JP6974089B2 - Freezing / refrigerating showcase - Google Patents

Description

The present invention relates to a freezing / refrigerating showcase.

In supermarkets, convenience stores, etc., frozen / refrigerated showcases are arranged to display frozen foods, fresh foods, etc. while freezing or refrigerating. The freezing / refrigerating showcase includes a case body composed of an outer box and an inner box, and an evaporator and a blower installed in a ventilation path formed between the outer box and the inner box, and evaporates. The vessel can be cooled by taking heat of the air around the evaporator by the heat of vaporization when the refrigerant flowing into the inside evaporates, and the air cooled by the evaporator is stored in the case body by the blower. Frozen foods and fresh foods that are sent out and displayed in the refrigerator are frozen or refrigerated.

In such a freezing / refrigerating showcase, by continuing the cooling operation of the evaporator, frost will occur on the evaporator, and as the frosting progresses, the cooling capacity of the evaporator will decrease. A freezing / refrigerating showcase having a defrosting operation pattern as shown in Document 1 has been developed.

The freezing / refrigerating showcase shown in Patent Document 1 includes a main cooler (evaporator), an expansion valve located on the upstream side of the main cooler, and an electromagnetic valve located on the upstream side of the expansion valve. It has a cooling operation pattern in which the refrigerant passes through the main cooler when the electromagnetic valve is open, and a defrosting operation pattern in which the refrigerant stays upstream of the electromagnetic valve when the electromagnetic valve is closed. .. This defrosting operation pattern is usually performed for about 30 to 45 minutes.

Japanese Patent No. 3271699 (Page 3, Fig. 3)

However, in Patent Document 1, in the freezing / refrigerating showcase, in the defrosting operation pattern, the inflow of the refrigerant to the main cooler is stopped by the closing operation of the electromagnetic valve located on the upstream side of the main cooler. It took about 30 to 45 minutes because the frost that frosts on the main cooler is melted by the air that is relatively warmer than the frost that passes through the ventilation path. In this way, the cooling by the main cooler is stopped and the cooling operation pattern is shortened, so that there is a risk that the temperature inside the refrigerator will rise.

The present invention has been made focusing on such a problem, and an object of the present invention is to provide a freezing / refrigerating showcase in which the time required for defrosting an evaporator is short.

In order to solve the above problems, the freezing / refrigerating showcase of the present invention is used.
A freezing / refrigerating showcase that cools the inside of a refrigerator using a refrigerating cycle equipped with an evaporator that cools the surrounding air by evaporating the refrigerant inside the heat transfer tube.
A first solenoid valve located on the downstream side of the evaporator and a second solenoid valve located on the upstream side of the evaporator are provided.
The evaporator has a cooling operation pattern in which the refrigerant passes through the evaporator depending on the open state of the first electromagnetic valve and the open state of the second electromagnetic valve, and the closed state of the first electromagnetic valve and the second electromagnetic valve. The pressure rise process in which the refrigerant stays in the evaporator due to the open state of the electromagnetic valve and raises the pressure in the evaporator, and the pressure in the evaporator increased in the pressure rise process are referred to as the second electromagnetic wave. It is characterized by having a pressure holding step of holding a substantially constant, and the defrosting operation pattern Ru Tona, the by closing of the valve.
According to this feature, in the defrosting operation pattern, the pressure of the refrigerant in the evaporator can be increased by the closed state of the first solenoid valve, and the temperature of the heat transfer tube can be raised. The heated heat transfer tube can directly heat the part attached to the frost heat transfer tube, resulting in good heat efficiency. In addition, it adheres to the frost evaporator without melting the entire frost. Frost can be removed from the evaporator by melting the portion. As a result, the time required for defrosting the evaporator is short.

In the defrosting operation pattern, the pressure increase process in which the pressure in the evaporator increases due to the open state of the second solenoid valve and the pressure in the evaporator increased in the pressure increase process are combined with the second solenoid valve. It is characterized by having a pressure holding process that keeps the pressure substantially constant depending on the closed state.
According to this feature, the temperature of the evaporator can be quickly reached to a temperature suitable for defrosting in the pressure rising process, and the temperature can be maintained in the pressure holding process.

After the defrosting operation pattern, the refrigerant has a cooling return pattern in which the refrigerant passes through the evaporator depending on the open state of the first solenoid valve and the open state of the second solenoid valve. ..
According to this feature, when the defrosting operation pattern is switched to the cooling return pattern, the cooling of the evaporator is started immediately. As a result, it is possible to accelerate the return to the cooling operation pattern.

After the defrosting operation pattern, the refrigerant has a cooling return pattern in which the refrigerant passes through the evaporator due to the open state of the first solenoid valve.
According to this feature, when the defrosting operation pattern is switched to the cooling return pattern, the cooling of the evaporator is started immediately. As a result, it is possible to accelerate the return to the cooling operation pattern.

The evaporator is characterized in that, in the defrosting operation pattern, the heat transfer tube is switched to the cooling return pattern after a predetermined time has elapsed after reaching a predetermined temperature.
According to this feature, since the heat transfer tube is defrosted for a predetermined time after reaching a predetermined temperature, the frost on the surface of the heat transfer tube is surely defrosted.

