JP2022096824A - Heat pump cycle device - Google Patents

Abstract

To provide a heat pump cycle device capable of accurately performing control of a refrigerant supercooling degree during a heating operation.SOLUTION: A heat pump cycle device in one embodiment of the present invention includes a refrigerant circuit, a discharge pressure sensor, a refrigerant temperature sensor and a control unit. The control unit includes: a calculation section calculating a refrigerant supercooling degree on the basis of discharge pressure that is pressure of a refrigerant discharged from a compressor and a temperature before an expansion valve that is a temperature of the refrigerant flowing out from a use side heat exchanger during a heating operation; an adjustment section adjusting an opening of the expansion valve so that the calculated refrigerant supercooling degree becomes a predetermined target refrigerant supercooling degree; and a correction section increasing the target refrigerant supercooling temperature by a predetermined value when the opening of the expansion valve is larger than a predetermined threshold opening.SELECTED DRAWING: Figure 7

Description

The present invention relates to a heat pump cycle device such as a heat pump type hot water supply device, a heat pump type hot water heating device, and a heat pump type hot / cold water air conditioner.

Conventionally, a heat pump cycle device has a refrigerant circuit in which a compressor, a four-way valve, a heat exchanger on the user side, an expansion valve, and an outdoor heat exchanger, which is a heat exchanger on the heat source side, are sequentially connected by piping. ing. When performing heating operation or hot water supply operation with this heat pump cycle device, the refrigerant circuit becomes a heating cycle, and the refrigerant that has become high temperature and high pressure gas compressed by the compressor passes through the four-way valve and heats in the heat exchanger on the user side. Is released to become a liquid refrigerant, and after being depressurized by the expansion valve, it evaporates in the outdoor heat exchanger to exchange heat with the outdoor air, becomes gas, and is compressed again by the compressor. During the cooling / defrosting operation, the refrigerant circuit has a cooling cycle in which the four-way valve is switched and the flow is in the direction opposite to the flow of the refrigerant described above.

When the heating operation is performed by such a heat pump cycle device, a method of controlling the opening degree of the expansion valve according to the magnitude of the degree of supercooling of the refrigerant (hereinafter, may be referred to as supercooling control) is known. There is. The degree of refrigerant supercooling is generally the degree of refrigerant that flows out of the user side heat exchanger and flows to the expansion valve from the condensation temperature of the refrigerant in the user side heat exchanger (corresponding to an indoor heat exchanger or a water refrigerant heat exchanger). Calculated by reducing the temperature. As a method of adjusting the opening degree of the expansion valve, the calculated refrigerant supercooling degree is compared with the target refrigerant supercooling degree which is a value necessary for the heat pump cycle device to exhibit the intended heating capacity. When the degree of supercooling of the refrigerant is larger than the target degree of supercooling of the refrigerant, the opening degree of the expansion valve is increased, and when the degree of supercooling of the refrigerant is smaller than the target degree of supercooling of the refrigerant, the opening degree of the expansion valve is decreased. The temperature of the refrigerant flowing out of the heat exchanger on the user side and flowing to the expansion valve is detected by a temperature sensor arranged in the refrigerant pipe connecting the heat exchanger on the user side and the expansion valve.

However, the liquid refrigerant flowing from the user-side heat exchanger to the expansion valve during the heating operation is gas-liquid due to the pressure loss of the refrigerant in the refrigerant pipe (liquid pipe) connecting the user-side heat exchanger and the expansion valve. It may be in a two-phase state. The value of the pressure loss of the refrigerant varies depending on the length of the pipe and the amount of foreign matter accumulated in the pipe, and the pressure drop due to the pressure loss causes the refrigerant to be in a gas-liquid two-phase state, and the refrigerant temperature is higher than the liquid-phase state refrigerant temperature. The temperature will be low. Then, when the temperature sensor described above is arranged in the vicinity of the expansion valve in the refrigerant pipe connecting the user side heat exchanger and the expansion valve, if the refrigerant temperature decreases due to the pressure loss, the reduced refrigerant temperature is used. The degree of refrigerant supercooling calculated by the above method is larger than that when the pressure loss is small. When the temperature sensor is arranged in the vicinity of the expansion valve in the refrigerant pipe connecting the user side heat exchanger and the expansion valve, for example, a compressor, a four-way valve, an expansion valve, and a heat source side heat exchanger are used. This is a case where a temperature sensor is provided in the outdoor unit in a heat pump cycle device in which the outdoor unit having the outdoor unit and the indoor unit having the heat exchanger on the user side are connected by a refrigerant pipe.

Generally, the target refrigerant overcooling degree is determined on the assumption that the refrigerant flowing out of the heat exchanger on the user side and flowing into the expansion valve is in a liquid phase state, that is, the temperature of the refrigerant due to pressure loss. Determined without taking into account the decline. Therefore, if the calculated refrigerant supercooling degree becomes large due to the influence of pressure loss, the refrigerant supercooling degree is smaller than the target refrigerant supercooling degree as compared with the case where the refrigerant flowing into the expansion valve is in the liquid phase state. The heat pump cycle device even if the expansion valve supercooling control is performed because the opening of the expansion valve is not reduced, or because the opening of the expansion valve is too large when the refrigerant supercooling degree is larger than the target refrigerant supercooling degree. There is a risk that the intended heating capacity cannot be achieved.

