Rotating electric machine

Abstract

This invention provides a rotating electric machine that reduces magnetic saturation of the rotor and increases torque. [Solution] The rotating electric machine comprises a rotor core 20 having a first magnet 22 arranged on the d-axis and magnetized radially, a field winding 24 arranged radially inward from the first magnet 22 and wound around the d-axis, and a second magnet 26 arranged between the d-axis and q-axis radially outward from the field winding 24 and magnetized circumferentially, wherein a q-axis magnetic circuit 1 is formed between the first magnet 22, the field winding 24 and the second magnet 26, and a q-axis magnetic circuit 2 is formed radially inward from the field winding 24.

Description

Technical Field

[0001] The present invention relates to a rotating electrical machine.

Background Art

[0002] There is disclosed a hybrid excitation rotating electrical machine having a stator provided with a polyphase Y-connected stator winding, a plurality of rotor magnets fixed to a rotor shaft at a predetermined interval in the circumferential direction thereof and facing an inner circumferential surface of the stator through a gap, a plurality of permanent magnets fixed to substantially central portions in the circumferential direction of respective rotor magnets and magnetized in the radial direction of the rotor shaft, and a plurality of field windings wound around respective rotor magnets (Patent Document 1). Further, a structure including inter-pole magnets magnetized in the circumferential direction between the magnets is shown.

Prior Art Documents

Patent Documents

[0003]

Patent Document - 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] FIG. 6(a) is a diagram showing the configuration and operation of a rotor in the prior art. In the rotor, a first magnet 12 and a field winding 14 are provided on a rotor core 10. The first magnet 12 is disposed near an outer peripheral surface of a tooth constituting a pole of the rotor core 10 so that the pole faces in the radial direction of the rotor core 10. The field winding 14 is wound around each tooth.

[0005] Figure 6(b) shows the magnetic flux formed by the first magnet 12 when no field current or stator current is flowing. Figure 6(c) shows the magnetic flux when only field current (enhanced field) is flowing through the field winding 14. As shown in Figure 6(c), both magnetic flux and field current flux are formed in core region A of the rotor core 10, causing magnetic saturation of core region A. Figure 6(d) shows the magnetic flux when field current (enhanced field) and stator current are flowing. As shown in Figure 6(d), both field current flux and stator current flux (q-axis current flux) are formed in core region B of the rotor core 10, causing magnetic saturation of core region B.

[0006] Thus, in a configuration in which the rotor core 10 is equipped with the first magnet 12 and the field winding 14, there is a problem in that core regions A and B become magnetically saturated, resulting in a decrease in output torque.

[0007] Figure 7(a) shows another example of the configuration and operation of a conventional rotor. In this rotor, in addition to the first magnet 12 and field winding 14, a second magnet 16 is provided. The second magnet 16 is positioned between the magnetic poles formed by the first magnet 12 of the rotor core 10, and its magnetic poles are positioned along the circumferential direction of the rotor core 10.

[0008] Figures 7(b) and 7(c) show the magnetic flux formed by the first magnet 12 and the second magnet 16 when no field current or stator current is flowing. Figure 7(b) shows the magnetic flux formed by the first magnet 12 and the second magnet 16, respectively. Figure 7(c) shows the total magnetic flux, which is the combined magnetic flux of the first magnet 12 and the second magnet 16. As shown in Figure 7(b), the magnetic flux formed by the first magnet 12 is the same as in Figure 6(b). On the other hand, the magnetic flux formed by the second magnet 16 has two magnetic circuits: an outer diameter side and an inner diameter side. Because there is a gap in the outer diameter side magnetic circuit, the magnetic resistance of the inner diameter side magnetic circuit is smaller than that of the outer diameter side. Therefore, most of the magnetic flux formed by the second magnet 16 passes through the inner diameter side magnetic circuit and not through the outer diameter side magnetic circuit. As a result, in the core region A of the rotor core 10, the magnetic fluxes of the first magnet 12 and the second magnet 16 cancel each other out. Therefore, when the magnetic fluxes formed by the first magnet 12 and the second magnet 16 are combined, the resulting combined magnetic flux is as shown in Figure 7(c).

