JP5390752B2 - Embedded magnet motor - Google Patents

Description

  The present invention relates to an embedded magnet motor whose performance is improved by using reluctance torque as a main component of output torque and using a permanent magnet together.

  As a background technology of the present invention, there is a flux barrier type reluctance motor as shown in Patent Document 1 as a first example. An example of the cross-sectional structure of this motor is shown in FIG. In this motor, a plurality of split magnetic paths 3 are formed by providing a plurality of slits 2 in a rotor 1 made by laminating electromagnetic steel plates. These divided magnetic paths 3 are configured to have a magnetic flux path so that the magnetic resistance is reduced with respect to the magnetic flux flowing from the magnetic pole P1 to the magnetic pole P2 in the figure, and the slit 2 is, for example, between the magnetic pole midpoint N1 and the magnetic pole. The magnetic flux barrier is configured so that the magnetic resistance is higher than the magnetic flux flowing to the point N2.

  In the motor shown in FIG. 4, the stator 4 is provided with a plurality of slots 5, and an electric wire is inserted into the slot 5 to form a stator winding. This stator winding is the same as a general AC motor.

  A partially enlarged view of FIG. 4 is shown in FIG. The divided magnetic path 3 is connected to the rotor 1 by bridges 12a and 12b, and is fixed so as not to be scattered by centrifugal force. Since this bridge 12 is formed using a magnetic steel sheet by punching together with the divided magnetic path 3, it is a magnetic path for the leakage magnetic flux flowing from the magnetic pole midpoint N1 to N2 in FIG. This leakage flux reduces the magnetic resistance between the magnetic pole midpoints N1 and N2, so that the torque efficiency of the motor is reduced. In order to avoid this, the bridges 12a and 12b are generally designed to be as thin as possible.

  The principle of torque generation of the flux barrier type reluctance motor in FIG. 4 will be described. The current flowing through the slot 5 of the stator 4 is controlled to flow to an arbitrary position by a power converter such as an inverter, and the relative relationship between the rotor 1 and the current application position is arbitrarily controlled. Assuming that the excitation current 14 is passed through the positions of the magnetic pole midpoints N1 and N2, an excitation magnetic flux is generated along the divided magnetic path 3. Since the magnetic resistance is small in the direction along the divided magnetic path 3, a sufficient amount of exciting magnetic flux is generated even if the exciting current 14 is small.

  This operation will be described on the enlarged view of FIG. In the figure, reference numeral 14 denotes an equivalent energization position of the excitation current, and the excitation magnetic flux generated thereby is indicated by a dotted line. Next, assuming that the electric current 15 flows through the magnetic pole positions P1 and P2 in FIG. 5, Lorentz force is generated by the action of the exciting magnetic flux and the electric current 15, and torque is generated.

  On the other hand, when the electric current 15 is applied, a leakage magnetic flux as shown by a dashed line in FIG. 5 is also generated. Since this leakage flux increases the terminal voltage of the motor as the rotation increases, high-speed rotation cannot be realized due to voltage limitation in driving by a voltage type inverter that is generally used.

  As a second example as the background of the present invention, there is an embedded magnet motor introduced as a prior art in Patent Document 2 below. The rotor structure in this case is shown in FIG. In this motor, one slit 2 is provided per magnetic pole, and a permanent magnet 6 (main magnet) is inserted and disposed therein. There is a salient pole portion 7 formed of an electromagnetic steel plate on the outer peripheral portion of the permanent magnet 6, and reluctance torque is generated as shown below by the action of the salient pole portion 7 and the slit 2.

  The principle of torque generation in the embedded magnet motor in FIG. 6 will be described. The current flowing through the slot 5 of the stator 4 is controlled to flow to an arbitrary position by a power converter such as an inverter, and the relative relationship between the rotor 1 and the current application position is arbitrarily controlled. Assuming that the q-axis current 10 is supplied to the position 10 in the figure, Lorentz force is generated by the action of the permanent magnet 6 and the q-axis current 10, and torque is generated. This torque is generally called magnet torque.

  On the other hand, a q-axis magnetic flux 8 is generated in the salient pole portion 7 by the q-axis current 10. Since the magnetic resistance of the rotor 1 with respect to the q-axis magnetic flux 8 is low, a sufficiently large q-axis magnetic flux 8 is generated even if the q-axis current 10 is small.

  Here, when the d-axis current 11 is passed through the position 11 in the figure, Lorentz force is generated by the action of the q-axis magnetic flux 8 and the d-axis current 11, and torque is generated. This torque is generally called reluctance torque.

