Refrigerator, permanent magnet plate for refrigerator, and preparation method for permanent magnet plate

Abstract

Provided in the present application are a refrigerator, a permanent magnet plate for the refrigerator, and a preparation method for the permanent magnet plate. The permanent magnet plate is configured to be arranged in a refrigeration compartment of the refrigerator, so as to generate a magnetic field in the refrigeration compartment. The permanent magnet plate is configured such that the strength attenuation rate of the magnetic field strength generated in the refrigeration compartment under the condition of the refrigeration compartment operating at a lowest temperature is less than or equal to 10%, and thus the difference between a magnetic field strength finally generated by the permanent magnet plate in the refrigeration compartment and an initial magnetic field strength is within an allowable range, thereby preventing failure to achieve an expected magnetic field preservation effect due to an excessive strength attenuation rate of the permanent magnet plate in a low-temperature environment.

Description

Refrigerator, permanent magnet sheet for refrigerator and preparation method of permanent magnet sheet

[0001] The present application is based on and claims priority to Chinese Patent Application No. 202410998900.3, filed on July 24, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of cold storage technology, in particular to a refrigerator, a permanent magnet sheet for a refrigerator and a preparation method of the permanent magnet sheet. BACKGROUND

[0003] As a common household appliance, a refrigerator can store food at low temperature to prolong the storage period of the food. Although the refrigerator prolongs the storage period of the food, the quality of the food inevitably decreases after being stored at low temperature. With continuous research, it is found that a magnetic field has a good auxiliary effect on the low-temperature storage of food, which not only further prolongs the storage period of the food, but also helps to maintain the freshness of the food for a longer storage time. Therefore, the field of refrigerators is actively exploring the introduction of a magnetic field into a refrigerator to achieve low-temperature storage under a magnetic field.

[0004] Any reference in the specification to any prior art does not constitute an admission that the prior art forms part of the common general knowledge in any jurisdiction or is considered relevant by those skilled in the art. SUMMARY

[0005] An object of the present application is to provide a refrigerator capable of realizing magnetic field preservation and improving the effect of magnetic field preservation, a permanent magnet sheet for a refrigerator and a preparation method of the permanent magnet sheet.

[0006] One embodiment of the present application provides a permanent magnet sheet for a refrigerator, wherein the permanent magnet sheet is configured to be arranged in a refrigeration compartment of the refrigerator to generate a magnetic field in the refrigeration compartment; and the permanent magnet sheet is configured to have a strength decay rate of the magnetic field generated in the refrigeration compartment less than or equal to 10% when the refrigeration compartment is operated at a minimum temperature. The strength decay rate is a ratio of a decay magnetic field strength amount of the permanent magnet sheet to an initial magnetic field strength, wherein the decay magnetic field strength amount is an amount of decrease of the permanent magnet sheet compared to the initial magnetic field strength generated in the refrigeration compartment. The initial magnetic field strength is a magnetic field strength generated in the refrigeration compartment when the permanent magnet sheet is first assembled in the refrigeration compartment.

[0007] In one embodiment, the permanent magnet sheet is configured to have a structure size shrinkage rate less than or equal to 0.5% when the refrigeration compartment is operated at a minimum temperature. The structure size shrinkage rate is a ratio of a decreased value of the permanent magnet sheet compared to an initial volume to the initial volume.

[0008] In one embodiment, the surface of the permanent magnet piece has a cured paint layer formed by dipping the shaped permanent magnet piece into a paint tank and curing the paint layer.

[0009] In one embodiment, the thickness of the cured paint layer is greater than or equal to 0.3 mm and less than or equal to 0.7 mm.

[0010] In one embodiment, the permanent magnet piece is a bonded permanent magnet, and the residual magnetic induction of the permanent magnet piece is greater than or equal to 60 mT and less than or equal to 350 mT.

[0011] In one embodiment, the permanent magnet piece has an intrinsic coercivity greater than or equal to 50 kA / m and less than or equal to 350 kA / m.

[0012] In one embodiment, the composition of the permanent magnet piece includes strontium ferrite, and the proportion of strontium ferrite in the total weight of the permanent magnet piece is greater than or equal to 80%.

[0013] In one embodiment, the permanent magnet piece is a sintered permanent magnet, and the residual magnetic induction of the permanent magnet piece is greater than or equal to 200 mT and less than or equal to 490 mT.

[0014] In one embodiment, the permanent magnet piece has an intrinsic coercivity greater than or equal to 200 kA / m and less than or equal to 450 kA / m.

[0015] In one embodiment, the composition of the permanent magnet piece includes ferric oxide and strontium carbonate, wherein the proportion of ferric oxide in the total weight of the permanent magnet piece is greater than or equal to 83% and less than or equal to 86%, and the proportion of strontium carbonate in the total weight of the permanent magnet piece is greater than or equal to 13% and less than or equal to 16%.

[0016] In another aspect of the present application, a method for manufacturing a permanent magnet piece is also provided, which is used to manufacture the permanent magnet piece of any of the above embodiments, and the method comprises:

[0017] The permanent magnet piece shaping process is used to manufacture a permanent magnet piece with a desired size.

