JPH0833245B2 - Refrigeration system operation controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an operation control device for a refrigeration system, and more particularly to measures for improving refrigeration efficiency.

(Prior Art) Conventionally, as disclosed in, for example, Japanese Patent Publication No. Sho 59-12942, a refrigerant in a refrigeration system including a refrigerant circuit in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, The optimum temperature of the discharge pipe temperature that gives the optimum refrigeration effect is calculated based on the evaporation temperature and the condensation temperature of the compressor, and the opening of the electric expansion valve is controlled so that the discharge pipe temperature converges to the optimum temperature. It is a well-known technique to ensure highly efficient operation without changing the operating capacity of the.

(Problems to be solved by the invention) As in the conventional one, by maintaining the state of the discharged refrigerant in an appropriate state, it is possible to perform a smooth operation of the refrigerant circuit without controlling the capacity of the compressor. There is an advantage that a simple control can be performed by using a displacement type compressor. However, on the other hand, if the opening degree of the electric expansion valve is controlled using only the state quantity of the discharged refrigerant as a control index, the capacity of the evaporator may be left at a value apart from the required capacity during that time, depending on the operating conditions. There is a risk that the ability will not be fully satisfied.

The present invention has been made in view of the above circumstances, and an object thereof is to control the evaporating capacity so as to correspond to the required capacity while maintaining the state of the discharged refrigerant in an appropriate state, thereby improving the comfort of air conditioning. Is to improve.

(Means for Solving the Problem) A first means for achieving the above object is, as shown in FIG. 1A, a compressor (1), a condenser (3 or 6), and an electric expansion valve (5). And a refrigeration system provided with a refrigerant circuit (9) in which evaporators (6 or 3) are sequentially connected.

Then, as an operation control device of the refrigeration system, an evaporation temperature detecting means (The) for detecting the evaporation temperature of the refrigerant in the evaporator (6 or 3) and a condensation temperature of the refrigerant in the condenser (3 or 6) are detected. Condensing temperature detection means (Thc)
And the outputs of the evaporation temperature detecting means (The) and the condensation temperature detecting means (Thc), and calculates the optimum temperature of the discharged refrigerant temperature that gives the optimum refrigerating effect according to the evaporation temperature and the condensation temperature of the refrigerant. The optimum temperature calculating means (51), the discharge temperature detecting means (Th2) for detecting the discharge refrigerant temperature, and the output of the discharge temperature detecting means (Th2), the discharge refrigerant temperature is received by the optimum temperature calculating means (51). A normal range opening control means (52) for controlling the opening of the electric expansion valve (5) is provided so as to converge to the calculated optimum temperature.

Further, the suction temperature detection means (Thr) for detecting the suction air temperature of the evaporator (6 or 3), the outputs of the suction temperature detection means (Thr) and the discharge temperature detection means (Th2), and the discharge refrigerant When the temperature converges within a certain range above and below the optimum temperature calculated by the optimum temperature calculation means (51), the control of the normal range opening control means (52) is forcibly stopped,
A discharge temperature convergence region opening degree control means (53) for controlling the opening degree of the electric expansion valve (5) according to the suction temperature difference between the suction air temperature and its set value is provided.

As shown in FIG. 1B, the second solving means is premised on the same refrigerating apparatus as the first solving means, and as an operation control device of the refrigerating apparatus, the same evaporation temperature detection as that of the first solving means is performed. Means (The), condensation temperature detection means (Thc), optimum temperature calculation means (51), discharge temperature detection means (Th2), and normal range opening control means (52) are provided.

Further, the suction temperature detecting means (Thr) for detecting the suction air temperature of the evaporator (6 or 3) and the output of the suction temperature detecting means (Thr) are received, and the suction air temperature is within a predetermined range above and below the set temperature. When it converges within the range, the control of the normal range opening control means (52) is forcibly stopped, and a predetermined weight is given to the temperature difference between the discharge refrigerant temperature-the optimum temperature and the suction air temperature-the set temperature. A capacity convergence region opening control means (54) for controlling the opening degree of the electric expansion valve (5) based on the calculated value is provided.

