WO2017038859A1

WO2017038859A1 - Motor

Info

Publication number: WO2017038859A1
Application number: PCT/JP2016/075441
Authority: WO
Inventors: 赤津　観; 普衣山田
Original assignee: 学校法人芝浦工業大学
Priority date: 2015-08-31
Filing date: 2016-08-31
Publication date: 2017-03-09
Also published as: JPWO2017038859A1

Abstract

A motor (1) is provided with: a stator (2) in which a plurality of magnet parts (6), which have a coercive force functioning as a permanent magnet and in which the magnetization direction can be reversed by a predetermined magnetization reversal action, are provided so as to be lined up in a predetermined direction, and in which magnetization adjustment parts (7) for applying the magnetization reversal action to each of the magnet parts (6) are provided in correspondence with each of the magnet parts (6); a movable element (3) disposed so as to be capable of moving along the direction in which the magnet parts (6) are lined up; and a magnetization control means (10) for controlling the magnetization reversal action produced by the magnetization adjustment parts (7) so that the magnetization directions of the plurality of magnet parts (6) are alternatingly reversed and a moving magnetic field along the direction in which the magnet parts (6) are lined up is generated by a deviation in the timing of magnetization direction reversal between each of the magnet parts (6).

Description

Electric motor

The present invention relates to an electric motor that generates a moving magnetic field by sequentially reversing the magnetization direction of a magnet portion of a stator.

In a conventional electric motor, windings are applied to each of a plurality of teeth portions provided on the inner periphery of the stator, and a three-phase alternating current is applied to each winding, thereby extending along the circumferential direction of the stator. A rotating magnetic field is generated. The rotor is provided with permanent magnets so that N and S poles appear alternately in the circumferential direction, whereby the rotor rotates in synchronization with the rotating magnetic field of the stator (see, for example, Patent Document 1). .

Japanese Patent Laying-Open No. 2015-096022

In conventional motors, there are two types of losses: copper loss that occurs when a three-phase alternating current is passed through the windings and iron loss that occurs when an alternating magnetic field is generated in the teeth. Since copper loss is proportional to the square of the current, it is dominant when high torque is generated. On the other hand, since the iron loss is proportional to the square of the magnetic flux density of the alternating magnetic field and the square of the rotational speed, it is dominant when high speed rotation is required. As a method for reducing the iron loss, methods such as sine wave of magnetic flux density and thinning of an electromagnetic steel sheet have been proposed. In contrast, copper loss can be reduced by increasing the volume ratio of the winding in the winding space by making the winding thicker or setting the winding cross-sectional shape to a rectangle. There is no effective reduction method other than lowering the resistance of the wire. However, in a situation where the space for winding is limited, there is a limit in reducing the resistance value. As a result, the current that can be passed through the winding is limited and the torque generated by the motor is limited, or the copper loss is released as thermal energy and the temperature of the motor rises. A rise in temperature may cause problems such as demagnetization of the magnet and an increase in the size of the cooling device.

Therefore, an object of the present invention is to provide an electric motor capable of reducing energy loss due to copper loss or the like.

The electric motor according to one aspect of the present invention is provided with a plurality of magnet portions arranged in a predetermined direction, having a coercive force functioning as a permanent magnet and capable of reversing the magnetization direction by a predetermined magnetization reversal action, A stator provided with a magnetism adjustment unit that gives the magnetization reversal action to each magnet unit in association with each magnet unit, and a mover arranged to be movable along the direction in which the magnet units are arranged,
By the magnetization adjustment unit, the magnetization direction of each of the plurality of magnet units is alternately reversed, and a moving magnetic field is generated along the arrangement direction of the magnet units due to a shift in the magnetization direction reversal time in each magnet unit. Magnetization control means for controlling the magnetization reversal action.

