JPH04217763A - Freezing device - Google Patents

Abstract

PURPOSE:To perform high-reliable off-cycle defrost responding to a state of frosting produced at the vaporizer of a freezing device to hold temperature in a chamber at a value higher than an ice point. CONSTITUTION:A temperature detector 8 detects the temperature of a vaporizer 4. When the temperature is reduced to a value lower than a set temperature T approximately equal to the lowmost temperature of a set temperature in a regulatable chamber and a cooling operation integrating time exceeds a given time W, defrost operation is started. When, after defrost operation is effected for a given time W1, the temperature of the vaporizer 4 exceeds the set temperature T, defrost operation is stopped and cooling operation is newly started. When the temperature of the vaporizer 4 is lower than the set temperature T even if defrost operation is effected for a first set time W1, defrost operation is effected for a second set time W2 longer than a first set time W1 and cooling operation is started.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system that maintains an internal temperature above the freezing point, and more particularly to defrost control of a refrigeration system that performs defrost in an off-cycle.

0002

[Prior Art] In refrigeration equipment, such as low-temperature air conditioners, which maintains the temperature inside the refrigerator at a desired value above the freezing point, for example 2°C or above, defrosting is usually performed by an off-cycle defrost method. . This off-cycle defrost is, for example,
As shown in the publication, this refers to an operation in which compression refrigeration operation is stopped and defrosting is performed by air blowing operation.

FIG. 4 is an explanatory diagram of the operating temperature range of a refrigerator in this type of low-temperature air conditioner. As shown by the shaded area of frost formation, the lower the temperature inside the refrigerator, the higher the temperature outside the refrigerator. It is known that the amount of frost is large.

0004

[Problems to be Solved by the Invention] By the way, when the door for loading and unloading items in a prefabricated refrigerator is left open for a long time in an area where the internal temperature is low, or when a large number of high-humidity items are brought in. Depending on local usage conditions, such as
The amount of frost formation may be very large.

[0005] In such a case, the user is informed through the operation manual that the predetermined defrost period should not be changed, but the defrost operation time should be changed to a longer value. It is not easy to decide, and if you do not set the correct time, there is a problem that the temperature inside the refrigerator will not drop due to the residual frost operation, which will enter cooling mode even though there is a considerable amount of frost remaining, and the cooling capacity will decrease. If the defrost operation time is too long, the temperature inside the refrigerator will rise due to empty defrost operation.
The problem is that the large range of temperature fluctuations adversely affects the quality of the refrigerator.

[0006] Reliance on operating manuals and the like as described above causes various problems in terms of refrigeration operation.

An object of the present invention is to provide an off-cycle defrost type refrigeration system that can prevent residual frost and empty defrost and realize highly reliable off-cycle defrost operation even under severe usage conditions. .

[0008]

[Means for Solving the Problems] The present invention provides a refrigeration system in which the temperature inside the refrigerator, which is cooled by an evaporator, can be adjusted to a desired value above the freezing point, and in which defrosting is performed in an off cycle in which defrosting is performed by air blowing operation. , the cumulative cooling operation time from the end of the previous defrost operation or from the start of the first cooling operation is longer than the predetermined time W, and the predetermined temperature is approximately equal to the lowest temperature among the adjustable internal temperature settings. When the temperature of the evaporator falls below the set temperature T, defrost operation is started, and after this defrost operation is performed for another predetermined time W1, the temperature of the evaporator exceeds the set temperature T. The refrigeration system is characterized by stopping the defrosting operation and switching to the cooling operation if the

[0009] The present invention also provides a refrigeration system in which the temperature inside the refrigerator, which is cooled by an evaporator, can be adjusted to a desired value above the freezing point, and in which defrosting is performed in an off cycle in which defrosting is performed by blowing air. The cumulative cooling operation time from the end of the operation or from the start of the first cooling operation is longer than the predetermined time W, and the temperature is lower than the predetermined temperature T, which is approximately equal to the lowest temperature among the adjustable temperature settings inside the refrigerator. When the evaporator temperature drops, defrost operation starts,
This defrost operation is performed for another predetermined first set time W1, and when the temperature of the evaporator is below the preset temperature T, the defrost operation is performed for another predetermined time W1 longer than the first set time W1. This refrigeration system is characterized in that the defrost operation is performed only during the second set time W2.

