JPS6021308B2 - Cooling device control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a cooling system in which a plurality of evaporators installed in a plurality of refrigerators are operated in parallel by a single compressor, and particularly relates to a control circuit for a cooling system in which a plurality of evaporators installed in a plurality of refrigerators are operated in parallel by a single compressor. This invention relates to a circuit that controls a plurality of solenoid valves each provided in a cold butterfly passage on the input side.

Generally, there is a cooling system as shown in FIG. 1 in which a plurality of evaporators provided in a plurality of refrigerators are operated in parallel by a single compressor.

In FIG. 1, reference numerals 1, 2, and 3 are evaporator groups provided in different freezing or refrigerating showcases, each having a different set temperature. For example, evaporator group 1 is set to -2°C, evaporator group 2 is set to 1300°C, and evaporator group 3 is set to 17°C. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 4 is guided to the condenser 5 and liquefied. The liquid refrigerant that has passed through the condenser 5 is branched into three solenoid valves SV, SV2, and SV3 provided corresponding to the evaporator groups 1, 2, and 3, and the three solenoid valves SV, SV2, Each cold soot that has passed through the SV3 is led to the corresponding evaporator groups 1, 2, and 3 after being depressurized by the expansion valves 6, respectively. In the evaporator groups 1, 2, and 3, the lining medium is vaporized and removes heat from the surroundings, thereby cooling the inside of each showcase. The cold wires passing through the evaporator groups 1, 2, and 3 are commonly led to the suction side of the compressor 4. The solenoid valves SV, SV2, and SV3 open when energized. Solenoid valves SV, SV2, S in a cooling device that can form such a refrigerant circulation route
Conventionally, a circuit as shown in FIG. 2 has been used as a circuit for controlling V3.

That is, thermostat contacts TH, TH2, TH3 are connected in series to three electromagnetic valves SV, SV2, SV3 connected in parallel to the power supply 10', respectively. The thermostats are installed in showcases equipped with evaporator groups 1, 2, and 3, respectively, and when the temperature drops below a predetermined lower limit due to cooling, the contacts open and the power source 10 energizes the solenoid valves SV, SV2, and SV3. On the other hand, when the temperature rises above the upper limit of the predetermined temperature, the contact closes and allows the power source 10 to energize the solenoid valves SV, SV2, and SV3. For example, if the inside of the showcase in which the evaporator group 3 is equipped becomes too cold below the lower limit of a predetermined temperature, the thermostat contact TH3 cuts off the power to the solenoid valve SV3 and closes the valve. When the temperature rises above the upper limit, the solenoid valve SV3 is energized by the thermostat contact T ratio to open the valve, and this state is repeated thereafter. Like the solenoid valves SV, SV2, they are controlled by thermostat contacts TH, TH2. Figures 3 and 4 show the open states of solenoid valves SV, SV2, and SV3 (indicated by hatching), compressor load (%), and compressor efficiency when using the control circuit shown in Figure 2, respectively. (Mechanical output/electrical input x 100) (%) time chart,
Shown separately for summer and winter.

Because compressors are combined with showcases, freezers, refrigerators, etc. to match the peak load in midsummer, there are many low-load times in the winter and mid-season, causing the compressor motor, which is at its maximum efficiency at the appropriate load, to run at low efficiency. This has the disadvantage that the compressor is operated at low efficiency more frequently. In other words, as shown in Figure 3, during high loads in the summer, the input power to the compressor is often effectively used for compressor operation and the compressor is operated at high efficiency, but in the winter, the
As shown in the figure, the low load times indicated by S become extremely common, and the compressor operates at low efficiency, where the input power to the compressor is not effectively used for compression operation, and there are many times when power is wasted. . Furthermore, in order to cope with the problem of excessive compressive force at low loads, compressors are generally configured to be shut down by a pressure switch provided on the suction side of the compressor when the load becomes approximately 1/3 or less.

