JPS62294855A - Refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (a) Industrial Application Field The present invention uses a plurality of refrigerant closed circuits, and cools the condenser of the low temperature side refrigerant circuit by the evaporator of the high temperature side refrigerant circuit. The present invention also relates to a refrigeration system for obtaining an extremely low temperature by evaporating a refrigerant with a low boiling point in an evaporator of a low-temperature side refrigerant circuit.

(b) Prior Art Conventionally, this type of refrigeration system is called a binary refrigeration system, as described in, for example, Japanese Utility Model Publication No. 56-53236.
Two independent refrigerant closed circuits are prepared, and a heat exchanger, ie, a cascade condenser, is configured by the evaporator of the high temperature side refrigerant circuit and the condenser of the low temperature side refrigerant circuit. On the other hand, the low-temperature side refrigerant circuit is filled with a refrigerant with a relatively low boiling point, this refrigerant is condensed in the cascade condenser, and the refrigerant is evaporated in the evaporator of the low-temperature side refrigerant circuit. The structure is such that an extremely low temperature is obtained in the evaporator. Although the configuration as described in the above publication is limited to a final temperature of approximately -185°C, there is a method for obtaining an even lower temperature (for example, -150°C, etc.) as described in US Pat. No. 3,733,845. The low-temperature side refrigerant circuit is a so-called mixed refrigerant system, and by successively condensing a refrigerant with a lower boiling point with a refrigerant with a higher boiling point, an extremely low temperature is obtained in the final stage evaporator.

(c) Problems to be Solved by the Invention As mentioned in the above-mentioned publications and specifications, since the low-temperature side refrigerant circuit is usually filled with refrigerant having an extremely low boiling point, the load applied to the electric compressor is also large. Furthermore, if the space to be cooled by the evaporator of the low-temperature side refrigerant circuit becomes larger, the cooling capacity will need to be increased accordingly, so electric compressors with large capacity and high output will be required on both the high-temperature side and the low-temperature side. However, such electric compressors consume a large amount of power when starting up, etc.
This does not require special power supply equipment, and the amount of power consumed increases, as well as vibrations and noise during operation.

In addition, in such a binary refrigeration system, an extremely low temperature as described above is obtained in the evaporator of the low-temperature side refrigerant circuit, and for this purpose, a refrigerant with an extremely low boiling point, such as R50 (methane), is used as the low-temperature side refrigerant. must be used in the circuit,
As a result, a large load is applied to the compressor of the low-temperature side refrigerant circuit, causing an abnormal temperature rise and causing seizure.

(d) Means for Solving the Problems The present invention has been achieved in order to solve these problems, and the present invention will be described in detail below with reference to Examples.

The refrigeration system (RA) has a high temperature side refrigerant circuit (10) and a first low temperature side refrigerant circuit (11), which are independent refrigerant closed circuits.
) and a second low-temperature side refrigerant circuit (12).The evaporator of the high-temperature side refrigerant circuit (10) is composed of a first evaporator section (1
8A) and a second evaporator part (18B), the condenser (27) of the first low-temperature side refrigerant circuit (11) and the condenser (29) of the second low-temperature side refrigerant circuit (12), respectively. ) constitute a first cascade capacitor (28) and a second cascade capacitor (30), respectively. The refrigerant coming out of the first evaporator part (18A) is sent to the oil cooler (23) of the electric compressor (22) of the first low temperature side refrigerant circuit (11).
The refrigerant flows into the electric compressor (22) to cool the electric compressor (22), and the refrigerant exiting the second evaporator section (18B) is supplied to the electric compressor (25) of the second low-temperature side refrigerant circuit (12). The electric compressor (
25).

(f) Function According to the present invention, since two low-temperature side refrigerant circuits are used, the space to be cooled that should be shared by one refrigerant circuit can be reduced.
The load is reduced, and the capacity of the electric compressor in the low-temperature side refrigerant circuit can be reduced. In addition, since the electric compressor of the low-temperature side refrigerant circuit is cooled by the low-temperature refrigerant that has passed through the evaporator section of the high-temperature side refrigerant circuit, the electric compressor of the low-temperature side refrigerant circuit, which tends to reach high temperatures, can be well cooled, and the evaporator of each Since the electric compressor of the low-temperature side refrigerant circuit corresponding to that part is cooled, there is no possibility that one side will be insufficiently cooled.

