JP2014016119A - Heat pump type heating device - Google Patents

Abstract

There is provided a heat pump type heating device having a simple configuration and sufficiently improving the heating capacity.
A heat pump type heating device includes an indoor heat exchanger 26, an outdoor heat exchanger 27, a low pressure compressor 31 and a high pressure compressor that sequentially compress refrigerant sent from the outdoor heat exchanger 27. , A first decompressor 36 that decompresses the refrigerant sent from the indoor heat exchanger 26, and a gas-liquid separator 38 that separates the refrigerant sent from the first decompressor 36 into a gas phase and a liquid phase. Connected to the liquid phase side of the gas-liquid separator 38, connected to the gas phase side of the gas-liquid separator 38, the second pressure reducing device 37 for reducing the pressure of the refrigerant sent from the gas-liquid separator 38, The injection pipe 51 that guides the refrigerant sent from the separator 38 between the low-pressure compressor 31 and the high-pressure compressor 32, and the refrigerant flowing through the injection pipe 51 is in a gas-liquid two-phase state. A control unit 46 for controlling the pressure reduction ratio of the refrigerant in the pressure reducing device 37; Provided.
[Selection] Figure 1

Description

  The present invention generally relates to a heat pump type heating device, and more particularly to a two-stage compression type heat pump type heating device in which two compressors are provided on a heat pump cycle.

  Regarding a conventional heat pump type heating device, for example, Japanese Patent Application Laid-Open No. 8-210709 discloses a heat pump air conditioner for cold districts intended to enable heating operation even when the outdoor air temperature is −20 ° C. (Patent Document 1).

  In the heat pump air conditioner disclosed in Patent Document 1, a scroll compressor, a four-way valve, an indoor air heat exchanger, a receiver, an outdoor refrigerant control valve, and an outdoor air heat exchanger are sequentially connected by piping. Has been. A bypass passage for injecting liquid refrigerant into the scroll compressor is provided between the receiver and the scroll compressor via a liquid injection refrigerant control valve. The liquid injection refrigerant control valve is controlled by the difference between the discharge side temperature of the compressor and the target discharge temperature, and the outdoor refrigerant control valve has a temperature difference between temperature sensors provided before and after the outdoor air heat exchanger. Control is performed so that the degree of refrigerant superheat at the refrigerant outlet of the air heat exchanger is obtained.

  Japanese Patent Application Laid-Open No. 11-132575 discloses compression associated with mixing of liquid refrigerant into a gas refrigerant returned from a gas-liquid separator interposed in a liquid pipe to a compressor through a bypass pipe for gas injection. An air conditioner aimed at preventing a reduction in the reliability of the machine is disclosed (Patent Document 2).

  In the air conditioner disclosed in Patent Document 2, an outdoor heat exchanger and an indoor heat exchanger are sequentially connected to a compressor to form a refrigerant circulation circuit. A gas-liquid separator is interposed in the liquid pipe between the outdoor heat exchanger and the indoor heat exchanger. Between the gas-liquid separator and the suction side of the compressor, there is a bypass pipe for gas injection that returns the gas refrigerant in the gas-liquid separator to the compressor, and an on-off valve that opens and closes the flow path through the bypass pipe And are provided. The opening / closing valve is closed when the difference between the discharge temperature of the compressor and the condensation temperature of the refrigerant circulating in the refrigerant circuit becomes smaller than the reference temperature difference. The reference temperature difference is set to be larger as the operating frequency of the compressor is higher.

  Japanese Patent Application Laid-Open No. 2007-263440 discloses that during heating operation, by appropriately adjusting the injection amount of the refrigerant drawn into the compressor during the compression process, the operation is performed at high operation efficiency at low load. In this case, an air conditioner is disclosed that aims to improve the heating capacity (Patent Document 3).

  The air conditioner disclosed in Patent Document 3 includes an injection pipe for drawing a part of the refrigerant flowing out from the indoor heat exchanger into the compression process of the compressor via the injection decompression device, and the rotation speed of the compressor. Compressor rotation speed control means for controlling according to the magnitude of the load, and injection control means for controlling the injection pressure reducing device so that the discharge gas superheat degree or discharge temperature at the outlet of the compressor becomes a target value. The target value is set to be small when the rotation speed of the compressor controlled by the compressor rotation speed control means is high, and is set to be large when the rotation speed of the compressor is low.

JP-A-8-210709 Japanese Patent Laid-Open No. 11-132575 JP 2007-263440 A

  As a heat pump type heating device such as an air conditioner or a hot water supply device, there is a two-stage compression type in which two compressors, a low pressure side compressor and a high pressure side compressor, are provided on a heat pump cycle. However, in the two-stage compression heat pump type heating device, there is a problem that the refrigerant suction temperature and the discharge temperature in the high-pressure side compressor rise and exceed the operating range of the compressor. As a method for solving such a problem, a pipe line between the low-pressure side compressor and the high-pressure side compressor and a pipe line between the indoor heat exchanger (condenser) and the outdoor heat exchanger (evaporator) are connected. There may be a method in which an injection pipe is provided and a part of the refrigerant flowing through the pipe line between the indoor heat exchanger and the outdoor heat exchanger is injected into the pipe line between the low-pressure compressor and the high-pressure compressor through the injection pipe. . In this case, it is possible to reduce the refrigerant suction temperature in the high-pressure side compressor and realize operation with reliability.

  In a heat pump type heating apparatus using such an injection pipe, it is required to improve the heating capacity by injecting between the low pressure side compressor and the high pressure side compressor with an optimum amount of refrigerant. Moreover, although various apparatuses using the injection pipe are disclosed in the above-mentioned Patent Documents 1 to 3, in any of the apparatuses, the refrigerant injection control is performed by an on-off valve or a pressure reducing device provided on the pipe line of the injection pipe. It has been implemented. In this case, there exists a subject that an apparatus cannot be manufactured cheaply.