(Operation) With the above configuration, in the invention of claim (1), the evaporation temperature and the condensation temperature of the refrigerant detected by the evaporation temperature detection means (The) by the optimum temperature calculation means (51) during the operation of the refrigeration system. The optimum temperature of the discharge pipe that gives the optimum refrigerating effect is calculated in accordance with the condensation temperature of the refrigerant detected by the detection means (The).

Then, since the opening degree of the electric expansion valve (5) is controlled by the normal range opening degree control means (52) so that the discharge refrigerant temperature converges to the optimum temperature, the operating capacity of the compressor (1) is fixed. However, the refrigerant state in the refrigerant circuit (9) is maintained in an appropriate state.

In that case, if the operation is performed only based on such a frozen state, the air conditioning request may be ignored, and the comfort of the air conditioning may be impaired. When the control means (53) converges the discharge refrigerant temperature within a certain range above and below the optimum temperature, it is electrically driven according to the temperature difference between the intake air temperature detected by the intake air temperature detection means (Thr) and its set temperature. Since the opening degree of the expansion valve (5) is controlled, the capacity of the evaporator (6 or 3) is controlled to the capacity according to the required capacity, and the comfort of air conditioning is improved.

In the invention of claim (2), the opening of the electric expansion valve (5) is controlled by the normal range opening control means (52), and the refrigerant state is in the proper state, as in the invention of claim (1). Maintained at.

At that time, when the suction air temperature detected by the suction temperature detection means (Thr) converges to the set value, the capacity convergence range opening control means (54) changes the suction air temperature of the evaporator (6 or 3). Based on the correlation between the discharge refrigerant temperature and the change of the discharge refrigerant temperature, the temperature difference between the discharge refrigerant temperature and its optimum temperature, and the difference temperature between the intake air temperature and its set value, a predetermined weighted value for both Since the opening degree of the electric expansion valve (5) is controlled in accordance with the above, the refrigerant state is maintained in an appropriate state, the capacity of the evaporator (6 or 3) is maintained at a value corresponding to the required capacity, and the thermostat is turned off.・ Reliability will be improved by reducing the number of times the switch is turned on.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings starting from FIG.

FIG. 2 shows a refrigerant piping system of an air conditioner to which the present invention is applied. (1) is a fixed-capacity scroll type compressor, (2) is shown by a solid line in the figure during cooling operation, and in the figure during heating operation. Four-way switching valve that switches as shown by the broken line, (3)
Is an outdoor heat exchanger that is a heat source side heat exchanger that functions as a condenser during cooling operation and as an evaporator during heating operation,
(4) is a receiver for storing the liquid refrigerant, (5) is an electric expansion valve having a refrigerant pressure reducing function and a refrigerant flow rate adjusting function, (6) is installed indoors, and serves as an evaporator during cooling operation, An indoor heat exchanger, which is a utilization side heat exchanger that functions as a condenser during heating operation, (7) is an accumulator that is installed in the suction pipe of the compressor (1) and removes the liquid refrigerant in the suction refrigerant. is there. The above-mentioned devices (1) to (7) are sequentially connected by a refrigerant pipe (8), and a refrigerant circuit (9) configured to cause heat transfer by circulation of the refrigerant is configured.

Here, an oil recovery device (10) for recovering oil in the discharged refrigerant is provided on the discharge side of the compressor (1) of the refrigerant circuit (9), and the oil recovery device (10) is provided. From compressor (1)-
Oil collector (10) up to the suction pipe between the accumulator (7)
An oil return passage (11) is provided for returning the oil of (1) to the suction side of the compressor (1). And this oil return passage (1
In 1), an opening / closing valve (12) for opening and closing a passage is provided, and the opening / closing valve (12) is normally closed, while a predetermined control is performed when the compressor (1) is started. Opened by
Part of the oil and the discharged refrigerant of the oil recovery device (10) is returned to the suction side of the compressor (1).