As the overcooling degree control in consideration of the pressure loss described above, for example, in Patent Document 1, the pressure for calculating the pressure loss between the compressor and the indoor heat exchanger from the value of the frequency sensor that detects the operating frequency of the compressor. The pressure loss calculated by the pressure loss calculator is subtracted from the discharge pressure, which is the pressure of the refrigerant discharged from the loss calculator and the compressor, and the saturation temperature corresponding to the pressure obtained by subtracting the pressure loss from the discharge pressure is calculated. A corrected overcooling degree calculator that calculates the degree of overcooling of the indoor heat exchanger by subtracting the temperature of the refrigerant flowing out of the indoor heat exchanger from the saturation temperature calculated by the corrected saturation temperature calculator and the corrected saturation temperature calculator. And an air exchanger equipped with an expansion valve controller that controls the opening degree of the expansion valve by comparing the overcooling degree calculated by the corrected overcooling degree calculator with the preset overcooling degree. Has been done.

Japanese Unexamined Patent Publication No. 9-280681

By the way, when the refrigerant flowing out of the user-side heat exchanger and flowing into the expansion valve is in a gas-liquid two-phase state, the larger the opening of the expansion valve, that is, the expansion valve from the user-side heat exchanger. The greater the amount of refrigerant flowing into, the greater the pressure loss that the refrigerant receives. At this time, the refrigerant temperature flowing to the expansion valve becomes the maximum value at any opening between the minimum opening and the maximum opening of the expansion valve, the refrigerant cooling degree becomes the minimum value, and the refrigerant cooling degree becomes the minimum value. As the opening becomes larger than the opening, the temperature of the refrigerant flowing to the expansion valve due to the pressure loss becomes lower, and the degree of refrigerant overcooling becomes larger. Therefore, when the opening degree of the expansion valve is larger than the opening degree at which the refrigerant cooling degree becomes the minimum value and the refrigerant supercooling degree is larger than the target refrigerant supercooling degree, the refrigerant supercooling degree is set to the target refrigerant supercooling degree. Even if the opening degree of the expansion valve is increased to bring it closer, the degree of refrigerant supercooling does not decrease due to the increase in pressure loss. Further, even if the expansion valve reaches the maximum opening degree, the refrigerant supercooling degree does not reach the target refrigerant supercooling degree, and there is a problem that the intended heating capacity cannot be exhibited.

In view of the above circumstances, an object of the present invention is to provide a heat pump cycle device capable of appropriately controlling the degree of supercooling by reducing the influence of the pressure loss of the refrigerant during the heating operation.

In order to achieve the above object, the heat pump cycle device according to one embodiment of the present invention includes a refrigerant circuit, a discharge pressure sensor, a refrigerant temperature sensor, and a control unit.
The refrigerant circuit includes a compressor, a user-side heat exchanger, a heat source-side heat exchanger, an expansion valve arranged between the user-side heat exchanger and the heat source-side heat exchanger, and the compressor. It has a flow path switching valve for switching the flow direction of the refrigerant discharged from.
The discharge pressure sensor detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor.
The refrigerant temperature sensor measures the temperature before the expansion valve, which is the temperature of the refrigerant flowing out of the user-side heat exchanger during the heating operation in which the flow direction of the refrigerant discharged from the compressor is the user-side heat exchanger. To detect.
The control unit includes a calculation unit that calculates a refrigerant supercooling degree based on the discharge pressure and the temperature before the expansion valve, and the expansion so that the calculated refrigerant supercooling degree becomes a predetermined target refrigerant supercooling degree. It has an adjusting unit for adjusting the opening degree of the valve and a correction unit for increasing the target refrigerant supercooling temperature by a predetermined value when the opening degree of the expansion valve is larger than a predetermined threshold opening degree.

The predetermined threshold opening is such that the opening degree in which the refrigerant supercooling degree is larger than the target opening degree to be the target refrigerant supercooling degree and the refrigerant supercooling degree in the opening region larger than the opening degree are the targets. It may be any opening between the opening degree and the degree of refrigerant supercooling.

Further, the correction value of the target refrigerant supercooling degree may be set so that the refrigerant supercooling degree is always smaller than the corrected target refrigerant supercooling degree.

According to the present invention, it is possible to appropriately control the degree of supercooling by reducing the influence of the pressure loss of the refrigerant during the heating operation.

It is a schematic block diagram which shows the heat pump type hot water heating apparatus which is the heat pump cycle apparatus of this embodiment. It is a block diagram which shows the structure of a control unit. This is a typical example showing the relationship between the degree of supercooling and the opening degree of the expansion valve. It is explanatory drawing which shows the relationship between the pressure loss, the opening degree of an expansion valve, and the length of a liquid pipe. It is explanatory drawing which shows the relationship between the degree of supercooling and the opening degree of an expansion valve when the refrigerant in a liquid pipe is in a gas-liquid two-phase state. It is a figure which shows the experimental example at the time of the trouble that the refrigeration cycle control cannot be performed occurs. It is a figure which shows the relationship between the supercooling degree and the expansion valve opening degree for demonstrating the operation of a correction part. It is a flowchart which shows an example of the processing procedure executed by a control unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a heat pump type hot water heating device which is the heat pump cycle device of the present embodiment.