  Accordingly, an object of the present invention is to solve the above-described problem, and to provide a heat pump type heating apparatus that can sufficiently improve the heating capacity with a simple configuration.

  A heat pump heating device according to the present invention includes a first heat exchanger that exchanges heat between a refrigerant and a fluid to be heated, a second heat exchanger that exchanges heat between the refrigerant and outdoor air, The low pressure side compressor that compresses the refrigerant sent from the second heat exchanger, the high pressure side compressor that compresses the refrigerant sent from the low pressure side compressor, and the pressure sent from the first heat exchanger are reduced. The first decompressor, the gas-liquid separator that separates the refrigerant sent from the first decompressor into a gas phase and a liquid phase, and connected to the liquid phase side of the gas-liquid separator, and sent from the gas-liquid separator A second decompression device for decompressing the refrigerant and a gas phase connected to the gas phase side of the gas-liquid separator, and the refrigerant sent from the gas-liquid separator is placed on a pipe line between the low-pressure compressor and the high-pressure compressor In the second decompression device, the injection pipe to be guided and the refrigerant flowing through the injection pipe are in a gas-liquid two-phase state. And a control unit for controlling the vacuum ratio of the refrigerant.

  According to the heat pump type heating device configured in this way, the gas-liquid two-phase refrigerant flowing through the injection pipe and the high-temperature and high-pressure gas-phase refrigerant discharged from the low-pressure compressor are merged and saturated. The refrigerant in a vapor state or a state close to this flows into the high-pressure compressor. Thereby, it can inject with the optimal refrigerant | coolant amount between a pressure side compressor and a high pressure side compressor, and can fully improve a heating capability. At this time, since the refrigerant flowing through the injection pipeline is made into a gas-liquid two-phase state using the second decompression device that decompresses the refrigerant sent from the gas-liquid separator, the heat pump heating device can be configured simply. .

  Preferably, the control unit further controls the pressure reduction ratio of the refrigerant in the second pressure reducing device so that the ratio of the liquid phase to the gas-liquid two-phase refrigerant flowing through the injection pipe does not exceed a predetermined value.

  According to the heat pump type heating device configured as described above, it is possible to prevent a decrease in the reliability of the compressor and a decrease in the operation efficiency due to the liquid refrigerant flowing into the high-pressure side compressor.

  Preferably, the heat pump heating device is provided on a pipe line between the low-pressure compressor and the high-pressure compressor, and detects the temperature of the refrigerant before the refrigerant flowing through the injection pipe joins. The unit is further provided. The control unit controls the pressure reduction ratio of the refrigerant in the second pressure reducing device based on the time history of the refrigerant temperature detected by the first temperature detection unit.

  Preferably, the heat pump type heating device is provided on the injection pipe, and is provided on a pipe between the second temperature detection unit that detects the temperature of the refrigerant flowing in the injection pipe and the low-pressure compressor and the high-pressure compressor. And a third temperature detecting unit that detects the temperature of the refrigerant after the refrigerant flowing through the injection pipe joins. The control unit controls the decompression ratio of the refrigerant in the second decompression device based on the difference between the refrigerant temperature detected by the second temperature detection unit and the refrigerant temperature detected by the third temperature detection unit.

  Preferably, the heat pump heating device is provided on a pipe line between the low-pressure compressor and the high-pressure compressor, and detects a temperature of the refrigerant after the refrigerant flowing through the injection pipe joins. The unit is further provided. The control unit controls the pressure reduction ratio of the refrigerant in the second pressure reducing device based on the time history of the refrigerant temperature detected by the fourth temperature detection unit.

  According to the heat pump type heating device configured in this way, the pressure reduction ratio of the refrigerant in the second pressure reducing device is controlled by using various temperature histories and temperature differences correlated with the state of the refrigerant flowing through the injection pipe. To do.

  Preferably, the heat pump type heating device is provided on a pipe line between the low-pressure side compressor and the high-pressure side compressor, the refrigerant flowing after the refrigerant flowing through the injection pipe flows, A buffer unit for storing the refrigerant is further provided.

  According to the heat pump type heating device configured as described above, it is possible to more reliably prevent a decrease in the reliability of the compressor due to the liquid refrigerant flowing into the high-pressure side compressor.

  As described above, according to the present invention, it is possible to provide a heat pump type heating device that can sufficiently improve the heating capacity with a simple configuration.

It is a circuit diagram which shows the heat pump type heating apparatus in Embodiment 1 of this invention. It is a Mollier diagram which shows the refrigerating cycle by the heat pump type heating apparatus in FIG. FIG. 2 is a diagram showing a flowchart of control of an injection refrigerant amount in the heat pump type heating apparatus in FIG. 1. It is a circuit diagram which shows the 1st modification of the heat pump type heating apparatus in FIG. It is a graph which shows the relationship between the injection amount ratio with respect to the refrigerant | coolant amount before a branch in a gas-liquid separator, and heating capacity and COP. It is a circuit diagram which shows the 2nd modification of the heat pump type heating apparatus in FIG. FIG. 7 is a diagram showing a flowchart of control of the injection refrigerant amount in the heat pump heating apparatus in FIG. 6. It is a circuit diagram which shows the 3rd modification of the heat pump type heating apparatus in FIG. It is a figure which shows the flowchart of control of the injection refrigerant | coolant amount in the heat pump type heating apparatus in FIG.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

(Embodiment 1)
1 is a circuit diagram showing a heat pump type heating apparatus according to Embodiment 1 of the present invention. With reference to FIG. 1, the heat pump type heating apparatus in the present embodiment is typically applied to a heat pump type water heater or a heat pump type heater. The heat pump heating device includes a refrigeration circuit 20 and an injection circuit 50 as its circuit configuration. For example, R410A is sealed as a refrigerant in the refrigeration circuit 20 and the injection circuit 50.