For this reason, when there is no load, the compressor remains in a stopped state, but at low loads greater than 0 and 1/under milk, the compressor can cause a so-called short cycle in which it repeats the stopped state and operating state for a short period of time. There is sex. Such a short cycle requires a large amount of electric power to start up the compressor, which shortens the life of the compressor due to oil depletion. In Fig. 4, the parts that may cause short cycles are also the parts indicated by S. In Fig. 4, there are extremely many parts S that may cause such short cycles, and from the viewpoint of compressor life. Undesirable. In order to eliminate the above-mentioned drawbacks, it has been considered to use computer control to optimize the load, but this would result in high costs and difficult equipment and adjustment.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control circuit that can significantly reduce the proportion of time in which a compressor is required to operate at low efficiency, in which a short cycle in which a compressor repeatedly starts and stops may occur. The object of the present invention is to make it possible to achieve longer service life and lower power consumption.

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

The control circuit according to the embodiment of the invention shown in FIG.
This controls the opening and closing of the valve of SV3.

This control circuit includes a first relay RL4 for synchronization, a first circuit 20 that forcibly operates the first relay RL at regular intervals, and three second relays corresponding to three showcases. circuits 30, 302, 303, and a second circuit 30, 302, 303.
, 302, and 303 respectively connect the corresponding second relays among the three second relays RL, RS, and RL3 corresponding to the three showcases to the three solenoid valves SV, , SV2, and SV.
3, a circuit connected in parallel to the corresponding solenoid valve, and the corresponding second relay normally open contact r〆, . r evening 2, or r
A circuit in which part 3 and the normally open contact r〆4 of the first relay RL are connected in parallel, and the corresponding showcase storage among the three thermostat contacts TH, TH2, TH3 corresponding to the three showcases. Thermostat contacts that open when the internal temperature drops below a predetermined temperature are connected in series with each other, and three second circuits 30, 302, and 303 are each connected in parallel to the power supply 10. It is characterized by The first circuit 20 has two timers TM.
including. TimerTM. has a normally open contact tm, which closes after a predetermined time after being energized. Further, the timer T base has a normally closed contact tm2 that opens after a predetermined time after being energized, and a normally closed contact skin '2 that opens when energized. 1st
The normally open contact r of the first relay RL for synchronization described above is also provided in the circuit 20. In Figure 6, timer T
M,, that contact blood,, timer TM2, that contact skin 2,
TM'2, relay RL4, and its contact point R4 are shown in an operation time chart.

