JP3407918B2 - Cold air dryer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cool air dryer used for drying foods, agricultural products and the like. 2. Description of the Related Art Conventionally, in this kind of cool air dryer, for example, a refrigerant circuit as shown in FIGS. 3 and 4 has been used.
That is, the cool-air dryer 100 includes a drying cabinet 101 having an interior (not shown) for storing foods to be dried and an outdoor unit 102, and a three-way valve is provided on a discharge side of a compressor 103 provided on the drying cabinet 101 side. 104 is connected and the three-way valve 1
One outlet of 04 is connected to a condenser 105 provided in the outdoor unit 102. 106 is the condenser 10
5 is a blower for forced air cooling. The condenser 105 is connected to a liquid receiver 108 via a check valve 107 provided on the drying chamber 101 side, and the liquid receiver 108 is connected to a cooler provided in the chamber via an expansion valve 109. 110 is connected. The cooler 110 is connected to the suction side of the compressor 103 to form an annular refrigeration cycle. The expansion valve 109 detects the temperature on the outlet side of the cooler 110 and adjusts the opening degree so as to maintain the degree of superheat at a predetermined value. [0006] The other outlet of the three-way valve 104 is connected to a reheater 112 which is provided in a refrigerator together with the cooler 110 and forms a heat exchanger 111.
Is connected to the receiver 108 via a check valve 113. The check valve 113 and the check valve 107 are
In each case, the liquid receiver 108 side is forward. Also,
Reference numeral 114 denotes a blower for forcibly circulating air exchanged with the cooler 110 and the reheater 112 into the refrigerator. [0005] The compressor 10 before the three-way valve 104
3 is connected to a discharge side of the expansion valve 1 via an on-off valve 116.
09 and the cooler 110. On-off valve 11
6 detects the temperature on the outlet side of the evaporator 110 and opens and closes the defrost circuit 115 (indicated by * 2 in the figure). The three-way valve 104 is controlled by a control circuit 117 (indicated by * 1 in the figure), and the control circuit 11
7, a thermostat 118 for detecting the temperature in the refrigerator and a humistat 119 for detecting the humidity in the refrigerator are connected. Reference numeral 120 denotes an on-off valve, which is always open. Reference numeral 121 denotes a liquid injection circuit for cooling the compressor 103, and reference numeral 122 denotes a pressure regulating valve (VPR). The operation of the above-described conventional cool air dryer 100 will be described. The cold air dryer 100 has an internal temperature of, for example, + 10 ° C.
The control circuit 117 is set to, for example, the above-mentioned internal temperature of + 10 ° C. The control circuit 117 is connected to the compressor 10
3 is operated, and the flow path of the three-way valve 104 is set to the one outlet direction until the internal temperature decreases to the set temperature.
As a result, the high-temperature and high-pressure gas refrigerant discharged from the compressor 103 enters the condenser 105 through the three-way valve 104 as shown by the bold line in FIG. The liquid enters the liquid container 108 and reaches the expansion valve 109 via the on-off valve 120. The opening of the expansion valve 109 is adjusted based on the temperature at the outlet side of the cooler 110 as described above, and the condensed and liquefied refrigerant is throttled and supplied to the cooler 110. The refrigerant flowing into the cooler 110 evaporates, absorbs heat from the surroundings, exerts a cooling function, and is then sucked into the compressor 103. [0007] When the internal temperature decreases to the set temperature due to the cooling operation, the control circuit 117 operates the three-way valve 10.
4 is switched to the other outlet direction. As a result, the high-temperature and high-pressure gas refrigerant discharged from the compressor 103 passes through the three-way valve 104 as shown by a thick line in FIG.
12 and heat is released there to exert a heating effect. On the other hand, the refrigerant is condensed there, enters the receiver 108 via the check valve 113, and thereafter flows as described above. If the internal temperature rises due to the reheating operation, the control circuit 1
17 again switches to the cooling operation of FIG. 3, and thereafter, the cooling operation and the reheating operation are repeated. The air cooled by the cooler 109 and heated by the reheater 112 is supplied to a blower 114.
