A composite induction heating sensor, its preparation method and application

Abstract

This invention belongs to the field of induction heating materials technology, specifically relating to a composite induction heating sensor and its preparation method. The composite induction heating sensor provided by this invention is obtained by mixing a first sensor material and a second sensor material, followed by sintering. By adjusting and adapting the components and proportions of the two materials, the composite induction heating sensor provided by this invention can obtain sensors with different temperature ranges and Curie temperatures, greatly improving the applicability of the sensor and overcoming the limitations of material selection for the second sensor, which determines the temperature control point of the sensor. The sintering process yields a single-layer composite material, and the overall structure of the sensor has homogeneous material properties. During use, its heating temperature field is uniform, and the formed aerosol is uniform and stable.

Description

Technical Field

[0001] This invention belongs to the field of induction heating materials technology, specifically relating to a composite induction heating sensor, its preparation method, and its application. Background Technology

[0002] Currently, wireless temperature sensors used for induction heating aerosol formation matrix generally employ a single-material stainless steel strip or a double-layer metal sheet sensor. The double-layer metal sheet sensor is prepared by discrete patching or multi-layer bonding of a first sensor material and a second sensor material with different Curie temperatures.

[0003] Using a single material, stainless steel, for temperature control via apparent ohmic resistance has the drawback of low temperature control accuracy. Furthermore, because stainless steel is an iron-based alloy with a very high Curie temperature, using a single-layer stainless steel strip as a sensor only serves to heat and form an aerosol, rather than limiting the maximum temperature based on the material's inherent properties. Therefore, a temperature threshold control program needs to be added to the microcontroller, which complicates the structure of the induction heating device.

[0004] Double-layer or multi-layer metal sheet sensors typically use aluminum, iron, or stainless steel as the first sensor material and nickel or nickel alloys as the second sensor material. The temperature control logic of these two- or three-layer bonded sensors relies on the sensor's resistance-temperature curve showing a minimum resistance value near the Curie temperature of the second sensor material. The change in apparent resistance indicates the sensor temperature, thus achieving temperature control. However, the Curie temperature of the second sensor material determines the temperature control point. The types of materials suitable for the second sensor are limited, and materials whose Curie temperatures precisely match the temperature threshold required for aerosol formation protection are even rarer. Therefore, this temperature control method has limitations in the selection of the second sensor material. Furthermore, sensors fabricated using physical bonding methods can suffer from uneven temperature fields, sensor deformation, and even cracking due to differences in the physical properties of the two sensor materials, thereby affecting the sensor's lifespan. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing double-layer or multi-layer metal sheet sensors, such as the limited material selection of the second sensor that determines the temperature control point of the sensor, and the physical bonding preparation method that may result in uneven temperature field, sensor deformation, or even cracking. Thus, the present invention provides a composite induction heating sensor, its preparation method and application.

[0006] Therefore, the present invention provides the following technical solution:

[0007] The present invention provides a composite induction heating sensor, the raw materials of which include a first sensor material and a second sensor material, which are mixed and sintered to obtain the composite induction heating sensor.

[0008] Optionally, the Curie temperature of the first sensor material is between 400 and 1000°C;

[0009] Optionally, the material of the first sensor is selected from at least one of stainless steel, carbon steel, iron, or iron-based alloys.

[0010] Optionally, the Curie temperature of the second receptor material is between 200 and 400°C.

[0011] Preferably, the temperature is above 380°C.

[0012] Optionally, the second sensor material is selected from at least one of nickel, nickel-based alloys, or Invar alloys.

[0013] Optionally, the mass ratio of the first receptor material to the second receptor material is (3-7):(7-3).

[0014] The present invention also provides a method for preparing the above-mentioned composite inductive heating sensor, characterized by comprising the following steps:

[0015] S1, mix the first sensor material and the second sensor material, and prepare a slurry to obtain a mixed slurry;

[0016] S2, the mixed slurry is cast to obtain a green blank, which is then stacked and subjected to warm isostatic pressing to obtain a blank to be fired;

[0017] S3, remove the binder from the obtained blank and sinter it.

[0018] Optionally, the isostatic pressing treatment is performed at a temperature of 65-85℃ for 0.1-1h and a pressure of 5-45MPa.

[0019] Optionally, the temperature of the degumming treatment is 250-550℃, and the time is 1-10h;

[0020] And / or, the sintering temperature is 1100-1400℃ and the time is 0.5-15h.

[0021] The present invention also provides an application of the above-described composite induction heating sensor or the composite induction heating sensor prepared by the above-described preparation method in the field of magnetic induction heating.

[0022] Specifically, the pulping in step S1 is a conventional pulping process in the art, generally involving mixing metal powder with organic solvents and dispersants, and then ball milling to obtain the pulp. Typically, and not specifically, the pulping step involves uniformly mixing the first receptor material and the second receptor material, adding ethyl acetate, n-butanol, 5% PVB solution, and OP dispersant, and then ball milling the mixture in a ball mill jar to obtain the pulp.

