RUNNER AND MOTOR

Abstract

Runner (20), which has: a runner core (22); a plurality of magnetic poles (23) arranged in a circumferential direction of the rotor core (22), wherein each magnetic pole (23) has a field magnet which serves as a first magnetic pole; a plurality of salient poles (25), wherein each salient pole (25) is formed integrally with the rotor core (22) between the two adjacent magnetic poles (23), wherein each salient pole (25) serves as a second magnetic pole, and wherein the pole of the second magnetic pole is opposite to that of the first magnetic pole, characterized by the fact that the field magnet is a main magnet (24), and the rotor (20) further comprises a plurality of auxiliary magnets (26), each arranged between the magnetic pole (23) and the adjacent salient pole (25), wherein the auxiliary magnet (26) generates a magnetic flux in a circumferential direction of the rotor core (22), such that the magnetic pole (23) and an opposite pole of the auxiliary magnet (26) have the same polarity and the salient pole (25) and another opposite pole of the auxiliary magnet (26) have the same polarity.

Description

[0001] The present invention relates to a consequent pole type rotor and a motor. BACKGROUND OF THE INVENTION

[0002] A rotor used for a motor is known as a so-called consequent-pole type rotor. As described, for example, in Japanese Patent Laid-Open No. 9-327139, such a rotor has a plurality of magnetic poles and a plurality of salient poles. The magnetic poles are arranged in a circumferential direction of the rotor core, and each of the magnetic poles includes a field magnet serving as a first magnetic pole. Each of the salient poles is formed integrally with the rotor core between the two adjacent magnetic poles and serves as a second magnetic pole whose pole is opposite to that of the first magnetic pole. SUMMARY OF THE INVENTION

[0003] In a consequent-pole rotor as described in JP H09-327139 A, the magnetic poles are formed from magnetic poles with a stronger coercive field strength (induction) and the salient poles are formed from soft magnetic material with a weaker coercive field strength. Therefore, the magnetic density distribution in the rotor is not uniform. Therefore, there is a possibility of a short circuit occurring when a magnetic flux that should flow from the magnetic pole to the opposite stator flows from the magnetic pole to the adjacent salient pole. As a result, part of the magnetic flux generated by the field magnet becomes stray flux, which does not contribute to the motor torque. This leads to a reduction in the motor's output power.

[0004] Further prior art is known from the documents DE 10 2008 042 976 A1, JP 2007- 14 110 A, JP 2010- 63 201 A and JP 2005- 45 984 A.

[0005] It is an object of the present invention to provide a rotor with an increased amount of magnetic flux contributing to the motor torque and thus to a higher power of a motor, as well as a motor with such a rotor.

[0006] In one embodiment of the invention, a rotor (20) is provided, comprising: a rotor core (22), a plurality of magnetic poles (23) arranged in a circumferential direction of the rotor core (22), and a plurality of salient poles (25). Each magnetic pole (23) has a field magnetic pole serving as a first magnetic pole. Each salient pole (25) is formed integrally with the rotor core (22) between the two adjacent magnetic poles (23). Each salient pole (25) serves as a second magnetic pole. The pole of the second magnetic pole is opposite to that of the first magnetic pole.The rotor (20) is characterized in that the field magnet is a main magnet (24), and in that the rotor (20) further comprises a plurality of auxiliary magnets (26), each arranged between the magnetic pole (23) and the salient pole (25), wherein the auxiliary magnet (26) generates a magnetic flux in a circumferential direction of the rotor core (22) such that the magnetic pole (23) and an opposite pole of the auxiliary magnet (26) have the same polarity and the salient pole (25) and another opposite pole of the auxiliary magnet (26) have the same polarity.

[0007] In one embodiment, the central axis L1 is a straight line passing through the center of the main magnet (24) according to a circumferential direction of the rotor core (22) and extending in a radial direction of the rotor core (22), and the angle θ is an angle at the central axis (L1) between an axis (L2) perpendicular to the central axis (L1) and the magnetization direction (L3) of the auxiliary magnet (26); the angle θ is set in a range (H1) which 0.4≤θ / (360° / (2⋅P))≤2.35 where P is the number of pole pairs of the rotor core (22).