[0018] The paint dipping process is used to dip the shaped permanent magnet piece into a paint tank to form a cured paint layer on the surface of the permanent magnet piece.

[0019] The magnetizing process is used to apply a magnetic field to the permanent magnet piece to obtain a magnetic property.

[0020] In one embodiment, the paint dipping process is followed by:

[0021] The polishing process is used to polish the cured paint layer of the permanent magnet piece to make the surface of the cured paint layer of the permanent magnet piece flat, and to make the thickness of the cured paint layer greater than or equal to 0.3 mm and less than or equal to 0.7 mm.

[0022] In another aspect of the present application, a refrigerator is also provided, comprising:

[0023] a cabinet, a refrigeration compartment for storing foodstuff is arranged in the cabinet; and

[0024] at least one permanent magnet piece according to any one of the above embodiments, the permanent magnet piece is arranged in the refrigeration compartment to generate a magnetic field in the refrigeration compartment.

[0025] The permanent magnet piece of the present application is configured to generate a magnetic field in the refrigeration compartment with a strength decay rate of the magnetic field strength generated in the refrigeration compartment being less than or equal to 10% in the case that the refrigeration compartment is operated at the lowest temperature. Wherein, the strength decay rate is the ratio of the decay magnetic field strength of the permanent magnet piece to the initial magnetic field strength, wherein the decay magnetic field strength is the amount of magnetic field strength of the permanent magnet piece 200 reduced compared to the initial magnetic field strength generated in the refrigeration compartment 101. That is, the ratio of the difference between the initial magnetic field strength and the stable magnetic field strength finally reached under the influence of the low-temperature environment of the refrigeration compartment to the initial magnetic field strength is less than or equal to 10%, so that the difference between the magnetic field strength finally generated by the permanent magnet piece in the refrigeration compartment and the initial magnetic field strength is within the allowable range, avoiding the case that the strength decay rate of the permanent magnet piece is too large in the low-temperature environment, which leads to the failure to achieve the expected magnetic field preservation effect. That is, the permanent magnet piece of the present embodiment can more effectively ensure the preservation effect, that is, improve the magnetic field preservation effect.

[0026] The permanent magnet piece of the present application increases the paint dipping step after the permanent magnet piece is formed, that is, the formed permanent magnet piece is put into the paint tank for paint dipping, so that a solidified paint layer is formed on the surface of the permanent magnet piece. In this way, when the permanent magnet piece is in the low-temperature environment of the refrigeration compartment, the paint layer on the surface of the permanent magnet piece can play a protective role for the permanent magnet piece, reducing the influence of the low-temperature environment on the permanent magnet piece, so that the strength decay rate of the magnetic field strength generated in the refrigeration compartment is less than or equal to 10% in the case that the refrigeration compartment is operated at the lowest temperature. At the same time, the solidified paint layer formed by the paint dipping process also helps to make the structure of the permanent magnet piece more stable, so that the structure size shrinkage rate of the permanent magnet piece is less than or equal to 0.5% in the case that the refrigeration compartment is operated at the lowest temperature. Moreover, the cost of the paint dipping process is relatively small.

[0027] The above and other objects, advantages and features of the present application will become more apparent from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.

[0028] The terms "comprise" and variations of the term, such as "comprises" and "comprising," will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements that can be insubstantially non-essential to the subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0029] Some embodiments of the present application will be described in detail with reference to the drawings, wherein like reference numerals refer to like elements throughout the several views. The drawings are in simplified form and are not to precise scale. In the drawings:

[0030] FIG. 1 is a schematic view of a refrigerator according to an embodiment of the present application;

[0031] FIG. 2 is a schematic view of a permanent magnet sheet according to an embodiment of the present application;

[0032] FIG. 3 is a schematic view of a refrigerator according to another embodiment of the present application;

[0033] FIG. 4 is a schematic flowchart of a method of manufacturing a permanent magnet sheet according to an embodiment of the present application;

[0034] FIG. 5 is a schematic flowchart of a method of manufacturing a permanent magnet sheet according to another embodiment of the present application; DETAILED DESCRIPTION

[0035] It should be understood that the embodiments described below are only a few of the embodiments of the present application, and are intended to explain the technical principles of the present application, but not to limit the scope of protection of the present application. Based on the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0036] The flowcharts provided in the embodiments are not intended to indicate that the operations of the methods will be performed in any specific order, or that all of the operations included in the methods will be included in every case. In addition, the methods can include additional operations. Additional changes can be made to the above-described methods within the scope of the technical ideas provided in the embodiments.

