Rotor core

Abstract

The purpose of this invention is to provide a rotor core capable of suppressing air gap formation and rotating efficiently. The rotor core comprises: an inner core with magnet insertion holes; and an outer core covering the outer peripheral surface of the inner core. The saturation magnetic flux density of the outer core is lower than that of the inner core. By forming the outer core with a magnetic material, the formation of an air gap between the rotor core and the stator can be suppressed. Furthermore, the lower saturation magnetic flux density of the outer core compared to the inner core helps to suppress short circuits in the magnetic flux.

Description

Technical Field

[0001] This utility model relates to a rotor core. Background Technology

[0002] Conventionally, rotors are known to utilize non-magnetic components to cover the outer periphery of a rotor core with magnet insertion holes (for example, see Patent Document 1). Patent Document 1 improves the strength of the rotor core by placing non-magnetic components on its outer periphery. This increased strength allows the rotor core to withstand centrifugal forces. Furthermore, motors using such rotor cores can achieve high-speed rotation.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-174899

[0004] However, in Patent Document 1, the non-magnetic component is positioned opposite the stator, which is located outside the rotor core. Therefore, the air gap between the rotor core and the stator widens. This widening of the air gap is detrimental to improving the motor's output. Utility Model Content

[0005] Therefore, the purpose of this invention is to provide a rotor core that can suppress the generation of air gaps and rotate efficiently.

[0006] The above objective is achieved by a rotor core comprising: an inner core having a magnet insertion hole; and an outer core covering the outer peripheral surface of the inner core, wherein the saturation magnetic flux density of the outer core is less than that of the inner core.

[0007] It can provide a rotor core that can suppress the formation of air gaps and rotate efficiently. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating the configuration of a rotary electric motor with a rotor core having an embodiment.

[0009] Figure 2 (A) is an explanatory diagram of a rotor having a rotor core with an embodiment. Figure 2 (B) is an enlarged view of a portion of the rotor core of the embodiment.

[0010] Figure 3 (A-1) is a perspective view of the outer core of the embodiment. Figure 3 (A-2) is a perspective view of the outer core of the first modified example. Figure 3 (B) is a perspective view of the outer core of the second variation. Figure 3 (C) is a three-dimensional view representing the outer core of the third variation. Detailed Implementation

[0011] (Implementation Method)

[0012] Figure 1 The rotary electric motor 10 shown has a stator 12 and a rotor 14 concentrically arranged inside the stator 12.

[0013] The stator 12 has a generally cylindrical stator core 18 with multiple teeth (not shown) formed on its inner circumference and stator coils 20 wound around each tooth. The stator 12 consists of three phases: U-phase, V-phase, and W-phase, and the stator coils 20 are wound in a distributed manner (not shown). The stator core 18 has 24 slots in the circumferential direction, and coils are arranged in the slots. That is, the rotary motor 10 of this embodiment forms an 8-pole, 24-slot motor. However, the form of the motor is not limited to this, and various forms known in the art can be used.

[0014] A rotating shaft 16 is fixed at the center of the rotor 14. The rotor 14 has a rotor core 30 and permanent magnets 34 embedded in the rotor core 30. That is, the rotary motor 10 is a permanent magnet synchronous rotary motor, also known as an IPM (Interior Permanent Magnet) motor. An even number of magnets (in the q-axis) are formed on the rotor 14 at equal intervals along the circumference. Figure 2 There are 8 magnetic poles in the middle. The polarity of the even number of magnetic poles 2 alternates and reverses in the circumferential direction.

[0015] The rotor core 30 has an inner core 32 and a surface 32b covering its outer periphery (see reference). Figure 1 , Figure 2 ) of the outer core 38.

[0016] The inner core 32 is formed of a magnetic material, and each magnetic pole 2 has a center bridge 36. In each magnetic pole 2, the d-axis extends radially through the center of the center bridge 36. Each magnetic pole 2 has a circumferentially symmetrical structure across the d-axis. Therefore, the inner core 32 has magnet insertion holes 32a arranged symmetrically with respect to the center bridge 36 and adjacent in the circumferential direction at each magnetic pole 2. A pair of adjacent magnet insertion holes 32a have shapes that are reversed relative to the d-axis. Although the pair of magnet insertion holes 32a have reversed shapes, their structures are common. Therefore, a pair of magnet insertion holes 32a... Figure 2 (A) and Figure 2 The same reference number is marked in (B) to indicate this.