First, while also referring to FIG.
The operation of the circuit 20 will be explained. When the timer TM continues to be energized for a predetermined time T after it starts being energized via the normally closed contact tm'2, the timer TM closes the contact tm. Then, the relay RL is energized and becomes operational, and the contact r& connected in series with the contact ca 2 closes, thereby self-holding. When the relay RL4 is activated, the contacts RL4 provided in the second circuits 30, 302, 303 are synchronously closed. At the same time, timer T
Since the contact point r4 connected in series with M2 is also broken,
The timer T starts to be energized, and the timer TM2 connects its contact tm'2 when the energization starts, cuts off the energization to the timer TM, and opens the contact tm. The timer TM2 is energized for a predetermined period of time m2 after it starts being energized, and this contact point tm2 is connected to the timer TM2. As a result, the power to relay RL4 is cut off, and relay RL4 becomes inoperable and connects contact r4 in first circuit 20 and contacts provided in second circuits 30, 302, and 303, respectively. The contact r〆4 mentioned above is connected synchronously. When the contact point 4 in the first circuit 20 is opened, the timer TM
The power supply to 2 is cut off and the timer T ground connects to the contact points '2 and t.
Close m2. When the contact tm'2 is closed, the timer TM is again energized and the same operation as described above is repeated. In this way, the first circuit 20 connects the first relay R
L (the contacts 4 provided in the second circuits 30, 302, 303) are operated (synchronized and closed) for the time L set in the timer T, and the first The operating state of relay RL (closed state of contact rZ4)
The timer TM is set repeatedly at intervals of the time T. In other words, the first relay RL (second
It serves to operate (synchronize and open) the bush lights in the circuits 30, 302, and 303) at fixed time intervals (L + T). Next, the second circuit 30, 302, 30
The operation No. 3 will be explained. Now, assuming that the temperatures inside the three showcases equipped with evaporator groups 1, 2, and 3 are all higher than their respective set temperatures, the thermostat contacts TH, . T&, TH3 all remain closed. In this state, when the contacts 4 in each of the second circuits 30, 302, 303 are synchronously closed by the operation of the first synchronizing relay RL, the relay RL. ,RL
2, RL becomes operational, contacts rso, rZ2, rso3 close, solenoid valves SV,, SV2, SV3 are energized,
Relays RL, RL, RL are self-held, and contact rso4
Even if the solenoid valves SV, SV2, and SV3 are opened, current continues to be applied to the solenoid valves SV, SV2, and SV3. When the solenoid valves SV, SV2, SV3 are energized, the solenoid valves SV, SV2, SV3 shown in Fig. 1 open, and the interior of the three showcases equipped with evaporator groups 1, 2, and 3 opens. It will start to cool down. As mentioned above, the time period during which the contact point R4 is closed is set by the set time m2 of the timer T of the first circuit 20, but this set time value 2 is determined by the time when each relay RL, RL2, RL3 is energized. It is sufficient that the time required for the device to change from the state to the operating state is sufficient. For example, when the inside of the showcase in which the evaporator group 3 shown in Fig. 1 is installed is cooled to the set temperature, the thermostat contact T opens, so the relay RL becomes inactive and the solenoid valve S
The valve V3 is closed, and the cooling inside the showcase where the evaporator group 3 of FIG. 1 is installed is stopped. Then the first
The temperature inside the showcase where the evaporator groups 2 and 1 shown in the figure are installed will reach the set temperature one after another, but in these cases as well, relays RL2 and RL will become inactive one after another, and the inside of the showcase will sequentially reach the set temperature. Cooling will be stopped. Rele RL
, RL2, R- become inactive, the temperature inside the showcase rises and the thermostat contacts TH, , TH2, T
Even if H3 is closed, electromagnetic valves SV, SV2, and SV3 are not energized until relay RL4 is activated. In other words, the relays RL,,RL,R which are in the non-operating state
After a certain period of time (T20T,) from the time when the synchronizing relays RL4 put the L3s into the operating state simultaneously, the synchronizing relays RL4 simultaneously put the L3s into the operating state again, and the three showcases are cooled all at once. is started, and the same operations as described above are repeated. When the synchronizing relay RL4 operates, if the thermostat contacts TH,, TH2, and T are open, the showcase is left alone until the next relay RL4 operates. Therefore, in this embodiment, relay RL
4 is activated, the thermostat contact TH,,TH
2. Differential (like TH3 is closed)
A thermostat with a small on-off difference is used. Solenoid valves SV, SV when the control circuit shown in Fig. 5 is used in Fig. 7
2. SV3 open state (indicated by hatching), compressor load (%), and compressor efficiency (mechanical output/electrical input x 1)
00)(%) is shown.

