JP2015068564A - Heat pump system and heat pump type water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-stage compression type heat pump system that can easily maintain amounts of refrigerating machine oil in two compressors equally.SOLUTION: A heat pump system includes: a compression mechanism 10 that has a low stage side compressor 10a and a high stage side compressor 10b for compressing and discharging a refrigerant; a water-refrigerant heat exchanger 11 for exchanging heat between the refrigerant compressed by the compression mechanism 10 and a heat exchange target; an expansion valve 12 for decompressing and expanding the refrigerant flowing out from the water-refrigerant heat exchanger 11; a heat source side air heat exchanger 13 for exchanging heat between the refrigerant decompressed and expanded by the expansion valve 12 and the heat exchange target; an oil equalizing mechanism 20 that interconnects the low stage side compressor 10a and the high stage side compressor 10b for making refrigerant machine oil flow; and a four-way changeover valve 14 for selectively switching between a two-stage compression route for making the refrigerant flow in the low stage side compressor 10a and the high stage side compressor 10b in this order and a single-stage compression route for making the refrigerant flow in only one of the low stage side compressor 10a and the high stage side compressor 10b.

Description

  The present invention relates to a two-stage compression heat pump system in which two independent compressors are connected in series.

The hot water supply system is becoming a heat pump for the purpose of energy saving energy.
As this refrigerant system, there is known a two-stage compression refrigeration cycle that includes a refrigerant circuit in which a low-stage compressor and a high-stage compressor are connected in series, and circulates refrigerant in the refrigerant circuit (for example, Patent Documents). 1-3).

JP-A-5-93552 JP-A-6-2966 JP 2009-168330 A

In order to always operate the two-stage compression refrigeration cycle in an efficient state, it is necessary to operate the two compressors on the low-stage side and the high-stage side at independent rotation speeds. Therefore, the biggest problem is the control of the oil level of the refrigeration oil contained in each of the two compressors. Unlike a compressor in which two low-stage and high-stage compression mechanisms are mounted inside a single housing, when two independent compressors are connected in series, the two compressors Keeping the amount of refrigeration oil at an appropriate even level is necessary for the healthy operation of the two compressors.
The present invention has been made on the basis of this technical problem, and it is easy to keep the amount of refrigerating machine oil of the two compressors equal without stopping the operation or performing complicated operation. An object of the present invention is to provide a two-stage compression heat pump system. In addition, an object of the present invention is to provide a highly efficient heat pump water heater provided with this two-stage compression heat pump system.

For this purpose, the two-stage compression heat pump system of the present invention comprises a low-stage compressor and a high-stage compressor, compresses and discharges refrigerant, and discharges from the high-stage compressor. An oil separator provided on the side, a first heat exchanger that exchanges heat between the refrigerant compressed by the compression mechanism and a heat exchange target, an expansion valve that decompresses and expands the refrigerant flowing out of the first heat exchanger, and an expansion valve The second heat exchanger that exchanges heat between the refrigerant expanded under reduced pressure and the heat exchange target, and the low-stage compressor and the high-stage compressor are connected to each other between the low-stage compressor and the high-stage compressor. The oil leveling path through which the refrigeration oil flows, the main return pipe connecting the oil separator and the suction side of the high stage compressor, the oil return path connecting the main return pipe and the oil leveling path, and the oil return path. A two-stage pressure that causes the oil return on-off valve and refrigerant to flow through the low-stage compressor and the high-stage compressor in this order. And a refrigerant path switching mechanism that selectively switches between a compression path and a one-stage compression path through which only one of the low-stage compressor and the high-stage compressor flows.
For example, assuming a heat pump type water heater, the high pressure of the device is determined depending on the water temperature (for example, in the range of 35 to 75 ° C.) entering the heat exchanger of water and refrigerant (water-to-refrigerant heat exchanger). Therefore, the pressure difference between the suction side and the discharge side of the compressor can vary greatly depending on the water temperature. When the two-stage compression operation is performed in a state where the inlet water temperature of the water-to-refrigerant heat exchanger is low, the differential pressure between the low-stage compressor and the high-stage compressor is reduced. The pressure difference between the compressors determines the amount of refrigerating machine oil that is returned. Therefore, according to the present invention, when the differential pressure between the low-stage compressor and the high-stage compressor becomes low during the two-stage compression operation, the first-stage compression operation is switched.

