Motor

Abstract

To provide a motor with high torque and further weight reduction.SOLUTION: A motor 1 includes an annular stator 13, and a rotor 15 having a rotor magnet 153 surrounding the stator 13, the outer diameter of the rotor 15 is in the range of 80 mm to 100 mm, the stator 13 includes an annular yoke 133, a plurality of magnetic pole portions 134, a plurality of connecting portions 132 that connect the yoke 133 and the plurality of magnetic pole portions 134, and a plurality of coils 139 respectively wound around the plurality of connecting portions 132, and the rotor magnet 153 is made of resin and formed continuously in an annular shape, the number of magnetic poles of the rotor magnet 153 is 14×N (N is a positive integer), the number of the plurality of magnetic pole portions 134 is 12×N (pieces), and each of the plurality of magnetic pole portions 134 extends in the circumferential direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a motor. [Background technology]

[0002] For example, an outer rotor type motor is described in Patent Document 1 (Patent Document 1 refers to it as a "rotating electric machine" rather than a "motor"). Patent Document 1 describes a motor in which a stator core has teeth extending toward a rotor magnet, and the rotor magnet has specific conditions such as the number of magnetic poles and the number of teeth, and the slot gap angle, which is the angle formed by the slot gap, is designed within a predetermined range, thereby realizing a reduction in cogging torque and an increase in the back electromotive force constant.

[0003] For example, motors used in drones are desired to be as lightweight as possible while still providing high torque. However, many motors use materials with relatively high specific gravity, such as metals and magnetic materials, for the stator and rotor components. In addition, a certain level of size is required to ensure a certain level of power performance, such as high torque, and there are generally many restrictions on reducing the weight of motors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2012-143107 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a motor that has high torque and is lightweight. [Means for solving the problem]

[0006] The above problems can be solved by the present invention. That is, the motor of the present invention includes an annular stator and a rotor having a rotor magnet surrounding the stator; Equipped with The outer diameter of the rotor is in the range of 80 mm to 100 mm, the stator includes an annular yoke, a plurality of magnetic pole portions, a plurality of coupling portions that couple the yoke and the plurality of magnetic pole portions, and a plurality of coils wound around each of the plurality of coupling portions; The rotor magnet is made of resin and is continuously formed into an annular shape. The number of magnetic poles of the rotor magnet is 14×N (N is a positive integer), The number of the plurality of magnetic pole parts is 12×N (pieces), Each of the plurality of magnetic pole portions extends in the circumferential direction.

[0007] In the present invention, when the outer diameter of the rotor is taken as 100, the width of the connecting portion in the circumferential direction is preferably in the range of 1.5 to 2.5. In the present invention, when the outer diameter of the rotor is taken as 100, the thickness of the rotor magnet in the radial direction is preferably in the range of 1.5 to 2.5.

[0008] Further, in the present invention, the rotor includes an annular yoke, The rotor magnet is fixed to the inner surface of the rotor yoke, When the outer diameter of the rotor is taken as 100, the thickness of the yoke of the rotor in the radial direction is preferably in the range of 0.5 to 1.0. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the overall configuration of an outer rotor type motor according to an embodiment of the present invention; [Diagram 2] 1 is a cross-sectional perspective view of a motor according to an embodiment of the present invention; [Diagram 3]1 is a partially cutaway perspective view of a region in the vicinity of the outer periphery of a motor according to an embodiment of the present invention where a stator and a rotor 15 face each other in the radial direction. [Figure 4] FIG. 1 is a perspective view showing a state before a holder of a motor according to an embodiment of the present invention is attached, with some members removed for the purpose of explanation. [Diagram 5] 5 is an enlarged plan view of an area and its periphery in FIG. 4 with some members removed. [Figure 6] 1 is a graph showing experimental results showing the relationship between the rotor yoke thickness TY and the back electromotive force constant. [Figure 7] 13 is a graph showing experimental results showing the relationship between the electrical angle (°) of the rotating shaft and the back electromotive force e (V) when the motor is driven while varying the width WT of the stator connection portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing the overall configuration of an outer rotor type motor 1 according to one embodiment of the present invention. Fig. 2 is a cross-sectional perspective view of the motor 1 according to this embodiment. Fig. 3 is a partial cross-sectional perspective view of the periphery of the motor 1 according to this embodiment, where the stator 13 and the rotor 15 face each other in the radial direction.