[0008] In another embodiment, the angle θ is set in a range (H2) which 1≤θ / (360° / (2⋅P))≤1.75 fulfilled.

[0009] In yet another embodiment, the remanent magnetic induction (Br) of the auxiliary magnet (26) is smaller than that of the main magnet (24).

[0010] In yet another embodiment, the main magnet (24) is made of a rare earth magnet and the auxiliary magnet (26) is made of a ferrite magnet.

[0011] In a further embodiment, the rotor (20) further comprises: a connecting portion (41) for connecting the magnetic pole (23) and the salient pole (25) at a position located outside the auxiliary magnet (26) in the radial direction of the rotor (20), wherein the main magnet (24) is supported with the auxiliary magnet (26) in a circumferential direction of the rotor (20), the auxiliary magnet (26) is supported with the connecting portion (41) in the radial direction of the rotor (20), and an electrical resistance of the connecting portion (41) is higher than that of the remaining portion of the rotor core (22).

[0012] In another embodiment of the invention, a motor (M) is provided which has one of the rotors mentioned above. BRIEF DESCRIPTION OF THE DRAWING

[0013] It shows: Fig. 1A is a schematic diagram of a consequent pole type brushless motor according to one embodiment; Fig. 1B an enlarged view of the rotor; Fig. 2A is an enlarged view illustrating the magnetic flux of the rotor; Fig. 2B is an enlarged view illustrating the magnetic flux of a rotor in a comparative embodiment; Fig. 3 is an enlarged view illustrating a central axis of a main magnet and a magnetization orientation angle; Fig. 4 is a diagram showing the relationship between the magnetization orientation angle and a torque ratio; and Fig. 5 is an enlarged view illustrating the structure of a rotor according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the present invention will now be described with reference to the drawings.

[0015] As in the Fig. 1A and Fig. 1B, a brushless motor M (hereinafter referred to simply as "motor") is an internal rotor type motor in which a rotor 20 is rotatably housed inside a generally annular stator 10. The stator 10 includes a stator core 11 formed from a stack of a plurality of magnetic metal plates and twelve windings 12 concentrically wound around twelve teeth 11a provided at equal intervals on the stator core 11.

[0016] The rotor 20 arranged inside the stator 10 has a circular ring-shaped stator core 22 formed from a stack of a plurality of magnetic metal plates. The rotor core 22 is placed on the outer peripheral surface of the rotary shaft 21. On the circumference of the rotor core 22, four convex magnetic poles 23 are formed so as to protrude at a distance of 90° from each other in the radial direction of the rotor core 22. Each magnetic pole 23 has a fitting hole 23a with a generally rectangular parallelepiped shape. The longitudinal direction of the fitting hole 23a (right-left direction in Fig. 1) is perpendicular to the radial direction of the rotor 20. A main magnet 24, which is an N pole, is each adapted to the shape of the fitting hole 23a and inserted into the fitting hole 23a as a field magnet. At the position between the adjacent magnetic poles 23, a salient pole 25 is formed integrally with the outer peripheral portion of the rotor core 22. A gap K is provided between each magnetic pole 23 and the salient pole 25. The gap K has a fixed portion when viewed in a direction of the axis of the rotor 20. In other words, the magnetic poles 23 and the salient poles 25 are alternately arranged at 45° from each other. The rotor 20 is a so-called consequent-pole type rotor with 8 poles, in which the magnetic poles 23 serve as N poles, while the salient poles 25 serve as S poles. In this case, there are four (4) combinations of N poles and S poles, so the number of pole pairs is 4.

[0017] Each gap K is defined by a side surface 23b of the magnetic pole 23 and a side surface 25a of the salient pole 25. The gap K has a sector-like (fan-shaped) cross-sectional area with a width in the circumferential direction increasing from the radially inner side to the radially outer side of the rotor core 22. The side surface 23b is parallel to a straight line passing through the center of the magnetic pole 23 and extending in a radial direction of the rotor core 22. The side surface 25a extends in a generally radial direction of the rotor core 22. The side surface 23b and the side surface 25a are connected radially inward of the gap K by a surface generally perpendicular to the side surface 23b. An auxiliary magnet 26 is provided in the gap K and bridges the side surface 23b and the side surface 25a so as to close the radially outer portion of the gap K.