[0037] As shown in FIG. 1, in one embodiment, the refrigerator comprises a cabinet 100 and two permanent magnetic sheets 200. The cabinet 100 is configured with a refrigeration compartment 101 for storing foodstuffs. The permanent magnetic sheets 200 are arranged in the refrigeration compartment 101 to generate a magnetic field in the refrigeration compartment 101. The permanent magnetic sheets 200 are configured to have a strength decay rate of the magnetic field strength generated in the refrigeration compartment 101 less than or equal to 10% when the refrigeration compartment 101 is operated at a minimum temperature. The strength decay rate is a ratio of a decayed magnetic field strength amount of the permanent magnetic sheets 200 to an initial magnetic field strength, wherein the decayed magnetic field strength amount is a magnetic field strength amount of the permanent magnetic sheets 200 reduced compared to the initial magnetic field strength generated in the refrigeration compartment 101. The initial magnetic field strength is a magnetic field strength generated in the refrigeration compartment 101 when the permanent magnetic sheets 200 are first assembled in the refrigeration compartment 101, or in other words, a magnetic field strength generated in the refrigeration compartment 101 by the permanent magnetic sheets 200 when the refrigerator is first manufactured.

[0038] Referring to FIG. 1, in one embodiment, the refrigeration compartment 101 is a refrigeration compartment. The refrigerator further comprises a storage container 300. The storage container 300 is placed in the refrigeration compartment 101 for storing foodstuffs. The two permanent magnetic sheets 200 are respectively located at the top side and the bottom side of the storage container 300. The permanent magnetic sheets 200 can generate a magnetic field in the refrigeration compartment 101. The storage container 300 is arranged in the refrigeration compartment 101, that is, the magnetic field generated by the permanent magnetic sheets 200 can act on the foodstuffs when the storage container 300 is placed with foodstuffs, so as to achieve low-temperature storage of the foodstuffs in the magnetic field and improve the freshness of the foodstuffs.

[0039] During the refrigeration of the foodstuffs, the supercooling degree of the foodstuffs can be reduced by applying a magnetic field to the foodstuffs. That is, the foodstuffs can be kept in a non-frozen state at a lower temperature when the magnetic field is applied. In other words, the refrigeration temperature of the foodstuffs can be reduced, thereby further reducing the growth of bacteria and helping to preserve the foodstuffs. During the freezing process, the magnetic field can limit the free path of water molecules, so that the hydrogen bonds in the water molecule clusters are broken. The growth of crystal nuclei in the foodstuffs is inhibited, small ice crystals are generated inside the foodstuffs, and the damage to the cells of the foodstuffs caused by the ice crystals is reduced. Therefore, the present application helps to reduce the loss of juice after thawing of the foodstuffs, thereby reducing the loss of nutrients of the foodstuffs and ensuring the taste of the foodstuffs.

[0040] In addition, the permanent magnet 200 is configured to have a strength decay rate of the magnetic field strength generated in the refrigeration compartment 101 less than or equal to 10% when the refrigeration compartment 101 is operated at the lowest temperature. Here, the strength decay rate is a ratio of a decay magnetic field strength amount of the permanent magnet 200 to an initial magnetic field strength, wherein the decay magnetic field strength amount is an amount of the magnetic field strength generated by the permanent magnet 200 in the refrigeration compartment 101 that is reduced compared to the initial magnetic field strength. In an embodiment, the decay magnetic field strength amount is a difference between the initial magnetic field strength and a final stable magnetic field strength generated by the permanent magnet 200 at the same location in the refrigeration compartment 101, and the ratio of the decay magnetic field strength amount to the initial magnetic field strength is less than or equal to 10%.

[0041] For magnetic field preservation of a refrigerator, a required magnetic field strength needs to be satisfied to achieve an ideal preservation effect.

[0042] However, in the related art, those skilled in the art have not realized that the permanent magnet is in a low-temperature environment in a refrigerator. During use, the permanent magnet is affected by the low temperature, and the magnetic field strength generated by the permanent magnet in the refrigeration compartment is attenuated to a certain extent. That is, although the permanent magnet can initially generate a required magnetic field strength in the refrigeration compartment, the magnetic field strength generated by the permanent magnet decreases after a period of use. The final stable magnetic field strength is lower than the initial magnetic field strength generated by the permanent magnet in the refrigeration compartment at the time of shipment, resulting in a magnetic field preservation effect that does not meet the expected requirements.

[0043] Therefore, in the present application, the permanent magnet 200 is configured to have a strength decay rate of the magnetic field strength generated in the refrigeration compartment 101 less than or equal to 10% when the refrigeration compartment 101 is operated at the lowest temperature. That is, even if the refrigeration compartment 101 where the permanent magnet 200 is located is operated at the lowest temperature from the initial start of refrigeration, the strength decay rate of the magnetic field strength generated by the permanent magnet 200 at the same location in the refrigeration compartment 101 is less than 10%. That is, the ratio of the decay magnetic field strength amount of the permanent magnet 200 to the initial magnetic field strength is less than or equal to 10%, wherein the decay magnetic field strength amount is an amount of the magnetic field strength generated at the same location in the refrigeration compartment 101 that is reduced compared to the initial magnetic field strength.

[0044] For example, the initial magnetic field strength generated by the permanent magnet 200 at a certain location in the refrigeration compartment 101 is 40 Gauss. After a period of use in a low-temperature environment, the magnetic field strength generated by the permanent magnet 200 at the same location in the refrigeration compartment 101 is finally stabilized at 38 Gauss, and the magnetic field strength decay rate is (40 Gauss - 38 Gauss) / 40 Gauss, which is 5%.

