An electrical over-temperature magnetic trigger switch based on a heat-sensitive magnetic material

Abstract

This invention discloses an over-temperature magnetic trigger switch for electrical equipment based on a thermosensitive magnetic material, belonging to the field of electrical switch technology. It includes a permanent magnet (1), a magnetic yoke (2), a thermosensitive magnetic material (3), a magnetic gap (4), a normally closed reed switch (5), and a thermal coupling structure (6). The permanent magnet (1) is fixed on the magnetic yoke (2). The thermosensitive magnetic material (3) is disposed above, below, or to the side of the magnetic yoke (2), which serves as the main magnetic circuit, and is located near the sensitive area of ​​the magnetic gap (4). The magnetic gap (4) is formed on the magnetic yoke (2). The normally closed reed switch (5) is disposed within the magnetic field sensitive area formed by the magnetic gap (4). The thermal coupling structure (6) is disposed at the bottom of the magnetic yoke (2) or between the thermosensitive magnetic material (3) and the hot spot of the equipment. The switch of this invention can be structurally integrated, low-cost, and requires no power supply. It can automatically disconnect the normally closed circuit when over-temperature occurs, and its over-temperature threshold is adjustable and calibrable.

Description

Technical Field

[0001] This invention relates to the field of electrical switch technology, and in particular to an over-temperature magnetic trigger switch for electrical equipment based on a thermistor magnetic material. Background Technology

[0002] Existing over-temperature magnetic switches and temperature control protection technologies typically employ a combination of permanent magnets, reed switches, and temperature-sensitive magnetic materials. When the temperature reaches near the Curie point, the magnetic properties of the temperature-sensitive magnetic material undergo a sudden change, causing a weakening or interruption of the magnetic flux in the magnetic circuit. This, in turn, drives the reed switch from a closed to an open state, achieving over-temperature protection. Structurally, these solutions are often presented as independently packaged devices. The temperature-sensitive magnetic material generally acts as a series magnetic element in the main magnetic circuit, directly participating in flux transmission, and changes in its magnetic properties affect the overall state of the magnetic circuit. Examples include Chinese patent applications CN101364499A and CN102394198A.

[0003] However, in practical engineering applications, the aforementioned existing technical solutions still have significant shortcomings. First, since the temperature-sensitive magnetic materials are usually arranged in series in the main magnetic circuit, their demagnetization process causes the magnetic field strength to decrease rapidly in a short period of time. The reed switch action exhibits a clear "abrupt" characteristic, and the magnetic circuit state lacks transitional adjustment space, making it susceptible to the influence of material batch differences, assembly tolerances, and changes in environmental conditions, resulting in a large dispersion in operating temperature. Second, the temperature trigger threshold of existing solutions mainly depends on the Curie temperature of the temperature-sensitive magnetic material itself or the setting of a single magnetic circuit parameter. Once the device structure is determined, the threshold is basically fixed, making it difficult to achieve fine calibration without changing materials or the overall structure, which is not conducive to the engineering adaptation of different devices or different over-temperature levels. Third, since existing magnetic temperature control switches are mostly used in the form of packaged devices, the thermal coupling path between the temperature-sensitive magnetic material and the protected part is relatively indirect, and the thermal response speed and consistency are difficult to guarantee in complex installation environments.

[0004] Therefore, in application scenarios that require accurate response covering multiple different over-temperature threshold ranges (e.g., 60℃~120℃), and demand integrable structure, adjustable threshold, and stable and reliable magnetic reed contact action, existing over-temperature magnetic control switch solutions still have shortcomings in terms of magnetic circuit control methods, threshold engineering design capabilities, and thermal coupling adaptability with the protected equipment. A new technical solution is urgently needed to improve these aspects. Summary of the Invention

[0005] The purpose of this invention is to provide an over-temperature magnetic trigger switch for electrical equipment based on a thermosensitive magnetic material, so as to solve the above-mentioned problems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an over-temperature magnetic trigger switch for electrical equipment based on a thermistor magnetic material, comprising a permanent magnet, a magnetic yoke, a thermistor magnetic material, a magnetic gap, a magnetically controlled trigger element, and a thermal coupling structure, wherein...

[0007] The permanent magnet is fixedly disposed at one end of the magnetic yoke or near the magnetic flux input side of the magnetic gap. The permanent magnet and the magnetic yoke are closely fitted or isolated by non-magnetic pads, with a spacing preferably of 0 to 3 mm, so as to ensure stable magnetic flux injection and facilitate the engineering adjustment of magnetic circuit parameters.

[0008] The thermosensitive magnetic material is disposed above, below, or to the side of the magnetic yoke that serves as the main magnetic circuit, and is located near the magnetic gap sensitive region.

[0009] The magnetic gap is formed on the main magnetic path of the yoke, in the magnetic flux concentration area between the permanent magnet and the magnetically controlled triggering element. Its position is preferably close to the arrangement position of the normally closed magnetic reed switch to enhance the sensitivity of the magnetic field change to the magnetically controlled triggering element. The size of the magnetic gap can be set according to the threshold requirement, and its length is preferably 0.2 to 2.0 mm.

