JPH052901B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an improvement in a refrigeration system equipped with a compressor whose operating capacity is variable, in which the degree of superheating of a refrigerant is constantly controlled by the opening degree of an electric expansion valve. (Prior art) Conventionally, in refrigeration systems using variable capacity compressors such as inverters, refrigerant is circulated by changing the capacity of the compressor according to the system load and adjusting the opening degree of the electric expansion valve. Methods of controlling the amount and physical state characteristics in the evaporator are commonly practiced;
In particular, there is a method that measures the degree of superheat in the evaporator and attempts to control the opening degree of the electric expansion valve by PI to keep the value constant. However, when the opening degree of the electric expansion valve is controlled by PI, hunting is likely to occur because there is a time delay between the change in the opening degree and the resulting change in the degree of superheating. In order to prevent this hunting, there is a method of increasing the integration time to stabilize it, but this increases the response delay and, in a state where the capacitance is changing, there is a problem that hunting actually increases. . In order to deal with the above problems, for example,
As disclosed in Publication No. 178254, PID control is performed by adding a differential element to the above PI control, and the degree of superheating in the evaporator, the discharge gas temperature of the compressor, the suction gas temperature, or the temperature in the condenser and evaporator are controlled. Detects the intake air temperature, etc., and based on these refrigerant cycle operating conditions, changes and calculates the constants of the relational expression that PID controls the opening of the electric expansion valve using pre-stored data each time, and determines the opening. There is something to try. (Problem to be Solved by the Invention) However, in the above example, it is necessary to determine PID control constants for all modes, which makes the control complicated. There are situations in which the compressor capacity changes significantly even if the change is gradual, causing a large change in the system.In such cases, PID control is used because of problems such as the integration time mentioned above. This is difficult and the control becomes unstable. The present invention has been made in view of the above, and its purpose is to correct and control the opening degree of the electric expansion valve to a value determined from the capacity of the compressor before and after the change when the capacity of the compressor changes. This aims to prevent hunting and control delays and improve the controllability of superheat degree control with a simple configuration. (Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a variable capacity compressor 1, as shown in FIG.
The object is a refrigeration system equipped with a refrigerant circulation circuit formed by sequentially connecting a condenser 12, an electric expansion valve 8 that performs a refrigerant throttling action, and an evaporator 6. The storage means 31 stores the opening degree of the electric expansion valve 8 according to the capacity of the compressor 1, the determining means 51 determines when the capacity of the compressor 1 changes, and the output of the determining means 51 receives the output of the determining means 51. , when the capacity of the compressor 1 changes, the opening change amount ΔP of the electric expansion valve 8 is set as the current opening value P, and the opening value Po corresponding to the capacity of the compressor 1 before the change stored in the storage means 31. and an arithmetic means 52 which calculates based on the following formula ΔP=P(P1/Po)-P from the opening value P1 corresponding to the changed capacity, and an electric expansion valve 8 based on the output of the arithmetic means 52. The present invention is provided with a control means 53 for controlling the opening degree of the opening. (Function) With the above configuration, in the present invention, if the capacity of the compressor 1 changes while the capacity control of the compressor 1 is being performed,
This is determined by the determining means 51. In response to the output of the determination means 51, the calculation means 52 calculates the following equation from the opening degree Po, P1 corresponding to the capacity before and after the change of the compressor 1 stored in the storage means 31 in advance and the current opening value P. =P(P1/Po)-P, the opening degree change amount ΔP of the electric expansion valve 8 is calculated. Then, the control means 53 changes the opening degree of the electric expansion valve 8 by the opening degree change amount ΔP calculated by the calculation means 52 almost simultaneously with the change in the capacity of the compressor 1. This makes it possible to quickly follow changes in the operating capacity of the compressor 1 without causing large control delays, effectively preventing hunting and improving the controllability of superheat degree control with a simple configuration. obtain. (Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards. Figure 2 shows the refrigerant piping system of a multi-type air conditioner to which the present invention is applied, where A is the outdoor unit and B is the outdoor unit.
