JP3237548B2 - Heat pump system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pump system configured to perform a cooling hot water supply operation.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a refrigerant circuit of a conventional example of the above-described heat pump system (see, for example, JP-A-1-285758). In the figure, X is an outdoor unit, and two indoor units A and B and a hot water supply unit W are connected to the outdoor unit X. The refrigerant circuit connects the compressor 51 and the four-way switching valve 52 with a discharge pipe 63 and a suction pipe 64, as shown in the figure, and the outdoor heat exchanger 53 and the first electric motor are connected through the four-way switching valve 52. The expansion valve 54 is sequentially connected by a first gas pipe 65 and a first liquid pipe 66. A second liquid pipe 67 is connected to the first electric expansion valve 54 and the other end is connected to two liquid branch pipes 73.
a and 73b, while the four-way switching valve 52 has a second
A gas pipe 68 is connected and the other end is connected to two gas branch pipes 74.
a and 74b. And the liquid branch pipe 73
a and 73b are provided with second electric expansion valves 55a and 55b, and the liquid branch pipes 73a and 73b and the gas branch pipes 74a and 74b.
b, indoor heat exchangers 61 a and 61 b are provided, and a liquid receiver 72 is provided in the second liquid pipe 67.

A first solenoid valve 57 is provided in a discharge pipe 63 of the compressor 51, and a first pipe 69 provided with a second solenoid valve 58 is branched from a position before the first solenoid valve 57, and the tip thereof is double-tube type. Is connected to one end of the hot water supply heat exchanger 62, while the other end of the hot water supply heat exchanger 62 and the second liquid pipe 67 are connected by a second conduit 70 provided with a third electric expansion valve 56. . And the second solenoid valve 5
A first pipe 69 on the hot water supply heat exchanger 62 side of the pipe 8 is connected to a suction pipe 64 of the compressor 51 by a third pipe 71 provided with a third solenoid valve 59 interposed therebetween. Reference numeral 60 provided in the suction pipe 64 is an accumulator.

In the conventional heat pump system constructed as described above, the first solenoid valve 57 is opened, the other solenoid valves 58 and 59 are closed, the four-way switching valve 52 is switched in the direction of the solid line, and By allowing the outdoor heat exchanger 53 to function as a condenser and the indoor heat exchangers 61a and 61b to function as an evaporator, a cooling operation can be performed. Further, the second solenoid valve 58 is opened and the other solenoid valves 5 are opened.
7 and 59 are closed, the four-way switching valve 52 is set in the solid line direction, the hot water supply heat exchanger 62 functions as a condenser, and the indoor heat exchangers 61a and 61b function as evaporators. The cooling water supply operation can be performed by operating the supplied circulation pump 77 to flow the hot water in the hot water storage tank 76 through the heat exchange path 78. During the cooling hot water supply operation, excess refrigerant is generated due to a difference in heat exchange capacity between the outdoor heat exchanger 53 and the hot water supply heat exchanger 63.
The surplus refrigerant is stored in a liquid receiver 72 provided in the second liquid pipe 67.

[0005]

However, in the above-mentioned conventional heat pump system, since the liquid receiver 72 is provided for storing the surplus refrigerant, there is a problem that the cost is increased accordingly. On the other hand, if the liquid receiver 72 is simply omitted, there is a problem that a surplus refrigerant causes a problem such as a high pressure rise and a liquid compression during the cooling hot water supply operation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to avoid a problem caused by excess refrigerant during cooling and hot water supply operation without providing a liquid receiver in a refrigerant circuit. It is an object of the present invention to provide a heat pump system.

[0007]

The heat pump system according to the present invention comprises a compressor 1, an outdoor heat exchanger 3, a first electric expansion valve 4, second electric expansion valves 5a and 5b, an indoor heat exchanger 11a, 11b, a heat pump in which the hot water supply heat exchanger 12 and the third electric expansion valve 6 are connected in order from the compressor 1 side in parallel with the outdoor heat exchanger 3 and the first electric expansion valve 4. In the system, a control means 25 is provided, and the control means 25 drives the compressor 1 so that the hot water supply heat exchanger 12 functions as a condenser and the indoor heat exchangers 11a and 11b function as evaporators. During the cooling and hot water supply operation, the first electric expansion valve 4 is maintained at a predetermined opening degree, while the second electric expansion valves 5a and 5b perform superheat control and the third electric expansion valve 6 performs supercooling control. Success It is characterized in that it is.

