JP5812726B2 - Heat pump water heater - Google Patents

Description

  The present invention relates to a heat pump water heater using a supercritical refrigeration cycle.

Conventionally, as a heat pump water heater, a supercritical refrigeration cycle in which the high-pressure side refrigerant pressure (refrigerant pressure on the compressor discharge side) is equal to or higher than the critical pressure of the refrigerant, that is, vapor compression that pressurizes the high-pressure side refrigerant until it reaches a supercritical state. A formula refrigeration cycle is known.
When this type of supercritical refrigeration cycle employs a refrigerant whose critical temperature (for example, the critical temperature of CO ₂ is about 31 ° C.), such as carbon dioxide (CO ₂ ), can be lower than the outside temperature, When a high load operation is performed at a high outside air temperature at which the outside air temperature is equal to or higher than the critical temperature, the low-pressure side refrigerant pressure (the refrigerant pressure on the suction side of the compressor) may be higher than the critical pressure.
When the low-pressure side refrigerant pressure becomes equal to or higher than the critical pressure, the liquid-phase refrigerant cannot be evaporated in the evaporator, which is a heat exchanger for heat absorption, so that the refrigerant flowing into the evaporator can absorb the heat of latent heat of vaporization. However, only the endotherm of the sensible heat change can be made. As a result, there arises a problem that the heat absorption amount of the refrigerant in the evaporator is remarkably reduced. In addition, the amount of heat absorbed due to sensible heat changes easily due to fluctuations in the thermal load of the cycle, etc., so the balance between the amount of heat absorbed by the evaporator and the amount of heat released by the radiator becomes unstable, and the refrigeration cycle must operate stably. Can not be.

  In order to solve such a problem, the flow of the refrigerant flowing out of the water-to-refrigerant heat exchanger is branched, and one refrigerant is decompressed and expanded by the first electronic expansion valve and evaporated by the first evaporator. It has been proposed to construct a cycle in which the other refrigerant is decompressed and expanded by a second electronic expansion valve and evaporated by a second evaporator (Patent Document 1). In this refrigeration cycle, when the refrigerant evaporation pressure of at least one of the first evaporator and the second evaporator becomes equal to or higher than a reference pressure, the throttle opening degree of the corresponding electronic expansion valve is decreased, thereby the supercritical refrigeration cycle. The heat exchange capacity of the heat absorption heat exchanger as a whole is reduced, and the low pressure side refrigerant pressure is prevented from becoming higher than the critical pressure of the refrigerant.

JP 2009-9779A

By the way, since the density difference between the CO ₂ refrigerant and the oil responsible for lubrication in the cycle is smaller than that of Freon, the oil separator used so far is not sufficiently centrifuged and the oil separation efficiency is lowered. For this reason, the oil rate in the refrigeration cycle increases, and the compressor may run out of oil and break down. In particular, when the throttle opening of the expansion valve is reduced as in Patent Document 1, the refrigerant may be in a superheated gas state in the evaporator, and the oil may stay in the evaporator.
Further, when compared at the same high-pressure side refrigerant pressure, the temperature of the refrigerant discharged from the compressor decreases as the low-pressure side refrigerant pressure increases. Therefore, if the low-pressure side refrigerant pressure is controlled to be less than the critical pressure of the refrigerant as in Patent Document 1, the discharged refrigerant temperature may not rise, and hot hot water may not be produced.
The present invention has been made based on such a technical problem, and can prevent oil from staying in the evaporator, and can stably produce hot water even when the outside air temperature is high. An object of the present invention is to provide a heat pump water heater that can be used.

  In order to achieve the above object, the present inventor proposes four forms of first to fourth. Hereinafter, description will be made sequentially.

[First proposal]
A first proposal related to a heat pump water heater using a supercritical refrigeration cycle is that a supercritical refrigeration cycle compresses and discharges the refrigerant, and water-to-refrigerant heat exchanges between the refrigerant compressed by the compressor and water. Control the operation of the heat exchanger, the electronic expansion valve that decompresses and expands the refrigerant flowing out of the water-to-refrigerant heat exchanger, the evaporator that evaporates the refrigerant decompressed and expanded by the electronic expansion valve, and the operation of the supercritical refrigeration cycle A control unit. This control unit controls the operation so as not to exceed the upper limit value of the low-pressure side refrigerant pressure on the suction side of the compressor. The upper limit value of the low-pressure side refrigerant pressure is set according to the target hot water temperature of water flowing out from the water-to-refrigerant heat exchanger.

Since the heat pump water heater according to the first proposal is always operated below the upper limit value of the low-pressure side refrigerant pressure set according to the target hot water temperature, the target hot water temperature can be maintained regardless of the outside air temperature. That is, according to the first proposal, the higher the outside air temperature, the higher the low-pressure side refrigerant pressure, and there is no situation where the hot water temperature does not rise to the target hot water temperature when the outside air is high.
In addition, since the heat pump water heater according to the first proposal does not need to reduce the throttle opening of the expansion valve, the refrigerant does not stay in the superheated gas state in the evaporator and oil does not stay in the evaporator.

In the first proposal, two methods can be adopted to control the operation so as not to exceed the upper limit value of the low-pressure side refrigerant pressure.
The first method is premised on the provision of a blower that blows air toward the evaporator. And a control part will control an air blower so that the ventilation volume of the air toward an evaporator may be reduced, if the detected real low pressure side refrigerant | coolant pressure exceeds the set upper limit of the low voltage | pressure side refrigerant pressure.
In the second method, the refrigerant flowing out of the water-to-refrigerant heat exchanger is branched into the first flow path and the second flow path, and the refrigerant flowing through the first flow path and the second flow path is It is assumed that the air is drawn into the compressor after merging before the compressor.
The first flow path includes a first expansion valve that decompresses and expands one of the branched refrigerants, and a first evaporator that evaporates the refrigerant decompressed and expanded by the first expansion valve. Similarly, the second flow path includes a second expansion valve that decompresses and expands the other branched refrigerant, and a second evaporator that evaporates the refrigerant decompressed and expanded by the second expansion valve.
Then, when the detected actual low-pressure side refrigerant pressure exceeds the set upper limit value of the low-pressure side refrigerant pressure, the control unit controls to close either the first expansion valve or the second expansion valve. “Closed” here means fully closed.