[Heat pump type hot water heater]
As shown in FIG. 1, the heat pump type hot water heating device 100 includes a refrigerant circuit 10, a hot water circuit 20, and a control unit 60. In the refrigerant circuit 10, the compressor 1, the four-way valve 2, the water refrigerant heat exchanger 3 that exchanges heat between the refrigerant and water, the expansion valve 4, the heat source side heat exchanger 5, and the accumulator 6 are used. They are connected in order by the refrigerant pipe 11. In the hot water circuit 20, the water-refrigerant heat exchanger 3, the flow meter 31, the indoor unit (hot water unit) 40 as the user-side unit, and the circulation pump 30 are connected in order by the water pipe 16. Further, the heat pump type hot water heating device 100 includes an outdoor fan 90 that blows outdoor air to the heat source side heat exchanger 5, a temperature sensor 58 that detects the temperature of water in the water refrigerant heat exchanger 3, and a temperature sensor 59.

Here, the compressor 1, the four-way valve 2, the expansion valve 4, the heat source side heat exchanger 5, and the accumulator 6 are housed in the outdoor unit, and the water-refrigerant heat exchanger 3 and the indoor unit 40 are housed in the indoor unit. Between these outdoor units and the indoor unit, there is a liquid pipe 3A which is a refrigerant pipe connecting between the water refrigerant heat exchanger 3 and the expansion valve 4, and between the four-way valve 2 and the water refrigerant heat exchanger 3. It is connected to the gas pipe 3B, which is a connecting refrigerant pipe.

(Construction of refrigerant circuit)
The compressor 1 is driven by a motor (not shown) whose rotation speed is controlled by an inverter. The compressor 1 is a capacity variable compressor having a variable operating capacity. The four-way valve 2 is a flow path switching valve that switches the refrigerant circulation direction in the refrigerant circuit 10. The water-cooled heat exchanger 3 exchanges heat between the refrigerant flowing through the refrigerant pipe 11 and flowing into the water refrigerant heat exchanger 3 and the water flowing through the water pipe 16 and flowing into the water refrigerant heat exchanger 3. The water refrigerant heat exchanger 3 is a user-side heat exchanger.

The expansion valve 4 controls the opening degree of the valve by pulse control using a stepping motor. The expansion valve 4 adjusts the amount of refrigerant that flows into or out of the heat source side heat exchanger 5. The heat source side heat exchanger 5 exchanges heat between the refrigerant flowing through the refrigerant pipe 11 and flowing into the heat source side heat exchanger 5 and the outside air taken in by the rotation of the outdoor fan 90. The accumulator 6 separates the refrigerant flowing from the four-way valve 2 into a gas refrigerant and a liquid refrigerant, and causes only the gas refrigerant to be sucked into the compressor 1.

In the vicinity of the refrigerant discharge port of the compressor 1 in the refrigerant pipe 11, a discharge pressure sensor 51 that detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor 1, and the temperature of the refrigerant discharged from the compressor 1 are present. A discharge temperature sensor 52 for detecting the discharge temperature is provided. In the vicinity of the refrigerant inflow side of the accumulator 6 in the refrigerant pipe 11, a suction pressure sensor 53 that detects the suction pressure which is the pressure of the refrigerant sucked into the compressor 1 and the suction which is the temperature of the refrigerant sucked into the compressor 1 are sucked. A suction temperature sensor 54 for detecting the temperature is provided.

The discharge pressure sensor 51 may be arranged between the refrigerant discharge side of the compressor 1 in the refrigerant pipe 11 and the water refrigerant heat exchanger 3. For example, as virtually shown by the one-point chain line in FIG. 1, the four-way valve 2 It is arranged between the water refrigerant heat exchanger 3 and the water refrigerant heat exchanger 3. Further, the compressor 1 may be provided with a rotation speed sensor that detects the rotation speed of the compressor 1.

A refrigerant temperature sensor 55 is provided in the vicinity of the connection port of the expansion valve 4 between the water refrigerant heat exchanger 3 and the expansion valve 4 in the refrigerant pipe 11. The refrigerant temperature sensor 55 detects the temperature before the expansion valve, which is the temperature of the refrigerant flowing out from the water refrigerant heat exchanger 3 during the heating operation. When the refrigerant temperature sensor 55 is arranged near the connection port of the expansion valve 4, that is, when it is provided in the outdoor unit, for example, the indoor unit to which the heat pump type hot water heating device 100 is combined with the outdoor unit can be selected. In this case, it is desired to provide the outdoor unit with the refrigerant temperature sensor 55 so that the indoor unit on which the sensor corresponding to the refrigerant temperature sensor 55 is not mounted can be combined with the outdoor unit.

The refrigerant pipe 11 between the expansion valve 4 and the heat source side heat exchanger 5 is provided with a heat exchange temperature sensor 57 on the heat source side heat exchanger 5 side. The heat exchange temperature sensor 57 detects the temperature of the refrigerant flowing into the heat source side heat exchanger 5 during the heating operation. The heat exchange temperature sensor 57 detects the temperature of the refrigerant flowing out from the heat source side heat exchanger 5 during the defrosting operation. An outside air temperature sensor 56 for detecting the outside air temperature is provided in the vicinity of the heat source side heat exchanger 5.

