Brushless motor

Abstract

A brushless motor comprising a stator (5) with a plurality of teeth (3) around which coils (4) are wound and a rotor (6) rotatably arranged radially within the stator (5), wherein the rotor (6) has a plurality of magnetic pole regions (10) opposite the teeth (3), the magnetic pole regions (10) being formed by permanent magnets (11) arranged circumferentially at equal angular intervals and all having the same polarity, the rotor (6) having recesses (14) which act as magnetic resistance at the ends circumferentially of each magnetic pole region (10), such that an iron core region (16) is formed between the circumferentially adjacent magnetic pole regions (10), and the magnetic flux of the magnetic pole regions (10) flows through the iron core region (16) in the radial direction, wherein the rotor (6) is designed such thatthat the rotation is defined in one direction, and wherein the recesses (14) at the ends in the circumferential direction of each magnetic pole region (10) have a first recess (14a) at the front end of the magnetic pole region (10) in the direction of rotation of the rotor (6) and a second recess (14b) at the rear end of the magnetic pole region (10) in the direction of rotation of the rotor (6), and the width (W1) of the first recess (14a) in the circumferential direction is greater than the width (W2) of the second recess (14b) in the circumferential direction, wherein an angle is defined as the first angle of the gap (81) from a straight line (L1) passing through the center point (0) of the rotor (6) and the central position (P0) in the circumferential direction of each magnetic pole region (10), and a straight line (M1) passing through the center point (0) of the rotor (6) and the front end (P1) of the first The recess (14a) extends,and an angle is defined as the second angle of the gap (θ2) by a straight line (L2) passing through the center (0) of the rotor (6) and the central position (P0) in the circumferential direction of each magnetic pole region (10), and a straight line (M2) passing through the center (0) of the rotor (6) and the rear end (P2) of the second recess, wherein the first angle (θ1) of the gap is greater than the second angle (θ2) of the gap.

Description

Background of the invention

[0001] The present invention relates to a brushless motor having a rotor comprising magnetic pole regions arranged such that all have the same polarity, and an iron core region which is arranged between circumferentially adjacent magnetic pole regions and allows the magnetic flux of the magnetic pole regions to flow in the radial direction.

[0002] In known brushless motors with a rotor having magnetic pole regions formed by permanent magnets, it has been proposed to increase the motor torque by increasing the number of magnetic poles or by forming the magnetic pole regions by strong permanent magnets.

[0003] However, strong permanent magnets such as neodymium magnets are expensive, and there are limits to reducing the thickness of the magnets. Therefore, manufacturing costs increase when a multi-pole rotor (for example, an 8-pole 12-slit motor) is manufactured using strong permanent magnets, as disclosed in Japanese Patent Application Publication No. JP 2008-113531 A.

[0004] Japanese Patent Application Publication No. JP H10-150755 A proposes a brushless motor having a consequent pole rotor in which the magnetic pole portions are formed in the rotor and arranged such that the polarity of all the magnetic pole portions is the same, and further having an iron core portion provided between the circumferentially adjacent magnetic pole portions to allow the magnetic flux from the magnetic pole portions to flow along the radial direction of the rotor.

[0005] Further prior art can be found in the documents JP H09- 182 331 A and JP 2004- 236 471 A.

[0006] More specifically, four magnetic pole portions 33 are provided on the rotor 32 of the brushless motor 31 at equal intervals in the circumferential direction, as shown in Fig. 42. The polarity of all magnetic pole areas 33 is the same and all magnetic pole areas 33 are accommodated in magnet holders H in such a way that the radially outer sides in the rotor 32 are south poles, as in Fig. 42. The magnetic pole regions 33 are formed by plate-like permanent magnets 30. Furthermore, recesses 34 are provided at both ends of each magnetic pole region 33 in the circumferential direction. The recesses 34 function as a magnetic resistance. An iron core region 36 is formed between the circumferentially adjacent magnetic pole regions 33. The iron core region 36 is magnetically separated from the magnetic pole regions 33 in the circumferential direction.

[0007] As in Fig. 43, the magnetic flux of the magnetic pole regions 33 flows into the corresponding iron core region 36 through the inner part of the rotor 32, bypassing the recesses 34 formed at the ends of the magnetic pole regions 33 in the circumferential direction. When the magnetic flux passes each iron core region 36 in the radial direction, a pseudomagnetic pole is formed in the iron core region 36 with a different polarity than the magnetic pole regions 33 that are circumferentially adjacent to the iron core region 36. The pseudomagnetic poles are, as shown in Fig. 42, parts marked with α and the radially outer sides are north poles.

[0008] In this way, a follower pole rotor 32 reduces the number of permanent magnets 30 by half compared to a rotor 42 of a normal brushless motor 41, in which the permanent magnets 30 are arranged such that the polarity of the circumferentially adjacent magnetic poles (magnetic pole regions 43) is different from each other, as shown in Fig. 44. Thus, a consequent pole rotor 32 achieves the same advantages as a multi-pole rotor with increased manufacturing costs.

[0009] However, since a magnetic field is generated in the stator, which is provided radially outside the rotor and acts on the rotor during motor activation, the magnetic flux flowing in the radial direction is increased in some parts of the iron core regions, which form the pseudomagnetic poles as described above, and decreased in others. This shifts the central magnetic position of each iron core region, which may cause the magnetic balance of the rotor to fluctuate.

[0010] This usually happens when one of the magnetic poles provided on the rotor is in a position where it faces two teeth of a brushless motor, a magnetic field with a magnetic force that attracts the magnetic pole is formed in the front of the two teeth and a magnetic field with a magnetic force that repels the magnetic pole is formed in the rear tooth.

[0011] For a normal brushless motor 41 with a rotor 42 as in Fig. 45, the magnetic flux formed by the permanent magnets 30 is neither reduced nor increased by the magnetic field of the stator 35. Therefore, the magnetic balance of the rotor 42 cannot fluctuate, since the central magnetic position of the magnetic poles, as viewed in Fig. 45 and there the position in which the line N0 crosses the magnetic pole is not significantly shifted.

[0012] Nevertheless, in cases where the brushless motor 31 includes a follower pole rotor 32 as shown in Fig. 46, when one of the iron core portions 36 forming a pseudo-magnetic pole is located in a position opposite to two teeth 37 (37a, 37bb), the central magnetic position is shifted significantly forward in the rotation direction of the rotor 32, that is, toward the position where the line N1 in Fig. 46 runs along.

[0013] While the magnetic flux flows assisted by the magnetic attraction force formed by the tooth 37a and the coil 38 in the part of the iron core region 36 opposite to the front tooth 37a, the magnetic flux is hindered by a magnetic repulsion formed by the tooth 37b and the coil 38 in the part of the iron core region 36 opposite to the rear tooth 37b.

[0014] Therefore, while the magnetic field of the stator 35 draws the magnetic flux flowing through the iron core 36 in the radial direction in the front portion of the iron core 36, the magnetic field of the stator 35 obstructs the magnetic flux flowing in the radial direction in the rear portion of the iron core 36. As a result, the central magnetic position is shifted forward relative to the rotation direction. This causes a fluctuation in the magnetic balance of the rotor 32, which reduces the motor output or generates noise and vibration. There is still room for further development in this regard.

[0015] When the permanent magnets 30 are inserted into the magnet receptacles H in the rotor 32, as in Fig. As shown in Figure 56, the dimensional tolerance of the magnet receptacles H and the permanent magnets 30 is taken into account when forming the magnet receptacles H and the permanent magnets 30 to facilitate insertion. Thus, a gap is likely to form between the permanent magnets 30 and the magnet receptacle holes H. In particular, a gap in the radial direction reduces the permeance (the reciprocal of the magnetic resistance), and the magnetic flux generated in the permanent magnet cannot be effectively utilized. This reduces the output power. Summary of the invention

[0016] A first object of the present invention is to provide a brushless motor which reduces the fluctuation of the magnetic balance during rotation of a rotor and is powerful.

[0017] A second object of the present invention is to provide a brushless motor which improves the output performance.

[0018] To achieve the two above objects and in connection with a first aspect of the invention, a brushless motor is provided. This brushless motor comprises a rotor and a stator. The stator has teeth around which coils are wound. The rotor is rotatably arranged radially inside the stator. The rotor has magnetic pole portions which oppose the teeth. The magnetic pole portions are formed by permanent magnets arranged at equal angular intervals in the circumferential direction. The magnetic pole portions all have the same polarity. The rotor has recesses which act as magnetic resistance at the circumferential ends of each magnetic pole portion, so that an iron core portion is formed between circumferentially adjacent magnetic pole portions. The magnetic flux of the magnetic pole portions flows through the iron core portions along the radial direction.The rotor is configured such that the rotation direction is defined in one direction. The recesses at the circumferential ends of each magnetic pole region include a first recess at the front end of the magnetic pole region in the direction of rotation of the rotor and a second recess at the rear end of the magnetic pole region in the direction of rotation of the rotor. The width of the first recess in the circumferential direction is larger than the width of the second recess in the circumferential direction.

[0019] To achieve the above-mentioned objects and in connection with a second aspect of the present invention, a brushless motor is provided. The brushless motor comprises a rotor and a stator. The stator has teeth around which coils are wound. The rotor is rotatably disposed radially inside the stator and has magnetic pole portions opposite the teeth. The rotor includes magnet receiving portions arranged at equal intervals in the circumferential direction of the rotor. Permanent magnets form magnetic pole portions, which are received in the magnet receiving portions. The permanent magnets face the teeth and have magnetic pole surfaces of the same polarity. The rotor has recesses which act as magnetic resistance at the ends of each magnetic pole portion in the circumferential direction, so that an iron core portion is formed between the circumferentially adjacent magnetic pole portions.The magnetic flux of the magnetic pole regions flows through the iron core region along the radial direction. A magnetic element is arranged in each magnet receiving region to fill the gap between the magnetic pole surface of the corresponding permanent magnet and the inner surface of the magnet receiving region, which faces the magnetic pole surface.