[0011] 4 is a perspective view showing the motor 1 according to this embodiment in a state before the holder 17 is attached, with some members (such as the coil 139 and the insulator 135) removed for the sake of explanation. Furthermore, FIG. 5 is an enlarged plan view of the area and its surroundings in FIG. 4 with some members removed.

[0012] In the description of this embodiment, for convenience, the direction in which the axis X extends when the motor 1 rotates is referred to as the rotation axis X direction or axial direction. In the following description, for convenience, the direction of arrow a in the rotation axis X direction is referred to as the upper side, and the direction of arrow b is referred to as the lower side. In addition, in the radial direction perpendicular to the axis X, the direction of arrow c away from the axis X is referred to as the outer periphery side, and the direction of arrow d approaching the axis X is referred to as the inner periphery side. In the following description, the upper side (the direction of arrow a) and the lower side (the direction of arrow b) refer to the up-down relationship of the motor 1 on the drawing, and do not necessarily coincide with the up-down relationship in the direction of gravity.

[0013] As shown in Fig. 1, motor 1 is an outer rotor type brushless motor mounted on a floating mobile body such as a drone (not shown). It is known that impacts on the drone when it lands or falls can damage motor 1, which drives the blades. For this reason, motor 1 in this embodiment is designed to be lightweight in order to reduce impacts when the drone lands or falls.

[0014] A drone's propeller (not shown) is attached to the upper side (direction of arrow a) of motor 1, and the drone's body is attached to the lower side (direction of arrow b). As shown in Fig. 2, motor 1 mainly has a stator holder 11, a stator 13, a rotor 15, a holder 17, and a bearing 19. The drone's propeller is fixed to holder 17, and the drone's body is fixed to stator holder 11.

[0015] The stator holder 11 has a cylindrical inner peripheral portion 111, a cylindrical outer peripheral portion 112, and a connecting portion 115. The inner peripheral portion 111 of the stator holder 11 is formed in a cylindrical or approximately cylindrical shape extending in the direction of the rotation axis X. The inner peripheral portion 111 holds a bearing 19 on its surface (hereinafter referred to as the "inner peripheral surface") on the inner peripheral side (direction of the arrow d).

[0016] Specifically, the inner peripheral portion 111 holds an outer ring 19a of the bearing 19 on the upper side (arrow a direction) in the direction of the rotation axis X, and holds an inner ring 19b of the bearing 19 on the lower side (arrow b direction). In this case, the outer ring 19a of the bearing 19 is press-fitted into the inner peripheral surface of the inner peripheral portion 111 of the stator holder 11.

[0017] That is, the inner periphery 111 of the stator holder 11 functions as a bearing holder for the bearing 19. The bearing 19 is, for example, a ball bearing. However, the bearing 19 is not limited to this, and various other bearings such as a sleeve bearing may be used.

[0018] Similar to the inner peripheral portion 111, the outer peripheral portion 112 of the stator holder 11 is formed in a cylindrical or approximately cylindrical shape extending in the direction of the rotation axis X. The inner peripheral portion 111 and the outer peripheral portion 112 both have central axes along the axis X. The length of the outer peripheral portion 112 in the direction of the rotation axis X is shorter than the length of the inner peripheral portion 111 in the direction of the rotation axis X.

[0019] Between the inner peripheral portion 111 and the outer peripheral portion 112 of the stator holder 11, a connecting portion 115 is formed integrally with the inner peripheral portion 111 and the outer peripheral portion 112. The connecting portion 115 connects the inner peripheral portion 111 and the outer peripheral portion 112 to each other. The connecting portion 115 extends from the outer peripheral end of the inner peripheral portion 111 toward the outer peripheral side (in the direction of arrow c) and is connected to the inner peripheral end of the outer peripheral portion 112.

[0020] A yoke 131 of the stator 13 (hereinafter referred to as the "stator yoke") is fixed to the outer peripheral surface (hereinafter referred to as the "outer peripheral surface") of the outer peripheral portion 112. The stator 13 has the stator yoke 131, an insulator 135, and a plurality of coils 139 wound around the stator yoke 131 with the insulator 135 interposed therebetween.

