Rotor core and rotating electric machine

Abstract

A rotor core of a rotary electric machine according to the present application is capable of adjusting the flow of magnetic flux at the tip of a tooth. The rotor core of the rotary electric machine is provided with a slot portion in which a coil is wound, and a tooth portion that forms a space in which the coil is wound in the slot portion, a boundary portion of the inner peripheral side of the tooth portion with the slot portion being formed by a flat portion and a curved portion, the flat portion being formed in a straight line perpendicular to the radial direction, the curved portion being formed in a curved line continuous with the flat portion via a corner provided at the boundary with the flat portion, the curved portion being located at a position closer to the tip than the flat portion in the circumferential direction of the tooth portion.

Description

Technical Field

[0001] This invention relates to a rotating electric machine, represented by a DC motor, and particularly to the composition of the rotor core. Background Technology

[0002] A brushed motor energizes a coil wound on an armature core, generating torque through the interaction of the coil with the magnetic field produced by a magnet. As background technology in this field, Japanese Patent Application Publication No. 2006-280172 (Patent Document 1) provides a DC motor in which the inner center of curvature of a magnet housed within the motor housing is eccentrically positioned radially from its outer center of curvature, and the inner center of curvature of the tooth tips of the armature core is eccentrically positioned radially from its outer center of curvature towards the opposite tip (see abstract).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-280172 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In brushed motors, the torque during rotation varies with the motor's rotation angle. This torque pulsation affects the actuator's controllability and is a major cause of degraded product performance, such as worsened system response. Therefore, it is necessary to reduce cogging torque. In the aforementioned background technology, the flow of magnetic flux is adjusted by changing the shape of the tooth tips by setting an eccentricity on the inner circumference of the core slot. However, if the inner diameter eccentricity increases, the tooth tips become thinner, resulting in low freedom of adjustment of magnetic flux flow and sometimes failing to achieve the desired motor characteristics.

[0008] Technical means to solve the problem

[0009] A representative example of the invention disclosed in this application is described below. Specifically, a rotor core for a rotary electric motor is characterized by comprising: a slot for winding a coil; and a toothed portion forming a space for winding the coil in the slot, wherein the boundary portion of the inner circumference of the toothed portion with the slot is formed by a flat portion and a curved portion, the flat portion being formed as a straight line perpendicular to the radial direction, and the curved portion being formed as a curve continuous with the flat portion via an inflection point provided at the boundary with the flat portion, the curved portion being located in the circumferential direction of the toothed portion at a position closer to the top of the flat portion.

[0010] The effects of the invention

[0011] According to the present invention, the flow of magnetic flux at the tip of the tooth can be adjusted. The following description of embodiments will clarify issues, configurations, and effects beyond those described above. Attached Figure Description

[0012] Figure 1 This is a longitudinal cross-sectional view showing the structure of a DC motor according to an embodiment of the present invention.

[0013] Figure 2 This is an exploded perspective view of a DC motor according to an embodiment of the present invention.

[0014] Figure 3 This is a perspective view showing the structure of the armature core according to an embodiment of the present invention.

[0015] Figure 4 This is a cross-sectional view showing the structure of a DC motor according to an embodiment of the present invention.

[0016] Figure 5 This is a diagram illustrating the effect of the armature core in an embodiment of the present invention. Detailed Implementation

[0017] The following is for reference Figures 1-5 This describes an embodiment of a representative DC motor in rotating electrical machinery.

[0018] Figure 1 This is a cross-sectional view showing the structure of the DC motor 1 in this embodiment, showing the longitudinal section cut along axis 5. Figure 2 This is an exploded perspective view of the DC motor 1 in this embodiment.

[0019] The DC motor 1 generates rotational torque by supplying power to the external power supply terminals 26, and transmits the torque to the system side via the mounted motor gear 19. The DC motor 1 has a magnetic yoke 2, which forms a housing and a magnetic circuit. Magnetic support bars 27 and multiple magnets 3 are mounted on the inner surface of the magnetic yoke 2, and generate magnetic flux as permanent magnets. Further, an armature 4 is housed inside the magnets 3 with an arbitrary gap from the inner surface of the magnets 3. A shaft 5 connected to the motor gear 19 is provided at the radial center of the armature 4. The shaft 5 is rotatably supported on the front bracket 7 and the rear bracket 21 via bearings 6 and 20, and outputs the torque generated by the armature core 8 and the magnets 3. The front bracket 7 and the rear bracket 21 are mounted on the magnetic yoke 2. The armature 4 is constructed by fixing the armature core 8 and the commutator 9 on the shaft 5. The armature coil 11 is wound between multiple slots 10 formed on the circumferential outer periphery of the armature core 8. The commutator 9 is formed into a cylindrical shape by an insulating material such as resin, and has a plurality of commutator plates 12 made of conductive material on its outer periphery. The commutator plates 12 are electrically connected to the armature coils 11 wound between the slots 10.

