JP5413799B2 - Brushless motor - Google Patents

Description

  The present invention relates to a brushless motor, and more particularly to an improvement of a brushless motor suitably used in an electric power steering apparatus.

  Conventionally, in order to reduce loss torque of an electric power steering (hereinafter referred to as “EPS”) motor, the hysteresis loss per frequency of 1 Hz when magnetized to a maximum magnetic flux density of 1.5 T is 0.10 J / kg or less. A technology using electromagnetic steel sheets for motor cores has been introduced. (For example, refer to Patent Document 1).

  Moreover, the hysteresis loss characteristics are improved by performing heat treatment on the electromagnetic steel sheet for EPS motor core so that the slab heating temperature during hot rolling is 1050 to 1180 ° C, and more preferably, the annealing temperature during magnetic annealing is 720 to 900 ° C. Technology to reduce loss torque is also introduced. (For example, refer to Patent Document 2).

  And a stator core in which a ring-shaped core piece formed by forming an electromagnetic steel sheet is laminated, the electromagnetic steel sheet having magnetic anisotropy by rolling, and rolling of core pieces adjacent in the vertical direction of the lamination An EPS motor has also been introduced that reduces loss torque by laminating the core pieces so that the directions differ by a predetermined angle. (For example, refer to Patent Document 3).

  A stator iron core comprising an annular stator yoke portion and a plurality of stator salient poles formed separately from the stator yoke portion and fixed to the stator yoke portion. In addition, an EPS motor that reduces loss torque by using an amorphous iron core as the iron core of the stator salient pole is also introduced. (For example, refer to Patent Document 4).

  Still further, the stator unit includes a stator core accommodated in a case, and a rotor that is rotatable with respect to the stator unit, and the stator core and the case are fixed by a protruding portion that protrudes to receive a load. In addition, an EPS motor that reduces loss torque by introducing a structure in which the stator core and the case are not in contact with each other except for the protrusion is also introduced. (For example, refer to Patent Document 5).

JP 2001-11585 A JP 2001-335843 A JP 2004-350369 A JP 2005-253168 A JP 2006-333657 A

  However, the electromagnetic steel sheet for EPS motor core described in Patent Document 1 has good magnetic characteristics of the material itself constituting the electromagnetic steel sheet, but when the stator core is press-fitted into the case, the magnetic characteristics of the stator core are affected by the press-fitting. It is difficult to obtain sufficient characteristics such as deterioration and iron loss. Further, Patent Documents 2 to 4 do not describe a method of disposing a stator core in the case or a configuration when the stator core is disposed in the case (relationship between the case and the stator core).

  In the EPS motor described in Patent Document 5, since the protrusion is in surface contact with the case, the effect of preventing deterioration of magnetic characteristics is small, and the protrusion is not necessary as a magnetic path. Since it is a part, the outer diameter and mass of the motor become large, and it is difficult to achieve miniaturization.

  The present invention has been made in view of such circumstances, and even if a stator core is press-fitted into a case, it is possible to prevent a decrease in magnetic characteristics of the stator core due to the press-fitting and to achieve a reduction in size and weight. An object is to provide a brushless motor that can be used.

In order to achieve this object, the present invention is a brushless motor comprising a stator having a stator core and a coil wound around the stator core, and a case for accommodating the stator, and the stator is press-fitted into the case. The stator core has an annular back yoke portion and a plurality of teeth protruding from the back yoke portion toward the radial center of the back yoke portion, and the outer shape of the back yoke portion is regular n-gon is (n = S or n = 2S, S is the number of teeth), each corner portion of the back yoke unit, Ri Na in contact with the inner peripheral surface of the case, the back yoke unit, A brushless motor in which an inner peripheral surface and an outer peripheral surface corresponding to the inner peripheral surface are parallel to each other is provided.

  In the brushless motor having this configuration, since the corner portion of the back yoke portion is in contact with the inner peripheral surface of the case, the contact area between the back yoke portion and the case is reduced (that is, the back yoke portion and the case are wired). Contact). Therefore, even if the stator is press-fitted into the case, the deformation of the back yoke due to the press-fitting can be suppressed, and the magnetic flux can be stabilized. For this reason, it can prevent that the magnetic characteristic of the said stator core falls. Further, since the back yoke portion can be formed with the minimum necessary area as a magnetic path, the outer diameter and mass of the brushless motor can be suppressed to the minimum necessary, and a reduction in size and weight can be achieved. If n is 3S or more (that is, 3 times or more of the number of teeth), the number of contact points with the inner peripheral surface of the case increases, and the magnetic characteristics of the stator core may be deteriorated.