-F are indoor units connected in parallel to the outdoor unit A. Inside the outdoor unit A, there is a first compressor 1a whose capacity is adjusted by an inverter 2a whose output frequency is variably switched in 10Hz increments in the range of 30 to 70Hz, and an unloader 2b which operates differentially depending on the pilot pressure. A compressor 1 configured by connecting in parallel via a check valve 1e a second compressor 1b whose capacity is adjusted to two stages of full load (100%) and unload (50%) states; An oil separator 4 that separates oil from the gas discharged from the compressor 1, a four-way switching valve 5 that switches as shown in the solid line in the figure during heating operation and as shown in the broken line in the figure during cooling operation, and Outdoor heat exchanger 6 and its fan 6, which sometimes functions as a condenser and as an evaporator during heating operation
a, a supercooling coil 7, an outdoor electric expansion valve 8 that adjusts the refrigerant flow rate during cooling operation and throttles the refrigerant during heating operation, a receiver 9 that stores liquefied refrigerant, and an accumulator 10. Each of the devices 1 to 10 is connected with a refrigerant communication pipe 11 so that the refrigerant can flow therein. In addition, the indoor units B to F have the same configuration, and are each equipped with an indoor heat exchanger 12 that serves as an evaporator during cooling operation and as a condenser during heating operation, and its fan 12a... The liquid refrigerant branch pipes 11a are each provided with an indoor electric expansion valve 13 that adjusts the refrigerant flow rate during heating operation and throttles the refrigerant during cooling operation. 11
It is connected to the outdoor unit A via b. In addition, TH1... is a room temperature thermostat that detects each indoor temperature, TH2... and TH3... are temperature sensors that detect the refrigerant temperature in the liquid side and gas side pipes of the indoor heat exchanger 12, respectively, and TH4 is a compressor TH5 is a temperature sensor that detects the evaporation temperature in outdoor heat exchanger 6 (evaporator) during heating operation, TH6 is the temperature of suction gas taken into compressor 1 P1 is a pressure sensor that detects the pressure of discharge gas during heating operation and the pressure of intake gas during cooling operation. In addition, in FIG. 2, various auxiliary devices are provided in addition to the above-mentioned main devices. 1f is interposed in the bypass circuit 11c of the second compressor 1b, and the second
An unloader solenoid valve that opens when the compressor 1b is stopped and unloaded and closes when fully loaded; 1g is a capillary reach tube; 1h and 1i are oil return pipes 11u from the oil separator 4; The first compressor 1a and the second compressor 1
A capillary tube 21 is installed in the branch pipes 11v and 11w that return lubricating oil to control the amount of oil returned;
This is a hot gas electromagnetic valve that opens when the cooling operation indoor heat exchanger 12 (evaporator) is in a low load state and during defrosting. Moreover, 11e is a heating overload control bypass circuit, and the bypass circuit 11e includes an auxiliary capacitor 22, a first check valve 2
3. A high-pressure control valve 24 and a second check valve 25, which open when the indoor heat exchanger 12 (condenser) is under low load during heating operation, are connected in series, and some of them open when the indoor heat exchanger 12 (condenser) is under low load. A liquid seal prevention bypass circuit 11f for preventing liquid seal at times is provided via the third check valve 27 and the capillary reach tube CP3. Furthermore, 11g is a liquid injector bypass circuit that connects between the liquid refrigerant side pipe of the heating overload bypass circuit 11e and the suction gas pipe of the main pipe, and adjusts the degree of superheat of the suction gas during heating and cooling operation. The liquid injection bypass circuit 11g is provided with an injection solenoid valve 2 that opens and closes in conjunction with the on/off of the compressor 1.
9, and an automatic expansion valve 30 whose opening degree is adjusted according to the degree of superheating of the intake gas detected by the temperature sensing cylinder TP1.
is interposed. In addition, in Fig. 2, F1 to F6 are liquid purification filters installed in the refrigerant circuit or oil return pipe,
HPS is a high pressure switch for compressor protection, and SP is a service port. The above-mentioned solenoid valves and sensors are connected to an outdoor control unit 15 (described later) by signal lines along with each main equipment, and the outdoor control unit 15 can send and receive signals to each indoor control unit 16 by connecting wiring. It is connected. FIG. 3 is an electrical circuit diagram showing the interior of the outdoor control unit 15 disposed on the outdoor unit A side and the wiring relationship of each connected device. In the figure,
MC1 is the motor of the first compressor 1a connected to the frequency conversion circuit INV of the inverter 2a, MC2 is the motor of the second compressor 1b, MF is the motor of the outdoor fan 6a, 52F, 52C1 and 52C2 are the fan motor MF, frequency Conversion circuit INV and motor
The electromagnetic contactor operates the MC2, and each of the above devices is connected to a three-phase AC power source via a fuse box FS and an earth leakage breaker BR1, and is also connected to the outdoor control unit 15 by a single-phase AC power source. Next, inside the outdoor control unit 15, the normally open contacts RY1 to RY7 of the electromagnetic relays are connected in parallel to the single-phase alternating current, and these are sequentially connected to the electromagnetic relay 20S of the four-way switching valve 5, Electromagnetic contactor 52C1 of frequency conversion circuit INV, electromagnetic contactor 52C2 of second compressor 1b, electromagnetic contactor 52F for outdoor fan, electromagnetic relay SVL of electromagnetic valve 1f for unloader, electromagnetic relay of electromagnetic valve 21 for hot gas.