[0017] The magnet insertion hole 32a has a magnet insertion part 32a1. A permanent magnet 34 is inserted into the magnet insertion part 32a1.

[0018] The magnet insertion hole 32a has a first air hole 32a2 on the side farther from the central bridge 36 than the magnet insertion portion 32a1, that is, on the side closer to the q-axis. The outer periphery of the inner core 32 of the first air hole 32a2 is open. However, the inner core 32 may also be formed with an outer peripheral bridge on the radially outer side of the first air hole 32a2 to close the first air hole 32a2. The magnet insertion hole 32a has a second air hole 32a3 on the side closer to the central bridge 36 than the magnet insertion portion 32a1, that is, on the side closer to the d-axis. The first air hole 32a2 and the second air hole 32a3 can be gaps, or they can be filled with resin. By filling the first air hole 32a2 and the second air hole 32a3 with resin, the permanent magnet 34 is fixed. In addition, the strength of the inner core 32 is improved.

[0019] The outer core 38 is formed of a magnetic material and can be in any form as long as it covers the outer peripheral surface 32b of the inner core 32. For example, ... Figure 3 As shown in (A-1), a first cylindrical component 38a can also be prepared and disposed on the outside of the inner core 32. The first cylindrical component 38a is formed of a magnetic material. The axial dimension of the first cylindrical component 38a corresponds to the axial dimension of the inner core 32. That is, the first cylindrical component 38a has no axial seam and can cover the entire area of ​​the outer peripheral surface 32b of the inner core 32 independently. The first cylindrical component 38a is integrated with the inner core 32 by press-fitting or thermoforming to form the outer core 38.

[0020] The outer core 38 is formed of a magnetic material. Therefore, air gaps between the core and the stator 12, which are arranged around the rotor 14, are less likely to occur. By suppressing air gap formation, the rotor 14 can rotate efficiently. As a result, the efficiency of the rotary motor 10 can be improved. Consequently, the rotational speed of the rotary motor 10 can be increased, or the rotary motor 10 can be miniaturized.

[0021] Here, the saturation magnetic flux density of the outer core 38 will be explained. Both the inner core 32 and the outer core 38 are formed of magnetic material. However, the saturation magnetic flux density of the outer core 38 is lower than that of the inner core 32. That is, the outer core 38 has a lower magnetic flux density compared to the inner core 32. Therefore, short circuits in the magnetic flux of the outer core 38 can be suppressed. As a result, the rotor 14 can rotate efficiently, and the efficiency of the rotary motor 10 can be improved. Consequently, the rotational speed of the rotary motor 10 can be increased, or the amount of magnets can be reduced to miniaturize the rotary motor 10.

[0022] Next, the strength of the outer core 38 will be explained. The outer core 38 is formed of a magnetic material. The mechanical strength of the outer core 38 is higher than that of the inner core 32, which is also formed of a magnetic material. As a result, the overall strength of the rotor core 30 can be improved. With the increased strength, the rotor core 30 can cope with a higher rotational range of the rotary motor 10. In addition, the strength of the rotor core 30 is compensated by providing the outer core 38. Therefore, the width of the center bridge 36 can be narrowed or eliminated, or, as in this embodiment, the first air hole 32a2 can be made into an open shape. As a result, short circuits of magnetic flux can be suppressed, which in turn allows the rotor 14 to rotate efficiently, and the efficiency of the rotary motor 10 can be improved.

[0023] The inner core 32 and the outer core 38 can be appropriately selected to combine magnetic materials that satisfy the relationship between mechanical strength and saturation magnetic flux density.

[0024] Furthermore, the rotary motor 10 in this embodiment is an IPM motor, but it can also be based on an SPM (Surface Permanent Magnet) motor with an outer core provided on the outer periphery of the SPM motor.