(Structure of hot water circuit)
A refrigerant pipe 11 and a water pipe 16 are connected to the water-refrigerant heat exchanger 3. The flow meter 31, the indoor unit 40, and the circulation pump 30 are sequentially connected to the water pipe 16. The circulation pump 30 is driven by a motor having a fixed rotation speed or a motor having a variable rotation speed. As a result, in the hot water circuit 20, water circulates in the direction of the arrow 80. In particular, when a motor whose rotation speed can be changed is used as the circulation pump 30, the flow rate of water flowing through the hot water circuit 20 can be changed. When the circulation pump 30 does not use a motor whose rotation speed can be changed, the flow rate of water flowing through the water pipe 16 is a predetermined fixed flow rate when the heat pump type hot water heating device 100 is arranged. The indoor unit 40 is a terminal for heating the room such as a floor heating device and a radiator. The flow meter 31 measures the flow rate of water per unit time in the hot water circuit 20.

The hot water circuit 20 has a detecting means for detecting the temperature of water. For example, a temperature sensor 58 for detecting the forward temperature, which is the temperature of the water flowing out from the water refrigerant heat exchanger 3, is provided on the water outlet side of the water refrigerant heat exchanger 3 in the water pipe 16. A temperature sensor 59 for detecting the return temperature, which is the temperature of the water flowing into the water refrigerant heat exchanger 3, is provided on the water inlet side of the water refrigerant heat exchanger 3 in the water pipe 16.

(Controller unit)
FIG. 2 is a block diagram showing the configuration of the control unit 60. The control unit 60 includes a CPU (Central Processing Unit) 601, a storage unit 602 that stores various programs related to operation control of the heat pump type hot water heating device 100, and control parameters used when executing various programs, and a refrigerant circuit 10. It has a sensor input unit 603 for capturing the detected values of various sensors provided in the hot water circuit 20 and a receiving unit 604 for receiving a signal transmitted from a remote controller (not shown) for operating the indoor unit 40.

The control unit 60 captures the values detected by various sensors via the sensor input unit 603. The control unit 60 captures various requests related to the operation of the indoor unit 40 transmitted by the remote control operation of the user via the receiving unit 604. The control unit 60 controls the drive of the compressor 1 and the circulation pump 30, the switching control of the four-way valve 2, the opening degree adjustment of the expansion valve 4, etc., based on the values detected by the various sensors taken in and various demands related to the operation. , Each device of the heat pump type hot water heating device 100 is controlled.

[Operation of refrigerant circuit and hot water circuit]
Subsequently, when the heat pump type hot water heating device 100 performs the heating operation, the flow of the refrigerant in the refrigerant circuit 10 and the operation of each part, and the flow of water in the hot water circuit 20 and the operation of each part will be described with reference to FIG. do. First, a case where the heat pump type hot water heating device 100 performs a heating operation will be described. Next, a case where the heat pump type hot water heating device 100 performs the defrosting operation will be described.

(Heating operation)
When the heat pump type hot water heating device 100 performs the heating operation, the four-way valve 2 is operated and the refrigerant circuit 10 is set as the heating cycle. Further, the circulation pump 30 is activated and water circulates in the water circuit 16 in the direction of the solid arrow 80. When the compressor 1 is driven in this state, the refrigerant flows in the refrigerant circuit 10 in the direction of the solid arrow 70. The refrigerant discharged from the compressor 1 flows through the refrigerant pipe 11, passes through the four-way valve 2, and flows into the water refrigerant heat exchanger 3. The rotation speed of the compressor 1 is controlled so that the forward temperature, which is the water temperature detected by the temperature sensor 58, becomes the target forward temperature according to the heating capacity required by the user in the indoor unit 40.

The refrigerant flowing into the water-refrigerant heat exchanger 3 exchanges heat with the water flowing into the water-refrigerant heat exchanger 3 to condense. The refrigerant flowing out from the water-refrigerant heat exchanger 3 to the refrigerant pipe 11 is decompressed when passing through the expansion valve 4 and flows into the heat source side heat exchanger 5. As will be described later, the opening degree of the expansion valve 4 is such that the degree of supercooling of the refrigerant on the outlet side (the side of the expansion valve 4 during heating operation) of the water refrigerant heat exchanger 3 becomes a preset target supercooling degree. Is adjusted to.

The refrigerant flowing into the heat source side heat exchanger 5 exchanges heat with the outside air and evaporates. The refrigerant flowing out from the heat source side heat exchanger 5 to the refrigerant pipe 11 is sucked into the compressor 1 via the four-way valve 2 and the accumulator 6 and compressed again.

On the other hand, in the hot water circuit 20, water flows in the hot water circuit 20 in the direction of the solid arrow 80 by driving the circulation pump 30 as described above. The water flowing through the water pipe 16 and flowing into the water refrigerant heat exchanger 3 is heated by the refrigerant to become hot water and flows into the indoor unit 40. By flowing hot water through the indoor unit 40, the room in which the indoor unit 40 is arranged is heated. The direction in which water flows in the hot water circuit 20 is the direction of the solid arrow 80 regardless of whether the refrigerant circuit 10 is in the heating cycle or the cooling cycle.

[Refrigerant supercooling degree control (expansion valve opening control)]
The opening degree of the expansion valve 4 during the heating operation is such that the degree of refrigerant supercooling on the outlet side (expansion valve 4 side during the heating operation) of the water refrigerant heat exchanger 3 has a desired heating capacity in the heat pump type hot water heating device 100. It is adjusted to the target refrigerant overcooling degree, which is the value required to be exhibited. The degree of refrigerant supercooling is calculated by subtracting the temperature of the refrigerant before flowing into the expansion valve 4 (hereinafter, also referred to as the temperature before the expansion valve) from the condensation temperature of the refrigerant in the water refrigerant heat exchanger 3 as follows. To.

