JP4318959B2 - Permanent magnet rotor and brushless motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet type rotor in which a permanent magnet is provided on a rotor core and a brushless motor including the same.
[0002]
[Prior art]
As a rotor used in a motor, a permanent magnet type rotor in which a permanent magnet is provided on a plurality of magnet mounting portions arranged on a rotor iron core is known. This permanent magnet type rotor includes a type having salient poles between magnets (for example, see Patent Document 1) and a type having no salient poles between magnets (for example, see Patent Document 2).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-76146 [Patent Document 2]
Japanese Patent Laid-Open No. 10-285849
[Problems to be solved by the invention]
Both types of permanent magnet rotors and brushless motors having the same have advantages and disadvantages.
A permanent magnet type rotor having a salient pole and a brushless motor including the same are: (1) Reluctance torque is relatively large; (2) Magnetic flux from the stator passes through the salient pole and is radially inward of the magnet However, there is a demerit that the heat generation of the magnet is large and the magnet is weak against demagnetization. Here, the sensorless position detection means that the position of the rotor is detected by a motor current when a high frequency voltage for position detection is applied to the winding of the stator.
[0005]
On the other hand, the permanent magnet rotor of the type having no salient pole and having a recess and the brushless motor provided with the same have the advantages of small magnet heat generation and strong demagnetization, but (1) reluctance torque is relatively small. (2) Since there is no salient pole, the magnetic flux from the stator does not pass through the yoke portion radially outside the magnet, so the magnetic flux is easily saturated and the accuracy of sensorless position detection is poor. (3) The yoke portions on both sides in the circumferential direction of the magnet Since the wall thickness of the tube becomes thin, there is a demerit that the strength against centrifugal force at high rotation is weak.
Accordingly, the present invention provides a permanent magnet rotor and a brushless motor that have the advantages of both types and eliminate the disadvantages.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a plurality of magnet mounting portions (for example, described later) provided on an outer peripheral portion or an inner peripheral portion of a rotor iron core (for example, a rotor yoke 40 in an embodiment described later). Permanent magnet rotors (for example, later-described implementations) in which permanent magnet pieces (for example, permanent magnet segments 60 in the later-described embodiments) are respectively fixed to the magnet insertion holes 43 and the magnet accommodating recesses 71 in the embodiments to be performed. In the rotor 20), the rotor iron core is a magnetic steel sheet (for example, implementation described later ) having salient poles (for example, salient poles 46 and 72 in embodiments described later) between the permanent magnet pieces adjacent to each other. first rotor core formed by laminating electromagnetic steel plates 47A, a 73A) number in the form (for example, the first rotor core in the embodiment described below 44 If, recesses (e.g., recesses 48 and 74 in the embodiment described below) between the permanent magnet pieces adjacent electromagnetic steel sheet having a (e.g., electromagnetic steel plates 47B in the embodiment described below, 73B) are stacked a large number of comprising Te second rotor core (e.g., the second rotor core 45 in the embodiment described below) and a, the second rotor core arranged axially central portion, said first rotor core in the axial ends The permanent magnet piece is provided so as to penetrate through the first rotor core and the second rotor core .
By comprising in this way, by providing the 1st rotor core which has a salient pole, reluctance torque becomes large, the intensity | strength with respect to a centrifugal force can also be enlarged, and a magnet is provided by providing the 2nd rotor core which has a recessed part. Heat generation can be reduced and demagnetization can be made difficult.
[0007]
In particular, since the second rotor core having the concave portion is arranged in the central portion in the axial direction where the magnet can generate heat most easily, the heat generation of the magnet can be suppressed and the demagnetization can be made difficult.
[0008]
The invention according to claim 2 is a plurality of magnet mounting portions (for example, magnet insertion holes in the embodiments described later) provided in the outer peripheral portion or the inner peripheral portion of the rotor iron core (for example, the rotor yoke 40 in the embodiments described later). 43, a magnet housing recess 71), each of which includes a permanent magnet rotor (for example, the rotor 20 in the embodiment described later) formed by fixing a permanent magnet piece (for example, the permanent magnet piece 60 in the embodiment described later). When a high frequency voltage for position detection is applied to a winding (for example, a winding 12 in an embodiment described later) of a stator (for example, a stator 10 in an embodiment described later) disposed opposite to the rotor In a brushless motor (for example, a brushless motor 1 in an embodiment described later) capable of detecting the position of the rotor by a motor current, It said rotor iron core of the rotor, the electromagnetic steel sheets in the embodiment of an electromagnetic steel plate (e.g., to be described later with salient poles between the permanent magnet pieces which are adjacent to each other (e.g., the salient pole 46, 72 in the embodiment described below) 47A, 73A) are laminated between a plurality of first rotor cores (for example, first rotor cores 44, 44 in the embodiments described later) and the permanent magnet pieces adjacent to each other (for example, implementation described later). The second rotor core (for example, the second rotor core in the embodiment described later ) formed by laminating a large number of electromagnetic steel sheets (for example, the electromagnetic steel plates 47B, 73B in the embodiment described later ) having the recesses 48, 74 in the embodiment of FIG. 45) and provided with a second rotor core arranged axially central portion, it is arranged the first rotor core in the axial direction both end portions, the said permanent magnet piece Characterized in that provided through the first rotor core and a second rotor core.
