JPS6242232B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a refrigeration system, and more specifically, it detects the suction temperature of an evaporator and controls the capacity and starts/stops a compressor during refrigeration operation to control the temperature inside the refrigerator. The present invention relates to a temperature control device for a refrigeration device that prevents overcooling by controlling, detecting the outlet temperature of an evaporator and stopping a compressor.

Conventional technology temperature control device for refrigeration equipment
-165466 Publication) As shown in Figure 1, refrigerated items are placed inside the warehouse at the suction (inside) temperature detected by the interior temperature sensing element RS installed in the duct DT of the maritime container SC. While controlling the temperature to R to maintain it within a set range, there is a system that prevents overcooling of refrigerated items by using the blowout temperature detected by the blowout temperature sensing element SS. In this type of conventional temperature control device, for example, as shown in Fig. 2, there is a thermostat _S1 for starting and stopping the compressor that turns on and off in response to the suction temperature detected by the internal temperature sensing element RS, and a capacity control system. thermostat S ₂ for air outlet temperature control, thermostat S ₃ for air outlet temperature control that turns on and off in response to the air outlet temperature detected by air outlet temperature sensing element SS, normally closed contact ARC ₁ , normally open contact
An auxiliary relay that combines an auxiliary relay consisting of ARC ₂ and a coil AR to turn on and off the solenoid valve HV provided in the hot gas bypass pipe, the solenoid valve LV provided in the liquid pipe, and both contacts ARC ₁ and ARC ₂ . The operation of the coil AR is controlled to achieve stable operation through pull-down operation and capacity control within an appropriate temperature range. In internal temperature control using such a temperature control device, as shown in Fig. 3, when the refrigeration operation switch of the refrigeration device is turned on and the compressor is started, the suction temperature T _R and the outlet temperature T _S decrease. However, since it is full-load operation, the temperature difference between the suction temperature T _R and the blowout temperature T _S becomes large, and when the suction temperature T _R reaches 2°C at time t ₀ , the blowout temperature T _S becomes -3°C or lower. It's getting old. Therefore, the capacity control thermostat _S2 turns on and the auxiliary relay coil turns on.
When the normally closed contact ARC ₁ turns off and the normally open contact ARC ₂ turns on when AR is energized, the thermostat _S3 for controlling the blowout temperature is already turned off, so the hot gas bypass solenoid valve HV is turned off. "Closed"
It remains as it has become. Furthermore, at this time, the liquid solenoid valve LV is also "closed", so the compressor will eventually stop even if the compressor start/stop thermostat _S1 is on. As a result, both temperatures T _R and T _S rise, but then the time
When the blowout temperature T _S reaches 0℃ at t ₁ , the blowout temperature control thermostat _S4 turns on and the liquid solenoid valve
The compressor is started again by LV becoming "open", and in this case, since the normally open contact ARC ₂ is on, the hot gas bypass solenoid valve HV is also "open", resulting in low load operation. Next, when both temperatures T _R and T _S decrease and the blowout temperature T _S reaches -3° C. at time t ₂ , the blowout temperature control thermostat S ₃ is turned off and the compressor is stopped. In this manner, the compressor is repeatedly turned on and off from time _t3 to time _t11 by turning on and off the blowout temperature control thermostat _S3 . and,
When the suction temperature T _R reaches 0° C. at time t ₁₂ , the compressor start/stop thermostat S ₁ is turned off, and the compressor, which had been started, is stopped by turning on the blowout temperature control thermostat S ₃ . After this time _t12 , the suction temperature T _R is low and the evaporation temperature is low, so the amount of refrigerant circulation is small, and the proportion of hot gas bypass is also large, so the cooling capacity is small, and the blowout temperature control thermostat _S3 is The compressor is kept on and the compressor is normally controlled in capacity by turning on and off the compressor thermostat _S1 , that is, by turning on and stopping the compressor at the suction temperature _T.sub.R.

By the way, during the transition period until the suction temperature T _R reaches the set temperature 0°C and the normal capacity control operation starts, the blowout temperature control thermostat S ₃
As the compressor repeatedly starts and stops due to the on/off of the air, that is, depending on the blowout temperature T _S , (i) the compressor starts and stops frequently, which affects the durability of the compressor, and (ii) compressor start/stop control. It took a long time for the compressor to start and stop normally using the thermostat _S1 , and there were problems such as poor quality of refrigerated items inside the refrigerator.