Refrigerant supercooling degree = condensation temperature-temperature before expansion valve ... (1)

That is, the refrigerant supercooling degree is the temperature difference between the condensation temperature of the refrigerant in the water-refrigerant heat exchanger 3 and the temperature of the refrigerant flowing out from the water-refrigerant heat exchanger 3, and the larger the temperature difference, the higher the refrigerant supercooling degree. growing. In the present embodiment, the condensation temperature is converted from the pressure detected by the discharge pressure sensor 51, and the temperature before the expansion valve is the detected value of the refrigerant temperature sensor 55.

Further, in general, the target refrigerant supercooling degree is determined on the premise that the refrigerant flowing out from the water refrigerant heat exchanger 3 and flowing into the expansion valve 4 is in a liquid phase state. The target refrigerant supercooling degree is a variable value determined according to the rotation speed (circulation amount of the refrigerant) and the discharge pressure (or the condensation temperature) of the compressor 1. For example, a table value in which the target refrigerant supercooling degree is determined in advance corresponding to the rotation speed and discharge pressure (or condensation temperature) of the compressor 1 is created in advance, and the target refrigerant supercooling degree is determined with reference to this table. Will be done. This table value is stored in the storage unit 602 of the control unit 60. As a specific example of the target refrigerant supercooling degree, for example, it is set in the range of 3 ° C to 5 ° C depending on the operating conditions.

FIG. 3 shows the relationship between the degree of supercooling and the opening degree of the expansion valve 4 when the refrigerant flowing from the water refrigerant heat exchanger 3 to the expansion valve 4 is a liquid refrigerant. As shown in FIG. 3, the degree of refrigerant supercooling decreases as the opening degree of the expansion valve 4 increases, and when the opening degree becomes the maximum, the degree of refrigerant supercooling becomes the minimum value. Therefore, when the calculated value of the refrigerant supercooling degree is lower than the target refrigerant supercooling degree Sc0, the opening degree of the expansion valve 4 is reduced, and when the calculated value of the refrigerant supercooling degree is higher than the target refrigerant supercooling degree Sc0, the opening degree is reduced. By increasing the opening degree of the expansion valve 4, the degree of refrigerant supercooling can be set to the target degree of refrigerant supercooling ScO. In FIG. 3, the opening degree of the expansion valve 4 when the refrigerant supercooling degree becomes the target refrigerant supercooling degree is set as the target opening degree X0.

By the way, when the liquid refrigerant flowing through the liquid pipe 3A connecting between the water-refrigerant heat exchanger 3 and the expansion valve 4 during the heating operation flows between the water-refrigerant heat exchanger 3 and the expansion valve 4 in the refrigerant pipe 11. A gas-liquid two-phase state may occur due to the pressure loss received in the air. At this time, the temperature of the refrigerant drops due to the pressure loss, and the temperature before the expansion valve becomes lower than that in the case where the refrigerant is in the liquid phase state, so that the calculated degree of refrigerant supercooling becomes large. As described above, the target refrigerant supercooling degree is the liquid phase state in which the refrigerant flowing out of the heat exchanger on the user side and flowing into the expansion valve has a short liquid pipe 3A and the pressure loss received by the refrigerant flowing through the liquid pipe 3A is small. That is, it is determined on the premise that the pressure loss is not taken into consideration. Therefore, if the calculated refrigerant supercooling degree changes due to the influence of the pressure loss, it expands as described later with reference to FIG. Even if the overcooling control of the valve 4 is performed, there is a possibility that the heating capacity intended by the heat pump cycle device 100 cannot be exhibited.

Here, as a condition for the refrigerant to be in the gas-liquid two-phase state during the heating operation, for example, there is a pressure loss received when the refrigerant flows through the liquid pipe 3A. FIG. 4 is an explanatory diagram showing the relationship between the pressure loss and the opening degree of the expansion valve 4, and “long”, “medium”, and “short” correspond to the length of the liquid pipe 3A, respectively. As shown in the figure, the longer the pipe length of the liquid pipe 3A, the larger the pressure loss. Further, the larger the opening degree of the expansion valve 4, the larger the circulation amount of the refrigerant and the larger the pressure loss. That is, the longer the pipe length of the liquid pipe 3A and the larger the opening degree of the expansion valve 4, the larger the pressure loss received by the refrigerant flowing through the liquid pipe 3A, and the ratio of the gas refrigerant in the gas-liquid two-phase state becomes larger. The temperature increases and the temperature before the expansion valve decreases.

FIG. 5 is an explanatory diagram showing the relationship between the degree of refrigerant supercooling and the opening degree of the expansion valve 4 when the refrigerant in the liquid pipe 3A is in a gas-liquid two-phase state. If the refrigerant flowing through the liquid pipe 3A is in the gas-liquid two-phase state, the refrigerant supercooled as the opening degree of the expansion valve 4 is increased as in the case where the refrigerant flowing through the liquid pipe 3A is in the liquid phase state as shown in FIG. The opening degree is larger than the target opening degree X0, where the liquidator supercooling degree calculated by maximizing the temperature before the expansion valve is the minimum value smaller than the target refrigerant supercooling degree Sc0, instead of lowering the cooling degree. There is an opening X1 which is. When the opening degree of the expansion valve 4 is larger than the opening degree X1, the degree of refrigerant supercooling increases as the opening degree increases. This is because, as described with reference to FIG. 4, as the opening degree of the expansion valve 4 increases, the amount of the refrigerant flowing through the liquid pipe 3A increases and the pressure loss received by the refrigerant increases, so that the gas-liquid two-phase state is achieved. This is because the ratio of the gas refrigerant to the refrigerant increases and the temperature before the expansion valve decreases.
The opening degree X1 is a value determined by the pipe length of the liquid pipe 3A shown in FIG. 4, and the longer the pipe length, the closer the opening degree X1 approaches the target opening degree X0.

