JPH0570073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a method of operating an air circulation type low temperature show case.

(b) Conventional technology The following low-temperature case has a configuration in which two evaporators are arranged in one air circulation passage.
There are (A) and (B).

(A) As seen in Japanese Patent Publication No. 52-16914 (70B18), the second evaporator is placed on the windward (upstream) side of the first evaporator, and the first evaporator and second evaporator are connected in sequence. Configuration for defrosting operation.

(B) As seen in Japanese Patent Application Laid-Open No. 62-217080 (F25D21/06), a reversible blower fan and both first and second evaporators are placed in the passage, and both evaporators are operated alternately. The configuration allows the fan to perform cooling and defrosting operations, and also rotates the fan in the forward and reverse directions.

(C) Problems to be Solved by the Invention In (A) above, since all of the high-humidity air that has passed through the second evaporator during defrosting passes through the first evaporator during cooling, the first evaporator The amount of frost on the evaporator increases rapidly, the heat exchange of the first evaporator becomes poor, and if the second evaporator is heated with an electric heater for defrosting, all of the air heated by this electric heater is Since this becomes a refrigeration load on the first evaporator during cooling, the temperature of the air curtain becomes higher than when only the first evaporator is cooled, and the temperature in the storage room increases significantly in the latter stages of defrosting the second evaporator. This caused problems that led to

In addition, in (B) above, in addition to the same problem as in (A) above, when switching between forward and reverse rotation of the fan, the motor must be completely stopped to avoid locking the motor. A problem arises in that the curtain is not formed temporarily, and during this time a large amount of outside air enters the storage room, causing the temperature of the storage room to rise significantly.

The present invention aims to solve the above-mentioned problems, and is designed to suppress the temperature rise of the air curtain during defrosting of both the first and second evaporators.

(d) Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a passageway for airflow circulation with two sections, one for a high pressure region and one for a low pressure region.
a second evaporator arranged in a low-pressure region between the fan case and the suction port, and a second evaporator arranged in a low-pressure region between the fan case and the air outlet; , a partition plate dividing the first evaporator into an inner path and an outer path in which the first evaporator is disposed; in the first mode, both the first and second evaporators perform a cooling function; in the second mode, the first evaporator has a defrosting effect by forced heating, and the second evaporator has a cooling effect.
In the third mode, the first evaporator performs a cooling action, and the second evaporator performs a cooling action and a defrosting action by forced heating.

(E) Action In the second mode, the cold air flow whose temperature has been lowered through heat exchange in the second evaporator is divided into the inner path and the outer path, and among the divided cold air flows, the cold air flow which has flowed into the inner path The airflow gradually rises in temperature under the influence of the heat of the first electric heater that heats the first evaporator, and is blown out to the opening as an inner layer air curtain, but the cold airflow flowing to the outer path is The air is blown out through the opening without being affected by the heat of the first electric heater, and is formed as a low-temperature outer layer air curtain.

In the third mode, the amount of heat exchanged by the second evaporator is slightly greater than the amount of heat exchanged by the second electric heater, so that it is possible to eliminate residual frost on the second evaporator, and to In addition to being able to suppress the temperature rise of the airflow itself that has passed through it, the amount of heat contained in the cold airflow that has passed through the second evaporator is reduced because part of this airflow is divided into the inner path and the other part is divided into the outer path. Approximately half of the airflow flows to the first evaporator, and the temperature of the airflow heat exchanged in the first evaporator is significantly lowered to become a cold airflow, and the temperature of the inner layer air curtain of the opening can be brought to approximately a predetermined temperature. can.

(f) Examples Examples of the present invention will be described below based on the drawings.