In the heat pump system of the present invention, when any of the following conditions (1) to (3) is satisfied while the two-stage compression path is selected, the refrigerant path is switched to the one-stage compression path.
Condition (1): T _W ≦ T _R
T _W ; When the heat exchange target of the first heat exchanger is water, the water temperature entering the heat exchanger (hydrothermal exchange) of water and refrigerant, T _R ; Specified value condition (2): (P _HO − _PLI ) ≦ ΔP _R1
P _LI ; suction pressure of the low stage compressor P _HO ; discharge pressure of the high stage compressor Specified value: ΔP _R1
Condition _{(3) (P LO -P LI} ) ≦ ΔP R2
P _LI ; Low-stage compressor suction pressure P _LO ; Low-stage compressor discharge pressure Specified value: ΔP _R2

In the heat pump system of the present invention, when the refrigerant path switching mechanism selects the one-stage compression path, the oil return on / off valve is opened, so that the refrigeration oil from the oil separator can be supplied to the oil without going through the high-stage compressor. It is possible to return to the oil leveling path via the return path.
By providing the oil return path and the oil equalization path having the above-described configuration, the oil amount can be easily recovered when the amount of refrigeration oil in each of the low-stage compressor and the high-stage compressor is insufficient.

In the heat pump system of the present invention, the opening and closing of the return on-off valve and the opening and closing of the oil equalizing on-off valve are predicted for the amount of refrigeration oil expected in the low-stage compressor and in the high-stage compressor. It is preferable to control based on the amount of refrigerating machine oil.
Refrigerating machine oil can be controlled at an appropriate timing based on the respective oil amounts of the two compressors obtained from the pressure sensor and temperature sensor detection results provided in the heat pump system.

  The heat pump type hot water heater in which the first heat exchanger of the heat pump system described above is a water-to-refrigerant heat exchanger that heats water by exchanging heat between refrigerant and water includes a low-stage compressor and a high-stage compressor. Since the amount of refrigerating machine oil is secured, stable and highly efficient hot water supply can be realized.

  According to the present invention, the low-stage compressor and the high-stage compressor can be connected to the high-stage compressor and the high-stage compressor only by a simple operation of opening and closing the first solenoid valve and the second solenoid valve without stopping the operation of the high-stage compressor. It is possible to make the refrigerating machine oil uniform in the stage side compressor.

It is a figure which shows the circuit structure of the heat pump system which concerns on 1st Embodiment. It is a figure which shows operation | movement of the heat pump system of 1st Embodiment, (a) shows two-stage compression operation, (b) shows one-stage compression operation. It is a figure which shows the circuit structure which switches the two-stage compression operation and the one-stage compression operation of the heat pump system of FIG. 1 with two solenoid valves. It is a figure which shows the circuit structure which added two oil separators to the heat pump system of FIG. It is a figure which shows the circuit structure of the heat pump type hot-water supply and air conditioner which concerns on 2nd Embodiment. The circuit configuration of the heat pump type hot water supply / air conditioner according to the second embodiment is shown, and an operation mode different from FIG. 5 is shown.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[First Embodiment]
As shown in FIG. 1, the heat pump system 1 according to the first embodiment is compressed by a low-stage compressor 10a and a high-stage compressor 10b that compress and discharge a refrigerant, and a high-stage compressor 10b. A first heat exchanger 11 for exchanging heat between the refrigerant and a fluid to be heat exchanged, an expansion valve (hereinafter simply referred to as an expansion valve) 12 for decompressing and expanding the refrigerant flowing out of the first heat exchanger 11, and an expansion valve 12 and a second heat exchanger 13 for exchanging heat between the refrigerant expanded under reduced pressure and the fluid to be heat exchanged, and connected in series in this order along the circulation direction of the refrigerant. In the present embodiment, the first heat exchanger 11 can function as a condenser that radiates heat by exchanging heat with water, for example, and the second heat exchanger 13 can exchange heat with the outside air. It can function as an evaporator that absorbs heat.
The heat pump system 1 includes a four-way switching valve 14 that switches the connection state between the low-stage compressor 10a and the high-stage compressor 10b as follows. That is, the four-way switching valve 14 is configured so that the refrigerant passes through both the low-stage compressor 10a and the high-stage compressor 10b, and the refrigerant passes through only the low-stage compressor 10a. A single-stage compression operation (one-stage compression path) that passes but bypasses the high-stage compressor 10b is switched.
Further, the heat pump system 1 includes an oil leveling mechanism 20 for keeping the amount of the refrigerating machine oil held in the low stage side compressor 10a and the amount of the refrigerating machine oil held in the high stage side compressor 10b even.

