Magnetic steel coating protection structure of permanent magnet motor speed sensor

Abstract

The invention discloses a magnetic steel coating protection structure of a permanent magnet motor speed sensor, belongs to the technical field of permanent magnet motor accessory protection, and aims at solving the problems that an existing magnetic steel protection coating is weak in binding force, poor in corrosion resistance and mechanical protection performance, lack of corner protection and poor in protection performance. The magnetic steel is easy to corrode and damage; and the detection precision of the speed sensor is reduced. The protection structure comprises a magnetic steel substrate, a transition bonding layer, a main protection layer and a surface protection layer are sequentially arranged on the surface of the magnetic steel substrate, corner strengthening protection layers are arranged at corners, and the four layers jointly form a complete protection system. And the transition bonding layer is a titanium-chromium alloy layer. All-directional long-acting protection of the magnetic steel is achieved, interlayer binding force, corrosion resistance and mechanical performance are remarkably improved, magnetic flux attenuation of the magnetic steel is avoided, the service life of the magnetic steel and the speed sensor is prolonged, the speed detection precision is guaranteed, and the method is suitable for various permanent magnet motor speed sensors and particularly suitable for severe working conditions.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motor accessory protection technology, and more specifically, to a magnetic steel coating protection structure for a permanent magnet motor speed sensor. Background Technology

[0002] Permanent magnet motors, with their advantages of high efficiency, energy saving, high power density, and fast response speed, are widely used in new energy vehicles, industrial automation, rail transportation, aerospace, and other fields. As a core component of the permanent magnet motor control system, the speed sensor's detection accuracy directly determines the motor's operational stability and control precision. The magnet is the core element for speed sensor to achieve speed detection, and its magnetic stability and structural integrity are crucial.

[0003] Currently, the magnets used in permanent magnet motor speed sensors are mostly neodymium iron boron magnets. Although these magnets possess excellent magnetic properties, they are chemically reactive. In particular, the iron component in the magnet is highly susceptible to oxidation and corrosion in the presence of oxygen and moisture, leading to rust, pulverization, and even cracking. This results in a decrease in magnetic flux and a decline in magnetic performance, ultimately affecting the detection accuracy of the speed sensor. In severe cases, it can cause sensor failure and motor malfunction. Furthermore, permanent magnet motors generate vibration and friction during operation, and in some applications, the magnets may come into contact with dust, oil, corrosive gases, and other impurities, further accelerating wear and corrosion and shortening their lifespan.

[0004] To address the aforementioned issues, existing technologies typically involve applying a protective coating to the surface of the magnet. Commonly used coating types include nickel-copper-nickel multilayer coatings, zinc coatings, and epoxy coatings. Among them, the nickel-copper-nickel three-layer plating is a widely used traditional protection solution. It forms a three-layer metal structure through electrolytic plating, achieving preliminary corrosion and mechanical protection. However, this solution has obvious defects: First, the bonding force between the plating and the magnet substrate is limited. Under long-term vibration of the motor, the plating is prone to peeling and cracking, leading to protection failure. Second, the salt spray and damp heat resistance of traditional plating is limited. In harsh corrosive environments, the salt spray test time is usually short, which cannot meet the long-term protection requirements. Third, the surface smoothness of the plating is insufficient, making it easy to attract dust and oil, and its wear resistance is poor. After long-term friction, the plating is easily damaged, thus losing its protective function. Fourth, the traditional plating structure is simple and does not strengthen the protection of vulnerable and corroded parts such as the edges and corners of the magnet. These parts often become weak points in the protection, and corrosion and damage occur first, eventually leading to the failure of the entire magnet.

[0005] In addition, some existing technologies use a single metal plating or epoxy coating. Although the single metal plating has good mechanical properties, its corrosion resistance is limited and it is prone to pinhole defects, so it cannot achieve all-round protection. Although the epoxy coating has strong corrosion resistance, it is brittle and has poor impact resistance. It is prone to cracking and peeling under the vibration and friction of motors, resulting in insufficient protection reliability.

