A heating element, a method of manufacturing the same, a cylindrical heating device, and a hair dryer

Abstract

The present application relates to the field of electronic ceramics manufacturing, in particular to a heating body, a preparation method thereof, a wind tube type heating device and a hair dryer, the heating body comprising a first wire, a second wire and a heat conducting pipe material, an insulating layer being arranged on the outer periphery of the heat conducting pipe material, a heating layer being arranged on the outer periphery of the insulating layer, the heating layer comprising a circuit, a first solder pad connected with the first wire and a second solder pad connected with the second wire, two ends of the circuit being connected with the first solder pad and the second solder pad respectively, and a surface encapsulation being arranged on the outer periphery of the circuit. The heating body is formed by screen printing a very thin thick film heating circuit on the heat conducting pipe material. The design makes the heating layer have very small heat capacity, the temperature rising speed can reach 50-150 DEG C / s, and hot air can be generated in an instant when the device is started. In addition, silver and ruthenium thick film paste is used, the resistance temperature coefficient of which is far superior to that of iron-chromium-aluminum, ensuring stable power at high temperature without significant attenuation, and cooperating with the surface encapsulation, the heating body has excellent corrosion resistance, water vapor resistance and oxidation resistance, and the service life is far longer than that of traditional heating wires.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramics manufacturing, specifically to a heating element and its preparation method, a blower-type heating device, and a hair dryer. Background Technology

[0002] Traditional hair dryers and other hot air devices often use superconducting heating wires made of iron-chromium-aluminum alloys as heating elements. However, these heating wires have revealed many significant defects during long-term use. First, under repeated hot and cold cycles of 600-800℃, the internal grains of the alloy tend to grow and become brittle, leading to breakage during frequent start-ups and shutdowns or vibrations, resulting in a very short lifespan. Simultaneously, the metal softens and creeps at high temperatures, making it prone to sagging and potentially causing short circuits and fires. Second, the alumina protective film on its surface is unstable at excessive temperatures, easily pulverizing and crumbling, producing black and gray debris that affects cleanliness. Furthermore, the heating wires also suffer from a large temperature coefficient of resistance, severe power attenuation, inaccurate temperature control, poor corrosion and moisture resistance, and uneven heating leading to localized hot spots. These defects make it difficult for traditional heating wires to meet the stringent requirements of modern high-speed hair dryers for miniaturization, high efficiency, long lifespan, and precise temperature control. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art by providing a heating element and its preparation method, a blower-type heating device, and a hair dryer. This heating element has the advantages of rapid heating, uniform heating, stable power, long life, and safety and reliability.

[0004] The objective of this invention is achieved through the following technical solution: a heating element, comprising a first wire, a second wire, and a heat-conducting pipe, wherein an insulating layer is provided on the outer periphery of the heat-conducting pipe, and a heating layer is provided outside the insulating layer, wherein the heating layer comprises a circuit, a first pad connected to the first wire, and a second pad connected to the second wire, wherein the two ends of the circuit are respectively connected to the first pad and the second pad, and the circuit is provided with a surface encapsulation.

[0005] Furthermore, the circuit layer is formed by screen printing thick-film circuit silver ruthenium resistor paste.

[0006] Furthermore, the thickness of the circuit layer is 5-20 μm; the thickness of the insulation layer is 80-100 μm.

[0007] Furthermore, the heat-conducting pipe is made of stainless steel.

[0008] In this invention, the heating element is screen-printed onto a heat-conducting tube to form an extremely thin thick-film heating circuit. This design results in a very small heat capacity of the heating layer, achieving a heating rate of 50-150℃ / s, enabling instantaneous hot air output upon power-on. Simultaneously, through a precisely designed resistance pattern, the power density across the entire surface of the heating element can be controlled, ensuring uniform heating and eliminating the localized overheating defects of traditional heating wires. Furthermore, the use of silver and ruthenium-based thick-film pastes, whose resistance temperature coefficient is far superior to that of iron-chromium-aluminum alloys, ensures stable power output at high temperatures without significant attenuation. The overall inorganic material combined with a dense surface encapsulation gives it excellent corrosion resistance, moisture resistance, and oxidation resistance, resulting in a service life far exceeding that of traditional heating wires.

