2898 results about "Magnetic shield" patented technology

The invention relates to the technical field of discharge detection, in particular to a high-precision detection method and device for partial discharge of totally-enclosed GIS equipment. The method comprises the following steps: carrying out metal shell three-dimensional structure modeling on the GIS equipment, and carrying out electromagnetic shielding evaluation so as to obtain a multi-point electromagnetic shielding evaluation value; acquiring an original discharge signal of each sampling point based on the electromagnetic wave sensor, and performing interference suppression processing and back propagation attenuation compensation according to a multi-point electromagnetic shielding evaluation value, so as to obtain an attenuation compensation discharge signal waveform; micro-vibration response parameters are collected based on an MEMS micro-vibration sensor, actual influence waveform point detection marking and physical vibration interference filtering are carried out on attenuation compensation discharge signal waveforms, and therefore pure optimized discharge signal waveforms are obtained. According to the invention, through efficient and accurate partial discharge detection, real-time early warning of the state of the GIS equipment is realized, and the stability and safety of the equipment are improved.

The invention discloses a system for testing an electromagnetic shielding coupler of a testing transformer based on intelligent sensing, and relates to the technical field of electrical equipment testing, and the system comprises a flexible distributed intelligent sensing array which is composed of a plurality of high-density miniature electromagnetic sensors and a temperature-vibration composite sensing unit, a non-uniform topological structure is embedded into a seam and an insulating interface area on the surface of the electromagnetic shielding coupler. According to the test system of the test transformer electromagnetic shielding coupler based on intelligent sensing, through dynamic electromagnetic field reconstruction of the flexible distributed intelligent sensing array and multi-band interference coupling modeling, the limitation of a traditional static test is broken through; and real-time capture and multi-dimensional decoupling of shielding effectiveness attenuation characteristics in a complex alternating electromagnetic environment are realized. Compared with a traditional method, the method has the advantages that the shielding effectiveness dynamic quantization error is reduced, and the engineering guidance value of test data is improved.

The invention discloses a single-end open type high-performance magnetic shielding system and a design method thereof. The system is formed by combining a passive magnetic shielding subsystem and an active magnetic compensation subsystem. The passive magnetic shielding subsystem is formed by alternately nesting single-end open type high-permeability and high-conductivity metal barrels, and the structure is beneficial to synchronously improving the shielding capability for full-band magnetic interference; the active magnetic compensation subsystem is composed of a group of axial nonlinear gradient coils, two groups of radial nonlinear gradient coils with orthogonal magnetic fields and a magnetic compensation control circuit, and three groups of magnetic compensation coil windings are obtained based on specific nonlinear distributed magnetic interference reverse design in a single-end open type magnetic shielding barrel; different from conventional shimming and linear gradient coils, accurate compensation of magnetic interference in a working area in the barrel can be realized. According to the invention, the shielding capability of the single-end open type magnetic shielding system is improved, and a required near-zero magnetic environment is provided for extremely weak magnetic measurement.

A mobile phone control handle assembly is suitable for holding a mobile phone, and is connected to the mobile phone. The mobile phone control handle assembly includes a handle body, a control module, two handle auxiliary accessories, and at least two magnetic shielding members. The handle body is used to hold the mobile phone. The handle body includes buttons and joysticks. When at least one of the buttons and the joysticks is pressed, the control module transmits a corresponding control signal to the mobile phone. The two handle auxiliary accessories are respectively and detachably fixed on two gripping parts of the handle body through magnets. The two magnetic shielding members are used to shield magnetic fields of the magnets. The two handle auxiliary accessories are configured to enhance a gripping experience of a user when gripping the two gripping parts.

