JP5934916B2 - Refrigeration cycle apparatus and hot water generator provided with the same - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus including a dual refrigeration cycle in which a low temperature side refrigerant circuit and a high temperature side refrigerant circuit are connected via a cascade heat exchanger.

  Conventionally, a refrigeration cycle apparatus and a hot water generator of this type use a dual refrigeration cycle for the purpose of generating high-temperature hot air or hot water (see, for example, Patent Document 1).

  FIG. 5 shows a conventional refrigeration cycle apparatus described in Patent Document 1. As shown in FIG.

  As shown in FIG. 5, the refrigeration cycle apparatus 100 includes a low temperature side refrigerant circuit 110 that circulates a low temperature side refrigerant, a high temperature side refrigerant circuit 120 that circulates a high temperature side refrigerant, and a hot water circuit 130 that circulates hot water. Yes. The low-temperature side refrigerant circuit 110 includes a low-temperature side compressor 111, a low-temperature side four-way valve 112, a cascade heat exchanger 113 that exchanges heat with the high-temperature side refrigerant and functions as a condenser, a low-temperature side expansion valve 114, and an evaporator 115 that are annular. Connected to and configured.

  The high temperature side refrigerant circuit 120 includes a high temperature side compressor 121, a high temperature side four-way valve 122, a high temperature side heat exchanger 123 that exchanges heat with hot water and functions as a condenser, a high temperature side expansion valve 124, and a low temperature side refrigerant and heat. A cascade heat exchanger 113 that exchanges and functions as an evaporator is configured to be connected annularly by piping.

  On the other hand, in the hot water circuit 130, a circulation pump 131, a high temperature side heat exchanger 123 that generates heat by exchanging heat with a high temperature side refrigerant, and a radiator 132 such as a hot water storage tank or a fan convector are annularly connected by piping. Configured.

  Furthermore, the refrigeration cycle apparatus 100 is started from a state in which the pressure sensor 151 that detects the pressure of the refrigerant discharged from the compressor 111 (compressor discharge pressure) Pd, and the low temperature side compressor 111 and the high temperature side compressor 121 are stopped. When starting, the low temperature side compressor 111 is started first, and after the discharge pressure Pd detected by the pressure sensor 151 becomes equal to or higher than a predetermined pressure, the compressor is controlled to start the high temperature side compressor 121. And a compressor control unit 141.

JP 2010-196951 A

  However, in the conventional configuration, when the high-pressure shell type compressor is started in a state where the temperature of hot water heated by the high-temperature side refrigerant is high due to heat storage in a hot water storage tank or the like after a long-time shutdown state, Since the condensation temperature in the high temperature side heat exchanger is high and the evaporation temperature in the cascade heat exchanger is high due to the preceding operation of the low temperature side compressor, the discharge pressure on the high temperature side suddenly increases as the high temperature side compressor starts. To rise.

On the other hand, the shell temperature of the high-temperature side compressor gradually rises from a state where the temperature has dropped due to a long-term stoppage. Therefore, the discharged refrigerant condenses inside the shell of the high-temperature side compressor to become liquid refrigerant, and is discharged in large quantities from the compressor into the system in a state of being mixed with the oil inside the compressor shell.

  As a result, the amount of oil in the compressor is insufficient, and in the worst case, the compressor may be damaged, and the reliability of the equipment cannot be ensured.

  In addition, in order to prevent oil discharge at the time of start-up due to refrigerant condensation inside the compressor shell, when the compressor shell being stopped is heated with a heater to keep the compressor shell temperature high in advance, it is very large. Standby power was consumed, and there was a problem of lack of energy saving.

  An object of the present invention is to solve the above-described conventional problems, and to provide a refrigeration cycle apparatus that prevents energy shortage of the compressor and that is energy-saving and highly reliable by appropriately starting the compressor. And