Figure 7 shows the case where the temperature settings are almost the same as in Figure 4.
As is clear from Fig. 7, the low load times indicated by S are much fewer and shorter than those shown in Fig. 4, and the compressor stop time is longer, so the times when the compressor is operating at low efficiency are extremely low. This means less time to waste power. Furthermore, the S part is also a part that may cause short cycles, and it is possible to significantly reduce short cycles and extend the life of the compressor compared to the case shown in FIG. Figure 7, 4th
Both figures are based on the assumption that a short cycle does not occur; if a short cycle actually occurs, the temperature inside the refrigerator will fall more slowly and the compressor stop time will be shorter. Therefore, in this embodiment with fewer short cycles, the compressor efficiency is improved more than in the case of FIG. 4 as explained above. Furthermore, in order to prevent short cycles and improve compressor efficiency at low loads, a multi-compressor system in which there are multiple compressors and some of them are stopped at low loads is extremely effective, but as shown in Figure 1. Furthermore, by providing a capacity control mechanism and operating the compressor according to the control circuit of this embodiment, it is possible to obtain effects similar to those of the multi-compressor system described above. As shown in FIG. 8, in the capacity control mechanism, when the load becomes low, the capacity control valve 7 acts through the electromagnetic valve 11 to return the high temperature and high pressure gaseous cold soot discharged from the compressor 4 to the suction side of the compressor 4. , is a mechanism that prevents the suction pressure from falling below a certain value, and when this mechanism is included in the control circuit shown in Fig. 5, the normally open contacts rZ, , r〆 2
, r 3 and the parallel circuits of the solenoid valves 8 and 11 are connected in series and connected in parallel to the power source 10. At this time, the gaseous cold soot discharged from the compressor 4 is at a high temperature, so if it is returned to the suction side of the compressor 4 and compressed, it will overheat the compressor 4. Therefore, the solenoid valve 8 is opened and the output liquid refrigerant from the condenser 5 is When refrigerant is being supplied to any of the evaporator groups 1, 2, and 3 through the solenoid valve 8 and the expansion valve 9, as is clear from the phantom line in FIG. The compressor 4 is injected to the suction side of the compressor 4 to cool the compressor 4. However, compressor 4
The hot gaseous cold soot discharged from the compressor 4 and the liquid refrigeration output from the condenser 5 which are returned to the suction side of the evaporator group 1, 2, 3 are wasted energy that cannot be used for cooling. Fourth
The capacity control mechanism shown in Fig. 8 is activated in order to prevent short cycles in the S part of Figs. It's over. If there is no capacity control mechanism, a short cycle may occur in the S part in Figure 7, making the S part longer; however, if the capacity control mechanism in Figure 8 is provided,
The system operates as shown in the diagram, preventing short cycles and greatly improving compressor efficiency. Figure 9 is the fifth
Solenoid valves SV,,S when using the control circuit of the embodiment shown in the figure
It is a time chart showing the open states of V2 and SV3 (indicated by hatching) and the temperature inside the showcase controlled by the solenoid valves SV, SV2 and SV3, respectively, and A is the synchronous cycle of the synchronous circuit 20 ( When L+T,) is short, B is a case where the synchronization period (L+T,) is long.

The hysteresis day, which is the difference between the maximum and minimum temperature inside the refrigerator, is determined by the synchronization cycle (L+T,) of the synchronization circuit 20,
If the synchronization period (T20T,) is shortened as shown in FIG. 9A, the hysteresis mark will become smaller, and if the synchronization period (L0T,) is lengthened as shown in FIG. 9B, the hysteresis mark will become larger. If the synchronization period (T20T,) is shortened, the compressor 4 will have to start and stop more often, which is unfavorable in terms of durability. A cycle of IQ minutes to 18 minutes is good. Figure 10A shows the open states of the solenoid valves SV, SV2, SV3 (indicated by hatching) and the thermostat contact T when the control circuit of the embodiment shown in Figure 5 is used.
This is a diagram showing a time chart showing the closed state of H,, TH2, TH8 (indicated by hatching) and the temperature inside the showcase. 10A is a diagram similar to FIG. 10A in the case where a thermostat with a large open cut difference ○ is used.

As is clear from FIG. 10A, in the embodiment of FIG. 5, the differential D is such that the thermostat contacts TH, , T ratio, and TH3 are closed when the synchronizing relay RL operates as described above. Since a small thermostat is used, each time synchronization relay RL4 is operated, 3
Energization to the three solenoid valves SV, SV2, and SV3 starts at the same time, but if a thermostat with a large differential D is used as shown in Figure 10B, the range of temperature inside the refrigerator will become large. , fin valve SV, SV2, SV
The opportunity to open the solenoid valves SV, SV2, and SV3 is lost as energization starts at the same time, and there is no point in opening and closing the solenoid valves SV, SV2, and SV3 together as much as possible to increase motor efficiency through heavy load operation. The differential D of the thermostat will vary depending on the mounting position of the thermostat, etc., but if IK is possible, it will be 0. Shoes or smaller are preferable. Fifth
In the illustrated embodiment, by selecting a commercially available gas-filled mechanical thermostat or electronic thermostat that satisfies the above-mentioned differential conditions as the thermostat, the thermostat can be used without any modification to the interior. As described above, one of the advantages of the embodiment shown in FIG. 5 is that a commercially available thermostat can be used, but its effectiveness is lost if the differential is large.