Sectional drawing in the axis orthogonal direction of the motor which concerns on one form of this invention. The figure which shows the relationship between the coercive force and magnetic flux density of typical hard magnetic material. The figure which shows an example of the relationship between the waveform of the electric current supplied to a coil | winding part, and the magnetic flux density of the magnet part corresponding to the coil | winding part. The figure which shows an example of the relationship between the external magnetic field by a coil | winding part, and the magnetic flux density of a magnet part. The figure which shows the relationship between the magnetization direction of the three magnet parts of a stator, and the magnetic pole equivalent to a half circumference of a rotor at the time of energizing to each coil | winding part with the motor of FIG. The figure which shows the generated torque at the time of controlling electricity supply according to FIG. 5, and its average torque. The figure which shows the relationship between the electrical angle of a motor, and the phase current supplied to a coil | winding part by comparing with the motor of this form, and the conventional motor. The figure which shows the calculation result of the copper loss based on the change of the phase current of FIG. Sectional drawing in the axis orthogonal direction of the motor which concerns on the modification which employ | adopted the rotor which has a salient pole part. Sectional drawing in the axis orthogonal direction of the motor which concerns on the modification which used the GMR element for the magnet part. Sectional drawing in the axis orthogonal direction of the motor which concerns on the other modification which used the GMR element for the magnet part. The figure which shows one form which comprises a single magnet part combining several GMR element. The figure which shows the modification of FIG. The figure which shows the other modification of FIG. The figure which shows the further modification of FIG.

FIG. 1 shows an embodiment in which the electric motor according to the present invention is applied to a rotary motion output type electric motor. The motor 1 is configured as a synchronous motor, and includes a stator (stator) 2 and a rotor 3 as a mover disposed coaxially inside the stator 2. The stator 2 includes a stator yoke 4 formed in a cylindrical container shape with a circular or polygonal cross section, and a plurality (six in the illustrated example) provided at regular intervals in the circumferential direction on the inner periphery of the stator yoke 4. The teeth part 5 is provided. The stator yoke 4 is formed of an electromagnetic steel plate. The teeth portion 5 is provided with a magnet portion 6 so as to protrude toward the center of the stator 2. On the outer periphery of each magnet portion 6, a winding portion 7 is provided as a magnetization adjusting portion that causes an external magnetic field to act on the magnet portion 6 as a magnetization reversal effect on the magnet portion 6. The winding part 7 is formed by winding around the magnet part 6. The winding part 7 is provided so that the magnetic field lines of the external magnetic field acting on the magnet part 6 face the radial direction of the stator 2.

The magnet portion 6 is composed of a permanent magnet and is fixed at a fixed position on the inner periphery of the stator yoke 4. A permanent magnet is an object that can maintain a magnetized state in a certain direction even when no magnetic field or current is supplied from the outside. As a material to be used for the magnet portion 6, a ferromagnetic material having a coercive force that can function as a permanent magnet, particularly a hard magnetic material, is used. Among them, the coercive force is relatively low and the magnetic flux density is compared. A high material is preferably selected. For example, as shown in FIG. 2, an alnico magnet has a low coercive force and a high magnetic flux density as compared with a neodymium magnet, and therefore can be suitably used as a material for the magnet portion 6. However, in the present invention, the use of materials other than alnico magnets, that is, hard magnetic materials such as neodymium magnets, samarium cobalt magnets, and ferrite magnets is not denied. In addition, although the GMR element shown in FIG. 2 means a giant magnetoresistive element (Giant Magnet Resistance), the magnet part 6 can also be comprised using this. This point will be described later.

Returning to FIG. 1, the rotor 3 is configured as an embedded magnet type rotor in which a plurality of plate-type permanent magnets 9 are arranged at equal intervals in the circumferential direction on a rotor body 8 formed in a substantially cylindrical shape by an electromagnetic steel plate. Has been. The number of permanent magnets 9 is associated with the number of poles of the stator 2. In the illustrated example, four permanent magnets 9 are provided for the six magnet portions 6. That is, the number of poles of the stator 2 is 6, and the number of poles of the rotor 3 is 4. Each permanent magnet 9 is provided so that the polarization directions of the N pole and the S pole coincide with the radial direction of the rotor 3. In addition, between the pair of permanent magnets 9 adjacent in the circumferential direction, the positions of the N pole and the S pole are opposite to each other in the radial direction of the rotor 3. That is, the permanent magnets 9 are arranged so that the polarity of the outer periphery of the rotor 3 is alternately reversed along the circumferential direction.

