JP6796474B2 - Brushless motor - Google Patents

Description

The present invention relates to a brushless motor having a stator and a rotor and rotating the rotor by a rotating magnetic field generated in the stator.

As an industrial DC motor, a brushless motor that omits a brush to make it maintenance-free and has a long life has been widely used in recent years.
Brushless motors have a wide range of applications, one of which is to drive the Provera and rotor blades of small unmanned aerial vehicles and unmanned helicopters. Such unmanned aerial vehicles and the like used to be limited to hobbies and models due to the difficulty of supplying electric power to generate sufficient driving force for the motor. However, due to recent advances in battery and drive control technology, multicopters (drones) that are equipped with multiple rotors and can fly with sufficient propulsion even when loaded with heavy objects have become practical. Has reached.

As an example of a conventional brushless motor applicable to such a multicopter, there is one disclosed in Japanese Patent Application Laid-Open No. 2016-152750.

Japanese Unexamined Patent Publication No. 2016-152750

The conventional brushless motor has the configuration shown in the above patent document, and particularly in a multicopter (drone) rotary wing drive application, the rotary wing is driven so as to generate a force (lift) required for flight. Therefore, the amount of heat generated by the coil was large because a large current was required.

In the case of driving such a rotary blade, in order to efficiently dissipate the heat generated by the coil of the brushless motor, as shown in the above patent document, a part of the coil is made to appear to the outside, and a part of the coil is exposed to the wind. It was an outer rotor type that can be forcibly cooled. However, the outer rotor type brushless motor cannot be made waterproof and dustproof because it adopts a structure that exposes the coil.

On the other hand, the inner rotor type brushless motor can have a waterproof and dustproof structure by covering the stator and rotor with a case, but it is required to drive a high-load drive object such as a rotor blade. Since it is structurally difficult to properly release the heat generated when the current is applied to the coil to the outside, and the temperature inside the case rises due to the heat that cannot be completely released, seizure is likely to occur. There was no example of using a brushless motor for driving a multicopter rotor blade.

In this way, as the conventional brushless motor for multicopters, the outer rotor type was adopted with priority given to maintaining the operating state by heat dissipation, so it is difficult to ensure waterproofness and dustproofness, and due to the restrictions of such brushless motors, multi The usage environment of the copter is limited, and there is a problem that it is difficult to adapt it to various environmental conditions.

The present invention has been made to solve the above problems, and it is possible to dissipate heat from the coil to the outside while adopting an inner rotor type structure, and it operates continuously even in a heavy load application such as a rotary blade drive. It is an object of the present invention to provide a brushless motor that can be used in various environments by utilizing the waterproof and dustproof performance.

The brushless motor according to the disclosure of the present invention is a brushless motor including a substantially annular stator that generates a rotating magnetic field and a rotor that is rotatably arranged inside the stator and rotates based on the rotating magnetic field. It is formed in a hollow cylindrical trapezoidal shape symmetrical about the same central axis as the center of rotation of the rotor, and includes a case that covers the stator and the rotor, and the stator is arranged along the inner circumference of the cylindrical side surface of the case. A core portion made of a magnetic material formed by forming a plurality of teeth portions protruding in the radial direction with respect to the rotation center of the rotor, and a coil wound around each of the teeth portions to generate a magnetic field. At least the end face portion of the case in the rotation axis direction of the rotor is made of a good thermal conductive material, and in the state of being arranged in the case of the stator, the end portion of the coil outer peripheral portion in the rotation axis direction of the rotor A heat transfer body made of a heat conductive insulating material is housed and arranged in a gap between the inner surface of the end face portion of the case in close contact with the coil surface and the inner surface of the case, and the coil is placed on the outer periphery of the coil. The distance between the part and the inner surface of the end face of the case is arranged so as to be the minimum size that can maintain insulation to the case in the energized state, and heat can be transferred from the coil to the end face of the case via the heat transfer body. Is to be done.