[0009] The present invention also provides a method for preparing a heating element, comprising the following steps: S1. Substrate pretreatment: The heat-conducting pipe is cleaned with degreasing agent and then ultrasonically cleaned with alcohol in sequence. The cleaning time is 20-40 minutes. After cleaning, a cleanliness test is performed. S2. Insulation layer printing: Using curved screen printing technology, the silica insulating coating is uniformly printed on the surface of the heat-conducting pipe. The pipe is then baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 850-900℃ and a holding time of 8-12 minutes. S3. Repeat printing and baking: Repeat step S2 2-3 times to achieve the required thickness of the insulating layer. S4. Circuit Printing and Baking: Using screen printing technology, thick film circuit silver ruthenium resistor paste is printed on the surface of the insulating layer through a patterned screen, and the circuit is electrically connected to the pad. The circuit is baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 850-900℃ and a holding time of 8-12 minutes. S5. Surface encapsulation printing and baking: The surface encapsulation material is evenly printed on the circuit surface using screen printing technology, leaving the solder pad positions uncovered. The surface is then baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 850-900℃ and a holding time of 8-12 minutes. S6. Wire soldering: Solder the wires at the reserved solder pad positions to complete the electrical connection.

[0010] In this invention, the above-mentioned preparation method ensures a dense and high-strength metallurgical bond between the insulation layer, heating circuit layer, and surface encapsulation layer on the curved metal substrate by precisely controlling the printing, drying, and high-temperature sintering processes of each layer. This process not only guarantees the precise thickness of the heating layer and insulation layer, but also enables the final product to possess extremely high insulation withstand voltage, thermal shock resistance, and long-term operational stability, solving problems such as hidden cracks and latent defects that are easily generated in traditional heating wire processing.

[0011] Furthermore, in step S2, the thickness of each silicon dioxide insulating coating print is 25-35 μm.

[0012] The present invention also provides a duct-type heating device, including a tube body, a first support, a first fuse, and a plurality of heating elements. The plurality of heating elements are concentrically spaced within the tube body and are coaxially arranged with the tube body. The lower end of the tube body and the lower ends of the plurality of heat-conducting pipes are both connected to the first support. The upper end of the tube body is provided with a second support, and the top ends of the heat-conducting pipes are connected to the second support. The plurality of first wires are connected in parallel to the first fuse.

[0013] In this invention, by concentrically arranging multiple heating elements at intervals, the airflow can be uniformly heated as it passes through the cylinder, greatly improving the temperature uniformity at the air duct outlet. The axial and circumferential temperature differences of the entire cylinder are minimal (controllable within ±3℃), preventing localized high temperatures from scorching hair or producing a burnt smell. Simultaneously, the multiple heating elements are connected in parallel and monitored by the same fuse; any abnormal overheating of any heating element will trigger the main fuse to blow, achieving overall protection and enhancing safety.

[0014] Furthermore, the number of heating elements is three, namely a first heating element, a second heating element, and a third heating element. The first heating element has the smallest diameter heat-conducting pipe and is located at the center of the pipe. The second heating element is fitted outside the first heating element, the third heating element is fitted outside the second heating element, and the pipe is fitted outside the second heating element. This three-layer concentric nested layout forms an annular airflow gap channel between the heating elements. As the airflow passes through each gap, it simultaneously exchanges heat with the inner and outer walls of adjacent heating elements, increasing the effective heat exchange area per unit volume of airflow. This achieves omnidirectional and efficient heating of the airflow, significantly improving heating uniformity and heat utilization efficiency.

[0015] Furthermore, the power ratio of the first, second, and third heating elements is 4:7:8~10. By setting a gradient power configuration that increases from the inside out, the outer heating element matches the airflow with a higher power to the larger airflow between the outer layers, while the inner heating element matches the airflow with a lower power to the smaller airflow between the inner layers. This ensures that the airflow in each layer receives uniform heat supply, achieving a consistent outlet temperature. At the same time, the low-power design of the inner layers helps reduce the accumulation of heat in the central area, improving the overall heat dissipation performance of the system.

[0016] Furthermore, the duct-type heating device also includes a first vertical rod and a second vertical rod arranged parallel to the first vertical rod. The edge of the second bracket is provided with a first extension and a second extension arranged opposite to each other. The upper end of the first vertical rod is engaged with the first extension, the upper end of the second vertical rod is engaged with the second extension, the lower end of the first vertical rod and the lower end of the second vertical rod are respectively connected to the two ends of the upper part of the first bracket, and the first fuse is provided on the first vertical rod.