Figure 1 shows opening 3 on the front for storing and taking out products.
This is a low-temperature storage case whose main body is composed of a heat insulating wall 2 formed with a heat insulating wall 2, and a storage chamber 6 equipped with a plurality of shelves 5 by arranging a partition plate 4 at an appropriate distance from the inner surface of the heat insulating wall 2. , a passage 9 for airflow circulation comprising a fan case 7 disposed in the bottom area and first and second blowing fans 8A, 8B supported by the fan case. The passage 9 has one end provided along the upper edge of the opening 3 as both first and second air outlets 10A and 10B, and the other end provided as a suction port 11 along the lower edge of the opening 3. One of the first and second outlets 10A and 10B blows out a cold airflow shown by a solid line arrow, and the other blows out a protective airflow shown by a chain line arrow toward the opening 3. By arranging a partition plate to be described later, It is formed. 1
2 is a fan case 7 and both first and second air outlets 10
A, 10B is a partition plate arranged to divide the inside of the passage 9 into two parts, the inside and the outside, and along with the arrangement of the partition plate 12, the first evaporator 13 is arranged and the inner passage 9A passes through the cool air flow. Outer channel 9B for passing protective airflow
is formed. 14 is a second evaporator disposed in the passage 9 between the fan case 7 and the suction port 11. 15 is a first electric heater disposed on the air inlet side of the first evaporator 13; 16 is a first electric heater disposed on the air inlet side of the first evaporator 13;
A second electric heater is disposed on the air inlet side of the evaporator 14 and is energized when defrosting the corresponding evaporator. The fan case 7 functions to partition the passage 9 into a high pressure area and a low pressure area, and a first evaporator 13 is disposed in the high pressure area on the leeward side when viewed from both the first and second blowing fans 8A, 8B. Further, a second evaporator 14 is arranged in the low pressure region on the windward side. As shown in FIGS. 2 and 3, the fan case 7 includes first blowing fans 8A for circulating cold air on both left and right sides, and a second blowing fan 8B for circulating protective air in the center.
It is provided with an auxiliary duct 17 that guides the airflow from the blower fan 8B to the outer path 9B.

FIG. 4 shows the refrigerant circuit of the low-temperature case 1, in which 20 is a refrigerant compressor, 21 is a refrigerant condenser, and 22 is a refrigerant circuit.
- 24 are first to third electromagnetic valves, 25 and 26 are pressure reducing devices such as expansion valves, and both the first and second evaporators 1
3 and 14 are mutually parallel and corresponding first and second
It is connected in series with both electromagnetic valves 22, 23 and pressure reducing devices 25, 26. Both the second and third solenoid valves 2
3 and 24 are opened and closed by a thermostat, which will be described later, and the first solenoid valve 22 is opened and closed based on signals from the thermostat and a defrost timer, which will be described later. Note that when the third solenoid valve 24 is closed, a pump-down operation is performed to recover the residual liquid refrigerant in the first and second evaporators 13 and 14 to the condenser 21, and as a result of this pump-down operation, the low pressure When the power decreases to a predetermined value, the compressor 20 is stopped by a low pressure switch (not shown).

Figure 5 is a single-phase 100V electric circuit, Figure 6 is a single-phase electric circuit.
A 200V electrical circuit is shown.

