WO2015045247A1

WO2015045247A1 - Heat pump system, and heat pump water heater

Info

Publication number: WO2015045247A1
Application number: PCT/JP2014/004029
Authority: WO
Inventors: 峰正大村; 岡田　拓也; 太一舘石; 創佐藤
Original assignee: 三菱重工業株式会社
Priority date: 2013-09-30
Filing date: 2014-07-31
Publication date: 2015-04-02
Also published as: ES2708779T3; CN107270570A; EP3040643A4; EP3040643B1; CN105593610B; CN105593610A; EP3040643A1

Abstract

　Provided is a two-stage compression heat pump with which the amount of refrigerant oil in the two compressors is easily kept uniform. The system is provided with: a compression mechanism (10) provided with a lower stage-side compressor (10a) and a higher stage-side compressor (10b), for compressing and discharging a refrigerant; a water-refrigerant heat exchanger (11) for heat exchange between a target to undergo heat exchange and the refrigerant compressed by the compression mechanism (10); an expansion valve (12) for decompression and expansion of the refrigerant outflowing from the water-refrigerant heat exchanger (11); a heat source-side heat exchanger (13) for heat exchange between a target to undergo heat exchange and the refrigerant decompressed and expanded by the expansion valve (12); an oil equalizing mechanism (20) connecting the lower stage-side compressor (10a) and the higher stage-side compressor (10b), through which a refrigerant oil flows; and a four-way switching valve (14) for selectively switching between a two-stage compression path in which the refrigerant flows in order to the lower stage-side compressor (10a) and the higher stage-side compressor (10b), and a one-stage compression path in which it flows either to the lower stage-side compressor (10a) or the higher stage-side compressor (10b) only.

Description

Heat pump system and heat pump type water heater

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

The heat pump system of the hot water supply system is advanced for the purpose of energy saving energy.
As this refrigerant system, a two-stage compression refrigeration cycle including a refrigerant circuit in which a low-stage compressor and a high-stage compressor are connected in series and circulating the refrigerant in the refrigerant circuit is known (for example, patent document 1 to 3).

JP-A-5-93552 Japanese Patent Application Laid-Open No. 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 low-stage and high-stage compressors at independent rotational speeds. For this purpose, the biggest issue is the control of the oil level of refrigeration oil contained in each of the two compressors. Unlike a compressor having two low-stage and high-stage compression mechanisms mounted in one housing, when two independent compressors are connected in series, two compressors may be connected between the two compressors. Maintaining the amount of refrigeration oil at a proper and even level is necessary to operate the two compressors properly.
The present invention has been made based on this technical problem, and it is easy to keep the amount of refrigeration oil of two compressors equal without stopping operation or complicated operation. It is an object of the present invention to provide a two-stage compression heat pump system. Another object of the present invention is to provide a highly efficient heat pump water heater provided with this two-stage compression heat pump system.

The present invention made under such an object is divided into a first invention and a second invention.
A heat pump system according to a first aspect of the present invention comprises a low-stage compressor and a high-stage compressor, and a compression mechanism that compresses and discharges a refrigerant, and 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 object, an expansion valve that decompresses and expands the refrigerant flowing out of the first heat exchanger, and the refrigerant decompressed and expanded by the expansion valve An oil equalizing system that connects a low-stage compressor and a high-stage compressor by connecting a second heat exchanger that exchanges heat with a heat exchange target, the low-stage compressor and the high-stage compressor, and distributes refrigerator oil between the low-stage compressor and the high-stage compressor A path, 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 equalizing path, and an oil return on-off valve provided in the oil return path , A two-stage compression path for flowing the refrigerant, a low-stage compressor and a high-stage compressor in this order, and A stage compression channels passing only one of the compressor and the high-pressure stage compressor, and the refrigerant passage switching mechanism for selectively switching the, characterized in that it comprises a.
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 for water and refrigerant (water to refrigerant heat exchanger) Therefore, the pressure difference between the suction side and the discharge side of the compressor may greatly change depending on the water temperature. If the two-stage compression operation is performed in a state where the inlet temperature of the water-to-refrigerant heat exchanger is low, the differential pressure between the low-stage compressor and the high-stage compressor decreases. The differential pressure between the compressors determines the amount of refrigeration oil returned. Therefore, according to the present invention, when the differential pressure between the low-stage compressor and the high-stage compressor becomes low while performing the two-stage compression operation, the mode is switched to the one-stage compression operation.

In the heat pump system according to the first aspect of the invention, the refrigerant path is switched to the one-stage compression path when any of the following conditions (1) to (3) is satisfied while the two-stage compression path is selected. .
Condition (1): T _W ≦ T _R
T _W ; when the heat exchange target of the first heat exchanger is water, the water temperature that enters the heat exchanger (water heat exchange) between water and refrigerant, T _R ; prescribed value condition (2): (P _HO- P _LI ) ≦ ΔP _R1
P _LI; low suction pressure stage compressor P _HO; high-stage compressor discharge pressure specified value: [Delta] P _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: ΔPR ₂

In the heat pump system according to the first aspect of the invention, when the refrigerant path switching mechanism selects the one-stage compression path, the oil return on / off valve is opened to pass the refrigerator oil from the oil separator through the high-stage compressor. Instead, it can be returned to the oil equalization path via the oil return path.
By providing the oil return path and the oil equalization path of the above configuration, it is possible to easily recover the oil amount when the amount of refrigerating machine oil in each of the low-stage compressor and the high-stage compressor runs short.

In the heat pump system according to the first aspect of the 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 in the amount of refrigerating machine oil predicted in the low stage compressor and in the high stage compressor. It is preferable to control based on the amount of refrigeration oil.
The refrigeration oil can be controlled at an appropriate timing based on the pressure sensor included in the heat pump system and the oil amount of each of the two compressors obtained from the temperature sensor detection result.

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

Next, the heat pump system according to the second aspect of the invention includes a low-stage compressor and a high-stage compressor, and the compression mechanism that compresses and discharges the refrigerant, and the refrigerant compressed by the compression mechanism exchanges heat with the refrigerant. First heat exchanger, an expansion valve for decompressing and expanding the refrigerant flowing out of the first heat exchanger, a second heat exchanger for exchanging heat with the refrigerant decompressed and expanded by the expansion valve, and a second heat exchanger; Oil equalizing piping that connects a stage side compressor and a high stage side compressor and distributes refrigerating machine oil between a low stage side compressor and a high stage side compressor, an oil equalizing valve that opens and closes the oil equalizing pipe, oil equalizing And a controller for controlling the opening and closing operation of the valve.
The controller according to the present invention is characterized in that, when it is determined that the refrigerant is flowing through the oil equalizing piping, the controller instructs to open the oil equalizing valve which is open.

In the heat pump system according to the second aspect of the present invention, the control device is configured to detect the detected temperature T ₀ in the oil equalizing pipe, the detected temperature T ₁ in the refrigerant pipe for flowing the refrigerant from the low stage compressor to the high stage compressor, and one or both of the detected temperature T ₂ at the stage compressor, based on a comparison of the oil equalization pipe can be determined whether the refrigerant is flowing.