[0017] Furthermore, a first conductive sleeve is fitted at the connection between the first bracket and the first vertical rod, and a second conductive sleeve is fitted at the connection between the first bracket and the second vertical rod. A plurality of first wires extend along the side wall of the first bracket toward the first conductive sleeve and are wrapped around the outside of the first conductive sleeve. The first fuse is connected to the first conductive sleeve. The second wires extend along the side wall of the first bracket toward the second conductive sleeve and are wrapped around the outside of the second conductive sleeve. A third wire is provided outward from the second conductive sleeve.

[0018] Furthermore, a third conductive sleeve is fitted into the middle of the first bracket, and a fourth wire is provided at the upper end of the first fuse. The fourth wire extends sequentially along the outer wall of the first vertical rod and the first bracket, wraps around the third conductive sleeve, and then extends outward.

[0019] Furthermore, the duct-type heating device also includes a second fuse and two guide sleeves. The second support includes an outer ring, a central ring, and two opposing crossbars. The central ring is located between the two crossbars. The two opposite ends of the two crossbars pass through the sidewalls of the outer ring and are sleeved with the corresponding guide sleeves. The upper end of the tube body is connected to the lower end of the outer ring. The upper end of the heat-conducting tube located at the center of the tube body is engaged with the central ring. The two ends of the upper parts of multiple heat-conducting tubes away from the center of the tube body are engaged with the two crossbars. Guide sleeves are provided on the two opposite outer sides of the two crossbars. The second fuse is located at the center of the upper end of the central ring. Both ends of the second fuse are provided with fifth wires. The two fifth wires extend along the outer wall of the corresponding crossbars and wrap around the corresponding guide sleeves before extending outwards.

[0020] The present invention also provides a hair dryer, including a blower-type heating device.

[0021] The beneficial effects of this invention are as follows: 1. This invention uses screen printing technology to integrally form heating circuitry on the surface of a heat-conducting tube, allowing for the design of resistance patterns. This enables controllable power density across the entire heating element, eliminating localized hot spots. Multiple heating elements are concentrically spaced within the tube, ensuring uniform heating as airflow passes through. The axial and circumferential temperature differences across the entire tube are minimal (controllable within ±3℃), effectively avoiding the gap temperature differences and localized high temperatures caused by the winding structure of traditional heating wires. This enhances the hair care experience and eliminates the burnt smell.

[0022] 2. The heating circuit of this invention uses a silver- and ruthenium-based thick-film paste, whose temperature coefficient of resistance (TCR) is far superior to that of iron-chromium-aluminum heating wires, resulting in extremely low power drop after high-temperature heating. It eliminates the vibration-induced breakage problem caused by the coarse grains and brittleness of traditional metal heating wires. It provides stable output at a constant temperature over long periods, with high temperature control consistency, and long-term aging attenuation of less than 5%, while traditional iron-chromium-aluminum heating wires can experience power attenuation of over 15% in just six months. This invention effectively solves the problem of power attenuation caused by increasingly weaker hot air output.

[0023] 3. The heating layer of the present invention is only 5-20μm thick, with a small substrate heat capacity and a heating rate of 50-150℃ / s, enabling hot air to be generated instantly upon power-on; it cools down rapidly after power-off, with no residual heat and no sustained high temperature, reducing the risk of dry burning and fire.

[0024] 4. The electrothermal conversion efficiency of this invention is as high as 95%-98%, with heat directly transferred to the airflow through the substrate, resulting in low heat loss and energy savings of 10%-30% compared to traditional wire winding. It also boasts high power density (up to 50W / cm²). 2 With the same power, it is smaller in size and thinner in body, does not require mica frame support, reduces heat insulation layer, has higher air duct space utilization, lower wind resistance, and is perfectly adapted to the compact air duct structure of brushless high-speed hair dryer.

[0025] 5. This invention employs a multi-layered insulation layer combined with stainless steel heat-conducting pipes, with a pressure resistance of ≥1500VAC, extremely high insulation resistance, and negligible leakage current. Made entirely of inorganic materials, it is resistant to corrosion from bathroom moisture and hair oil volatiles, avoiding issues such as mica delamination due to moisture or oxidation of iron, chromium, and aluminum by moisture. With no open flame and no exposed metal heating elements, it is less prone to short circuits and fires when the air duct is blocked, providing greater safety redundancy.