Thus, the articles stored in the refrigerator are dried by repeating the cooling / reheating operation. Here, when the temperature in the refrigerator is + 15 ° C. or more, the evaporation temperature of the refrigerant in the cooler 110 is 0 ° C. or more, so that no frost is formed. Since the evaporating temperature of the refrigerant in the cooler 110 becomes −5 ° C., frost forms on the cooler 110. When frost forms on the cooler 110, the temperature of the cooler 110 decreases because heat exchange is not performed. Defrost circuit 115
The on-off valve 116 provided in the cooler 1
When the outlet temperature of 10 drops to, for example, −3 ° C., the flow path is opened, and the high-temperature and high-pressure gas refrigerant discharged from the compressor 103 flows downstream of the expansion valve 109 and directly flows into the cooler 110. The cooler 110 is heated and defrosted by the flow of the high-temperature and high-pressure gas refrigerant. As described above, in the conventional cool air dryer 100, when the cooler 110 is defrosted, the compressor 1
Since the high-temperature and high-pressure gas refrigerant discharged from the discharge valve 03 is flowing to the outlet side of the expansion valve 109, the amount of the defrosted refrigerant is
When the superheat degree exceeds the function range for keeping the superheat degree of 09 constant, the superheat degree becomes unstable, and there is a danger that the liquid back occurs in the compressor 103. In addition, since the high-temperature refrigerant flows through the cooler 110, the flow rate to the reheater 112 decreases, and there is a problem that the dehumidifying action decreases. Further, the control circuit 117 performs constant-rate drying for normal drying and reduced-rate drying with reduced drying capacity. However, when the load in the refrigerator is reduced due to reduced-rate drying, cooling / cooling is performed.
There is also a problem that the switching time of the reheating operation is shortened, and the life of each component is shortened due to pressure fluctuation due to frequent switching. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional technical problems, and it is intended to prevent the liquid back to the compressor and the reduction of the dehumidifying action at the time of defrosting, and to extend the life of parts. It is an object to provide a cool air dryer that can be realized. [0012] The cold-air dryer 1 of the present invention.
Is a cooler 21, a reheater 23, a compressor 6, an expansion valve
19 and a temperature sensor (thermosta
And the condenser 8 is provided outside the refrigerator.
The high-temperature gaseous refrigerant from the compressor 6 is condensed in the condenser 8
The cooled liquid refrigerant is converted into a low-temperature gas refrigerant by the expansion valve 19,
Cooling operation to cool the inside of the refrigerator by flowing into
And the inside temperature detected by the temperature sensor is
When the temperature drops to the set value, stop the cooling operation and
A part of the body refrigerant flows into the reheater 23 to heat the inside of the refrigerator
At the same time, the remaining portion of the high-temperature gaseous refrigerant flows into the cooler 21
The defrosting of the cooler 21 is performed, and the capacity of the compressor 6 is reduced.
Capability control device (capacity control circuit 27, control
Circuit 31), which is detected by the temperature sensor.
The internal temperature drops to a second set value higher than the first set value
The cooling operation is reduced by reducing the capacity of the compressor 6.
Temperature detected by the temperature sensor reaches the first set value
Capacity control device to continue is al provided to decrease
It is characterized by the following. According to the cold-air dryer 1 of the present invention, when the temperature in the refrigerator drops to the second set value higher than the first set value at which a part of the high-temperature gaseous refrigerant flows into the reheater 23. Has a capacity control device (capacity control device 27, control circuit 3
Since 1) reduces the capacity of the compressor 6, the cooling action in the cooler 21 is reduced, thereby reducing the amount of frost on the cooler 21. Accordingly, the supply amount of the high-temperature gaseous refrigerant for defrosting is also reduced, so that the danger of liquid back to the compressor 6 is eliminated and the high-temperature gas supplied to the reheater 23 is eliminated.