[0010] The magnetically controlled triggering element is disposed within the magnetic field sensitive area formed by the magnetic gap;

[0011] The thermal coupling structure is located at the bottom of the magnetic yoke or between the thermal magnetic material and the hot spot of the device.

[0012] The functions of each of the above components are as follows:

[0013] Permanent magnets: provide a bias magnetic field as a source of magnetomotive force for the magnetic circuit; permanent magnets can be neodymium iron boron or ferrite permanent magnets, etc.

[0014] Magnetic yoke: A magnetically conductive framework, using high-permeability materials (such as low-carbon steel, silicon steel, permalloy, etc.) to form the main magnetic circuit and concentrate magnetism;

[0015] Thermosensitive magnetic material: Temperature-sensitive soft magnetic material, set near the magnetic gap sensitive area, as a magnetic circuit modulator; it can bridge the magnetic conductive parts on both sides of the magnetic gap to form a temperature-sensitive bypass magnetic circuit, or be set near the magnetic gap to form an equivalent structure with temperature-sensitive modulation effect on magnetic flux distribution;

[0016] This invention preferably uses NiCuZn-based thermistor ferrite as the thermistor magnetic material, but is not limited to specific chemical formulations, element ratios, or preparation processes. Without affecting the technical effect of this invention, any thermistor magnetic material that exhibits a significant change in permeability with temperature within the target temperature range, including but not limited to other ferrite systems, magnetic composite materials, or magnetic materials with equivalent temperature magnetic response characteristics, such as NiCuZn, can be used. 0.4 Cu 0.2 Zn0.4 Fe2O4, Ni 0.5 Cu 0.1 Zn 0.4 The Curie temperature of NiCuZn-based thermistor ferrites such as Fe2O4 can be controlled to the range of 60–120℃ by adjusting the composition ratio and sintering process.

[0017] It should be noted that the NiCuZn-based thermistor ferrite is a spinel-structured ferrite material. As is well known in the art, its Curie temperature can be set by the Ni / Cu / Zn ratio, and Tc can be calibrated and fine-tuned in conjunction with the sintering process to ensure that Tc covers or falls within the target temperature range of 60–120°C (e.g., 90°C, DOI: 10.1023 / A:1004671732746). NiZn and NiCuZn are in the same system and have almost identical material properties. Alternatively, doped ferrites or magnetic composite materials can also be used, as long as they exhibit significant permeability changes within the target temperature range. Any material that functions as a temperature-driven flux modulation element in the magnetic circuit can be considered an equivalent alternative to this invention.

[0018] Magnetic gap: Set at a specific position on the magnetic yoke to form a sensitive region with controllable magnetic reluctance; the magnetic gap can be an air gap, a gap in non-magnetic materials, or an equivalent magnetic reluctance region formed by a structural fracture.

[0019] Magnetic trigger element: As a circuit switching device, it is preferably arranged in the slot / hole / cavity of the magnetic yoke and located near the magnetic gap sensitive area, so that the contact can be changed from closed state to open state by the change of magnetic field;

[0020] Thermal coupling structure: This structure enables a stable thermal coupling between the thermistor magnetic material and the magnetic gap region and the hot spot of the protected equipment, thereby improving the consistency and repeatability of temperature response.

[0021] As a preferred technical solution, the thermosensitive magnetic material forms a magnetic coupling with the magnetic yokes on both sides of the magnetic gap, and is fixed by a heat-resistant adhesive, clamping device or structural limiting method.

[0022] More preferably, the thermal magnetic material forms a magnetic coupling with the magnetic yokes on both sides of the magnetic gap by bridging to form a thermally sensitive bypass magnetic circuit, or by forming an equivalent thermally sensitive modulation structure.

[0023] As a preferred technical solution, the magnetic gap is an air gap, a non-magnetic material gap, or an equivalent magnetic reluctance region formed by a structural fracture.

[0024] As a preferred technical solution, the magnetically controlled triggering element is a normally closed reed switch, which is disposed in a pre-made groove, hole or cavity provided in the magnetic yoke, or disposed on the surface of the magnetic yoke and its adjacent area.

[0025] As a preferred technical solution, the thermal coupling structure is a thermally conductive pad, a thermally conductive filler, or a thermally conductive adhesive. The thermally conductive pad can be a silicone thermally conductive pad, a graphite thermally conductive sheet, or a ceramic-filled thermally conductive pad; the thermally conductive filler can be alumina or boron nitride-filled thermally conductive grease; the thermally conductive adhesive can be a single-component or two-component high-temperature resistant thermally conductive silicone or an epoxy thermally conductive adhesive.

[0026] The inventive point of this invention is that, in a magnetic circuit composed of a permanent magnet, a yoke, and a gap, a thermistor magnetic material is arranged near the gap-sensitive region as a magnetic circuit modulator. By utilizing the characteristic that its permeability changes significantly with temperature (usually showing a significant decrease) near the Curie temperature Tc, the equivalent magnetic reluctance and magnetic flux distribution near the gap are changed, so that the normally closed reed switch located near the gap will activate and disconnect when the temperature reaches the threshold, thereby achieving over-temperature protection without the need for an external power supply and control circuit.