In the heat pump system according to the second aspect of the present invention, the controller preferably instructs, during non-stationary operation, to keep the oil equalizing valve closed even if the open conditions are satisfied.

In the heat pump system according to the second aspect of the present invention, the controller determines whether or not the refrigerant is flowing through the oil equalizing pipe when the rotational speed of the high-stage compressor is smaller than a predetermined value. Regardless, it is preferable to instruct the oil equalizing valve to alternately open and close alternately at fixed time intervals.

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

According to the first invention of the present application, the low pressure side compression is performed only by the simple operation of opening and closing the first solenoid valve and the second solenoid valve without stopping the operation of the low pressure side compressor and the high pressure side compressor. It is possible to make uniform the refrigerating machine oil in the machine and the high stage side compressor.
Further, according to the second aspect of the present invention, the refrigeration oil can be made uniform among the compression mechanisms without stopping the operation of the compression mechanism and by the simple operation of opening / closing the oil equalizing valve. Moreover, according to the present invention, when it is judged that the refrigerant flows in the oil equalizing piping, the oil equalizing valve which is open is closed, so that the space cost of the compression mechanism caused by the refrigerant flowing in the oil equalizing piping is avoided. it can.

It is a figure showing the circuit composition of the heat pump system concerning a 1st embodiment. It is a figure which shows operation | movement of the heat pump system of 1st Embodiment, (a) shows a two-stage compression driving | operation, (b) shows a one-step compression driving | operation. It is a figure which shows the circuit structure which switches the two-step compression driving | operation of the heat pump system of FIG. 1, and a one-step compression driving | operation 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. It is a figure which shows the modification of oil equalizing piping. It is a figure which shows the circuit structure of the refrigerating cycle which concerns on 3rd Embodiment. It is a figure which shows the operation | movement of the refrigerating cycle of FIG. 8, (a) is closing oil equalization piping, (b) is opening oil equalization piping. It is a flowchart which shows the procedure of opening and closing of the valve provided in oil equalization piping of the refrigerating cycle of FIG. It is a flowchart which shows the modification of the opening and closing procedure of the valve 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 4th Embodiment. It is a figure which shows the circuit structure of the heat pump-type hot water supply and air conditioner which concerns on 4th Embodiment, and has shown the driving | operation mode different from FIG.

Hereinafter, embodiments of the present invention will be described 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 the low-stage compressor 10a and the high-stage compressor 10b, which compress and discharge the refrigerant, and the high-stage compressor 10b. A first heat exchanger 11 for heat exchange between the refrigerant and a fluid to be subjected to heat exchange, 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 A second heat exchanger 13 is provided, which exchanges heat between the refrigerant decompressed and expanded at 12 and the fluid to be heat-exchanged, and is connected in series in this order along the circulation direction of the refrigerant. In the present embodiment, for example, the first heat exchanger 11 can function as a condenser that releases heat by exchanging heat with water, and the second heat exchanger 13 exchanges 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 of the low-stage compressor 10a and the high-stage compressor 10b as follows. In other words, the four-way switching valve 14 is a two-stage compression operation (two-stage compression path) in which the refrigerant passes both the low-stage compressor 10a and the high-stage compressor 10b, and the refrigerant is only the low-stage compressor 10a. The single-stage compression operation (one-stage compression path) that passes through but bypasses the high-stage compressor 10b is switched.
Further, the heat pump system 1 includes an oil equalizing mechanism 20 for keeping the oil amount of the refrigerator oil held by the low-stage compressor 10a equal to that of the refrigerator oil held by the high-stage compressor 10b.

The heat pump system 1 includes a pipe L1 connecting the low-stage compressor 10a and the high-stage compressor 10b, a pipe L2 linking the high-stage compressor 10b and the first heat exchanger 11, and a first heat exchanger 11 By providing the pipe L3 connecting the second heat exchanger 13 and the pipe L4 connecting the second heat exchanger 13 and the low-stage compressor 10a, a refrigerant circuit in which the refrigerant circulates is configured. Among them, for the low-stage compressor 10a, the pipe L4 connects the suction-side pipe, and the pipe L1 connecting the low-stage compressor 10a and the high-stage compressor 10b connects intermediate pressure pipes for the high-stage compressor 10b. L2 constitutes the discharge side piping.
The heat pump system 1 further includes a pipe L5 connecting 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 passes the refrigerant discharged from the low-stage compressor 10a through the pipe L1 as it is and is sucked into the high-stage compressor 10b or through the pipe L5 and through the pipe L2. It is switched whether to supply the first heat exchanger 11. 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 distinction.

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

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

[First heat exchanger 11]
The first heat exchanger 11 heats the fluid by heat exchange between a fluid to be heat-exchanged, such as water, air, and a high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant discharged from the high-stage compressor 10b is cooled and condensed here. As the first heat exchanger 11, a known heat exchanger can be used. The same applies to the second heat exchanger 13 described next.
When the target of heat exchange is air, the first heat exchanger 11 is additionally 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, Heat exchange.

[Expansion valve 12, second heat exchanger 13]
The second heat exchanger 13 exchanges heat between the refrigerant decompressed and expanded through the expansion valve 12 and the outside air (blowing air), and in the process of this heat exchange, the refrigerant evaporates, and the outside air is exchanged. Absorb heat from The second heat exchanger 13 is also provided with a blower fan 13f, and heat exchange between the air blown by the blower fan 13f and the refrigerant causes the low-pressure refrigerant to evaporate to generate a heat absorbing action.
The expansion valve 12 can use, for example, an expansion valve provided with a needle-like valve body and a pulse motor for driving the valve body.

[Soiling mechanism 20]
The oil equalizing mechanism 20 includes an oil equalizing pipe 21 connecting the low-stage compressor 10a and the high-stage compressor 10b, a bypass pipe 23 connecting the oil equalizing pipe 21 and the oil return pipe 27, and electromagnetics provided in the bypass pipe 23. And a valve 25.
The oil equalizing mechanism 20 distributes refrigerating machine oil between the low-stage compressor 10 a and the high-stage compressor 10 b through the oil equalizing piping 21. Further, the oil equalizing mechanism 20 returns the refrigeration oil from the discharge side of the high stage compressor 10 b to the oil equalizing pipe 21 via the bypass pipe 23. The function of the bypass pipe 23 is exerted when the single-stage compression operation is performed, thereby providing the oil pressure pipe 21 with a necessary differential pressure.
The oil equalizing piping 21 is based on the oil level indicating the amount of refrigeration oil required by each of the low stage compressor 10a and the high stage compressor 10b. It is connected with 10a and high stage side compressor 10b.