In Fig. 5, DT is a defrosting timer consisting of a 24-hour cycle timer, for example, and when two hours have elapsed from the start of operation, the normally open contacts DT _a
for example, for 30 minutes. 1X is a first auxiliary relay connected in series to the contact piece DT _a , and is energized while the contact piece DT _a is closed. TH is a temperature switch such as a thermostat for regulating the storage room temperature, and the first and second solenoid valves 22 and 23 form a series circuit with the third solenoid valve 24 connected in parallel. This temperature switch TH opens at -4℃, for example, and 0
By repeating the opening and closing operation that closes at ℃, the third
The opening and closing of the solenoid valve 24 is controlled to maintain the temperature of the storage chamber 6 at a temperature of approximately -2° C., which is in the freezing temperature range. 1X _a1
is the first contact piece of the first auxiliary relay 1X, and when the first auxiliary relay 1X is de-energized, it contacts the normally closed contact piece b connected in series to the first solenoid valve 22, and the first auxiliary relay 1X During excitation, it comes into contact with a normally open contact a connected in series to the third auxiliary relay 3X. This first contact piece 1X _a1 , the first solenoid valve 22, and the third auxiliary relay 3X are used as a defrosting switching circuit for the first evaporator 13.
Configure DF. 2X is the normally closed contact piece TM _b of the auxiliary timer and the first normally open contact piece 2X _a1 for self-holding, which will be described later.
This is a second auxiliary relay connected in series with the second auxiliary relay. The first normally open contact 2X _a1 has the second contact of the first auxiliary relay 1X.
Contact pieces 1X _a2 are connected in parallel. This second contact piece _1Xa2 is a normally open contact piece. TM is an auxiliary timer consisting of a cycle timer, and the first auxiliary relay 1X
The third contact piece 1X _b, which is a normally closed contact piece, and the second normally open contact piece 2X _a2 of the second auxiliary relay 2X are connected in series.
It is provided with a normally closed contact piece TM _b which performs an opening operation after a minute has elapsed, and is reset after opening of this contact piece TM _b . This auxiliary timer TM has a 4th auxiliary relay 4X.
are connected in parallel. Incidentally, both the first and second blowing fans 8A, 8B are connected in parallel to the defrosting timer DT and are constantly operated.

In FIG. 6, the first electric heater 15 includes the normally open contact piece 3X _a of the third auxiliary relay 3X and the overheat protector 2.
7 in series, and the second electric heater 16 is connected in series with the fourth electric heater 16.
It is connected in series with the normally open contact 4Xa of the auxiliary relay _4X and the overheat protector 28.

Next, the operation of the low-temperature case 1 will be explained.

Now, when the contact piece DT _a of the defrost timer DT is open, the temperature switch TH is closed, and the third solenoid valve 24 is energized and opened, the first auxiliary valve 1X is de-energized and its 1 contact piece 1X _a1 is normally closed contact b
Due to its contact with the first evaporator 13, the first electromagnetic valve 22 is energized and opened, and reduced pressure liquid refrigerant is supplied to the first evaporator 13. In addition, the second solenoid valve 23 is also a temperature switch.
Since the TH is energized and is open, the second evaporator 14 is also supplied with reduced pressure liquid refrigerant.

Therefore, in such an operation, the first and second evaporators 1
3 and 14 are operating in a first mode, in which the return cold air flow that has passed through the suction port 11 is first heat exchanged in the second evaporator 14 and lowered to a temperature of, for example, 4°C. 1. Second ventilation fan 8
By passing through A and 8B, the flow is divided into an inner path 9A and an outer path 9B. The cold air flow divided into the inner path 9A undergoes heat exchange in the first evaporator 13 and is lowered to a temperature of -5°C, and then is blown out from the outlet 10A to the opening 3 to form an air curtain CA, and then to the inlet. Return to passage 9 from 11. On the other hand, the outer path 9
The cold air flow diverted to B is used as a protective air flow through outlet 1.
After being blown out from 0B and forming a protective air curtain GA that flows along the outside of the air curtain CA, it joins the cold air flow that formed the air curtain CA at the suction port 11. This first mode of airflow circulation is represented by arrows in FIGS. 1 and 2.

When the drive time of the defrost timer DT has passed for 2 hours, a defrost signal is output and the contact piece DT _a
Close. As the contact piece DT _a closes, the first auxiliary relay 1X is energized, and the first contact piece 1X _a1 switches from the normally closed contact b to the normally open contact a, and the second
The contact piece 1X _a2 is closed, and the third contact piece 1X _b is open. 1st
When the contact piece ₁ The third auxiliary relay 3X is energized and its normally open contact piece _3Xa is closed, the first electric heater 15 is energized, and defrosting of the first evaporator 13 is started.
Also, when the first contact piece 1X _a2 closes, the second auxiliary relay 2X is energized, and both the first and second normally open contact pieces 2X _a1 and 2X _a2 are closed, and the first normally open contact piece 2X _{a1 closes the second auxiliary relay 2X} . Then, the second auxiliary relay 2X is self-held. still,
Although the second normally open contact piece _2Xa2 is closed, the auxiliary timer TM is not energized because the third contact piece _1Xb of the first auxiliary relay 1X is open. In addition, temperature switch TH
Since the second electromagnetic piece 23 is energized and opened via the second electromagnetic piece 23, reduced pressure liquid refrigerant is supplied to the second evaporator 14.