[0006] Therefore, it is necessary to develop a protective structure for the magnetic steel coating of a permanent magnet motor speed sensor. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of existing permanent magnet motor speed sensor magnetic steel protective coatings, such as weak bonding force, easy peeling and cracking, insufficient corrosion resistance and mechanical protection performance, and lack of protection for weak parts. The invention provides a magnetic steel coating protective structure for permanent magnet motor speed sensors, which achieves all-round and long-term protection for the magnetic steel, ensures the stability of the magnetic properties of the magnetic steel, extends the service life of the magnetic steel and the speed sensor, and ensures the accuracy of speed detection.

[0008] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution. A protective structure for a permanent magnet motor speed sensor with a magnetic steel coating includes a magnetic steel substrate. A transition bonding layer, a main protective layer, and a surface protective layer are sequentially provided on the surface of the magnetic steel substrate. An edge and corner reinforcement protective layer is provided at the corners of the magnetic steel substrate. The transition bonding layer, the main protective layer, the surface protective layer, and the edge and corner reinforcement protective layer together constitute a complete protective system, achieving all-round protection for the magnetic steel substrate. The transition bonding layer is a titanium-chromium alloy layer with a thickness of 0.5-2 μm. The transition bonding layer is prepared by ion sputtering and has a uniformly distributed micro-pit structure on its surface. The diameter of the micro-pit structure is 50-200 nm and the depth is 20-80 nm. It is used to increase the contact area between the transition bonding layer and the main protective layer and improve the interlayer bonding force. The main protective layer is an amorphous aluminum-manganese alloy layer with a thickness of 3-8 μm. It is prepared using an ionic liquid electroplating process and is doped with nano-zirconia particles. These nano-zirconia particles have a particle size of 30-100 nm and a doping amount of 2-5% of the total mass of the main protective layer. The nano-zirconia particles are uniformly dispersed within the amorphous aluminum-manganese alloy matrix to enhance the hardness, wear resistance, and corrosion resistance of the main protective layer. The corrosion potential of the main protective layer is lower than that of the magnetic steel substrate and the transition bonding layer, thus providing sacrificial anode protection to the magnetic steel substrate and further improving the corrosion resistance. The surface protective layer is a fluorocarbon coating with a thickness of 0.8-2μm. The surface protective layer is prepared by spraying process and has a smooth hydrophobic structure with a water contact angle ≥110°. It is used to isolate moisture, dust and oil, prevent impurities from adhering, and at the same time improve the weather resistance and anti-fouling properties of the protective structure. The corner reinforcement protective layer is a nickel-tungsten alloy layer with a thickness of 2-5μm. The corner reinforcement protective layer wraps around the corners of the magnet substrate, and its two ends extend to the transition bonding layer and the surface protective layer, respectively. It is tightly bonded to the transition bonding layer, the main protective layer, and the surface protective layer to enhance the protective performance of the corners of the magnet substrate and prevent the coating from being damaged and corroded due to stress concentration, friction and collision. Before the preparation of the transition bonding layer, the surface of the magnetic steel substrate undergoes a pretreatment process, which includes sequential steps of degreasing, derusting, water washing, alcohol dehydration, and vacuum drying. Specifically, the magnetic steel substrate is first immersed in a degreasing agent to remove oil, then immersed in 3% dilute nitric acid to remove rust, then washed sequentially with deionized water and alcohol, and finally dried in a vacuum environment at a temperature of 80-120℃ for 30-60 minutes. After the pretreatment, the magnetic steel substrate is placed in an argon-protected glove box for anodic activation to provide good surface conditions for the preparation of the transition bonding layer. The total thickness of the protective system is 6.8-19μm, with no obvious interface gaps between the coating layers, tight bonding, and no defects such as pinholes or cracks. Furthermore, the magnet substrate is a neodymium iron boron magnet with a surface roughness Ra≤0.2μm, ensuring that the transition bonding layer can be uniformly attached; Furthermore, the mass ratio of titanium to chromium in the transition bonding layer is 3:1-5:1. This ratio allows the transition bonding layer to possess both excellent toughness and bonding strength, enabling it to bond tightly with the magnetic steel substrate and provide a good foundation for the subsequent adhesion of the main protective layer. Furthermore, the manganese content in the amorphous aluminum-manganese alloy in the main protective layer is 13.8-15.4 at.%, which ensures that the main protective layer has a good amorphous structure, thereby improving its corrosion resistance and mechanical properties. Furthermore, the fluorine content of the fluorocarbon coating in the surface protective layer is ≥65%, ensuring that the surface protective layer has excellent hydrophobic, antifouling and weather-resistant properties. Furthermore, the mass ratio of nickel to tungsten in the corner reinforcement protective layer is 7:1-9:1. This ratio enables the corner reinforcement protective layer to have good hardness and toughness, which can resist friction and collision, and avoid cracking due to excessive brittleness. Furthermore, the parameters of the ion sputtering process are: sputtering power of 100-300W, sputtering gas pressure of 0.1-0.5Pa, sputtering temperature of 150-250℃, and sputtering time of 10-30min; Furthermore, the parameters of the ionic liquid electroplating process are as follows: MnCl2-AlCl3-EMIC ionic liquid is used, wherein the concentration of MnCl2 is 0.10-0.20 mol / L, the molar ratio of AlCl3 to EMIC is 2.0, the electroplating current density is 6-12 mA / cm², the electroplating temperature is 25-80℃, and the electroplating time is 12-120 min; Furthermore, the parameters of the spraying process are as follows: spraying pressure is 0.3-0.6MPa, spraying distance is 150-250mm, spraying temperature is 80-120℃, and curing treatment is performed after spraying, with curing temperature at 180-220℃ and curing time at 20-40min.