  In this configuration, the inner peripheral surface of the back yoke portion can be formed to be parallel to the outer peripheral surface corresponding to the inner peripheral surface. By doing so, in addition to the advantages, the area of the back yoke portion can be made constant, and the magnetic path becomes the shortest path, so that the loss torque can be reduced.

Further, the present invention is a brushless motor comprising a stator core and a stator having a coil wound around the stator core, and a case for housing the stator, wherein the stator is press-fitted into the case. Has an annular back yoke portion and a plurality of teeth protruding from the back yoke portion toward the radial center of the back yoke portion, and the outer peripheral shape of the back yoke portion is It is composed of n (n = S or n = 2S, S is the number of teeth) curved surfaces having a constant curvature different from the curvature of the inner peripheral surface, and the maximum diameter portion of each curved surface of the back yoke portion is the case. Ri in the inner peripheral surface Na abuts of the back yoke unit, and the inner peripheral surface, in which the outer peripheral surface corresponding to the inner peripheral surface to provide a brushless motor which is concentric

  In the brushless motor having this configuration, since the maximum diameter portion of the back yoke portion is in contact with the inner peripheral surface of the case, the contact area between the back yoke portion and the case is reduced (that is, the back yoke portion and the case are Line contact). Therefore, even if the stator is press-fitted into the case, the deformation of the back yoke due to the press-fitting can be suppressed, and the magnetic flux can be stabilized. For this reason, it can prevent that the magnetic characteristic of the said stator core falls. Further, since the back yoke portion can be formed with the minimum necessary area as a magnetic path, the outer diameter and mass of the brushless motor can be suppressed to the minimum necessary, and a reduction in size and weight can be achieved. If n is 3S or more (that is, 3 times or more of the number of teeth), the number of contact points with the inner peripheral surface of the case increases, and the magnetic characteristics of the stator core may be deteriorated.

  Further, in this configuration, the back yoke portion can be formed so that the curvature of the inner peripheral surface is the same as the curvature of the outer peripheral surface corresponding to the inner peripheral surface. By doing so, in addition to the advantages, the area of the back yoke portion can be made constant, and the magnetic path becomes the shortest path, so that the loss torque can be reduced.

In the brushless motor according to the present invention, the coils are wound around each of the teeth to form a plurality of coil groups each including three-phase coils, and the plurality of coil groups are continuously arranged. The stator core may have a configuration in which the stator core is rolled at a constant angle θ represented by the following formula 1.
θ = 360 ° × (m / S) (Formula 1)
Where m is the number of phases and S is the number of teeth.

  By rolling the stator core in this way, in addition to the above-described advantages, the variation in magnetic flux can be further suppressed, so that the loss torque can be further reduced. Further, as described above, the outer peripheral shape of the back yoke portion is composed of an n-sided shape or n curved surfaces, and therefore the length of the diameter varies depending on the position (different diameter). This makes it easy to set the phase, and assembly can be performed easily.

When the above formula 1 is satisfied, the number P of stacked stator cores is represented by the following formula 2.
P = At (Formula 2)
Where t = S / m, A and t are integers, S is the number of teeth, and m is the number of phases.

  By setting the number P of stacked stator cores in this way, the balance of the outer peripheral shape of the stator core is improved. Here, in order to press-fit the stator core into the case, it is necessary to reduce the variation in the circumferential direction of the stator core and to suppress the variation in the stacking direction. For this purpose, the relationship between the angles θ and t is The number of teeth (S) and the number of phases (m) are preferably determined.

  ADVANTAGE OF THE INVENTION According to this invention, even if it press-fits a stator core in a case, while being able to prevent the fall of the magnetic characteristic of the stator core by the said press-fit, the brushless motor which can achieve size reduction and weight reduction can be provided. .

