JPH09145175A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use an evaporator and improve the efficiency of the evaporator by correcting the pressure loss value of the evaporator. SOLUTION: An air conditioner comprises a capacity variable compressor 16, and evaporators 18 and 20 so as to set a target degree of superheating SHtgt and control the degree of superheating of the evaporators 18 and 20. The air conditioner further comprises a control means 100 for changing the target degree of superheating SHtgt depending on the output (horse power) of the compressor 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner which has a compressor with variable capacity and an evaporator and which sets a target superheat degree to control the superheat degree of the evaporator.

[0002]

2. Description of the Related Art Conventionally, in an air conditioner, an electric expansion valve is used to efficiently operate a compressor and to efficiently use an indoor heat exchanger that functions as an evaporator during cooling operation. The degree of superheat of the indoor heat exchanger that functions as an evaporator is controlled (the flow rate of the refrigerant is controlled) by controlling the opening degree of the.

[0003]

In the above control, the target degree of superheat is set, but if the operating horsepower of the compressor (corresponding to the circulation amount of the refrigerant) is large, the pressure loss of the refrigerant in the evaporator is reduced. The increase is inevitable, and the pressure loss value of the refrigerant in the evaporator changes due to a change in the refrigerant circulation amount in the refrigerant circuit, that is, a change in the operating horsepower of the compressor. There is a problem that can not be used efficiently.

Therefore, the present invention solves the above problems and provides an air conditioner capable of improving the efficiency of the evaporator by correcting the pressure loss value of the evaporator to effectively use the evaporator. The purpose is to do.

[0005]

The invention according to claim 1 is an air conditioner having a compressor and an evaporator with variable capacity, and setting a target superheat degree to control the superheat degree of the evaporator. , And a control means for changing the target degree of superheat according to the output of the compressor.

According to this, since it has the control means for changing the target degree of superheat according to the output of the compressor, the control means corrects the pressure loss of the refrigerant in the evaporator according to the output of the compressor. Target superheat (temperature difference between the inlet and outlet of the evaporator)
By changing the above, it is possible to prevent the refrigerant from overheating in the evaporator and effectively utilize it, thereby improving efficiency and reducing the discharge temperature of the refrigerant.

According to a second aspect of the present invention, in an air conditioner that has a compressor with variable capacity and an evaporator, and sets a target superheat degree to control the superheat degree of the evaporator, the target superheat degree evaporates. The control unit has a control unit that obtains the difference between the temperature of the refrigerant inlet to the compressor and the temperature of the refrigerant outlet from the evaporator, and changes the target superheat degree according to the output of the compressor.

According to this, the target superheat degree is obtained from the difference between the temperature of the refrigerant inlet to the evaporator and the temperature of the refrigerant outlet from the evaporator, and the target superheat degree is changed according to the output of the compressor. Since the control means has the control means, based on the information on the difference between the temperature of the refrigerant inlet to the evaporator and the temperature of the refrigerant outlet from the evaporator, the pressure loss of the refrigerant in the evaporator depends on the output of the compressor. By changing the target superheat degree (the temperature difference between the inlet and outlet of the evaporator) in a form that compensates for the above, the refrigerant is prevented from overheating in the evaporator and is effectively used to improve efficiency and reduce the discharge temperature of the refrigerant. Can be achieved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a refrigerant circuit of an air conditioner according to an embodiment of the present invention. The refrigerant circuit of FIG. 1 includes an outdoor unit 10 and a plurality of indoor units 12, 14
And a compressor 16, indoor heat exchangers 18, 20 arranged in parallel, an outdoor heat exchanger 24, and a four-way valve 26.
However, they are arranged in this order, and in the refrigerant circuit of the air conditioner, the refrigerant circulates in this order during the heating operation, and in the reverse order during the cooling operation. Indoor heat exchanger 18,
The 20 and the outdoor heat exchanger 24 each include a fan, and exchange heat with the indoor air or the outdoor air. The outdoor heat exchanger 24 functions as a condenser during the cooling operation and as an evaporator during the heating operation.
Acts as an evaporator during cooling operation and as a condenser during heating operation.