[0009] Beneficial effects Compared with the prior art, the fixed point-to-point fire extinguisher device and system provided by the present invention have the following significant advantages: 1. This invention adopts a multi-layer composite protective structure, in which the transition bonding layer, main protective layer, surface protective layer and corner reinforcement protective layer work together to achieve all-round and multi-layer protection for the magnetic steel substrate, solving the problems of incomplete protection and poor protection effect of existing single coating or traditional three-layer coating. Among them, the transition bonding layer improves the interlayer bonding force, the main protective layer achieves core corrosion protection and mechanical protection, the surface protective layer isolates impurities and moisture, and the corner reinforcement protective layer specifically solves the protection problem of weak corners. Each layer has a clear division of labor and works together to enhance the effectiveness, significantly improving the reliability and long-term effectiveness of protection.

[0010] 2. The transition bonding layer is prepared by ion sputtering of titanium-chromium alloy and has a micro-pit structure on its surface. On the one hand, the titanium-chromium alloy has a strong bonding force with the neodymium iron boron magnet substrate, which can effectively prevent the coating from falling off. On the other hand, the micro-pit structure increases the contact area with the main protective layer, forming a mechanical interlocking effect, which further enhances the interlayer bonding force. At the same time, the transition bonding layer prepared by the ion sputtering process is uniform and dense, without pinhole defects, which can effectively block the penetration of corrosive media. The pretreatment process and the anodic activation step further improve the bonding stability between the transition bonding layer and the magnet substrate.

[0011] 3. The main protective layer is prepared by ionic liquid electroplating of amorphous aluminum-manganese alloy and doped with nano-zirconia particles. The amorphous structure has excellent corrosion resistance, and its salt spray resistance is significantly improved compared with the traditional nickel-copper-nickel plating. The doping of nano-zirconia particles significantly improves the hardness and wear resistance of the main protective layer. At the same time, the corrosion potential of amorphous aluminum-manganese alloy is lower than that of the magnetic steel substrate, forming a sacrificial anode protection, further preventing corrosion of the magnetic steel substrate. Compared with traditional electrolytic electroplating, the ionic liquid electroplating process produces a more uniform, dense, and stronger coating with no obvious defects.