  In order to solve the conventional problems, a refrigeration cycle apparatus according to the present invention includes a low temperature side compressor that compresses a low temperature side refrigerant, a low temperature side four-way valve that switches a flow direction of the low temperature side refrigerant, and condensation of the low temperature side refrigerant. A low-temperature side refrigerant circuit having a cascade heat exchanger functioning as an evaporator or an evaporator, a low-temperature side expansion means, a low-temperature side heat exchanger functioning as an evaporator or a condenser of the low-temperature side refrigerant, and compressing the high-temperature side refrigerant A high temperature side compressor, a high temperature side four-way valve for switching the flow direction of the high temperature side refrigerant, a high temperature side heat exchanger functioning as a radiator or evaporator of the high temperature side refrigerant, a high temperature side expansion means, and evaporation of the high temperature side refrigerant A high temperature side refrigerant circuit having the cascade heat exchanger functioning as a condenser or a condenser, a first temperature sensor for detecting a temperature of the high temperature side compressor, and the high temperature side in the high temperature side heat exchanger A second temperature sensor for detecting a temperature of the heat medium exchanged with the medium, and a control device, wherein the control device detects a temperature detected by the second temperature sensor by the first temperature sensor. When the temperature is higher than a predetermined value by a temperature, the cascade heat exchanger functions as an evaporator for the low-temperature side refrigerant and a condenser for the high-temperature side refrigerant, and starts up and operates the low-temperature side compressor and the high-temperature side compressor. Then, the cascade heat exchanger is switched to an operation that functions as a condenser for the low-temperature side refrigerant and an evaporator for the high-temperature side refrigerant.

  Thus, when the cascade heat exchanger functions as a low-temperature side refrigerant evaporator and a high-temperature side refrigerant condenser and starts up and operates the low-temperature side compressor and the high-temperature side compressor, the high-temperature side refrigeration cycle Since the discharged refrigerant is condensed by exchanging heat with the low-pressure low-temperature refrigerant in the low-temperature side refrigeration cycle, a rapid increase in discharge pressure in the high-temperature side refrigeration cycle is suppressed.

  Therefore, at the start of operation in which the cascade heat exchanger that is performed thereafter functions as a condenser for the low-temperature side refrigerant and an evaporator for the high-temperature side refrigerant, the shell temperature of the high-temperature side compressor and the heat medium temperature of the high-temperature side heat exchanger are The temperature difference between the refrigerant and the refrigerant is reduced, and the condensation of the discharged refrigerant inside the compressor shell is suppressed, so that the amount of oil mixed with the condensed refrigerant and flowing out into the cycle can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, by starting a compressor appropriately, the shortage of the oil quantity of a compressor can be prevented, and an energy saving and highly reliable refrigeration cycle apparatus can be provided.

Schematic configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. A graph showing the change over time of the refrigeration cycle at the start of operation of the conventional refrigeration cycle apparatus The graph which shows the time-dependent change of the refrigerating cycle at the time of the driving | operation of the refrigerating-cycle apparatus in Embodiment 1 of this invention. Flowchart of operation control of the refrigeration cycle apparatus in Embodiment 1 of the present invention. Schematic configuration diagram of a conventional refrigeration cycle apparatus

  A first invention includes a low temperature side compressor that compresses a low temperature side refrigerant, a low temperature side four-way valve that switches a flow direction of the low temperature side refrigerant, a cascade heat exchanger that functions as a condenser or an evaporator of the low temperature side refrigerant, A low temperature side refrigerant circuit having a low temperature side expansion means, a low temperature side heat exchanger functioning as an evaporator or a condenser of the low temperature side refrigerant, a high temperature side compressor that compresses the high temperature side refrigerant, and a flow path of the high temperature side refrigerant High-temperature side four-way valve for switching the direction, high-temperature side heat exchanger functioning as a radiator or evaporator for the high-temperature side refrigerant, high-temperature side expansion means, and the cascade heat exchanger functioning as an evaporator or condenser for the high-temperature side refrigerant , A first temperature sensor that detects the temperature of the high-temperature side compressor, and a second temperature that detects the temperature of the heat medium that exchanges heat with the high-temperature side refrigerant in the high-temperature side heat exchanger. Warm When the temperature detected by the second temperature sensor is higher than the temperature detected by the first temperature sensor by a predetermined value or more, the control device includes the sensor and the control device. The cascade heat exchanger condenses the low temperature side refrigerant after the low temperature side compressor and the high temperature side compressor are started and operated in a state of functioning as a side refrigerant evaporator and a high temperature side refrigerant condenser. And a refrigeration cycle apparatus that switches to an operation that functions as an evaporator for the high-temperature refrigerant.

  Thus, in the state where the cascade heat exchanger functions as a low temperature side refrigerant evaporator and a high temperature side refrigerant condenser, when the low temperature side compressor and the high temperature side compressor are started and operated, the high temperature side refrigeration cycle Since the discharged refrigerant is condensed by exchanging heat with the low-pressure and low-temperature refrigerant in the low-temperature refrigeration cycle that is sufficiently lower than the heat medium (for example, aqueous medium) in the high-temperature side heat exchanger, It is suppressed.

