JP6594744B2 - Magnetic bearing - Google Patents

Description

  The present invention relates to a magnetic bearing. In particular, the rotor is improved so as to reduce iron loss.

Patent Document 1 proposes a magnetic bearing. An object of the present invention is to provide a magnetic bearing that has high position estimation accuracy and can be further reduced in size and weight.
In particular, the purpose of the second form of Patent Document 1 is to make “control magnetic flux by the exciting coil of the main pole” and “bias magnetic flux by the permanent magnet of the complementary pole” independent magnetic circuits, thereby reducing mutual interference and improving control responsiveness. Further, it is to eliminate the influence of the control magnetic flux on the displacement detection by the magnetic flux sensor and to improve the position estimation accuracy.
The effect of the second embodiment is that the auxiliary pole tooth portion can be omitted, so that the size can be reduced, and the cross-sectional area of the control magnetic flux generated from the exciting coil can be made wider than that of the first embodiment.

A similar structure is also described in the fifth embodiment of Patent Document 2 as shown in FIG.
In paragraph 0020 of Patent Document 2, “in this embodiment, permanent magnets are arranged so as to straddle the main pole. That is, the tips of the four main poles 83 constituting the stator 81 are adjacent to each other. Arc-shaped permanent magnets 86 are arranged so as to communicate corners to be connected, and an auxiliary pole 84 is formed by the permanent magnets 86. In this embodiment, the exciting coil 85 is compared to that in FIG. It has the advantage that the cross-sectional area of the control magnetic flux Φc generated in the above can be widened.

Japanese Patent No. 4220859 JP 2005-61578 A

The loss of the core portion that occurs in the magnetic bearing is not negligible. To increase the efficiency of the drive system, it is necessary to reduce the iron loss that occurs in the magnetic bearing. The iron loss of the magnetic bearing is particularly large because the rotor core occupies a large amount.
However, Patent Document 1 has a structure in which a permanent magnet is disposed with a gap from the tooth tip, so that the magnetic flux Φb of the permanent magnet easily affects the shaft support force.

Further, in the fifth embodiment of Patent Document 2, as shown in FIG. 4, the tip of the tooth where the main pole 83 is located is the N pole, whereas the tip of the slot located between the tips of the teeth is the permanent magnet 86. Because of the complementary pole 84 formed in step S, it is the south pole, and the north and south poles are alternated.
Therefore, the control magnetic flux Φc generated by the exciting coil 85 and the bias magnetic flux Φb supplied from the permanent magnet 86 overlap as shown in the drawing, and the region A surrounded by the alternate long and short dash line in the drawing has a high magnetic flux density, In the region B surrounded by the alternate long and short dash line, the magnetic flux density is sparse. That is, the magnetic flux density was uneven and iron loss was generated.

  The magnetic bearing according to claim 1 of the present invention for solving the above-mentioned problems is a magnetic bearing comprising a stator and a rotor that rotates while being supported by the stator in a non-contact state by a magnetic force. Comprises a radial stator core in which permanent magnets are arranged at equal intervals on the outer peripheral portion and a radial winding is wound around a tooth on the inner peripheral side to form a magnetic pole, while a solid core is provided between the tips of the teeth. A permanent magnet having a magnetization direction set in the same direction as the permanent magnet is provided on the inner diameter side of the solid core.

  A magnetic bearing according to a second aspect of the present invention for solving the above-mentioned problems is the magnetic bearing according to the first aspect, wherein the magnetic flux of the permanent magnet arranged on the outer periphery of the stator is the same as that of the permanent magnet provided in the solid core. It is stronger than magnetic flux and is dominant in the teeth.

  A magnetic bearing according to a third aspect of the present invention for solving the above-described problems is that, in the first aspect, a notch for preventing magnetic flux leakage between the magnetic poles is formed on the outer peripheral side of the solid core. Features.

  A magnetic bearing according to a fourth aspect of the present invention for solving the above-mentioned problems is the magnetic bearing according to the first aspect, wherein the permanent magnet provided in the solid core does not have a circumferential gap between the magnetic pole and the magnetic pole. And

  A magnetic bearing according to a fifth aspect of the present invention for solving the above-described problems is the magnetic bearing according to the first aspect, wherein the stator includes a thrust stator core that accommodates the radial stator core, the permanent magnet, and a radial winding. .

  In the present invention, the permanent magnet provided on the inner diameter side of the solid core has the magnetization direction set in the same direction as the permanent magnet disposed on the outer peripheral portion of the radial stator core. As a result, the change in the magnetic flux density of the rotor core is reduced, and the iron loss of the rotor core is less likely to occur.