With this configuration, the rotor includes the first rotor iron core having salient poles, so that the reluctance torque increases, and when detecting the rotor position without a sensor, it is difficult to saturate the magnetic flux, thereby detecting the rotor position. The accuracy can be increased, the strength against centrifugal force can be increased, and the rotor can be provided with a second rotor iron core having a recess, whereby the heat generated by the magnet can be reduced and demagnetization can be made difficult.
[0009]
In particular, since the second rotor core having the concave portion is arranged in the central portion in the axial direction where the magnet can generate heat most easily, the heat generation of the magnet can be suppressed and the demagnetization can be made difficult.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a permanent magnet rotor and a brushless motor having the same according to the present invention will be described below with reference to the drawings of FIGS.
As shown in FIG. 1, the brushless motor 1 includes a stator 10 fixed to a casing 2 and a rotor (permanent magnet rotor) 20 that is rotatably supported by the casing 2. The stator 10 and the rotor 20 are disposed concentrically and are opposed to each other in the radial direction.
The stator 10 has a substantially cylindrical shape, and a plurality of teeth cores 11 are provided so as to protrude radially inward, and windings 12 are wound around the teeth cores 11.
This brushless motor 1 can detect the position of the rotor 20 based on the motor current when a high frequency voltage for position detection is applied to the winding 12 of the stator 10, and so-called sensorless position detection is possible. Since this sensorless position detection method is a well-known technique, a detailed description thereof will be omitted.
[0011]
As shown in FIGS. 2 and 3, the rotor 20 includes a rotor shaft 30, a rotor yoke (rotor core) 40, a pair of end face plates 50 </ b> A and 50 </ b> B, and a plurality of permanent magnetic pole pieces 60.
The rotor shaft 30 is formed in a hollow drum shape and is integrally formed by casting or forging, and an extending portion 32 extending radially outward is provided on one end side in the axial direction of the outer peripheral surface 31. Three grooves 33 are formed in the surface 31 along the axial direction at equal intervals in the circumferential direction.
[0012]
The end face plates 50 </ b> A and 50 </ b> B have an annular shape, and a hole 51 formed in the center thereof has an inner diameter slightly smaller than the outer diameter of the outer peripheral face 31 in order to press fit into the outer peripheral face 31 of the rotor shaft 30. The end face plates 50A and 50B are made of a nonmagnetic material such as austenitic stainless steel SUS304.
[0013]
The rotor yoke 40 is formed by laminating a large number of electromagnetic steel plates and has an annular shape. A through hole 41 into which the rotor shaft 30 is inserted is provided in the center of the rotor yoke 40, and three protrusions 42 are provided along the axial direction at equal intervals in the circumferential direction on the inner peripheral surface thereof.
A plurality of magnet insertion holes (magnet mounting portions) 43 into which the permanent magnets 60 are inserted are provided on the outer peripheral portion of the rotor yoke 40 at equal intervals in the circumferential direction, and each magnet insertion hole 43 extends in the axial direction of the rotor yoke 40. Has penetrated.
[0014]
The rotor yoke 40 is divided into three regions in the axial direction. As shown in FIG. 4, both end portions in the axial direction are the first rotor cores 44 and 44, and the central portion in the axial direction is the second rotor core 45. Has been. That is, the rotor yoke 40 is configured by alternately arranging the first rotor core 44 and the second rotor core 45 in the axial direction. As shown in FIG. 5, the first rotor cores 44, 44 have salient poles 46 provided so as to be interposed between and connected to the magnet insertion holes 43, 43 that are adjacent to each other, or to protrude. A large number of electromagnetic steel sheets 47A are laminated. On the other hand, as shown in FIG. 6, the second rotor core 45 is configured by laminating a number of electromagnetic steel plates 47 </ b> B each having a recess 48 formed between the magnet insertion holes 43, 43 adjacent to each other. That is, the second rotor core 45 has no salient poles between the magnet insertion holes 43 and 43 adjacent to each other. The only difference between the first rotor cores 44 and 44 and the second rotor core 45 is the presence or absence of salient poles 46. When laminating the electromagnetic steel sheets 47B, the recesses 48 are overlapped at the same position in the circumferential direction.
