A brushless motor rotor and a design method for the motor rotor

Abstract

The invention discloses a brushless motor and a design method for the motor rotor, and relates to the technical field of brushless motors. The motor comprises a motor rotor and a motor stator, and an air gap is formed between the motor rotor and the motor stator; the outer contour curve of the motor rotor is formed by a fitting curve, so that the air gap value changes in a sinusoidal law; the contour curve of the outer surface of the motor rotor is fitted, so that the air gap value between the motor rotor and the motor stator can be distributed along a sine, so as to optimize the air gap magnetic resistance distribution, weaken the motor tooth slot torque, improve the sinusoidality of the air gap magnetic field, reduce the back electromotive force harmonic distortion rate and the starting resistance torque, and improve the overall performance of the motor; the formula provided by the invention is used to fit the outer contour curve of the motor rotor, and the motor rotor is molded and manufactured, which is easy to process and has high precision without additionally increasing the amount of raw materials.

Description

Technical Field

[0001] The present invention relates to the technical field of brushless motors, and in particular to a brushless motor rotor and a design method for the motor rotor. Background Art

[0002] The automotive condenser fan is an important component of the cooling system of motor vehicles and construction machinery. Its main function is to dissipate the heat of the coolant in the water tank. The condenser fan uses a brushless motor to drive the fan blades to rotate at high speed, driving the air to flow quickly to achieve the purpose of rapid heat exchange. The torque fluctuation when the brushless motor rotates at high speed directly affects the stability of the fan blade rotation, which has a significant impact on the vibration and noise of the fan.

[0003] In order to reduce the torque fluctuation when the motor rotates at high speed, there are many measures that are usually adopted, mainly increasing the air gap between the stator and rotor of the motor, stator skew slots or rotor skew poles, unequal width design of stator core slots, slotting on the inner surface of the stator core, etc., and evaluating the improvement of torque fluctuation through modeling simulation; the essence of the above methods is to improve the torque fluctuation by optimizing the sinusoidality of the air gap flux density waveform. Although they have certain effects to a certain extent, the problem is that some measures need to rely on a significant increase in the amount of raw materials to achieve the purpose, otherwise it will significantly affect other performance indicators; others are not regular and it is difficult to quantitatively grasp the changing trends, so they must be modeled and simulated one by one to select a more suitable solution, which is often a very large workload and the optimization effect is not satisfactory.

[0004] The patent with announcement number CN104184236B discloses a permanent magnet for a motor, wherein the motor includes a motor rotor and a motor stator, an air gap is formed between the motor rotor and the motor stator, and the permanent magnet includes a base surface, the base surface is in contact with the outer surface of the motor rotor; an upper top surface, the upper top surface is arranged opposite to the air gap, and the contour line of the upper top surface is a curve formed by superposition of a sine wave and a third harmonic function. The advantage is that a new permanent magnet structure is obtained by adding a sine wave to an optimal third harmonic function, and the torque output is increased without increasing the torque pulsation of the motor. The motor has the advantages of high power density, high efficiency and energy saving, smooth operation, low noise, etc. However, the above scheme needs to stick the permanent magnet material during use, the structural stability is not high, and each magnet needs to be specially contoured during the processing, resulting in large errors, low forming rate, and high cost. Summary of the invention

[0005] The main technical problem to be solved by the present invention is to provide a brushless motor rotor and a design method for the motor rotor, which can solve the problems mentioned in the above background technology.

[0006] In order to solve the above-mentioned main technical problems, the following technical solutions are adopted:

[0007] A brushless motor rotor, the motor comprising a motor rotor and a motor stator, an air gap being formed between the motor rotor and the motor stator; an outer contour curve of the motor rotor is formed by a fitting curve so that the air gap value changes in a sinusoidal manner;

[0008] The specific shape of the fitting curve can be expressed as:

[0009] R(θ)=R1-F(θ) (1)

[0010] In formula (1), R(θ) is the pole diameter of any point P in the outer contour of the motor rotor, R1 is the inner radius of the motor stator, and F(θ) is the function expression of the air gap value δ;

[0011] The F(θ) can be determined by the following function:

[0012] F(θ)=δmin+A / 2+A / 2*cos(2θ) (2)

[0013] In formula (2), δmin is the minimum value of the air gap, θ is the electrical angle of the motor, cos(2θ) is the cosine value of twice the electrical angle; and A is a selected constant.

