Tangential built-in brushless direct current motor rotor structure

Abstract

The invention relates to the technical field of permanent magnet brushless direct current motors, in particular to a tangential built-in brushless direct current motor rotor structure which comprises a rotating shaft sleeved with a first punching sheet and a second punching sheet. The first punching sheet comprises an inner punching sheet unit used for sleeving the rotating shaft and a plurality of outer punching sheet units arranged along the circumferential direction of the inner punching sheet unit at intervals, and gaps between the outer punching sheet units form permanent magnet grooves used for installing permanent magnets; the second punching sheet structure is the same as the first punching sheet structure, and the difference is that the outer punching sheet unit of the second punching sheet and the outer punching sheet unit of the first punching sheet are in a mirror image structure; through the first punching sheets and the second punching sheets of the outer punching sheet units which are arranged in a mirror image manner, a novel segmented rotor optimization structure is designed, the amplitudes of the torque at the wave crests and the wave troughs in the circumferential direction are reduced, the magnetic field waveform of the motor is optimized, and the effect of weakening the cogging torque is achieved; meanwhile, through an air magnetic isolation structure, magnetic flux leakage path magnetic resistance is increased, and the magnetic flux leakage coefficient is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnet brushless DC motors, in particular to a tangential built-in brushless DC motor rotor structure. Background Art

[0002] The built-in brushless DC motor has the advantages of simple structure, low material cost and high mechanical strength. At present, this type of motor is widely used in traditional fuel vehicles and hybrid vehicles. Compared with the surface-mounted rotor, the built-in brushless DC motor has an asymmetric structure of AC and DC axis magnetic circuit, which generates magnetic resistance torque and increases the output torque of the motor. Its permanent magnet is placed in the rotor, which increases the robustness of the motor rotor, makes the dynamic performance more stable, and has a stronger weak magnetic field speed expansion capability.

[0003] In permanent magnet brushless DC motors, cogging torque is inevitable due to the presence of rotor permanent magnets. The presence of cogging torque will seriously affect the low-speed performance of the motor. Therefore, many domestic scholars have studied the cogging torque of built-in permanent magnet brushless DC motors and achieved certain results. At the same time, the magnetic flux per pole of the tangential built-in brushless DC motor is provided by two permanent magnets, which greatly improves the magnetic flux and air gap flux density compared with the radial built-in rotor structure, playing a "magnetic concentration" role. However, the tangential built-in brushless DC motor has a large leakage coefficient. Therefore, it is necessary to focus on optimizing the rotor magnetic isolation structure to improve the motor performance. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a tangential internal brushless DC motor rotor structure capable of reducing cogging torque and motor magnetic leakage coefficient.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A tangential built-in brushless DC motor rotor structure comprises a rotating shaft, on which a first punching sheet and a second punching sheet are sleeved; the first punching sheet comprises an inner punching sheet unit for sleeved on the rotating shaft and a plurality of outer punching sheet units arranged at intervals along the circumference of the inner punching sheet unit, and the gaps between the outer punching sheet units constitute permanent magnet slots for installing permanent magnets; the second punching sheet structure is the same as the first punching sheet structure, except that the outer punching sheet unit of the second punching sheet is a mirror image structure with the outer punching sheet unit of the first punching sheet.

[0007] Preferably, a further technical solution of the present invention is:

[0008] Preferably, the rotating shaft is divided into two sections, namely, rotating shaft section A and rotating shaft section B. The rotating shaft section A is used to install a plurality of first punching sheets, and the rotating shaft section B is used to install a plurality of second punching sheets.

[0009] Preferably, the outer punching unit of the first punching sheet is in a fan-shaped structure, and one of the two outer corners of the fan-shaped sheet away from the rotating shaft is chamfered.

[0010] Preferably, the outer punching units of the first punching sheet and the second punching sheet are both provided with riveted connection parts, which are formed by press riveting, with a convex body on one side and a groove matching the convex body on the other side; the adjacent first punching sheets and the second punching sheets are connected to each other through the riveted connection parts.

[0011] Preferably, a recess is provided on the inner punch unit relative to the outer punch unit, and the recess constitutes an air magnetic isolation structure between the inner punch unit and the outer punch unit.

