JP5929147B2 - Rotor structure of rotating electrical machine - Google Patents

Description

  The present invention relates to a rotor structure of a rotating electrical machine, and more particularly to a rotor structure of an embedded magnet type synchronous motor.

  Conventionally, a motor having a permanent magnet type rotor such as an embedded magnet type synchronous motor (IPMSM) is an automobile drive motor, a pump drive motor, a power steering drive motor, a refrigerator, a washing machine, and a dryer. It is used for the drive motor of such household appliances, and its high output and high efficiency are required.

  In such a situation, it is easy to control the magnetization direction, which is an advantage of the so-called bonded magnet, in which permanent magnet powder is dispersed in the resin, high degree of freedom in shape molding, and ease of integral molding with other members. Attempts have been made to improve the performance of a motor having a conventional permanent magnet type rotor.

  For example, Patent Document 1 describes that a dust core and a magnet are simultaneously compression-molded with a rotor composed of a dust core and a magnet. Specifically, in the invention described in Patent Document 1, a rotor core of a motor is formed by molding a powder material, and the molded body is composed of a bond magnet portion mainly composed of a binder and magnet powder, a binder and a soft material. This is a permanent magnet type rotor that has a soft magnetic part mainly composed of magnetic powder and is formed by using compression molding means, and is intended to realize low cogging and high output.

JP 2006-320036 A

  By the way, the thing of the said patent document 1 is a motor of the type which has not arrange | positioned the permanent magnet inside a rotor core (it is not embed | buried), Therefore The vibration reduction and noise reduction of a motor by low cogging are one of the important technical subjects. Even in an embedded magnet type synchronous motor in which a permanent magnet is arranged inside a rotor core, it is required to achieve low cogging.

  The present invention has been made in view of such points, and an object of the present invention is to provide a technique for reducing cogging torque with a simple configuration in a rotor structure of an embedded magnet type synchronous motor. .

  In order to achieve the above object, the rotor structure of a rotating electrical machine according to the present invention is a ring-shaped member including a soft magnetic material having a function of suppressing a steep change in the air gap magnetic flux density between the rotor and the stator. The outer peripheral surface of the rotor core is covered.

  Specifically, the first invention is a substantially cylindrical body in which a rotating shaft member serving as a rotation center and a substantially annular soft magnetic steel plate provided outside the rotating shaft member are laminated in the axial direction of the rotating shaft member. And a rotor structure of a rotating electrical machine in which a plurality of permanent magnets extending in the axial direction of the rotating shaft member are arranged at substantially equal intervals in the circumferential direction of the rotor core on the outer peripheral portion of the rotor core. set to target.

And a soft magnetic ring member including a soft magnetic material powder having an easy magnetization axis and a resin material covering the outer peripheral surface of the rotor core, wherein each soft magnetic material powder has a magnetic flux density waveform on the outer peripheral surface of the rotor core. So that the axis of easy magnetization protrudes toward the approximate center of the rotary shaft member at a portion corresponding to the adjacent permanent magnets of the plurality of permanent magnets in the soft magnetic ring member. It is characterized by being bonded by the resin material in a state of being oriented along a circular arc .

According to the first invention, each soft magnetic material powder included in the soft magnetic ring member covering the outer peripheral surface of the rotor core has a sinusoidal magnetic flux density waveform on the outer peripheral surface of the rotor core covered by the soft magnetic ring member. In order to approach the wave, the easy axis of magnetization is along a circular arc protruding toward the approximate center of the rotating shaft member at a portion of the soft magnetic ring member corresponding to the adjacent permanent magnets among the plurality of permanent magnets. In other words, since it is oriented like a magnet powder magnetized with polar anisotropy in a bonded magnet, magnetic anisotropy is imparted to the outer peripheral surface of the rotor core, and the outer peripheral surface of the rotor core. The magnetic flux density waveform in FIG. 6 approaches a sine wave, and a steep change in the air gap magnetic flux density between the rotor and the stator can be suppressed. As a result, the cogging torque can be reduced in the rotor of the embedded magnet type synchronous motor, and noise and vibration caused by the cogging torque can be reduced.

  In the present invention, the “magnetization easy axis” does not mean only “a crystal orientation that is easily magnetized in a magnetic material having crystal magnetic anisotropy”, but includes a broader shape magnetic anisotropy. This means an axis in which the direction of magnetization in the magnetic material is easily oriented.

According to a second aspect of the present invention, there is provided a rotary shaft member serving as a rotation center, a substantially cylindrical rotor core provided on the outer side of the rotary shaft member, and a substantially annular soft magnetic steel plate laminated in the axial direction of the rotary shaft member And a rotor structure of a rotating electrical machine in which a plurality of permanent magnets extending in the axial direction of the rotating shaft member are arranged at substantially equal intervals in the circumferential direction of the rotor core.