As described above, according to the disclosure of the present invention, in the inner rotor type motor, a heat transfer body having thermal conductivity is arranged between the coil winding surface of the stator located in the case and the inner surface of the case end surface. By securing a heat conduction path from the coil to the case, the heat generated by the coil is released to the case through the heat transfer body and dissipated from the case to the outside, suppressing the temperature rise inside the case and heating the motor. As an inner rotor type, it can be operated continuously without any adverse effects, and it can handle a high load of the object to be driven while ensuring waterproof and dustproof performance. For example, it can continue to operate without problems even when used for driving a rotary blade. , A brushless motor can be used as a drive source in response to various environmental conditions.

Further, in the brushless motor according to the disclosure of the present invention, each tooth portion of the core portion is formed so that the protrusion dimension in the radial direction is larger than the dimension in the rotor rotation axis direction, and each tooth portion is formed. Of the wound parts around which the coil is wound, the end portion in the direction of the rotor rotation axis is formed in a planar shape parallel to the inner surface of the end face portion of the case, and the coil winding is dense with respect to at least the flat portion. The windings of the coil in a parallel state are arranged flat along the planar portion.

As described above, according to the disclosure of the present invention, the core portion has a flat shape in which the radial protrusion dimension of each tooth portion is larger than the rotor rotation axis direction dimension, and the portion of the coil facing the inner surface of the case end surface portion is the teeth. By arranging it in a flat shape along the portion, the maximum number of coil windings close to the case end face can be secured, and the parallel windings of the coils and the case end face can be uniformly brought close to each other. It is possible to easily transfer heat to the case side, improve the efficiency of heat dissipation, reduce the adverse effects of heat, and stabilize the operation of the motor.

Further, in the brushless motor according to the disclosure of the present invention, if necessary, the rotor is integrally mounted around a shaft for mounting a drive object, and is rotatably supported by the case via a bearing. The end portion to which the drive object of the shaft can be attached is disposed so as to project outward from at least one end surface portion side of the case, and the core portion connects the windings of each tooth portion to each other. The conductors to be routed are arranged together on one end side in the rotor rotation axis direction, and the side on which the conductors are arranged is arranged in the case toward the other end surface side of the case. The driven object is a rotary blade, and the flow of fluid generated by the rotary blade rotating with the rotor is brought into contact with at least one end surface of the case.

As described above, according to the disclosure of the present invention, the rotary blade is attached to the shaft integrated with the rotor as a drive object, and the flow of the fluid generated by the rotary blade is coiled without arranging the lead wire for connection in the core portion. By reaching the outer surface of one end face of the case where the inner surface of the case is closer to each other, the fluid continuously flows along one end face of the case where the heat generated by the coil is easily transferred, resulting in an air flow. The flow of fluid such as water or water promotes heat dissipation from the end face, and efficient heat dissipation can be performed to maintain the temperature inside the case at no problem.

Further, the brushless motor according to the disclosure of the present invention is a composite material in which the heat transfer body is a composite material in which an additive which is fine particles made of a good heat conductive material is added to a base material made of an insulating material, if necessary. The additive contains at least one of aluminum oxide, silicon nitride, boron nitride, and aluminum nitride.

As described above, according to the disclosure of the present invention, the heat transfer body disposed between the coil and the end face of the case has a composite structure in which fine particles of the additive are added to the base material, and the addition is excellent in thermal conductivity. By connecting the materials in the base material to form a heat path, heat can be quickly reached from the coil to the outside of the case end face through the additive in the heat transfer body, and heat dissipation can be promoted.

It is a front view of the brushless motor which concerns on one Embodiment of this invention. It is a top view of the brushless motor which concerns on one Embodiment of this invention. It is a bottom view of the brushless motor which concerns on one Embodiment of this invention. It is a vertical sectional view of the brushless motor which concerns on one Embodiment of this invention. It is a schematic plan view of the case of the brushless motor according to one embodiment of the present invention in a state where one divided body and a shaft are removed. It is explanatory drawing of the heat transfer state in the brushless motor which concerns on one Embodiment of this invention.