[0015]
The rotor 20 is assembled as follows, for example.
First, the end face plate 50 </ b> A is press-fitted and fitted into the outer peripheral surface 31 of the rotor shaft 30 from the other end face 34 side of the rotor shaft 30.
Next, the rotor yoke 40 formed by alternately arranging the first rotor core 44 and the second rotor core 45 is press-fitted into the outer peripheral surface 31 of the rotor shaft 30 from the other end surface 34 side of the rotor shaft 30 and fitted. At that time, the protrusion 42 of the rotor yoke 40 is press-fitted while being engaged with the groove 33 of the outer peripheral surface 31 of the rotor shaft 30.
Subsequently, one permanent magnetic pole piece 60 is inserted into each magnet insertion hole 43 of the rotor yoke 40, and then the end face plate 50B is press-fitted into the outer peripheral face 31 of the rotor shaft 30 from the other end face 34 side of the rotor shaft 30. Fit.
By assembling as described above, the rotor shaft 30, the rotor yoke 40, the permanent magnetic pole piece 60, and the end face plates 50A and 50B are integrated, and the rotor 20 as shown in FIG. 2 is completed. In the rotor 20 assembled in this way, both end openings of each magnet insertion hole 43 are blocked by the end face plates 50A and 50B, and the permanent magnetic pole piece 60 is prevented from being detached from the rotor yoke 40.
[0016]
According to the brushless motor 1 configured as described above, since the rotor 20 includes the first rotor core 44 having the salient poles 46, the reluctance torque can be increased as compared with the case where there is no salient pole.
Further, as shown in FIG. 7, in the first rotor core 44 having the salient poles 46, the magnetic flux G <b> 1 from the stator 10 can pass through the yoke portion 49 radially inward from the permanent magnet piece 60. It is difficult to saturate, and therefore the accuracy of sensorless position detection of the rotor 20 is extremely high.
Furthermore, since the first rotor iron core 44 having the salient poles 46 has a thick yoke portion 49, the rotor 20 including the first rotor iron core 44 has high mechanical strength against centrifugal force.
[0017]
Also, with regard to the magnet heat generation of the rotor, it is generally known experimentally and empirically that the magnet heat generation is relatively small at both ends in the axial direction and the magnet heat generation is relatively large at the central portion in the axial direction. However, in the rotor 20 of the brushless motor 1, the central portion in the axial direction is constituted by the second rotor core 45 having the recess 48, so that the heat generation of the magnet in the central portion can be reduced. The rotor 20 as a whole can suppress the heat generation of the magnet and can make it difficult to demagnetize.
That is, in the rotor 20 and the brushless motor 1, the reluctance torque can be used effectively, the sensorless position detection accuracy of the rotor 20 can be increased, and the heat generation of the magnet can be suppressed to make it difficult to demagnetize. And mechanical strength can be increased.
[0018]
In addition, the ratio of the 1st rotor iron cores 44 and 44 and the 2nd rotor iron core 45 can be suitably set according to the intended purpose.
For example, in the brushless motor 1 with relatively large magnet heat generation, the ratio of the second rotor core 45 is increased, and in the brushless motor 1 with relatively small magnet heat generation, the ratio of the first rotor cores 44 and 44 is increased.
In the above-described embodiment, one second rotor core 45 is disposed between the two first rotor cores 44, 44. However, the first rotor core 44 and the second rotor core 45 are alternately arranged in the axial direction. There is no limit to the number of iron cores as long as they are arranged.
[0019]
In the above-described embodiment, the permanent magnet rotor in which the permanent magnet is embedded in the rotor iron core is described. However, as shown in FIGS. 8 to 10, the permanent magnet is fixed to the outer peripheral surface of the rotor iron core. It can also be applied to a magnet rotor.
The rotor 20 shown in FIGS. 8 to 10 will be briefly described. On the outer circumferential surface of the rotor yoke 40, a magnet receiving recess (magnet mounting portion) 71 is provided instead of the magnet insertion hole 43, and the first rotor is provided. As shown in FIG. 9, the iron cores 44, 44 are configured by laminating a number of electromagnetic steel plates 73 </ b> A having salient poles 72 between the magnet receiving recesses 71, 71 adjacent to each other. As shown in FIG. 2, a large number of electromagnetic steel plates 73B each having a recess 74 between adjacent magnet housing recesses 71 and 71 are laminated. The electromagnetic steel plate 73B constituting the second rotor core 45 is provided with a magnet locking portion 75 between the magnet housing recess 71 and the recess 74, and the magnet 60 is a salient pole of the first rotor core 44. 72 and the second rotor iron core 45 are latched by the magnet latching portions 75 to prevent the detachment outward in the radial direction. Since other configurations are the same as those of the above-described embodiment (FIGS. 1 to 7), the same reference numerals are given to the same mode portions and the description thereof is omitted.