And a soft magnetic ring member including a soft magnetic material powder having an easy magnetization axis and a resin material, which covers the outer peripheral surface of the rotor core, and each of the soft magnetic material powders has an easy magnetization axis in the soft magnetic material. Bonded by the resin material in a state in which the ring member is oriented so as to be along an arc protruding toward the substantial center of the rotating shaft member at a portion corresponding to between adjacent permanent magnets among the plurality of permanent magnets. It is characterized by being.

Even in the second invention , since the soft magnetic material powder is oriented so that its easy magnetization axis is along an arc protruding toward the substantial center of the rotating shaft member, in other words, in a bonded magnet Since it is oriented like magnetically magnetized magnet powder, magnetic anisotropy is imparted to the outer peripheral surface of the rotor core. As a result, a sharp change in the air gap magnetic flux density between the rotor and the stator is suppressed, so that the cogging torque can be reduced.

  A third invention is characterized in that, in the first or second invention, each soft magnetic material powder has a major axis and a minor axis, and the major axis direction coincides with the easy axis of magnetization. To do.

  By the way, in the soft magnetic material having shape magnetic anisotropy, the magnitude of the demagnetizing field is inversely proportional to the distance between the magnetic poles, so that the magnetic flux easily flows in the major axis direction of the soft magnetic material powder and the magnetic flux flows in the minor axis direction. It becomes difficult. Thus, in the third invention, the major axis direction coincides with the easy axis of magnetization, in other words, the magnetic properties of the soft magnetic material depend on the shape magnetic anisotropy regardless of the crystal magnetic anisotropy, and the major axis Since the soft magnetic material powder is oriented so that the direction is along an arc that protrudes toward the approximate center of the rotating shaft member, the magnetic flux density waveform on the outer peripheral surface of the rotor core can be made closer to a sine wave.

According to the rotor structure of a rotating electric machine according to the present invention, the soft magnetic material powder contained in the soft magnetic ring member covering the outer peripheral surface of the rotor core, its easy magnetization axis is in the soft magnetic ring member, said plurality The air gap between the rotor and the stator is oriented along an arc that protrudes toward the substantial center of the rotary shaft member at a portion corresponding to the permanent magnets adjacent to each other. The cogging torque can be reduced by suppressing a steep change in the magnetic flux density.

It is a perspective view which shows the rotor of the rotary electric machine which concerns on embodiment of this invention. It is an arrow line view of the II-II line | wire of FIG. It is a schematic diagram which shows a soft magnetic material powder. It is a figure which shows typically the orientation state of the soft-magnetic material powder in a soft-magnetic ring member. It is a figure showing the magnetic flux density waveform in a rotor core outer peripheral surface when taking a rotation angle on a horizontal axis and taking a magnetic flux density on a vertical axis | shaft. It is a flowchart of the manufacturing method of the rotor of a rotary electric machine. It is sectional drawing which shows a metal mold | die and the rotor core arrange | positioned at this. It is a schematic diagram explaining magnetic field orientation injection molding. It is a figure which illustrates typically the manufacturing method of the rotor concerning other embodiments.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a rotor of a rotating electrical machine according to the present embodiment, and FIG. 2 is a view taken along the line II-II in FIG. The rotor 1 is preferably used for a relatively low output motor of 2 kW or less, such as a pump driving motor, a power steering driving motor, and a household appliance driving motor in a vehicle. As shown, a metal rotor shaft (rotary shaft member) 3 serving as a rotation center, a substantially cylindrical rotor core 5 provided outside the rotor shaft 3, and a soft magnetic ring member covering the outer peripheral surface of the rotor core 5. 7.

  The rotor core 5 is made of a thin soft magnetic steel plate 15 punched by a press. More specifically, the rotor core 5 has a substantially annular shape having a circular opening 15a formed in the center and eight rectangular openings 15b formed at equal intervals on the outer periphery. The thin soft magnetic steel plate 15 is laminated and integrated so that the circular opening 15 a and the rectangular opening 15 b are continuous in the axial direction of the rotor shaft 3. Thus, the rotor core 5 has a central through hole (a series of circular openings 15a) 5a having a circular cross section at the center thereof, and eight rectangular cross sections arranged at equal intervals in the circumferential direction of the rotor core 5 at the outer peripheral portion thereof. The through-hole (a series of rectangular openings 15b) 5b has a substantially cylindrical shape.