0010

[Operation] According to the present invention, the start of the defrost operation is a predetermined time W set as the defrost cycle, for example, 3
Defrosting is not performed based on the passage of time, but when both of the following conditions hold true: the predetermined time W has elapsed, and the temperature has dropped to below the set temperature T due to a considerable amount of frost adhering to the evaporator. Since the defrost operation is started only when frost formation is ensured, so-called empty defrost operation is prevented.

[0011] Then, this defrosting operation is performed for a first set time W1, for example, 10 minutes, but this time W1 is a time corresponding to defrosting is performed in just the right amount under standard frosting conditions, and under normal conditions. This is sufficient for defrost operation, but in the present invention, after reaching this time W1, it is confirmed that the temperature of the evaporator exceeds the set temperature T, for example, 2°C, and then the defrost operation is stopped. Since the defrosting is completed, the defrosting is terminated by detecting that the defrosting is finished, thus preventing residual frost operation.

Furthermore, if the evaporator temperature is still below the set temperature T even after reaching the first set time W1, the defrost operation is forced for a second set time W2, for example 30 minutes. In some cases, defrosting may also be complete to prevent residual frost from forming.

[0013] Here, the first set time W1 is realistically set to about 10 minutes, but in order to maintain the temperature inside the refrigerator at, for example, 2°C, it is preferably longer than this time. This time is necessary to melt the amount of frost formed when the cooling operation is performed for a predetermined time W when the temperature inside the refrigerator is the lowest temperature above the freezing point among the adjustable temperatures, and
It is a sufficient amount of time and is usually determined first, taking into consideration the various conditions of the refrigeration equipment.

[0014] Once the first set time W1 is determined in this way, a predetermined time W, for example 3 hours, is set as the cooling operation time to form an amount of frost that can melt the defrost in W1 time. It will be decided.

[0015] Next, there is the second set time W2, which is a time period in which the refrigeration equipment will not lose the commercial value of the refrigerator, that is, if it is not refrigerated for more than a certain period of time, the temperature inside the refrigerator will rise. Considering that excessive rise in temperature may adversely affect the quality of the product, an appropriate time period is assumed for the refrigeration equipment, which is usually about 30 minutes.

[0016] As described above, it is possible to provide a refrigeration system that can perform appropriate defrost operation without causing residual frost or empty defrost.

[0017]

Embodiment FIG. 1 is a refrigerant piping system diagram according to an embodiment of the present invention. A compressor 1, a condenser 2, an expansion means 3, such as a temperature-sensitive automatic expansion valve, an evaporator 4, and an accumulator 5 are provided, and these devices are cyclically connected by refrigerant piping to form a known refrigeration cycle, The condenser 2 releases the latent heat of condensation to the atmosphere, and the evaporator 4 extracts the latent heat of vaporization from the air inside the refrigerator, thereby cooling the refrigerator 6 to a temperature above the freezing point, for example, 2°C.

In FIG. 1, 7 is an evaporator fan, and 8 is a temperature sensor attached to the U-shaped tube at the bottom of the heat exchange tube of the evaporator 4.

The refrigeration system having the above-mentioned configuration stops the cooling operation using the compression refrigeration cycle, and performs defrosting through an off cycle using only the air blown by the fan 7.

FIG. 2 is a flowchart showing the operation of the defrost operation, and FIG. 3 is a diagram of the defrost operation temperature over time.

In FIG. 2, the operation starts at step A1, and the process moves to step A2, where cooling operation begins.

