A defrost control method for air-cooled refrigerator

Abstract

The present invention discloses a defrost control method for an air-cooled refrigerator. While the refrigerator compressor is running and the refrigerator door is closed, the method determines whether to defrost the evaporator based on changes in the outlet air temperature T1 and the compartment temperature T2 of the refrigerator evaporator compartment during adjacent time periods. The more severe the evaporator frosting, the worse the refrigerator's cooling performance, the higher the outlet air temperature, and the slower the compartment temperature change rate. Therefore, based on the compartment outlet air temperature and compartment temperature changes, the degree of frost on the evaporator and the degree of frost's impact on the refrigerator's cooling performance can be intuitively and accurately determined. Defrost control based on this determination ensures efficient heat exchange in the refrigerator, thereby improving the refrigerator's energy consumption.

Description

Technical Field

[0001] The invention relates to a defrost control method for an air-cooled refrigerator, belonging to the technical field of household appliance control. Background Art

[0002] During operation, air in an air-cooled refrigerator continuously passes through the evaporator for heat exchange. During this process, because the evaporator is cold, moisture in the air condenses on the evaporator, forming a frost layer that gradually thickens with operating time. This can seriously affect the evaporator's heat exchange efficiency. Therefore, air-cooled refrigerators require defrosting the evaporator after a certain period of operation to ensure efficient heat exchange.

[0003] The most common defrost control method for air-cooled refrigerators currently uses a timer calculated based on the cumulative compressor operating time and the cumulative refrigerator door open time. If this timer reaches the preset defrost cycle, the compressor stops and the defrost heater begins operating. When the defrost temperature sensor on the evaporator reaches a preset temperature, the defrost heater stops, completing the defrost.

[0004] Under this control method, the evaporator is defrosted once every fixed period, and the degree of frost on the evaporator cannot be accurately determined. Therefore, the evaporator may be severely frosted and have affected the cooling effect of the refrigerator, but it has not been defrosted yet. Or the evaporator may be slightly frosted and has not affected the cooling effect of the refrigerator, but it has been defrosted yet. Both will increase the energy consumption of the refrigerator. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a defrost control method, so that defrost is performed at an appropriate time to ensure that the refrigerator has a better heat exchange effect and optimize the energy consumption of the refrigerator.

[0006] The more severe the evaporator frosting, the worse the heat exchange effect, the higher the outlet air temperature of the compartment where the evaporator is located, and the slower the temperature change rate of the compartment. Therefore, the degree of frost on the evaporator can be accurately determined by the change in the outlet air temperature of the compartment where the evaporator is located and the temperature change rate of the compartment where the evaporator is located. Defrosting under appropriate conditions can maintain efficient heat exchange in the refrigerator and improve the refrigerator's energy consumption. As such, the present invention adopts the following technical solutions to solve its technical problems:

[0007] A defrost control method for an air-cooled refrigerator determines whether to defrost the evaporator based on changes in the outlet air temperature T1 of the compartment where the refrigerator evaporator is located and the temperature T2 of the compartment where the evaporator is located in adjacent time periods when the refrigerator compressor is running and the refrigerator door is closed.

[0008] The air outlet temperature T1 and the compartment temperature T2 are both average values ​​of the temperatures in the corresponding time periods.

[0009] According to the change of the outlet air temperature T1 of the compartment where the refrigerator evaporator is located and the temperature T2 of the compartment where the evaporator is located in adjacent time periods, the specific method for determining whether to defrost the evaporator is as follows:

[0010] 1) Frequency increase step

[0011] Calculate the difference ΔT1 between the temperature value T1(N + 1) collected in the (N + 1)-th period and the temperature value T1(N) collected in the N-th period, and the temperature change rate S of the compartment where the evaporator is located from the N-th period to the (N + 1)-th period:

[0012] If ΔT1 is greater than the first preset temperature difference A and S is lower than the first preset temperature change rate S1, then increase the gear of the compressor operating frequency; after the set number of cycles or when the compressor frequency reaches the maximum, proceed to the next step;

[0013] 2) Defrosting step

[0014] If ΔT1 is greater than the second preset temperature difference B and S is lower than the third preset temperature change rate S3, then defrost the refrigerator, where S3 < S1 and B > A.

[0015] In order to adjust the frequency increase speed of the compressor according to specific situations, the present invention optimizes step 1) as follows:

[0016] If ΔT1 is greater than the first preset temperature difference A and S is lower than the first preset temperature change rate S1, then increase the compressor operating frequency by 1 gear; if ΔT1 is greater than the first preset temperature difference A and S is lower than the second preset temperature change rate S2, then increase the compressor operating frequency by 2 gears; S3 < S2 < S1; after the set number of cycles or when the compressor frequency reaches the maximum, proceed to the next step.