[0045] The permanent magnet piece 200 is configured to have a strength attenuation rate of the magnetic field strength generated in the refrigeration compartment 101 less than or equal to 10% when the refrigeration compartment 101 is operated at the lowest temperature. The strength attenuation rate is a ratio of the decay magnetic field strength of the permanent magnet piece 200 to the initial magnetic field strength, where the decay magnetic field strength is a difference between the initial magnetic field strength generated by the permanent magnet piece 200 in the refrigeration compartment 101 and the stable magnetic field strength finally reached by the permanent magnet piece 200 under the influence of the low-temperature environment in the refrigeration compartment 101. In other words, the difference between the initial magnetic field strength and the magnetic field strength finally generated by the permanent magnet piece 200 in the refrigeration compartment 101 is within an allowable range, and the permanent magnet piece 200 does not have an excessively large strength attenuation rate under the low-temperature environment, so that the expected magnetic field preservation effect is achieved. In other words, the permanent magnet piece 200 of the present embodiment can effectively ensure the preservation effect for a longer period of time, that is, improve the magnetic field preservation effect.

[0046] Referring to FIG. 1, in addition, the permanent magnet piece 200 is configured to have a structural size contraction rate less than or equal to 0.5% when the refrigeration compartment 101 is operated at the lowest temperature. The structural size contraction rate is a ratio of the reduced value of the initial volume of the permanent magnet piece 200 to the initial volume.

[0047] The permanent magnet piece is in a low-temperature environment in the refrigerator, and during use, the permanent magnet piece is affected by the low temperature and also undergoes certain shrinkage and deformation. In other words, after a period of use, the final stable volume of the permanent magnet piece decreases compared to the initial volume at the time of factory shipment, and thus the magnetic field strength generated by the permanent magnet piece at the same position in the refrigeration compartment also decreases.

[0048] Therefore, the permanent magnet piece 200 is configured to have a structural size contraction rate less than or equal to 0.5% when the refrigeration compartment 101 is operated at the lowest temperature. In other words, the refrigeration compartment 101 in which the permanent magnet piece 200 is located is operated at the lowest temperature from the initial refrigeration operation, and the structural size contraction rate of the permanent magnet piece 200 is less than or equal to 0.5%. That is, the ratio of the reduced volume value of the initial volume of the permanent magnet piece 200 to the initial volume is less than or equal to 0.5%.

[0049] For example, the initial volume of the permanent magnet piece 200 is 120 cubic centimeters. After a period of use in a low-temperature environment, the permanent magnet piece 200 finally stabilizes at 119.5 cubic centimeters. The structural size contraction rate is (120 cubic centimeters - 119.5 cubic centimeters) / 120 cubic centimeters, that is, the structural size contraction rate is 0.42%.

[0050] By configuring the permanent magnet piece 200 to have a structure size shrinkage rate less than or equal to 0.5% when the refrigeration compartment 101 is operated at the lowest temperature, the structure size shrinkage rate is a ratio of a reduced volume of the permanent magnet piece 200 to an initial volume. That is, the ratio of a difference between the initial volume of the permanent magnet piece 200 and a final volume of the permanent magnet piece 200 reached under the influence of the low-temperature environment of the refrigeration compartment 101 to the initial volume is less than or equal to 0.5%, so that the final volume of the permanent magnet piece 200 is less different from the initial volume. In this way, the magnetic field strength generated at the same position in the refrigeration compartment 101 can be prevented from changing too much due to the excessive structure size shrinkage rate of the permanent magnet piece 200 in the low-temperature environment, thereby ensuring the magnetic field preservation effect of the refrigerator. In addition, it also helps to avoid problems such as cracking of the permanent magnet piece due to excessive structure size shrinkage rate.

[0051] As shown in FIG. 2, the surface of the permanent magnet piece 200 has a cured paint layer 210. The cured paint layer 210 is formed by immersing the shaped permanent magnet piece 200 in a paint tank and then curing. That is, in the production process of the permanent magnet piece 200, after obtaining the shaped permanent magnet piece 200, that is, obtaining the permanent magnet piece 200 with the desired size, the permanent magnet piece 200 is immersed in the paint tank. The surface of the permanent magnet piece 200 forms a cured paint layer. The cured paint layer 210 is wrapped on the surface of the permanent magnet piece 200.

[0052] The permanent magnet piece 200 has a cured paint layer 210. When the permanent magnet piece 200 is in the low-temperature environment of the refrigeration compartment 101, the cured paint layer 210 on the surface of the permanent magnet piece 200 can play a protective role for the permanent magnet piece 200, reducing the influence of the low-temperature environment on the permanent magnet piece 200. Therefore, the strength attenuation rate of the magnetic field strength generated in the refrigeration compartment 101 of the permanent magnet piece 200 is less than or equal to 10% when the refrigeration compartment 101 is operated at the lowest temperature. At the same time, the cured paint layer 210 also helps to make the structure of the permanent magnet piece 200 more stable, so that the structure size shrinkage rate of the permanent magnet piece 200 is less than or equal to 0.5% when the refrigeration compartment 101 is operated at the lowest temperature.