The outdoor heat exchanger 24 includes a temperature sensor S1 for measuring the temperature of the coil inside the outdoor heat exchanger 24, and a temperature sensor S2 for measuring the temperature of the refrigerant liquid at the refrigerant liquid outlet side during the cooling operation of the outdoor heat exchanger 24. Equipped with.

The indoor heat exchanger 18 includes a temperature sensor E3 for measuring the temperature of the refrigerant on the refrigerant outlet side during the cooling operation of the indoor heat exchanger 18, a temperature sensor E2 for measuring the temperature of the coil inside the indoor heat exchanger 18, and Temperature sensor E1 for measuring the temperature of the refrigerant at the refrigerant inlet side during the cooling operation of the heat exchanger 18.
And

Similarly, the indoor heat exchanger 20 includes a temperature sensor E3 for measuring the temperature of the refrigerant at the refrigerant outlet side of the indoor heat exchanger 20 during the cooling operation of the indoor heat exchanger 20, and a temperature sensor for measuring the temperature of the coil therein. E2 and a temperature sensor E1 for measuring the temperature of the refrigerant at the refrigerant inlet side during the cooling operation of the indoor heat exchanger 20 are provided.

The indoor heat exchanger 18 is equipped with an electric expansion valve 30 on the refrigerant inlet side during the cooling operation.
0 can adjust the degree of opening and closing by the motor 34. Similarly, the indoor heat exchanger 20 includes an electric expansion valve 32 on the refrigerant inlet side during the cooling operation.
The degree of opening and closing can be adjusted by the motor 36.

The control means 100 is a compressor 16 with variable capacity.
, And can obtain a signal relating to the operating capacity of the compressor 16. The control means 100 sets the target superheat degree and controls the superheat degree of the evaporator so that the target superheat degree can be changed according to the output of the compressor 16. The degree of opening and closing of the electric expansion valves 30 and 32, which are That is,
The control means 100 includes temperature sensors S1, S2, E1, E
2, based on the temperature information of each part from E3, the motor 3
It is possible to control the opening / closing degree of the electric expansion valves 30 and 32 by giving a command to the motors 4 and 36.

Next, the operation of the above embodiment will be described focusing on the cooling operation. In the refrigerant circuit of FIG. 1, during cooling operation, the four-way valve 26 switches as shown by the broken line in FIG. 1, and the compressor 16, the four-way valve 26, and the outdoor heat exchanger 2
4, the refrigerant is circulated in the order of the electric expansion valves 30, 32 and the indoor heat exchangers 18, 20.

The refrigerant from the compressor 16 is heat-exchanged with the outdoor air by the outdoor heat exchanger 24 acting as a condenser, and the refrigerant passes through the electric expansion valves 30 and 32, and the indoor heat exchange acting as an evaporator. Since the refrigerant passing through the containers 18 and 20 is vaporized, heat is drawn from room air to cool each room.

FIG. 2 shows a Mollier diagram in the refrigerant circuit of FIG.

The compression process of the Mollier diagram of FIG. 2 is indicated by the refrigerant suction port (portion in FIG. 1) and the refrigerant discharge port (portion) of the compressor 16, and the condensation process is performed by the refrigerant discharge port of the compressor 16. An outlet (part), a condenser (outdoor heat exchanger 24) (part), and an outlet (part) of this condenser. The expansion step is indicated by the outlet (part) of the condenser and the inlet (part) of the evaporator (indoor heat exchanger 18, 20), and the evaporation step is indicated by the inlet (part) of the evaporator and this evaporator (part). ) And a suction port (portion) for the refrigerant of the compressor 16. In the evaporation process of FIG. 4, 'is an evaporator (indoor heat exchanger 18, 2
The refrigerant in 0) is overheated, and the degree of superheat is indicated by SH.