In the liquid pipe of the refrigerant circuit (9), the receiver (4) and the electric expansion valve (5) have a common path (so that the electric expansion valve (5) communicates with the lower part of the receiver (4), that is, the liquid part. 8a) is arranged in series, and the point (P), which is the end of the common path (8a) on the upper side of the receiver (4), and the outdoor heat exchanger (3) are connected to the receiver (4) side. First inflow passage (8b) through the first check valve (21) that allows only the circulation of the refrigerant of
Therefore, between the point (P) of the common path (8a) and the indoor heat exchanger (6), a second check valve (22) that allows only the refrigerant to flow to the receiver (4) side is provided. Point (Q), which is the end of the common path (8a) on the side of the electric expansion valve (5) and is connected to the second inflow path (8c), respectively, and the first check valve (21) -outdoor The point (S) between the heat exchangers (3) is the first
A point between the point (Q) on the common channel (8a) and the second check valve (22) -indoor heat exchanger (6) by the first outflow channel (8d) via the capillary tube (C ₁ ). (R) is connected by the second outflow passage (8e) via the second capillary tube (C ₂ ).

That is, during the cooling operation, the liquid refrigerant condensed and liquefied in the outdoor heat exchanger (3) is stored in the receiver (4) through the first check valve (21), and the electric expansion valve (5) and the second capillary tube are stored. After decompressing with (C ₂ ), indoor heat exchanger (6)
In the heating operation, the liquid refrigerant condensed and liquefied in the indoor heat exchanger (6) passes through the second check valve (22) to the receiver (4). Is stored,
After the pressure is reduced by the electric expansion valve (5) and the first capillary tube (C ₁ ), it is evaporated in the outdoor heat exchanger (3) and returned to the compressor (1).

In addition, (8f) is a liquid seal prevention bypass passage provided by bypassing the first check valve (21) in the first inflow passage (8b) between the point (P) and the point (S), A third capillary tube (C ₃ ) for depressurizing the refrigerant is provided in the liquid seal prevention bypass passage (8f).

Further, sensors are arranged in the air conditioner, (Th2) is arranged in the discharge pipe of the compressor (1), and a discharge pipe sensor as a discharge temperature detecting unit for detecting the discharge pipe temperature T ₂ , (Thc) is arranged in the liquid pipe of the outdoor heat exchanger (3) and is an external heat exchange sensor as a condensation temperature detecting means for detecting the evaporation temperature of the refrigerant during the cooling operation, and (Tha) is the outdoor heat exchanger (3). The outside air temperature sensor, which is arranged at the air inlet of the unit, detects the outside air temperature, (The) is arranged in the liquid pipe of the indoor heat exchanger (6), and serves as an evaporation temperature detecting means for detecting the evaporation temperature Te during the cooling operation. The internal heat exchange sensor (Thr) is an indoor suction sensor which is arranged at the air suction port of the indoor heat exchanger (6) and serves as a suction temperature detecting means for detecting the suction air temperature Tr.
Each of the above sensors is connected to a controller (not shown) for controlling the operation of the air conditioner so that signals can be input, and the controller controls the operation of each device according to the signal of the sensor. Has been done.

Next, the control contents of the controller will be described with reference to FIGS. 3 and 4.

FIG. 3 shows the contents of the EER control for maintaining the refrigeration effect EER at the maximum during the cooling operation. In step S ₁ , the evaporation temperature Te and the external heat exchange sensor detected by the inner heat exchange sensor (The) are shown. the discharge pipe temperature T ₂ detected respectively input at the condensation temperature Tc and the discharge pipe sensor is detected by (Thc) (Th2), in step S _2, the following equation (1) Tk = 4-1.13Te + 1.72Tc ( Based on 1), calculate the optimum temperature Tk, which is the discharge pipe temperature that gives the optimum refrigeration effect EER.

