JP6029569B2 - Heat pump system and heat pump type water heater - Google Patents

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 issue is the control of the oil level of the refrigeration oil contained in each of the two compressors. Unlike a compressor that has two compression mechanisms on the low and high stages inside a single housing, when two independent compressors are connected in series, 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 based on this technical problem, and it is easy to keep the amount of refrigeration 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 heat pump system of the present invention includes a low-stage compressor and a high-stage compressor, and compresses and discharges the refrigerant, and the refrigerant compressed by the compression mechanism and the heat exchange target are A first heat exchanger that exchanges heat, an expansion valve that decompresses and expands the refrigerant flowing out of the first heat exchanger, and a second heat exchanger that exchanges heat between the refrigerant decompressed and expanded by the expansion valve and a heat exchange target , An oil leveling pipe that connects the low stage compressor and the high stage side compressor and distributes refrigeration oil between the low stage side compressor and the high stage side compressor, and an oil leveling valve that opens and closes the oil leveling pipe, And a control device for controlling the opening / closing operation of the oil equalizing valve.
The control device of the present invention is characterized by instructing to close the open oil equalizing valve when it is determined that the refrigerant flows through the oil equalizing pipe.

In the heat pump system of the present invention, the control device includes a detected temperature T ₀ in the oil leveling pipe, a detected temperature T ₁ in the refrigerant pipe that flows the refrigerant from the low-stage compressor toward the high-stage compressor, and a high stage. and one or both of the detected temperature T ₂ at the side compressor, based on a comparison of the oil equalization pipe can be determined whether the refrigerant is flowing.

  In the heat pump system of the present invention, it is preferable that the control device instructs the oil leveling valve to keep closing even if the conditions for opening are satisfied during unsteady operation.

  In the heat pump system of the present invention, the control device, regardless of 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. The oil leveling valve is preferably instructed to alternately open and close at regular intervals.

  The heat pump 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 the 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, it is possible to make the refrigerating machine oil uniform between the compression mechanisms by a simple operation of opening / closing the oil leveling valve without stopping the operation of the compression mechanism. Moreover, according to the present invention, when the refrigerant is judged to be flowing through the oil equalizing pipe, the open oil equalizing valve is closed, so that the waste of the compression mechanism caused by the refrigerant flowing through the oil equalizing pipe can be avoided. it can.

It is a figure which shows the circuit structure of the refrigerating cycle which concerns on 1st Embodiment. It is a figure which shows operation | movement of the refrigerating cycle of FIG. 1, (a) has closed the oil equalizing piping, (b) has opened the oil equalizing piping. It is a flowchart which shows the procedure of opening and closing of the valve provided in the 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 2nd Embodiment. 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, and has shown the operation mode different from FIG.

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. The first heat exchanger 11 that exchanges heat between the refrigerant and the fluid to be heat exchanged, the expansion valve 12 that decompresses and expands the refrigerant flowing out of the first heat exchanger 11, and the expansion valve 12 is decompressed and expanded. And a second heat exchanger 13 that exchanges heat between the refrigerant and the fluid to be heat exchanged, and are connected in series in this order along the circulation direction of the refrigerant. In the present embodiment, the first heat exchanger 11 functions as, for example, a condenser that radiates heat by exchanging heat with water, and the second heat exchanger 13 is an evaporator that absorbs heat by exchanging heat with outside air. Can function as.
The heat pump system 1 includes an oil leveling mechanism 20 for keeping the oil amounts of the refrigerating machine oil held in the low stage side compressor 10a and the refrigerating machine oil held in the high stage side compressor 10b even. Details of the oil equalizing mechanism 20 which is a feature of the present embodiment will be described later.

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 low-stage compressor 10a and the high-stage compressor 10b may be collectively referred to as the compression mechanism 10 without being distinguished.

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 first heat exchanger 11 heats a fluid by exchanging heat between a fluid such as water or air to be subjected to heat exchange 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. 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 object 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 the refrigerant. Heat exchanged.

[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. In the process of this heat exchange, the refrigerant evaporates and absorbs heat from the outside air. To do. 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.
The expansion valve 12 is composed of, for example, an electronic expansion valve provided with a needle-like valve body and a pulse motor for driving the valve body.