Hereinafter, the brushless motor according to the embodiment of the present invention will be described with reference to FIGS. 1 to 6.
In each of the above figures, the brushless motor 1 according to the present embodiment includes a substantially annular stator 10 that generates a rotating magnetic field, and a rotor 20 that is rotatably arranged inside the stator 10 and rotates based on the rotating magnetic field. The configuration includes a hollow cylindrical trapezoidal case 30 that covers the stator 10 and the rotor 20.

The brushless motor 1 according to this embodiment is driven by a known so-called sensorless method in which the rotor position and the rotation speed are estimated based on the counter electromotive force generated by the rotation of the rotor.

The stator 10 has a core portion 11 made of a magnetic material arranged along the inner circumference of the cylindrical side surface of the case 30, and the stator 10 is wound around the inner circumference side of the core portion 11 to generate a magnetic field. The configuration includes a coil 13 and a lead wire 15 that is electrically connected to the coil 13 and is arranged so as to extend a part outside the case.

The brushless motor 1 according to the present embodiment employs a sensorless drive system that can simplify the motor configuration, such as omitting the built-in sensor, but the present invention is not limited to this, and the rotation angle of the rotor 20 is detected by the stator 10. A detection means such as a Hall element is provided, and the rotor 20 is provided with a detection means such as a magnet paired with the detection means so that the rotor position and the like are acquired based on the measurement by the detection means to drive the motor. You can also do it.

The core portion 11 is formed by laminating thin plate-shaped magnetic metal materials, and has a configuration in which a plurality of tooth portions (slip poles) 12 are projected in a direction perpendicular to the rotation center of the rotor 20. A coil 13 is wound around each of the teeth portions 12 via a predetermined insulator (insulator).

The tooth portion 12 is formed so that the protruding dimension in the radial direction is larger than the dimension in the rotor rotation axis direction. Further, among the wound parts of the core portion 11 around which the coil 13 of each tooth portion 12 is wound, the end portion in the rotation axis direction of the rotor is formed as a flat portion 12a parallel to the end surface of the case 30.
The windings of the coil 13 are tightly aligned and wound around the flat portion 12a of each tooth portion 12, so that the windings of the coil 13 in a parallel state are arranged flat along the flat portion 12a.

In such a core portion 11, the coil 13 is wound and arranged around each tooth portion 12 after reaching the final completed shape in which the outer shape does not change until the motor is completed, but the present invention is not limited to this, and is semi-finished. It is also possible to assemble or deform the core portion after winding and arranging the coil around each tooth portion in the core portion in the state, so that the coil winding arrangement work can be easily performed. If the coil is arranged with respect to the core portion of the semi-finished form, the manufacturing efficiency can be improved and the cost can be reduced.

Further, in the core portion 11, the lead wires 14 that are routed to connect the windings of each tooth portion 12 are collectively arranged on one end side in the rotor rotation axis direction, and the lead wires are arranged. The arranged side is arranged in the case 30 with the other end surface portion 32 side of the case 30 facing.

In such a state of being arranged in the case of the stator 10, heat can be conducted in the gap between both ends of the outer peripheral portion of the coil 13 in the direction of the rotor rotation axis and the inner surfaces of the two end surface portions 31 and 32 of the case 30. The heat transfer body 40 made of an insulating material is housed and arranged in close contact with the surface of the coil 13 and the inner surface of the case 30.

In this case, the coil 13 is arranged so that the distance between the outer peripheral portion of the coil and the inner surfaces of the end surface portions 31 and 32 of the case 30 is the minimum size capable of maintaining insulation with respect to the case 30 in the energized state. By energizing the coil 13, while a magnetic field is generated, heat is also generated, but the heat of the coil 13 can be transferred to the end faces 31 and 32 of the case 30 via the heat transfer body 40.

