A permanent magnet direct current brushless outer rotor motor with rubber magnetic strip

Abstract

The application discloses a kind of rubber magnetic strip's permanent magnet DC brushless outer rotor motor, including outer rotor assembly, stator assembly, control circuit board, the outer rotor assembly includes magnetic ring and the transmission shell of setting in the magnetic ring outside, the magnetic ring is by rectangular parallelepiped rubber magnetic strip and is made into circular ring by deformation, the end face of the rubber magnetic strip one end forms first inclined plane, the end face of the rubber magnetic strip other end forms second inclined plane, so that motor air gap is adjacent to magnetic field intensity greater than outer ring surface magnetic field intensity, improve effective magnetic energy product, improve weak magnetic performance into medium magnetic performance, satisfy motor work demand;The first inclined plane and the second inclined plane of the magnetic ring ring body made of the rubber magnetic strip are oppositely arranged to form inclined pole gap, and the design of inclined pole gap can weaken total tooth harmonic strength, and have certain noise reduction effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnet DC outer rotor motor, and particularly relates to a permanent magnet DC brushless outer rotor motor with rubber magnetic strips. BACKGROUND

[0002] A motor is an electromagnetic device for realizing conversion or transmission of electric energy by magnetic induction law. A DC brushless motor mainly comprises a permanent magnet assembly and an excitation assembly. The excitation assembly is composed of a varnished coil winding. During operation, electric control technology is used to continuously change the current phase to form a rotating magnetic field, so as to drive the permanent magnet assembly made of permanent magnet material to rotate. The excitation assembly is generally referred to as a stator of the motor, and the permanent magnet assembly is generally referred to as a rotor.

[0003] A DC brushless motor with a rotor arranged outside the stator is referred to as an outer rotor brushless DC motor. The outer rotor is generally assembled with the shell. At present, the outer rotor generally uses heavy metal permanent magnet materials such as ferrite magnets and neodymium-iron-boron magnets. Although the metal materials have excellent magnetic properties, they generally have a large temperature coefficient, are heavy in quality, and the neodymium-iron-boron magnet is prone to rust. In addition, the metal material used as the permanent magnet also uses rare earth, and the price or cost of the outer rotor will also increase. Rubber magnets are a kind of ferrite magnetic material series composed of bonded ferrite magnetic powder and synthetic rubber to form a flexible magnet. Since the magnetic properties of rubber magnets are lower than those of full metal magnets, they are less used in motor permanent magnet rotors. However, rubber magnets have excellent processing performance, and the size and distribution of the magnetism can be controlled according to the shape or the composite ratio of the magnetic powder and the rubber. In addition, the cost is relatively low. Through reasonable design, a permanent magnet outer rotor with good magnetic properties can be made to meet the needs of different fields and functions. SUMMARY

[0004] In view of this, the present application aims to provide a permanent magnet DC brushless outer rotor motor with relatively high magnetic energy product and relatively low cost.

[0005] The technical scheme adopted by the present application to solve the technical problems is as follows:

[0006] The permanent magnet DC brushless outer rotor motor of rubber magnetic strip comprises an outer rotor assembly, a stator assembly and a control circuit board, the outer rotor assembly comprises a magnetic ring and a transmission housing sleeved outside the magnetic ring, the magnetic ring is a circular ring made of a cuboid rubber magnetic strip through deformation, one side of the magnetic ring facing the stator assembly forms an inner ring surface, and the other side of the magnetic ring facing the transmission housing forms an outer ring surface, the end surface of one end of the rubber magnetic strip forms a first inclined surface of parallelogram, the included angle η of the first inclined surface and the inner ring surface is greater than 90°, the diagonal line of two acute angles on the plane of the first inclined surface and the horizontal plane γ form an inclined pole angle α, the end surface of the other end of the rubber magnetic strip forms a second inclined surface, and the included angle β of the second inclined surface and the horizontal plane γ is 90°>β>α.

[0007] The first inclined surface and the second inclined surface on the magnetic ring body made of the rubber magnetic strip are oppositely arranged to form an inclined pole gap.