[0012] Preferably, an injection hole is provided on the outer punch unit.

[0013] Preferably, the permanent magnet and the permanent magnet slot are clearance-matched.

[0014] Preferably, the gap between the permanent magnet and the permanent magnet slot, the air magnetic isolation structure, and the injection molding hole are filled with injection molding material, so that the first punching sheet, the second punching sheet, and the permanent magnet are an integrated structure.

[0015] Compared with the prior art, the present invention adopting the above technical solution has the following outstanding features:

[0016] 1. The present invention adopts the means of cutting peaks and filling valleys. Through the first punching sheet and the second punching sheet that are mirror images of each other in the outer punching sheet unit, a new type of "segmented" rotor optimization structure is designed. Under the premise that the segmented tilting pole (circumferential rotation angle) of the permanent magnet cannot be achieved, the outer corners of one side of the outer punching sheet unit of the first punching sheet and the second punching sheet are cut to reduce the amplitude of the torque peaks and troughs in the circumferential direction, optimize the motor magnetic field waveform, and play the effect of weakening the cogging torque.

[0017] 2. By designing the punching sheet into a structure of an outer punching sheet unit and an inner punching sheet unit, and designing an air magnetic isolation structure between the outer punching sheet unit and the inner punching sheet unit, the magnetic resistance of the leakage magnetic path is increased, the path of the magnetic lines of force formed by the permanent magnet, the first punching sheet, the second punching sheet, and the rotating shaft is suppressed, and the leakage magnetic coefficient is reduced.

[0018] 3. The rotor structure of the tangential built-in brushless DC motor is an integrated injection molding structure, which improves the integrity of the motor rotor and further improves the mechanical strength of the motor rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the overall structure of the motor rotor in an embodiment of the present invention;

[0020] Figure 2 It is a schematic diagram of the matching structure of the first punching sheet, the second punching sheet and the permanent magnet in an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of a first punching sheet in an embodiment of the present invention;

[0022] Figure 4 is a schematic structural diagram of a second punching sheet in an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of a motor rotor with a traditional magnetic isolation structure;

[0024] Figure 6 Schematic diagram of a motor rotor with an air magnetic isolation structure according to an embodiment of the present invention;

[0025] Figure 7 It is a 2D model diagram of a 12-slot 8-pole tangential internal brushless DC motor;

[0026] Figure 8 This is the no-load magnetic induction intensity distribution diagram of a 12-slot 8-pole tangential internal brushless DC motor;

[0027] Fig. 9 This is the no-load flux density distribution diagram of a 12-slot, 8-pole tangential internal brushless DC motor;

[0028] Fig.10 It is the relationship between the width of the magnetic isolation bridge and the magnetic leakage coefficient;

[0029] Fig.11 The torque-speed curves of two rotor structures: the magnetic isolation bridge width of 0.8mm and the air magnetic isolation structure;

[0030] Fig.12 The torque-current curves of two rotor structures: the magnetic isolation bridge width of 0.8mm and the air magnetic isolation structure;

[0031] Fig.13 It is a structural diagram of the rotor of the tangential built-in brushless DC motor formed by integral injection molding in an embodiment of the present invention;

[0032] Fig.14 is a stress cloud diagram of a rotor assembly in an embodiment of the present invention;

[0033] Fig.15 is a strain cloud diagram of a rotor assembly in an embodiment of the present invention;

[0034] Fig.16 is a stress cloud diagram at the injection molding material in an embodiment of the present invention;

[0035] Fig.17 1 is a relative position diagram of the permanent magnet and the first punching sheet and the second punching sheet;

[0036] Fig.18 1. is a comparison diagram of no-load back EMF waveforms of the new segmented rotor optimized structure and the original structure in the embodiment of the present invention;

[0037] Fig.19 : is a diagram of the motor cogging torque simulation result of the new segmented rotor optimized structure and the original structure in the embodiment of the present invention;

[0038] Fig. 20 It is a comparison chart of the simulated and measured torque-speed curves of the traditional magnetic isolation bridge structure and the air magnetic isolation structure;

[0039] Fig.21 It is a comparison chart of the simulated and measured torque-current curves of the traditional magnetic isolation bridge structure and the air magnetic isolation structure;

[0040] Fig. 22 These are the no-load torque fluctuation test results of the motor with the existing original structure and the new segmented rotor optimized structure.