When the opening degree of the expansion valve 4 is larger than the opening degree X1, the degree of refrigerant supercooling increases as the opening degree of the expansion valve 4 increases as described above. Therefore, as shown in FIG. 5, the expansion valve starts from the opening degree X1. Between the maximum opening degree X2 of 4, there is an opening degree Xa in which the calculated refrigerant supercooling degree becomes the target refrigerant supercooling degree Sc0. Here, when the opening degree of the expansion valve 4 is adjusted according to the difference between the calculated refrigerant supercooling degree and the target refrigerant supercooling degree Sc0, when the calculated refrigerant supercooling degree is lower than the target refrigerant supercooling degree Sc0. In other words, the opening degree of the expansion valve is reduced, that is, the opening degree X1 is exceeded and the target opening degree X0 is approached, so that there is no problem. On the other hand, when the calculated refrigerant supercooling degree is higher than the target refrigerant supercooling degree Sc0, the opening degree of the expansion valve 4 is increased. In this case, the larger the opening degree of the expansion valve 4, the higher the temperature before the expansion valve. Since the degree of refrigerant supercooling calculated to be low becomes large, the target degree of refrigerant supercooling cannot be obtained even if the opening degree of the expansion valve 4 reaches the maximum opening degree X2. As a result, the desired heating performance may not be exhibited.

FIG. 6 shows an experiment in which the supercooling degree calculated when the opening degree of the expansion valve 4 becomes larger than the opening Xa cannot be set as the target supercooling degree during the heating operation by the heat pump cycle device 100. It is reproduced in. In this example, when the outside air temperature is 10 ° C., the set temperature of the hot water circulating in the indoor unit 40 is 55 ° C., and the pipe length of the liquid pipe 3A is 30 m. FIG. 6A shows the hot water flow temperature detected by the temperature sensor 58, the hot water return temperature detected by the temperature sensor 59, and the time change of the heating capacity, and FIG. 6B shows the expansion valve. It shows the time change of the pulse (opening) and the compressor rotation speed.

As shown in FIGS. 6A and 6B, after the operation is started and the normal operation at which the rotation speed of the compressor 1 is stable is reached, the heating capacity increases with the hot water flow temperature. However, the heating capacity drops sharply when the hot water flow temperature reaches the maximum value. This is because the refrigerant flowing through the liquid pipe 3A is in a gas-liquid two-phase state due to pressure loss. That is, when the refrigerant is in the gas-liquid two-phase state, the opening degree of the expansion valve 4 is larger than the opening degree Xa shown in FIG. 5 immediately after the start of the heating operation (the calculated value of the refrigerant supercooling degree is the target refrigerant excess). (When the degree of cooling is higher), in this case, even if the opening degree of the expansion valve 4 is increased, the target refrigerant supercooling degree is not reached and continues to increase, and finally the opening degree of the expansion valve 4 is increased. When the maximum opening degree X2 is reached, the degree of supercooling cannot be controlled, and the heating capacity cannot be exhibited (see FIG. 6A).

[Details of control unit]
In order to solve such a problem, the CPU 601 of the control unit 60 has a calculation unit 611, an adjustment unit 612, and a correction unit 613 (see FIG. 2). The calculation unit 611 calculates the degree of supercooling of the refrigerant based on the discharge pressure, which is the detection value of the discharge pressure sensor 51, and the temperature before the expansion valve, which is the detection value of the refrigerant temperature sensor 55, during the heating operation. The adjusting unit 613 adjusts the opening degree of the expansion valve 4 so that the calculated refrigerant supercooling degree becomes a predetermined target refrigerant supercooling degree. When the opening degree of the expansion valve 4 is larger than the predetermined threshold opening degree, the correction unit 613 increases the target refrigerant supercooling temperature by a predetermined value.

FIG. 7 is a diagram showing the relationship between the degree of refrigerant supercooling and the opening degree of the expansion valve for explaining the operation of the correction unit 613, and is a diagram showing a case where the refrigerant flowing through the liquid pipe 3A is in a gas-liquid two-phase state. The threshold opening X and the correction value Y described below are added to 5. When the opening degree of the expansion valve 4 is larger than the predetermined threshold opening degree X, the correction unit 613 increases the target refrigerant supercooling degree Sc0 by a predetermined value Y. Here, the refrigerant supercooling degree obtained by increasing a predetermined value Y from the target refrigerant supercooling degree Sc0 is referred to as a correction target refrigerant supercooling degree Sc1.