[0020] Further aspects and advantages of the invention will become apparent from the following description with reference to the accompanying figures, which illustrate by way of example the principles of the invention. Description of the characters

[0021] The invention, together with its objects and advantages, will best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings, in which: Fig. 1 is a schematic view showing a brushless motor according to a first embodiment of the present invention; Fig. 2 is an enlarged view showing the pole area and its surroundings of the rotor from Fig. 1 shows: Fig. 3 is a perspective view showing the rotor core with embedded permanent magnets; Fig. 4 is an exemplary diagram showing the relationship between the pole areas of the rotor of Fig. 1 and the recesses at both ends of each pole area and the iron core area; Fig. Figure 5 is a diagram showing the operation of a brushless motor from Fig. 1 shows; Fig. 6 is a graph illustrating the relationship between a fifth angle of a gap defining the circumferential width of the pole portions and the motor torque; Fig. 7 is a graph illustrating the relationship between a first angle of a gap defining the circumferential width of the first recesses and the engine torque; Fig. 8 is a graph illustrating the relationship between a second angle of a gap defining the circumferential width of the second recess and the engine torque; Fig. 9 is a diagram illustrating the comparison of the engine torque of an engine according to the first embodiment with that of a conventional engine; Fig. 10 is a diagram explaining the shape of a rotor of a brushless motor according to a second embodiment of the present invention; Fig. 11 is a graph showing the relationship between the shape of the rotor according to Fig. 10 and the offset moment; Fig. 12 is a diagram explaining the shape of a rotor of a motor according to a modified embodiment of the first and second embodiments; Fig. 13 is a graph showing the relationship between the shape of the rotor according to the modified embodiment of the first and second embodiments and the cogging moment; Fig. 14 is a plan view showing the rotor core according to a modified embodiment of the first and second embodiments; Fig. 15 is a perspective view of the rotor core of the Fig. 14; Fig. 16 is a plan view showing the rotor core of a modified embodiment of the first and second embodiments; Fig. 17 is a perspective view of the rotor core of the Fig. 16; Fig. 18 is a schematic diagram showing a brushless motor according to a modified embodiment of the first and second embodiments; Fig. 19 is an explanatory diagram showing the relationship between the magnetic pole portions formed in the rotor of the brushless motor according to the modified embodiment of the first and second embodiments and the recesses at both ends of each magnetic pole portion and the iron core portions; Fig. 20 is a graph showing the relationship between the fifth angle of a gap of the brushless motor according to the modified embodiment of the first and second embodiments and the motor torque; Fig. 21 is a graph showing the relationship between the first angle of a gap of the brushless motor according to the modified embodiment of the first and second embodiments and the motor torque; Fig. 22 is a graph showing the relationship between the second angle of a gap of the brushless motor according to the modified embodiment of the first and second embodiments and the motor torque; Fig. 23 is a diagram for explaining the operation of the brushless motor according to the modified embodiment of the first and second embodiments; Fig. 24 is a schematic diagram showing a brushless motor according to a third embodiment of the present invention; Fig. 25 is an exemplary diagram showing the relationship between the pole areas of the rotor of Fig. 24 and the recesses at both ends of each pole area and the iron core area; Fig. 26 is an exemplary diagram showing the relationship between the pole areas of the rotor of Fig. 24 and the recesses at both ends of each pole area and the iron core area; Fig. 27 is a graph showing the relationship between a first angle of a gap of the motor according to the third embodiment and the motor torque; Fig. 28 is a graph showing the relationship between the second gap angle of the motor according to the third embodiment and the motor torque; Fig. 29 is a graph showing the relationship between the third angle of the gap of the motor according to the third embodiment and the motor torque; Fig. 30 is a graph showing the relationship between the fourth angle of the gap of the motor according to the third embodiment and the motor torque; Fig. 31 is a plan view showing a rotor core according to a modified embodiment of the third embodiment; Fig. 32 is a plan view showing a rotor core according to a modified embodiment of the third embodiment; Fig. 33 is a schematic diagram showing a brushless motor according to a fourth embodiment of the present invention; Fig. 34 is a diagram showing the arrangement of each element in the rotor core of the brushless motor according to Fig. 33 embedded permanent magnets and the magnetic elements; Fig. 35 is a graph showing the comparison between an engine according to the fourth embodiment and a conventional engine; Fig. 36A and Fig. 36B are diagrams showing the arrangement of each permanent magnet and the magnetic elements according to a modified embodiment of the third embodiment; Fig. 37A and Fig. 37B are diagrams explaining the arrangement of each permanent magnet and the magnetic elements according to a modified embodiment of the third embodiment; Fig. 38 is a schematic diagram showing a rotor according to a modified embodiment of the fourth embodiment; Fig. 39 is a schematic diagram of a rotor according to a modified embodiment of the fourth embodiment; Fig. 40 is a schematic diagram showing a brushless motor according to a fifth embodiment of the present invention; Fig. 41A is an enlarged partial view of the engine from Fig. 40; Fig. 41b is a partial side view of the brushless motor of Fig. 40; Fig. Figure 42 is a schematic diagram of a conventional brushless motor with a consequent pole rotor; Fig. 43 is a diagram explaining the formation of pseudomagnetic poles in the iron nuclei according to Fig. 42; Fig. Figure 44 is a schematic diagram showing a normal brushless motor with a classic rotor; Fig. Figure 45 is a diagram showing the distribution of magnetic flux between the stator and the rotor of a brushless motor according to Fig. 43 shows; and Fig. Figure 46 is a diagram showing the distribution of magnetic flux between the stator and the rotor of the brushless motor according to Fig. 42 shows; Description of the preferred embodiments

[0022] A brushless motor (IPM motor) 1 with an embedded permanent magnet in the rotor 6 according to a first embodiment of the present invention will be described below with reference to the Fig. 1 to 9 described.

[0023] As in Fig. As shown in Figure 1, the brushless motor 1 of the present embodiment includes a stator 5 and a rotor 6. The stator 5 has an annular portion 2, teeth 3 extending radially inward from the annular portion 2, and coils 4 wound around the teeth 3.

[0024] According to the present embodiment, the stator 5 has twelve teeth 3 and, accordingly, twelve slots. A three-phase alternating current flows through the coils 4.

[0025] The rotor 6 has a rotatable axle 7 and a columnar rotor core 8, which is securely attached to the rotatable axle. The rotatable axle is supported in bearings (not shown). The rotatable axle 7 is arranged radially inside the stator 5, surrounded by the teeth 3, and freely rotatable. Magnetic pole regions 10, which are opposite the teeth 3 surrounding the rotor 6, are provided in the circumferential region of the rotor 6.

[0026] Further in detail, as can be seen from the Fig. 1 to 3, the magnetic pole portions 10 are plate-shaped permanent magnets 11 embedded in the peripheral portion of the rotor core 8. The brushless motor according to the present embodiment is an IPM motor having permanent magnets embedded in the rotor. Typically, magnet receiving portions, which in this embodiment are magnet receptacles 13, are provided at equal angular intervals in the circumferential direction (at angular intervals of 90° in the present embodiment) near the peripheral portion of the rotor core 8. The magnet receptacles 13 extend in the axial direction through the rotor core 8. The permanent magnets 11 are received and secured in the magnet receptacles 13 such that the permanent magnets 11 are perpendicular to the radial direction of the rotor core 8.

[0027] All permanent magnets 11 are arranged in the magnet receptacles 13 such that the radially outer surfaces have the same polarity. In the present embodiment, all permanent magnets 11 are arranged in the magnet receptacles 13 such that the radially outer surfaces are south poles. In a rotor 6 according to the present embodiment, four magnetic pole regions 10 with the same polarity are arranged along the circumferential direction of the rotor 6 at equal angular intervals. Furthermore, two recesses 14 (14a, 14b) are formed at both ends in the circumferential direction of each magnetic pole region 10. Since the recesses 14 act as a magnetic resistance, an iron core region 16, which is separated from the magnetic pole regions 10, is formed between the circumferentially adjacent magnetic pole regions 10.

[0028] In this respect, the magnetic flux of each magnetic pole region 10 flows into the corresponding iron core region 16 through the inner part of the rotor core 8, bypassing the recesses 14 formed at the ends in the circumferential direction of the magnetic pole regions 10. When the magnetic flux flows radially outward through the iron core region 16, a pseudomagnetic region is formed in the iron core region 16 with a polarity opposite to the polarity of the magnetic pole regions 10 that border the iron core region 16 in the circumferential direction. With regard to the mechanism for the formation of the pseudomagnetic poles in the iron core regions 16, reference is made here to the Fig. 43.

[0029] This means that the rotor 6 according to the present embodiment is a consequent pole rotor. When comparing a brushless motor 1 according to the first embodiment with a normal brushless motor (see also Fig. 44), in which all magnetic poles are formed with permanent magnets, the brushless motor 1 has the advantage of multipolarization while reducing the number of permanent magnets by half. Therefore, the brushless motor 1 has a structure that allows for a reduction in size and an increase in performance compared to a normal motor as in Fig. 43 shown, allowed.

[0030] A brushless motor 1 according to the present embodiment is designed to function optimally in a mode in which the rotational direction of the rotor 6 is limited to a single rotational direction. This means that in the present embodiment, the rotational direction of the rotor 6 in Fig. 1 and 2 is defined counterclockwise. The recess 14 at the front end of each magnetic pole region 10 with respect to the direction of rotation of the rotor 6 is hereinafter referred to as the first recess 14a, and the recess 14 at the rear end of each magnetic pole region 10 with respect to the direction of rotation of the rotor 6 is hereinafter referred to as the second recess 14b. As in Fig. 2, the width W1 of the first recess 14a in the circumferential direction is greater than the width W2 of the second recess 14b in the circumferential direction.

[0031] As in Fig. As shown in Fig. 4, an angle formed by a straight line L (L1) passing through the center O of the rotor 6 and the center P0 of the magnetic pole portion 10 (10a) in the circumferential direction, and a straight line L (L2) passing through the center O of the rotor 6 and an end P1 at the front end of the first recess 14a, is defined as the first gap angle θ1. The angle formed by a straight line L (L2) passing through the center O of the rotor 6 and the center P0 of the magnetic pole portion 10 (10b), and a straight line M2 passing through the center O of the rotor 6 and an end P2 at the rear end of the second recess 14b, is referred to as the second gap angle θ2. The angle defined by the straight line L (L1) and a straight line M5 passing through the end portion P5 of the magnetic pole portion 10 (10a) in the circumferential direction is called the fifth angle θ5 of the gap.Thus, twice the fifth gap angle θ5 corresponds to the circumferential width W5 of the magnetic pole region 10 (10a). In a rotor 6 according to the present embodiment, the first gap angle θ1 is larger than the second gap angle θ2.

