JP2701623B2 - Operation control device for refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control device for a refrigeration system, and more particularly, to an improvement of a refrigeration system in which the capacity is increased during a pull-down operation.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 62-2589
As disclosed in Japanese Patent Publication No. 79, an evaporator is arranged in the storage,
In a refrigeration system equipped with a variable displacement compressor, the capacity of the compressor is reduced when the temperature in the refrigerator reaches the in-range, while the capacity of the compressor is increased when the temperature in the refrigerator moves out of the in-range. It is a known technique that attempts to ensure the capacity of the refrigeration apparatus according to the load by controlling the refrigerating apparatus to perform the control.

[0003]

By the way, in a refrigeration system for a container or the like, normally, control is performed such that the capacity is increased during the pull-down operation as in the above-mentioned conventional apparatus, and the capacity of the compressor is increased when the compressor enters the in-range. However, when the outside air temperature is very high (for example, 50 ° C.)
In some cases, operating the compressor with a low capacity to delay the establishment of the defrost condition during pull-down operation may shorten the pull-down operation time, and such control is actually performed. ing. In such a case, when the temperature in the refrigerator reaches a predetermined value, the temperature difference between the temperature in the refrigerator and the outside air temperature becomes very large. Therefore, in order to further reduce the temperature in the refrigerator and approach the in-range, the capacity of the compressor must be reduced. High capacity is required.

However, when the capacity of the compressor is switched to a high capacity, an overload condition is apt to occur particularly when the outside air temperature is high. There was a possibility that continuation would not be possible. In order to avoid such a situation, it is effective to limit the opening of the electric expansion valve during the pull-down operation to a small degree. However, in this case, the pull-down capability is reduced and the pull-down operation time is lengthened.

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide a means for eliminating an overload state caused by an increase in capacity of a compressor while maintaining a high pull-down capability. The purpose is to expand operating conditions such as outside air conditions.

[0006]

In order to achieve the above object, a solution of the present invention is to change the upper limit opening of the electric expansion valve to a small value when the compressor is switched to a high capacity during the pull-down operation. is there.

Specifically, the means taken by the invention of claim 1 is:
As shown in FIG. 1 (not including the dotted line), the variable displacement compressors (2a, 3a) and the evaporator (2
i, 3i) and electric expansion valves (EV1, EV) for variably adjusting the degree of pressure reduction of the refrigerant supplied to the evaporators (2i, 3i).
2) is disposed in the refrigerant circuit (1), and a refrigerating device provided with a protection device (41) that detects an overload state and outputs an abnormal signal is assumed.

When the operation of the refrigeration apparatus is started, the upper limit opening of the electric expansion valves (EV1, EV2) is set to a predetermined value, and the operation of the compressor (2a, 3a) is started.
Pull-down operation control means (45A) for controlling the operation capacity to be low to lower the internal temperature of the storage, the internal temperature detection means (Th1) for detecting the internal temperature of the storage, and the pull-down operation control means (45A) ) During pulldown operation,
A capacity increasing means (46A) for switching the capacity of the compressor (2a, 3a) to a high capacity when the inside temperature detected by the inside temperature detecting means (Th1) reaches a predetermined temperature or lower is provided.

Further, when the protection device (41) operates when the capacity is increased by the capacity increasing means (46A),
Abnormality control means (47) for controlling the upper limit opening of the electric expansion valves (EV1, EV2) to be restarted after reducing the upper limit opening from the above-mentioned predetermined value by a certain value is provided.

As shown in FIG. 1 (excluding the broken line portion), the means adopted by the invention of claim 2 is based on the same refrigeration apparatus as that of the invention of claim 1 described above, and is used as an operation control device of the refrigeration apparatus. When the operation of the refrigerating apparatus is started, the compressor (2a, 3
a) Pull-down operation control means (45B) for controlling the operation capacity to be low so as to lower the temperature in the refrigerator, temperature detection means in the refrigerator (Th1) for detecting the temperature in the refrigerator, and the pull-down operation control means During the pull-down operation by (45B), when the internal temperature detected by the internal temperature detecting means (Th1) reaches a predetermined temperature or less, the compressor (2a, 3)
Ability increasing means for switching the capacity of a) to a high capacity (46B)
Are provided.