The motor 1 is further provided with a control circuit unit 10 as magnetization control means. The control circuit unit 10 shapes a current from a predetermined power source 11 into a predetermined waveform and supplies the current to each winding unit 7 at a predetermined cycle. The power source 11 is a three-phase AC power source. FIG. 1 shows a state in which the control circuit unit 10 and the winding unit 7 of the pair of adjacent teeth units 5 are connected, but each winding unit 7 is connected to the control circuit unit 10. ing.

FIG. 3 shows an example of the relationship between the waveform of the current supplied from the control circuit unit 10 to one winding unit 7 and the magnetic flux density of the magnet unit 6 corresponding to the winding unit 7. The control circuit unit 10 shapes the current from the power supply 11 into a pulse shape and supplies the current to the winding unit 7 at a predetermined cycle. The magnitude of the pulse current (peak current value) is set within a range that can overcome the coercive force of the magnet portion 6 and make the magnetization direction of the magnet portion 6 coincide with the direction of the external magnetic field created by the winding portion 7. Is done. In addition, the direction of the pulse current supplied to the winding section 7 is set to be alternately reversed every cycle. Accordingly, the polarity of the magnet portion 6 on the side facing the rotor 3 is periodically reversed between the N pole and the S pole.

FIG. 4 shows an example of the relationship between the external magnetic field that the winding portion 7 acts on the magnet portion 6 and the magnetic flux density of the magnet portion 6. When a positive pulse current is supplied to the winding part 7, the magnet part 6 is magnetized in the + direction according to the initial magnetization curve. When the pulse current disappears, the external magnetic field disappears, and accordingly the operating point of the magnet unit 6 moves in the negative coercive force direction and operates at the point A1. Therefore, as shown in FIG. 3, the magnetic force in the positive direction remains in the magnet portion 6 even after the pulse current disappears. Next, when a negative pulse current is supplied to the winding part 7, the operating point of the magnet part 6 moves from A1 in the negative magnetic flux density direction and becomes saturated. When the pulse current disappears, the operating point of the magnet unit 6 moves in the positive coercive force direction and operates at point A2. Therefore, as shown in FIG. 3, a negative magnetic force remains in the magnet portion 6 even after the pulse current disappears.

The control circuit unit 10 controls the current of each winding unit 7 according to the same driving method as the 120-degree energization method used for the brushless DC motor. As shown in FIG. 3, the pulse current is energized at 120 ° intervals, and the current value is set to 0 during the energization timing. Moreover, the energization timing to each winding part 7 is shifted by 60 degrees in the circumferential direction. As a result, six drive patterns (energization patterns) are generated for all the winding portions 7. FIG. 5 shows the relationship between the magnetization directions of the three magnet portions 6 of the stator 2 and the magnetic poles corresponding to the half circumference of the rotor 3 when the energization to each winding portion 7 is controlled according to the 120-degree energization method. By controlling the current of the winding part 7 according to the 120-degree energization method, the magnetization direction of each magnet part 6 is sequentially reversed at intervals of 120 degrees to generate a rotating magnetic field around the rotor 3, thereby making the rotor 3 constant. Can be rotated in the direction.

FIG. 6 shows the torque generated in the rotor 3 when the energization of the winding part 7 is controlled by the method described above. Although the torque changes in a pulse shape with the reversal of the magnetization direction of the magnet unit 6, it is possible to output an average torque and to drive the motor 1 as an output source of the rotational motion. Note that the hysteresis of the magnetization curve shown in FIG. 4 changes according to the peak value of the pulse current. Therefore, the torque generated by the motor 1 can be changed by changing the magnitude of the pulse current.

