JP2011133712A - Electronic signboard and cooling control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic signboard capable of preventing the occurrence of dew condensation in a casing by controlling a temperature distribution in the casing in which a liquid crystal display is sealed; and to provide a cooling control method for the same. <P>SOLUTION: The electronic signboard 1 includes: a glass plate 12 which is provided to a position facing the display surface 11 of a liquid crystal display 10 in a casing 8 housing the liquid crystal display 10; a gap between the display surface 11 and the glass plate 12; an evaporator 42 disposed in the casing 8; a circulation fan 50 for guiding air cooled by the evaporator 42 to the gap and then returning the air to the evaporator 42; a freezing cycle 40 having a compressor 44, a condenser 46, and an expansion valve 48 disposed below the liquid crystal display 10. The electronic signboard 1 also includes a temperature sensor 36F for detecting the cooling temperature of the liquid crystal display 10, and a controller 35 for controlling rotation of the circulation fan 50 and a heat discharge fan 51 according to the detected temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronic signboard that displays an advertisement on a flat panel display such as a liquid crystal display, and more particularly to a technique for preventing deterioration in visibility due to condensation accompanying cooling of the flat panel display.

  An electronic signboard (also referred to as “digital signage”) that includes a liquid crystal display and displays advertisement information such as images and characters on the liquid crystal display is known. In addition, in order to make it possible to use an electronic signboard outdoors on a street or the like, a liquid crystal display sealed in a casing and protected from wind and rain and dust is known. When the liquid crystal display is sealed in the casing in this way, heat does not escape from the inside of the casing to the outside, and the liquid crystal display cannot be naturally cooled. Therefore, conventionally, an air cooling means for air-cooling the liquid crystal display is built in the casing, and the liquid crystal display is forcibly air-cooled (see, for example, Patent Document 1).

JP 2006-308726 A

By the way, in the above-mentioned conventional electronic signboard, dew condensation may occur in the case depending on the temperature distribution state in the case. In particular, if dew condensation occurs at a position overlapping the display surface of the liquid crystal display, the visibility of the display is improved. There was a problem of lowering.
The present invention has been made in view of the above-described circumstances, and an electronic signboard that can prevent the occurrence of condensation in the casing by controlling the temperature distribution in the casing in which the liquid crystal display is sealed, and cooling in the electronic signboard An object is to provide a control method.

  In order to achieve the above object, the present invention provides a flat display housed in a housing, a transparent plate is provided in the housing at a position facing the display surface of the flat display, and the display surface and the transparent A gap is provided between the plates, an evaporator is provided inside the casing, an air cooled by the evaporator is guided to the gap, and then a circulation fan is returned to the evaporator, connected to the evaporator, In an electronic signboard provided with a refrigeration cycle having a compressor, a condenser, and an expansion means provided below the flat display, a cooling temperature of the flat display provided in the housing is detected. A temperature sensor; and a controller that controls rotation of the heat dissipation fan of the condenser along with rotation of the circulation fan during operation of the compressor according to a temperature detected by the temperature sensor. And wherein the door.

  Further, the present invention is the above electronic signboard, wherein the flat display is disposed in a sealed space of the casing, and the sealed space is formed by the casing and the transparent plate, The evaporator and the circulation fan are provided.

  Further, the present invention is the above electronic signboard, wherein the control unit is configured so that the temperature difference between the temperature of the suction refrigerant of the compressor and the evaporation temperature of the evaporator exceeds a preset value. And the heat dissipating fan are controlled.

  Further, the present invention provides the electronic sign as described above, wherein the control unit has a temperature difference between a temperature of the suction refrigerant of the compressor and an evaporation temperature of the evaporator exceeding a preset value, and the compressor The number of rotations of the circulation fan and the heat dissipating fan is controlled so that the case temperature or the discharge temperature of the compressor does not exceed a predetermined temperature.

  In the present invention, a second temperature sensor is provided at a predetermined position where condensation may occur in the sealed space, and the controller is configured to radiate heat from the circulation fan and the condenser during operation of the compressor. The rotation with the fan is controlled, and the compressor and the heat dissipating fan are stopped when the temperature detected by the second temperature sensor is higher than a preset temperature. It is characterized by.

  In order to achieve the above object, the present invention includes a flat display in a housing, a transparent plate is provided in the housing at a position facing the display surface of the flat display, and the display surface. A gap is provided between the transparent plates, an evaporator is provided inside the housing, a circulation fan is provided to return air cooled by the evaporator to the gap and then returned to the evaporator, and is connected to the evaporator. And a cooling control method for an electronic signboard provided with a refrigeration cycle having a compressor, a condenser, and expansion means provided below the flat display, and a control unit for controlling the refrigeration cycle. The controller detects a cooling temperature of the flat display provided in the housing by a temperature sensor, and rotates the circulation fan during the operation of the compressor according to the detected temperature. Wherein controlling the rotation of the radiating fan of the condenser it is also characterized by comprising a.

  According to the present invention, in the configuration in which the flat display housed in the housing is cooled by the refrigeration cycle, the circulation fan and the condenser are operated by the control unit during the operation of the compressor according to the cooling temperature of the flat display. By controlling the rotation of the heat dissipating fan, it is possible to prevent condensation in the housing containing the flat display.