[0041] Explanation of the accompanying drawings: 1. first punch; 2. second punch; 3. injection hole; 4. riveted connection; 5. convex portion; 6. rotating shaft; 7. inner punch unit; 701. concave portion; 8. outer punch unit; 10. air magnetic isolation structure; 11. permanent magnet; 12. integrated punch; 13. traditional magnetic isolation bridge structure; 14. injection molded part. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific embodiments, the purpose of which is only to provide a better understanding of the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0043] The stator of the permanent magnet motor of the hybrid vehicle adopts a centralized winding. When running stably, the influence of the winding inductance can be ignored in the simplified model. The time constant is much smaller than the commutation period, so the voltage balance equation is:

[0044] U=E eq +iR eq (1)

[0045] In formula (1), U is the inverter output voltage, E eq is the back electromotive force of the motor, i is the armature current, R eq is the winding resistance.

[0046] According to formula (1) and the law of conservation of energy, the electromagnetic power is equal to the rotor output mechanical power, and the open-loop mechanical characteristic equation of the built-in brushless DC motor is:

[0047]

[0048] In formula (2), Ω is the motor mechanical angular velocity (rad / s), Ω 0 is the ideal no-load mechanical angular velocity of the motor (rad / s), T av is the average torque of the motor, K E is the back electromotive force coefficient, K Tis the torque coefficient. According to formula (2), it can be concluded that the mechanical characteristics of the built-in brushless DC motor are similar to those of the brushed motor. When the inductance is ignored, the mechanical characteristics are an approximately linear straight line.

[0049]

[0050] In formula (3), K rms K is the effective value coefficient of the back electromotive force during the conduction period, av The average value coefficient of the back EMF during the conduction period of the conduction angle, K eq is the equivalent back electromotive force coefficient.

[0051] K T =K eq K av (4)

[0052] According to formulas (2) to (4), it can be concluded that the back-EMF coefficient determines the no-load speed of the motor, and the back-EMF coefficient and the winding resistance determine the stiffness of the motor's mechanical characteristics. Therefore, in view of the characteristics of the magnetic leakage of the tangential built-in brushless motor, under the condition that the motor stator size and stator winding parameters remain unchanged, the present invention chooses to improve the motor's back-EMF coefficient and torque coefficient by optimizing the rotor structure and reducing the magnetic leakage coefficient, thereby improving the mechanical characteristic stiffness and the motor electromagnetic power of the tangential built-in brushless DC motor.

[0053] like Figures 1 to 4 , Fig.13 As shown, this embodiment provides a tangential built-in brushless DC motor rotor structure, including a rotating shaft 6, on which a plurality of first punching sheets 1 and a plurality of second punching sheets 2 are sleeved; the first punching sheet 1 includes an inner punching sheet unit 7 for sleeved on the rotating shaft 6 and a plurality of outer punching sheet units 8 circumferentially spaced along the inner punching sheet unit 7, and the gaps between the outer punching sheet units 8 constitute permanent magnet slots for installing permanent magnets 11; the structure of the second punching sheet 2 is the same as that of the first punching sheet 1, and the only difference is that the outer punching sheet unit 8 of the second punching sheet 2 is a mirror image structure with the outer punching sheet unit 8 of the first punching sheet 1.

[0054] In the prior art, the stator of a small-power brushless DC motor mostly adopts a block core structure, which effectively improves the power density of the motor by increasing the slot fill rate of the stator winding; the rotor structure mostly adopts a segmented pole tilting method to reduce the cogging torque of the motor; but due to the structural characteristics of the built-in tangential brushless DC motor itself, the traditional rotor pole tilting method is difficult to implement in terms of process and cannot be automated; therefore, based on the overall idea of ​​weakening the cogging torque by unequal width air gaps, the present invention adopts the means of peak shaving and valley filling to divide the rotating shaft 6 into two sections, namely, a rotating shaft A section and a rotating shaft B section, wherein the rotating shaft A section is used to install a number of first punching sheets 1, and the rotating shaft B section is used to install a number of second punching sheets 2, and the outer punching sheet unit 8 of the second punching sheet 2 is a mirror image structure with the outer punching sheet unit 8 of the first punching sheet 1; wherein the permanent magnet 11 is not segmented in the axial direction; in this embodiment, this structure is called a new segmented rotor optimization structure, which changes the width of adjacent slots, achieves the effect of reducing the amplitude of the torque peaks and troughs in the circumferential direction, optimizes the motor magnetic field waveform, and plays an effect of weakening the cogging torque.