The decrease of the body refrigerant can be suppressed low. In addition, since the cooling and reheating capabilities are also reduced, the switching time between the cooling and reheating operations is lengthened, and thus the life of the parts is extended. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a refrigerant circuit diagram of a cool air dryer 1 of the present invention. That is, the cool-air dryer 1 includes an interior (not shown) for storing articles such as foods to be dried, a drying oven 3 having an indoor unit 2, and a condenser 4 serving as an outdoor unit.
A three-way valve 7 is connected to a discharge side of a compressor 6 provided on the indoor unit 2 side, and one outlet of the three-way valve 7 is connected to a condenser 8 provided on the condenser 4. . Reference numeral 9 denotes a blower for forcibly cooling the condenser 8. The compressor 6 is, for example, a scroll compressor as disclosed in Japanese Patent Application No. Hei 4-5612 filed by the applicant of the present invention. Circuit 11 is attached. The capacity control circuit 11 communicates the discharge side and the suction side of the compressor 6 before the three-way valve 7 by a thin tube including on-off valves 12 and 13 and a check valve 14 connected in series. Further, a portion between the on-off valves 12 and 13 is connected to a scroll of the compressor 6. When both of the on-off valves 12 and 13 are opened, the refrigerant discharged from the compressor 6 is returned to the suction side, and its operation capability is greatly reduced. When the on-off valve 12 is opened and the on-off valve 13 is closed, the discharged refrigerant is discharged. Is returned to the scroll and its driving ability is reduced to a small extent. The condenser 8 is connected to a liquid receiver 17 via a check valve 16 provided on the drying chamber 3 side, and the liquid receiver 17 is connected to a cooler provided in the chamber via an expansion valve 19. 21. The cooler 21 is connected to the suction side of the compressor 6 via an accumulator 22 to form an annular refrigeration cycle. The expansion valve 19 detects the temperature at the outlet side of the cooler 21 and adjusts the opening degree so as to maintain the degree of superheat at a predetermined value. The other outlet of the three-way valve 7 is connected to the cooler 2
1 is connected to a reheater 23 provided in the refrigerator, and the reheater 23 is connected to the liquid receiver 1 via a check valve 24.
7 is connected. The check valve 24 and the check valve 1
In each case 6, the liquid receiver 17 is directed forward. Reference numeral 26 denotes a blower for forcibly circulating the air exchanged with the cooler 21 and the reheater 23 into the refrigerator. A defrost circuit 27 is connected to the discharge side of the compressor 6 before the three-way valve 7. The defrost circuit 27 is connected between the expansion valve 19 and the cooler 21 through an on-off valve 28 and a capillary tube 29. It is connected to the. The on-off valve 28 detects the temperature on the outlet side of the evaporator 21 and opens and closes the defrost circuit 27 (indicated by * 2 in the figure). The three-way valve 7 is controlled by a control circuit 31 constituting a capacity control device (indicated by * 1 in the figure), and the control circuit 31 controls the on-off valves 12 and 13 (* 3 and * in the figure). * 4), a thermostat 32 as a temperature sensor for detecting the temperature in the refrigerator, a thermostat 33 as a temperature sensor for detecting the temperature in the refrigerator to control the three-way valve 7, and a humidity in the refrigerator. A humistat 34 as a humidity sensor is connected. A liquid injection circuit 38 having an on-off valve 36 and a thermo valve 37 is connected to the compressor 6 from the outlet of the liquid receiver 17. Reference numeral 39 denotes an on-off valve, and 41 denotes a liquid solenoid valve, which is always open. Furthermore,
Reference numerals 42, 43, and 44 denote a dryer, an indicator, and a strainer, respectively. Reference numeral 46 denotes an oil control circuit that returns lubricating oil to the compressor 6. Next, the operation of the cool air dryer 1 of the present invention having the above configuration will be described. The cold air dryer 1 has an internal temperature of, for example, +1.
It is used in a range of 0 ° C. to + 30 ° C., and the control circuit 31 is set to, for example, the above-mentioned internal temperature of + 10 ° C. Then, the control circuit 31 operates the compressor 6, and sets the flow path of the three-way valve 7 to the one outlet direction until the internal temperature decreases to the set temperature. As a result, the high-temperature and high-pressure gas refrigerant discharged from the compressor 6 enters the condenser 8 through the three-way valve 7 as shown by the thick line in FIG. The liquid enters the liquid container 17 and reaches the expansion valve 19 via the liquid electromagnetic valve 41.