(f) Embodiments Next, embodiments will be explained with reference to the drawings. FIG. 1 shows a perspective view of a freezer 1) to which the present invention is applied. freezer(
1) is installed in, for example, a physical and chemical laboratory,
A storage chamber with an upward opening formed inside the main body (2) constituted by a heat insulating box is divided into left and right sides by a heat insulating partition wall (3).
The first storage room (4) and the second storage room (5) are configured.

(6A) and (6B) are insulating doors that open and close the upper openings of both storage chambers (4) and (5), respectively, and (7) is a machine that houses the components of the refrigeration system (RA), which will be detailed later. It is formed laterally in a chamber.

FIG. 2 shows the refrigerant circuit of the refrigeration system (RA) of the present invention.

The refrigeration system (RA) is composed of a high-temperature side refrigerant circuit (10), a first low-temperature side refrigerant circuit (11), and a second low-temperature side refrigerant circuit (12), each of which constitutes an independent refrigerant closed circuit. There is. (13) is an electric compressor constituting the high temperature side refrigerant circuit (10), and its discharge side pipe (13D) is connected to the condenser (14). (15) is the condenser (14)
This is a blower for cooling. The refrigerant pipe exiting the condenser (14) passes through the liquid receiver (16) and then splits into two directions at a branch point (P,), one of which is a solenoid valve (19A) and a thermostatic expansion valve (17).
) to the first evaporator section (18A>), and
The other side is connected to the second evaporator section (18B) via a solenoid valve (19B> and a thermostatic expansion valve (20).The first and second evaporator sections (18A) (18B) are connected to the high temperature side. It is an evaporator of the refrigerant circuit (10).The first evaporator part (18
The refrigerant pipe passing through A) passes through an accumulator (21) as a refrigerant reservoir, and then connects to the first low temperature side refrigerant circuit (11).
> can be connected to the oil cooler (23) of the electric compression @ (22). Furthermore, the refrigerant pipe that has passed through the second evaporator section (18B>) is connected to the oil cooler (26) of the electric compression a (25) of the second low-temperature side refrigerant circuit (12) through a similar accumulator (24). Both oil coolers (23) (,2
The refrigerant pipes that have passed through 6) join together at a merging point (P,) and then are connected to the suction side pipe (135) of the electric compressor (13).

Temperature sensing part (17A) of expansion valve (17) (20) <2OA)
are attached to the accumulators (21) (24) in a thermally conductive manner, respectively, and the evaporator parts (18A) (18B
) to supply the appropriate amount of refrigerant.

R502 refrigerant (88% by weight) is used in the high temperature side refrigerant circuit (10).
) and R12 refrigerant (12% by weight) are sealed. now,
To explain the refrigerant circulation assuming that both the solenoid valves (19A) and (19B) are open, the high-temperature, high-pressure gaseous refrigerant discharged from the electric compressor (13) is liquefied with heat dissipation in the condenser (14), and then The liquid flows through the receiver (16) and is divided into the expansion valve (1
7)<20), the pressure is reduced, and the liquid flows into each evaporator section (18A) (18B) and evaporates. Here, the first evaporator part (18A) is connected to the first low temperature side refrigerant circuit (
11) constitutes the condenser (27) and the first cascade condenser (28), and the second evaporator part (18B) constitutes the condenser (29) of the second low temperature side refrigerant circuit (12). Second
This constitutes a cascade capacitor (30). Furthermore, in each evaporator section (18A) (18B), each cascade condenser (28) (30) is cooled to about -50°C by evaporation of R502 refrigerant in a steady state, so R12 refrigerant is Vessel part (18A) (18B)
(Because the evaporation temperature is 135°C)
, Therefore, R12 refrigerant is used in a cascade condenser (2g>
(It hardly contributes to the cooling of 30>.