Next, in step S ₃ , the temperature difference ΔT ₂ between the discharge pipe temperature T ₂ and the optimum temperature Tk is calculated based on the formula ΔT ₂ = T ₂ −Tk, and then in step S ₄ , | ΔT ₂ | ≦ 5? Whether or not, that is, whether or not the discharge pipe temperature T ₂ has converged within a certain range above and below the optimum temperature Tk, until it converges, the process proceeds to step S _5, and whether ΔT ₂ is positive, that is, the discharge It is determined whether the pipe temperature T ₂ is higher than the optimum temperature Tk, and if the discharge pipe temperature T ₂ is higher, step S
_6, while controlling to open the motor-operated expansion valve (5) to moderate, the lower the better of the discharge pipe temperature T _2, at step S _7, to close moderately opening degree of the electronic expansion valve (5) To control.

On the other hand, when it is determined in step S ₄ that | ΔT ₂ | ≦ 5 and the discharge pipe temperature T ₂ converges within a certain range above and below the optimum temperature Tk, the process proceeds to step S ₈ and the following fuzzy control is executed. To do.

That is, as shown in FIG. 4, in step R ₁ , P-
After updating the opening drive pulse P of the electric expansion valve (5) with 1 = P (P-1 is the previous drive pulse), the discharge pipe sensor abnormality becomes “1” at the time of abnormality in step R _2. flag
Ft2 is determined whether or not "1", if not abnormal, the process proceeds to step R _3, temperature difference ΔTr of the suction air temperature Tr and the set temperature Trs detected by the indoor inlet sensor (Thr) (where ,
During cooling operation, ΔTr = Tr-Trs) is determined to be 2.5 deg or more, and if ΔTr ≧ 2.5, the process proceeds to step R ₄ and the following equation (2) P = 3.2 ΔT ₂ (2) The drive pulse P for the opening degree of the electric expansion valve (5) is calculated on the basis of the above, while if ΔTr ≧ 2.5, that is, the intake air temperature T
When r is converged within the upper and lower predetermined range of the set temperature Trs, the procedure proceeds to step R _5, the following equation (3) _{P = 3.2ΔT 2 + 6.4ΔTr (3} ) the basis electric expansion valve (5) opening drive of The pulse P is calculated. That is, in the above formula (3), the temperature difference ΔT ₂ between the discharge pipe temperature T ₂ and the optimum temperature Tk, and the intake air temperature Tr−the set temperature Trs.
The opening degree of the electric expansion valve (5) is controlled based on the value obtained by weighting the differential temperature ΔTr of 1 to 2 with.

Next, when the control of the above step R ₄ or R ₅ is completed, it proceeds to step R ₆ and determines whether or not | P | ≦ 5, and when the commanded drive pulse P is small, the control state is changed. it is determined that the poor need, the program returns to the main flow, | P | ≦ 5 Otherwise, the process proceeds to step R _7, P> 0
It is determined whether or not. Then, when P> 0, the electric expansion valve (5)
If command to increase the opening degree, at step R _10, P
−1 ≦ P, that is, whether the current drive pulse P is larger than the previous drive pulse P−1, and if this time is larger, in step R ₁₁ , the drive command value P is obtained. When the opening degree of the electric expansion valve (5) is opened and the current drive command value P is less than or equal to the previous drive command value P-1, the process directly returns to the main flow.

In the judgment at the step R _6, when not P> 0, the process proceeds to step R _8, last from the drive command P-1 of this drive command P is small that is, if the electric expansion valve (5)
If the opening change amount of is larger this time, step R ₉
Then, the opening degree of the electric expansion valve (5) is controlled to be closed according to the drive command P, while the opening degree of the electric expansion valve (5) is changed when the change amount by the present drive command P is smaller. Without returning to the main flow.