[0026] 6. The preparation method of this invention adopts a process route of printing layer by layer and then baking and sintering each layer at high temperature, ensuring that the insulation layer, heating circuit layer and surface encapsulation layer are densified layer by layer, with high interlayer bonding strength and no microscopic cracks or bubble defects. The curved surface screen printing technology combined with precise baking temperature control ensures uniform thickness and consistent resistance value of each layer, avoiding problems such as dark cracks and hidden defects that are easy to occur in traditional heating wire processing. The product has a high withstand voltage qualification rate and good consistency in batch manufacturing.

[0027] 7. The duct-type heating device of the present invention forms a stable frame through components such as a first support, a second support, and a vertical rod, with multiple heating elements concentrically fixed, providing strong vibration resistance. Multiple heating elements can be conveniently connected in parallel via a first conductive sleeve and a second conductive sleeve, resulting in simple and reliable wiring. Simultaneously, a first fuse (monitoring the temperature of the heating element) and a second fuse (monitoring the temperature of the air outlet) are provided for dual over-temperature protection; any abnormality in either component will result in timely power cut-off, significantly improving safety.

[0028] Figure Labels 1. Heating element; 11. Heat-conducting pipe; 111. Insert; 12. Insulation layer; 13. Circuit; 14. First solder pad; 15. Second solder pad; 14. First conductor; 15. Second conductor; 16. First heating element; 17. Second heating element; 18. Third heating element; 2. Tube body; 3. First support; 31. First conductive sleeve; 32. Second conductive sleeve; 33. Third conductive sleeve; 34. Third slot; 35. Fourth slot; 4. Second support; 41. Central ring; 42. Crossbar; 43. First slot; 44. Second slot; 45. Guide sleeve; 46. Outer ring; 47. First extension; 48. Second extension; 6. First fuse; 61. Fourth conductor; 7. First vertical rod; 8. Second vertical rod; 9. Second fuse; 91. Fifth conductor; 10. Third conductor. Attached Figure Description

[0029] Figure 1 This is a three-dimensional structural diagram of the heating element in Example 1; Figure 2 This is a three-dimensional structural diagram of the air-cooled heating device in Example 2; Figure 3 This is a three-dimensional structural schematic diagram of the air-cooled heating device of Example 2 from another perspective; Figure 4 This is a three-dimensional structural diagram of the first support in Example 2; Figure 5 This is a three-dimensional structural diagram of the second support in Example 2. Detailed Implementation

[0030] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0031] Example 1 like Figure 1 As shown, this embodiment provides a heating element 1, including a first wire 14, a second wire 15, and a heat-conducting pipe 11. The heat-conducting pipe 11 has an insulating layer 12 on its outer periphery. A heating layer is provided outside the insulating layer 12. The heating layer includes a circuit 13, a first pad 14 connected to the first wire 14, and a second pad 15 connected to the second wire 15. The two ends of the circuit 13 are respectively connected to the first pad 14 and the second pad 15. The circuit 13 is covered with a surface encapsulation.

[0032] Furthermore, the 13 layers of the circuit are formed by screen printing of thick-film circuit silver ruthenium resistive paste.

[0033] Furthermore, the thickness of the circuit layer 13 is 13 μm; the thickness of the insulation layer 12 is 90 μm.

[0034] Furthermore, the heat-conducting pipe 11 is a stainless steel pipe.

[0035] This embodiment also provides a method for preparing the heating element 1, including the following steps: S1. Substrate pretreatment: The heat-conducting pipe 11 is sequentially cleaned with degreasing agent and ultrasonically cleaned with alcohol for 30 minutes. After cleaning, a cleanliness test is performed. S2, Insulation layer 12 printing: Using curved screen printing technology, the silica insulating coating is uniformly printed on the surface of the heat-conducting pipe 11, and baked in an air atmosphere using a mesh belt kiln. The peak baking temperature is 880℃ and the holding time is 10min. S3. Repeat printing and baking: Repeat step S2 three times to make the insulating layer 12 reach the required thickness. S4. Printing and baking of line 13: Using screen printing technology, the thick film circuit silver ruthenium resistor paste is printed on the surface of the insulating layer 12 through a patterned screen, and the line 13 is electrically connected to the pad. The circuit is baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10min. S5. Surface encapsulation printing and baking: The surface encapsulation material is evenly printed on the surface of the circuit 13 using screen printing technology, and the pad positions are left uncovered. The surface is baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10min. S6. Wire soldering: Solder the wires at the reserved solder pad positions to complete the electrical connection.