[0032] Therefore, all fifth angles θ5 of the gap are identical because the plate-like permanent magnets 11 forming the magnetic pole portions are arranged at identical angular intervals in the circumferential direction of the rotor core 8. In other words, all widths W5 of the magnetic pole portions 10 in the circumferential direction are identical. Due to the fact that the first angle θ1 of the gap is larger than the second angle θ2 of the gap, as described above, the width W1 of the first recess 14a in the circumferential direction is larger than the width W2 of the second recess 14b in the circumferential direction (see also Fig. 2). Therefore, the present embodiment reduces the above-described offset of the magnetic center of the iron core regions 16 during rotation of the rotor 6 and the associated fluctuation of the magnetic balance.

[0033] If each iron core area in a conventional follower pole rotor is located opposite two teeth, as in Fig. As shown in Figure 46, the magnetic flux flows more easily through the front part of the iron core region, where a magnetic attraction exists between the iron core region and the opposing tooth. In contrast, the magnetic flux is obstructed in the rear part of the iron core region, where a magnetic repulsion force acts between the iron core region and the opposing tooth. This causes the magnetic balance to fluctuate during rotor rotation.

[0034] However, in a brushless motor 1 of the present embodiment, the circumferential width W1 of the first recess 14a is larger than the circumferential width W2 of the second recess 14b. Therefore, as shown in Fig. As shown in Fig. 5, when the iron core portion 16 formed between the second recess 14b of a magnetic pole portion and the first recess 14a of the magnetic pole portion 10 adjacent thereto is opposed to two teeth 3 (3a, 3b), the proportion of the iron core portion 16 facing the rear tooth 3b becomes small. This reduces the amount of magnetic flux prevented from flowing from the iron core portion 16 to the tooth 3b by the repulsive magnetic force formed between the tooth 3b and the iron core portion 16 facing the tooth 3b. Further, the amount of magnetic flux flowing from the iron core portion 16 to the tooth 3a by the magnetic attraction force formed between the tooth 3a and the iron core portion 16 facing the tooth 3a is thus reduced.

[0035] The total amount of magnetic flux flowing from the magnetic pole regions 10 separated by the recesses 14 (14a, 14b) to the corresponding iron core region 16 via the inner part of the rotor core 8 is substantially constant. Therefore, the amount of magnetic flux hindered by the magnetic repulsion force between the tooth 3b and the iron core region 16 opposite to the tooth 3b is equal to the amount of magnetic flux attracted by the magnetic attraction force between the tooth 3a and the iron core region 16 opposite to the tooth 3a. As described above, by reducing the amount of magnetic flux caused by the magnetic repulsion force generated between the tooth 3b and the iron core region opposite to the tooth 3b, the magnetic center of the iron core region 16 (in Fig. 5 (the circumferential position through which the straight line N2 passes) is prevented from being displaced in the rotation direction of the rotor 6 during the rotation of the rotor 6. In the present embodiment, the fluctuation of the magnetic balance during the rotation of the rotor 6 is thus reduced, and the output power of the brushless motor 1 is further increased.

[0036] Further, in the present embodiment, the first recesses 14a are formed so as to open in a circumferential surface 18 of the rotor 6 (rotor core 8), as shown in the Fig. 1 to 3. This increases the magnetic resistance of the first recesses 14a and further reduces the influence on the magnetic repulsion force between the tooth 3b and the iron core region 16 opposite the tooth 3b.

[0037] In the present embodiment, a bridge portion 19, which defines the first recess 14a and the magnet receptacle 13, is formed between the first recess 14a and the magnet receptacle 13, as shown in Fig. 2. This prevents the force of the rotor 6 from being reduced by the openings of the first recesses 14a in the circumferential surface 18 of the rotor core 8.

[0038] The brushless motor 1 according to the present embodiment has four magnetic pole portions 10, four iron core portions 16, and twelve teeth 3, so that the structure is substantially the same as an 8-pole, 12-slot brushless motor. Thus, when one iron core portion 16 faces two teeth 3, all other iron core portions 16 face corresponding teeth 3 (see also Fig. 1), since the number of slots formed between the adjacent teeth 3 is a multiple of the number of iron core regions 16. Thus, the fluctuation of the magnetic balance during rotation of the rotor 6 can be further efficiently reduced, as described above.

[0039] The optimal design of the angle θ5 of the gap, which defines the width W5 of the magnetic pole regions 10 in the circumferential direction, and the angles θ1 and θ2 of the gap, which define the widths W1 and W2 of the first and second recesses 14 at the ends of the magnetic pole regions 10 in the circumferential direction, are explained below.

[0040] Fig. 6 is a graph showing the relationship between the fifth angle θ5 of the slit (see also Fig. 2 and Fig. 4) and the torque of the motor 1. Considering that the brushless motor 1 of the present embodiment has substantially the same structure as an 8-pole 12-slot brushless motor, the upper limit for the fifth angle θ5 of the gap is approximately 22°. Fig. As can be seen from Figure 6, the torque of motor 1 reaches a maximum value (100%) when the fifth gap angle θ5 is approximately 18°, and reliably reaches a value greater than or equal to 99.5% of the maximum value when the fifth gap angle θ5 is in the range between 17° and 19°. Therefore, the fifth gap angle θ5 is preferably set in the range between 17° and 19°.

[0041] Also Fig. 7 is a graph showing the relationship between the first angle θ1 of the slit (see also Fig. 2 and Fig. 4) and the torque of motor 1. Fig. 8 is a graph showing the relationship between the second angle θ2 of the slit (see also Fig. 2 and Fig. 4) and the torque of motor 1.

[0042] Since a brushless motor 1, as described above, has twelve slots, the first gap angle θ1 is preferably greater than 30°. This is because the first gap angle θ1 is preferably larger than the distances between the teeth 3, which are 30°, to achieve the advantage of the present embodiment. Since the second gap angle θ2 must necessarily be smaller than the first gap angle θ1, the second gap angle θ2 is smaller than 30°.

[0043] In addition, the torque of the motor 1 reaches the maximum value (100%) once the first angle θ1 of the gap is approximately 35°, and the value of the torque is certainly greater than 99.5% of the maximum value when the first angle θ1 of the gap is in the range between 33° and 36°, as Fig. 7. Therefore, the first angle θ1 of the gap is preferably in the range between 33° and 36°.

[0044] Similarly, the torque of the motor 1 reaches a maximum value (100%) when the second angle θ2 of the gap is approximately 28°, and the value of the torque is certainly greater than 99.5% of the maximum value when the second angle θ2 of the gap is in the range between 27° and 29°, as Fig. 8. Therefore, the second angle θ2 of the gap is preferably in the range between 27° and 29°.

[0045] Based on the above considerations, the rotor 6 is designed such that in the present embodiment, the fifth angle θ5 of the gap is 18°, the first angle θ1 of the gap is 35°, and the second angle θ2 of the gap is 28°. In comparison between a brushless motor and a conventional consequent pole rotor (see also Fig. 42) and a brushless motor 1 according to the present embodiment, the torque of the motor 1 according to the present embodiment is improved, as Fig. 9. In Fig. 9 is the torque of a conventional engine, as in Fig. 44 shown as 100%.

[0046] The present embodiment has the following advantages. (1) The rotor 6 has the magnetic pole portions 10 arranged at equal angular intervals along the circumferential direction of the rotor 6, and the magnetic pole portions 10 are arranged so that they all have the same polarity. Also, the recesses 14 (14a, 14b) are formed at the ends of each magnetic pole portion 10 in the circumferential direction. Therefore, the iron core portion 16, which is separated from the magnetic pole portions 10, is formed between the circumferentially adjacent magnetic pole portions 10. Also, the rotation direction of the rotor 6 is defined in a single direction. Besides the recesses 14 (14a, 14b), the circumferential width W1 of the first recess 14a formed at the front end is larger than the circumferential width W2 of the second recess 14b formed at the rear end. This structure prevents the magnetic center from shifting toward the front end of the iron core portion 16 in the rotational direction, thus reducing the fluctuation of the magnetic balance in the present embodiment. The advantage of magnetic balance brings with it the further advantage of improving the performance in terms of motor torque. (2) The first gap angle θ1 is larger than the second gap angle θ2. Thus, the circumferential width W1 of the first recess 14a is reliably larger than the circumferential width W2 of the second recess 14b. (3) The brushless motor 1 has four magnetic pole sections 10, four iron core sections 16, and twelve slots. Thus, when one iron core section 16 faces two teeth 3, all other iron core sections 16 face corresponding two teeth in the same way, since the number of slots is a multiple of the number of iron core sections 16. Thus, as described above, the brushless motor 1 is designed to utilize the advantage described in (1) even more efficiently. (4) The first angle θ1 of the gap is selected to be greater than 30° and the second angle θ2 of the gap is selected to be less than 30°. In this way, the brushless motor 1 is essentially identical to an 8-pole 12-split brushless motor, since the brushless motor 1 has four magnetic pole sections 10 and four iron core sections 16. The first gap angle θ1 is preferably greater than 30° to further exploit the advantage described in (1). The second gap angle θ2 is smaller than 30° because the second gap angle θ2 must be smaller than the first gap angle θ1. (5) The rotor 6 is designed such that the fifth angle θ5 of the gap, which defines the width W5 of the magnetic pole regions 10 in the circumferential direction, is 18°, the first angle θ1 of the gap, which defines the width W1 of the first recesses 14a in the circumferential direction, is 35°, and the second angle θ2 of the gap, which defines the width W2 of the second recesses 14b in the circumferential direction, is 28°. In this way, the relationship between the magnetic pole regions 10 and the iron core regions 16 is optimized. Consequently, improving the magnetic balance further improves the performance in terms of increasing the torque of the motor 1. (6) The magnetic pole regions 10 are formed by plate-shaped permanent magnets 11 embedded near the peripheral region of the rotor core 8. The first recesses 14a are open in the peripheral surface 18 of the rotor 6 (rotor core 8). With such a configuration, the magnetic resistance of the first recesses 14a is increased and thus the influence of the magnetic repulsion force existing between the tooth 3 (3b) opposite to the rear portion of the iron core portion 16 and the portion of the iron core portion 16 opposite to the tooth 3b is further reduced.

