High torque density electric motor

Abstract

The utility model belongs to the field of electrical engineering, particularly relates to a motor for an airplane, and provides a high-torque-density motor, which comprises an annular stator and a rotor positioned in the center of the stator, in the annular stator, a coil is wound on a plurality of radially arranged teeth, and the rotor is wound on the annular stator. The rotor comprises an annular rotor core, a plurality of rotor teeth and a plurality of magnets, the rotor teeth protrude from the annular rotor core to the stator, the magnets are positioned among the rotor teeth, the magnets are tangentially polarized, the teeth of the stator and the annular rotor core with the rotor teeth are made of grain orientation steel, the cross section of a coil wire is rectangular, the stator is of an opening structure, and the coil wire is arranged in the opening structure. A coil of the stator is wrapped by insulating paper which is impregnated with varnish and has high thermal conductivity. The high-torque-density motor provided by the utility model has high specific torque per unit volume, and can provide sufficiently high torque density when being used as an aircraft engine as shown in Figure 7.

Description

Technical Field

[0001] The utility model belongs to the field of electrical engineering, and in particular relates to an electric motor that can be used for airplanes, unmanned aerial vehicles and vertical take-off and landing aircraft. Background Art

[0002] Prior art US7679256B2 (published on March 16, 2010) discloses a rotary electric motor, wherein a rotor pole comprises a first portion and a second portion, the first portion of the rotor pole is magnetized in the radial direction, the second portion of the rotor pole is magnetized in the direction of the rotation axis, and a stator comprises a first stator pole portion generating a radial magnetic flux and a second stator pole portion generating a magnetic flux in the direction of the rotation axis. However, the motor has a low specific torque per unit volume to per unit mass, and is inefficient when used as an aircraft engine.

[0003] Prior art US2006061228A1 (published on March 23, 2006) discloses a flux-concentrated motor, comprising an annular stator with coils wound around a plurality of radially spaced teeth, a rotor located at the center of the stator, and the rotor comprising an annular rotor core, wherein a small-diameter hole is provided in the connection portion between the annular rotor core and the teeth, the small-diameter hole is used to guide the insertion of a pin, and a barrier is also provided in the bridge connecting adjacent teeth or at the end of the annular rotor core adjacent to the teeth to prevent the magnetic flux of the magnet from being dispersed. However, the motor has a low specific torque per unit volume to per unit mass, and is inefficient when used as an aircraft engine. Utility Model Content

[0004] Compared with other motors in the prior art, the utility model provides a high torque density motor with high specific torque per unit volume and per unit mass, so that the high torque density motor can provide a sufficiently high torque density when used as an aircraft engine.

[0005] The utility model provides a high torque density motor, comprising an annular stator and a rotor located at the center of the stator, in which a coil is wound on a plurality of radially arranged teeth, the rotor comprises an annular rotor core and a plurality of teeth protruding from the annular rotor core toward the stator, and a plurality of magnets located between the teeth, wherein the magnets are tangentially polarized, the teeth of the stator and the annular rotor core with the rotor teeth are made of grain-oriented steel, the cross section of the coil wire is rectangular, the stator is an open structure, and the coil of the stator is wrapped by insulating paper impregnated with varnish and having high thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a cross-sectional schematic diagram of a high torque density motor shown in an embodiment of the utility model;

[0007] Figure 2 A cross-sectional schematic diagram of a high torque density motor shown in an embodiment of the utility model (side walls are not shown);

[0008] Figure 3 It is an enlarged schematic diagram of a cross section of a high torque density motor shown in an embodiment of the utility model, and shows magnetic induction lines;

[0009] Figure 4 It is an enlarged schematic diagram of a coil in a high torque density motor shown in an embodiment of the utility model;

[0010] Figure 5 It is a schematic diagram of some optional components when two high torque density motors shown in an embodiment of the utility model are coaxially arranged, wherein the motor has a propeller;

[0011] Figure 6 It is a schematic diagram of the assembly of the stator in the high torque density motor shown in the embodiment of the utility model;

[0012] Figure 7 This is a schematic diagram of optional components when two high torque density motors shown in an embodiment of the present invention are coaxially arranged, and the two high torque density motors are connected by a propeller.

[0013] The utility model provides a high torque density motor, comprising an annular stator 1 and a rotor 4 located at the center of the stator, wherein a coil 2 is wound around a plurality of radially arranged teeth 3 of the stator 1, and the rotor 4 comprises an annular rotor core 5. Figure 2 As shown, the teeth 3 of the stator 1 and the annular rotor core 5 with the rotor teeth 6 are made of grain-oriented steel, the cross section of the coil wire 2 is rectangular, a plurality of rotor teeth 6 protrude from the annular rotor core 5 toward the stator 1, and a plurality of magnets 7 are located between the rotor teeth 6. Figure 3-4 As shown, the stator 1 is an open structure, and the coil 2 of the stator 1 is wrapped by insulating paper impregnated with varnish and having high thermal conductivity. DETAILED DESCRIPTION

[0014] like Figure 4 As shown, this embodiment discloses a high torque density motor, wherein the annular stator 1 is made into an annular shape, composed of sector steel 8, and connected by dovetail locks 9. The coil 2 is wound on a plurality of radially arranged teeth 3. The teeth 3 are steel teeth, fixed to the housing of the stator 1 by dovetail locks 10. The coil 2 is made of copper wire, such as Figure 2 , Figure 3 As shown, the cross section of the coil 2 is rectangular. The coil with a rectangular cross section can increase the filling factor of the coil space by 70% and increase the current density and specific torque in the coil 2. The ohmic loss in the coil 2 is calculated by the formula L = R × I 2Calculation, where R represents the coil resistance and I represents the current intensity. Since the present embodiment uses a coil with a rectangular cross section, its resistance R is 2 to 2.5 times lower than the resistance R of a motor using a coil with a circular cross section. In addition, the heat dissipation effect of the coil with a rectangular cross section is significantly better than that of a standard circular coil or a twisted wire.