[0036] Furthermore, in step S2, the thickness of each silicon dioxide insulating coating print is 30 μm.

[0037] Example 2 like Figure 2-5As shown, this embodiment also provides a duct-type heating device, including a tube body 2, a first support 3, a first fuse 6, and multiple heating elements 1 as described in Embodiment 1. The multiple heating elements 1 are concentrically spaced within the tube body 2, and are coaxially arranged with the tube body 2. The lower end of the tube body 2 and the lower ends of multiple heat-conducting pipes 11 are both connected to the first support 3. A second support 4 is provided at the upper end of the tube body 2, and the top ends of the heat-conducting pipes 11 are connected to the second support 4. Multiple first wires 14 are connected in parallel to the first fuse 6. The first fuse 6 is connected to an external power source, i.e., the current flow is: power source → first fuse 6 → multiple first wires 14 branching out in parallel at the node → respectively connected to each heating element 1. The first fuse 6 is used to monitor the temperature of the multiple heating elements 1. When the highest temperature of one of the heating elements 1 exceeds a predetermined value, the first fuse 6 melts, and all heating elements 1 are simultaneously de-energized.

[0038] This embodiment, by concentrically arranging multiple heating elements 1 at intervals, ensures uniform heating of the airflow as it passes through the cylinder, significantly improving the temperature uniformity at the air duct outlet. The axial and circumferential temperature differences throughout the cylinder are minimal (controllable within ±3℃), preventing localized high temperatures from scorching hairs or producing a burnt smell. Furthermore, the multiple heating elements 1 are connected in parallel and monitored by the same fuse; any abnormal overheating of any heating element 1 will trigger the main fuse to blow, achieving overall protection and enhanced safety.

[0039] In this embodiment, there are three heating elements 1, namely a first heating element 16, a second heating element 17, and a third heating element 18. The first heating element 16 has the smallest diameter heat-conducting pipe 11 and is located at the center of the pipe body 2. The second heating element 17 is sleeved outside the first heating element 16, the third heating element 18 is sleeved outside the second heating element 17, and the pipe body 2 is sleeved outside the second heating element 17.

[0040] Furthermore, the heating power ratio among the first heating element 16, the second heating element 17, and the third heating element 18 is 4:7:9.

[0041] Furthermore, the duct-type heating device also includes a first vertical rod 7 and a second vertical rod 8 arranged parallel to the first vertical rod 7. The edge of the second support 4 is provided with a first extension 47 and a second extension 48 arranged opposite to each other. The upper end of the first vertical rod 7 is engaged with the first extension 47, and the upper end of the second vertical rod 8 is engaged with the second extension 48. The lower ends of the first vertical rod 7 and the second vertical rod 8 are respectively connected to the two ends of the upper part of the first support 3. The first fuse 6 is provided on the first vertical rod 7. The first vertical rod 7 and the second vertical rod 8, as a supporting frame, together with the first support 3 and the second support 4, form a stable frame structure, providing reliable support for multiple concentrically spaced heating elements 1, ensuring the positional stability and structural integrity of the heating elements 1 under high-speed airflow impact and transportation vibration.

[0042] In this embodiment, the tube body 2, the first vertical rod 7, the second vertical rod 8, the first bracket 3, and the second bracket 4 are all made of mica.

[0043] Furthermore, a first conductive sleeve 31 is fitted at the connection between the first bracket 3 and the first vertical rod 7, and a second conductive sleeve 32 is fitted at the connection between the first bracket 3 and the second vertical rod 8. Multiple first wires 14 extend along the sidewall of the first bracket 3 toward the first conductive sleeve 31 and are wound around the outside of the first conductive sleeve 31. The first fuse 6 is connected to the first conductive sleeve 31. Second wires 15 extend along the sidewall of the first bracket 3 toward the second conductive sleeve 32 and are wound around the outside of the second conductive sleeve 32. A third wire 10 is provided outward from the second conductive sleeve 32. The third wire 10 is connected to the positive or negative terminal of the power supply, thereby forming a conductive circuit to supply power to the heating element 1. In this embodiment, the third wire 10 is formed by winding multiple second wires 15 of the heating element 1 in parallel. The first conductive sleeve 31 and the second conductive sleeve 32 not only serve as structural connectors but also as current collector terminals. Multiple heating elements 1 can be connected in parallel by winding their wires around them, which simplifies the wiring process, improves the reliability of the connection, and effectively prevents the wires from coming loose due to high temperature or vibration.