The electromagnetic contacts mentioned above are connected in series to the coil of the electromagnetic relay SVT of the SVP and injection solenoid valve 29, and are opened and closed in response to signals from the room temperature thermostat TH1 and temperature sensors TH2 to TH6 input to the outdoor control unit 15. It opens and closes the contacts of a device or an electromagnetic relay. Further, a coil of a pulse motor EV that adjusts the opening degree of the outdoor electric expansion valve 8 is connected to the terminal CN. In addition, in the circuit on the right side of Figure 3, CH1,
CH2 is the first compressor 1a and the second compressor 1, respectively.
The oil forming prevention heater c is connected in series with the electromagnetic contactors 52C1 and 52C2, respectively, so that current flows when the compressors 1a and 1b are stopped. Furthermore, 51C2 is an overcurrent relay for motor MC2, 49C1 and 49C2 are temperature rise protection switches for first compressor 1a and second compressor 1b, respectively, and 63H1 and 63H2 are for first compressor 1a and second compressor 1b, respectively. The pressure rise protection switch 51F is the overcurrent relay for the fan motor MF, and these are connected in series and turn on the electromagnetic relay 30Fx at startup.
It has a protection circuit that turns it off in the event of a failure. The outdoor control unit 15 has a built-in outdoor control device 15a indicated by a broken line, and the outdoor control device 15a has a relationship between the capacity of the compressor 1 and the opening degree of the outdoor electric expansion valve 8 (details will be described later). The outdoor control device 15 is provided with a storage device 31 as a storage means in which the following information is stored in advance.
a controls the operation of each device in accordance with signals input from each indoor control unit 16 or each sensor. Next, FIG. 4 is an electrical circuit diagram showing the interior of the indoor control unit 16 and the main wiring of each connected device. In Fig. 4, MF is the motor of the indoor fan 12a, which receives single-phase AC power and connects each relay terminal RY.
1 to RY3, the air flow is switched between strong wind and weak wind, and the breeze is set to light only when the heating operation is stopped by a signal from the room temperature thermostat TH1. A pulse motor EV for adjusting the opening degree of the indoor electric expansion valve 13 is connected to the terminal CN of the printed circuit board of the indoor control unit 15, while a room temperature thermostat TH1, a temperature sensor TH2,
The TH3 signal is being input. Further, each indoor control unit 16 is connected to the outdoor control unit 15 via a signal line so that signals can be sent and received.
It is connected for input from the remote control switch RCS. The indoor control unit 16 has a built-in indoor control device 16a shown by a broken line, and the indoor electric expansion valve 13 or the indoor The operation of the fan 12a is controlled. In Figure 2, during heating operation of the air conditioner,
The refrigerant is compressed in a gas state by a compressor 1, and is branched and sent to each of the indoor units B to F via a four-way switching valve 5. In each of the indoor units B to F, the water undergoes heat exchange in each of the indoor heat exchangers 12 and is condensed, and then merges. In the outdoor unit A, the liquid is stored in the receiver 9, and in a liquid state is passed through the outdoor electrical equipment expansion valve 8. It is then evaporated in the outdoor heat exchanger 6 under the throttling action and returned to the compressor 1 in a gas state. During the heating operation of the above refrigerant flow, the opening degree of each indoor electric expansion valve 13 is controlled according to the indoor air conditioning load in indoor units B to F, and the opening degree of each indoor electric expansion valve 13 is controlled depending on the overall refrigerant flow rate. The distribution flow rate to ~F is determined by the following procedure. Figure 5 shows the deviation (Ts-
This is a graph showing the relationship between Ta) and the target opening degree of the indoor electric expansion valve 13, where (Amax) is the maximum opening degree, (Amin) is the minimum control opening degree when closing,
(Ao) indicates fully closed. Then, the indoor control unit 16 receives the signal from the room temperature thermostat TH1, calculates the target opening degree AR at every predetermined sampling time, compares it with the current opening degree A, and adjusts the opening degree of the indoor electric expansion valve 13 to AR. <
When AR>A, it closes by a predetermined pulse, and when AR>A, it outputs an opening change signal that opens by a predetermined pulse, and the opening A of the indoor electric expansion valve 16 is changed, and the refrigerant flow rate is distributed according to each opening. . Next, in outdoor unit A, each indoor heat exchanger 1
2. Average value of refrigerant condensation temperature in (condenser)
Capacity control of the compressor 1 is performed to keep Tc constant. The control target value Tcs of the condensing temperature Tc is set to H, M, L by a switch inside the outdoor control unit 15.