Although FIG. 1 shows an example in which a single oil equalizing pipe 21 is provided, as shown in FIG. 7, a plurality of oil equalizing pipes 21 (21A, 21B, 21C) can be provided in parallel. The

oil equalizing pipes

21B and 21C are provided with on-off

valves

22B and 22C, respectively.
By thus providing the plurality of

oil equalizing pipes

21A, 21B, 21C and opening / closing the on-off

valves

22B, 22C, the refrigeration oil may flow excessively in a single oil equalizing pipe 21, The amount of flow of refrigeration oil can be adjusted. The oil equalizing pipe 21A can also be provided with an on-off valve.
The

oil equalizing pipes

21A, 21B, 21C can equalize or differ the maximum amount of refrigerant oil flowing. In addition, the opening and closing of the on-off

valves

22B and 22C can be controlled by, for example, detecting the temperature of the refrigerator oil flowing into 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, a refrigerant circulates and a two-stage compression operation is performed. However, one-stage compression operation is performed when specific conditions are provided.

First, the two-stage compression operation will be described.
In the case of the two-stage compression operation, as shown in FIG. 2A, the four-way switching valve 14 is switched so that the pipes L1 (L11 and L12) communicate with each other. The pressurized refrigerant is drawn into the high-stage compressor 10b through the pipe L11, the four-way switching valve 14, and the pipe L12. In FIG. 2A, the arrow indicates the direction in which the refrigerant flows. The same applies to FIG. 2 (b) described later.
The high-pressure refrigerant that has been compressed to a high temperature and high pressure by the high-stage compressor 10b and then discharged flows into the first heat exchanger 11 through the pipe L2, and radiates heat to the heat exchange object. The high-pressure refrigerant that has dissipated heat in the first heat exchanger 11 expands in the process of passing through the expansion valve 12 through the pipe L3, and becomes a low-pressure refrigerant. The 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 drawn into the low pressure side 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 pressure side compressor 10a to the pipe L1 is drawn into the high pressure side compressor 10b. The refrigerant drawn 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 refrigerating machine oil through the oil equalizing pipe 21 in the process of repeating the cycles of compression, condensation, expansion, and evaporation of the refrigerant described above, so that the low-stage compressor 10a and the high-stage compressor Secure each oil level of 10b within the required range.
Here, as a method for returning refrigeration oil contained in the refrigerant discharged from the compressor to the compressor, an apparatus called an oil separator for separating the refrigerant and the oil is disposed on the discharge side of the compressor, and the separated refrigeration is performed In general, the system oil is returned to the suction side of the compressor via an oil return circuit provided with a fixed throttle such as a capillary tube.
However, assuming, for example, a heat pump type water heater, the high pressure of the device depends on the temperature of water (for example, in the range of 35 to 75 ° C.) entering the heat exchanger for water and refrigerant (water to refrigerant heat exchanger). Therefore, the pressure difference between the suction side and the discharge side of the compressor may greatly change depending on the water temperature. When the two-stage compression operation is performed with the inlet water temperature of the water-to-refrigerant heat exchanger low, the differential pressure between the low-stage compressor 10a and the high-stage compressor 10b decreases. The differential pressure between the compressors determines the amount of refrigeration oil returned. Therefore, in the present embodiment, when the differential pressure between the low-stage compressor 10a and the high-stage compressor 10b decreases while performing the two-stage compression operation, switching to the single-stage compression operation and the solenoid valve are performed. Open 25 Thus, the heat pump system 1 always returns the refrigerating machine oil from the oil separator 26 via the bypass pipe 23 to the oil equalizing pipe 21 without passing through the high-stage compressor 10b, so that the differential pressure in the oil equalizing mechanism 20 is always constant. It can be kept above the specified value. Moreover, since the heat pump system 1 can return the oil to the low-stage compressor 10a without passing through the fixed throttle 27a and the high-stage compressor 10b in the oil return pipe 27, the fixed throttle 27a and the high-stage compressor It is possible to prevent the pressure loss from occurring in the side compressor 10b to reduce the oil return flow rate.

The heat pump system 1 switches to the one-stage compression operation when the following conditions (1) to (3) are provided during the two-stage compression operation. The following conditions are all indicators 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, but are determined corresponding to the respective components of the heat pump system 1 to be applied and the operating conditions. . The water temperature T _W , the suction pressure P _LI , the discharge pressure P _LO and the discharge pressure P _HO are not shown, but a temperature sensor attached to the first heat exchanger 11, the low stage compressor 10a, the high stage The pressure is detected by a pressure sensor attached to the side compressor 10b. The detected information is sent to the control device 30 shown in FIG. The control device 30 determines the conditions (1) to (3) using the acquired information on the water temperature T _W , the suction pressure P _LI , the discharge pressure P _LO and the discharge pressure P _HO . The control device 30 continues to determine the conditions (1) to (3) even during the one-stage compression operation.

(1) Water temperature that enters the heat exchanger (water heat exchanger) of water and refrigerant: T _W , specified value: T _R
T _W ≦ T _R
(2) The suction pressure P _{LI of the} low-stage compressor 10 a, the discharge pressure P _HO of the high-stage compressor 10 b, and the prescribed value: ΔP _R1
(P _HO -P _LI ) ≦ ΔP _R1
(3) Suction pressure P _{LI of the} low-stage compressor 10 a, discharge pressure P _LO specified value: ΔP _R2
(P _LO -P _LI ) ≦ ΔP _R2

[Two-stage compression operation → One-stage compression operation]
If the control device 30 determines that one of the conditions (1) to (3) is satisfied while performing the two-stage compression operation, the control device 30 performs the four-way switching valve 14 in the one-stage compression operation shown in FIG. Instructs to switch to the position. Also, the control device 30 instructs the solenoid valve 25 to open. Then, the heat pump system 1 operates as follows.
The high-pressure refrigerant, which has been compressed to a high pressure by the low-stage compressor 10a and then discharged, 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 object Do. Here, the low-stage compressor 10a improves the operation capacity more than in the two-stage compression operation, and compresses the refrigerant to a high pressure. In addition, the high-stage compressor 10b is stopped in operation.
The high-pressure refrigerant that has dissipated heat in the first heat exchanger 11 expands in the process of passing through the expansion valve 12 through the pipe L3, and becomes a low-pressure refrigerant. The 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 drawn into the low pressure side compressor 10a through the pipe L4.
In the one-stage compression operation, the solenoid valve 25 is opened in the process of repeating the cycles of compression, condensation, expansion, and evaporation of the refrigerant described above, so the refrigerator oil passes through the bypass piping 23 and the high-stage compressor 10b Is returned to the oil equalizing pipe 21 without passing through. Therefore, the differential pressure in the oil equalizing mechanism 20 can always be maintained at or above the specified value, so the oil level between the low stage compressor 10a and the high stage compressor 10b can be maintained in a well-balanced manner.