  Thus, the rotor shaft 3 is inserted and fixed in the central through hole 5a, whereas the eight through holes 5b in the outer peripheral portion have permanent rectangular magnets (for example, a rectangular section extending in the axial direction of the rotor shaft 3). , Nd sintered magnet, ferrite, etc.) 11 are respectively inserted and fixed. In other words, in this rotor core 5, eight permanent magnets 11 are arranged at equal intervals so that the longitudinal direction thereof is along the circumferential direction, and these eight permanent magnets 11 form eight magnetic poles. It has become. That is, the rotor 1 of this embodiment is an embedded magnet type synchronous motor, and can use both the reluctance torque caused by the magnetization of the rotor core 5 and the magnet torque caused by the magnetization of the permanent magnet 11.

  The soft magnetic ring member 7 includes a binder resin 27 (for example, polyamide (PA12, etc.), polyphenylene sulfide (PPS), etc.) and a soft magnetic material powder 17 (for example, pure iron, iron silicon, permalloy, etc.). As will be described later, after the binder resin 27 (resin material) and the soft magnetic material powder 17 are mixed and compounded, the soft magnetic material powder 17 is subjected to orientation magnetic field injection molding with a mold 9 in which the rotor core 5 is installed. The inner peripheral surface of the magnetic ring member 7 and the outer peripheral surface of the rotor core 5 are bonded with a binder resin 27.

  By the way, in the embedded magnet type synchronous motor, the permanent magnet embedded in the rotor core generates a magnetic flux semi-permanently to the outside. Cogging torque (pulsation torque) is generated, and this cogging torque acts on the torque (reluctance torque and magnet torque) generated by the motor in an energized state, thereby increasing the noise and vibration of the motor. is there. In order to suppress the cogging torque, for example, it is conceivable to increase the number of poles. However, if the number of magnetic poles is increased, there is a problem in that the number of switching of the inverter is increased, resulting in an increase in inverter loss.

Therefore, in the rotor 1 of this embodiment, the soft magnetic material powder 17 contained in the soft magnetic ring member 7 are bonded by the binder resin 27 with its axis of easy magnetization is oriented to face in a predetermined direction ing. Specifically, each soft magnetic material powder 17 has an easy axis of magnetization at a portion of the soft magnetic ring member 7 corresponding to a position between adjacent permanent magnets 11 among the eight permanent magnets 11. 3, in other words, a portion of the soft magnetic ring member 7 that covers a fan-shaped portion between one magnetic pole center line 5 c and the adjacent magnetic pole center line 5 c of the rotor core 5 along an arc that protrudes toward the substantial center of the rotor 3. 2 are oriented along an arc that curves inward in the radial direction (see arrows in FIGS. 2 and 4). The “magnetization easy axis” in the present embodiment does not mean only “a crystal orientation easily magnetized in a magnetic material having crystal magnetic anisotropy” (hereinafter referred to as “magnetization easy axis”). In addition, it means the “axis in which the direction of magnetization in the magnetic material is easily oriented” including the shape magnetic anisotropy more broadly.

  More specifically, as shown in FIG. 3, each soft magnetic material powder 17 (soft magnetic material particles) is granulated into an elliptical shape having a major axis (major axis) and a minor axis (minor axis). The magnetic characteristics depend on the shape magnetic anisotropy without depending on the magnetocrystalline anisotropy. In other words, each soft magnetic material powder 17 has a major axis direction that is a magnetization direction (long axis coincides with the easy magnetization axis) even if a narrowly defined easy axis is taken into account, and a magnetic flux is generated in the major axis direction. It is easy to flow.

  Thus, in the soft magnetic ring member 7, as viewed from the axial direction, the soft magnetic ring member 7 protrudes toward the substantial center of the rotor shaft 3 at a portion corresponding to between the adjacent permanent magnets 11. By applying an orientation magnetic field parallel to the arc using the orientation electromagnet 25 at the time of forming the rotor core 5, as shown in FIG. 4, each soft magnetic material powder 17 has a long axis along each arc. The magnetic material powder 17 is oriented. In FIG. 4, only a part of the soft magnetic material powder 17 is shown for easy understanding of the drawing, but the soft magnetic material powder 17 (not shown) is also oriented so that its major axis is along an arc. In this state, it is bonded with a binder resin 27.

  Thus, by orienting the soft magnetic material powder 17 so that its long axis is along the arc, the soft magnetic ring member 7 makes it easier for magnetic flux to flow in the direction indicated by the arrows in FIGS. Since magnetic anisotropy is imparted to the outer peripheral surface of the rotor core 5, the magnetic flux density waveform (the magnetic flux density distribution of the gap) on the outer peripheral surface of the rotor core 5 is the same as when a ring-shaped bonded magnet is magnetized with polar anisotropy. ) Can be approximated to a sine wave.