[0020] A brush holder 13 is housed inside the yoke 2. At least one pair of brushes 14 and a spring 15, which supply power to the commutator segments 12, are disposed on the brush holder 13. A choke coil 16 for eliminating electromagnetic noise is also disposed on the brush holder 13. The brushes 14 are electrically connected to the external power supply terminal 26 of the DC motor 1. The brushes 14 slide in contact with the outer peripheral surface of the commutator segments 12 via the elasticity of the spring 15 held by the brush holder 13, supplying power to the armature coil 11 through the commutator segments 12. Thus, the external power supply terminal 26 is electrically connected to the armature coil 11, forming a circuit.

[0021] Figure 3 This is a perspective view showing the structure of the armature core 8 in this embodiment.

[0022] The armature core 8 is constructed by stacking soft magnetic metal plates such as electromagnetic steel plates, and has slots 10 for winding the armature coil 11 and teeth 81 that form the magnetic path through which the magnetic flux passes. The teeth 81 are T-shaped, consisting of a radial extension extending radially from the center of rotation and a circumferential extension extending laterally to the left and right at the top of the radial extension. Adjacent teeth 81 are interrupted by slot openings 82 on the outer periphery, and the slots 10 communicate radially with the outside through the slot openings 82. The armature core 8 shown in the figure is a skewed (twisted) type with inclined slot openings 82, reducing torque fluctuations accompanying the rotation of the motor.

[0023] The slot 10 is formed as the space between adjacent teeth 81, and the number of slots is the number of times the armature core 8 is divided by teeth 81 in the circumferential direction.

[0024] Figure 4 This is a cross-sectional view showing the structure of the DC motor 1 in this embodiment. The cross-section is cut in a plane perpendicular to the shaft 5, mainly showing the shape of the tooth 81.

[0025] The outer periphery of the tooth 81 is formed by a predetermined arc centered on axis 5, maintaining an arbitrary gap with the inner surface of the magnet 3. Furthermore, the inner periphery of the tooth 81 (the boundary surface of the outer periphery of the groove 10) is composed of a flat portion 83 formed as a straight line perpendicular to the radial direction of the tooth 81 and a curved portion 84 formed by a curve with a different curvature than the flat portion 83. The flat portion 83 and the curved portion 84 are continuously connected, with a curvature change inflection point 85 formed at their boundary. Viewed from the radial centerline of each tooth 81, the flat portion 83 is symmetrically formed on the inner side, and the curved portion 84 is symmetrically formed on the outer side. As described above, the flat portion 83 is ideally formed as a straight line perpendicular to the radial direction of the tooth 81, but a predetermined range of error (e.g., ±0.2 mm of unevenness or tilt) is permissible. This predetermined error can also be determined by the radial width of the circumferential extension of the tooth 81, the thickness of the electromagnetic steel plate constituting the armature core 8, etc. The curved portion 84 is formed by a surface with a curvature different from that of the flat portion 83, but ideally it is formed as a concentric circle centered on the axis of rotation.

[0026] In this embodiment, a flat portion 83 is provided on the inner side of the tip of the tooth 81, and the outer side of the inflection point 85 is formed by the curved portion 84. Therefore, the width of the circumferential extension of the tip of the tooth 81 becomes wider near the radial extension of the tooth 81 and narrower away from the radial extension. Thus, the flow of magnetic flux through the tip of the tooth 81 can be adjusted, and the tooth cogging torque can be reduced.

[0027] Furthermore, since the radial width of the portion of the circumferential extension forming a T-shape is wider near the radial extension, the magnetic flux through the armature core 8 reaches the top of the circumferential extension, suppressing the decrease in magnetic flux density at the slot opening 82 and reducing cogging torque. On the other hand, if the radial width of the circumferential extension is widened, the duty cycle of the armature coil 11 decreases, resulting in a decrease in torque. Therefore, by adjusting the range of the flat portion 83, the cogging torque is reduced, and the decrease in torque is suppressed.

[0028] Furthermore, regarding the circumferential angle range (the angle formed by the line connecting the end (inflection point 85) of the flat portion 83 and the center of rotation) θs, if the flat portion 83 is formed within the range of the following formula using the angle range occupied by each pole magnet 3 (i.e., the range in contact between the magnet 3 and the inner surface of the yoke 2) θe, the number of poles p of the magnet 3 (2 in the figure), and the number of slots s of the armature core 8 (5 in the figure), then it can be known that a reduction in cogging torque is suitable.