The heat pump system 1 includes a pipe L1 that connects the low-stage compressor 10a and the high-stage compressor 10b, a pipe L2 that connects the high-stage compressor 10b and the first heat exchanger 11, and the first heat exchanger 11. By providing the pipe L3 that connects the second heat exchanger 13 and the pipe L4 that connects the second heat exchanger 13 and the low-stage compressor 10a, a refrigerant circuit in which the refrigerant circulates is configured. Among these, the pipe L4 is a suction side pipe for the low stage compressor 10a, the pipe L1 connecting the low stage compressor 10a and the high stage compressor 10b is an intermediate pressure pipe, and a pipe for the high stage compressor 10b. L2 constitutes the discharge side piping.
The heat pump system 1 also includes a pipe L5 that connects the discharge side (pipe L1) of the low-stage compressor 10a and the discharge side (pipe L2) of the high-stage compressor 10b. The four-way switching valve 14 described above is provided at the connection end on the discharge side of the low-stage compressor 10a of the pipe L5. The four-way switching valve 14 allows the refrigerant discharged from the low-stage compressor 10a to be sucked into the high-stage compressor 10b through the pipe L1 as it is, or through the pipe L5 and further through the pipe L2. Whether to supply to the first heat exchanger 11 is switched. By this switching, switching between the two-stage compression path and the one-stage compression path) is realized.
The low-stage compressor 10a and the high-stage compressor 10b may be collectively referred to as the compression mechanism 10 without being distinguished.

Next, the heat pump system 1 includes an oil separator 26 on the pipe L2. The oil separator 26 is directly connected to the high stage compressor 10 b and the oil return pipe 27. The oil return pipe 27 includes a fixed throttle 27a.
During the two-stage compression operation, the oil separator 26 separates the refrigeration oil from the refrigerant discharged from the high-stage compressor 10 b and returns it to the high-stage compressor 10 b via the return pipe 27. During the one-stage compression operation, the oil separator 26 separates the refrigeration oil from the refrigerant discharged from the low-stage compressor 10 a and returns it to the high-stage compressor 10 b via the oil return pipe 27.

Hereinafter, each component of the heat pump system 1 is demonstrated in order.
[Compression mechanism 10]
The low-stage compressor 10a is rotationally driven by an integrally configured electric motor, thereby sucking in the low-temperature and low-pressure refrigerant that has passed through the second heat exchanger 13 and compressing it to an intermediate pressure. Discharge toward the machine 10b.
As a compression mechanism applied to the low-stage compressor 10a, a known type compression mechanism such as a scroll-type compression mechanism or a rotary compression mechanism can be applied. The same applies to the high-stage compressor 10b.
The high stage compressor 10b sucks and compresses the refrigerant discharged from the low stage compressor 10a, and discharges the refrigerant toward the first heat exchanger 11 as a high-temperature and high-pressure refrigerant.

[First heat exchanger 11]
The 1st heat exchanger 11 heats the said fluid by carrying out heat exchange of fluids, such as water and air used as the object of heat exchange, and a high temperature / high pressure refrigerant | coolant. The high-temperature and high-pressure refrigerant discharged from the high-stage compressor 10b is cooled and condensed here. A known heat exchanger can be used as the first heat exchanger 11. The same applies to the second heat exchanger 13 described next.
When the heat exchange target is air, the first heat exchanger 11 is provided with a blower fan 11f, and in the process in which the air blown by the blower fan 11f passes through the first heat exchanger 11, And heat exchange.

[Expansion valve 12, second heat exchanger 13]
The second heat exchanger 13 exchanges heat between the refrigerant that has passed through the expansion valve 12 and is decompressed and expanded, and the outside air (blast air). During this heat exchange, the refrigerant evaporates, and the outside air Absorbs heat. The second heat exchanger 13 is also provided with a blower fan 13f, and heat exchange is performed between the air blown by the blower fan 13f and the refrigerant, thereby evaporating the low-pressure refrigerant and causing an endothermic effect.
As the expansion valve 12, for example, an expansion valve provided with a needle-like valve body and a pulse motor for driving the valve body can be used.

[Oil leveling mechanism 20]
The oil leveling mechanism 20 includes an oil leveling pipe 21 that connects the low stage side compressor 10a and the high stage side compressor 10b, a bypass pipe 23 that connects the oil leveling pipe 21 and the oil return pipe 27, and an electromagnetic wave provided in the bypass pipe 23. And a valve 25.
The oil leveling mechanism 20 distributes the refrigerating machine oil between the low stage side compressor 10a and the high stage side compressor 10b through the oil leveling pipe 21. Further, the oil leveling mechanism 20 returns the refrigeration oil to the oil leveling pipe 21 from the discharge side of the high stage compressor 10 b via the bypass pipe 23. The function of the bypass pipe 23 is exerted when the one-stage compression operation is performed, thereby giving a necessary differential pressure to the oil leveling pipe 21.
If the oil leveling pipe 21 is based on the oil level indicating the amount of refrigerating machine oil required by each of the low stage side compressor 10a and the high stage side compressor 10b, the low stage side compressor 21 is directly above the reference oil level. 10a and the high stage compressor 10b.