[0027] This invention achieves adaptive adjustment of the magnetic flux path by introducing magnetic materials with temperature-dependent permeability at key locations in the magnetic circuit. The switch of this invention is mainly applied in magnetically controlled devices requiring temperature adaptation or over-temperature protection. Temperature changes cause changes in the magnetic properties of the magnetic material, altering the magnetic flux distribution in the magnetic circuit, thereby achieving automatic switching of the magnetic switch's on / off state (including off and optional reset). This switch can be used in electronic equipment, motors, transformers, power devices, power distribution units, and other electrical equipment or functional modules for temperature protection, status control, and safety interlocking. It offers advantages such as requiring no external power supply, relatively simple structure, and high reliability.

[0028] The operating threshold temperature of this invention can be set and calibrated according to the over-temperature protection requirements of electrical equipment (e.g., 60℃–120℃). Preferably, the following two methods can be used in combination:

[0029] A) Material threshold setting: By selecting commercially available or prepared NiCuZn thermistor ferrite with different Curie temperatures Tc as the thermistor magnetic material of the component, a significant change in magnetic permeability is made near the target temperature range, thereby forming an over-temperature action point.

[0030] B) Structural Threshold Calibration: To compensate for batch variations in materials and assembly tolerances, the actuation point can be fine-tuned and calibrated by adjusting the length / section of the magnetic gap, the relative position of the permanent magnet and the magnetic gap sensitive area (including shims), the relative position of the normally closed reed switch within the slot / hole / cavity, and the thickness, coverage area, and magnetic coupling method of the thermistor magnetic material with the yoke. Threshold calibration can be completed at the factory or on-site by replacing or adjusting structural components.

[0031] At the magnetic circuit structure level, the parallel bypass magnetic circuit of this invention is not limited to a specific geometric shape or arrangement direction. The thermistor magnetic material can be disposed above, below, or to the side of the main magnetic circuit, and its bypass magnetic circuit can present a linear, zigzag, or partially embedded structure. As long as both ends of the thermistor magnetic material can form an effective magnetic connection with the key magnetic nodes of the main magnetic circuit, thereby constituting a magnetic flux distribution relationship in parallel with the main magnetic circuit, and can change the magnetic flux distribution state when the temperature changes, it should be considered to fall within the technical concept scope of this invention. The parallel or bypass magnetic flux distribution relationship is the core basis for determining whether it constitutes an equivalent technical solution of this invention.

[0032] At the level of the switching actuator, the normally closed reed switch described in this invention can be replaced with other magnetically controlled triggering elements capable of responding to changes in the magnetic circuit state and thereby changing the electrical conduction state, including but not limited to equivalent magnetically sensitive contact structures or magnetically controlled actuators. As long as the actuator can switch between on and off states according to changes in magnetic field strength or magnetic flux distribution, it should be considered an equivalent implementation of the technical solution of this invention.

[0033] Furthermore, in terms of over-temperature protection applications, this invention can be used to directly cut off the main circuit of the protected circuit, or it can be used as a control signal source to drive external devices such as relays, control modules, or safety interlocking systems. Its specific application does not constitute a limitation on the scope of protection of this invention.

[0034] Compared with the prior art, the innovative points of this invention include:

[0035] (1) Over-temperature triggering mechanism based on parallel bypass magnetic circuit modulation:

[0036] The primary innovation of this invention lies in proposing a parallel bypass magnetic circuit modulation structure, which differs from the traditional series magnetic circuit failure mode. By introducing a magnetic flux bypass made of a thermistor magnetic material outside the main magnetic circuit, temperature changes are primarily manifested as a redistribution of magnetic flux between the main and bypass magnetic circuits, rather than a sudden disappearance of the overall magnetic flux of the main magnetic circuit.

[0037] This design breaks through the single-path approach of existing magnetic temperature control switches where "the entire system demagnetizes when the temperature-sensing material loses its magnetism." It transforms the action of the normally closed reed switch from "triggered by a sudden change in material magnetism" to "triggered by a change in the magnetic circuit distribution," thereby improving the stability and controllability of the over-temperature triggering process from a mechanistic perspective. This parallel magnetic circuit modulation concept should be the core independent claim protected by this invention.

[0038] (2) Functional application of thermistor magnetic materials such as NiCuZn ferrite in parallel magnetic circuits:

[0039] Unlike existing technologies that simply use temperature-sensitive ferrite as a series element in the main magnetic circuit, this invention uses NiCuZn thermistor ferrite as a magnetoresistive modulation unit in a parallel magnetic circuit, so that the characteristic of its permeability changing with temperature directly affects the magnetic flux distribution ratio, rather than directly determining the "on / off" state of the magnetic circuit.

[0040] Through this application method, the NiCuZn thermistor ferrite no longer merely serves the function of determining "whether it has lost magnetism," but participates in the continuous modulation process of the magnetic circuit, making the over-temperature action smoother and significantly reducing the dependence on the limit value of a single material parameter. This innovation, together with the parallel magnetic circuit structure, constitutes the core technical concept combination of this invention.