The rotor 20 is formed as a rotationally symmetric body made of a magnetic metal material in which a central hub portion 21 and an outermost annular yoke portion 22 are integrally connected, and a plurality of permanent magnets 23 for driving rotation are arranged side by side on the outer peripheral surface. It is configured to be rotatably supported by a bearing 24 provided and arranged in the center of the case 30.

The rotor 20 is integrally mounted and fixed to a hub portion 21 at the center of a metal shaft 25 for mounting a rotary blade 50 as a drive object, and the shaft 25 is supported by a bearing 24 with respect to the case 30. It is a structure that can be rotated. Then, the end portion of the shaft 25 to which the rotary blade 50 can be attached is arranged so as to project outward from one end surface portion 31 side of the case 30.

A fixture 26 for mounting the rotary blade 50 is fixed to the end of the shaft 25 protruding outside the case. A mechanism is provided between the fixture 26 and the case 30 to prevent water and dust from entering the case from the outside such as a labyrinth and a fringer, so that the case 30 is waterproof and dustproof. ..

By attaching the rotary blade 50 to the shaft 25, the fluid flow generated by the rotary blade 50 rotating together with the rotor 20 comes into contact with at least the outer surface of one end surface portion 31 of the case 30.

The rotor 20 including the shaft 25 is made of metal having good thermal conductivity, and the heat generated by the permanent magnet 23 due to the operation of the motor can be conducted to the shaft 25 via the yoke portion 22 and the hub portion 21. Further, heat is released to the outside of the motor from the shaft 25 partially protruding to the outside of the case 30, thereby preventing adverse effects such as overheating of the permanent magnet 23 in the rotor 20 and accompanying performance deterioration.

The case 30 is formed in a hollow cylindrical (cylindrical) trapezoidal shape symmetrical about the same central axis as the rotation center of the rotor 20, and the entire case including the end face portions 31 and 32 at both ends in the rotor rotation axis direction is made of metal or the like. It is made of a material with good thermal conductivity.

A shaft 25 integrated with the rotor 20 penetrates through one end surface portion 31 of the case 30 to project a part thereof to the outside. The shaft penetrating portion of one of the end face portions 31 is provided with a mechanism such as a labyrinth seal so that water and dust do not enter the inside of the case from between the shaft 25 and the end face portion 31 while allowing the shaft 25 to rotate. is there. The other end face portion 32 of the case 30 is provided only with a screw hole 34 or the like for installing the motor, and is closed without being provided with a hole or the like leading to the inside of the case.

Further, a lead wire 15 penetrates and extends to the outside at a predetermined position on the side surface portion of the case 30 near the other end face portion 32 while ensuring a waterproof state, and the end portion of the lead wire 15 is an external motor driver. Is connected to equipment such as.

This case 30 has a two-divided structure in the direction of the rotor rotation axis, and is a cylindrical case in which one divided body 30a including one end face portion 31 and another divided body 30b including the other end face portion 32 are formed into a cylindrical case. It is a configuration that is integrally connected and combined at a predetermined position on the side surface portion. Specifically, the male-threaded portion and the female-threaded portion provided at the end of one divided body 30a of the case and the end of the other divided body 30b, which are intermediate predetermined points of the side surface of the case in the combined state, are screwed together. By doing so, it will be connected and integrated while ensuring a waterproof state. As described above, the case 30 has a structure divided into two in the direction of the rotor rotation axis, but the structure is not limited to this, and a structure in which a larger number of divided bodies are combined as long as the inside and outside of the case can be separated (for example, a simple extrusion type) It can also be a structure in which a material plate or cylinder is combined).
As shown in FIGS. 2 and 4, it is preferable that a plurality of fins 33 that promote heat dissipation to the surroundings are projected on one end surface portion 31 of the case 30.

