A permanent magnet magnetic compartment transmission device and a method for calculating eddy current losses thereof

Abstract

The present invention belongs to the technical field of permanent magnet magnetic force transmission, and provides a permanent magnet magnetic bulkhead transmission device and a method for calculating eddy current loss thereof. First, a sealing cover fixed on the bulkhead is used to isolate the inner rotor permanent magnet and the outer rotor permanent magnet to achieve dynamic sealing, so that the seawater and oil on the bulkhead section side cannot leak to the power shaft side. Finally, a motor is used to drive the power shaft to rotate, and under the magnetic force between the outer rotor permanent magnet and the inner rotor permanent magnet, the bulkhead transmission and dynamic sealing are achieved. The method for calculating eddy current loss of the permanent magnet magnetic bulkhead transmission device involved is based on Maxwell's electromagnetic induction theory, combined with the slowly varying time domain characteristics of the magnetic field, and effectively reflects the mutual coupling between the magnetic-electric-thermal multi-physical fields during the operation of the device, which maintains the advantages of simple and convenient calculation, and can make the calculation results more accurate. The present invention has good practical application performance in actual engineering applications, is simple to operate, and has a small amount of calculation.

Description

Technical Field

[0001] The invention belongs to the technical field of permanent magnet magnetic transmission, and in particular relates to a permanent magnet magnetic compartment transmission device and a method for calculating eddy current losses thereof. Background Art

[0002] The bulkhead transmission device is a necessary equipment for connecting the stern of the power source shaft system and the watertight bulkhead section shaft system. It is widely used in the marine industry such as surface ships and unmanned submersibles. Traditional bulkhead transmission devices usually adopt a combination of drive shafts, bearings, and oil seals. Although they have the characteristics of simple structure and easy maintenance, they will inevitably produce mechanical friction, vibration, and noise during operation. Especially for long-term continuous operation conditions of marine ships, their service life and reliability cannot be guaranteed. With the breakthrough of the preparation technology of high magnetic energy product rare earth permanent magnet materials, permanent magnet magnetic transmission devices have been developed rapidly, which can greatly improve the vibration reduction and noise reduction performance of the transmission shaft system in the marine field. Conventional permanent magnet magnetic transmission devices only have the function of transmitting force and torque. If they are directly applied, they cannot meet the needs of the stern compartment of the ship to take into account both bulkhead sealing and transmission. In addition, in the study of transmission performance of permanent magnet magnetic transmission devices, the finite element analysis method is usually used to solve the torque under the action of nonlinear magnetic field. The calculation time is long, the hardware performance requirements are high, and the transmission efficiency characteristics are not paid attention to, which seriously restricts the application and promotion of permanent magnet magnetic transmission devices in the field of ship compartment transmission.

[0003] Regarding the bulkhead transmission device, Zhang Hongsheng proposed a mechanical contact bulkhead transmission device composed of a transmission shaft, a bulkhead body, an oil cup, a skeleton oil seal and a large pressure cover in his patent "A bulkhead transmission device" (CN102635683A). Although it can simply realize the transmission between the shaft system and the outer side of the bulkhead, it still has shortcomings such as large friction loss, seawater leakage, and large vibration and noise, and cannot be applied to the development of high-performance ships. Regarding the analysis and calculation method of the transmission performance of permanent magnetic transmission devices, Tian Jie, Li Yumeng and others used the finite element analysis method in the article "Research on the Transmission Performance of Double Alternating Pole Magnetic Couplings" to analyze the air gap magnetic density, magnetic field distribution and torque performance of permanent magnetic transmission devices represented by magnetic couplings. The calculation accuracy is high, but the overall calculation time is long and the cost is high, and it does not involve the analysis and calculation of eddy current losses, which cannot be directly applied to the design, analysis and rapid optimization process of permanent magnetic bulkhead transmission devices.