[0041] (3) Engineering design of over-temperature threshold achieved through the synergy of material parameters and magnetic circuit structure:

[0042] This invention further proposes to achieve engineered control of the over-temperature trigger threshold through the coordinated design of thermistor ferrite material parameters and magnetic circuit geometry. Specifically, without changing the normally closed reed switch and the permanent magnet body structure, by adjusting the Curie temperature range, volume size, effective magnetic flux coupling area, and reluctance ratio of the parallel magnetic circuit of the NiCuZn thermistor ferrite, fine adaptation to multiple different over-temperature threshold ranges (e.g., 60℃–120℃) can be achieved. For example, in one embodiment, the thermistor magnetic material is a NiCuZn-based thermistor ferrite with an effective thickness of 1–3 mm and an effective magnetic flux coupling area of ​​20–50 mm². 2 The ratio of the equivalent magnetic reluctance of the parallel bypass magnetic circuit to the magnetic reluctance of the main magnetic circuit is preferably 0.3 to 1.5. By combining the above parameters, fine adjustment of different over-temperature threshold ranges can be achieved. When the Curie temperature Tc of the selected thermistor magnetic material is slightly lower than the target over-temperature operating temperature (e.g., the target is 90°C), the effect of premature decrease in permeability can be compensated by reducing the magnetic gap length or increasing the coupling strength of the main magnetic circuit, thereby shifting the actual operating temperature of the normally closed reed switch to the target value; for example, the magnetic gap length can be adjusted from 1.0 mm to 0.5 to 0.8 mm.

[0043] This design makes the over-temperature protection threshold no longer entirely dependent on the single physical property parameter of the material itself, but rather the result of multiple parameters jointly determined by "material-structure-magnetic circuit", providing a good engineering foundation for product serialization and deployment in multiple application scenarios.

[0044] (4) Structured arrangement of normally closed reed switches in the magnetic gap region:

[0045] In an embodiment of the present invention, the normally closed reed switch is preferably arranged near the magnetic gap of the main magnetic circuit, and the magnetic field strength change in its location is controlled by a magnetic circuit modulation structure. This arrangement enables the normally closed reed switch to remain highly sensitive to changes in the magnetic circuit state, while avoiding direct participation in the magnetic circuit load, thereby improving its operational reliability and service life.

[0046] (5) Thermal response optimization design of heat conduction path and magnetic circuit structure in coordination:

[0047] This invention introduces a thermally conductive pad or equivalent thermally conductive structure into the magnetic circuit structure, enabling a stable and efficient thermal coupling path between the thermistor and the protected equipment, thereby shortening the thermal response time and improving operational consistency. This design avoids the problem of uncertain heat transfer paths in traditional encapsulated temperature controllers, making over-temperature triggering more closely resemble the actual heat source state.

[0048] (6) Non-encapsulated, structurally integrated over-temperature protection implementation

[0049] Unlike existing magnetic temperature control switches that are primarily based on independently packaged devices, this invention allows the over-temperature magnetic triggering structure to be directly integrated into the internal magnetic or structural components of the protected equipment, achieving a "functionally structured" over-temperature protection solution. This innovation expands the application forms of magnetic temperature control technology, freeing it from being limited to standard device formats.

[0050] Compared with the prior art, the advantages of the present invention are as follows:

[0051] (1) Passive triggering, no power supply or control circuit required

[0052] This invention utilizes temperature-sensitive magnetic changes in materials such as NiCuZn thermistor ferrite as thermistor magnetic material to modulate the magnetic circuit, directly driving a normally closed reed switch to achieve over-temperature disconnection. This eliminates the need for external power supply, temperature sampling, MCU, or drive circuit, reducing the number of components and failure links, and lowering sensitivity to electromagnetic interference.

[0053] (2) Simple structure, easy to modularize and integrate

[0054] The switch of the present invention is composed of a permanent magnet, a magnetic yoke, a magnetic gap, a thermistor magnetic material, and a normally closed reed switch. It can be designed as a planar / sheet or small module, suitable for attachment or embedding near the hot spot area of ​​electrical equipment (winding end, heat sink, housing, power device substrate, etc.). Compared with packaged independent magnetic temperature controllers, it is easier to integrate with the equipment structure and optimize the thermal path.

[0055] (3) Thresholds are settable, adjustable and calibrable

[0056] This invention provides a dual-dimensional threshold implementation method of "material Tc setting + structural parameter calibration": the action point can be set by selecting / preparing NiCuZn thermistor ferrites with different Tc values, and the engineering fine-tuning and calibration can be performed by the magnetic gap size, the relative position of the magnet and the magnetic spring, the geometry of the thermistor ferrite and the magnetic coupling method, etc., to adapt to the over-temperature point requirements of different devices.

[0057] (4) The consistency of movements is more easily controlled and repeatability can be improved through engineering methods.