  Here, a d-axis magnetic flux 9 is simultaneously generated inside the rotor 1 by the d-axis current 11. The d-axis magnetic flux 9 corresponds to the leakage magnetic flux shown in the first example and is preferably a small magnetic flux because it is a harmful magnetic flux for obtaining the reluctance torque. However, since the magnetic resistance to this magnetic flux is large by the slit 2, Even when a large d-axis current 11 is passed, the amount of d-axis magnetic flux 9 generated is relatively small. Furthermore, since the d-axis magnetic flux 9 and the magnetic flux generated by the permanent magnet 6 are configured to cancel in the opposite directions, the leakage flux can be kept small by selecting an appropriate d-axis current value at the time of load.

  Further, a bridge 12 and a space 13 for reducing leakage magnetic flux are formed between the salient pole portions 7 adjacent to the rotor 1. The bridge 12 physically connects the salient pole part 7 to the rotor 1 and needs a certain thickness so that the salient pole part 7 is not scattered by centrifugal force. The space portion 13 is configured to increase the magnetic resistance by narrowing the magnetic path between the adjacent salient pole portions 7. In order to reduce the leakage magnetic flux between the adjacent salient pole portions 7, it is necessary to make the bridge 12 thin and the space portion 13 large. However, in order to ensure the strength against centrifugal force, the bridge 12 is thickened. Since it is necessary to make the space 13 small, it is usually designed in consideration of the balance between the leakage magnetic flux amount and the centrifugal strength.

JP-A-11-206082 Japanese Patent Laid-Open No. 7-231589

  As described above, in the first case of the prior art as well as in the second case, it is necessary to increase the thickness of the bridge 12 in order to ensure the rotor strength against the centrifugal force, but as a result, the leakage magnetic flux increases. There are problems that the torque efficiency is reduced and the output torque is reduced, and that the motor terminal voltage is increased and high-speed operation becomes impossible.

  Further, in the second example of the prior art, the magnetic flux of the permanent magnet 6 is canceled when the d-axis current is applied at the time of loading, but the permanent magnet is not applied at the time of no load. Since the magnetic flux 6 interlinks the stator 4, iron loss occurs in the stator 4. For this reason, there is a problem that the temperature rise of the motor is large particularly in applications where light load finishing is frequently used at high speed rotation, such as a spindle of a machining center.

  As described above, an object of the present invention is to provide an embedded magnet motor suitable for high-speed rotation, which can suppress a rise in the temperature of the stator and can efficiently obtain reluctance torque.

The problem described above is an n-pole motor having a structure in which a stator is disposed on the outer peripheral side and a rotor is disposed on the inner peripheral side, and n main magnets magnetized in the radial direction of the rotor are embedded in the rotor core. An auxiliary magnet magnetized in a substantially circumferential direction on both sides of the rotation direction of the n main magnets, and the main magnet and the auxiliary magnet are arranged in a Halbach array so as to increase the magnetic flux in the rotor inner diameter direction. This is solved by an embedded magnet motor.

Further, in order to solve the above-described problems, a structure in which a stator is disposed on the outer peripheral side and a rotor is disposed on the inner peripheral side, and n main magnets magnetized in the radial direction of the rotor are embedded in the rotor iron core. An n-pole motor having 2n auxiliary magnets magnetized in a substantially circumferential direction on both sides of the rotation direction of the n main magnets, the main magnet and the auxiliary magnets having a magnetic flux in the rotor inner diameter direction. By arranging a space in the rotor iron core between the auxiliary magnets belonging to the magnetic poles adjacent to each other so as to increase the magnetic resistance, a further effect can be obtained. Can be obtained.

  FIG. 1 is a sectional structural view of an embedded magnet motor according to the present invention. Components identical to those of the prior art examples shown in FIGS. 4, 5, and 6 are assigned the same reference numerals, and descriptions thereof are omitted. This motor has a rotor structure particularly suitable for a high-speed spindle in a high-speed machine such as a machining center.

  A slit 2 is formed inside a rotor 1 formed by laminating electromagnetic steel plates, and a main magnet 6 is arranged inside the slit 2. Auxiliary slits 20 are formed on both sides of the main magnet 6 in the rotational direction, and an auxiliary magnet 16 is disposed inside the slit. The main magnet 6 is magnetized in the radial direction of the rotor as indicated by an arrow in the figure, and in this figure, a four-pole motor is shown, so four permanent magnets are used.

  The auxiliary magnet 16 is magnetized in a direction perpendicular to the main magnet 6, that is, in a substantially circumferential direction, and the relationship with the main magnet 6 is arranged in a Halbach array that increases the magnetic flux in the inner diameter direction of the rotor 1. ing. That is, the auxiliary magnets 16 located on both sides of the main magnet 6 arranged so that the N pole faces radially outward are arranged so that the N pole is located on the side far from the main magnet 6 and the S pole is located on the near side. Is done. Conversely, the auxiliary magnets 16 located on both sides of the main magnet 6 arranged so that the north pole faces inward in the radial direction are arranged so that the north pole is located on the side close to the main magnet 6. Here, the magnetic flux distribution inside the rotor 1 will be described with reference to FIG. The magnetic flux of the main magnet 6 generated toward the outer diameter direction of the rotor 1 is attracted to the auxiliary magnet 16, almost all of which passes through the bridge 12 and does not go out of the rotor 1. Therefore, since there is no interlinkage with the stator 4, iron loss of the stator does not occur.