  The refrigeration circuit 20 extends in an annular shape and constitutes a heat pump cycle. On the path of the refrigeration circuit 20, an indoor heat exchanger (condenser) 26 and an outdoor heat exchanger (evaporator) 27 are provided. The indoor heat exchanger 26 performs heat exchange between the refrigerant circulating in the heat pump cycle and the fluid to be heated (water or air). The outdoor heat exchanger 27 performs heat exchange between the refrigerant circulating in the heat pump cycle and the outside air (outdoor air).

  On the path of the refrigeration circuit 20, a first decompression device 36, a gas-liquid separator 38, and a second decompression device 37 are further provided. The first decompression device 36, the gas-liquid separator 38, and the second decompression device 37 are provided between the indoor side heat exchanger 26 and the outdoor side heat exchanger 27. The first decompression device 36, the gas-liquid separator 38, and the second decompression device 37 are arranged in series in the refrigerant flow direction in the refrigeration circuit 20. On the path of the refrigeration circuit 20 from the indoor heat exchanger 26 toward the outdoor heat exchanger 27, the first decompressor 36, the gas-liquid separator 38, and the second decompressor 37 are arranged in the order given.

  The first decompression device 36 decompresses the refrigerant sent from the indoor heat exchanger 26. The first decompressor 36 is provided as a decompressor for controlling the supercooling of the refrigerant in the indoor heat exchanger 26. The gas-liquid separator 38 separates the refrigerant sent from the first decompression device 36 into a gas-phase refrigerant and a liquid-phase refrigerant (liquid refrigerant). The gas-liquid separator 38 has a gas-phase refrigerant space 38a in which a gas-phase refrigerant is disposed and a liquid-phase refrigerant space 38b in which a liquid-phase refrigerant is disposed. The second decompression device 37 is connected to the liquid phase refrigerant space 38b of the gas-liquid separator 38 through a pipe. The second decompression device 37 decompresses the liquid refrigerant sent from the gas-liquid separator 38. The second pressure reducing device 37 is provided as a pressure reducing device for controlling the degree of superheat of the refrigerant in the outdoor heat exchanger 27 and the amount of injection refrigerant by an injection circuit 50 described later. In the present embodiment, expansion valves are used as the first pressure reducing device 36 and the second pressure reducing device 37.

  A low-pressure compressor 31 and a high-pressure compressor 32 are further provided on the path of the refrigeration circuit 20. The low-pressure compressor 31 and the high-pressure compressor 32 are provided between the outdoor heat exchanger 27 and the indoor heat exchanger 26. The low-pressure compressor 31 and the high-pressure compressor 32 are arranged in series in the refrigerant flow direction in the refrigeration circuit 20. On the path of the refrigeration circuit 20 from the outdoor heat exchanger 27 toward the indoor heat exchanger 26, the low-pressure compressor 31 and the high-pressure compressor 32 are arranged in the order listed. The low-pressure compressor 31 compresses the low-pressure refrigerant sent from the outdoor heat exchanger 27 to an intermediate pressure. The high-pressure side compressor 32 compresses the intermediate-pressure refrigerant sent from the low-pressure side compressor 31 to a higher pressure.

  In the present embodiment, the low pressure side compressor 31 is a variable capacity type compressor capable of controlling the refrigerant discharge capacity (for example, an inverter specification compressor capable of changing the rotation speed), and the high pressure side compressor 32. However, this is a constant speed type compressor. It should be noted that at least one of the low-pressure side compressor 31 and the high-pressure side compressor 32 may be a variable capacity type, and a combination of a low-pressure side compressor with a constant rotation speed and a variable-capacity high-pressure side compressor, A combination of a variable-capacity low-pressure compressor and a variable-capacity high-pressure compressor may be used. In addition, when the low-pressure side compressor is a variable capacity type, the operable range at a high load is widened.

  The injection circuit 50 includes an injection pipe 51 through which a refrigerant can flow. The injection pipe 51 guides a part of the refrigerant separated into the gas-phase refrigerant space 38 a of the gas-liquid separator 38 to the refrigeration circuit 20 between the low-pressure side compressor 31 and the high-pressure side compressor 32. Is provided.

  More specifically, both ends of the injection pipeline 51 are respectively connected to the gas-phase refrigerant space 38a of the gas-liquid separator 38 and the refrigeration circuit 20 between the low-pressure side compressor 31 and the high-pressure side compressor 32. It is provided to connect. The refrigerant inlet of the injection pipe 51 is connected to the gas-phase refrigerant space 38 a of the gas-liquid separator 38, and the refrigerant outlet of the injection pipe 51 is a refrigeration circuit between the low-pressure compressor 31 and the high-pressure compressor 32. 20 is connected.

  In the present embodiment, no on-off valve that allows or blocks the flow of the refrigerant or a flow rate adjustment valve that can adjust the flow rate of the refrigerant is provided on the route of the injection pipeline 51.

  A buffer unit 41 and a buffer unit 42 are further provided on the path of the refrigeration circuit 20. The buffer part 41 and the buffer part 42 are comprised by the accumulator which can store a liquid refrigerant. The buffer unit 41 is provided between the outdoor heat exchanger 27 and the low-pressure compressor 31 on the path of the refrigeration circuit 20. The buffer unit 42 is provided between the low-pressure compressor 31 and the high-pressure compressor 32 on the path of the refrigeration circuit 20. When the position where the injection pipe 51 is connected to the refrigeration circuit 20 is referred to as a connection part 53, the buffer part 42 is provided between the connection part 53 and the high-pressure compressor 32. The buffer unit 41 and the buffer unit 42 are provided to prevent liquid refrigerant from entering the low-pressure compressor 31 and the high-pressure compressor 32 and reducing the reliability of the compressor, respectively.