It is a longitudinal cross-sectional view of the brushless motor which concerns on the Example of this invention. It is a top view of the stator core which is a component of the brushless motor shown in FIG. It is a cross-sectional view which shows the state which press-fit the stator core which is a component of the brushless motor shown in FIG. 1 in the case. FIG. 4 is an enlarged cross-sectional view showing a part of a stator core press-fitted into the case shown in FIG. 3. It is a top view of the stator core which is a component of the brushless motor which concerns on the other Example of this invention. FIG. 6 is an enlarged cross-sectional view showing a part of the stator core press-fitted into the case shown in FIG. 5. It is sectional drawing which expands and shows a part of the state which press-fitted the stator core which is a component of the brushless motor which concerns on the other Example of this invention in the case.

  Next, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, the Example described below is the illustration for demonstrating this invention, and this invention is not limited only to these Examples. Therefore, the present invention can be implemented in various forms without departing from the gist thereof.

  1 is a longitudinal sectional view of a brushless motor according to an embodiment of the present invention, FIG. 2 is a plan view of a stator core that is a component of the brushless motor shown in FIG. 1, and FIG. 3 is a configuration of the brushless motor shown in FIG. FIG. 4 is an enlarged cross-sectional view showing a part of the stator core press-fitted into the case shown in FIG. 3. In the drawings, for easy understanding, the thickness, size, enlargement / reduction ratio, etc. of each member are not matched with the actual ones.

  As shown in FIGS. 1 to 4, the brushless motor 1 according to the present embodiment includes a substantially cylindrical case 2 </ b> A formed of a magnetic material and a substantially disk shape that closes one open end of the case 2 </ b> A. The front bracket 2B is provided. A bottom 2a is formed integrally with the case 2A at the end of the case 2A opposite to the side on which the front bracket 2B is provided so as to close the end. As the magnetic material forming the case 2A, for example, a general steel material such as SPCC (Steel Plate Cold Commercial), electromagnetic soft iron, or the like can be applied. The front bracket 2B serves as a flange when the brushless motor 1 is attached to a desired device.

  Inside the case 2A, a bearing 3A is disposed at a substantially central portion of the front bracket 2B, and a bearing 3B is disposed at a substantially central portion of the bottom portion 2a. The bearing 3A rotatably supports one end of the rotating shaft 4 disposed inside the case 2A, and the bearing 3B supports the other end of the rotating shaft 4 rotatably.

  A rotor core 10 is disposed on the outer peripheral side of the rotary shaft 4, and a motor driving magnet 5 is fixed on the outer peripheral side of the rotor core 10. The magnet 5 is a permanent magnet having S poles and N poles alternately magnetized in the circumferential direction of the rotary shaft 4 at equal intervals, and the brushless motor 1 is freely rotatable by the rotary shaft 4, the rotor core 10 and the magnet 5. The rotor 6 is configured. The magnet 5 may have a divided shape (segment structure) or a ring shape. Reference numeral 11 denotes a magnet cover.

  Further, the end of the rotating shaft 4 on the front bracket 2B side protrudes to the outside, and a joint 19 is provided at the end protruding to the outside. By connecting a desired shaft or the like to the joint 19, the rotational output of the brushless motor 1 can be taken out. A resolver 25 that detects the rotational position of the rotor 6 and a terminal block 26 that supports the resolver 25 are provided on the front bracket 2 </ b> B side of the rotating shaft 4. The resolver 25 includes a resolver rotor 31 fixed to the circumferential surface of the rotary shaft 4 and a resolver stator 32 disposed to face the resolver rotor 31 with a predetermined gap.

  A stator 9 is disposed between the outer peripheral side of the rotor 6 and the inner peripheral surface 12 of the case 2A. The stator 9 includes a stator core 7 and three-phase exciting coils 8 (see FIG. 1) wound around teeth 18A to 18L, which will be described in detail after the stator core 7.

  The stator core 7 includes an annular back yoke portion 17 constituting an outer peripheral portion, and a plurality of (in this embodiment, twelve) teeth 18 </ b> A to 18 </ b> A protruding from the back yoke portion 17 toward the radial center of the back yoke portion 17. 18L. The stator core 7 is concentric with the inner peripheral surface 12 of the case 2A.