In view of the above, the present invention provides that during the transition period from the start of controlling the internal temperature to the normal capacity control operation by suction temperature control, the blowout temperature falls to the lower limit of the supercooling prevention temperature range. By controlling low-load operation in two stages, the suction temperature is quickly lowered and overcooling is prevented, reducing the frequency of unnecessary compressor starts and stops during this transient period and maintaining the quality of refrigerated products. The purpose is to

The configuration of the present invention includes an internal temperature sensing element that detects the suction temperature of the evaporator and is used to control the internal temperature during refrigeration operation, and a temperature sensing element that detects the outlet temperature of the evaporator and is used to prevent overcooling. When the suction temperature detected by the outlet temperature sensing element and the interior temperature sensing element decreases to the lower limit of the first set temperature range, a first low load operation signal is output, and the temperature rises to the first setting. The first capacity control thermostat outputs a full-load operation signal when the upper limit of the temperature range is reached, and the suction temperature detected by the internal temperature sensing element decreases to the first capacity control thermostat, which is lower than the first set temperature range. A thermostat for starting and stopping the compressor outputs a compressor stop signal when the temperature reaches the lower limit of the second set temperature range, and outputs a compressor start signal when the temperature rises to the upper limit of the second set temperature range, and a blowout temperature sensing element. When the detected blow-out temperature falls and reaches the lower limit of the third set temperature range, which is lower than the second set temperature range, a second low-load operation signal is output, and when it rises and reaches the upper limit of the third set temperature range, the second low-load operation signal is output. 2 The air outlet temperature detected by the second capacity control thermostat that outputs the low load operation stop signal and the air outlet temperature sensing element decreases to a point where it is lower than the second set temperature range and lower than the lower limit of the third set temperature range. A blowout temperature control thermostat that outputs a compressor stop signal when the temperature reaches the lower limit of a supercooling prevention temperature range having a low temperature lower limit, and outputs a compression start signal when the temperature increases and reaches the upper limit of the supercooling prevention temperature range;
Composed of circuit means that starts the compressor by outputting compressor start signals from both thermostats for starting and stopping the compressor and for controlling blowout temperature, and stops the compressor by outputting either one of the compressor stop signals. However, during the transition period from the start of refrigeration operation to almost steady operation, the suction temperature is lowered by controlling the low-load operation in two stages until the outlet temperature falls to the lower limit of the supercooling prevention temperature range. This is what I did.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 4 is a diagram showing a refrigeration cycle of a marine container refrigeration system to which an embodiment of the present invention is applied.
In FIG. 4, A is a compressor, B is a condenser, C is a temperature-sensitive expansion valve, D is a capillary tube, E is an evaporator, and F is a fan. LV is a liquid solenoid valve provided in the high pressure liquid pipe G, HV ₁ and HV ₂ are first and second hot gas bypass solenoid valves provided in the first and second hot gas bypass pipes H ₁ and H ₂ and each solenoid valve
LV, HV ₁ , and HV ₂ are turned "open" or "closed," respectively, by applying an open signal to "open" the valve or a close signal to "close" the valve to the opening/closing control section. Note that there is _a pressure switch (not shown) in the low-pressure liquid pipe _J that detects the low-pressure pressure. is stopped when activated.