  FIG. 2 is a Mollier diagram showing a refrigeration cycle by the heat pump type heating device in FIG. 1.

  The Mollier diagram is also called a Ph diagram, and the vertical axis represents pressure [MPa] and the horizontal axis represents specific enthalpy [kJ / kg]. The Mollier diagram is a diagram showing characteristics unique to the refrigerant such as the pressure, specific enthalpy, temperature, phase state, enthalpy, and specific volume of the refrigerant used in the refrigeration cycle. The refrigerant states A to H shown in FIG. 2 correspond to the refrigerant states A to H in FIG. 1, respectively.

  With reference to FIGS. 1 and 2, first, the gas refrigerant (state A) discharged from the high-pressure compressor 32 flows into the indoor heat exchanger (condenser) 26 and is condensed into a high-temperature liquid refrigerant (condensed). State B). When this high-temperature liquid refrigerant passes through the first decompression device 36, the pressure and temperature of the refrigerant decrease (state C).

  Next, the refrigerant flows into the gas-liquid separator 38 and is separated into a gas phase and a liquid phase. When the separated liquid refrigerant (state D) passes through the second decompression device 37, the pressure and temperature of the refrigerant further decrease (state E). Next, when the refrigerant passes through the outdoor heat exchanger 27, the refrigerant absorbs heat from the outside air and evaporates (state F). The refrigerant in the state F flows into the low-pressure compressor 31 and is compressed to an intermediate pressure (state G).

  On the other hand, the refrigerant (injection refrigerant) separated into the gas-phase refrigerant space 38 a of the gas-liquid separator 38 merges with the refrigerant discharged from the low-pressure compressor 31 through the injection pipeline 51. Since the temperature of the injection refrigerant is lower than the temperature of the refrigerant discharged from the low-pressure compressor 31, the refrigerant temperature after joining the injection refrigerant decreases (state H).

  During the heating operation, when the outside air temperature is low and the evaporation pressure is reduced, the compression ratio increases, but after the compression process by the low-pressure side compressor 31 and before the compression process by the high-pressure side compressor 32. By injecting the injection refrigerant into the intermediate-pressure refrigerant and increasing the refrigerant flow rate, it is possible to ensure the heating (heating) capability without abnormally increasing the discharge temperature. Thus, due to the effect of the injection refrigerant, for example, even if the outside air temperature is an extremely low temperature of about −20 ° C., sufficient heating capacity can be obtained.

  The heat pump heating device further includes a temperature detection unit 61 and a control unit 46. The temperature detector 61 is provided between the low pressure side compressor 31 and the high pressure side compressor 32. The temperature detection unit 61 is provided between the low-pressure compressor 31 and the connection unit 53. The temperature detection unit 61 detects the temperature of the refrigerant discharged from the low-pressure compressor 31 and before the refrigerant flowing through the injection pipe 51 joins. The control unit 46 controls the refrigerant pressure reduction ratio in the second pressure reducing device 37 based on the time history of the refrigerant temperature detected by the temperature detection unit 61.

  In the heat pump heating device in the present embodiment, the injection refrigerant is changed from the state of only the gas phase by controlling the opening degree of the second decompression device 37 based on the temperature history of the refrigerant discharged from the low-pressure compressor 31. Then, a gas-liquid two-phase state immediately after the liquid phase starts to mix is set. Thereby, it can hold | maintain to an appropriate quantity of injection refrigerant | coolants irrespective of the magnitude | size of the load of a compressor, and can improve a heating capability.

  Furthermore, in the heat pump type heating apparatus in the present embodiment, an apparatus for controlling the state of the injection refrigerant is not provided in the injection pipe line 51, and the outdoor heat exchanger with respect to the refrigerant flow direction during the heating operation. By using the second pressure reducing device 37 provided on the upstream side of 27, an effect equivalent to the case where the pressure reducing device is provided in the injection pipe and the flow rate of the injection refrigerant is directly controlled is obtained, and the injection is performed. Since it is not necessary to install an on-off valve or a pressure reducing device in the pipeline, the device can be configured at low cost.

  Then, the said control method of the injection refrigerant | coolant amount is demonstrated concretely. First, since the rotation speed of the compressor is an operation amount that can most directly adjust the heating capacity, the rotation speed of the variable capacity type low-pressure compressor 31 is controlled according to the load. For example, the rotational speed of the low-pressure compressor 31 is increased or decreased according to the deviation between the target heating temperature set by the user or the target heating temperature preset in the apparatus and the measured heating temperature.

  FIG. 3 is a diagram showing a flowchart of control of the injection refrigerant amount in the heat pump heating apparatus in FIG. The control flow shown in the figure is executed by the control unit 46.

  Referring to FIGS. 1 and 3, before the control of the injection refrigerant amount, at the start of operation, the indoor heat exchanger by controlling the rotational speed of the low-pressure compressor 31 and adjusting the opening of the first decompressor 36. 26, and the degree of superheat of the outlet of the outdoor heat exchanger 27 by adjusting the opening degree of the second decompressor 37 is performed. The refrigerant to be sealed is set so that the injection refrigerant is in a gas phase state after these series of controls are completed.