[0025] (Modified Example)

[0026] Here, a modified example of the outer core will be explained. First, refer to... Figure 3 (A-2) describes a first modified example. In this first modified example, instead of the first cylindrical member 38a, the outer core 38 is formed by a plurality of second cylindrical members 38b. The first cylindrical member 38a has an axial dimension capable of individually covering the entire area of ​​the outer peripheral surface 32b of the inner core 32. The axial dimension of the second cylindrical members 38b is shorter than that of the first cylindrical member 38a. Figure 3 In the example shown in (A-2), the outer peripheral surface 32b of the inner core 32 is covered by stacking three second cylindrical components 38b. The magnetic material forming the second cylindrical components 38b is selected to be the same as the magnetic material forming the first cylindrical component 38a. That is, the material for the second cylindrical components 38b is selected to have a saturation magnetic flux density of the outer core 38 that is lower than that of the inner core 32. Similar to the first cylindrical component 38a, the stacked second cylindrical components 38b are integrated with the inner core 32 by pressing or thermoforming. Thus, the outer core 38 can be formed in the same way as the first cylindrical component 38a. The number of stacked second cylindrical components 38b can be appropriately selected.

[0027] Next, refer to Figure 3(B) will describe the outer core 48 of the second modification. The outer core 48 of the second modification is formed by winding a thin plate member 48a of width W around the outer peripheral surface 32b of the inner core 32 while applying a tight force. The thin plate member 48a is formed of the same magnetic material selected as the first cylindrical member 38a. The thin plate member 48a is configured such that the direction of its width W is aligned with the axial direction of the inner core 32. The thin plate member 48a can be a single layer or wound in a manner that makes it multi-layered in the radial direction. The ends of the thin plate member 48a in the longitudinal direction are joined by using adhesive material or by welding. The ends of the thin plate member 48a in the longitudinal direction can also be joined by riveting. The thin plate member 48a does not require a heated hot-press fitting during assembly. This reduces manufacturing costs. The outer core 48 of the second modification achieves the same effects as the outer core 38.

[0028] Next, refer to Figure 3 Section (C) describes the outer core 58 of the third modification. The outer core 58 of the third modification is formed by winding a strip-shaped or wire-shaped winding member 58a around the outer peripheral surface 32b of the inner core 32 while applying a tight force. The winding member 58a is formed of the same magnetic material selected as the first cylindrical member 38a. The winding member 58a is wound around the outer peripheral surface 321b of the inner core 32 in a manner that moves along the axial direction of the inner core 32. The winding member 58a can be a single layer or multiple layers in the radial direction. The ends of the winding member 58a in the longitudinal direction are joined by using adhesive material or by welding. The ends of the winding member 58a in the longitudinal direction can also be joined by riveting. The winding member 58a does not require a heated hot-press fitting during assembly. This reduces manufacturing costs. The outer core 58 of the third modification achieves the same effects as the outer core 38.

[0029] [Effect]

[0030] The rotor core 30 of this embodiment includes an inner core 32 with a magnet insertion hole 32a and an outer core 38 (48, 58) covering the outer peripheral surface 32b of the inner core 32. Furthermore, the saturation magnetic flux density of the outer core 38 (48, 58) is lower than that of the inner core 32. By forming the outer core 38 (48, 58) with a magnetic material, the generation of an air gap with the stator 12 can be suppressed. Additionally, by making the saturation magnetic flux density of the outer core 38 (48, 58) lower than that of the inner core 32, short circuits in the magnetic flux within the outer core 38 (48, 58) can be suppressed. Therefore, the rotor 14 can rotate efficiently.

[0031] The embodiments of the present utility model have been described in detail above, but the present utility model is not limited to the specific embodiments described above. Various modifications and alterations can be made within the scope of the spirit of the present utility model as described in the scope of protection claimed in this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 2…Magnetic pole; 10…Rotating motor; 12…Stator; 14…Rotor; 18…Stator core; 20…Stator coil; 30…Stator core; 32…Inner core; 32a…Magnet insertion hole; 32a1…Magnet insertion part; 32a2…First air hole; 32a3…Second air hole; 32b…Outer peripheral surface; 34…Permanent magnet; 36…Center bridge; 38, 48, 58…Outer core; 38a…First annular component; 38b…Second annular component; 48a…Sheet component; 58a…Winding component.

Claims

1. A rotor core comprising: an inner core having a magnet insertion hole; and an outer core covering the outer peripheral surface of the inner core, wherein, The saturation magnetic flux density of the outer core is less than that of the inner core.

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