[Operation of heat pump system 1]
Hereinafter, the operation of the heat pump system 1 will be described.
In the heat pump system 1, the refrigerant circulates and a two-stage compression operation is performed. However, if a specific condition is provided, a one-stage compression operation is performed.

First, the two-stage compression operation will be described.
At the time of the two-stage compression operation, as shown in FIG. 2 (a), the four-way switching valve 14 is switched so that the pipe L1 (L11 and L12) communicates, and the low-stage compressor 10a reaches the intermediate pressure. The pressurized refrigerant passes through the pipe L11, the four-way switching valve 14, and the pipe L12 and is sucked into the high stage compressor 10b. In FIG. 2A, the arrow indicates the direction in which the refrigerant flows. The same applies to FIG. 2B described later.
The high-pressure refrigerant discharged after being compressed to high temperature and high pressure by the high-stage compressor 10b flows into the first heat exchanger 11 through the pipe L2, and radiates heat to the heat exchange target. The high-pressure refrigerant radiated by the first heat exchanger 11 expands into a low-pressure refrigerant in the process of passing through the expansion valve 12 through the pipe L3. This low-pressure refrigerant further flows into the second heat exchanger 13 through the pipe L3, absorbs heat from the outdoor air, and evaporates. Thereafter, the low-pressure refrigerant flowing out of the second heat exchanger 13 is sucked into the low-stage compressor 10a through the pipe L4.

  The low-pressure refrigerant sucked into the low-stage compressor 10a is compressed into an intermediate-pressure refrigerant and then discharged to the pipe L1. The intermediate pressure refrigerant discharged from the low stage compressor 10a to the pipe L1 is sucked into the high stage compressor 10b. The refrigerant sucked into the high-stage compressor 10b is compressed into a high-pressure refrigerant and then discharged to the pipe L2.

The heat pump system 1 distributes the refrigeration oil through the oil equalizing pipe 21 in the process in which the above-described cycle of refrigerant compression, condensation, expansion, and evaporation is repeated, so that the low-stage compressor 10a and the high-stage compressor Each oil level of 10b is ensured within a necessary range.
Here, as a method of returning the refrigeration oil contained in the refrigerant discharged from the compressor to the compressor, a device called an oil separator that separates the refrigerant and oil is arranged on the discharge side of the compressor, and the separated refrigeration is performed. Generally, the machine oil is returned to the intake side of the compressor via an oil return circuit having a fixed throttle such as a capillary tube.
However, assuming a heat pump type water heater, for example, the high pressure of the device depends on the water temperature (for example, in the range of 35 to 75 ° C.) entering the heat exchanger of water and refrigerant (water-to-refrigerant heat exchanger). Therefore, the pressure difference between the suction side and the discharge side of the compressor can vary greatly depending on the water temperature. When the two-stage compression operation is performed in a state where the inlet water temperature of the water-to-refrigerant heat exchanger is low, the differential pressure between the low-stage compressor 10a and the high-stage compressor 10b becomes small. The pressure difference between the compressors determines the amount of refrigerating machine oil that is returned. Therefore, in the present embodiment, when the differential pressure between the low-stage compressor 10a and the high-stage compressor 10b becomes low during the two-stage compression operation, the solenoid valve is switched to the single-stage compression operation. Open 25. Thus, the heat pump system 1 always returns the differential pressure in the oil leveling mechanism 20 by returning the refrigeration oil from the oil separator 26 to the oil leveling pipe 21 via the bypass pipe 23 without passing through the high stage compressor 10b. It can be kept above the specified value. Moreover, the heat pump system 1 can return the oil to the low stage compressor 10a without going through the fixed throttle 27a and the high stage compressor 10b in the oil return pipe 27, so that the fixed throttle 27a and the high stage It is possible to prevent the oil return flow rate from being reduced due to the pressure loss in the side compressor 10b.

The heat pump system 1 switches to the single-stage compression operation when the following conditions (1) to (3) are satisfied during the two-stage compression operation. Each of the following conditions is an indicator that the differential pressure between the low-stage compressor 10a and the high-stage compressor 10b is low. The prescribed values T _R , ΔP _R1, and ΔP _R2 of the conditions (1) to (3) are not uniquely determined, and are determined corresponding to each component and operating condition of the applied heat pump system 1. . Although the water temperature T _W , the suction pressure P _LI , the discharge pressure P _LO and the discharge pressure P _HO are not shown, the temperature sensor attached to the first heat exchanger 11, the low stage compressor 10 a, the high stage It is detected by a pressure sensor attached to the side compressor 10b. The detected information is sent to a control unit (not shown). The control unit determines the conditions (1) to (3) using the acquired information about the water temperature T _W , the suction pressure P _LI , the discharge pressure P _LO and the discharge pressure P _HO . The control unit continues to determine the conditions (1) to (3) even during the one-stage compression operation.