  When executing the control of the injection refrigerant amount, first, the temperature T1 of the refrigerant discharged from the low-pressure compressor 31 is detected by the temperature detector 61, and the temperature T1 is stored in the controller 46 (S101). Next, the opening degree of the second decompression device 37 is reduced by an arbitrary number of steps (S102). When the opening degree of the second decompression device 37 is reduced, the decompression ratio of the refrigerant in the second decompression device 37 is increased. At this time, the amount of liquid refrigerant in the gas-liquid separator 38 increases, and eventually the liquid refrigerant overflows into the gas-liquid separator 38 and flows into the injection pipe 51, and the gas-phase refrigerant in the injection pipe 51 becomes gas-liquid. It changes to a two-phase state.

  After an arbitrary time t has elapsed, the temperature detection unit 61 detects again the temperature T1 ′ of the refrigerant discharged from the low-pressure compressor 31, and stores the temperature T1 ′ in the control unit 46 (S103). The control unit 46 calculates T1′−T1 and determines whether the value is equal to or greater than ΔT4 (S104). ΔT4 is a temperature difference of the refrigerant discharged from the low-pressure compressor 31 until the injection refrigerant changes from a gas phase state to a state in which a part of the gas phase starts to change into a liquid phase. It is specified in advance by an experiment for observing the state. As an example, ΔT4 = 3 ° C. when t = 30 sec.

  When satisfy | filling the relationship of T1'-T1 <(DELTA) T4, it returns to S102 and makes the opening degree of the 2nd decompression device 37 still smaller. When the relationship of T1′−T1 ≧ ΔT4 is satisfied, the control unit 46 determines whether or not the value of T1′−T1 is equal to or less than ΔT5 (S105). ΔT5 is the temperature of the refrigerant discharged from the low-pressure compressor 31 until the injection refrigerant changes from a gas phase state to a liquid phase and a liquid refrigerant flows too much into the injection pipeline 51. This is a difference, and is specified in advance by an experiment of observing the state of the injection refrigerant while changing ΔT5. As an example, ΔT5 = 15 ° C. when t = 30 sec.

  In the control flow, the temperature T1 is detected at the start of the control and is set as a constant thereafter. However, the present invention is not limited to this, and the temperature T1 can be defined as a detected value before a certain time before T1 ′. For example, the temperature T1 t seconds before T1 ′ can always be variable.

  Note that there is a certain correlation between the temperature difference of the refrigerant discharged from the low-pressure compressor 31 and the state of the injection refrigerant, and this relationship is related to the rotational speed of the low-pressure compressor 31 and the first pressure reducing device. 36 and the opening of the second decompression device 37 are not affected.

  If the relationship of T1′−T1> ΔT5 is satisfied, the liquid phase ratio of the injection refrigerant is too large, so the opening of the second decompression device 37 is increased (S106). When the relationship of T1′−T1 ≦ ΔT5 is satisfied, the process returns to S103, and the temperature T1 ′ of the refrigerant discharged from the low-pressure compressor 31 is detected again by the temperature detection unit 61.

  That is, in the method for controlling the injection refrigerant amount in the present embodiment, the temperature of the refrigerant discharged from the low-pressure compressor 31 and the opening of the second decompression device 37 before the opening of the second decompression device 37 is changed. A difference from the temperature of the refrigerant at the same point after the change is obtained, and the opening of the second decompression device 37 is adjusted so that the value falls within an arbitrary range. At this time, the number of steps for adjusting the opening degree of the second pressure reducing device 37 may be set to a small value if the control accuracy is increased, and set to a large value if the control is performed quickly to the target opening degree.

  When the supercooling degree of the indoor heat exchanger 26 is controlled by the first decompressor 36 and the superheat degree of the outdoor heat exchanger 27 is controlled by the second decompressor 37, the injection pipe is operated by the gas-liquid separator 38. The state of the refrigerant flowing into the passage 51 is a gas phase. If the opening degree of the second decompression device 37 is further reduced from that state, the amount of liquid refrigerant flowing out to the outdoor heat exchanger 27 side is limited, and the liquid refrigerant overflows into the gas-liquid separator 38 and the injection pipe. It flows into the channel 51. In this case, liquid refrigerant flows into the high-pressure side compressor 32, and there is a concern that the reliability of the compressor deteriorates due to liquid compression. In this embodiment, the liquid refrigerant is provided on the suction side of the high-pressure side compressor 32. The concerned buffer unit 42 can eliminate this concern.

  However, there is a limit to the amount of refrigerant that can be stored in the buffer unit 42, and if the amount of liquid refrigerant flowing through the injection pipe 51 is excessively increased, the reliability of the compressor is likely to deteriorate. Moreover, if the amount of the liquid refrigerant flowing through the injection pipe 51 is excessively increased, there is a problem that COP (Coefficient Of Performance) of the heat pump type heating device is lowered.

  Therefore, in the heat pump type heating device in the present embodiment, in the process of reducing the opening of the second decompression device 37, the liquid phase starts to mix from the state where the injection refrigerant is only in the gas phase, and the gas-liquid two-phase state immediately after that. Control to keep. The refrigerant state before the discharge refrigerant and the injection refrigerant of the low-pressure side compressor 31 are merged is changed from the gas phase + gas phase state to the gas phase + gas / liquid two phase state. Becomes a gas phase due to the phase change, and as a result, the refrigerant flow rate to the indoor heat exchanger 26 increases and the heating capacity increases. That is, in the present embodiment, the state of the injection refrigerant before joining the refrigerant discharged from the low-pressure compressor 31 is changed from the gas phase to the gas-liquid two-phase state regardless of the rotational speed of the compressor and the outside air temperature. The cycle can be easily controlled by controlling the second pressure reducing device 37 so as to be immediately after.