[0023] The composite induction heating sensor provided by this invention can be in the form of a plate, tube, needle, pin, mesh, wire, granule, or cup.

[0024] The composite inductive heating sensor provided by this invention is suitable for inductive heating aerosol forming sensor materials for electronic cigarettes, aerosol forming sensor materials for medical atomization, or other scenarios requiring inductive heating temperature control, such as beauty devices.

[0025] The temperature control logic of the composite induction heating sensor provided by this invention is as follows:

[0026] In the initial heating stage, the sensor is heated, and the electronic controller detects an initial apparent current. As the sensor temperature rises, the magnetoresistance of the sensing metal plate increases, and the electronic controller detects a decrease in the apparent current. When the sensor temperature continues to rise, approaching the Curie temperature of the low Curie temperature point material in the composite induction heating sensor, the low Curie temperature point material begins to gradually demagnetize, leading to a decrease in the total magnetoresistance of the sensor. Therefore, the electronic controller detects a gradual increase in the apparent current, resulting in a minimum current inflection point (I1). During the subsequent heating process, there is a one-to-one correspondence between the apparent current detected by the electronic controller and the sensor temperature. This one-to-one correspondence allows the establishment of a standard curve, enabling wireless temperature control. As the temperature rises further, the low Curie temperature point material in the sensor continues to demagnetize, causing a sharp decrease in its heating efficiency. Simultaneously, the magnetoresistance of the high Curie temperature point material also increases with temperature. The superposition of the temperature-dependent magnetoresistance characteristics of the low and high Curie temperature point materials leads to the appearance of a current inflection point (I2). Currents I1 and I2 are characteristic properties of the heating element. As the current continues to increase, electromagnetic induction heating is dominated by materials with high Curie temperatures. As the heating temperature continues to rise, the current decreases due to the increased magnetic reluctance of the high Curie temperature materials. It is understandable that in the later stages of heating, the high Curie temperature materials heat in the form of a porous framework (a uniform mixture of low and high Curie temperature materials; after the low Curie temperature materials are completely demagnetized, only the high Curie temperature materials remain for heating; removing the low Curie temperature materials can be equivalently viewed as a porous "high Curie temperature material" framework). Its heating efficiency decreases sharply, causing the current to be unable to increase significantly further, and the temperature also corresponds to a maximum temperature, i.e., the maximum threshold temperature, thus achieving temperature control. The composite induction heating sensor provided by this invention can achieve adjustable standard curves and maximum threshold temperatures by controlling the composition and proportion of different sensor materials.

[0027] There are two types of temperature control logic in existing technologies:

[0028] A sensor with a conventional two-layer physical bond structure, comprising a first sensor material and a second sensor material, wherein the resistance-temperature profile of the sensor assembly is measured during preheating from room temperature. Figure 5(Referencing Chinese patent document CN112739229A) The second sensor material has a minimum resistance value within a temperature range of ±5°C near its Curie temperature. This minimum resistance value is used to calibrate a specific temperature point for temperature control. In this sensor, the first sensor material is used for primary heating, while the second sensor material acts as a temperature marker. At its Curie temperature, the magnetic properties of the second sensor change from ferromagnetic or ferrimagnetic to paramagnetic, accompanied by a temporary change in its resistance. By monitoring the corresponding change in the current absorbed by the sensing source, it is possible to detect when the second sensor material reaches its Curie operating temperature, thus indicating when the predetermined operating temperature is reached. However, this temperature control logic can only calibrate the Curie temperature of the second sensor material, limiting its application due to material limitations and the single temperature point; it cannot perform range-based temperature control.

[0029] Another approach uses a single stainless steel sheet as the sensor. During the heating process in the induction heating device, the sensor's temperature has a strictly monotonic relationship with the apparent ohmic resistance determined by the DC supply voltage from the DC power supply and the DC current drawn from the DC power supply. Since each single value of the apparent ohmic resistance represents a unique temperature, this strict monotonic relationship allows the sensor's temperature to be determined solely by the magnitude of the apparent ohmic resistance without contacting the induction heating device. This temperature control logic requires a high degree of precision in controlling the change in the apparent ohmic resistance of the stainless steel sheet relative to temperature. Currently, with common stainless steel sheets, the change in apparent ohmic resistance is often too small for a given temperature range, hindering precise temperature control.