[0012] 4. The surface protective layer adopts a fluorocarbon coating, forming a smooth hydrophobic structure that can effectively isolate moisture, dust and oil, prevent impurities from adhering, and avoid wear and corrosion of the protective structure by impurities. At the same time, the fluorocarbon coating has excellent weather resistance and anti-fouling properties, which can adapt to different environmental conditions and extend the service life of the protective structure. The smooth surface can also reduce the friction loss of the magnets during motor operation, further protecting the magnets and the protective coating.

[0013] 5. To address the issue of easy damage and corrosion at the corners of the magnetic steel substrate, a corner reinforcement protective layer is installed. This layer is made of nickel-tungsten alloy, which has good hardness and toughness and can effectively resist damage to the corners from vibration, friction and collision. At the same time, the corner reinforcement protective layer is tightly bonded to each other to avoid gaps and prevent corrosive media from penetrating from the corners, thus solving the technical pain point of weak corner protection in existing protective structures.

[0014] 6. The thickness and composition ratio of each coating layer in this invention have been optimized, and the total thickness of the protective system is moderate. It will not affect the magnetic properties of the magnet due to excessive thickness, nor will it cause the protection to fail due to insufficient thickness. Each process parameter has been adjusted to ensure that each coating layer is uniform, dense, and tightly bonded, without defects such as pinholes and cracks, and the overall structure is stable and reliable. The preparation process is mature, highly operable, suitable for large-scale production, and has broad application prospects.

[0015] 7. The protective structure of the present invention can effectively delay the oxidation, corrosion and wear of the magnet substrate, avoid the attenuation of the magnetic flux of the magnet, ensure the detection accuracy of the speed sensor, extend the service life of the magnet and the speed sensor, reduce the maintenance cost and failure rate of the permanent magnet motor, and is applicable to various permanent magnet motor speed sensors. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of the protective structure of the magnetic steel coating of a permanent magnet motor speed sensor according to the present invention. The markings in the diagram are: 1. Magnet substrate; 2. Transition bonding layer; 3. Main protective layer; 4. Surface protective layer; 5. Corner reinforced protective layer; 6. Micro-dimpled structure; 7. Nano-zirconia particles. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0018] Example 1 A protective structure for the magnetic steel coating of a permanent magnet motor speed sensor, such as Figure 1As shown, it includes a magnet substrate 1, which is a neodymium iron boron magnet with a surface roughness Ra=0.15μm; the surface of the magnet substrate 1 is sequentially provided with a transition bonding layer 2, a main protective layer 3, and a surface protective layer 4; the corners of the magnet substrate 1 are provided with corner reinforcement protective layers 5; the transition bonding layer 2, the main protective layer 3, the surface protective layer 4, and the corner reinforcement protective layer 5 together constitute a complete protective system with a total thickness of 10μm; The transition bonding layer 2 is a titanium-chromium alloy layer with a thickness of 1 μm and a titanium to chromium mass ratio of 4:1. The transition bonding layer 2 is prepared by ion sputtering. The parameters of the ion sputtering process are: sputtering power of 200 W, sputtering gas pressure of 0.3 Pa, sputtering temperature of 200 °C, and sputtering time of 20 min. The surface of the transition bonding layer 2 has uniformly distributed micro-pit structures 6 with a diameter of 120 nm and a depth of 50 nm. The main protective layer 3 is an amorphous aluminum-manganese alloy layer with a thickness of 5 μm. The manganese content in the amorphous aluminum-manganese alloy is 14.5 at.%. The main protective layer 3 is prepared by an ionic liquid electroplating process. The parameters of the ionic liquid electroplating process are as follows: MnCl2-AlCl3-EMIC ionic liquid is used, wherein the concentration of MnCl2 is 0.15 mol / L, the molar ratio of AlCl3 to EMIC is 2.0, the electroplating current density is 9 mA / cm², the electroplating temperature is 50℃, and the electroplating time is 60 min. The main protective layer 3 is doped with nano-zirconia particles 7 with a particle size of 60 nm, and the doping amount is 3.5% of the total mass of the main protective layer 3. The surface protective layer 4 is a fluorocarbon coating with a thickness of 1.2 μm and a fluorine content of 68%. It is prepared using a spraying process with the following parameters: spraying pressure of 0.45 MPa, spraying distance of 200 mm, and spraying temperature of 100 °C. After spraying, a curing treatment is performed at 200 °C for 30 min. The surface of the surface protective layer 4 has a smooth, hydrophobic structure with a water contact angle of 115°. The corner reinforcement protective layer 5 is a nickel-tungsten alloy layer with a thickness of 3μm and a nickel to tungsten mass ratio of 8:1. The corner reinforcement protective layer 5 wraps around the corner of the magnetic steel substrate 1, and its two ends extend to the transition bonding layer 2 and the surface protective layer 4 respectively, and are tightly bonded to the transition bonding layer 2, the main protective layer 3 and the surface protective layer 4. Before the preparation of the transition bonding layer 2, the surface of the magnetic steel substrate 1 undergoes a pretreatment process. The pretreatment process is as follows: first, the magnetic steel substrate 1 is immersed in a degreasing agent to remove oil, then immersed in 3% dilute nitric acid to remove rust, then cleaned with deionized water and alcohol in sequence, and finally dried in a vacuum environment at a drying temperature of 100℃ for 45 minutes. After the pretreatment is completed, the magnetic steel substrate 1 is placed in an argon-protected glove box for anodic activation.