[0058] Compared with mechanical thermo-actuated components such as bimetallic strips, this invention uses the magnetic properties-temperature relationship of thermistor ferrite as the sensing mechanism. The temperature (Tc) and temperature-sensitive curve can be controlled through material formulation and sintering process. In addition, the magnetic gap sensitive area and assembly calibration methods can be used to improve the dispersion and repeatability of the action. The thermally conductive structure makes the thermal coupling path more designable, which is conducive to improving the consistency of response. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the overall structure of one of the over-temperature magnetic trigger switch structures of the present invention;

[0060] Figure 2 This is a cross-sectional view of another over-temperature magnetic trigger switch structure according to the present invention;

[0061] Figure 3 This is a cross-sectional view of another over-temperature magnetic trigger switch structure according to the present invention;

[0062] Figure 4 This is a schematic diagram of the magnetic circuit / magnetic flux distribution under the condition of no over-temperature.

[0063] Figure 5 This is a schematic diagram of the magnetic circuit / magnetic flux distribution under over-temperature conditions;

[0064] Figure 6 The results are from 20 thermal cycle tests on the prototype.

[0065] Figure 7 The results are from a COMSOL 2000-cycle thermal cycling simulation experiment.

[0066] In the diagram, 1 is a permanent magnet; 2 is a magnetic yoke; 3 is a thermistor magnetic material; 4 is a magnetic gap; 5 is a normally closed reed switch; and 6 is a thermal coupling structure. Detailed Implementation

[0067] To explain the technical content, objectives, and effects of the present invention in detail, the following specific embodiments are provided to further illustrate the content of the present invention. However, the content of the present invention is far more than the following examples.

[0068] Example 1

[0069] An over-temperature magnetic trigger switch for electrical equipment based on a thermistor magnetic material, see [link / reference]. Figures 1 to 3 It includes a permanent magnet 1, a magnetic yoke 2, a thermistor magnetic material 3, a magnetic gap 4, a normally closed reed switch 5, and a thermal coupling structure 6, wherein,

[0070] The permanent magnet 1 is fixedly disposed at one end of the magnetic yoke 2, near the magnetic flux input side of the magnetic gap 4. It is directly attached to the magnetic yoke, or it can be isolated by a non-magnetic pad. The spacing is preferably 0-3mm to ensure stable magnetic flux injection and facilitate threshold fine adjustment.

[0071] The thermosensitive magnetic material 3 is disposed above the magnetic yoke 2, which serves as the main magnetic circuit (e.g., Figure 2 ), below (such as Figure 3 ) or side (such as Figure 1 ), and is located near the magnetic gap sensitive region;

[0072] The magnetic gap 4 is formed on the main magnetic circuit path of the yoke 2, located in the magnetic flux concentration region between the permanent magnet 1 and the normally closed reed switch 5. Its length is preferably 0.2–2.0 mm, and the specific size can be set according to the target operating temperature to form a magnetic field sensitive region with controllable reluctance. In one embodiment, when the target operating temperature is set to approximately 60°C, the length of the magnetic gap 4 can be selected as 0.2–0.5 mm; in another embodiment, when the target operating temperature is set to approximately 90°C, the length of the magnetic gap 4 can be selected as 0.5–1.2 mm; in yet another embodiment, when the target operating temperature is set to approximately 120°C, the length of the magnetic gap 4 can be selected as 1.2–2.0 mm. By selecting the above-mentioned magnetic gap size, the magnetic reluctance and magnetic flux distribution of the magnetic circuit can be adjusted within different target operating temperature ranges, enabling the normally closed reed switch 5 to reliably operate when the permeability of the thermistor magnetic material changes significantly.

[0073] The normally closed reed switch 5 is located within the magnetic field sensitive area formed by the magnetic gap 4;

[0074] The thermal coupling structure 6 is disposed at the bottom of the magnetic yoke 2 (e.g., Figure 1 (or the thermosensitive magnetic material 3 between the hot spot of the equipment.)

[0075] in, Figure 2 One embodiment is shown: the normally closed reed switch 5 is located in the slot / hole of the yoke 2, the magnetic gap 4 is located in the sensitive area, and the thermosensitive magnetic material 3 is arranged near the magnetic gap 4 to form a thermosensitive modulation structure;

[0076] Figure 3Another embodiment is shown: by changing the arrangement position of the thermosensitive magnetic material 3 relative to the magnetic gap 4, that is, located on the bottom side of the yoke 2 or in different directions, equivalent temperature-sensitive magnetic circuit modulation can still be achieved under different installation space conditions. Under different arrangement modes, as long as the thermosensitive magnetic material is located near the magnetic field sensitive area formed by the magnetic gap and maintains an equivalent magnetic coupling relationship, its modulation effect on the magnetic flux distribution remains consistent in the magnetic circuit equivalent model; the above equivalence can be verified through finite element magnetic field simulation or prototype comparison tests.