It is a perspective view which shows the external appearance structure of the electronic signboard which concerns on embodiment of this invention. It is a figure which abbreviate | omits and shows the longitudinal cross-section of an electronic signboard. It is a cross-sectional view of a signboard body. It is a schematic diagram which shows a circulation channel and a liquid crystal display. It is a figure which shows the structure of the refrigerating cycle provided in the electronic signboard in detail. It is a flowchart which shows control of a refrigerating cycle. It is a flowchart which shows the control of a refrigerating cycle in detail.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an electronic signboard 1 includes a signboard body 2 that has a flat rectangular parallelepiped appearance, a base 4 that supports the signboard body 2, and a cooling unit 6 that cools the inside of the signboard body 2. I have.

  The signboard body 2 has a vertically long flat rectangular parallelepiped housing 8 having a height of about 2 meters and a width of about 1 meter, and a liquid crystal display 10 is housed in the interior thereof with the display surface 11 facing the front. . The front surface of the housing 8 facing the display surface 11 has a large opening, and a transparent hard glass plate 12 (transparent plate) is fitted into the opening so that the inside can be visually recognized. 11 is configured to be visible. Various images and character information are displayed on the display surface 11 and used as a variable display type advertising medium. In addition, the signboard body 2 has a sealed structure such that a packing is disposed between the glass plate 12 and the housing 8, and has a structure that can withstand outdoor use such as on a street.

  The base 4 includes a frame frame 14 assembled in a rectangular frame shape and a pair of left and right support legs 16 that support the frame frame 14, and the signboard body 2 is fitted and fixed in the frame of the frame frame 14. The cooling unit 6 includes a unit case 18 in which a later-described refrigeration cycle 40 (FIG. 2) is incorporated, and is disposed on the lower end side of the signboard body 2. The inside of the signboard body 2, in particular, the liquid crystal display 10 is cooled by the cold air generated by the refrigeration cycle 40 of the cooling unit 6.

FIG. 2 is a view in which a vertical section of the electronic signboard 1 is partially omitted, and FIG. 3 is a cross-sectional view of the signboard body 2. FIG. 4 is a schematic diagram showing the circulation flow path 30 and the liquid crystal display 10.
As shown in FIGS. 2 and 3, a board mounting plate 20 is provided inside the housing 8 included in the signboard body 2, and is partitioned into a front side space 21 </ b> A and a back side space 21 </ b> B by the board mounting plate 20. The liquid crystal display 10 is arranged in the front space 21A. The circuit board mounting plate 20 is provided with various circuits on the surface facing the back space 21B. These circuits include, for example, a display control circuit that controls the display of the liquid crystal display 10, a storage circuit that acquires and holds advertisement information including images and still images displayed on the liquid crystal display 10 from the outside, and a cooling unit 6 includes a controller 35 (FIG. 5) or the like as a control unit for driving and controlling the motor 6.

  The liquid crystal display 10 is a flat display and includes a display panel 22. The display panel 22 can have various shapes depending on the application. In the liquid crystal display 10 of this embodiment, the display panel 22 is a vertically long rectangle. The liquid crystal display 10 is fixed in a sealed space 28 formed in the front space 21 </ b> A of the housing 8 by providing a circulation channel 30 through which air circulates.

  As shown in FIG. 2, the circulation flow path 30 includes gaps 30 </ b> A to 30 </ b> D between the sealed space 28 and the liquid crystal display 10. That is, in the sealed space 28 of the front side space 21A, a gap 30A is formed between the display surface 11 of the display panel 22 and the glass plate 12, and a gap 30B is formed between the upper end portion 22A of the display panel 22, A gap 30 </ b> C is formed between the back surface of the liquid crystal display 10, and a gap 30 </ b> D is formed with the lower end portion 22 </ b> B of the display panel 22. These gaps 30 </ b> A to 30 </ b> D are connected in an annular shape around the display panel 22 in this order, and surround the display panel 22. The glass plate 12 can be adjusted by a spacer 60 provided in the housing 8 so that the upper end of the glass plate 12 protrudes toward the front side.

  By forming such a circulation channel 30, the heat generated in the display surface 11 side portion of the display panel 22 passes through the circulation channel 30 and efficiently moves to the back side of the display panel 22. That is, as shown in FIG. 4, when two circulation fans 50 provided on the back surface side of the display panel 22 operate in the sealed space 28 of the housing 8, air circulates as indicated by arrows in the figure. Then, heat is transported from the display surface 11 side to the back surface side. A refrigeration cycle 40 that recovers heat generated on the display surface 11 side is provided on the rear surface of the liquid crystal display 10.

As shown in FIG. 2, the outline of the refrigeration cycle 40 includes an evaporator 42, a compressor 44, a condenser 46, and an expansion valve 48 disposed below the evaporator 42. Heat is recovered and the recovered heat is released by the condenser 46. That is, the evaporator 42 is installed in the gap 30 </ b> C on the back surface side at a position near the lower end portion 22 </ b> B of the display panel 22, and recovers heat from the air flowing through the circulation channel 30.
Further, as shown in FIGS. 2 and 4, the compressor 44, the condenser 46, and the expansion valve 48 are disposed at the lower part of the casing 8 and outside the sealed space 28, respectively. For example, a heat dissipating fan 51 that is disposed facing the vent hole provided in the body 8 and that dissipates heat by ventilating the condenser 46 is disposed adjacent to the condenser 46, and is blown by the heat dissipating fan 51, The heat recovered by the evaporator 42 is released to the outside through the vent hole.