Further, as the overload state in which the protection device (41) operates is approached, the electric expansion valves (EV1, EV2) become closer.
First change pattern set to reduce the upper limit opening of
And the second change pattern, wherein the second change pattern
The upper limit of the opening is the upper limit of the first change pattern.
Two change patterns set to be smaller than the opening
And storing the memory means (42), based on the storage of the storage means (42), the upper limit of the time the pull-down operation by the pull-down operation means (45B) in response to said first change pattern electric expansion valve (EV1, EV2) While changing the opening,
When the capacity is increased by the capacity increasing means (46B),
The electric expansion valves (EV1, EV1
An upper limit opening changing means (48) for switching so as to change the upper limit opening of 2) is provided.

[0012]

With the above arrangement, according to the first aspect of the present invention, at the start of the operation of the refrigeration system, the pull-down operation control means (45A)
As a result, the operating capacity of the compressor (2a, 3a) is reduced,
The upper limit opening of the electric expansion valves (EV1 and EV2) is set to a predetermined value, and a pull-down operation is performed to quickly bring the temperature in the refrigerator closer to the in-range. When the temperature in the refrigerator reaches a predetermined temperature, the operating capacity of the compressor (2a, 3a) is switched to a high capacity by the capacity increasing means (46A) in order to increase the refrigerating capacity.

When the capacity is increased, especially when the outside air temperature is high, an overload condition occurs, and the high-pressure side pressure rises excessively to activate the protection device (41). In addition, since the upper limit of the electric expansion valves (EV1, EV2) is controlled to be reduced from the predetermined value by a certain amount and then restarted, the overload state is eliminated by the decrease in the refrigerant flow rate, and the continuation of operation is continued. Will be possible. Therefore, even if the upper limit opening of the electric expansion valves (EV1, EV2) is increased from the beginning, the inoperable state is avoided, and the range of operating conditions such as the outside air temperature that can be used while maintaining the pull-down capability as much as possible is reduced. It will expand.

According to the second aspect of the present invention, the pull-down operation is performed by reducing the capacity of the compressors (2a, 3a) by the pull-down operation control means (45B). The capacity of the compressor (2a, 3a) is switched to the high capacity side by the increasing means (46B).

At this time, two types of change patterns, large and small, are set in advance in the storage means (42) so that the upper limit opening of the electric expansion valves (EV1, EV2) is reduced as the overload state is approached. When the compressor (2a, 3a) has a low capacity, the upper limit opening is large by the opening changing means (48) .
According to 1 change pattern , upper limit opening is small at high capacity
The degree of opening of the electric expansion valves (EV1, EV2) is limited according to the second change pattern, so that approach to the overload state is always prevented during the pull-down operation, and abnormal stop is avoided beforehand.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a refrigerant piping system of the refrigerant circuit (1) of the container refrigeration system (A) according to the embodiment of the present invention. The refrigerant circuit (1) is provided with a first circuit system (2) and a second circuit system (3) which are independent from each other.

Each of the circuit systems (2, 3) includes one scroll compressor (2a, 3a), and filters (2b, 3b) from the discharge side of the compressor (2a, 3a).
And an air-cooled condenser (2) with an external fan (F2)
c, 3c), water-cooled condensers (2d, 3d), receivers (2e, 3e), dryers (2f, 3f), liquid indicators (2g, 3g), and an accumulator (2h, 3h), the electric expansion valves (EV1, EV2), which are expansion mechanisms, and the evaporator (2i, 3i) provided with the internal fan (F1) are sequentially connected to the closed circuit via the refrigerant pipe (11). Provided main circuit (21, 31),
The air-cooled condenser (2c, 3) in each of the circuit systems (2, 3)
c), a water-cooled condenser (2d, 3d) and an evaporator (2i, 3).
i) and are integrated.