FIG. 5 is a configuration diagram of a temperature control device that controls the temperature inside the refrigerator by controlling the start and stop of the compressor A shown in FIG.
Portions corresponding to those in FIG. 2 are given the same reference numerals. In Fig. 5, S ₂ is the internal temperature sensing element RS
When the detected suction temperature T _R falls to the lower limit of the first set temperature range T _S2 (e.g. 2°C to 3°C), it turns on and outputs the first low-load operation signal, and then rises to output the first low-load operation signal. This is the first capacity control thermostat that turns off when the upper limit of the set temperature range T _{S2 is} reached and outputs a full load operation signal _. and a second set temperature range T _S1 that is lower than the first set temperature range T _S2 .
(for example, 0℃ to 1℃), the compressor turns off and outputs a compressor stop signal, and when it rises to the upper limit of the second set temperature range T _S1 , it turns on and outputs a compressor start signal. It is a stop thermostat,
S ₃ ′ is the temperature at which the air outlet temperature T _S detected by the air outlet temperature sensing element SS decreases to a third set temperature range T _S3 that is lower than the second set temperature range T _S1 (for example, -1.2°C to -2.4°C).
℃), the second capacitor turns on and outputs a second low-load operation signal, and when the temperature rises to the upper limit of the third set temperature range T _S3 ', it turns off and outputs a second low-load operation stop signal. It is a control thermostat and S ₃
is the air outlet temperature T _S detected by the air outlet temperature sensing element SS
decreases and the third set temperature range is lower than the second set temperature range T _S1 .
The supercooling prevention temperature range T _S3 has a lower limit lower than the lower limit of the set temperature range T _{S3 '} (for example, 0°C to -4
This is a blowout temperature control thermostat that turns off and outputs a compressor stop signal when it reaches the lower limit of temperature (°C), and turns on and outputs a compressor start signal when it rises and reaches the upper limit of the supercooling prevention temperature range T _S3 . M is a normally closed contact
This is an auxiliary relay as a circuit means consisting of a normally open contact ARC ₁ , a normally open contact ARC ₂ and a coil AR energized by the first low load operation signal. Note that _S4 turns off when the suction temperature T _R falls to, for example, -3°C.
This is a thermostat for indicating the appropriate temperature that turns on when the temperature rises to, for example, -2°C, and LP is a lamp for indicating the appropriate temperature.

Next, the operation will be explained.

First, the refrigeration operation switch of the refrigeration device is turned on and pull-down operation is started. With this start, the compressor A starts up and the suction temperature T _R and the blowout temperature T _S decrease as shown in FIG. 6, but since the compressor A is operating at full load, the difference between the two temperatures becomes large. In this temperature decrease, the blowout temperature T _S reaches the third level at time t ₀₀ .
When the lower limit (-2.4°C) of the set temperature range T _S3 is reached, the second capacity control thermostat S ₃ ' is turned on and outputs the second low load operation signal, thereby turning on the second hot gas bypass solenoid valve HV ₂ . becomes “open”. Therefore, the decrease in both temperatures T _R and T _S becomes slow. Next, at time _t20 , the suction temperature T _R reaches 2°C below the first set temperature range T _S2 and the first capacity control thermostat _S2 is turned on to output the first low load operation signal. This activates the auxiliary relay M, turning off the normally closed contact ARC ₁ , turning on the normally open contact ARC ₂ , and opening the first hot gas bypass solenoid valve HV ₁ .
become. Therefore, the decrease in both temperatures T _R and T _S becomes even slower. In this way, the suction temperature T _R quickly decreases by the time the blowout temperature T _S reaches the lower limit (-4° C.) of the supercooling prevention temperature range T _S3 . Next, the time
At t ₃₀ , when the blowout temperature T _S reaches the lower limit (-4°C) of the supercooling prevention temperature range T _S3 , the blowout temperature control thermostat _S3 turns off and outputs a compressor stop signal, thereby stopping the compressor. A stops. Due to this stop, both temperatures T _R and T _S rise, and the blowout temperature T _S
reaches the upper limit (0° C.) of the supercooling prevention temperature range T _S3 , and the blowout temperature control thermostat _S3 is turned on to output a compressor start signal. At this time, the compressor start/stop thermostat _S1 is also turned on and outputs a compressor start signal, so the compressor A is started again. Next, at time _t50 , the second capacity control thermostat _S3 ' is turned on again and outputs the second low load operation signal, thereby turning on the second hot gas bypass solenoid valve.
As HV ₂ becomes "open", the decrease in both temperatures T _R and T _S slows down, and at time t ₆₀ , the suction temperature T _R reaches the lower limit (0°C) of the second set temperature range T _S1 , and the compressor Start/stop thermostat _S1 turns off and outputs a compressor stop signal. This output causes compressor A to stop. After this time _t60 , the compressor starts and stops steady operation by turning on and off the thermostat _S1 for starting and stopping the compressor. Note that at time t _o0 , the second capacity control thermostat S ₃ ' is turned on and the second low-load operation starts, and at the same time the refrigerator door opens and outside air enters, causing the suction temperature T _R to rise. Indicates the condition. As described above, in this embodiment, the compressor only needs to be stopped once during the transition period from the start of the refrigeration operation to the almost stable steady operation, and the frequency of starting and stopping of the compressor is reduced.