  According to this configuration, since the heavy refrigeration cycle 40 is disposed below the electronic signboard 1, the electronic signboard 1 has a low center of gravity, and the stability of the electronic signboard 1 is improved in outdoor use where the installation environment is unstable. To do. Further, since the evaporator 42 is disposed below the sealed space 28, the cooling efficiency in the sealed space 28 is good, and the heat generated in the display panel 22 is efficiently handled by the evaporator 42 in the process of circulating the air in the circulation channel 30. The recovered liquid is efficiently discharged from the condenser 46 through the vent hole provided in the housing 8, and the liquid crystal display 10 is thereby cooled. Also, the piping efficiency of the evaporator 42, the compressor 44, the condenser 46, and the expansion valve 48 is good.

  As shown in FIG. 2, the circulation channel 30 is provided with a circulation fan (blower fan) 50 that circulates air in the circulation channel 30 to generate cooling air. As shown in FIG. 2, the circulation fan 50 includes a gap 30 </ b> C on the back side of the liquid crystal display 10 and a position near the upper end 22 </ b> A of the display panel 22 and a position near the lower end 22 </ b> B. It is arranged in each. The evaporator 42 is disposed downstream of the circulation fan 50 on the lower end 22B side. Although not shown, a plurality of circulation fans 50 are arranged in parallel in the cross section of the flow path (in the same horizontal plane) at each location. These circulation fans 50 are driven and controlled by a controller 35 (FIG. 5) provided on the board mounting plate 20.

  Each circulation fan 50 provided on the back side circulates the cooling air along the circulation flow path 30 in the direction of the solid arrow A (FIGS. 2, 4, and 5). That is, when the circulation fan 50 is driven, the cooling air flows in the gap 30A on the display surface 11 side from the lower end inlet 30A-2 to the upper end outlet 30A-1 in the vertical direction. Then, the air flows from the outlet 30A-1 of the gap 30A through the gap 30B on the upper end 22A side of the display panel 22 to the gap 30C on the back surface side. As shown in FIG. 4, the cooling air flowing into the gap 30C flows from top to bottom in the vertical direction, passes through the evaporator 42, passes through the gap 30D on the lower end portion 22B side of the display panel 22, and is displayed on the display surface. Return to the 11th clearance 30A.

In the electronic signboard 1 of this embodiment, in order to prevent the display surface 11 of the liquid crystal display 10 from being bent due to the static pressure of the gap 30A and causing display unevenness, the lower end 22B side and the upper end 22A side of the gap 30A are respectively provided. The air volume and type of the arranged circulation fan 50 are adjusted.
As shown in FIG. 4, the cooling air is circulated in the circulation flow path 30 by the circulation fans 50 provided at two locations of the upper end portion 22A and the lower end portion 22B of the gap 30C on the back side. The pressure increases discontinuously at each of the position Y1 of the circulation fan 50 at the upper end 22A and the position Y2 of the circulation fan 50 at the lower end 22B, and gradually decreases along the flow of the cooling air. The degree of reduction in static pressure (static pressure reduction amount / flow path length) is determined by the flow rate structure such as the width of each gap 30A to 30D and the air volume of each circulation fan 50 at the upper end 22A and the lower end 22B. It depends on the pressure loss due to the difference. In the circulation channel 30 of the present embodiment, the gap on the back surface side is smaller than the gap 30A on the display surface 11 side and the gaps 30B and 30D that connect the gap 30A and the gap 30C on the back surface side. The degree of static pressure reduction is moderate in the gap 30C. Considering such a difference in the degree of decrease in static pressure, the static pressure at the center X1 of the display surface 11 (the position of L / 2 when the height of the display surface 11 is L) and the back side The air volume (static pressure at the air outlet) of each circulation fan 50 at the upper end portion 22A and the lower end portion 22B is set so that the static pressure at the position of the central portion X2 is substantially equal.
Then, the pressure loss during the period from the center portion X2 on the back side to the center portion X1 of the display surface 11 through the circulation fan 50 (position Y2) of the lower end portion 22B (indicated by an arrow Z1 in FIG. 4) The circulation fan 50 of the portion 22B covers the interval from the center portion X1 of the display surface 11 through the circulation fan 50 (position Y1) of the upper end portion 22A to the center portion X2 on the back side (in FIG. 4, an arrow Z2). The circulation fan 50 of the upper end portion 22A covers the pressure loss of (shown), so that the static pressure difference between the central portion X1 of the display surface 11 and the central portion X2 on the back side can be eliminated.

  In the refrigeration cycle 40, even when the heat generation Wa (unit W) of the liquid crystal display 10 and the heat generation Wb (unit W) due to solar radiation are generated, the temperature of the display panel 22 of the liquid crystal display 10 is set to a target temperature (unit ° C) or less. Designed for cooling capacity that can be maintained. This target temperature is set to a temperature (for example, 60 ° C.) that is lower by a predetermined temperature than a temperature (for example, 65 ° C.) at which a phenomenon that an image cannot be displayed on the display panel 22 (so-called blackout) can occur. The electronic signboard 1 also has a function of reducing the brightness of the display panel 22 when the solar radiation is strong and the cooling capacity is insufficient (when the temperature of the display panel 22 does not fall below the target temperature).