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 the two

solenoid valves

14a and 14b in the pipes L1 and L5, respectively, and selectively controlling the opening and closing. be able to. In the case of the example shown in FIG. 3, the two-stage compression operation is performed when the solenoid valve 14a is opened and the solenoid valve 14b is closed, and the two-stage compression operation is performed when the solenoid valve 14a is closed and the solenoid valve 14b is opened. The same elements as in FIG. 1 are assigned the same reference numerals as in FIG. 1 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, but as in the heat pump system 3 shown in FIG. An oil separator 28 for the low pressure side compressor 10 a can be provided on the discharge side of the side compressor 10 a and in front of the four-way switching valve 14. The oil separator 28 is connected to the oil equalizing pipe 21 by an oil return pipe 29.
The oil separator 26 separates the refrigerator oil from the refrigerant discharged from the low pressure side compressor 10 a during any of the two-stage compression operation and the one-stage compression operation, and passes the oil return pipe 29 and the oil equalizing pipe 21. And return to the low pressure side compressor 10a. Therefore, the heat pump system 3 shown in FIG. 4 can efficiently return the refrigerator oil to the lower stage compressor 10a.

Second Embodiment
Hereinafter, a heat pump type hot water supply and 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 is composed of a heat pump system 200 and a water system 300.
[Heat pump system 200]
The heat pump system 200 utilizes a circuit provided with only one oil separator 26 shown in the heat pump system 1 (FIG. 1) described in the first embodiment, and it is between outdoor air (outside air) and a refrigerant. Heat exchange at. When there is an element corresponding to the heat pump system 1, the heat pump system 200 attaches | subjects the code | symbol same as 1st Embodiment, and abbreviate | omits the description. However, the first heat exchanger 11 should be read as a water-to-refrigerant heat exchanger 11. The water-to-refrigerant heat exchanger 11 heats the water by heat exchange between the water on the water system 300 side and the refrigerant. Further, the second heat exchanger 13 should 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 have.

The heat pump system 200 includes a four-way switching valve 15 between the piping L2 on the discharge side of the high-stage compressor 10b and the piping L4 on the suction side of the low-stage compressor 10a. And a cooling cycle (defrost cycle) in which the refrigerant is circulated clockwise to the water-to-refrigerant heat exchanger 11 via the heat source side air heat exchanger 13 and the heat source via the water-to-refrigerant heat exchanger 11 One of the heating cycles for circulating the refrigerant counterclockwise to the side air heat exchanger 13 is selectable.

The heat pump system 200 includes, 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, a first pressure reducing means for controlling the temperature of the outlet-side refrigerant of the water-to-refrigerant heat exchanger 11. An expansion valve 12a, an intermediate pressure receiver 16a for gas-liquid separation of the refrigerant, a subcooling coil 17, a second expansion valve 12b for depressurizing the intermediate pressure refrigerant, and an accumulator 18 are provided on the refrigerant circuit. The accumulator 18 separates the liquid refrigerant that has not been evaporated by the heat source side air heat exchanger 13.
Further, the heat pump system 200 injects 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, the solenoid valve 16b, the check valve 16c and the injection. It comprises an injection circuit 16 comprising a tube 16d.
The solenoid valve 16b closes the injection circuit 16, for example, to prevent the liquid refrigerant from being supplied to the high-stage compressor 10b at the time of start-up when the inside of the intermediate pressure receiver 16a is full of liquid refrigerant. It also plays a role as a valve.

In addition, the heat pump system 200 includes a sub pipe 121 in parallel with the oil equalizing pipe 21, and the sub pipe 121 includes a solenoid 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 a solenoid valve 128. Each of the

sub pipes

121 and 127 is provided with a throttle.
The

sub pipes

121 and 127 open the

solenoid valves

122 and 128 when it is desired to flow more refrigerator oil because there is a limit to the amount of refrigerator oil flowing through the oil equalizing pipe 21 and the return pipe 27.

[Water system 300]
In the water system 300, water circulated through the pump 307 is absorbed from the refrigerant by the water-to-refrigerant heat exchanger 11 provided in the heat pump system 200 to be hot water, and the hot water is used as a radiator on the load side (use side A hot water circulation channel 301 is provided which is used as a heat source or the like for heating by circulating between the heat exchangers) 303. A hot water is introduced from the hot water circulation flow path 301 via the three-way switching valve 306 capable of adjusting the flow rate to the hot water circulation flow path 301, and a heat storage tank 305 capable of storing the hot water as heat storage hot water is connected There is.

The heat storage tank 305 takes the hot water heated in the water-to-refrigerant heat exchanger 11 from the upper part thereof via the three-way switching valve 306 provided in the hot water circulation passage 301 circulating to the radiator 303 The water is discharged to the hot water circulation channel 301 at the necessary timing.

In addition, in the heat storage tank 305, a sanitary water supply circuit (not shown) for supplying hot water for hot water heating using the heat of stored heat stored hot water (not shown), an electric heater (energized according to need) Not shown) is provided.

In the water system 300 configured as described above, the heating operation for supplying hot water to the radiator 303 or the thermal storage operation for supplying hot water to the heat storage tank 305 by controlling the opening and closing of the three-way switching valve 306 Either one is selected and implemented, or warm water is separately supplied to both the radiator 303 and the heat storage tank 305 so that both heating operation and heat storage operation by the hot water can be performed simultaneously.
Further, the water system 300 is heated by heat exchange of the water to be heated 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 low pressure gas refrigerant is compressed by the compression mechanism 10 (low stage compressor 10a, high stage compressor 10b), and the heat pump is operated as a high temperature high pressure gas refrigerant. It is discharged into the system 200. The gas refrigerant is led to the water-to-refrigerant heat exchanger 11 by the four-way switching valve 14 and circulated clockwise, as shown 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 of the water system 300 circulated by the water circulation pump 307 and the high-temperature high-pressure gas refrigerant, and the condensation heat released by condensation of the refrigerant is 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 is condensed 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 open first expansion valve 12a. In the intermediate pressure receiver 16a, gas-liquid separation of the refrigerant is performed, and the separated intermediate pressure gas refrigerant passes through the solenoid valve 16b and the check valve 16c, and the low-stage compressor 10a and the high-stage compressor It is injected at an intermediate pressure between 10b.

On the other hand, the liquid refrigerant separated by the intermediate pressure receiver 16a is decompressed by the second expansion valve 12b via the subcooling coil 17, and becomes a low temperature low pressure gas-liquid two-phase refrigerant, and the heat source side air heat exchanger It is led to 13. The gas-liquid two-phase refrigerant introduced to the heat source side air heat exchanger 13 functioning as an evaporator exchanges heat with the outside air, absorbs heat from the outside air, and is vaporized.
Thus, by passing through the heat source side air heat exchanger 13, the low-temperature low-pressure gas refrigerant which absorbs heat from the outside air and is vaporized is again drawn into the low-stage compressor 10a through the four-way switching valve 15. The low-temperature low-pressure gas refrigerant thus sucked to the low-stage compressor 10a is sequentially compressed by the low-stage compressor 10a and the high-stage compressor 10b to become a high-temperature high-pressure gas refrigerant, and the same route And change the state of gas and liquid repeatedly. At this time, moisture and the like in the air may freeze on the outer peripheral surface of the heat source side air heat exchanger 13 which has a low temperature, and a frosting phenomenon may occur.