[0044] Furthermore, a third conductive sleeve 33 is fitted over the middle of the first bracket 3, and a fourth wire 61 is provided at the upper end of the first fuse 6. The fourth wire 61 extends sequentially along the outer wall of the first vertical rod 7 and the first bracket 3, wraps around the third conductive sleeve 33, and then extends outward until it is connected to an external power source. The third conductive sleeve 33 serves as an intermediate conductive node, providing a stable, low-resistance connection point for the fourth wire 61, facilitating reliable connection of the first fuse 6 to an external power source, and optimizing the internal circuit layout of the device.

[0045] Furthermore, the duct-type heating device also includes a second fuse 9 and two guide sleeves 45. The second bracket 4 includes an outer ring 46, a central ring 41, and two opposing crossbars 42. The central ring 41 is located between the two crossbars 42. The two opposite ends of the two crossbars 42 pass through the sidewall of the outer ring 46 and are sleeved with the corresponding guide sleeves 45. The upper end of the tube body 2 is connected to the lower end of the outer ring 46. The upper end of the heat-conducting pipe 11 located at the center of the tube body 2 is snapped with the central ring 41. The two ends of the upper parts of the multiple heat-conducting pipes 11 away from the center of the tube body 2 are snapped with the two crossbars 42. The second fuse 9 is located at the center of the upper end of the central ring 41. Both ends of the second fuse 9 are provided with fifth wires 91. The two fifth wires 91 extend along the outer wall of the corresponding crossbar 42 and wrap around the corresponding guide sleeves 45 before extending outward until they are connected to the positive and negative terminals of the power supply. The second fuse 9 is used to monitor the temperature at the outlet of the tube body 2. When the temperature exceeds a predetermined value, the second fuse 9 will automatically trip, thereby disconnecting the circuit for current flow to the heating element 1 and preventing damage to the heating element 1. The central ring 41 is used to fix the central heating element 1, and the two crossbars 42 are used to fix the outer ring of heating elements 1, together ensuring the concentricity and spacing of the ends of each heating element 1. The second fuse 9, located in the center, is used to monitor the center temperature of the air outlet. When the temperature is abnormal, it will melt, providing double safety protection. The guide sleeve 45 provides a neat routing diameter 13 and fixed support for the fifth wire 91, preventing the wire from shaking or contacting the heating element 1 in the high-temperature airflow, thus improving the safety and reliability of the device.

[0046] In this embodiment, the two crossbars 42 are respectively provided with multiple spaced first slots 43 and second slots 44 along their length. The upper ends of the heat-conducting pipe 11 are respectively provided with inserts 111, which engage with the first slots 43 and second slots 44. The upper ends of the first bracket 3 are respectively provided with multiple spaced third slots 34 and fourth slots 35 along their length. One side of the lower part of the heat-conducting pipe 11 engages with the third slot 34, and the other side engages with the fourth slot 35. By providing slots on the bracket, rapid and precise positioning and engagement of the heating pipe are achieved, simplifying assembly and eliminating the need for additional fasteners, effectively reducing manufacturing costs. Simultaneously, the multi-point engagement structure restricts the radial and axial movement of the heating element 1, enhancing overall vibration resistance.

[0047] Comparative Example 1 Unlike Example 1, this comparative example provides a method for preparing a heating element, comprising the following steps: A1. Substrate pretreatment: The heat-conducting pipes are sequentially cleaned with degreasing agent and ultrasonically cleaned with alcohol for 30 minutes. After cleaning, a cleanliness test is performed. A2. Insulation layer printing: Using curved screen printing technology, the silica insulating coating is uniformly printed on the surface of the heat-conducting pipe and left to stand until it is surface dry. A3. Repeat printing and baking: Repeat step S2 three times to achieve the required thickness of the insulation layer. Bake in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10 minutes. A4. Circuit Printing and Baking: Using screen printing technology, the thick film circuit silver ruthenium resistor paste is printed on the surface of the insulating layer through a patterned screen, and the circuit is electrically connected to the pad. The circuit is baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10min. A5. Surface encapsulation printing and baking: The surface encapsulation material is evenly printed on the circuit surface using screen printing technology, leaving the solder pads uncovered. The surface is then baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10 minutes. A6. Wire soldering: Solder the wires at the reserved solder pad positions to complete the electrical connection.