[0021] The stator yoke 131 is a laminate of silicon steel plates or the like, and is made up of an annular portion 132, a plurality of connecting portions (hereinafter also referred to as "teeth portions") 133 extending from the annular portion 132 toward the outer periphery (the direction of the arrow d), and magnetic pole portions 134 continuing to the outer periphery ends of the connecting portions 133. In this embodiment, the plurality of magnetic pole portions 134 extend in the circumferential direction, and the number of magnetic pole portions 134 (equal to the number of connecting portions 133) is 36.

[0022] The inner peripheral surface of the annular portion 132 of the stator yoke 131 is fixed to the outer peripheral surface of the outer peripheral portion 112 of the stator holder 11. In addition, the magnetic pole portions 134 of the stator yoke 131 protrude toward both circumferential sides (the clockwise direction e and the counterclockwise direction f), and the gap between adjacent magnetic pole portions 134 is narrower than the gap (slot) between adjacent connecting portions 133.

[0023] 3, an insulator 135 made of an insulating material is attached to the connecting portion 133 of the stator yoke 131. A coil 139 is wound around the connecting portion 133 via the insulator 135. The connecting portion 133 of the stator yoke 131 and the coil 139 are electrically insulated from each other via the insulator 135.

[0024] The rotor 15 has a yoke (hereinafter referred to as the "rotor yoke") 151 and a rotor magnet 153. The rotor yoke 151 is an annular, cylindrical iron core extending in the direction of the rotation axis X. The rotor yoke 151 surrounds the rotor magnet 153 and holds the rotor magnet 153 as a unit. The rotor yoke 151 prevents leakage of the magnetic field of the rotor magnet 153, and is made of a magnetic material such as an iron core.

[0025] The rotor magnet 153 has a cylindrical shape extending in the direction of the rotation axis X, similar to the rotor yoke 151. The rotor magnet 153 is held in close contact with an inner surface 151n of the rotor yoke 151, which is formed with high precision. The rotor magnet 153 surrounds the stator 13.

[0026] Rotor magnet 153 is a continuous ring-shaped resin molded magnet, generally referred to as a "bonded magnet" (hereinafter, may be referred to simply as a "bonded magnet"). More specifically, rotor magnet 153 is a magnet in which fine powders of rare earth elements such as neodymium and other magnetic materials are mixed and solidified with resin as a binder, and the magnetic materials are dispersed and arranged. Bonded magnets have a lower magnetic flux density than sintered magnets, but are lightweight and can be easily molded into any shape, offering many advantages such as improved freedom of design and ease of assembly.

[0027] The inner circumferential surface of rotor magnet 153 facing magnetic pole portion 134 of stator yoke 131 is arranged such that regions magnetized to S poles and regions magnetized to N poles alternate along the circumferential direction. The number of magnetic poles (the total of both S-pole and N-pole regions) of rotor magnet 153 will be described later. The height of rotor magnet 153 in the direction of rotation axis X is formed to be lower than the height of rotor yoke 151 in the direction of rotation axis X.

[0028] The holder 17 is made of an aluminum alloy and has an overall disk shape. However, this is not a limitation, and the holder 17 may be made of other materials such as resin or plastic. The holder 17 is also formed with high precision by cutting out the material through cutting work. However, this is not a limitation, and the holder 17 may be formed by press molding or the like.

[0029] As shown in Figures 1 and 2, holder 17 has an inner peripheral portion 171 provided on the inner peripheral side (the side in the direction of arrow c), an outer peripheral end portion 173 provided at the end on the outer peripheral side (the side in the direction of arrow d), and spokes 175.

[0030] The inner peripheral portion 171 of the holder 17 has a cylindrical protrusion 171d provided with a through hole 171h centered on the axis X, and a flange portion 171f extending radially from an end portion on the outer peripheral side of the protrusion 171d. The flange portion 171f has a size capable of covering the inner peripheral portion 111 of the stator holder 11 from above (the direction of the arrow a).