FIG. 7 is a circuit diagram when the embodiment shown in FIG. 4 is applied to another electric circuit, and parts corresponding to those in FIG. 5 are given the same reference numerals. In Fig. 7, the symbol V is a volume that adjusts the first and second set temperatures and the set temperature of the thermostat _S4 for displaying the appropriate temperature, and _B1 to _B3 are the volume V, the internal temperature sensing element RS, and the air outlet. The first to third converters correspond to each electrical resistance of the temperature sensing element SS and convert it into an electrical signal.
The converter AMP is an amplifier that amplifies and outputs a signal corresponding to the difference between the first converter _B1 and the second converter _B2 ,
AND ₁ to AND ₅ and I are first to fifth AND circuits and inverters, respectively, as circuit means M'. S _{1 , S 2} , S ₃ , S ₃ ′, _and S ₄ are thermostats corresponding _to those shown in FIG _. Each converter B ₁ ~ corresponds to the suction temperature T _R and the blowout temperature T _S detected by the temperature sensing element RS and the blowout temperature sensing element SS
The output signal from B ₃ is the reference signal V ₁ ,
By comparing V ₂ , V ₃ , V ₃ ', and V ₄ , a logic "1" or "0" signal is output. Thermostats S ₁ and S ₃ for starting and stopping the compressor and controlling the outlet temperature
outputs a logic "1" signal as a compressor start signal and a logic "0" signal as a compressor stop signal, and the first capacity control thermostat _S2 outputs a logic "0" signal as a full load operation signal and a logic "0" signal as a first low load signal. A logic "1" signal is output as the operation signal, and the second capacity control thermostat _S3 ' outputs logic "1" as the second low load operation signal and logic "0" as the second low load operation stop signal.
Outputs the signal.

Next, the operation of this circuit will be explained.

First, the refrigeration operation switch is turned on and pull-down operation starts, which causes the first and second
Each thermostat for compressor start/stop and first capacity control is connected via converters B ₁ and B ₂ and amplifier AMP.
A signal corresponding to the value obtained by adjusting the suction temperature T _R with the volume V is sent to S ₁ and S ₂ , and is also sent to each thermostat S ₃ , for blowout temperature control and second capacity control via the third converter B ₃ . A signal corresponding to the blowout temperature T _S is input to S ₃ ′. At this time, both temperatures T _R and T _S are high, and the respective thermostats for starting/stopping the compressor and controlling the blowout temperature are activated by the corresponding input signals.
S ₁ and S ₃ output the compressor start signal of logic “1” to the first,
The second capacity control thermostats S ₂ and S ₃ ' each output a logic "0" signal. Therefore, the first AND circuit AND ₁ receives a logic "1" open signal, and the third and fourth AND circuits AND ₃ and AND ₄ receive a logic "0".
The liquid current valve LV is supposed to output a close signal.
is open, and the first and second hot gas bypass solenoid valves HV ₁ and HV ₂ are closed, resulting in full-load operation. Next, when the blowout temperature T _S reaches the lower limit (-2.4° C.) of the third set temperature range T _S3 ', the second capacity control thermostat _S3 ' outputs a signal of logic "1". With this output, the fourth AND circuit
AND ₄ outputs an open signal of logic "1" and the second hot gas bypass solenoid valve HV ₂ becomes "open" [time t ₀₀ in FIG. 6]. This slows down the drop in both temperatures. Next, the suction temperature T _R is the first set temperature range T _S2
When the lower limit (2℃) is reached, the first capacity control thermostat _S2 outputs the first low-load operation signal with logic "1", and the third AND circuit _AND3 outputs an open signal with logic "1". Then, the first hot gas bypass solenoid valve HV ₁ becomes "open" [at the time shown in Figure 6].
_t20 ]. This further slows down the decrease in both temperatures T _R and T _S . Next, when the outlet temperature T _S falls and reaches the lower limit of the supercooling prevention temperature range T _S3 (-4°C), the outlet temperature control thermostat _S3 outputs a compressor stop signal of logic "0". 1st, 3rd, 4th
The AND circuits AND ₁ , AND ₃ , AND ₄ output logic "0" close signals, and all the solenoid valves LV, HV ₁ , HV ₂ become "closed" [time t ₃₀ in FIG. 6]. As a result, compressor A stops, both temperatures T _R and T _S rise, and the blowout temperature T _S becomes the upper limit (0) of the supercooling prevention temperature range T _S3.
°C), the blowout temperature control thermostat _S3 outputs a compressor start signal with logic "1", and the first and third AND circuits _AND1 and _AND3 output open signals with logic "1". . At this time, the second capacity control thermostat _S3 ' outputs the second low load operation stop signal of logic "0", so the fourth AND circuit _AND4 outputs a close signal of logic "0".