That is, R12 refrigerant flows through the electric compressor (13
) with the lubricating oil dissolved in it.
13). Also, each evaporator part (
The low-temperature refrigerant that has passed through 18A) (18B>) passes through accumulators (21) and (24), and then goes to oil coolers (23).
(26), and as described later, the electric compressors (22)<25) of both low-temperature side refrigerant circuits (11) and (12), which tend to reach high temperatures, can be effectively cooled by enclosing a refrigerant with a low boiling point. In addition, liquid R is discharged from the oil return holes normally formed in the outlet pipes from the accumulators (21) and (24).
Since the refrigerant flows into the oil cooler (23) (26) and evaporates there, the cooling of each electric compressor (22) (25) becomes even better.
13) is also eliminated and damage can be prevented.

In addition, each electric compressor (22) (25) is cooled by the refrigerant that has passed through the evaporator section (18A bar 18B) corresponding to the condenser (27) (29) of the respective low temperature side refrigerant circuit (11) (12). Therefore, there is no shortage of cooling on the downstream side, which occurs when the oil coolers (23) and (26) are configured in series in the piping downstream of the confluence point (P,). When the circuit (11) or (12) is not operated, the solenoid valve (19A) or (19B) is closed, so that no refrigerant flows to the oil cooler (23) or (26), and the electric compressor (22) is stopped. Or (2
5) can be prevented from being cooled wastefully, and frost formation due to overcooling can also be prevented.

Next, the discharge side pipe (22D) of the electric compressor (22) constituting the first low temperature side refrigerant circuit (11) is connected to the condenser (27), and then connected to the gas-liquid separator (31). Ru. The gas phase piping (32) coming out of the gas-liquid separator (31) passes through an intermediate heat exchanger (33) and is read directly to the next gas-liquid separator (34), and the liquid phase piping (35) After passing through a dryer (36), it passes through a pressure reducer (37) and is connected between intermediate heat exchangers (33) and (38). Further, the liquid phase pipe (39) coming out of the gas-liquid separator (34) is connected between the intermediate heat exchangers (38) and (42) via a dryer (40) and a pressure reducer (41). The gas phase pipe (43) coming out of the gas-liquid separator (34) passes through the intermediate heat exchanger (3B), then the intermediate heat exchanger (42), and then the dryer (44) where it is depressurized. It passes through the vessel (45) and is connected to the evaporator (46).

This evaporator (46) is attached to the outside wall of the first storage chamber (4). After passing through the evaporator (46), the refrigerant pipe is connected to the intermediate heat exchanger in the order of <42> (38) and (33), and then passes through the accumulator (47) to the electric compressor (
22) is connected to the suction side piping (225).

Similarly to the first low temperature side refrigerant circuit (11), the second low temperature side refrigerant circuit (12) also has a discharge side pipe (2) of the electric compressor (25).
5D) and a condenser (29) between the suction side pipe (255),
Gas-liquid separator (50) (53), each gas phase piping (51) (6
2) and liquid phase piping (54) (58), dryer (55) (
59) (63), pressure reducer (56) (60) (64), intermediate heat exchanger (52) (57) (61), evaporator (65)
) and an accumulator (66) are connected to each other to form a similar refrigerant closed circuit. The evaporator (65) is attached to the outside wall of the second storage chamber (5).

Four types of mixed refrigerants having different boiling points are sealed in both low-temperature side refrigerant circuits (11) and (12). That is, R12 (35 heavy view%
), R13B1 (39% by weight), R14 (22% by weight)
and R50 (4% by weight) are sealed in a pre-mixed state.