(H: Tcs=48℃, M: Tcs=46℃, L: Tcs=44
It can be switched in three ways (°C). That is, the capacity control of the compressor 1 is performed in the following procedure. First, when the average value Tc of the condensing temperature is detected by the pressure sensor P1, the change amount ΔFk in the operating frequency (capacity) of the compressor 1 is determined by the following formula according to the difference from the control target value Tcs. ΔFk=Kc [{e(t)−e(t−Δt)} +(Δt/2Ti){e(t) +e(t−Δt)}] …(1) Here, Kc is the gain, e(t ) is the deviation value between the actual condensing temperature Tc and the control target value Tcs at time t, that is, Te (t) - Tcs (t), e (t - Δt) is the deviation value before the start of sampling, and Δt is the sampling Time, Ti is the integration time. Then, depending on the sum of the value of ΔFk calculated as above and the operating frequency Fk before change, for example,
The operating capacity of compressor 1 is changed in 10Hz steps. Here, the operating capacity of the second compressor 1b is 60Hz when fully loaded and 30Hz when unloaded, so
By combining the capacity change in 10Hz steps of the inverter 2a of the first compressor 1a, the total
It can be adjusted in 10Hz increments within a range of 130Hz. Once the operating frequency (capacity) of the compressor 1 is determined by the above procedure, the opening degree of the outdoor electric expansion valve 8 is changed based on the contents stored in the storage device 31 in accordance with the operating capacity. The relationship between the operating capacity of the compressor 1 and the electric expansion valve 8, which is preset in the storage device 31, will be explained below. First, the evaporation temperature of the refrigerant detected by the temperature sensor TH5 when the compressor 1 shown in FIG. 6 is operating at full capacity.
Based on the relationship characteristic line between Te and the refrigerant circulation amount of the compressor 1, the refrigerant circulation amount of the compressor 1 at that time is determined, and then the refrigerant flow rate and the outdoor electric expansion valve 8, an example of which is shown in FIG. The opening degree of the outdoor electric expansion valve 8 is determined from the refrigerant flow rate based on the relationship characteristic line with the opening degree (this graph is shown when the differential pressure across the electric expansion valve is constant). Examples are shown in Table 1 below.

[Table] However, Table 1 above shows the set values when the evaporation temperature Te=0°C and the condensation temperature Te=50°C. Also,
The opening is determined by the pulse motor EV that drives the electric expansion valve 8)
It is expressed by the pulse value P, and 500 pulses corresponds to full opening. During heating operation, when the condensing temperature Tc changes due to fluctuations in the heating load, etc., and the operating frequency Fk of the compressor 1 changes accordingly, the outdoor control unit 15 controls the outdoor heat exchanger 6 (evaporation The opening degree of the electric expansion valve 8 is controlled so as to maintain the superheat degree SH of the refrigerant in the refrigerant (vehicle) within an appropriate range. The procedure will be explained below based on the flowchart shown in FIG. In the flowchart of Figure 8, the steps
In S1, it is determined whether compressor 1 has changed from starting to stopping.
If NO, the process moves to step S2 and it is determined whether the compressor 1 has been started from a stopped state. Step S2
If the result of the determination is NO, indicating that the compressor 1 is stopped or running, the process proceeds to step S3, where the operating state of the compressor 1 is sampled, and it is determined whether the capacity of the compressor 1 has changed. As a result of the judgment in step S3,
If YES, indicating that the capacity of the compressor 1 has changed, the process proceeds to step S4, where the current pulse value P of the opening and the pulse value of the opening corresponding to the capacity of the compressor 1 before the change are calculated.