Here, the threshold opening X is determined by using the pipe length of the liquid pipe 3A and the opening X1 and the opening Xa. Specifically, the heating operation was performed on a trial basis by the heat pump type hot water heating device 100 with different heating loads at the maximum pipe length of the assumed liquid pipe 3A, and the opening X1 and the opening at the time of each heating load were tested. Xa is obtained, and the opening degree between the maximum value of the opening degree X1 and the minimum value of the opening degree Xa is defined as the threshold opening degree X. Further, the value of Y, which is the correction amount of the target refrigerant supercooling degree Sc0, is a value obtained by conducting a test or the like in advance, and is, for example, 5 ° C. This correction amount Y is set so that the correction target refrigerant supercooling degree Sc1 becomes a value larger than the refrigerant supercooling degree when the opening degree of the expansion valve 4 is fully opened (opening X2). Yes, it is individually determined by the heat pump type hot water heating device 100.

As described above, when the opening degree of the expansion valve 4 is larger than the threshold opening degree X, the target refrigerant supercooling degree Sc0 is corrected by the correction amount Y, and the refrigerant supercooling degree calculated by the calculation unit 611 is the correction target. It will not be larger than the refrigerant supercooling degree Sc1. As a result, the opening degree of the expansion valve 4 is always adjusted by the adjusting unit 612 in the direction of reducing the opening degree of the expansion valve, so that the opening degree of the expansion valve 4 becomes smaller toward the target opening degree X0. Then, when the opening degree of the expansion valve 4 becomes smaller than the threshold opening degree X, the original target refrigerant supercooling degree is restored. As a result, when the refrigerant flowing through the liquid pipe 3A is in a gas-liquid two-phase state due to the influence of pressure loss, the opening degree of the expansion valve 4 is not increased by correcting the target refrigerant supercooling degree Sc0. That is, since the refrigerant supercooling degree does not increase, the refrigerant supercooling degree can be set as the target refrigerant supercooling degree, and the desired heating capacity is maintained.

The threshold opening X may be the opening Xa. As described above, when the refrigerant flowing through the liquid pipe 3A is in a gas-liquid two-phase state, if the expansion valve 4 has an opening larger than the opening Xa, the refrigerant supercooling degree is larger than the target refrigerant supercooling degree Sc0. In this case, since the refrigerant supercooling degree does not decrease even if the opening degree of the expansion valve 4 is increased, the target refrigerant supercooling degree Sc0 is corrected when the opening degree of the expansion valve 4 becomes larger than the opening degree Xa. In this case, the threshold opening X may be set to an opening slightly smaller than the opening Xa in consideration of the variation in the opening adjustment of the expansion valve 4. Specifically, the threshold opening X is a value obtained by subtracting the opening corresponding to one pulse of the control pulse from the opening Xa, or in addition to this, any variation in the opening adjustment is taken into consideration. It may be a value obtained by subtracting the value.

Further, the threshold opening X may be the opening X1. However, when the opening degree of the expansion valve 4 is the opening degree X1, the degree of refrigerant supercooling is smaller than the target degree of supercooling degree Sc0, and the opening degree of the expansion valve 4 is larger than the opening degree X1. The refrigerant flowing through the liquid pipe 3A is not affected by the pressure loss. At this time, if the target refrigerant supercooling degree Sc0 is corrected to a large value, the difference between the refrigerant supercooling degree and the corrected target refrigerant supercooling degree Sc1 becomes larger than before the correction, and the opening degree of the expansion valve 4 becomes smaller. Therefore, the amount of the refrigerant flowing through the water-refrigerant heat exchanger 3 may be reduced and the heating capacity may be lowered. Therefore, it is preferable that the threshold opening X is larger than the opening X1.

FIG. 8 is a flowchart showing a process related to the opening degree adjustment of the expansion valve 4 during the heating operation executed by the control unit 60. Hereinafter, the operation of the heat pump type hot water heating device 100 of the present embodiment will be described with reference to FIG.

When the heating operation is started, the control unit 60 reads the rotation speed of the compressor 1 and the pressure (discharge pressure) of the refrigerant discharged from the compressor 1 (step 101). The rotation speed of the compressor 1 can be obtained from a detection value of a rotation speed sensor (not shown), and the discharge pressure can be obtained from the discharge pressure sensor 51.

Subsequently, the control unit 60 calculates the target refrigerant supercooling degree Sc0 based on the rotation speed and the discharge pressure of the compressor 1 (step 102). As described above, the target refrigerant supercooling degree Sc0 is determined with reference to the table value prepared in advance based on the correspondence between the rotation speed of the compressor 1 and the discharge pressure (or the condensation temperature).

Subsequently, the control unit 60 determines whether or not the opening degree of the expansion valve 4 is equal to or greater than the threshold opening degree X (step 103). When the opening degree of the expansion valve 4 is less than the threshold opening degree X (“N” in step 103), the process proceeds to step 105. On the other hand, when the opening degree of the expansion valve 4 is equal to or greater than the threshold opening degree X (“Y” in step 103), the control unit 60 corrects the target refrigerant supercooling degree Sc0 by Y ° C. to correct the target refrigerant supercooling degree Sc0. Is set to the correction target refrigerant supercooling degree Sc1 (step 104, FIG. 7).

Subsequently, the control unit 60 calculates the condensation temperature of the refrigerant in the water refrigerant heat exchanger 3 based on the detected value of the discharge pressure sensor 51 (step 105). Further, the control unit 60 takes in the temperature before the expansion valve, which is the detection value of the refrigerant temperature sensor 55 (step 106). Then, the control unit 60 calculates the current degree of refrigerant supercooling, which is the difference between the condensation temperature calculated in steps 105 and 106 and the temperature before the expansion valve (step 107).