[0055] Cogging torque is an inherent property of permanent magnet brushless DC motors. It is generated by the interaction between the motor core punchings and the permanent magnets 11 when the motor is not powered. Its value is the negative derivative of the magnetic field energy W with respect to the relative position angle ɑ of the stator and rotor.

[0056]

[0057] The relative position angle ɑ of the motor stator and rotor is the circumferential angle between the center line of a certain stator tooth and the center line of the rotor permanent magnet 11, such as Fig.17 As shown, the position where θ=0 is set is on the center line of the rotor permanent magnet 11, and θ is the angle of change of the air gap magnetic induction intensity along the circumferential direction of the motor.

[0058] The magnetic field energy W in formula (5) is determined by the motor structure size. In order to derive the analytical expression of the cogging torque of the built-in permanent magnet motor, it is assumed that the magnetic permeability of the motor punching is infinite, the magnetic permeability of the permanent magnet 11 is the same as the magnetic permeability of air, the punching stacking coefficient is 1, and the shape and performance of the permanent magnet 11 in the same motor are the same; therefore, compared with the magnetic field energy stored in the motor air gap, the magnetic field energy stored in the stator and rotor punchings can be approximately ignored. Therefore, when analyzing and calculating the cogging torque, the magnetic field energy stored in the motor can be expressed as:

[0059]

[0060] Where W air is the magnetic field energy contained in the motor air gap; W PM is the magnetic field energy in the permanent magnet 11; μ 0 is the air magnetic permeability, and B(θ,α) is the distribution of air gap flux density along the circumferential direction when the relative position of the rotor changes.

[0061] The distribution function B(θ,α) of the air gap flux density along the circumferential direction can be approximately expressed as:

[0062]

[0063] In formula (7), B r (θ),h m (θ), δ(θ,ɑ) are the distribution of the remanence of the permanent magnet 11, the length of the permanent magnet 11 in the magnetizing direction, and the effective air gap length along the circumferential direction respectively; Substituting formula (7) into formula (6) yields:

[0064]

[0065] Respectively and Perform Fourier series expansion to obtain:

[0066]

[0067] In formula (9) and (10), B r is the remanence of permanent magnet 11, ɑ p is the pole arc coefficient, p is the number of motor pole pairs, G n is the Fourier coefficient of the square of the relative air gap permeance, and z is the number of stator slots of the motor. Substituting equations (8), (9), and (10) into equation (5), using the integral characteristics of trigonometric functions, the expression of the non-skewed pole slot torque can be obtained as follows:

[0068]

[0069] In formula (11), R 2 is the inner radius of the stator core, R 1 The outer radius of the rotor yoke, n is an integer such that the term nz / 2p is an integer.

[0070] The new segmented rotor has an optimized structure and is divided into two sections. The first 1 / 2 section uses the first punching plate 1, and the second 1 / 2 section uses the second punching plate 2. Due to the uniform distribution of permanent magnetic poles, the permanent magnets 11 corresponding to the two sections have a residual magnetic field B r (θ) and the length h of the permanent magnet 11 in the magnetizing direction m Due to the difference in the circumferential assembly of the two rotor segments and the permanent magnets 11, the distribution of the effective air gap length δ(θ,α) along the circumferential direction is not the same. The effective air gap lengths corresponding to the first 1 / 2 segment and the last 1 / 2 segment are δ A (θ,α) and δ B (θ, α), then the expression of the first 1 / 2 section of non-skewed pole slot torque can be obtained as:

[0071]

[0072] The expression of the non-skewed cogging torque in the last 1 / 2 section is:

[0073]

[0074] Then the cogging torque expression of the new segmented rotor optimized structure is:

[0075]

[0076] The outer punching unit 8 of the first punching sheet 1 is in a fan-shaped structure, and one of the two outer corners of the fan-shaped sheet away from the rotating shaft 6 is cut off. By comparing equations (11) and (14), a reasonable air gap permeability is designed through the optimization structure of the new segmented rotor. As long as (G nA +G nB ) / 2<<G n That is, under this structure, although the sizes of the front 1 / 2 section and the rear 1 / 2 section punching sheets are the same, the air gap magnetic permeability of the two sections is changed through mirror assembly, that is, the amplitude and phase are different. The idea of ​​peak shaving and valley filling is adopted to effectively reduce the cogging torque, thereby reducing the torque pulsation of the motor.