Since frost inhibits the heat exchange between the refrigerant and the outside air in the heat source side air heat exchanger 13 and reduces the heat exchange efficiency, the defrosting is detected for each suitable operation time by detecting the presence or absence of the accumulation of frost. It is necessary to carry out the operation to remove the frost. In the defrosting operation, in the heat pump system 200 described above, the four-way switching valve 15 is switched to reverse the circulating direction of the refrigerant, and the refrigerant cycle is switched to circulate in the direction of the dashed 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 heat radiation (condensation heat) is used to melt the frost adhering to the heat source side air heat exchanger 13. Done by

At the time of defrost operation by this 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 to vaporize the refrigerant, and uses the heat to heat the heat source side air The frost formed on the exchanger 13 is melted. At this time, if the water temperature is excessively lowered, the water freezes in the water-to-refrigerant heat exchanger 11, and a risk of heat exchanger breakage occurs. For this reason, 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 at the time of defrosting.

Also in the hot water supply and air conditioner 100 described above, as in the first embodiment, if the following conditions (1) to (3) are satisfied 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 that enters the heat exchanger (water heat exchanger) of water and refrigerant: T _W , specified value: T _R
T _W ≦ T _R
(2) The suction pressure P _{LI of the} low-stage compressor 10 a, the discharge pressure P _HO of the high-stage compressor 10 b, and the prescribed value: ΔP _R1
(P _HO -P _LI ) ≦ ΔP _R1
(3) Suction pressure P _{LI of the} low-stage compressor 10 a, discharge pressure P _LO specified value: 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 a 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. Dissipate heat to the heat exchange target. Here, the low-stage compressor 10a improves the operation capacity more than in the two-stage compression operation, and compresses the refrigerant to a high pressure. In addition, the high-stage compressor 10b is stopped in operation.

Third Embodiment
The heat pump system 4 according to the third embodiment, as shown in FIG. 8, is compressed by the low stage compressor 10a and the high stage compressor 10b for compressing and discharging the refrigerant, and the high stage compressor 10b. The first heat exchanger 11 for heat exchange between the refrigerant and the fluid to be subjected to heat exchange, the expansion valve 12 for decompressing and expanding the refrigerant flowing out from the first heat exchanger 11, and the pressure reducing and expanding by the expansion valve 12 And a second heat exchanger 13 for exchanging heat between the refrigerant and the fluid to be heat-exchanged, and is connected in series in this order along the circulation direction of the refrigerant. In the present embodiment, for example, the first heat exchanger 11 functions as a condenser that releases heat by exchanging heat with water, and the second heat exchanger 13 absorbs heat by exchanging heat with outside air. Can function as
The heat pump system 4 includes an oil equalizing mechanism 20 for keeping the oil amount of the refrigerator oil held by the low-stage compressor 10a equal to that of the refrigerator oil held by the high-stage compressor 10b. Details of the oil equalizing mechanism 20 that is the feature of the present embodiment will be described later.

The heat pump system 4 includes a pipe L1 connecting the low-stage compressor 10a and the high-stage compressor 10b, a pipe L2 linking the high-stage compressor 10b and the first heat exchanger 11, and a first heat exchanger 11 By providing the pipe L3 connecting the second heat exchanger 13 and the pipe L4 connecting the second heat exchanger 13 and the low-stage compressor 10a, a refrigerant circuit in which the refrigerant circulates is configured. Among them, for the low-stage compressor 10a, the pipe L4 connects the suction-side pipe, and the pipe L1 connecting the low-stage compressor 10a and the high-stage compressor 10b connects intermediate pressure pipes for the high-stage compressor 10b. L2 constitutes the discharge side piping.
The low-stage compressor 10a and the high-stage compressor 10b may be collectively referred to as a compression mechanism 10 without distinction.

Hereinafter, each component of the heat pump system 4 will be described in order.
[Compression mechanism 10]
The low-stage compressor 10a is rotationally driven by an integrally-constructed electric motor to suck in the low-temperature low-pressure refrigerant that has passed through the second heat exchanger 13 and compress it to an intermediate pressure, thereby performing high-stage compression. Discharge toward the machine 10b.
As a compression mechanism applied to the low-stage compressor 10a, a known type of compression mechanism such as a scroll-type compression mechanism or a rotary-type compression mechanism can be applied. The same applies to the high stage compressor 10b.
The high stage compressor 10b sucks in and compresses the refrigerant discharged from the low stage compressor 10a, and discharges it toward the first heat exchanger 11 as a high-temperature high-pressure refrigerant.

[First heat exchanger 11]
The first heat exchanger 11 heats a fluid by heat exchange between a fluid to be heat-exchanged, such as water or air, and a high-temperature high-pressure refrigerant. The high-temperature and high-pressure refrigerant discharged from the high-stage compressor 10b is cooled and condensed here. As the first heat exchanger 11, a known heat exchanger can be used. The same applies to the second heat exchanger 13 described next.
When the target of heat exchange is air, the first heat exchanger 11 is provided with a blower fan 11f, and the air blown by the blower fan 11f passes through the first heat exchanger 11 with a refrigerant in the process of passing through the first heat exchanger 11. Heat is exchanged.

[Expansion valve 12, second heat exchanger 13]
The second heat exchanger 13 exchanges heat between the refrigerant, which has been decompressed and expanded through the expansion valve 12, and the outside air, and in the process of this heat exchange, the refrigerant evaporates and absorbs heat from the outside air Do. The second heat exchanger 13 is also provided with a blower fan 13f, and heat exchange between the air blown by the blower fan 13f and the refrigerant causes the low-pressure refrigerant to evaporate to generate a heat absorbing action.
The expansion valve 12 is constituted by, for example, an electronic expansion valve provided with a needle-like valve body and a pulse motor for driving the valve body.

[Soiling mechanism 20]
The oil equalizing mechanism 20 is provided in the oil equalizing piping 21 connecting the low-stage compressor 10a and the high-stage compressor 10b, and the oil equalizing piping 21, and between the low-stage compressor 10a and the high-stage compressor 10b. Oil pressure control valve (on-off valve) 23 for controlling the flow of refrigerating machine oil, and a first temperature sensor 34 provided close to the oil equalization pipe 21 for detecting the temperature inside the oil equalization pipe 21; And a second temperature sensor 35 provided in the vicinity of L2 for detecting the temperature inside the pipe L2.
The respective temperature information (detected temperatures) T ₀ and T ₁ detected by the first temperature sensor 34 and the second temperature sensor 35 are transferred to the control device 30. The controller 30 controls the opening / closing of the oil equalizing valve 23 based on the transferred temperature information T ₀ , T ₁ .

The oil equalizing mechanism 20 controls the opening / closing of the oil equalizing valve 23 to supply refrigeration oil surplus in the high stage compressor 10 b to the low stage compressor 10 a or stop the supply. .
In the low-stage compressor 10a and the high-stage compressor 10b, reference oil levels indicating the amount of refrigeration oil required for normal operation are respectively set, and the oil equalizing piping 21 is set to the reference oil level. The low-stage compressor 10a and the high-stage compressor 10b are connected at corresponding positions. And it is preferable that each connection end of oil equalizing piping 21 is always immersed in refrigeration oil.