Next, both low temperature side refrigerant circuits (11) (12) in steady state
) refrigerant circulation will be explained. Electric compressor (22) (
The high-temperature, high-pressure gaseous mixed refrigerant discharged from the first
Or second cascade capacitor (28) (30)
The R12 and R13B1 refrigerants in the cooled mixed refrigerant flow into the gas-liquid separator (31) <50> in a fully condensed state. At this point, R14 and R50 in the mixed refrigerant are still in a gaseous state due to their extremely low boiling points.
is the gas phase pipe (32) (51), R12 and R13B1
is separated into liquid phase pipes (35) and (54>).The refrigerant mixture that has flowed into the gas phase pipes (32) (st) exchanges heat with intermediate heat exchangers (33) and (52>), respectively, and is completely condensed. After that, it reaches the gas-liquid separator (34) (53). Here, the low-temperature refrigerant returning from the evaporator (46) (65) flows into the intermediate heat exchanger (33) (52), respectively. Furthermore, the R13B1 refrigerant that has flowed into the liquid phase pipes (35) and (54) passes through the dryers (36) and (55) to the pressure reducer (37) (
56), and then the intermediate heat exchanger (33)
(52) and evaporates there, contributing to cooling, so the temperature of the intermediate heat exchangers (33) and (52) is approximately -80"C. Therefore, the gas phase piping (32) (
51) in the mixed refrigerant is condensed and liquefied, and R50 is still in a gas state because it has an even lower boiling point. Therefore, R14 connects the gas-liquid separator (34) (53) to the liquid phase piping (39) (58>), and R50 connects the gas phase piping (4).
3) (62), and R14 is separated into a dryer (62).
40) (59), the pressure is reduced in the pressure reducer (41) (60), and the intermediate heat exchanger (42) (38) or (61) (
57) Intermediate heat exchanger (38) (
57) evaporates within. The return low-temperature refrigerant from the evaporators (46) and (65) flows into the intermediate heat exchangers (38) and (57), respectively, and the evaporation of R14 further contributes to cooling. ) temperature is -100″
It is about C. Furthermore, intermediate heat exchangers (42) (61)
Since the return low-temperature refrigerant from the evaporators (46) and (65) immediately flows into the evaporators, its temperature is as low as -120"C, so the intermediate heat exchanger (38)
The refrigerant R50 with the lowest boiling point passing through the gas phase pipes (43) and (62) that exchanged heat with (42) or (57) and (61), respectively, is condensed and liquefied, and then passed through the dryer (44) and (63) to the pressure reducer. After being depressurized at (45) and (64), they flow into evaporators (46) and (65), respectively, and evaporate there.

At this time, the temperature of the evaporator (46>(65) has reached -150°C. This is the final temperature reached by the refrigeration system (RA), and the temperature of the first and second storage chambers (4) ( 5)
It becomes possible to create an ultra-low temperature environment inside. Evaporator (4
The refrigerant R50 discharged from the intermediate heat exchanger (42) (38
) (33), and the refrigerant R50 coming out of the evaporator (65)
The refrigerants R14, R13B1, and R12 sequentially flow into and out of the intermediate heat exchangers (61), (57), and (52), respectively.
After separating the unevaporated refrigerant in the accumulators (47) and (66) while merging with the refrigerant, the electric compressor (22)
(25) can be inhaled respectively. Also, in this circulation, R12 refrigerant hardly contributes to cooling, and the electric compressor (
22) Functions to return the lubricating oil from (25).

Next, FIG. 3 shows an electric circuit for controlling the refrigeration apparatus (RA) of the freezer 1). (AC) (AC) is an alternating current power supply,
(70) is a power switch, which turns on and off the power to all devices at the subsequent stage. (13M) is a motor for driving the electric compressor (13) of the high temperature side refrigerant circuit (10), and is connected in series with the normally closed contact (ss + ) of the relay coil (R8), and the contact (S, , ) If it is closed, continuous operation is performed while the power switch (70) is closed. The relay coil (R6) is connected in series with the normally open contacts (s7, ) (S□) of the relay fills (Ry) (Ra). (71) is a temperature regulator for the first storage chamber (4) that includes a rectifier circuit, etc., and a temperature detector (72) that senses the temperature of the evaporator (46).
), for example, when the temperature reaches -150℃, the generation of output voltage between the output terminals (71A) and (71B) is stopped, and -
The temperature rises to 140°C to generate an output voltage. Output terminal (
A relay coil (it>) and a high voltage switch (73) are connected in series between 71A) and 71B.
3) senses the discharge side pressure of the electric compressor (22), for example, 26 kg/crIl! Rise to 8 kg and open the contact.
/cm" and closes the contacts. (74) is a cold start thermostat which senses the temperature of the accumulator (21) and closes the contacts when the temperature drops to -35°C, for example, -1
The temperature rises to 0℃, the contact opens, and the relay coil (R
1) can be connected in series with the normally open contact (S, ) and relay coil (R8) to the power supply (AC>(AC). (22M) is the electric compressor (22) of the first low temperature side refrigerant circuit (11). ) drive motor, which has a normally closed contact (57,) of the relay coil (R2) and a normally open contact (S2, ) of the relay coil (R1>).
) can be read serially. (19CA) is a solenoid valve (19CA)
A) is connected in series with the normally closed contact (Sys) of the relay coil (R2). Also, (SW,) is a holding type manual switch that can be connected in series with the relay coil (R7).