In the heat pump system according to the first aspect, when excess refrigerant is generated, the degree of supercooling increases. Therefore, the control means 25 controls the third electric expansion valve 6 to increase the degree of opening. Then, the pressure on the side of the outdoor heat exchanger 3 increases, and the refrigerant condenses in the outdoor heat exchanger 3. Therefore, it is possible to store the surplus refrigerant in the outdoor heat exchanger 3. On the other hand, if the amount of the refrigerant circulating in the refrigerant circuit tends to be insufficient, the degree of superheat is large, so the control means 25 controls the second electric expansion valves 5a and 5b to increase the degree of opening. Then, the pressure on the outdoor heat exchanger 3 side decreases, and the refrigerant evaporates in the outdoor heat exchanger 3. Therefore, the refrigerant stored in the outdoor heat exchanger 3 can be returned to the refrigerant circuit.

The heat pump system according to claim 2 is
The control means 25 is characterized in that the first electric expansion valve 4 is maintained at a predetermined minute opening during the cooling hot water supply operation.

In the heat pump system according to the second aspect, by maintaining the first electric expansion valve 4 at a minute opening, it is possible to avoid a sudden return of the gas refrigerant from the outdoor heat exchanger 3.

[0011]

Next, specific embodiments of the heat pump system of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a refrigerant circuit diagram of the heat pump system. In the figure, X is an outdoor unit,
Two indoor units A and B and a hot water supply unit W are connected to the outdoor unit X. This refrigerant circuit is basically the same as the refrigerant circuit of the conventional heat pump system shown in FIG. 4, except that no liquid receiver is provided in the refrigerant circuit. That is, the refrigerant circuit of the heat pump system shown in FIG. 1 connects the compressor 1 and the four-way switching valve 2 with the discharge pipe 13 and the suction pipe 14 as shown in FIG. Outdoor heat exchanger 3
The first electric expansion valve 4 and the first electric expansion valve 4 are sequentially connected by a first gas pipe 15 and a first liquid pipe 16. A second liquid pipe 17 is connected to the first electric expansion valve 4 and the other end is connected to two liquid branch pipes 23.
a, 23b, while connecting the second gas pipe 18 to the four-way switching valve 2 and connecting the other end to two gas branch pipes 24a,
It branches to 24b. And the liquid branch pipes 23a, 2
The second electric expansion valves 5a and 5b are interposed in 3b, and the indoor heat exchangers 11a and 11b are provided between the liquid branch pipes 23a and 23b and the gas branch pipes 24a and 24b.

The first solenoid valve 7 is connected to a discharge pipe 13 of the compressor 1.
A first pipe line 19 provided with a second solenoid valve 8 is branched from the front side, and the end thereof is connected to one end of a double pipe type hot water supply heat exchanger 12, while a hot water supply heat exchanger is provided. The second liquid pipe 17 is connected to the other end of the second liquid pipe 17 via a third electric expansion valve 6.
They are connected by a pipe 20. The first pipe 19 on the hot water supply heat exchanger 12 side of the second solenoid valve 8 is connected to the suction pipe 14 of the compressor 1 by a third pipe 21 having the third solenoid valve 9 interposed. Reference numeral 10 provided in the suction pipe 14 is an accumulator.

Further, in the same figure, 31a provided in the indoor unit A and 31b provided in the indoor unit B
Is an indoor heat exchange temperature sensor that detects an intermediate temperature between the indoor heat exchangers 11a and 11b, respectively. In the outdoor unit X, 34 provided on the discharge pipe 13 of the compressor 1 is
This is a discharge pipe temperature sensor that detects the discharge pipe temperature. The hot water supply unit W is provided with a hot water supply heat exchange temperature sensor 33 for detecting an intermediate temperature of the hot water supply heat exchanger 12 and a liquid pipe temperature sensor 32 for detecting a liquid pipe temperature at an outlet side thereof.
The detection results of the indoor heat exchange temperature sensors 31a and 31b, the discharge pipe temperature sensor 34, the liquid pipe temperature sensor 32, and the hot water supply heat exchange temperature sensor 33 indicate the functions of a microcomputer including a CPU, a memory, and an input / output interface. Is output to the control means 25 including