As shown in FIG. 9 (b), when the oil equalizing valve 23 of the oil equalizing piping 21 is opened, the refrigerator oil flows from the high stage compressor 10b toward the low stage compressor 10a. This is because the pressure inside the high stage compressor 10b is higher than the pressure inside the low stage compressor 10a. In FIG. 9, the oil equalizing valve 23 which is closed is shown in black (FIG. 9 (a)), and the oil equalizing valve 23 which is open is shown in white (FIG. 9 (b)) In 9, the oil equalizing piping 21 is indicated by a solid line when the refrigerating machine oil is flowing, and is indicated by a broken line when the refrigerating machine oil is not flowing.

However, refrigerant oil flows from the high-stage compressor 10b toward the low-stage compressor 10a on the premise that the connection end of the oil equalizing piping 21 in the high-stage compressor 10b is immersed in the refrigerator oil. is there. Without this premise, the oil equalizing piping 21 becomes a passage for the refrigerant. Then, part of the refrigerant compressed by the high stage compressor 10b is returned to the low stage compressor 10a. This means that the power for compressing the refrigerant is consumed in both the low-stage compressor 10a and the high-stage compressor 10b. Therefore, when the refrigeration oil is not flowing through the oil equalizing pipe 21, as shown in FIG. 9A, the oil equalizing valve 23 is closed so that the refrigerant does not flow to the lower stage compressor 10a. It is desirable to close the

[Control device 30]
The control device 30 controls the operation of the heat pump system 4, and particularly in the present embodiment, controls the opening / closing of the oil equalizing valve 23 of the oil equalizing piping 21. The control device 30 acquires temperature information T ₀ and T ₁ from the first temperature sensor 34 and the second temperature sensor 35 to control the opening / closing of the oil equalizing valve 23. The controller 30 determines whether the oil equalizing valve 23 is open or closed by comparing the acquired temperature information T ₀ and T ₁ . That is, when the temperatures of the refrigerating machine oil flowing in the oil equalizing piping 21 and the refrigerant flowing in the piping L2 are compared, the temperature of the refrigerant is remarkably low. However, if that refrigerant flows through not the refrigerating machine oil in the oil equalizing pipe 21, the difference between the temperature information T ₁ detected in the temperature information T ₀ and the pipe L2 to be detected in the oil equalizing pipe 21 is reduced. Accordingly, the control device 30, by comparing the temperature information T ₀ and the temperature information T _1, it can be determined whether the refrigerant oil equalizing pipe 21 to the refrigerating machine oil is flowing is flowing.

[Operation of heat pump system 4]
Hereinafter, the operation of the heat pump system 4 will be described.
In the heat pump system 4, a refrigerant circulates and a two-stage compression refrigeration cycle is performed.

In the heat pump system 4, the high-temperature and high-pressure refrigerant discharged from the high-stage compressor 10b flows into the first heat exchanger 11 through the pipe L2, and radiates heat to the heat exchange object. The refrigerant that has dissipated heat in the first heat exchanger 11 expands in the process of passing through the expansion valve 12 through the pipe L3, and becomes a low-pressure refrigerant. The 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 drawn into the low pressure side 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 medium pressure refrigerant discharged from the low pressure side compressor 10a to the pipe L1 is drawn into the high pressure side compressor 10b. The refrigerant drawn into the high-stage compressor 10b is compressed into a high-pressure refrigerant and then discharged to the pipe L2.

In the heat pump system 4, the oil equalizing valve 23 is closed during the closing period t _w and is opened during the oil equalizing period t _m in a process in which the cycles of compression, condensation, expansion and evaporation of the refrigerant described above are repeated. Repeat the action alternately. This embodiment has a feature be between oil equalizing period t _m in the Hitoshiaburaben 23 forcibly close place. Hereinafter, with reference to FIG. 10, the procedure of opening / closing operation of the oil equalizing valve 23 will be described.

As shown in FIG. 10, the control device 30 instructs to start the operation of the heat pump system 4 and instructs the oil equalizing valve 23 to close (OFF) as initial setting (FIG. 10 S101). When the oil equalizing valve 23 is closed from the beginning, it is continued as it is.

The controller 30 measures an elapsed time t after the start of the operation is instructed, and opens the oil equalizing valve 23 when the elapsed time t reaches a predetermined closing period t _w (ON). To instruct (Fig. 10, S103). Controller 30, after the instruction to open Hitoshiaburaben 23, if reached the oil equalizing period _{t m} predetermined, it instructs to close the Hitoshiaburaben 23 (FIG. 10 S 111). As described above, the oil equalizing valve 23 according to the first embodiment alternately repeats the operation of closing during the closing period t _w and opening during the oil equalizing period t _m .

However, the control device 30 is provided with the following two exceptions regarding the opening and closing of the oil equalizing valve 23.
First, the control device 30 determines whether or not the heat pump system 4 is in steady operation, and in the case of steady operation, proceeds to the determination of the second exception (step 105 Yes, S107). If not, the oil equalizing valve 23 is kept closed (No in FIG. 10, S105). Here, the non-steady-state operation which does not correspond to the steady-state operation corresponds to, for example, the defrosting operation. During this unsteady operation, the premise of the present embodiment may not hold that the temperature of the refrigeration oil flowing through the oil equalizing valve 23 is higher than the temperature of the refrigerant drawn into the high-stage compressor 10b. . Further, it is also applicable to non-steady operation during the initial start of the heat pump system 4, the present embodiment is a folding already as occlusion period t _w the aforementioned the initial start-up.

Next, as a second exception, the control device 30 compares the number of revolutions R of the high-stage compressor 10b with the predetermined number of revolutions R ₀ (FIG. 10, S107). If less than R ₀ is instructed to open Hitoshiaburaben 23 every fixed time (oN) is repeated close the (OFF) alternately (FIG. 10 S107 Yes, S108).

If the above two exceptions do not apply, the controller 30 instructs the oil equalizing valve 23 to be opened (FIG. 10, S109). Hitoshiaburaben 23 after receiving this instruction, remain open only during the oil equalizing period _{t m} (Fig. 3 S 111).
During this time, the control device 30 determines that the difference (T ₀ −T ₁ ) between the temperature information T ₀ acquired from the first temperature sensor 34 and the temperature information T ₁ acquired from the second temperature sensor 35 is a predetermined value ΔT. It is determined whether it becomes the following or less (FIG. 10 S 113). Here, the temperature information T ₀ is considered as the temperature of the fluid (refrigerating machine oil or refrigerant) flowing through the oil equalizing pipe 21, the temperature information T ₁ is considered as the temperature of the refrigerant sucked into the high stage side compressor 10b.

When the difference (T ₀ -T ₁ ) becomes ΔT or less, the control device 30 determines that the oil equalizing pipe 21 is not refrigerant oil but refrigerant and is flowing, and closes the oil equalizing valve 23 (FIG. 10). S113 Yes). On the other hand, if the difference _(T 0 -T ₁₎ exceeds the [Delta] T, Hitoshiaburaben 23 continues to open up the oil-equalizing period _{t m} expires, the oil equalizing period _{t m} expires, Hitoshiaburaben 23 It is closed (FIG. 10 S113 No, S111 Yes).

