JPH0526107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air conditioner, and more particularly to an air conditioner with an improved superheat control method for evaporative refrigerant.

(Prior Art) As a specific example of a control system for controlling the degree of superheating, etc. in a conventional device, for example, the applicant's earlier application (Japanese Patent Application No. 1983)
-248527). This device will be explained based on FIG. 2, which is an embodiment of the present invention. As shown in the figure, this device has a configuration in which one outdoor unit X is connected to a plurality of indoor units A to D. , each indoor heat exchanger 18 is connected between the liquid side branch pipes 15...15 and the gas side branch pipes 17...17. Further, a liquid receiver 11 is interposed between the first liquid pipe 10 and the second liquid pipe 12, and this liquid receiver 11 is connected to the capillary reach tube 2.
1 and a suction pipe 4 of the compressor 1 via a pipe 20. Note that the first liquid pipe 10 has a first
An electric expansion valve 13 is interposed, and second electric expansion valves 16...16 are interposed in each of the liquid side branch pipes 15...15, respectively. Further, a first temperature sensor 31 is installed on the pipe 20, a second temperature sensor 32 is installed on the suction pipe 4 of the compressor 1, and a fourth temperature sensor 32 is installed on the gas side branch pipe 17.
A temperature sensor 34 is attached to each. The first temperature sensor 31 is for detecting the pressure-equivalent saturation temperature T1 of the low-pressure gas refrigerant.

In the above-described apparatus, during cooling operation, the temperature of the evaporative refrigerant at the outlet of the indoor heat exchangers 18...18 serving as evaporators is measured by the fourth temperature sensor 34.
At the same time, the degree of superheat of the evaporative refrigerant is determined from this detected temperature T4 and the detected temperature T1 of the first temperature sensor 31, and each of the second electric expansion valves 16... 16 opening degree controls are performed. On the other hand, during heating operation, the degree of superheat is determined from the temperature T2 detected by the second temperature sensor 32 and the temperature T1 detected by the first temperature sensor 31, and the opening degree of the first electric expansion valve 13 is controlled in the same manner as above. Do the following.

(Problems to be Solved by the Invention) Incidentally, in recent years, in the multi-type air conditioners as described above, inverter type compressors are being adopted from the viewpoint of providing comfortable air conditioning and saving energy. In such air conditioners, when there is an increase or decrease in the number of operating rooms, relatively large capacity control can be carried out in a short period of time, such as increasing or decreasing the compressor inverter frequency accordingly. It is necessary to do it. On the other hand,
In the conventional superheat degree control method described above, each electric expansion valve 13, 16, . is normal.
Therefore, when using a compressor with variable compression capacity such as an inverter compressor, if the conventional superheat degree control method described above is adopted as is, the opening degree of each electric expansion valve 13, 16...16 will not be adjusted to the compression capacity. It is not possible to follow or change accordingly, and as a result, a problem arises in that the optimum operating condition cannot be maintained.

This invention was made in order to solve the above-mentioned conventional drawbacks, and its purpose is to maintain the degree of superheat of the evaporative refrigerant to a state close to the optimum state even when a relatively large change occurs in the capacity of the compressor. The object of the present invention is to provide an air conditioner that can be maintained and, therefore, can maintain good operating efficiency.