Therefore, an embodiment in which this point is removed will be described below. In these embodiments, a mechanical thermostat such as a gas type cannot be used, but a commercially available electronic thermostat can be used without any internal modification. FIG. 11 shows a control circuit according to another embodiment of the invention, and the TH of FIG.
, , T ratio, TH3 are the relays RT, , RT2 ., which are included in the electronic thermostat body, respectively. RT3
Normally related contacts n,,re2,rt3 are used.

FIG. 12 shows a control section for the normally open contacts 9, , n2, and rt3 in FIG. 11. In Figure 12, 40., 402, 40
3 is the main body of a commercially available electronic thermostat, which includes relays RT, , RT2, and RL, respectively.
Thermistors The, The2, The3, resistors Re, rectifier circuit B, smoothing capacitor SC, etc. are connected to the thermostat bodies 40, 402, 403, and the power supply 10
FIG. 12 shows a state in which one is connected. The electronic thermostat bodies 40, 402, and 403 are composed of identical circuits, each forming a Schmitt circuit that is a general circuit for temperature control. The electronic thermostat main bodies 40, 402, and 403 have the output of the power supply 10 rectified by a bridge circuit B consisting of four diodes (after step-down with a transformer if necessary), and a smoothing capacitor SC.
A smoothed current is given by . Thermistor me,,Th
e2 and me3 are installed in a showcase containing the evaporator groups 1, 2, and 3 shown in FIG. 1, respectively. The set temperature inside the showcase is adjusted by variable resistors VR in the corresponding electronic thermostat bodies 40, 402, 403. The thermistors me, The2, and The3 have characteristics as shown in FIG. 13, and the resistance value decreases as the temperature increases.

When the resistance values of the thermistors The, , The2, and The3 fall to a value R2 that can turn off the transistor TR^ in the thermostat body 40, , 402, and 403, the transistor TR^ is turned off, and conversely, the transistor TR^ is turned off.
8 turns on, relays RT, RL, Rt are energized and become operational, contacts n, , r, etc. are closed, and the service is activated.
Mostat turns on. The temperature at this time is the set temperature value for turning on the thermostat. On the other hand, when the temperature inside the refrigerator is decreasing, the thermostat is turned off at a value slightly lower than the above-mentioned set temperature value for turning on the thermostat. This value is the set temperature value for thermostat off. That is, when the resistance values of the thermistors The,, The2, and The3 rise to a value R, (Fig. 13) that can turn on the transistors in the thermostats 401, 402, and 403, the transistor TR^ turns on, and conversely, the transistor TRB turns on. Since it turns off, relay RT,. RT2 and RL are de-energized and become non-operating, contacts n, , 2 and rt3 are opened and the thermostat is turned off. The difference between the set temperature value when the thermostat is on and the set temperature value when the thermostat is off is the differential D (FIG. 13). In Figure 12, the resistance R
e is selected so that the combined resistance when connected in parallel with the thermistors The, , The2, and The3 is equal to or less than R2 in FIG. 13 (resistance value that can turn on the thermostat).

When the synchronization relay RL shown in FIG. 11 opens the contact 4 shown in FIG. 12 at regular intervals, the thermostats whose temperature has not yet reached the thermostat-on set temperature are also forcibly turned on, and the thermostats shown in FIG. The contact point rt,,n2
, n3 are open. At this time, the contacts 4 in Fig. 11 are also closed, so the relays RL, RL, RL3 are energized and are in operation, and the solenoid valves SV, SV2 are energized as in the case of Fig. 5.
, SV3 starts to be energized, and the interiors of the three showcases begin to cool down. After the set time L of timer TM2, the first
The relay RL shown in Figure 1 becomes inactive and the contact R shown in Figure 12 opens, but at that time, the temperature inside the showcase is higher than the set temperature value of the thermostat off relay relay RT,,RL.
, RT3 are kept in the operating state and the cooling operation continues, and when the temperature inside the showcase falls to the set temperature value of the thermostat off, the relays RT, , RT2, and RT3 become inactive and the cooling is stopped. In addition, Fig. 11 Nori Ray R
When L is in a non-operating state, if the temperature inside the showcase is equal to or lower than the set temperature value of the thermostat off, cooling is stopped. After the cooling stops, the temperature inside the showcase rises and the thermostat turns on, and the normally open contacts r, rt2, and 3 in Fig. 11 close, but the contacts r, , r, and r
Since contact 3 and contact 4 are open, solenoid valve SV
,,SV2 and SV3 are not energized. As described above, in this embodiment, what determines the temperature inside the refrigerator is only the set temperature value of the thermostat off, and the differential is no longer involved.