FIG. 7 shows a comparison of waveforms of phase currents supplied to one winding part 7 of the motor 1 and one winding part of the conventional motor. In the motor 1 of this embodiment, it is only necessary to periodically apply a pulse current to the winding portion 7, whereas in a conventional motor, it is necessary to continuously energize a sinusoidal current. Therefore, according to the motor 1 of the present embodiment, the integrated amount of current can be reduced as compared with the conventional motor. Therefore, the motor 1 of this embodiment is advantageous in reducing copper loss as compared with a conventional motor. An example of the copper loss calculation result is shown in FIG. According to this, in comparison with a conventional motor, the copper loss can be reduced to about 1/10 in the motor 1 of the present embodiment.

The present invention is not limited to the above-described form, and various changes or modifications are possible. For example, the number of poles of the stator 2 and the rotor 3 can be changed as appropriate. In the above embodiment, the rotor is configured as an embedded magnet type rotor in which permanent magnets 9 are embedded, but the rotor may be configured as a surface magnet type rotor in which permanent magnets are arranged on the outer peripheral surface thereof. Good. Further, the rotor is not limited to the one provided with a permanent magnet, and may be configured to be formed of a ferromagnetic material such as iron without using a permanent magnet and to have a plurality of salient pole portions on the outer periphery. A motor having such a rotor is called an SRM (Switched Reluctance Motor) type. FIG. 9 shows an embodiment in which the present invention is applied to an SRM type motor. In FIG. 9, the same reference numerals are assigned to the parts common to FIG. In FIG. 9, the control circuit unit as the magnetization control means is not shown.

In the motor 1A shown in FIG. 9, the stator 2A has the same configuration as the stator 2 except that the number of the tooth portions 5 is changed to 12 compared to the stator 2 of FIG. On the other hand, as for the rotor 20, the permanent magnet 9 is omitted as compared with the rotor 3 of FIG. 1, and the entire rotor 20 is formed of a ferromagnetic material. In particular, the rotor 20 is made of iron, which is a typical soft magnetic material that has a small coercive force and cannot function as a permanent magnet. On the outer periphery of the rotor 20, a plurality of salient pole portions 21 are formed at regular intervals in the circumferential direction. The number of salient pole portions 21 is set to 8 corresponding to 2/3 of the number of poles of the stator 2A.

Also in the motor 1A as described above, a rotating magnetic field is generated around the rotor 20 by periodically supplying a pulse current to each winding part 7 of the stator 2A and sequentially reversing the magnetization direction of the magnet part 6. Torque can be generated in the rotor 20. The number of salient pole portions 21 of the rotor 20 is not limited to the illustrated form, and may be appropriately changed according to the number of poles of the stator 2A. According to the example of FIG. 9, since it is not necessary to provide a magnet in the rotor 20, the configuration of the rotor 20 can be simplified, thereby providing the motor 1A having a simple structure.

In the above embodiment, the magnet portion 6 of the tooth portion 5 is formed of a permanent magnet, but a magnetization reversal device such as a GMR element can be used instead. An example is shown in FIG. In the motor 1 </ b> B shown in FIG. 10, a GMR element 30, which is an example of a magnetization reversal device, is disposed in place of the permanent magnets of the teeth portions 5. The GMR element 30 has a structure in which a magnetization fixed layer 31 and a magnetization variable layer 32 made of a ferromagnetic material are laminated with an intermediate layer 33 interposed therebetween. The magnetization fixed layer 31 and the magnetization variable layer 32 are formed as perpendicular magnetization type magnetization layers whose magnetization directions coincide with the stacking direction (vertical direction in the figure). In each magnet portion 6, the GMR element 30 includes a stator so that the direction in which the stator 2 and the rotor 3 face each other matches the magnetization direction of the GMR element 30, and the magnetization variable layer 32 faces the rotor 3. 2 is arranged on the inner circumference. The magnetization direction of the magnetization fixed layer 31 is constant, and is set so as to face the rotor 3 side (radial direction center side), for example, as shown by a white arrow in FIG. On the other hand, the magnetization direction of the magnetization variable layer 32 corresponds to the magnetization direction of the magnetization fixed layer 31 (the direction indicated by the solid white arrow) according to the direction of the external magnetic field created by the winding portion 7 and the magnetization fixed layer. It changes between the direction opposite to the magnetization direction of 31 (the direction indicated by the dashed white arrow). The magnetization variable layer 32 may be referred to as a free layer. The intermediate layer 33 is made of a nonmagnetic material metal. As an example, copper (Cu), platinum (Pt), or gold (Au) is used as the material of the intermediate layer 33.