The invention discloses a non-contact magnetoelectric composite current sensor with magnetism gathering and magnetic shielding. A sensor core is composed of a magnetoelectric sensing element, a magnetofluid layer, a magnetism gathering structure and a magnetic shielding layer. The magnetoelectric sensing element is made of manganese-doped lead magnesium niobate and amorphous alloy film composite materials, the outer side of the sensing element is coated with a magnetofluid layer made of soft magnetic composite materials, the magnetism gathering structure is made of permalloy materials with high magnetic conductivity and is divided into an upper part and a lower part, the upper part accommodates the sensing element and the magnetofluid layer, and the lower part accommodates the magnetic gathering structure. And the lower part is provided with a standardized groove for placing a conductor to be tested. The outermost layer is a magnetic shielding layer composed of multiple layers of nanocrystalline alloy strips, the vertical split type design is also adopted, and it is ensured that the magnetic shielding layer is tightly matched with the magnetic gathering structure through precision machining. The upper magnetic shielding layer and the lower magnetic shielding layer are detachably connected, and field installation is facilitated. The overall structure is compact, a circuit does not need to be disconnected during installation, and the device is especially suitable for on-line current monitoring requirements in the fields of smart grids, industrial automation and the like.

The invention relates to the technical field of magnetic field intensity detection, in particular to an automatic detection device and method for residual magnetic field intensity of a concrete material. Comprising a conveying mechanism, a magnetic shielding mechanism and a magnetizing mechanism, a plurality of magnetic detection devices are uniformly distributed in the magnetic shielding cylinder, the magnetic detection devices detect the residual magnetic field intensity of a concrete material sample, and the magnetization assembly magnetizes the concrete material sample; the control system is used for controlling the magnetic detection device and the magnetization mechanism, calculating the data detected by the magnetic detection device to obtain the residual magnetic field intensity of the sample before and after magnetization, judging whether the detection result exceeds the standard or not, and displaying the calculation result of the residual magnetic field intensity on the display; assembly line type and circulating automatic detection of the residual magnetic field intensity of the concrete material is achieved, the problems that the workload is large and the detection efficiency is low due to the fact that a large batch of concrete materials depend on manual detection are solved, the conveying mechanisms are all made of non-magnetic materials, and interference of ferromagnetic materials on the detection process is avoided.

The invention discloses an external magnetic field active-disturbance-rejection control method and system based on Kalman filtering, and the method comprises the steps: firstly, building an external coil control system to compensate a residual magnetic field in a magnetic shielding cabin measured by a three-axis fluxgate sensor, and enabling the residual magnetic field to be reduced to a normal working range of Quspin; then starting a Quspin sensor, performing data filtering and fusion on the fluxgate sensor and the Quspin sensor through a Kalman filter, and inputting a fusion value and a control quantity into an extended state observer to realize online estimation of a state and total disturbance; and performing feedback control of related linear state errors on the total disturbance estimator so as to compensate a residual magnetic field and magnetic field disturbance in the magnetic shielding cabin. The magnetic field interference resistance of the active magnetic compensation device can be enhanced, the control precision of an external coil control system on the magnetic field in the cabin is effectively improved, and the cost of the magnetic shielding cabin is reduced.

The invention relates to the field of gravity measurement, and aims to provide a small-size high-precision gravimeter based on an anti-magnetic suspension principle. The gravimeter comprises a low-frequency magnetic potential well unit, a suspension mechanical oscillator unit, a displacement detection unit and a cavity enclosing unit, and lens groups of the low-frequency magnetic potential well unit, the suspension mechanical oscillator unit and the displacement detection unit are all located in a cavity of a heat preservation shell on the innermost side. According to the invention, a measurement environment without external influence can be provided for the displacement detection of the suspension oscillator, the adjustment of the frequency in the vertical direction in a magnetic suspension potential well is resisted, the movement of an object to be measured is reflected by the voltage fluctuation brought by the laser intensity change measured by the photoelectric converter, and the high-precision gravity measurement is realized; the vibrator adopts a magnetic suspension mode and does not make mechanical contact with the environment, and long-term irreversible deformation can be avoided; and a temperature control and magnetic shielding device or other auxiliary equipment with a large volume is not needed, so that the gravimeter is small in overall size, convenient to move, low in cost and beneficial to popularization.

