JP6474283B2 - Brushless motor - Google Patents

Description

  The present invention relates to a rotor core structure of a brushless motor, and more particularly to a core plate fixing structure of a rotor core used in a magnet-embedded motor (IPM motor: Interior Permanent Magnet Motor).

  In general, the rotor core of a brushless motor is formed by laminating a large number of thin core plates made of electromagnetic steel plates in order to reduce iron loss. The laminated core plates are fixed by fixing means such as bosses and rivets, and a rotor core for a motor is laminated and formed. Conventionally, in an SPM motor (Surface Permanent Magnet Motor) in which a magnet is arranged on the outer surface of the rotor core, the boss for stacking the core plate is provided near the center of the rotor core at the center of the magnet so as not to disturb the magnetic path of the magnet. May be.

  On the other hand, in recent years, the use of IPM motors in which magnets are embedded in the rotor and the rotor is rotated by both the magnet torque generated by the magnetic force of the magnet and the reluctance torque generated by the magnetization of the rotor has been expanded. Since IPM motors can utilize reluctance torque in addition to magnet torque, they are used as drive sources for electric power steering devices for automobiles as high-efficiency and high-torque motors, and are also increasingly used in hybrid vehicles and air conditioners. doing. And also in this IPM motor, the laminated core which laminated | stacked many core plates is used for the rotor core.

JP 2004-350345 A JP 2002-10548 A

  However, in the IPM motor, there is a thin bridge portion used as a magnetic circuit near the outer periphery of the rotor core, and the strength of the outer peripheral portion is lower than that of the SPM type. For this reason, if the fixing means (caulking pin) for the core plate is arranged at the same position as the SPM type as in Patent Document 1, the bridge portion is twisted during stacking, or the peeling of the stack occurs at the bridge portion. There is a fear. That is, at the boss position as in Patent Document 1, lamination itself is difficult, and there is a problem that welding of the outer peripheral portion and adhesion of the core are necessary to suppress peeling after lamination.

  On the other hand, if the fixing means (caulking pin) of the core plate is arranged at a position close to the bridge portion on the outer side in the radial direction of the magnet as in Patent Document 2, the bridge portion is hardly twisted or peeled off. However, if bosses or pins are arranged at these positions, the flow of the main magnetic flux of the magnet is hindered, and there is a problem that the magnetic flux cannot be effectively used and the motor efficiency is lowered.

  An object of the present invention is to provide a laminated fixing structure of a core plate that can prevent twisting and peeling of a bridge portion while minimizing the influence on a magnetic circuit in an IPM type brushless motor.

The brushless motor of the present invention is a brushless motor having a stator and a rotor that is rotatably disposed inside the stator, and the rotor includes a rotor core in which a plurality of core plates made of a magnetic material are stacked. A plurality of magnets fixed in the rotor core, wherein the rotor core is provided at equal intervals along a circumferential direction of the core body, and the magnet accommodates the core body. A plurality of magnet housing portions to be arranged, a plurality of salient pole portions formed on the outer circumference side of the magnet housing portion and disposed on the outer circumference portion of the rotor, and the salient poles between the adjacent salient pole portions part and has a bridge portion connecting the core body, the magnet accommodating portion includes a magnet fixing step for restricting the movement in the circumferential direction of the magnet, the magnetic Has a preparative accommodating portion of the formed in the circumferential end the magnet gap portion provided on both sides of the magnet is restricted movement of at a fixed step in the circumferential direction, the width in the thickness direction of the magnet, the The core body is set to be larger than the width in the same direction as the thickness direction of the magnet in the gap portion, and the core body is formed by the magnet fixing step near the gap portion on the radial inside of the bridge portion. possess a protruding portion provided in a manner to expand the core body in the radial direction, and fixing means for stacking fixing the core plates adjacent to each other, the said fixing means, utilizing the projecting portion It is arranged in the vicinity of the bridge part .

  In the present invention, fixing means for stacking and fixing the core plates to each other is disposed on the projecting portion formed in the radial direction inside of the bridge portion in the vicinity of the gap. Even if the fixing means is disposed in the portion of the overhanging portion, the influence on the main magnetic flux flow of the magnet is small, and by using the overhanging portion, the fixing means can be arranged on the outer peripheral side. For this reason, by arranging the fixing means at the position, it is possible to effectively suppress twisting and the like during lamination without affecting the magnetic circuit.