As described above, according to the present embodiment, the operation of the low-stage compressor 10a and the high-stage compressor 10b is not stopped, and the high oil pressure valve 23 is simply opened and closed. Refrigerant oil can be supplied from the stage side to the lower stage side, and homogenization of both of them can be achieved. Moreover, according to the present embodiment, when the control device 30 determines that the refrigerant, not the refrigerator oil, is flowing in the oil equalizing pipe 21, the oil equalizing valve 23 is closed, so the refrigerant flows in the oil equalizing pipe 21. The space cost of the compression mechanism 10 which arises can be avoided.

As mentioned above, although this invention was demonstrated based on embodiment, it is possible to sort out the structure quoted by the said embodiment, or to change into another structure suitably, unless it deviates from the main point of this invention.
In the above, the principle opening and closing of the oil equalizing valve 23 is controlled by the closing period t _w and the oil equalizing period t _m, but the present invention is not limited thereto. As the condition for opening the oil equalizing valve 23, temperature information T ₀ and T ₁ can be used. That is, as shown in FIG. 11, if T ₀ −T ₁ exceeds ΔT, the oil equalizing valve 23 is opened (FIG. 11 step 203, step 109), and if T ₀ −T ₁ is ΔT or less, oil equalization is performed. The valve 23 can be closed (FIG. 11, step 113, S101).

The temperature information is compared with the temperature information T ₀ is not limited to temperature information T _1, it may be compared with the detected temperature (temperature information) T ₂ in the high pressure side compressor 10b. The difference obtained in this case is T ₂ −T ₀ , and when this difference becomes equal to or less than a predetermined value ΔTT, the control device 30 determines that the refrigerant is flowing through the oil equalizing pipe 21. The temperature in the high-stage compressor 10b is detected below the storage of the refrigeration oil.

Fourth Embodiment
Hereinafter, a heat pump-type hot water supply / air conditioner 100 to which the heat pump system 4 described as the first embodiment is applied will be described as a fourth embodiment of the present invention.
As shown in FIGS. 12 and 13, 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 the heat pump system 4 described in the first embodiment, and performs heat exchange between outdoor air (outside air) and a refrigerant. When there is an element corresponding to the heat pump system 4, the same reference numeral as that of the third embodiment is given and the description thereof is omitted. However, the first heat exchanger 11 should be read as a water-to-refrigerant heat exchanger 11. The water-to-refrigerant heat exchanger 11 heats the water by heat exchange between the water on the water system 300 side and the refrigerant. Further, the second heat exchanger 13 should 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 4 does not have.

The heat pump system 200 is provided with a cooling expansion valve 12 a as a throttling mechanism, a heating expansion valve 12 b and a receiver 39 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. There is. The cooling expansion valve 12 a and the heating expansion valve 12 b are disposed in series with the receiver 18 interposed therebetween.
Further, in the heat pump system 200, the economizer circuit 36 is provided in the pipe L3. The economizer circuit 36 includes an economizer heat exchanger 36a, an economizer expansion valve 36b, and an injection pipe 36c. A part of the liquid refrigerant passing through the water-to-refrigerant heat exchanger 11 is introduced into the economizer heat exchanger 36a through the economizer expansion valve 36b, and after heat exchange with the liquid refrigerant flowing through the pipe L3 is evaporated, A gas refrigerant is injected into a pipe L1 at an intermediate pressure between the low-stage compressor 10a and the high-stage compressor 10b via an injection pipe 36c.
The heat pump system 200 further includes an oil separator 37 on the discharge side of the low-stage compressor 10a and an oil separator 38 on the discharge side of the high-stage compressor 10b. The refrigeration oil contained in the refrigerant discharged from the low-stage compressor 10a is separated from the refrigerant in the oil separator 37 and returned to the low-stage compressor 10a via the return pipe 37L. Similarly, refrigeration oil contained in the refrigerant discharged from the high-stage compressor 10b is separated from the refrigerant in the oil separator 38 and returned to the high-stage compressor 10b via the return pipe 38L.

[Water system 300]
In the water system 300, the water circulated through the water circulation pump 307 absorbs heat from the refrigerant in the water-to-refrigerant heat exchanger 11 provided in the heat pump system 200 to be hot water, and the hot water is used as a radiator 303 on the load side. The hot water circulation flow path 301 used as a heat source for heating etc. is provided by circulating between them. A hot water is introduced from the hot water circulation flow path 301 via the three-way switching valve 306 capable of adjusting the flow rate to the hot water circulation flow path 301, and a heat storage tank 305 capable of storing the hot water as heat storage hot water is connected There is.

The water system 300 configured as described above selects either one of a heating operation for supplying hot water to the radiator 303 or a heat storage operation for supplying hot water to the heat storage tank 305 by selectively switching the three-way switching valve 306. Alternatively, warm water can be supplied separately to both the radiator 303 and the heat storage tank 305 so that both heating operation and heat storage operation can be performed simultaneously.
Further, the water system 300 is heated by heat exchange of the water to be heated 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 low pressure gas refrigerant is compressed by the compression mechanism 10 (low stage compressor 10a, high stage compressor 10b), and the heat pump is operated as a high temperature high pressure gas refrigerant. It is discharged into the system 200. This gas refrigerant is led to the water-to-refrigerant heat exchanger 11 by the four-way switching valve 15 and circulated counterclockwise as shown 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 of the water system 300 circulated by the water circulation pump 307 and the high-temperature high-pressure gas refrigerant, and the condensation heat released by condensation of the refrigerant is 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 is condensed 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 receiver 39 through the fully open cooling expansion valve 12a. In the receiver 39, gas-liquid separation of the refrigerant is performed, and adjustment of the amount of the circulating refrigerant is performed. On the downstream side of the receiver 39, a heating expansion valve 12b that decompresses the high-temperature high-pressure liquid refrigerant is disposed. When the refrigerant passes through the heating expansion valve 12 b, the high temperature / high pressure liquid refrigerant is decompressed to become a low temperature / low pressure gas-liquid two-phase refrigerant, and is led to the heat source side air heat exchanger 13. The gas-liquid two-phase refrigerant introduced to the heat source side air heat exchanger 13 functioning as an evaporator exchanges heat with the outside air, absorbs heat from the outside air, and is vaporized.

Thus, by passing through the heat source side air heat exchanger 13, the low-temperature low-pressure gas refrigerant which absorbs heat from the outside air and is vaporized is again drawn into the low-stage compressor 10a through the four-way switching valve 15. The low-temperature low-pressure gas refrigerant thus sucked to the low-stage compressor 10a is sequentially compressed by the low-stage compressor 10a and the high-stage compressor 10b to become a high-temperature high-pressure gas refrigerant, and the same route And change the state of gas and liquid repeatedly. At this time, moisture and the like in the air may freeze on the outer peripheral surface of the heat source side air heat exchanger 13 which has a low temperature, and a frosting phenomenon may occur.