[0018] A radially outer side surface 26a of the auxiliary magnet 26 is formed along the outer circumference of the rotor core 22. A radially inner side surface 26a of the auxiliary magnet 26 is curved with a predetermined curvature. The auxiliary magnet 26 is fitted into the gap K such that the outer side surface 26a extends along the outer circumference of the rotor 20. In this attached state, a radial length of the auxiliary magnet 26 is adjusted such that the position of the inner side surface 26b of the auxiliary magnet 26 is substantially aligned with the position of the radially inner end of the main magnet 24. Due to this length adjustment, a portion of the gap K in the radial direction remains within the inner side surface 26b of the auxiliary magnet 26.

[0019] The magnetization direction of the auxiliary magnet 26 (magnetic pole direction) is set so that a magnetic flux is generated in a circumferential direction of the rotor core 22. Regarding the magnetic poles of the auxiliary magnet 26, a portion of the auxiliary magnet 26 on the magnetic pole 23 side is an N pole, and a portion of the auxiliary magnet 26 on the salient pole 25 side is an S pole. Each magnetic pole faces a magnetic pole of the same polarity. The auxiliary magnet 26 and the main magnet 24 are connected by the end connecting portion 27 integrally formed with the rotor core 22 at each end of the fitting hole 23a in a longitudinal direction (right-left direction in Fig. 1A) of the fitting hole 23a.

[0020] The remanent magnetic induction (Br) of the auxiliary magnet 26 is lower than that of the main magnet 24. This can reduce the cost of the magnets required to manufacture the rotor 20. In this regard, it is preferable to use a rare earth magnet as the main magnet 24 and a ferrite magnet as the auxiliary magnet 26.

[0021] Next, with reference to the Fig. 2A and Fig. 2B, the flow state of the rotor 20 in the present embodiment and that of the rotor 30 in the comparative embodiment are described. The arrows in the Fig. 2A and Fig. 2B on and around main magnet 24 and auxiliary magnet 26 indicate magnetization directions.

[0022] Fig. 2B is a rotor 30 as a comparative embodiment in which the auxiliary magnets 26 are not inserted into the respective gaps K. With the configuration of the rotor 30, the coercive field strengths at the salient poles 25 are weaker than in the normal rotor in which all the magnetic poles are formed by the main magnets 24. This makes the distribution of the magnetic density in the rotor 30 uneven, and there is a likelihood that a magnetic flux from the main magnet 24 generates or causes a short circuit between the magnetic poles. For example, part of the magnetic flux G1 generated by the main magnet 24 becomes a leakage flux GM1 that short-circuits the end connection portion 27 of the magnetic pole 23, and a leakage flux GM2 that flows from the side surface 23b to the side surface 25a around the gap K and short-circuits the salient pole 25. That is,, a part of the magnetic flux G1 generated from the magnetic pole 23 toward the opposite teeth 11a becomes the leakage fluxes GM1, GM2, which do not contribute to the motor torque, resulting in a reduction in the output power of the motor.

[0023] In the rotor 20 of the present embodiment as illustrated in Fig. 2A, however, a part of the magnetic flux generated at the auxiliary magnet 26 flows, e.g., as a magnetic flux GB1, which flows from the side surface 23b (N-pole) of the auxiliary magnet 26 via a path in the radial direction outside the rotor 20 to the side surface 25a (S-pole) of the auxiliary magnet 26, and as a magnetic flux GB2, which flows from the side surface 23b via a path in the radial direction inside the rotor 20 (in the rotor core 22) to the S-pole. By the magnetic fluxes generated at the auxiliary magnet 26, which include the magnetic fluxes GB1 and GB2, an area R around the end connection section 27 (a Fig. 2A (circled by the dashed line) is essentially magnetically saturated. This prevents the generation of the Fig. 2B illustrates leakage fluxes GM1. Furthermore, by providing each auxiliary magnet 26 in the gap K as a magnetoresistance in which each magnetic pole opposes a magnetic pole of the same polarity, the generation of leakage fluxes GM2 is also reduced. Accordingly, by providing the respective auxiliary magnets 26 between the pair of magnetic poles, the leakage fluxes GM1 and GM2 are reduced, and the magnetic flux G1 flowing from the main magnet 24 toward the opposing teeth 11a can be increased. That is, the magnetic flux G1 of the main magnet 24 can effectively contribute to generating motor torque.

