ES2708779T3 - Heat pump system, and heat pump water heater - Google Patents

Abstract

A heat pump system (1; 2; 3) comprising: a compression mechanism including a low-stage compressor (10a) and a high-stage compressor (10b) configured to compress and discharge a refrigerant ; an oil separator (26) which is provided on a discharge side of the high stage compressor (10b); a first heat exchanger (11) configured to exchange heat between the refrigerant compressed by the compression mechanism and an object to be heat exchanged; an expansion valve (12) configured to decompress and expand the refrigerant circulating outside the first heat exchanger (11); a second heat exchanger (13) configured to exchange heat between the refrigerant decompressed and expanded by the expansion valve (12) and an object to be subjected to heat exchange; and a main return pipe (27) connecting the oil separator (26) to a suction side of the high stage compressor (10b); characterized in that it comprises an oil equalization path (21) that connects the low stage compressor (10a) to the high stage compressor (10b) configured to allow the refrigerant oil to flow between the stage compressor low (10a) and the compressor of the high stage (10b); an oil return path (23) connecting the main return pipes (27) to the oil equalization path (21); an oil return on-off valve (25) which is provided on the oil return path (23); and a refrigerant path changeover mechanism (14) configured to selectively change a refrigerant path between a two-stage compression path along which the refrigerant circulates through the low-stage compressor (10a) and the high-stage compressor (10b) in this order and a one-stage compression stroke along which the refrigerant circulates through only one of the low-stage compressor and the high-stage compressor , a control device (30) configured to instruct the refrigerant path change mechanism (14) and the oil return on-off valve (25) so that when the control device (30) instructs the mechanism for changing the refrigerant path (14) to select the compression path in one stage, the control device (30) instructs the oil return on-off valve (25) to be opened and the oil from Refrigerant from the oil separator (26) is returned to the oil equalization path (21) through the oil return path (23) without passing through the high-stage compressor (10b).

Description

DESCRIPTION

Heat pump system, and heat pump water heater

Sector of the technique

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

State of the art

Hot water systems have used a heat pump to save energy.

A two-stage compression refrigeration cycle, which includes a refrigerant circuit in which a compressor of the low stage and a compressor of the high stage are connected in series and circulates refrigerant using the refrigerant circuit, is known as a refrigerant system (for example, patent literature 1 to 3).

List of citations

Patent bibliography

[BLP 1] Unexamined Japanese Patent Application Publication No. 5-93552

[BLP 2] Unexamined Japanese Patent Application Publication No. 6-2966

[BLP ³ ] Unexamined Japanese Patent Application Publication No. 2009-168330

[BLP 4] JP 2001 349629 A discloses a heat pump system according to the preamble of claim 1.

[BLP 5] JP 2013139902 A discloses a refrigeration device.

Object of the invention

Technical problem

It is necessary to operate two compressors of a low stage and a high stage with rotation speeds, which are independent of each other, to always operate the two-stage compression refrigeration cycle with high efficiency. The control of the refrigerant oil level contained in each of the two compressors is of the utmost importance for this purpose. When two independent compressors are connected in series unlike a compressor that includes two compression mechanisms of a low stage and a high stage provided in a housing, it is necessary to keep the quantity of refrigerant oil at an appropriate uniform level between the two compressors to operate satisfactorily the two compressors.

The invention has been made on the basis of this technical problem, and the object of the invention is to provide a heat pump system of the two-stage compression type in which the amount of refrigerant oil of the two compressors remains uniform without that the operation is stopped or a complicated operation has to be carried out. Also, an object of the invention is to provide a high efficiency heat pump water heater that includes a two stage compressor type heat pump system.

Solution to the problem

The invention, which has been made to achieve the objectives as defined in claim 1, and is divided into a first disclosure and a second disclosure.

First, according to the first disclosure, a heat pump system is provided which includes: a compression mechanism including a low stage compressor and a high stage compressor and compressing and discharging a refrigerant; an oil separator that is provided on a discharge side of the compressor of the discharge stage; a first heat exchanger that exchanges heat between the refrigerant compressed by the compression mechanism and an object to be subjected to heat exchange; an expansion valve that decompresses and expands the refrigerant circulating outside the first heat exchanger; a second heat exchanger that exchanges heat between the decompressed and expanded refrigerant by the expansion valve and the object to be subjected to heat exchange; an oil equalization path that connects the compressor from the low stage to the high stage compressor and allows the refrigerant oil to flow between the compressor of the low stage and the high stage compressor; a main return pipe that connects the oil separator to a suction side of the compressor of the discharge stage; a return path of the oil that connects the main return lines to the oil equalization path; an all-nothing oil return valve that is provided on the return path of the oil; and a refrigerant path change mechanism that selectively changes a refrigerant path between a two-stage compression path along which the refrigerant circulates through the compressor of the low stage and the compressor of the refrigerant. the high stage in this order and a compression stroke in a stage along which the refrigerant circulates through only one of the compressor of the low stage and the compressor of the high stage.

For example, when a heat pump water heater is assumed, the high pressure of the device is determined depending on the temperature (for example, in the range of 35 ° C to 75 ° C) of water entering a heat exchanger. heat (a water-coolant heat exchanger) for water and a coolant. Accordingly, a difference in pressure between the suction side and the discharge side of the compressor can be changed significantly according to the water temperature. When a two-stage compression operation is performed while the water temperature at an inlet of the water-cooling heat exchanger is low, the differential pressure between the compressor of the low stage and the compressor of the high stage is reduced. The amount of refrigerant oil to be returned is determined according to the differential pressure between the compressors. Accordingly, when a differential pressure between the compressor of the low stage and the compressor of the high stage is reduced in the middle of the two stage compression operation in the disclosure, a compression operation is changed to the compression operation in one stage.

In the heat pump system of the first disclosure, the refrigerant path is changed to a one-stage compression path when the two-stage compression path is selected and any one of the following conditions is met (1) a ( 3).

Condition (1): T ^w ^ T ^r

T ^w : The temperature of the water entering a heat exchanger (water heat exchanger) for the water and the refrigerant when the object, which has to be subjected to heat exchange, of the first heat exchanger is water

T ^r : Prescribed value

Condition (2): (P ^ho -P ^li ) ^ AP ^ri

P ^li : The compressor suction value of the low stage

P ^ho : The compressor discharge pressure of the high stage

AP ^ri : Prescribed value

Condition (3): (P ^lo -P ^li ) ^ AP ^r 2

P ^li : The compressor suction value of the low stage

P ^lo : The compressor discharge value of the low stage

AP ^r 2: Prescribed value

Also, in the heat pump system of the first disclosure, when the refrigerant travel change mechanism selects the compression stroke in one stage, the all-nothing return valve of the oil is opened and the refrigerant oil from the Oil separator can return to the oil equalization path through the return path of the oil without passing through the compressor of the discharge stage.

Since the return path of the oil and the oil equalization path formed as described above are provided, it is possible to easily recover the amount of refrigerant oil when the amount of refrigerant oil from each of the compressor of the stage of low and the compressor side of the high stage is insufficient.

In the heat pump system of the first disclosure, it is preferable that the opening / closing of the return valve of the return oil be controlled based on an estimated amount of refrigerant oil from the compressor of the low stage and an estimated amount of compressor refrigerant oil from high stage.

It is possible to control the refrigerant oil at an appropriate time based on the amount of oil in each of the two compressors obtained from the detection results of pressure sensors and a temperature sensor of the heat pump system.

Since the amount of refrigerant oil from each of the compressor of the low stage and the compressor of the high stage are secured in a heat pump water heater that includes the first heat exchanger of the heat pump system As mentioned above, which is a water-coolant heat exchanger for water heating by heat exchange between the refrigerant and the water, the heat pump water heater can stably supply hot water with high efficiency.

Next, according to a second disclosure, a heat pump system is provided which includes: a compression mechanism that includes a low stage compressor and a high stage compressor and compresses and discharges a refrigerant; a first heat exchanger in which the refrigerant compressed by the compression mechanism exchanges heat with an object to be subjected to heat exchange; a valve of expansion that decompresses and expands the refrigerant circulating outside the first heat exchanger; a second heat exchanger in which the refrigerant decompressed and expanded by the expansion valve exchanges heat with an object to be subjected to heat exchange; an oil equalization path that connects the compressor from the low stage to the high stage compressor and allows the refrigerant oil to flow between the compressor of the low stage and the high stage compressor; an oil equalization valve that opens and closes the oil equalization line; and a control device that controls an operation for opening / closing the oil equalization valve.

When the control device determines that the refrigerant is circulating in the oil equalization line, the control device instructs the oil equalization valve to close.

In the heat pump system of the second disclosure, the control device can determine whether or not the coolant is circulating in the oil equalization pipeline based on the comparison of the detected temperature T0 of the oil equalization pipe and one or both of the detected temperature T1 of a refrigerant pipe, which allows the refrigerant to flow to the compressor of the high stage from the compressor of the low stage, and a detected temperature T2 of the compressor of the high stage.