  According to these configurations, since the vertically long liquid crystal display 10 is stood in the casing 8 and the cooling air is flowed from the lower end portion 22B of the display surface 11 toward the upper end portion 22A, Hot air that tends to accumulate in the upper end portion 22A due to the influence of solar radiation or the like can be efficiently discharged from the display surface 11 side, and blackout at the upper end portion 22A of the display surface 11 can be prevented. Further, since the circulation fan 50 is arranged on the back side, the width of the gap 30A can be narrowed to increase the flow velocity of the cooling air passing through the gap 30A, so that the display surface 11 can be efficiently cooled. In addition, since the evaporator 42 is disposed downstream of the circulation fan 50, the evaporator 42 can efficiently recover the heat generated by the various electrical components on the display surface 11 and the back side.

While the temperature of the display panel 22 of the liquid crystal display 10 is sufficiently lower than the target temperature, the refrigeration cycle 40 is a so-called thermo-off in which the compressor 44 is stopped, but after the thermo-off, the glass plate 12 in the sealed space 28 is turned off. Condensation may occur on the inside.
The inventor has obtained the following knowledge as a cause of the occurrence of this condensation. That is, while the refrigeration cycle 40 is in operation (thermo-on), the evaporator 42 has the lowest temperature in the sealed space 28 and a part of the water in the sealed space 28 is condensed in the evaporator 42. When the thermostat is turned off, a high-temperature refrigerant flows into the evaporator 42, and the temperature of the evaporator 42 rises to evaporate the moisture condensed in the vicinity of the evaporator 42. This moisture is then evaporated in the sealed space 28. Condensation occurs at a temperature lower than 42. As a place where condensation easily occurs, in the present embodiment, the vicinity of the inlet 30A-2, which is a circulating air passage for cold air, has the lowest temperature, and is, for example, the inner lower portion of the glass plate 12.
Therefore, in the electronic signboard 1 of the present embodiment, when switching between thermo-on / thermo-off, the refrigeration cycle 40 is controlled so as to prevent condensation on the inside of the glass plate 12 or the like.

FIG. 5 is a diagram showing the configuration of the refrigeration cycle 40 in detail. A broken line in FIG. 5 indicates a control line.
As shown in FIG. 5, the refrigeration cycle 40 includes a refrigerant pipe provided with an accumulator 47 provided in the suction pipe of the compressor 44 in the evaporator 42, the compressor 44, the condenser 46 and the expansion valve 48 described above. The compressor 44 is driven by the motor 43, and the refrigerant discharged from the compressor 44 flows into the condenser 46 and is condensed. The liquid refrigerant condensed in the condenser 46 is decompressed by the expansion valve 48 and flows into the evaporator 42, evaporates in the evaporator 42, returns to the suction pipe of the compressor 44 through the accumulator 47.
In this embodiment, the compressor 44 is a constant speed compressor driven by a motor 43 having a constant rotation speed, the circulation fan 50 is configured as a constant speed fan having a constant rotation speed, and the heat dissipation fan 51 is A case where the fan is configured as a variable rotation speed fan will be described as an example.

The refrigeration cycle 40 includes a controller 35 for controlling operation, and operates / stops the motor 43, the valve opening degree of the expansion valve 48, the operation / stop of the circulation fan 50 that circulates the air in the circulation flow path 30, and The controller 35 controls the number of revolutions and the operation / stop and the number of revolutions of the heat dissipating fan 51 that blows and radiates heat to the condenser 46.
The controller 35 includes a temperature sensor 36A for measuring (detecting) the case temperature of the compressor 44, a temperature sensor 36B for measuring the discharge refrigerant temperature of the compressor 44, and a temperature sensor for measuring the temperature of the suction refrigerant of the compressor 44. 36C, a temperature sensor 36D that is provided in the evaporator 42 and measures the refrigerant temperature in the evaporator 42, 36E that measures the temperature of the lower part of the glass plate 12 in the sealed space 28, and the upper part on the back side of the display panel 22 For example, a temperature sensor 36 </ b> F disposed on the substrate mounting plate 20 and measuring the temperature of the back surface of the liquid crystal display 10 is connected to each other. The controller 35 controls the operation of the motor 43, the expansion valve 48, the circulation fan 50, and the heat dissipation fan 51 based on the temperatures measured by the temperature sensors 36A to 36F. The temperature measurement using the temperature sensors 36A to 36F is performed by the controller 35 acquiring the detection values of the temperature sensors 36A to 36F and calculating the detection values.

FIG. 6 is a flowchart showing the operation of the refrigeration cycle 40 controlled by the controller 35.
The operation shown in FIG. 6 is executed after the controller 35 starts the operation of the refrigeration cycle 40 (thermo-on).
After starting the operation of the refrigeration cycle 40, the controller 35 measures the temperature of the back surface of the liquid crystal display 10 by the temperature sensor 36F (step S1), and the measured temperature of the liquid crystal display 10 is a preset specified temperature T1. It is determined whether or not it is higher (step S2). The specified temperature T1 corresponds to the above-described target temperature T for cooling the liquid crystal display 10, and the set value of the specified temperature T1 is stored in a memory (not shown) built in the controller 35. When the temperature of the liquid crystal display 10 is higher than the specified temperature T1 (step S2; Yes), the controller 35 proceeds to step S14 in order to continue the cooling operation by the refrigeration cycle 40.