[0031] The protruding portion 171d of the inner peripheral portion 171 has a cylindrical inner cylinder portion 172 extending in the up-down direction (the direction of the arrow ab) centered on the axis X. The inner rings of the bearings 19a and 19b are held on the outer circumferential surface of the inner cylinder portion 172 of the inner peripheral portion 171. That is, the inner cylinder portion 172 of the holder 17 functions as a rotating shaft in the motor 1.

[0032] A plurality of (e.g., six) spokes 175 are connected to the end of the flange portion 171f on the outer circumferential side (in the direction of arrow c), and the annular outer circumferential end portion 173 is connected to the radial tip portions of the spokes 175. That is, the spokes 175 connect the flange portion 171f of the inner circumferential portion 171 and the outer circumferential end portion 173.

[0033] The outer peripheral end portion 173 of the holder 17 extends downward (in the direction of arrow b) along the direction of the rotation axis X from the edge on the outer peripheral side in the radial direction (in the direction of arrow c), and its lower end 173g is fixed in contact with the upper ends of the rotor yoke 151 and the rotor magnet 153.

[0034] In the motor targeted by the present invention, the outer diameter of the rotor (reference numeral 15 in this embodiment) is in the range of 80 mm to 100 mm. The "outer diameter of the rotor" here refers to the outer diameter of the rotor yoke (reference numeral 151) (the same applies hereinafter in the present invention). In the present invention, for example, the outer diameter size useful for a motor used in a drone is in the range of 80 mm to 100 mm, preferably in the range of 85 mm to 95 mm. Such an outer diameter size is suitable for balancing light weight and high torque.

[0035] In this embodiment, which is an example of the present invention, each of the magnetic pole portions 134 extends in the circumferential direction. By using rotor magnet 153 that is continuously formed from resin, the weight of motor 1 can be reduced, and by providing magnetic pole portions 133 on stator 13, the back electromotive force of motor 1 can be improved, ensuring a balance between torque and weight reduction.

[0036] In the conditions of the motor targeted by the present invention, the number of magnetic poles X (pieces) of the rotor magnet (reference numeral 153 in this embodiment) suitable for improving the back electromotive force while reducing the weight satisfies the following formula (1). X=14×N ··· Formula (1) In the above formula (1), X is the number of magnetic poles, and N is a positive integer.

[0037] In addition, in the conditions of the motor that is the subject of the present invention, the number Y of magnetic pole portions (133) of the stator (reference numeral 13 in this embodiment) that is suitable for improving the back electromotive force while reducing the weight satisfies the following formula (2). Y = 12 × N Equation (2) In the above formula (2), Y is the number of magnetic pole parts, and N is a positive integer, which is the same as N in the above formula (1).

[0038] In this embodiment, the number X of magnetic poles of the rotor magnet 153 is 28, and the number Y of the magnetic pole portions 133 of the stator 13 is 24. That is, in this embodiment, N=3 satisfies the above formula (1) (=14×3) and the above formula (2) (=12×3).

[0039] In the conditions of the motor targeted by the present invention, it is preferable that the value of N in the above formula (1) and formula (2) is not too large, and specifically, it is preferable that N≦4, and more preferably N≦3. On the other hand, the lower limit of N in the above formula (1) and formula (2) may be N=1, but it is more preferable that N≧2.

[0040] In the motor that is the subject of this invention, a bonded magnet is used as the rotor magnet (reference numeral 153 in this embodiment) to reduce weight, while the back electromotive force e is improved to achieve high torque, aiming to balance weight reduction and torque. Note that the back electromotive force e is equal to the generated voltage that appears at the motor terminals.

[0041] The counter electromotive force e can be expressed by the following equation (3). e=2RNBLω=K E ω...Equation (3) In the above formula (3), e is the back electromotive force (V), R is the radius of rotation (m), N is the number of turns of the coil, B is the magnetic flux density (T), L is the length of the wire in the magnetic field (m), ω is the rotation speed (rad / s), and K E and represent the back electromotive force constant (Vs / rad).

[0042] Therefore, in order to increase the torque, the back electromotive force e can be increased by increasing the values ​​of the elements on the right side of equation (3). Specific methods include, for example, the following measures.

[0043] · Increasing the rotation radius R (m)...If the diameter is made too large, the rotor will become large and heavy, so in the present invention, as described above, the outer diameter of the rotor is in the range of 85 mm to 95 mm as an appropriate balance.