  Therefore, as shown in FIG. 5, the case of the rotor 1 of the present embodiment (solid line a in FIG. 5) is compared with the case of the conventional rotor in which the bonded magnet member 7 is not provided (broken line b in FIG. 5). In other words, the steep change in the magnetic flux density can be suppressed, in other words, the gradient of the magnetic flux change can be made smooth, and the cogging torque can be greatly reduced. As a result, the vibration reduction and noise of the embedded magnet type synchronous motor can be reduced. Reduction can be realized.

-Rotor manufacturing method-
Next, a method for manufacturing the rotor 1 of the rotating electrical machine according to the present embodiment will be described based on the flowchart shown in FIG.

  First, in step S1, a substantially annular soft magnetic steel sheet 15 having a circular opening 15a formed in the central portion and eight rectangular openings 15b formed at equal intervals in the outer peripheral portion is punched out with a press, and the soft magnetic The steel plate 15 is laminated and integrated so that the circular opening 15a and the rectangular opening 15b are continuous in the axial direction, and the rotor core 5 is formed.

  In the next step S2, the soft magnetic material powder 17 and the binder resin 27 are mixed and compounded.

  Next, a mold 9 is prepared. As shown in FIG. 7, the mold 9 includes a fixed mold 19 having a ring-shaped protruding portion 19a, and a bottomed cylindrical movable mold 29 having a cylindrical portion 29a at the center. The distal end of the cylindrical portion 29a is inserted into a portion 19b that is relatively recessed by the portion 19a, and the cylindrical portion 29b of the movable mold 29 is externally fitted to the ring-shaped protruding portion 19a so that the fixed mold 19 and the movable mold 29 are fitted. Are combined to form a substantially cylindrical cavity 9a. Further, eight gate portions 13 are formed through the outer peripheral portion of the ring-shaped protrusion 19a of the fixed mold 19, and these eight gate portions 13 are composed of compounded soft magnetic material powder 17 and Each is connected to an injection unit 23 for injecting the binder resin 27.

  In step S3, the cylindrical portion 29a is inserted into the central through hole 5a of the rotor core 5 and the mold 9 is clamped to place the rotor core 5 in the cavity 9a formed in the mold 9 ( Installation process). As a result, a ring-shaped space 9b where the eight gate portions 13 face is formed around the rotor core 5 installed in the cavity 9a.

  In the next step S4, as shown in FIG. 8, eight orienting electromagnets are positioned outside the mold 9 and radially opposite to each through hole 5b of the rotor core 5 installed in the cavity 9a. 25 is arranged. Thus, an orientation magnetic field parallel to an arc projecting toward the substantial center of the rotor shaft 3 is applied from the eight orientation electromagnets 25 at a portion corresponding to between the adjacent permanent magnets 11 in the soft magnetic ring member 7. While being applied, the material compounded in step S2 is injected from the gate portion 13 into the cavity 9a, and the soft magnetic ring member 7 is molded so as to cover the outer peripheral surface of the rotor core 5. In FIG. 8, the mold 9 is not shown for easy understanding of the drawing.

  The molding conditions in the magnetic field orientation injection molding are as follows. When the binder resin 27 is polyamide, the cylinder temperature is 220 to 270 (° C.), the mold temperature is 50 to 100 (° C.), and the injection pressure is 120 to 170 (MPa). ), The orientation magnetic field is preferably 5 to 15 (kOe), and when the binder resin 27 is polyphenylene sulfide, the cylinder temperature is 270 to 340 (° C.), and the mold temperature is 120 to 150 (° C.). It is desirable that the injection pressure is 130 to 180 (MPa) and the orientation magnetic field is 5 to 15 (kOe).

  When the soft magnetic material powder 17 is bonded by the binder resin 27, in step S5, the mold 9 is opened by moving the movable mold 29 away from the fixed mold 19, and the rotor core 5 and the soft magnetic ring member bonded thereto are opened. 7 is removed from the mold 9.

  In the next step S6, the rotor shaft 3 is inserted and fixed in the central through-hole 5a formed in the rotor core 5, and in the next step S7, the eight magnetized permanent magnets 11 are arranged with the N pole and the S on the radially outer side. The eight through holes 5b are inserted and fixed so that the poles are alternately arranged.