(Means for Solving the Problems) Therefore, the air conditioner of the present invention, as shown in FIG. Exchanger 1
A refrigerant circulation circuit is constructed by connecting a plurality of indoor units A... having 8, and one of the outdoor heat exchanger 8 and the indoor heat exchanger 18 functions as an evaporator, and the other functions as a condenser. In the air conditioner, when the load capacity is changed, the compressor 1 starts operating at the set capacity determined by the relationship between the load capacity of the indoor unit A that is requested to operate and the air conditioning load, and thereafter the compressor 1 starts operating according to the air conditioning load. 1
It has a compression capacity control means 41 for controlling the compression capacity of the evaporator 8, and a superheat degree control valve 13 interposed on the refrigerant inlet side to the evaporator 8, and a superheat degree control valve 13 for detecting the degree of superheat of the evaporated refrigerant in the evaporator 8. superheat degree detection means 46;
The superheat degree control valve control means 42 controls the opening degree of the superheat degree control valve 13 so that the detected degree of superheat approaches the reference degree of superheat, and the compression capacity is increased or decreased by the compression capacity control means 41 when changing the load capacity. The above-mentioned superheat degree control valve 13
After the opening correction means 43 corrects the opening, the opening is held at this opening for a predetermined period of time, and then the superheat control valve control means 42 controls the opening. It is characterized by having a switching means 47.

(Function) In the above air conditioner, when the capacity of the compressor 1 is changed by the compression capacity control means 41 when the load capacity is changed, the opening degree of the superheat degree control valve 13 is corrected by the opening degree correction means 43. On the other hand, at other times, the superheat degree control valve control means 42 controls the opening degree of the valve 13 such that the detected degree of superheat approaches the reference degree of superheat. Therefore, even if the compression capacity changes considerably, the degree of superheat of the evaporative refrigerant approaches the appropriate value within a shorter time than in the past.

(Example) Next, an example of the air conditioner of the present invention will be described in detail with reference to the drawings.

First, Figure 2 shows a refrigerant circuit diagram of a multi-model air conditioner equipped with four indoor units.
In the figure, X indicates the outdoor unit, and A to D indicate the first unit.
~The fourth indoor unit is shown, respectively. The above-mentioned outdoor unit 5. A first gas pipe 6 and a second gas pipe 7 are connected to the four-way switching valve 5, respectively, and an outdoor heat exchanger 8 is connected to the second gas pipe 7. Note that an outdoor fan 9 is attached to the outdoor heat exchanger 8. Further, a first liquid pipe 10, a liquid receiver 11, and a second liquid pipe 12 are sequentially connected to the outdoor heat exchanger 8, and a first electric expansion valve 13 is interposed in the first liquid pipe 10. has been done.
The second liquid pipe 12 is connected to a header 14, and a plurality of liquid side branch pipes 15, four in the case of the figure, branch from the header 14.
A second electric expansion valve 16...16 is provided in each liquid side branch pipe 15...15, respectively. On the other hand, from the first gas pipe 6, there are also four gas side branch pipes 1 corresponding to the above.
7...17 is branched, and each of the above branch pipes 15, 17
Indoor heat exchangers 8...18 are connected between them.
In addition, each indoor heat exchanger 18 is attached with an indoor fan 19, and both 18 and 19 connect the indoor unit A.
~D are configured. Further, the liquid receiver 11,
The compressor 1 is connected to the suction pipe 4 by a pipe 20, and a capillary reach tube 21 is interposed in the pipe 20. In addition, in the same figure, 22 is a gas shut-off valve, 23 is a liquid shut-off valve, 24,
25 represents a muffler, and 26 represents an accumulator. In the above air conditioner, as shown by the solid arrow in the figure, the refrigerant discharged from the compressor 1 is recirculated from the outdoor heat exchanger 8, which serves as a condenser, to the indoor heat exchangers 18, which serve as evaporators. In contrast, the refrigerant discharged from the compressor 1 is circulated from the indoor heat exchanger 18, which serves as a condenser, to the outdoor heat exchanger 8, which serves as an evaporator. Therefore, heating operation is performed (dashed line arrow in the figure).

In the refrigerant circuit, a first temperature sensor 31 is attached to the outlet side of the capillary reach tube 21, and this first temperature sensor 31 detects the pressure-equivalent saturation temperature T1 of the low-pressure gas refrigerant. It is for detection. Also compressor 1
A second temperature sensor 32 is installed in the suction pipe 4, third temperature sensors 33...33 are installed in each of the liquid side branch pipes 15...15, and each of the gas side branch pipes 16...
16 are respectively attached with fourth temperature sensors 34...34, and each of these temperature sensors 32,
The functions of 33 and 34 will be described later.