  On the other hand, when the temperature of the liquid crystal display 10 is equal to or lower than the specified temperature T1 (step S2; No), the controller 35 stops the two circulation fans 50 and 50 provided on the back side of the liquid crystal display 10 ( Step S3), the number of rotations of the heat dissipation fan 51 is adjusted (Step S4). The controller 35 performs operation control for preventing the occurrence of condensation after step S3, and keeps the evaporator 42 at a low temperature so that there is no place in the sealed space 28 lower than the evaporator 42. During this control, the compressor 44 is driven by the motor 43 to keep the evaporator 42 at a low temperature. However, since the circulation fan 50 is stopped, the refrigerant is not completely evaporated by the evaporator 42, and the liquid back There is a concern to cause. In order to prevent liquid back, it is effective to reduce the cooling capacity by reducing the number of rotations of the heat dissipating fan 51 to suppress heat dissipating in the condenser 46. On the other hand, if the rotational speed of the heat radiating fan 51 is too low, the discharge temperature of the compressor 44 and the case temperature of the compressor 44 become high, and there is a concern about the reliability of the compressor 44. Therefore, in step S4, the controller 35 ensures the rotational speed of the heat dissipation fan 51 so that the discharge temperature and / or case temperature of the compressor 44 does not exceed the specified value, and the refrigerant superheat degree is the specified value. Adjust to such a speed.

FIG. 7 is a flowchart showing in detail the process shown in step S4 of FIG.
First, the controller 35 sets the rotational speed of the heat dissipation fan 51 to a predetermined rotational speed (step S21). This rotational speed is preset as a reference value for the dew condensation prevention operation, and is stored in a memory (not shown) built in the controller 35.
Immediately thereafter or after a predetermined time has elapsed, the controller 35 uses the temperature sensors 36 </ b> A to 36 </ b> D to cause the case temperature of the compressor 44 or the temperature of the refrigerant discharged from the compressor 44, the temperature of the suction refrigerant of the compressor 44, The evaporation temperature is measured (step S22). Here, either one or both of the case temperature of the compressor 44 and the temperature of the refrigerant discharged from the compressor 44 may be measured.

  The controller 35 compares the measured case temperature of the compressor 44 or the temperature of the refrigerant discharged from the compressor 44 with the specified temperature T2 (step S23). The specified temperature T2 is a temperature value set in advance as a reference for preventing overheating of the compressor 44, and is stored in a memory (not shown) of the controller 35. The specified temperature T2 may be a different value when the controller 35 measures the case temperature of the compressor 44 and when the temperature of the refrigerant discharged from the compressor 44 is measured. When the case temperature of the compressor 44 or the temperature of the refrigerant discharged from the compressor 44 is equal to or higher than the specified temperature T2 (step S23; No), the controller 35 rotates the rotational speed of the heat dissipation fan 51 in order to protect the compressor 44. Is increased by a predetermined width (step S24), and the process returns to step S22.

When the case temperature of the compressor 44 or the temperature of the refrigerant discharged from the compressor 44 is equal to or lower than the specified temperature T2 (step S23; Yes), the controller 35 determines the temperature of the suction refrigerant of the compressor 44 and the evaporation temperature of the evaporator 42. Is determined, and it is determined whether or not the calculated temperature difference is greater than a specified value T3 (step S25). The specified value T3 is a value that serves as a reference for the temperature difference between the temperature of the refrigerant sucked by the compressor 44 and the evaporation temperature in the evaporator 42 when the degree of superheat of the refrigerant is suppressed. It is stored in a memory (not shown). When the temperature difference between the temperature of the refrigerant sucked by the compressor 44 and the evaporation temperature in the evaporator 42 is smaller than the specified value T3 (step S25; No), since the degree of superheat of the refrigerant has not been taken, the controller 35 has a heat radiating fan. The number of rotations 51 is reduced by a predetermined width (step S26), and the process returns to step S21. Then, it is determined whether or not the case temperature of the compressor 44 or the temperature of the refrigerant discharged from the compressor 44 is lower than the specified temperature T2.
In addition, when the temperature difference between the temperature of the refrigerant sucked by the compressor 44 and the evaporation temperature in the evaporator 42 is larger than the specified value T3 (step S25; Yes), the degree of superheat of the refrigerant is sufficiently high, and thus for heat dissipation. Since the rotation speed of the fan 51 is a suitable value, the controller 35 proceeds to step S5 in FIG.