[0077] The simulation model takes a 12-slot 8-pole tangential internal brushless DC motor as an example, and calculates and simulates the back EMF and cogging torque of the oil pump motor with the original structure and the new segmented rotor optimized structure. The simulation results are shown in the figure. Fig.18 , 19 As shown; wherein, the original structure is the prior art in which the rotating shaft 6 is not segmented, there is no corner cutting on the punching sheet, it is an integrated punching sheet structure 12, and there is no mirror-image design of the rotor structure.

[0078] from Fig.18 It can be concluded that the 5th harmonic content of the no-load back EMF of the original structure is relatively large, accounting for 5.7%, and the voltage waveform sinusoidal distortion rate is 6.4%. The 7th harmonic content of the no-load back EMF of the new segmented rotor optimized structure is the largest, accounting for 3%, and the voltage waveform sinusoidal distortion rate is 4.1%, a decrease of 56%. The new segmented rotor optimized structure effectively improves the no-load back EMF of the motor, and the waveform is more sinusoidal. Fig.19 The finite element cogging torque simulation results of the original structure and the new segmented rotor optimized structure are given. The cogging torque simulation value of the original structure motor is 130mNm, while the cogging torque value of the new segmented rotor optimized structure is reduced to 32mNm, and the motor cogging torque is reduced by 75.4%. It can be seen that the new segmented rotor optimized structure is an effective method to reduce the cogging torque of the tangential built-in brushless DC motor, and has good processability.

[0079] The motor cogging torque test bench was used to test the no-load torque fluctuation of the original oil pump motor and the new segmented rotor optimized oil pump motor at 30rpm. The test results are as follows: Fig. 22As shown in the figure, the torque of the no-load torque fluctuation test results of the two structures of oil pump motors is decomposed, the differential mode component is the cogging torque of the motor, and the common mode component is the friction torque of the motor; among them, the cogging torque of the original structure oil pump motor is 138mNm, and the friction torque is 21.3mNm; the cogging torque of the new segmented rotor optimized structure oil pump motor is 36.5mNm, and the friction torque is 18.2mNm, and the cogging torque is reduced by 73.5%. Its simulation results are close to the test results, and the error is <2%. The simulation results are slightly smaller than the test results, which is mainly caused by the deviation of the motor assembly and test system. By adopting the idea of ​​peak shaving and valley filling, the "segmented" rotor optimized structure can effectively reduce the cogging torque of the tangential built-in brushless DC motor, reduce the difficulty of product process, and greatly improve the feasibility.

[0080] In order to ensure the integrity of the rotor after the first punching sheet 1 and the second punching sheet 2 are connected, a riveted connection part 4 is provided on the outer punching unit 8 of the first punching sheet 1 and the second punching sheet 2. The riveted connection part 4 is formed by riveting, one side is a convex body, and the other side is a groove adapted to the convex body; the adjacent first punching sheet 1 and the second punching sheet 2 are connected to each other through the riveted connection part 4.