In the above flow, the control of step S ₂ constitutes the optimum temperature calculation means (51) for calculating the optimum temperature Tk of the discharge pipe temperature that gives the optimum refrigerating effect in accordance with the evaporation temperature Te and the condensation temperature Tc of the refrigerant. is under the control of the step S ₅ to S _7, the discharge refrigerant temperature T ₂ controls the degree of opening of the electric expansion valve (5) to converge to the optimum temperature Tk is calculated at the optimum temperature calculating means (51) A normal range opening control means (52) is configured.

Also, after proceeding from step R ₃ to R ₄ , steps R _{6 to} R ₁₁
When the discharged refrigerant temperature T ₂ converges within a certain range above and below the optimum temperature Tk calculated by the optimum temperature calculation means, the control of the normal range opening control means (52) is forcibly stopped. The discharge temperature convergence region opening degree control means (53) is configured to control the opening degree of the electric expansion valve (5) according to the suction temperature difference ΔTr between the suction air temperature Tr and its set value Trs. .

Meanwhile, in the present invention (2), from Step R ₃ by control performing step R ₆ to R ₁₁ after shifting to R _5, when the inlet air temperature Tr converges within upper and lower predetermined range of the set temperature, The control of the normal range opening control means (52) is forcibly stopped, and based on the value obtained by weighting the temperature difference between the discharge refrigerant temperature-the optimum temperature and the suction air temperature-the set temperature with a predetermined weight. A capacity convergence region opening degree control means (54) for controlling the opening degree of the electric expansion valve is configured.

Therefore, in the above-described embodiment, during the operation of the air conditioner, the evaporation temperature T of the refrigerant detected by the internal heat exchange sensor (evaporation temperature detection means) (The) by the optimum temperature calculation means (51).
The discharge refrigerant temperature T ₂ that gives the optimum refrigerating effect EER is calculated based on the above equation (1) according to e and the refrigerant condensing temperature Tc detected by the external heat exchange sensor (condensing temperature detecting means) (Thc). To be done.

That is, as shown in the Mollier diagram of FIG. 5, the high-pressure side pressure is Hp, the low-pressure side pressure is Lp, the inlet temperature of the gas refrigerant in the compressor (1) is T ₁ , and the outlet temperature is T ₂ (that is, Assuming that the discharge pipe temperature is T ₂ ), in polytropic compression, the following equation (4) T ₂ = T ₁ (Hp / Lp) ^{n-1 / n} (4) (where n is a polytropic index and the compressor ( 1)
Is determined by the type, volume, etc.), but the pressure value on the high-pressure side
Hp can be replaced by the condensation temperature Tc, and the low-pressure side pressure value Lp can be replaced by the evaporation temperature Te, and the superheat degree Sh can be, for example, 2 ° C.
The degree is determined as optimum by (5 see figure) that, as T ₂
T ₁ from the relationship between T ₁ is determined, after all, would be expressed in the form of the following equation (5) _{T 2 = αTe + βTc + γ} (5). Then, in the present embodiment, the optimum temperature Tk of the discharge pipe temperature T ₂ that gives the optimum refrigeration effect EER is expressed by the above formula (1) by experiments.

Therefore, since the opening degree of the electric expansion valve (5) is controlled by the normal range opening degree control means (52) so that the discharge pipe temperature T ₂ converges to the optimum temperature Tk, the operating capacity of the compressor (1) is increased. Even if is fixed, the refrigerant state in the refrigerant circuit (9) is controlled within an appropriate range, and smooth operation is maintained.

In that case, if the operation is performed only based on such a frozen state, the air conditioning request may be ignored, which may impair the comfort of the air conditioning. However, in the invention of claim (1), When the discharge pipe temperature T ₂ converges within a certain range above and below the optimum temperature Tk (± 5 deg (see FIG. 5) in the above embodiment) by the temperature convergence region opening control means (53), the indoor suction sensor ( Since the opening degree of the electric expansion valve (5) is controlled according to the temperature difference ΔTr between the suction air temperature Tr detected by the suction temperature detection means (Thr) and its set temperature Trs, the indoor heat exchanger (6) The amount of heat exchange in (1) is controlled to a capacity according to the required capacity, and the comfort of air conditioning is improved.