[0047] Further embodiments of the present invention will be described below. In each embodiment, the same reference numerals are used for components corresponding to the same components of the first embodiment, and drawings and all or part of the descriptions are omitted.

[0048] A brushless motor (IPM motor) 1B according to a second embodiment will be described with reference to Fig. 10 and Fig. 11.

[0049] Fig. 10 shows the part of a cross section of an engine 1B according to the second embodiment. Fig. 10 shows an iron core portion 61 of a rotor of the second embodiment. A circumferential center point of an outer surface 61x is located on an imaginary reference circumferential surface C (for example, the radius of the rotor center point is 22m) formed by connected outer surfaces 10x of all magnetic pole portions 10. The outer surface 61x is curved so that it moves radially inward from the circumferential surface C as the distance from the ends decreases in the circumferential direction. Thus, the outer surface 61x of the iron core portion 61 has a greater curvature than the circumferential surface C. In other words, the outer surface 61x has a small radius of curvature, so that toward the end portions of the circumferential center portion, the outer surface 61x is further away from the stator 5 (the teeth 3).

[0050] Also, the outer surface 61x of the iron core portion 61 is shaped to fit an arc centered at a predetermined location X1 along a straight line CL (a straight line shifted by 15° from the straight line L2 and the straight line L1) passing through a circumferentially intermediate position between circumferentially adjacent magnetic pole portions 10 and the center point O of the rotor 60, and having a radius R1. Thus, the end P2 located at the front end of the iron core portion 61 is located radially inward of the end P1 located at the rear end of the iron core portion 61 with respect to the stator 5 (the teeth 3).

[0051] If the radius of the circumferential surface C is denoted as R0 and the radius of the outer surface 61x of the iron core portion 61 is denoted as R1, the offset torque of the rotor 60 changes with changes in the ratio R1 / R0 as shown in Fig. 11 shown. Fig. 11 shows the results when the fifth gap angle θ5 is approximately 18°, the first gap angle θ1 is approximately 35°, and the second gap angle θ2 is approximately 28°, as described with respect to the first embodiment.

[0052] Also in Fig. 11, a cogging moment of 100% is assumed when the ratio R1 / R0 is 1, that is, when the curvature of the outer surface 61x of the iron core region 61 has the same curvature as the circumferential surface C. The cogging moment is reduced gradually as the ratio R1 / R0 decreases, that is, when the curvature of the outer surface 61x of the iron core region 61 becomes larger compared to the curvature of the circumferential surface C. In the range where the ratio 0.7 s R1 / R0 < 1, the cogging moment is reduced by a relatively large amount. The reduction rate of the cogging moment is reduced when the ratio R1 / R0 becomes less than 0.7, and the reduction rate of the cogging moment is further reduced from the point where the ratio R1 / R0 approaches 0.6. Once the ratio R1 / R0 is 0.6, the offset torque is reduced to approximately 37%. Furthermore, the reduction rate drops to almost zero once the ratio R1 / R0 is less than 0.6.

[0053] Based on the foregoing description, in a rotor 61 of the present invention, the curvature of the outer surface 61x of the iron core portion 61 is set to obtain a ratio R1 / R0 in the range of 0.6 s R1 / R0 < 1. Particularly, when only the reduction of the cogging torque is considered, the ratio R1 / R0 is preferably set in the range of 0.6 s R1 / R0 ≤ 0.7, and when the reduction rate of the cogging torque is considered, the effect can also be expected when the ratio R1 / R0 is in the range of 0.7 ≤ R1 / R0 < 1. Thus, in the present embodiment, a rapid change in the magnetic flux density, which may occur between the magnetic pole portions 10 and the iron core portions 61, and the cogging torque are reduced.

[0054] The present embodiment has the following advantages. (7) The outer surface 61x of each iron core portion is shaped such that, as the distance to the ends P1 and P2 in the circumferential direction decreases, the outer surface 61x gradually moves radially inward from the reference circumferential surface C formed by the connection of the outer surfaces 10x of the magnetic pole portions 10. Since the radial distance between the iron core portion 61 and the stator 5 gradually increases toward the ends P1 and P2 of the iron core portion 61 in the circumferential direction, the degree of change in the magnetic flux density near the magnetic pole end portions of the iron core portion 61 is correspondingly reduced. The rapid change in the magnetic flux density is thus suppressed, and thus the cogging torque is reduced. (8) The entire outer surface 61x of the iron core area 61 has a curved shape with a defined curvature. The ratio R1 / R0 of the radius R1 of the curvature of the outer surface 61x and the radius R0 of the reference circumferential surface C is set in the range 0.6 ≤ R1 / RO < 1. This reduces the offset moment (see also Fig. 11). The closer the ratio R1 / R0 comes to the value 0.6 in the above-mentioned range, the more the offset moment is reduced.

[0055] The first and second embodiments may be modified as follows.

[0056] In the second embodiment, the relationship between the ratio R1 / R0 and the offset moment is defined at a fifth gap angle θ5 of approximately 18°, a first gap angle θ1 of approximately 35°, and a second gap angle θ2 of approximately 28°, but is not limited thereto. For example, the offset moment is also reduced in the same manner as in the second embodiment when the fifth gap angle θ5 is in the range of 17° to 19°, the first gap angle θ1 is in the range of 33° to 36°, and the second gap angle θ2 is in the range of 27° to 29°, as shown in the Fig. 6 to 8 is shown.

[0057] In the second embodiment, the offset moment is reduced by changing the curvature of the outer surface 61x of the iron core portion 61 from the curvature of the imaginary reference circumferential surface C, which is formed by connecting the outer surfaces 10x of all magnetic pole portions 10. In addition, the curvature of the outer surfaces 10x of the magnetic pole portions 10 can be changed from the curvature of the circumferential surface C, as shown in Fig. 12. In particular, as shown in Fig. As shown in Figure 12, the pole regions 62 are formed such that the circumferentially central region of the radially outer surface 62x is located on the reference circumferential surface C, and the outer surface 62x is curved such that it moves radially inward from the circumferential surface C with decreasing distance from the ends in the circumferential direction. Thus, the outer surface 62x of each magnetic pole region 10 has a greater curvature or a smaller radius of curvature than the circumferential surface C and is formed such that, from the circumferentially central region toward the end regions, the outer surface 62x gradually moves away from the stator 5 (the teeth 3). The magnetic pole regions 62 are each shaped to fit an arc having its center at a predetermined point X2 located on the straight line L1 and the straight line L2 and having a radius R2. Fig. 12, the point X2 is selected such that the distance between the point X2 and the center O of the rotor 60 is equal to the distance between the point X1 and the center O of the rotor 60. In this way, the outer surfaces 62x of the magnetic pole regions 62 are shaped such that the radius R1 and the radius R2 are equal.

[0058] Fig. 13 shows the offset torque of the rotor 60 when the ratio R1 / R0 of the radius R0 of the peripheral surface C and the radius R1 of the outer surface 61x of the iron core portion 61 and the ratio R2 / R0 of the radius R0 of the peripheral surface C and the radius R2 of the outer surface 62x of the magnetic pole portion 62 are changed. Fig. Figure 13 shows the results for the case as in the second embodiment, in which the fifth angle θ5 of the gap is approximately 18°, the first angle θ1 of the gap is approximately 35°, and the second angle θ2 of the gap is approximately 28°. With such a structure, the same result as in Fig. 13 when the fifth angle θ5 of the gap is in the range 17° to 19°, the first angle θ1 of the gap is in the range 33° to 36° and the second angle θ2 of the gap is in the range 27° to 29°, as shown in the Fig. 6 to 8 is shown.

[0059] In Fig. 13, the offset torque is assumed to be 100% when R1 / R0 = R2 / R0 = 1, and thus the curvature of the outer surface 61x of the iron core region 61 and the curvature of the outer surface 62x of the magnetic pole region 62 are identical to the curvature of the circumferential surface C. The offset torque is gradually reduced when the ratio R1 / R0 and the ratio R2 / R0 are reduced. The offset torque is reduced relatively strongly in the range in which the ratio R1 / R0 and the ratio R2 / R0 are defined as follows: 0.7 ≤ R1 / R0 = R2 / R0 < 1. The reduction degree of the offset torque becomes smaller as soon as the ratio R1 / R0 and the ratio R2 / R0 become less than 0.7, is further reduced near the value 0.6 for the ratio R1 / R0 and the ratio R2 / R0, and decreases to the value 19% as soon as the ratios R1 / R0 = R2 / R0 = 0.6 is reached.Thus, the offset moment is further reduced by the change in the curvature of the circumferential surface C of both the curvature of the outer surfaces 61x of the iron core regions 61 and the outer surfaces 62x of the magnetic pole regions 62.

[0060] In the structure described above, the radius R2 and the radius R1 are identical, but not limited to this. The radius R1 can be larger than the radius R2, or alternatively, the radius R1 can be smaller than the radius R2, as long as the radii R1 and R2 are both smaller than the radius R0 of the circumferential surface C.

[0061] In the first and second embodiments, the rotor 6 has four magnetic pole portions 10 and four iron core portions 16, and the stator 5 has twelve slots (3 teeth). However, the number of magnetic pole portions (and hence the number of iron core portions) and the number of slots can be changed as long as the brushless motor has a follower-pole rotor with iron core portions between adjacent magnetic pole portions. As described as advantage (3) of the first embodiment, a better effect is achieved with a structure in which the number of slots is a multiple of the number of iron core portions.