The invention discloses an electrostatic induction and optical imaging principle-fused online monitoring device and method for wear particles of a water-lubricated bearing, and belongs to the field of state monitoring of mechanical equipment. The device comprises a square insulation detection cavity, a detection electrode array, an electromagnetic shielding shell, a high-speed optical imaging module and a signal processing unit, the square insulation detection cavity is installed in a bearing lubrication water loop. The detection electrode array is fixed to the outer wall of the cavity and used for capturing electrostatic signals generated when the abrasion particles pass through. The electromagnetic shielding shell wraps the detection cavity and is grounded through a wire to eliminate environmental electromagnetic interference. The high-speed optical imaging module integrates a high-magnification microscope lens and a CMOS sensor, is coaxially mounted with the detection cavity, and obtains the morphology characteristics of the wear particles in real time; and the signal processing unit performs multi-modal data fusion analysis on the electrostatic signal and the optical image. Through cooperative detection of electrostatic induction and optical imaging, the monitoring precision and reliability of the wear particles of the water-lubricated bearing are remarkably improved.

The invention relates to a composite electromagnetic shielding structure for a power terminal and a preparation method thereof, the structure comprises an accommodating shell, the accommodating shell is formed by connecting a plurality of composite electromagnetic shielding plates, and each composite electromagnetic shielding plate comprises an inner surface shielding layer and an outer surface shielding layer which are attached to each other; a heat conduction layer is arranged between the inner surface shielding layer and the outer surface shielding layer, and the inner surface shielding layer is located in the accommodating shell; a protective layer is arranged on the outer layer of the outer surface shielding layer and comprises an insulating layer and a waterproof layer, and the waterproof layer is located on the outer layer of the insulating layer; the outer surface shielding layer is made of a low-frequency electromagnetic field shielding material formed by mixing amorphous magnetic alloy powder, magnetic fibers and nickel powder; and the inner surface shielding layer is made of a high-frequency electromagnetic shielding material formed by mixing silicon carbide and resin foam rubber fibers. The structure can cope with various electromagnetic interference environments, provides electromagnetic shielding protection, and also has better electromagnetic shielding effectiveness for electromagnetic interference of different frequency bands.

The invention discloses a composite electromagnetic shielding mechanism for wireless power transmission. The composite electromagnetic shielding mechanism comprises a primary side shielding assembly and a secondary side shielding assembly, each of the primary side shielding assembly and the secondary side shielding assembly comprises a coil, an integrated shielding plate, a heat dissipation plate and an aluminum plate which are sequentially arranged from inside to outside, and the primary side shielding assembly and the secondary side shielding assembly are symmetrically arranged; the integrated shielding plate is formed by compounding ferrite blocks and nanocrystalline strips, wherein the ferrite blocks are distributed in a contact area of a coil winding path and the integrated shielding plate in a matrix arrangement mode; the nanocrystalline strips are distributed in the area, except the ferrite blocks, of the integrated shielding plate to form nanocrystalline plates distributed in double rows; the heat dissipation plate is arranged between the integrated shielding plate and the aluminum plate; the aluminum plate is of an outermost shielding structure.

According to the cable multi-parameter fusion sensor and method, in the cable multi-parameter fusion sensor, a shielding shell is of an open-close type metal annular structure; the zero-flux sensor module is arranged on the inner layer of the shielding shell so as to detect a cable sheath ring current signal; the pulse current sensor module is arranged on the outer side of the zero-flux sensor module so as to detect a cable partial discharge pulse current signal and an overvoltage impact current signal; the magnetic shielding layer is arranged between the zero-flux sensor module and the pulse current sensor module to shield low-frequency magnetic field interference; the zero magnetic flux sensor module and the pulse current sensor module share the shielding shell to form an electromagnetic shielding structure.

The invention discloses an electromagnetic shielding film and a circuit board, the battery shielding film comprises a protective layer, the tensile strength of the protective layer is greater than or equal to 40MPa, and the elongation of the protective layer is greater than or equal to 50%. According to the electromagnetic shielding film, the tensile strength of the protective layer is controlled to be larger than or equal to 40 MPa, and the elongation is controlled to be larger than or equal to 50%, so that the protective layer can bear large tension and has good flexibility and ductility, the tear resistance of the electromagnetic shielding film can be effectively improved, and the service life of the electromagnetic shielding film is prolonged. Therefore, the electromagnetic shielding film can be prevented from being damaged when being pressed on an area with offset on the circuit board while ensuring the complex effect and the shielding effectiveness of pressing.