Each of the circuit systems (2, 3) is provided with a hot gas bypass circuit (22, 32) and an injection circuit (23, 33). A check valve (CV) is provided between the filter (2b, 3b) and the air-cooled condenser (2c, 3c).
1, CV2), the receiver (2e, 3e) and the dryer (2
f, 3f) and stop valve (TV1, TV2)
However, there is a liquid valve (LV) between the liquid indicator (2g, 3g) and the accumulator (2h, 3h).
1, LV2), the evaporator (2i, 3i) and the compressor (2a,
3a), suction valves (SV1, SV2) are interposed respectively. The liquid valves (LV1, LV2) store a predetermined amount of refrigerant used in the defrost operation in the accumulators (2h, 3h). In addition, the above suction valve (SV1,
SV2) is provided with a bleed port to control the refrigeration capacity.

The hot gas bypass circuit (2)
2, 32) is connected at one end to a hot gas valve (HV1, HV2) comprising a three-way solenoid valve interposed between the filter (2b, 3b) and the check valve (CV1, CV2). The other end is an electric expansion valve (EV1, EV2) and an evaporator (2
i, 3i), the refrigerant from the compressors (2a, 3a) during the defrost operation is supplied to each of the condensers (2c, 3c).
2d, 3c, 3d) bypassing the evaporator (2i, 3d).
i). On the other hand, the injection circuits (23, 33) include injection valves (IV1, IV
2) is provided, and the inflow side port thereof is connected between the receivers (2e, 3e) and the stop valves (TV1, TV2) via the capillaries (23a, 33a), and one of the outflow sides. Port is at the intermediate pressure section of the compressor (2a, 3a), and the other port on the outflow side is the compressor (2a, 3a).
a) are connected to the suction side, respectively.
a, 3a) when the injection valves (IV1, IV
2) is opened, and is configured to supply the liquid refrigerant to the compressor (2a, 3a) to cool the refrigerant discharged from the compressor (2a, 3a) and reduce the high-pressure refrigerant pressure.

In the refrigerant circuit (1), a high-pressure sensor (HPS) for detecting the high-pressure refrigerant pressure on the discharge side of the compressor (2a, 3a) is connected to a low-pressure sensor on the suction side of the compressor (2a, 3a). A low pressure sensor (LPS) for detecting refrigerant pressure is provided, and a check valve and an air-cooled condenser (2c, 3) are provided.
A high-pressure control sensor (HPCS) for controlling the high-pressure refrigerant pressure is provided between the high-pressure control sensor and (c). Also, in FIG.
(Th1) is a suction sensor as an inside temperature detecting means for detecting an intake air temperature Tr corresponding to the inside temperature, (Th2) is a blowout sensor for detecting a blown air temperature, and (Tha) detects an outside air temperature. It is an outside air sensor.

Although not shown, each of the above sensors (HP
S, LPS, HPCS, Th1, Th2, and Th) are controllers (4)
Connected to the respective sensors (HPS, LPS, HPCS, Th1, Th2,
Tha) is inputted to the controller (4), and the controller (4) is configured to
a, 3a), electric expansion valves (EV1, EV2), liquid valves (LV1, LV2), suction valves (SV1, SV2),
Hot gas valves (HV1, HV2), injection valves (IV
1, IV2) and each fan (F1, F2) to output a control signal. The controller (4) has an abnormality in the operation of the refrigeration system in response to an excessive increase in the high-pressure side pressure Hp, an excessive increase in the internal temperature of the compressor (2a, 3a), or an overload state such as an overcurrent. A protection device (41) for stopping and a storage device (42) for storing various data required for operation of the refrigeration system are incorporated.