  In the brushless motor, the fixing means may be arranged with an interval equal to or greater than the thickness of the core plate with respect to the magnet housing portion, thereby forming or attaching the fixing means. Processability is improved.

Moreover, when the line segment which extended the radial inner periphery of the said magnet accommodating part is set to P and the intersection Q of the said line segment P of the said adjacent magnet accommodating part is made, the said fixing means is said rotor core rather than the said intersection Q. The intersection point Q may exist in the region of the fixing means so as not to leave the outer periphery . As described above, the intersection point Q is set as an index of the fixing means arrangement, and at least the intersection point Q falls within the fixing means region so that the fixing means is arranged at a position that is not further from the outer periphery of the rotor core than the intersection point Q. Can do. In this case, when the length of the bridge portion is L, and the length of the bridge portion when the length of the bridge portion is maximized without setting the magnet fixing step is Lmax, the ratio L between L and Lmax is L / Lmax may be set to L / Lmax ≧ 0.36.

Furthermore, as the fixing means, a boss may be provided on the core plate and the bosses of the adjacent core plates may be fitted to each other so that the core plates are stacked and fixed. As a result, the core plate can be stacked and fixed without using separate parts such as rivets and pins, and the number of parts can be reduced. In this case, the circumferential width of the bridge portion may be formed smaller than the outer diameter of the boss portion. In addition, for each of the plurality of magnets, the corners thereof are chamfered in a curved shape, and the inner surface of the magnet housing portion is bent in a radial direction so as to follow the curved shape of the corners of the magnet. The magnet fixing step may be formed.

  In the brushless motor of the present invention, in the IPM type brushless motor in which the magnet is embedded in the rotor, the fixing means for stacking and fixing the core plates to each other is provided on the radially inner side of the bridge portion provided in the rotor core. It arrange | positions in the formed overhang | projection part. The position near the radially inner side of the bridge portion has little influence on the main magnetic flux flow of the magnet even if the fixing means is arranged, and the fixing means is arranged on the outer peripheral side by arranging the fixing means on the overhanging portion. It becomes possible. Accordingly, it is possible to suppress twisting and peeling of the bridge portion when the core plate is laminated while minimizing a decrease in motor efficiency.

It is sectional drawing of the brushless motor which is one Embodiment of this invention. It is sectional drawing along the AA line of FIG. It is an enlarged explanatory view showing the configuration near the bridge portion. It is explanatory drawing which shows the structural example of a bridge | bridging part, (a) has shown the case where there is no bridge part (L = 0), (b) has each shown the case where the bridge part is taken as large as possible (L = Lmax). It is a graph which shows the relationship between the length L of a bridge | bridging part, and the change of output torque. It is explanatory drawing which shows.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a brushless motor 1 (hereinafter abbreviated as motor 1) according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. The motor 1 is an IPM type brushless motor that rotates a rotor by a reluctance torque based on an inductance difference and a magnet torque generated by a magnetic force of a magnet. As shown in FIG. 1, the motor 1 is an inner rotor type brushless motor in which a stator (stator) 2 is arranged on the outside and a rotor (rotor) 3 is arranged on the inside.

  The stator 2 is fixed inside a bottomed cylindrical motor case 4 (hereinafter abbreviated as case 4). The stator 2 is electrically connected to the stator core 5, a stator coil 6 (hereinafter abbreviated as a coil 6) wound around a plurality of teeth 9 of the stator core 5 via an insulator 11, and the stator core 5. The bus bar unit (terminal unit) 7 is connected. In the present embodiment, there are nine teeth 9, and the coil 6 is arranged in nine slots between adjacent teeth 9. The case 4 is formed in a bottomed cylindrical shape with iron or the like, and an aluminum die cast bracket 8 is attached to an opening of the case 4 with a fixing screw (not shown).

  The stator core 5 is formed by laminating a stator core plate 17 (for example, an electromagnetic steel plate having a thickness of 0.5 mm) which is a thin steel plate material. The stator core 5 has a plurality of teeth 9 projecting radially inward. A slot 10 is formed between adjacent teeth 9, and a coil 6 is accommodated therein. An insulator 11 made of synthetic resin is attached to the stator core 5, and a coil 6 is wound around the outside of the insulator 11. A bus bar unit 7 positioned by an insulator 11 is attached to one end side in the axial direction of the stator core 5. The bus bar unit 7 has a structure in which a copper bus bar is insert-molded in a synthetic resin main body.