The invention provides a cement-based material residual magnetism intensity detection device, a detection method and an evaluation method. The cement-based material residual magnetism intensity detection device comprises a magnetic shielding cylinder, a fluxgate magnetometer and a test tool, the magnetic shielding cylinder is used for shielding a magnetic field to ensure stable test environment magnetic field; the fluxgate magnetometer comprises a fluxgate probe and a fluxgate digital display meter, the fluxgate probe is used for measuring a vector value of space magnetic induction intensity at a position corresponding to the fluxgate probe, and the fluxgate digital display meter is used for displaying a residual magnetism intensity measured value measured by the fluxgate probe; the test tool is arranged in the magnetic shielding cylinder and is used for placing a sample to be tested and fixing a fluxgate probe; according to the invention, a fluxgate magnetometer and a magnetic shielding cylinder are adopted to detect the residual magnetism intensity of the cement-based material, a standardized detection process and a test method are provided for solid components, a liquid mixture and a molded test block, and quantitative characterization of the distribution rule of the residual magnetism intensity of the cement-based material is realized through fewer detection points.

The invention discloses a defect detection sensor and a defect detection method based on a quantum technology, and relates to the technical field of defect detection.The defect detection sensor comprises a central controller, an orthogonal differential detection unit, a quantum magnetometer and a magnetic shielding cylinder; the orthogonal differential detection unit is used for collecting a first magnetic field change signal on the surface of a preset area of the preset part, transmitting the first magnetic field change signal to the quantum magnetometer and applying the first magnetic field change signal to alkali metal atoms of the quantum magnetometer; the quantum magnetometer is used for obtaining a second magnetic field change signal and sending the second magnetic field change signal to the central controller; and the central controller is used for analyzing the second magnetic field change signal and determining whether the preset area of the preset part has defects or not. According to the invention, the sensitivity and accuracy of defect detection can be improved.

The invention discloses a scanning electron microscope. The scanning electron microscope comprises a scanning electron microscope main body and a sample table located in a sample cavity, the scanning electron microscope main body is fixedly connected with the upper cover of the sample cavity, so that a closed space is formed in the sample cavity; a closed-loop groove is formed in an upper cover of the sample cavity; wherein the groove is located outside the connection position of the upper cover of the sample cavity and the scanning electron microscope main body, and the bottom of the groove is not higher than the supporting surface of the sample table; a magnetic shielding layer is arranged in the groove; wherein the length of the magnetic shielding layer is not less than the distance from the objective lens of the scanning electron microscope main body to the supporting surface of the sample stage.

The invention relates to a direct current motor with an anti-electromagnetic interference structure in the field of motors, which is characterized in that the surfaces of a commutator and an electric brush are blown in real time through a magnetic shielding cylinder arranged on the outer side of the commutator and an air blowing blade arranged in the magnetic shielding cylinder, and carbon powder on the surfaces of the commutator and the electric brush is cleaned; the commutator and the electric brush are subjected to synchronous blowing heat dissipation, so that the commutator and the electric brush have relatively good contact stability, the condition of contact resistance increase caused by carbon powder accumulation is reduced, the probability of arc generation between the commutator and the electric brush is reduced, and the electromagnetic compatibility of the motor is further improved; the influence of a high-frequency magnetic field generated by the arc on a rotor winding coil is reduced, and electromagnetic interference is further reduced; in addition, the insulating groove formed in the commutator improves the collecting and cleaning effects of the carbon powder, and the insulating groove is matched with the diversion disc to realize ejection of the lower contact surface of the electric brush, so that the cleaning effect of the carbon powder is further improved.