The outer peripheral shape of the back yoke portion 17 is a regular 24 square as shown in FIGS. That is, the outer peripheral shape of the back yoke portion 17 is a polygon (n-square: n = 2S, S is the number of teeth) twice the number of teeth (12 in this embodiment). Of the positive 24 constituting the rectangular 24 corner X ₁ to X _24, corner X ₁ to X _12, the center line of the tooth 18a to 181 (the center line extending in a radial direction of the back yoke portion 17) above Is located. Further, the corner portion X ₁₃ is located in the middle between the corner portions X ₁ and X ₂ , and the other corner portions X _{14 to} X ₂₄ are located in the middle between the adjacent corner portions similarly to the corner portion X _13. positioned. Further, the inner peripheral surface (inner peripheral shape) of the back yoke portion 17 is parallel to the corresponding outer peripheral surface (outer peripheral shape). Accordingly, in the back yoke portion 17, the distance between the inner peripheral surface and the outer peripheral surface is the same in all the regions except for the region where the teeth 18A to 18L are projected. For this reason, since the area of the back yoke part 17 can be made constant and the magnetic path is the shortest path, loss torque can be reduced.

  In addition, the stator 9 has a configuration in which four coil groups, each including a three-phase excitation coil, are continuously arranged. Specifically, the stator core 7 is, for example, by exciting coils 8 wound around the teeth 18A, 18B, and 18C (exciting coils are not shown in FIGS. 2 to 4 for easy understanding). One coil group (first coil group) is formed, and another coil group (second coil group) is formed by the exciting coil 8 wound around each of the teeth 18D, 18E, and 18F. The other one coil group (third coil group) is formed by the exciting coil 8 wound around 18G, 18H and 18I, and the exciting coil 8 wound around each of the teeth 18J, 18K and 18L, Another one coil group (fourth coil group) is formed.

The stator core 7 is rolled at a constant angle θ expressed by Equation 1. As described above, in this embodiment, the number of phases of the coil is three and the number of teeth is twelve.
θ = 360 ° × (m / S) = 360 ° × (3/12) = 90 ° (Equation 1)
Where m is the number of phases and S is the number of teeth.

  By rolling the stator core 7 in this way, it is possible to minimize a thickness error that occurs when the stator cores 7 are stacked. For this reason, the variation in magnetic flux can be further suppressed, and the loss torque can be further reduced. In addition, since the back yoke portion 17 constituting the outer peripheral portion of the stator core 7 is a regular 24-gonal shape, the length of the diameter varies depending on the position (different diameter), so that the phase during rolling can be easily set. Thus, assembly can be performed easily.

Further, a plurality of the stator cores 7 are laminated in the axial direction of the rotating shaft 4. In order to balance the outer peripheral shape of the stator core 7, it is preferable that the number P of stacked stator cores 7 is the number that satisfies Formula 2.
P = At (Formula 2)
Where t = S / m, t is an integer, S is the number of teeth, m is the number of phases

  In addition, when the stator core 7 is rolled at a constant angle θ = 360 ° × (m / S) = 360 ° × (3/12) = 90 °, the angle of rolling is 0 °, 90 °, 180 °, There are four types of 270 °. Therefore, since the number P of stacked layers is an integral multiple of 4 as calculated from t = S / m = 12/3 = 4, the total number of stacked layers for each transposition angle can be made the same. The balance can be improved. Reference numeral 28 denotes an insulator.

As shown in FIGS. 1, 3, and 4, the stator 9 having this configuration is disposed in the case 2A by being press-fitted into the case 2A. At this time, corner portions X _{1 to} X ₂₄ formed on the outer peripheral surface of the back yoke portion 17 abut on the inner peripheral surface 12 of the case 2A. (That is, the region other than the corner portions X _{1 to} X _{24 on} the outer peripheral surface of the back yoke portion 17 is not in contact with the inner peripheral surface 12 of the case 2A). Therefore, since the stator 9 is in line contact with the case 2A at 24 locations, the contact area between the stator 9 and the case 2A can be reduced. For this reason, even if the stator 9 is press-fitted into the case 2A, the deformation of the back yoke portion 17 due to the press-fitting can be suppressed, the magnetic flux can be stabilized, and the magnetic characteristics of the stator core are prevented from deteriorating. can do. Further, since the back yoke portion 17 can be formed with a minimum necessary area as a magnetic path, the outer diameter and mass of the brushless motor 1 can be suppressed to the minimum necessary, and a reduction in size and weight can be achieved. .

