
The lubricating oil of the multistage compressor is a polyol ester oil or a mixed oil thereof,
Based on the solubility of the oil in the CO2 refrigerant under the pressure and temperature of the intermediate pressure refrigerant, the viscosity of the oil is determined from the solubility and temperature, and the viscosity of the oil should be kept above a certain viscosity zone. A supercritical cycle heat pump comprising: a control unit that controls the pressure of the intermediate pressure refrigerant through the first electronic expansion valve and controls the pressure to a preset use restriction range. 前記制御部は、前記インジェクション回路より注入される中間圧冷媒および前記多段圧縮機の吸入冷媒の圧力および温度を検出し、それぞれの冷媒過熱度を前記第１電子膨張弁および前記第２電子膨張弁により目標過熱度に制御するとともに、前記油の粘度を一定の粘度ゾーン以上にキープすべく、前記第１電子膨張弁を介して前記中間圧冷媒の圧力を制御し、その圧力を予め設定されている使用制限範囲に制御する構成とされていることを特徴とする請求項１に記載の超臨界サイクルヒートポンプ。   The control unit detects the pressure and temperature of the intermediate-pressure refrigerant injected from the injection circuit and the suction refrigerant of the multistage compressor, and determines the degree of superheat of each of the first electronic expansion valve and the second electronic expansion valve. And controlling the pressure of the intermediate pressure refrigerant via the first electronic expansion valve to keep the viscosity of the oil above a certain viscosity zone, and the pressure is set in advance. The supercritical cycle heat pump according to claim 1, wherein the supercritical cycle heat pump is controlled to be within a limited use range. 前記制御部は、低圧と中間圧および中間圧と高圧の関係により予め設定されている低段側使用制限範囲および高段側使用制限範囲内において、前記密閉ハウジング内の前記油の粘度に応じて使用制限範囲を変化させ、該油の粘度が規定値に満たない場合でも、該規定値よりも低い第２の規定値を満たしておれば、一部の制限された圧力範囲での運転を可能としていることを特徴とする請求項１または２に記載の超臨界サイクルヒートポンプ。
In accordance with the viscosity of the oil in the hermetic housing within the low-stage side use restriction range and the high-stage side use restriction range set in advance by the relationship between low pressure and intermediate pressure and intermediate pressure and high pressure. Even if the oil usage limit range is changed and the viscosity of the oil is less than the specified value, operation within a limited pressure range is possible if the second specified value lower than the specified value is satisfied. The supercritical cycle heat pump according to claim 1 or 2, wherein
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