[0024] In the configuration of the rotor 30 of the comparative embodiment as shown in Fig. 2B, the leakage flux GM2 can be reduced by providing a sufficient width of the gap K in a circumferential direction of the rotor 30 by magnetically separating the magnetic pole 23 and the salient pole 25. For example, by making the width of the gap K approximately three times larger than the width of the gap (not shown) between the rotor 20 and the stator 10, the leakage flux GM2 can be preferably reduced. However, increasing the width (size) of the gap K enlarges the rotor 20. On the other hand, in the rotor 20 of the present embodiment, the generation of the leakage flux GM2 can be reduced and the width of the gap K (i.e., the distance between the poles) can be kept small by using the auxiliary magnet 26 to magnetically space the magnetic poles from each other. This enables the rotor 20 to be downsized.

[0025] Furthermore, the auxiliary magnet 26 is arranged between the magnetic pole 23 with a stronger coercive force and the salient pole 25 with a weaker coercive force. Thus, in the rotor 20 of the present embodiment, compared with the conventional rotor in which all magnetic poles consist of the main magnets 24 and the auxiliary magnet 26 is arranged between the adjacent main magnets 24 each with a stronger coercive force, a magnetic flux generated at the auxiliary magnet 26 easily flows toward the stator 10. For example, the magnetic flux GB1 flows from the end of the salient pole 25 toward the stator 1 and couples to the opposing teeth 11a.In other words, in the consequent-pole type rotor 20 as in the present embodiment, an auxiliary magnet 26 is arranged between each pair of magnetic poles, generating a magnetic flux against the opposing stator 10, thereby increasing the amount of magnetic flux effective for motor torque. By manufacturing the rotor 20 with a suitable configuration including the auxiliary magnet 26, downsizing and high output of the motor M are expected.

[0026] Next, details of the additional magnet 26 provided in the rotor 20 of the present embodiment will be discussed.

[0027] As in Fig. 3, the central axis L1 is a straight line passing through the center of the main magnet 24 along a circumferential direction of the rotor 20 and extending in a radial direction of the rotor 20. The axis L2 is a straight line perpendicular to the central axis L1. The axis L3 indicates the magnetization direction of the auxiliary magnet 26. In this embodiment, the magnetization direction of the auxiliary magnet 26 is aligned with the central axis L1, that is, the angle θ between the axis L3 and the axis L2 (hereinafter referred to as "magnetization orientation angle") is set to a preferable value, as described below. The magnetization direction of the auxiliary magnet 26 is arranged at a predetermined angle with respect to the axis L2 perpendicular to the central axis L1.

[0028] Next, Fig. 4 is a diagram showing the torque ratio of the rotor 20 when the magnetization orientation angle θ is varied. The axis of ordinate in Fig. 4 is the torque ratio (%). The torque of the motor M in the rotor 20 when the auxiliary magnet 26 is not provided is indicated as 100%. As indicated by the arrow on the upper right side of the graph, the torque performance improves with an increasing torque ratio. The abscissa axis is the value indicated by θ / (360° / (2 · P)), where θ is the degree of magnetization orientation and P is the number of pole pairs of the rotor 20 (four (4) in this embodiment). For example, if the magnetization angle θ is 45°, a value of one (1) results for θ / (360° / (2 · P)).

[0029] As in Fig. As illustrated in Figure 4, the applicant conducted simulations in the range H1 where 0.4 ≤ θ / (360° / (2 · P)) ≤ 2.35 (when P = 4, then the magnetization orientation angle θ is 18° ≤ θ ≤ 105.75°), the torque ratio is 105% or more. It was found that this range is a preferable range for obtaining sufficient torque. Furthermore, in the range H2 where 1 ≤ θ / (360° / (2 · P)) ≤ 1.75 (when P = 4, then the magnetization orientation angle θ is 45° ≤ θ ≤ 78.75°), the torque ratio is 106% or more. It was found that the torque ratio reached approximately a maximum value.