In the invention of claim (2), as in the invention of claim (1), the normal range opening control means (52) is used to perform the above (1).
Based on the equation, the opening degree of the electric expansion valve (5) is controlled, and the refrigerant state is maintained in an appropriate state.

At that time, when the suction air temperature Tr detected by the suction sensor (Thr) converges to the set value Trs, it is generally necessary to finely adjust the opening degree of the electric expansion valve (5). Therefore, it is necessary to satisfy both the required capacity and the suitability of the refrigerant state.

By the way, generally, there is a correlation between the change in the intake air temperature Tr of the indoor heat exchanger (6) and the change in the discharge pipe temperature T ₂ . For example, in the case of the present embodiment, from the experimental data, when the intake air temperature Tr rises by 1 deg, the discharge pipe temperature T ₂ rises by ₂ deg.

Here, in the invention of claim (2), the capacity convergence range opening control means (54) controls the temperature difference ΔT ₂ between the discharge pipe temperature T ₂ and its optimum temperature Tk, the suction air temperature Tr and its set value. The opening degree of the electric expansion valve (5) is controlled based on a value obtained by weighting both of them with respect to the temperature difference ΔTr with Trs. That is,
By performing the control based on the production rule of the fuzzy control with the weighting of ΔTr and ΔT _{2 set} to 2: 1 as in the formula (3) of the above-described embodiment, the properness of the refrigerant state is maintained, and The capacity of the indoor heat exchanger (6) is secured to a value corresponding to the required capacity. As a result, it is possible to improve reliability by reducing the number of times the thermostat is turned off and on while maintaining the comfort of air conditioning.

It should be noted that, in the above-mentioned embodiment, the air conditioner is explained in the cooling operation, but it goes without saying that the present invention can be applied in the heating operation, and not only the air conditioner but also the container refrigerating apparatus and the like. It is also applicable to the refrigerator.

(Effect of the invention) As described above, according to the invention of claim (1),
In a refrigeration system equipped with a refrigerant circuit in which a compressor, an evaporator, an electric expansion valve, and an evaporator are sequentially connected, the discharge refrigerant temperature becomes an optimum temperature calculated based on the evaporation temperature and condensation temperature of the refrigerant at that time. While controlling the opening of the electric expansion valve to converge, when the discharge refrigerant temperature converges within a certain range above and below the optimum temperature, the opening of the electric expansion valve is adjusted according to the difference between the intake air temperature and its set value. Since the control is performed, the comfort of the air conditioning can be improved while properly maintaining the refrigerant state and ensuring a good refrigeration effect.

According to the invention of claim (2), in a refrigerating device including a refrigerant circuit in which a compressor, an evaporator, an electric expansion valve, and an evaporator are sequentially connected, the discharge pipe temperature is the evaporation temperature of the refrigerant at that time. While controlling the opening of the electric expansion valve to converge to the optimum temperature calculated based on the condensation temperature, if the intake air temperature converges within a certain range above and below the set value, the temperature between the discharge pipe temperature and the optimum temperature Since the opening degree of the electric expansion valve is controlled by a value weighted according to the difference and the temperature difference between the intake air temperature and the set value, the refrigerant state and the capacity of the evaporator have appropriate values. It is possible to improve reliability by reducing the number of times the thermostat is turned on and off while performing such fine control.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 and the following shows an embodiment of the present invention, FIG. 2 is a refrigerant piping system diagram showing a configuration of an air conditioner, FIGS. 3 and 4 show control contents during a cooling operation of a controller, and FIG. FIG. 4 is a flow chart showing a main flow for controlling the opening degree of the electric expansion valve, FIG. 4 is a flow chart showing a sub-flow relating to a fuzzy control portion of the main flow, and FIG. It is a Mollier diagram for. 1 ... Compressor 3 ... Outdoor heat exchanger (condenser or evaporator) 5 ... Electric expansion valve 6 ... Indoor heat exchanger (evaporator or condenser) 9 ... Refrigerant circuit 51 ... Optimum temperature calculation Means 52 …… Normal area opening degree control means 53 …… Discharge temperature convergence area opening degree control means 54 …… Capacity convergence area opening degree control means Thc …… External heat exchange sensor (condensation temperature detection means) The …… Internal heat exchange Sensor (evaporation temperature detection means) Th2 …… Discharge pipe sensor (discharge temperature detection means) Thr …… Indoor suction sensor (suction temperature detection means)