As apparent from FIG. 2, the magnetization variable layer 32 of the GMR element 30 can function as a magnet having a considerably high magnetic flux density by the action of a slight external magnetic field. Moreover, the magnetization variable layer 32 has a coercive force that functions as a permanent magnet that is magnetized in a certain direction even when there is no external magnetic field. Therefore, the GMR element 30 can be used as a magnet portion having a low coercive force and a high magnetic flux density. In addition, what is necessary is just to control the electric current supplied to the coil | winding part 7 similarly to the case where the magnet part 6 made from a permanent magnet is used by the control circuit part 10 of the form of FIG. That is, the control circuit unit 10 in FIG. 1 can be used as the magnetization control means.

In the example of FIG. 10, the magnetization direction of the magnetization variable layer 32 of the GMR element 30 is reversed by an external magnetic field created by the winding portion 7. However, the magnetization reversal action is not limited to the example using an external magnetic field, for example, external A magnetization reversal action can also be given using an electric current. For example, in the motor 1 </ b> C shown in FIG. 11, the electrode 34 is disposed outside the magnetization fixed layer 31 and the magnetization variable layer 32 of the GMR element 30. For example, when a current in the direction of the arrow C1 is passed between the electrodes 34, the magnetization direction of the magnetization variable layer 32 coincides with that of the magnetization fixed layer 31, and when a current in the direction of the arrow C2 is passed between the electrodes 34, the magnetization of the magnetization variable layer 32 is obtained. The direction is reversed in the opposite direction to that of the magnetization fixed layer 31. In this case, similarly to the pulse current applied to the winding section 7 in FIG. 1 or FIG. 10, the pulse current for magnetization reversal may be energized between the electrodes 34 while alternately reversing the direction at a constant period. . That is, the control circuit unit 10 in FIG. 1 can be used as the magnetization control means. In this example, the electrode 34 functions as a magnetization adjusting unit.

11, it is not necessary to arrange the winding part 7 around the magnet part 6. Therefore, it is advantageous for miniaturization of the motor 1C. In addition to the above, by providing an external magnetic field or external current as a magnetization reversal action, a magnetization variable layer having a coercive force that can reverse the magnetization direction and functions as a permanent magnet even after the magnetization reversal action is lost. If it is a device provided, it can replace with a permanent magnet and can use the device for a magnet part.

10 and 11, the single magnet portion 6 can be composed of one or a plurality of GMR elements 30. In particular, in the form of FIG. 11, it is not necessary to provide a winding portion around the GMR element 30, so that it is easy to configure a single magnet unit 6 by combining a number of GMR elements 30. In addition, by adjusting the arrangement of the GMR elements 30 and the magnetic field of each GMR element 30 in one magnet part 6, the magnetic field produced by the magnet part 6 can be appropriately changed. Specific embodiments in which a single magnet unit 6 is configured using a plurality of GMR elements 30 of the type shown in FIG. 11 are shown in FIGS. In each figure, similarly to FIGS. 10 and 11, the magnet unit 6 is depicted as a rotor positioned above the magnet unit 6. In each figure, the arrow in the GMR element 30 indicates the magnetization direction, the length of the arrow indicates the strength of the magnetic field (magnetic flux density), and the waveform above the GMR element 30 indicates the magnetic flux density distribution of the magnetic field.