In the heat pump system configured as described above, the first solenoid valve 7 is opened, the other solenoid valves 8 and 9 are closed, and the four-way switching valve 2 is switched in the solid line direction.
The cooling operation can be performed by causing the outdoor heat exchanger 3 to function as a condenser and the indoor heat exchangers 11a and 11b to function as evaporators. Further, the second solenoid valve 8 is opened and the other solenoid valves 7, 9 are closed, the four-way switching valve 2 is set in the solid line direction, the hot water supply heat exchanger 12 functions as a condenser and the indoor heat exchanger 11a. , 11b function as an evaporator, and the circulation pump 27 provided in the hot water supply unit is operated to flow hot water in the hot water storage tank 26 through the heat exchange path 28, thereby performing a cooling hot water supply operation. Then, during the cooling hot water supply operation, surplus refrigerant generated due to a difference in heat exchange capacity between the outdoor heat exchanger 3 and the hot water supply heat exchanger 13 is stored in the outdoor heat exchanger 3 by control performed by the control means 25. ing.
Therefore, next, this control will be described.

First, the control means 25 performs supercooling control by controlling the opening of the third electric expansion valve 6. FIG.
Is a flowchart showing this supercooling control. In step S1, the condensing temperature T is detected from the hot water supply heat exchange temperature sensor 33.
c from the liquid pipe temperature sensor 32 and the liquid pipe temperature Tl.
Enter Then, the supercooling degree SC is obtained by subtracting the liquid tube temperature Tl from the condenser Tc.
And a value SC · SET + α obtained by adding a small value α for preventing hunting to the supercooling target value SC · SET. If the comparison shows that the degree of supercooling SC is larger, the process proceeds to step S2, where the opening EVW of the third electric expansion valve 6 is opened by the predetermined opening β, and Return to S1.

On the other hand, if the result of the comparison indicates that the degree of supercooling SC is not larger, the process proceeds to step S3. In this step S3, the supercooling degree SC obtained by subtracting the liquid tube temperature Tl from the condensing temperature Tc of the hot water supply heat exchanger 12,
The value SC · SET−α obtained by subtracting the minute value α from the supercooling target value SC · SET is compared. As a result of the comparison, if the supercooling degree SC is smaller, the process proceeds to step S4, where the opening EVW of the third electric expansion valve 6 is closed by the predetermined opening β, and Return to S1.

The control means 25 controls the operation of the second electric expansion valve 5.
The superheat control is performed by controlling the opening degrees of a and 5b. FIG. 3 is a flowchart for performing the superheat degree control, in which the opening degree of the second electric expansion valves 5a and 5b is adjusted so that the discharge pipe temperature To approaches the target discharge pipe temperature Tm. First, in step S1, the condensing temperature Tc is input from the hot water supply heat exchange temperature sensor 33, and in step S2, the evaporation temperature Te is input from the indoor heat exchange temperature sensors 31a and 31b. In step S3, the slope K of the slope characteristic line on the Mollier diagram is obtained from the energy efficiency EER of the compressor 1 alone. In step S4, the target discharge pipe temperature Tm is calculated, which is performed as follows.
That is, since the condensing temperature Tc and the evaporating temperature Te are grasped as described above, the state A at the start of compression can be specified by giving an appropriate degree of superheat SH on the Mollier diagram. Then, the slope characteristic line having the slope K is extended from the point A, and the temperature at the intersection of the slope characteristic line and the condensation temperature Tc is set as the target discharge pipe temperature Tm. On the other hand, in step S5, the discharge pipe temperature To is input from the discharge pipe temperature sensor 34. Then, in step S6, the control amounts of the opening degrees of the second electric expansion valves 5a, 5b are grasped so that the discharge pipe temperature To approaches the target discharge pipe temperature Tm. Electric expansion valve 5a,
5b is controlled. Thus, the degree of superheat of the refrigerant is controlled. That is, the indoor heat exchanger 1
When the degree of superheat is large in 1a and 11b, the opening of the second electric expansion valves 5a and 5b is controlled to be large, and when the degree of superheat is small, the degree of opening is controlled to be small. That is.

Further, the first electric expansion valve 4 is always kept at a constant minute opening.

