Variable field rotor

Abstract

To reduce magnetic flux by a rotor 1 of a rotary electric machine, in which a permanent magnet 2 is placed, in the case of a high rotation speed region more than in the case of a low rotation speed region without requiring field weakening control in the rotor.SOLUTION: In a rotor formed of an electromagnetic steel plate, a hole portion 3 accommodating a permanent magnet and a movable piece is formed, the movable piece 4 is displaceable in a radial direction of the rotor in the hole portion, centrifugal force by rotation of the rotor acts so as to displace the movable piece outward in a radial direction, magnetic force of the permanent magnet acts to displace the movable piece inward in the radial direction, both side surfaces of the permanent magnet in a circumferential direction of the rotor abut on each of a wall surface of the hole portion and the movable piece when action of centrifugal force received by the movable piece is smaller than action of the magnetic force, a gap is formed on one of both side surfaces of the permanent magnet in the circumferential direction of the rotor when action of the centrifugal force received by the movable piece is larger than action of the magnetic force, and magnetic flux Φ by the rotor is reduced more than when the action of the centrifugal force received by the movable piece is smaller than the action of the magnetic force.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotor for a permanent magnet type rotating electric machine, and more particularly to a rotor in which magnetic flux is reduced in the high rotation speed range. [Background technology]

[0002] In permanent magnet rotating electrical machines that use permanent magnets in the rotor, "field weakening control" is sometimes performed to suppress motor induced voltage (back electromotive force) at high rotation speeds. This control passes current through the coil to generate magnetic flux in the opposite direction to the magnetic velocity of the rotor magnet. However, this field weakening control reduces efficiency because it passes current that does not contribute to driving. Therefore, a configuration has been proposed that reduces the magnetic flux from the rotor magnet at high rotation speeds without relying on field weakening control. For example, Patent Document 1 proposes a configuration in which a moving field magnet part has magnetic poles of different polarities arranged sequentially in the direction of rotation on the surface of the rotor, and a yoke part of the rotor core that forms a magnetic path inside the field magnet and is fixed to the shaft, and a centrifugal mechanism is provided inside the moving field magnet part that automatically changes the position of the moving field magnet part in the direction of rotation relative to the yoke part in accordance with the rotation speed of the rotor, and the field magnetic flux that links to the stator windings is changed by changing the position of the moving field magnet part in the direction of rotation relative to the yoke part in accordance with the rotation speed of the rotor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2006-6026 Summary of the Invention [Problem to be solved by the invention]

[0004] Motor rotors for electric vehicles mainly use IPM (Interior Permanent Magnet) rotors with permanent magnets inside the rotor. Conventional IPM rotors have a structure in which permanent magnets 2 are embedded in holes 3 that are approximately complementary to the shape of rotor 1, as shown in Figure 3. This means that the magnetic flux Φ generated by the rotor is constant regardless of the rotation speed range (low ω, high ω), and reduction of rotor magnetic flux at high rotation speeds has been achieved by field-weakening control as described above. Therefore, it would be advantageous if an IPM rotor could achieve reduction of rotor magnetic flux at high rotation speeds without relying on field-weakening control by passing current through the stator coil.

[0005] Thus, the main object of the present invention is to provide a rotor having a permanent magnet disposed therein, which is configured so that the magnetic flux generated by the rotor in the high rotation speed range can be reduced more than in the low rotation speed range, without requiring additional energy such as the field weakening control described above. [Means for solving the problem]

[0006] According to the present invention, the above-mentioned problem is solved by providing a rotor for a permanent magnet type rotating electric machine, which is made of an electromagnetic steel plate and has a permanent magnet disposed therein, wherein a hole is formed in the rotor and houses the permanent magnet and a movable piece made of an electromagnetic steel plate adjacent thereto, the hole has a volume larger than the sum of the volumes of the permanent magnet and the movable piece, the movable piece is displaceable in the radial direction of the rotor within the hole, and centrifugal force due to rotation of the rotor acts to displace the movable piece outward in the radial direction, and the magnetic force of the permanent magnet moves the movable piece This is achieved by a rotor configured such that when the centrifugal force acting on the movable piece is smaller than the magnetic force, both circumferential side surfaces of the permanent magnet of the rotor abut against the wall surfaces of the hole and the movable piece, respectively, and when the centrifugal force acting on the movable piece is larger than the magnetic force, a gap is formed on one of both circumferential side surfaces of the permanent magnet of the rotor, so that the magnetic flux from the rotor is reduced more than when the centrifugal force acting on the movable piece is smaller than the magnetic force.

[0007] In the above configuration, the "permanent magnet" and the magnetic steel sheets forming the rotor and the movable piece may be those commonly used in this field, and the shape and dimensions of the permanent magnet may be those commonly used in IPM rotors.