[0053] Referring to FIG. 2, the thickness of the cured paint layer 210 is greater than or equal to 0.3 mm and less than or equal to 0.7 mm. For example, the thickness of the cured paint layer 210 can be 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, or 0.7 mm, etc. The thickness of the cured paint layer 210 is greater than or equal to 0.3 mm and less than or equal to 0.7 mm. On the basis of ensuring the protective effect of the cured paint layer 210, the entire permanent magnet piece 200 is prevented from being too thick, so that the permanent magnet piece 200 can be more flexibly selected in the installation position in the refrigeration compartment 101.

[0054] As shown in FIG. 3, in another embodiment, the refrigerator comprises a cabinet 100 and two permanent magnetic sheets 200. The cabinet 100 is configured with a refrigeration compartment 101 for storing foodstuffs. The permanent magnetic sheets 200 are arranged in the refrigeration compartment 101 to generate a magnetic field in the refrigeration compartment 101. The permanent magnetic sheets 200 are configured to have a strength decay rate of the magnetic field strength generated in the refrigeration compartment 101 less than or equal to 10% when the refrigeration compartment 101 is operated at a minimum temperature. The strength decay rate is a ratio of a decayed magnetic field strength amount of the permanent magnetic sheets 200 to an initial magnetic field strength, wherein the decayed magnetic field strength amount is a magnetic field strength amount of the permanent magnetic sheets 200 reduced compared to the initial magnetic field strength generated in the refrigeration compartment 101. In this embodiment, the refrigeration compartment 101 is a freezing compartment.

[0055] In addition, in this embodiment, the permanent magnetic sheets 200 are configured to have a structural size shrinkage rate less than or equal to 0.5% when the refrigeration compartment 101 is operated at a minimum temperature.

[0056] The technical effects of this embodiment are described above and will not be repeated here.

[0057] It should be noted that the number of refrigeration compartments of the refrigerator can be one, two, or three or more. The functions of the refrigeration compartments can be refrigeration, freezing, or temperature variation, etc. In the case of multiple refrigeration compartments, the multiple refrigeration compartments can be distributed longitudinally or laterally. Those skilled in the art can configure the number, function, and layout of the specific compartments according to the needs.

[0058] It should also be noted that the refrigerator can be provided with a storage container for storing foodstuffs, or the foodstuffs can be placed using a partition plate arranged in the refrigeration compartment, or the foodstuffs can be placed directly using the permanent magnetic sheets.

[0059] In addition, it should be noted that one permanent magnetic sheet can be arranged in one refrigeration compartment, or multiple permanent magnetic sheets can be arranged. In the case of multiple refrigeration compartments, permanent magnetic sheets can be arranged only in some of the refrigeration compartments, or permanent magnetic sheets can be arranged in all of the refrigeration compartments.

[0060] In one embodiment, the permanent magnetic sheets are bonded permanent magnets, and the residual magnetic induction strength of the permanent magnetic sheets is greater than or equal to 60 mT and less than or equal to 350 mT. Thus, the magnetic induction strength at each location in the refrigeration compartment can meet the requirements when used in the refrigeration compartment. In one embodiment, the residual magnetic induction strength of the permanent magnetic sheets is greater than or equal to 240 mT and less than or equal to 270 mT.

[0061] In one embodiment, the intrinsic coercivity of the permanent magnetic sheet is greater than or equal to 50 kiloAmpere per meter and less than or equal to 350 kiloAmpere per meter. In one embodiment, the intrinsic coercivity of the permanent magnetic sheet is greater than or equal to 190 kiloAmpere per meter and less than or equal to 240 kiloAmpere per meter. By having the intrinsic coercivity of the permanent magnetic sheet greater than or equal to 50 kiloAmpere per meter and less than or equal to 350 kiloAmpere per meter, the permanent magnetic sheet is less susceptible to external interference, thereby reducing the strength decay rate of the permanent magnetic sheet in the refrigeration compartment and ensuring that the strength decay rate is less than or equal to 10%.

[0062] In addition, the coercivity of the permanent magnetic sheet is greater than or equal to 50 kiloAmpere per meter and less than or equal to 260 kiloAmpere per meter. In one embodiment, the coercivity of the permanent magnetic sheet is greater than or equal to 150 kiloAmpere per meter and less than or equal to 180 kiloAmpere per meter. The maximum energy product of the permanent magnetic sheet is greater than or equal to 0.8 kiloJoule per cubic meter and less than or equal to 25 kiloJoule per cubic meter. In one embodiment, the maximum energy product is greater than or equal to 11 kiloJoule per cubic meter and less than or equal to 14 kiloJoule per cubic meter.

[0063] The above configuration parameters allow the magnetic induction of the permanent magnetic sheet to meet the magnetic field preservation requirements and to be less susceptible to external interference, thereby reducing the strength decay rate of the permanent magnetic sheet.

[0064] In addition, the permanent magnetic sheet is a bonded permanent magnet. The composition of the permanent magnetic sheet includes strontium ferrite. The proportion of strontium ferrite in the total weight of the permanent magnetic sheet is greater than or equal to 80%, which helps to ensure that the configuration parameters of the bonded permanent magnetic sheet meet the above requirements, thereby ensuring that the strength decay rate of the bonded permanent magnetic sheet is within the allowable range.