[0017] To further eliminate the defrosting false appearance caused by the refrigerator operating at overload, the present invention adds step 1a) between step 1) and step 2): If ΔT1 is greater than the second preset temperature difference B and S is lower than the first preset temperature change rate S1, then increase the gear of the compressor operating frequency; after the set number of cycles or when the compressor frequency reaches the maximum, proceed to the next step.

[0018] As an optimization of step 1a):

[0019] If ΔT1 is greater than the second preset temperature difference B and S is lower than the first preset temperature change rate S1, then increase the compressor operating frequency by 1 gear; if ΔT1 is greater than the second preset temperature difference B and S is lower than the second preset temperature change rate S2, then increase the compressor operating frequency by 2 gears; after the set number of cycles or when the compressor frequency reaches the maximum, proceed to the next step.

[0020] In step 2), defrosting is performed by turning on the defrost heater. Specifically, when the evaporator temperature rises to C, the defrost heater is turned off and defrosting ends; wherein C is greater than B.

[0021] Beneficial effects:

[0022] The more severe the evaporator frosting, the worse the refrigerator's cooling effect, the higher the outlet air temperature, and the slower the compartment temperature change rate. Therefore, the degree of evaporator frosting can be intuitively and accurately determined based on the compartment outlet air temperature and the compartment temperature change. Based on this law, the present invention measures the outlet air temperature T1 of the compartment where the evaporator is located and the compartment temperature T2 of the compartment where the evaporator is located, calculates the outlet air temperature difference ΔT1 and the compartment temperature change rate S between adjacent time periods, and uses this to determine the degree of evaporator frosting and the degree of frosting's impact on the refrigerator's cooling effect. Based on this, defrost control is performed to ensure efficient heat exchange in the refrigerator, thereby improving the refrigerator's energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the refrigerator of the present invention;

[0024] Figure 2 The figure is a flow chart of the defrost control method of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 Schematic diagram of the structure of a refrigerator according to an embodiment of the present invention, which includes a compressor 01, a defrost heater 02, a defrost temperature sensor 03, an air outlet temperature sensor 04 for the compartment where the evaporator is located, and a temperature sensor 05 for the compartment where the evaporator is located.

[0027] The outlet air temperature sensor 04 is used to obtain the compartment outlet air temperature, and the compartment temperature sensor 05 is used to obtain the compartment temperature. The defrost heater 02 is generally placed at the bottom of the evaporator and is used to defrost the evaporator.

[0028] The present invention obtains the compartment outlet air temperature T1 and the compartment temperature T2, calculates the outlet air temperature difference ΔT1 in adjacent time periods, and the compartment temperature change rate S during this period, judges ΔT1 and S, and confirms whether to turn on the defrost heater 02 for defrosting.

[0029] The control of defrosting end is judged by the temperature of the defrosting temperature sensor 03 to avoid the defrosting time being too long and affecting the storage of food in the refrigerator.

[0030] The following combination Figure 2 The defrost control method of the refrigerator is described in detail with reference to the flowchart of FIG.

[0031] The present invention obtains the compartment outlet air temperature T1 and the compartment temperature T2, calculates the outlet air temperature in adjacent time periods to obtain the difference ΔT1, and the compartment temperature change rate S during this period. It should be clear that the temperature difference and the temperature change rate here are both used to calibrate the temperature change, and other methods can also be used for calibration.

[0032] The more severe the evaporator frosting is, the worse the refrigerator's cooling effect will be, that is, the larger the ΔT1 value is, the smaller the S value is.

[0033] This embodiment uses the ΔT1 value and the S value to control the defrost of the refrigerator. The specific method is as follows: Figure 2 As shown:

[0034] Step 1: If ΔT1 is greater than the first preset temperature difference A, and S is less than the first preset temperature change rate S1, the compressor 01 increases the operating frequency by one level. If the compressor is already at the highest frequency, it is maintained;

[0035] If ΔT1 is greater than the first preset temperature difference A, and S is less than the second preset temperature change rate S2, the compressor 01 increases the operating frequency by 2 gears. If the compressor is already at the highest frequency, it is maintained, and S2 is less than S1;

[0036] Step 2: After the first step, continue to judge. If ΔT1 is greater than the second preset temperature difference B, and S is less than the first preset temperature change rate S1, the compressor 01 increases the operating frequency by 1 level. If the compressor is already at the highest frequency, it is maintained. B is greater than A, and A is greater than 0.

