Oil friction loss calculation method and device for split-tooth permanent magnet vernier motor

Abstract

The application discloses a kind of oil friction loss calculation method and device of split tooth permanent magnet vernier motor, it is related to motor oil friction loss calculation technical field, comprising: based on the topology structure of stator split tooth, the air gap region is divided into several sub-regions with different geometric characteristics;For each sub-region, according to its geometric size and flow field state parameter, the oil friction loss of each sub-region is calculated;Based on the number of stator slots, the oil friction loss of each sub-region is accumulated, and the total oil friction loss of stator side air gap is obtained;Calculate the import oil friction loss and export oil friction loss, and accumulate to obtain the total oil friction loss of import and export;Friction resistance torque is integrated, and the oil friction loss power of single-sided rotor end face is obtained;The total oil friction loss of double-sided end face is taken as the total oil friction loss of rotor side;Sum each oil friction loss to obtain the total oil friction loss of motor.The application can quickly and accurately predict the friction loss in oil cooling structure during motor design stage.

Description

Technical Field

[0001] This invention relates to the field of motor oil friction loss calculation technology, specifically to a method and apparatus for calculating oil friction loss of a split-tooth permanent magnet vernier motor. Background Technology

[0002] As electric motors continue to evolve towards higher torque and power densities, thermal management has become a core bottleneck restricting performance breakthroughs. Among various cooling solutions, in-cavity self-circulating oil cooling technology, with its advantages of compact structure, no external pump, and high cooling efficiency, has become the preferred cooling method for high-power-density permanent magnet motors. Meanwhile, the slotted tooth structure, as an advanced magnetic field modulation method, effectively suppresses harmful harmonics and improves torque density and efficiency by precisely controlling the air gap magnetic permeability harmonic distribution, demonstrating significant potential for electromagnetic performance optimization in permanent magnet vernier motors.

[0003] However, while oil cooling systems improve heat dissipation capabilities, they also introduce new engineering challenges: when the cooling oil circulates at high speed within the stator-rotor gap, it undergoes intense viscous shearing with the complex tooth surface, resulting in significant oil friction loss (OFL). This loss not only directly reduces motor efficiency but also exacerbates local temperature rise, interfering with the accuracy of the thermo-electric-current coupling model and consequently affecting system reliability design. Therefore, establishing a high-precision, high-efficiency oil friction loss prediction model has become a crucial prerequisite for achieving multi-physics-based collaborative optimization of motors.

[0004] Currently, the calculation of oil friction loss mainly relies on two types of methods:

[0005] (1) CFD numerical simulation method: Although it has high precision and can capture the details of complex flow fields, it is complex in modeling, consumes a lot of computing resources, and has a long iteration cycle, making it difficult to meet the needs of rapid evaluation in the early stage of design.

[0006] (2) Analytical model method: such as the classic Yamada model, which is computationally efficient, but its core assumption is "uniform concentric cylindrical gap". Even if the tooth groove correction is introduced later, it can only deal with the single main tooth groove structure of conventional motors. It cannot handle the local flow field disturbance caused by the multiple air gap height changes of "main tooth-groove-tooth" in the cracked tooth permanent magnet vernier motor. This results in significant errors in motors with non-uniform tooth profiles such as cracked teeth, limiting its practicality.

[0007] In recent years, some studies have attempted to introduce tooth groove correction coefficients to improve the applicability of analytical models, but three key shortcomings still exist:

[0008] ① Oversimplification of geometric features: The entire tooth groove area is treated as homogeneous and average, without distinguishing the geometric non-uniformity of key areas such as tooth tip, tooth flank, and groove opening and their differential impact on shear stress distribution;

[0009] ② Lack of physical mechanisms: Most modified models rely on empirical fitting or parameter tuning, lack theoretical derivation based on the Navier-Stokes equations, have vague physical connotations, and poor generalization ability;

[0010] ③ Insufficient structural adaptability: Existing methods are completely unsuitable for novel structures such as asymmetric toothed teeth, hybrid tooth profiles, and stepped tooth profiles. The error increases exponentially with the complexity of the structure, making it impossible to support the design of next-generation high-precision motors. Summary of the Invention