In the heat pump system configured and operated as described above, during the cooling hot water supply operation, excess refrigerant is generated due to the difference in heat exchange capacity between the outdoor heat exchanger 3 and the hot water supply heat exchanger 13. When excess refrigerant is generated, the degree of supercooling SC
Becomes large, the control means 25 controls the third electric expansion valve 6 to increase its opening. Since the opening degree of the first electric expansion valve 4 is constant, the pressure on the side of the outdoor heat exchanger 3 increases in this way, and when the pressure becomes higher than the pressure corresponding to the outside air temperature, the refrigerant condenses in the outdoor heat exchanger 3. As a result, the amount of the refrigerant circulating in the refrigerant circuit decreases. That is, the excess refrigerant is stored in the outdoor heat exchanger 3. On the other hand, if the amount of the refrigerant circulating in the refrigerant circuit tends to be insufficient, the degree of superheat SH increases, so the control means 25 controls the second electric expansion valves 5a and 5b to increase the degree of opening. Since the opening of the first electric expansion valve 4 is kept constant, the pressure on the side of the outdoor heat exchanger 3 is reduced, so that the liquid refrigerant in the outdoor heat exchanger 3 evaporates, and Increases the amount of refrigerant circulating through. Therefore, it is possible to avoid problems such as high pressure rise and liquid compression caused by excess refrigerant during the cooling and hot water supply operation without providing a liquid receiver in the refrigerant circuit, and to reduce the cost of the system. Also, by maintaining the first electric expansion valve 4 at a minute opening, it is possible to avoid a sudden return of the gas refrigerant from the outdoor heat exchanger 3 to prevent the generation of abnormal noise and the like and to prevent the refrigerant circuit from being generated. It is possible to prevent the occurrence of a hunting phenomenon in which the amount of refrigerant flowing repeatedly increases and decreases.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention. In the above, the target discharge pipe temperature control is used as the superheat degree control using the second electric expansion valves 5a and 5b. This may be SH control for directly controlling the degree of superheat, or may be control using an outside air temperature correction term as proposed earlier by the present applicant (see JP-A-7-198187). Or according to a difference between the target discharge pipe temperature Tm and the discharge pipe temperature To.
(See Japanese Patent Application Laid-Open No. 8-289996)
It may be. The hot water supply heat exchange temperature sensor 33 may use a pressure sensor instead.

[0022]

According to the heat pump system of the first aspect, the excess refrigerant generated during the cooling and hot water supply operation is stored in the outdoor heat exchanger. Therefore, it is possible to avoid problems such as high pressure rise and liquid compression without using a separate member such as a liquid receiver, and thereby it is possible to reduce costs.

In the heat pump system according to the second aspect, by preventing a sudden return of the gas refrigerant from the outdoor heat exchanger, generation of abnormal noise and the like can be prevented, and the amount of refrigerant flowing through the refrigerant circuit can be increased or decreased. It is possible to prevent the occurrence of the repeated hunting phenomenon.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of one embodiment of a heat pump system of the present invention.

FIG. 2 is a flowchart showing supercooling control in the heat pump system.

FIG. 3 is a flowchart showing superheat degree control in the heat pump system.

FIG. 4 is a refrigerant circuit diagram of a conventional heat pump system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 3 Outdoor heat exchanger 4 1st electric expansion valve 5a 2nd electric expansion valve 5b 2nd electric expansion valve 6 3rd electric expansion valve 11a Indoor heat exchanger 11b Indoor heat exchanger 12 Hot water supply heat exchanger 25 Control means

Claims (2)

(57) [Claims] 1. A compressor (1), an outdoor heat exchanger (3), a first electric expansion valve (4), a second electric expansion valve (5a) (5)
b), the indoor heat exchangers (11a) and (11b) are sequentially connected in a ring shape, and in parallel with the outdoor heat exchanger (3) and the first electric expansion valve (4), sequentially from the compressor (1) side. In the heat pump system in which the hot water supply heat exchanger (12) and the third electric expansion valve (6) are connected to each other, a control means (25) is provided, and the control means (25) drives the compressor (1). During the cooling hot water supply operation in which the hot water supply heat exchanger (12) functions as a condenser and the indoor heat exchangers (11a) and (11b) function as evaporators, the first electric expansion valve (4) is opened for a predetermined time. While the superheat degree is controlled by the second electric expansion valves (5a) and (5b) and the third
A heat pump system wherein supercooling control is performed by an electric expansion valve (6). 2. The heat pump system according to claim 1, wherein the control means (25) maintains the first electric expansion valve (4) at a predetermined minute opening during the cooling and hot water supply operation.