  Around the bus bar unit 7, a plurality of connection terminals 12 project in the radial direction. When the bus bar unit 7 is attached, the connection terminals 12 are welded to the end portions 6 a of the coils 6 drawn from the stator core 5. In the bus bar unit 7, the number of bus bars corresponding to the number of phases of the motor 1 (here, three for the U phase, V phase, W phase and one for connecting each phase) is provided. Yes. Each coil 6 is electrically connected to a connection terminal 12 corresponding to the phase. After the bus bar unit 7 is attached, the stator core 5 is fixed in the case 4 by fixing means such as press fitting or adhesion.

  Inside the stator 2, a rotor 3 is inserted concentrically with the stator 2. The rotor 3 has a rotor shaft 13, and the rotor shaft 13 is rotatably supported by bearings 14a and 14b. The bearing 14 a is fixed to the center of the bottom of the case 4, and the bearing 14 b is fixed to the center of the bracket 8. A cylindrical rotor core 15 and a rotor (resolver rotor) 22 of a resolver 21 serving as a rotation angle detection unit are attached to the rotor shaft 13. A stator (resolver stator) 23 of the resolver 21 is housed in a resolver holder 24a, and is fixed to the inside of the bracket 8 by a mounting screw 25 via a resolver bracket 24b made of synthetic resin.

  The rotor core 15 is also formed by laminating a rotor core plate 18 (for example, an electromagnetic steel plate having a thickness of 0.5 mm) which is a thin steel plate material. A plurality of slits (magnet accommodating portions) 31 for attaching magnets are provided on the outer peripheral portion of the rotor core 15 along the circumferential direction. The slit 31 penetrates the rotor core 15 in the axial direction. A pair of magnet fixing steps (magnet movement restricting portions) 32 are formed at the left and right ends of the slit 31 in the circumferential direction. The magnet 16 is clamped and fixed between the left and right magnet fixing steps 32 in a state where movement in the circumferential direction is restricted. An arcuate salient pole portion 33 is formed on the outer peripheral side of each magnet 16 accommodated in the slit 31. Six magnets 16 are arranged along the circumferential direction, and the motor 1 has a 6-pole 9-slot configuration. In the slit 31, gaps 34 are formed on both sides of the magnet 16 in the circumferential direction. The air gap 34 functions as a flux barrier that hardly allows magnetic flux to pass through.

  When a rare earth magnet such as a neodymium magnet is used as the magnet 16, it is preferable that the magnet be disposed as radially as possible outside the rotor core 15 in order to effectively use the magnetic flux. Therefore, in the motor 1, the radial direction of both end portions of the slit 31 is arranged so that the magnet 16 is arranged on the outer peripheral side of the rotor core 15 in the radial direction while the gap portions 34 as flux barriers are arranged on both sides of the magnet 16. A magnet fixing step 32 is provided on the inner side, and the magnet 16 is disposed therebetween. In this case, the gap portion 34 is formed in a substantially trapezoidal shape at both ends of the slit 31, and a bridge portion 35 is formed between the adjacent gap portions 34. The bridge portion 35 is disposed between the adjacent salient pole portions 33 and connects the core body 15a on the central side and the salient pole portion 33 on the outer peripheral side.

  FIG. 3 is an enlarged explanatory view showing a configuration in the vicinity of the bridge portion 35. As shown in FIG. 3, a laminated boss (fixing means) 36 for laminating and fixing the rotor core plate 18 is provided on the rotor center side of the bridge portion 35. According to the inventors' magnetic field analysis, both sides of the bridge portion 35 may be gap portions 34, and even if the laminated boss 36 is disposed in the vicinity of the bridge portion 35, the influence on the main magnetic flux flow of the magnet 16 is small. I understood that. Further, in order to increase the bridge strength, it is optimal to provide the laminated boss 36 in a portion close to the bridge portion 35 that is the weakest portion in terms of strength. Therefore, in the motor 1, the position and shape of the air gap 34 are devised to arrange the magnet 16 closer to the outer periphery, while being able to prevent twisting at the time of stacking and the best position that does not affect the magnetic circuit. A laminated boss 36 is disposed.