(75) is a temperature regulator for the second storage chamber (5), and based on the temperature detector (76) that senses the temperature of the evaporator (65), when the temperature reaches -150°C, the output terminal ( 7
5A) (stops generation of output voltage between 75B> and -14
The temperature rises to 0°C and an output voltage is generated. Output terminal (75
A) and (75B), a relay coil (R3) and a high voltage switch (77) are connected in series. High pressure switch (77)
is electric compression I! (25) senses the discharge side pressure and operates in the same way as the high pressure switch (73). (78) is a low-temperature start thermostat that senses the temperature of the accumulator (24), operates in the same way as the low-temperature start thermostat (c), and connects the normally open contact (S, ) of the relay coil (R8) to the relay coil ( Connected in series with R4) (25M)
is the electric compressor (25) of the second low temperature side refrigerant circuit (12)
It is a driving motor and has a normally closed contact (S) of a relay coil (R,).

), can be connected in series with the normally open contact (S4) of the relay coil (R1) and the normally open contact (S, ) of the relay coil (R9). <SW*) is a holding type manual switch and is read directly in series with the relay coil (R, ). (19CB) is the fill of the solenoid valve (19), and the solenoid valve (19A) (19B
) is used to open the flow path by energizing the coils (19CA) (19CB), and the coil (19CB') connects the normally open contact (sa + ) of the relay coil (R6), the relay coil (R
It can be connected in series with the parallel circuit of the normally closed contact (Sss) of the relay fill (R9), the normally open contact (Sat) of the relay fill (R9), and the normally open contact (ss4) of the relay coil (R2). <80)
is a temperature detector that senses the temperature of the evaporator (46), for example, and closes the contact when the temperature of the evaporator (46) drops to, for example, -150"C, and the normally open contact of the relay coil (R,) (Sag) and this parallel circuit is connected in series with the normally closed contact (Sat) of the relay coil (R6> and relay fill (R6). (81) is connected to the first cascade capacitor (28 ), which closes the contact when the temperature of the first cascade capacitor (28) drops to -40°C, for example, and opens the contact when it rises to -20°C. Detector(
81) may sense the temperature of the accumulator (21).

Next, the operation of the refrigeration system (RA) will be explained. Now, power supply (A
C) With (AC) connected, switch (SW,
) (S back, ) is open, so the relay coil (R
t)fls> cannot be energized, and the contacts (sy, )(s
t a )(s, , ) are open and the contacts (sy,)(s
, 5) (s,) (s, ,) is assumed to be closed. Also, the relay coil (R8) cannot be energized and the contact (Sat)
(Sst) is also assumed to be closed. When the freezer (1) is installed and the power switch (70) is closed, the motor (13M) starts, the electric compressor (13) operates, and refrigerant begins to circulate in the high temperature side refrigerant circuit (10).