In the heat pump system of the second disclosure, it is preferable that the instruction control device to the oil equalization valve to continue to be closed during an unstable operation even if an opening condition is satisfied.

Also, in the heat pump system of the second disclosure, it is preferable that the instruction control device to the oil equalization valve be opened and closed alternately and repeatedly at each of the predetermined times regardless of the determination whether the refrigerant is circulating or not in the oil equalization pipe when the speed of rotation of the compressor of the high stage is smaller than a predetermined value.

Since the amount of refrigerant oil from each of the compressor of the low stage and the compressor of the high stage are secured in a heat pump water heater that includes the first heat exchanger of the heat pump system Above mentioned of the second disclosure which is a water-coolant heat exchanger for water heating by heat exchange between the refrigerant and water, the heat pump water heater can stably supply hot water with high efficiency. Advantageous effects of the disclosure

According to the first disclosure, it is possible to equalize the refrigerant oil of the compressor of the low stage and the compressor of the high stage only by a simple operation of the opening / closing of the first electromagnetic valve and of the second electromagnetic valve. without stopping the operation of the compressor of the low stage and the compressor of the high stage.

Also, according to the second disclosure, it is possible to equalize the refrigerant oil in the compression mechanism by a simple opening / closing operation of the oil equalization valve without stopping the operation of the compression mechanism. In addition, according to the disclosure, when the control device determines that the refrigerant is circulating in the oil equalization line, the control device closes the open oil equalization valve. Accordingly, it is possible to avoid the wasteful use of the compression mechanism that is caused when the coolant circulates in the oil equalizing pipe.

Description of the figures

Fig. 1 is a diagram showing the configuration of a circuit of a heat pump system according to a first embodiment.

Fig. 2 is a diagram showing the operation of the heat pump system of the first embodiment in which Fig. 2A shows a two-stage compression operation and Fig. 2B shows a one-stage compression operation.

Fig. 3 is a diagram showing the configuration of a circuit that changes a compression operation between the two-stage compression operation and the compression operation in one stage of the heat pump system of Fig. 1 by two valves electromagnetic

Fig. 4 is a diagram showing the configuration of a circuit in which two oil separators are added to the heat pump system of Fig. 1.

Fig. 5 is a diagram showing the configuration of a circuit of a water heater / air conditioner of the heat pump type according to a second embodiment.

Fig. 6 shows the configuration of the water heater / air conditioner circuit of the heat pump type according to the second embodiment and shows an operation mode different from that of Fig. 5.

Fig. 7 is a diagram showing an example of modification of an oil equalizing pipe.

Fig. 8 is a diagram showing the configuration of a circuit of a refrigeration cycle according to a third embodiment.

Fig. 9 is a diagram showing the operation of the refrigeration cycle of Fig. 8 in which the oil equalizing pipe is closed in Fig. 9A and in which the oil equalizing pipe is open in Fig. 9. 9B.

Fig. 10 is a flow chart illustrating a procedure for opening / closing a valve that is provided on the oil equalizing pipe of the refrigeration cycle of Fig. 8.

Fig. 11 is a flow chart illustrating an example of modification of the procedure for opening / closing the valve of Fig. 10.

Fig. 12 is a diagram showing the configuration of a circuit of a water heater / air conditioner of the heat pump type according to a fourth embodiment.

Fig. 13 is a diagram showing the configuration of the water heater / air conditioner circuit of the heat pump type according to the fourth embodiment and shows an operation mode different from that of Fig. 12.

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the invention will be described below with reference to the accompanying drawings.

[First performance]

As shown in Fig. 1, a heat pump system 1 according to a first embodiment includes a compressor of the low stage 10a and a compressor of the high stage 10b which compresses and discharges a coolant, a first exchanger of heat 11 exchanging heat between the refrigerant compressed by the compressor of the high stage 10b and a fluid as an object to be subjected to heat exchange, an expansion valve 12 decompresses and expands the refrigerant circulating outside the first heat exchanger heat 11 (from hereon onwards, simply referred to as an expansion valve), and a second heat exchanger 13 which exchanges heat between the decompressed and expanded refrigerant by the expansion valve 12 and the fluid as an object to be exchanged thermal. The compressor of the low stage 10a, the compressor of the high stage 10b, the first heat exchanger 11, the expansion valve 12 and the second heat exchanger 13 are connected in series in this order in the direction of circulation of the refrigerant. In this embodiment, the first heat exchanger 11 can function as a condenser that radiates heat by thermal exchange with, for example, water and the second heat exchanger 13 can function as an evaporator that absorbs heat by thermal exchange with outside air .

The heat pump system 1 includes a four-way switching valve 14 which changes a connection state of the compressor of the low stage 10a and the compressor of the high stage 10b as described below. That is, the four-way switching valve 14 changes the state of connection between the two-stage compression operation (two-stage compression stroke) in which a refrigerant passes through both the compressor of the low stage 10a and of the compressor of the high stage 10b and a compression operation in one stage (a compression stroke in a stage) in which a refrigerant passes through only the compressor of the low stage 10a and contours the compressor of the stage of high 10b.

Also, the heat pump system 1 includes an oil equalization mechanism 20 which keeps the amount of refrigerant oil held in the compressors on the side of the low and high stage 10a and 10b uniform.

The heat pump system 1 includes a line L1 connecting the compressor of the low stage 10a to the compressor of the high stage 10b, a line L2 connecting the compressor of the high stage 10b to the first heat exchanger 11, a pipe L3 connecting the first heat exchanger 11 to the second heat exchanger 13, and a pipe L4 connecting the second heat exchanger 13 to the compressor of the low stage 10a. Accordingly, the heat pump system 1 forms a refrigerant circuit in which a refrigerant circulates. Between the pipes, the pipe L4 forms a pipe on the suction side of the compressor of the low stage 10a, the pipe L1 connecting the compressor of the low stage 10a to the compressor of the high stage 10b forms an intermediate pressure pipeline , and the tubena L2 forms a tubena on the discharge side of the compressor of the high stage 10b.

Also, the heat pump system 1 includes a line L5 connecting the discharge side (line L1) of the compressor of the low stage 10a to the discharge side (line L2) of the compressor of the stage 10b. The aforementioned four-way switching valve 14 is provided at a connecting end of the line L5 corresponding to the discharge side of the compressor of the low stage 10a. The four-way switching valve 14 is changed so that the refrigerant discharged from the compressor of the low stage 10a is sucked into the compressor of the high stage 10b through the pipeline L1 just like this or supplied to the compressor of the high stage 10b. first heat exchanger 11 through the pipes L5 and L2. The switching between the two-stage compression stroke and the compression stroke in one stage is carried out by switching.

For its part, the compressor of the low stage 10a and the compressor of the high stage 10b are referred to as a compression mechanism 10 without distinction between them.

Next, the heat pump system 1 includes an oil separator 26 which is provided on the pipe L2. The oil separator 26 is connected directly to the compressor of the high stage 10b by means of an oil return pipe 27. The oil return pipe 27 includes a fixed throttle 27a.

In the middle of the two-stage compression operation, the oil separator 26 separates the refrigerant oil from the refrigerant, which is discharged from the compressor of the high stage 10b, and returns the refrigerant oil to the compressor of the stage of refrigerant. high 10b through the return pipe 27. In the middle of the one-stage compression operation, the oil separator 26 separates the refrigerant oil from the refrigerant, which is discharged from the compressor of the low stage 10a, and returns the refrigerant oil to the compressor of the high stage 10b through the return pipe 27.

The respective components of the heat pump system 1 will now be described one by one.

[Compression mechanism 10]

When the compressor of the low stage 10a is rotationally driven by an electric motor which is formed integrally with the compressor of the low stage 10a, the compressor of the low stage 10a sucks the coolant, which has passed through the second heat exchanger 13 and has a low temperature and low pressure, compresses the refrigerant to an intermediate pressure, and discharges the compressed refrigerant to the compressor of the high stage 10b.

A publicly known compression mechanism, such as the scroll compression mechanism or a rotary compression mechanism, can be applied as the compression mechanism that is applied to the compressor of the low stage 10a. In the same way, the same applies to the compressor of the high stage 10b.

The compressor of the high stage 10b sucks and compresses the refrigerant, which is discharged from the compressor of the low stage 10a, and discharges the compressed refrigerant to the first heat exchanger 11 as a refrigerant having a high temperature and a high pressure .

[First heat exchanger 11]

The first heat exchanger 11 heats the fluid, such as water or air, as an object to be subjected to heat exchange by exchanging heat between the fluid and a refrigerant having a high temperature and a high pressure. The refrigerant, which is discharged from the compressor of the high stage 10b and has a high temperature and a high pressure, is cooled and condensed in the first heat exchanger 11. A heat exchanger publicly known as the first heat exchanger can be used. heat 11. The same applies to the second heat exchanger 13 to be described below.

When an object to be subjected to thermal exchange is air, the first heat exchanger 11 is provided with a fan 11f and heat is exchanged between the air blown by the fan 11f and the refrigerant while the air driven by the fan 11f goes to through the first heat exchanger 11.