The heat transfer body 40 is a composite material in which an additive made of a good thermal conductive material is added to a base material (matrix) made of an insulating material, and can be adhered to these along the surface shape of the coil winding and the inner surface of the case. Moreover, it has the property of being able to stably maintain the close contact state.

As the additive, for example, fine particles of a ceramic material having thermal conductivity and high electric resistance, such as aluminum oxide, silicon nitride, boron nitride, and aluminum nitride, are used. Further, as the base material, in addition to a resin material such as silicone, rubber or an elastomer can be used.

When the additive and the base material are combined as the heat transfer body 40, a high-viscosity grease-like substance (compound) having a certain fluidity and a rubber-like sheet body that is flexible and highly elastically deformable are formed. .. The thermal conductivity of the heat transfer body 40 in the state is preferably, for example, 1 W / m · K or more, and more preferably 5 W / m · K or more.

In the configuration in which the heat transfer body 40 is a sheet body, the orientation of the additive may be adjusted to give directionality to the heat conductivity. In that case, the direction in which the heat transfer body 40 has good thermal conductivity is adjusted to the thickness direction of the sheet body so as to coincide with the direction from the coil to the end face of the case in the case arrangement state of the heat transfer body 40. Is desirable.

Next, the heat transfer state from the coil to the outside of the case in the brushless motor according to the present embodiment will be described.
When an electric current is passed through the coil 13 to rotate the motor, heat is generated in the winding of the coil 13 based on the resistance component of each part of the motor. The heat generated in the coil 13 is due to the heat conductivity of the heat transfer body 40 interposed between the outer periphery of the coil and the inner surface of the case due to the heat conductivity of the air around the coil and the insulator between the coil and the core. Since it is excellent, it is transmitted to others mainly through the heat transfer body 40.

That is, the heat generated in the coil 13 is transferred from both ends of the outer peripheral portion of the coil 13 in the direction of the rotor rotation axis to the heat transfer body 40 which is in close contact with the surface thereof, and further, the heat transfer body 40 is in close contact with the heat transfer body 40. It will be transmitted to the inner surface side of the two end face portions 31 and 32 of 30.

Here, in addition to the teeth portion 12 being formed so that the protruding dimension in the radial direction is larger than the dimension in the rotor rotation axis direction, the rotation of the rotor in the wound portion around which the coil 13 of the teeth portion 12 is wound. The end portion in the axial direction is formed as a planar portion 12a parallel to the end surface of the case 30, and the windings of the coil 13 are wound around the planar portion 12a so as to be closely aligned with the planar portion 12a. The windings of the coil in parallel are arranged flat along 12a.

As a result, the maximum number of coil windings close to the case end face can be secured at the portion of the coil 13 facing the inner surface of the case end face portion. Further, on the one end face portion 31 side of the case, the parallel windings of the coil 13 and the inner surface of the one end face portion 31 can be uniformly brought close to each other. Therefore, the heat of the coil 13 is easily transferred to one end face portion 31, and the efficiency of heat dissipation can be improved.

On the other hand, in the core portion 11, the lead wires drawn to connect the coil windings of each tooth portion 12 are collectively arranged on the end side closer to the other end face portion 32 of the case 30. As a result, due to the presence of such a conducting wire, it is not possible to obtain a state in which the winding of the coil uniformly approaches the inner surface of the end face portion 32 on the other end face portion 32 side of the case 30. For this reason, the heat of the coil is more efficiently transferred to the case side on the one end face portion 31 side in which many windings are in a state of being close to the inner surface of the end face portion 31.

The heat transferred from the coil 13 to the case end faces 31 and 32 through the heat transfer body 40 is released from the outer surface of the end face portion into the surrounding air, and is also transmitted to the case side surface portion by heat conduction in the case. It is also emitted from the outer surface to the surroundings.