[0014] Preferably, the minimum value δmin of the air gap in the formula (2) is 2-3 times the constant A.

[0015] Preferably, the number of magnetic poles of the motor is 8; a plurality of annularly distributed slots are provided on the motor rotor, and the permanent magnets are inserted into the slots.

[0016] A method for designing a brushless motor rotor comprises the following steps:

[0017] S1: Initially design the motor according to its usage requirements and determine the inner radius of the motor stator R1 and the minimum air gap value δmin;

[0018] S2: Select the value of constant A according to the multiple relationship between the minimum value δmin of the air gap value and constant A;

[0019] S3: Substitute the constant A and the minimum air gap value δmin into the formula F(θ)=δmin+A / 2+A / 2*cos(2θ), thereby determining the function curve F(θ) of the air gap value δ and the motor electrical angle θ;

[0020] S4: According to the function curve F(θ) determined in step S3 and the formula R(θ)=R1-F(θ), the outer contour curve of the motor rotor is fitted.

[0021] Compared with the prior art, the present invention applied to brushless motors has the following advantages:

[0022] (1) Fitting the contour curve of the outer surface of the motor rotor allows the air gap value between the motor rotor and the motor stator to be distributed along the sine, thereby optimizing the air gap magnetic resistance distribution, weakening the motor cogging torque, improving the sinusoidality of the air gap magnetic field, reducing the back-EMF harmonic distortion rate and starting resistance torque, and improving the overall performance of the motor.

[0023] (2) The formula provided by the present invention is used to fit the outer contour curve of the motor rotor, and the motor rotor is molded and manufactured. The processing is easy and accurate, and no additional raw material consumption is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a schematic diagram of the outer contour of the motor rotor with a mechanical angle of 90° in the motor;

[0026] Figure 2 This is a curve diagram showing the relationship between electrical angle and air gap value.

[0027] In the figure: 1 is the motor rotor, 2 is the motor stator, and 3 is the permanent magnet. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, all the connection relationships mentioned in the text do not refer to the direct connection of components, but refer to the fact that a better connection structure can be formed by adding or reducing connection accessories according to the specific implementation situation.

[0029] See also Figure 1-2As shown, a brushless motor rotor is provided, the motor comprising a motor rotor 1 and a motor stator 2, an air gap being formed between the motor rotor 1 and the motor stator 2; the number of magnetic poles of the motor is 4p=8; a plurality of annularly distributed slots are provided on the motor rotor 1, the permanent magnets 3 are inserted into the slots, and the shape of the permanent magnets 3 is a rectangle or other common and easy-to-process shapes; the outer contour curve of the motor rotor 1 is formed by a fitting curve, so that the air gap value changes in a sinusoidal manner; after the fitting curve of the outer contour curve of the motor rotor 1 is determined, a mold is opened and then the outer contour of the motor rotor 1 is processed, the processing is convenient, the forming rate is high and the precision is high.

[0030] The specific shape of the fitting curve of the outer contour of the motor rotor 1 can be expressed as:

[0031] R(θ)=R1-F(θ) (1)

[0032] In formula (1), R(θ) is the pole diameter of any point P in the outer contour of the motor rotor 1, R1 is the inner radius of the motor stator 2, F(θ) is the function expression of the air gap value δ; θ is the electrical angle of the motor.