It is a cross-sectional view showing a magnetic bearing according to an embodiment of the present invention. It is a principal part cross-sectional view which shows the magnetic bearing which concerns on one Example of this invention. It is a longitudinal cross-sectional view which shows the magnetic bearing which concerns on one Example of this invention. It is a cross-sectional view which shows the magnetic bearing which concerns on a prior art. It is a principal part cross-sectional view which shows the flow of the magnetic flux of the magnetic bearing which concerns on one Example of this invention. It is a cross-sectional view concerning the principal part which shows the flow of the magnetic flux of the magnetic bearing which concerns on a comparative example. It is a cross-sectional view showing a magnetic bearing according to a comparative example. FIG. 8A is an explanatory diagram showing the magnetic flux density distribution in the vicinity of the slots in the stator and rotor according to the first embodiment, and FIG. 8B is the magnetic flux density distribution in the vicinity of the slots in the stator and rotor according to the comparative example. FIG. 8C is a scale of magnetic flux density [T]. It is a graph which shows gap magnetic flux density.

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

A magnetic bearing according to an embodiment of the present invention is shown in FIGS.
The magnetic bearing of the present embodiment includes a thrust stator core (material: solid magnetic material) 1, two thrust windings 3, 4, a radial stator core (material: magnetic material laminated steel plate) 5, and a plurality of radial windings 6. And a stator including a plurality of permanent magnets 7, and a rotor core 8 and a shaft 9, which are rotors that are supported by the stator in a non-contact state by a magnetic force and rotate.

The thrust stator core 1 has a substantially cylindrical shape, and includes a cylindrical portion surrounding the rotor core 8 and the shaft 9 and two annular portions arranged inwardly on both axial sides of the cylindrical portion. The rotor core 8 and the shaft 9 pass through the center of the portion.
In the space formed in the thrust stator core 1, the thrust windings 3 and 4, the radial stator core 5, the radial winding 6 and the permanent magnet 7 are accommodated.

That is, between the radial stator core 5 and the annular portion of the thrust stator core 1, thrust windings 3 and 4 wound in the circumferential direction are respectively disposed.
A plurality of permanent magnets (hereinafter referred to as outer magnets) 7 magnetized in the radial direction are inserted into the outer peripheral portion of the radial stator core 5, and the radial winding 6 is wound around the teeth on the inner peripheral side of the radial stator core 5. Turned to form the magnetic pole.

Further, a solid core (material: solid magnetic material) 2 is spanned between the slots between the magnetic poles of the radial stator core 5, that is, between the tips of the teeth.
On the inner diameter side of the solid core 2, a permanent magnet (hereinafter referred to as a slot tip magnet) 10 having a magnetization direction set in the same direction as the outer magnet 7 is provided.

Therefore, as shown in FIG. 1, if the inner diameter side of the outer magnet 7 is the S pole and the outer diameter side is the N pole, the inner diameter side and the outer diameter side of the slot tip magnet 10 are both the N pole.
Further, there is no circumferential gap between the slot tip magnet 10 and the magnetic pole. Therefore, there is an advantage that the magnetic flux density becomes uniform as will be described later.
Further, a notch 21 for preventing magnetic flux leakage between the magnetic poles is formed on the outer peripheral side of the solid core 2.

Therefore, in FIG. 1, the magnetic flux φa generated by the permanent magnet 7 flows radially in the radial direction through the radial stator core 5 as indicated by a thick broken line.
In FIG. 3, the magnetic flux φa is divided into two in the axial direction at the cylindrical portion of the thrust stator core 1, and one magnetic flux φa flows through one cylindrical portion to the right side in the drawing, and the inner diameter at the annular portion at the right end in the drawing. The rotor core 8 changes direction to the left side in the figure and returns to the radial stator core 5, while the other magnetic flux φa flows through the cylindrical part 1a to the left side in the figure, and flows to the inner diameter side at the annular part at the left end in the figure, In the rotor core 8, the direction is changed to the right side in the drawing, and the rotor stator 8 returns to the radial stator core 5.

Here, as shown in FIG. 2, the magnetic flux φa returning to the radial stator core 5 causes the notch 21 formed on the outer peripheral side of the solid core 2 to interfere with the radial stator core 5 without passing through the solid core 2. It will flow to the outer diameter side.
On the other hand, in FIG. 2, the magnetic flux φe generated by the slot tip magnet 10 is bifurcated in the circumferential direction by the solid core 2 from the slot tip magnet 10 as indicated by a thin two-dot chain line, and passes through the rotor core 8 from the tooth tip, A small loop is drawn back to the slot tip magnet 10.