Therefore, the compressor A is started with the liquid and first hot gas bypass solenoid valves LV and HV ₁ open, and the second hot gas bypass solenoid valve HV ₂ closed. [Time t ₄₀ in Figure 6]. As a result of this activation, when the blowout temperature T _S decreases to the lower limit (-2.4°C) of the third set temperature range T _S3 ', the second capacity control thermostat _S3 ' switches to the second low-load operation with logic "1". By outputting the signal, the second hot gas bypass solenoid valve HV ₂ becomes "open" [time t ₅₀ in FIG. 6]. For this reason, both temperatures T _R and T _S decrease slowly. In this way, when the suction temperature T _R decreases and reaches the lower limit (0°C) of the second set temperature range T _S1 , the compressor start/stop thermostat _S1 becomes logic "0".
By outputting the compressor stop signal, the first, third, and fourth AND circuits AND ₁ , AND ₃ , AND ₄ output logic "0" close signals, and all solenoid valves LV, HV ₁ ,
HV ₂ becomes “closed” and compressor A stops [6th
Time t ₆₀ in the figure]. After this stop, both temperatures T _R and T _S
Since the difference between the two is small, the compressor A enters a steady operation in which it is started and stopped by the compressor start/stop thermostat _S1 [after time _t60 in FIG. 6].

In the above description of the embodiment, the first and second low-load operations were performed by opening the first and second solenoid valves for hot gas bypass, but the compressors were rotated at the first and second low speeds. Even if the known low-load operation is performed, such as reducing the compression volume of the compressor in stages (for example, in the case of a reciprocating compressor, unloading some of the many cylinders in stages). good. In addition to the above embodiments, a microcomputer may be used as the electric circuit. In this case, each thermostat is constituted by a microcomputer, and the microcomputer performs the functions of each thermostat. Furthermore, regarding the first, second, and third set temperature ranges and supercooling prevention temperature range, the upper limit of the set temperature range on the low temperature side may be higher than the lower limit of the set temperature range on the high temperature side, and the set temperature range on the low temperature side may be higher than the lower limit of the set temperature range on the high temperature side. It is sufficient that the center value of the range is lower than the center value of the set temperature range on the high temperature side. Furthermore, the second low load operation is performed by the second low load operation signal from the second capacity control thermostat _{S3 '} , regardless of the first low load operation signal from the first capacity control thermostat S2. Although,
It may be configured to be performed only when both signals are output. In this case, for example in FIG.
The series circuit of the second capacity control thermostat S3 _' and the second hot gas bypass solenoid valve _HV2 may be connected in parallel only to the first hot gas bypass solenoid valve _HV1 .

As described above, the present invention includes an internal temperature sensing element that detects the suction temperature of the evaporator and is used to control the internal temperature during refrigeration operation, and a temperature sensing element that detects the outlet temperature of the evaporator to prevent overcooling. The suction temperature detected by the outlet temperature sensing element used and the internal temperature sensing element is
When the temperature decreases to the lower limit of the first set temperature range, a first low-load operation signal is output, and when the temperature rises to the upper limit of the first set temperature range, a full-load operation signal is output.
When the suction temperature detected by the capacity control thermostat and the internal temperature sensing element decreases to the lower limit of a second set temperature range that is lower than the first set temperature range, a compressor stop signal is output. , the compressor start/stop thermostat outputs a compressor start signal when the temperature rises to the upper limit of the second set temperature range, and the blowout temperature detected by the blowout temperature sensing element decreases to the upper limit of the second set temperature range. A second capacity control thermos outputs a second low-load operation signal when the lower limit of the third set temperature range, which is lower temperature, is reached, and outputs a second low-load operation stop signal when the temperature rises to the upper limit of the third set temperature range. The air outlet temperature detected by the air outlet temperature sensing element is
When the temperature drops to the lower limit of the supercooling prevention temperature range, which has a lower limit lower than the second set temperature range and lower than the lower limit of the third set temperature range, a compressor stop signal is output, and the temperature rises to the lower limit of the supercooling prevention temperature range. When the upper limit of The circuit is configured to stop the compressor by outputting a compressor stop signal on one side, and during the transition period from the start of refrigeration operation to almost steady operation, the blowout temperature falls to the lower limit of the supercooling prevention temperature range. In this step, the suction temperature is lowered by using two-stage control of low-load operation, so after the start of operation, the blow-out temperature decreases until it reaches the lower limit of the supercooling prevention temperature range.
Due to low-load operation in stages, the suction temperature quickly reaches the first stage.
When the temperature drops below the lower limit of the set temperature range, the compressor stops, the blowout temperature rises, and reaches the upper limit of the supercooling prevention temperature range, and when the compressor starts again, the suction is resumed by two-stage low-load operation. The temperature quickly enters the second set temperature range, and the compressor can enter into almost stable steady operation. Therefore, according to the present invention, while overcooling of refrigerated products during the transition period can be prevented, the frequency of starting and stopping of the compressor can be extremely reduced, and the durability of the compressor can be improved as well as Good quality of products can be maintained.