At this time, the solenoid valve (19A) opens, and the evaporator (46)
Since the accumulators (21) and (24) or the first cascade capacitor (28) are in a state close to room temperature, the temperature detectors (80) (81) and the low temperature start thermostat (
74) and (78) are open, so the relay coils (R6) and (R9) are not energized and the contacts (Ss, > (S
at) is open 'Ft, the valve (19B) is closed, and regardless of the temperature regulators (71)' (75), the relay coil (Rt) (l is not energized,
Contact (5,) (S,) is open, and contact (S, □
) are also open, so the motors (22M) (25M) will not start. Therefore, in the freezer bag fl (RA), the cooling operation of only the high temperature side refrigerant circuit (10) continues R1, and the solenoid valve (1
9A) is open and (19B,) is closed, the refrigerant flows only to the first evaporator portion (18A) and evaporates. As a result, the first cascade capacitor (28) is completely cooled down to -40℃, and the temperature detector (28) is detected.
81) closes the contact, so the relay coil (R9) is energized and the contact (ss, > (s-ox) is closed. Also, the first
As the temperature of the evaporator section (18A) decreases, liquid refrigerant accumulates in the accumulator (21), and when the temperature decreases to -35°C, the low temperature start thermostat (74) closes.At this time, the evaporation starts. Since the temperature of the device (46) is high, the temperature controller (71) also generates an output voltage and the contact (
S,) is closed. Therefore, the cold start thermostat (
When the relay coil (R) is closed, the relay coil (R) is energized, the switch (S,) is closed, the motor (22H) is started, and the mixed refrigerant is discharged from the electric compressor @ (22) and the circuit (11) is closed.
) begins to circulate within. At this time, the first low temperature side refrigerant circuit iM(
Since most of the refrigerant in 11) is in a gas state, the pressure on the discharge side of the electric compressor (22) rises rapidly to 26 kg/Cr1.
When reaching l', the high voltage switch (73) opens, cutting off the current to the relay coil (R7), and opening the switch (Sl).
The relay fill (R1) is de-energized and the switch (S,)
opens and the motor (22M) stops. This prevents a pressure increase on the discharge side of the electric compressor (22), and prevents damage to the electric compressor (22).

When the electric compressor (22) is stopped, the discharge side piping (22D
) (7) JE When the force decreases to 9 kg/cm'', the high pressure switch 7 (73) closes again and the motor (22M> can be started as before, but the pressure in the discharge side piping (22D) is 26 kg/Cr1l). '', the high pressure switch (73) opens again and the motor (22M) stops. As the motor (22M') starts and stops like this, the refrigerant with a high boiling point evaporates. By gradually exerting a cooling effect, the temperature gradually decreases from the intermediate heat exchanger (33), and the pressure rise in the discharge side piping (22D) when the motor (22M) is started reaches 26 kg/CTII'. When it runs out, the motor (22M) will operate continuously.As the electric compressor (22) continues to operate, the refrigerant with a low boiling point will also be condensed and will gradually begin to exert its cooling effect, causing each intermediate heat exchanger (33) (3g) (42) and the temperature of the evaporator 46) gradually decrease to reach the final temperature (-1).
50"C). As a result, the temperature controller (71) stops generating the output voltage, the relay fill (R8) becomes de-energized, the contact (S,) opens, and the contact (S) also opens and the motor starts. (22M) stops, and when the temperature of the evaporator (46) rises to 1140°C again, an output voltage is generated to drive the motor (22M).
2M). As a result, the inside of the first storage chamber (4) is maintained cooled to an average of about -145°C.

On the other hand, when the evaporator (46) reaches -150°C, the temperature detector (80) closes the contact and the relay coil (R6) is energized, which closes the contact (Ss + ) (552) and the relay coil (R6) is energized. ) itself is self-retained by closing the contacts (S, , ). When the contact (SS,) closes, the contact (S
, t) are closed, the fill (19CB) is energized, and the solenoid valve (19B> is opened to open the second evaporator section (18).
Refrigerant also flows into B> and begins to evaporate, causing the temperature to drop. Eventually, the temperature of the accumulator (24) also drops to -35°C, when the low temperature start thermostat (7)
8) closes the contact and energizes the relay coil (R4),
The contact (S4) closes and the motor (25M) starts. Below, the intermediate heat exchanger (52) (57) (61) and evaporator (
The temperature of the second storage compartment (5) decreases, and the temperature of the second storage compartment (5
) is cooled to an average of -145°C.