Subsequently, the control unit 60 calculates a deviation Z which is a value obtained by subtracting the current refrigerant supercooling degree from the target refrigerant supercooling degree (step 108), and whether or not the deviation Z is -1 ° C. or more and + 1 ° C. or less. (Step 109). When the deviation Z is -1 ° C. or higher and + 1 ° C. or lower (“Y” in step 109), the control unit 60 determines that the current refrigerant supercooling degree matches the target refrigerant supercooling degree, and opens the expansion valve 4. The current opening degree is maintained without changing (the number of expansion valve pulses) (step 110).

Further, when the deviation Z is not -1 ° C. or higher and + 1 ° C. or lower (“N” in step 109), the control unit 60 determines whether or not the deviation Z is higher than + 1 ° C. (step 111). When the deviation Z is more than 1 ° C. lower than the degree of refrigerant supercooling (“Y” in step 111), the control unit 60 closes the expansion valve 4 by a predetermined amount by subtracting the number of expansion valve pulses by a predetermined amount (step). 112). As a result, the opening degree of the expansion valve 4 is adjusted so as to move from an opening degree larger than the target opening degree X0 toward the target opening degree X0 (see FIG. 7).

On the other hand, when the deviation Z is not higher than + 1 ° C. (“N” in step 111), that is, when the current refrigerant supercooling degree is more than 1 ° C. higher than the target refrigerant supercooling degree, the control unit 60 is a expansion valve. By adding a predetermined amount of pulses, the expansion valve 4 is opened by a predetermined amount (step 113). As a result, the opening degree of the expansion valve 4 is adjusted so as to move from an opening degree smaller than the target opening degree X0 toward the target opening degree X0 (see FIG. 7).

After that, the control unit 60 returns to step 101 and executes the above-mentioned process again. By repeatedly executing these processes at predetermined intervals, the opening degree of the expansion valve 4 can be adjusted to the target opening degree X0. The temperature range indicating the amount of variation in the deviation Z is not limited to ± 1 ° C., and can be set to any value. Further, although the description is omitted in the flow shown in FIG. 8, when the opening degree of the expansion valve 4 is less than the threshold opening degree X in step 103, the target refrigerant supercooling degree is corrected by the correction amount Y. If so, return to the original target refrigerant supercooling degree.

As described above, according to the present embodiment, when the opening degree of the expansion valve 4 is equal to or larger than the threshold opening degree, the target refrigerant supercooling degree Sc0 is set to the correction target refrigerant supercooling degree Sc1. Even when the refrigerant flowing through the pipe 3A is in a gas-liquid two-phase state, the refrigerant supercooling degree calculated in the opening region where the opening degree of the expansion valve 4 is larger than the threshold opening X is set from the target refrigerant supercooling degree. Can also be made smaller. As a result, whenever the refrigerant supercooling degree is lower than the target refrigerant supercooling degree by a predetermined amount, the control to reduce the opening degree of the expansion valve 4 is realized, so that the influence of the pressure loss of the refrigerant flowing through the liquid pipe 3A is affected. It is possible to realize stable supercooling degree control without receiving it and maintain the desired heating capacity.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.
For example, in the above embodiment, the heat pump type hot water heating device 100 has been described as an example of the heat pump cycle device, but the present invention is not limited to this, and the heat pump cycle device such as a heat pump type hot water supply device or a heat pump type hot / cold water air conditioner is used. Also, the present invention is applicable.

1 ... Compressor 2 ... Four-way valve (flow path switching valve)
3 ... Water refrigerant heat exchanger (heat exchanger on the user side)
4 ... Expansion valve 5 ... Heat source side heat exchanger 10 ... Refrigerant circuit 20 ... Hot water circuit 30 ... Circulation pump 40 ... Indoor unit 60 ... Control unit 611 ... Calculation unit 612 ... Adjustment unit 613 ... Correction unit 100 ... Heat pump type hot water heating device (Heat pump cycle device)

Claims (3)

A compressor, a user-side heat exchanger, a heat source-side heat exchanger, an expansion valve arranged between the user-side heat exchanger and the heat source-side heat exchanger, and a refrigerant discharged from the compressor. A compressor circuit having a flow path switching valve for switching the flow direction of the
A discharge pressure sensor that detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor, and
A refrigerant temperature sensor that detects the temperature before the expansion valve, which is the temperature of the refrigerant flowing out from the user side heat exchanger during the heating operation in which the flow direction of the refrigerant discharged from the compressor is the user side heat exchanger. ,
The calculation unit that calculates the refrigerant supercooling degree based on the discharge pressure and the temperature before the expansion valve, and the opening degree of the expansion valve so that the calculated refrigerant supercooling degree becomes a predetermined target refrigerant supercooling degree. A heat pump cycle device including a control unit having an adjusting unit for adjusting and a correction unit for increasing the target refrigerant supercooling degree by a predetermined value when the opening degree of the expansion valve is larger than a predetermined threshold opening degree. The heat pump cycle device according to claim 1.
The predetermined threshold opening is such that the opening degree in which the refrigerant supercooling degree is larger than the target opening degree to be the target refrigerant supercooling degree and the refrigerant supercooling degree in the opening region larger than the opening degree are the targets. A heat pump cycle device that has an arbitrary opening between the opening that is the degree of refrigerant supercooling. The heat pump cycle device according to claim 1 or 2.
The correction value of the target refrigerant supercooling degree is determined so that the refrigerant supercooling degree is always smaller than the corrected target refrigerant supercooling degree.

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