Next, based on FIG. 3, the superheat degree control operation of the electric expansion valves 30, 32 of the evaporator (indoor heat exchanger 18, 20) during the cooling operation of the refrigerant circuit of the air conditioner of FIG. 1 will be described. explain. During the cooling operation, the control unit 100 controls the motors 34 and 36 of the electric expansion valves 30 and 32 to control the superheat degree of the evaporator (the indoor heat exchangers 18 and 20). The opening / closing degree of 32 is adjusted as follows.

First, the control means 100 controls the target superheat degree (S
Htgt) is set based on the table of FIG. 4 (step SP1).

This table shows the correspondence between the capacity (horsepower) of the compressor 16 and the value of the target superheat degree (SHtgt). That is, the control means 100 refers to the table and determines the target superheat degree (S) according to the value of the capacity (horsepower) of the compressor 16.
Htgt) value can be set. For example, when the compressor 16 has 3 to 4 horsepower, the control means 100 sets the target superheat degree to 4 ° C according to the table.

When the refrigerant circuit of FIG. 1 is in the cooling operation, the temperature difference ΔT between the temperature measured by the temperature sensor E3 of the indoor heat exchangers 18, 20 and the temperature measured by the temperature sensor E1 is obtained, and this temperature difference ΔT is the target overheat. It is compared whether the value is greater than the value of the degree (SHtgt) (step SP2 in FIG. 3). Temperature difference Δ
When T is larger than the value of the target superheat degree (SHtgt) (step SP2), the control means 100 causes the electric expansion valve 3 to operate.
Move on to an operation for instructing to open 0, 32 (step SP
3).

If the temperature difference ΔT is equal to or smaller than the target superheat degree (SHtgt), the process proceeds to step SP4. If the temperature difference ΔT has the same target superheat degree (SHtgt), the control means 100 is electrically operated. The opening / closing degree of the expansion valves 30 and 32 is currently maintained (step SP5). Otherwise, if the temperature difference ΔT is different from the value of the target superheat degree (SHtgt),
The control means 100 moves to an operation of issuing a command to close the electric expansion valves 30 and 32 (step SP6). Step SP
3, SP5 or step SP6, the control means 100, as shown in step SP7, the electric expansion valve 30,
For the motors 34, 36 of 32, the electric expansion valves 30, 3
The pulse increase amount (decrease amount) for setting the opening / closing degree of 2 is set.

As described above, the control means 100 controls the compressor 1
The indoor expansion valve 3 based on the temperature measured by the temperature sensors E1 and E3 according to the current capacity (horsepower) of No. 6
By controlling the opening and closing of 0, 32, the evaporator (18,
Since the superheat degree control of 20) is performed, overheating of the evaporator can be avoided. In other words, the control means 100 is the compressor 1
According to the current capacity of No. 6, transient overheat operation can be prevented, the evaporator can be operated efficiently, and the rise of the discharge temperature of the refrigerant discharged from the evaporator can be suppressed.

Next, referring to FIGS. 5 to 8, the target superheat S
The difference between Htgt and the actual superheat degree SH will be described with reference to actual numerical examples.

FIG. 5 shows a Mollier diagram with a theoretical cycle. If there is no pressure drop in the evaporator, even if the capacity of the compressor 16 (corresponding to horsepower and refrigerant circulation amount) changes,
The actual superheat degree SH and the target superheat degree are always constant. For example, the measured temperature of the temperature sensor E3 of FIG.
The temperature difference ΔT (target superheat degree SHtgt) of the measured temperature of 1 is 1 ° C, and the actual superheat degree SH (superheat) is also 1 ° C with reference to the isotherm, which is the same.

However, in reality, it is impossible that there is no pressure loss in the evaporator. Even if there is a pressure drop in the evaporator,
For example, as shown in FIG. 6, when the capacity of the compressor 16 is low, the pressure loss in the evaporator is small, so the target superheat degree SH
Even if tgt (temperature difference ΔT) is set to 4 ° C, the temperature measured by the temperature sensor E3 in FIG. 1 is (5 ° C + 4 ° C = 9).
° C), the temperature measured by the temperature sensor E1 is 5 ° C, and the actual superheat degree SH is 5 ° C at (9 ° C-5 ° C).
With such a difference, it can be considered that the actual superheat degree SH and the target superheat degree are substantially equal to each other, and therefore there is no practical problem.