The opening of the expansion valve 19 is adjusted based on the outlet temperature of the cooler 21 as described above, and the condensed and liquefied refrigerant is throttled and supplied to the cooler 21. The refrigerant flowing into the cooler 21 evaporates,
After absorbing heat from the surroundings and exerting a cooling function, it is sucked into the compressor 6 via the accumulator 22. By the cooling operation, the temperature in the refrigerator becomes, for example, +
When the temperature drops to 12 ° C. (set in the control circuit 31 at an arbitrary value within a range from + 12 ° C. to + 13 ° C.), the control circuit 31 detects this based on the thermostat 32 and controls the on-off valves 12 and 13. A capacity control operation for reducing the operating capacity of the compressor 6 to 60% is executed.
By the capacity control operation of the compressor 6, the rate of decrease in the internal temperature becomes slow. Then, the internal temperature is set to the set temperature (+10
° C), the control circuit 31 detects this based on the thermostat 33, and sets the flow path of the three-way valve 7 to the other outlet direction. As a result, the high-temperature and high-pressure gas refrigerant discharged from the compressor 6 enters the reheater 23 via the three-way valve 7 as shown by the thick line in FIG. On the other hand, the refrigerant is condensed there, enters the receiver 17 via the check valve 24, and thereafter flows as described above. When the inside temperature of the refrigerator rises to a predetermined upper limit (a value set with a predetermined hysteresis width above + 10 ° C.) by the reheating operation, the control circuit 31 switches again to the cooling operation of FIG. Thereafter, the cooling operation and the reheating operation are repeated. Since the air cooled by the cooler 21 and heated by the reheater 23 is circulated in the refrigerator by the blower 26, the articles stored in the refrigerator are dried by repeating the cooling / reheating operation. By the way, as described above, the control circuit 3
1 is a stage in which the capacity control operation of the compressor 6 is executed at the stage when the temperature in the refrigerator has decreased to + 12 ° C., so that the rate of decrease in the temperature in the refrigerator becomes slow thereafter, and one cooling time (until the temperature reaches + 10 ° C.) ), The switching time of the cooling / reheating operation becomes longer. Here, when the cooling / reheating operation is switched, the pressure in the refrigerant circuit fluctuates greatly, so that a large load is applied to the circuit components. However, according to the present invention, the switching time is long, so the number of times of switching is small. As a result, the load applied to these circuit components is also reduced, and the life of the components is extended. When the temperature in the refrigerator is higher than + 15 ° C., the cool air dryer 1 changes from constant-rate drying to reduced-rate drying, and the humidity in the refrigerator becomes, for example, 60% (arbitrary value in the range of 60% to 70%). (Set in the control circuit 31), the control circuit 31 detects this based on the humistat 34, and controls the open / close valves 12 and 13 as described above to reduce the operating capacity of the compressor 6 by 60%. Perform the capacity control operation to reduce the pressure. Therefore, as in the above, the rate of decrease in the internal temperature becomes slow, so that the time for switching between the cooling and reheating operations is lengthened, and the life of the components is prolonged. When the temperature in the refrigerator becomes higher than, for example, + 12 ° C. and the humidity in the refrigerator becomes higher than 60%,
The control circuit 31 closes the on-off valves 12 and 13 to interrupt the capacity control operation. The articles in the refrigerator are dried by repeating the cooling / reheating operation. However, when frost grows on the cooler 21 and the temperature at the outlet side of the cooler 21 drops to, for example, -3.degree.