[0008] The rotor of the present invention is basically an IPM rotor, and as described above, the holes that house the permanent magnets also house movable pieces made of electromagnetic steel plates, and the movable pieces are displaceable in the radial direction of the rotor. The centrifugal force caused by the rotation of the rotor acts to displace the movable pieces radially outward of the rotor, and the magnetic force of the permanent magnets acts to displace the movable pieces radially inward of the rotor. With this configuration, the movable pieces remain displaced radially inward of the rotor while the centrifugal force acting on them is smaller than the magnetic force, but as the rotor speed increases and the centrifugal force acting on the movable pieces becomes greater than the magnetic force, they are displaced radially outward of the rotor. The permanent magnet and the movable piece are arranged so that when the movable piece is displaced radially inward of the rotor, one of the two circumferential side surfaces of the permanent magnet abuts against the wall surface made of electromagnetic steel sheet of the hole, and the other abuts against the movable piece, while when the movable piece is displaced radially outward of the rotor, a gap is formed on one of the two circumferential side surfaces of the permanent magnet. In this way, at low rotation speeds of the rotor, the magnetic flux penetrates the rotor as both circumferential side surfaces of the permanent magnet abut against the electromagnetic steel sheet layers, but at high rotation speeds of the rotor, a gap is formed on one circumferential side surface of the permanent magnet, and the magnetic permeability is reduced, thereby making it possible to reduce the magnetic flux of the rotor at high rotation speeds of the rotor without requiring the additional energy required for field-weakening control.

[0009] In the above configuration, the permanent magnet may or may not be movable within the hole. The shapes of the hole and the movable piece may be arbitrary, for example, the fan-shaped hole may be formed so that both ends are shifted in the radial direction of the rotor, and the movable piece may be similarly formed in a roughly fan shape, with its main portion pivotally fixed to the wall of the hole, and placed within the hole so that the center of gravity of the movable piece is shifted in the radial direction of the rotor.

[0010] In the above configuration, a spring mechanism may be provided that applies a biasing force to displace the movable piece radially outward or inward of the rotor, thereby making it possible to adjust the force that displaces the movable piece radially of the rotor. [Effects of the Invention]

[0011] Thus, according to the present invention, in a so-called IPM rotor, it is possible to reduce the rotor's magnetic flux at high rotation speeds more than at low rotation speeds, without using field-weakening control, which requires additional energy. Furthermore, the configuration of the present invention can reduce the rotor's magnetic flux at high rotation speeds without using additional energy, thereby suppressing the motor's induced voltage, which is expected to improve the energy efficiency of rotating electric machines. The configuration of the present invention may be employed in rotating electric machines for driving electric vehicles and other rotating electric machines for any other machinery and equipment.

[0012] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are schematic cross-sectional views of a rotor of a rotating electric machine to which a first aspect of this embodiment is applied, viewed along the direction of the rotation axis. (A) shows the low rotation speed range, and (B) shows the high rotation speed range. Permanent magnets are arranged along the entire circumference of the rotor, but only a portion of them is shown in the figure. [Figure 2] 2A and 2B are schematic cross-sectional views of a rotor of a rotating electric machine to which a second aspect of this embodiment is applied, viewed along the direction of the rotation axis. (A) shows the low rotation speed range, and (B) shows the high rotation speed range. The permanent magnets are arranged along the entire circumference of the rotor, but only a portion of them is shown in the figure. [Figure 3] 3 is a schematic cross-sectional view of a rotor of a conventional rotating electric machine, viewed along the direction of the rotation axis. The permanent magnets are arranged along the entire circumference of the rotor, but only a portion of them is shown in the figure. [Explanation of symbols]

[0014] 1... rotor, 2... permanent magnet, 3... hole, 4... moving piece, 5... main part, 6... gap BEST MODE FOR CARRYING OUT THE INVENTION

[0015] 1(A) and 1(B), in the rotor 1 of the rotating electric machine (not shown) according to this embodiment, basically, as in a conventional IPM rotor, permanent magnets 2 are housed in holes 3 formed in a rotor core made of electromagnetic steel plate, and in addition to the permanent magnets 2, a movable piece 4 is also housed in the hole 3. The movable piece 4 is made of electromagnetic steel plate, just like the rotor core, and is disposed in the hole 3 so that its center of gravity can be displaced in the radial direction of the rotor. Therefore, the volume of the hole 3 is larger than the sum of the volumes of the permanent magnets 2 and the movable piece 4. More specifically, in the embodiment illustrated in FIG. 1, when viewed in a cross section perpendicular to the central axis of the rotor, the permanent magnets 2 are formed rectangular, and the movable piece 4 is formed approximately fan-shaped, and the movable piece 4 may be fixed to a pivot point 5 of the fan shape together with the permanent magnets 2 so as to be pivotable. The cross section of the hole 3 may be formed in a fan shape with an opening angle at the main part 5 larger than that of the fan shape of the movable piece 4, and the positions of both ends of the arc part are arranged to be offset in the radial direction of the rotor. The arc part of the movable piece 4 may be formed to slide on the arc part of the hole 3. The permanent magnet 2 is arranged in the hole 3, radially inward of the movable piece 4.