The present invention may be employed only one eye of the hand method, may be adopted both. In the latter case, the first method and the second method can be performed simultaneously, and the first method and the second method can be performed in order. Among these, as will be described in an embodiment described later, it is preferable to perform the first method in advance and to perform the second method if the blower amount of the blower reaches the minimum value.

[Second proposal]
In the second proposal, the supercritical refrigeration cycle includes a bypass channel connecting the discharge-side channel and the suction-side channel of the compressor, and an opening degree adjusting valve provided in the middle of the bypass channel. . When the temperature difference between the target hot water temperature flowing out of the water-to-refrigerant heat exchanger and the detected actual hot water temperature of water flowing out of the water-to-refrigerant heat exchanger reaches a specified value, the control unit Then, the opening of the opening adjusting valve is controlled so as to increase.
As the opening adjustment valve in the second proposal, in addition to a valve capable of adjusting the opening continuously or stepwise, a valve whose opening can be selected only in two stages of fully open and fully closed can be used. In the former case, the opening is adjusted so that the temperature difference is less than the specified value. In the latter case, the opening adjustment valve may be fully opened until the temperature difference becomes equal to or less than the predetermined value.
The heat pump water heater according to the second proposal also exhibits the same effect as the first proposal. In particular, the target hot water temperature can be set regardless of the outside air temperature without special control on the evaporator side. Can be maintained.
In the second proposal, an oil separator is installed between the discharge pipe of the compressor and the water refrigerant heat exchanger, an oil return pipe connecting the oil separator and the suction pipe of the compressor is installed, and the oil return pipe is in the middle. You may provide an opening degree adjustment valve in.

  Although omitted from the description here, it is assumed that the heat pump water heater according to the second proposal also includes the same compressor as the first proposal, a water-to-refrigerant heat exchanger, and an electronic expansion valve. The same applies to the third proposal.

[Third proposal]
The third proposal is characterized in that the supercritical refrigeration cycle is provided with a pressure reducing valve whose opening degree can be adjusted in the refrigerant flow path between the evaporator and the compressor. The opening degree of the pressure reducing valve is controlled as follows. That is, when the temperature difference between the target hot water temperature flowing out of the water-to-refrigerant heat exchanger and the detected actual hot water temperature of water flowing out of the water-to-refrigerant heat exchanger reaches a specified value, the control unit Control the opening of the pressure reducing valve to be small.
In the heat pump water heater according to the third proposal, the same effect as that of the first proposal is exhibited. In particular, the target hot water temperature can be set regardless of the outside air temperature without special control on the evaporator side. Can be maintained.

[Fourth proposal]
A heat pump water heater according to a fourth proposal includes a compressor in which a supercritical refrigeration cycle compresses and discharges a refrigerant, a water-to-refrigerant heat exchanger that exchanges heat between the refrigerant compressed by the compressor and water, A third expansion valve for decompressing and expanding the refrigerant flowing out from the refrigerant heat exchanger, a receiver for separating the refrigerant decompressed by the third electronic expansion valve into saturated gas and saturated liquid, and heat exchange with the refrigerant flowing out from the evaporator A first internal heat exchanger that supercools the refrigerant in the saturated liquid state separated by the receiver, and a fourth expansion valve that decompresses and expands the refrigerant that has passed through the first internal heat exchanger. The flow path of the refrigerant flowing out from the first internal heat exchanger is branched into a third flow path toward the compressor and a fourth flow path toward the second internal heat exchanger.
The supercritical refrigeration cycle includes a second internal heat exchanger for exchanging heat between the refrigerant flowing out of the water refrigerant heat exchanger and the refrigerant flowing through the fourth flow path, and a second internal heat exchanger on the fourth flow path. Also includes a first shut-off valve provided on the upstream side, an injection circuit for introducing the saturated gas refrigerant separated by the receiver into the compressor, and a second shut-off valve provided in the middle of the injection circuit.
In the heat pump water heater according to the fourth proposal, the control unit has a target hot water temperature of water flowing out of the water-to-refrigerant heat exchanger and an actual hot water temperature detected of water flowing out of the water-to-refrigerant heat exchanger. When the temperature difference is equal to or less than the specified value, control is performed so that the opening degree of the first cutoff valve is increased. Thereby, the temperature of the refrigerant | coolant discharged from a compressor is increased by increasing the superheat degree of the refrigerant | coolant suck | inhaled by a compressor.
In the heat pump water heater according to the fourth proposal, the same effect as that of the first proposal is exhibited. In particular, the target hot water temperature can be set regardless of the outside air temperature without special control on the evaporator side. Can be maintained.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to avoid that oil stays in an evaporator, the heat pump water heater which can make hot hot water stably even if external temperature is high is provided.

It is a figure which shows the whole structure of the heat pump water heater of 1st Embodiment. It is a figure which shows an example of the relationship between the target hot water temperature in the heat pump water heater of 1st Embodiment, and a low voltage | pressure side refrigerant pressure. It is a flowchart which shows the control procedure of the heat pump water heater of 1st Embodiment. It is a flowchart which shows the control procedure following FIG. It is a figure which shows the whole structure of the heat pump water heater of 2nd Embodiment. It is a flowchart for the control procedure of the heat pump water heater of the second embodiment. It is a figure which shows the whole structure of the heat pump water heater by the modification of 2nd Embodiment. It is a figure which shows the whole structure of the heat pump water heater of 3rd Embodiment. It is a flowchart for the control procedure of the heat pump water heater of the third embodiment. It is a figure which shows the whole structure of the heat pump water heater of 4th Embodiment. It is a flowchart for the control procedure of the heat pump water heater of the fourth embodiment.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
[First Embodiment]
As shown in FIG. 1, the heat pump water heater 100 according to the first embodiment includes a heat pump unit 2 and a hot water storage unit 3.
The heat pump unit 2 constitutes a refrigerant circuit through which CO ₂ refrigerant circulates, and performs heat exchange between outdoor air (outside air) and the refrigerant. The heat pump unit 2 compresses and discharges a refrigerant, a water-to-refrigerant heat exchanger 11 that exchanges heat between the refrigerant compressed by the compressor 10 and water, and a water-to-refrigerant heat exchanger 11. And a branch portion D that branches the refrigerant flow from the common flow path L to the first flow path L1 and the second flow path L2, and constitutes a supercritical refrigeration cycle.
The refrigerant flowing through each of the first flow path L1 and the second flow path L2 joins at the joining portion J before the compressor 10, and then is sucked into the compressor 10 through the common flow path L.
The first flow path L1 includes a first electronic expansion valve 12 that decompresses and expands one of the refrigerants branched at the branch portion D, and a first evaporator that evaporates the refrigerant decompressed and expanded by the first electronic expansion valve 12. 13.
In addition, the second flow path L2 is a second electronic expansion valve 14 that decompresses and expands the other refrigerant branched at the branch portion D, and a second that evaporates the refrigerant decompressed and expanded by the second electronic expansion valve 14. And an evaporator 15.
The heat pump unit 2 further sets a pressure sensor 16 for detecting the refrigerant pressure on the suction side of the compressor 10 (actual low pressure refrigerant pressure P _L ), and the temperature of water flowing out of the water-to-refrigerant heat exchanger 11 (target) A setting unit 17 that discharges the hot water, a temperature sensor 18 that detects the temperature of water flowing out of the water-to-refrigerant heat exchanger 11, and a control unit 19 that controls the operation of the heat pump unit 2.