[Expansion valve 12 and second heat exchanger 13]

The second heat exchanger 13 exchanges heat between the refrigerant, which passes through the expansion valve 12 and decompresses and expands, and the external air (blown air), and the refrigerant evaporates and absorbs heat from the outside air while Heat is exchanged between the refrigerant and the outside air. The second heat exchanger 13 is also provided with a fan 13f and heat is exchanged between the air blown by the fan 13f and the refrigerant, so that the low pressure refrigerant evaporates and a heat absorbing operation is generated.

For example, an expansion valve, which includes a needle-shaped valve body and a pulse motor for actuating the valve body, can be used as the expansion valve 12.

[Oil equalization mechanism 20]

The oil equalization mechanism 20 includes an oil equalizing pipe 21 which connects the compressor of the low stage 10a to the high stage compressor 10b, a bypass pipe 23 which connects the oil equalization pipe 21 to the oil return pipe 27, and an electromagnetic valve 25 that is provided on the bypass pipe 23.

The oil equalization mechanism 20 allows the refrigerant oil to flow between the compressor of the low stage 10a and the compressor of the high stage 10b through the oil equalizing pipe 21. Likewise, the equalization mechanism of the The oil 20 returns refrigerant oil to the oil equalizing line 21 from the discharge side of the compressor of the high stage 10b through the bypass line 23. The function of the Derivation tubena 23 is achieved during the compression operation in one stage, and is to apply the necessary differential pressure to the oil equalizing line 21.

When a level representing the amount of refrigerant oil, which is necessary in each of the compressor of the low stage 10a and the compressor of the high stage 10b, is defined as a reference level, the oil equalization line 21 is connected to the compressor of the low stage 10a and to the compressor of the high stage 10b directly above the reference level.

Fig. 1 shows an example in which a single oil equalizing pipe 21 is provided, but a plurality of oil equalizing pipes 21 (21A, 21B and 21C) can be provided in parallel as shown in Fig. 7. Likewise, the oil equalization pipes 21B and 21C are provided with all-nothing valves 22B and 22C, respectively.

When the single oil equalization tube 21 is provided, excess refrigerant oil can flow. However, when the plurality of oil equalization tubes 21A, 21B and 21C are provided as described above and the all-nothing valves 22B and 22C are operated so that they open and close, the amount of oil in the oil can be adjusted to a minimum. refrigerant in circulation. Also, the oil equalization tube 21A can also be provided with an all-nothing valve.

On the other hand, the maximum quantities of refrigerant oil circulating through the oil equalization pipes 21A, 21B and 21C can be adjusted to be equal to each other and can be adjusted to be different from each other. Also, the opening and closing of the all-nothing valves 22B and 22C can be controlled by detecting the temperature of the refrigerant oil circulating inside the compressor of the high stage 10b. [Operation of heat pump system 1]

The operation of the heat pump system 1 will be described below.

In the heat pump system 1, a refrigerant circulates and the compression operation is performed in two stages. However, the compression operation is performed in one stage under specific conditions.

The two-stage compression operation will be described first.

As shown in Fig. 2A, during the two-stage compression operation, the four-way switching valve 14 is changed so that the pipes L11 and L12 (L1) communicate with each other. Accordingly, the refrigerant, which is compressed at an intermediate pressure by the compressor of the low stage 10a, is sucked into the compressor of the high stage 10b through the pipeline L11, the four-way switching valve 14. and the L12 tubena. In Fig. 2A, the arrows indicate a direction in which the refrigerant flows. The same applies to Fig. 2B to be described below.

The high pressure refrigerant, which is discharged after the refrigerant is compressed to a high temperature and a high pressure by the compressor of the high stage 10b, flows into the first heat exchanger 11 through the pipeline L2 and radiates heat to an object to be subjected to heat exchange. The high pressure refrigerant, which has radiated heat in the first heat exchanger 11, becomes a low pressure refrigerant as it is expanded as it passes through the expansion valve 12 through the pipeline L3. The low pressure refrigerant circulates further into the second heat exchanger 13 through the pipeline L3, absorbs heat from the outside air, and evaporates. After this, the low pressure refrigerant, which flows out of the second heat exchanger 13, is sucked into the compressor of the low stage 10a through the pipe L4.

After the low pressure refrigerant, which is sucked into the compressor of the low stage 10a, is compressed and becomes an intermediate pressure refrigerant, the intermediate pressure refrigerant is discharged to the line L1. The intermediate pressure refrigerant, which is discharged to the line L1 from the compressor of the low stage 10a, is sucked into the compressor of the high stage 10b. After the refrigerant, which is sucked into the compressor of the high stage 10b, is compressed and converted into a high pressure refrigerant, the high pressure refrigerant is discharged to the pipeline L2.

The heat pump system 1 ensures the refrigerant oil level of each of the compressor of the low stage 10a and the compressor of the high stage 10b within a necessary interval to allow the refrigerant oil to flow through the compressor. the oil equalizing pipe 21 while repeating the cycle of compression, condensation, expansion and evaporation of the refrigerant described above.

In this case, a method in which a device, which is called an oil separator for the separation of the oil from a refrigerant, is disposed on the discharge side of the compressor and the separated refrigerant oil returns to the suction side of the compressor. through an oil return circuit that includes a fixed choke such as a capillary tube is generally used as a method of return of the coolant oil, which is contained in the refrigerant discharged from the compressor, to the compressor.

However, for example, when a heat pump water heater is assumed, the high pressure of the device is determined depending on the temperature (for example, in the range of 35 ° C to 75 ° C) of water entering into the water. a heat exchanger (a water-coolant heat exchanger) for water and a refrigerant. Accordingly, a difference in pressure between the suction side and the discharge side of the compressor can be changed significantly according to the water temperature. When the two-stage compression operation is performed while the water temperature at an inlet of the water-cooling heat exchanger is low, the differential pressure between the compressor of the low stage 10a and the compressor of the high stage 10b is reduced. The amount of refrigerant oil to be returned is determined according to the differential pressure between the compressors. Accordingly, when the differential pressure between the compressor of the low stage 10a and the compressor of the high stage 10b is reduced in the middle of the two stage compression operation in this embodiment, a compression operation is changed to the operation of compression in one stage and the electromagnetic valve 25 is opened. In this way, the heat pump system 1 returns coolant oil to the oil equalization pipe 21 from the oil separator 26 through the bypass pipe 23 so that the refrigerant oil does not pass through the compressor of the high stage 10b. Accordingly, the differential pressure of the oil equalization mechanism 20 can always be maintained at a value equal to or greater than a preset value. Furthermore, since the heat pump system 1 can return oil to the compressor of the low stage 10a so that the oil does not pass through the fixed choke 27a provided on the oil return pipe 27 and the compressor of the stage high 10b, the reduction of the flow rate of the oil to be returned is prevented, which is caused by a loss of pressure generated in the fixed choke 27a or the compressor of the high stage 10b.

The heat pump system 1 changes a compression operation to the one-stage compression operation when the following conditions (1) to (3) are satisfied in the middle of the two-stage compression operation. All of the following conditions are indices of the reduction of the differential pressure between the compressor of the low stage 10a and the compressor of the high stage 10b. The pre-established values T ^r , AP ^r 1, and AP ^r 2 of conditions (1) to (3) are not determined uniquely but are determined in correspondence with the respective components and operating conditions of the heat pump system 1 to be applied. For its part, although not shown, a temperature sensor provided on the first heat exchanger 11 and pressure sensors provided on the compressor of the low stage 10a and the compressor of the high stage 10b detect the temperature T ^w of the water, a suction pressure P ^li , a discharge pressure P ^lo , and a discharge pressure P ^ho . The detected information is sent to a control device 30 shown in Fig. 1. The control device 30 determines conditions (1) to (3) by using the information about the temperature T ^w of the water, the pressure of aspiration P ^li , the discharge pressure P ^lo , and the discharge pressure P ^ho that have been acquired. The control device 30 continues to determine conditions (1) to (3) even in the middle of the one-stage compression operation.

(1) The temperature of the water entering the heat exchanger (water heat exchanger) for water and a refrigerant: T ^w ,

Prescribed value: T ^r

T ^w <T ^r

(2) The suction pressure of the compressor of the low stage 10a: P ^li

The compressor discharge pressure of the high stage 10b: P ^ho

Prescribed value: AP ^r 1

(P ^ho -P ^li ) <AP ^r1

(3) The compressor suction pressure of the low stage 10a: P ^li

The discharge pressure of the compressor of the low stage 10a: P ^lo

Prescribed value: AP ^r 2

(P ^lo -P ^li ) <AP ^r2

[Compression operation in two stages ^ one-stage compression operation]

When the control device 30 determines that any one of conditions (1) to (3) is satisfied in the middle of the two-stage compression operation, the control device 30 instructs the four-way switching valve 14 to to be changed to a position of the compression operation in a stage shown in Fig. 2B. Also, the control device 30 instructs the electromagnetic valve 25 to be opened. In this case, the heat pump system 1 operates as follows.