Po and the opening pulse value P1 corresponding to the changed capacity of the compressor 1 are read from the storage device 31, respectively. Then, in step S5, the amount of change ΔP in the pulse value for changing the opening degree is calculated using the relational expression ΔP=P×
Calculate by (P1/Po)-P. For example, when the current operating frequency Fk of the compressor 1 is 40Hz and the pulse value of the outdoor electric expansion valve 8 is 100 pulses, if the operating frequency Fk changes to 50Hz, the corresponding new pulse value will be shown in Table 1. 100×151/129 from the relationship
It is calculated as = 117 (pulse). Also, as a result of the determination in step S5, the compressor 1
If NO, the capacity has not changed even when the sampling time is stopped or running, the process proceeds to step S6, and it is determined whether or not the predetermined sampling time has elapsed.If NO, the predetermined sampling time has not elapsed yet, the process returns to step S1. When the result is YES, in step S7, the increment/decrement of the opening degree for PI control to keep the degree of superheat constant is calculated according to the following procedure. First, the degree of superheating SH is determined based on the temperature difference between temperature sensors TH5 and TH6 arranged at the inlet and outlet sides of the outdoor heat exchanger 6 (evaporator), respectively. Next, find the pulse change amount ΔP using the formula below. ΔP=K[{E(t)-E(t-Δt)} +(Δt/2Ti){E(t) +E(t-Δt)}] …(2) Here, E(t) is time t Real side superheat degree at
Deviation value between SH and target superheat degree SHs, E (t-Δt)
Similarly, K is the deviation value at the start of sampling, K is the gain, Δt is the sampling time, and Ti is the integration time. If the determination in step S1 is YES, indicating that the compressor 1 has stopped from being in operation, the process proceeds to step S8, where the pulse change amount ΔP=0-P, and the outdoor electric expansion valve 8 is fully closed. In addition, if the determination in step S2 is YES that the compressor 1 has started from a stopped state, then in step S9 the opening degree P1 is calculated according to the capacity of the compressor 1 at the time of change using the same calculation as that in step S4. Then, in step S10, the pulse change amount ΔP is determined by setting ΔP=P1. Finally, in step S11, each of the above steps S5,
Pulse change amount ΔP found at S7, S8 and S10
The opening degree of the outdoor electric expansion valve 8 is changed accordingly. In the above flow, by step S3,
A determining means 51 is configured to determine when the capacity of the compressor 1 changes, and in step S5, when the capacity of the compressor 1 changes as determined by the determining means 51,
Storage device 31 according to the capacity before and after the change of compressor 1
A calculation means 52 is configured to calculate the amount of change in the opening degree of the outdoor electric expansion valve 8 based on the amount of change in the opening degree set in . Then, in step S11, a control means 53 is configured to control the opening degree of the outdoor electric expansion valve according to the calculation result by the calculation means 52. With the above configuration, in this embodiment, when the capacity of the compressor 1 changes, the opening degree of the outdoor electric expansion valve 8 is controlled in a feedforward manner based on the refrigerant flow rate determined from the capacity of the compressor 1. by
Hunting due to control delay that occurs with PI control or PID control does not occur, and it follows changes in the compressor with a quick pulse-like response. after that,
The opening degree is controlled to the target opening degree by PI control. At this time, the integration time Ti in equation (2) is set so that the pulse change value ΔP is a sufficiently stable and reliable value. When controlling the opening degree of the outdoor electric expansion valve 8 only by conventional PI control or PID control, Ti
If the time is too long, the degree of superheat will change during that time, which will cause hunting due to the control delay, but with the above method including feedforward control, there will be no large change in the degree of superheat. Furthermore, when the capacity of the compressor 1 changes during PI control and feedforward control is performed, the opening degree of the electric expansion valve 8 is changed immediately in response to the change in the capacity of the compressor 1 based on the current opening degree. Therefore, stable control can be performed without sudden changes that ignore the previous control state. As described above, in this embodiment, each indoor unit B
The opening degree of the indoor electric expansion valve 13 is controlled according to the fluctuation of the load of each indoor unit B to F.
Appropriately distribute the amount of refrigerant circulated to the In addition, in the outdoor unit A, the capacity of the compressor 1 is controlled to maintain the condensing temperature in the indoor heat exchanger 12 within an appropriate range, and the opening degree of the outdoor electric expansion valve 8 is controlled to prevent overheating in the outdoor heat exchanger 6. The air conditioning capacity of the indoor units B to F can be fully exerted through stable control without control delay and without hunting. Furthermore, the configuration for control is simplified, since there is no need for procedures for changing various constants, etc., which are required when controlling the opening using only PI control or PID control. In addition, if the total load of indoor units B to F is still small even with respect to the minimum capacity (30Hz) of the compressor 1, the high pressure control valve 24 is activated to connect the auxiliary capacitor 22 to the heating overload control bypass 11e.