[0030] The technical solution of this invention has the following advantages:

[0031] The composite induction heating sensor provided by this invention is obtained by mixing and sintering a first sensor material and a second sensor material. By adjusting and adapting the components and proportions of the two materials, the composite induction heating sensor provided by this invention can obtain sensors with different temperature control ranges and Curie temperatures, greatly improving the applicability of the sensor and overcoming the limitations of material selection for the second sensor that determines the temperature control point. The resulting sensor has a stable current-temperature linear relationship, and the temperature control of the sensor in magnetic induction heating can be achieved through this new temperature control logic. Simultaneously, the sintering method yields a single-layer composite material, and the overall structure of the sensor has homogeneous material properties, preventing deformation, bending, and cracking during use. Its heating temperature field is uniform, and the formed aerosol is uniform and stable.

[0032] The composite induction heating sensor provided by this invention, by further defining the materials of the first and second sensors, can uniformly and controllably adjust the physical properties of the sensors, such as the coefficient of thermal expansion, strength, toughness, magnetic properties, and electrical properties, according to the application requirements, thereby broadening the application range.

[0033] The method for preparing a composite induction heating sensor provided by the present invention involves uniformly mixing the first sensor material and the metal powder of the second sensor, then preparing a slurry, and finally molding, debinding and sintering the slurry according to the desired sensor shape to obtain the composite induction heating sensor. The preparation process is simple and mature, and the post-processing (such as roll forming) is simple and easy to implement, which greatly reduces the manufacturing cost.

[0034] The composite induction heating sensor provided by this invention exhibits a monotonically stable current-temperature curve within a specific temperature range during magnetic induction heating. During periods of current variation, the corresponding temperature range can serve as the sensor's temperature control range. Furthermore, once the sensor reaches a certain temperature, its temperature will not rise further even with continuous current supply, indicating a maximum protection temperature. By monitoring the heater current, the sensor's temperature can be controlled, achieving the desired temperature regulation. The existence of a one-to-one correspondence between current and temperature during magnetic induction heating allows for zoned temperature control with high precision. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is the current-temperature correlation curve during the electromagnetic induction heating process provided by the sensor in Embodiment 1 of the present invention;

[0037] Figure 2 This is the current-temperature correlation curve during the electromagnetic induction heating process provided by the sensor in Embodiment 2 of the present invention;

[0038] Figure 3 This is the current-temperature correlation curve during the electromagnetic induction heating process provided by the sensor in Embodiment 3 of the present invention;

[0039] Figure 4 This is the current-temperature correlation curve during the electromagnetic induction heating process provided by the sensor in Embodiment 4 of the present invention.

[0040] Figure 5 The resistance-temperature curve is shown in the existing technology for a sensor prepared by conventional physical bonding method, which is heated by electromagnetic induction. Detailed Implementation

[0041] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0042] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0043] Example 1

[0044] This embodiment provides a composite induction heating sensor, the raw material composition of which includes:

[0045] The two components of the sensor are a low Curie temperature material and a high Curie temperature material. The low Curie temperature material is nickel, and the high Curie temperature material is stainless steel. The stainless steel is 400 series stainless steel, and in this embodiment, it is stainless steel 430.

[0046] 1) Mix 50g of nickel and 50g of stainless steel 430 powder, add 30g of ethyl acetate, 20g of n-butanol, 3g of 5% PVB solution and 1g of OP dispersant, put them into a ball mill jar for ball milling, and take them out after ball milling for 3 hours to obtain the slurry;

[0047] 2) A green blank is prepared by tape casting, and the obtained green blank is stacked and then subjected to warm isostatic pressing to obtain a single-layer blank to be fired; wherein, the temperature of the warm isostatic pressing treatment is 75℃, the time is 0.5h, and the pressure is 40MPa.

[0048] 3) Place the above-formed blank into a vacuum furnace for debinding and sintering. The heating rate is 3℃ / min. After heating to 450℃, hold for 60min. Then, heat to 1250℃ at a rate of 5℃ / min and hold for 30min. After holding, cool with the furnace.

[0049] 4) After the above sintered body is taken out of the furnace, it is cut to obtain the desired sensor product.

[0050] The two-component composite induction heating sensor prepared using the above two components and processes exhibits a monotonically stable current-temperature relationship during electromagnetic induction heating (electromagnetic heating frequency 6.78MHz) (e.g. Figure 1 As shown, I1 and I2 are the current inflection points, corresponding to temperatures T1 and T2, respectively. This temperature range (the T1 and T2 temperature ranges corresponding to I1 and I2) during the current abrupt change phase can be used as the control range for the sensor temperature. Furthermore, this composite material sensor has the characteristic of having a maximum heatable temperature, such as... Figure 1 As shown, neither the current nor the temperature continues to increase; this characteristic can serve as a temperature self-protection mechanism in the sensor assembly.

[0051] Example 2

[0052] This embodiment provides a composite induction heating sensor. Compared with Embodiment 1, the difference is that the mass ratio of nickel to stainless steel 430 is 44.5:55.5.

[0053] The current-temperature relationship curve during the electromagnetic induction heating process provided in this embodiment is as follows: Figure 2 As shown.