The high pressure refrigerant, which is discharged after the refrigerant is compressed at a high pressure by the compressor of the low stage 10a, flows into the first heat exchanger 11 through the pipeline L11, the four-way switching valve 14 and the line L5 and radiates heat to an object to be subjected to heat exchange. For its part, in this case, since the operating capacity of the compressor of the low stage 10a is higher than at the time of the two stage compression operation, the compressor of the low stage 10a compresses the refrigerant to a high pressure. Also, the compressor of the high stage 10b stops its operation. The high pressure refrigerant, which has radiated heat in the first heat exchanger 11, becomes a low pressure refrigerant as it is expanded as it passes through the expansion valve 12 through the pipeline L3. The low pressure refrigerant circulates further into the second heat exchanger 13 through the pipeline L3, absorbs heat from the outside air, and evaporates. After this, the low pressure refrigerant, which flows out of the second heat exchanger 13, is sucked into the compressor of the low stage 10a through the pipe L4.

Since the electromagnetic valve 25 is opened in a one-stage compression operation while repeating a cycle of compression, condensation, expansion and evaporation of the refrigerant described above, the refrigerant oil is returned to the oil equalization line. 21 through the branch pipe 23 without passing through the compressor of the high stage 10b. Accordingly, since the differential pressure of the oil equalization mechanism 20 can always be maintained at a value equal to or greater than a pre-set value, the level of refrigerant oil between the compressor of the low stage 10a and the compressor of the stage High 10b can be kept in balance.

The aforementioned heat pump system 1 has used the four-way switching valve 14 to change a compression operation between the two-stage compression operation and the one-stage compression operation, but the invention is not limited to the same As shown in Fig. 3, a heat pump system 2 includes two electromagnetic valves 14a and 14b which are arranged on pipes L1 and L5, respectively, and can change a compression operation between the two-stage compression operation and the one-stage compression operation by selectively controlling the opening and closing of the electromagnetic valves 14a and 14b. In the case of an example shown in Fig. 3, the two-stage compression operation is performed when the electromagnetic valve 14a is open and the electromagnetic valve 14b is closed, and the two-stage compression operation is performed when the valve is closed. electromagnetic 14a is closed and the electromagnetic valve 14b is open. On the other hand, the same components as the components of Fig. 1 are indicated in Fig. 3 by the same reference numbers as the reference numbers of Fig. 1. The same applies to Fig. 4.

Fig. 1 shows an example in which the oil separator 26 is provided so that it corresponds to both the compressor of the low stage 10a and the compressor of the high stage 10b. However, in a heat pump system 3 shown in Fig. 4, an oil separator 28 can be provided for the compressor of the low stage 10a in front of the four-way switching valve 14 on the discharge side of the 10a low stage compressor. The oil separator 28 is connected to the oil equalization pipe 21 through an oil return pipe 29.

Even in the middle of both the two-stage compression operation and the one-stage compression operation, the oil separator 26 separates the refrigerant oil from the refrigerant, which is discharged from the compressor of the low stage 10a, and returns the refrigerant oil to the compressor of the low stage 10a through the oil return pipe 29 and the oil equalization pipe 21. Accordingly, the heat pump system 3 shown in Fig. 4 can return efficiently the refrigerant oil to the compressor of the low stage 10a.

[Second realization]

A type of water heater / air conditioner heat pump 100 to which the heat pump system 1 is applied as a second embodiment of the invention will now be described.

As shown in Fig. 5, the water heater / air conditioner 100 includes a heat pump system 200 and a water system 300.

[Heat pump system 200]

The heat pump system 200 uses a circuit in which an oil separator 26 shown in the heat pump system 1 (Fig. 1) described in the first embodiment is provided, and exchanges heat between the outside air (external air). ) and a refrigerant. When the heat pump system 200 includes components corresponding to the heat pump system 1, the components are indicated by the same reference numbers as the reference numbers of the first embodiment and the description thereof will be omitted. However, the first heat exchanger 11 is replaced with a water-coolant heat exchanger 11. The water-coolant heat exchanger 11 heats the water of the water system 300 by heat exchange between the water and a coolant. Also, the second heat exchanger 13 is replaced with a heat exchanger on the side of the heat source 13. Furthermore, the heat pump system 200 includes the following components that are not included in the heat pump system 1.

The heat pump system 200 includes a four-way switching valve 15 between a line L2, which is provided on the discharge side of the compressor of the high stage 10b, and a line L4, which is provided on the side of the compressor. suction of the compressor of the low stage l0a, and can reverse the direction of circulation of a refrigerant through the four-way switching valve 15, so that any one of a refrigeration cycle (thawing cycle) in the that a refrigerant is circulated in a clockwise direction to the water-coolant heat exchanger 11 through the heat exchanger on the side of the heat source 13 and a heating cycle in which a refrigerant is circulated in the counter-clockwise direction to the heat exchanger on the side of the heat source 13 through the water-coolant heat exchanger 11.

The heat pump system 200 includes a first expansion valve 12a, an intermediate pressure receiver 16a, a supercooling coil 17, a second expansion valve 12b, and an accumulator 18 on a refrigerant circuit in addition to the heat exchanger. heat from the side of the heat source 13, the water-coolant heat exchanger 11, and the four-way switching valve 15. The first expansion valve 12a serves as a decompression means for controlling the temperature of a refrigerant at an outlet of the water-coolant heat exchanger 11, the intermediate pressure receiver 16a separates the refrigerant into a gas refrigerant and a liquid refrigerant, and the second expansion valve 12b decompresses a refrigerant at intermediate pressure. The accumulator 18 separates a liquid refrigerant that has not been evaporated by the heat exchanger on the side of the heat source 13.

Also, the heat pump system 200 includes an injection circuit 16 which includes an electromagnetic valve 16b, a check valve 16c, and an injection pipe 16d. The electromagnetic valve 16b injects the refrigerant gas at intermediate pressure, which is separated by the intermediate pressure receiver 16a, in an intermediate pressure refrigerant gas to be sucked into the compressor of the high stage 10b.

For its part, the electromagnetic valve 16b also serves as a valve for closing the injection circuit 16 so that no liquid refrigerant is supplied to the compressor of the high stage 10b at the time of activation in which the pressure receiver intermediate 16a is filled with a liquid refrigerant.

In addition, the heat pump system 200 includes a sub-line 121 which is provided in parallel to the oil equalizing line 21, and the sub-line 121 is provided with an electromagnetic valve 122. In the same way, the system of heat pump 200 includes a sub-pipe 127 which is provided in parallel to the return pipe 27, and the sub-pipe 127 is provided with an electromagnetic valve 128. For its part, each of the sub-pipes 121 and 127 is provided with a choke.

Since the quantity of refrigerant oil circulating through each of the oil equalizing pipes 21, and the return pipe 27 has a limit, the electromagnetic valves 122 and 128 of the sub-pipes 121 and 127 are opened when it is necessary to circulate a larger quantity of refrigerant oil.

[Water system 300]

The water system 300 includes a hot water circulation flow passage 301 in which the water circulated by a pump 307 absorbs heat from a refrigerant and is converted into hot water in the water-cooling heat exchanger 11 of the heat pump system 200 and using the hot water as the heat source for heating or the like by circulating the hot water between the charge side radiator (user side heat exchanger) 303 and the water-coolant heat exchanger 11. A heat storage tank 305, in which hot water is introduced from the hot water circulation flow passage 301 through a three-way switching valve 306 capable of adjusting a flow rate ratio and which can store the hot water As hot water heat storage, it is connected to the hot water circulation flow passage 301.

The heat storage tank 305 takes hot water from heat storage from an upper part thereof through the three-way switching valve 306, which is provided over the hot water circulation flow passage 301 through which the hot water heated by the water-cooling heat exchanger 11 is circulated to the radiator 303, and discharges the hot water of heat storage to the hot water circulation flow passage 301 at a required time.

Also, the heat storage tank 305 is provided with a sanitary water supply circuit (not shown) for supply of hot water to be supplied, which is heated by the heat of the stored storage hot water, and a heater electric (not shown) to which current is applied when necessary.

The water system 300 having the aforementioned configuration is adapted to selectively perform one of a heating operation in which hot water is supplied to the radiator 303 and an operation is carried out. heat storage in which hot water is supplied to the heat storage tank 305 by controlling the opening and closing of the three-way switching valve 306 to selectively change the three-way switching valve 306, and to simultaneously perform both the heating operation and the heat storage operation using hot water by distributing and supplying hot water to both the radiator 303 and the heat storage tank 305.

Furthermore, in the water system 300, the water, which is supplied from the storage tank 305 by the water circulation pump 307, as an object to be heated is carried out by heat exchange with the refrigerant of the pump system of the water pump 300. heat 200 in the water-coolant heat exchanger 11.