When the degree of superheating SH is still larger than the target value SHs even if the outdoor motorized valve 8 is fully opened, the automatic expansion valve 30 is operated by the temperature sensing tube TP1 and the refrigerant is refilled. Excessive rise in superheat degree SH is prevented by performing an in-line injection. Although the explanation has been given above regarding the heating operation, the same applies to the cooling operation of a refrigeration system equipped with one indoor unit and one outdoor unit. In that case, during cooling operation, the indoor electric expansion valve 1
The present invention is applied to the opening degree control of No. 3, and the degree of superheating is determined in the same manner as above using temperature sensors TH2 and TH3 arranged at the entrance and exit of the indoor heat exchanger 12, respectively. At this time, the compressor 1 has a pressure sensor
Based on the signal from P1, the capacity is controlled to keep the evaporation temperature Te constant. Further, by applying a defrost bypass circuit to the above configuration, a positive cycle defrost circuit can be configured. Figure 9 shows an example of this.
11h is a defrost bypass circuit connecting the discharge pipe and the refrigerant inlet of the outdoor heat exchanger 6;
A defrost solenoid valve 35 is interposed in the middle (all other configurations are the same as in FIG. 2, so explanations are omitted). During heating operation, when a defrost command is issued due to frost formation on the outdoor heat exchanger 6, the defrost solenoid valve 3
5 opens, the discharged gas is directly passed through the outdoor heat exchanger 6 to perform a defrost operation, and the completion of defrosting is detected by the increase in the discharged gas pressure at the pressure sensor P1, and the defrost solenoid valve 35 is closed to end the defrost operation. . In this way, since the completion of defrosting is detected using the pressure sensor P1 of the discharged gas during heating, false detection can be prevented and highly reliable positive cycle defrost operation can be performed. (Effects of the Invention) As explained above, according to the refrigeration system of the present invention, when controlling the opening degree of the electric expansion valve that reduces the pressure of the refrigerant,
When the capacity of the compressor is changing, the opening is changed to the current opening multiplied by the opening ratio corresponding to the change in compressor capacity, which reduces control delays and hunting. It is possible to perform stable opening control of the electric expansion valve without any lag, and to fully utilize the refrigerating capacity. Further, there is an advantage that the configuration for control is also simplified.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant system diagram showing the configuration of the present invention. 2 to 9 show embodiments of the present invention, FIG. 2 is a refrigerant system diagram, FIG. 3 is an electric circuit diagram of the outdoor control unit, FIG. 4 is an electric circuit diagram of the indoor control unit, and FIG. Figure 5 is a graph showing the relationship between the deviation between the room temperature thermostat set value and intake air temperature and the opening degree of the indoor electric expansion valve, and Figure 6 is a compressor characteristic line showing the relationship between evaporation temperature and refrigerant flow rate. Figure 7 is a characteristic diagram showing the relationship between the opening degree of the outdoor electric expansion valve and the refrigerant flow rate, Figure 8 is a flowchart diagram showing the opening degree control procedure of the outdoor electric expansion valve, and Figure 9 is a positive cycle diagram. It is a refrigerant system diagram showing a modified example in which defrost operation is added. 1...Compressor, 6...Outdoor heat exchanger (evaporator),
8...Outdoor electric expansion valve, 12...Indoor heat exchanger (condenser), 31...Storage device (storage means), 51
...discrimination means, 52 ... calculation means, 53 ... control means.

Claims (1)

[Scope of Claims] 1. A refrigeration system equipped with a refrigerant circulation circuit formed by sequentially connecting a variable capacity compressor 1, a condenser 12, an electric expansion valve 8 that throttles the refrigerant, and an evaporator 6. A storage means 31 for storing the opening degree of the electric expansion valve 8 according to the capacity of the compressor 1; a determination means 51 for determining when the capacity of the compressor 1 has changed; When the capacitance changes by 1,
The opening change amount ΔP of the electric expansion valve 8 is the current opening value P,
From the opening value Po corresponding to the capacity of the compressor 1 before the change and the opening value P1 corresponding to the capacity after the change, which are stored in the storage means 31, the following formula ΔP=P(P1/Po)-P is obtained. 1. A refrigeration system comprising: a calculation means 52 for calculating based on the calculation means 52; and a control means 53 for controlling the opening degree of the electric expansion valve 8 in response to the output of the calculation means 52.