[Oil leveling mechanism 20]
The oil leveling mechanism 20 is provided in the oil leveling pipe 21 connecting the low stage side compressor 10a and the high stage side compressor 10b, and the oil leveling pipe 21, and between the low stage side compressor 10a and the high stage side compressor 10b. An oil equalizing valve (open / close valve) 23 for controlling the flow of the refrigeration oil, a first temperature sensor 25 provided in the vicinity of the oil equalizing pipe 21 for detecting the temperature inside the oil equalizing pipe 21, and a pipe And a second temperature sensor 26 provided in the vicinity of L2 for detecting the temperature inside the pipe L2.
Each temperature information (detected temperature) T ₀ and T ₁ detected by the first temperature sensor 25 and the second temperature sensor 26 is transferred to the control device 30. The control device 30 controls the opening / closing of the oil equalizing valve 23 based on the transferred temperature information T ₀ , T ₁ .

The oil leveling mechanism 20 supplies the refrigeration oil surplus in the high stage side compressor 10b to the low stage side compressor 10a or stops the supply by controlling the opening / closing of the oil leveling valve 23. .
Each of the low-stage compressor 10a and the high-stage compressor 10b has a reference oil level indicating the amount of refrigerating machine oil required for normal operation, and the oil equalizing pipe 21 is connected to the reference oil level. Connected to the low-stage compressor 10a and the high-stage compressor 10b at corresponding positions. And it is preferable that each connection end of the oil equalizing piping 21 is always immersed in refrigeration oil.

  As shown in FIG. 2B, when the oil leveling valve 23 of the oil leveling pipe 21 is opened, refrigeration oil flows from the high stage compressor 10b toward the low stage side 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. 2, the closed oil leveling valve 23 is shown in black (FIG. 2A), and the open oil leveling valve 23 is shown in white (FIG. 2B). 2, the oil equalizing pipe 21 is indicated by a solid line when the refrigeration oil is flowing, and is indicated by a broken line when the refrigeration oil is not flowing.

  However, the refrigeration 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 pipe 21 in the high stage compressor 10b is immersed in the refrigeration oil. is there. Without this premise, the oil equalizing pipe 21 becomes a refrigerant passage. If it does so, a part of refrigerant | coolant compressed with the high stage side compressor 10b will reversely return toward the low stage side compressor 10a. This means that the power for compressing the refrigerant is wasted 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. 2A, the oil equalizing valve 23 is closed and the oil equalizing pipe 21 is prevented so that the refrigerant does not flow into the low-stage compressor 10a. It is desirable to occlude.

[Control device 30]
The control device 30 governs the operation of the heat pump system 1. In particular, in the present embodiment, the control device 30 controls the opening / closing of the oil leveling valve 23 of the oil leveling piping 21. The control device 30 acquires temperature information T ₀ and T ₁ from the first temperature sensor 25 and the second temperature sensor 26, respectively, in order to control the opening / closing of the oil equalizing valve 23. The control device 30 determines whether the oil equalizing valve 23 is open / closed by comparing the acquired temperature information T ₀ and T ₁ . That is, when the temperature of the refrigerating machine oil flowing through the oil leveling pipe 21 and the temperature of the refrigerant flowing through the pipe L2 are compared, the temperature of the refrigerant is significantly 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. Therefore, the control device 30 can determine whether the refrigerating machine oil or the refrigerant flows through the oil equalizing pipe 21 by comparing the temperature information T ₀ and the temperature information T ₁ .

[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 refrigeration cycle is executed.

  In the heat pump system 1, 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 target. The refrigerant that has dissipated heat in 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, in the process of above-described compression of the refrigerant, condensation cycle of expansion and evaporation is repeated, Hitoshiaburaben 23, closed during the closed period t _w, between the oil equalizing period t _m is open, These operations are repeated alternately. This embodiment has a feature be between oil equalizing period t _m in the Hitoshiaburaben 23 forcibly close place. Hereinafter, the procedure for opening and closing the oil equalizing valve 23 will be described with reference to FIG.

  As shown in FIG. 3, the control device 30 instructs the oil equalizing valve 23 to be closed (OFF) as an initial setting in which an operation start instruction of the heat pump system 1 is given (S <b> 101 in FIG. 3). When the oil equalizing valve 23 is closed from the beginning, the operation is continued as it is.

Controller 30, also seeks the elapsed time t from been instructed to start operation, if the elapsed time t has reached the closed period t _w the predetermined opening the Hitoshiaburaben 23 (ON) (S103 in FIG. 3). After instructing the oil leveling valve 23 to open and then reaching a predetermined oil leveling period t _m , the control device 30 instructs the oil leveling valve 23 to close (S111 in FIG. 3). As described above, oil equalizing valve 23 of the first embodiment, closed during the closed period t _w, opens during the oil equalizing period t _m, are alternately repeated operation of.