(1) Water temperature entering the heat exchanger (hydrothermal exchange) of water and refrigerant: T _W , Specified value: T _R
T _W ≦ T _R
(2) suction pressure _{P LI} of the low-stage compressor 10a, the high-stage discharge pressure _{P HO} specified value of the compressor 10b: [Delta] P _{R1
(P HO -P LI) ≦ ΔP} R1
(3) Suction pressure P _LI and discharge pressure P _LO specified values of low stage compressor 10a: ΔP _R2
(P _LO −P _LI ) ≦ ΔP _R2

[Two-stage compression operation → One-stage compression operation]
When the control unit determines that any one of the conditions (1) to (3) is satisfied during the two-stage compression operation, the controller switches the four-way switching valve 14 to the position of the one-stage compression operation shown in FIG. To switch to. Further, the control unit 40 instructs to open the electromagnetic valve 25. Then, the heat pump system 1 operates as follows.
The high-pressure refrigerant discharged after being compressed to high pressure by the low-stage compressor 10a flows into the first heat exchanger 11 through the pipe L11, the four-way switching valve 14 and the pipe L5, and dissipates heat to the heat exchange target. To do. Here, the low-stage compressor 10a improves the operation capability compared with the two-stage compression operation, and compresses the refrigerant to a high pressure. Further, the operation of the high stage compressor 10b is stopped.
The high-pressure refrigerant radiated by the first heat exchanger 11 expands into a low-pressure refrigerant in the process of passing through the expansion valve 12 through the pipe L3. This low-pressure refrigerant further flows into the second heat exchanger 13 through the pipe L3, absorbs heat from the outdoor air, and evaporates. Thereafter, the low-pressure refrigerant flowing out of the second heat exchanger 13 is sucked into the low-stage compressor 10a through the pipe L4.
In the one-stage compression operation, the solenoid valve 25 is open in the process in which the cycle of refrigerant compression, condensation, expansion, and evaporation described above is repeated. Therefore, the refrigeration oil passes through the bypass pipe 23 and passes through the high-stage compressor 10b. Is returned to the oil equalizing pipe 21 without going through. Therefore, since the differential pressure in the oil leveling mechanism 20 can always be kept at a specified value or higher, the oil level between the low-stage compressor 10a and the high-stage compressor 10b can be kept in a good balance.

  The heat pump system 1 described above uses the four-way switching valve 14 to switch between the two-stage compression operation and the one-stage compression operation, but the present invention is not limited to this. As shown in FIG. 3, the heat pump system 2 switches between the two-stage compression operation and the one-stage compression operation by arranging two electromagnetic valves 14 a and 14 b in the pipes L <b> 1 and L <b> 5 and selectively controlling opening and closing. be able to. In the case of the example shown in FIG. 3, when the electromagnetic valve 14a is opened and the electromagnetic valve 14b is closed, a two-stage compression operation is performed, and when the electromagnetic valve 14a is closed and the electromagnetic valve 14b is opened, a two-stage compression operation is performed. The same elements as those in FIG. 1 are denoted by the same reference numerals as those in FIG. The same applies to FIG.

FIG. 1 shows an example in which the oil separator 26 is provided corresponding to both the low-stage compressor 10a and the high-stage compressor 10b. However, as in the heat pump system 4 shown in FIG. An oil separator 28 for the low-stage compressor 10a can be provided on the discharge side of the side compressor 10a and before the four-way switching valve 14. The oil separator 28 is connected to the oil leveling pipe 21 by an oil return pipe 29.
The oil separator 26 separates the refrigerating machine oil from the refrigerant discharged from the low-stage compressor 10 a during both the two-stage compression operation and the one-stage compression operation, and passes through the oil return pipe 29 and the oil equalizing pipe 21. Return to the low-stage compressor 10a. Therefore, the heat pump system 4 shown in FIG. 4 can efficiently return the refrigeration oil to the low-stage compressor 10a.

[Second Embodiment]
Hereinafter, a heat pump type hot water supply / air conditioner 100 to which the heat pump system 1 described as the first embodiment is applied will be described as a second embodiment of the present invention.
As shown in FIG. 5, the hot water supply / air conditioner 100 includes a heat pump system 200 and a water system 300.
[Heat pump system 200]
The heat pump system 200 uses a circuit in which only one oil separator 26 shown in the heat pump system 1 (FIG. 1) described in the first embodiment is provided, and between the outdoor air (outside air) and the refrigerant. Perform heat exchange at. When there is an element corresponding to the heat pump system 1, the heat pump system 200 attaches the same reference numerals as those in the first embodiment, and a description thereof is omitted. However, the 1st heat exchanger 11 shall be read as the water-to-refrigerant heat exchanger 11. The water-to-refrigerant heat exchanger 11 heats water by exchanging heat between water on the water system 300 side and the refrigerant. Moreover, the 2nd heat exchanger 13 shall be read as the heat source side air heat exchanger 13. Furthermore, the heat pump system 200 includes the following elements that the heat pump system 1 does not include.