Therefore, even if a thermostat with a large differential D is used without operating as shown in FIG. 10B, the temperature inside the refrigerator will change as shown in FIG. 10A. In FIG. 12, R is a resistor, C is a capacitor, and D is a diode. In FIG. 12, the parts including the thermistor The, the resistor Re, the normally open contact R4, and the variable resistor VR can be connected by inverting them into ten lines and one line as shown in FIG. .

In this case, when the temperature inside the refrigerator rises, the relay RT becomes inoperative, so a normally open contact point n', as shown in FIG. 14, is provided in place of the normally open contact point rt, shown in FIG. 11. The same thing is possible for the part including the thermistors The2 and The3 in FIG. 12, and the normally open contact ratios 2 and rt3 in FIG. In this way, the relay RT,,RL depending on the temperature
, RL are opposite to those in FIG. In addition, FIGS. 16 and 17 show the thermistors The,
This is a case where a resistance wire mR of platinum or the like is used as a temperature sensor instead.

In these cases, a normally closed contact R' is connected in series with the resistance wire ThR.
4 and a resistor Re are connected in parallel. When the resistance Re is connected in series with the resistance line ThR, the combined resistance is the transistor T.
The value is selected so that it is at least a value that can turn on R^ (in the case of FIG. 16) or a value that can turn off transistor TR^ (in the case of FIG. 17). In this way, when the ant-resistant T-suit is used as a temperature sensor, the resistance value increases as the temperature rises, as shown in FIG. 18. Therefore, when using FIG. 16, it is necessary to partially modify the circuit of FIG. 11 as shown in FIG. 14, similar to the circuit of FIG. 15. On the other hand, the 17th
If you use a diagram, you can leave it as is in Figure 11. The case where a resistance wire made of platinum or the like is used as a temperature sensor instead of the thermistors The2 and me3 shown in FIG. 12 is completely similar to the above. In the circuits shown in FIGS. 15 and 16, by cutting off the power supply when the synchronizing relay RL is operating, the relay RL can be brought into a non-operating state, and the cooling operation can be forced to start. I can do it.

That is, the circuits shown in FIGS. 19 and 20 can be used in place of the circuits shown in FIGS. 15 and 16, respectively.
In FIGS. 19 and 20, rl'4 is a normally closed contact inserted and connected to the power supply line, and the resistor e and normally open contact r14 in FIGS. 15 and 16 are unnecessary. Naturally, when using the circuits shown in Figures 19 and 20, the 14th
The circuit shown in the figure shall be used. Furthermore, as is clear from FIG. 6, in the first circuit 20 in FIGS. 5 and 11, the timer TM and the timer T operate alternately and output pulses with a pulse width L at fixed time intervals T. It is something.

Therefore, as the first circuit 20, any circuit may be used as long as it can output pulses of a constant pulse width at constant time intervals, such as an astable multipipulator. As explained above, according to the present invention, there is provided a control circuit that can significantly reduce the proportion of time during which the compressor is required to operate at low efficiency, in which a short cycle in which the compressor repeatedly starts and stops may occur. Therefore, it is possible to achieve the effect of increasing the lifespan of the compressor and reducing power consumption.