[0081] In order to reduce the magnetic leakage on the inner surface of the tangential built-in brushless DC motor rotor, two optimization methods are generally used: non-magnetic materials and magnetic isolation bridges. Traditional magnetic isolation bridges such as Figure 5 As shown, the conventional magnetic isolation bridge structure 13 is designed in Figure 5 At the position shown by point A, the narrow traditional magnetic isolation bridge structure 13 is used to saturate the magnetic circuit at this point to achieve the purpose of magnetic isolation; however, due to the bottleneck of the rotor punching process, the width of the magnetic isolation bridge needs to be strictly controlled, so the magnetic isolation effect is general and the magnetic leakage coefficient is still large. Figure 6 As shown, the rotor sheet is cut at point B, and the rotor sheet consists of two major parts: an inner sheet unit 7 and an outer sheet unit 8. A recess 701 is provided on the inner sheet unit 7 relative to the outer sheet unit 8, and the gap between the outer sheet unit 8 and the recess 701 of the inner sheet unit 7 constitutes an air magnetic isolation structure 10. The rotor magnetic isolation bridge material is changed from silicon steel sheet to a high magnetic resistance air magnetic isolation structure 10, which increases the magnetic resistance of the leakage magnetic path, suppresses the path of magnetic lines formed by the permanent magnet 11, the first sheet 1, the second sheet 2, and the shaft 6, and reduces the magnetic leakage coefficient.

[0082] In order to measure the influence of different magnetic isolation bridge widths on the leakage flux coefficient of the motor, a parametric finite element model of a tangential built-in brushless DC motor is established. The magnetic isolation bridge width on the rotor punching is parameterized. The initial value of the magnetic isolation bridge width is 1mm (the material property is set to silicon steel sheet at this time), the terminal width is 0mm (the material property is set to vacuum at this time), the step length is 0.1mm, and there are 11 steps in total. The brushless DC motors with different magnetic isolation bridge widths are simulated respectively, and the magnetic flux integration method is used to obtain the leakage flux coefficient. The Maxwell post-processing function is used to obtain the relationship between the magnetic isolation bridge width of the rotor punching and the leakage flux coefficient, as shown in Figure 2. Fig.10 shown; from Fig.10 It can be seen that when the width of the magnetic isolation bridge on the rotor punching of the hybrid vehicle motor is reduced from 1mm to 0mm (when the width of the magnetic isolation bridge is 0mm, the outer ring of the rotor punching is divided into 9 parts), the motor leakage coefficient is reduced from 1.53 to 1.18; as the width of the magnetic isolation bridge decreases, the rotor leakage coefficient gradually decreases, and the amplitude is reduced to 25.3%, thereby effectively improving the magnetic flux per pole of the motor, the magnetic field utilization rate is improved, and the motor back electromotive force coefficient is indirectly improved.

[0083] The 12-slot 8-pole tangential internal brushless DC motor is used as the simulation model. The motor 2D model is as follows: Figure 7 As shown in Table 1, the main parameters of the motor model are given, and the motor operating temperature is 25℃.

[0084]

[0085] Table 1

[0086] like Figure 8 , 9 As shown, due to the use of the air magnetic isolation structure 10, the leakage flux on the inner surface of the rotor is greatly suppressed, and the magnetic density at the rotor magnetic isolation bridge is ≤0.3T, which effectively reduces the rotor core loss.

[0087] Taking into account the configuration of computer resources and shortening the simulation time, on the basis of ensuring the simulation accuracy, according to the characteristics of motor symmetry, a 1 / 4 motor model was selected for simulation. The two right-angle boundaries were set as the master and slave boundaries respectively. Through field-circuit coupling joint simulation, the no-load magnetic induction intensity distribution and magnetic flux density distribution of the motor were obtained.

[0088] The load conditions of two tangential built-in brushless DC motors with a rotor magnetic isolation bridge width of 0.8mm (the stamping width limit of the rotor punching sheet) and a magnetic isolation bridge width of 0mm (air magnetic isolation structure 10) were simulated respectively. The load torque was parameterized, with a starting torque of 0Nm, an ending torque of 1.4Nm, a step length of 0.1Nm, a total of 15 steps, and a starting speed of 0rpm. The motor speed and current corresponding to different torques of the two structures were obtained through simulation, and the relationship curves between the motor torque and speed and the motor torque and current under the two structures were obtained by using the post-processing function. The comparison diagram is shown in the figure below. Fig.11 , Fig.12 shown.