Opens the flow path, flows the high-temperature and high-pressure gas refrigerant discharged from the compressor 6 downstream of the expansion valve 19, and directly flows into the cooler 21. The cooler 21 is heated and defrosted by the inflow of the high-temperature and high-pressure gas refrigerant, but as described above, when the temperature in the refrigerator has decreased to + 12 ° C. or when the humidity in the refrigerator has decreased to 60%. Since the operation capacity of the compressor 6 is controlled to be 60%, the amount of frost formed on the cooler 21 is small. Accordingly, the amount of bypass of the high-temperature refrigerant to the defrost circuit 27 can be reduced, so that it does not fall outside the functional range of the control of the degree of superheat by the expansion valve 19, and the occurrence of liquid back to the compressor 6 is eliminated. Is done. Further, since the amount of the high-temperature refrigerant to the defrost circuit 27 is reduced, the amount of the high-temperature refrigerant supplied to the reheater 23 during the defrosting is reduced, and therefore, the dehumidifying capacity of the cooler 21 during the defrosting is reduced. Will also be minimized. In the embodiment, the capacity control of the compressor 6 is executed both when the internal temperature decreases to + 12 ° C. or when the internal humidity decreases to 60%. There may be. Further, in the embodiment, the compressor 6 is a scroll compressor, and the operation capacity is controlled by the capacity control of the cylinder bypass system. However, the present invention is not limited to this. Can be done. Further, each value shown in the embodiment is not limited thereto, and it goes without saying that various changes can be made without departing from the spirit of the present invention. According to the present invention as described in detail above ,
Is lowered to a second set value higher than the first set value at which a part of the high-temperature gaseous refrigerant flows into the reheater , the capacity control device reduces the capacity of the compressor. , The amount of frost on the cooler is reduced. Therefore, since the supply amount of the high-temperature gas refrigerant for defrosting is also reduced, the danger of liquid back to the compressor is eliminated, and the decrease in the high-temperature gas refrigerant supplied to the reheater is also suppressed, The reduction in the dehumidifying capacity during defrosting can be minimized. Further, since the switching time between the cooling and the reheating operation becomes longer, it is possible to extend the life of the component.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a refrigerant circuit diagram showing a refrigerant flow during a cooling operation of a cool air dryer of the present invention. FIG. 2 is a refrigerant circuit diagram showing a flow of a refrigerant during a reheating operation of the cool air dryer of the present invention. FIG. 3 is a refrigerant circuit diagram illustrating a flow of a refrigerant during a cooling operation of a conventional cool air dryer. FIG. 4 is a refrigerant circuit diagram illustrating a flow of a refrigerant during a reheating operation of a conventional cool air dryer. [Description of Signs] 1 Cold air dryer 6 Compressor 7 Three-way valve 8 Condenser 11 Capacity control circuit 19 Expansion valve 21 Cooler 23 Reheater 27 Defrost circuit 31 Control circuit

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hiroshi Arai               2-18-18 Keihanhondori, Moriguchi-shi, Osaka               Yo Electric Co., Ltd.                (56) References JP-A-4-265109 (JP, A)                 JP-A-1-277160 (JP, A)                 Actual opening Hei 2-127190 (JP, U)                 Actual opening 63-155984 (JP, U)

Claims (1)

(57) [Claims] [Claim 1] A cooler, a reheater, a compressor, and an expansion valve in a refrigerator.
And a temperature sensor to detect the temperature inside the refrigerator
Is provided with a condenser, and hot gas from the compressor is provided.
The refrigerant is condensed by the condenser, and the liquid refrigerant is condensed by the expansion valve.
By making it a low-temperature gas refrigerant and flowing into the cooler
Performing a cooling operation for cooling the inside of the refrigerator, wherein the temperature sensor
The temperature inside the chamber detected by the
When the cooling operation is stopped,
When a part is flowed into the reheater to heat the interior of the
The remaining portion of the high-temperature gaseous refrigerant is allowed to flow into the cooler.
In the cool air dryer for defrosting the cooler, the compression
A capacity control device for controlling the capacity of the
Sensor temperature is lower than the first set value.
When the pressure drops to a second set value higher than
Ability to reduce the cooling operation by the temperature sensor.
Until the detected internal temperature drops to the first set value.
It is characterized by having a capacity control device to continue with
And cold air dryer.