[0019] Example 2 A protective structure for a permanent magnet motor speed sensor includes a magnet substrate 1, which is a neodymium iron boron magnet with a surface roughness Ra=0.1μm. A transition bonding layer 2, a main protective layer 3, and a surface protective layer 4 are sequentially provided on the surface of the magnet substrate 1. An edge and corner reinforcement protective layer 5 is provided at the corners of the magnet substrate 1. The transition bonding layer 2, the main protective layer 3, the surface protective layer 4, and the edge and corner reinforcement protective layer 5 together constitute a complete protective system with a total thickness of 6.8μm. The transition bonding layer 2 is a titanium-chromium alloy layer with a thickness of 0.5 μm and a titanium to chromium mass ratio of 3:1. The transition bonding layer 2 is prepared by ion sputtering. The parameters of the ion sputtering process are: sputtering power of 100 W, sputtering gas pressure of 0.1 Pa, sputtering temperature of 150 °C, and sputtering time of 10 min. The surface of the transition bonding layer 2 is provided with uniformly distributed micro-pit structures 6, with a diameter of 50 nm and a depth of 20 nm. The main protective layer 3 is an amorphous aluminum-manganese alloy layer with a thickness of 3 μm. The manganese content in the amorphous aluminum-manganese alloy is 13.8 at.%. The main protective layer 3 is prepared by an ionic liquid electroplating process. The parameters of the ionic liquid electroplating process are as follows: MnCl2-AlCl3-EMIC ionic liquid is used, wherein the concentration of MnCl2 is 0.10 mol / L, the molar ratio of AlCl3 to EMIC is 2.0, the electroplating current density is 6 mA / cm², the electroplating temperature is 25℃, and the electroplating time is 12 min. The main protective layer 3 is doped with nano-zirconia particles 7, the particle size of which is 30 nm, and the doping amount is 2% of the total mass of the main protective layer 3. The surface protective layer 4 is a fluorocarbon coating with a thickness of 0.8 μm and a fluorine content of 65%. The surface protective layer 4 is prepared by a spraying process with the following parameters: spraying pressure of 0.3 MPa, spraying distance of 150 mm, spraying temperature of 80 °C, followed by curing at 180 °C for 20 min. The surface of the surface protective layer 4 has a smooth hydrophobic structure with a water contact angle of 110°. The corner reinforcement protective layer 5 is a nickel-tungsten alloy layer with a thickness of 2μm and a nickel to tungsten mass ratio of 7:1. The corner reinforcement protective layer 5 wraps around the corner of the magnetic steel substrate 1, and its two ends extend to the transition bonding layer 2 and the surface protective layer 4 respectively, and are tightly bonded to the transition bonding layer 2, the main protective layer 3 and the surface protective layer 4. Before the preparation of the transition bonding layer 2, the surface of the magnetic steel substrate 1 undergoes a pretreatment process. The pretreatment process is as follows: first, the magnetic steel substrate 1 is immersed in a degreasing agent to remove oil, then immersed in 3% dilute nitric acid to remove rust, then cleaned with deionized water and alcohol in sequence, and finally dried in a vacuum environment at a drying temperature of 80℃ for 30 minutes. After the pretreatment is completed, the magnetic steel substrate 1 is placed in an argon-protected glove box for anodic activation.