[0054] Example 3

[0055] This embodiment provides a composite induction heating sensor. Compared with Embodiment 1, the difference is that stainless steel 420 is used instead of stainless steel 430.

[0056] The current-temperature relationship curve during the electromagnetic induction heating process provided in this embodiment is as follows: Figure 3 As shown.

[0057] Example 4

[0058] This embodiment provides a composite induction heating sensor, which differs from Embodiment 1 in that it uses nickel alloy 1J36 instead of nickel.

[0059] The current-temperature relationship curve during the electromagnetic induction heating process provided in this embodiment is as follows: Figure 4 As shown.

[0060] Test case (Test case of Example 2)

[0061] The heating element provided in Embodiment 2 of the present invention was tested, specifically including...

[0062] Step 1: Cut the prepared inductive metal sheet into standard dimensions of 8.6 mm in width and 16 mm in length;

[0063] Step 2: Attach the thermocouple to the standard-sized metal sheet mentioned above. The thermocouple is used for temperature measurement.

[0064] Step 3: Place the induction heating element with the thermocouple attached above inside the center of the electromagnetic induction heating coil, and fix the heating element;

[0065] Step 4: Set the electromagnetic induction heating coil voltage to 7.8V, and set the currents to 2.1, 2.15, 2.2, 2.25 and 2.3A respectively. Read the stable temperature of the thermocouple under different current modes (heat for 60 seconds and test the final stable temperature).

[0066] Step 5: Repeat steps 1-4 to test the 4 heating elements and evaluate their consistency.

[0067] The test results are as follows: For a single heating element, there is a one-to-one correspondence between the current and the temperature of the sensing element; for different heating elements (four heating elements were randomly selected to test the consistency of the heating elements), the consistency of the heating elements is good. Under different currents, the temperature control deviation of different metal sheets is within 3℃. The specific test results are shown in the table below (the temperature control deviation of other embodiments is also within 3℃, and the specific test results are not shown one by one):

[0068] Table 1

[0069]

[0070] As can be seen from the current-temperature correlation curves obtained from the above embodiments, the composite induction heating sensor provided by the present invention can obtain sensors with different temperature control ranges and Curie temperatures by adjusting and adapting the components and proportions of the two materials, which greatly improves the applicability of the sensor and breaks through the limitations of material selection of the second sensor that determines the temperature control point of the sensor.

[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A composite induction heating sensor, characterized in that, The raw materials include: a first sensor material and a second sensor material, which are mixed and sintered to obtain the composite induction heating sensor; the Curie temperature of the first sensor material is between 400-1000℃; the Curie temperature of the second sensor material is between 200-400℃; the mass ratio of the first sensor material to the second sensor material is (3-7):(7-3). The method for preparing the composite induction heating sensor includes the following steps: S1, mix the first sensor material and the second sensor material, and prepare a slurry to obtain a mixed slurry; S2, the mixed slurry is cast to obtain a green blank, which is then stacked and subjected to warm isostatic pressing to obtain a blank to be fired; S3, remove the binder from the obtained blank and sinter it; The isostatic pressing treatment is performed at a temperature of 65-85℃ for 0.1-1h and a pressure of 5-45MPa; the debinding treatment is performed at a temperature of 250-550℃ for 1-10h; and the sintering treatment is performed at a temperature of 1100-1400℃ for 0.5-15h.

2. The composite induction heating sensor according to claim 1, characterized in that, The material of the first sensor is selected from at least one of stainless steel and carbon steel.

3. The composite induction heating sensor according to claim 1, characterized in that, The first sensor material is selected from at least one of iron or iron-based alloys.

4. The composite induction heating sensor according to claim 1, characterized in that, The Curie temperature of the second receptor material is above 380°C.

5. The composite induction heating sensor according to claim 1, characterized in that, The second receptor material is selected from at least one of nickel and nickel-based alloys.

6. The composite induction heating sensor according to claim 1, characterized in that, The second receptor material is selected from Invar alloy.

7. A method for preparing the composite induction heating sensor according to any one of claims 1-6, characterized in that, Includes the following steps: S1, mix the first sensor material and the second sensor material, and prepare a slurry to obtain a mixed slurry; S2, the mixed slurry is cast to obtain a green blank, which is then stacked and subjected to warm isostatic pressing to obtain a blank to be fired; S3, remove the binder from the obtained blank and sinter it; The isostatic pressing treatment is performed at a temperature of 65-85℃ for 0.1-1h and a pressure of 5-45MPa; the debinding treatment is performed at a temperature of 250-550℃ for 1-10h; and the sintering treatment is performed at a temperature of 1100-1400℃ for 0.5-15h.

8. The application of the composite induction heating sensor according to any one of claims 1-6 in the field of magnetic induction heating.

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