The first solenoid valve is characterized in that it is in a closed state when energized and in an open state when it is not energized.
According to this feature, it is possible to prevent the refrigerant from remaining in the evaporator when the power is not supplied. This makes it possible to prevent the liquid back phenomenon from occurring when the operation is restarted.

It is sectional drawing which shows the structure of the freezing / refrigerating showcase in Example 1 of this invention. It is a block diagram which shows the structure of the piping system of a refrigeration cycle. It is a schematic diagram which shows the structure of an evaporator. It is a block diagram which shows the structure of the evaporator, the 1st solenoid valve and the 2nd solenoid valve in a cooling operation pattern or a cooling return pattern. It is a block diagram which shows the structure of the evaporator, the 1st solenoid valve and the 2nd solenoid valve in the pressure rise process of a defrosting operation pattern. It is a block diagram which shows the structure of the evaporator, the 1st solenoid valve and the 2nd solenoid valve in the pressure holding process of a defrosting operation pattern. It is a graph which shows the temperature in a refrigerator, the temperature of an outlet, and the surface temperature of an evaporator. FIG. 7 is a chart showing changes in the states of the evaporator, the first solenoid valve, the second solenoid valve, the first temperature sensor, and the second temperature sensor of each pattern in FIG. 7. It is a graph which shows the temperature in the refrigerator, the outlet temperature, and the surface temperature of an evaporator in Example 2 of this invention. It is a block diagram which shows the structure of the evaporator, the 1st solenoid valve and the 2nd solenoid valve in Example 3 of this invention.

A mode for carrying out the freezing / refrigerating showcase according to the present invention will be described below based on examples.

The freezing / refrigerating showcase according to the first embodiment will be described with reference to FIGS. 1 to 8. Hereinafter, the left side of the paper surface of FIG. 1 will be the front side (front side) of the freezing / refrigerating showcase, and the description will be described with reference to the vertical / horizontal directions when viewed from the front side.

As shown in FIG. 1, the frozen / refrigerated showcase 1 is installed mainly in stores, supermarkets, convenience stores, and other retail stores that handle food products, and is kept cold or frozen while keeping the products at a low temperature. It is installed for display, and in the cold storage room 5 surrounded by the inner box 3 having an opening on the front side, a plurality of shelves 6, 6, ... For displaying products are installed in the vertical direction, and the inner box is installed. Products can also be displayed on the bottom 3b provided at the bottom of 3. The freezing / refrigerating showcase 1 of the present embodiment will be described by taking as an example an embodiment in which products are displayed in a refrigerated state.

The freezing / refrigerating showcase 1 has a substantially U-shaped outer box 2 with an open front surface (left side of the figure) and a substantially U-shaped inner box 3 with an open front surface. It is equipped with a case body consisting of the above, and its internal space is a cold insulation room 5 (inside the refrigerator). The rear ends of the brackets 28, 28, ... Extending back and forth are attached to the back surface portion 3a of the inner box 3, and the shelf plates 6, 6, ... Are arranged on the brackets 28, 28, ... .. Products are displayed on the upper surfaces of the shelves 6, 6, ... And the bottom 3b of the inner box 3.

A ventilation passage 7 is formed between the outer box 2 and the inner box 3, and an evaporator 8 and a blower 9 are installed at the vertical portion and the horizontal bottom portion of the ventilation passage 7, respectively. As will be described later, the evaporator 8 can cool the air around the evaporator 8. Further, a heat insulating material 29 is provided on the front side of the evaporator 8 to suppress heat exchange between the evaporator 8 and the cold insulation chamber 5 side via the inner box 3. A cold air outlet 10 communicating with the ventilation passage 7 is formed downward at the front end of the upper part of the case body, and a cold air suction port 11 that opens upward is formed at the upper end of the lower front end of the case body.

The evaporator 8 is set so that the cooling set temperature (outlet temperature) during normal operation (during business hours) is around -3 ° C, and the internal temperature is 3 ° C under the conditions of this embodiment. It is before and after (see Fig. 7). The temperature inside the refrigerator refers to the temperature near the shelves 6, 6, ... (Places close to the products), and is shown according to the products displayed in the cold storage room 5 of the freezing / refrigerating showcase 1. It can be changed by operating the control unit.

When the blower 9 is operated, the cold air cooled by the evaporator 8 flows upward in the ventilation passage 7 as shown by the arrow, and is blown out from the cold air outlet 10 toward the lower suction port 11. .. As a result, the cold air curtain 12 is formed on the open surface on the front surface of the case body, and a part of the cold air flows into the cold storage chamber 5, so that the displayed products are kept cold.

Next, the evaporator 8 in the freezing / refrigerating showcase 1 will be described. As shown in FIGS. 1 and 3, the evaporator 8 includes a heat transfer tube 15 which is a copper tube through which the refrigerant 16 flows, and the heat transfer tube 15 penetrates a plurality of fins 30, 30, .... As a result, the contact area between the heat transfer tube 15 and the surrounding air is increased, the air blown from the blower 9 is efficiently hit, and the cooling efficiency is improved. The heat transfer tube 15 is not limited to a copper tube, and may be a tube made of metal or resin having high thermal conductivity.