In the present invention, the magnet mounting portion includes not only the magnet insertion hole 43 shown in FIGS. 2 to 6 but also a magnet housing recess 71 shown in FIGS. 8 to 10.
In the above-described embodiment, the inner rotor that fixes the permanent magnet to the outer peripheral portion of the rotor core is shown. However, the present invention may be applied to the outer rotor that fixes the permanent magnet to the inner peripheral portion of the rotor core. Similar effects can be obtained.
[0020]
【The invention's effect】
As described above, according to the first aspect of the present invention, by providing the first rotor core having salient poles, the reluctance torque can be increased, the strength against centrifugal force can be increased, and the second portion having a recess. By providing the rotor core, the heat generation of the magnet can be reduced, and demagnetization can be made difficult.
In particular, since the second rotor core having the concave portion is arranged in the central portion in the axial direction where the magnet can generate heat most easily, the heat generation of the magnet can be suppressed and the demagnetization can be made difficult.
[0021]
According to the second aspect of the present invention, since the rotor includes the first rotor iron core having the salient poles, the reluctance torque is increased, and the magnetic flux is not easily saturated when detecting the position of the rotor without the sensor. The accuracy of detection can be increased, the strength against centrifugal force can be increased, and the rotor can be provided with a second rotor core having a recess, so that the heat generated by the magnet can be reduced and the demagnetization can be made difficult.
In particular, since the second rotor core having the concave portion is arranged in the central portion in the axial direction that is most likely to generate heat in the rotor core of the rotor, the heat generation of the magnet can be suppressed and demagnetization can be made difficult. .
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a brushless motor according to a first embodiment of the present invention.
FIG. 2 is an external perspective view of a rotor that constitutes a part of the brushless motor according to the first embodiment.
FIG. 3 is an exploded perspective view of the rotor according to the first embodiment.
FIG. 4 is an enlarged perspective view showing a main part of the rotor according to the first embodiment.
FIG. 5 is a front view showing a part of the electromagnetic steel sheet constituting the first rotor iron core of the rotor in the first embodiment.
FIG. 6 is a front view showing a part of the electromagnetic steel sheet constituting the second rotor iron core of the rotor in the first embodiment.
FIG. 7 is a diagram illustrating a portion through which magnetic flux passes in the first rotor core.
FIG. 8 is an exploded perspective view of a rotor in a second embodiment of a brushless motor according to the present invention.
FIG. 9 is a partial front view of the first rotor core of the rotor according to the second embodiment.
FIG. 10 is a partial front view of a second rotor iron core of the rotor according to the second embodiment.
[Explanation of symbols]
1 Brushless motor 10 Stator 20 Rotor (permanent magnet rotor)
40 Rotor yoke (rotor core)
43 Magnet insertion hole (Magnet mounting part)
44 1st rotor core 45 2nd rotor core 46 Salient pole 48 Recessed part 60 Permanent magnet piece 71 Magnet accommodation recessed part (magnet mounting part)
72 Salient pole 74 Recess

Claims (2)

In the permanent magnet type rotor formed by fixing permanent magnet pieces to a plurality of magnet mounting portions provided on the outer peripheral portion or inner peripheral portion of the rotor core,
The rotor core includes a first rotor core formed by laminating a number of electromagnetic steel plates having salient poles between the adjacent permanent magnet pieces, and a number of electromagnetic steel plates having recesses between the adjacent permanent magnet pieces. A laminated second rotor core , wherein the second rotor core is disposed at an axially central portion, the first rotor core is disposed at both axial end portions, and the permanent magnet piece is disposed on the first rotor core. A permanent magnet rotor characterized by being provided to penetrate through the rotor core and the second rotor core . A permanent magnet-type rotor, in which a permanent magnet piece is fixed to each of a plurality of magnet mounting portions provided on the outer peripheral portion of the rotor core, and a high frequency for position detection is provided on a stator winding disposed opposite to the rotor. In a brushless motor capable of detecting the position of the rotor by a motor current when a voltage is applied,
The rotor core of the rotor has a recess between a first rotor core formed by laminating a number of electromagnetic steel plates having salient poles between the permanent magnet pieces adjacent to each other and the permanent magnet pieces adjacent to each other. and a second rotor core formed by laminating many magnetic steel sheets, the second rotor core arranged axially central portion, Ri name by arranging the first rotor core in the axial end portions, the permanent magnet A brushless motor , wherein a piece is provided so as to penetrate through the first rotor core and the second rotor core .

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