[0062] In the first and second embodiments, the present invention is embodied by using a permanent magnet (IPM) rotor 6, in which the magnetic pole regions 10 are formed by permanent magnets 11 embedded in the peripheral region of the rotor core 8. However, the present invention can also be embodied by a rotor in which the magnetic pole regions are formed by permanent magnets mounted on the peripheral surface of the rotor.

[0063] In the first and second embodiments, the magnetic pole regions 10 are formed by plate-shaped permanent magnets 11. However, within the scope of the present invention, a structure is also possible in which the magnetic pole regions 20 are formed by curved plate-shaped permanent magnets 21, as in Fig. 14 and Fig. 15, or another structure is possible in which the plate-shaped permanent magnets 11 are arranged in a V-shape to form magnetic pole areas as in the Fig. 16 and Fig. 14 shown.

[0064] In the first and second embodiments, the stator 5 is formed by dense winding, wherein the coils are wound around each tooth 3, but a stator 52 can also be formed, for example, by distributed winding, wherein coils 51 are wound around several (for example, three) teeth 50, as in Fig. 18 and Fig. 19. With such a structure, the same advantages as in the previous embodiments can be achieved. The number of teeth 50 of the stator 52, which is formed by distributed winding, can be changed, if necessary, in relation to the number of poles. For example, the stator 52 of a motor 55 as shown in the Fig. 18 and Fig. 19 is shown twenty-four slots.

[0065] With such a structure, since the number of slots is a multiple of the number of iron core regions, when one iron core region 16 faces three teeth 50, all other iron core regions 16 face corresponding three teeth 50 in the same way.

[0066] In such a structure, the fifth angle θ5 of the gap is, for example, approximately 16°, as in Fig. 19 and is similar to the embodiments explained above. For example, the torque of the motor 55 is at the maximum value (100%) when the fifth angle θ5 of the gap is approximately 16°, and is assuredly 99.5% or more of the maximum value when the fifth angle θ5 of the gap is in the range of 15° to 17°, as shown in Fig. 20. Therefore, the fifth angle θ5 of the gap is preferably set in the range of 15° to 17°.

[0067] Further, the first gap angle θ1 is preferably approximately 34°. For example, the torque of the motor 55 reaches a maximum value (100%) when the first gap angle θ1 is approximately 34°, and is assured to be 99.5% or more of the maximum value when the first gap angle θ1 is in the range of 33° to 36°, as shown in Fig. 21. Therefore, the first angle θ1 of the gap is preferably set in the range of 33° to 36°.

[0068] Furthermore, the second gap angle θ2 is preferably approximately 29°. For example, the torque of the motor 55 reaches a maximum value (100%) when the second gap angle θ2 is approximately 29°, and is assured to be 99.5% or more of the maximum value when the second gap angle θ2 is in the range of 28° to 30°, as shown in Fig. 22. Therefore, the second angle θ2 of the gap is preferably set in the range of 28° to 30°.

[0069] Further, first recesses 14a are formed open in the circumferential surface 18 of the rotor 53 (rotor core 8), and the brushless motor 55 has a stator 52 formed by distributed winding. As a result, the magnetic resistance of the first recesses 14a is increased. Therefore, as described in the first embodiment, the structure further reduces the influence of the magnetic repulsion force between the iron core portion 16 and the teeth 50a, which are located in the rear direction with respect to the rotation direction of the rotor 53, from the teeth 50a that are opposite to the iron core portion 16. As a result, the difference between the magnetic flux density at the front end and the magnetic flux density at the rear end of the iron core portion 16 becomes relatively small, as shown by the length of the dashed arrows in Fig. 3, and the magnetic balance is satisfactory. This further increases the torque of a brushless motor 55 with a stator 52 formed by distributed winding.

[0070] A brushless motor 1C according to a third embodiment of the present invention will now be described with reference to Fig. 24 to 32 described.

[0071] In the present embodiment, the coils 4 are formed of three phases, namely a U phase, a V phase, and a W phase. The three phases are arranged such that the forward winding and the reverse winding are arranged side by side at each phase, so that the order of a W phase (forward winding), a W phase (reverse winding), a V phase, a V phase, a U phase, a U phase, a W phase, a W phase, a V phase, a V phase, a U phase, and a U phase is clockwise in Fig. 24 prevails. Three-phase alternating current (U-phase, V-phase, and W-phase) flows through the coils 4 wound around the teeth 3.

[0072] The rotor 6 of the present embodiment has five magnetic pole regions 10 on the peripheral portion of the rotor 6.

[0073] More in detail, as in the Fig. As shown in Figures 24 to 32, the magnet receptacles 13, which extend along the axial direction of the rotor 6, are provided near the peripheral portion of the rotor core 8 at intervals of approximately 72° in the circumferential direction. The permanent magnets 11 are housed in the magnet receptacles and secured in such a way that the permanent magnets 11 are perpendicular to the radial direction of the rotor core 8.

[0074] In the present embodiment, the number of teeth 3 is not a multiple of the number of permanent magnets 11 and is greater than the number of poles. As shown in Fig. 25, the width W1 of the first recesses 14a in the circumferential direction is wider than the width W2 of the second recesses 14b in the circumferential direction.

[0075] As in Fig. 26, the angle defined by a straight line (L1, L2) passing through the center O of the rotor 6 and the central portion relative to the circumference of the magnetic pole portion 10, and a straight line M3 passing through the center O of the rotor 6 and an end P3 at the rear end of the first recess 14a is referred to as the third gap angle θ3, and the angle defined by a straight line (L1, L2) passing through the center O of the rotor 6 and the central portion relative to the circumference of the magnetic pole portion 10, and a straight line M4 passing through the center O of the rotor 6 and an end P4 at the front end of the second recess 14a is referred to as the fourth gap angle θ4.

[0076] Since the plate-shaped permanent magnets 11 constituting the magnetic pole regions 10 are arranged at equal intervals in the circumferential direction of the rotor core 8, the third gap angle θ3 is equal to the fourth gap angle θ4. Thus, by setting the first gap angle θ1 larger than the second gap angle θ2 as described above, the circumferential width W1 of the first recess 14a is larger than the circumferential width W2 of the second recess 14b.

[0077] The design with regard to the optimization of the angles (θ1,θ2, θ3, θ4) of the gap is now described.

[0078] Fig. Figure 29 is a graph showing the relationship between the third angle θ3 of the gap and the torque of the motor 1C. Fig. 30 is a graph showing the relationship between the fourth gap angle θ4 and the torque of the motor 1C. Considering that a brushless motor 1C of the present embodiment has substantially the same configuration as a 10-pole, 12-slot brushless motor with the iron core portions 16 formed between the adjacent magnetic pole portions 10, the upper limit of the gap angles θ3 and θ4 is assumed to be approximately 18°.

[0079] After Fig. 29, the torque of the motor 1C reaches a maximum value (100%) when the third angle θ3 of the gap is approximately 11.5°, and the torque decreases when the third angle θ3 of the gap moves away from 11.5°. The torque of the motor 1C is assured to be 99% or more of the maximum value when the third angle θ3 of the gap is in the range of 9° to approximately 14°. Fig. 29. Therefore, the third angle θ3 of the gap is preferably selected in the range of 9° to about 14°.

[0080] After Fig. 30, the torque of the motor 1C reaches a maximum value (100%) when the fourth angle θ4 of the gap is approximately 13°, and the torque decreases when the fourth angle θ4 of the gap is away from 13°. The torque of the motor 1C is assured to be 99% or more of the maximum value when the fourth angle θ4 of the gap is in the range of 10° to approximately 16°. Fig. 30. Therefore, the fourth angle θ4 of the gap is preferably selected in the range of 10° to about 16°.

[0081] Fig. 27 shows a graph showing the relationship between the first angle θ1 of the gap and the torque of the motor 1C. Fig. 28 is a graph showing the relationship between the second angle θ2 of the gap and the torque of the motor 1C.

[0082] After Fig. 27, the torque of the motor 1C reaches a maximum value (100%) when the first gap angle θ1 is approximately 30°, and the torque of the motor 1C is assured to be 99% or more of the maximum value when the first gap angle θ1 is in the range of 27° to 33°. The torque of the motor 1C is assured to be 96% or more of the maximum value when the first gap angle θ1 is in the range of 22.5° to 36.5°. Therefore, the first gap angle θ1 is preferably selected in the range of 27° to 33°.

[0083] Similarly, according to Fig. 28, the torque of the motor 1C reaches a maximum value (100%) when the second gap angle θ2 is approximately 24°, and is assured to be 99% or more of the maximum value when the second gap angle θ2 is in the range between 21.5° and 27°. Therefore, the second gap angle θ2 is preferably selected in the range of 21.5° to 27°.

[0084] Taking the foregoing into consideration, the rotor 6 is designed such that in the present embodiment, the third angle θ3 of the gap is 11.5°, the fourth angle θ4 of the gap is 13°, the first angle θ1 of the gap is 30°, and the second angle θ2 of the gap is 24°.

[0085] As in Fig. 25, a straight line RCL passes through the center O of the rotor 6 and the circumferential central region of the iron core region 16, which is shifted forward in the rotation direction of the rotor 6 from a straight line ICL passing through the circumferential central region of a circumferential region defined by the straight line L1 and the straight line L2. Therefore, the end P2 at the rear end of the second recess 14b is shifted forward from the straight line LA passing through the circumferential central region of the front of the teeth 3 corresponding to the iron core region 16 (the tooth 3a in Fig. 25). Also, the end P1 at the front end of the first recess 14a, which is arranged at the rear end of the iron core area 16, is delimited by a tooth end position T1 of the front of the teeth 3, which corresponds to the iron core area 16 (tooth 3a in Fig. 25) are displaced backwards. The end P3 at the rear end of the first recess 14a is displaced backwards by a straight line LB passing through the central region of the rear of the teeth 3, which correspond to the iron core region 16 (tooth 3b in Fig. 25) are opposite each other.