Here, a magnetic flux φa (thick broken line) generated by the outer magnet 7 and passed through the thrust stator core 1 and the rotor core 8 and a magnetic flux φe (thin two-dot chain line) generated by the slot tip magnet 10 and drawing a small loop A sparse / dense relationship can be established with the rotor magnetic flux.
Here, it is assumed that the magnetic flux of the outer magnet 7 is stronger than the magnetic flux of the slot tip magnet 10 as a condition.
Then, as shown in FIG. 5, the center portion of the slot, which is the region C surrounded by the one-dot chain line in the figure, is caused by the magnetic flux φe (thin two-dot chain line) by the slot tip magnet 10 and the magnetic flux φa (thick broken line) of the outer magnet 7. Since the magnetic fluxes strengthen each other, the magnetic flux density becomes dense.

Moreover, in the area | region (tooth part) adjacent to the circumferential direction of the area | region C, magnetic flux will mutually weaken by magnetic flux (phi) e (thin dashed-two dotted line) by the slot tip magnet 10, and magnetic flux (phi) a (thick broken line) of the outer magnet 7. FIG. However, since the magnetic flux φa of the outer magnet 7 is stronger than the magnetic flux φe of the slot tip magnet 10, that is, the magnetic flux φa of the outer magnet 7 is dominant, the magnetic flux φa of the outer magnet 7 is slightly weakened. The magnetic pole at the tip is the S pole.
The magnetic flux may be increased or decreased by any method such as a difference in holding force depending on a magnet grade and a difference in magnet thickness.

Here, as shown in FIG. 5, the teeth tip portions, which are the regions D and E surrounded by the alternate long and short dash line in the figure, which are not affected by the magnetic flux φe by the slot tip magnet 10, are the magnetic flux φa of the outer magnet 7 (thick broken line). The magnetic flux is strengthened by the magnetic flux φd (thin broken line) of the radial winding 6 and the magnetic flux density becomes dense.
Therefore, in this embodiment, the slot tip and the tooth tip are all S poles, and the structure is such that iron loss is less likely to occur with little change in the magnetic flux of the opposing rotor.

  Contrary to the case illustrated in the figure, if the outer magnet 7 has an N pole on the inner diameter side and an S pole on the outer diameter side, the inner diameter side of the slot tip magnet 10 has an N pole and the outer diameter side has an S pole. The tip and teeth tip are all N poles. Also in this case, there is no change in that the structure is such that the change in magnetic flux of the opposing rotor is small and iron loss is unlikely to occur.

In the magnetic bearing of the present embodiment, the principle of generating the shaft support force is such that the rotor core 8 and the shaft 9 are rotatably supported by receiving the radial force, as will be described later in the comparative example.
The thrust force will be briefly described. Due to the density of the magnetic flux generated by the permanent magnet 7 and the current flowing through the thrust windings 3, 4, the rotor core 8 and the shaft 9, which are rotors, are densely formed. Axial thrust force is generated.

[Comparative example]
As a comparative example, FIG. 6 and FIG. 7 show the magnetic bearing according to Example 1 with the slot tip magnet 10 and the solid core 2 removed.
That is, in the magnetic bearing according to this comparative example, as shown in FIGS. 6 and 7, a plurality of radially magnetized permanent magnets (outer magnets) 7 are inserted into the outer periphery of the radial stator core 5, and the radial On the inner peripheral side of the stator core 5, a radial winding 6 is wound around a tooth to form a magnetic pole.

There is no permanent magnet (slot tip magnet) or solid core at the tip of the slot between the magnetic poles of the radial stator core 5.
The radial stator core 5, the outer magnet 7 and the radial winding 6 are housed in a thrust stator core (not shown) to form a stator, which is supported and rotated in a non-contact state by a magnetic force (radial force). The rotor core 8 and the shaft 9 as the child rotate.
That is, FIG. 7 shows the principle of radial force generation, in which the magnetic flux φa generated by the outer magnet 7 is indicated by a thick broken line, and the magnetic flux φd generated by the current flowing in the radial winding 6 is indicated by a thin broken line.

  As shown in FIG. 7, the outer magnet 7 has an S-pole on the inner peripheral side and an N-pole on the outer peripheral side. Therefore, the magnetic flux φa generated by the outer magnet 7 flows radially in the radial direction through the radial stator core 5, while the magnetic flux φd generated by the current flowing through the radial winding 6 follows the right-handed screw law and the radial stator core 5 and the rotor core In FIG. 8, the current flows alternately clockwise or counterclockwise in the figure.