  The compressor 10 is rotationally driven by an integrally configured electric motor, so that the low-pressure refrigerant that has passed through the first evaporator 13 and the second evaporator 15 is sucked and compressed, and the high-temperature and high-pressure refrigerant is converted into water. It discharges toward the refrigerant heat exchanger 11. The operation of the electric motor, that is, the compressor 10 is controlled by the control unit 19. As the compressor 10 in the present embodiment, a single-stage compression mechanism having a single compression mechanism or a multi-stage compression mechanism including a low-stage compression mechanism and a high-stage compression mechanism can be used. As the compression mechanism, a known type of compressor such as a scroll compression mechanism or a rotary compression mechanism can be used.

  The water-to-refrigerant heat exchanger 11 heats water by exchanging heat between the water on the hot water storage unit 3 side and the refrigerant. The high-temperature and high-pressure refrigerant discharged from the compressor 10 is cooled here.

The first evaporator 13 and the second evaporator 15 exchange heat between the refrigerant that has been decompressed and expanded after passing through the first electronic expansion valve 12 and the second expansion valve 14, respectively, and the outside air (blast air). A known heat exchanger can be used. During this heat exchange process, the refrigerant evaporates and absorbs heat from the outside air.
In the first embodiment, the evaporator is divided into two separate bodies such as the first evaporator 13 and the second evaporator 15, but is configured with a fin-and-tube heat exchanger, The heat exchange fins of the first evaporator 13 and the second evaporator 15 are made common, and the tubes through which the refrigerant flowing out from the first electronic expansion valve 12 and the second electronic expansion valve 14 are provided independently of each other, The evaporator 13 and the second evaporator 15 may be configured integrally in appearance.
A blower fan 20 is attached to the first evaporator 13 and the second evaporator 15. By heat exchange between the blown air blown by the blower fan 20 and the refrigerant, the low-pressure refrigerant is evaporated to exert a heat absorbing action. The operation of the blower fan 20, that is, the rotation speed is controlled by a control signal from the control unit 19. The control unit 19 acquires the rotational speed (actual rotational speed N _F ) of the blowing fan 20 during operation. In this example, a common blower fan 20 is provided for the first evaporator 13 and the second evaporator 15, but a blower fan 20 corresponding to each of the first evaporator 13 and the second evaporator 15 is provided. You can also.

  The refrigeration cycle circuit of the heat pump unit 2 includes the first electronic expansion valve 12 and the water-to-refrigerant heat exchanger 11 between the outlet side of the water-to-refrigerant heat exchanger 11 and the inlet side of the first evaporator 13. A second electronic expansion valve 14 is provided between the outlet side and the inlet side of the second evaporator 15. The first electronic expansion valve 12 and the second electronic expansion valve 14 are pressure-reduced by adiabatic expansion of a high-pressure refrigerant to obtain a low-pressure refrigerant. The opening degree is adjusted by a control signal from the control unit 19. The The first electronic expansion valve 12 and the second electronic expansion valve 14 also have a function of adjusting the flow rate of the refrigerant supplied to the first evaporator 13 and the second evaporator 15.

  A user who uses the heat pump water heater 100 sets a target temperature of water discharged from the water-to-refrigerant heat exchanger 11 in the setting unit 17 (target hot water temperature). When the target hot water temperature is input to the setting unit 17, the information is notified to the control unit 19.

The control part 19 controls operation | movement of control objects, such as the compressor 10, the 1st electronic expansion valve 12, the 2nd electronic expansion valve 14, the ventilation fan 20, and the water circulation pump 22 mentioned later based on target hot-water temperature.
The control unit 19 acquires the suction side refrigerant pressure (low pressure side refrigerant pressure) of the compressor 10 detected by the pressure sensor 16. In addition, the control unit 19 acquires the temperature of water flowing out from the water-to-refrigerant heat exchanger 11 (actual hot water temperature) detected by the temperature sensor 18. The control unit 19 controls the operations of the first electronic expansion valve 12, the second electronic expansion valve 14, and the blower fan 20 based on the acquired low-pressure side refrigerant pressure and actual hot water temperature. Details of this control content will be described later.
The heat pump unit 2 includes a rotational speed detection sensor that detects the rotational speed of the compressor 10 in order to control the rotational speed of the compressor 10, but is not a characteristic part for the first embodiment. Omit.

  In the heat pump unit 2, the branch part D and the junction part J may be configured by a pipe joint having a three-way joint structure, or may be configured by providing two refrigerant passages in a metal block or a resin block. In addition, since the exit side of the 1st evaporator 13 and the 2nd evaporator 15 will connect by the junction part J, in 1st Embodiment, refrigerant | coolant evaporation in the 1st evaporator 13 and the 2nd evaporator 15 is carried out. The pressure (low pressure side refrigerant pressure) is the same. The refrigerant outlet of the junction J is connected to the suction side of the compressor 10.

The hot water storage unit 3 includes a hot water storage tank 21 covered with a heat insulating material. The hot water storage unit 3 is provided with a water circulation pump 22 in the heat pump unit 2 for feeding the water in the hot water storage tank 21 to the water-to-refrigerant heat exchanger 11. The operation of the water circulation pump 22 is controlled by the control unit 19.
Such a hot water storage unit 3 is heated by heat exchange of water as a heating target supplied from the hot water storage tank 21 by the water circulation pump 22 with the refrigerant on the heat pump unit 2 side in the water-to-refrigerant heat exchanger 11.