[0086] When the iron core portion 16 is radially opposite the teeth 3 (3a and 3b), the largest portion of the second recess 14b at the front end of the iron core portion 16 (in the present embodiment, the entire second recess 14a) is shifted forward from the central portion (the position on the straight line LA) of the front tooth 3a of the teeth 3a and 3b. Also, the largest portion of the first recess 14a, which is located at the rear end of the iron core portion 16, is shifted forward from the central portion (the position on the straight line LB) of the rear tooth 3b of the teeth 3a and 3b. Fig. 25, a straight line LC passes through the actual center point between the ends P1 and P4 of the second recess 14b, which line LC is shifted forward from the straight line LA. The above description is also evident from the fact that the straight line LD passing through the actual center point between the ends P1 and P3 of the first recess 14a is shifted forward from the straight line LB in Fig. 25 is shifted forward.

[0087] This structure allows magnetic flux generated from a radially inner portion of each permanent magnet 11 to easily and favorably flow to the front tooth 3a through the associated iron core portion 16. Thus, the magnetic attraction force acts on the iron core portion 16, so that the iron core portion 16 is securely attracted to the front tooth 3a, thereby improving the torque of the motor 1C.

[0088] The present embodiment has the following advantages. (9) The rotation direction of the rotor 6 is defined in a single direction, and the number of permanent magnets 11 and the number of magnetic pole portions 10 are selected as an odd number (in the present embodiment, five). Of the recesses 14a and 14b provided at each magnetic pole portion, the circumferential width W1 of the first recess 14a, which is located at the front with respect to the rotation direction of the rotor 6, is larger than the circumferential width W2 of the second recess 14b, which is located at the rear with respect to the rotation direction of the rotor 6.Furthermore, the iron core portion 16 is configured such that the straight line RCL passing through the central portion of the iron core portion 16 is shifted forward in the rotation direction of the rotor 6 from a straight line ICL passing through the center of the circumferential portion between the straight lines L1 and L2 passing through the central portion of circumferentially adjacent two magnetic pole portions 10 with an iron core portion 16 therebetween. This allows the magnetic flux generated by the radially inner part of each permanent magnet 11 to flow securely and favorably to the leading tooth 3a through the associated iron core portion 16. Thus, the magnetic attraction force acts on the iron core portion 16 such that the iron core portion 16 is securely attracted to the leading tooth 3a. This increases the torque of the motor. (10) The rotor 6 has five magnetic pole portions 10 and five iron core portions 16. The first gap angle θ1, defined by a straight line L (L1, L2) passing through the center portion of the magnetic pole portion 10 and a straight line M1 passing through the front end P1 of the first recess 14a, is greater than 22.5°. The second gap angle θ2, defined by the straight line L (L1, L2) and a straight line M2 passing through the rear end P2 of the second recess 14b, is also less than 30°. With such a structure, the positional relationship between the magnetic pole portions 10 and the iron core portion 16 can be optimized. This further increases the torque of the motor 1C. (11) A third gap angle θ3 is defined by a straight line L (L1, L2) passing through the central portion of the magnetic pole portion 10 and a straight line M3 passing through the center O of the rotor 6 and the end P3 at the rear end of the first recess 14a, and is between 9° and 14°. Further, a fourth gap angle θ4 is defined by the straight line L (L1, L2) and the straight line M4 passing through the center O of the rotor 6 and the end P4 at the front end of the second recess 14b, and is between 10° and 16°. In this case, the first gap angle θ1 is between 27° and 33°, and the second gap angle θ2 is between 21.5° and 27°. With such a structure, the positional relationship between the magnetic pole areas 10 and the iron core areas 16 is optimized (see also Fig. 27 to 30). This increases the torque of motor 1C.

[0089] The third embodiment can be modified as follows.

[0090] In the third embodiment, the magnetic pole regions 10 are formed by plate-shaped (I-shaped cross-section) permanent magnets 11, but are not limited thereto. For example, the magnetic pole regions 20 may also be formed by curved plate-shaped (bent cross-section) permanent magnets 11, as shown in Fig. 31. The plate-shaped permanent magnets 11 can also be arranged in a V-shape to create magnetic pole regions 10, as shown in Fig. 32 are shown.

[0091] In the third embodiment, the rotor 6 provided with embedded permanent magnets (IPM) is designed such that the permanent magnets 11 form the magnetic pole regions in the magnet receptacles 13 of the rotor core 8. However, a rotor 6 equipped with surface magnets (SPM) is also possible, in which the magnetic pole regions 10 are formed by attaching the permanent magnets to the outer peripheral surface of the rotor core.

[0092] In the third embodiment, five magnetic pole regions 10 and five iron core regions 16 are provided, resulting in ten poles, but this is not limiting. The same odd number of magnetic pole regions 10 and iron core regions 16 may be provided.

[0093] In the third embodiment, twelve teeth 3 are provided, but the number of teeth can be changed, for example, to twenty-four or forty-eight teeth.

[0094] A brushless motor 1D according to a fourth embodiment of the present invention will be described below with reference to Fig. 33 to 39 described.

[0095] The stator 5 of the brushless motor 1D of the present embodiment Fig. 33 is provided with a housing (not shown) and has twelve teeth 3 and coils 4 wound around the teeth 3. The coils 4 are formed in three phases and include a U phase, a W phase, and a V phase. They are arranged such that the U phase, W phase, and V phase follow one another in a clockwise direction. Three-phase alternating current (U phase, W phase, and V phase) flows through the coils 4 wound around the teeth 3.

[0096] The permanent magnet 11 and magnetic elements (in the present embodiment, two magnetic elements) comprising a first magnetic steel sheet 25 and a second magnetic steel sheet 26 are received and secured in each of the magnet receiving portions formed by the magnet receptacles 13.

[0097] The first magnetic steel sheet 25 is arranged such that it is in surface contact with a radially inner magnetic pole surface 11a (north pole surface) of the permanent magnet 11, and the second magnetic steel sheet 26 is arranged such that it is in surface contact with a radially inner magnetic plate surface 25a of the first magnetic steel sheet 25. Also, the magnetic steel sheets 25 and 26 are designed such that the widthwise extension (left and right extension in Fig. 34) is greater than the width of the permanent magnet 11 and smaller than the width of the magnet holders 13. This allows the magnetic steel sheets 25 and 26 to securely cover the permanent magnet 11.

[0098] In a brushless motor 1D configured as above, the rotatable shaft 7 with the rotor 6 is rotated by the flow of a three-phase alternating current through the coil 4. The permanent magnet 11 and the magnetic steel sheets 25 and 26 are housed in the respective magnet housings 13. In this way, the gap between the radially inner magnetic pole surface 11a of the permanent magnet 11 and the inner surface 13a of the magnet housing 13 is reduced by the magnetic steel sheets 25 and 26. This allows the magnetic flux generated by the radially inner magnetic pole surfaces 7 to flow toward the iron core portion 16 in an appropriate manner.

[0099] The inventors of the present invention conducted a simulation to demonstrate the effectiveness of the present embodiment. The simulation was carried out under the conditions that the two magnetic steel sheets 25 and 26 with a thickness of approximately 0.1 mm (total thickness approximately 0.2 mm) were arranged in each gap, the thickness of the permanent magnet 11 was 2.25 mm, and the gap in the radial direction between each permanent magnet 11 and the associated magnet receptacles 13 was 0.335 mm. While the induced voltage in a conventional brushless motor is 100% with an assumed gap of 0.335 mm, the induced voltage in a brushless motor of the present embodiment was increased to approximately 106.1% (see also Fig. 35). This is because the permanence is increased by inserting the magnetic steel sheets 25 and 26 into the magnet holders 13, the effective magnetic flux is increased, and thus the induced voltage is also increased. Therefore, disposing the magnetic steel sheets 25 and 26 between each permanent magnet 11 and the corresponding magnet holder 13 as in the present embodiment increases the effectiveness of the magnetic flux and improves the output of the motor 1D.

[0100] For example, a gap in the radial direction between the radially outer magnetic pole surface 11b of each permanent magnet 11 and the corresponding magnet holder 13 can also be somewhat maintained by disposing the first magnetic steel sheet 25 adjacent to the radially inner magnetic pole surface 11a of the permanent magnet 11. This reduces an eddy current that may be generated radially outside the permanent magnet 11 and thus prevents the deterioration of the output performance due to eddy current loss. Also, the magnetic steel sheets 25 and 26, which are used as magnetic elements to fill the gap in the radial direction between each permanent magnet 11 and the corresponding magnet holder 13, are formed of iron with a high magnetic permeability from among the ferromagnetic elements and are elements with low core loss, which is the sum of hysteresis loss and eddy current loss.This contributes to improving the output performance of the 1D engine.

[0101] The present embodiment has the following advantages. (12) The magnetic elements formed by the magnetic steel sheets 25 and 26 are arranged in the magnetic receiving portions formed by the magnet receiving portions 13 to fill the gap between the magnetic pole surface 11a of each permanent magnet 11 and the associated magnet receiving portion 13. Thus, the gap in the radial direction between each magnet receiving portion 13 and the associated permanent magnet 11 is securely reduced by the magnetic steel sheets 25 and 26. Since the magnetic steel sheets 25 and 26 are magnetic elements, the magnetic steel sheets 25 and 26 allow the magnetic flux of the associated permanent magnet 11 to flow properly. This increases the amount of magnetic flux flowing through the iron core portion 16 and improves the output performance of the motor 1D.A kickback in the radial direction of the permanent magnets 11 is also reduced because the gap has been reduced by the magnetic steel sheets 25 and 26. (13) The rotor 6 is arranged radially inside the stator 5. The magnetic steel sheets 25 and 26 are arranged to abut against the radially inner magnetic pole surface 11a of the permanent magnet. With this structure, for example, the gap in the radial direction between the radially outer magnetic pole surface 11a of the permanent magnet 11 and the magnet holder 13 is slightly maintained, while the magnetic flux can flow satisfactorily through the iron core portion 13. This prevents the generation of eddy current, which may occur at the radially outer portion, and the deterioration of the output of the motor 1D due to eddy current loss. (14) The surfaces of the magnetic steel sheets 25 and 26 facing the permanent magnet 11 are larger than the magnetic pole surfaces 11a of the permanent magnet 11. In this way, when the permanent magnet 11 and the magnetic steel sheets 25 and 26 are inserted into each magnet receptacle 13, the magnetic pole surface 11a of the permanent magnet 11 is more securely covered by the magnetic steel sheets 25 and 26. Thus, the magnetic flux generated by the permanent magnet 11 is allowed to flow toward the iron core portion 16 appropriately. This further improves the output performance of the motor 1D. (15) The first and second steel sheets 25 and 26 are elements with high magnetic permeability among the ferromagnetic elements, and are elements with low core loss, which is the sum of hysteresis loss and eddy current loss. The first and second magnetic steel sheets 25 and 26 thus contribute to improving the output performance of the motor 1D.