Therefore, in the upper right and upper left part of the radial stator core 5 (region H surrounded by the alternate long and short dash line in the figure), the magnetic flux φa indicated by the thick broken line and the magnetic flux φd indicated by the thin broken line are generated in the same direction. In the lower right and lower left of the stator core 5 (region I surrounded by a one-dot chain line in the figure), the magnetic flux φa indicated by the thick broken line and the magnetic flux φd indicated by the thin broken line are generated in opposite directions, so that the magnetic flux weakens. As a result, a radial force G is generated upward in the rotor core 8 by an unbalanced suction force, as indicated by an arrow in the figure.
The point that the radial force G is generated in this way is the same in the first embodiment.

On the other hand, as shown in FIG. 6, a slot central portion, which is a region J surrounded by a one-dot chain line in the figure, has a magnetic flux φd (thin broken line) generated by a current flowing in the radial winding 6 and a magnetic flux φa (thick broken line) of the outer magnet 7. ), The magnetic flux density weakens because the magnetic fluxes weaken each other.
However, as shown in FIG. 6, the teeth tip portions that are the regions J and K surrounded by the alternate long and short dash line in the figure are caused by the magnetic flux φa of the outer magnet 7 (thick broken line) and the magnetic flux φd of the radial winding 6 (thin broken line). The magnetic flux density becomes dense by strengthening the magnetic fluxes.

As described above, in the comparative example, the magnetic flux density is uneven and the magnetic flux density is uneven, and iron loss occurs. In this regard, the fifth embodiment of Patent Document 2 is considered to be the same.
FIG. 8 shows a simulation result of a specific magnetic flux density by comparing the comparative example and the first embodiment.
As shown in FIG. 8B, the magnetic flux density distribution in the rotor of the comparative example is lower in the magnetic flux density in the vicinity of the stator (slot portion) than in the vicinity of the stator (tooth portion). The change in magnetic flux density of the (tooth portion) and stator (slot portion) is large, and the iron loss of the rotor core is large.
On the other hand, as shown in FIG. 8A, in the magnetic flux density distribution in the rotor of Example 1, the change in the magnetic flux density in the vicinity of the slot tip magnet 10 and in the vicinity of the stator (tooth portion) is suppressed to be small. The change in the magnetic flux density of the core is small, and iron loss of the rotor core is difficult to occur.

In particular, in the first embodiment, there is no circumferential gap between the slot tip magnet 10 and the magnetic pole, so that there is an advantage that the magnetic flux density is made more uniform.
On the other hand, Patent Document 1 is considered to have a large change in magnetic flux density and a large iron loss of the rotor core because a permanent magnet is arranged with a gap from the tooth tip.
As shown in FIG. 9, the gap magnetic flux density is 1 to 0.964 [p. u. ] In the range of 1 to 0.271 [p. u. ]. In FIG. 9, the vertical axis represents the gap magnetic flux density [p. u. ], The horizontal axis is the circumferential angle [deg].
Table 1 shows the ratio of iron loss occurring in the rotor cores of the comparative example and the example 1 in a certain stator shape.

The numerical values in the table indicate the ratio of the rotor iron loss of this example when the rotor iron loss of the comparative example at each load is 100%.
As shown in Table 1, it can be seen that Example 1 can suppress the rotor iron loss to 20% or less of the comparative example even under load.

  The magnetic bearing of the present invention has a low iron loss and can be widely used industrially.

1 Thrust stator core 2 Solid core 3, 4 Thrust winding 5 Radial stator core 6 Radial winding 7 Permanent magnet (outer magnet)
8 Rotor core 9 Shaft 10 Permanent magnet (slot end magnet)
21 Notch

Claims (5)

In a magnetic bearing comprising a stator and a rotor that is supported and rotated in a non-contact state by magnetic force on the stator,
The stator includes a radial stator core in which permanent magnets are arranged at equal intervals on the outer periphery and a radial winding is wound around a tooth on the inner periphery to form a magnetic pole.
A solid core is spanned between the tips of the teeth,
The magnetic bearing according to claim 1, wherein a permanent magnet having a magnetization direction set in the same direction as the permanent magnet is provided on an inner diameter side of the solid core.   The magnetic flux of the permanent magnet disposed on the outer periphery of the stator is stronger than the magnetic flux of the permanent magnet provided in the solid core, and is dominant in the teeth. The magnetic bearing described.   The magnetic bearing according to claim 1, wherein a notch for preventing leakage of magnetic flux between the magnetic poles is formed on an outer peripheral side of the solid core.   The magnetic bearing according to claim 1, wherein the permanent magnet provided in the solid core does not have a circumferential gap between the permanent magnet and the magnetic pole.   The magnetic bearing according to claim 1, wherein the stator includes a thrust stator core that accommodates the radial stator core, the permanent magnet, and a radial winding.