[0089] pass Fig.11 and Fig.12 From the comparison curves of the two structural motors, it can be seen that compared with the motor with a magnetic isolation bridge width of 0.8mm, the motor back-electromotive force coefficient of the air magnetic isolation structure 10 motor is increased by 14.5%, the torque coefficient is increased from 0.0253Nm / A to 0.0312Nm / A, the torque coefficient is increased by 21.7%, the viscous damping coefficient is increased from 0.00318Nm / (rad / s) to 0.00456Nm / (rad / s), the viscous damping coefficient is increased by 43%, and the new air magnetic isolation structure improves the mechanical characteristic stiffness of the motor; under the rated torque of 0.9Nm, the power of the traditional magnetic isolation structure motor is 250W, and the power of the air magnetic isolation structure 10 motor is 275W, and the motor power is increased by 10%; in summary, through the design of the new air magnetic isolation structure, the leakage magnetic coefficient is effectively reduced, the back-electromotive force coefficient, torque coefficient and viscous damping coefficient of the motor are improved, and the motor performance is improved by more than 10%.

[0090] By using the air magnetic isolation structure 10, the outer punching unit 8 and the inner punching unit 7 of the first punching sheet 1, the outer punching unit 8 and the inner punching unit 7 of the second punching sheet 2 and the permanent magnet 11 cannot form a whole, in order to ensure the reliability of the oil pump motor operation; Figures 1 to 4 As shown, the outer punch unit 8 is provided with an injection hole 3; the permanent magnet 11 is gap-matched with the permanent magnet slot; Fig.13 The gap between the permanent magnet 11 and the permanent magnet slot, the air magnetic isolation structure 10, and the injection hole 3 are filled with injection molding material, so that the first punching sheet 1, the second punching sheet 2, and the permanent magnet 11 are integrated. The rotor structure is injection molded with pure nylon material to form a whole rotor assembly, improve the mechanical strength of the motor rotor, and ensure the reliability of the motor rotor operation.

[0091] The strength of the injection molded rotor assembly was calculated using the workbench simulation software. According to the symmetry of the motor, the simulation model was a 1 / 8 rotor model. The maximum rotor rotation speed was 5500 r / min. The rotor core material was B50A470, the permanent magnet 11 material was DM4545, and the injection molding material was PA66. The material properties of each component are shown in Table 2. The rotor stress and strain are shown in Table 2. Fig.14 , 15 shown.

[0092]

[0093] Table 2

[0094] Depend on Figure 14-16It can be seen that the maximum stress of the rotor assembly is in the middle position of the rotor punching, and the maximum stress value is 18.32MPa, which is much smaller than the yield strength of the silicon steel sheet of 241Mpa; the largest deformation of the rotor assembly is the injection molded part 14, whose deformation is 7.9μm, located on the outside of the rotor, blocking the middle position of the magnet injection molding; the maximum stress of the injection molded part 14 is located at the intersection of the outer diameter of the magnet, and the maximum stress value is 8.9Mpa, which is much smaller than the tensile yield strength of PA66 of 70Mpa; therefore, the rotor strength of the tangential rotor injection molding structure meets the requirements, and the oil pump motor can operate stably.

[0095] The mechanical properties of the oil pump motor were tested using a hysteresis dynamometer. The driver adopted an open-loop control mode and the Tn curves of two motors with a traditional silicon steel sheet magnetic isolation structure and an air magnetic isolation structure 10 were tested. The results are shown in Figure 2. Fig. 20 , 21 Shown: Through Fig. 20 , 21 From the measured data, it can be seen that compared with the motor with traditional magnetic isolation bridge structure 13 (magnetic isolation bridge width 0.8mm), the back electromotive force coefficient of the air magnetic isolation structure 10 motor is increased by 15.1%, the torque coefficient is increased from 0.0242Nm / A to 0.03Nm / A, the torque coefficient is increased by 23%, the viscous damping coefficient is increased by 46.5%, the slope of the motor mechanical characteristics is stiffer, and under rated load (rated torque 0.9Nm), the motor power is increased by 11%.

[0096] Comparing the simulation data with the measured data, the measured motor no-load speed is slightly lower than the simulated no-load speed; the simulated back-EMF coefficient, torque coefficient, and viscous damping coefficient are all within 3.5% of the measured data, verifying the correctness of the simulation results. At the same time, the effectiveness of the new air-insulated rotor structure is verified. This structure effectively improves the performance indicators of the tangential built-in brushless DC motor, and the mechanical characteristics have stronger stiffness.