During the cooling operation, the time and temperature are checked in step A3, and if the cooling operation time from the start of operation has reached a predetermined time W, for example 3 hours, and the temperature detector 8 of the evaporator 4 has detected If the temperature is lower than the set temperature T, for example 2°C, move to step A4,
Cooling operation switches to defrost operation. This point in time is the position indicated by a circle in FIG. The operation time of this defrost operation is checked in step A5, and the operation time is the first.
If the set time W1 has reached, for example, 10 minutes, the process moves to step A6, and if the temperature detected by the temperature detector 8 is higher than the set temperature T, the process moves to step A2 and switches to cooling operation. This point in time is the position indicated by the ▽ mark in FIG.

On the other hand, if the detected temperature is 2° C. or lower, the process moves to step A7, where the defrost operation time is compared with the second set time W2, for example 30 minutes, and it is determined that 30 minutes has not been reached, and If the temperature is still below 2℃, the defrost operation continues until it reaches 30 minutes until it reaches the position indicated by the △ mark in Figure 3. If the temperature exceeds 2℃ midway through, the defrost operation moves to step A2 and the defrost operation continues to cool down. Switch to driving.

[0024] In this way, even though the defrost has been completely done,
Problems such as continuing defrosting or stopping defrosting even though some frost remains unmelted will be resolved.

[0025]

As described above, according to the present invention, the defrost operation is started not only at a predetermined period, but also at a comparison with the set temperature T, which indicates that the evaporator is sufficiently frosted. Since the defrosting condition is reliably detected and defrosted, empty defrosting, which starts defrosting operation even though there is no need for defrosting, is prevented. In addition, the completion of defrosting is checked by the temperature of the heat exchange part of the evaporator, and if the frost has melted, the defrost operation is stopped, and if the frost has not melted, the defrost operation is limited to the second set time W2 necessary for defrosting. Since the defrosting apparatus is operated, it is possible to prevent residual frost from occurring due to stopping defrosting even when frost remains, and thus to realize highly reliable off-cycle defrosting.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant piping system diagram according to an embodiment of the present invention.

FIG. 2 is a flowchart of defrost operation.

FIG. 3 is an operating temperature change diagram over time.

FIG. 4 is an explanatory diagram of the operating temperature range of the refrigerator.

[Explanation of symbols]

1 Compressor 2 Condenser 3. Expansion valve 4 Evaporator 7 Evaporator fan 8 Temperature detector

Claims (2)

[Claims] Claim 1: A refrigeration system in which the temperature inside the refrigerator, which is cooled by the evaporator 4, can be adjusted to a desired value above the freezing point, and in which defrosting is performed in an off-cycle in which defrosting is performed by blowing air, when the previous defrosting operation has ended. or from the start of the first cooling operation, the cumulative cooling operation time is longer than the predetermined time W, and the evaporator is lowered to a predetermined temperature T, which is approximately equal to the lowest temperature among the adjustable internal temperature settings. When the temperature of the evaporator falls, the defrost operation is started, and after this defrost operation is performed for another predetermined time W1, if the temperature of the evaporator exceeds the set temperature T,
A refrigeration system characterized by stopping defrosting operation and switching to cooling operation. [Claim 2] In a refrigeration system in which the temperature inside the refrigerator to be cooled by the evaporator 4 can be adjusted to a desired value above the freezing point, and in which defrosting is performed in an off-cycle in which defrosting is performed by air blowing operation, when the previous defrosting operation has ended. or from the start of the first cooling operation, the cumulative cooling operation time is longer than the predetermined time W, and the evaporator is lowered to a predetermined temperature T, which is approximately equal to the lowest temperature among the adjustable internal temperature settings. When the temperature of the evaporator falls, the defrost operation is started, and this defrost operation is performed for another predetermined first set time W1, and when the temperature of the evaporator is below the set temperature T, the first defrost operation is performed. A refrigeration system characterized in that a defrost operation is performed only during yet another second set time W2 that is predetermined longer than a set time W1.