[0044] Increasing the number of turns N of the coil...In the present invention, as will be described later, by making the connecting parts of the stator thinner, the gaps (slots) between the connecting parts can be enlarged, and the number of turns N of the coil can be increased.

[0045] Increasing the magnetic flux density (T)B: To increase the magnetic flux density (T)B, specifically, the strength of the magnet can be improved and the thickness of the stator joint can be made appropriate. In the present invention, as described below, the circumferential width of the stator joint is set within an appropriate range.

[0046] · Increasing the length L (m) of the electric wire in the magnetic field...To increase the length L of the electric wire in the magnetic field, specifically, the height of the magnet (height in the axial direction, the same as "height" in this paragraph) and the height of the stator core (magnetic pole parts and connecting parts) should be increased. Increasing these will increase the thickness of the motor, making it larger and heavier, so appropriate sizes should be selected and designed accordingly. Therefore, although the height of the magnet and the height of the stator core are not specified in this invention, taking into account the outer diameter of the rotor in this invention and the volume of the magnet required to rotate the rotor, the magnet height and stator core height that achieve an appropriate balance should be selected from a range of about 3 mm to 30 mm.

[0047] In the motor to which the present invention is applied, when the outer diameter of the rotor (in this embodiment, reference numeral 15) is taken as 100, the width in the circumferential direction of the connecting portion (133) of the stator (13) in the circumferential direction (in this embodiment, reference numeral W in FIG. 5) is taken as 100. T . Below, “Width W T ") is preferably in the range of 1.5 to 2.5, and more preferably in the range of 1.7 to 2.2.

[0048] In the motor targeted by this invention, a bonded magnet is used as the rotor magnet (reference numeral 153 in this embodiment), and the maximum energy product of the bonded magnet is 10 to 12 MGOe, which is smaller than the maximum energy product of a rare earth sintered magnet (e.g., 40 MGOe). As a result, the magnetic flux density at the magnetic pole portion (reference numeral 134) of the stator, which receives the magnetic flux of the rotor magnet, becomes smaller, and the width W of the connecting portion (reference numeral 133) T Therefore, the weight of the stator can be reduced.

[0049] However, the width of the connecting part W T If W is made too small, magnetic saturation will occur at the connection, reducing the drive efficiency of the motor. TAs described above, the preferred range of is 1.5 to 2.5, and more preferably 1.7 to 2.2, when the outer diameter of the rotor is 100.

[0050] In the motor to which the present invention is applied, when the outer diameter of the rotor (reference numeral 15 in this embodiment) is taken as 100, the thickness of the rotor magnet (reference numeral 153 in this embodiment) in the radial direction (reference numeral T in FIG. 5 in this embodiment) is taken as 100. M Hereafter, simply "thickness T M ") is preferably in the range of 1.5 to 2.5, and more preferably in the range of 1.7 to 2.4.

[0051] In the motor to which the present invention is applied, when the outer diameter of the rotor (reference numeral 15 in this embodiment) is taken as 100, the thickness of the yoke (rotor yoke 151 in this embodiment) of the rotor (reference numeral 15 in this embodiment) in the radial direction (reference numeral T in FIG. 5 in this embodiment) is taken as 100. Y Hereafter, simply "thickness T Y ") is preferably in the range of 0.5 to 1.0, more preferably in the range of 0.6 to 0.9, even more preferably in the range of 0.7 to 0.9, and particularly preferably in the range of 0.8 to 0.9.

[0052] The inventors have determined that the width W T , rotor magnet thickness T M , rotor yoke thickness T Y In order to determine an appropriate range for the thickness T of the rotor yoke 151, various conditions are varied and numerous experiments are carried out to verify the optimum range. Y The thickness T of the rotor yoke 151 is changed while other conditions are kept constant. Y The relationship between the back electromotive force constant and the rotor yoke 151 constant is shown in the graph of FIG. 6. In the graph of FIG. 6, the horizontal axis "thickness of rotor yoke 151" is the thickness T Y This shows that.