  The laminated boss 36 is formed in a cylindrical shape, and is formed by a boss extending process so as to protrude in the axial direction. When the rotor core plate 18 is laminated, the laminated bosses 36 of adjacent layers are fitted together. Thereby, the plurality of rotor core plates 18 are fixed in a stacked state. In the motor 1, the laminated boss 36 is provided by utilizing a dead space formed inside the bridge portion 35 by the magnet fixing step 32. As shown in FIG. 3, when the magnet fixing step 32 is formed at the end of the slit 31, the inner edge 31a of the slit 31 is bent in the radial direction. The magnet fixing step 32 is a step of about 0.7 mm (height: H) in consideration of the chamfering of the finished machining of the magnet 16 (about R 0.4 mm), and the step portion is viewed from the center side. When the core body 15a is enlarged in the radial direction by the level difference, the projecting protruding portion 37 is formed. The overhang portion 37 is wider than the bridge portion 35, and a laminated boss 36 is provided in the vicinity of the bridge portion 35 using the overhang portion 37.

  Here, it is desirable to provide an interval equal to or greater than the plate thickness (0.5 mm in this case) of the rotor core plate 18 between the inner edge portion 31a of the slit 31 and the laminated boss 36 because the laminated boss 36 is pressed. . On the other hand, it is desirable to arrange the laminated boss 36 on the outer peripheral side of the rotor core 15 as much as possible with respect to torsion during lamination. Therefore, in the motor 1, the inner edge that is the peripheral edge on the radially inner side of the adjacent slit 31 is arranged so that the laminated boss 36 is arranged as far as possible on the outer peripheral side while ensuring a space greater than the plate thickness between the inner edge portion 31 a. The laminated boss 36 is disposed at a position where the intersection point Q of the line segment P extending from the portion 31 a exists in the laminated boss 36. That is, the intersection point Q is set as an index of the laminated boss arrangement, and at least the intersection point Q falls within the boss region. Based on the reference, the laminated boss 36 is disposed at a position that is not further from the outer periphery of the rotor core than the intersection Q.

  As described above, in the motor 1, the boss position is set closer to the outer periphery with the intersection point Q as an index, but from the viewpoint that it is better to provide the laminated boss 36 on the outer peripheral side as much as possible with respect to torsion or the like during lamination. Then, it is preferable that the length L of the bridge portion 35 is zero. However, the bridge portion 35 has not only a function of connecting the inner and outer peripheral portions of the rotor 3 as described above, but also a function of suppressing magnetic flux leakage by being a magnetic resistance and reducing magnetic flux leakage between the poles. doing. For this reason, as shown in FIG. 4A, if the bridge portion 35 is eliminated (L = 0), the magnetic resistance decreases, the magnetic flux easily leaks, and the output torque decreases. Therefore, from the viewpoint of making it difficult for magnetic flux to leak, L should be large, and must be at least larger than 0 (L> 0). However, the laminated boss 36 is closer to the center side, which is disadvantageous with respect to torsion and the like during lamination.

  Therefore, looking at the relationship between the length L of the bridge portion 35 and the change in the output torque, as shown in FIG. 5, there is almost no effect on the torque when L = 0.7, but L is 0.6 mm. When it falls below, the torque starts to fall, and when it falls below 0.2 mm, it falls sharply. From this result, it can be seen that the length L of the bridge portion 35 is preferably set to at least 0.2 mm or more, and preferably set to 0.5 mm or more where there is practically no torque drop. This is because L / Lmax in comparison with the case where the bridge portion 35 is taken as large as possible in the form shown in FIG. 4B without providing the magnet fixing step 32 (Lmax, here, 1.4 mm). Is at least 0.2 / 1.4 (= 0.14) or more, preferably 0.5 / 1.4 (= 0.36) or more. Accordingly, in the motor 1, L = 0.5 mm is set.

  As described above, in the motor 1 according to the present invention, the laminated boss 36 is disposed on the outer peripheral side as much as possible at a position that does not affect the magnetic circuit as much as possible. The laminated boss 36 can be disposed as close to the bridge portion 35 as possible as much as possible. For this reason, although it is a boss | hub of the form similar to the past, the lamination | stacking boss | hub 36 can suppress the twist of a bridge | bridging part at the time of rotor core lamination | stacking, and lamination | stacking peeling. As a result, the lamination of the core plate is facilitated, and the processing for suppressing the peeling of the lamination such as the welding of the outer peripheral portion and the bonding of the core becomes unnecessary, and the manufacturing cost of the rotor core can be reduced. Further, since the laminated boss 36 is disposed at a position where the influence on the magnetic circuit is small, it is possible to suppress a reduction in torque, and to solve the problems at the time of laminating the rotor core without lowering the motor efficiency.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, an example in which the laminated boss 36 is used as the means for laminating and fixing the rotor core plate 18 is shown. However, as the core plate fixing means, for example, a member other than the boss such as a rivet or a pin is used. It is possible. Further, as a configuration for holding the magnet 16 in the slit 31, not only the stepped magnet fixing step 32 but also a taper-shaped fixing portion whose width becomes narrower toward both ends in the circumferential direction can be adopted. is there. Furthermore, if the rotor core has a large outer diameter and the laminated boss 36 alone may cause insufficient fixing strength of the rotor core plate 18, a laminated boss is provided at the same position as the SPM type together with the laminated boss 36. Also good. In addition, the rotor magnetic pole portion adopts not only a deformed rotor composed of salient poles formed in an arc shape with a center radially outward from the center of the rotor core, but also a rotor having a perfectly circular outer periphery. It is also possible.

