A simulation method for winding process of carbon fiber sleeve of high-speed permanent magnet motor rotor

Abstract

The application discloses a kind of high-speed permanent magnet motor rotor carbon fiber maintenance sleeve winding process simulation method.The method will have continuous spiral structure carbon fiber maintenance sleeve discretization, the winding process is simulated by activation scaling method or activation release scaling method, and is realized based on finite element simulation.The application compares the mechanical energy change of carbon fiber layer in winding process with the chemical energy change in chemical reaction, and introduces activation force to simulate the carbon fiber winding process.The method not only retains the real physical properties of each component of the rotor, but also simulates the stretching effect of winding tension on the carbon fiber layer.Based on the simulation of the carbon fiber winding process using the method described in the application, the stress of the rotor bound by carbon fiber under various working conditions can be accurately calculated.

Description

Technical Field

[0001] This invention belongs to the field of high-speed motor rotor strength analysis technology, and more specifically, relates to a simulation method and stress calculation method for the winding process of carbon fiber sheath of high-speed permanent magnet motor rotor. Background Technology

[0002] High-speed permanent magnet motors, characterized by high efficiency, high power density, and high-speed direct drive, have attracted widespread attention in modern industry. However, the centrifugal force generated by high-speed rotation poses a significant risk of damage to permanent magnets. To provide sufficient preload to the rotor, composite carbon fibers with high tensile strength, low density, and low conductivity are required to bind the rotor. During the design phase of high-speed permanent magnet motors, it is necessary to verify the strength of the carbon fiber-bound rotor under different operating conditions to ensure rotor safety. Currently, the commonly used method to simulate the actual carbon fiber winding process is the equivalent temperature field method, which applies a false coefficient of thermal expansion or temperature rise to the carbon fiber layer, making the thermal stress of the carbon fiber layer equal to the stress generated by the winding tension. However, this method sacrifices the coefficient of thermal expansion or temperature rise of the carbon fiber layer and cannot accurately calculate the rotor stress under high-temperature conditions after winding.

[0003] Therefore, new calculation methods are urgently needed to simulate the winding process of carbon fiber sheaths in order to accurately calculate the rotor stress under different working conditions after winding. Summary of the Invention

[0004] To address the shortcomings of existing methods for simulating the carbon fiber sheath winding process, this invention aims to propose a simulation method for the carbon fiber sheath winding process of a high-speed permanent magnet motor rotor. This method employs either an activated scaling method or an activated expansion method to simulate the rotor's carbon fiber sheath winding process. The proposed method is based on finite element simulation, preserving the true physical properties of each rotor component to calculate rotor stress under different operating conditions. The technical solution of this invention is as follows:

[0005] A simulation method for the winding process of a carbon fiber sheath for a high-speed permanent magnet motor rotor is provided, which discretizes the carbon fiber sheath having a continuous helical structure, and the winding process is simulated by an activated scaling method or an activated shrinking method.

[0006] Furthermore, the activation scaling method is implemented based on the three-dimensional motion unit method, and its steps include:

[0007] A1. Construct an initial finite element model, requiring the outer diameter of the permanent magnet rotor to be greater than the inner diameter of the first layer of carbon fiber, and the outer diameter of the i-th layer of carbon fiber to be greater than the inner diameter of the (i+1)-th layer of carbon fiber.

[0008] A2. The inward-pointing compressive activation force acts on the permanent magnet rotor, causing the radius of the permanent magnet rotor to decrease until it is smaller than the inner diameter of the first layer of carbon fiber.

[0009] A3. The first layer of carbon fiber moves to the surface of the permanent magnet rotor, the activation force is removed, and the permanent magnet rotor pushes the carbon fiber layer outward to complete the winding of the first layer of carbon fiber.

[0010] A4. Repeat steps A2 and A3 until all layers of carbon fiber winding are completed.