In the example of FIG. 12, the magnetization direction of the GMR element 30 changes between the center side and the outer peripheral side of the magnet unit 6. That is, the GMR element 30 on the center side is arranged so that the magnetization direction is parallel to the radial direction of the rotor, and the GMR element 30 on the outer peripheral side is magnetized at one end facing the rotor more than the end on the opposite side. It is arranged to be inclined with respect to the radial direction of the rotor so as to be shifted toward the center side of the portion 6. According to this, the magnetic field of the GMR element 30 can be concentrated on the center side of the magnet portion 6, thereby strengthening the magnetic field of the stator and increasing the motor torque.

In the example of FIG. 13, the GMR element 30 on the center side is arranged in the same manner as in the example of FIG. 12, while the outer GMR element 30 is opposite to the end of the rotor opposite to the example of FIG. It is arranged to be inclined with respect to the radial direction of the rotor so as to be shifted to the outer peripheral side of the magnet portion 6 from the end portion on the side. According to this, the magnetic field of each GMR element 30 can be dispersed, thereby increasing the harmonic magnetic field of the stator and increasing the torque of the motor.

In the example of FIG. 14, as in the example of FIG. 12, the GMR element 30 on the center side is arranged so that the magnetization direction faces a direction parallel to the radial direction of the rotor, and the GMR element 30 on the outer peripheral side faces the rotor. The one end that is tilted with respect to the radial direction of the rotor is arranged so as to be shifted toward the center of the magnet portion 6 with respect to the opposite end. However, in the example of FIG. 12, the inclination of the GMR element 30 on the outer peripheral side is constant, whereas in the example of FIG. 14, the GMR element 30 close to the outer periphery of the magnet unit 6 is the inner GMR element. The inclination of the GMR element 30 is differentiated so that it is more inclined than the rotor 30 in the radial direction of the rotor. Thereby, a magnetic field having a sinusoidal intensity distribution is generated. In this case, the torque ripple of the motor can be reduced.

In the example of FIG. 15, the direction of each GMR element 30 is aligned in a direction parallel to the radial direction of the rotor, and the strength of the magnetic field of each GMR element 30 is decreased from the center side of the magnet portion 6 toward the outside. Differentiated. For this purpose, the magnitude of the pulse current applied to each GMR element 30 in order to reverse the magnetization direction may be controlled so as to decrease from the center side of the magnet unit 6 toward the outside. In this example, a magnetic field having a sinusoidal intensity distribution can be generated as in the example of FIG.

Not only the example described above, but also when a single magnet unit 6 is configured by combining a plurality of GMR elements 30, the magnet unit 6 is adjusted by adjusting the arrangement of the GMR elements 30 and the magnetic field of each GMR element 30. It is possible to appropriately change the magnetic field. 12 to 15 show a state in which a plurality of GMR elements 30 are arranged in one direction. However, in the single magnet portion 6, the GMR elements 30 may be arranged in a matrix shape, a honeycomb shape, or the like. It may be arranged in a dimensional direction.

In the above embodiment, the inner rotor type electric motor in which the rotor is arranged inside the stator is taken as an example, but the present invention is also applicable to an outer rotor type electric motor in which the rotor is arranged outside the stator. In addition, the present invention is not limited to an electric motor that outputs a rotational motion, and can also be applied to an electric motor such as a linear motor that outputs a motion along a non-arc-shaped locus by opening the stator and the rotor. .

Various aspects of the present invention derived from each of the above-described embodiments and modifications will be described below. In the following description, in order to facilitate understanding of each aspect of the present invention, the corresponding members illustrated in the accompanying drawings are added in parentheses, but the present invention is thereby limited to the illustrated embodiments. It is not a thing.