In such operation, a second mode is performed in which the first evaporator 13 serves as a defrosting heat source, the first electric heater 15 performs a defrosting action, and the second evaporator 14 performs a cooling action.
The circulation of the airflow is the same as in the first mode, but the cold airflow flowing into the inner path 9A is heated by the first electric heater 15.

When 30 minutes have passed since the normally open contact piece DT _a of the defrost timer DT is closed, the defrost timer DT outputs a defrosting end signal for the first evaporator 13 and opens the contact piece DT _a . As the first auxiliary relay 1X becomes de-energized due to the opening operation of the contact piece DT _a , the first contact piece 1X _a1
is switched from the normally open contact a to the normally closed contact b, and the second contact piece 1X _a2 is opened and the third contact piece 1X _b is closed. First contact piece 1X _a1 is from normally open contact a to normally closed contact b
, the first solenoid valve 22 is energized and opened to supply reduced pressure liquid refrigerant to the first evaporator 13, while the third auxiliary relay 3X is de-energized and its normally open contact 3X _A is opened to cut off the power supply to the first electric heater 15, and the cooling action of the first evaporator 13 is restarted. Also, with the closing operation of the third contact piece 1X _b ,
The fourth auxiliary relay 4X and the auxiliary timer TM are energized through the third contact 1X _b and the second normally open contact 2X _a2 of the second auxiliary relay 2X, and as a result of this energization, the fourth auxiliary relay 4X is normally open. The contact piece _4Xa is closed and the second electric heater 16 is energized. Note that since the second solenoid valve 23 is energized and open via the temperature switch TH, the reduced pressure liquid refrigerant is still being supplied to the second evaporator 14.

In such operation, the first evaporator 13 performs a cooling action, while the second evaporator 14 performs a cooling action by supplying reduced pressure liquid refrigerant and a defrosting action by the second electric heater 16 serving as a defrosting heat source. A third mode is performed, in which the circulation of the airflow is the same as in the first mode, but the airflow flowing into the inner path 9A is cooled by the first evaporator 13.

When 30 minutes have elapsed since the start of driving of the auxiliary timer TM, the auxiliary timer TM outputs a defrosting end signal for the second evaporator 14 and opens the contact piece TM _b . With the opening operation of this contact piece TM _b , the second auxiliary relay 2X
becomes de-energized and releases its self-holding, and the first and second
Open both normally open contacts 2X _a1 and 2X _a2 , and also open the auxiliary timer.
While resetting the TM as de-energized, the fourth
Second electric heater 1 with auxiliary relay 4X de-energized
6 is cut off, and only the defrosting action of the second evaporator 14 ends. As the auxiliary timer TM is reset, the contact piece TM _b closes, and the first and second
The mode returns to the first mode in which both the evaporators 13 and 14 are cooled.

The energization (ON) and de-energization (OFF) of the first to third solenoid valves 22, 23, 24 and both the first and second electric heaters 15, 16 in the first to third modes are as shown in FIG. Represented as a sequence.
The defrost timer DT is set so that the opening and closing time (set time) of the first solenoid valve 22 is longer during non-business hours such as at night when the air conditioning load in the store is low compared to business hours.