  Therefore, since the shell temperature of the high-temperature side compressor becomes equal to or higher than the discharge pressure saturation temperature in a short time, the compressor shell temperature can be sufficiently increased while suppressing oil discharge due to condensation of the discharge refrigerant inside the compressor shell. it can.

  Therefore, during the subsequent operation in which the cascade heat exchanger functions as a low-temperature refrigerant condenser and a high-temperature refrigerant evaporator, the temperature between the shell temperature of the high-temperature side compressor and the heat medium temperature of the high-temperature side heat exchanger. By reducing the difference and condensing the discharged refrigerant inside the compressor shell, the amount of oil mixed with the condensed refrigerant and flowing out into the cycle is reduced.

  As a result, it is possible to prevent the compressor from being damaged due to a decrease in the amount of oil in the compressor, and to improve the reliability of the equipment while suppressing standby power consumption to heat the shell of the stopped compressor with a heater etc. Can do.

  In a second aspect of the invention, particularly in the first aspect of the invention, the cascade heat exchanger is detected by the second temperature sensor in an operation in a state where the cascade heat exchanger functions as an evaporator of the low-temperature side refrigerant and a condenser of the high-temperature side refrigerant. The operation is switched when the temperature difference between the temperature and the temperature detected by the first temperature sensor becomes less than a predetermined temperature difference.

  As a result, since it is determined that the shell temperature of the high-temperature side compressor has increased to a temperature at which the refrigerant condensation inside the compressor shell does not occur, operation switching can be performed. The oil discharge amount can be reduced more reliably.

  In a third aspect of the invention, particularly in the first or second aspect of the invention, the high temperature side refrigerant circuit includes pressure detection means for detecting the pressure of the refrigerant discharged from the high temperature side compressor, and the cascade heat exchanger includes In the operation in a state of functioning as the evaporator of the low-temperature side refrigerant and the condenser of the high-temperature side refrigerant, the operation is performed so that the pressure detected by the pressure detecting means becomes a predetermined pressure. .

  As a result, the condensation temperature of the high temperature side refrigeration cycle in the cascade heat exchanger becomes stable, so the suction pressure of the low temperature side refrigeration cycle that absorbs heat from the high temperature side refrigerant becomes stable, and the operation in the high temperature side and low temperature side refrigeration cycles An excessive increase or decrease in pressure is suppressed.

  Therefore, in addition to the effects of the first or second invention, the operating pressure in the refrigeration cycle on the high temperature side and the low temperature side is prevented from deviating from the pressure usage range of the compressor. Can be improved. Further, the reliability can be improved even in various installation conditions such as when the pipe length is long.

  According to a fourth aspect of the present invention, there is provided a hot water generating apparatus including the refrigeration cycle apparatus according to any one of the first to third aspects of the invention, wherein the heat medium is water or an antifreeze liquid, and is heated by the high temperature side heat exchanger. The heat medium is used for at least one of hot water supply and heating.

  Thereby, there is no need to limit a kind of radiator, such as a water-air heat exchanger or an antifreeze-water heat exchanger.

  Therefore, the heat medium heated by the high temperature side heat exchanger can be widely used for heating equipment (hot air machines, radiators, floor heating panels, etc.), hot water supply equipment, and the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a schematic configuration diagram of a refrigeration cycle apparatus and a hot water generator in a first embodiment of the present invention. In FIG. 1, the refrigeration cycle apparatus 1 </ b> A includes a low temperature side refrigerant circuit 2 that circulates a low temperature side refrigerant and a high temperature side refrigerant circuit 3 that circulates a high temperature side refrigerant.

  Here, as the refrigerant, for example, a non-azeotropic mixed refrigerant such as R407C, a pseudo-azeotropic mixed refrigerant such as R410A, or a single refrigerant such as R134a can be used.

  The low-temperature side refrigerant circuit 2 includes a high-pressure shell-type low-temperature side compressor 21, a low-temperature side four-way valve 25, a cascade heat exchanger 22 that exchanges heat with the high-temperature side refrigerant and functions as a condenser or an evaporator, A low temperature side expansion means) 23 and a low temperature side heat exchanger 24 functioning as an evaporator or a condenser are connected in a ring shape by piping.