However, when the capacity of the compressor 16 is high as shown in FIG. 7, the pressure loss in the evaporator becomes large, and even if the target superheat degree SHtgt is set to 4 ° C., the temperature sensor E3 of FIG. The measurement temperature is (5 ° C + 4 ° C = 9 °
C), the saturation temperature of the temperature sensor E3 is 1 ° C, and the actual degree of superheat SH is 8 ° C at (9 ° C-1 ° C). In this case, the superheat degree in the evaporator becomes too large, and the discharge temperature of the refrigerant in the evaporator rises to, for example, 120 ° C. as shown in FIG. 7.

In such a case, according to this embodiment, the target superheat degree SHtgt is corrected as shown in FIG.
Set as small as Htgt = 1 ° C. According to this, since the actual superheat degree SH can be lowered to 5 ° C at (6 ° C-1 ° C), the superheat degree in the evaporator becomes small, and the discharge temperature of the refrigerant in the evaporator becomes As shown in FIG. 8, the temperature can be lowered to 100 ° C., for example, and the evaporator can be operated efficiently.

The present invention can be variously modified without departing from the scope of the claims. For example, if two indoor units are connected to one outdoor unit,
Similar effects can be obtained by connecting one or three or more indoor units to one outdoor unit or connecting a plurality of indoor units to a plurality of outdoor units.

[0031]

As described above, according to the first aspect of the invention, the control means corrects the pressure loss of the refrigerant in the evaporator according to the output of the compressor so that the target superheat degree (at the inlet / outlet of the evaporator). Temperature difference). As a result, it is possible to prevent the refrigerant from overheating in the evaporator and effectively utilize it, thereby improving efficiency and reducing the discharge temperature of the refrigerant.

According to the second aspect of the invention, the control means is based on the information of the difference between the temperature of the refrigerant inlet to the evaporator and the temperature of the refrigerant outlet from the evaporator, and the evaporator is output according to the output of the compressor. The target degree of superheat (temperature difference between the inlet and outlet of the evaporator) can be changed by correcting the pressure loss of the refrigerant in the above. As a result, it is possible to prevent the refrigerant from overheating in the evaporator and effectively utilize it, thereby improving efficiency and reducing the discharge temperature of the refrigerant.

[Brief description of the drawings]

FIG. 1 is a diagram showing a refrigerant circuit of an air conditioner of the present invention.

FIG. 2 is a diagram showing a Mollier diagram.

FIG. 3 is a diagram showing a control example of an electric expansion valve during a cooling operation in the refrigerant circuit of FIG.

Fig. 4 Compressor capacity (horsepower) and target superheat (SHtg
It is a contrast figure of t).

FIG. 5 is a diagram showing a Mollier diagram of a theoretical cycle.

FIG. 6 is a diagram showing an example of a low compression functional force when the pressure loss of the refrigerant is small.

FIG. 7 is a diagram showing an example of a high compression function force when the pressure loss of the refrigerant is large.

FIG. 8 is a diagram showing an example of a high compression function force when the pressure loss of the refrigerant is large.

[Explanation of symbols]

 10 Outdoor unit 12,14 Indoor unit 16 Compressor 18,20 Indoor heat exchanger (evaporator during cooling operation) E1, E2, E3, S1, S2 Temperature sensor 100 Control means SHtgt Target superheat degree SH Actual superheat degree ( Actual superheat)

Claims (2)

[Claims] 1. An air conditioner having a variable capacity compressor and an evaporator, wherein the target superheat is set to control the superheat of the evaporator, wherein the target superheat is determined according to the output of the compressor. An air conditioner having control means for changing the air conditioner. 2. An air conditioner having a variable capacity compressor and an evaporator, wherein a target superheat is set to control the superheat of the evaporator, the target superheat being the inlet of the refrigerant to the evaporator. An air conditioner having control means for obtaining a target superheat degree in accordance with an output of a compressor, which is obtained from a difference between a temperature and a temperature of a refrigerant outlet from an evaporator.