[0004] Therefore, the invention of a permanent magnetic bulkhead transmission device with compact structure, low noise, good sealing performance and fast transmission characteristic calculation and a method for calculating its transmission efficiency has irreplaceable value and significance for improving the vibration reduction and isolation capability of the ship shafting and realizing the large-scale promotion of permanent magnetic bulkhead transmission devices in the ship field. Summary of the invention

[0005] In order to make up for the defects of the prior art, the present invention invents a permanent magnet magnetic bulkhead transmission device. Its purpose is to use the non-contact magnetic force of the outer rotor permanent magnet, the sealing cover and the inner rotor permanent magnet as the medium to achieve non-contact sealing and transmission between the power source shaft system and the stern bulkhead section shaft system, thereby reducing the vibration and noise of the ship shaft system and improving the service life and reliability of the shaft system.

[0006] The technical solution of the present invention:

[0007] A permanent magnet magnetic bulkhead transmission device, firstly, inserting an inner rotor permanent magnet into a fixing groove formed by an inner rotor hub and a bulkhead section shaft, and limiting the inner rotor permanent magnet by using the cross section of the bulkhead section shaft exceeding the inner rotor hub; secondly, inserting an outer rotor permanent magnet into a fixing groove formed by an outer rotor hub and a power shaft, and limiting the outer rotor permanent magnet by using the inner end face of the outer rotor hub; then, fixing the device on the bulkhead through a sealing cover to isolate the inner rotor permanent magnet and the outer rotor permanent magnet, and at the same time, dynamically isolating the outer rotor bearing bush from the bulkhead section shaft by using a bidirectional sealing ring and a sealing end cover, so that seawater and oil on the bulkhead section side cannot leak to the power shaft side; then, using a motor to drive the power shaft to rotate, and realizing bulkhead transmission and dynamic sealing under the magnetic force between the outer rotor permanent magnet and the inner rotor permanent magnet; the device is convenient to operate, compact in structure, has no mechanical contact in transmission, has low vibration and noise, and has a dynamic sealing effect, and has high practicality and engineering application promotion value in ship bulkhead transmission.

[0008] A permanent magnet magnetic bulkhead transmission device comprises a power shaft, an outer rotor fixing screw, an outer rotor hub, an outer rotor permanent magnet, a sealing cover, a sealing screw, a bulkhead, a bearing bush fixing screw, an outer rotor bearing bush, an oil inlet screw, a stern bidirectional sealing ring, a stern sealing screw, a bulkhead section shaft, a stern sealing end cover, an oil unloading screw, a bow bidirectional sealing ring, a bow sealing limit screw, a bow sealing end cover, an inner rotor fixing screw, an inner rotor permanent magnet and an inner rotor hub;

[0009] The outer rotor hub is installed on the power shaft through the outer rotor fixing screws; the outer rotor permanent magnet is inserted into the fixing groove of the outer rotor hub, and the inner end surface of the outer rotor hub is used to axially limit the outer rotor permanent magnet; the sealing cover is installed on one side of the bulkhead through the sealing screws; the outer rotor bearing is installed on the other side of the bulkhead through the bearing fixing screws; the stern sealing end cover is fixed to the stern of the outer rotor bearing through the stern sealing screws; the oil inlet screw, the stern double-acting sealing ring, the oil unloading screw, and the bow double-acting sealing ring are connected to the outer rotor bearing through the corresponding inner cavity surface and screw holes; the bow sealing end cover is installed on the bow of the outer rotor bearing through the bow sealing limit screw; the inner rotor hub is installed on the bulkhead section shaft through the inner rotor fixing screws, the inner rotor permanent magnet is inserted into the fixing groove of the inner rotor hub, and the end surface of the bulkhead section shaft exceeding the inner rotor hub is used for axial limitation.