Specifically, as shown in FIG. 3, the heat transfer tube 15 is adjacent to a plurality of straight tube portions 15a, 15a, ... Penetrating the plurality of fins 30, 30, ... (Partially shown for convenience of explanation). It is composed of U bend portions 15b, 15b, ... That connect the ends of the straight pipe portions 15a, 15a to each other, and is easy to assemble.

Due to the structure of the heat transfer tube 15, the U bend portions 15b, 15b, ... Are located at the ends, and it is difficult for the blower 9 to hit the U bend portions 15b, 15b, ... The bend portions 15b, 15b, ... Are more likely to frost than the straight pipe portions 15a, 15a, ...

Further, among the U-bend portions 15b, 15b, ... In which heat exchange is unlikely to occur in the heat transfer tube 15 of the evaporator 8, the U-bend portion 15b'located on the upstream side of the ventilation passage 7 is the air in the ventilation passage 7 before cooling. Due to contact with, frost formation is the largest. The straight pipe portion 15a'connected to the upstream side of the U bend portion 15b'is provided with a first temperature sensor t1 on the upstream side and a second temperature sensor t2 on the downstream side.

The detection signals of the first temperature sensor t1 and the second temperature sensor t2 are input to a control unit (not shown), and the control unit compares the detected temperature with the threshold value and outputs an ON / OFF signal. 2 It has the function of the return thermostat T2 (see FIG. 8). Further, the control unit is connected to a first solenoid valve S1 and a second solenoid valve S2, which will be described later.

The surface temperatures on the upstream side and the downstream side of the straight tube portion 15a'of the heat transfer tube 15 are measured by the first temperature sensor t1 and the second temperature sensor t2, and will be described in detail later, but the measured straight tube portion 15a'. When both of the surface temperatures of the above are equal to or higher than the threshold value, both the first return thermostat T1 and the second return thermostat T2 are in the operating state (ON), and the control unit gives a closing operation signal to the second solenoid valve S2 to display the defrosting operation pattern β. The pressure rising process β1 is switched to the pressure holding process β2. In other words, if the surface temperature of the straight pipe portion 15a'measured is within the threshold value, the first return thermo T1 and the second return thermo T2 are in the standby state (OFF). A temperature sensor (not shown) is also provided in the vicinity of the shelves 6, 6, ... And in the vicinity of the cold air outlet 10, so that the temperature inside the refrigerator and the temperature of the air that has passed through the evaporator 8 can be measured. There is.

In this embodiment, the first temperature sensor t1 and the second temperature sensor t2 measure the surface temperature on the upstream side and the downstream side of the straight tube portion 15a'of the heat transfer tube 15, although the embodiment of the heat transfer tube 15 is illustrated. The surface temperature of other parts may be measured by one or more temperature sensors. Further, the surface temperature of the heat transfer tube 15, the temperature of the air passing through the evaporator 8 and the temperature inside the refrigerator were measured by each temperature sensor, but the temperature sensor measured the surface temperature of the heat transfer tube 15 and the evaporator 8. It suffices if it is provided at a position where at least one of the temperature of the passed air and the temperature inside the refrigerator can be measured.

As shown in FIG. 2, the evaporator 8 is a part of the piping system C of the refrigeration cycle. Specifically, an expansion valve 17 is provided at the upstream end of the heat transfer tube 15 of the evaporator 8 to reduce the pressure of the liquefied refrigerant 16 to a predetermined evaporation pressure to vaporize it, and to expand it. A supply pipe 19 provided with a second solenoid valve S2 is connected to the upstream side of the valve 17, and a liquid receiver 18 is connected to the upstream side of the second solenoid valve S2 via the supply pipe 19. The second solenoid valve S2 can appropriately open and close the flow path of the supply pipe 19 between the expansion valve 17 and the liquid receiver 18.

Further, a lead-out tube 23 provided with the first solenoid valve S1 is connected to the downstream end of the heat transfer tube 15 of the evaporator 8, and vaporized in the evaporator 8 on the downstream side of the first solenoid valve S1. A compressor 21 (pump) that sucks in the vaporized refrigerant 16 and compresses the refrigerant 16 and sends it out to the liquid receiver 18 side is connected, and the compressor 21 is connected to the liquid receiver 18 via the condenser 22. It is connected to the. The condenser 22 releases the heat of the high-pressure vaporized refrigerant 16 compressed by the compressor 21 to the outside to bring the refrigerant 16 into a liquefied state.

In FIG. 2, the liquid (liquefied) state refrigerant 16 is shown by a solid line, and the gas (vaporized) state refrigerant 16 is shown by a broken line. Further, the temperature of the liquefied refrigerant 16 in the receiver 18 is, for example, about 35 ° C to 40 ° C in the summer and about 20 ° C in the winter.