In the heat pump water heater 100, the high-temperature and high-pressure supercritical refrigerant compressed by the compressor 10 is guided to the water-to-refrigerant heat exchanger 11. This refrigerant exchanges heat with water on the hot water storage unit 3 side in the water-to-refrigerant heat exchanger 11, that is, dissipates heat toward water.
Then, the high-temperature and high-pressure supercritical refrigerant is cooled inside the water-to-refrigerant heat exchanger 11 and becomes a low-temperature and high-pressure supercritical refrigerant.
On the other hand, water absorbs the heat of the refrigerant in the water-to-refrigerant heat exchanger 11 and is supplied to the hot water storage tank 21 as heated hot water.

The refrigerant flowing out of the water-to-refrigerant heat exchanger 11 is led to the first evaporator 13 and the second evaporator 15 via the first electronic expansion valve 12 and the second electronic expansion valve 14, and between the outside air (air). Heat exchange, that is, absorb the heat of the outside air. Therefore, the low-temperature and low-pressure liquid-phase refrigerant evaporates inside the first evaporator 13 and the second evaporator 15 and becomes a gas-phase refrigerant.
The gas-phase refrigerant flowing out from the first evaporator 13 and the second evaporator 15 is sucked into the compressor 10. The sucked refrigerant is compressed by the compressor 10 and then discharged again toward the water-to-refrigerant heat exchanger 11, and the above-described refrigeration cycle is repeated.

The control unit 19 is responsible for controlling the operation of the heat pump water heater 100. In particular, in this embodiment, the upper limit value of the low-pressure side refrigerant pressure is set according to the target hot water temperature set by the setting unit 17. There are features. A control procedure of the control unit 19 in the heat pump water heater 100 will be described with reference to FIGS.
The control unit 19 controls the low-pressure side refrigerant pressure within a low-pressure side refrigerant pressure control range (hereinafter, also referred to as “control pressure”) shown in FIG. The control unit 19 holds information (target hot water temperature-control pressure information) in which the target hot water temperature and the control pressure shown in FIG. 2 are associated, and the control pressure (upper limit pressure P) corresponding to the set target hot water temperature. _LU , lower limit pressure P _LL ) can be specified. The control part 19 can hold | maintain target hot-water temperature-control pressure information as table data, and can also hold | maintain as a function.
The upper limit pressure _PLU that is the upper limit value of the control pressure is set to maintain the target hot water temperature at a predetermined value even when the outside air temperature is high. On the other hand, the rotational speed of the blower fan 20 can be stably controlled by giving the lower limit pressure P _LL of the control pressure to a certain extent with respect to the upper limit pressure P _LU .
The control unit 19 controls the low-pressure side refrigerant pressure through adjustment of the rotational speed of the blower fan 20 and capacity adjustment of the evaporators (the first evaporator 13 and the second evaporator 15).

Here, the rotation speed of the blower fan 20 can be adjusted steplessly. On the other hand, the adjustment of the evaporator capacity is performed by opening and closing one of the two evaporators of the first evaporator 13 and the second evaporator 15, so that the evaporator capacity is 50%. It can only be adjusted in two stages of 100%. If the capacity of the evaporator is changed by 50%, the low-pressure side refrigerant pressure also changes significantly, and there is a risk that the capacity change will deviate from the low-pressure side refrigerant pressure range. Therefore, priority is given to controlling the rotation speed of the blower fan 20, but the evaporator capacity is adjusted when the blower fan 20 alone cannot be controlled. However, this is only a preferred example of the present invention.
Since the evaporator capacity cannot be controlled directly, when it is desired to reduce the evaporator capacity to 50%, the electronic expansion valve (first electron) located in front of the evaporator (the first evaporator 13 and the second evaporator 15) is used. One of the expansion valve 12 and the second electronic expansion valve 14) is fully closed.

  In the present embodiment, when changing the capacity of the evaporator, the operation is interrupted. This is because the refrigerant temporarily accumulates in the water-to-refrigerant heat exchanger 11 with a rapid change in the evaporator capacity, and a transient increase in the high-pressure side refrigerant pressure may occur. However, since a transient increase in the high-pressure side refrigerant pressure can be avoided by other means, it is not always necessary to interrupt the operation.

A control procedure according to the present embodiment considering the above will be described with reference to FIGS.
When the target hot water temperature is input to the setting unit 17 (S101 in FIG. 3), the control unit 19 acquires this setting information, and the compressor 10, the first electronic expansion valve 12, and the second electronic expansion valve 14 that are control targets. Then, an operation start command signal is sent to the blower fan 20 and the water circulation pump 22 (hereinafter sometimes collectively referred to as a control target) (S102 in FIG. 3). In addition to the target hot water temperature, the set value input to the setting unit 17 includes, for example, a target hot water storage amount for the hot water storage tank 21 and an operation start time.
Each control object that has received the operation start command starts the start-up operation (S103 in FIG. 3). The start-up operation is performed until each control object starts under initial conditions and the operation is stabilized (S104 and S105 in FIG. 3). For example, if the initial condition is the compressor 10, the blower fan 20, and the water circulation pump 22, the initial rotational speed is set, and if the first electronic expansion valve 12 and the second electronic expansion valve 14 are used, the initial opening is set. The

When the start-up operation is completed, the operation proceeds to normal operation, and the control unit 19 continuously acquires operation information (S106 in FIG. 3). The operation information is the actual rotational speed N _F and the actual low-pressure side refrigerant pressure of the blower fan 20 (actual pressure) P _L. The actual rotation speed N _F is obtained from the blower fan 20, also the actual pressure P _L is obtained from the pressure sensor 16. The conditions of normal operation of the compressor 10, the first electronic expansion valve 12, the second electronic expansion valve 14, and the water circulation pump 22 are arbitrary. For example, the first electronic expansion valve 12 and the second electronic expansion valve 14 are: The opening degree is set in accordance with the degree of superheat of the refrigerant sucked in the compressor 10.
Further, the control unit 19 sets an upper limit pressure _PLU and a lower limit pressure _PLL of the control pressure (S107 in FIG. 3). For example, the control unit 19 sets the control pressure (upper limit pressure _PLU and lower limit pressure _PLL ) based on the target hot water temperature-control pressure information shown in FIG.