  In the embedded magnet motor according to the present invention, the stator 4 is provided with a plurality of slots 5, and electric wires are inserted into the slots 5 to form a stator winding. This stator winding is the same as a general AC motor, and for example, a winding configuration example in the case of driving with a three-phase AC is as shown in FIG. For example, a U-phase winding is inserted into a slot indicated by a black circle in the figure, and a three-phase winding is configured such that a V-phase winding is indicated by a black triangle and a W-phase winding is indicated by a black square. To do.

  The operation when current is supplied to the stator 4 will be described. When a d-axis current 11 is applied to a position indicated by reference numeral 11 in the figure, a d-axis magnetic flux 9 indicated by a dotted line in the figure is generated. Next, when a q-axis current 10 is applied to a position indicated by reference numeral 10 in the figure, Lorentz force is generated between the d-axis magnetic flux 9 and torque is generated. At this time, the q-axis current 10 tries to generate a q-axis magnetic flux 8 indicated by a one-dot chain line in the figure, and the inside of the bridge 12 and the space portion 13 which are the main paths of the q-axis magnetic flux 8 are as follows. For this reason, magnetic flux is difficult to pass. That is, the bridge 12 is in a magnetic saturation state and has a high magnetic resistance because the magnetic fluxes of the main magnet 6 and the auxiliary magnet 16 pass at a high density as shown in FIG. Moreover, about the inner side of the space part 13, since the magnetic flux of the main magnet 6 is passing in the reverse direction, the q-axis magnetic flux 8 is canceled.

  As described above, in the embedded magnet motor of the present invention, the bridge 12 can be magnetically saturated with high density by the magnetic fluxes of the main magnet 6 and the auxiliary magnet 16, so that the bridge 12 is sufficiently thick to maintain the centrifugal force strength. Even so, the magnetic resistance can be kept large, and harmful leakage magnetic flux can be kept small.

  According to the embedded magnet motor of this embodiment, it is possible to provide a rotor structure that sufficiently secures centrifugal force strength and has little decrease in output torque due to leakage magnetic flux in applications that require high-speed rotation. In addition, since the iron loss of the stator can be suppressed to a small level, the motor temperature rise during high-speed rotation is small, the thermal deformation of the machine can be suppressed to a small level, and a motor suitable for a machine tool can be provided.

1 is a cross-sectional view of a rotor and a stator of an embedded magnet motor according to an embodiment of the present invention. It is sectional drawing explaining the flow of the magnetic flux inside the rotor of the embedded magnet motor by this invention. It is a figure explaining the stator winding | coil of the embedded magnet motor by this invention. It is a rotor and stator sectional drawing of the flux barrier type reluctance motor by a prior art. It is an enlarged view of the rotor of the flux barrier type reluctance motor by a prior art. It is a rotor sectional view of an embedded magnet motor according to the prior art.

Explanation of symbols

  1 rotor, 2 slits, 3 divided magnetic paths, 4 stators, 5 slots, 6 permanent magnets (main magnets), 7 salient poles, 8 q-axis magnetic flux, 9 d-axis magnetic flux, 10 q-axis current, 11 d-axis current, 12 bridge, 13 space, 14 exciting current, 15 electron current, 16 auxiliary magnet.

Claims (2)

An n-pole motor having a structure in which a stator is disposed on the outer peripheral side, a rotor is disposed on the inner peripheral side, and n main magnets magnetized in the radial direction of the rotor are embedded in the rotor core.
An auxiliary magnet magnetized in a substantially circumferential direction on both sides in the rotational direction of the n main magnets;
The embedded magnet motor according to claim 1, wherein the main magnet and the auxiliary magnet are arranged in a Halbach array so as to increase a magnetic flux in a rotor inner diameter direction. An n-pole motor having a structure in which a stator is disposed on the outer peripheral side, a rotor is disposed on the inner peripheral side, and n main magnets magnetized in the radial direction of the rotor are embedded in the rotor core.
2n auxiliary magnets magnetized in a substantially circumferential direction on both sides of the rotation direction of the n main magnets,
The main magnet and the auxiliary magnet are arranged in a Halbach array so as to increase the magnetic flux in the rotor inner diameter direction,
An embedded magnet motor characterized in that a space portion is provided in a rotor iron core between the auxiliary magnets belonging to magnetic poles adjacent to each other to increase the magnetic resistance.

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