The invention provides a magnetic memory and a preparation method thereof. The magnetic memory comprises a plurality of memory units, at least part of the memory units are arranged along a first direction, and each memory unit comprises a magnetic tunnel junction; at least part of the magnetic shielding structure is located between the adjacent storage units in the first direction, and the magnetic shielding structure and the adjacent storage units are arranged at intervals; wherein the magnetic shielding structures and the adjacent storage units are arranged at intervals. Due to the fact that the magnetic shielding structure is arranged between every two adjacent storage units, the storage area can be saved through the design, meanwhile, the magnetic shielding structures can prevent the storage units from making contact with the magnetic shielding structures to cause short circuit, and the storage units have the anti-magnetic characteristic of an opposite internal magnetic field. Therefore, the magnetic memory has the diamagnetic properties of a vertical magnetic field and an in-plane magnetic field, the diamagnetic capability of the magnetic memory is improved, and the reliability of the magnetic memory in a magnetic field environment is further improved.

The invention provides a comprehensive shielding signal cable and a manufacturing method thereof.The comprehensive shielding signal cable comprises a cable core and a protective layer wrapping the cable core, and the protective layer sequentially comprises a composite shielding layer and an outer sheath layer from inside to outside; the composite shielding layer comprises an iron-based amorphous nanocrystalline alloy layer, a 3D woven mesh layer and a conductive polymer coating which are sequentially arranged on the outer side of the cable core from inside to outside; through the gradient composite structure of the iron-based amorphous nanocrystalline alloy layer (low-frequency magnetic shielding), the 3D woven mesh layer (medium-frequency electromagnetic shielding) and the conductive polymer coating (high-frequency electric field shielding), the full-band shielding effectiveness is realized for the first time, meanwhile, the return loss is greatly reduced, the electromagnetic transmission performance and reliability of the cable are improved, and the service life of the cable is prolonged. And the structural stability of the cable is improved.

The invention discloses an electromagnetic shielding film and a circuit board, the electromagnetic shielding film comprises a first shielding layer, a flexible conductive adhesive layer and a second shielding layer which are stacked in sequence, and the flexible conductive adhesive layer is arranged between the first shielding layer and the second shielding layer, so that the bending resistance of the electromagnetic shielding film is effectively improved, interference signals are effectively weakened, and the electromagnetic shielding effect is improved. According to the electromagnetic shielding film, the shielding performance is improved, the elastic modulus of the flexible conductive adhesive layer is set between 80 MPa and 120 MPa, the elastic modulus of the flexible conductive adhesive layer is limited within a reasonable range, the bending resistance of the electromagnetic shielding film is better improved, and the electromagnetic shielding film is suitable for products needing to be folded or opened and closed for a long time and at high frequency.

The invention discloses a command vehicle rack-mounted power supply management system, and the system comprises a power supply filtering module which carries out the filtering of power supply input, and removes the high-frequency electromagnetic interference possibly carried by a power line; the electromagnetic shielding module is used for shielding electromagnetic radiation inside and outside the system; the grounding management module is used for providing a unified grounding point of the system and ensuring that all electrical connections have the same potential so as to reduce electromagnetic interference generated by the difference of the grounding point; the signal transmission optimization module is used for ensuring that signal transmission channels inside and outside the system are not influenced by electromagnetic interference; the electromagnetic interference suppression module is used for suppressing transient high-frequency interference generated in the system; and the environment monitoring and feedback module is used for monitoring electromagnetic environments inside and outside the rack in real time and automatically adjusting an EMC protection strategy of the system according to monitoring data so as to adapt to different working conditions. The command vehicle can adapt to a complex electromagnetic environment and ensure stable operation of equipment in the command vehicle.