The control unit 19 compares the actual pressure _PL with the control pressure (the upper limit pressure _PLU and the lower limit pressure _PLL ) (S108 in FIG. 3). This comparison is performed for determining whether or not the actual pressure _PL is within the range of the control pressure, and the determination result is classified into the following three cases I, II and III.
Case I: P _LL ≦ P _L ≦ P _LU (actual pressure _PL is within control pressure range)
Case II: P _L <P _LL (actual pressure _PL is lower than lower limit pressure P _LL )
Case III: P _L > P _LU (actual pressure _PL exceeds upper limit pressure P _LU )

If the determination result of the case I (within the actual pressure _PL is controlled pressure), so as to maintain the actual rotational speed N _F, the control unit 19 sends a control signal to the blower fan 20 (Fig. 3 S109).

Determination if the result is Case II (less than the actual pressure _PL is lower limit pressure _{P LL)} may compare the actual rotational speed _{N F} and the control rotation speed of the blower fan 20 (the upper limit rotational speed _{N FU} and the lower limit engine speed _{N FL),} It judges (FIG. 3 S110). The judgment results are divided into the following cases II-I and II-II. In addition, the control rotation speed (the upper limit rotation speed _NFU and the lower limit rotation speed _NFL ) of the blower fan 20 is the upper limit and the lower limit of the rotation speed permitted for the blower fan 20.
Case II-I: Actual rotation speed N _F = Upper rotation speed N _FU
Case II-II: Actual speed N _F <Upper limit speed N _FU

If the determination result is Case II-I, since it can not be the actual rotational speed N _F beyond it, so as to maintain the actual rotational speed N _F, the control unit 19 sends a control signal to the blower fan 20 (FIG. 3 S109).
If the determination result is Case II-II is to increase the actual rotational speed N _F, the control unit 19 sends a control signal to the blower fan 20 (FIG. 3 S 111).
The control unit 19 returns to step S108 and continues the comparison between the actual pressure _PL and the control pressure (upper limit pressure _PLU and lower limit pressure _PLL ).

Judgment result in each case of the case III (the actual pressure _PL is the upper limit pressure _{P LU} greater), comparing the actual rotational speed _{N F} and the control rotation speed of the blower fan 20 (the upper limit rotational speed _{N FU} and the lower limit engine speed _{N FL),} It judges (FIG. 3 S112). The judgment results are classified into the following cases III-I and III-II.
Case III-I: Actual rotation speed N _F > Lower limit rotation speed N _FL
Case III-II: Actual rotation speed N _F = Lower limit rotation speed N _FL

If the determination result is Case III-I is to reduce the actual rotational speed N _F, the control unit 19 sends a control signal to the blower fan 20 (Fig. 3 S113). The control unit 19 returns to step S108 and continues the comparison between the actual pressure _PL and the control pressure (upper limit pressure _PLU and lower limit pressure _PLL ).
If the determination result is Case III-II, since it can not be the less actual rotation speed N _F, the control unit 19 sends a control signal for operation interrupt command (Fig. 3 S114). By this command, the compressor 10, the blower fan 20, and the water circulation pump 22 stop rotating. The opening degree of the first electronic expansion valve 12 and the second electronic expansion valve 14 becomes zero (fully closed) (S115 in FIG. 3). The reason for interrupting the operation is as described above.

For example, after a predetermined interruption time has elapsed, the control unit 19 sends an operation restart command signal (S201 in FIG. 4). Each control object that has received this operation resumption command signal starts an activation operation at the time of operation resumption (FIG. 4, S202). In this starting operation, the first electronic expansion valve 12 (or the second electronic expansion valve 14) is kept fully closed, and the second electronic expansion valve 14 (or the first electronic expansion valve 12) is set to the initial opening. The The starting operation at this time is also performed until each control object is started under the initial conditions and the operation is stabilized (S203 and S204 in FIG. 4). As for this initial condition, for the blower fan 20, the rotation speed is set to the lower limit rotation speed _NFL . The first electronic expansion valve 12 remains fully closed, while the second electronic expansion valve 14 is set to the same initial opening as when the operation is started. The compressor 10 and the water circulation pump 22 are set to the same initial rotational speed as at the start of operation.

Launch After operation is completed, the actual rotational speed _{N F} so as to maintain the lower limit engine speed _{N FL,} the control unit 19 sends a control signal to the blower fan 20 (FIG. 4 S205).
The control unit 19 acquires the actual low-pressure side refrigerant pressure (actual pressure) P _L from the pressure sensor 16 (S206 in FIG. 4), and further sets the upper limit pressure _PLU and the lower limit pressure _PLL of the control pressure (S207 in FIG. 4). ). The control pressure is set as before the interruption.

The control unit 19 compares and determines the actual pressure _PL and the control pressure (the upper limit pressure _PLU and the lower limit pressure _PLL ) (S208 in FIG. 4). This comparison is performed to determine whether or not the actual pressure _PL is within the range of the control pressure, and the determination result is divided into the following cases IV and V.
Case IV: P _L ≧ P _LL (actual pressure _PL is lower than the lower limit pressure P _LL )
Case V: P _L <P _LL (actual pressure _PL is lower than lower limit pressure P _LL )

When the determination result is Case IV, the control unit 19 sends a control signal to the second electronic expansion valve 14 so that the opening degree corresponds to the degree of superheat of the refrigerant sucked in the compressor 10. On the other hand, the first electronic expansion valve 12 is kept fully closed (S209 in FIG. 4). In this case, the control unit 19 sequentially compares and determines the actual pressure _PL and the control pressure (the upper limit pressure _PLU and the lower limit pressure _PLL ) (S208 in FIG. 4).

  When the determination result is case V, the control unit 19 sends a control signal for an operation stop command (S210 in FIG. 4). By this command, the compressor 10, the blower fan 20, and the water circulation pump 22 stop rotating. The opening degree of the first electronic expansion valve 12 and the second electronic expansion valve 14 is zero (fully closed) (S211 in FIG. 4). In this case, the process returns to step S101 in FIG. 4 and the operation is restarted from the beginning by inputting the target hot water temperature to the setting unit 17 or the like.

  Since the operation of the heat pump water heater 100 is controlled within the range of the control pressure corresponding to the target hot water temperature, the target hot water temperature can be maintained regardless of the outside air temperature. Moreover, since the heat pump water heater 100 does not need to reduce the throttle opening degree of the first electronic expansion valve 12 (second electronic expansion valve 14), the refrigerant becomes a superheated gas state, and the oil becomes the first evaporator 13 ( It does not stay in the second evaporator 15).