As described above, in the process shown in FIG. 7, the rotational speed of the heat dissipation fan 51 is adjusted so that the following conditions (1) and (2) are satisfied.
(1) The case temperature of the compressor 44 or the temperature of the refrigerant discharged from the compressor 44 is lower than the specified temperature T2. That is, the temperature of the discharged refrigerant is sufficiently low.
(2) The temperature difference between the suction refrigerant temperature of the compressor 44 and the evaporation temperature in the evaporator 42 is larger than the specified value T3. That is, the degree of superheat of the refrigerant is sufficiently ensured.
Thereby, the refrigeration cycle 40 can maintain the evaporator 42 at a low temperature by setting the thermo-on state in which the compressor 44 is driven by the motor 43, and can prevent condensation inside the glass plate 12. Further, during this operation control, the circulation fan 50 is stopped and the rotational speed of the heat dissipating fan 51 is reduced, so that the liquid crystal display 10 is not excessively cooled and the normal liquid crystal display 10 is Power consumption can be suppressed compared to during cooling operation.

  After adjusting the number of rotations of the fan in step S4 in FIG. 5 and shifting to the operation to prevent dew condensation, the controller 35 again measures the temperature of the liquid crystal display 10 by the temperature sensor 36F (step S5), and the measured liquid crystal display 10 It is determined whether or not the temperature is higher than the specified temperature T1 (step S6). Here, when the temperature of the liquid crystal display 10 is higher than the specified temperature T1 (step S6; Yes), the controller 35 causes the refrigeration cycle 40 to perform a normal cooling operation. The rotational speed of the heat dissipation fan 51 is returned to the rotational speed during normal operation (step S7), and the process proceeds to step S14.

When the temperature of the liquid crystal display 10 is equal to or lower than the specified temperature T1 (step S6; No), the controller 35 measures the temperature of the front surface of the housing 8, that is, the vicinity of the glass plate 12, with the temperature sensor 36E (step S8). The measured temperature is compared with the specified temperature T4 (step S9). The specified temperature T4 is a temperature value set in advance as a reference for determining whether or not the glass plate 12 is not condensed, and is stored in a memory (not shown) of the controller 35. When the temperature measured by the temperature sensor 36E is equal to or lower than the specified temperature T4 (step S9; No), the controller 35 returns to step S5 in order to continue the condensation prevention operation.
On the other hand, if the temperature measured by the temperature sensor 36E is higher than the specified temperature T4 (step S9; Yes), the controller 35 stops the motor 43 and the heat dissipating fan 51 and shifts to thermo-off because there is no risk of condensation (step S9). S10).

After shifting to thermo-off, the controller 35 measures the temperature of the liquid crystal display 10 with the temperature sensor 36F (step S11), and determines whether or not the measured temperature of the liquid crystal display 10 is higher than the specified temperature T1 (step S12). . Here, when the temperature of the liquid crystal display 10 is equal to or lower than the specified temperature T1 (step S12; No), the process returns to step S11 to continue the thermo-off state. Note that an interval of a predetermined length may be provided before the temperature measurement of the liquid crystal display 10 is performed from step S12 to step S11.
When the temperature of the liquid crystal display 10 is higher than the specified temperature T1 (step S12; Yes), the controller 35 causes the refrigeration cycle 40 to perform a normal cooling operation. Therefore, the motor 43, the circulation fan 50, and the heat dissipation fan that have been stopped are stopped. 51 is started (step S13), and the process proceeds to step S14.

Therefore, the refrigeration cycle 40 included in the electronic signboard 1 performs a cooling operation for cooling the inside of the sealed space 28 while the temperature of the liquid crystal display 10 is higher than the specified temperature T1, and the temperature of the liquid crystal display 10 becomes equal to or lower than the specified temperature T1. In such a case, a dew condensation prevention operation is performed to prevent dew condensation without immediately shifting to thermo-off.
As described above, according to the present embodiment, the liquid crystal display 10 is housed in the housing 8, and the glass plate 12 is provided in the housing 8 at a position facing the display surface 11 of the liquid crystal display 10. A gap 30A is provided between the plates 12, an evaporator 42 is provided inside the housing 8, a circulation fan 50 is provided for returning the air cooled by the evaporator 42 to the gap 30A and then returning to the evaporator 42. 42, the electronic signboard 1 provided with a refrigeration cycle 40 having a compressor 44, a condenser 46, and an expansion valve 48 provided below the liquid crystal display 10. A temperature sensor 36F that detects the cooling temperature of the liquid crystal display 10 and a controller 35 that controls the rotation of the circulation fan 50 during operation of the compressor 44 in accordance with the temperature detected by the temperature sensor 36F. Therefore, after the cooling temperature of the liquid crystal display 10 reaches the target temperature, the compressor 44 is operated, and the circulation fan 50 and the heat dissipation fan 51 are controlled to make the liquid crystal display 10 and the sealed space 28 excessive. The evaporator 42 can be kept at a low temperature without cooling. Thereby, dew condensation such as the inside of the glass plate 12 in the sealed space 28 can be prevented, and a decrease in the visibility of the liquid crystal display 10 can be prevented.

  Further, according to the present embodiment, the liquid crystal display 10 is disposed in the sealed space 28 of the housing 8, and the sealed space 28 is formed by the housing 8 and the glass plate 12, and the evaporator 42 is contained in the sealed space 28. And a circulation fan 50 is provided. As a result, the air cooled by the evaporator 42 is circulated inside the sealed space 28, and the heat generated by the liquid crystal display 10 and the heat generated by solar radiation can be effectively cooled.