[Brief explanation of the drawing]

Figure 1 is a cold soot circulation system diagram showing an example of a cooling system in which multiple evaporators installed in multiple refrigerators are operated in parallel by a single compressor, and Figure 2 is a diagram showing the cooling system shown in Figure 1. 3 and 4 are circuit diagrams showing slave control circuits for controlling the solenoid valves SV, .
Figure 5 shows a time chart of the open states of SV2 and SV3, compressor load (%), and compressor efficiency (%), divided into summer and winter. Figure 5 controls the cooling rhombus shown in Figure 1. FIG. 6 is a circuit diagram showing a control circuit according to an embodiment of the present invention for the first circuit 20 and the first relay RL of FIG.
FIG. 7 is a diagram similar to FIGS. 4 and 5 when the control circuit of FIG. 5 is used.
Fig. 8 is a refrigerant circulation system diagram showing the capacity control mechanism, and Fig. 9 shows the solenoid valves SV, SV when using the control circuit shown in Fig. 5.
2. It is a time chart showing the open state of SV3 and the temperature inside the showcase controlled by the solenoid valves SV, SV2, and SV3, respectively, and A is the synchronous period (T2
,) is short, B is a diagram showing the case where the synchronization period (T20T,) is long, and Figure 10A is the open state of solenoid valves SV,, SV2, and SV3 when the control circuit of Figure 5 is used. Figure 10 shows a time chart of the closed states of thermostat contacts TH, TH2, TH3 and the temperature inside the showcase.
Figure B is a diagram similar to Figure 10A when a thermostat with a large differential D is used as the thermostat in the control circuit of Figure 5, and Figure 11 shows a control circuit according to another embodiment of the present invention. The circuit diagram, FIG. 12, shows the contacts n, . A circuit diagram showing the control section of &, 3, and FIG.
14 and 15 are circuit diagrams for explaining still another embodiment of the present invention,
16 and 17 are circuit diagrams for explaining other embodiments of the present invention, respectively, and FIG. 18 is the temperature-resistance characteristics of the resistance wire mR, such as platinum, shown in FIGS. 16 and 1.7. , FIG. 19, and FIG. 20 are circuit diagrams for explaining still other embodiments of the present invention. 1, 2, 3... Evaporator group, 4... Compressor, 5... Condenser, 6... Expansion valve, 1
0...Power supply, SV,, SV2, SV3...
... Solenoid valve, RL4... First relay for synchronization, 20... First circuit, 30, 302, 303...
・Second circuit, RL, RL2, RL... younger brother 2 relay, TH,, T ratio, TH3, rL, n2, n3, re'. ...A temperature-responsive contact that opens when the temperature inside the corresponding showcase falls below a predetermined temperature. Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Drawing diagram Figure 8 Figure 3 Figure 14 Figure 18 Figure 9 Figure 11 Figure 12 Figure 10 Figure 15 Figure 16 Figure 17 Figure 19 Figure 20

Claims (1)

[Claims] 1. In order to operate a plurality of evaporators corresponding to the plurality of refrigerators provided in a plurality of refrigerators in parallel with one compressor, the refrigerant discharged from the compressor is led to a condenser, and the condenser is branching and inputting the refrigerant that has passed through a plurality of solenoid valves corresponding to the plurality of refrigerators, and guiding each refrigerant that has passed through the plurality of solenoid valves to a corresponding one of the plurality of evaporators after being depressurized,
A first relay for synchronization in a circuit for controlling the plurality of electromagnetic valves in a cooling device capable of forming a refrigerant circulation route that commonly guides each refrigerant that has passed through the plurality of evaporators to the suction side of the compressor. , a first circuit that forcibly operates the first relay at regular intervals, and a plurality of second circuits corresponding to the plurality of refrigerators, each of the second circuits , a circuit in which a corresponding second relay among the plurality of second relays corresponding to the plurality of refrigerators is connected in parallel to a corresponding solenoid valve among the plurality of solenoid valves, and the corresponding second relay. A circuit in which the normally open contact of the above-mentioned first relay is connected in parallel with the normally open contact of the first relay, and the temperature in the corresponding refrigerator among the plurality of temperature-responsive contacts corresponding to the plurality of refrigerators becomes below a predetermined temperature. and temperature-responsive contacts that open when the relay falls, are connected in series to each other, and the plurality of second circuits are connected in parallel to the power supply, and each time the first relay is operated, the plurality of second circuits are connected in series. A control circuit for a cooling device, characterized in that energization of solenoid valves is started all at once.