[0011] The purpose of this application is to address the technical problem that traditional analytical methods applicable to single-slot motors can no longer accurately describe the air gap flow field characteristics of split-tooth motors due to the multiple height abrupt changes between the main tooth and the split tooth within a single tooth pitch. This application proposes a method and device for calculating oil friction loss in split-tooth permanent magnet vernier motors. Based on the tooth geometry, the air gap region is divided into several sub-regions, and an independent loss analytical model is established for each sub-region based on fluid mechanics principles. The total oil friction loss in the stator side air gap is obtained by superimposing the losses of each sub-region. Further, inlet and outlet energy loss corrections are introduced to obtain the total oil friction loss at the inlet and outlet. Finally, the total oil friction loss on the rotor side is calculated, and the oil friction losses of each sub-region are superimposed. This method enables rapid and accurate prediction of friction loss in oil-cooled structures during the motor design phase.

[0012] On the one hand, a method for calculating the oil friction loss of a split-tooth permanent magnet vernier motor includes:

[0013] Based on the topological structure of the stator tooth, the air gap region is divided into several sub-regions with different geometric features; each sub-region includes at least one tooth region and a slot region.

[0014] For each sub-region, the corresponding Coetreynolds number is calculated based on its geometric dimensions and flow field state parameters, and the friction coefficient of the air gap is determined based on the Coetreynolds number; the shear force of each sub-region is calculated based on the friction coefficient, and the oil friction loss of each sub-region is calculated by integrating the shear force.

[0015] The total oil friction loss of the stator side air gap is obtained by summing the oil friction loss of each sub-region based on the number of stator slots.

[0016] Calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the slot space, and calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the stator tooth space.

[0017] The total oil friction loss at the inlet and outlet is obtained by summing the oil friction losses of each inlet and outlet channel based on the number of stator slots.

[0018] Calculate the area of ​​the annular infinitesimal element on the rotor end face of the motor, calculate the frictional resistance torque based on the area of ​​the annular infinitesimal element, integrate the frictional resistance torque to obtain the oil friction loss power on one side of the rotor end face; obtain the total oil friction loss on both sides of the rotor end face based on the oil friction loss power on one side of the rotor end face, and use it as the total oil friction loss on the rotor side.

[0019] The total oil friction loss of the motor is obtained by summing the total oil friction loss in the stator air gap, the total oil friction loss at the inlet and outlet, and the total oil friction loss on the rotor side.

[0020] Preferably, the oil friction loss in each tooth area , means as follows:

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] in, Indicates the first district; Indicates rotational speed; Indicates the length of the iron core; Indicates the first Shear force on the surface of the toothed area; Indicates the first The arc length corresponding to the tooth width on the rotor surface; Indicates the density of the cooling oil; Indicates the rotor's outer diameter; Indicates the first The friction coefficient of the air gap; Indicates the air gap length; Indicates the first District Couretren number; Indicates the first The height of the teeth, Greater than or equal to 0; This indicates the viscosity of the cooling oil.

[0026] Preferably, the oil friction loss in the groove area , means as follows:

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] in, Indicates rotational speed; Indicates the length of the iron core; This represents the shear force on the surface of the groove area; Indicates the width of the stator slot; Indicates the density of the cooling oil; Indicates the rotor's outer diameter; This represents the friction coefficient of the air gap in the slot area; Indicates the air gap length; Indicates the Coetreno number in the slot region; Indicates the first The height of the teeth, Greater than or equal to 0; Indicates the height of the slot; This indicates the viscosity of the cooling oil.

[0032] Preferably, the oil friction loss of each sub-region is accumulated based on the number of stator slots to obtain the total oil friction loss of the stator side air gap, as shown below:

[0033] ;

[0034] in, Indicates the total oil friction loss in the stator side air gap; N represents the number of grooves; I represents the number of tooth zones; This indicates the oil friction loss in each tooth area; This indicates the oil friction loss in the groove area.

[0035] Preferably, the frictional losses of the inlet oil entering the groove space and the frictional losses of the outlet oil in the tooth space are expressed as follows:

[0036] ;

[0037] in, This indicates the frictional loss of the inlet oil entering the slot space from the tooth space. Frictional loss of the oil exiting the slot space from the toothed space; Indicates the density of the cooling oil; The distance through which the fluid flows is the air gap length. The cross-sectional area, The distance between the slot openings where the fluid flows is the air gap length. The flow rate; The distance between the slot openings where the fluid flows is the air gap length. with the height of the slot The cross-sectional area of ​​the sum; The distance between the slot openings where the fluid flows is the air gap length. with the height of the slot The sum of the flow rates; Indicates rotational speed; Indicates the rotor outer diameter; N indicates the number of slots; Indicates the width of the stator slot;