As shown in FIGS. 2 and 4 to 6, the first solenoid valve S1 cuts off the mode in which the heat transfer tube 15 and the outlet tube 23 communicate with each other (see FIG. 4) and the heat transfer tube 15 and the outlet tube 23. (See FIGS. 5 and 6). Further, the second solenoid valve S2 has a mode in which the supply pipe 19 and the heat transfer tube 15 communicate with each other (see FIGS. 4 and 5), a mode in which the supply pipe 19 and the heat transfer tube 15 are shut off (see FIG. 6). It is possible to switch to.

Here, the open / closed states of the first solenoid valve S1 and the second solenoid valve S2 in the cooling operation pattern α, the defrosting operation pattern β, and the cooling return pattern γ will be described with reference to FIG. First, in the cooling operation pattern α, the refrigerant 16 passes through the evaporator 8 depending on the open state of the first solenoid valve S1 and the open state of the second solenoid valve S2 (see FIG. 4), so that the evaporator 8 is surrounded. Can cool the air.

Next, the defrosting operation pattern β has a pressure increasing process β1 and a pressure holding process β2, and can defrost the frost adhering to the heat transfer tube 15. In the pressure increasing process β1, the surface temperature of the heat transfer tube 15 of the evaporator 8 is raised by the closed state of the first solenoid valve S1 and the open state of the second solenoid valve S2 (see FIG. 5). In the pressure holding process β2, the pressure in the evaporator 8 (heated transmission) increased in the pressure rising process β1 due to the closed state of the first solenoid valve S1 and the closed state of the second solenoid valve S2 (see FIG. 6). The surface temperature of the heat tube 15) is kept substantially constant.

Next, in the cooling return pattern γ, the cooling of the evaporator 8 after the defrosting operation pattern β is immediately started depending on the open state of the first solenoid valve S1 and the open state of the second solenoid valve S2 (see FIG. 4). be able to. The operation modes of the evaporator 8 in the cooling operation pattern α, the defrosting operation pattern β, and the cooling return pattern γ will be described in detail later.

Further, since the first solenoid valve S1 is a so-called normally open valve that is closed when energized and open when not energized, the first solenoid valve S1 is opened when the power is off such as a power failure. It becomes a state, and it is possible to prevent the refrigerant 16 from remaining in the evaporator 8. This makes it possible to prevent the liquid back phenomenon from occurring when the operation is restarted. In addition, in order to prevent the occurrence of the liquid back phenomenon, a check valve may be arranged between the first solenoid valve S1 and the compressor 21.

In the freezing / refrigerating showcase 1 configured in this way, as shown in FIGS. 7 to 8, the defrosting operation pattern β and the cooling return pattern γ are performed every set time (for example, 6 hours). Next, the operation mode of the piping system C of the refrigeration cycle in these cooling operation pattern α, defrosting operation pattern β, and cooling return pattern γ will be individually described.

First, the operation mode of the piping system C of the refrigeration cycle in which the evaporator 8 has a cooling operation pattern α will be described. As shown in FIGS. 2 and 4, the first solenoid valve S1 is in the open state, the heat transfer tube 15 and the outlet tube 23 are communicated with each other, and the second solenoid valve S2 is in the open state. The heat transfer tube 15 and the supply tube 19 are communicated with each other. By the operation of the compressor 21, the liquefied refrigerant 16 stored in the liquid receiver 18 is sent out to the evaporator 8 through the supply pipe 19 and the expansion valve 17. The refrigerant 16 in the liquefied state is decompressed by the expansion valve 17 so as to have a predetermined evaporation pressure, and is in the vaporized state. The vaporized refrigerant 16 that has flowed into the heat transfer tube 15 of the evaporator 8 takes heat from the air in the ventilation passage 7, so that the air in the ventilation passage 7 is cooled.

Further, in the cooling operation pattern α, in order to keep the temperature inside the refrigerator substantially constant, control of the control unit is performed while keeping the output (rotation speed) of the compressor 21 constant, in other words, without changing the output of the compressor 21. The cooling capacity of the evaporator 8 can be controlled by repeatedly supplying and stopping the refrigerant 16 into the evaporator 8 by opening and closing the second electromagnetic valve S2 (for example, PWM control).

The vaporized refrigerant 16 that has passed through the heat transfer tube 15 of the evaporator 8 flows into the outlet tube 23 that communicates with the heat transfer tube 15, and is returned to the liquid receiver 18 via the compressor 21 and the condenser 22. By repeating this circulation, the cooling operation pattern α of the evaporator 8 is continuously continued. The surface temperature of the heat transfer tube 15 in the cooling operation pattern α of the evaporator 8 is around −13 ° C. due to the vaporized refrigerant 16 flowing into the heat transfer tube 15 (see FIG. 7).

Next, the operation mode of the piping system C of the refrigeration cycle in which the evaporator 8 has the defrosting operation pattern β will be described. The point that the evaporator 8 overlaps with the description of the operation mode of the piping system C of the refrigeration cycle in the cooling operation pattern α will be omitted. As shown in FIGS. 7 and 8, in the defrosting operation pattern β, the temperature of the evaporator 8 is quickly reached to a temperature suitable for defrosting in the pressure rising process β1, and the temperature is brought to a temperature suitable for defrosting by the pressure holding process β2. Can be retained.