[0009] Figure 7(d) shows the magnetic flux when only the field current (enhanced field) is flowing. As shown in Figure 7(d), since only the field current flux flows in core region A of the rotor core 10, magnetic saturation in core region A is mitigated compared to the configuration in Figure 6(a). Figure 7(e) shows the magnetic flux when both the field current (enhanced field) and the stator current are flowing. As shown in Figure 7(e), both the field current flux and the stator current flux flow in core region B of the rotor core 10, and core region B becomes magnetically saturated.

[0010] Thus, in a configuration in which the rotor core 10 is equipped with a first magnet 12, a field winding 14, and a second magnet 16, magnetic saturation in core region A can be eliminated, but magnetic saturation still occurs in core region B, leaving the problem of reduced torque.

[0011] Furthermore, when no field current is flowing, the magnetic flux density is high in the center of the magnetic pole, while it is extremely low at the ends of the magnetic pole and between the magnetic poles. Even if a second magnet 16 is placed between the magnetic poles, the extremely low magnetic flux density at the ends of the magnetic poles and between the magnetic poles is hardly improved. As a result, the third harmonic of the gap magnetic flux density of the motor increases, and the iron loss of the motor increases. [Means for solving the problem]

[0012] One aspect of the present invention is a rotating electric machine comprising a rotor core having a first magnet arranged on the d-axis and magnetized radially, a field winding arranged radially inward from the first magnet and wound around the d-axis, and a second magnet arranged radially outward from the field winding between the d-axis and the q-axis and magnetized circumferentially, wherein a first q-axis magnetic circuit is formed between the first magnet, the field winding and the second magnet, and a second q-axis magnetic circuit is formed radially inward from the field winding.

[0013] In this case, it is preferable that the first q-axis magnetic circuit has a second region having a cross-sectional area narrower than the cross-sectional area of ​​the first region between the first magnet and the second magnet on the surface of the rotor core.

[0014] Furthermore, the cross-sectional area of ​​the second region is preferably 50% to 75% of the cross-sectional area of ​​the first region. [Effects of the Invention]

[0015] According to the present invention, magnetic saturation of the rotor can be alleviated and torque can be increased. Furthermore, the third harmonic of the gap magnetic flux density of the motor can be reduced, thereby reducing motor iron loss. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows the configuration and operation of the rotor of a rotating electric machine in an embodiment of the present invention. [Figure 2] This figure shows the gap magnetic flux density of a conventional rotating electric machine. [Figure 3] It is a diagram showing another example of the configuration and operation of the rotor of a rotating electrical machine in an embodiment of the present invention. [Figure 4] It is a diagram showing the gap magnetic flux density of a rotating electrical machine in an embodiment of the present invention. [Figure 5] It is a diagram showing another example of the configuration and operation of the rotor of a rotating electrical machine in an embodiment of the present invention. [Figure 6] It is a diagram showing the configuration and operation of a rotor in the prior art. [Figure 7] It is a diagram showing the configuration and operation of a rotor in the prior art.

Embodiments for Carrying Out the Invention

[0017] As shown in FIG. 1, the rotor 100 of a rotating electrical machine in an embodiment of the present invention includes a rotor core 20, a first magnet 22, a field winding 24, and a second magnet 26. FIG. 1 shows a part of a cross-sectional view of the rotor 100 of the rotating electrical machine cut along a plane orthogonal to the rotation axis.

[0018] The rotor 100 is a member having a cylindrical shape with a circular cross-section and is disposed inside a stator not shown. That is, FIG. 1 shows only a part of the rotor 100 divided in the circumferential direction, and the rotor 100 is formed by arranging these parts in the circumferential direction to form a cylindrical shape. The rotor 100 rotates inside the stator by a magnetic field formed by the stator.

[0019] The rotor core 20 is a structure that mechanically supports the rotor 100 and is a member that constitutes a magnetic circuit for efficiently passing magnetic flux. The rotor core 20 is formed, for example, by stacking circular magnetic steel plates.