[0065] In one embodiment, the permanent magnetic sheet is a sintered permanent magnet. The residual magnetic induction of the permanent magnetic sheet is greater than or equal to 200 milliTesla and less than or equal to 490 milliTesla, thereby ensuring that the magnetic induction at all locations in the refrigeration compartment meets the requirements when the permanent magnetic sheet is used in the refrigeration compartment. In one embodiment, the residual magnetic induction of the permanent magnetic sheet is greater than or equal to 370 milliTesla and less than or equal to 390 milliTesla.

[0066] Further, the intrinsic coercivity of the permanent magnetic sheet is greater than or equal to 200 kiloAmpere per meter and less than or equal to 450 kiloAmpere per meter. In one embodiment, the intrinsic coercivity of the permanent magnetic sheet is greater than or equal to 310 kiloAmpere per meter and less than or equal to 330 kiloAmpere per meter. By having the intrinsic coercivity of the permanent magnetic sheet greater than or equal to 200 kiloAmpere per meter and less than or equal to 450 kiloAmpere per meter, the permanent magnetic sheet is less susceptible to external interference, thereby reducing the strength decay rate of the permanent magnetic sheet in the refrigeration compartment and ensuring that the strength decay rate is less than or equal to 10%.

[0067] In addition, the coercive force of the permanent magnet piece is greater than or equal to 120 kilo-Ampere per meter and less than or equal to 360 kilo-Ampere per meter. In an embodiment, the coercive force of the permanent magnet piece is greater than or equal to 260 kilo-Ampere per meter and less than or equal to 290 kilo-Ampere per meter. The maximum magnetic energy product of the permanent magnet piece is greater than or equal to 6.4 kilo-Joule per cubic meter and less than or equal to 45 kilo-Joule per cubic meter. In an embodiment, the maximum magnetic energy product of the permanent magnet piece is greater than or equal to 25 kilo-Joule per cubic meter and less than or equal to 29 kilo-Joule per cubic meter.

[0068] The above configuration parameters make the magnetic induction intensity of the permanent magnet piece meet the magnetic field preservation requirement and not easily interfered by external interference, thereby reducing the strength decay rate of the permanent magnet piece. It should be noted that because the sintered permanent magnet piece is more likely to decay than the bonded permanent magnet piece, the related parameters need to be higher.

[0069] In addition, the permanent magnet piece is a sintered permanent magnet. The composition of the permanent magnet piece includes ferric sesquioxide and strontium carbonate. The proportion of ferric sesquioxide in the total weight of the permanent magnet piece is greater than or equal to 83% and less than or equal to 86%. The proportion of strontium carbonate in the total weight of the permanent magnet piece is greater than or equal to 13% and less than or equal to 16%. This helps to ensure that the configuration parameters of the sintered permanent magnet piece meet the requirements of the above-mentioned various requirements, thereby ensuring that the strength decay rate of the sintered permanent magnet piece is within the allowable range.

[0070] As shown in FIG. 4, in an embodiment, the preparation method of the permanent magnet piece generally includes:

[0071] Step S401, permanent magnet piece shaping process. Used to make permanent magnet pieces of the required size.

[0072] For the permanent magnet piece being a bonded permanent magnet, this step includes densifying and crushing the raw materials to obtain a material mixture. Then the preliminarily obtained block-shaped material mixture is calendered to obtain a sheet structure of the required thickness. The obtained sheet structure is cut to obtain permanent magnet pieces of the required size of the final product, that is, the shaped permanent magnet pieces.

[0073] For the permanent magnet piece being a sintered permanent magnet, this step includes granulating the raw materials, that is, stirring and mixing the raw materials with auxiliary materials such as binders. The granulating equipment is used to make granules with a certain shape and size. Then the granules are pre-burned to remove the auxiliary agents introduced in the granulation process. Then the pre-burned material is crushed to obtain finer powder particles. The powder particles are oriented and shaped, usually under the action of external force, so that the crystals or magnetic domains in the material are arranged in a specific direction. Then the oriented and shaped powder particles are sintered at high temperature to diffuse and bond between the powder particles, to obtain a preliminary sheet structure. Then the preliminary sheet structure is processed to obtain permanent magnet pieces of the required size of the final product, that is, the shaped permanent magnet pieces.

[0074] Step S402, a varnish dipping process. In one embodiment, the varnish dipping process is to put the shaped permanent magnet piece into a varnish tank to dip the varnish. After the varnish dipping, the permanent magnet piece is taken out and put into a constant temperature oven at 50-200℃ to bake for 3-7h to solidify, that is, put into a constant temperature oven at 50-200℃ to bake for 3-7h, so that the surface of the permanent magnet piece forms a solidified varnish layer. That is, by putting the permanent magnet piece into the varnish tank filled with varnish, the varnish is wrapped on the surface of the permanent magnet piece, and after the varnish is solidified, a solidified varnish layer is formed on the surface of the permanent magnet piece.