In particular, on the outer surface side of one end surface portion 31 of the case 30, an air flow is generated along with the rotational drive of the rotary blade 50, and a part of the air flow flows along the outer surface side of the end face portion 31 to form a high temperature case outer surface. It becomes a forced cooling state in which contact with air is promoted, and cooling can be achieved more efficiently.

As described above, the brushless motor according to the present embodiment is an inner rotor type motor, which has thermal conductivity between the coil 13 winding surface of the stator 10 located in the case 30 and the inner surfaces of the case end surfaces 31 and 32. Since a certain heat transfer body 40 is arranged to secure a heat conduction path from the coil 13 to the case 30, the heat generated by the coil 13 is released to the case 30 through the heat transfer body 40 and radiated from the case 30 to the outside. The temperature rise inside the case 30 is suppressed, and the motor can be operated continuously without being adversely affected by heat. As an inner rotor type, it can handle a high load of the driving object while ensuring waterproof and dustproof performance. The brushless motor can be used as a drive source in response to various environmental conditions, such as being able to continue operation without problems even when used for driving the rotary blade 50.

1 Brushless motor 10 Stator 11 Core part 12 Teeth 12a Flat part 13 Coil 14 Lead wire 15 Lead wire 20 Rotor 21 Hub part 22 Yoke part 23 Permanent magnet 24 Bearing 25 Shaft 26 Fixture 30 Case 30a, 30b Split body 31, 32 End face Part 33 Fin 34 Screw hole 40 Heat transfer element 50 Rotor

Claims (2)

In a brushless motor including a substantially annular stator that generates a rotating magnetic field and a rotor that is rotatably arranged inside the stator and rotates based on the rotating magnetic field.
It is provided with a case formed in a hollow cylindrical trapezoidal shape symmetrical about the same central axis as the rotation center of the rotor and covering the stator and the rotor.
The stator is arranged along the inner circumference of the cylindrical side surface of the case, and has a core portion made of a magnetic material formed by forming a plurality of tooth portions protruding in the radial direction with respect to the rotation center of the rotor. Each tooth portion has at least a coil that is wound and arranged to generate a magnetic field.
At least the end face portion of the case in the rotation axis direction of the rotor is made of a good thermal conductive material.
In the state of being arranged in the case of the stator, a heat transfer body made of a heat conductive insulating material is placed in the gap between the end portion of the outer peripheral portion of the coil in the rotation axis direction of the rotor and the inner surface of the end face portion of the case. , It is housed and arranged in close contact with the coil surface and the inner surface of the case.
The coil is arranged so that the distance between the outer peripheral portion of the coil and the inner surface of the end face portion of the case is the minimum size that can maintain insulation with respect to the case in the energized state, and the case is provided from the coil via a heat transfer body. It is possible to transfer heat to the end face of
The rotor is integrally mounted around a shaft for mounting a drive object, and is rotatably supported by the case via a bearing, and at least an end portion on which the drive object of the shaft can be mounted is attached. It is arranged so as to project outward from one end face side of the case.
The core portion is arranged with the conductors drawn to connect the windings of each tooth portion together on one end side in the rotor rotation axis direction, and the side on which the conductors are arranged is arranged. Arranged in the case toward the other end face side of the case,
A brushless motor characterized in that the driving object is a rotary blade, and the flow of fluid generated by the rotary blade rotating together with the rotor is brought into contact with at least one end face outer surface of the case . In the brushless motor according to claim 1,
Each tooth portion of the core portion is formed so that the protruding dimension in the radial direction is larger than the dimension in the rotor rotation axis direction.
Of the wound parts around which the coil of each tooth portion is wound, the end portion in the direction of the rotor rotation axis is formed in a planar shape parallel to the inner surface of the end face portion of the case, and the coil is formed with respect to at least the planar portion. A brushless motor characterized in that the windings are tightly aligned and wound, and the windings in a parallel state of the coil are arranged flat along the planar portion.

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