  The high temperature side refrigerant circuit 3 includes a high pressure shell type high temperature side compressor 31, a high temperature side four-way valve 35, a high temperature side heat exchanger 32 functioning as a condenser or an evaporator, a high temperature side expansion valve (high temperature side expansion means) 33, and A cascade heat exchanger 22 that functions as an evaporator or a condenser by exchanging heat with the low-temperature side refrigerant is connected in a ring shape by piping.

  In the present embodiment, the refrigeration cycle apparatus 1A constitutes a heating means of a hot water generating apparatus that uses hot water generated by the heating means for hot water supply or heating, and the high temperature side heat exchanger 32 includes a high temperature side refrigerant and water. It is a heat exchanger that heats water by exchanging heat with the water.

  Specifically, there is provided a hot water circuit 7 in which a high temperature side heat exchanger 32, a water pump 71, and a radiator 72 such as a hot water storage tank or a fan convector are annularly connected by piping, and the high temperature side The hot water heated by the heat exchanger 32 is radiated by the radiator 72, and heat storage and heating are performed.

  In a normal operation in which the cascade heat exchanger 22 is used as a low temperature side refrigerant condenser and a high temperature side refrigerant evaporator, the low temperature side refrigerant circuit 2 causes the refrigerant discharged from the low temperature side compressor 21 to pass through the low temperature side four-way valve 25. In the high temperature side refrigerant circuit 3, the refrigerant discharged from the high temperature side compressor 31 is sent to the high temperature side heat exchanger 32 via the high temperature side four-way valve 35.

  On the other hand, in the defrost operation, in the low temperature side refrigerant circuit 2, the refrigerant discharged from the low temperature side compressor 21 is sent to the low temperature side heat exchanger 24 via the low temperature side four-way valve 25. The refrigerant discharged from the side compressor 31 is sent to the cascade heat exchanger 22 via the high temperature side four-way valve 35. In FIG. 1, the direction of refrigerant flow during normal operation is indicated by arrows.

  Hereinafter, the state change of the refrigerant in the normal operation will be described.

  In the low temperature side refrigerant circuit 2, the high pressure low temperature side refrigerant discharged from the low temperature side compressor 21 flows into the cascade heat exchanger 22, and the low pressure high temperature side refrigerant in the refrigeration cycle circulating in the high temperature side refrigerant circuit 3 Heat exchange to dissipate heat. The high-pressure low-temperature side refrigerant that has flowed out of the cascade heat exchanger 22 is decompressed and expanded by the low-temperature side expansion valve 23, and then flows into the low-temperature side heat exchanger 24. The low-pressure low-temperature side refrigerant flowing into the low-temperature side heat exchanger 24 absorbs heat from the air and evaporates. The low-pressure low-temperature side refrigerant evaporated in the low-temperature side heat exchanger 24 is sucked into the low-temperature side compressor 21 again.

  On the other hand, in the high temperature side refrigerant circuit 3, the low temperature high temperature side refrigerant in the refrigeration cycle circulating in the high temperature side refrigerant circuit 3 is heated and evaporated by the heat radiation of the low temperature side refrigerant in the cascade heat exchanger 22. The low-pressure high-temperature side refrigerant evaporated in the cascade heat exchanger 22 is sucked into the high-temperature side compressor 31 and compressed after being compressed to a high pressure in the refrigeration cycle, and then discharged.

  The high-pressure high-temperature side refrigerant discharged from the high-temperature side compressor 31 flows into the high-temperature side heat exchanger 32 and exchanges heat with the aqueous medium circulating in the hot water circuit 7 by the circulation pump 71 to radiate heat. The high-pressure high-temperature side refrigerant that has flowed out of the high-temperature side heat exchanger 32 is decompressed by the high-temperature side expansion valve 33 and expanded, and then flows into the cascade heat exchanger 22 again.

  In the configuration of the refrigeration cycle apparatus 1A of the present embodiment, as described above, the low-pressure high-temperature side refrigerant circulating in the high-temperature side refrigerant circuit 3 is heated by the heat radiation of the high-pressure low-temperature side refrigerant circulating in the low-temperature side refrigerant circuit 2. Thus, the condensation temperature of the refrigeration cycle in the high temperature side refrigerant circuit 3 can be higher than the condensation temperature of the refrigeration cycle in the low temperature side refrigerant circuit 2.

  Therefore, a high temperature aqueous medium can be obtained by the heat radiation of the high temperature side refrigerant in the high temperature side heat exchanger 32.