[0010] A method for calculating eddy current loss of a permanent magnetic bulkhead transmission device is proposed. The eddy current loss of the sealing cover is analytically calculated based on Maxwell's electromagnetic induction theory. The structure and physical parameters of the sealing cover are fully considered. Combined with the speed of the motor at the drive end, an eddy current loss calculation method that meets the parameter design of the sealing cover is finally established. On this basis, vector magnetic potential is introduced to describe the air gap magnetic field in space, and the slowly varying time domain characteristics of the magnetic field are fully considered. Compared with the conduction current, the influence of the displacement current is ignored. While ensuring the calculation accuracy, the calculation efficiency of the theoretical model is greatly improved, providing important theoretical calculation support for the structural design and performance optimization of the bulkhead transmission device.

[0011] The specific steps of this method are as follows:

[0012] Step 1: Determine the key parameters of the compartment transmission device

[0013] The key parameters include the sealing cover thickness t, the sealing cover axial length L, the sealing cover radius r, the sealing cover material conductivity γ, the internal and external rotor angle difference φ, the maximum magnetic flux density B0 in the working air gap, and the maximum induced electromotive force E that varies with the internal and external rotor angle difference. Z , the number of permanent magnet poles m and the speed of the driving end motor n;

[0014] Step 2: Determine the air gap magnetic field and induced electromotive force of the compartment transmission device

[0015] Since eddy current loss has a great influence on the compartment transmission device under actual working conditions, the negative effect of this influence should be fully considered in the theoretical calculation and design stage. Therefore, the air gap magnetic field and induced electromotive force are used as the maximum value instead of the actual value in the entire magnetic field and electric field during calculation; the magnetic field B is taken along the radius r of the sealing cover, and changes with the angle difference φ between the inner and outer rotors in the sealing cover. Therefore:

[0016] B r =B0sinmφ (1)

[0017] Among them: B r is the radial component of the magnetic field;

[0018] The sealing cover rotates counterclockwise relative to the inner and outer rotors. The current generated by the time-varying magnetic field is along the axial direction, so the electromotive force E changes along the axial direction. Therefore:

[0019] E=E Z (2)

[0020] Step 3: Solve the eddy current loss in the compartment transmission device

[0021] According to the law of electromagnetic induction in Maxwell's equations:

[0022]

[0023] Right now:

[0024]

[0025] in: is the partial derivative of time;

[0026] Substituting equation (1) into the left side of equation (4), we get

[0027]

[0028] Since the drive end motor drives the outer rotor to rotate, considering that the time-varying magnetic field changes in seconds,

[0029]

[0030] Where: ω is the angular velocity of the relative rotation of the inner and outer rotors;

[0031] Substituting equations (5) and (6) into equation (4), we obtain:

[0032]

[0033] Integrate both sides of the equation to get:

[0034]

[0035]

[0036] Where: E(φ) is the electromotive force at different rotation angles; E Z (φ) is the maximum electromotive force at different rotation angles;

[0037] The current density generated by electromagnetic induction in the sealing cover is:

[0038]

[0039] The eddy current loss per unit area dA = rdφt is:

[0040]

[0041] Eddy current loss P in the entire sealing cover j for:

[0042]

[0043] At this point, the calculation of the eddy current loss of the permanent magnet magnetic compartment transmission device is completed.

[0044] The beneficial effect of the present invention is that a permanent magnet magnetic bulkhead transmission device is proposed, which realizes non-contact sealing and transmission of the power source shaft system and the stern bulkhead section shaft system through the non-contact magnetic force generated by the inner and outer rotor permanent magnets and the sealing cover; the introduction of the isolation cover can not only realize the power sealing of the load end and prevent salt water and moisture from corroding the internal equipment of the cabin, but also can provide a certain shielding effect, fully protect the magnets in the air gap and the time-varying magnetic field generated by it, reduce the interference of the external magnetic field, and ensure the stability of its transmission performance; in addition, the present invention considers the conductivity and structural parameters of the sealing cover to optimize its design to meet the application requirements of low eddy current loss; eddy current loss will generate unnecessary heat, causing overheating of the equipment and the air gap magnetic field, and then affecting the performance and electrical characteristics of the material, reducing eddy current loss and maintaining a low operating temperature can extend the service life of the device and improve the stability of its transmission performance. At the same time, the eddy current loss calculation method of the permanent magnetic bulkhead transmission device proposed in the present invention can effectively avoid complex finite element simulation calculations, greatly save the calculation time of the eddy current loss of the permanent magnetic bulkhead transmission device, and greatly facilitate the structural optimization of the sealing cover in the permanent magnetic bulkhead transmission device; in addition, the calculation method fully considers the mutual coupling between the magnetic-electric-thermal multi-physical fields during the operation of the device, and can more accurately reflect the eddy current loss in the isolation cover, that is, it maintains the advantages of simple and convenient calculation, and can make the calculation results more accurate. This method is widely used in the structural design optimization and practical application of permanent magnetic couplings, and is a calculation method with engineering universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a structural schematic diagram of a permanent magnetic compartment transmission device;