[0020] The first magnet 22 is arranged near the outer peripheral surface constituting the magnetic poles of the rotor core 20 such that the magnetic poles face radially along the d-axis of the rotor core 20. That is, the first magnet 22 is magnetized so that the S pole to N pole of the magnet faces in the direction of the white arrow in Fig. 1(a). The adjacent first magnets 22 along the circumferential direction are magnetized in opposite directions along the radial direction of the rotor core 20.

[0021] The field winding 24 is a winding wound around the d-axis for each magnetic pole of the rotor core 20. The field winding 24 is wound so as to generate magnetic flux in the same direction as the magnetic pole direction (d-axis direction) of the first magnet 22 with respect to the radial direction of the rotor core 20. The field winding 24 is arranged inside the rotor core 20 in the radial direction compared to the first magnet 22.

[0022] The second magnet 26 is arranged between the d-axis and the q-axis of the rotor core 20. The second magnet 26 is arranged between the magnetic poles constituted by the first magnets 22 of the rotor core 10 and is arranged such that the magnetic poles are along the circumferential direction of the rotor core 20. That is, the second magnet 26 is magnetized so that the S pole to N pole of the magnet faces in the direction of the white arrow in Fig. 1(a). Two second magnets 26 are arranged so as to sandwich the q-axis, which is the middle of adjacent d-axes along the circumferential direction of the rotor core 20. The adjacent second magnets 26 sandwiching the first magnet 22 are magnetized in opposite directions along the circumferential direction of the rotor core 20.

[0023] Here, a q-axis magnetic circuit 1 is formed between the first magnet 22, the field winding 24, and the second magnet 26. As shown in Fig. 1(a), the q-axis magnetic circuit 1 is composed of a portion of the rotor core 20 connecting the regions between one second magnet 26 and one first magnet 22, the region between the field winding 24 and the first magnet 22, and the region between another second magnet 26 and the first magnet 22.

[0024] Furthermore, the q-axis magnetic circuit 2 is formed radially inward from the field winding 24. As shown in Figure 1(a), the q-axis magnetic circuit 2 consists of a portion of the rotor core 20 that connects the region between two adjacent second magnets 26, the region radially inward from the field winding 24, and the region between another pair of adjacent second magnets 26.

[0025] Figures 1(b) and 1(c) show the magnetic flux formed by the first magnet 22 and the second magnet 26 when no field current or stator current is flowing. Figure 1(b) shows the magnetic flux formed by the first magnet 22 and the second magnet 26, respectively. Figure 1(c) shows the total magnetic flux, which is the combined magnetic flux of the first magnet 22 and the second magnet 26.

[0026] As shown in Figure 1(b), the magnetic flux formed by the first magnet 22 and the second magnet 26 is the same as in the prior art. There are two magnetic circuits, one on the outer diameter side and one on the inner diameter side, for the magnetic flux formed by the second magnet 26. Because there is a gap in the outer diameter side magnetic circuit, the magnetic resistance of the inner diameter side magnetic circuit is smaller than that of the outer diameter side magnetic circuit. Therefore, most of the magnetic flux formed by the second magnet 26 passes through the inner diameter side magnetic circuit and not through the outer diameter side magnetic circuit. As a result, in the core region A along the d axis of the rotor core 20, the magnetic fluxes of the first magnet 22 and the second magnet 26 cancel each other out. Therefore, when the magnetic fluxes formed by the first magnet 22 and the second magnet 26 are combined, the combined magnetic flux is as shown in Figure 1(c).

[0027] Figure 1(d) shows the magnetic flux when only the field current (enhanced field) is flowing. As shown in Figure 1(d), since only the field current flux flows in the core region A of the rotor core 20, magnetic saturation in the core region A is mitigated.