  However, the temperature of the aqueous medium is higher than the shell temperature of the high-temperature compressor 31 and the temperature difference is large (for example, the refrigeration cycle apparatus 1A performs a heating operation in which the aqueous medium becomes a high temperature state, and is stopped by thermo-off or the like. After that, when the heating operation is started in a state where the shell temperature of the high temperature side compressor 31 is lowered to the vicinity of the ambient temperature), a large amount of oil in the high temperature side compressor 31 is discharged, resulting in poor lubrication inside the compressor. As a result, there is a problem that the compressor is damaged.

  This is because, when the low temperature side compressor 21 and the high temperature side compressor 31 are operated by starting the heating operation in the above-described environmental conditions, the high temperature side heat exchanger 32 has a high temperature of the radiating aqueous medium, and cascade. This is because, in the heat exchanger 22, the discharge pressure of the high-temperature side compressor 31 rapidly increases because the heat absorption source is sufficiently supplied by the high-pressure low-temperature side refrigerant circulating in the low-temperature side refrigerant circuit 2.

  That is, the shell temperature of the high-temperature side compressor 31 is heated by the operation, but gradually increases from around the ambient temperature due to the heat capacity of the compressor itself. Therefore, as in the section ab in FIG. 2, the shell temperature of the high temperature side compressor 31 becomes lower than the saturation temperature of the discharge pressure, and the discharged high temperature side refrigerant is inside the high temperature side compressor 31. It is condensed by exchanging heat with the shell of the high temperature side compressor 31.

  And the high temperature side refrigerant | coolant which became the liquid refrigerant by condensation is mixed with the oil in the high temperature side compressor 31, and a large amount from a compressor by the rise of a liquid level (oil + liquid refrigerant), diluting the oil inside a shell. Discharged. Thereafter, as shown in FIG. 2b and thereafter, when the shell temperature of the high-temperature side compressor 31 becomes higher than the discharge pressure saturation temperature, the refrigerant component in the diluted oil evaporates, so the liquid level drops at a stretch. It will be below the liquid level that can be refueled.

  Further, in the above-described environmental conditions, in order to prevent a large amount of oil in the high temperature side compressor 31 from being discharged, a heating source such as a heater is used to heat the stopped compressor shell. The standby power is increased and the energy saving performance is impaired.

  Therefore, in order to generate a high-temperature aqueous medium and use it in a wide range of applications and environmental conditions to ensure energy saving and device reliability, it is important to suppress oil discharge at the time of startup.

  In the present embodiment, as will be described in detail later, the control device 4 first starts the heating operation in a state where the temperature of the aqueous medium is higher than the shell temperature of the high temperature side compressor 31 by a predetermined temperature difference or more. As a preliminary operation, the flow paths of the low temperature side four-way valve 25 and the high temperature side four way valve 35 are set so that the cascade heat exchanger 22 functions as a low temperature side refrigerant evaporator and a high temperature side refrigerant condenser. After starting the low temperature side compressor 21 and the high temperature side compressor 31, the rotational speed of the low temperature side compressor 21 is adjusted and operated so that the discharge pressure of the high temperature side refrigeration cycle becomes a predetermined pressure.

  When the temperature difference between the temperature of the aqueous medium and the shell temperature of the high temperature side compressor 31 becomes less than the predetermined temperature difference, the preliminary operation is terminated, and the cascade heat exchanger 22 is connected to the low temperature side refrigerant condenser and the high temperature side. The flow paths of the low-temperature side four-way valve 25 and the high-temperature side four-way valve 35 are set so as to function as a refrigerant evaporator, and the operation is switched to the normal operation.

  Thus, as in the section ab in FIG. 3, during the preliminary operation, the low-pressure low-temperature of the low-temperature side refrigeration cycle in which the refrigerant discharged from the high-temperature side refrigeration cycle is sufficiently lower than the aqueous medium temperature in the high-temperature side heat exchanger 32. Since it is condensed by exchanging heat with the refrigerant, an increase in discharge pressure of the high temperature side refrigeration cycle is suppressed.

  Therefore, since the shell temperature of the high-temperature side compressor 31 becomes equal to or higher than the discharge pressure saturation temperature in a short time, the compressor shell temperature is sufficiently increased in a state where oil discharge due to discharge refrigerant condensation inside the compressor shell is suppressed. I can keep it.