[0011] The activation scaling method based on the three-dimensional motion unit method is described as follows: Initially, there is a permanent magnet rotor (referred to as layer 0 for convenience) and N carbon fiber layers in space, where the outer diameter of layer i (i≥0) is greater than the inner diameter of layer i+1. When winding layer i (i≥1), the condition for winding to occur is that the inner diameter of layer i is greater than the outer diameter of layer i-1. Therefore, to enable winding, a compressive activation force is applied to layer i-1, causing the outer diameter of layer i-1 to be smaller than the inner diameter of layer i. After the carbon fiber layer i moves to the surface of carbon fiber layer i-1, the activation force is removed. At this time, the internal components will expand the carbon fiber layer i outward, completing the winding of layer i. From the inside to the outside, the winding of all carbon fiber layers is completed. Under the action of the activation force, each carbon fiber layer completes a "contraction" and "expansion" process in two time steps, realizing the simulation of the actual winding process.

[0012] Furthermore, the activation scaling method is implemented based on the two-dimensional birth and death unit method, and its steps include:

[0013] B1. Construct an initial finite element model, requiring the outer diameter of the permanent magnet rotor to be greater than the inner diameter of the first layer of carbon fiber, and the outer diameter of the i-th layer of carbon fiber to be greater than the inner diameter of the (i+1)-th layer of carbon fiber.

[0014] B2. The activation force starts from the outermost carbon fiber, causing the carbon fiber layer to expand outward and increase its radius until the inner diameter of the i-th carbon fiber layer is greater than the outer diameter of the (i-1)-th carbon fiber layer. At this point, the (i-1)-th layer is activated.

[0015] B3. Repeat step B2 until the permanent magnet rotor is activated, during which the activation force on each layer of carbon fiber continues to act.

[0016] B4. Starting from the first layer of carbon fiber, the activation force is removed layer by layer, the carbon fiber layers shrink, and the winding of all layers of carbon fiber is completed.

[0017] The activation and shrinkage method based on the two-dimensional birth and death unit method is described as follows: Initially, the "dead" space contains a permanent magnet rotor (referred to as layer 0 for convenience) and N layers of carbon fibers, where the outer diameter of layer i (i≥0) is larger than the inner diameter of layer i+1. To meet the winding conditions of the carbon fiber layers, starting from layer N, the carbon fiber layers are activated layer by layer inward, and an expansion-type activation force is applied, driving the outer diameter of layer i (i≥1) to be larger than the inner diameter of layer i-1 (i≥1). Before activating the permanent magnet rotor, all activation forces need to be continuously applied. After activating all components, the activation forces acting on the carbon fiber layers are removed layer by layer starting from layer 1. Removing the activation forces will cause the carbon fiber layers to shrink inward, producing a binding effect on the inner components, thus simulating the actual winding process.

[0018] In this invention, the main difference between the activated scaling method and the activated shrinking method lies in the direction and duration of the activation force. In the method described, the activation force only changes the radius of the carbon fiber layer to meet the winding conditions. Within the range of elastic deformation, the magnitude and nature of the activation force do not affect the stress calculation results; it only needs to be large enough to allow winding to occur. The role of the activation force is the same as that of the activation energy in a chemical reaction.

[0019] When simulating the winding process of carbon fiber layers using the described method, the radius of each carbon fiber layer increases before and after winding, leading to an increase in its elastic potential energy. Therefore, each carbon fiber layer tends to contract inward to an equilibrium position. This tendency generates circumferential stress on the carbon fiber layer and radial pressure on the inner components; the change in elastic potential energy of the carbon fiber layer before and after winding can be analogous to the change in chemical energy of a substance before and after a chemical reaction. The method uses the circumferential stress generated by this contraction tendency to simulate the stress generated by the winding tension. The winding tension is controlled by changing the initial radius of each carbon fiber layer, where the radius refers to the radius at the middle position of the carbon fiber layer. The method for solving the initial radius of the carbon fiber layer is described below:

[0020] The circumferential stress in the carbon fiber layer caused by the shrinkage tendency is an explicit function of the carbon fiber layer radius, i.e., σ θ =f(r), at r = R0, its Taylor expansion can be expressed as,

[0021] σ θ =f(R0)+f'(R0)(r-R0)+f”(R0)(r-R0) 2 / 2+… (1)

[0022] Furthermore, retaining only the linear principal part, equation (1) can be simplified to:

[0023] σ θ =f(R0)+f'(R0)(r-R0) (2)

[0024] Equation (2) is a linear univariate function of R0, so the initial radius of the carbon fiber layer under a given winding tension can be determined by two iterations.