[0046] Figure 2 It is the basic model of the magnetic field of the inner and outer rotors of the permanent magnetic compartment transmission device;

[0047] Figure 3 It is the basic model of sealing cover;

[0048] Figure 4 It is a flow chart of the method for calculating eddy current loss of a permanent magnetic compartment transmission device;

[0049] In the figure: 1-power shaft, 2-outer rotor fixing screw, 3-outer rotor hub, 4-outer rotor permanent magnet, 5-sealing cover, 6-sealing screw, 7-bulkhead, 8-bearing bush fixing screw, 9-outer rotor bearing bush, 10-oil inlet screw, 11-stern two-way acting sealing ring, 12-stern sealing screw, 13-bulkhead section shaft, 14-stern sealing end cover, 15-oil unloading screw, 16-bow two-way acting sealing ring, 17-bow sealing limit screw, 18-bow sealing end cover, 19-inner rotor fixing screw, 20-inner rotor permanent magnet, 21-inner rotor hub; 22-outer rotor basic model, 23-sealing cover basic model, 24-inner rotor basic model. DETAILED DESCRIPTION

[0050] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0051] This embodiment selects a permanent magnet magnetic compartment transmission device with 8 pairs of magnetic poles and calculates its eddy current loss.

[0052] Among them, the radius of the power shaft 1 is 35mm, the outer rotor fixing screws 2 are 8 M8×20 hexagon socket screws, the outer diameter of the outer rotor hub 3 is 200mm, the inner diameter is 140mm, the length of the outer rotor permanent magnet 4 and the inner rotor permanent magnet 20 are both 10mm, the inner diameter of the sealing cover 5 is 132mm, the outer diameter is 136mm, and the length is 87mm. The sealing screws 6 are 12 M6×14 hexagon socket screws, the diameter of the bulkhead 7 is 300mm, and the thickness is 10mm. The bearing fixing screws 8 are 12 M8×14 hexagon socket screws, and the diameter of the outer rotor bearing 9 is 26 0mm, the oil inlet screw 10 and the oil discharge screw 15 are both M10×16 fastening screws, the stern double-acting sealing rings 11 and 16 are both G80×65×20 rubber sealing rings, the stern sealing screw 12 is 8 M6×14 hexagon socket screws, the diameter of the bulkhead section shaft 13 is 70mm, the diameter of the stern sealing end cover 14 is 100mm, the bow sealing limit screw 17 is 8 M6×14 hexagon socket screws, the bow sealing end cover 18, the inner rotor fixing screw 19 is 8 M8×20 hexagon socket screws, and the diameter of the inner rotor hub 21 is 130mm;

[0053] The installation steps of the permanent magnet magnetic compartment transmission device are as follows:

[0054] First, the outer rotor hub 3 is mounted on the power shaft 1 by means of 8 M8×20 outer rotor fixing screws 2, the outer rotor permanent magnet 4 is inserted into the fixing groove of the outer rotor hub 3, and the inner end surface of the outer rotor hub 3 is used to axially limit the outer rotor permanent magnet 4 to achieve the arrangement and fixation of the magnet;