  The heat pump system 200 includes a four-way switching valve 15 between a discharge side pipe L2 of the high stage compressor 10b and a suction side pipe L4 of the low stage compressor 10a. The recirculation direction is reversible, the cooling cycle (defrost cycle) in which the refrigerant is circulated clockwise through the heat source side air heat exchanger 13 to the water-to-refrigerant heat exchanger 11, and the heat source through the water-to-refrigerant heat exchanger 11. Any one of the heating cycle in which the refrigerant is circulated counterclockwise to the side air heat exchanger 13 can be selected.

In addition to the heat source side air heat exchanger 13, the water-to-refrigerant heat exchanger 11, and the four-way switching valve 15, the heat pump system 200 is a first decompression unit that controls the outlet-side refrigerant temperature of the water-to-refrigerant heat exchanger 11. An expansion valve 12a, an intermediate pressure receiver 16a that separates the refrigerant into gas and liquid, a supercooling coil 17, a second expansion valve 12b that depressurizes the intermediate pressure refrigerant, and an accumulator 18 are provided on the refrigerant circuit. The accumulator 18 separates the liquid refrigerant that has not completely evaporated in the heat source side air heat exchanger 13.
The heat pump system 200 also includes an electromagnetic valve 16b, a check valve 16c, and an injection for injecting the intermediate-pressure refrigerant gas separated by the intermediate-pressure receiver 16a into the intermediate-pressure refrigerant gas sucked into the high-stage compressor 10b. An injection circuit 16 including a tube 16d is provided.
The electromagnetic valve 16b closes the injection circuit 16 so that the liquid refrigerant is not supplied to the high-stage compressor 10b at the start-up when the inside of the intermediate pressure receiver 16a is filled with the liquid refrigerant, for example. It also serves as a valve.

The heat pump system 200 includes a sub pipe 121 in parallel with the oil equalizing pipe 21, and the sub pipe 121 includes an electromagnetic valve 122. Similarly, the heat pump system 200 includes a sub pipe 127 in parallel with the return pipe 27, and the sub pipe 127 includes an electromagnetic valve 128. Note that each of the sub pipes 121 and 127 includes a throttle.
The sub pipes 121 and 127 open the solenoid valves 122 and 128 when more refrigeration oil is desired to flow because the amount of the refrigeration oil flowing through the oil leveling pipe 21 and the return pipe 27 is limited.

[Water system 300]
In the water system 300, water circulated through the pump 307 absorbs heat from the refrigerant in the water-to-refrigerant heat exchanger 11 provided in the heat pump system 200, and the hot water is converted into a load-side radiator (use side). A hot water circulation channel 301 used as a heat source for heating or the like is provided by circulating between the heat exchanger and the heat exchanger 303. Connected to the hot water circulation channel 301 is a heat storage tank 305 that can introduce hot water from the hot water circulation channel 301 via a three-way switching valve 306 that can adjust the flow rate ratio and store the hot water as heat storage hot water. Yes.

  The heat storage tank 305 takes in the hot water stored in water from the upper part of the hot water heated by the water-to-refrigerant heat exchanger 11 via a three-way switching valve 306 provided in the hot water circulation passage 301 that circulates to the radiator 303. Then, it is discharged to the hot water circulation channel 301 side at a necessary timing.

  The heat storage tank 305 has a sanitary water supply circuit (not shown) for supplying hot water for hot water supply that is heated using the heat of the stored hot water, and an electric heater (not shown) that is energized as necessary. (Not shown) is provided.

The water system 300 configured as described above performs heating operation for supplying warm water to the radiator 303 or heat storage operation for supplying warm water to the heat storage tank 305 by selectively opening and closing the three-way switching valve 306. Either one is selected and implemented, or the hot water is dividedly supplied to both the radiator 303 and the heat storage tank 305 so that both the heating operation and the heat storage operation using the hot water can be performed simultaneously.
The water system 300 is heated by heat exchange of water as a heating target supplied from the heat storage tank 305 by the water circulation pump 307 with the refrigerant of the heat pump system 200 in the water-to-refrigerant heat exchanger 11.