Next, the control contents of the first embodiment according to the first aspect of the present invention will be described with reference to the flowchart of FIG. First, in step ST1, when the pull-down operation is started, in step ST2, the suction air temperature Tr as the internal temperature detected by the suction sensor (Th1) is input,
In step ST3, only the first circuit system (2) is operated and the second circuit system (3) is stopped. That is, only one compressor (2a) is operated, and the opening of the electric expansion valve (EV1) is fixed to the upper limit opening Amax. Then, step ST4
Then, the upper limit opening Amax of the electric expansion valve (EV1) is set to a constant K (for example, a value of about 350 pulses with respect to the full opening value of 480 pulses).
Is compared with a predetermined value (0 ° C.), and returns to step ST2 to repeat the above control until Tr ≦ 0 ° C.

On the other hand, while the above control is repeated, the internal temperature T
When r decreases and Tr ≦ 0 ° C., since the temperature difference from the outside air temperature increases due to the decrease in the internal temperature Tr, it is determined that the refrigeration capacity needs to be increased to further lower the temperature. Proceeding to step ST6, not only the first circuit system (2) but also the second circuit system (3) is operated. That is, the two compressors (2a, 3a) are operated. Then, step ST7
Then, while the opening of each of the electric expansion valves (EV1, EV2) is fixed to the upper limit opening Amax (that is, the above constant K) and the pull-down operation is continued, the protection device (41) is determined by the determination in step ST8. When activated, in step ST9, the apparatus is stopped, and in step ST10, the upper limit opening Amax of the electric expansion valves (EV1, EV2) is set to a constant value in order to avoid the abnormal stop and the continuation of operation becomes impossible. K is reduced by a constant value α (for example, a value of about 50 pulses), and in step ST11, each compressor (2a, 3a) is restarted to return to the pull-down operation. And step ST
In step 12, the control in steps ST6 to ST11 is repeated until the in-compartment temperature Tr enters the in-range, and when the internal temperature Tr enters the in-range, the pull-down operation ends.

In the above flow, the pull-down operation control means (45A) according to the invention of claim 1 is constituted by the control of steps ST3 and ST4, and the capacity increasing means (45) of the invention of claim 1 is controlled by the control of step ST6. 46
A) is constituted, and the control in steps ST9 to ST11 constitutes the abnormal time control means (47) according to the first aspect of the present invention.

Therefore, in the first embodiment, when the operation of the refrigerating apparatus is started, the operating capacity of the compressors (2a, 3a) is reduced to a low capacity by the pull-down operation control means (45A), and the upper limit of the electric expansion valve (EV1) is set. With the opening Amax fixed at a constant K,
A pull-down operation for rapidly bringing the in-compartment temperature Tr close to the in-range is performed. When the temperature Tr in the refrigerator reaches a predetermined value (0 ° C. in the above embodiment), a refrigeration capacity is required to further cool the refrigerator.
A) is controlled so as to increase the operating capacity of the compressor (2a, 3a).

In this case, in order to shorten the pull-down operation time, the upper limit opening Amax of the electric expansion valves (EV1, EV2) is required.
It is necessary to set slightly larger, and when the capacity increases, and especially when the outside air temperature is high (50 ° C. in this embodiment), the electric
If the opening degree of the expansion valves (EV1, EV2) is too large, an overload condition occurs, and the high-pressure side pressure Hp rises excessively, and the protection device (41)
May operate. And, as it is, the refrigeration apparatus stops abnormally, and it becomes impossible to continue the operation.

However, according to the present invention, the abnormal time control means (4)
7), the upper limit opening Ama of the electric expansion valves (EV1, EV2)
Since is controlled to restart after having reduced x from the constant K by a predetermined angle alpha, excessive increase state of the high side pressure Hp is eliminated, allowing continued operation. Therefore, the upper limit opening Amax of the electric expansion valves (EV1, EV2) is set to be large from the beginning, and the range of operating conditions such as the usable outside air temperature Ta is expanded while maintaining the pull-down capability as large as possible. Can be .