[0102] The fourth embodiment may be modified as follows.

[0103] In the fourth embodiment, two magnetic steel sheets 25 and 26 are provided as magnetic elements, but one or three magnetic elements may be provided as long as the magnetic steel sheets fill the gap in the radial direction between each permanent magnet 11 and the associated magnet holder 13.

[0104] In the fourth embodiment, the radially inner pole surface (north pole) 11a of the permanent magnet 11 abuts against the magnetic element, which is the first magnetic steel sheet 25. Instead, the radially outer magnetic pole surface (south pole) 11b may abut against the magnetic element. Each permanent magnet 11 may also be sandwiched between various magnetic elements.

[0105] Although not explicitly mentioned in the fourth embodiment, the gap between each magnetic pole surface 11a and the associated magnet holder 13 is more securely filled by a press fit of the magnetic steel sheets 25 and 26 in the magnet holder 13.

[0106] In the fourth embodiment, the magnetic elements formed by the magnetic steel sheets 25 and 26 may be formed as plate-shaped elements, but the magnetic elements (magnetic steel sheets 25 and 26) may also be formed by a combination of various elements. For example, strip-like magnetic elements 40 and 41 may be provided in the width direction of the permanent magnet 11 (left and right extension in the figure), as shown in the Fig. 36A and Fig. 36B. Furthermore, block-like magnetic elements 50 are also possible, which are provided in the direction of the width and depth (perpendicular to the plane of the drawing in the figure) of the permanent magnet 11, as in the Fig. 37A and Fig. 37B. As explained above, the multi-element magnetic elements reduce eddy current and thus reduce eddy current loss.

[0107] Although not explicitly explained in the fourth embodiment, slots may also be provided in the magnetic elements formed by the magnetic steel sheets 25 and 26. With such a structure, eddy current is reduced and thus eddy current loss is reduced.

[0108] In the fourth embodiment, the magnetic pole regions 10 are formed by plate-shaped permanent magnets 11, but are not limited thereto. For example, magnetic pole regions 60 may also be formed by curved plate-like permanent magnets 61, as shown in Fig. 38. Alternatively, magnetic pole regions 66 are also possible, which are formed by plate-like permanent magnets 65, which are arranged in a V shape, such as the one shown in Fig. 39. By such a structure, the same advantages as in the above embodiments can be achieved by arranging magnetic elements 75, which are in surface contact with the permanent magnets 61, 65 and the magnetic pole surfaces 61a, 61b, in the gap between the magnet holder 70 and the permanent magnets 61, 65. When curved permanent magnets 61 are used, as shown in Fig. 38, magnetic elements following the curved shape are preferably arranged.

[0109] In the fourth embodiment, the coils are arranged in the order of U-phase, W-phase, and V-phase clockwise by forward winding in the 8-pole 12-slot motor 10, but not limited thereto. For example, in a 10-pole 12-slot motor, the coils may be arranged such that the forward winding and the reverse winding are arranged side by side at each phase, thus forming the order of W-phase (forward winding), W-phase (reverse winding), V-phase, V-phase, U-phase, U-phase, W-phase, W-phase, V-phase, V-phase, U-phase, and U-phase in the clockwise direction. In this case, too, the application of the present invention increases the induced voltage, and the output of the motor 1D is improved.

[0110] In the fourth embodiment, the magnetic elements are formed by, but not limited to, magnetic steel sheets 25 and 26. For example, the magnetic elements can also be formed by a ferromagnetic damping alloy. Vibration that may occur in connection with the rotation of the rotor 6 is reduced by magnetic elements made of ferromagnetic damping alloy.

[0111] In the fourth embodiment, the recesses 14a and 14b between the magnetic pole regions 10 and the iron core regions 16 are of asymmetrical shape, but may also be symmetrical.

[0112] In the fourth embodiment, the motor is designed as an internal rotor brushless motor in which the rotor 6 is arranged inside the stator 5, but the motor may also be an external rotor brushless motor.

[0113] A brushless motor 1E according to a fifth embodiment of the present invention will now be described with reference to Fig. 40 to 41B.

[0114] As in Fig. 40, in the present embodiment, each of the recesses 14a is closed from a bridge portion (cover portion) 80 to the peripheral surface 18 of the rotor 6 (the rotor core 8). More specifically, the rotor core 8 is formed by laminating disc-like core receptacles 81 along the axial direction of the rotor core 8. Holes are provided in each of the disc-like core receptacles 81, so that the magnet receptacles 13 and the first and second recesses 14a, 14b are formed when the core receptacles 81 are laminated. As shown in Fig. 41A and Fig. 41B, the circumferential portion of each core receptacle 81 corresponding to the first recess 14a forms a bridge portion 80a that is thinner than the rest of the core receptacle 81. In the situation where the core receptacles 81 are laminated, the bridge portions 80a are arranged to form slots (communication holes) 82 between adjacent bridge portions 80a. The bridge portions 80a are arranged as described above to form the bridge portions (cover portions) 80 that partially close the first recesses 14a. The bridge portions 80a are formed, for example, by pressing, so that portions of the core receptacles 81 become thin. In the radial view of the rotor core 8, as shown in Fig. 41B, the bridge parts 80a and the slots 82 are alternately arranged along the axial direction of the rotor core 8 on the peripheral portion of the rotor core 8 corresponding to the first recesses 14a.

[0115] The present embodiment has the following advantages. (16) The first recesses 14a are partially closed by the bridge portions 80 on the peripheral surface 18 of the rotor 6 (rotor core 8). Thus, compared with the case where the first recesses 14 are fully open to the peripheral surface 18 of the rotor 6, the power of the rotor 6 is increased while reducing the vortex loss during rotation of the rotor 6, and further reducing the cogging moment. In addition, compared with the case where the first recesses 14a are fully closed, the magnetic resistance of the first recesses 14a is further increased, which increases the output of the motor 1E.

[0116] The fifth embodiment may be modified as follows.

[0117] The permanent magnets 11 are arranged such that the radially outer surfaces are south poles. However, the magnetic pole regions can also be arranged such that the radially outer surfaces are north poles.

[0118] The second recesses 14b are formed without opening to the peripheral surface 18 of the rotor 6 (rotor core 8), but the second recesses 14b may also be open to the outer surface 18.

[0119] At least two of the embodiments described above can be combined with each other.