[0077] Under different arrangement modes, as long as the thermosensitive magnetic material 3 is located near the magnetic field sensitive area formed by the magnetic gap 4 and maintains an effective magnetic coupling relationship with the yokes on both sides of the magnetic gap in the magnetic circuit, its modulation effect on the magnetic circuit reluctance and magnetic flux distribution remains consistent in the magnetic circuit equivalent model. Specifically, in the magnetic circuit equivalent analysis, as long as the position change of the thermosensitive magnetic material 3 does not deviate from the main action area of the magnetic gap magnetic field, it is equivalent to a variable magnetic conductance unit that changes with temperature in the magnetic circuit, and different geometric arrangement modes only correspond to the spatial rearrangement of the magnetic circuit parameters without changing the basic mechanism of temperature-driven magnetic flux modulation. Therefore, under different installation space conditions, by adjusting the relative position relationship between the thermosensitive magnetic material 3 and the magnetic gap 4, an equivalent temperature-sensitive magnetic circuit modulation function can be achieved. The key of the present invention lies in the structural idea of introducing a temperature-sensitive soft magnetic modulation body near the magnetic gap magnetic field sensitive area, rather than limiting its specific geometric installation position. That is, the key of the present invention lies in the structural idea of "temperature-sensitive soft magnetic modulation body near the magnetic gap sensitive area", rather than limiting a specific geometric position.

[0078] Regarding the working principle of the above switch, first in combination with Figure 4 and Figure 5 it will be described.

[0079] The key of the present invention is not the parallel control at the circuit level, but the temperature-sensitive bypass shunt / magnetic reluctance modulation at the magnetic circuit level. Its action logic includes two states: not over-temperature and over-temperature:

[0080] (1) Not over-temperature state (T < Tc, such as Figure 4 )

[0081] The thermosensitive magnetic material 3 is in a high magnetic conductance state and can form an effective magnetic circuit modulation effect near the magnetic gap 4 (such as providing temperature-sensitive bypass / shunt or changing the local magnetic reluctance distribution). The magnetic flux generated by the permanent magnet 1 is conducted in the yoke 2 and forms a magnetic potential drop at the magnetic gap 4; at this time, the thermosensitive magnetic material 3 makes the magnetic flux distribution in the magnetic gap sensitive area in the designed state, so that the effective magnetic field at the normally closed magnetic reed switch 5 is maintained within the range that does not cause its contacts to disconnect, and the normally closed contacts remain closed and conducting. The thermal coupling structure 6 ensures that the temperature of the thermosensitive magnetic material 3 can change synchronously with the temperature rise of the protected object, improving the action consistency.

[0082] (2) Over-temperature state (T ≥ Tc, such as Figure 5 )

[0083] When the temperature T rises to near or above the Curie temperature Tc of the thermistor magnetic material 3, its permeability changes significantly with temperature (usually manifested as a significant decrease). This is equivalent to a weakening of the temperature-sensitive modulation capability of the magnetic gap region or a significant increase in the bypass magnetic reluctance, which in turn causes a change in the magnetic circuit distribution of the sensitive area of ​​the magnetic gap 4. This causes a change in the effective magnetic field at the normally closed reed switch 5 and exceeds its action threshold. The enhancement or weakening of this effective magnetic field depends on the magnetic circuit topology and the arrangement of each magnetic component, thereby causing the normally closed contact to change from the closed state to the open state, achieving over-temperature protection.

[0084] It should be noted that the changes in the aforementioned effective magnetic field can manifest as enhancement or weakening, depending on the polarity of the permanent magnet, the arrangement direction of the normally closed reed switch, the geometry of the magnetic gap, and the magnetic circuit structure. However, the goal is to achieve the over-temperature protection function of the normally closed reed switch transitioning from a closed state to an open state. This invention can be designed for self-recovering disconnection, or it can be latched or delayed for recovery via external circuitry; its main structure is not limited.

[0085] To further verify the stability and reliability of the technical solution of this invention,

[0086] During the prototype verification phase, the solution of this invention can be compared and tested with existing technical solutions.

[0087] The comparison object can be one or more of a bimetallic strip temperature controller, a packaged magnetic temperature controller, or an electronic temperature control solution.

[0088] The comparative test content includes, but is not limited to:

[0089] (1) The average value and dispersion of the action temperature threshold (e.g., standard deviation or range, in °C);

[0090] (2) Changes in operating temperature threshold drift and hysteresis after multiple thermal cycles (e.g., comparison before and after 1000 cycles, in °C).

[0091] In prototype comparison tests or verification experiments, the above-mentioned indicators can be used to evaluate the present invention and existing technical solutions, and to analyze the stability and consistency of the operating temperature under multiple thermal cycles. Such comparative tests help verify the potential of the present invention to improve operating temperature drift and hysteresis under temperature-driven magnetic circuit modulation. Furthermore, indicators such as operating temperature dispersion, response time, and malfunction rate under vibration or shock resistance conditions are also considered.

[0092] During the prototype verification phase, the inventors, through the adoption of, such as Figure 1 The prototype with the structure shown was subjected to 20 thermal cycle tests, and the following analytical results were obtained: Figure 6As shown: Average operating temperature: The average operating temperature of the prototype after 20 thermal cycles is approximately 89.0℃, indicating that the response temperature of the prototype gradually stabilizes during actual operation. Dispersion: By calculating the temperature fluctuation of the prototype during 20 cycles, the standard deviation of the operating temperature is approximately 0.3℃, and the hysteresis range also shows a gradually stabilizing trend. The hysteresis was initially 4.0℃, and after 20 thermal cycles, the hysteresis gradually decreased to 3.0℃, reflecting the convergence and consistency of the system's temperature response.