Since frost inhibits the heat exchange between the refrigerant and the outside air in the heat source side air heat exchanger 13 and reduces the heat exchange efficiency, the defrosting is detected for each suitable operation time by detecting the presence or absence of the accumulation of frost. It is necessary to carry out the operation to remove the frost. In this defrosting operation, in the above-described heat pump system 200, the four-way switching valve 15 is switched to reverse the circulating direction of the refrigerant, and the refrigerant is switched to the cooling cycle (defrost cycle) for circulating the refrigerant in the arrow direction of the one-dot chain line in FIG. The high-temperature high-pressure gas refrigerant discharged from the high-stage compressor 10b is introduced into the heat source air heat exchanger 13, and the heat released (condensed heat) melts the frost adhering to the heat source air heat exchanger 13. It is done by doing.

Also in the hot water supply and air conditioner 100 described above, the opening and closing of the oil equalizing valve 23 provided between the low stage compressor 10a and the high stage compressor 10b is controlled in the same manner as in the first embodiment. Therefore, according to the hot water supply and air conditioner 100 of the present embodiment, the low pressure side compressor 10a and the high pressure side compressor 10b are not stopped by the simple operation of opening and closing the oil equalizing valve 23 without stopping the operation. The refrigeration oil can be made uniform in the stage compressor 10a and the high stage compressor 10b.

As mentioned above, although the present invention was explained based on an embodiment, unless it deviates from the main point of the present invention, it is possible to sort out the composition quoted by the above-mentioned embodiment, or to change suitably to other composition. is there.
For example, parts other than the minimum elements in the present invention described in the first embodiment are optional. Therefore, the present invention can be applied to a hot water supply / air conditioner further including a heat exchanger for room, and conversely, it can also be applied to a heat pump water heater having 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, cooling expansion valve 12b second expansion valve, heating expansion valve 13 second heat exchanger, heat source side air heat exchanger

13f blower fan

14, 15 four-

way switching valve

14a, 14b solenoid valve 16 injection circuit 16a intermediate pressure receiver 16b solenoid valve 16c reverse stop Valve 16d Injection pipe 17 Overcooling coil 18 Accumulator 20 Oil equalizing mechanism 21 Oil equalizing pipe 23 Oil equalizing valve 25

Solenoid valve

26, 28

Oil separator

27, 29 Oil return pipe 30 Control device 34 First temperature sensor 35 Second temperature sensor 36 Economizer circuit 36a Heat exchanger 36b for economizer Expansion valve 36c for economizer

Inge Suction pipes

37, 38

oil separators

37L, 38L return piping 39 receiver 100 water heater /

air conditioner

121, 127 sub piping 122, 128 solenoid valve 200 heat pump system 300 water system 301 hot water circulation flow path 303 radiator 305 heat storage tank 306 three-way switching valve 307 Water circulation pump L1, L11, L12, L2, L3, L4, L5 Piping

Claims

A compression mechanism provided with a low stage compressor and a high stage compressor for compressing and discharging a 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 that decompresses and expands the refrigerant flowing out of the first heat exchanger;
A second heat exchanger that exchanges heat between the refrigerant decompressed and expanded by the expansion valve and a heat exchange target;
An oil equalizing path that connects the low-stage compressor and the high-stage compressor, and distributes refrigerating machine oil between the low-stage compressor and the high-stage compressor.
A main return pipe that connects between the oil separator and the suction side of the high stage compressor;
An oil return path connecting the main return pipe and the oil equalizing path;
An oil return on-off valve provided in the oil return path;
A two-stage compression path for flowing the refrigerant in the low-stage side compressor and the high-stage side compressor in this order; a one-stage compression path for flowing only one of the low-stage side compressor and the high-stage side compressor; Selectively switching the refrigerant path switching mechanism,
A heat pump system comprising:
When any one of the following conditions (1) to (3) is satisfied while the two-stage compression path is selected, the path of the refrigerant 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 that enters the heat exchanger (water heat exchange) between water and refrigerant, T R ; prescribed value condition (2): (P HO- P LI ) ≦ ΔP R1
P LI; low suction pressure stage compressor P HO; high-stage compressor discharge pressure specified value: [Delta] P 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: ΔPR 2
When the refrigerant path switching mechanism selects the one-stage compression path,
By opening the oil return on-off valve, the refrigerator oil from the oil separator is returned to the oil equalizing path via the oil return path without passing through the high-stage compressor.
The heat pump system of Claim 1 or Claim 2.
The opening and closing of the return on-off valve and the opening and closing of the oil equalizing on-off valve are as follows:
It is controlled based on the predicted amount of refrigeration oil in the low pressure side compressor and the expected amount of refrigeration oil in the high pressure side compressor,
The heat pump system according to any one of claims 1 to 3.
The heat pump system according to any one of claims 1 to 4, wherein the first heat exchanger is a water-to-refrigerant heat exchanger that heats water by exchanging heat between a refrigerant and water.
Heat pump type water heater characterized by.
A compression mechanism provided with a low stage compressor and a high stage compressor for compressing and discharging a refrigerant;
A first heat exchanger in which the refrigerant compressed by the compression mechanism exchanges heat with a heat exchange target;
An expansion valve that decompresses and expands the refrigerant flowing out of the first heat exchanger;
A second heat exchanger in which the refrigerant decompressed and expanded by the expansion valve exchanges heat with a heat exchange target;
An oil equalizing pipe that connects the low-stage compressor and the high-stage compressor, and distributes refrigerating machine oil between the low-stage compressor and the high-stage compressor;
An oil equalizing valve for opening and closing the oil equalizing pipe;
A control device that controls the opening and closing operation of the oil pressure valve;
The controller is
If it is determined that the refrigerant is flowing through the oil equalizing piping, the open oil equalizing valve is instructed to close.
Heat pump system characterized by
The controller is
The detected temperature T 0 in the oil equalizing piping,
Detection temperature T 1 in a refrigerant pipe for flowing the refrigerant from the low-stage compressor to the high-stage compressor, and / or one or both of detection temperatures T 2 in the high-stage compressor;
Determine whether the refrigerant is flowing through the oil equalizing pipe based on the comparison of
The heat pump system according to claim 6.
The controller is
In non-steady-state operation, even if the opening conditions are in place, instruct to keep the oil equalizing valve closed.
The heat pump system of Claim 6 or Claim 7.
The controller is
When the number of revolutions of the high-stage compressor is smaller than a predetermined value,
Regardless of the determination as to whether the refrigerant is flowing through the oil equalizing piping,
Instructing the oil equalizing valve to alternately repeat opening and closing at fixed time intervals,
The heat pump system according to any one of claims 6 to 7.
10. The heat pump system according to any one of claims 6 to 9, wherein the first heat exchanger is a water-to-refrigerant heat exchanger that heats water by exchanging heat between a refrigerant and water.
Heat pump type water heater characterized by.