  On the other hand, in the heat pump system 200, when the heating cycle is selected, the low-temperature and low-pressure gas refrigerant is compressed by the compression mechanism 10 (the low-stage compressor 10a and the high-stage compressor 10b), and the heat pump is used as the high-temperature and high-pressure gas refrigerant. It is discharged into the system 200. This gas refrigerant is guided to the water-to-refrigerant heat exchanger 11 by the four-way switching valve 14 and circulated in the clockwise direction, as indicated by solid arrows in FIG. In this case, the water-to-refrigerant heat exchanger 11 is a heat exchanger that exchanges heat between the water in the water system 300 circulated by the water circulation pump 307 and the high-temperature high-pressure gas refrigerant, and the heat of condensation radiated by the condensation of the refrigerant. It functions as a condenser that heats water. As a result, the high-temperature and high-pressure gas refrigerant flowing through the heat pump system 200 condenses to become a high-temperature and high-pressure liquid refrigerant, and the water flowing through the water system 300 absorbs heat from the refrigerant and becomes hot water.

  The refrigerant condensed in the water-to-refrigerant heat exchanger 11 flows into the intermediate pressure receiver 16a through the fully opened first expansion valve 12a. In the intermediate pressure receiver 16a, gas-liquid separation of the refrigerant is performed, and the separated gas refrigerant of the intermediate pressure passes through the electromagnetic valve 16b and the check valve 16c, and the low-stage compressor 10a and the high-stage compressor. The intermediate pressure between 10b is injected.

On the other hand, the liquid refrigerant separated by the intermediate pressure receiver 16a is depressurized by the second expansion valve 12b via the supercooling coil 17 and becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and the heat source side air heat exchanger. 13 leads to. The gas-liquid two-phase refrigerant introduced into the heat source side air heat exchanger 13 functioning as an evaporator absorbs heat from the outside air and vaporizes by exchanging heat with the outside air.
In this way, the low-temperature and low-pressure gas refrigerant that has been vaporized by absorbing heat from the outside air by passing through the heat source side air heat exchanger 13 is again sucked into the low-stage compressor 10a through the four-way switching valve 15. The low-temperature and low-pressure gas refrigerant sucked into the low-stage compressor 10a in this way is compressed in turn by the low-stage compressor 10a and the high-stage compressor 10b to become a high-temperature and high-pressure gas refrigerant, and circulates through the same path thereafter. Repeat the change of gas-liquid state. At this time, moisture in the air may freeze on the outer peripheral surface of the heat source side air heat exchanger 13 that is at a low temperature, resulting in a frosting phenomenon.

  The frost formation inhibits the heat exchange between the refrigerant and the outside air in the heat source side air heat exchanger 13 and lowers the heat exchange efficiency. Therefore, by detecting the presence or absence of frost accumulation, defrosting is performed every appropriate operation time. It is necessary to carry out operation to remove frost. This defrost operation is performed in the above-described heat pump system 200 by switching the four-way switching valve 15 to reverse the refrigerant circulation direction and switching to the cooling cycle (defrost cycle) in which the refrigerant is circulated in the direction of the broken line arrow in FIG. The high-temperature and high-pressure gas refrigerant discharged from the stage side compressor 10b is introduced into the heat source side air heat exchanger 13, and the frost adhering to the heat source side air heat exchanger 13 is melted by the heat radiation (condensation heat). Is done by.

  During the defrost operation by the reverse cycle method, the water-to-refrigerant heat exchanger 11 functions as an evaporator, absorbs heat from the water flowing through the hot water circulation passage 301, vaporizes the refrigerant, and uses the heat to heat air on the heat source side. The frost that has formed on the exchanger 13 is melted. At this time, if the water temperature is too low, the water freezes in the water-to-refrigerant heat exchanger 11 and a risk of damage to the heat exchanger occurs. For this reason, at the time of defrosting, it is necessary to prevent the evaporation temperature of the refrigerant from being excessively lowered together with the water temperature circulated to the water-to-refrigerant heat exchanger 11.

In the hot water supply / air conditioner 100 described above, as in the first embodiment, when the following conditions (1) to (3) are provided during the two-stage compression operation, the one-stage compression operation is performed. Switch. This switching is as described with reference to FIGS. 2 (a) and 2 (b).
(1) Water temperature entering the heat exchanger (hydrothermal exchange) of water and refrigerant: T _W , Specified value: T _R
T _W ≦ T _R
(2) suction pressure _{P LI} of the low-stage compressor 10a, the high-stage discharge pressure _{P HO} specified value of the compressor 10b: [Delta] P _{R1
(P HO -P LI) ≦ ΔP} R1
(3) Suction pressure P _LI and discharge pressure P _LO specified values of low stage compressor 10a: ΔP _R2
(P _LO −P _LI ) ≦ ΔP _R2

[Two-stage compression operation → One-stage compression operation]
When switched to the single-stage compression operation, the high-pressure refrigerant discharged after being compressed to high pressure by the low-stage compressor 10a flows into the water-to-refrigerant heat exchanger 11 through the pipe L11, the four-way switching valve 14, and the pipe L5. And radiate heat to the heat exchange target. Here, the low-stage compressor 10a improves the operation capability compared with the two-stage compression operation, and compresses the refrigerant to a high pressure. Further, the operation of the high stage compressor 10b is stopped.