[0037] If ΔT1 is greater than the second preset temperature difference B, and S is less than the second preset temperature change rate S2, the compressor 02 increases the operating frequency by 2 levels, and if the compressor is already at the highest frequency, it is maintained;

[0038] Step 3: After the second step, continue to judge, if ΔT1 is greater than the second preset temperature difference B, and S is less than the third preset temperature change rate S3, turn on the defrost heater 02 for defrosting, S3 is less than S2. S3 can be positive, 0 or negative, S3 = 0, that is, the compartment temperature remains unchanged, is a negative value, that is, the compartment temperature rises, specifically set according to actual conditions.

[0039] If the refrigerator compartment door is opened during the operation of the compressor 01, the determination of ΔT1 and S is stopped. After the refrigerator compartment door is closed, the compartment outlet air temperature T1 and the compartment temperature T2 are obtained again, and the ΔT1 and S values ​​are calculated for judgment.

[0040] After the defrost heater 02 is turned on, the temperature of the defrost temperature sensor 03 rises and reaches the preset value C, the defrost heater is turned off, and defrosting ends.

[0041] Depend on Figure 2It can be seen that in this embodiment, the first and second frequency increase determination steps are only cycled once, and other setting methods are not excluded.

[0042] The more serious the evaporator frosting, the worse the refrigerator's cooling effect, the air outlet temperature will rise, and the compartment temperature change rate will slow down. Therefore, based on the compartment air outlet temperature and the compartment temperature change, the degree of frost on the evaporator and the degree of influence of frost on the refrigerator's cooling effect can be judged intuitively and accurately. Based on this, defrost control can ensure that the refrigerator has an efficient heat exchange effect, thereby improving the refrigerator's energy consumption level.

[0043] The first step of the present invention is to appropriately increase the frequency of the compressor when a specific situation occurs, and the second step is to further increase the frequency of the compressor when the situation does not improve, so as to eliminate the defrosting illusion caused by the overload operation of the refrigerator.

[0044] In the first and second steps, the present invention sets two frequency modulation rates respectively, so as to control the frequency increase speed of the compressor according to the actual situation of the refrigerator.

[0045] The settings for thresholds A, B, S1, S2, and S3 in this invention are all related to the size of the cabinet, the insulation performance, the evaporator size, and the fan air volume (which promotes the release of cooling energy from the evaporator). Therefore, it is necessary to conduct testing to determine whether the threshold settings are appropriate. The parameters in this embodiment are as follows: the acquisition time period is 5 minutes, A = 1, B = 2, S1 = 0.4, S2 = 0.15, S3 = -0.1, and C = 8. The applicable refrigerator is a 400L two-door air-cooled refrigerator. The ambient temperature for the threshold confirmation test is 43°C.

Claims

1. A defrost control method for an air-cooled refrigerator, characterized in that: During the operation of the refrigerator compressor and while the refrigerator door is closed, it is determined whether to defrost the evaporator according to the change of the outlet air temperature T1 of the compartment where the refrigerator evaporator is located and the temperature T2 of the compartment where the evaporator is located in adjacent time periods. The specific method is as follows: 1) Frequency increase step Calculate the difference ΔT1 between the temperature value T1(N + 1) collected in the (N + 1)-th period and the temperature value T1(N) collected in the N-th period, and the temperature change rate S of the compartment where the evaporator is located from the N-th period to the (N + 1)-th period: If ΔT1 is greater than the first preset temperature difference A and S is lower than the first preset temperature change rate S1, increase the compressor operating frequency by 1 gear; if ΔT1 is greater than the first preset temperature difference A and S is lower than the second preset temperature change rate S2, increase the compressor operating frequency by 2 gears; After cycling for a set number of times or when the compressor frequency reaches the maximum, proceed to the next step; 2) Defrosting step If ΔT1 is greater than the second preset temperature difference B and S is lower than the third preset temperature change rate S3, defrost the refrigerator; The above S3 < S2 < S1, and B > A.

2. The defrost control method according to claim 1, characterized in that: Between step 1) and step 2), add step 1a): If ΔT1 is greater than the second preset temperature difference B and S is lower than the first preset temperature change rate S1, increase the gear of the compressor operating frequency; after cycling for a set number of times or when the compressor frequency reaches the maximum, proceed to the next step.

3. The defrost control method according to claim 2, characterized in that: Step 1a) is improved as follows:

4. The defrost control method according to claim 3, characterized in that: If ΔT1 is greater than the second preset temperature difference B and S is lower than the first preset temperature change rate S1, increase the compressor operating frequency by 1 gear; if ΔT1 is greater than the second preset temperature difference B and S is lower than the second preset temperature change rate S2, increase the compressor operating frequency by 2 gears; after cycling for a set number of times or when the compressor frequency reaches the maximum, proceed to the next step. In step 2), defrosting is carried out by turning on the defrost heater. Specifically, when the temperature of the evaporator rises to C, turn off the defrost heater and the defrosting ends; where C is greater than B.

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