According to such an operation of the low-temperature show case 1, in the second mode in which the first evaporator 13 performs a defrosting function and the second evaporator 14 performs a cooling function, the second evaporator 1
The cold air flow whose temperature has been lowered through heat exchange in Step 4 is divided into an inner path 9A and an outer path 9B, respectively, and among these divided cold air flows, the cold air flow which flows into the inner path 9A is heated by the first evaporator. The temperature gradually rises under the thermal influence of the first electric heater 15 heating the air passage 13 and is blown out to the opening 3 as an inner layer air curtain CA. Since the outer layer air curtain GA is blown out to the opening 3 without being affected by heat and is formed as a low temperature outer layer air curtain GA, it is possible to suppress the temperature rise of the inner layer air curtain CA and also to Entry of outside air can be suppressed.

In addition, the first evaporator 13 has a cooling function, and the second evaporator 1 has a cooling function.
In the third mode in which the electric heater 4 has both cooling and defrosting functions, the amount of heat exchanged by the second evaporator 14 is slightly greater than the amount of heat exchanged by the second electric heater 16, so that the frost of the second evaporator 14 is reduced. In addition to being able to eliminate the remaining airflow and suppressing the temperature rise of the airflow itself that has passed through the second evaporator 14, a part of this airflow is divided into the inner passage 9A and the other part into the outer passage 9B. For this reason, approximately half of the heat contained in the cold air flow that has passed through the second evaporator 14 will flow to the first evaporator 13, and as a result, the temperature of the air flow with which heat is exchanged in the first evaporator 13 will be significantly increased. It is possible to lower the temperature of the inner layer air curtain CA of the opening 3 to approximately a predetermined temperature by lowering it to a cold air flow.

(g) Effects of the invention The present invention described above produces the effects listed below.

In the second mode, the cold air flowing into the outer path is blown out to the opening without being affected by the heat of the first electric heater and is formed as a low-temperature outer layer air curtain. It is possible to suppress the rise in temperature of the curtain, and also to suppress the entry of outside air into the storage room, and as a result, it is possible to suppress the rise in temperature of the storage room.

In the third mode, approximately half of the heat contained in the cold air stream that has passed through the second evaporator will flow to the first evaporator, thereby significantly increasing the temperature of the air stream heat exchanged in the first evaporator. It is possible to lower the temperature of the inner layer air curtain of the opening to approximately a predetermined temperature by lowering the temperature to create a cold air flow, thereby suppressing a temperature rise in the storage chamber.

[Brief explanation of the drawing]

The drawings all show embodiments of the present invention; FIG. 1 is a longitudinal cross-sectional view of a low-temperature shower case, FIG. 2 is a perspective view of the same essential parts, FIG. 3 is a perspective view of a fan case, and FIG. 4 is a refrigerant circuit diagram. , Figures 5 and 6 are electrical circuit diagrams, Figure 7
The figure is a sequence diagram. 6... Storage room, 7... Fan case, 8A, 8
B...Blower fan, 9...Passage, 9A...Inner path, 9B...Outer path, 10A, 10B...Blower outlet, 11...Suction port, 12...Partition plate, 13,1
4... Evaporator, 15, 16... Electric heater.

Claims (1)

[Claims] 1. In an air circulation type low-temperature show case in which an air curtain is formed by blowing air from an air outlet along one edge of an opening for storing and taking out products to an air inlet along the other edge of said opening, a fan case disposed in the passage so as to divide the passage into a high-pressure region and a low-pressure region, and provided with a blower fan; and a second evaporator disposed in the low-pressure region between the fan case and the suction port. and a partition plate that partitions the high pressure area between the fan case and the outlet into an inner path and an outer path in which a first evaporator is disposed, and a first
In mode, both the first and second evaporators perform a cooling action, in the second mode, the first evaporator performs a defrosting action by forced heating, and the second evaporator performs a cooling action, and in the third mode, the first evaporator performs a cooling action. A method of operating a low-temperature case in which the second evaporator has a cooling effect, and the second evaporator has a cooling effect and a defrosting effect by forced heating.