[0038] The frictional losses of the inlet oil and outlet oil entering the stator tooth space from the tooth space are represented as follows:

[0039] ;

[0040] in, This indicates the frictional loss of the inlet oil as it enters the stator tooth space from the tooth space. Frictional loss of the outlet oil entering the stator tooth space from the tooth space; The distance between the teeth indicates the air gap length. The flow rate; The distance between the teeth indicates that the fluid flows through the air gap. Height of teeth The cross-sectional area of ​​the sum; The distance between the teeth indicates the air gap length. Height of teeth The sum of the flow rates; This indicates the arc length corresponding to the tooth width of the corresponding tooth region on the rotor surface.

[0041] Preferably, the oil friction loss power on one side of the rotor end face is... , means as follows:

[0042] ;

[0043] in, This represents the frictional resistance torque; Indicates rotational speed; This represents the surface shear stress at the rotor end face; This represents the area of ​​the annular element on the end face; Indicates the rotor's outer diameter; Indicates the outer diameter of the shaft; Indicates the density of the cooling oil; Let be the integral radius at the infinitesimal element; This indicates the viscosity of the cooling oil.

[0044] Preferably, the surface shear stress at the rotor end face , means as follows:

[0045] ;

[0046] in, This represents the rate of change of the fluid circumferential velocity at the end face wall.

[0047] Preferably, the total oil friction loss on the rotor side , means as follows:

[0048] .

[0049] On the other hand, a device for calculating oil friction loss of a split-tooth permanent magnet vernier motor includes:

[0050] The sub-region division module is used to divide the air gap region into several sub-regions with different geometric features based on the topological structure of the stator tooth; the sub-regions include at least one tooth region and a slot region;

[0051] The sub-region oil friction loss calculation module is used to calculate the corresponding Coetreynolds number for each sub-region based on its geometric dimensions and flow field state parameters, and determine the friction coefficient of the air gap based on the Coetreynolds number; calculate the shear force of each sub-region based on the friction coefficient, and calculate the oil friction loss of each sub-region by integrating the shear force.

[0052] The total oil friction loss acquisition module for the air gap is used to accumulate the oil friction loss of each sub-region based on the number of stator slots to obtain the total oil friction loss of the stator side air gap.

[0053] The inlet and outlet oil friction loss calculation module is used to calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the slot space, and to calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the stator tooth space.

[0054] The module for obtaining total oil friction loss at inlet and outlet is used to accumulate the oil friction loss of each inlet and outlet channel based on the number of stator slots to obtain the total oil friction loss at inlet and outlet.

[0055] The rotor-side total oil friction loss calculation module is used to calculate the area of ​​the annular micro-element on the end face of the motor rotor, calculate the friction resistance torque based on the area of ​​the annular micro-element, integrate the friction resistance torque to obtain the oil friction loss power of a single rotor end face, and obtain the total oil friction loss of both end faces based on the oil friction loss power of a single rotor end face, which is used as the rotor-side total oil friction loss.

[0056] The total oil friction loss acquisition module is used to sum the total oil friction loss of the stator side air gap, the total oil friction loss of the inlet and outlet, and the total oil friction loss of the rotor side to obtain the total oil friction loss of the motor.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] Existing analytical methods for oil friction loss typically target the single main tooth slot structure of conventional permanent magnet synchronous motors. This single main tooth slot structure only exhibits a single height abrupt change from the main tooth to the slot opening, thus the accuracy requirements can be met by using existing analytical methods for overall calculation. However, the split-tooth permanent magnet vernier motor addressed in this invention contains both the main tooth and the split tooth within a single tooth pitch, resulting in multiple height abrupt changes from the main tooth to the slot opening, back to the main tooth, and finally back to the split tooth. This makes the air gap flow field more complex, and existing analytical methods for oil friction loss can no longer accurately describe its characteristics. Therefore, this invention divides the air gap into multiple sub-regions based on the split tooth topology and models them independently. This accurately distinguishes the shear force changes between the main tooth region and the split tooth region due to differences in air gap length. Furthermore, it introduces corrections for energy losses at the inlet and outlet of the tooth space entering the split tooth space, improving the calculation accuracy of existing methods for structures with multiple abrupt changes. While ensuring high efficiency in analytical calculations, it controls the prediction error of oil friction loss in split-tooth motors within a small range, providing a reliable basis for rapid evaluation during the motor design phase. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0060] Figure 1 This is a flowchart illustrating the method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to an embodiment of this application.