The pressure rising process β1 is started by the closing operation of the first solenoid valve S1 which is in the open state in the cooling operation pattern α (agreeing with the “start of the defrosting operation pattern β”), and is in the closed state as shown in FIG. The first solenoid valve S1 of the above means that the refrigerant 16 stays in the evaporator 8, and the subsequent refrigerant 16 sent out by the operation of the compressor 21 continues to flow into the evaporator 8, so that the first solenoid valve S1 is closed. Immediately after, the pressure of the refrigerant 16 in the evaporator 8 rises sharply, and the heat transfer tube 15 rapidly rises in temperature (see FIG. 7).

As shown in FIG. 8, the temperature measured individually by the first temperature sensor t1 and the second temperature sensor t2 both reached the threshold value or more (in this embodiment, + 3 ° C. or more (see FIG. 7)), that is, In response to the surface temperature of the heat transfer tube 15 reaching the threshold value or higher, the first return thermo T1 corresponding to the first temperature sensor t1 and the second return thermo T2 corresponding to the second temperature sensor t2 are individually operating (the second return thermo T2 corresponding to the second temperature sensor t2). ON), and the second electromagnetic valve S2 is closed. As a result, the pressure rising process β1 is switched to the pressure holding process β2, and the temperature rise of the heat transfer tube 15 is stopped.

As described above, since both the temperatures measured by the first temperature sensor t1 and the second temperature sensor t2 are set as the conditions for closing the second solenoid valve S2, frost is surely removed from the entire surface of the heat transfer tube 15. can. Further, since the first temperature sensor t1 and the second temperature sensor t2 are arranged on the straight tube portion 15a'on the upstream side where frost easily adheres, frost can be reliably removed from the surface of the entire heat transfer tube 15. In addition, since the first temperature sensor t1 and the second temperature sensor t2 are arranged at positions separated from each other to the left and right of the straight tube portion 15a', frost can be reliably removed from the surface of the entire heat transfer tube 15.

Next, in the pressure holding process β2, since the second solenoid valve S2 is closed for a predetermined time in a state where the surface temperature of the heat transfer tube 15 reaches the threshold value or more (a temperature suitable for defrosting), the refrigerant 16 is used. While staying on the upstream side of the second solenoid valve S2, the refrigerant 16 filled in the evaporator 8 is held by the first solenoid valve S1 and the second solenoid valve S2. In other words, in the pressure holding process β2, the pressure and temperature in the evaporator 8 are kept substantially constant for a predetermined time (5 minutes in this embodiment). It should be noted that the predetermined time referred to here is measured by a timer that is a part of a control unit (not shown), and it is sufficient that the time required for defrosting is surely set.

Further, as shown in FIGS. 7 and 8, in the pressure holding process β2, the first return thermo T1 and the second return thermo T2 are in the OFF state. This is because after both the first return thermo T1 and the second return thermo T2 are in the operating state (ON), they are set to be in the standby state until the cooling operation pattern α is reached.

As described above, in the state of the pressure rising process β1 and the pressure holding process β2, heat is transferred from the inside of the heat transfer tube 15 to the outer surface of the heat transfer tube 15 by the refrigerant 16 whose temperature has risen to 3 ° C. or higher. Reportedly. Therefore, in the heat transfer tube 15 bent by the heat of the refrigerant 16, even the U-bend portions 15b, 15b, ... Which are particularly easy to frost and difficult to defrost can be defrosted to every corner. Further, since the portion attached to the frost heat transfer tube 15 (in other words, the root of the frost) can be directly heated, the heat efficiency is high, and in addition, the frost adheres to the frost evaporator 8 without melting the entire frost. Frost can be desorbed from the evaporator 8 by melting the frosted portion. As a result, the time required for defrosting the evaporator is short.

Next, the operation mode of the piping system C of the refrigeration cycle in which the evaporator 8 has the cooling return pattern γ will be described. The point that the evaporator 8 overlaps with the description of the operation mode of the piping system C of the refrigeration cycle in the cooling operation pattern α or the defrosting operation pattern β will be omitted.

The cooling return pattern γ is started by the opening operation of the first solenoid valve S1 and the opening operation of the second solenoid valve S2 under the control of the control unit at the same time that the pressure holding process β2 is executed for a predetermined time and ends. As a result, the refrigerant 16 can pass through the evaporator 8, and the refrigerant 16 flows into the compressor 21 from the evaporator 8 in the high pressure state. Therefore, the pressure in the evaporator 8 is the cooling operation pattern. Since the pressure is rapidly restored to substantially the same as α and the cooling of the evaporator 8 is started immediately, the restoration to the cooling operation pattern α can be accelerated.