FIG. 3 shows a block diagram of the control system of the air conditioner. As shown in the figure, the outdoor unit X has an outdoor control device 35, and each of the indoor units A to D has an indoor control device 36. The indoor control device 36 includes an operation switch 37 and an indoor thermostat 3.
8 are connected to each other, and the indoor control device 3
The following three signals are sent from 6 to the outdoor control device 35, namely, the operation command signal issued when the operation switch 37 is ON and the room temperature has not reached the set temperature, and the temperature between the detected room temperature and the set temperature. A ΔT signal and model code signal corresponding to the difference are output.

On the other hand, the outdoor control device 35 has a load capacity value grasping section 39 that grasps the total load capacity value ΣS of the indoor units A to D that have the operation command, and integrates the ΔT signals of the indoor units A to D that have the operation command. teΣΔT
It has a temperature difference detection section 40 for determining ΣS and ΣΔT, and a frequency control section (that is, compression capacity control means) 41 for controlling the frequency of the inverter 2 based on the above-mentioned ΣS and ΣΔT. Further, the outdoor control device 35 further includes the first and second electric expansion valves 13,
16...16 (i.e., superheat degree control valve control means) 42, and the first and/or second electric expansion valve 13 according to the change in inverter frequency by the frequency control section 41. 16...1
The opening correction section (that is, the opening correction means) 43 corrects the opening of No. 6.

In the outdoor control device 35, as described above, based on the model code signal output from each indoor control device 36...36, the load capacity grasping section 39 determines the total load capacity of the indoor units A to D for which the operation command is given. Efforts have been made to understand ΣS, and this is done through the following steps. First, the model code signal output from the indoor control devices 36...36 is determined according to the capacity of each indoor heat exchanger 18, and is, for example, 2240kcal/
For the capacity of h, the code “000” is
2800kcal/h is defined as "001", 3550kcal/h as "010", 4500kcal/h as "011", and these codes are stored in each indoor unit A to D. has been done. In addition, in the load capacity grasping section 39, the storage section 44 has the following information:
A load capacity value S corresponding to the above model code is stored. This load capacity value S is 2240kcal/
h (model code “000”) is the standard value “1”,
2800kcal/h (model code "001"), "1.25"
3550kcal/h (model code "010") to "1.5"
4500kcal/h (model code "011") to "2"
The load capacity grasping circuit 45 reads out the load capacity value S for each of the indoor units A to D for which an operation command is given, and calculates their total ΣS.

In the outdoor control device 35, the total load capacity value ΣS of the indoor units A to D for which the operation command is given as described above is grasped, and the difference between this and the room temperature set by the indoor thermometer 38 is determined. The frequency of the compressor 1 is controlled by the frequency control section 41 based on the corresponding signal ΣΔT. That is, this frequency control unit (compression capacity control means) 41 stores an initial set frequency corresponding to the above-mentioned ΣS and ΣΔT, and operates at the above-mentioned initial set frequency at the start of operation and when the number of operating rooms increases. At the same time, after a predetermined period of time, P control is performed based on ΣΔT.
The frequency is changed using PID control or the like. Therefore, for example, if there are a large number of indoor units A to D that have operation commands, the total load capacity value ΣS will generally increase, and in this case, the compressor 1 will be driven at a high frequency, thereby increasing the air conditioning capacity. This allows each room to be air-conditioned at the same time with a capacity that meets the demand.