As described above, the present invention has been described based on the embodiment. However, the configuration described in the above embodiment may be selected or changed to another configuration as long as it does not depart from the gist of the present invention.
For example, the portions excluding the minimum elements in the present invention described in the first embodiment are arbitrary. Therefore, the present invention can be applied to a hot water supply / air conditioner further provided with an indoor heat exchanger, and conversely, can also be applied to a heat pump type water heater provided with only a hot water storage function.

1, 2, 3, 4 Heat pump system 10a Low stage compressor 10b High stage compressor 11 First heat exchanger, water-to-refrigerant heat exchanger 11f Blower fan 12 Expansion valve 12a First expansion valve 12b Second expansion valve 13 Second heat exchanger, heat source side air heat exchanger 13f Blower fans 14, 15 Four-way switching valves 14a, 14b Solenoid valve 16 Injection circuit 16a Intermediate pressure receiver 16b Solenoid valve 16c Check valve 16d Injection pipe 17 Supercooling coil 18 Accumulator 20 Oil leveling mechanism 21 Oil leveling pipe 23 Bypass pipe 25 Solenoid valve 26, 28 Oil separator 27, 29 Oil return pipe 100 Hot water supply / air conditioner 121, 127 Sub pipe 122, 128 Solenoid valve 200 Heat pump system 300 Water system 301 Hot water circulating flow Path 303 Radiator 305 Heat storage tank 306 Three-way switching valve 30 Water circulation pump L1, L11, L12, L2, L3, L4, L5 pipe

Claims (5)

A compression mechanism that includes a low-stage compressor and a high-stage compressor, and compresses and discharges the refrigerant;
An oil separator provided on the discharge side of the high stage compressor;
A first heat exchanger that exchanges heat between the refrigerant compressed by the compression mechanism and a heat exchange target;
An expansion valve for decompressing and expanding the refrigerant flowing out of the first heat exchanger;
A second heat exchanger for exchanging heat between the refrigerant expanded under reduced pressure by the expansion valve and the heat exchange target;
An oil equalizing path that connects the low-stage compressor and the high-stage compressor, and distributes refrigeration oil between the low-stage compressor and the high-stage compressor;
A main return pipe connecting the oil separator and the suction side of the high stage compressor;
An oil return path connecting the main return pipe and the oil leveling path;
An oil return on-off valve provided in the oil return path;
A two-stage compression path for flowing the refrigerant through the low-stage compressor and the high-stage compressor in this order; a single-stage compression path for flowing only one of the low-stage compressor and the high-stage compressor; A refrigerant path switching mechanism for selectively switching,
A heat pump system comprising: While the two-stage compression path is selected, if any one of the following conditions (1) to (3) is satisfied, the refrigerant path is switched to the one-stage compression path.
The heat pump system according to claim 1.
Condition (1): T _W ≦ T _R
T _W ; When the heat exchange target of the first heat exchanger is water, the water temperature entering the heat exchanger (hydrothermal exchange) of water and refrigerant, T _R ; Specified value condition (2): (P _HO − _PLI ) ≦ ΔP _R1
P _LI ; suction pressure of the low stage compressor P _HO ; discharge pressure of the high stage compressor Specified value: ΔP _R1
Condition _{(3) (P LO -P LI} ) ≦ ΔP R2
P _LI ; Low-stage compressor suction pressure P _LO ; Low-stage compressor discharge pressure Specified value: ΔP _R2 When the refrigerant path switching mechanism selects the one-stage compression path,
By opening the oil return on-off valve, the refrigerating machine oil from the oil separator is returned to the oil leveling path via the oil return path without passing through the high stage compressor.
The heat pump system according to claim 1 or 2. Opening and closing of the return on-off valve and opening and closing of the oil equalizing on-off valve
Controlled based on the predicted amount of refrigeration oil in the low stage compressor and the predicted amount of refrigeration oil in the high stage compressor,
The heat pump system according to any one of claims 1 to 3. The first heat exchanger of the heat pump system according to any one of claims 1 to 4 is a water-to-refrigerant heat exchanger that heats water by causing heat exchange between the refrigerant and water.
A heat pump type water heater characterized by that.

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