However, the control device 30 provides two exceptions described below for opening and closing the oil equalizing valve 23.
First, the control device 30 determines whether or not the heat pump system 1 is in steady operation. In the case of steady operation, the control device 30 proceeds to the second exception determination (step 105 Yes, S107). If not, the oil leveling valve 23 is kept closed (No in FIG. 3 S105). Here, the case of the non-steady operation not corresponding to the steady operation corresponds to, for example, the case of performing the defrost operation. This is because during this unsteady operation, the premise of the present embodiment that the temperature of the refrigerating machine oil flowing through the oil equalizing valve 23 is higher than the temperature of the refrigerant sucked into the high-stage compressor 10b may not be satisfied. . Moreover, although it corresponds to a non-steady operation during the start-up stage of the heat pump system 1, this embodiment has been inserted into the start-up period _tw as described above.

Next, as a second exception, the control device 30 compares the rotational speed R of the high-stage compressor 10b with a predetermined rotational speed _R0 (S107 in FIG. 3), and the rotational speed R is the rotational speed. If less than R ₀ is instructed to open Hitoshiaburaben 23 every fixed time (oN) is repeated close the (OFF) alternately (Fig. 3 S107 Yes, S108).

If it does not correspond to the above two exceptions, the control device 30 instructs to open the oil equalizing valve 23 (S109 in FIG. 3). 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 25 and the temperature information T ₁ acquired from the second temperature sensor 26 is a predetermined value ΔT. It is determined whether or not the following occurs (S113 in FIG. 3). 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 equal to or smaller than ΔT, the control device 30 determines that the refrigerant is flowing in the oil leveling pipe 21 instead of the refrigerating machine oil, and closes the oil leveling valve 23 (FIG. 3). 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. 3 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 a simple operation of opening / closing the oil equalizing valve 23 is performed. Refrigerating machine oil can be supplied from the stage side to the lower stage side, and the refrigerating machine oil of both can be made uniform. Moreover, according to the present embodiment, when the control device 30 determines that the refrigerant is flowing in the oil leveling pipe 21 instead of the refrigerating machine oil, the oil leveling valve 23 is closed, so that the refrigerant flows through the oil leveling pipe 21. The resulting waste of the compression mechanism 10 can be avoided.

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.
In the above, although controlled by the principle opening and closing of Hitoshiaburaben 23 closed period t _w the oil equalizing period t _m, the present invention is not limited thereto. Temperature conditions T ₀ and T ₁ can be used as conditions for opening the oil equalizing valve 23. That is, as shown in FIG. 4, if T ₀ -T ₁ exceeds ΔT, the oil leveling valve 23 is opened (step 203 and step 109 in FIG. 4), and if T ₀ -T ₁ is equal to or less than ΔT, the oil leveling is performed. The valve 23 can also be closed (FIG. 4, 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 is 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. In addition, the temperature in the high stage side compressor 10b is detected in the lower part where the refrigerating machine oil is stored.

[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 FIGS. 5 and 6, 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 1 described in the first embodiment, and performs heat exchange between outdoor air (outside air) and the refrigerant. When there is an element corresponding to the heat pump system 1, the same reference numerals as those in the first embodiment are given, and the 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.

The heat pump system 200 is provided with a cooling expansion valve 12a, a heating expansion valve 12b, and a receiver 18 as a throttle mechanism 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. Yes. The cooling expansion valve 12a and the heating expansion valve 12b are arranged in series with the receiver 18 in between.
In the heat pump system 200, the economizer circuit 16 is provided in the pipe L3. The economizer circuit 16 includes an economizer heat exchanger 16a, an economizer expansion valve 16b, and an injection pipe 16c. A part of the liquid refrigerant that has passed through the water-to-refrigerant heat exchanger 11 is introduced into the economizer heat exchanger 16a via the economizer expansion valve 16b, and after evaporating by exchanging heat with the liquid refrigerant flowing through the pipe L3, The gas refrigerant is injected into the intermediate pressure pipe L1 between the low stage compressor 10a and the high stage compressor 10b via the injection pipe 16c.
The heat pump system 200 includes an oil separator 27 on the discharge side of the low-stage compressor 10a and an oil separator 28 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 27 and returned to the low-stage compressor 10a via the return pipe 27L. Similarly, the refrigeration oil contained in the refrigerant discharged from the high-stage compressor 10b is separated from the refrigerant in the oil separator 28 and returned to the high-stage compressor 10b through the return pipe 28L.