[0061] Figure 2 This is a schematic diagram of the topological structure of the stator crack tooth according to an embodiment of this application;

[0062] Figure 3 A flowchart illustrating the calculation of oil friction loss in an embodiment of this application, which is divided into four sub-regions;

[0063] Figure 4 This is a schematic diagram of the motor model related to an embodiment of this application;

[0064] Figure 5 This is a schematic diagram of the hybrid tooth-shaped structure topology of an embodiment of this application;

[0065] Figure 6 This is a schematic diagram of the oil friction loss calculation device for a split-tooth permanent magnet vernier motor according to an embodiment of this application. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0067] like Figure 1 As shown, this application provides a method for calculating the oil friction loss of a split-tooth permanent magnet vernier motor, which includes the following steps.

[0068] S101, based on the topological structure of the stator tooth, divides the air gap region into several sub-regions with different geometric features; the sub-regions include at least one tooth region and a slot region.

[0069] In this embodiment, Figure 2 Taking the topology of the stator tooth shown as an example, the air gap region is divided into multiple sub-regions with different geometric characteristics (air gap length, flow channel shape) according to the geometry of the stator tooth, specifically including region I, region II, region III and region IV.

[0070] based on Figure 2 The topological structure of the stator teeth shown is as follows: Figure 3 The diagram shows the calculation flowchart for oil friction loss. It details the entire process from motor structural partitioning to the final loss calculation.

[0071] S102, for each sub-region, calculate the corresponding Coetreynolds number based on its geometric dimensions and flow field state parameters, and determine the friction coefficient of the air gap based on the Coetreynolds number; calculate the shear force of each sub-region based on the friction coefficient, and calculate the oil friction loss of each sub-region by integrating the shear force.

[0072] Some geometric dimensions and flow field state parameters are defined as follows: rotor outer diameter air gap length The rotational speed is Cooling oil density viscosity , The arc length corresponding to the tooth width in zone I on the rotor surface. The arc length corresponding to the tooth width in zone II on the rotor surface. The arc length corresponding to the tooth width in zone III on the rotor surface, and the number of slots. Groove width slot height Core length .

[0073] Specifically, based on the geometric dimensions and flow field state of each sub-region, an analytical sub-model of oil friction loss applicable to each region is established, wherein the air gap friction coefficient is corrected and adjusted according to different Reynolds numbers.

[0074] Based on the partitions in S101, the expressions for oil friction loss in zones I, II, III, and IV are as follows.

[0075] The calculation process for oil friction loss in Zone I is as follows.

[0076] (1);

[0077] (2);

[0078] (3);

[0079] in, The shear force on the tooth surface of region I. It is the friction coefficient of the air gap in region I. For the Coetreno number in zone I.

[0080] From (1)-(3), the oil friction loss corresponding to the teeth in region I can be obtained:

[0081] (4).

[0082] The calculation process for oil friction loss in Zone II is as follows:

[0083] (5);

[0084] (6);

[0085] (7);

[0086] From (5)-(7), we can obtain the oil friction loss corresponding to the teeth in region II in (8):

[0087] (8).

[0088] Similarly, among them The shear force on the tooth surface of region II. It is the friction coefficient of the air gap in zone II. For zone II, the Coetreno number.

[0089] The calculation process for oil friction loss in Zone III is as follows.

[0090] (9);

[0091] (10);

[0092] (11);

[0093] in, The shear force on the tooth surface of zone III. It is the friction coefficient of the air gap in zone III. For the Coetreno number in zone III.

[0094] From (9)-(11), we can obtain the oil friction loss corresponding to the teeth in zone III (12):

[0095] (12).

[0096] The calculation process for oil friction loss in zone IV is as follows.

[0097] (13);

[0098] (14);

[0099] (15);

[0100] From (13)-(15), we can obtain (16) the oil friction loss corresponding to one groove:

[0101] (16);

[0102] Similarly, This refers to the shear force on the surface of the groove.

[0103] S103, based on the number of stator slots, the oil friction loss of each sub-region is accumulated to obtain the total oil friction loss of the stator side air gap.