The heat pump water heater 100 described above includes the first evaporator 13 and the second evaporator divided into two parts in addition to adjusting the amount of air blown to the first evaporator 13 and the second evaporator 15 by the blower fan 20. It is used in combination with closing one of 15.
However, the present invention is not limited to this embodiment, and the present invention independently adjusts the amount of air blown to the first electronic expansion valve 12 and the second electronic expansion valve 14 by the blower fan 20. Is included. In this case, it is not necessary to divide the evaporator into two. In addition, the present invention also includes that one of the first evaporator 13 and the second evaporator 15 divided into two is closed alone. However, dividing the first evaporator 13, the second evaporator 15 and the evaporator into two is an example, and the present invention allows the evaporator to be divided into three or more. Furthermore, the order of combined use is also arbitrary, and it may be possible to perform the closing of one of the first evaporator 13 and the second evaporator 15 divided into two in advance, and then adjust the air flow rate. Both may be performed simultaneously.

[Second Embodiment]
Next, a heat pump water heater 200 according to the second embodiment will be described with reference to FIGS. 5 and 6.
Since the heat pump water heater 200 has the same configuration as the heat pump water heater 100 of the first embodiment, the following description will focus on the differences from the first embodiment. The same reference numerals as those in FIG. 1 are attached to the same components as those in FIG.

The heat pump water heater 200 includes a bypass channel 25 that connects the discharge side channel OC and the suction side channel IC of the compressor 10. An opening adjustment valve 26 is provided on the bypass flow path 25. As the opening adjustment valve 26, in addition to a valve that can adjust the opening continuously or stepwise, a valve that can be adjusted only in two stages of fully open and fully closed can also be used.
The heat pump water heater 200 is different from the heat pump water heater 100 in that only one set of the electronic expansion valve 23 and the evaporator 24 is provided. A combination of an electronic expansion valve and an evaporator may be provided.

The heat pump water heater 200 is controlled by the procedure shown in FIG. In FIG. 6, the setting of the hot water temperature and the start-up operation performed in the first embodiment are omitted. The same applies to the third embodiment and the fourth embodiment.
When the operation of the heat pump water heater 200 is started, the control unit 19 acquires the temperature of water flowing out from the water-to-refrigerant heat exchanger 11 (actual hot water temperature Tt) detected by the temperature sensor 18 (S301 in FIG. 6). . Moreover, the control part 19 acquires the target hot water temperature (Tr) input into the setting part 17 (FIG. 6 S302).

  Next, the control unit 19 obtains a difference (ΔT = Tt−Tr) between the acquired target hot water temperature (Tt) and the actual hot water temperature (Tr) (S303 in FIG. 6). For example, if the target hot water temperature (Tt) is 90 ° C. and the actual hot water temperature (Tr) is 80 ° C., ΔT is 10 ° C. In the case where ΔT is large, the present embodiment aims to increase the discharge temperature of the refrigerant from the compressor 10.

Therefore, the control unit 19 determines whether ΔT is equal to or greater than the specified value Ts ₁ (S304 in FIG. 6).
When ΔT is equal to or greater than the prescribed value Ts ₁ , that is, when the actual hot water temperature (Tr) is considerably lower than the target hot water temperature (Tt), the opening degree of the opening adjustment valve 26 is increased (S305 in FIG. 6). For example, when the specified value Ts ₁ is 10 ° C. and ΔT is 13 ° C., the control unit 19 controls the opening adjustment valve 26 so that the opening becomes large. Then, the amount of high-temperature refrigerant flowing from the discharge side flow path OC into the suction side flow path IC increases. Thereby, the temperature of the refrigerant | coolant discharged from the compressor 10 to the discharge side flow path OC can be raised.
If ΔT is less than the specified value Ts ₁ , that is, if the actual hot water temperature (Tr) is close to the target hot water temperature (Tt), the process returns to steps S301 and S302. For example, when the specified value Ts ₁ is 10 ° C. and ΔT is 8 ° C., the control unit 19 returns the control procedure to steps S301 and S302.

After increasing the opening degree of the opening degree adjusting valve 26, the control unit 19 determines whether ΔT is equal to or less than the specified value Ts ₂ (S306 in FIG. 6). As an effect of increasing the opening degree of the opening adjustment valve 26, it is evaluated whether the actual hot water temperature (Tr) is approaching the target hot water temperature (Tt).
When ΔT is equal to or less than the specified value Ts ₂ , that is, when the actual hot water temperature (Tr) approaches the target hot water temperature (Tt), the opening degree of the opening adjustment valve 26 is decreased (S306 in FIG. 6). For example, when the specified value Ts ₂ is 3 ° C. and ΔT is 2 ° C., the control unit 19 controls the opening adjustment valve 26 so that the opening becomes large. Then, the amount of high-temperature refrigerant flowing from the discharge side flow path OC into the suction side flow path IC is reduced. Thereby, the temperature of the refrigerant | coolant discharged from the compressor 10 to the discharge side flow path OC can be lowered | hung.
If ΔT exceeds the specified value Ts ₂ , that is, if the actual hot water temperature (Tr) is not sufficiently close to the target hot water temperature (Tt), the process returns to steps S301 and S302. For example, when the specified value Ts ₂ is 3 ° C. and ΔT is 2 ° C., the control unit 19 returns the control procedure to steps S301 and S302.

Also in the heat pump water heater 200 described above, the target hot water temperature can be obtained by simple control without being influenced by the outside air temperature. Moreover, the oil does not stay in the evaporator 24.
In the above description, the opening adjustment valve 26 has been described as being capable of adjusting the opening continuously or stepwise. However, it is also possible to use the opening adjustment valve 26 that can be adjusted only by opening and closing. It is as follows. In this case, if it is determined that ΔT is the prescribed value Ts ₁ or more, it continues opening the opening regulating valve 26 until ΔT becomes less than the specified value Ts _1.