In this way, when the freezer (1) is installed, at the start of later cooling operation, both low-temperature side refrigerant circuits (11) and (12) can start cooling operation from one side at a time, that is, from the first low-temperature side refrigerant circuit (11),
Since they are not started at the same time, the load applied to the electric compressor (13) of the high temperature side refrigerant circuit (10) at the start of the cooling operation is reduced. Moreover, after the first low temperature side refrigerant circuit (11) starts to exhibit the target cooling capacity, that is, it becomes a stable state, the first low temperature side refrigerant circuit (11) becomes the high temperature side refrigerant circuit (10).
) is started after the load on the high temperature side refrigerant circuit (12) is lightest, so the load on the high temperature side refrigerant circuit (10) at the start of the cooling operation becomes the lightest. In addition, since the low-temperature side refrigerant circuit is composed of two circuits (11) (12), the electric compressors (13) (22) (25) can also be of small capacity, reducing power consumption during startup. This reduction eliminates the need for large-capacity power supplies, and achieves low vibration and noise.

The above description is based on the case where the cooling operation progresses smoothly, but after the solenoid valve (19B) is completely opened and the cooling operation of the second low temperature side refrigerant circuit (12) is completely opened, the door (6A) or the door 6B is closed. ) is left open for a long time, or the second storage chamber (5) is overloaded and the second evaporator section (1
8B), or when the load on the first storage chamber (4) is large and a large amount of refrigerant is required in the first evaporator section (18A). The refrigerant supplied to the first evaporator section (18A) becomes insufficient. When the refrigerant flowing into the first evaporator section (18A) becomes insufficient, the temperature of the first cascade condenser (28) increases due to insufficient cooling, and at the same time, the amount of liquid refrigerant accumulated in the accumulator (21) decreases. Therefore, the temperature of the accumulator (21) also rises. The expansion valve (17) that senses this is located in the first evaporator section (18A).
The system works to increase the amount of refrigerant supplied to the system, but there is a limit to this because the original amount of refrigerant has become insufficient. As a result, the temperature of the first cascade condenser (28) increases, and since the amount of refrigerant flowing into the second evaporator section (18B) also decreases, the temperature of the second cascade condenser (30) does not decrease.

If this situation continues, both low temperature side refrigerant circuits (1
1) The decrease in cooling capacity (12) will continue for a long time, and the temperature will remain higher than the target temperature for a long time, and the pressure in the low-temperature side refrigerant circuit (11> or (12) will also increase.) A problem also arises in the lifespan of the electric compressors (22) and (25).

Therefore, in the present invention, when the temperature of the first cascade condenser (28) rises to -20°C due to refrigerant shortage (before the contact of the low temperature start thermostat (74) opens), the temperature detector (81) is activated. Open the contacts. As a result, the relay coil (R9) becomes de-energized and the contact (ss
I) (si- is opened, so the electric compressor (25) is stopped and the solenoid valve (19B) is forcibly closed. This is because the first cascade condenser ( 28) is also carried out when the temperature rises.As a result, a sufficient amount of refrigerant is supplied to the first evaporator section (18A), so the first low-temperature side refrigerant circuit (11) is immediately activated. The cooling capacity is restored. Also, during this process, the temperature of the first cascade condenser (28) drops to -4
When the temperature drops to 0°C, that is, the temperature at which the first low-temperature side refrigerant circuit (11) can sufficiently exhibit its cooling capacity, the temperature detector (81)
) closes the contact point, so the solenoid valve (19B) opens and the second low temperature side refrigerant circuit (12) also starts cooling operation again. As a result, the temperature of the second storage chamber (5) may rise temporarily, but the temperature of the first storage chamber (4) can be reliably maintained at the target temperature. By storing valuable samples in chamber (4), deterioration can be reliably prevented. Furthermore, since the time required to recover the cooling capacity of both low-temperature side refrigerant circuits (11, 12) is reduced in total, deterioration of the electric compressors (22, 25) is also suppressed.