In the present embodiment, the case where the outer peripheral shape of the back yoke portion 17 is a regular 24 square has been described. However, the present invention is not limited to this, and the outer peripheral shape of the back yoke portion 17 is, for example, as shown in FIGS. Alternatively, it may be a regular dodecagon. In this case, the corners Y _{1 to} Y ₁₂ come into contact with the inner peripheral surface 12 of the case 2A. The corner Y ₁ to Y _12, the position that may have been respectively formed, the corners X ₁ to X ₁₂ described above is formed at a position where the corner portion X ₁₃ to X ₂₄ described above is formed May be formed respectively. Moreover, the outer peripheral shape of the back yoke part 17 should just be the polygon which is the same as the number of teeth, or twice the number of teeth.

In the present embodiment, since the case where the outer peripheral shape of the back yoke portion 17 is a regular 24 square has been described, the corner (for example, X ₁ shown in FIG. 2) and the corner adjacent to the corner (for example, X ₁ , for example) X ₁₃ and X ₂₄ ) shown in FIG. 2 are connected by a plane (a straight line in the plan view as shown in FIG. 2), but not limited to this, the outer peripheral shape of the back yoke portion 17 is, for example, 7, n pieces having a curvature different from the curvature of the inner peripheral surface 12 of the case 2A (n = S or n = 2S, S is the number of teeth: in the case of FIG. 7, the number of teeth is twelve. And n = 12). In this case, the maximum diameter portion of the back yoke portion 17 comes into contact with the inner peripheral surface 12 of the case 2A. The position of the maximum diameter portion of the back yoke portion 17 may be a position where the corner portion X ₁₃ to X ₂₄ described above is formed, the position of corner X ₁ to X ₁₂ described above is formed It may be. Further, the curvature of the inner peripheral surface of the back yoke portion 17 is preferably matched with the curvature of the outer peripheral surface of the back yoke portion 17. By doing in this way, the area of the back yoke part 17 can be made constant, and since the said magnetic path becomes the shortest path | route, loss torque can also be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Brushless motor, 2A ... Case, 4 ... Rotating shaft, 7 ... Stator core, 8 ... Excitation coil, 9 ... Stator, 17 ... Back yoke part, 18A-18L ... Teeth

Claims (4)

A brushless motor comprising a stator core and a stator having a coil wound around the stator core, and a case accommodating the stator, wherein the stator is press-fitted into the case,
The stator core has an annular back yoke portion and a plurality of teeth protruding from the back yoke portion toward the radial center of the back yoke portion,
The outer shape of the back yoke portion is a regular n-square shape (n = S or n = 2S, S is the number of teeth), and each corner portion of the back yoke portion is not in contact with the inner peripheral surface of the case. The
The back yoke portion is a brushless motor in which an inner peripheral surface and an outer peripheral surface corresponding to the inner peripheral surface are parallel to each other . A brushless motor comprising a stator core and a stator having a coil wound around the stator core, and a case accommodating the stator, wherein the stator is press-fitted into the case,
The stator core has an annular back yoke portion and a plurality of teeth protruding from the back yoke portion toward the radial center of the back yoke portion,
The outer peripheral shape of the back yoke portion is composed of n curved surfaces (n = S or n = 2S, S is the number of teeth) having a constant curvature different from the curvature of the inner peripheral surface of the case, and the back yoke maximum diameter portion of the curved surface of the section is, Ri Na in contact with the inner peripheral surface of the case,
The back yoke portion is a brushless motor in which an inner peripheral surface and an outer peripheral surface corresponding to the inner peripheral surface are concentric . A three-phase brushless motor in which the coils are wound around each of the teeth to form a plurality of coil groups each having a set of three-phase coils, and the plurality of coil groups are continuously arranged.
The brushless motor according to claim 1, wherein the stator core is rolled at a constant angle θ expressed by Formula 1.
θ = 360 ° × (m / S) (Formula 1)
Where m is the number of phases and S is the number of teeth. The brushless motor according to claim 3 , wherein the number P of stacked stator cores is represented by Formula 2.
P = At (Formula 2)
Where t = S / m, A and t are integers, S is the number of teeth, and m is the number of phases.

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