[0028] Figure 1(e) shows the magnetic flux when field current (enhanced field) and stator current are flowing. As shown in Figure 1(e), the stator current magnetic flux passes not only through the q-axis magnetic circuit 1 but also through the q-axis magnetic circuit 2 on the inner diameter side of the field winding 24. As a result, the stator current magnetic flux flowing through the core region B of the rotor core 20 is reduced, and the magnetic saturation in the core region B, which is the region between the first magnet 22 and the field winding 24, is mitigated compared to the conventional technology.

[0029] As described above, in the rotating electric machine of this embodiment, magnetic saturation can be suppressed in both core region A and core region B of the rotor core 20. Therefore, the rotational torque can be increased compared to the conventional technology.

[0030] Furthermore, if the cross-sectional area (width) of the q-axis magnetic circuit 2 is made too large, the cross-sectional area (width) of the q-axis magnetic circuit 1 will become narrower, causing a decrease in field current flux and, consequently, a decrease in rotational torque. Therefore, it is preferable for the cross-sectional area (width) of the q-axis magnetic circuit 2 to be narrower than that of the q-axis magnetic circuit 1. Here, the cross-sectional area (width) of the q-axis magnetic circuit 1 and the q-axis magnetic circuit 2 refers to the average cross-sectional area (width) of the rotor core 20 that constitutes each magnetic circuit.

[0031] Next, we will explain the gap magnetic flux density in the gap between the stator and rotor of a rotating electric machine when no field current is flowing. In the conventional technology shown in Figure 6(a), the magnetic flux density is high in the center of the magnetic poles, and almost zero at the ends of the magnetic poles. Figure 2 shows the gap magnetic flux density in the conventional technology. As shown in Figure 2, in the rotor configuration of the conventional technology, a large third harmonic is superimposed on the gap magnetic flux density. When the third harmonic is large in this way, the motor iron loss increases and the efficiency decreases.

[0032] As shown in Figure 3, another example of a rotor 102 in an embodiment of the present invention comprises a rotor core 20, a first magnet 22, a field winding 24, and a second magnet 26. Figure 3 shows a portion of a cross-sectional view of the rotor 102 of the rotating electric machine, cut by a plane perpendicular to the axis of rotation. That is, Figure 3 shows only a portion of the rotor 102 divided in the circumferential direction, and the rotor 102 is constructed by arranging these portions in the circumferential direction to form a cylindrical shape.

[0033] In the rotor 102, the q-axis magnetic circuit 1 between the first magnet 22 and the field winding 24 and the second magnet 26 is configured such that the cross-sectional area (width D) between the first magnet 22 and the field winding 24 is smaller than the cross-sectional area (width C) between the first magnet 22 and the second magnet 26, which are located on the rotor surface.

[0034] Here, width refers to the distance on a cross-section obtained by cutting the rotor core 20 with a plane perpendicular to the axis of rotation, as shown in Figure 3. That is, the width C between the first magnet 22 and the second magnet 26, which are on the rotor surface, refers to the distance between the first magnet 22 and the second magnet 26 at the point closest to the outer surface of the rotor core 20 in that cross-section. Also, the width D between the first magnet 22 and the field winding 24 refers to the distance between the first magnet 22 and the field winding 24 at the point closest to each other in that cross-section.

[0035] The rotor core 20 has a cylindrical shape, and its length in the rotational axis direction is equal at all points. Therefore, the width C of the q-axis magnetic circuit 1 and the cross-sectional area of ​​the q-axis magnetic circuit 1 (width C × length in the rotational axis direction of the rotor core 20) are proportional. Also, the width D of the q-axis magnetic circuit 1 and the cross-sectional area of ​​the q-axis magnetic circuit 1 (width D × length in the rotational axis direction of the rotor core 20) are proportional.

[0036] In the rotor 102, it is preferable that the cross-sectional area (width D) between the first magnet 22 and the field winding 24 be 50% to 75% of the cross-sectional area (width C) between the first magnet 22 and the second magnet 26, which corresponds to the rotor surface.

[0037] Figures 3(b) and 3(c) show the magnetic flux formed by the first magnet 22 and the second magnet 26 when no field current or stator current is flowing. Figure 3(b) shows the magnetic flux formed by the first magnet 22 and the second magnet 26, respectively. Figure 3(c) shows the total magnetic flux, which is the combined magnetic flux of the first magnet 22 and the second magnet 26.