Next, while both low-temperature side refrigerant circuits (11) and (12) are performing cooling operation, for example, the first low-temperature side refrigerant circuit (
11) fails, closing the switch (SWI) will energize the relay coil (R2) and close the contact (SF).
So) opens, the electric compressor (22) stops, and the solenoid valve (1
9A) closes. This allows the first evaporator section (18
Refrigerant will no longer flow through A). In this state, the first low temperature side refrigerant circuit (11) can be repaired. In addition, even if there is no malfunction, the switch (
By closing SWI), cooling in the first storage chamber (4) can be interrupted and cleaning can be performed. At this time, the contact <574) is closed, so even if the contact (sex) opens, the second low-temperature side refrigerant circuit (12) continues to perform cooling operation to keep the inside of the second storage chamber (5) at a predetermined level. Because it is cooled to the temperature
By moving the articles stored in the first storage chamber (4) to the second storage chamber (5), they can be kept cool and stored in good condition, eliminating the risk of deterioration.

Conversely, when cleaning the second storage compartment (5) or when the second low-temperature side refrigerant circuit (12) breaks down, the switch (
By closing SW*), the relay coil (R,) is energized, and by opening the contact (s, *) (ss s), the electric compression m (25) is stopped and the solenoid valve (19B) is closed. can. This allows cleaning inside the second storage room (5) and repairing the second low-temperature side refrigerant circuit (12).
At the same time, articles can be stored in the first storage room (4). Here, when both switches (SWI) (SW, ) are closed, the contacts (sy + ) (si I) are closed together, so the relay fill (R6) is energized and the contact (s
s1) (ss*) opens, so the high temperature side refrigerant circuit (1
The electric compressor (13) of No. 0) is stopped to prevent unnecessary operation, and the self-holding of the relay fill (R6) is released to return to the initial state.

(G) Effects of the Invention According to the present invention, two low-temperature refrigerant circuits are configured for one high-temperature refrigerant circuit, so the structure can be simplified compared to a configuration in which each system has two refrigerant circuits. At the same time, since the load shared by the low-temperature side refrigerant circuit is reduced, the electric compressor of the low-temperature side refrigerant circuit can be made small in capacity, and low noise and vibration can be achieved. Furthermore, since the electric compressor of the low temperature side refrigerant circuit is cooled by the low temperature refrigerant that has passed through the evaporator section of the high temperature side refrigerant circuit, the electric compressor of the low temperature side refrigerant circuit, which tends to reach high temperatures, can be cooled well.

Furthermore, at this time, the electric compressors of the low-temperature side refrigerant circuits corresponding to each evaporator section are cooled, so for example, the refrigerants exiting both evaporator sections are combined, one electric compressor is cooled, and then the other electric compressor is cooled. Unlike when cooling a compressor, there is no problem such as insufficient cooling on the downstream side, and a good operating condition can be achieved.

[Brief explanation of drawings]

Each figure shows an embodiment of the present invention; FIG. 1 is a perspective view of a refrigeration system, FIG. 2 is a refrigerant circuit diagram of a refrigeration system, and FIG. 3 is an electric circuit diagram thereof. (RA')... Refrigeration device, (10)... High temperature side refrigerant circuit, (11)<12)... First and second low temperature side refrigerant circuits, (18A) (18B)... First and second evaporator parts, (22) (25)... electric compressor, (
23) (26)...Oil cooler.

Claims (1)

[Claims] 1. A high-temperature side refrigerant circuit, each consisting of a refrigerant closed circuit independent from a compressor, a condenser, an evaporator, etc., and a first and second refrigerant circuit.
and a low-temperature side refrigerant circuit, and the evaporator of the high-temperature side refrigerant circuit is constituted by first and second evaporator parts, and together with the condensers of both the low-temperature side refrigerant circuits, respectively constitute a heat exchanger. A refrigeration system characterized in that the refrigerant returned from both the evaporator parts to the compressor of the high temperature side refrigerant circuit cools the corresponding compressor of the low temperature side refrigerant circuit.