  Next, the reason why the heating capacity is improved in the heat pump type heating apparatus in the present embodiment will be described.

  The supply of the injection refrigerant has the effect of increasing the heating capacity by increasing the refrigerant flow rate on the heating side, and further increases the limit of the operating pressure ratio of the compressor. In order to increase the refrigerant flow rate on the heating side, the liquid phase injection refrigerant is more effective than the gas phase injection refrigerant. However, excessive supply of the liquid-phase injection refrigerant may cause deterioration of COP and deterioration of the reliability of the compressor due to liquid compression. That is, it is preferable to perform injection so that the liquid phase in the injection refrigerant is phase-changed by the high-temperature gas refrigerant discharged from the low-pressure compressor 31 to become a saturated vapor state.

  Therefore, in the present embodiment, the injection refrigerant is in a state that can be easily determined based on the temperature history of the refrigerant discharged from the low-pressure compressor 31, immediately after the injection refrigerant changes from the gas phase state to the gas-liquid two-phase state. By maintaining the state, the cycle in which the refrigerant flow rate on the heating side is increased is maintained. When the condensation temperature, the evaporation temperature, and the rotation speed of the compressor are the same, it can be said that the largest factor that determines the cycle performance is the suction pressure of the high-pressure compressor 32 (state H in FIG. 2). If the suction pressure is set to the same value as before, in this embodiment, it is possible to increase the heating capacity by increasing the refrigerant flow rate on the heating side. it can.

  If the liquid-phase refrigerant flows in before the high-pressure side compressor 32 sucks, the starting point of the high-pressure side compression step approaches a saturated vapor state. Thereby, the temperature of the refrigerant discharged from the low-pressure side compressor 31 is reliably lowered by the injection refrigerant, and the temperature of the refrigerant discharged from the high-pressure side compressor 32 is suppressed, so that the limit of the operating pressure ratio of the compressor can be increased. it can.

  Next, the reason why the controllability is improved in the heat pump type heating apparatus in the present embodiment will be described.

  The control method in the present embodiment includes the compressor speed control according to the heating load, the injection control based on the temperature of the refrigerant discharged from the low-pressure compressor 31, and the rear side of the indoor heat exchanger 26 in the refrigerant flow direction. And a control means for controlling the decompression device, and the cycle can be controlled by two decompression devices. Thereby, the controllability can be improved by minimizing the number of pressure reducing devices and control means which are control factors.

  FIG. 4 is a circuit diagram showing a first modification of the heat pump type heating device in FIG. Referring to FIG. 4, in the heat pump type heating apparatus in the present modification, an internal heat exchanger 43 is further provided on the path of refrigeration circuit 20. The internal heat exchanger 43 is provided between the indoor heat exchanger 26 and the first pressure reducing device 36. The injection conduit 51 is provided so as to pass through the internal heat exchanger 43. The internal heat exchanger 43 performs heat exchange between the refrigerant that has flowed out of the indoor heat exchanger 26 and the refrigerant that flows through the injection pipe line 51.

  According to such a configuration, when a refrigerant in a liquid phase flows into the injection pipe line 51, the liquid phase is vaporized by being heated by the internal heat exchanger 43, and as a result, the flow rate of the injection refrigerant is increased. An increase in heating capacity is expected due to the increase.

  When the load is low, for example, when the outside air temperature is high, there is a problem that the amount of the injection refrigerant is large and the COP is too low. Such a problem is solved by providing an opening / closing valve in the injection pipeline 51 and opening / closing it based on the outside air temperature or the like.

  FIG. 5 is a graph showing the relationship between the ratio of the injection amount to the refrigerant amount before branching in the gas-liquid separator, the heating capacity, and the COP. In FIG. 5, the horizontal axis represents the injection amount ratio, and the vertical axis represents the heating capacity and the experimental value of COP.

  Referring to FIG. 5, when the opening of second decompression device 37 is decreased and the flow rate of the injection refrigerant is increased, the heating capacity is improved. Further, when the injection state becomes a gas-liquid two-phase state, the flow rate of the injection refrigerant further increases, and thus the heating capacity takes a high value. However, if a large amount of liquid refrigerant flows through the injection pipe line 51, it leads to a reduction in heating capacity. On the other hand, the COP gradually decreases as the injection amount increases.

  The heat pump heating device according to Embodiment 1 of the present invention described above includes the indoor heat exchanger 26 as the first heat exchanger that performs heat exchange between the refrigerant and the fluid to be heated, the refrigerant, and the outdoor. An outdoor heat exchanger 27 as a second heat exchanger that exchanges heat with air, a low-pressure compressor 31 that compresses the refrigerant sent from the outdoor heat exchanger 27, and a low-pressure compressor 31 The high pressure side compressor 32 that compresses the refrigerant sent from the interior, the first decompression device 36 that decompresses the refrigerant sent from the indoor heat exchanger 26, and the refrigerant sent from the first decompression device 36 as the gas phase A gas-liquid separator 38 that separates into the liquid phase; a second decompression device 37 that is connected to the liquid phase side of the gas-liquid separator 38 and depressurizes the refrigerant sent from the gas-liquid separator 38; and a gas-liquid separator. The refrigerant sent from the gas-liquid separator 38 is compressed to the low pressure side. The pressure reduction ratio of the refrigerant in the second pressure reducing device 37 so that the refrigerant flowing through the injection pipe 51 and the refrigerant flowing through the injection pipe 51 is in a gas-liquid two-phase state. And a control unit 46 for controlling.

  According to the heat pump type heating device in Embodiment 1 of the present invention configured as described above, it is possible to realize a heat pump type heating device that is excellent in controllability and sufficiently improved in heating capacity.