[Brief explanation of the drawing]

Figures 1 to 3 show conventional examples. Figure 1 is a schematic diagram of a marine container refrigeration system, Figure 2 is its temperature control device, and Figure 3 shows the suction temperature of the device shown in Figure 2. Diagram showing changes with blowout temperature, Figure 4~
Fig. 7 shows an embodiment of the present invention, Fig. 4 shows a refrigeration cycle in the embodiment, Fig. 5 shows its temperature control device, and Fig. 6 provides an explanation of the operation of the device shown in Fig. 5. FIG. 7 is a diagram showing changes in suction temperature and blowout temperature, and is a diagram illustrating the device constructed by an electric circuit. RS... Suction temperature sensing element, SS... Outlet temperature sensing element, A... Compressor, S ₁ ... Thermostat for compressor start/stop, S ₂ ... Thermostat for first capacity control, S ₃ ...Thermostat for controlling outlet temperature,
S ₃ ′...Second capacity control thermostat, AR...
Auxiliary relay coils, ARC ₁ , ARC ₂ ...Normally closed/
Normally open contact, LV...Liquid solenoid valve, HV ₁ , HV ₂ ...
First and second hot gas bypass solenoid valves, M,
M′...Circuit means, AND ₁ ~ AND ₅ ...And circuit.

Claims (1)

[Claims] 1 An internal temperature sensing element RS is used to control the internal temperature during refrigeration operation by detecting the suction temperature T _R of the evaporator E, and a thermosensing element RS is used to detect the outlet temperature T _S of the evaporator E to prevent overcooling. Blowing temperature sensing element SS used
When the suction temperature T _R detected by the internal temperature sensing element RS falls and reaches the lower limit of the first set temperature range T _S2 , the first low load operation signal is output, and the temperature rises to the first set temperature. The first capacity control thermostat _S2 outputs a full load operation signal when the upper limit of the range T _S2 is reached.
Then, when the suction temperature T _R detected by the internal temperature sensing element RS decreases to the lower limit of the second set temperature range T _S1 which is lower than the first set temperature range T _S2 , a compressor stop signal is issued. a compressor start/stop thermostat _S1 that outputs a compressor start signal, and outputs a compressor start signal that outputs a compressor start signal when the temperature rises to the upper limit of the second set temperature range T _S1 ; When the blowout temperature T _S detected by the temperature sensing element SS decreases to the lower limit of the third set temperature range T _S3 ', which is lower than the second set temperature range T _S1 , a second low load operation signal is output. , and outputs a second load operation stop signal when the temperature rises to the upper limit of the third set temperature range T _S3 '.
The air outlet temperature T _S detected by the capacity control thermostat S ₃ ' and the air outlet temperature sensing element SS decreases to the lower limit of the third set temperature range T _S ' ₃ which is lower than the second set temperature range T _S1 . Blowout temperature control outputs a compressor stop signal when the lower limit of the supercooling prevention temperature range T _S3 , which has _a lower limit lower than The compressor A is started by the output of both compressor start signals from the thermostat S ₃ and the thermostats S ₁ and S ₃ for starting/stopping the compressor and controlling the outlet temperature, and the stop signal for either compressor is activated. A temperature control device for a refrigeration system comprising circuit means M and M' for stopping the compressor A by the output of the refrigeration system.