[0055] Secondly, the sealing cover 5 is installed on the bulkhead 7 through 12 M6×14 sealing screws 6, and the outer rotor bearing 9 is installed on the other side of the bulkhead 7 through 12 M8×14 bearing fixing screws 8. The stern sealing end cover 14 is fixed to the stern of the outer rotor bearing 9 through 8 M6×14 stern sealing screws 12. The oil inlet screw 10, the stern double-acting sealing ring 11, the oil unloading screw 15, and the bow double-acting sealing ring 16 are connected to the outer rotor bearing 9 through the corresponding inner cavity surface and the screw hole. The bow sealing end cover 18 is installed on the bow of the outer rotor bearing 9 through 8 M6×14 bow sealing limit screws 17 to finally achieve the sealing effect;

[0056] Again, the inner rotor hub 21 is mounted on the bulkhead section shaft 13 by means of 8 M8×20 inner rotor fixing screws 19, the inner rotor permanent magnet 20 is inserted into the fixing groove of the inner rotor hub 21, and the end surface of the bulkhead section shaft 13 extending beyond the inner rotor hub 21 is used for axial limitation.

[0057] Finally, after the inner and outer rotors and the sealing structure of the permanent magnet magnetic compartment transmission device are installed respectively, the inner rotor is embedded in the outer rotor, and the outer rotor permanent magnet 4 is aligned with the inner rotor permanent magnet 20.

[0058] At this point, a permanent magnetic bulkhead transmission device has been installed.

[0059] A method for calculating eddy current loss of a permanent magnet magnetic compartment transmission device is as follows: Figure 4 The specific steps of the eddy current loss calculation method of the permanent magnet magnetic compartment transmission device are as follows:

[0060] Step 1: Determine the key parameters of the compartment transmission device

[0061] The key parameters include the sealing cover thickness t = 2 mm, axial length L = 50 mm, radius r = 66 mm, material conductivity γ = 0.625 × 10 6 s / m; the angle difference between the inner and outer rotors φ∈(0,2π); the maximum magnetic flux density in the working air gap B0=0.4996T; the number of permanent magnet poles m=8; the speed of the driving end motor n=2950r / min;

[0062] Step 2: Determine the air gap magnetic field and induced electromotive force of the compartment transmission device

[0063] The magnetic field B is taken along the radius r of the sealing cover, and the coordinate changes with the angle difference φ between the inner and outer rotors in the sealing cover. According to formula (1), B is obtained r ∈(-0.4996,0.4996)T

[0064] Step 3: Solve the eddy current loss in the compartment transmission device

[0065] From formula (6), the angular velocity of the relative rotation of the inner and outer rotors can be obtained:

[0066] Finally, the eddy current loss P in the entire sealing cover is obtained by formula (12): j =60.7w

[0067] At this point, the calculation of eddy current losses of the permanent magnet magnetic compartment transmission device is completed.

[0068] The permanent magnetic bulkhead transmission device of this novel structure is mainly composed of inner and outer hubs and arc-shaped permanent magnets alternately distributed in N and S levels. The inner and outer rotor partition assembly scheme adopted by the present invention enables the device to achieve no mechanical contact, which not only effectively avoids mechanical friction and loss, but also can achieve torque transmission in a misaligned state. Since there is no direct mechanical contact, the vibration and noise generated during operation are relatively low. In addition, the present invention achieves dynamic complete sealing through a closed cover fixed on the bulkhead, effectively preventing external seawater and moisture from entering the interior of the transmission device, protecting the internal mechanical and electronic components from corrosion, improving the reliability of the device, and reducing the frequency and cost of maintenance and repair.

[0069] This method is based on Maxwell's electromagnetic induction theory to analyze and calculate the eddy current loss of the sealing cover, fully consider the structure and physical parameters of the sealing cover, and combine the speed of the motor at the drive end to finally establish an eddy current loss calculation method that meets the parameter design of the sealing cover. On this basis, the vector magnetic potential is introduced to describe the air gap magnetic field in space, and the slowly varying time domain characteristics of the magnetic field are fully considered. Compared with the conduction current, the influence of the displacement current is ignored. While ensuring the calculation accuracy, the calculation efficiency of the theoretical model is greatly improved, providing important theoretical calculation support for the structural design and performance optimization of the compartment transmission device. In practical applications, it has strong adaptability, simple calculation, and low time cost. It is a highly applicable calculation method.