[0033] The F(θ) can be determined by the following function:

[0034] F(θ)=δmin+A / 2+A / 2*cos(2θ) (2)

[0035] In formula (2), δmin is the minimum value of the air gap value, θ is the electrical angle of the motor, cos(2θ) is the cosine value of twice the electrical angle; A is a selected constant; the minimum value of the air gap value δmin in formula (2) is 2-3 times the constant A, that is, the air gap value fluctuates between the minimum value and the maximum value.

[0036] When θ=0°, δ is at its maximum value. d max When θ=π / 2, δ is at its minimum value, i.e., δ=δmin; when θ=π, δ returns to its maximum value, i.e., δ=δmax, completing a change cycle.

[0037] A method for designing a brushless motor rotor comprises the following steps:

[0038] S1: Perform an initial design according to the use requirements of the motor, and determine the inner radius value of the motor stator 2R1 and the minimum air gap value δmin; the selection and design of the value of the motor stator 2R1 and the minimum air gap value δmin can refer to the prior art;

[0039] S2: According to the multiple relationship between the minimum value δmin of the air gap value and the constant A, the value of constant A is selected. The value of constant A can be adjusted. By adjusting the value of constant A, the variation range of δ can be adjusted.

[0040] S3: Substitute the constant A and the minimum air gap value δmin into the formula F(θ)=δmin+A / 2+A / 2*cos(2θ), thereby determining the function curve F(θ) of the air gap value δ and the motor electrical angle θ;

[0041] S4: According to the function curve F(θ) determined in step S3 and the formula R(θ)=R1-F(θ), the outer contour curve of the motor rotor 1 is fitted.

[0042] The design method provided by the present invention is simple and efficient. The motor rotor 1 and the motor stator 2 are manufactured according to the design method, with high forming rate and easy processing. At the same time, because the air gap value continuously approaches the sinusoidal distribution, the air gap magnetic resistance distribution can be optimized, the motor cogging torque can be weakened, the sinusoidality of the air gap magnetic field can be improved, the back electromotive force harmonic distortion rate and the starting resistance torque can be reduced, and the overall performance of the motor can be improved.

[0043] It should be noted that the "up, down, left, right, inside, and outside" in the present invention are defined based on the relative positions of the components in the figure. This is only for the clarity and convenience of describing the technical solution. It should be understood that the use of these directional words does not constitute a limitation on the scope of protection of this application.

[0044] The implementation modes described above are only preferred implementation modes and are not used to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions recorded in the aforementioned implementation modes or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a brushless motor rotor, wherein the motor comprises a motor rotor and a motor stator, and an air gap is formed between the motor rotor and the motor stator; an outer contour curve of the motor rotor is formed by a fitting curve, so that the value of the air gap changes in a sinusoidal manner; The specific shape of the fitting curve can be expressed as: R(θ) = R1 - F(θ) (1) In formula (1), R(θ) is the pole diameter of any point P in the outer contour of the motor rotor, R1 is the inner radius of the motor stator, and F(θ) is the function expression of the air gap value δ; The F(θ) can be determined by the following function: F(θ) = δmin + A / 2 + A / 2*cos(2θ)(2) In formula (2), δmin is the minimum value of the air gap value, θ is the electrical angle of the motor, and cos(2θ) is the cosine value of the electrical angle twice; A is a selected constant, the minimum value of the air gap value δmin in formula (2) is 3 times the constant A, and the number of magnetic poles of the motor is 8; a plurality of annularly distributed slots are provided on the motor rotor, and permanent magnets are inserted into the slots; it is characterized in that, The following steps are involved: S1: Initially design the motor according to its usage requirements and determine the inner radius of the motor stator R1 and the minimum air gap value δmin; S2: Select the value of constant A according to the multiple relationship between the minimum value δmin of the air gap value and constant A; S3: Substitute the constant A and the minimum air gap value δmin into the formula F(θ) = δmin + A / 2 + A / 2*cos(2θ) to determine the function curve F(θ) of the air gap value δ and the motor electrical angle θ; S4: According to the function curve F(θ) determined in step S3 and the formula R(θ) =R1 - F(θ), the outer contour curve of the motor rotor is fitted.

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