Next, the first and second valves are controlled by the valve controller 42.
A method of controlling the electric expansion valves 13, 16, . . . 16 will be explained. When the air conditioner is still operating, the first electric expansion valve 1
3 fully open, and each second electric expansion valve 1
6...16 opening degree control is performed, and each indoor heat exchanger 1
Control is performed so that the degree of superheating of the gas refrigerant that evaporates within 8...18 is approximately constant. In this case, the low pressure equivalent saturation temperature T1 detected by the first temperature sensor 31
and the evaporative refrigerant temperature T4...T4 detected by the fourth temperature sensor 34, that is, the detected superheat degree (T4-
Deviation E between T1) and standard superheat degree SHO = (T4−
T1) - Increase or decrease the opening degree of each second electric expansion valve 16...16 by the opening degree P=C・E (C is a positive constant) proportional to SHC (P>0 is open, P<0 is closed) , so-called P control is performed.

On the other hand, during heating operation, the degree of superheat of the refrigerant evaporated in the outdoor heat exchanger 8 is controlled by the first electric expansion valve 13.
PID control is performed, and in each of the second electric expansion valves 16...16, control (referred to as FD control) is performed to equalize the condensed refrigerant temperature at the outlet of each indoor heat exchanger 18...18 during operation. The former is the first
The difference between the low pressure equivalent saturation temperature T1 detected by the temperature sensor 31 and the evaporative refrigerant temperature T2 detected by the second temperature sensor 32, that is, the detected superheat degree (T2-
T1) and this detected superheat degree (T2−
Deviation E between T1) and standard superheat degree SHO = (T2 - T1)
-SHO is determined at each predetermined sampling time, and the opening degree of the first electric expansion valve 13 is controlled using the following formula based on the deviations E0, E1, E2, . . . for each sampling.

P=K0・E0+K1・(E0−E1) +K2・(E0−2E1+E2) (However, K0, K1, and K2 are constants) In other words, if P>0, the first electric expansion valve 13 is opened only by P pulse, and one If P<0, P (absolute value)
Control is performed to close the valve only during pulses.

Further, the FD control by each of the second electric expansion valves 16...16 is performed by detecting the condensed refrigerant temperature T3...T3 at the outlet of the indoor heat exchanger 18...18 in operation with each third temperature sensor 33...33, and The average temperature Tm of these detected temperatures T3...T3 is determined, and the opening degree of each of the second electric expansion valves 16...16 is determined by the average temperature Tm.
and detected temperature T3...Temperature difference between T3 (Tm-T3)
Quantity proportional to P=D・(Tm−T3) (however, D
is a positive constant) (P>0 is open, P<0 is closed).

By the way, in a multi-type air conditioner using the inverter 2 as described above, the load ΣS changes significantly as the number of operating rooms increases or decreases, and the inverter frequency also changes significantly based on this. If the P, PID, and FD controls described above were continued even when the inverter frequency changed in this way, it would take time for the refrigerant flow in the circuit to stabilize, and the Since it takes time for the control to become stable, a problem arises in that the degree of superheating, etc. cannot be controlled in accordance with the frequency change. Therefore, in this air conditioner, in order to eliminate this problem, an opening correction section 43 is provided, and control as shown in the flowchart of FIG. 4 is performed. Note that this control method is based on the above P,
Since this is substantially common to both PID and FD controls, for convenience, the explanation will be given here using PID control and FD control as examples. First, after the start of operation, the opening degrees of the first electric expansion valve 13 and the second electric expansion valve 16 are set to predetermined initial opening degrees (step
S1), this opening degree is maintained for a predetermined time t1 (step S2), and after this time the PID control and FD
Shift to control (step S3). Then, in the next step S4, it is determined whether or not the inverter frequency should be changed due to a change in the number of rooms, etc., and if NO, the process returns to step S3 to continue PID and FD control. On the other hand, if there is a change in the inverter frequency, the first electric expansion valve 13 is changed in the next step S5.
And the opening degrees of the second electric expansion valves 16...16 corresponding to the indoor units A to D for which the operation command is given are corrected as follows.