Claims

1. A method for calculating eddy current loss of a permanent magnet magnetic compartment transmission device, characterized in that: The permanent magnet magnetic compartment transmission device comprises a power shaft, an outer rotor fixing screw, an outer rotor hub, an outer rotor permanent magnet, a sealing cover, a sealing screw, a bulkhead, a bearing bush fixing screw, an outer rotor bearing bush, an oil inlet screw, a stern bidirectional sealing ring, a stern sealing screw, a bulkhead section shaft, a stern sealing end cover, an oil unloading screw, a bow bidirectional sealing ring, a bow sealing limit screw, a bow sealing end cover, an inner rotor fixing screw, an inner rotor permanent magnet and an inner rotor hub; the outer rotor hub is mounted on the power shaft by the outer rotor fixing screw; the outer rotor permanent magnet is inserted into the fixing groove of the outer rotor hub, and the inner end surface of the outer rotor hub is used to perform Axial limit; the sealing cover is installed on one side of the bulkhead through the sealing screw; the outer rotor bearing is installed on the other side of the bulkhead through the bearing fixing screw; the stern sealing end cover is fixed to the stern of the outer rotor bearing through the stern sealing screw; the oil inlet screw, the stern double-acting sealing ring, the oil unloading screw, and the bow double-acting sealing ring are connected to the outer rotor bearing through the corresponding inner cavity surface and the screw hole; the bow sealing end cover is installed on the bow of the outer rotor bearing through the bow sealing limit screw; the inner rotor hub is installed on the bulkhead section shaft through the inner rotor fixing screw, the inner rotor permanent magnet is inserted into the fixing groove of the inner rotor hub, and the axial limit is performed by using the end face of the bulkhead section shaft exceeding the inner rotor hub; The specific steps of the method are as follows: Step 1: Determine the key parameters of the compartment transmission device Key parameters include seal cover thickness , Axial length of sealing cover , Sealing cover radius , Conductivity of sealing cover material 、Angle difference between inner and outer rotors , the maximum magnetic flux density in the working air gap , the maximum induced electromotive force changes with the angle difference between the inner and outer rotors , Number of permanent magnet poles and the drive end motor speed ; Step 2: Determine the air gap magnetic field and induced electromotive force of the compartment transmission device Since eddy current loss has a great influence on the compartment transmission device under actual working conditions, the negative effect of this influence should be fully considered in the theoretical calculation and design stage. Therefore, the maximum value of the air gap magnetic field and induced electromotive force is used instead of the actual value of the entire magnetic field and electric field in the calculation; Along the seal cover radius Direction value, and in the sealing cover with the inner and outer rotor angle difference The coordinates change, so: in: is the radial component of the magnetic field; The sealing cover rotates counterclockwise relative to the inner and outer rotors. The current generated by the time-varying magnetic field is along the axial direction, so the electromotive force varies along the axis, so: Step 3: Solve the eddy current loss in the compartment transmission device According to the law of electromagnetic induction in Maxwell's equations: Right now: in: is the partial derivative of time; Substituting equation (1) into the left side of equation (4), we get Since the drive end motor drives the outer rotor to rotate, considering that the time-varying magnetic field changes in seconds, in: is the angular velocity of the relative rotation of the inner and outer rotors; Substituting equations (5) and (6) into equation (4), we obtain: Integrate both sides of the equation to get: in: is the electromotive force at different rotation angles; is the maximum electromotive force at different rotation angles; The current density generated by electromagnetic induction in the sealing cover is: In unit area The eddy current loss inside is: Eddy current losses in the entire sealing cover for: At this point, the calculation of the eddy current loss of the permanent magnet magnetic compartment transmission device is completed.

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