On the other hand, when the heating cycle is selected in the heat pump system 200, a refrigerant gas, having a low temperature and a low pressure, is compressed by the compression mechanism 10 (the compressor of the low stage). 10a and the compressor of the high stage 10b) and discharge to the heat pump system 200 as a gas refrigerant having a high temperature and a high pressure. As shown in FIG. 5 by the continuous line arrows, this gas refrigerant is guided to the water-coolant heat exchanger 11 by the four-way switching valve 14 and is circulated in the clockwise direction. In this case, the water-coolant heat exchanger 11 is a heat exchanger for heat exchange between the water, which is circulated by the water circulation pump 307, the water system 300 and a gas refrigerant having a high temperature. temperature and high pressure; and it functions as a condenser in which water is heated by the radiated heat of condensation due to condensation of the refrigerant. As a result, the gas refrigerant, which has a high temperature and a high pressure and circulates in the heat pump system 200, becomes a liquid refrigerant, which has a high temperature and a high pressure, when condensed; and the water, which circulates in the water system 300, absorbs heat from the refrigerant and becomes hot water.

The refrigerant, which condenses in the water-coolant heat exchanger 11, circulates into the intermediate pressure receiver 16a through the first expansion valve 12a which is fully open. The refrigerant is separated in a gas refrigerant and a liquid refrigerant in the intermediate pressure receiver 16a, and the separated gas refrigerant having an intermediate pressure is injected through the electromagnetic valve 16b and the non-return valve 16c with an intermediate pressure between the 10a low stage compressor and high 10b stage compressor.

For its part, the liquid refrigerant, which is separated by the intermediate pressure receiver 16a, passes through the supercooling coil 17 and becomes a gas-liquid two-phase refrigerant having a low temperature and a low pressure when it is decompressed by means of the second expansion valve 12b and is guided to the heat exchanger on the side of the heat source 13. The gas-liquid two-phase refrigerant, which is introduced into the heat exchanger on the side of the heat source 13 functioning as an evaporator, absorbs heat from outside air and vaporizes by exchanging heat with outside air.

A refrigerant gas, having a low temperature and a low pressure, is obtained when the gas-liquid two-phase refrigerant absorbs heat from the outside air and vaporizes as it passes through the heat exchanger side of the heat source. as described above, it is sucked into the compressor of the low stage 10a through the four-way switching valve 15 again. The gas refrigerant, which has a low temperature and a low pressure and is sucked into the compressor of the low stage 10a as described above, becomes a gas refrigerant, having a high temperature and a high pressure, at be compressed in phases by the compressor of the low stage 10a and the compressor of the high stage 10b; and repeatedly undergoes a gas-liquid phase change while being circulated along the same path as described below. In this case, moisture or the like in the air freezes on the outer periphery surface, having a low temperature, of the heat exchanger on the heat source side 13, so that a phenomenon of frost formation takes place.

Since the formation of frost inhibits the exchange of heat between the refrigerant and the outside air in the heat exchanger on the heat source side 13 and reduces the efficiency of the heat exchange, it is necessary to detect whether frost has accumulated or not and remove the frost by performing a de-icing operation at each of the appropriate operating moments. In the aforementioned heat pump system 200, the four-way switching valve 15 is switched to reverse the circulation direction of a refrigerant and to change a cycle to a refrigeration cycle (de-icing cycle) circulating the refrigerant in a direction indicated by the dashed line arrows of Fig. 6, a refrigerant gas, having a high temperature and a high pressure and discharged from the compressor of the high stage 10b, is introduced into the heat exchanger of the side of the heat source 13, and the frost attached to the heat exchanger on the side of the heat source 13 is melted by the heat (condensation heat) of the gas refrigerant. In this way, the de-icing operation is performed.

During the de-icing operation using the reverse cycle method, the water-cooling heat exchanger 11 functions as an evaporator, absorbs heat from the water circulating through the hot water circulation flow passage 301, vaporizes the refrigerant, and melts the frost, which is formed on the heat exchanger on the side of the heat source 13, by the use of heat. In this case, when the water temperature drops excessively, the water freezes in the water-coolant heat exchanger 11 and a risk of damage to the heat exchanger is generated. For this reason, it is necessary to prevent the water temperature, which is circulated in the water-coolant heat exchanger 11 and the evaporating temperature of the refrigerant, from being lowered excessively.

Also in the aforementioned water heater / air conditioner 100, a compression operation is changed to a one stage compression operation as in the first embodiment when the following conditions (1) to (3) are satisfied in the middle of the compression operation in two stages. The change is the same as that described with reference to Figs. 2A and 2B.

(1) The temperature of the water entering the heat exchanger (water heat exchanger) for water and a refrigerant: T ^w ,

Prescribed value: T ^r

T ^w <T ^r

(2) The suction pressure of the compressor of the low stage 10a: P ^li

The compressor discharge pressure of the high stage 10b: P ^ho

Prescribed value: AP ^r 1

(P ^ho -P ^li ) <AP ^r1

(3) The compressor suction pressure of the low stage 10a: P ^li

The discharge pressure of the compressor of the low stage 10a: P ^lo

Prescribed value: AP ^r 2

(P ^lo -P ^li ) <AP ^r2

[Compression operation in two stages ^ one-stage compression operation]

When a compression operation is changed to the one-stage compression operation, the high-pressure refrigerant, which is discharged after the refrigerant is compressed at a high temperature by the compressor of the low stage 10a, flows into the interior of the compressor. water-coolant heat exchanger 11 through pipeline L11, the four-way switching valve 14 and pipeline L5 and radiates heat to an object to be subjected to heat exchange. For its part, in this case, since the operating capacity of the compressor of the low stage 10a is higher than at the time of the two stage compression operation, the compressor of the low stage 10a compresses the refrigerant to a high pressure. Also, the compressor of the high stage 10b stops its operation.

[Third realization]

As shown in Fig. 8, a heat pump system 4 according to a third embodiment includes a compressor of the low stage 10a and a compressor of the high stage 10b which compresses and discharges a coolant, a first exchanger of heat 11 exchanging heat between the refrigerant compressed by the compressor of the high stage 10b and a fluid as an object to be subjected to heat exchange, an expansion valve 12 decompresses and expands the refrigerant flowing out of the first heat exchanger heat 11, and a second heat exchanger 13 which exchanges heat between the decompressed and expanded refrigerant by the expansion valve 12 and the fluid as an object to be subjected to heat exchange. The compressor of the low stage 10a, the compressor of the high stage 10b, the first heat exchanger 11, the expansion valve 12 and the second heat exchanger 13 are connected in series in this order in the direction of circulation of the refrigerant. In this embodiment, the first heat exchanger 11 can function as a condenser that radiates heat by thermal exchange with, for example, water and the second heat exchanger 13 can function as an evaporator that absorbs heat by thermal exchange with outside air .

Also, the heat pump system 4 includes an oil equalization mechanism 20 which keeps the amount of refrigerant oil held in the compressors on the side of the low and high stage 10a and 10b uniform. The details of the oil equalization mechanism 20, which are the features of this embodiment, will be described below.

The heat pump system 4 includes a line L1 connecting the compressor of the low stage 10a to the compressor of the high stage 10b, a line L2 connecting the compressor of the high stage 10b to the first heat exchanger 11, a pipe L3 connecting the first heat exchanger 11 to the second heat exchanger 13, and a pipe L4 connecting the second heat exchanger 13 to the compressor of the low stage 10a. Accordingly, the heat pump system 1 forms a refrigerant circuit in which a refrigerant circulates. Between the pipes, the pipe L4 forms a pipe on the suction side of the compressor of the low stage 10a, the pipe L1 connecting the compressor of the low stage 10a to the compressor of the high stage 10b forms an intermediate pressure pipeline , and the tubena L2 forms a tubena on the discharge side of the compressor of the high stage 10b.

For its part, the compressor of the low stage 10a and the compressor of the high stage 10b are referred to as a compression mechanism 10 without distinction between them.

The respective components of the heat pump system 4 will then be described one by one.

[Compression mechanism 10]

When the compressor of the low stage 10a is rotationally driven by an electric motor which is formed integrally with the compressor of the low stage 10a, the compressor of the low stage 10a sucks the coolant, which has passed through the second heat exchanger 13 and has a low temperature and low pressure, compresses the refrigerant to an intermediate pressure, and discharges the compressed refrigerant to the compressor of the high stage 10b.

A publicly known compression mechanism, such as the scroll compression mechanism or a rotary compression mechanism, can be applied as the compression mechanism that is applied to the compressor of the low stage 10a. In the same way, the same applies to the compressor of the high stage 10b.

The compressor of the high stage 10b sucks and compresses the refrigerant, which is discharged from the compressor of the low stage 10a, and discharges the compressed refrigerant to the first heat exchanger 11 as a refrigerant having a high temperature and a high pressure .

[First heat exchanger 11]

The first heat exchanger 11 heats the fluid, such as water or air, as an object to be subjected to heat exchange by exchanging heat between the fluid and a refrigerant having a high temperature and a high pressure. The refrigerant, which is discharged from the compressor of the high stage 10b and has a high temperature and a high pressure, is cooled and condensed in the first heat exchanger 11. A heat exchanger publicly known as the first heat exchanger can be used. heat 11. The same applies to the second heat exchanger 13 to be described below.