[0075] Step S403, a magnetizing process. The magnetizing process is to apply a magnetic field to the permanent magnet piece to make the permanent magnet piece have magnetism. In one embodiment, by applying an external magnetic field to the permanent magnet piece for a certain time, the permanent magnet piece has magnetism, that is, has a residual magnetic induction intensity, so that the permanent magnet piece can generate a magnetic field.

[0076] The permanent magnet piece is a bonded permanent magnet. After the magnetizing process, the residual magnetic induction intensity of the permanent magnet piece is greater than or equal to 60mT and less than or equal to 350mT, so that when the permanent magnet piece is used in a refrigeration compartment, the magnetic induction intensity at each position in the refrigeration compartment can meet the requirements. In one embodiment, the residual magnetic induction intensity of the permanent magnet piece is greater than or equal to 240mT and less than or equal to 270mT.

[0077] In one embodiment, the intrinsic coercive force of the prepared permanent magnet piece is greater than or equal to 50kA / m and less than or equal to 350kA / m. In one embodiment, the intrinsic coercive force of the permanent magnet piece is greater than or equal to 190kA / m and less than or equal to 240kA / m. The coercive force of the permanent magnet piece is greater than or equal to 50kA / m and less than or equal to 260kA / m. In one embodiment, the coercive force of the permanent magnet piece is greater than or equal to 150kA / m and less than or equal to 180kA / m. The maximum magnetic energy product of the permanent magnet piece is greater than or equal to 0.8kJ / cm3 and less than or equal to 25kJ / cm3. In one embodiment, the maximum magnetic energy product of the permanent magnet piece is greater than or equal to 11kJ / cm3 and less than or equal to 14kJ / cm3.

[0078] The permanent magnet piece is a sintered permanent magnet. After the magnetizing process, the residual magnetic induction intensity of the permanent magnet piece is greater than or equal to 200mT and less than or equal to 490mT, so that when the permanent magnet piece is used in a refrigeration compartment, the magnetic induction intensity at each position in the refrigeration compartment can meet the requirements. In one embodiment, the residual magnetic induction intensity of the permanent magnet piece is greater than or equal to 370mT and less than or equal to 390mT.

[0079] In one embodiment, the prepared permanent magnet sheet has an intrinsic coercivity greater than or equal to 200 kA / m and less than or equal to 450 kA / m. In one embodiment, the permanent magnet sheet has an intrinsic coercivity greater than or equal to 310 kA / m and less than or equal to 330 kA / m. The permanent magnet sheet has a coercivity greater than or equal to 120 kA / m and less than or equal to 360 kA / m. In one embodiment, the permanent magnet sheet has a coercivity greater than or equal to 260 kA / m and less than or equal to 290 kA / m. The permanent magnet sheet has a maximum energy product greater than or equal to 6.4 kJ / cm3 and less than or equal to 45 kJ / cm3. In one embodiment, the permanent magnet sheet has a maximum energy product greater than or equal to 25 kJ / cm3 and less than or equal to 29 kJ / cm3.

[0080] By adding a varnish dipping process after the permanent magnet sheet is formed, i.e., by placing the formed permanent magnet sheet into a varnish tank to dip the varnish, a cured varnish layer is formed on the surface of the permanent magnet sheet. In this way, when the permanent magnet sheet is in the low temperature environment of the refrigeration chamber, the varnish layer on the surface of the permanent magnet sheet can protect the permanent magnet sheet, reducing the impact of the low temperature environment on the permanent magnet sheet. Thus, the strength decay rate of the magnetic field strength generated in the refrigeration chamber 101 is less than or equal to 10% when the permanent magnet sheet is operated at the lowest temperature in the refrigeration chamber. At the same time, the cured varnish layer formed by the varnish dipping process also helps to make the structure of the permanent magnet sheet more stable, so that the structural size shrinkage rate is less than or equal to 0.5% when the permanent magnet sheet is operated at the lowest temperature in the refrigeration chamber. Moreover, the cost of the varnish dipping process is relatively small.

[0081] As shown in FIG. 5, in one embodiment, the method for preparing the permanent magnet sheet includes a polishing process after the varnish dipping process. The polishing process polishes the cured varnish layer of the permanent magnet sheet to make the surface of the cured varnish layer flat. And the thickness of the cured varnish layer is greater than or equal to 0.3 mm and less than or equal to 0.7 mm.

[0082] In one embodiment, the method for preparing the permanent magnet sheet generally includes:

[0083] Step S501, permanent magnet sheet shaping process. That is, to obtain a permanent magnet sheet with a desired size.

[0084] Step S502, varnish dipping process. In one embodiment, the varnish dipping process is to place the formed permanent magnet sheet into a varnish tank to dip the varnish, and after the varnish dipping is completed, the permanent magnet sheet is taken out and placed into a constant temperature oven at 50-200°C for baking for 3-7 hours for curing. That is, the permanent magnet sheet is placed into a constant temperature oven at 50-200°C (including 50°C and 200°C) for baking for 3-7 hours (including 3 hours and 7 hours) to form a cured varnish layer on the surface of the permanent magnet sheet. That is, by placing the permanent magnet sheet entirely into a varnish tank containing varnish, the varnish is wrapped around the surface of the permanent magnet sheet, and after the varnish is cured, a cured varnish layer is formed on the surface of the permanent magnet sheet.