  According to the present embodiment, the controller 35 uses the circulation fan 50 and the heat dissipating fan of the condenser 46 during the operation of the compressor 44 according to the temperature on the back side of the liquid crystal display 10 detected by the temperature sensor 36F. The rotation of 51 is controlled. Thereby, after the cooling temperature of the liquid crystal display 10 reaches the target temperature, the circulation fan 50 and the heat dissipating fan 51 are controlled in a state where the compressor 44 is operated, and the heat exchange amount in the condenser 46 is adjusted. Therefore, the evaporator 42 can be kept at a low temperature without excessively cooling the liquid crystal display 10 and the sealed space 28, and condensation in the sealed space 28 can be prevented.

  Further, according to the present embodiment, the controller 35 allows the circulation fan 50 and the heat dissipation fan so that the temperature difference between the suction refrigerant temperature of the compressor 44 and the evaporation temperature in the evaporator 42 exceeds a preset value. 51. As a result, the compressor 44 can be operated so as not to excessively cool the sealed space 28 and the liquid crystal display 10 to prevent condensation, and liquid back to the compressor 44 can be prevented.

  Further, according to the present embodiment, the controller 35 is configured such that the temperature difference between the temperature of the suction refrigerant of the compressor 44 and the evaporation temperature of the evaporator 42 exceeds a preset value, and the case temperature of the compressor 44 or The rotational speeds of the circulation fan 50 and the heat dissipation fan 51 are controlled so that the discharge temperature of the compressor 44 does not exceed a predetermined temperature. Accordingly, the compressor 44 can be operated so as not to excessively cool the sealed space 28 and the liquid crystal display 10 to prevent dew condensation, and liquid back to the compressor 44 and overheating of the compressor 44 can be prevented. .

Furthermore, according to the present embodiment, the evaporator 42 is provided on the back side of the liquid crystal display 10, and the circulation fan 50 is arranged to circulate between the gap 30A and the back side of the display panel 22. The evaporator 42 is disposed at a position that does not obstruct the display by the air 22, and the air cooled by the evaporator 42 is circulated by being sent to the gap 30 </ b> A by the circulation fan 50, so that the inside of the housing 8 is effected by the refrigeration cycle 40. Can be cooled.
Furthermore, according to the present embodiment, the temperature sensor 36E is provided at a predetermined position where there is a possibility of condensation in the sealed space 28, and the controller 35 presets the temperature detected by the temperature sensor 36E during the condensation prevention operation. When the temperature becomes higher than the specified temperature T4, the compressor 44 and the heat dissipation fan 51 are stopped. That is, during the condensation prevention operation, if the temperature in a place where condensation is likely to occur, such as in the vicinity of the glass plate 12, is higher than the specified temperature T4 and the condensation is difficult to occur, the condensation prevention operation is stopped and the thermo-off is performed. Condensation can be reliably prevented and power consumption can be suppressed without performing unnecessary operation. Furthermore, in the dew condensation prevention operation, the circulation fan 50 is stopped and the rotation speed of the heat dissipation fan 51 is reduced to the minimum rotation speed, so that power consumption can be suppressed as compared with the normal cooling operation.

In the above description, the case where the compressor 44 is configured as a constant speed compressor, the circulation fan 50 is configured as a constant speed fan, and the heat radiation fan 51 is configured as a variable rotation speed fan is described as an example. The circulation fan 50 can also be configured as a variable rotation speed type fan.
In this case, the controller 35 does not stop the circulation fan 50 in step S3 in FIG. 6 but reduces the rotation speed of the circulation fan 50 from the normal level, and in the process in step S4 (steps S21 to S26 in FIG. 7). The rotational speed of the circulation fan 50 may be adjusted together with the rotational speed of the heat dissipation fan 51. In this operation, the rotation speeds of the circulation fan 50 and the heat dissipation fan 51 are adjusted so that both of the above conditions (1) and (2) are satisfied.

The above configuration is advantageous in terms of cost in that a constant speed compressor that is cheaper than the inverter compressor is used for the compressor 44, but an inverter type compressor can also be used as the compressor 44. In this case, the controller 35 adjusts the rotation speed of the heat dissipation fan 51 or the rotation speed of the heat dissipation fan 51 and the rotation speed of the circulation fan 50 in the process of step S4 (steps S21 to S26 in FIG. 7). Furthermore, the operating speed of the compressor 44 may be adjusted. In this operation, the operation speed of the compressor 44 and the rotational speeds of the circulation fan 50 and the heat dissipation fan 51 are adjusted so that both of the above conditions (1) and (2) are satisfied.
Furthermore, in any of the above cases, the controller 35 may adjust the valve opening degree of the expansion valve 48 in the process of step S4 in FIG. 6 (steps S21 to S26 in FIG. 7).

  In any case, the controller 35 controls the operation of the refrigeration cycle 40 so that (1) the refrigerant discharged from the compressor 44 is sufficiently cooled and (2) the degree of superheat of the refrigerant is sufficiently suppressed. . Thus, while the vicinity of the glass plate 12 is in a state where condensation is likely to occur, the evaporator 42 can be kept at a low temperature to prevent evaporation of moisture from the evaporator 42 and to prevent the formation of condensation in the sealed space 28. Further, during the dew condensation prevention operation, the operation of the circulation fan 50 is stopped and the rotational speed of the heat dissipation fan 51 is reduced, power consumption is suppressed, and the sealed space 28 is not excessively cooled. Furthermore, even if the heat exchange amount decreases due to the circulation fan 50 being stopped, by adjusting the rotational speed of the heat dissipating fan 51 to make the air flow appropriate, liquid back is prevented and the compressor 44 is overheated. Can be prevented.