[0053] As can be seen from the graph of FIG. 6, there is a tendency that the back electromotive force constant increases as the rotation radius (m) in the formula (3) increases. In detail, when the thickness T Y If the thickness T is too thin, the back electromotive force constant will be low and it will be difficult to ensure the torque required for the motor. Y If is 0.5 or more, the back electromotive force constant becomes high to some extent, and the thickness T Y If the thickness T is 0.6 or more, or even 0.7 or more, the back electromotive force constant will be even higher. Y If is 0.8 or more, the back electromotive force constant is almost saturated. Y It can be seen that a value of 0.5 or more is preferable, a value of 0.6 or more is more preferable, a value of 0.7 or more is even more preferable, and a value of 0.8 or more is particularly preferable.

[0054] In addition, from the results of numerous experiments conducted by the present inventors, it was found that the width W T Fig. 7 shows the relationship between the electrical angle (°) of the rotating shaft and the back electromotive force e (V) when the motor is driven, by varying the width W T The results for the different motors are plotted on a graph with the horizontal axis representing the electrical angle (°) and the vertical axis representing the back electromotive force e (V).

[0055] As can be seen from the graph in Figure 7, the width W T As the width W becomes smaller, the back electromotive force waveform becomes distorted and the peak becomes lower. Therefore, from the above results, it can be seen that the distortion of the back electromotive force waveform is relatively small (the peak value is equal to or greater than the dashed line in the graph), and the width W T It can be seen that a value of 1.5 or more is preferable in terms of achieving high torque.

[0056] As mentioned above, the graphs in Figures 6 and 7 show results under specific conditions, but it has been confirmed that, under the conditions of the motor targeted by the present invention, even if the various conditions are changed slightly, the results do not change significantly and similar trends are observed.Y and width W T , and also the thickness T M There is no doubt that the above-mentioned ranges are each preferable ranges.

[0057] Although the motor of the present invention has been described above with reference to preferred embodiments, the motor of the present invention is not limited to the configuration of the above embodiments. For example, in the above embodiments, the number of spokes 175 of the holder 17 is six, but the number of spokes is not particularly limited, and the holder may be a cover-like holder that covers the entire motor instead of spokes.

[0058] In addition, those skilled in the art can appropriately modify the motor of the present invention in accordance with conventionally known knowledge. As long as the motor of the present invention is still provided after such modification, it is of course included in the scope of the present invention. [Explanation of symbols]

[0059] 1...motor, 11...stator holder, 13...stator, 15...rotor, 17...holder, 19 (19a, 19b)...bearing, 111...inner circumference, 112...outer circumference, 115...connection portion (connection portion of stator holder), 131...stator yoke (yoke of stator), 132...annular portion, 133...connection portion (teeth portion, connection portion of stator), 134...magnetic pole portion, 135...insulator, 139...coil, 151...rotor yoke (yoke of rotor), 153...rotor magnet, 171...inner circumference, 171d...projection portion, 171f...flange portion, 171h...through hole, 172...inner cylinder portion, 173...outer circumference end portion, 173g...lower end of outer circumference end portion

Claims

1. An annular stator; a rotor having a rotor magnet surrounding the stator; Equipped with The outer diameter of the rotor is in the range of 80 mm to 100 mm, the stator includes an annular yoke, a plurality of magnetic pole portions, a plurality of connecting portions connecting the yoke and the plurality of magnetic pole portions, and a plurality of coils wound around each of the plurality of connecting portions; The rotor magnet is made of resin and is continuously formed into an annular shape. The number of magnetic poles of the rotor magnet is 14×N (N is a positive integer), The number of the plurality of magnetic pole parts is 12×N (pieces), Each of the magnetic pole portions protrudes toward both sides in a circumferential direction, A motor in which, when the outer diameter of the rotor is 100, the width of the connection portion in the circumferential direction is in the range of 1.5 to 2.

5.

2. 2. The motor according to claim 1, wherein, when the outer diameter of the rotor is 100, a thickness of the rotor magnet in the radial direction is in a range of 1.5 to 2.

5.

3. The rotor includes an annular yoke. The rotor magnet is fixed to the inner surface of the rotor yoke, 3. The motor according to claim 1, wherein, when an outer diameter of the rotor is taken as 100, a thickness of the yoke of the rotor in a radial direction is in a range of 0.5 to 1.0.

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