Therefore, at the start of normal operation, as shown in FIG. 3c, the temperature difference between the aqueous medium temperature of the high temperature side heat exchanger 32 and the shell temperature of the high temperature side compressor 31 becomes small, and the discharge inside the compressor shell By suppressing the refrigerant condensation, the amount of oil mixed with the condensed refrigerant and flowing out into the cycle is reduced.

  Further, during the preliminary operation, the condensation temperature of the high temperature side refrigeration cycle in the cascade heat exchanger 22 becomes stable, so that the suction pressure of the low temperature side refrigeration cycle that absorbs heat from the high temperature side refrigerant becomes stable, and the high temperature side and low temperature side An excessive increase or decrease in pressure during operation in the refrigeration cycle is suppressed.

  Further, it can be determined from the measured values of the two temperature sensors that the shell temperature of the high-temperature side compressor 31 has risen to a temperature at which the refrigerant condensation inside the compressor shell does not occur at the start of normal operation. In this preliminary operation, the oil discharge amount at the start of normal operation is reliably reduced.

  Therefore, since the amount of oil in the compressor at the time of start-up is maintained without using a heater for heating the compressor shell, energy saving and reliability of the refrigeration cycle apparatus 1A can be improved.

  Hereinafter, the operation control operation will be described. The high temperature side refrigerant circuit 3 includes a first temperature sensor 51 that detects a shell temperature (shell temperature) Td of the high temperature side compressor 31, and a pressure of refrigerant discharged from the high temperature side compressor 31 (high temperature side discharge pressure) Pd. And a pressure sensor 61 for detecting. On the other hand, the hot water circuit 7 is provided with a second temperature sensor 52 that detects the temperature (warm water temperature) Tw of the aqueous medium flowing into the high temperature side heat exchanger 32.

  Based on detection values detected by various sensors such as the first temperature sensor 51, the second temperature sensor 52, and the pressure sensor 61, the control device 4 rotates the rotational speeds of the low temperature side compressor 21 and the high temperature side compressor 31, The switching of the low temperature side four-way valve 25 and the high temperature side four way valve 35 and the opening degree of the low temperature side expansion valve 23 and the high temperature side expansion valve 33 are operated.

  In the present embodiment, when the hot water temperature Tw is higher than the shell temperature Td by a predetermined temperature difference ΔTx or more, the control device 4 uses the cascade heat exchanger 22 as a low temperature side refrigerant evaporator and a high temperature side refrigerant condenser. The flow paths of the low-temperature side four-way valve 25 and the high-temperature side four-way valve 35 are set so as to function (cooling circuit), the low-temperature side compressor 21 and the high-temperature side compressor 31 are started, and the preliminary operation is started. .

  Further, the controller 4 adjusts the rotation speed of the low temperature side compressor 21 so that the high temperature side discharge pressure Pd becomes a predetermined pressure Pdt during the preliminary operation.

  Further, after the temperature difference ΔTa between the hot water temperature Tw and the shell temperature Td becomes less than the predetermined temperature Tdt, the control device 4 ends the preliminary operation, and the cascade heat exchanger 22 is a low-temperature refrigerant condenser and a high temperature. The flow paths of the low-temperature side four-way valve 25 and the high-temperature side four-way valve 35 are set so as to function as a side refrigerant evaporator (heating circuit), and the operation is switched to the normal operation.

  Next, startup control at the start of operation of the control device 4 will be described in detail with reference to a flowchart shown in FIG.

  First, the control device 4 receives a heating operation start instruction input from a remote controller or the like (step S1), and operates the hot water pump 71 (step S2). Next, the hot water temperature Tw is detected by the second temperature sensor 52, and the shell temperature Td is detected by the first temperature sensor 51 (step S3), and the temperature difference ΔTa between the hot water temperature Tw and the shell temperature Td is set to ΔTa = Tw-Td (Step S4).

  Next, the control device 4 compares the temperature difference ΔTa with a predetermined temperature difference ΔTx and determines whether ΔTa is equal to or greater than ΔTx (step S5). If the temperature difference ΔTa is less than the predetermined temperature difference ΔTx (NO in step S5), it is determined that the high-temperature-side discharged refrigerant is unlikely to be condensed inside the shell of the high-temperature-side compressor 31, and the activation control ends. . That is, it shifts to normal operation without performing preliminary operation.