[0104] In this step, the total oil friction loss of the stator side air gap is obtained by accumulating the oil friction loss of each sub-region, as follows:

[0105] (17).

[0106] S104, calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the slot space, and calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the stator tooth space.

[0107] The fluid gap in the air gap is made of Enter and This results in two separate inlet and outlet losses. The following example illustrates this: [The gap is...] The tooth space enters The slot space analysis. Similarly, the gap can also be obtained as... The tooth space enters The loss of space in the stator tooth.

[0108] Let the fluid flow through the spacing of zone IV be... The cross-sectional area of ​​the air gap is Flow velocity is The pressure is Flow through the gap The cross-sectional area is Flow velocity is The pressure is The fluid flows through the spacing of zone II. The cross-sectional area of ​​the air gap is Flow velocity is The pressure is The flow spacing is The cross-sectional area is Flow velocity is The pressure is According to the law of conservation of mass, we have:

[0109] (18);

[0110] (19);

[0111] in, The volumetric flow rate through the air gap; , , Satisfy the following expression:

[0112] (20);

[0113] According to the fluid momentum equation:

[0114] (twenty one);

[0115] (twenty two);

[0116] (twenty three);

[0117] According to the energy equation:

[0118] (twenty four);

[0119] (25);

[0120] (26);

[0121] (27);

[0122] in, Pressure head of energy loss This is the acceleration due to gravity.

[0123] According to (18)-(27), the oil friction loss at the inlet and outlet of Zone IV can be obtained as follows:

[0124] (28);

[0125] Similarly, when the fluid flows from a width of The width of the outlet space is equal to the length of the air gap. The air gap can also be obtained from Enter Energy loss at the inlet and outlet of Zone II As shown in equation (29).

[0126] (29).

[0127] S105, based on the number of stator slots, the oil friction loss of each inlet and outlet channel is accumulated to obtain the total oil friction loss at the inlet and outlet.

[0128] In this step, the oil friction losses of each inlet and outlet channel are accumulated based on the number of stator slots to obtain the total inlet and outlet oil friction losses. .

[0129] S106, calculate the area of ​​the annular micro-element on the end face of the motor rotor, calculate the frictional resistance torque based on the area of ​​the annular micro-element, integrate the frictional resistance torque to obtain the oil friction loss power on one side of the rotor end face; obtain the total oil friction loss on both sides of the end face based on the oil friction loss power on one side of the rotor end face, and use it as the total oil friction loss on the rotor side.

[0130] In internal circulation oil-cooled motors, besides the fluid shear friction at the stator-rotor air gap, significant viscous friction losses also occur at the rotor's front and rear end faces as it rotates at high speed in the cooling oil. The oil flow at the rotor end faces can be approximated as boundary layer flow on a rotating disk. (In cylindrical coordinates...) Below, the Navier-Stokes differential equations for the fluid properties of the end-face boundary layer can be simplified to:

[0131] (30);

[0132] In the formula, The density of the cooling oil, The kinematic viscosity of the cooling oil; These are the radial and circumferential velocity components of the fluid, respectively. This refers to fluid pressure.

[0133] Based on the von Kármán similarity solution of the end-face fluid mathematical model, the rate of change of the fluid circumferential velocity at the end-face wall can be obtained as follows:

[0134] (31);

[0135] In the formula, The mechanical angular velocity of the rotor, Let be the integral radius at the infinitesimal element.

[0136] According to Newton's law of internal friction, the surface shear stress at the rotor end face can be further calculated. :

[0137] (32);

[0138] Considering that the end face of the motor rotor is a circular effective area, its friction integral range extends from the outer diameter of the shaft. To the outer diameter of the rotor core Take the area of ​​the annular infinitesimal element at the end face. By calculating the frictional resistance torque on this infinitesimal element and integrating it, the oil friction loss power on one side of the rotor end face can be obtained. .

[0139] (33);

[0140] Since the rotor has two identical end faces, the total oil friction loss on both end faces is:

[0141] (34);

[0142] S107 sums the total oil friction loss of the motor by summing the total oil friction loss of the stator side air gap, the total oil friction loss of the inlet and outlet, and the total oil friction loss of the rotor side.

[0143] In summary, the total oil friction loss is:

[0144] (35).

[0145] Where i refers to the number of sub-regions, and j is the number of times the corresponding import / export occurs.