The invention discloses a magnetic moment comparator device and a measurement method. The magnetic moment of the current-carrying standard coil is in direct proportion to the magnetic field generated at a fixed distance on the axis, and according to the principle that a magnetic dipole layer and the current-carrying coil have equivalence in electromagnetism, when the space magnetic field can be accurately measured, the current-carrying standard coil can be used for measuring the magnetic moment of a magnetic sample at the same position. A magnetic moment comparator is designed in a magnetic shielding cylinder, an atomic magnetometer is used for measuring an absolute magnetic field with high sensitivity, a current-carrying standard coil is placed at the position, with the distance being r0, of one side of an atomic gas chamber in the direction of a background magnetic field, and the axis of the current-carrying standard coil is parallel to the direction of the background magnetic field; the magnetic moment direction of the magnetic sample is parallel to the background magnetic field direction, when the magnetic sample is moved by the sample transfer rod to the position, which is r0 away from the atomic gas chamber, of the other side of the atomic gas chamber, the current introduced into the standard coil is changed in real time by keeping the background magnetic field unchanged as a judgment condition, and the magnetic moment of the magnetic sample is equal to the magnetic moment of the current-carrying standard coil; the directions are opposite.

The embodiment of the utility model provides a circuit board assembly and electronic equipment. The electromagnetic shielding piece is arranged on the mainboard, the detection module is used as an independent module and can be arranged on the electromagnetic shielding piece, the mainboard, the electromagnetic shielding piece and the detection module are stacked and assembled to form a circuit board assembly, the circuit board assembly is assembled on the middle frame, and the bottom shell is installed on the middle frame. And the detection module and the mainboard are conductively connected to realize signal transmission. No safety gap is reserved between the electromagnetic shielding piece and the detection module, and no support with a certain thickness is arranged on the bottom shell. According to the electronic equipment, miniaturization can be achieved, the thickness of the whole electronic equipment is small, and the thickness of the whole electronic equipment can be reduced by 0.15 mm or above. In the production process or under the condition of falling and extrusion in a user use scene, the detection module, the electromagnetic shielding piece and the mainboard synchronously slightly deform, and the failure or damage caused by collision of the detection module is reduced. The electronic equipment is easy to assemble, and the assembling process is simple.

The invention provides a power communication network risk identification method and system and a storage medium. The method comprises the following steps: acquiring electromagnetic interference environment parameters, acquiring optical cable laying path and tower structure data, and analyzing a distribution rule of grounding points of an electromagnetic shielding layer; the influence of electromagnetic interference on signals is eliminated according to a grounding point distribution rule; acquiring optical cable strain information, and extracting optical cable strain change characteristics; determining an optical cable fault and a fault point initial position; correcting the position of a fault point; evaluating the damage degree caused by the magnetic field; and generating a fault point repair suggestion, updating the optical cable state database, and generating an optical cable health state report focusing high magnetic field influence. By implementing the method, the optical cable fault can be effectively positioned, the damage degree of the optical cable can be accurately evaluated, and the stability of a power communication network can be improved.

The present invention discloses an electromagnetic shielding film and a circuit board. The electromagnetic shielding film comprises: a first shielding layer, an interlayer and a second shielding layer which are stacked in sequence; the thickness of the first shielding layer, the thickness of the second shielding layer and the thickness of the interlayer satisfy: 0.05≤d3 / (d1+d2)≤6.5. The interlayer is provided to increase the flexibility of the electromagnetic shielding film, and the provision of two shielding layers further enhances the shielding effect. The ratio of the thickness of the interlayer to the sum of the thickness of the two shielding layers is limited within a certain range, so that the thickness of the interlayer is within a suitable thickness range, which can have better stress, the device is resistant to bending, and the overall thickness of the electromagnetic shielding film is not too thick, which is conducive to the thinning of the device. At the same time, the thickness of the interlayer is relatively close to the sum of the thicknesses of the two shielding layers, which improves the stress transmission performance, makes the stress transmission more uniform, and avoids the breakage of the electromagnetic shielding film.

A lithium battery detection device based on BB optical pump magnetic imaging comprises a magnetic shielding cylinder and a substrate arranged in the magnetic shielding cylinder, and a laser, an optical lens system, an atomic gas chamber system, an array lens and an array photoelectric detector are sequentially arranged on the working face of the substrate from left to right; the atomic gas chamber system contains alkali metal atoms and buffer gas; a non-magnetic objective table for placing a lithium battery to be tested is arranged above the atomic gas chamber; according to the device, the array lens is adopted to split and focus a single beam of detection laser into small light spots which are respectively irradiated on different photoelectric detectors, and magnetic field information of a plurality of space point locations is detected at one time, so that the consistency and imaging quality of a subsystem are improved, and the system cost is saved.