[0025] Furthermore, after the carbon fiber layers are wound, they adhere tightly together, with a radius R c Given that the initial radius R1 of the first iteration satisfies

[0026] σ T =(R c -R1) / R1×E / / (3)

[0027] Where, σ T The stress generated by the winding tension is calculated as σ. T =F t / (ab), F t E represents the winding tension, where a and b are the width and thickness of the carbon fiber layer, respectively. ∥ Let be the Young's modulus along the direction parallel to the carbon fiber. The proposed method can be used to calculate the circumferential stress σ corresponding to an initial radius R1 of the carbon fiber layer. θ1 The initial radius of the second iteration is R1 + ΔR, and the corresponding circumferential stress is σ. θ2 . Will (R1,σ θ1 ) and (R1+ΔR,σ θ2 Substituting into (2) will give the initial radius of the carbon fiber layer under a given winding tension.

[0028] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0029] The method provided by this invention, while preserving the true physical properties of each material in the rotor, uses the circumferential stress generated by the shrinkage trend caused by the change in the radius of the carbon fiber layer before and after winding to equivalently simulate the winding tension, thereby simulating the winding process of the carbon fiber sheath. After the winding process simulation is completed, applying rotational speed and temperature rise conditions to the rotor allows for verification of the rotor stress under various operating conditions. Attached Figure Description

[0030] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments of this application in conjunction with the accompanying drawings.

[0031] Figure 1 This is a schematic diagram illustrating the activation scaling method based on the three-dimensional motion unit method.

[0032] Figure 2 This is a schematic diagram illustrating the activation scaling method based on the two-dimensional birth and death unit method.

[0033] Figure 3A schematic diagram of an interference fit between a preformed carbon fiber sheath and a permanent magnet rotor;

[0034] Figure 4 The relationship between the radius of the permanent magnet rotor and temperature in this embodiment of the invention is as follows: when using liquid nitrogen to cool the interference fit.

[0035] Figure 5 The first principal stress of the permanent magnet under high-speed and high-temperature conditions is calculated using the proposed method.

[0036] Figure 6 The maximum circumferential stress of the carbon fiber sheath in a rotor with a pre-formed carbon fiber sheath under high-speed and high-temperature conditions is calculated using the proposed method.

[0037] Figure 7 A schematic diagram showing the simplified multi-layer discrete ring structure of a carbon fiber sheath with a continuous spiral structure.

[0038] Figure 8 A schematic diagram of a surface-mounted permanent magnet motor rotor structure with a multi-layer carbon fiber sheath.

[0039] Figure 9 The circumferential stress change of the carbon fiber layer during the carbon fiber winding process is calculated using the proposed activation scaling method and activation shrinkage method in this embodiment of the invention.

[0040] Figure 10 To calculate the circumferential stress of the carbon fiber layer under different working conditions using the activated scaling method;

[0041] Figure 11 To calculate the stress of the permanent magnet and the shaft under different working conditions using the activation scaling method;

[0042] In all the attached figures, Condition A is a stationary condition at room temperature (22℃); Condition B is a stationary condition at room temperature (1.2 times the rated speed); Condition C is a stationary condition at hot temperature (150℃); and Condition D is a stationary condition at hot temperature.

[0043] Among them, 1-rotating shaft, 2-permanent magnet, 3-first layer of carbon fiber, 4-Nth layer of carbon fiber, 5-pre-formed carbon fiber sheath, 6-permanent magnet rotor, 7-activation force. Detailed Implementation

[0044] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways than those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0046] To address the issue of existing methods for simulating the carbon fiber sheath winding process of high-speed permanent magnet motor rotors sacrificing the true physical properties of the carbon fiber, this invention, starting from the mechanical energy variation law of the carbon fiber layer during winding, proposes an activated scaling method and an activated shrinking method based on finite element simulation that preserve the true physical properties of each material. Their implementation processes are as follows: Figure 1 , Figure 2 As shown. Driven by activation force 7, the winding process can occur. The method controls the circumferential stress of the winding layer after winding by changing the initial radius of the carbon fiber layer, and uses this circumferential stress to equivalently represent the stress generated by the winding tension. Compared with the traditional method of using thermal stress to equivalently represent the stress generated by the winding tension, this method retains the true physical properties and temperature rise of each material, and can accurately verify the stress of the rotor bound by carbon fiber under various working conditions after winding.