[0146] To verify the accuracy and effectiveness of the method proposed in this application, a permanent magnet vernier motor was selected as the verification object. The main structure and cooling oil parameters of the motor are shown in Table 1, and the specific locations of the relevant parameters in the motor model are shown below. Figure 4 As shown.

[0147] Table 1. Motor parameters and cooling oil parameters;

[0148]

[0149] Substituting the parameters in Table 1 into the analytical formula derived in this paper, the analytical values ​​of oil friction loss under different speeds and oil injection volumes are calculated, as shown in Table 2. To further illustrate the advantages of the proposed method, the calculation results of the traditional Yamada method and the analytical method of this application are compared with the CFD finite element simulation results (based on the finite element simulation results). The results show that under different operating conditions, the traditional method has a large calculation error because it does not distinguish the air gap difference between the main tooth and the crack tooth region and omits the energy loss at the inlet and outlet of the crack tooth. In contrast, the analytical method proposed in this application reduces the calculation error by about 6%–7% compared with the traditional method, verifying that the proposed method has higher accuracy in predicting motor oil friction loss.

[0150] Table 2. Analytical values ​​of oil friction loss under asymmetric cracked teeth, analytical values ​​of the present invention, and simulation values;

[0151]

[0152] It should be noted that the above calculation process and structure are only one embodiment. In other embodiments, the topology of the stator teeth can also be as follows: Figure 5 The hybrid tooth-shaped structure topology shown is... Figure 5 In this paper, the hybrid tooth structure is divided into six sub-regions: four different tooth regions and two groove regions. The total oil friction loss can be obtained from the above formula as follows:

[0153] (37).

[0154] Here, i refers to the number of sub-regions, and j is the number of times the corresponding inlet and outlet are entered. Therefore, the region can be expanded to n, where nl corresponds to the number of tooth regions, and l represents the number of slots.

[0155] In summary, compared with the prior art, this application has the following significant advantages:

[0156] (1) Refined partition modeling;

[0157] Existing analytical models (such as Yamada) simplify the air gap to a uniform concentric cylinder, failing to characterize the abrupt change in circumferential air gap length caused by the tooth structure. Even when some literature considers the tooth groove, it is mostly a global correction, failing to distinguish the geometric differences between different tooth profile regions. This invention, for the first time, divides the air gap into multiple sub-regions (tooth tip, tooth flank, groove, etc.) based on the tooth profile geometry, and independently establishes an analytical model based on local geometric dimensions for each sub-region, fundamentally solving the problem of loss calculation under complex tooth profile structures.

[0158] (2) Rigorous physical derivation basis;

[0159] The friction coefficients of each sub-region are derived based on the Cuyet flow theory in fluid mechanics, and a local air gap length correction is introduced, giving them clear physical significance. The inlet and outlet energy losses are rigorously derived based on mass conservation and the Bernoulli equation, avoiding the arbitrariness of empirical fitting. This makes the method of this invention not only highly accurate but also physically interpretable, facilitating subsequent optimization design.

[0160] (3) Significant improvement in accuracy;

[0161] Through comparative verification (Table 2), the calculation error of the method of the present invention is controlled within 2% under different speeds and different oil injection volumes, while the error of traditional methods is generally between 6% and 10%. This improvement in accuracy (approximately 4%-8%) is a qualitative leap, enabling the method of this application to meet the stringent requirements for loss prediction in high power density motor design.

[0162] (4) Excellent versatility and scalability;

[0163] The partitioning concept of this invention is based on the geometric features of tooth shape, and therefore has wide applicability—no matter how complex the tooth shape is (such as asymmetric cracked teeth, mixed teeth, etc.), the same modeling process can be applied simply by dividing the region according to the actual geometric shape. Figure 2 The process framework shown is applicable to any number of sub-regions, and the method itself is not limited by tooth shape, providing a unified solution for calculating oil friction loss of various types of split-tooth motors.

[0164] (5) Balancing accuracy and efficiency;

[0165] This application adopts a purely analytical approach, which has a fast calculation speed and can be directly integrated into motor design optimization software. It supports large-scale parameter scanning and optimization in the early stages of design and overcomes the disadvantage of long processing time of CFD methods.

[0166] like Figure 6 As shown, this embodiment also discloses a device for calculating the oil friction loss of a split-tooth permanent magnet vernier motor, comprising:

[0167] The sub-region division module 601 is used to divide the air gap region into several sub-regions with different geometric features based on the topological structure of the stator tooth; the sub-regions include at least one tooth region and a slot region.