Claims

[1] A brushless motor comprising a stator (5) with a plurality of teeth (3) around which coils (4) are wound and a rotor (6) which is arranged to rotate radially inside the stator (5), wherein the rotor (6) has a plurality of magnetic pole regions (10) opposite the teeth (3), wherein the magnetic pole regions (10) are formed by permanent magnets (11) which are arranged at the same angular distance in the circumferential direction and all have the same polarity, the rotor (6) has recesses (14) which act as a magnetic resistance at the ends in the circumferential direction of each magnetic pole region (10), so that an iron core region (16) is formed between the circumferentially adjacent magnetic pole regions (10), and the magnetic flux of the magnetic pole regions (10) flows through the iron core region (16) along the radial direction, wherein the rotor (6) is designed such thatthat the rotation is defined in one direction, and wherein the recesses (14) at the ends in the circumferential direction of each magnetic pole region (10) have a first recess (14a) at the front end of the magnetic pole region (10) in the direction of rotation of the rotor (6) and a second recess (14b) at the rear end of the magnetic pole region (10) in the direction of rotation of the rotor (6), and the width (W1) of the first recess (14a) in the circumferential direction is greater than the width (W2) of the second recess (14b) in the circumferential direction, wherein an angle is defined as the first angle of the gap (81) by a straight line (L1) passing through the center point (0) of the rotor (6) and the central position (P0) in the circumferential direction of each magnetic pole region (10), and a straight line (M1) passing through the center point (0) of the rotor (6) and the front end (P1) of the first recess (14a),and an angle is defined as the second angle of the gap (θ2) by a straight line (L2) passing through the center (0) of the rotor (6) and the central position (P0) in the circumferential direction of each magnetic pole region (10), and a straight line (M2) passing through the center (0) of the rotor (6) and the rear end (P2) of the second recess, wherein the first angle (θ1) of the gap is greater than the second angle (θ2) of the gap. [2] Engine according to claim 1, characterized by that the rotor (6) has four magnetic pole regions (10) and four iron core regions (16), wherein the stator (5) has twelve gaps, each between the circumferentially adjacent teeth (3), and wherein a 3-phase alternating current is passed through the coils (4). [3] The engine according to claim 2, characterized by that the first angle (θ1) of the gap is greater than 30° and the second angle (θ2) of the gap is less than 30°. [4] Engine according to claim 3, characterized by that an angle (θ5) is defined by a straight line (L1) passing through the center (0) of the rotor (6) and the central position (P0) in the circumferential direction of each magnetic pole region (10), and a straight line (M3) passing through the center (0) of the rotor (6) and the end (P5) in the circumferential direction of the magnetic pole region (10), which angle (θ5) is set to 17° to 19°, the first angle (θ1) of the gap is set to 33° to 36° and the second angle (θ2) is set to 27° to 29°. [5] The engine according to claim 1, characterized byin that the rotor includes four magnetic pole regions (10) and four iron core regions (16), wherein the stator (5) has twenty-four gaps, each between the circumferentially adjacent teeth (3), and wherein a 3-phase alternating current is passed through the coils (4), wherein the coils around the teeth (3) are formed by distributed winding, and wherein the first angle (θ1) of the gap is greater than 30° and the second angle (θ2) is less than or equal to 30°. [6] The engine according to claim 5, characterized bythat an angle (θ5) is defined by a straight line (L1) passing through the center (0) of the rotor (6) and the central position (P0) in the circumferential direction of each magnetic pole region (10), and a straight line (M3) passing through the center (0) of the rotor (6) and the end (P5) in the circumferential direction of the magnetic pole region (10), which angle (θ5) is set to 17° to 19°, the first angle (θ1) of the gap is set to 33° to 36° and the second angle (θ2) is set to 28° to 30°. [7] The engine according to any one of claims 1 to 6, characterized by that the permanent magnets (11) are embedded in the rotor (6), and wherein the first recesses (14a) are formed such that they are partially or completely open to the outer surface (61x) of the rotor (6) in the circumferential direction. [8] The engine according to claim 7, characterized bythat the rotor (6) has slots (81) in partial areas of the outer surface (61x) of the rotor (6) in the circumferential direction, which slots correspond to the first recesses (14a) such that the first recesses (14a) are partially open to the outer surface (61x) of the rotor (6) in the circumferential direction. [9] The engine according to any one of claims 1 to 8, characterized by that the circumferential centers of the outer surfaces (61x) of the iron core regions (16) are arranged on a common reference surface (C) in the circumferential direction, and wherein each iron core region (16) is curved such that the ends of its outer surface in the circumferential direction are spaced radially inwardly from the common reference surface (C), so that the distance from the common reference surface (C) gradually increases towards the ends in the circumferential direction. [10] The engine according to claim 9, characterized bythat the entire outer surface of each iron core region (16) has a certain curvature, and wherein the ratio R1 / R0 of a radius R1 of the curvature of the outer surface (61x) of each iron core region (16) and a radius R0 of the common reference surface (C) in the circumferential direction is in the range 0.6 ≤ R1 / R0 < 1. [11] The engine according to any one of claims 1 to 10, characterized by that the circumferential centers of the outer surfaces (10x) of the magnetic pole regions (10) are arranged on a common reference surface (C) in the circumferential direction, and wherein each magnetic pole region (10) is curved such that the ends of its outer surface in the circumferential direction are spaced radially inwardly from the common reference surface (C), so that the distance from the common reference surface (C) gradually increases towards the ends in the circumferential direction. [12] The engine according to claim 11, characterized bythat the entire outer surface of each magnetic pole region (10) has a certain curvature, and wherein the ratio R2 / R0 of a radius R2 of the curvature of the outer surface (10x) of each magnetic pole region (10) and a radius R0 of the common reference surface (C) in the circumferential direction is in the range 0.6 ≤ R2 / R0 < 1. [13] A brushless motor comprising a stator (5) with a plurality of teeth (3) around which coils (4) are wound and a rotor (6) which is arranged to rotate radially inside the stator (5), wherein the rotor (6) has a plurality of magnetic pole regions (10) opposite the teeth (3), wherein the magnetic pole regions (10) are formed by permanent magnets (11) which are arranged at the same angular distance in the circumferential direction and all have the same polarity, the rotor (6) has recesses (14) which act as a magnetic resistance at the ends in the circumferential direction of each magnetic pole region (10), so that an iron core region (16) is formed between the magnetic pole regions (10) arranged adjacent in the circumferential direction, and the magnetic flux of the magnetic pole regions (10) flows through the iron core region (16) along the radial direction, wherein the rotor (6) is designed such thatthat the rotation is defined in one direction, and wherein the recesses (14) at the ends in the circumferential direction of each magnetic pole region (10) have a first recess (14a) at the front end of the magnetic pole region (10) in the direction of rotation of the rotor (6) and a second recess (14b) at the rear end of the magnetic pole region (10) in the direction of rotation of the rotor (6), and the width (W1) of the first recess (14a) in the circumferential direction is greater than the width (W2) of the second recess (14b) in the circumferential direction, wherein the circumferential center of each iron core region (16) is shifted forward in the direction of rotation from a straight line (ICL) passing through the circumferential center of a circumferential region defined by straight lines (L1, L2) passing through the center (0) of the rotor and the circumferential center of two circumferentially adjacent magnetic pole regions (10) with the iron core region (16) therebetween, wherein the number of magnetic pole regions (10) and the number of iron core regions (16) is five each, wherein an angle formed by a straight line (L1, L2) passing through the center point (0) of the rotor (6) and the circumferential center point of each magnetic pole region (10), and a straight line (M1) passing through the center point of the rotor (6) and the front end (P1) of the first recess (14a) is defined as a first angle (θ1) of the gap, and an angle formed by a straight line (L1, L2) passing through the center point of the rotor (6) and the circumferential center points of each magnetic pole region (10), and a straight line (M2) passing through the center point (0) of the rotor (6) and the rear end (P2) of the second recess (14b) is defined as a second angle of the gap (θ2), and wherein the first angle (θ1) of the gap greater than 22.5° and the second angle (θ2) of the gap is less than 30°. [14] The engine according to claim 13, characterized bythat an angle between a straight line (L1, L2) passing through the center (0) of the rotor (6) and the circumferential center of each magnetic pole region (10), and a straight line (M3) passing through the center (0) of the rotor (6) and the rear end (P3) of the first recess (14a) is defined as the third angle (θ3) of the gap, and an angle between a straight line (L1, L2) passing through the center (0) of the rotor (6) and the circumferential center of each magnetic pole region (10), and a straight line (M4) passing through the center (0) of the rotor (6) and the front end (P4) of the second recess (14b) is defined as the fourth angle (θ4) of the gap, wherein the first angle (θ1) of the gap is set to 27° to 33°, wherein the second angle (θ2) of the gap is set at 21.5° to 27°, with the third angle (θ3) of the gap being set at 9° to 14°,and wherein the fourth angle (θ4) of the gap is set to 10° to 16°., [15] The engine according to any one of claims 1 to 14, characterized by that the rotor (6) has a rotatable shaft (7) and a rotor core (8) which is provided radially outside the rotatable axis, and wherein the rotor (6) has magnet receiving areas (13) which extend in the axial direction through the rotor core (8), and the permanent magnets (11) are embedded in the magnet receiving areas (13). [16] The engine according to claim 13, characterized bythat a three-phase alternating current runs through the coils (4), wherein the coils (4) are designed as a compressed winding around each tooth (3), and three phases of the coils (4) are arranged one after the other in the circumferential direction, so that two coils (4) of the same phase are arranged adjacent to each other in the circumferential direction, and wherein the circumferentially adjacent coils (4) with the same phases are each wound in the opposite direction, and the circumferentially adjacent coils (4) with different phases are wound in the same direction. [17] A brushless motor comprising a stator (5) with a plurality of teeth (3) around which coils (4) are wound and a rotor (6) which is arranged rotatably with respect to the teeth (4), wherein the rotor (6) has a plurality of magnetic pole regions (10) opposite the teeth (3), wherein the rotor (6) has a plurality of magnet receiving regions (13) which are arranged at equal angular intervals along the circumferential direction of the rotor (6), permanent magnets (11) form the magnetic pole regions (10) and are received in the magnet receiving regions (13), and the permanent magnets (11) are opposite the teeth and have magnetic pole surfaces (11a) of the same polarity, wherein the rotor (6) has recesses (14) which act as a magnetic resistance at the ends in the circumferential direction of each magnetic pole region (10),such that an iron core region (16) is formed between the circumferentially adjacent magnetic pole regions (10), and the magnetic flux of the magnetic pole regions (10) flows through the iron core region (16) along the radial direction, wherein a magnetic element (25, 26) is arranged in each magnet receiving region (13) to fill a radial gap between the magnetic pole surface (11a) of the associated permanent magnet (11) and the inner surface (13a) of the magnet receiving region (13) which is opposite to the magnetic pole surface (11a), and wherein each magnetic element (25, 26) is formed by an element having a slot or by a plurality of elements which reduce eddy currents. [18] The motor according to claim 17, characterized in that each magnetic element (25, 26) is a magnetic steel sheet. [19] A brushless motor comprising a stator (5) with a plurality of teeth (3) around which coils (4) are wound and a rotor (6) which is arranged rotatably with respect to the teeth (4), wherein the rotor (6) has a plurality of magnetic pole regions (10) opposite the teeth (3), wherein the rotor (6) has a plurality of magnet receiving regions (13) which are arranged at equal angular intervals along the circumferential direction of the rotor (6), permanent magnets (11) form the magnetic pole regions (10) and are received in the magnet receiving regions (13), and the permanent magnets (11) are opposite the teeth and have magnetic pole surfaces (11a) of the same polarity, wherein the rotor (6) has recesses (14) which act as a magnetic resistance at the ends in the circumferential direction of each magnetic pole region (10),such that an iron core region (16) is formed between the circumferentially adjacent magnetic pole regions (10), and the magnetic flux of the magnetic pole regions (10) flows through the iron core region (16) along the radial direction, wherein a magnetic element (25, 26) is arranged in each magnet receiving region (13) to fill a radial gap between the magnetic pole surface (11a) of the associated permanent magnet (11) and the inner surface (13a) of the magnet receiving region (13) which is opposite to the magnetic pole surface (11a), wherein each magnetic element (25, 26) is made of a ferromagnetic damping alloy. [20] The engine according to claim 17 or 19, characterized bythat the rotor (6) is arranged to rotate radially inside the stator (5), and wherein each magnetic element (25, 26) is arranged in the magnet receiving areas (13) such that it abuts against the radially inner pole surface (11a) of the corresponding permanent magnet (11). [21] The engine according to claim 19, characterized by that each magnetic element (25, 26) is formed by an element having a slot or by a plurality of elements which reduce eddy currents. [22] The engine according to claim 17 or 19, characterized by that the surface of each magnetic element (25, 26) which is opposite the associated permanent magnet (11) is larger than the magnetic pole surface (11a) of the permanent magnet (11). [23] The engine according to claim 17 or 19, characterized byin that the recesses (14) provided at the ends in the circumferential direction of each magnetic pole region (10) have a first recess (14a) at the front end of the magnetic pole region (10) with respect to the direction of rotation of the rotor (6) and a second recess (14b) at the rear end of the magnetic pole region (10) with respect to the direction of rotation of the rotor (6), and the rotor (6) has slots (82) in the outer surface in the circumferential direction which correspond to the first recesses (14a) such that the first recesses (14a) on the outer surface in the circumferential direction of the rotor (6) are partially open.

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