  On the other hand, if the temperature difference ΔTa is greater than or equal to the predetermined temperature difference ΔTx (YES in step S5), it is determined that the high-temperature side discharged refrigerant is likely to condense inside the shell of the high-temperature side compressor 31, and the low-temperature side four-way valve 25 and the high temperature side four-way valve 35 are set to the cooling circuit side (step S6), the low temperature side compressor 21 and the high temperature side compressor 31 are started, and the preliminary operation is started (step S7).

  Thereafter, the control device 4 detects the high temperature side discharge pressure Pd with the pressure sensor 61 (step S8), and adjusts the rotation speed of the low temperature side compressor 21 so that the high temperature side discharge pressure Pd becomes equal to the predetermined pressure Pdt. (Step S9).

  Next, the control device 4 detects the shell temperature Td with the first temperature sensor 51 and the hot water temperature Tw with the second temperature sensor 52 again (step S10), and the temperature difference ΔTa between the hot water temperature Tw and the shell temperature Td. Is calculated in the same manner as in step S4 (step S11).

  Next, the control device 4 compares the temperature difference ΔTa with a predetermined temperature difference ΔTx and determines whether ΔTa is less than ΔTx (step S12). If the temperature difference ΔTa is equal to or greater than the predetermined temperature difference ΔTx (NO in step S12), it is determined that there is a possibility that refrigerant condensation inside the high-temperature compressor 31 shell may occur when shifting to normal operation. Returning to S8, the preliminary operation is continued.

  On the other hand, if the temperature difference ΔTa is less than the predetermined temperature difference ΔTx (YES in step S12), it is determined that refrigerant condensation does not occur inside the high-temperature side compressor 31 shell even when the normal operation is started. End driving. And the low temperature side four-way valve 25 and the high temperature side four way valve 35 are set to the heating circuit side (step S13), and this starting control is complete | finished.

  As described above, the refrigeration cycle apparatus and the hot water generator of the present embodiment detect the first temperature sensor 51 for detecting the shell temperature Td and the high temperature side discharge pressure Pd in the control device 4 and the high temperature side refrigerant circuit 3. And the second temperature sensor 52 for detecting the hot water temperature Tw in the hot water circuit 7. The control device 4 is configured such that the temperature detected by the second temperature sensor 52 is the first temperature. The flow path of the low-temperature side four-way valve 25 and the high-temperature side four-way valve 35 is set so as to be on the cooling circuit side at the start of operation that is higher than a temperature detected by the sensor 51 by a predetermined value or more. The side compressor 31 is started and a preliminary operation is performed.

  As a result, the shell temperature Td can be sufficiently increased in a state in which oil discharge caused by condensation of the discharged refrigerant inside the compressor shell during the preliminary operation is suppressed, so that the internal temperature of the compressor shell at the start of normal operation can be increased. Condensation of the discharged refrigerant is suppressed, and the amount of oil flowing out into the cycle is reduced.

  Therefore, it is possible to prevent the compressor from being damaged due to a decrease in the amount of oil in the compressor, and it is possible to ensure the reliability of the device while suppressing standby power consumption for heating the shell of the stopped compressor with a heater.

  Further, during the preliminary operation, the control device 4 adjusts and controls the rotation speed of the low temperature side compressor 21 so that the high temperature side discharge pressure Pd detected by the pressure sensor 61 becomes a predetermined pressure Pdt.

  As a result, the condensation temperature of the high temperature side refrigeration cycle in the cascade heat exchanger 22 becomes stable, so that the suction pressure of the low temperature side refrigeration cycle that absorbs heat from the high temperature side refrigerant becomes stable, and in the high temperature side and low temperature side refrigeration cycles. An excessive increase or decrease in pressure during operation is suppressed.

  Therefore, the operating pressure in the high temperature side and low temperature side refrigeration cycles is prevented from deviating from the pressure usage range of the compressor, so that the reliability of the compressor is further improved. Further, reliability can be ensured even in various installation conditions such as when the pipe length is long.

  Further, the control device 4 sets the standby temperature after the temperature difference ΔTa between the hot water temperature Tw detected by the second temperature sensor 52 and the shell temperature Td detected by the first temperature sensor becomes less than the predetermined temperature difference ΔTx. The operation is terminated and the flow paths of the low temperature side four-way valve 25 and the high temperature side four way valve 35 are set so as to be on the heating circuit side, and the operation is switched to the normal operation.

  As a result, it can be determined that the shell temperature Td has risen to a temperature at which the refrigerant condensation inside the compressor shell does not occur at the start of normal operation, so the amount of oil discharged at the start of normal operation is the minimum necessary preliminary operation. Is reliably reduced.