As an additional note, defrosting only by the off-cycle method that stops the flow of refrigerant (defrosting of the prior art (hereinafter referred to as "defrosting of the prior art")) and defrosting only by the heating method using a defrost heater (hereinafter referred to as "defrosting"). , "Heating method defrosting") will be briefly explained. In the defrosting of the prior art and the defrosting of the heating method, the second solenoid valve S2 in the present embodiment is first closed, but at this time, the evaporation pressure of the refrigerant 16 in the heat transfer tube 15 suddenly increases due to the suction of the compressor 21. Defrosting is performed from the state where the temperature of the refrigerant 16 drops momentarily (for example, −20 ° C.). Further, in the conventional technique of defrosting, the temperature inside the refrigerator rises to, for example, about 16 to 18 ° C. because it takes time, and in the defrosting of the heating method, the temperature inside the refrigerator is heated by the defrosting heater. There is a risk that the temperature will rise more than the conventional defrosting.

Next, the defrosting mode of the evaporator 8 and the changes in the temperature inside the refrigerator, the outlet temperature, and the surface temperature of the heat transfer tube 15 will be described with reference to FIGS. 7 to 8. First, in the pressure rising process β1, the surface temperature of the heat transfer tube 15, which has been changing at around −13 ° C. in the cooling operation pattern α, is rapidly raised to + 3 ° C. or higher. When the surface temperature of the heat transfer tube 15 rises above the melting point of frost (0 ° C.), the frost adhering to the surface of the heat transfer tube 15 begins to melt.

As shown in FIG. 8, immediately after the pressure rising process β1 is started, the surface temperature of the heat transfer tube 15 is immediately started to rise by the closing operation of the first solenoid valve S1, so that the temperature rise is short. Can be defrosted. In the conventional defrosting and heating method defrosting, the frost adhering to the outer surface of the heat transfer tube 15 is difficult to melt due to the temporary decrease in the surface temperature of the heat transfer tube 15. It was necessary to raise the temperature of the heat pipe 15, and it took a long time to shift to the defrosting operation.

As shown in FIGS. 7 to 8, as the surface temperature of the heat transfer tube 15 rises, the outlet temperature, which had been changing at around -3 ° C in the cooling operation pattern α, rises to + 5 ° C, and the cooling operation pattern α The temperature inside the refrigerator, which had been around + 3 ° C, rises to + 6 ° C. Regarding these, in addition to raising the temperature of the air circulating in the ventilation passage 7 due to the rise in the surface temperature of the heat transfer tube 15, the high temperature air outside the cold insulation chamber 5 in a state where the cooling capacity of the evaporator 8 is reduced. The air outlet temperature rises when the air flows into the ventilation passage 7, and the air circulating in the heated ventilation passage 7 and the high temperature air outside the cold insulation chamber 5 flow into the cold insulation chamber 5 to store the refrigerator. This is because the internal temperature rises.

Next, when it is detected by the first temperature sensor t1 and the second temperature sensor t2 that the surface temperature of the heat transfer tube 15 has risen to + 3 ° C., control of the control unit is performed as shown in FIGS. 7 and 8. By closing the second solenoid valve S2 (see FIG. 6), the pressure holding process is switched to β2. In the state where the pressure rising process β1 is switched to the pressure holding process β2, frost remains on the outer peripheral surface of the heat transfer tube 15.

The pressure holding process β2 is continued for 5 minutes as described above. As a result, the surface temperature of the heat transfer tube 15 is maintained at + 3 ° C. or higher for 5 minutes, so that not only the frost adhering to the surface of the heat transfer tube 15 is melted, but also the water generated by the melting of the frost is transferred to the heat transfer tube 15. Can be cut from the surface of. Further, when the frost adhering to the surface of the heat transfer tube 15 is a lump, the portion of the frost in contact with the surface of the heat transfer tube 15 melts one after another, so that even if the entire frost lump is not melted. , The frost mass can be peeled off from the surface of the heat transfer tube 15.

As a result, the time required for defrosting the evaporator 8 is short, and when the cooling by the evaporator 8 is restarted, the water is drained from the surface of the heat transfer tube 15, so that frost formation starts. It takes a long time. As a result, the defrosting operation pattern β can be completed in a short time, and the cooling operation pattern α can be lengthened, so that the cooling efficiency is good.

Further, after switching to the pressure holding process β2, the surface temperature of the heat transfer tube 15 is held at + 3 ° C. or higher for 5 minutes, but the outlet temperature and the inside of the refrigerator are affected by the high temperature air outside the cold insulation chamber 5. As for the temperature, the temperature rises. Specifically, the outlet temperature rises to about + 10 ° C, and the temperature inside the refrigerator rises to about + 8 ° C. However, as compared with the above-mentioned defrosting of the prior art, it is possible to suppress an increase in the temperature inside the refrigerator.

Further, since the air whose outlet temperature is raised to about + 10 ° C. circulates in the ventilation passage 7, the frost formed on the surface of the heat transfer tube 15 of the evaporator 8 is melted by the air circulating in the ventilation passage 7. be able to. As a result, the frost on the surface of the heat transfer tube 15 can be melted from the surface side and the surface side of the heat transfer tube 15, respectively, so that the time required for defrosting the evaporator 8 is further shortened. There is.