[0085] In step S503, a polishing process is performed. The polishing process is to polish the cured paint layer of the permanent magnet piece, so that the surface of the cured paint layer is smoother. In addition, after the polishing process, the thickness of the cured paint layer of the permanent magnet piece is greater than or equal to 0.3 mm and less than or equal to 0.7 mm.

[0086] In step S504, a magnetizing process is performed. The magnetizing process is to apply a magnetic field to the permanent magnet piece, so that the permanent magnet piece has magnetism. In an embodiment, the permanent magnet piece has magnetism, i.e., has a remanence, by applying an external magnetic field to the permanent magnet piece for a certain time, so that the permanent magnet piece can generate a magnetic field.

[0087] By polishing the cured paint layer after the paint dipping process, the surface of the cured paint layer is smoother, which is more conducive to installation in the refrigeration compartment. In addition, the polishing process ensures that the thickness of the cured paint layer of the permanent magnet piece is greater than or equal to 0.3 mm and less than or equal to 0.7 mm. On the basis of ensuring the protection effect of the cured paint layer, the entire permanent magnet piece is not too thick, so that the permanent magnet piece can be more flexibly selected for installation in the refrigeration compartment.

[0088] At this point, those skilled in the art should recognize that, although the present application has been shown and described in detail with respect to several exemplary embodiments, many other variations and modifications can be determined or deduced directly from the disclosure of the present application in accordance with the principles of the present application without departing from the spirit and scope of the present application. Therefore, the scope of the present application should be understood and recognized as covering all such other variations or modifications.

Claims

1. A permanent magnet sheet for a refrigerator, wherein, The permanent magnet piece is configured to have a strength decay rate of the magnetic field generated in the refrigeration compartment less than or equal to 10% when the refrigeration compartment is operated at the lowest temperature.

2. The permanent magnet sheet for a refrigerator according to claim 1, wherein The permanent magnet piece is configured to have a structural size shrinkage rate less than or equal to 0.5% when the refrigeration compartment is operated at the lowest temperature.

3. The permanent magnet sheet for a refrigerator according to claim 2, wherein The surface of the permanent magnet piece has a cured paint layer formed by dipping the shaped permanent magnet piece into a paint tank for paint dipping and then curing.

4. The permanent magnet sheet for a refrigerator according to claim 3, wherein The thickness of the cured paint layer is greater than or equal to 0.3 mm and less than or equal to 0.7 mm.

5. The permanent magnet sheet for a refrigerator according to claim 1, wherein The permanent magnet piece is a bonded permanent magnet, and the residual magnetic induction intensity of the permanent magnet piece is greater than or equal to 60 mT and less than or equal to 350 mT.

6. The permanent magnet sheet for a refrigerator according to claim 5, wherein The intrinsic coercive force of the permanent magnet piece is greater than or equal to 50 kA / m and less than or equal to 350 kA / m.

7. The permanent magnet sheet for a refrigerator according to claim 5, wherein The composition of the permanent magnet piece includes strontium ferrite, and the proportion of the strontium ferrite in the total weight of the permanent magnet piece is greater than or equal to 80%.

8. The permanent magnet sheet for a refrigerator according to claim 1, wherein The permanent magnet piece is a sintered permanent magnet, and the residual magnetic induction intensity of the permanent magnet piece is greater than or equal to 200 mT and less than or equal to 490 mT.

9. The permanent magnet sheet for a refrigerator according to claim 8, wherein The intrinsic coercive force of the permanent magnet piece is greater than or equal to 200 kA / m and less than or equal to 450 kA / m. 10.The permanent magnet sheet for a refrigerator according to claim 8, wherein The composition of the permanent magnet piece includes ferric oxide and strontium carbonate, wherein the proportion of the ferric oxide in the total weight of the permanent magnet piece is greater than or equal to 83% and less than or equal to 86%, and the proportion of the strontium carbonate in the total weight of the permanent magnet piece is greater than or equal to 13% and less than or equal to 16%.

11. A preparation method of a permanent magnet piece for producing the permanent magnet piece according to any one of claims 1 to 10, the preparation method comprising: a permanent magnet piece shaping process for producing a permanent magnet piece with a desired size; a paint dipping process for dipping the shaped permanent magnet piece into a paint tank for paint dipping to form a cured paint layer on the surface of the permanent magnet piece; a magnetization process for applying a magnetic field to the permanent magnet piece to make the permanent magnet piece have magnetism.

12. The preparation method of the permanent magnet piece according to claim 11, the paint dipping process further comprising: a polishing process for polishing the cured paint layer of the permanent magnet piece to make the surface of the cured paint layer of the permanent magnet piece flat and to make the thickness of the cured paint layer greater than or equal to 0.3 mm and less than or equal to 0.7 mm.

13. A refrigerator comprising: a cabinet in which a refrigeration compartment for storing food is arranged; and at least one permanent magnet piece according to any one of claims 1 to 10 arranged in the refrigeration compartment to generate a magnetic field in the refrigeration compartment.

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