(Embodiment 2)
In the present embodiment, various modifications of the method for controlling the state of the injection refrigerant will be described. Hereinafter, as compared with the heat pump heating device in the first embodiment, the description of the overlapping structure will not be repeated.

  FIG. 6 is a circuit diagram showing a second modification of the heat pump type heating device in FIG. FIG. 7 is a diagram showing a flowchart of the control of the injection refrigerant amount in the heat pump type heating apparatus in FIG.

  Referring to FIGS. 6 and 7, the heat pump heating apparatus includes a temperature detection unit 62 and a temperature detection unit 63 instead of temperature detection unit 61 in FIG. 1. The temperature detector 62 is provided in the injection pipeline 51. The temperature detection unit 62 detects the temperature of the refrigerant flowing through the injection pipe 51 before joining the pipe between the low-pressure compressor 31 and the high-pressure compressor 32. The temperature detection unit 63 is provided between the low pressure side compressor 31 and the high pressure side compressor 32. The temperature detection unit 63 is provided between the connection unit 53 and the high-pressure compressor 32. The temperature detection unit 63 detects the temperature of the refrigerant discharged from the low-pressure compressor 31 and after the refrigerant flowing through the injection pipe 51 joins. The temperature detector 63 detects the temperature of the refrigerant sucked into the high pressure side compressor 32. The control unit 46 controls the decompression ratio of the refrigerant in the second decompression device 37 based on the difference between the refrigerant temperature detected by the temperature detection unit 62 and the refrigerant temperature detected by the temperature detection unit 63.

  Also in this modified example, before the injection refrigerant amount is controlled, when the operation is started, the number of revolutions of the low-pressure compressor 31 is controlled, and the outlet of the indoor heat exchanger 26 is supercooled by adjusting the opening of the first decompressor 36. Control and superheat degree control of the outlet of the outdoor heat exchanger 27 by adjusting the opening of the second decompression device 37 are performed. The refrigerant to be sealed is set so that the injection refrigerant is in a gas phase state after these series of controls are completed.

  In executing the control of the injection refrigerant amount, first, the temperature detection unit 62 detects the refrigerant temperature T2 before the injection merge, and the temperature detection unit 63 detects the refrigerant temperature T3 sucked into the high-pressure side compressor 32, These temperatures T2 and T3 are stored in the controller 46 (S111). Next, the control unit 46 calculates T3-T2, and determines whether or not the value is greater than 0 (S112). If the relationship of T3-T2> 0 is satisfied, the opening degree of the second pressure reducing device 37 is decreased by an arbitrary number of steps (S113). On the other hand, when the relationship of T3-T2 ≦ 0 is satisfied, the opening degree of the second pressure reducing device 37 is increased by an arbitrary number of steps (step 114).

  That is, in the control method of the injection refrigerant amount in the present embodiment, the degree of superheat of the outdoor heat exchanger 27 can be obtained at the temperature T3 of the refrigerant sucked into the high-pressure compressor 32, compared to the temperature T2 of the injection refrigerant. If so, the opening of the second decompression device 37 is decreased, and the flow rate of the injection refrigerant is increased. On the other hand, if the degree of superheat of the outdoor heat exchanger 27 can no longer be obtained, the opening of the second decompression device 37 is increased and the state of the refrigerant becomes saturated steam at the suction portion of the high-pressure compressor 32. Control as follows.

  The number of steps for adjusting the opening degree of the second decompression device 37 may be set to a small value if the control accuracy is increased, and set to a large value if the control is performed quickly to the target opening degree. Further, in this modification, whether or not the degree of superheat is taken is determined based on 0. However, if it is desired to set the injection refrigerant to a small value, an arbitrary value T6 is set, and T3 in S112 above It may be determined whether or not −T2> T6 is satisfied.

  FIG. 8 is a circuit diagram showing a third modification of the heat pump type heating device in FIG. FIG. 9 is a diagram showing a flowchart of control of the injection refrigerant amount in the heat pump type heating apparatus in FIG.

  Referring to FIGS. 8 and 9, the heat pump heating device has a temperature detection unit 64 instead of temperature detection unit 61 in FIG. 1. The temperature detection unit 64 is provided between the low pressure side compressor 31 and the high pressure side compressor 32. The temperature detection unit 64 is provided between the connection unit 53 and the high-pressure side compressor 32. The temperature detection unit 64 detects the temperature of the refrigerant discharged from the low-pressure compressor 31 and after the refrigerant flowing through the injection pipe 51 joins. The temperature detector 64 detects the temperature of the refrigerant sucked into the high pressure side compressor 32. The control unit 46 controls the refrigerant decompression ratio in the second decompression device 37 based on the time history of the refrigerant temperature detected by the temperature detection unit 64.

  Also in this modified example, before the injection refrigerant amount is controlled, when the operation is started, the number of revolutions of the low-pressure compressor 31 is controlled, and the outlet of the indoor heat exchanger 26 is supercooled by adjusting the opening of the first decompressor 36. Control and superheat degree control of the outlet of the outdoor heat exchanger 27 by adjusting the opening of the second decompression device 37 are performed. The refrigerant to be sealed is set so that the injection refrigerant is in a gas phase state after these series of controls are completed.

  When executing the control of the injection refrigerant amount, first, the temperature T3 of the refrigerant sucked into the high-pressure compressor 32 is detected by the temperature detector 64, and the temperature T3 is stored in the controller 46 (S121). Next, the opening degree of the second decompression device 37 is decreased by an arbitrary number of steps so that the decompression ratio of the refrigerant in the second decompression device 37 is increased (S122).