[0016] 1(A), when the rotor speed in the rotating electric machine is low (low ω), the centrifugal force acting on the movable piece 4 is small, so the magnetic force of the permanent magnet 2 attracts the movable piece 4 to the permanent magnet 2, causing their side surfaces (perpendicular to the circumferential direction of the rotor) to come into contact, and the opposite side surface of the permanent magnet 2 is also attracted by the magnetic force to come into contact with the wall surface of the hole 3, so that both side surfaces of the permanent magnet 2 perpendicular to the circumferential direction of the rotor come into contact with the layer made of electromagnetic steel sheet, and the magnetic permeability around the permanent magnet 2 becomes higher (than that of air). This results in a correspondingly stronger magnetic flux Φ penetrating from the permanent magnet 2 to the rotor.

[0017] On the other hand, as shown in FIG. 1(B), as the rotor speed of the rotating electric machine increases (ω high), the centrifugal force acting on the movable piece 4 and permanent magnet 2 increases. This centrifugal force overcomes the magnetic force of the permanent magnet 2, displacing the movable piece 4 and permanent magnet 2 within the hole 3 so that their centers of gravity move radially outward (arrow x). This causes the permanent magnet 2 to move away from the wall of the hole 3, forming an air gap 6 between them. This reduces the magnetic permeability around the permanent magnet 2, and the magnetic flux Φ penetrating from the permanent magnet 2 to the rotor is reduced compared to the low rotation speed range shown in FIG. 1(A). Then, as the rotor rotation speed decreases, the movable piece 4 and permanent magnet 2 are pulled back radially inward by the magnetic force of the permanent magnet 2. Both sides of the permanent magnet 2 perpendicular to the rotor circumferential direction come into contact with the layers made of electromagnetic steel sheets, and the self-saturation Φ increases again. Thus, with the above configuration, when the rotor rotation speed is high, the magnetic flux generated by the rotor is reduced compared to when the rotor rotation speed is low, and when the rotor rotation speed is reduced, the magnetic flux generated by the rotor is increased.

[0018] Although not shown, a spring mechanism may be provided that applies a force in a direction returning the movable piece 4 and the permanent magnet 2 to the state shown in Fig. 1(A). In this case, it becomes possible to adjust the balance between the force acting on the movable piece 4 and the permanent magnet 2 radially outward from the rotor and the force acting on the movable piece 4 and the permanent magnet 2 radially inward from the rotor.

[0019] In another aspect of this embodiment, as shown in Figures 2(A) and 2(B), the position of the permanent magnet 2 may be fixed regardless of the rotor rotation speed, and only the movable piece 4 may be displaced depending on the rotor rotation speed. In the case of the figures, when the rotor rotation speed increases, as shown in Figure 2(B), the side surface of the movable piece 4 and the side surface of the permanent magnet 2 are separated from each other, forming a gap 6, reducing the magnetic permeability around the permanent magnet 2 and reducing the magnetic flux Φ passing from the permanent magnet 2 to the rotor compared to the case of the low rotation speed range of Figure 2(A).

[0020] Thus, according to the configuration of this embodiment, the holes 3 that house the permanent magnets 2 in the rotor are formed larger than usual, and the movable piece 4 made of electromagnetic steel plate is housed in the holes 3 adjacent to the permanent magnets 2. The centrifugal force generated by the rotor rotation displaces the movable piece 4, thereby varying the magnetic permeability around the permanent magnets 2, thereby achieving a reduction in rotor magnetic flux at high rotation speeds. With this configuration, the increase or decrease in rotor magnetic flux is due to the centrifugal force generated by the rotor rotation, and does not require additional energy as in field-weakening control that requires current to flow through a coil, so improved energy efficiency is expected.

[0021] The above description has been made in relation to the embodiments of the present invention, but it will be apparent that many modifications and changes will be readily apparent to those skilled in the art, and the present invention is not limited to the above-described exemplary embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A rotor for a permanent magnet type rotating electric machine is formed from an electromagnetic steel plate and has a permanent magnet disposed therein, the rotor having a hole formed therein that houses the permanent magnet and a movable piece made of an electromagnetic steel plate adjacent thereto, the hole having a volume greater than the sum of the volumes of the permanent magnet and the movable piece, the movable piece being displaceable in the radial direction of the rotor within the hole, and centrifugal force due to rotation of the rotor acts to displace the movable piece radially outward, and the magnetic force of the permanent magnet moves the movable piece radially outward. when the centrifugal force acting on the movable piece is smaller than the magnetic force, both side surfaces of the permanent magnet in the circumferential direction of the rotor abut against the wall surfaces of the hole and the movable piece, respectively; when the centrifugal force acting on the movable piece is larger than the magnetic force, a gap is formed on one of both side surfaces of the permanent magnet in the circumferential direction of the rotor, so that the magnetic flux of the rotor is reduced more than when the centrifugal force acting on the movable piece is smaller than the magnetic force.

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