The present invention discloses a demagnetization method based on a weak magnetic environment. A three-axis geomagnetic compensation coil is built outside a passive shielding device. Current is injected into the coil to generate a reverse magnetic field to offset the geomagnetism, thereby providing a weak magnetic environment for the shielding device. Based on the weak magnetic environment, a demagnetization power supply control system and a demagnetization coil are used to demagnetize the passive shielding layer of the magnetic shielding device, thereby further improving the demagnetization performance. This method can not only reduce the cost of using high-performance shielding materials when the magnetic shielding device adopts multi-layer shielding, but also effectively reduce the residual magnetism inside the shielding space, thereby constructing an extremely weak magnetic environment.

The invention relates to the technical field of magnetic suspension bearings, and provides a magnetic leakage prevention bearing structure which comprises a flux sleeve, a shell, a magnetic part, an inner-layer magnet yoke and an outer-layer magnet yoke. The shell is sleeved outside the flux sleeve, and an inner ring of the shell is provided with a mounting space; the magnetic part is arranged in the mounting space; the inner-layer magnet yoke is arranged in the mounting space and connected with the shell, the inner-layer magnet yoke is concaved inwards to form a first containing groove, and the magnetic part is contained in the first containing groove; the outer-layer magnet yoke is arranged in the installation space and connected with the shell, the outer-layer magnet yoke is concaved inwards to form a second containing groove, and the inner-layer magnet yoke is contained in the second containing groove. A closed magnetic circuit is formed through a double-layer magnet yoke nested structure, the axial magnetic shielding layer design is matched, magnetic flux leakage is effectively restrained, the magnetic field energy utilization rate is increased, electromagnetic interference to external equipment is reduced, and meanwhile the bearing performance and operation stability of the bearing are remarkably improved by optimizing magnet yoke thickness distribution and the permanent magnet arrangement mode.

The invention relates to an electromagnetic shielding film and a circuit board, and the electromagnetic shielding film comprises a shielding layer, the thickness d of the shielding layer in a slicing state and in a preset observation range satisfies # imgabs0 #, the thickness uniformity of the shielding layer is less than or equal to 20% through the modes of adjusting a production technology and the like, the shielding layer with uniform thickness is formed, the consistency of impedance characteristics can be improved, and the electromagnetic shielding film has good electromagnetic shielding performance. And meanwhile, the skin effect of the shielding layer is reduced, the surface current is better borne, the influence of electromagnetic interference of a high-frequency and high-speed line on an internal circuit is reduced, the shielding effect of the electromagnetic shielding film on the high-frequency and high-speed line is improved, and the working reliability of the circuit board is further improved. Besides, the first protection layer forms an undulating surface through the particle member, and the shielding layer conformal to the undulating surface of the first protection layer can be grounded with the circuit board by using a downward projection, so that non-conductive particle grounding is realized, more use scenes are satisfied, and the material applicability is improved.

The invention discloses a heat-conducting electromagnetic shielding multilayer composite film as well as a preparation method and application thereof. The heat-conducting electromagnetic shielding multilayer composite film comprises an insulating heat-conducting layer, a magnetic shielding layer, a conductive shielding layer and an insulating heat-conducting layer which are sequentially stacked, the insulating heat-conducting layer is a cellulose film containing heat-conducting filler, and the magnetic shielding layer is a cellulose film containing magnetic filler and expanded microspheres. And the conductive shielding layer is a cellulose membrane containing conductive filler and expanded microspheres. The heat-conducting electromagnetic shielding multilayer composite film has the advantages of excellent in-plane heat conduction performance, excellent electromagnetic shielding performance, high mechanical strength, small thickness and the like, the preparation process is simple, convenient, green and environment-friendly, and the heat-conducting electromagnetic shielding multilayer composite film has very wide application prospects in the fields of 5G communication, consumer electronics, new energy batteries, national defense and military industry and the like.