That is, in the first electric expansion valve 13, ΔP=A・ΔF, and in each of the second electric expansion valves 16...16, ΔP=A・ΔF+(B0−B1), where ΔP: opening correction value ΔF: frequency change Minutes A: Constant B0: Constant depending on the current number of operating rooms B1: Constant depending on the previous number of operating rooms After performing the opening correction as described above, time guard is started in step S6, Predetermined time t
2, that is, until the refrigerant circuit system stabilizes (step S7), and then,
Return to step S3 and set PID and FD in the same manner as above.
It exercises control. The control switching means 47 shown in FIG. 1 is constituted by step S6 and step S7.

When the above control is performed, the first and second electric expansion valves 13, 16...
16 can be tracked and changed, it is possible to maintain the degree of superheating during cooling operation and both the degree of superheating and the degree of subcooling during heating operation to a state close to the appropriate value, so that the air It becomes possible to improve the operating efficiency (EER) of the harmonizer.

In the above embodiment, the superheat degree detecting means 46 is composed of the first temperature sensor 31 and the fourth temperature sensor 34 during cooling, and the first temperature sensor 31 and the second temperature sensor 32 during heating. Although an example has been shown, this superheat degree detection means 46
is not limited to the above. Further, in the above description, both cooling and heating operation modes have been described, but the above can also be implemented in a device that performs only one of the modes, and in this case, the first electric expansion valve 13 and the second electric expansion valve 13 Valve 16...1
6 will function as a superheat degree control valve.

(Effects of the Invention) As described above, in the air conditioner of the present invention, when the capacity of the compressor is changed when changing the load capacity, the opening degree correction means corrects the opening degree of the superheat degree control valve. On the other hand, at other times, the superheat control valve control means controls the detected superheat to approach the reference superheat, so the superheat of the evaporative refrigerant when the compression capacity is changed is lower than before. will approach the appropriate value within a short time, and therefore the degree of superheat of the evaporative refrigerant can be maintained close to the appropriate state, making it possible to maintain good operating efficiency.

[Brief explanation of the drawing]

The figures show an embodiment of the air conditioner of the present invention, in which Fig. 1 is a functional system diagram, Fig. 2 is a refrigerant circuit diagram,
FIG. 3 is a block diagram of the operation control system, and FIG. 4 is a flowchart of the control method. 1...Compressor, 8...Outdoor heat exchanger (evaporator),
13...first electric expansion valve (superheat degree control valve), 16
...Second electric expansion valve (superheat degree control valve), 18...
Indoor heat exchanger (condenser), 41... Frequency control section (compression capacity control means), 42... Valve control section (superheat degree control valve control means), 43... Opening degree correction section (opening degree correction means) , 46... Superheat degree detection means, 47... Control switching means.

Claims (1)

[Claims] 1 A refrigerant circulation circuit is constructed by connecting a plurality of indoor units A... each having an indoor heat exchanger 18 to an outdoor unit X having a compressor 1 with variable compression capacity and an outdoor heat exchanger 8, In an air conditioner in which either the heat exchanger 8 or the indoor heat exchanger 18 functions as an evaporator and the other as a condenser, the load capacity and air conditioning load of the indoor unit A that requires operation when changing the load capacity. The refrigerant inlet to the evaporator 8 has a compression capacity control means 41 that starts the operation of the compressor 1 at a set capacity determined by the relationship between the compressor 1 and thereafter controls the compression capacity of the compressor 1 according to the air conditioning load. A superheat degree control valve 13 provided on the side, a superheat degree detection means 46 for detecting the degree of superheat of the evaporated refrigerant in the evaporator 8, and a superheat degree detection means 46 for detecting the degree of superheat of the evaporated refrigerant in the evaporator 8; The superheat degree control valve control means 42 controls the opening degree of the control valve 13, and the superheat degree control valve 13 is further provided with a correction amount according to the amount of increase/decrease in the compression capacity by the compression capacity control means 41 when the load capacity is changed. After the opening correction means 43 corrects the opening, the opening is held at this opening for a predetermined time, and then the superheat control valve control means 4
2. An air conditioner characterized in that it has a control switching means 47 for performing control according to No. 2.