[0008] The outer rotor assembly and the stator assembly form a motor air gap, the stator assembly comprises a plurality of stacked magnetic core laminations and a plurality of windings wound on the magnetic core laminations, the adjacent windings form stator slots, x is the number of stator slots, y is the number of motor poles, δ is the size of the motor air gap, μ is the magnetic permeability, K T is the torque coefficient, [x, y] is the greatest common multiple of the number of stator slots and the number of motor poles, the

[0009] The included angle β is 2°-10° larger than the inclined pole angle α.

[0010] The elastic coefficient k of the rubber magnetic strip (12) is 1.02-1.2.

[0011] The stacking height of the magnetic core lamination (20) is h, and the height of the magnetic ring (10) is H, wherein H is 6mm-8mm larger than h.

[0012] The beneficial effects of the present application are:

[0013] Rubber magnet is a kind of elastic and convenient processing permanent magnet material, the permanent magnet DC brushless outer rotor motor adopts rectangular strip rubber magnet strip to be formed into magnetic ring by calendering and bending to serve as outer rotor. When the rubber magnet is in rectangular strip shape, the internal bonded ferrite magnetic powder is uniformly distributed, when it is deformed into ring shape, the inner ring surface facing the stator assembly and the outer ring surface facing the transmission shell are formed, due to the structural characteristics of the circular ring, the inner ring surface after deformation is formed by extrusion of one side of the cuboid before deformation, the area will be smaller, the outer ring surface before deformation is formed by stretching of the other side of the cuboid before deformation, the area will be larger, so when the rubber magnet is in circular ring shape, the density of the bonded ferrite magnetic powder near the inner ring surface will be greater than that near the outer ring surface, in the same arc range, the magnetic induction lines near the inner ring surface are denser than those near the outer ring surface, so that the magnetic field strength of the motor air gap adjacent to the inner ring surface is greater than that of the outer ring surface, the effective magnetic energy product is improved, the weak magnetic performance is improved to medium magnetic performance, the bending processing of the rubber magnet strip is utilized, the motor working demand is met under the condition of lower cost.

[0014] Further, the motor air gap is the gap between the stator assembly and the outer rotor assembly, which is the prerequisite for the relative rotation of the stator and the outer rotor, and is also part of the magnetic circuit, during the motor operation, there will be air gap magnetic field, due to the discontinuity of the motor air gap and the influence of the stator core laminations and winding shape in practice, the magnetic permeability of the magnet and air is quite different, for example, the air gap magnetic field between the winding and the outer rotor is stronger than that between the stator slot and the outer rotor, due to the stator slot structure, tooth harmonic magnetic field will be generated, the harmonic number is relatively high, and these harmonic magnetic fields make the motor generate corresponding harmonics during operation, which may cause resonance of the motor base and cause excessive vibration and generate noise. The ring body of the magnetic ring of the outer rotor is designed as a not completely closed ring body, and the slant pole gap is arranged on the ring body, during the motor operation, the outer rotor, like the stator, also generates tooth harmonic magnetic field, due to the fact that the slant pole gap is not parallel to the motor axis but is twisted at an angle, the generated harmonic can partially offset the harmonic generated by the stator slot, thereby weakening the total tooth harmonic strength and having a certain effect of reducing noise. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the main structure schematic diagram of the motor;

[0016] Figure 2 is the schematic diagram of the motor front view after disassembling the control circuit board;

[0017] Figure 3 is the cross-sectional view schematic diagram of the motor;

[0018] Figure 4 is the structure schematic diagram of the magnetic ring;

[0019] Figure 5 is a schematic diagram of magnetic ring local inner and outer ring surface magnetic field lines;

[0020] Figure 6 is a structural schematic diagram of rubber magnetic strip;

[0021] Figure 7 is Figure 6 is a schematic diagram of the first inclined surface view angle A;

[0022] Figure 8 is Figure 6 is a schematic diagram of the rubber magnetic strip above view angle B;

[0023] Figure 9 is a schematic diagram of the rubber magnetic strip side. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described clearly and completely below in combination with the drawings.