Next, a second embodiment according to the second aspect of the present invention will be described. Also in the present embodiment, the configuration of the refrigerant circuit (1) and the basic configuration of the controller (4) are the same as those in the first embodiment. Then, as shown in FIG. 4, the storage device (42) of the controller (4) includes an electric expansion valve (EV).
1, EV2) of the first change pattern P1 and the second change pattern P2 with respect to the outside air temperature Ta of the upper limit opening degree Amax
One change pattern is stored. In the figure, the first change pattern P1 is for one compressor (EV1, EV2), and the second change pattern P2 is for two compressors.
That is, the higher the outside air temperature Ta, the more the overload condition occurs, and the high pressure side pressure Hp rises excessively and the compressor (2a, 3a)
Since the operation of the protection device (41) due to the overcurrent is likely to occur, the outside air temperature T is set using the outside air temperature Ta as a parameter.
In view of the fact that the refrigerating capacity changes between the single-unit operation and the two-unit operation of the compressors (2a, 3a), the upper limit opening degree Amax is linearly reduced so that the upper limit opening Amax decreases as the value of a increases. Therefore, in the second change pattern P2, the first
The upper limit opening Amax is set to be always smaller by 50 pulses than the change pattern P1. That is,
The storage device (42) functions as storage means in the second aspect of the present invention.

Here, the control contents of the controller (4) will be described with reference to the flowchart of FIG. First, in step SS1, when the pull-down operation is started,
In step SS2, the suction air temperature Tr and the outside air temperature Ta are obtained from the signals of the suction sensor (Th1) and the outside air sensor (Tha).
Is input, and in step SS3, control is performed such that only the first circuit system (2) is operated and the second circuit system (3) is not operated. That is, only one compressor (2a) is operated, and the opening of the electric expansion valve (EV1) is fixed at the upper limit opening Amax. Then, in step SS4, the first change pattern P in FIG.
Set the upper limit opening Amax of the electric expansion valve (EV1) according to 1.
Then, in step SS5, the internal temperature Tr becomes 0 ° C. or less.
Judge whether or not. Then, the determination in step SS5
Step SS until the internal temperature Tr becomes 0 ° C. or less at
The control of 2 to SS4 is repeated, and when Tr ≦ 0 ° C., the process proceeds to step SS6.

That is, in order to increase the refrigerating capacity in accordance with the increase in the temperature difference between the inside temperature Tr and the outside air temperature Ta, in step SS6, not only the first circuit system (2) but also the second circuit system (3). To operate each compressor (2a, 3a) and fix the opening of each electric expansion valve (EV1, EV2) to the upper limit opening Amax. In step SS7, the inside temperature Tr and the outside air temperature Ta are input, and in step SS8
In, which therefore determines an upper limit opening degree Amax to the second pattern P 2 of FIG 4 of the electric expansion valves (EV1, EV2). afterwards,
In step SS9, it is determined whether the vehicle has entered the in-range.
I do. Then, in the judgment of step SS9, the in-range collision occurs.
The control in steps SS6 to SS8 is repeated until the vehicle enters the in-range, and the pull-down operation ends when the vehicle enters the in-range.

In the above flow, the pull-down operation control means (45B) according to the second aspect of the invention is constituted by the control of step SS3, and the capacity increasing means (46B) according to the second aspect of the invention is controlled by the control of step SS6. The opening degree changing means (48) according to the second aspect of the present invention is constituted by the control of steps SS4 and SS8.