[0020] Example 3 A protective structure for a permanent magnet motor speed sensor includes a magnet substrate 1, which is a neodymium iron boron magnet with a surface roughness Ra=0.2μm. A transition bonding layer 2, a main protective layer 3, and a surface protective layer 4 are sequentially provided on the surface of the magnet substrate 1. An edge and corner reinforcement protective layer 5 is provided at the corners of the magnet substrate 1. The transition bonding layer 2, the main protective layer 3, the surface protective layer 4, and the edge and corner reinforcement protective layer 5 together constitute a complete protective system with a total thickness of 19μm. The transition bonding layer 2 is a titanium-chromium alloy layer with a thickness of 2 μm and a titanium to chromium mass ratio of 5:1. The transition bonding layer 2 is prepared by ion sputtering. The parameters of the ion sputtering process are: sputtering power of 300 W, sputtering gas pressure of 0.5 Pa, sputtering temperature of 250 °C, and sputtering time of 30 min. The surface of the transition bonding layer 2 has uniformly distributed micro-pit structures 6 with a diameter of 200 nm and a depth of 80 nm. The main protective layer 3 is an amorphous aluminum-manganese alloy layer with a thickness of 8 μm. The manganese content in the amorphous aluminum-manganese alloy is 15.4 at.%. The main protective layer 3 is prepared by an ionic liquid electroplating process. The parameters of the ionic liquid electroplating process are as follows: MnCl2-AlCl3-EMIC ionic liquid is used, wherein the concentration of MnCl2 is 0.20 mol / L, the molar ratio of AlCl3 to EMIC is 2.0, the electroplating current density is 12 mA / cm², the electroplating temperature is 80℃, and the electroplating time is 120 min. The main protective layer 3 is doped with nano-zirconia particles 7 with a particle size of 100 nm, and the doping amount is 5% of the total mass of the main protective layer 3. The surface protective layer 4 is a fluorocarbon coating with a thickness of 2μm and a fluorine content of 70%. The surface protective layer 4 is prepared by a spraying process with the following parameters: spraying pressure of 0.6MPa, spraying distance of 250mm, and spraying temperature of 120℃. After spraying, a curing treatment is performed at a curing temperature of 220℃ for 40min. The surface of the surface protective layer 4 has a smooth hydrophobic structure with a water contact angle of 120°. The corner reinforcement protective layer 5 is a nickel-tungsten alloy layer with a thickness of 5μm and a nickel to tungsten mass ratio of 9:1. The corner reinforcement protective layer 5 wraps around the corner of the magnetic steel substrate 1, and its two ends extend to the transition bonding layer 2 and the surface protective layer 4 respectively, and are tightly bonded to the transition bonding layer 2, the main protective layer 3 and the surface protective layer 4. Before the preparation of the transition bonding layer 2, the surface of the magnetic steel substrate 1 undergoes a pretreatment process. The pretreatment process is as follows: first, the magnetic steel substrate 1 is immersed in a degreasing agent to remove oil, then immersed in 3% dilute nitric acid to remove rust, then cleaned with deionized water and alcohol in sequence, and finally dried in a vacuum environment at a drying temperature of 120℃ for 60 minutes. After the pretreatment is completed, the magnetic steel substrate 1 is placed in an argon-protected glove box for anodic activation.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Obviously, the embodiments described above are only some embodiments of this invention, not all embodiments. The accompanying drawings show preferred embodiments of this invention, but do not limit the patent scope of this invention. This invention can be implemented in many different forms; on the contrary, the purpose of providing these embodiments is to make the disclosure of this invention more thorough and complete. Although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A protective structure for the magnetic steel coating of a permanent magnet motor speed sensor, characterized in that, The system includes a magnetic steel substrate, on the surface of which a transition bonding layer, a main protective layer, and a surface protective layer are sequentially formed. Corner reinforcement protective layers are provided at the edges and corners of the magnetic steel substrate. These layers together constitute a complete protective system. The transition bonding layer is a titanium-chromium alloy layer, prepared using an ion sputtering process, and its surface has a uniformly distributed micro-pit structure. The main protective layer is an amorphous aluminum-manganese alloy layer, prepared using an ion liquid electroplating process, and internally doped with nano-zirconia particles. The corrosion potential of the protective layer is lower than that of the magnetic steel substrate and the transition bonding layer; the surface protective layer is a fluorocarbon coating, prepared by spraying process, and its surface has a smooth hydrophobic structure; the corner reinforcement protective layer is a nickel-tungsten alloy layer, which wraps around the corners of the magnetic steel substrate, and its two ends extend to the transition bonding layer and the surface protective layer respectively and are tightly bonded; the surface of the magnetic steel substrate undergoes a pretreatment process before the preparation of the transition bonding layer, and the pretreatment process includes degreasing, derusting, water washing, alcohol dehydration and vacuum drying steps in sequence, and anodic activation is performed after the pretreatment is completed.

2. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The magnet substrate is neodymium iron boron magnet with a surface roughness Ra≤0.2μm.

3. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The thickness of the transition bonding layer is 0.5-2 μm, and the mass ratio of titanium to chromium in the transition bonding layer is 3:1-5:1; the diameter of the micro-pit structure is 50-200 nm, and the depth is 20-80 nm.

4. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The parameters of the ion sputtering process are as follows: sputtering power of 100-300W, sputtering gas pressure of 0.1-0.5Pa, sputtering temperature of 150-250℃, and sputtering time of 10-30min.

5. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The thickness of the main protective layer is 3-8 μm, and the manganese content in the amorphous aluminum-manganese alloy in the main protective layer is 13.8-15.4 at.%; the particle size of the nano-zirconia particles is 30-100 nm, and the doping amount is 2-5% of the total mass of the main protective layer.

6. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The parameters of the ionic liquid electroplating process are as follows: MnCl2-AlCl3-EMIC ionic liquid is used, wherein the concentration of MnCl2 is 0.10-0.20 mol / L, the molar ratio of AlCl3 to EMIC is 2.0, the electroplating current density is 6-12 mA / cm², the electroplating temperature is 25-80℃, and the electroplating time is 12-120 min.

7. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The thickness of the surface protective layer is 0.8-2μm, the fluorine content of the fluorocarbon coating in the surface protective layer is ≥65%, and its surface water contact angle is ≥110°.

8. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The parameters of the spraying process are as follows: spraying pressure is 0.3-0.6MPa, spraying distance is 150-250mm, spraying temperature is 80-120℃, and curing treatment is performed after spraying. The curing temperature is 180-220℃ and the curing time is 20-40min.

9. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The thickness of the corner reinforcement protective layer is 2-5 μm, and the mass ratio of nickel to tungsten in the corner reinforcement protective layer is 7:1-9:

1.

10. The protective structure for the magnet plating of a permanent magnet motor speed sensor according to claim 1, characterized in that, The total thickness of the protective system is 6.8-19μm, with no obvious interface gaps between the coating layers, and the bonding is tight without pinholes or cracks. In the pretreatment process, the vacuum drying temperature is 80-120℃, the drying time is 30-60min, and the anodic activation is carried out in an argon-protected glove box.

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