[0168] The sub-region oil friction loss calculation module 602 is used to calculate the corresponding Coetreynolds number for each sub-region based on its geometric dimensions and flow field state parameters, and determine the friction coefficient of the air gap based on the Coetreynolds number; calculate the shear force of each sub-region based on the friction coefficient, and calculate the oil friction loss of each sub-region by integrating the shear force.

[0169] The air gap total oil friction loss acquisition module 603 is used to accumulate the oil friction loss of each sub-region based on the number of stator slots to obtain the stator side air gap total oil friction loss.

[0170] The inlet and outlet oil friction loss calculation module 604 is used to calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the slot space, and to calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the stator tooth space.

[0171] The total oil friction loss acquisition module 605 is used to accumulate the oil friction loss of each inlet and outlet channel based on the number of stator slots to obtain the total oil friction loss at the inlet and outlet.

[0172] The rotor-side total oil friction loss calculation module 606 is used to calculate the area of ​​the annular micro-element on the end face of the motor rotor, calculate the friction resistance torque based on the area of ​​the annular micro-element, integrate the friction resistance torque to obtain the oil friction loss power of a single rotor end face, and obtain the total oil friction loss of both end faces based on the oil friction loss power of a single rotor end face, which is used as the rotor-side total oil friction loss.

[0173] The total oil friction loss acquisition module 607 is used to sum the total oil friction loss of the stator side air gap, the total oil friction loss of the inlet and outlet and the total oil friction loss of the rotor side to obtain the total oil friction loss of the motor.

[0174] The specific implementation of each module of the oil friction loss calculation device for a split-tooth permanent magnet vernier motor is the same as the oil friction loss calculation method for a split-tooth permanent magnet vernier motor, and will not be repeated in this embodiment.

[0175] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the oil friction loss of a split-tooth permanent magnet vernier motor, characterized in that, include: Based on the topological structure of the stator tooth, the air gap region is divided into several sub-regions with different geometric features; each sub-region includes at least one tooth region and a slot region. For each sub-region, the corresponding Coetreynolds number is calculated based on its geometric dimensions and flow field state parameters, and the friction coefficient of the air gap is determined based on the Coetreynolds number; the shear force of each sub-region is calculated based on the friction coefficient, and the oil friction loss of each sub-region is calculated by integrating the shear force. The total oil friction loss of the stator side air gap is obtained by summing the oil friction loss of each sub-region based on the number of stator slots. Calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the slot space, and calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the stator tooth space. The total oil friction loss at the inlet and outlet is obtained by summing the oil friction losses of each inlet and outlet channel based on the number of stator slots. Calculate the area of ​​the annular infinitesimal element on the rotor end face of the motor, calculate the frictional resistance torque based on the area of ​​the annular infinitesimal element, integrate the frictional resistance torque to obtain the oil friction loss power on one side of the rotor end face; obtain the total oil friction loss on both sides of the rotor end face based on the oil friction loss power on one side of the rotor end face, and use it as the total oil friction loss on the rotor side. The total oil friction loss of the motor is obtained by summing the total oil friction loss in the stator air gap, the total oil friction loss at the inlet and outlet, and the total oil friction loss on the rotor side.

2. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 1, characterized in that, Oil friction loss in each gear zone , means as follows: ； ； ； ； in, Indicates the first district; Indicates rotational speed; Indicates the length of the iron core; Indicates the first Shear force on the surface of the toothed area; Indicates the first The arc length corresponding to the tooth width on the rotor surface; Indicates the density of the cooling oil; Indicates the rotor's outer diameter; Indicates the first The friction coefficient of the air gap; Indicates the air gap length; Indicates the first District Couretren number; Indicates the first The height of the teeth, Greater than or equal to 0; This indicates the viscosity of the cooling oil.

3. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 1, characterized in that, Oil friction loss in the groove area , means as follows: ； ； ； ； in, Indicates rotational speed; Indicates the length of the iron core; This represents the shear force on the surface of the groove area; Indicates the width of the stator slot; Indicates the density of the cooling oil; Indicates the rotor's outer diameter; This represents the friction coefficient of the air gap in the slot area; Indicates the air gap length; Indicates the Coetreno number of the slot region; Indicates the first The height of the teeth, Greater than or equal to 0; Indicates the height of the slot; This indicates the viscosity of the cooling oil.

4. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 1, characterized in that, The total oil friction loss of the stator side air gap is obtained by summing the oil friction losses of each sub-region based on the number of stator slots, as shown below: ； in, Indicates the total oil friction loss in the stator side air gap; N represents the number of grooves; I represents the number of tooth zones; This indicates the oil friction loss in each tooth area; This indicates the oil friction loss in the groove area.

5. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 1, characterized in that, The frictional losses of the inlet oil entering the slot space and the frictional losses of the outlet oil are represented as follows: ； in, This indicates the frictional loss of the inlet oil entering the groove space from the tooth space. Frictional loss of the outlet oil entering the slot space from the toothed space; Indicates the density of the cooling oil; The distance through which the fluid flows is the air gap length. The cross-sectional area, The distance between the slot openings where the fluid flows is the air gap length. The flow rate; The distance between the slot openings where the fluid flows is the air gap length. with the height of the slot The cross-sectional area of ​​the sum; The distance between the slot openings where the fluid flows is the air gap length. with the height of the slot The sum of the flow rates; Indicates rotational speed; Indicates the rotor outer diameter; N indicates the number of slots; Indicates the width of the stator slot; The frictional losses of the inlet oil and outlet oil entering the stator tooth space from the tooth space are represented as follows: ； in, This indicates the frictional loss of the inlet oil as it enters the stator tooth space from the tooth space. Frictional loss of the outlet oil entering the stator tooth space from the tooth space; The distance between the teeth indicates that the fluid flows through the air gap. The flow rate; The distance between the teeth indicates that the fluid flows through the air gap. With the height of the teeth The cross-sectional area of ​​the sum; The distance between the teeth indicates that the fluid flows through the air gap. With the height of the teeth The sum of the flow rates; This indicates the arc length corresponding to the tooth width of the corresponding tooth region on the rotor surface.

6. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 1, characterized in that, Oil friction loss power on one side of rotor end face , means as follows: ； in, This represents the frictional resistance torque; Indicates rotational speed; This represents the surface shear stress at the rotor end face; This represents the area of ​​the annular element on the end face; Indicates the rotor's outer diameter; Indicates the outer diameter of the shaft; Indicates the density of the cooling oil; Let be the integral radius at the infinitesimal element; This indicates the viscosity of the cooling oil.

7. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 6, characterized in that, Surface shear stress at rotor end face , means as follows: ； in, This represents the rate of change of the fluid circumferential velocity at the end face wall.

8. The method for calculating oil friction loss of a split-tooth permanent magnet vernier motor according to claim 6, characterized in that, Total oil friction loss on rotor side , means as follows: 。 9. A device for calculating oil friction loss of a split-tooth permanent magnet vernier motor, characterized in that, include: The sub-region division module is used to divide the air gap region into several sub-regions with different geometric features based on the topological structure of the stator tooth; the sub-regions include at least one tooth region and a slot region; The sub-region oil friction loss calculation module is used to calculate the corresponding Coetreynolds number for each sub-region based on its geometric dimensions and flow field state parameters, and determine the friction coefficient of the air gap based on the Coetreynolds number; calculate the shear force of each sub-region based on the friction coefficient, and calculate the oil friction loss of each sub-region by integrating the shear force. The total oil friction loss acquisition module for the air gap is used to accumulate the oil friction loss of each sub-region based on the number of stator slots to obtain the total oil friction loss of the stator side air gap. The inlet and outlet oil friction loss calculation module is used to calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the slot space, and to calculate the inlet oil friction loss and outlet oil friction loss when the tooth space enters the stator tooth space. The module for obtaining total oil friction loss at inlet and outlet is used to accumulate the oil friction loss of each inlet and outlet channel based on the number of stator slots to obtain the total oil friction loss at inlet and outlet. The rotor-side total oil friction loss calculation module is used to calculate the area of ​​the annular micro-element on the end face of the motor rotor, calculate the friction resistance torque based on the area of ​​the annular micro-element, integrate the friction resistance torque to obtain the oil friction loss power of a single rotor end face, and obtain the total oil friction loss of both end faces based on the oil friction loss power of a single rotor end face, which is used as the rotor-side total oil friction loss. The total oil friction loss acquisition module is used to sum the total oil friction loss of the stator side air gap, the total oil friction loss of the inlet and outlet, and the total oil friction loss of the rotor side to obtain the total oil friction loss of the motor.

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