[0093] To obtain more results on thermal cycling, 2000 thermal cycling experiments were simulated to predict the temperature stability of the prototype during actual use. The simulation results are as follows: Figure 7 As shown, after 2000 thermal cycles, the operating temperature of the material stabilizes at 88.2℃, and the hysteresis gradually decreases from 3.2℃ to 1℃. This indicates that after multiple thermal cycles, the magnetic response of the material gradually stabilizes and the thermal response gradually becomes consistent.

[0094] In some embodiments, performance indicators such as response time and malfunction rate under vibration or shock conditions may be further tested. The above-described tests are only for illustrating the potential technical effects of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0095] The following example, using an approximately 90°C over-temperature disconnection protection structure for the ends of motor windings, illustrates the implementation method of the present invention.

[0096] In one specific embodiment, to address the over-temperature disconnection protection requirement of approximately 90°C at the motor winding end, a NiCuZn thermistor ferrite with a Curie temperature of approximately 85–95°C is selected as the thermistor magnetic material 3. Its thickness can be 1–3 mm (e.g., 2 mm); the magnetic gap length can be 0.2–2.0 mm (e.g., 0.8 mm); and the distance between the permanent magnet and the magnetic gap can be 0–3 mm (e.g., 1 mm). By matching and setting the above parameters, the normally closed reed switch can undergo a state transition near the target threshold, thereby achieving over-temperature protection.

[0097] (1) Threshold determination

[0098] Based on the thermal design requirements of the protected equipment, the over-temperature protection activation temperature is determined to be approximately 90°C.

[0099] (2) Material selection

[0100] A NiCuZn thermistor ferrite with a Curie temperature Tc near the target threshold is selected. The NiCuZn thermistor ferrite can be selected from those with the general formula Ni... x Cu y Zn 1-x-yA spinel-type ferrite material of Fe2O4, where x+y<1, has a Curie temperature that can be controlled to a target range by adjusting the composition ratio and sintering temperature. In one specific embodiment, the thermistor magnetic material can be Ni. 0.4 Cu 0.2 Zn 0.4 Composed of Fe2O4, it was prepared using the existing oxide solid-state method and sintered at 1000–1050℃ for 2–4 h, with a Curie temperature in the range of 85–95℃, and was used as a thermistor magnetic material. When there is a deviation between the material's Tc and the target action point, fine-tuning can be performed subsequently through structural threshold calibration.

[0101] (3) Preparation and processing of magnetic circuit components

[0102] A high-permeability soft magnetic material is selected as the yoke material to process the magnetic yoke 2. The preferred material is electrical pure iron, low-carbon steel, or other low-coercivity soft magnetic alloy, with a relative permeability of approximately 10. 3 -10 4 The yoke is designed to be within a commonly used engineering range to ensure effective magnetic flux conduction within the yoke and reduce the total magnetic reluctance of the magnetic circuit. In one specific embodiment, the overall dimensions of the yoke are determined based on the size of the normally closed reed switch and the requirements of the magnetic circuit layout. Its characteristic dimensions can be in the range of millimeters to centimeters, for example, a length of approximately 15–40 mm and a thickness of approximately 3–10 mm, to meet the requirements of magnetic flux conduction and structural installation. A magnetic gap 4 (which can be an air gap, a non-magnetic gap, or a break, etc.) is formed on the yoke. The magnetic gap 4 is located in the magnetic flux path of the yoke near the normally closed reed switch to form a magnetic field sensitive area. In one specific embodiment, the magnetic gap can be located at the end of the yoke or adjacent to the normally closed reed switch, and its equivalent magnetic gap length is within the commonly used engineering range of approximately 0.1–2 mm to achieve effective adjustment of the magnetic circuit reluctance. The mounting slot of the normally closed reed switch is located in the magnetic field sensitive area near the magnetic gap. In one embodiment, the distance between the central axis of the normally closed reed switch and the center of the magnetic gap is preferably controlled within a few millimeters to ensure that the normally closed reed switch can stably sense changes in the magnetic field at the magnetic gap. Machining the mounting slot / hole / cavity of the normally closed reed switch ensures stable positioning of the normally closed reed switch 5 and reliable connection to external circuit leads. Insulating fasteners or brackets may be necessary to guarantee electrical insulation and vibration resistance.

[0103] (4) Installation of permanent magnets

[0104] A permanent magnet 1 is fixed to a predetermined installation position on the yoke 2 near the magnetic gap, with its magnetic pole direction aligned with the magnetic flux path of the yoke. In one embodiment, the distance between the permanent magnet and the magnetic gap is on the order of millimeters to centimeters, used to form a stable initial magnetic flux distribution. This ensures that the magnetic pole direction and the position of the magnetic gap form the desired magnetic flux distribution. The permanent magnet can be selected from neodymium iron boron or ferrite permanent magnets, depending on environmental temperature, cost, and magnetic stability requirements.

[0105] (5) Installation and circuit connection of normally closed reed switch

[0106] Install the normally closed reed switch 5 in the slot / hole / cavity of the yoke 2, so that it is located in the sensitive area near the magnetic gap 4, and connect its lead wire in series with the protected circuit to form a normally closed circuit (such as a control circuit, relay coil circuit or other circuit that needs to be cut off due to over-temperature).