[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, and the hot water is heated to the load-side radiator 303. Is provided with a hot water circulation channel 301 used as a heat source for heating. 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 selects either the heating operation for supplying warm water to the radiator 303 or the heat storage operation for supplying warm water to the heat storage tank 305 by selectively switching the three-way switching valve 306. Alternatively, it is configured such that warm water is dividedly supplied to both the radiator 303 and the heat storage tank 305 and 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 15 and circulated counterclockwise, 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 receiver 18 through the fully opened cooling expansion valve 12a. The receiver 18 performs gas-liquid separation of the refrigerant and adjusts the amount of circulating refrigerant. On the downstream side of the receiver 18, a heating expansion valve 12b that depressurizes high-temperature and high-pressure liquid refrigerant is disposed. When the refrigerant passes through the heating expansion valve 12b, the high-temperature and high-pressure liquid refrigerant is decompressed to become a low-temperature and 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 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 freezes on the outer peripheral surface of the heat source side air heat exchanger 13 that is at a low temperature, and a frosting phenomenon may occur.

  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 switched to a cooling cycle (defrost cycle) in the above-described heat pump system 200, which switches the four-way switching valve 15 to reverse the refrigerant circulation direction and circulates the refrigerant in the direction of the dashed line in FIG. The high-temperature and high-pressure gas refrigerant discharged from the high-stage 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 doing.

  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, similarly to the first embodiment, 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. Therefore, according to the hot water supply / air conditioner 100 of the present embodiment, the operation of the low stage compressor 10a and the high stage compressor 10b is not stopped, and the low level can be reduced by a simple operation of opening and closing the oil equalizing valve 23. It is possible to make the refrigerating machine oil uniform in the stage side compressor 10a and the high stage side compressor 10b.

As described above, the present invention has been described based on the embodiments. However, the configuration described in the above embodiments may be selected or changed to other configurations as appropriate without departing from the gist of the present invention. is there.
For example, the portions excluding the minimum elements in the present invention described in the first embodiment are arbitrary. For example, the present invention can be applied to a hot water supply / air conditioner further provided with an indoor heat exchanger, and conversely, it can also be applied to a heat pump hot water supply device having only a hot water storage function.

DESCRIPTION OF SYMBOLS 1 Heat pump system 10a Low stage side compressor 10b High stage side compressor 11 1st heat exchanger, water-to-refrigerant heat exchanger 11f Blower fan 12 Expansion valve 12a Cooling expansion valve 12b Heating expansion valve 13 Second heat exchanger , Heat source side air heat exchanger 13f blower fan 15 four-way switching valve 16 economizer circuit 16a economizer heat exchanger 16b economizer expansion valve 16c injection pipe 18 receiver 20 oil equalizing mechanism 21 oil equalizing pipe 23 oil equalizing valve 25 first temperature sensor 26 Second temperature sensors 27, 28 Oil separators 27L, 28L Return pipe 30 Control device 100 Hot water supply / air conditioner 200 Heat pump system 300 Water system 301 Hot water circulation channel 303 Radiator 305 Heat storage tank 306 Three-way switching valve 307 Water circulation pumps L1-L4 Piping

Claims (5)

A compression mechanism that includes a low-stage compressor and a high-stage compressor, and compresses and discharges the refrigerant;
A first heat exchanger in which the refrigerant compressed by the compression mechanism exchanges heat with a heat exchange target;
An expansion valve for decompressing and expanding 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 refrigeration oil between the low-stage compressor and the high-stage compressor;
An oil leveling valve for opening and closing the oil leveling pipe;
A control device for controlling the opening and closing operation of the oil equalizing valve,
The control device includes:
If it is determined that the refrigerant is flowing through the oil leveling pipe, the open leveling valve is instructed to close.
A heat pump system characterized by that. The control device includes:
A detected temperature T ₀ in the oil leveling pipe;
One or both of a detected temperature T ₁ in a refrigerant pipe for flowing the refrigerant from the low-stage compressor toward the high-stage compressor, and a detected temperature T ₂ in the high-stage compressor,
Based on the comparison of whether or not the refrigerant is flowing through the oil equalizing pipe,
The heat pump system according to claim 1. The control device includes:
In the case of unsteady operation, even if the conditions for opening are prepared, it is instructed to keep the oil equalizing valve closed.
The heat pump system according to claim 1 or 2. The control device includes:
When the rotational speed of the high stage compressor is smaller than a predetermined value,
Regardless of the determination of whether the refrigerant is flowing through the oil leveling pipe,
Instructing the oil leveling valve to alternately open and close at regular intervals.
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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