Claims (2)

[Claims] 1. A refrigeration system provided with a refrigerant circuit (9) comprising a compressor (1), a condenser (3 or 6), an electric expansion valve (5) and an evaporator (6 or 3) which are sequentially connected. Evaporation temperature detection means (The) for detecting the evaporation temperature of the refrigerant in the evaporator (6 or 3), and condensation temperature detection means (Thc) for detecting the condensation temperature of the refrigerant in the condenser (3 or 6) Optimum for receiving the outputs of the evaporation temperature detecting means (The) and the condensation temperature detecting means (Thc) and calculating the optimum temperature of the discharge refrigerant temperature which gives the optimum refrigerating effect in accordance with the evaporation temperature and the condensation temperature of the refrigerant. The temperature calculation means (51), the discharge temperature detection means (Th2) for detecting the discharge refrigerant temperature, and the output of the discharge temperature detection means (Th2), the discharge refrigerant temperature is calculated by the optimum temperature calculation means (51). Of the electric expansion valve (5) so that it converges to the optimum temperature. And a suction temperature detecting means (Thr) for detecting the suction air temperature of the evaporator (6 or 3), and a suction temperature detecting means (Thr). When the output of the discharge temperature detecting means (Th2) and the discharge refrigerant temperature converge within a certain range above and below the optimum temperature calculated by the optimum temperature calculating means (51), the normal range opening control means (52) ) Is forcibly stopped, and a convergence range opening control means (53) for controlling the opening of the electric expansion valve (5) according to the suction temperature difference between the suction air temperature and its set value. An operation control device for a refrigeration system, which is provided. 2. A refrigeration system provided with a refrigerant circuit (9) comprising a compressor (1), a condenser (3 or 6), an electric expansion valve (5) and an evaporator (6 or 3) which are sequentially connected. Evaporation temperature detection means (The) for detecting the evaporation temperature of the refrigerant in the evaporator (6 or 3), and condensation temperature detection means (Thc) for detecting the condensation temperature of the refrigerant in the condenser (3 or 6) An optimum temperature calculating means for receiving the outputs of the evaporation temperature detecting means (The) and the condensing temperature detecting means (Thc) and calculating an optimum temperature that gives an optimum refrigerating effect in accordance with the evaporation temperature and the condensation temperature of the refrigerant ( 51), a discharge temperature detecting means (Th2) for detecting the discharge refrigerant temperature, and an optimum temperature at which the discharge refrigerant temperature is calculated by the optimum temperature calculating means (51) by receiving the output of the discharge temperature detecting means (Th2). The opening degree of the electric expansion valve (5) is controlled to converge to Together and a normal range opening control means (52), the evaporator (6 or 3)
Suction temperature detection means (Thr) for detecting the suction air temperature of
And the output of the suction temperature detection means (Thr) and the discharge temperature detection means (Th2), and when the suction air temperature converges within a predetermined range above and below the set temperature, the normal range opening control means (52) Control is forcibly stopped, and the opening degree of the electric expansion valve (5) is determined based on a value obtained by weighting the temperature difference between the discharge refrigerant temperature-the optimum temperature and the suction air temperature-the set temperature by a predetermined weight. An operation control device for a refrigerating device, comprising: a capacity convergence range opening degree control means (54) for changing the temperature.