Here, changes in the internal temperature Tr and the high-pressure side pressure Hp during the pull-down operation in the second embodiment will be described.
Referring to FIG. 6, when the operation of the refrigeration apparatus is started (time to in the figure), the operation capacity of the compressors (2a, 3a) is reduced to a low capacity by the pull-down operation control means (45A), and the electric expansion valve (EV1) is operated. ), The upper limit opening Amax is changed to the outside air temperature Ta.
In accordance with the first change pattern P1 in accordance with
Meanwhile, a pull-down operation is performed to quickly bring the inside temperature Tr closer to the in-range. When the inside temperature Tr reaches a predetermined value (0 ° C. in the above embodiment), a refrigeration capacity is required to further cool the inside of the chamber, and the operating capacity of the capacity increasing means (46A) is reduced. It is controlled to increase (time t1 in the figure). At this time, the electric expansion valve (EV
1, EV2) of the compressor (2a, 3a)
The first change pattern that is appropriate when the operating capacity is small
To vary according to the changed pattern P1 is compressors (2a, 3a) to become overloaded with increasing capacity, the set pressure value of the high pressure cut-high-pressure side pressure is excessive rise to (e.g. 28 kg / (pressure of about cm2), the protection device (41) may be activated, and the refrigeration system may stop abnormally (see the solid line in the figure). However, in the present invention, the opening degree changing means (48) When the two units are operated, the control is switched to the control of the upper limit opening Amax by the second change pattern P2 set so that the upper limit opening Amax is smaller than the first change pattern P1 in the case of single unit operation. Hp decreases (see the broken line in the figure), and an overload state is avoided beforehand. Even during low-capacity operation, the electric expansion valve (EV
By changing the opening degree of 1) according to the first change pattern P1, the approach to the overload state is always prevented, and the operation of the protection device (41) is prevented beforehand. Therefore, the abnormal stop prevention effect can be remarkably exhibited.

In the second embodiment, the outside air temperature Ta is used as a parameter indicating that the overload state increases. However, the present invention is not limited to this embodiment, and the high-pressure side pressure Hp and the compression A change pattern for changing the upper limit opening Amax of the electric expansion valves (EV1, EV2) can be stored using the current values of the motors (2a, 3a) as parameters.

In each of the above embodiments, the opening of the electric expansion valves (EV1, EV2) is fixed to the upper limit opening Amax.
The present invention is not limited to such an embodiment, and the degree of opening of the electric expansion valves (EV1, EV2) may be adjusted by controlling the degree of superheat constant or by controlling the convergence of the target value of the blown air temperature. However, as in the above embodiments, the electric expansion valve (EV
By fixing the opening of (1, EV2) to the upper limit opening Amax, there is an advantage that the performance during the pull-down operation can be maximized.

In each of the above embodiments, the refrigerant circuit (1)
Has been described as an example in which two systems of a first circuit system (2) and a second circuit system (3) are provided, but the present invention is not limited to such an embodiment. One system in which two compressors are provided in one refrigerant circuit so that the operating capacity can be changed between one-unit operation and two-unit operation, or one unit having an unloader mechanism in one system refrigerant circuit The present invention can also be applied to an arrangement in which a compressor is arranged.

[0037]

As described above, according to the first aspect of the present invention, the variable capacity compressor, the evaporator installed in the storage, and the electric expansion valve are arranged in the refrigerant circuit, and In a refrigeration system equipped with a protection device that outputs an abnormal signal when it becomes in a state, the upper limit opening of the electric expansion valve is set to a predetermined value, the operating capacity of the compressor is set to the low capacity side, and a pull-down operation is performed. When the temperature inside the refrigerator reaches the predetermined temperature or less,
The capacity of the compressor is switched to a high capacity, and when an overload condition occurs due to an increase in the capacity of the compressor and the protection device is activated, the upper limit opening of the electric expansion valve is reduced by a certain value and then restarted. Therefore, the operation can be continued by eliminating the overload state, so that the upper limit opening of the electric expansion valve is set as large as possible to maintain a high pull-down capability and expand the operable range such as the outside air temperature. be able to.

According to the second aspect of the present invention, the variable displacement compressor, the evaporator installed in the refrigerator, and the electric expansion valve are arranged in the refrigerant circuit, and an abnormal signal is output when an overload occurs. In a refrigeration system equipped with a protection device, a pull-down operation is performed with the operating capacity of the compressor set to a lower capacity, and when the temperature in the refrigerator reaches a predetermined temperature or less during the pull-down operation, the capacity of the compressor is switched to a higher capacity. , The upper limit opening of the electric expansion valve is set to be smaller as the overload state is approached.
The first and second change patterns are stored, and when the pull-down operation is started, the opening of the electric expansion valve is set to a large upper limit.
While changing according to the first change pattern, when the capacity of the compressor is switched to a high capacity, the upper limit of the opening of the electric expansion valve is increased.
Since the change is made according to the small second change pattern , the operation of the protection device can be always prevented before the pull-down operation, and the effect of the invention of claim 1 can be more remarkably exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a refrigerant piping system diagram of the refrigeration apparatus according to the embodiment.