[0047] The technical solution of this application is further illustrated below with reference to the embodiments.

[0048] Example 1

[0049] For the pre-formed carbon fiber sheath 5, it is first wound and cured on a mandrel, and then the permanent magnet rotor 6 is interference-fitted to the pre-formed carbon fiber sheath 5 using a cold fitting method. The assembly diagram is shown below. Figure 3 As shown. The conventional approach is to immerse the permanent magnet rotor 6 in liquid nitrogen to cool it down, thereby reducing its outer diameter, so that the permanent magnet rotor 6 can be inserted into the pre-formed carbon fiber sheath 5. After returning to room temperature, the interference fit is completed.

[0050] Based on the interference fit process, the pre-formed carbon fiber sheath 5 is considered as a generalized layer of carbon fiber. Therefore, the assembly process is simulated using the activation scaling method. The compressive activation force 7 acts on the permanent magnet rotor to simulate the cooling effect of liquid nitrogen, and removing the activation force simulates the temperature rise to room temperature.

[0051] The initial radius of the carbon fiber layer is determined by the interference fit and the interference method. For example... Figure 4As shown, in this embodiment, when the rotor is cooled from room temperature to liquid nitrogen temperature, the radius reduction of the permanent magnet rotor 6 does not exceed 0.1 mm, therefore its interference fit can be determined to be 0.09 mm. When the tolerance acts on the sheath, it is called external interference; when the tolerance acts on the permanent magnet, it is called internal interference. Therefore, for the rotor in this embodiment, when the interference fit is external, the initial inner diameter of the sheath is 38.11 mm, and the outer diameter of the permanent magnet is 38.2 mm; when the interference fit is internal, the initial inner diameter of the sheath is 38.2 mm, and the outer diameter of the permanent magnet is 38.29 mm.

[0052] After assembly, the calculated maximum value of the first principal stress of the permanent magnet is as follows: Figure 5 As shown, the maximum circumferential stress of the preformed carbon fiber sheath is as follows: Figure 6 As shown. The results show that the stress calculation results of the preformed carbon fiber sheath 5 and the permanent magnet rotor 6 under interference fit using the two proposed methods are very close.

[0053] Example 2

[0054] When manufacturing carbon fiber rotors using high-tension winding, the carbon fibers are directly bound to the rotor surface. For example... Figure 7 As shown, due to the thinness of the carbon fiber, the continuous spiral structure is simplified into a discrete ring structure for ease of calculation.

[0055] for Figure 8 The key to simulating the winding process using the activated scaling and activated shrinking methods in the multi-layer carbon fiber rotor structure shown lies in determining the initial radius of each carbon fiber layer. This embodiment employs a constant tension dry winding method with a winding tension of 700 N, corresponding to a winding stress of 882 MPa. The initial radius of the first carbon fiber layer will be used as an example to illustrate how to determine the initial radius of the carbon fiber layer.

[0056] In this embodiment, the radius of the first layer of carbon fiber after winding is 38.2625 mm, which is close to the surface of the permanent magnet rotor. The elastic modulus of the carbon fiber in the parallel direction is 130 GPa. According to formula (3) in the specification, the initial radius of the first iteration is 38.0047 mm. Using the proposed method, the circumferential stress of the carbon fiber layer in the first iteration is calculated to be 875.7122 MPa using finite element method. Since formula (2) in the specification is a linear function, only two sets of data are needed to determine its expression. The initial radius of the second iteration is selected as (38.0047 + ΔR) mm, where ΔR is a very small value. The stress of the second iteration can be calculated. Thus, the expression of formula (2) is obtained, and the initial radius of the carbon fiber with the required circumferential stress of 882 MPa can be obtained by inverse solution. The solution method for the carbon fiber radius of the remaining layers is the same.

[0057] The winding process of the carbon fiber sheath in this embodiment was simulated using the activated scaling method and the activated shrinking method, respectively. Figure 9(a) and (b) show the circumferential stress changes of the carbon fiber layer during the winding process. The results show that the results obtained by the two methods are almost the same, and the stress changes of the carbon fiber layer during the winding process have the same trend. The proposed method realizes the simulation of the binding effect of the carbon fiber layer and can observe the stress relaxation phenomenon during winding.