  While the present invention has been described based on the embodiments, the present invention is not limited to this. In the present embodiment, the liquid crystal display 10 is used for the display panel 22 (planar display). However, the present invention is not limited to this, and for example, a configuration using a flat display such as an organic EL display or a plasma display may be used. good.

In the present embodiment, the temperature sensor 36E is installed near the lower part inside the glass plate 12, and the inside of the glass plate 12 is determined based on whether the temperature measured by the temperature sensor 36E is higher than the specified temperature T4. However, the present invention is not limited to this, and if there is a place where condensation easily occurs in the sealed space 28, more temperature sensors can be installed. Based on the temperature measured by each temperature sensor, it may be determined whether or not condensation is likely to occur. A temperature sensor provided in a place other than the lower portion of the glass plate 12 in the sealed space 28 is used as the temperature sensor 36E. Of course, it can be used instead.
In the present embodiment, the rotational speed of the heat dissipating fan 51 is controlled so that the discharge refrigerant temperature of the compressor 44 is within a predetermined temperature. However, a temperature sensor is provided on the peripheral surface of the compressor 44, It is good also as a structure which controls the rotation speed of the fan 51 for thermal radiation so that the surrounding surface temperature of the compressor 44 may not become more than predetermined temperature.
For example, in the above-described embodiment, the configuration using the expansion valve 48 as the expansion means has been described. However, a so-called capillary tube having a constant flow path resistance may be used as the expansion means. In particular, if the refrigeration cycle 40 is configured by combining the capillary tube and the constant speed compressor 44, it can be configured at a lower cost than the case where an inverter type compressor or expansion valve is used. It is advantageous.
Of course, other details and the like can be arbitrarily changed.

DESCRIPTION OF SYMBOLS 1 Electronic signboard 2 Signboard body 4 Base 6 Cooling unit 8 Housing 9 Opening 10 Liquid crystal display (flat display)
11 Display surface 12 Glass plate (transparent plate)
14 Frame frame 22 Display panel 28 Sealed space 30 Circulating flow path 30A Clearance 35 Controller (control unit)
36A to 36F Temperature sensor 40 Refrigeration cycle 42 Evaporator 44 Compressor 46 Condenser 48 Expansion valve 50 Fan for circulation 51 Fan for heat dissipation

Claims (6)

Put the flat display in the case,
A transparent plate is provided inside the housing at a position facing the display surface of the flat display, a gap is provided between the display surface and the transparent plate, an evaporator is provided inside the housing, and the evaporator is cooled by the evaporator. A circulation fan that guides the generated air to the gap and then returns to the evaporator, is connected to the evaporator, and is provided below the flat display; a condenser; an expansion means; In an electronic signboard provided with a refrigeration cycle having
A temperature sensor for detecting a cooling temperature of the flat display provided in the housing;
A controller that controls rotation of the circulation fan and rotation of the heat dissipation fan of the condenser according to a temperature detected by the temperature sensor;
An electronic signboard characterized by comprising   The flat display is disposed in a sealed space of the housing, the sealed space is formed by the housing and the transparent plate, and the evaporator and the circulation fan are provided in the sealed space. The electronic signboard according to claim 1, wherein:   The control unit controls the circulation fan and the heat dissipating fan so that a temperature difference between a temperature of the suction refrigerant of the compressor and an evaporation temperature in the evaporator exceeds a preset value. The electronic signboard according to claim 1 or 2.   The control unit has a temperature difference between a temperature of the suction refrigerant of the compressor and an evaporation temperature of the evaporator exceeding a preset value, and a case temperature of the compressor or a discharge temperature of the compressor is predetermined. The electronic signboard according to claim 1 or 2, wherein the number of rotations of the circulation fan and the heat dissipation fan is controlled so as not to exceed a temperature. A second temperature sensor is provided at a predetermined position where condensation may occur in the sealed space;
The control unit controls the rotation of the circulation fan and the heat dissipation fan of the condenser during operation of the compressor, and the temperature detected by the second temperature sensor is higher than a preset temperature. The electronic signboard according to any one of claims 1 to 4, characterized in that the compressor and the heat dissipating fan are stopped when it becomes. A flat display is housed in a housing, a transparent plate is provided inside the housing at a position facing the display surface of the flat display, a gap is provided between the display surface and the transparent plate, and evaporation is performed inside the housing. A compressor provided in the lower part of the flat display connected to the evaporator, provided with a circulation fan provided to return the air cooled by the evaporator to the gap and then returned to the evaporator And a cooling control method in an electronic signboard provided with a refrigeration cycle having a condenser and expansion means, and a control unit for controlling the refrigeration cycle,
By the control unit,
Detecting a cooling temperature of the flat display provided in the housing by a temperature sensor;
According to the detected temperature, controlling rotation of the heat dissipation fan of the condenser together with rotation of the circulation fan during operation of the compressor;
A cooling control method for an electronic signboard, comprising:

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