  As described above, the soft magnetic ring including the soft magnetic material powder 17 whose long axis is oriented so as to follow the arc that protrudes toward the substantial center of the rotor shaft 3 at a portion corresponding to between the adjacent permanent magnets 11. The rotor 1 of the embedded magnet type synchronous motor in which the outer peripheral surface of the rotor core 5 is covered by the member 7 can be manufactured by a simple method using magnetic field orientation injection molding.

-Effect-
According to the present embodiment, the soft magnetic material powder 17 is oriented so that its long axis is along an arc that protrudes toward the approximate center of the rotor shaft 3. Since the magnetic powder is oriented like isotropically magnetized magnet powder, magnetic anisotropy is imparted to the outer peripheral surface of the rotor core 5 and the magnetic flux density waveform on the outer peripheral surface of the rotor core 5 approaches a sine wave. As a result, a steep change in the air gap magnetic flux density between the rotor 1 and the stator can be suppressed, and the cogging torque can be reduced.

(Other embodiments)
The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

  In the above embodiment, the rotor core 5 and the soft magnetic ring member 7 are integrated in the magnetic field orientation injection molding. However, the present invention is not limited to this, and for example, the rotor core 5 and the soft magnetic ring member 7 are separately provided. As shown in FIG. 9, the rotor core 5 is inserted into the soft magnetic ring member 7 and the outer peripheral surface of the rotor core 5 and the inner peripheral surface of the soft magnetic ring member 7 are joined using an adhesive or the like. Good.

  In the above embodiment, polyamide and polyphenylene sulfide are used as the binder resin 27, pure iron, iron silicon and permalloy are used as the soft magnetic material powder 17, and Nd sintered magnet and ferrite are used as the permanent magnet 11. These are merely examples, and other binder resins, soft magnetic material powders, and permanent magnets may be used.

  Further, in the above embodiment, the magnetic properties of the soft magnetic material powder 17 are made to depend on the shape magnetic anisotropy without depending on the crystal magnetic anisotropy. In other words, it may depend on the magnetocrystalline anisotropy, in other words, the axis in which the direction of magnetization in the soft magnetic material powder 17 is easily oriented may coincide with the easy magnetization axis in a narrow sense.

  As described above, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, the present invention includes a rotating shaft member serving as a rotation center and a substantially cylindrical rotor core provided on the outer side thereof, and a plurality of permanent magnets are arranged at substantially equal intervals on the outer periphery of the rotor core. This is useful for a rotor of a rotating electrical machine provided.

1 Rotor 3 Rotor shaft (Rotating shaft member)
5 Rotor core 7 Soft magnetic ring member 11 Permanent magnet 15 Soft magnetic steel plate 17 Soft magnetic material powder 27 Binder resin (resin material)

Claims (3)

A rotation shaft member serving as a rotation center, and a substantially cylindrical rotor core provided on the outer side of the rotation shaft member and having a substantially annular soft magnetic steel plate laminated in the axial direction of the rotation shaft member. A rotor structure of a rotating electrical machine in which a plurality of permanent magnets extending in the axial direction of the rotary shaft member are arranged at substantially equal intervals in the circumferential direction of the rotor core on the outer peripheral portion,
A soft magnetic ring member including a soft magnetic material powder having a magnetization easy axis and a resin material covering the outer peripheral surface of the rotor core;
Each soft magnetic material powder has an easy magnetization axis between adjacent permanent magnets among the plurality of permanent magnets in the soft magnetic ring member so that the magnetic flux density waveform on the outer peripheral surface of the rotor core approaches a sine wave. A rotor structure of a rotating electrical machine, wherein the resin material is bonded in a state where the resin material is oriented along a circular arc protruding toward a substantially center of the rotating shaft member . A rotation shaft member serving as a rotation center, and a substantially cylindrical rotor core provided on the outer side of the rotation shaft member and having a substantially annular soft magnetic steel plate laminated in the axial direction of the rotation shaft member. A rotor structure of a rotating electrical machine in which a plurality of permanent magnets extending in the axial direction of the rotary shaft member are arranged at substantially equal intervals in the circumferential direction of the rotor core on the outer peripheral portion,
A soft magnetic ring member including a soft magnetic material powder having a magnetization easy axis and a resin material covering the outer peripheral surface of the rotor core;
Each of the soft magnetic material powders has an easy magnetization axis at a portion of the soft magnetic ring member corresponding to the adjacent permanent magnets of the plurality of permanent magnets, toward the approximate center of the rotating shaft member. A rotor structure of a rotating electrical machine, wherein the rotor is bonded by the resin material in a state of being oriented along a protruding arc. In the rotor structure of the rotating electrical machine according to claim 1 or 2,
Each of the soft magnetic material powders has a major axis and a minor axis, and a major axis direction coincides with an easy magnetization axis.

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