[0048] Comparative Example 2 Unlike Example 1, this comparative example provides a method for preparing a heating element, comprising the following steps: B1. Substrate pretreatment: The heat-conducting pipes are sequentially cleaned with degreasing agent and ultrasonically cleaned with alcohol for 30 minutes. After cleaning, a cleanliness test is performed. B2. Insulation layer printing: Using curved screen printing technology, the silica insulating coating is uniformly printed on the surface of the heat-conducting pipe. The pipe is then baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10min. B3. Circuit Printing and Baking: Using screen printing technology, the thick film circuit silver ruthenium resistor paste is printed on the surface of the insulating layer through a patterned screen, and the circuit is electrically connected to the pad. The circuit is baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10min. B4. Surface encapsulation printing and baking: The surface encapsulation material is evenly printed on the circuit surface using screen printing technology, leaving the solder pads uncovered. The surface is then baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 880℃ and a holding time of 10 minutes. B5. Wire soldering: Solder the wires at the reserved solder pad positions to complete the electrical connection.

[0049] Furthermore, in step B2, the thickness of the silicon dioxide insulating coating printed is 90 μm.

[0050] Performance testing The heating elements prepared in Example 1 and Comparative Examples 1-2 were subjected to pressure tests, and the results are shown in the table below:

[0051] The withstand voltage test is conducted using a withstand voltage tester with a test voltage of 2500V. The upper limit of leakage current is 1-2mA. The test time is 3 seconds. The results are judged as follows: Pass: No breakdown occurs throughout the test, and the leakage current does not exceed the limit. Fail: The leakage current rises sharply during the test and triggers an alarm, or sparks / smoke appear. The product is considered to have "failed the withstand voltage test".

[0052] The test data above shows that the heating element of Example 1 passed the withstand voltage test, while Comparative Examples 1 and 2 failed. This indicates that the "layer-by-layer printing - high-temperature baking after each printing" process (Example 1) used in this invention is key to ensuring the density and absence of microscopic defects in each layer of the thick film (especially the insulating layer). Comparative Example 1 only achieved surface drying after printing, failing to fully densify the insulating layer after each printing, resulting in poor interlayer bonding and the presence of bubbles or microcracks. Comparative Example 2, due to the single-print thickness of the insulating layer (90μm), was prone to cracking during the drying process due to solvent evaporation and excessive shrinkage stress. These defects all lead to a significant decrease in insulation withstand voltage strength, resulting in breakdown under high-voltage testing. The method of this invention effectively ensures the structural integrity of the insulating and heating layers, thereby ensuring the high insulation safety level and long-term reliability of the product.

[0053] The specific embodiments described above are further illustrations of the technical solution and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A heating element, characterized in that: It includes a first conductor (14), a second conductor (15) and a heat-conducting pipe (11). The heat-conducting pipe (11) has an insulating layer (12) on its outer periphery. The insulating layer (12) has a heating layer on its outer side. The heating layer includes a circuit (13), a first pad (14) connected to the first conductor (14) and a second pad (15) connected to the second conductor (15). The two ends of the circuit (13) are respectively connected to the first pad (14) and the second pad (15). The circuit (13) has a surface encapsulation on its outer side.

2. The heating element according to claim 1, characterized in that: The circuit (13) layer is formed by screen printing of thick film circuit silver ruthenium resistor paste.

3. The heating element according to claim 1, characterized in that: The thickness of the line (13) layer is 5-20 μm; the thickness of the insulation layer (12) is 80-100 μm.

4. A method for preparing a heating element according to claims 1-3, characterized in that: Includes the following steps: S1. Substrate pretreatment: The heat-conducting pipe (11) is cleaned with degreasing agent and ultrasonically cleaned with alcohol in sequence. The cleaning time is 20-40 minutes. After cleaning, the cleanliness is tested. S2, Insulation layer (12) printing: Using curved screen printing technology, the silicon dioxide insulating coating is uniformly printed on the surface of the heat-conducting pipe (11), and baked in an air atmosphere using a mesh belt kiln. The peak baking temperature is 850-900℃, and the heat preservation time is 8-12min. S3. Repeat printing and baking: Repeat step S2 2-3 times to make the insulating layer (12) reach the required thickness; S4. Printing and baking of circuit (13): Using screen printing technology, the thick film circuit silver ruthenium resistor paste is printed on the surface of the insulating layer (12) through a pattern screen, and the circuit (13) is electrically connected to the pad. The circuit is baked in an air atmosphere using a mesh belt kiln with a peak baking temperature of 850-900℃ and a holding time of 8-12min. S5. Surface encapsulation printing and baking: The surface encapsulation material is evenly printed on the surface of the circuit (13) using screen printing technology, and the position of the solder pad is left uncovered. The baking is carried out in an air atmosphere using a mesh belt kiln with a peak baking temperature of 850-900℃ and a holding time of 8-12min. S6. Wire soldering: Solder the wires at the reserved solder pad positions to complete the electrical connection.