When an object to be subjected to thermal exchange is air, the first heat exchanger 11 is provided with a fan 11f and heat is exchanged between the air blown by the fan 11f and the refrigerant while the air driven by the fan 11f goes to through the first heat exchanger 11.

[Expansion valve 12 and second heat exchanger 13]

The second heat exchanger 13 exchanges heat between the refrigerant, which passes through the expansion valve 12 and decompresses and expands, and the outside air blown, and the refrigerant evaporates and absorbs heat from the outside air while exchanging heat between the refrigerant and the external air. The second heat exchanger 13 is also provided with a fan 13f and heat is exchanged between the air blown by the fan 13f and the refrigerant, so that the low pressure refrigerant evaporates and a heat absorbing operation is generated.

The expansion valve 12 is formed of, for example, an electronic expansion valve that includes a needle-shaped valve body and a pulse motor for actuating the valve body.

[Oil equalization mechanism 20]

The oil equalization mechanism 20 includes an oil equalizing pipe 21 which connects the compressor of the low stage 10a to the high stage compressor 10b, an oil equalization valve (all-nothing valve) 23 which is provided on the oil equalization pipe 21 and controls the flow of the refrigerant oil between the low stage compressor 10a and the high stage compressor 10b, a first temperature sensor 34 that is provided near the equalization pipeline of oil 21 and detects the temperature inside the oil equalizing pipe 21, and a second temperature sensor 35 that is provided near the pipe L2 and detects the temperature inside the pipeline L2.

The temperature information (detected temperature) T ⁰ and the temperature information (detected temperature) T ¹ , which are detected by the first temperature sensor 34 and the second temperature sensor 35, are transmitted to the control device 30. The device control 30 controls the opening / closing of the oil equalization valve 23 based on the temperature information T ⁰ and the temperature information T ¹ that are transmitted.

The oil equalizing mechanism 20 supplies a surplus of refrigerant oil from the compressor of the high stage 10b to the compressor of the low stage 10a or stops the supply of surplus refrigerant oil through the control of the opening / closing of the compressor. the oil equalization valve 23.

A level representing the amount of refrigerant oil, which is necessary for normal operation of each of the compressor of the low stage 10a and the compressor of the high stage 10b, is established and the oil equalization pipe 21 is it connects the compressor of the low stage 10a and the compressor of the high stage 10b in a position corresponding to the reference level. Likewise, it is preferable that each of the connecting ends of the oil equalizing pipe 21 is always submerged in the coolant oil.

When the oil equalization valve 23 of the oil equalizing pipe 21 is opened as shown in Fig. 9B, the refrigerant oil flows to the low stage compressor 10a from the high stage compressor 10b. The reason for this is that the pressure inside the compressor of the high stage 10b is greater than the pressure inside the compressor of the low stage 10a. For its part, in Fig. 9, the closed oil equalization valve 23 is represented as a black valve (Fig. 9A) and the open oil equalization valve 23 is represented as an empty valve (Fig. 9B). Also, in Fig. 9, the oil equalizing pipe 21 is shown by a continuous line when the coolant oil flows in the oil equalizing pipe, and the oil equalizing pipe 21 is shown by a discontinuous line when the coolant oil does not flow in the oil equalization pipe.

However, the flow of the refrigerant oil to the compressor of the low stage 10a from the compressor of the high stage 10b is based on the fact that the connecting end of the oil equalizing pipe 21 corresponding to the compressor of the High stage 10b is immersed in the refrigerant oil. When this premise is not satisfied, the oil equalization tube 21 serves as a passage for a refrigerant. Accordingly, a part of the refrigerant, which is compressed by the compressor of the high stage 10b, returns to the compressor of the low stage 10a. This means that the energy used to compress the refrigerant is wasted both in the compressor of the low stage 10a and in the compressor of the high stage 10b. Therefore, when the refrigerant oil does not flow into the oil equalizing pipe 21, it is preferable that the oil equalizing valve 23 be closed to close the oil equalizing pipe 21 as shown in Fig. 9A of Fig. 9A. so that a refrigerant does not flow to the compressor of the low stage 10a.

[Control device 30]

The control device 30 takes charge of the operation of the heat pump system 4, but controls in particular the opening / closing of the oil equalization valve 23 of the oil equalizing pipe 21 in this embodiment. The control device 30 acquires the temperature information T ⁰ and the temperature information T ¹ from the first and second temperature sensors to 34 and 35, respectively, to control the opening / closing of the oil equalization valve 23. The control device 30 determines the opening / closing of the oil equalization valve 23 through the comparison of the temperature information T ⁰ and the temperature information T ¹ that are acquired. That is, when the temperature of the refrigerant oil flowing in the oil equalizing pipe 21 is compared to the temperature of the refrigerant flowing in the pipe L2, the temperature of the refrigerant is significantly low. However, when coolant flows in place of the coolant oil in the oil equalizing pipe 21, a difference between the temperature information T ⁰ , which is detected in the oil equalization pipe 21, and the temperature information T ¹ , which is detected in the tubena L2, is reduced. Accordingly, the control device 30 can determine if the refrigerant oil is flowing in the oil equalizing pipe 21 or if the refrigerant is flowing in the oil equalizing pipe 21 through the comparison of the temperature information. T ⁰ and the temperature information T ¹ .

[Operation of heat pump system 4]

The operation of the heat pump system 4 will be described below.

In the heat pump system 4, a refrigerant circulates and a compression refrigeration cycle is carried out in two stages.

In the heat pump system 4, the refrigerant, which is discharged from the compressor of the high stage 10b and has a high temperature and a high pressure, flows into the interior of the first heat exchanger 11 through the pipeline L2 and radiates heat to an object to be subjected to heat exchange. The refrigerant, which has radiated heat in the first heat exchanger 11, becomes a low pressure refrigerant as it is expanded as it passes through the expansion valve 12 through the line L3. The low pressure refrigerant circulates further into the second heat exchanger 13 through the pipeline L3, absorbs heat from the outside air, and evaporates. After this, the low pressure refrigerant, which flows out of the second heat exchanger 13, is sucked into the compressor of the low stage 10a through the pipe L4.

After the low pressure refrigerant, which is sucked into the compressor of the low stage 10a, is compressed and becomes an intermediate pressure refrigerant, the intermediate pressure refrigerant is discharged to the line L1. The intermediate pressure refrigerant, which is discharged to the line L1 from the compressor of the low stage 10a, is sucked into the compressor of the high stage 10b. After the refrigerant, which is sucked into the compressor of the high stage 10b, is compressed and becomes a high coolant. pressure, the high pressure refrigerant is discharged to the L2 pipe.

The heat pump system 4 alternately repeats an operation in which the oil equalization valve 23 is closed during a closing period tw and an operation in which the oil equalization valve 23 is opened during a period of equalization of the oil. tm oil while repeating a cycle of compression, condensation, expansion and evaporation of the refrigerant described above. This embodiment is characterized in that the oil equalization valve 23 is forcedly closed even during the oil equalization period tm. An operation procedure for opening / closing the oil equalization valve 23 will be described below with reference to Fig. 10.

As shown in Fig. 10, the control device 30 instructs the oil equalization valve 23 to be closed (OFF) as the initial setting at which the heat pump system 4 is instructed to start operation ( S101 of Fig. 10). When the oil equalization valve 23 is closed from the beginning, the process continues as it is.

The control device 30 measures a time t elapsed after the heat pump system 4 is instructed to start operation, and the control device 30 instructs the oil equalization valve 23 to open (CONNECT) when the elapsed time t reaches a predetermined closing period tw (S103 of Fig. 10). When the elapsed time reaches a predetermined closing period tm after the instruction control device 30 to the oil equalization valve 23 to open, the control device 30 instructs the oil equalization valve 23 to close ( S111 of Fig. 10). The operation in which the oil equalization valve 23 of the first embodiment is closed during a closing period tw and the operation in which the oil equalization valve 23 of the first embodiment is opened during a period of oil equalization tm are repeated alternately as described above.

However, the control device 30 has two exceptions to be described below in relation to the opening / closing of the oil equalization valve 23.

First, the control device 30 determines whether or not the heat pump system 4 is performing a stable operation. If the heat pump system 4 is performing a stable operation, the procedure proceeds to the determination of the second exception (Sf in step 105, S107). However, if the heat pump system 4 is not performing a stable operation, the oil equalization valve 23 is kept closed (Not in S105 of Fig. 10). In this case, the case of an unstable operation, which does not correspond to a stable operation, corresponds to a case in which, for example, a de-icing operation is carried out. The reason for this is that there is a concern about the premise of this embodiment that the temperature of the refrigerant oil flowing through the oil equalization valve 23 is higher than the temperature of the refrigerant sucked into the interior of the oil compressor. High stage 10b may not be satisfied during the unstable operation. Likewise, the primitive stage of the activation of the heat pump system 4 also corresponds to an unstable operation, but the primitive stage of the activation is considered as the closure period tw previously mentioned in this embodiment.