[0107] (6) Thermistor ferrite mounting and thermal coupling construction

[0108] Thermistor magnetic material 3 is arranged near the magnetic gap sensitive region; specifically, the thermistor magnetic material 3 is arranged near the magnetic yokes on both sides of the magnetic gap 4, forming a magnetic coupling relationship with the magnetic gap. In a specific embodiment, the distance between the thermistor magnetic material and the edge of the magnetic gap can be controlled within the range of approximately 0–3 mm to ensure that its permeability change can effectively modulate the magnetic flux distribution at the magnetic gap. Preferably, it forms a magnetic coupling with the magnetic yokes on both sides of the magnetic gap (which can bridge to form a temperature-sensitive bypass magnetic circuit, or form an equivalent temperature-sensitive modulation structure), and is fixed by a temperature-resistant adhesive, clamping device, or structural limiting method.

[0109] A thermal coupling structure 6, such as a thermally conductive pad / thermally conductive filler / thermally conductive adhesive, is set between the bottom of the magnetic yoke or between the thermally sensitive ferrite and the hot spot of the equipment, and is pressed or attached to the hot spot parts such as the motor housing / winding end / heat sink to obtain a stable heat conduction path;

[0110] (7) Threshold calibration and verification

[0111] By adjusting the size of the magnetic gap 4, the position of the permanent magnet 1 or the thickness of the shim, the position of the normally closed reed switch 5 in the mounting cavity, and the thickness and coverage area of ​​the thermistor magnetic material 3, the operating temperature point is fine-tuned and calibrated. A temperature rise test is then conducted to verify that the normally closed reed switch changes from normally closed to open near the target temperature; and the cooling return behavior is verified (it can be designed as self-recovery, or it can be latched or delayed in conjunction with an external circuit).

[0112] (8) Work process

[0113] At room temperature ( Figure 4 The normally closed reed switch closes, and the circuit is completed; the temperature rises to near or above the threshold. Figure 5 When the temperature changes, the magnetic properties of the thermistor ferrite change, causing a change in the magnetic circuit distribution in the sensitive area of ​​the magnetic gap. This causes the normally closed reed switch to open, cutting off the circuit and achieving over-temperature protection.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An over-temperature magnetic trigger switch for electrical equipment based on a thermistor magnetic material, characterized in that, It includes a permanent magnet (1), a magnetic yoke (2), a thermistor magnetic material (3), a magnetic gap (4), a magnetically controlled triggering element, and a thermal coupling structure (6), among which, The permanent magnet (1) is fixedly disposed at one end of the magnetic yoke (2) or near the magnetic flux input side of the magnetic gap (4), and the permanent magnet (1) and the magnetic yoke (2) are tightly attached to each other or isolated by non-magnetic pads. The thermosensitive magnetic material (3) is disposed above, below or to the side of the magnetic yoke (2) which serves as the main magnetic circuit, and is located near the sensitive area of ​​the magnetic gap (4); The magnetic gap (4) is formed on the main magnetic path of the magnetic yoke (2) in the magnetic flux concentration area between the permanent magnet (1) and the magnetically controlled triggering element, forming a sensitive area of ​​controllable magnetic resistance; The magnetically controlled triggering element is disposed within the magnetic field sensitive area formed by the magnetic gap (4); The thermal coupling structure (6) is disposed at the bottom of the magnetic yoke (2) or between the thermal magnetic material (3) and the hot spot of the device; The thermosensitive magnetic material (3) forms a magnetic coupling with the magnetic yokes on both sides of the magnetic gap (4). The thermosensitive magnetic material (3) forms a magnetic coupling with the magnetic yokes on both sides of the magnetic gap (4) by bridging to form a temperature-sensitive bypass magnetic circuit, or by forming an equivalent temperature-sensitive modulation structure. The thermosensitive magnetic material (3) is a NiCuZn-based thermosensitive ferrite.

2. The electrical equipment over-temperature magnetic trigger switch based on thermistor magnetic material according to claim 1, characterized in that, The permanent magnet (1) is selected from neodymium iron boron or ferrite permanent magnets.

3. The electrical equipment over-temperature magnetic trigger switch based on thermistor magnetic material according to claim 1, characterized in that, The thermosensitive magnetic material (3) and the magnetic yokes on both sides of the magnetic gap (4) are fixed by heat-resistant adhesive, clamps or structural limiting methods.

4. The over-temperature magnetic trigger switch for electrical equipment based on thermistor magnetic material according to claim 1, characterized in that, The magnetic gap (4) is an air gap, a non-magnetic material gap, or an equivalent magnetic resistance region formed by a structural fracture.

5. The over-temperature magnetic trigger switch for electrical equipment based on thermistor magnetic material according to claim 1, characterized in that, The magnetic triggering element is a normally closed reed switch (5), which is set in a prefabricated groove, hole or cavity in the yoke (2), or on the surface of the yoke (2) and its adjacent area.

6. The over-temperature magnetic trigger switch for electrical equipment based on thermistor magnetic material according to claim 1, characterized in that, The thermal coupling structure (6) is a thermally conductive pad, thermally conductive filler, or thermally conductive adhesive.

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