[0030] Thus, the rotor 20 of this embodiment can improve the torque of the motor M by adjusting the magnetization orientation angle θ based on these conditions.

[0031] The operation and effects of the present embodiment will now be described. (1) In the rotor 20 of the present embodiment, each auxiliary magnet 26 is arranged in the gap K between the magnetic pole 23 in which the main magnet 24 is arranged and the salient pole 25 serving as the counter magnetic pole. Each auxiliary magnet 26 generates a magnetic flux in a circumferential direction of the rotor core 22 so that each magnetic pole opposes the magnetic pole of the same polarity. By the magnetic fluxes (magnetic fluxes GB1 and GB2) generated by the auxiliary magnet 26, the predetermined region R around the end connecting portion 27 of the main magnet 24 is substantially magnetically saturated. This reduces the leakage flux GM1 that short-circuits the end connecting portion 27. In addition, since the auxiliary magnet 26 is inserted into the gap K as a magnetoresistance, with each magnetic pole opposing a magnetic pole of the same polarity, the generation of the leakage flux GM2 that short-circuits the gap K is also reduced.Accordingly, by providing the respective auxiliary magnets 26, the leakage fluxes GM1 and GM2 are reduced, and the magnetic flux G1 flowing from the main magnet 24 contributes to the generation of motor torque. This enables high output of the motor M. (2) In the rotor 20 of the present embodiment, each auxiliary magnet 26 is arranged in the gap K to create a magnetic spacing between the two poles. This reduces the width of the gap K and achieves a downsizing of the rotor 20. (3) In the present embodiment, the salient pole 25 with a weaker coercive force is arranged adjacent to the auxiliary magnet 26. Thus, part of the magnetic flux generated by the auxiliary magnet 26 (the magnetic flux GB1) is not induced toward the salient pole 25, but flows toward the teeth 11a of the stator 10. That is, part of the magnetic flux of the auxiliary magnet 26 can contribute to the generation of motor torque. This enables high output of the motor M. (4) In the present embodiment, the magnetization direction of the auxiliary magnet 26 is indicated by the magnetization orientation angle θ with respect to the axis L2, which is perpendicular to the center axis L1 of the magnetic pole of the main magnet 24. By setting the magnetization orientation angle θ so that the value of θ / (360° / (2 · P)) is within the range H1 (0.4 ≤ θ / (360° / (2 · P)) ≤ 2.35), where P is the number of pole pairs, an improvement in the torque of the motor M is ensured. Further, by setting the value of θ / (360° / (2 · P)) within the range H2 (1 ≤ θ / (360° / (2 · P)) ≤ 1.75), the torque of the motor M is improved to approximately the maximum value. (5) The residual magnetic induction (Br) of the auxiliary magnet 26 of the present embodiment is lower than that of the main magnet 24. The auxiliary magnet 26 is inexpensive, so the cost of the magnets required to manufacture the rotor 20 can be reduced. Here, a rare earth magnet is used as the main magnet 24 and a ferrite magnet is used as the auxiliary magnet 26. Thus, the rotor 20 can be configured appropriately while reducing costs.

[0032] The present embodiment may be modified as follows.

[0033] In the above embodiment, the auxiliary magnet 26 and the corresponding main magnet 24 are connected by the end connecting portion 27 at the end of the fitting hole 23a in a longitudinal direction of the fitting hole 23a. For example, as shown in Fig. However, as illustrated in Fig. 5, it is possible to omit the connecting portions 27 and directly connect the auxiliary magnet 26 to the main magnet 24 in a circumferential direction of the rotor 20. By omitting the end connecting portion 27, which is a member that short-circuits the magnetic flux at the end of the main magnet 24 (or a member that generates a leakage flux GM1), each auxiliary magnet 26 itself becomes a magnetoresistance, thereby reducing leakage flux.