Next, as the second exception, the control device 30 compares the rotation speed R of the compressor of the high stage 10b with a predetermined rotation speed R ⁰ (S107 of Fig. 10); and the control device 30 instructs the oil equalization valve 23 to open (CONNECT) and close (OFF) alternately and repeatedly at each of the predetermined times (Sf in S107 of Fig. 10, S108) if the Rotation speed R is smaller than the speed of rotation R ⁰ .

In a case not corresponding to the two abovementioned exceptions, the control device 30 instructs the oil equalization valve 23 to open (S109 of FIG. 10). After receiving this instruction, the oil equalization valve 23 is kept open during the oil equalization period tm (S111 of Fig. 3).

During this period, the control device 30 determines whether a difference (T ⁰ -T ¹ ) between the temperature information T ⁰ , which is acquired from the first temperature sensor 34, and the temperature information T ¹ , which is acquired from the second temperature sensor 35, it is equal to or smaller than a predetermined value AT (S113 of Fig. 10). In this case, the temperature information T ⁰ is considered as the temperature of the fluid (refrigerant oil or a refrigerant) flowing in the separation pipe of the oil 21 and the temperature information T ¹ is considered as the temperature of the refrigerant aspirated inside the compressor of the high stage 10b.

If the difference (T ⁰ -T ¹ ) is equal to or less than AT, the control device 30 determines that the refrigerant instead of the refrigerant oil is flowing in the oil evaluation pipe 21 and closes the oil equalization valve 23 (If in S113 of Fig. 10). On the other hand, if the difference (T ⁰ -T ¹ ) exceeds AT, the oil equalization valve 23 remains open until the oil equalization period tm ends. If the oil equalization period tm ends, the oil equalization valve 23 is closed (Not in S113 and Si in S111 Si of Fig. 10).

As described above, according to this embodiment, it is possible to supply refrigerant oil to the low stage from the high stage and equalize the refrigerant oil from both the low stage compressor 10a and the stage compressor. high 10b by a simple opening / closing operation of the oil equalization valve 23 without stopping the operation of the compressor of the low stage 10a or the compressor of the high stage 10b. Furthermore, according to this embodiment, when the control device 30 determines that a refrigerant is flowing instead of a refrigerant oil in the oil equalization pipe 21, the control device 30 closes the oil equalization valve 23. Accordingly, it is possible to avoid the wasteful use of the compression mechanism 10 which is caused when the refrigerant circulates in the oil equalizing pipe 21. The invention has been described above on the basis of the embodiments, but the components described in the embodiments The aforementioned can be appropriately selected or appropriately substituted with other components without departing from the essence of the invention.

In the above description, the general opening / closing of the oil equalization valve 23 has been controlled by the closing period tw and the oil equalization period tm. However, the invention is not limited thereto. The temperature information T ⁰ and the temperature information T ¹ can be used as conditions that are necessary to open the oil equalization valve 23. That is, as shown in Fig. 11, the oil equalization valve 23 can opening (step 203 and step 109 of FIG. 11) when T ⁰ -T ¹ exceeds AT, and the oil equalization valve 23 can be closed (step 113 and step S101 of FIG. 11) when T ⁰ -T ¹ is equal to or less than AT.

Likewise, the temperature information, to be compared with the temperature information T ⁰ , is not limited to the temperature information T ¹ , and the temperature information T ⁰ , can be compared to a detected temperature (temperature information) T ² of the high 10b stage compressor. One difference, which is obtained in this case, is T ² -T ⁰ , and the control device 30 determines that a coolant is flowing in the oil equalization pipe 21 when the difference is equal to or less than a predetermined ATT value. For its part, the temperature of the compressor of the high stage 10b is detected in a low zone of the compressor of the discharge stage in which the refrigerant oil is stored.

[Fourth realization]

A type of water heater / air conditioner heat pump 100 to which the heat pump system 4 described as the first embodiment, as a fourth embodiment of the invention, is applied will now be described.

As shown in Figs. 12 and 13, the water heater / 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 exchanges heat between the outside air (external air) and a coolant. When the heat pump system 200 includes components corresponding to the heat pump system 4, the components are indicated by the same reference numbers as the reference numbers of the third embodiment and the description thereof will be omitted. However, the first heat exchanger 11 is replaced with a water-cooling heat exchanger 11. The water-cooling heat exchanger 11 heats the water of the water system 300 by heat exchange between the water and a refrigerant. Also, the second heat exchanger 13 is replaced with a heat exchanger on the side of the heat source 13. Furthermore, the heat pump system 200 includes the following components that are not included in the heat pump system 4.

The heat pump system 200 includes a four-way switching valve 15 between a line L2, which is provided on the discharge side of the compressor of the high stage 10b, and a line L4, which is provided on the side of the compressor. suction of the compressor of the low stage 10a, and can reverse the direction of circulation of a refrigerant by means of the four-way switching valve 15, so that any one of a refrigeration cycle (thawing cycle) in the that a refrigerant is circulated in a clockwise direction to the water-coolant heat exchanger 11 through the heat exchanger on the side of the heat source 13 and a heating cycle in which a refrigerant is circulated in the counter-clockwise direction to the heat exchanger on the side of the heat source 13 through the water-coolant heat exchanger 11.

The heat pump system 200 includes an expansion valve 12a for cooling, an expansion valve 12b for heating, and a receiver 39 as a throttling mechanism, in addition to the heat exchanger on the side of the heat source 13, the exchanger of water-cooling heat 11, and the four-way switching valve 15. The expansion valve 12a for cooling and the expansion valve 12b for heating are arranged in series with the receiver 18 interposed therebetween.

Also, the heat pump system 200 includes an economizer circuit 36 that is provided on the pipeline L3. The economizer circuit 36 includes a heat exchanger 36a for an economizer, an expansion valve 36b for an economizer, and an injection tube 36c. After a portion of the liquid refrigerant that has passed through the water-coolant heat exchanger 11 is introduced into the heat exchanger 36a for an economizer through the expansion valve 36b for an economizer and evaporated by exchanging heat with a liquid refrigerant flowing in the pipeline L3, a gas refrigerant is injected to the intermediate pressure pipeline L1, which is provided between the compressor of the low stage 10a and the compressor of the high stage 10b, through the injection tube 36c.

In addition, the heat pump system 200 includes an oil separator 37 that is provided on the discharge side of the compressor of the low stage 10a and an oil separator 38 that is provided on the discharge side of the stage compressor. high 10b. The refrigerant oil, which is contained in the refrigerant discharged from the compressor of the low stage 10a, is separated from the refrigerant by the oil separator 37 and returned to the compressor of the low stage 10a through a return pipeline. 37L. In the same way, the refrigerant oil, which is contained in the refrigerant discharged from the compressor of the high stage 10b, is separated from the refrigerant by the oil separator 38 and is returned to the compressor of the high stage 10b through of a return pipe 38L.

[Water system 300]

The water system 300 includes a hot water circulation flow passage 301 in which the water circulated by a water circulation pump 307 absorbs heat from a refrigerant in the water-cooling heat exchanger 11 of the heat pump system 200 and converted to hot water and using the hot water as a heat source for heating or the like by circulating the hot water between the charge side radiator 303 and the water-coolant heat exchanger 11. A storage tank of heat 305, in which hot water is introduced from the hot water circulation flow passage 301 through a three-way switching valve 306 capable of adjusting a flow rate ratio and which can store the hot water as hot water of heat storage, is connected to the hot water circulation flow passage 301.

The heat storage tank 305 takes hot water from heat storage from an upper part thereof through the three-way switching valve 306, which is provided over the hot water circulation flow passage 301 through which the hot water heated by the water-cooling heat exchanger 11 is circulated to the radiator 303, and discharges the hot water of heat storage to the hot water circulation flow passage 301 at a required time.

Also, the heat storage tank 305 is provided with a sanitary water supply circuit (not shown) for supply of hot water to be supplied, which is heated by the heat of the stored storage hot water, and a heater electric (not shown) to which current is applied when necessary.

The water system 300 having the aforementioned configuration is adapted to selectively perform one of a heating operation in which hot water is supplied to the radiator 303 and a heat storage operation in which hot water is supplied to the tank. heat storage 305 by selectively changing the three-way switching valve 306, and for simultaneously performing both the heating operation and the heat storage operation using hot water by distributing and supplying hot water to both the radiator 303 and to the heat storage tank 305. Furthermore, in the water system 300, the water, which is supplied from the storage tank 305 by the water circulation pump 307, as an object to be heated is carried out by heat exchange with the coolant of the heat pump system 200 in the water-coolant heat exchanger 11.