[0025] Referring to Figure 1 , Figure 4 , Figure 6 and Figure 8 , the present application proposes a rubber magnetic strip permanent magnet DC brushless outer rotor motor, comprising an outer rotor assembly 1, a stator assembly 2, and a control circuit board 3, the outer rotor assembly 1 comprises a magnetic ring 10 and a transmission housing 11 sleeved outside the magnetic ring 10, the magnetic ring 10 is a circular ring made by deforming a rectangular parallelepiped-shaped rubber magnetic strip 12, one side of the magnetic ring 10 facing the stator assembly forms an inner ring surface 100, and one side facing the transmission housing 11 forms an outer ring surface 101, the end surface of one end of the rubber magnetic strip 12 forms a parallelogram-shaped first inclined surface 120, the included angle η of the first inclined surface 120 and the inner ring surface 100 is greater than 90°, the diagonal line of the two acute angles on the plane of the first inclined surface 120 forms an oblique pole angle α with the horizontal plane γ, the end surface of the other end of the rubber magnetic strip 12 forms a second inclined surface 122, and the second inclined surface 122 forms an included angle β with the horizontal plane γ, wherein 90°> β > α.

[0026] Rubber magnet is a kind of elastic and convenient processing permanent magnet material, the permanent magnet DC brushless outer rotor motor adopts rectangular strip rubber magnet strip 12 to be formed into magnetic ring 10 by calendering and bending to serve as outer rotor. When the rubber magnet is rectangular strip, the internal bonded ferrite magnetic powder is uniformly distributed, when it is deformed into ring shape, the inner ring surface 100 facing the stator assembly 1 and the outer ring surface 101 facing the transmission housing 11 are formed. Due to the structural characteristics of the circular ring, the inner ring surface 100 after deformation is formed by extruding one side of the cuboid before deformation, and the area will be smaller. The outer ring surface 101 before deformation is formed by stretching the other side of the cuboid before deformation, and the area will be larger. Therefore, when the rubber magnet is circular, the density of the bonded ferrite magnetic powder near the inner ring surface 100 is greater than that near the outer ring surface 101, referring to Figure 5 In the same range of curvature, the magnetic induction lines near the inner ring surface 100 are denser than those near the outer ring surface 101, that is, the magnetic field strength of the motor air gap 4 facing the inner ring surface 100 is greater than that of the outer ring surface 101, which improves the effective magnetic energy product and improves the weak magnetic performance to medium magnetic performance. By bending the rubber magnet strip, the motor working requirements are met at a lower cost.

[0027] Referring to Figure 4 The first inclined surface 120 and the second inclined surface 122 of the magnetic ring 10 ring body formed by the rubber magnet strip 12 are oppositely arranged to form an inclined pole gap 102.

[0028] Referring to Figure 2 And Figure 3 The motor air gap 4 is formed between the outer rotor assembly and the stator assembly, the stator assembly 2 includes a plurality of stacked magnetic core laminations 21 and a plurality of windings 21 wound on the magnetic core laminations 20, the adjacent windings 21 form stator slots 5, x is the number of stator slots, y is the number of motor poles, δ is the size of motor air gap, μ is the magnetic permeability, K T is the torque coefficient, [x, y] is the greatest common multiple of the number of stator slots and the number of motor poles, and the

[0029] The motor air gap 4 is the gap between the stator assembly 2 and the outer rotor assembly 1, and is the prerequisite for the relative rotation of the stator and the outer rotor, and is also part of the magnetic circuit. During the operation of the motor, there will be an air gap magnetic field in the motor air gap 4. Since the motor air gap 4 is discontinuous and is actually affected by the shape of the magnetic core laminations 20 and the windings 21 of the stator assembly 1, and the magnetic permeability of the magnet and air is quite different, the air gap between the windings 21 and the magnetic ring 10 is stronger than the air gap between the stator slot 5 and the magnetic ring 10. Due to the stator slot structure, a tooth harmonic magnetic field will be generated, and the harmonic number is relatively high. During the operation of these harmonic magnetic fields, the motor generates corresponding harmonics. The harmonics can cause resonance of the motor base, resulting in excessive vibration and generating a large amount of noise. The ring body of the magnetic ring 10 of the outer rotor is designed as a ring body that is not completely closed, and the ring body is provided with a skew pole gap 102. During the operation of the motor, the outer rotor formed by the magnetic ring 10 is the same as the stator, and the outer rotor also generates a tooth harmonic magnetic field. Since the skew pole gap 102 is not parallel to the motor axis but is twisted at an angle, the generated harmonic can partially offset the harmonic generated by the stator slot 5, thereby weakening the overall tooth harmonic strength and having a certain effect of reducing noise.

[0030] Further, the included angle β is 2°-10° larger than the skew pole angle α.