[0015] like Figure 3 As shown, the side walls 11, 12 are fixed to the side surfaces of the ring of the stator 1 by screws. Figure 1 , Figure 2 As shown, bearings 13 and 14 are installed in the side walls 11 and 12. The rotor 4 is arranged on the side walls 11 and 12, and the side walls 11 and 12 are made of aluminum. A plurality of rotor teeth 6 protruding toward the stator 1 are fixedly connected to the annular rotor core 5 of the rotor 4 through dovetail grooves 15, as shown in FIG. Figure 3 As shown, the stator 1, the annular rotor core 5, the rotor 4, the rotor teeth 6, and the bearings 13 and 14 are all made of steel. The magnet 7 is wedge-shaped, fixed between the rotor teeth 6, and is tangentially polarized. Therefore, the magnetic induction line 16 is tangential to the rotation direction of the rotor 4, and the tangentially polarized magnet 7 has a stronger ability to concentrate the magnetic field than the Halbach magnet array. Compared with an electric motor with an outer rotor of the same diameter and the same weight, arranging the tangentially polarized magnet 7 and the rotor 4 in the stator 1 can increase the specific torque per unit volume and per unit mass. Compared with an electric motor with magnets mounted on the surface, the tangentially polarized magnet 7 enhances the magnetic field between the rotor 4 and the stator 1 by 1.2 to 1.3 times.

[0016] The teeth 3 of the stator 1 and the annular rotor core 5 with the rotor teeth 6 are made of grain-oriented steel. The magnetic permeability of grain-oriented steel is high, and grain-oriented steel can achieve the same effect with a larger coil cross-sectional area based on a smaller tooth width, so the use of grain-oriented steel can increase the specific torque per unit volume and per unit mass of the motor by about 5%.

[0017] The stator 1 is designed as an open structure, that is, the stator 1 is not placed in a housing, and the stator housing is the only housing of the motor. Specifically, the teeth 3 are fixed to the sector-shaped part of the stator 1 housing by a dovetail lock 10 .

[0018] The rotation of the rotor 4 ensures effective convective heat transfer. In addition, the coil 2 of the stator 1 is wrapped with a highly thermally conductive insulating paper impregnated with varnish. The insulating paper is made of standard Nomex Nomex or high thermal conductivity paper ST6000. Due to the high specific heat release per unit volume of the motor, it is necessary to provide a cooling device to dissipate heat from the high torque density motor with high per unit volume and per unit mass. The more heat is removed from the motor, the greater the current the motor runs and the greater the torque of the motor.

[0019] Since the housing of the motor is the most expensive part, the use of an open stator 1 instead of the housing can also significantly reduce the cost of the motor. The motor is sealed and meets the IP67 regulations.

[0020] Industrial Applicability

[0021] The above embodiments have demonstrated the feasibility of implementing the present invention using existing industrial technology.

[0022] All of the aforementioned technical features in the high torque density motor, i.e., tangential polarization of the magnets, stator teeth and annular rotor core with rotor teeth made of grain-oriented steel, coil wires of rectangular cross-section, an open stator with coils wrapped by insulating paper having high thermal conductivity and impregnated with varnish, enable a motor with high specific torque and is therefore effective as an aircraft engine.

[0023] Aviation and drones require electric motors to have maximum torque per unit volume and per unit mass. The larger the diameter of the propeller, the slower its rotation speed, and the higher the efficiency of the motor in a specific application scenario. The technical solution proposed in the utility model has the above characteristics. In addition, since the motor in the utility model is small in size, the resistance to the oncoming airflow during flight is small, and the weight of the motor proposed in the utility model is small, the motor has higher energy efficiency.

[0024] Figure 5 The utility model shows an application example of the electric motor, which has two coaxially arranged electric motors 17 and 18 with high torque density, and screws are fixed on the electric motors 17 and 18. The shaft 19 is a stator bracket. The propeller is fixed to the electric motor by folding propeller connectors 20 and 21 to generate traction to move the aircraft.

[0025] High torque density motors have the following preferred options:

[0026] 1) Mass is 1.2kg, diameter is 100mm, and torque per unit mass is 6Nm / kg;

[0027] 2) The mass is 5kg, the diameter is 150mm, and the mass ratio per unit is 12Nm / kg;

[0028] 3) The mass is 15kg, the diameter is 250mm, and the mass ratio per unit is 17Nm / kg.

[0029] The above specific torque values ​​are those when the motor is running at rated speed, and its peak value is as high as twice.

Claims

1. A high torque density electric motor, comprising: an annular stator in which coils are wound around a plurality of teeth arranged radially; a rotor located at the center of the stator, the rotor comprising an annular rotor core and a plurality of rotor teeth protruding from the annular rotor core toward the stator, and a plurality of magnets located between the rotor teeth; It is characterized in that the magnet is tangentially polarized, the teeth in the stator and the annular rotor core with rotor teeth are made of grain-oriented steel, the cross-section of the coil wire is rectangular, the stator is an open structure, and the coil of the stator is wrapped by insulating paper impregnated with varnish and having high thermal conductivity.

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