[0029] θs÷θα=0.5~0.7θα=θe×p÷s

[0030] In the above formula, θα is the angle obtained by dividing the angle occupied by magnet 3 in the whole circumference by the number of slots, which is a parameter representing the angle occupied by magnet 3 in each slot.

[0031] Figure 5 This diagram illustrates the effect of the armature core 8 in this embodiment, and shows the change in cogging torque as the range of the flat portion 83 changes. Figure 5 In this diagram, θs÷θα (the ratio of the range θs of the flat portion 83 to θα) is used as the horizontal axis, and the ratio of the cogging torque based on the case where the flat portion 83 is not provided (θs=θo) is used as the vertical axis.

[0032] according to Figure 5 If θα is increased from θs = θo (if the range of the flat portion 83 widens), the cogging torque decreases; the cogging torque decreases within the range of θs ÷ θα of 0.5 to 0.7. Then, if θα is increased, the cogging torque increases. Therefore, the range of θs ÷ θα of 0.5 to 0.7 is the range within which the cogging torque can be reduced.

[0033] As explained above, the boundary between the inner circumference of tooth 81 and slot 10 is formed by a flat portion 83 and a curved portion 84. The flat portion 83 is formed as a straight line perpendicular to the radial direction, and the curved portion 84 is formed as a curve that continues continuously from the flat portion 83 via an inflection point 85 at the boundary with the flat portion 83. The curved portion 84 is located at a position closer to the top of the flat portion 83 in the circumferential direction of tooth 81. Therefore, the magnetic flux at the top of tooth 81 can be changed, adjusting the magnetic change generated when the motor rotates. This increases the magnetic flux at the end of tooth 81, suppresses the decrease in torque, and reduces the cogging torque. In addition, by making the curved portion 84 extend concentrically from the inflection point 85 and the outer diameter side of the armature core 8, the radial width of the top of tooth 81 does not decrease, which can suppress the deformation of armature core 8 caused by centrifugal force when the DC motor 1 rotates. Furthermore, the degree of freedom in adjusting the opening width of slot opening 82 can be increased. Therefore, the tip of the tooth 81 will not become sharp, thereby suppressing damage to the armature coil 11 caused by the armature coil 11 getting caught on the armature core 8 during coil winding.

[0034] Furthermore, the present invention is not limited to the embodiments described above, but includes various modifications and equivalent configurations within the spirit of the appended claims. For example, the above embodiments are detailed descriptions provided for ease of understanding of the invention, and the invention is not limited to possessing all the described configurations. Additionally, a portion of the configuration of one embodiment may be replaced with the configuration of another embodiment. Furthermore, the configuration of another embodiment may be added to the configuration of one embodiment. Additionally, for a portion of the configuration of each embodiment, other configurations may be added, deleted, or replaced.

[0035] Symbol Explanation

[0036] 1 DC motor, 2 yoke, 3 magnet, 4 armature, 5 shaft, 6 bearing, 7 front bracket, 8 armature core, 9 commutator, 10 slot, 11 armature coil, 12 commutator plate, 13 brush holder, 14 brush, 15 spring, 16 choke coil, 19 motor gear, 20 bearing, 21 rear bracket, 26 external power supply terminal, 27 magnetic support bar, 81 tooth, 82 slot opening, 83 flat section, 84 curved section, 85 inflection point.

Claims

1. A rotor core, which is the rotor core of a rotating electric motor, said rotor core comprising: The slot, which provides a winding for the coil; and The teeth form a space for the coil to be wound around the groove. In a cross-section perpendicular to the axis of the rotary motor, the boundary between the inner circumference of the tooth and the groove is formed by a flat portion and a curved portion. The flat portion is formed as a straight line perpendicular to the radial direction of the inner circumference of the tooth, and the curved portion is formed as a curve that continues to the flat portion via an inflection point provided at the boundary with the flat portion. The curved portion is located at a position closer to the top of the flat portion in the circumferential direction of the toothed portion. Using the angle θs between the inflection points as viewed from the center of rotation, the angle θe occupied by the magnet of each pole, the number of poles p of the magnet, and the number of slots s, θs÷(θe×p÷s) is in the range of 0.5 to 0.

7.

2. A rotary electric motor, characterized in that, Having the rotor core as described in claim 1; and Magnets are disposed on the outer periphery of the rotor core.

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