It should be noted that the outlet temperature rises to about + 10 ° C. and the internal temperature rises to about + 8 ° C., to be exact, after the end of the pressure holding process β2. This is because when the pressure holding process β2 shifts to the cooling return pattern γ, the evaporator 8 starts cooling immediately, but the cooling of the evaporator 8 cools the air circulating in the ventilation passage 7 to cool the air outlet. After the temperature starts to drop, the circulating air flows into the cold insulation chamber 5 and the temperature inside the refrigerator starts to drop, so that there is a time lag between the outlet temperature and the temperature inside the refrigerator. be.

Next, when the measurement time of the timer of the control unit elapses 5 minutes after switching to the pressure holding process β2, the first solenoid valve S1 is opened and the second solenoid valve S2 is opened under the control of the control unit ( (See FIG. 4), switching to the cooling return pattern γ. As shown in FIGS. 7 and 8, the surface temperature of the heat transfer tube 15 drops immediately after switching to the cooling return pattern γ, and the surface temperature of the heat transfer tube 15 is the lowest temperature in the temperature range in the cooling operation pattern α. It can be lowered to -15 ° C. As the surface temperature of the heat transfer tube 15 decreases, the outlet temperature decreases to -5 ° C, which is the lowest temperature in the cooling operation pattern α, and the temperature inside the refrigerator is the lowest in the cooling operation pattern α. The temperature drops to + 3 ° C. Upon reaching these temperatures, the cooling return pattern γ of the evaporator 8 is switched to the cooling operation pattern α under the control of the control unit.

Although not shown, when switching from the defrosting operation pattern β to the cooling return pattern γ, the heat transfer tube 15 is sucked by the compressor 21 due to the open state of the first solenoid valve S1 and the closed state of the second solenoid valve S2. By rapidly lowering the pressure of the refrigerant 16 and instantaneously cooling the temperature of the refrigerant 16, the evaporator 8 is cooled to -15 ° C, which is the lowest temperature in the cooling operation pattern α, in a shorter time. Can be done.

In the defrosting operation pattern β, a heater or the like may be additionally used from the outside to shorten the time until the defrosting is completed.

Regarding the switching from the cooling operation pattern α of the evaporator 8 to the defrosting operation pattern β, the control unit controls each of the first temperature sensor t1 and the second temperature sensor t2 instead of each set time described above. The amount of frost on the evaporator 8 may be determined based on the change in temperature, and the amount of frost may be automatically switched by determining that the amount of frost is equal to or higher than a certain level.

Next, the freezing / refrigerating showcase 1 according to the second embodiment will be described in detail with reference to FIG. It should be noted that the same configuration as that of the first embodiment and the overlapping configuration will be omitted.

As shown in FIG. 9, in the defrosting operation pattern β in Example 2, only the pressure increasing process β1 is carried out. By switching from the pressure rise process β1 to the cooling return pattern γ, the temperature at the outlet can be suppressed to about + 5 ° C and the temperature inside the refrigerator can be suppressed to about + 6 ° C. It is possible to quickly return to the pattern α. In addition, since a part of the pressure rise process β1 and the cooling return pattern γ exceeds the internal temperature (around 3 ° C.) in the cooling operation pattern α, the embodiment including the pressure holding process β2 in the first embodiment is included. Compared with, the time can be shortened. On the other hand, since it is necessary to defrost the evaporator 8 only by the pressure increasing process β1, it is preferable that the amount of frost deposited on the evaporator 8 is small.

That is, by carrying out only the pressure rising process β1 in a short cycle (for example, every hour) in the defrosting operation pattern β, the evaporator 8 in the initial stage of frost formation (state in which the frost density is dense) is defrosted. Since this can be done, the cooling capacity of the evaporator 8 can be maintained while reducing the influence on the temperature inside the refrigerator.

In addition, the defrosting operation pattern β in Examples 1 and 2 may be used in combination, and at that time, the evaporator is based on the change in the temperature of each of the first temperature sensor t1 and the second temperature sensor t2 by the control unit. The amount of frost that frosts on No. 8 may be determined, and the cooling return pattern γ may be carried out after the pressure increase process β1 according to the amount of frost.

Next, the freezing / refrigerating showcase 1 according to the third embodiment will be described in detail with reference to FIG. It should be noted that the same configuration as that of the first and second embodiments and the overlapping configuration will be omitted.

As shown in FIG. 10, the evaporators 8F and 8R in the third embodiment are a part of the piping system C of the refrigerating cycle and are arranged in parallel with the circuit in the piping system C of the refrigerating cycle. .. Specifically, expansion valves 17 and 17'are provided at the upstream end of the heat transfer tubes 15 and 15'of the evaporators 8F and 8R, and supply pipes are provided on the upstream side of the expansion valves 17 and 17'. The first branch supply pipe 119 and the second branch supply pipe 119'which are divided into two parts from 19 and are provided with the second solenoid valves S12 and S12'are connected. Further, at the downstream end of the heat transfer tubes 15 and 15'of the evaporators 8F and 8R, the first branch lead-out pipe 123 and the first branch lead-out pipe 123 and the first for which the first solenoid valves S11 and S11'are provided while being divided into two from the lead-out pipe 23. Two branch pipes 123'are connected.