[0034] In the above embodiment, the auxiliary magnet 26 is inserted into the gap K at the position where the outer side surface 26a of the magnet 26 extends along an outer circumference of the rotor 20. However, as shown in, for example, Fig.5, the outer peripheral connecting portion 41 may be formed in the gap K so as to connect the magnetic pole 23 and the salient pole 25 at the radially outer position of the rotor 20, and the auxiliary magnet 26 may be positioned radially inward of the outer peripheral connecting portion 41. This enables secure attachment of the auxiliary magnet 26 to the rotor core 22. In this regard, leakage flux is favorably reduced by making the magnetoresistance of the outer peripheral connecting portion 41 higher than that of the remaining portion of the rotor core 22 (e.g., by thin-wall processing or demagnetization by laser irradiation).

[0035] The shape of the auxiliary magnet 26 can be modified in a suitable manner. For example, the auxiliary magnet 26 can be designed to fill the entire gap K.

[0036] The rotor core 22 and the stator core 11 are not limited to a stack of magnetic metal plates. For example, the rotor core 22 and the stator core 11 can be formed by molding magnetic powder.

[0037] In the above embodiment, the rotor 20 is an IPM (Internal Permanent Magnet) type in which the main magnet 24 is embedded in the magnetic pole. However, the configuration is not limited to this, and the rotor can be changed to a SPM (Surface Permanent Magnet) type consequent-pole rotor in which the main magnet 24 is arranged on the outer peripheral surface of the rotor core 22.

[0038] The number of magnetic poles of the rotor 20 and the number of magnetic poles of the stator 10 can be varied in a suitable manner.

Claims

[1] Runner (20), which has: a rotor core (22); a plurality of magnetic poles (23) arranged in a circumferential direction of the rotor core (22), each magnetic pole (23) having a field magnet serving as a first magnetic pole; a plurality of salient poles (25), each salient pole (25) being formed integrally with the rotor core (22) between the two adjacent magnetic poles (23), each salient pole (25) serving as a second magnetic pole, and the pole of the second magnetic pole being opposite to that of the first magnetic pole, characterized by , that the field magnet is a main magnet (24), and the rotor (20) further comprises a plurality of auxiliary magnets (26) each arranged between the magnetic pole (23) and the adjacent salient pole (25), wherein the auxiliary magnet (26) generates a magnetic flux in a circumferential direction of the rotor core (22) such that the magnetic pole (23) and an opposite pole of the auxiliary magnet (26) have the same polarity and the salient pole (25) and another opposite pole of the auxiliary magnet (26) have the same polarity. [2] Rotor (20) according to claim 1, characterized bythat when the central axis L1 is a straight line passing through the center of the main magnet (24) according to a circumferential direction of the rotor core (22) and extending in a radial direction of the rotor core (22), and the angle θ is an angle at the central axis (L1) between an axis (L2) on the perpendicular to the central axis (L1) and the magnetization direction (L3) of the auxiliary magnet (26), the angle θ is set in a range (H1) satisfying 0.4 ≤ θ / (360° / (2·P)) ≤ 2.35, where P is the number of pole pairs of the rotor core (22). [3] Rotor (20) according to claim 2, characterized by that the angle θ is set in a range (H2) that 1≤θ / (360° / (2⋅P))≤1.75 fulfilled. [4] Rotor (20) according to one of claims 1 to 3, characterized by that the remanent magnetic induction (Br) of the auxiliary magnet (26) is smaller than that of the main magnet (24). [5] Rotor (20) according to one of claims 1 to 4, characterized bythat the main magnet (24) is made of a rare earth magnet and the auxiliary magnet (26) is made of a ferrite magnet. [6] Rotor (20) according to one of claims 1 to 5, characterized by that the rotor (20) further comprises: a connecting portion (41) for connecting the magnetic pole (23) and the salient pole (25) at a position located outside the auxiliary magnet (26) in the radial direction of the rotor (20), wherein the main magnet (24) is carried with the auxiliary magnet (26) in a circumferential direction of the rotor (20), the auxiliary magnet (26) is carried with the connecting portion (41) in the radial direction of the rotor (20), and an electrical resistance of the connecting portion (41) is higher than that of the remaining portion of the rotor core (22). [7] Motor (M) comprising a rotor (20) according to one of claims 1 to 6.

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