As a modification of the heat pump water heater 200 described above, a heat pump water heater 201 is shown in FIG.
The heat pump water heater 201 includes an oil separator 28 on the discharge side flow path OC between the compressor 10 and the water-to-refrigerant heat exchanger 11. An oil return flow path 27 connects the oil separator 28 and the suction side flow path IC. The oil return flow path 27 branches off from the oil separator 28 toward the suction side flow path IC, and an opening degree adjusting valve 26 is provided on one of the branched flow paths.
The heat pump water heater 201 returns the lubricating oil to the suction side flow path IC through the flow path where the opening degree adjustment valve 26 is not provided. On the other hand, the flow path provided with the opening adjustment valve 26 is used to return the high-temperature refrigerant discharged from the compressor 10 and flowing through the discharge side flow path OC to the suction side flow path IC, as described above.
In the heat pump water heater 201, the oil return flow path 27 is branched from the middle, but a flow path for returning lubricating oil to the suction side flow path IC and a high-temperature and high-pressure refrigerant flowing in the discharge side flow path OC are sucked. The flow path returning to the flow path IC can also be provided independently.

[Third Embodiment]
Next, a heat pump water heater 300 according to the third embodiment will be described with reference to FIGS.
Since the heat pump water heater 300 has a configuration common to the heat pump water heater 100 (first embodiment) and the heat pump water heater 200 (second embodiment), differences from the first and second embodiments are mainly described below. Explained. In FIG. 8, the same components as those in FIG. 1 (first embodiment) and FIG. 5 (second embodiment) are denoted by the same reference numerals as in FIG.

  The heat pump water heater 300 includes a pressure reducing valve 29 that can adjust the opening degree between the evaporator 24 and the compressor 10. The opening degree of the pressure reducing valve 29 is adjusted by the control unit 19. The heat pump water heater 300 raises the temperature of the refrigerant discharged from the compressor 10 by reducing the opening of the pressure reducing valve 29 as necessary.

The heat pump water heater 300 is controlled by the procedure shown in FIG.
When the operation of the heat pump water heater 300 is started, the control unit 19 acquires the temperature of water flowing out from the water-to-refrigerant heat exchanger 11 (actual hot water temperature Tt) detected by the temperature sensor 18 (S401 in FIG. 9). . Moreover, the control part 19 acquires the target hot water temperature (Tr) input into the setting part 17 (FIG. 9 S402).

  Subsequently, the control part 19 calculates | requires the difference ((DELTA) T = Tt-Tr) of the acquired target hot water temperature (Tt) and actual hot-water temperature (Tr) (FIG. 9 S403). The present embodiment is also aimed at increasing the refrigerant discharge temperature from the compressor 10 when ΔT is large.

Therefore, the control unit 19 determines whether ΔT is greater than or equal to the specified value Ts ₁ (S404 in FIG. 9).
When ΔT is equal to or greater than the specified value Ts ₃ , that is, when the actual hot water temperature (Tr) is considerably lower than the target hot water temperature (Tt), the opening of the pressure reducing valve 29 is reduced (S405 in FIG. 9). If it does so, the pressure of the refrigerant | coolant suck | inhaled by the compressor 10 will become low, As a result, the discharge temperature of the refrigerant | coolant discharged to the discharge side flow path OC will go up.
When ΔT is less than the specified value Ts ₃ , that is, when the actual hot water temperature (Tr) is close to the target hot water temperature (Tt), the process returns to steps S 401 and 402.

After reducing the opening of the pressure reducing valve 29, the control unit 19 determines whether ΔT is equal to or less than the specified value Ts ₄ (S406 in FIG. 9). As an effect of reducing the opening degree of the pressure reducing valve 29, it is evaluated whether the actual hot water temperature (Tr) is close to the target hot water temperature (Tt).
When ΔT is equal to or less than the specified value Ts ₄ , that is, when the actual hot water temperature (Tr) approaches the target hot water temperature (Tt), the opening degree of the pressure reducing valve 29 is increased (S407 in FIG. 6). If it does so, the pressure of the refrigerant | coolant suck | inhaled by the compressor 10 will become high, As a result, the discharge temperature of the refrigerant | coolant discharged to the discharge side flow path OC will fall.
If ΔT exceeds the specified value Ts ₄ , that is, if the actual hot water temperature (Tr) is not sufficiently close to the target hot water temperature (Tt), the process returns to steps S401 and S402.

  Also in the heat pump water heater 300 described above, the target hot water temperature can be obtained by simple control without being influenced by the outside air temperature. Moreover, the oil does not stay in the evaporator 24.

[Fourth Embodiment]
Next, a heat pump water heater 400 according to the fourth embodiment will be described with reference to FIGS. 10 and 11.
Since the heat pump water heater 400 has the same configuration as the heat pump water heater 100 (first embodiment) and the heat pump water heater 200 (second embodiment), the differences from the first and second embodiments will be described below. I will explain it mainly. In FIG. 10, the same components as those in FIG. 1 (first embodiment) and FIG. 5 (second embodiment) are denoted by the same reference numerals as in FIG. FIG. 10 omits the hot water storage unit 3.

The heat pump water heater 400 includes a two-stage compressor 40 and includes an injection circuit 36 that introduces a saturated gas refrigerant into the intermediate pressure region of the compressor 10. The two-stage compressor 40 includes a low-stage compression mechanism 41 and a high-stage compression mechanism 42.
Further, the heat pump water heater 400 includes a third electronic expansion valve 30 that decompresses and expands the refrigerant that has passed through the water-to-refrigerant heat exchanger 11 in the flow path downstream of the water-to-refrigerant heat exchanger 11, and a third electronic expansion valve 30. A receiver 31 that separates the refrigerant depressurized by the electronic expansion valve 30 into a saturated gas and a saturated liquid, and a supercooled refrigerant of the saturated liquid separated by the receiver 31 by exchanging heat with the refrigerant discharged from the evaporator 24. 1 internal heat exchanger 32, and a fourth electronic expansion valve 33 that decompresses and expands the refrigerant that has passed through the first internal heat exchanger 32. The refrigerant expanded under reduced pressure by the fourth electronic expansion valve 33 is sent to the evaporator 24 and evaporated.