  After an arbitrary time t has elapsed, the temperature detection unit 64 detects again the temperature T3 ′ of the refrigerant sucked into the high-pressure compressor 32, and stores the temperature T3 ′ in the control unit 46 (S123). When the liquid refrigerant begins to flow into the injection pipe 51, the refrigerant flow rate increases, so that the temperature of the refrigerant discharged from the low-pressure side compressor 31 can be effectively lowered. As a result, the high-pressure side compressor 32 The temperature of the suction refrigerant also decreases. The control unit 46 calculates T3−T3 ′ and determines whether or not the value is equal to or greater than ΔT7 (S124). ΔT7 is the temperature difference of the suction refrigerant of the high-pressure compressor 32 until the injection refrigerant changes from the gas phase state to a state where a part of the gas phase starts to change into the liquid phase. It is specified in advance by an experiment for observing the state. As an example, ΔT7 = 3 ° C. when t = 30 sec.

  When satisfy | filling the relationship of T3-T3 '<(DELTA) T7, it returns to S122 and makes the opening degree of the 2nd pressure reduction device 37 still smaller. When satisfy | filling the relationship of T3-T3 '> = (DELTA) T7, the control part 46 judges whether the value of T3-T3' is below (DELTA) T8 (S125). ΔT8 is the temperature of the refrigerant sucked by the high-pressure compressor 32 until the injection refrigerant changes from a gas phase state to a liquid phase and the liquid refrigerant flows too much into the injection pipeline 51. It is a difference, and is specified in advance by an experiment in which the state of the injection refrigerant is observed while changing ΔT8. As an example, ΔT8 = 15 ° C. when t = 30 sec.

  When the relationship of T3-T3 ′> ΔT8 is satisfied, the liquid phase ratio of the injection refrigerant is too large, so the opening degree of the second decompression device 37 is increased (S126). When satisfy | filling the relationship of T3-T3 '<= ΔT8, it returns to S123 and the temperature T3' of the refrigerant | coolant discharged from the low pressure side compressor 31 by the temperature detection part 61 is detected again.

  The number of steps for adjusting the opening degree of the second decompression device 37 may be set to a small value if the control accuracy is increased, and set to a large value if the control is performed quickly to the target opening degree.

  According to the heat pump type heating device in the second embodiment of the present invention configured as described above, the effects described in the first embodiment can be similarly obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is applied to, for example, a heat pump type water heater or a heat pump type heater.

  20 Refrigeration Circuit, 26 Indoor Heat Exchanger, 27 Outdoor Heat Exchanger, 31 Low Pressure Compressor, 32 High Pressure Compressor, 36 First Decompression Device, 37 Second Decompression Device, 38 Gas-Liquid Separator, 38a Gas Phase refrigerant space, 38b Liquid phase refrigerant space, 41, 42 Buffer part, 43 Internal heat exchanger, 46 control part, 50 injection circuit, 51 injection pipeline, 53 connection part, 61, 62, 63, 64 Temperature detection part.

Claims (6)

A first heat exchanger that exchanges heat between the refrigerant and the fluid to be heated;
A second heat exchanger for exchanging heat between the refrigerant and the outdoor air;
A low-pressure compressor that compresses the refrigerant sent from the second heat exchanger;
A high-pressure side compressor that compresses the refrigerant sent from the low-pressure side compressor;
A first decompression device that decompresses the refrigerant sent from the first heat exchanger;
A gas-liquid separator that separates the refrigerant sent from the first decompression device into a gas phase and a liquid phase;
A second decompression device connected to the liquid phase side of the gas-liquid separator and decompressing the refrigerant sent from the gas-liquid separator;
An injection pipe connected to the gas phase side of the gas-liquid separator and guiding the refrigerant sent from the gas-liquid separator onto a pipe line between the low-pressure compressor and the high-pressure compressor;
A heat pump heating device, comprising: a control unit that controls a pressure reduction ratio of the refrigerant in the second pressure reduction device so that the refrigerant flowing through the injection pipeline is in a gas-liquid two-phase state.   The control unit further controls a decompression ratio of the refrigerant in the second decompression device so that a ratio of a liquid phase in a gas-liquid two-phase refrigerant flowing through the injection pipe does not exceed a predetermined value. Item 2. A heat pump heating apparatus according to Item 1. A first temperature detector that is provided on a pipe line between the low-pressure compressor and the high-pressure compressor, and that detects the temperature of the refrigerant before the refrigerant flowing through the injection pipe merges;
The heat pump heating device according to claim 1 or 2, wherein the control unit controls a decompression ratio of the refrigerant in the second decompression device based on a time history of the refrigerant temperature detected by the first temperature detection unit. . A second temperature detection unit that is provided on the injection pipe and detects the temperature of the refrigerant flowing through the injection pipe;
A third temperature detection unit that is provided on a pipe line between the low-pressure side compressor and the high-pressure side compressor, and that detects a temperature of the refrigerant after the refrigerant flowing through the injection pipe joins;
The control unit controls a decompression ratio of the refrigerant in the second decompression device based on a difference between the refrigerant temperature detected by the second temperature detection unit and the refrigerant temperature detected by the third temperature detection unit. The heat pump type heating device according to claim 1 or 2. A fourth temperature detection unit that is provided on a pipe line between the low-pressure side compressor and the high-pressure side compressor, and that detects a temperature of the refrigerant after the refrigerant flowing through the injection pipe line joins;
The heat pump heating device according to claim 1 or 2, wherein the control unit controls a decompression ratio of the refrigerant in the second decompression device based on a time history of the refrigerant temperature detected by the fourth temperature detection unit. .   A buffer between the low-pressure compressor and the high-pressure compressor, provided on a conduit through which the refrigerant flowing through the injection conduit merges and storing liquid refrigerant; The heat pump heating device according to any one of claims 1 to 5, further comprising:

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