  Therefore, the startup time of normal operation can be shortened, and comfort is improved.

  In FIG. 1, the first temperature sensor 51 is provided in the shell of the high temperature side compressor 31, but the first temperature sensor 51 is configured to discharge refrigerant between the high temperature side compressor 31 and the high temperature side four-way valve 35. As long as it is on the flowing pipe, it may be provided at any position.

  Moreover, in FIG. 1, although the 2nd temperature sensor is provided in the entrance side of the high temperature side heat exchanger 32 in the hot water circuit 7, the 2nd temperature sensor may be provided in any position of the hot water circuit 7. .

  Furthermore, in the embodiment of the present invention, the aqueous medium is heated by the refrigeration cycle in the high temperature side refrigerant circuit 3, but the medium to be heated may be brine, and the radiator 72 may be a radiator or a fan controller. It may be a vector, a floor heating panel, or a hot water storage tank.

  According to the present invention, by appropriately starting the compressor, it is possible to improve the reliability of the equipment while suppressing the condensing refrigerant discharged inside the compressor shell and suppressing standby power consumption when the compressor is stopped. Therefore, it can be applied as a refrigeration cycle apparatus used for applications such as hot water generation, hot water supply, and air conditioning harmony.

1A Refrigeration cycle apparatus 2 Low temperature side refrigerant circuit 3 High temperature side refrigerant circuit 4 Controller 21 Low temperature side compressor 22 Cascade heat exchanger 23 Low temperature side expansion valve (low temperature side expansion means)
24 Low temperature side heat exchanger 25 Low temperature side four-way valve 31 High temperature side compressor 32 High temperature side heat exchanger 33 High temperature side expansion valve (high temperature side expansion means)
35 High-temperature side four-way valve 51 First temperature sensor 52 Second temperature sensor 61 Pressure sensor

Claims (4)

A low temperature side compressor that compresses a low temperature side refrigerant, a low temperature side four-way valve that switches a flow direction of the low temperature side refrigerant, a cascade heat exchanger that functions as a condenser or an evaporator of the low temperature side refrigerant, a low temperature side expansion means, A low-temperature side refrigerant circuit having a low-temperature side heat exchanger that functions as an evaporator or a condenser for the low-temperature side refrigerant; and
A high temperature side compressor that compresses the high temperature side refrigerant, a high temperature side four-way valve that switches a flow direction of the high temperature side refrigerant, a high temperature side heat exchanger that functions as a radiator or an evaporator of the high temperature side refrigerant, a high temperature side expansion means, The high temperature side refrigerant circuit having the cascade heat exchanger functioning as an evaporator or condenser of the high temperature side refrigerant;
A first temperature sensor for detecting a temperature of the high temperature side compressor; a second temperature sensor for detecting a temperature of a heat medium exchanging heat with the high temperature side refrigerant in the high temperature side heat exchanger; and a control device. ,
When the temperature detected by the second temperature sensor is higher than the temperature detected by the first temperature sensor by a predetermined value or more,
After the cascade heat exchanger functions as an evaporator for the low-temperature side refrigerant and a condenser for the high-temperature side refrigerant, the cascade heat exchange is performed after the low-temperature side compressor and the high-temperature side compressor are started and operated. The refrigeration cycle apparatus is characterized in that the apparatus switches to an operation that functions as a condenser for the low-temperature side refrigerant and an evaporator for the high-temperature side refrigerant. In an operation in which the cascade heat exchanger functions as an evaporator for the low-temperature side refrigerant and a condenser for the high-temperature side refrigerant, the temperature detected by the second temperature sensor and the temperature detected by the first temperature sensor The refrigeration cycle apparatus according to claim 1, wherein the operation is switched when the temperature difference becomes less than a predetermined temperature difference. The high temperature side refrigerant circuit includes pressure detection means for detecting the pressure of the refrigerant discharged from the high temperature side compressor, and the cascade heat exchanger functions as an evaporator for the low temperature side refrigerant and a condenser for the high temperature side refrigerant. 3. The refrigeration cycle apparatus according to claim 1, wherein the refrigeration cycle apparatus is operated so that a pressure detected by the pressure detection unit becomes a predetermined pressure in the operation in a state of being performed. The heat medium is water or an antifreeze, and the heat medium heated by the high temperature side heat exchanger is used for at least one of hot water supply and heating. A hot water generator comprising the refrigeration cycle apparatus according to any one of the preceding claims.

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