Regarding the cooling operation pattern α, the defrosting operation pattern β, and the cooling return pattern γ on the evaporator 8F side and the evaporator 8R side of the piping system C of the refrigeration cycle, the cooling operation pattern α in the evaporator 8 of the first embodiment is described. , The defrosting operation pattern β and the cooling return pattern γ are substantially the same, and thus the description thereof will be omitted. Furthermore, the cooling performances of the evaporator 8F and the evaporator 8R are both substantially the same.

Next, the operation mode of the evaporators 8F and 8R will be described. First, the evaporators 8F and 8R are adapted to alternately operate the cooling operation pattern α and the defrosting operation pattern β or the cooling return operation pattern γ.

By alternating operation of the evaporators 8F and 8R, the influence on the internal temperature due to the increase in the surface temperature of the heat transfer tube 15 or the heat transfer tube 15'in the defrosting operation pattern β can be suppressed as much as possible, and the internal temperature can be maintained. In addition, when one evaporator has the defrosting operation pattern β, the inflow of the refrigerant 16 into the other evaporator is increased, so that the cooling capacity of the other evaporator is improved and the heat is removed. The influence of the increase in the surface temperature of the heat transfer tube 15 or the heat transfer tube 15'in the frost operation pattern on the internal temperature can be minimized. By alternately operating the evaporators 8F and 8R in a short cycle (for example, every 30 minutes), the heat transfer tubes 15 and 15'are defrosted in the initial stage of frost formation (the state where the frost density is dense). Therefore, the defrosting efficiency can be made extremely high.

Although Examples 1 and 2 of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these Examples 1 and 2, and there are changes and additions within the range not deviating from the gist of the present invention. Even included in the present invention.

For example, in Examples 1 to 3, the embodiment in which one evaporator 8 or two evaporators 8F, 8R arranged in parallel are used has been described, but three or more evaporators may be used, and a plurality of evaporators may be used. The evaporators may be arranged in series. Further, the evaporators 8F and 8R have been described as having substantially the same cooling performance, but the present invention is not limited to this, and when there are a plurality of evaporators, the cooling performance may be different from each other.

Further, in the evaporators 8F and 8R of the third embodiment, the first solenoid valves S11 and S11'are arranged on the downstream side thereof, and the second solenoid valves S12 and S12'are arranged on the upstream side of each. However, not limited to this, one first solenoid valve is provided on the downstream side of the flow path connecting the evaporators 8F and 8R in parallel, and on the upstream side of the flow path connecting the evaporators 8F and 8R in parallel. It may be an embodiment in which one second solenoid valve is provided.

The first solenoid valve S1 has been described as a mode in which the pressure in the evaporator 8 is increased by the closing operation of the first solenoid valve S1 in the pressure rising process β1, but the temperature is not limited to this and is suitable for defrosting. When the temperature exceeds the limit, the surface temperature of the heat transfer tube 15 may be adjusted by reducing the pressure in the evaporator 8 by opening the first solenoid valve S1.

The pressure increasing process β1 may be performed in an embodiment of 1 to 60 minutes, and the predetermined time of the pressure holding process β2 may be set between 0 and 10 minutes. Further, in the pressure increasing process β1 and the pressure holding process β2, the surface temperature of the heat transfer tube 15 may be set to be between 0 and + 10 ° C.

1 Refrigerator showcase 5 Refrigerator room (inside the refrigerator)
8,8F, 8R Evaporator 15,15'Heat transfer tube 16 Refrigerant S1, S11, S11'First solenoid valve S2, S12, S12'Second solenoid valve t1 First temperature sensor t2 Second temperature sensor α Cooling operation pattern β Defrosting operation pattern β1 Pressure rise process β2 Pressure holding process γ Cooling recovery pattern

Claims (4)

A freezing / refrigerating showcase that cools the inside of a refrigerator using a refrigerating cycle equipped with an evaporator that cools the surrounding air by evaporating the refrigerant inside the heat transfer tube.
A first solenoid valve located on the downstream side of the evaporator and a second solenoid valve located on the upstream side of the evaporator are provided.
The evaporator has a cooling operation pattern in which the refrigerant passes through the evaporator depending on the open state of the first electromagnetic valve and the open state of the second electromagnetic valve, and the closed state of the first electromagnetic valve and the second electromagnetic valve. The pressure increase process in which the refrigerant stays in the evaporator to increase the pressure in the evaporator due to the open state of the electromagnetic valve , and the pressure in the evaporator increased in the pressure increase process are referred to as the second electromagnetic wave. refrigerated showcases, characterized in that it comprises a pressure holding step of holding a substantially constant by the closed state of the valve, and defrosting operation pattern Ru Tona, the. After the defrosting operation pattern, the refrigerant has a cooling return pattern in which the refrigerant passes through the evaporator depending on the open state of the first solenoid valve and the open state of the second solenoid valve. The frozen / refrigerated showcase according to claim 1. The freezing / refrigerating show according to claim 2 , wherein the evaporator is switched to the cooling return pattern after a predetermined time has elapsed from the heat transfer tube reaching a predetermined temperature in the defrosting operation pattern. Case. The freezing / refrigerating showcase according to any one of claims 1 to 3 , wherein the first solenoid valve is in a closed state when energized and in an open state when not energized.

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