[0031] The included angle β is the angle formed by the second inclined surface 122 and the horizontal plane γ. If the second inclined surface 122 is viewed, the second inclined surface 122 can be rectangular. The skew pole angle α is the included angle of a line and a surface. When the first inclined surface 120 is viewed, the first inclined surface 120 is not rectangular, but is a parallelogram with a pair of acute angles and a pair of obtuse angles. This is because the angle η formed by the first inclined surface 120 and the inner ring surface 100 is greater than 90 degrees. The skew pole angle α is the diagonal line 121 of the two acute angles of the first inclined surface 120 and the horizontal plane γ.

[0032] Further, the elastic coefficient k of the rubber magnetic strip 12 is 1.02-1.2. When the rubber magnetic strip 12 is processed into a magnetic ring through bending, the deformation degree of each part of the rubber magnetic strip 12 is different. The part near the inner ring surface 100 of the magnetic ring 10 is subjected to more extrusion, and the part near the outer ring surface 101 of the magnetic ring 10 is subjected to more stretching. Finally, after the bending and shaping, the first inclined surface 120 and the second inclined surface 122 are oppositely arranged, and the two surfaces do not contact, but form a skew pole gap 102 in the middle. Therefore, the size selection and size relationship of the included angle β and the skew pole angle α are the ideal solution obtained through experience and experiment, and the calculation of the skew pole angle α can be obtained according to the parameters of the motor in the actual process.

[0033] Reference Figure 3Further, the height of the magnetic core laminations 20 is h, and the height of the magnetic ring 10 is H, wherein H is 6mm-8mm larger than h. During the operation of the motor, when the winding 21 of the stator assembly 1 is energized to excite the magnetic core laminations 20, the magnetic ring 10 as an outer rotor is driven to rotate under the action of the magnetic field. The height H of the magnetic ring 10 is higher than the height h of the magnetic core laminations 20 by a certain value, so that the magnetic ring 10 can fully interact with the stator assembly 1, and the load characteristics of the outer rotor are better, and the stability and efficiency during operation are increased to a certain extent.

Claims

1. A permanent magnet brushless DC external rotor motor with rubber magnetic strips, comprising an external rotor assembly (1), a stator assembly (2), and a control circuit board (3), wherein the external rotor assembly (1) comprises a magnetic ring (10) and a transmission housing (11) sleeved outside the magnetic ring (10), characterized in that, The magnetic ring (10) is a circular ring made by deforming a cuboid rubber magnetic strip (12). The side of the magnetic ring (10) facing the stator assembly (2) forms an inner ring surface (100), and the side facing the transmission housing (11) forms an outer ring surface (101). The end face of one end of the rubber magnetic strip (12) forms a first inclined plane (120) of a parallelogram. The angle η between the first inclined plane (120) and the inner ring surface (100) is greater than 90°. The diagonal line (121) connecting the two acute angles on the plane of the first inclined plane (120) forms a slant angle α with the horizontal plane γ. The end face of the other end of the rubber magnetic strip (12) forms a second inclined plane (122). The angle β between the second inclined plane (122) and the horizontal plane γ is 90°>β>α. The magnetic ring (10) made of the rubber magnetic strip (12) has a first inclined surface (120) and a second inclined surface (122) on the ring body, which are arranged opposite to each other to form an inclined pole gap (102); An air gap (4) is formed between the outer rotor assembly (1) and the stator assembly (2). The stator assembly (2) includes several stacked magnetic core laminations (20) and several windings (21) wound on the magnetic core laminations (20). Stator slots (5) are formed between adjacent windings (21). Let x be the number of stator slots, y be the number of motor poles, δ be the size of the motor air gap, μ be the permeability, and K be the value of the stator slots. T [x, y] is the torque coefficient, and [x, y] is the greatest common multiple of the number of stator slots and the number of motor poles. The magnetic core stack (20) has a stack height of h, and the magnetic ring (10) has a height of H, where H is 6mm to 8mm larger than h.

2. The permanent magnet brushless DC external rotor motor with rubber magnetic strips according to claim 1, characterized in that, The included angle β is 2° to 10° larger than the sloping polar angle α.

3. The permanent magnet brushless DC external rotor motor with rubber magnetic strips according to claim 1, characterized in that, The elastic coefficient k of the rubber magnetic strip (12) is 1.02 to 1.2.

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