On the other hand, when the heating cycle is selected in the heat pump system 200, a refrigerant gas, having a low temperature and a low pressure, is compressed by the compression mechanism 10 (the compressor of the low stage). 10a and the compressor of the high stage 10b) and discharge to the heat pump system 200 as a gas refrigerant having a high temperature and a high pressure. As shown in Fig. 12 by the continuous line arrows, this gas refrigerant is guided to the water-cooling heat exchanger 11 by the four-way switching valve 15 and is circulated counter-clockwise. In this case, the water-coolant heat exchanger 11 is a heat exchanger for heat exchange between the water, which is circulated by the water circulation pump 307, the water system 300 and a gas refrigerant having a high temperature. temperature and high pressure; and it functions as a condenser in which water is heated by the radiated heat of condensation due to condensation of the refrigerant. As a result, the gas refrigerant, which has a high temperature and a high pressure and circulates in the heat pump system 200, becomes a liquid refrigerant, which has a high temperature and a high pressure, when condensed; and the water, which circulates in the water system 300, absorbs heat from the refrigerant and It turns into hot water.

The refrigerant, which is condensed by the water-coolant heat exchanger 11, flows into the receiver 39 through the expansion valve 12a for cooling that is fully open. In the receiver 39, the refrigerant is separated into a refrigerant gas and a liquid refrigerant and the amount of refrigerant in circulation is adjusted. The expansion valve 12b for heating, which decompresses a liquid refrigerant having a high temperature and a high pressure, is disposed on the downstream side of the receiver 39. The liquid refrigerant having a high temperature and a high pressure becomes a gas-liquid two-phase refrigerant having a low temperature and a low pressure when being decompressed while the refrigerant passes through the expansion valve 12b for heating. Then, the gas-liquid two-phase refrigerant is guided to the heat exchanger on the side of the heat source 13. The gas-liquid two-phase refrigerant, which is introduced into the heat exchanger on the side of the heat source 13 functioning as an evaporator, it absorbs heat from outside air and vaporizes by exchanging heat with outside air.

A refrigerant gas, having a low temperature and a low pressure, is obtained when the gas-liquid two-phase refrigerant absorbs heat from the outside air and vaporizes as it passes through the heat exchanger side of the heat source. as described above, it is sucked into the compressor of the low stage 10a through the four-way switching valve 15 again. The gas refrigerant, which has a low temperature and a low pressure and is sucked into the compressor of the low stage 10a as described above, becomes a gas refrigerant, having a high temperature and a high pressure, at be compressed in phases by the compressor of the low stage 10a and the compressor of the high stage 10b; and repeatedly undergoes a gas-liquid phase change while being circulated along the same path as described below. In this case, moisture or the like in the air freezes on the outer periphery surface, having a low temperature, of the heat exchanger on the heat source side 13, so that a phenomenon of frost formation takes place.

Since the formation of frost inhibits the exchange of heat between the refrigerant and the outside air in the heat exchanger on the heat source side 13 and reduces the efficiency of the heat exchange, it is necessary to detect whether frost has accumulated or not and remove the frost by performing a de-icing operation at each of the appropriate operating moments. In the aforementioned heat pump system 200, the four-way switching valve 15 is switched to reverse the circulation direction of a refrigerant and to change a cycle to the refrigeration cycle (de-icing cycle) circulating the refrigerant in a direction indicated by the dot and line line arrows of Fig. 13, a refrigerant gas, which has a high temperature and a high pressure and is discharged from the compressor of the high stage 10b, is introduced into the exchanger of heat from the side of the heat source 13, and the frost adhered to the heat exchanger on the side of the heat source 13 is melted by the heat (condensation heat) of the gas refrigerant. In this way, the de-icing operation is performed.

During the de-icing operation using the reverse cycle method, the water-cooling heat exchanger 11 functions as an evaporator, absorbs heat from the water circulating through the hot water circulation flow passage 301, vaporizes the refrigerant, and melts the frost, which is formed on the heat exchanger on the side of the heat source 13, by the use of heat. In this case, when the water temperature drops excessively, the water freezes in the water-coolant heat exchanger 11 and a risk of damage to the heat exchanger is generated. For this reason, it is necessary to prevent the water temperature, which is circulated in the water-coolant heat exchanger 11 and the evaporating temperature of the refrigerant, from becoming excessively low.

Even in the aforementioned water heater / air conditioner 100, the opening / closing of the oil equalization valve 23 provided between the compressor of the low stage 10a and the compressor of the high stage 10b is controlled as in FIG. first realization Accordingly, according to the water heater / air conditioner 100 of this embodiment, it is possible to equalize the refrigerant oil of the compressor of the low stage 10a and the compressor of the high stage 10b by a simple opening / closing operation of the oil equalization valve 23 without stopping the operation of the compressor of the low stage 10a or the compressor of the high stage 10b.

The invention has been described above on the basis of the embodiments, but the components described in the aforementioned embodiments may be appropriately selected or appropriately substituted with other components without departing from the essence of the invention.

List of reference signs

1, 2, 3, 4: heat pump system

10th: low stage compressor

10b: high stage compressor

11: first heat exchanger, water-coolant heat exchanger

11f: fan

12: expansion valve

12a: first expansion valve, expansion valve for cooling

12b: second expansion valve, expansion valve for heating

13: second heat exchanger, heat exchanger on the side of the heat source 13f: fan

14, 15: four-way switching valve

14a, 14b: electromagnetic valve

16: injection circuit

16a: intermediate pressure receiver

16b: electromagnetic valve

16c: non-return valve

16d: injection tube

17: super-refrigeration serpentm

18: accumulator

20: oil equalization mechanism

21: oil equalization pipe

23: oil equalization valve

25: electromagnetic 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 for an economizer

36b: expansion valve for an economizer

36c: injection tube

37, 38: oil separator

37L, 38L: return tube

39: receiver

100: water heater / air conditioner

121, 127: sub-tubena

122, 128: electromagnetic valve

200: heat pump system

300: water system

301: flow passage of hot water

303: radiator

305: heat storage tank

306: Three-way switching valve

307: water circulation pump

L1, L11, L12, L2, L3, L4, L5:

Claims (4)

1. A heat pump system (1; 2; 3) comprising: a compression mechanism including a compressor of the low stage (10a) and a compressor of the high stage (10b) configured to compress and discharge a refrigerant; an oil separator (26) that is provided on a discharge side of the compressor of the discharge stage (10b); a first heat exchanger (11) configured to exchange heat between the refrigerant compressed by the compression mechanism and an object to be subjected to heat exchange; an expansion valve (12) configured to decompress and expand the refrigerant circulating outside the first heat exchanger (11); a second heat exchanger (13) configured to exchange heat between the decompressed and expanded refrigerant by the expansion valve (12) and an object to be subjected to heat exchange; Y a main return pipe (27) connecting the oil separator (26) to a suction side of the compressor of the discharge stage (10b); characterized in that it comprises an oil equalization path (21) which connects the compressor of the low stage (10a) to the compressor of the high stage (10b) configured to allow the refrigerant oil to flow between the compressor of the low stage (10a) ) and the compressor of the high stage (10b); a return path of the oil (23) connecting the main return lines (27) to the oil equalization path (21); an all-nothing oil return valve (25) that is provided on the return path of the oil (23); Y a refrigerant path change mechanism (14) configured to selectively change a refrigerant path between a two stage compression path along which the refrigerant circulates through the compressor of the low stage (10a) and the compressor of the high stage (10b) in this order and a compression stroke in a stage along which the refrigerant circulates through only one of the compressor of the low stage and the compressor of the high stage, a control device (30) configured to instruct the refrigerant path change mechanism (14) and the all-nothing oil return valve (25) so that when the control device (30) instructs the mechanism of change of the refrigerant path (14) to select the compression path in one step, the control device (30) instructs the all-nothing return valve of the oil (25) to be opened and the refrigerant oil from the oil separator (26) is returned to the oil equalization path (21) through the return path of the oil (23) without passing through the compressor of the discharge stage (10b). 2. The heat pump system (1; 2; 3) according to claim 1, wherein when the two-stage compression path is selected and any one of the following conditions (1) to (3) is satisfied, the control device (30) is configured to change the refrigerant path to the compression path in one stage Condition (1): T ^w ^ T ^r T ^w : The temperature of the water entering a heat exchanger (water heat exchanger) for the water and the refrigerant when the object, which has to be subjected to heat exchange, of the first heat exchanger is water T ^r : Prescribed value Condition (2): (P ^ho -P ^li ) ² AP ^r 1 P ^li : The compressor suction value of the low stage P ^ho : The compressor discharge pressure of the high stage AP ^r 1: Prescribed value Condition (3): (P ^lo -P ^l 1) ^ AP ^r 2 P ^li : The compressor suction value of the low stage P ^lo : The compressor discharge value of the low stage AP ^r 2: Prescribed value 3. The heat pump system (1; 2; 3) according to claim 1 or 2, wherein the control device (30) is configured to control the opening / closing of the all-over valve of the return oil (25) based on an estimated amount of refrigerant oil from the compressor of the low stage (10a) and an estimated amount of compressor refrigerant oil from the high stage (10b). 4. A heat pump water heater comprising: the first heat exchanger (11) of the heat pump system (1; 2; 3) according to any one of the claims 1 to 3 which is a water-coolant heat exchanger for heating water by exchanging heat between the coolant and water.