5. A duct-type heating device, characterized in that: The device includes a tube body (2), a first support (3), a first fuse (6), and a plurality of heating elements (1) as described in any one of claims 1-3. The plurality of heating elements (1) are concentrically spaced inside the tube body (2) and the heating elements (1) are coaxially arranged with the tube body (2). The lower end of the tube body (2) and the lower ends of the plurality of heat-conducting pipes (11) are both connected to the first support (3). The upper end of the tube body (2) is provided with a second support (4). The top end of the heat-conducting pipes (11) is connected to the second support (4). The plurality of first wires (14) are connected in parallel to the first fuse (6).

6. The duct-type heating device according to claim 5, characterized in that: The number of heating elements (1) is three, namely the first heating element (16), the second heating element (17) and the third heating element (18). The first heating element (16) has the smallest diameter heat-conducting tube (11) and is located at the center of the tube body (2). The second heating element (17) is sleeved outside the first heating element (16), the third heating element (18) is sleeved outside the second heating element (17), and the tube body (2) is sleeved outside the second heating element (17). The heating power ratio between the first heating element (16), the second heating element (17) and the third heating element (18) is 4:7:8~10.

7. The duct-type heating device according to claim 5, characterized in that: It also includes a first vertical rod (7) and a second vertical rod (8) arranged parallel to the first vertical rod (7). The edge of the second bracket (4) is provided with a first extension (47) and a second extension (48) arranged opposite to each other. The upper end of the first vertical rod (7) is engaged with the first extension (47), the upper end of the second vertical rod (8) is engaged with the second extension (48), the lower end of the first vertical rod (7) and the lower end of the second vertical rod (8) are respectively connected to the two ends of the upper part of the first bracket (3), and the first fuse (6) is provided on the first vertical rod (7).

8. The duct-type heating device according to claim 7, characterized in that: A first conductive sleeve (31) is fitted at the connection between the first support (3) and the first vertical rod (7), and a second conductive sleeve (32) is fitted at the connection between the first support (3) and the second vertical rod (8). A plurality of first wires (14) extend along the side wall of the first support (3) toward the first conductive sleeve (31) and are wrapped around the outside of the first conductive sleeve (31). The first fuse (6) is connected to the first conductive sleeve (31). The second wires (15) extend along the side wall of the first support (3) toward the second conductive sleeve (32) and are wrapped around the outside of the second conductive sleeve (32). The second conductive sleeve (32) is provided with a third wire (10) extending outward. A third conductive sleeve (33) is fitted in the middle of the first support (3). A fourth wire (61) is provided at the upper end of the first fuse (6). The fourth wire (61) extends along the outer wall of the first vertical rod (7) and the first support (3) in sequence and is wrapped around the outside of the third conductive sleeve (33) before extending outward.

9. The duct-type heating device according to claim 6, characterized in that: It also includes a second fuse (9) and two guide sleeves (45). The second bracket (4) includes an outer ring (46), a central ring (41), and two opposing crossbars (42). The central ring (41) is located between the two crossbars (42). The two opposite ends of the two crossbars (42) pass through the side wall of the outer ring (46) and are sleeved with the corresponding guide sleeves (45). The upper end of the tube body (2) is connected to the lower end of the outer ring (46) and is located at the center of the tube body (2). The upper end of the heat-conducting pipe (11) is engaged with the central ring (41). The two ends of the upper part of the multiple heat-conducting pipes (11) far away from the center of the pipe body (2) are engaged with two crossbars (42). The second fuse (9) is located at the center of the upper end of the central ring (41). The two ends of the second fuse (9) are provided with fifth wires (91). The two fifth wires (91) extend along the outer wall of the corresponding crossbar (42) and wrap around the corresponding guide sleeve (45) before extending outward.

10. A hair dryer, characterized in that: Includes the duct-type heating device as described in any one of claims 5-9.

Images