  The present invention can be widely applied to a drive source of an electric power steering device, other in-vehicle electric devices, electric products such as hybrid vehicles, electric vehicles, and air conditioners.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 3 Rotor 4 Motor case 5 Stator core 6 Stator coil 6a End part 7 Bus bar unit 8 Bracket 9 Teeth part 10 Slot 11 Insulator 12 Connection terminal 13 Rotor shaft 14a, 14b Bearing 15 Rotor core 15a Core main body 16 Magnet 17 Stator core plate 18 Rotor Core Plate 21 Resolver 22 Resolver Rotor 23 Resolver Stator 24a Resolver Holder 24b Resolver Bracket 25 Mounting Screw 31 Slit (Magnet Housing)
31a Inner edge 32 Magnet fixing step (magnet movement restriction part)
33 Salient pole part 34 Gap part 35 Bridge part 36 Laminated boss (fixing means)
37 Overhang portion L Bridge portion length H Magnet fixed step height P Line segment Q that extends radially inner edge (inner edge) of slit Q Intersection of line segment P

Claims (7)

A brushless motor having a stator and a rotor rotatably disposed inside the stator,
The rotor has a rotor core in which a plurality of core plates made of a magnetic material are stacked, and a plurality of magnets fixed in the rotor core,
The rotor core includes a core body fixed to the rotor shaft, a plurality of magnet housing parts provided at equal intervals along the circumferential direction of the core body and housing the magnets, and an outer peripheral side of the magnet housing part A plurality of salient pole portions formed on the outer peripheral portion of the rotor and a bridge portion connecting the salient pole portions and the core body between the adjacent salient pole portions,
The magnet accommodating portion includes a magnet fixing step for restricting the movement in the circumferential direction of the magnet, the magnet moving in is formed in a circumferential end of the magnet housing section the magnet fixing step in the circumferential direction is restricted A gap provided on both sides of the
The thickness in the thickness direction of the magnet is set to be larger than the width in the same direction as the thickness direction of the magnet in the gap,
Said core body, said bridge portion radially inwardly into the gap portion in proximity to the magnet is formed by a fixed step protruding portion provided in a manner to expand the core body in the radial direction of adjacent said core and fixing means for stacking fixing the plates to each other, it was closed,
The brushless motor is characterized in that the fixing means is disposed in the vicinity of the bridge portion using the overhang portion . The brushless motor according to claim 1,
The brushless motor according to claim 1, wherein the fixing means is disposed with a gap larger than a plate thickness of the core plate with respect to the magnet housing portion. The brushless motor according to claim 1 or 2,
P is a line segment extending the radially inner periphery of the magnet housing part,
When making the intersection point Q of the line segments P of the adjacent magnet housing parts,
The brushless motor , wherein the intersection point Q exists in the region of the fixing means so that the fixing means is not further away from the outer periphery of the rotor core than the intersection point Q. The brushless motor according to claim 3,
The length of the bridge portion is L,
A brushless motor , wherein L / Lmax ≧ 0.36, where Lmax is the maximum length of the bridge portion without providing the magnet fixing step . In the brushless motor according to any one of claims 1 to 4,
The fixing means is a boss projecting from the core plate, and the core plate is laminated and fixed by fitting the bosses of the adjacent core plates together. The brushless motor according to claim 5, wherein
The width of the bridge portion in the circumferential direction is smaller than the outer diameter of the boss portion. In the brushless motor according to any one of claims 1 to 6,
Each of the plurality of magnets has its corners chamfered into a curved shape,
The magnet fixing step is formed by bending the inner surface of the magnet housing portion in a radial direction so as to follow the curved shape of the corner portion of the magnet.

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