[0097] A convex portion 5 is provided on the inner punching unit 7 at a position opposite to the permanent magnet slot, and the convex portion 5 is in contact with the permanent magnet 11 , thereby further increasing the integrity of the rotor and ensuring the reliability of the motor rotor operation.

[0098] The permanent magnet 11 of the built-in brushless DC motor is mostly made of sintered NdFeB. Although it has high magnetic properties, the material itself has a negative temperature coefficient and is prone to high-temperature demagnetization, which weakens the high-temperature performance of the oil pump motor in the hybrid vehicle field and reduces product safety and stability. Therefore, the present invention uses low-cost, high-temperature stable ferrite permanent magnet material (no rare earth material) to make the permanent magnet 11.

[0099] The beneficial effects of this application are as follows:

[0100] 1. Through the air magnetic isolation structure 10, the magnetic bridge width increases from 1mm to 0mm, and the rotor leakage coefficient gradually decreases, which is about 25.3%, which is an approximately linear relationship. Under the same volume and stator size, the no-load back EMF coefficient and torque coefficient of the air magnetic isolation structure 10 motor are compared with the traditional silicon steel sheet magnetic isolation structure motor, which effectively improves the mechanical characteristic stiffness of the motor.

[0101] 2. The new segmented rotor optimized structure can effectively reduce the cogging torque of the motor, with a reduction of 75.4% and good processability. This method has certain reference significance for reducing the cogging torque of tangential internal permanent magnet motors.

[0102] 3. Under the operating conditions of the motor, the stresses on the overall injection-molded rotor structure and components are within the allowable range of each material, which can effectively ensure the reliability of the tangential built-in air magnetic isolation structure 10 motor.

[0103] 4. Ferrite permanent magnet materials (no rare earth materials) are used to make permanent magnets, which improves product safety and stability.

[0104] The above description is only the preferred embodiment of the present invention, and does not limit the scope of rights of the present invention. All equivalent changes made by using the contents of the present invention specification and its drawings are included in the scope of rights of the present invention.

Claims

1. A tangential internal brushless DC motor rotor structure, characterized in that: It includes a rotating shaft, on which a first punching sheet and a second punching sheet are sleeved; the first punching sheet includes an inner punching sheet unit for sleeved on the rotating shaft and a plurality of outer punching sheet units arranged at intervals along the circumference of the inner punching sheet unit, and the gaps between the outer punching sheet units constitute permanent magnet slots for installing permanent magnets; the structure of the second punching sheet is the same as that of the first punching sheet, except that the outer punching sheet unit of the second punching sheet is a mirror image structure with the outer punching sheet unit of the first punching sheet.

2. The tangential internal brushless DC motor rotor structure according to claim 1, characterized in that: The rotating shaft is divided into two sections, namely, a rotating shaft section A and a rotating shaft section B. The rotating shaft section A is used to install a plurality of first punching sheets, and the rotating shaft section B is used to install a plurality of second punching sheets.

3. The tangential internal brushless DC motor rotor structure according to claim 2, characterized in that: The outer punching unit of the first punching sheet is in a fan-shaped structure, and one of the two outer corners of the fan-shaped sheet away from the rotating shaft is chamfered.

4. The tangential internal brushless DC motor rotor structure according to claim 2, characterized in that: The outer punching units of the first punching sheet and the second punching sheet are both provided with riveted connection parts, which are formed by riveting, with a convex body on one side and a groove matched with the convex body on the other side; the adjacent first punching sheets and the second punching sheets are connected to each other through the riveted connection parts.

5. The tangential internal brushless DC motor rotor structure according to claim 1, characterized in that: A concave portion is arranged on the inner punching unit relative to the outer punching unit, and the concave portion forms an air magnetic isolation structure between the inner punching unit and the outer punching unit.

6. The tangential internal brushless DC motor rotor structure according to claim 5, characterized in that: The outer punching unit is provided with an injection hole.

7. The tangential internal brushless DC motor rotor structure according to claim 6, characterized in that: The permanent magnet and the permanent magnet slot are clearance-matched.

8. The tangential internal brushless DC motor rotor structure according to claim 7, characterized in that: The gap between the permanent magnet and the permanent magnet slot, the air magnetic isolation structure, and the injection hole are filled with injection material, so that the first punching sheet, the second punching sheet, and the permanent magnet are an integrated structure.

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