The heat pump water heater 400 is overheated by exchanging heat from the evaporator 24 with the saturated refrigerant separated in the receiver 31 in the first internal heat exchanger 32. The refrigerant flowing out from the first internal heat exchanger 32 is branched at the branching section D into a third flow path L3 toward the compressor 10 and a fourth flow path L4 toward the second internal heat exchanger 34.
The heat pump water heater 400 is provided between the second internal heat exchanger 34 that exchanges heat between the refrigerant discharged from the water-body refrigerant heat exchanger 11 and the branched refrigerant, and between the branch portion D and the second internal heat exchanger 34. A first shut-off valve 35. The heat pump water heater 400 includes an injection circuit 36 for introducing the saturated gas refrigerant separated by the receiver 31 into the compressor 40, and a second shut-off valve 37 is provided in the middle of the injection circuit 36. The saturated gas refrigerant is introduced into the intermediate pressure portion between the low-stage compression mechanism 41 and the high-stage compression mechanism 42 of the compressor 40 via the injection circuit 36. According to the opening and closing of the second shut-off valve 37, the saturated gas refrigerant is selectively injected.

The heat pump water heater 400 is controlled by the procedure shown in FIG.
When the operation of the heat pump water heater 400 is started, the control unit 19 acquires the temperature of the water flowing out from the water-to-refrigerant heat exchanger 11 (actual hot water temperature Tr) detected by the temperature sensor 18 (S501 in FIG. 11). . Moreover, the control part 19 acquires the target hot-water temperature (Tt) input into the setting part 17 (FIG. 11 S502).

  Subsequently, the control part 19 calculates | requires the difference ((DELTA) T = Tt-Tr) of the acquired target hot water temperature (Tt) and actual hot-water temperature (Tr) (FIG. 11 S503). The present embodiment is also aimed at increasing the refrigerant discharge temperature from the compressor 10 when ΔT is large.

Therefore, the control unit 19 determines whether ΔT is equal to or greater than the specified value Ts ₁ (S504 in FIG. 11).
When ΔT is not less than the specified value Ts ₅ , that is, when the actual hot water temperature (Tr) is considerably lower than the target hot water temperature (Tt), the first shutoff valve 35 is opened (S505 in FIG. 11). If it does so, the superheat degree of the refrigerant | coolant suck | inhaled by the compressor 10 will increase, As a result, the discharge temperature of the refrigerant | coolant discharged to the discharge side flow path OC will go up.
When ΔT is less than the prescribed value Ts ₅ , that is, when the actual hot water temperature (Tr) is close to the target hot water temperature (Tt), the process returns to steps S501 and S502.

After opening the first shut-off valve 35, the control unit 19 determines whether ΔT is equal to or less than the specified value Ts ₆ (S506 in FIG. 9). As an effect of opening the first shutoff valve 35, it is evaluated whether the actual hot water temperature (Tr) is approaching the target hot water temperature (Tt).
ΔT is a specified value Ts ₂ below, that is, when the actual hot water temperature to the target hot water temperature (Tt) (Tr) approaches closes the first shut-off valve 35 (FIG. 11 S507). If it does so, the pressure of the refrigerant | coolant suck | inhaled by the compressor 10 will become high, As a result, the superheat degree of the refrigerant | coolant suck | inhaled by the compressor 10 will reduce.
If ΔT exceeds the specified value Ts ₆ , that is, if the actual hot water temperature (Tr) is not sufficiently close to the target hot water temperature (Tt), the process returns to steps S501 and S502.

  Also in the heat pump water heater 400 described above, the target hot water temperature can be obtained by simple control without being influenced by the outside air temperature. Moreover, the oil does not stay in the evaporator 24.

  Unless deviating from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

100, 200, 201, 300, 400 Heat pump water heater 2 Heat pump unit 3 Hot water storage unit 10 Compressor 11 Water body refrigerant heat exchanger 12 First electronic expansion valve 13 First evaporator 14 Second electronic expansion valve 15 Second evaporator 16 Pressure sensor 17 Setting unit 18 Temperature sensor 19 Control unit 20 Blower fan 21 Hot water storage tank 22 Water circulation pump 23 Electronic expansion valve 24 Evaporator 25 Bypass channel 26 Opening adjustment valve 27 Oil return channel 28 Oil separator 29 Pressure reducing valve 30 3rd electronic expansion valve 31 Receiver 32 1st internal heat exchanger 33 4th electronic expansion valve 34 2nd internal heat exchanger 35 1st shut-off valve 36 Injection circuit 37 2nd shut-off valve D Branch part J Junction part IC Suction side Channel OC Discharge side channel L Common channel L1 First channel L2 Second channel L3 Third channel L4 Fourth channel

Claims (3)

A heat pump water heater using a supercritical refrigeration cycle,
The supercritical refrigeration cycle is
A compressor that compresses and discharges the refrigerant;
A water-to-refrigerant heat exchanger for exchanging heat between the refrigerant compressed by the compressor and water;
An electronic expansion valve for decompressing and expanding the refrigerant flowing out of the water-to-refrigerant heat exchanger;
An evaporator for evaporating the refrigerant decompressed and expanded by the electronic expansion valve;
A control unit for controlling the operation of the supercritical refrigeration cycle,
Wherein the control unit is set according to the target hot water temperature of the water flowing out from the water-refrigerant heat exchanger, to control the operation based on the upper limit of the low-pressure side refrigerant pressure in the suction side of the compressor,
The supercritical refrigeration cycle is
A blower for blowing air toward the evaporator;
The controller is
When the detected actual low-pressure side refrigerant pressure exceeds the set upper limit value of the low-pressure side refrigerant pressure, the blower is controlled so as to reduce the amount of air blown toward the evaporator;
A heat pump water heater characterized by that. The supercritical refrigeration cycle is
The flow of the refrigerant flowing out of the water-to-refrigerant heat exchanger is branched into a first flow path and a second flow path, and the refrigerant flowing through each of the first flow path and the second flow path is After merging before this, it is sucked into the compressor,
The first flow path includes a first expansion valve that decompresses and expands one of the branched refrigerants, and a first evaporator that evaporates the refrigerant decompressed and expanded by the first expansion valve,
The second flow path includes a second expansion valve that decompresses and expands the other branched refrigerant, and a second evaporator that evaporates the refrigerant decompressed and expanded by the second expansion valve,
The controller is
The set upper limit value of the low-pressure side refrigerant pressure, when the sensed the real low-pressure side refrigerant pressure exceeds controls to close one of the first expansion valve and the second expansion valve,
The heat pump water heater according to claim 1 . The controller is
Done by preceding the control of the previous Symbol blower,
If the blower amount of the blower reaches a minimum value, the control to close either one of the first expansion valve and the second expansion valve according to claim 2 is performed.
Heat pump water heater.