[0058] After winding, different rotational speeds and temperature rises were applied to the rotor to verify the rotor stress under four typical operating conditions: room temperature stationary (condition A), room temperature overspeed (condition B), high temperature overspeed (condition C), and high temperature stationary (condition D). The circumferential stress of the carbon fiber layer under different operating conditions is shown below. Figure 10 As shown. Figure 11 (a) represents the maximum value of the first principal stress of the permanent magnet under different working conditions. Figure 11 (b) represents the maximum von Mises stress of the shaft under different working conditions.

[0059] The proposed method was used to simulate the carbon fiber sheath winding process of this embodiment. After winding, the stress of the carbon fiber rotor under different operating conditions can be accurately calculated. The proposed method provides strong support for verifying rotor strength in the design phase of such high-speed motors.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A simulation method for the winding process of carbon fiber sheath on a high-speed permanent magnet motor rotor, characterized in that, The carbon fiber sheath with a continuous helical structure is discretized. The winding process is simulated by constructing a finite element model using the activated scaling method or the activated shrinking method. When constructing the initial finite element model, the initial radius of the carbon fiber layer needs to be determined. The steps include: The circumferential stress in the carbon fiber layer caused by the shrinkage tendency is an explicit function of the carbon fiber layer radius, i.e., σ θ =f(r), at r=R0, its Taylor expansion can be expressed as, Furthermore, retaining only the linear principal part, equation (1) can be simplified to: Equation (2) is a linear univariate function of R0, so the initial radius of the carbon fiber layer under a given winding tension can be determined by two iterations. Because the carbon fiber layers are tightly bonded together after winding, their radius R c Given that the initial radius R1 of the first iteration satisfies Where, σ T The stress generated by the winding tension is calculated as σ. T =F t / (ab), F t E represents the winding tension, where a and b are the width and thickness of the carbon fiber layer, respectively. ∥ This represents Young's modulus along the direction parallel to the carbon fiber. The initial radius of the second iteration is R1 + ΔR, and the corresponding circumferential stress is σ. θ2 , convert (R1, σ θ1 ) and (R1+ΔR,σ θ2 Substituting into (2) will give the initial radius of the carbon fiber layer under a given winding tension.

2. The simulation method according to claim 1, characterized in that, The activation scaling method is based on the three-dimensional motion unit method, and its steps include: A1. Construct an initial finite element model, requiring the outer diameter of the permanent magnet rotor to be greater than the inner diameter of the first layer of carbon fiber, and the outer diameter of the i-th layer of carbon fiber to be greater than the inner diameter of the (i+1)-th layer of carbon fiber. A2. The inward-pointing compressive activation force acts on the permanent magnet rotor, causing the radius of the permanent magnet rotor to decrease until it is smaller than the inner diameter of the first layer of carbon fiber. A3. The first layer of carbon fiber moves to the surface of the permanent magnet rotor, the activation force is removed, and the permanent magnet rotor pushes the carbon fiber layer outward to complete the winding of the first layer of carbon fiber. A4. Repeat steps A2 and A3 until all layers of carbon fiber winding are completed.

3. The simulation method according to claim 1, characterized in that, The activation scaling method is based on the two-dimensional birth and death unit method, and its steps include: B1. Construct an initial finite element model, requiring the outer diameter of the permanent magnet rotor to be greater than the inner diameter of the first layer of carbon fiber, and the outer diameter of the i-th layer of carbon fiber to be greater than the inner diameter of the (i+1)-th layer of carbon fiber. B2. The activation force starts from the outermost carbon fiber, causing the carbon fiber layer to expand outward and increase its radius until the inner diameter of the i-th carbon fiber layer is greater than the outer diameter of the (i-1)-th carbon fiber layer. At this point, the (i-1)-th layer is activated. B3. Repeat step B2 until the permanent magnet rotor is activated, during which the activation force on each layer of carbon fiber continues to act. B4. Starting from the first layer of carbon fiber, the activation force is removed layer by layer, the carbon fiber layers shrink, and the winding of all layers of carbon fiber is completed.

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