[0038] As shown in Figure 3(b), the magnetic flux formed by the first magnet 22 is the same as that of the rotor 100. On the other hand, the magnetic flux formed by the second magnet 26 has two magnetic circuits: one on the outer diameter side and one on the inner diameter side. Because there is a gap in the outer diameter side magnetic circuit, the magnetic resistance of the inner diameter side magnetic circuit is smaller than that of the outer diameter side. However, in the rotor 102, the cross-sectional area (width D) between the first magnet 22 and the field winding 24 is smaller than the cross-sectional area (width C) between the first magnet 22 and the second magnet 26, which are located on the rotor surface. Therefore, the magnetic resistance of the inner diameter side magnetic circuit is larger than that of the rotor 100. As a result, a portion of the magnetic flux of the second magnet 26, which passed through the inner diameter side magnetic circuit in the rotor 100, now passes through the outer diameter side magnetic circuit. Consequently, as shown in Figure 3(c), the combined magnetic flux of the first magnet 22 and the second magnet 26 passes through.

[0039] Figure 4 shows the gap magnetic flux density in a rotating electric machine to which rotor 102 is applied. As shown in Figure 4, the third harmonic in the gap magnetic flux density is reduced in the rotor 102 configuration. Because the third harmonic can be suppressed almost completely in this way, motor iron losses are reduced and efficiency is improved.

[0040] As shown in Figure 5, in the rotor 100 and rotor 102 of the embodiment of the present invention, the first magnet 22 may be divided into the first magnet 22a and the first magnet 22b, and the first magnet 22a and the first magnet 22b may be arranged in a V-shape. Alternatively, the first magnet 22 may be divided into two or more parts, such as three parts.

[0041] [Overview of the prefecture] [Configuration 1] A first magnet positioned on the d-axis and magnetized radially, A field winding is positioned radially inward from the first magnet and wound around the d-axis, The rotor core comprises a second magnet, which is arranged between the d-axis and q-axis radially outside the field winding and is magnetized in the circumferential direction, A rotating electric machine characterized in that a first q-axis magnetic circuit is formed between the first magnet, the field winding, and the second magnet, and a second q-axis magnetic circuit is formed radially inward from the field winding. [Configuration 2] The rotating electric machine described in Configuration 1, A rotating electric machine characterized in that the first q-axis magnetic circuit has a second region having a cross-sectional area narrower than the cross-sectional area of ​​the first region between the first magnet and the second magnet on the surface of the rotor core. [Configuration 3] The rotating electric machine described in configuration 2, A rotating electric machine characterized in that the cross-sectional area of ​​the second region is 50% or more and 75% or less of the cross-sectional area of ​​the first region. [Explanation of symbols]

[0042] 1 q-axis magnetic circuit, 2 q-axis magnetic circuits, 10 rotor core, 12 first magnet, 14 field winding, 16 second magnet, 20 rotor core, 22 first magnet, 24 field winding, 26 second magnet, 100, 102 rotor.

Claims

1. A first magnet positioned on the d-axis and magnetized radially, A field winding is positioned radially inward from the first magnet and wound around the d-axis, The rotor core comprises a second magnet, which is arranged between the d-axis and q-axis radially outside the field winding and is magnetized in the circumferential direction, A rotating electric machine characterized in that a first q-axis magnetic circuit is formed between the first magnet, the field winding, and the second magnet, and a second q-axis magnetic circuit is formed radially inward from the field winding.

2. A rotating electric machine according to claim 1, A rotating electric machine characterized in that the first q-axis magnetic circuit has a second region having a cross-sectional area narrower than the cross-sectional area of ​​the first region between the first magnet and the second magnet on the surface of the rotor core.

3. A rotating electric machine according to claim 2, A rotating electric machine characterized in that the cross-sectional area of ​​the second region is 50% or more and 75% or less of the cross-sectional area of ​​the first region.

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