FIG. 3 is a flowchart showing control contents in the first embodiment.
FIG.

FIG. 4 is a diagram illustrating setting of a change pattern of an upper limit opening of an electric expansion valve with respect to a change in outside air temperature according to a second embodiment.

FIG. 5 is a flowchart showing control contents of a second embodiment.

FIG. 6 is a diagram showing changes in the internal temperature and the high-pressure side pressure during a pull-down operation.

[Explanation of symbols]

 2a, 3a Compressor 2i, 3i Evaporator EV1, EV2 Electric expansion valve 4 Controller 41 Protector 42 Storage device (Storage device) 45 Pull-down operation control device 46 Capacity increasing device 47 Abnormal control device 48 Upper limit opening degree changing device Th1 suction Sensor (inside temperature detection means)

Claims (2)

(57) [Claims] 1. A variable displacement compressor (2a, 3a), an evaporator (2i, 3i) disposed in a refrigerator, and a pressure reduction degree of a refrigerant supplied to the evaporator (2i, 3i). The refrigeration system is provided with a variably adjusted electric expansion valve (EV1, EV2) in the refrigerant circuit (1) and a protection device (41) for detecting an overload state and outputting an abnormal signal. At the start of operation, the above-mentioned electric expansion valves (EV1, EV2)
The upper limit opening of the compressor (2a, 3a) is set to a predetermined value.
a) a pull-down operation control means (45A) for controlling the operation capacity to be low to lower the internal temperature, a temperature detection means (Th1) for detecting the internal temperature, and the pull-down operation control means During the pull-down operation by (45A), when the internal temperature detected by the internal temperature detecting means (Th1) reaches a predetermined temperature or lower, the compressor (2a, 3)
Ability increasing means for switching the capacity of a) to a high capacity (46A)
When the protection device (41) is activated when the capacity is increased by the capacity increasing means (46A), the electric expansion valve (EV
(1), EV2), an abnormal-state control means (4) that controls to restart after reducing the upper limit opening degree by a certain value from the predetermined value.
7) An operation control device for a refrigeration system, comprising: 2. A variable displacement compressor (2a, 3a), an evaporator (2i, 3i) disposed in a refrigerator, and a decompression degree of a refrigerant supplied to the evaporator (2i, 3i). The refrigeration system is provided with a variably adjusted electric expansion valve (EV1, EV2) in the refrigerant circuit (1) and a protection device (41) for detecting an overload state and outputting an abnormal signal. At the start of operation, a pull-down operation control means (45B) for controlling the compressor (2a, 3a) to reduce the operation capacity by reducing the operation capacity thereof, and a temperature detection means for detecting the temperature in the chamber. (Th1) During the pull-down operation by the pull-down operation control means (45B), when the internal temperature detected by the internal temperature detection means (Th1) reaches a predetermined temperature or less, the compressor (2a, 3a). Capacity increasing means (46) for switching the capacity of B), and the first change pattern and the second change pattern set so that the upper limit opening of the electric expansion valves (EV1, EV2) decreases as the overload state in which the protection device (41) is activated approaches . Change pattern
And the upper limit opening degree according to the second change pattern is
It is smaller than the upper limit opening according to the first change pattern.
Storage means (42) for storing the two change patterns set in the storage means (42), based on the storage of the storage means (42), the first pull-down operation by the pull-down operation means (45B) .
While the upper limit opening of the electric expansion valves (EV1, EV2) is changed according to the change pattern, the electric expansion valves (EV1, EV2) according to the second change pattern when the capacity is increased by the capacity increasing means (46B). An operation control device for a refrigeration system, comprising: an upper limit opening changing means (48) for changing over the upper limit opening.