The electric motor (1; 1A; 1B; 1C) according to one aspect of the present invention has a plurality of magnet portions (having a coercive force functioning as a permanent magnet and capable of reversing the magnetization direction by a predetermined magnetization reversal action) 6; 30) are arranged side by side in a predetermined direction, and further, a stator (2; 2A) in which a magnetism adjusting section (7; 34) that imparts the magnetization reversal action to each magnet section is provided in association with each magnet section. And the mover (3; 20) arranged to be movable along the direction in which the magnet parts are arranged, and the magnetization directions of the plurality of magnet parts are alternately reversed, and the magnetization directions of the magnet parts are Magnetization control means (10) for controlling the magnetization reversal action by the magnetization adjusting section so as to generate a moving magnetic field along the arrangement direction of the magnet sections due to the reversal timing shift.

According to the electric motor according to the above aspect, by sequentially reversing the magnetization directions of the plurality of magnet portions, a moving magnetic field is generated along the direction in which the magnet portions are arranged, thereby driving the mover in the direction of the moving magnetic field. Can do. Since the magnet portion has a coercive force that functions as a permanent magnet, the magnetization adjustment portion causes a magnetization reversal action to magnetize the magnet portion in a specific direction, and then reaches a time to reverse the magnetization direction. In the meantime, it is not necessary to supply a current or the like to the magnetization adjusting unit in order to maintain the magnetic field of the magnet unit. Therefore, it is possible to reduce energy loss due to copper loss or the like.

In one aspect of the present invention, the magnet part is formed of a ferromagnetic material that can be a permanent magnet, and the winding for causing an external magnetic field to act on the magnet part as the magnetization reversal action by supplying current as the magnetization adjusting part. Part (7) is provided, and the magnetization control means is configured so that the magnetization directions of the plurality of magnet parts are alternately reversed, and the moving magnetic field is generated due to a shift in the magnetization direction reversal timing of the magnet parts. The current to be supplied to the winding part may be controlled. According to this, the magnet part can be magnetized in a specific direction by an external magnetic field generated by supplying a current to the winding part, and the magnetization direction can be reversed by switching the direction of the current. By forming the magnet portion from a ferromagnetic material, the magnet portion can function as a permanent magnet even if the supply of current to the winding portion is stopped.

In the above embodiment, the magnet portion may be formed of a hard magnetic material. The magnet part formed of a hard magnetic material can reverse the magnetization direction by applying an external magnetic field that exceeds the coercive force, and remains magnetized in a certain direction even after the external magnetic field is lost. It can be maintained and function reliably as a permanent magnet. In particular, among hard magnetic materials, hard magnetic materials such as alnico magnets and samarium cobalt magnets that have a relatively low coercive force and a relatively high magnetic flux density after the loss of an external magnetic field are used as materials for the magnet portion of the present invention. It can be suitably used.

In the above embodiment, the magnetization control means may reverse the magnetization direction of the magnet unit by supplying a pulsed current to the winding unit. According to this, it is not necessary to supply a pulse current to the winding part at a time when the magnetization should be reversed and to supply a current to the winding part in other periods. Therefore, the effect of reducing energy loss due to copper loss or the like can be enhanced.

In another embodiment of the present invention, the magnet portion has a magnetization direction in a direction coinciding with a direction in which the mover and the stator face each other, and depends on the direction of the supplied external magnetic field or external current. At least one magnetization reversal device (30) having a magnetization variable layer (32) whose magnetization direction is reversed is provided so that the magnetization variable layer faces the mover, and the magnetization adjusting unit (7; 34) may supply the external electric field or the external current to the magnetization switching device as the magnetization switching action. A magnetization reversal device such as a GMR element can easily reverse the magnetization direction of the magnetization reversal layer with low energy by applying an external magnetic field or external current, and even after the external electric field or external current is lost. The magnetic flux density is kept relatively high. Therefore, a magnetization reversal device can be suitably used as a means for realizing the magnet unit of the present invention. A magnetization reversal device of the type that reverses magnetization with an external current is advantageous in reducing the size of an electric motor because it is not necessary to provide a means for generating an external magnetic field such as a winding part separately from a magnet part. .

In the above embodiment, a single magnet unit may be configured by combining a plurality of magnetization reversal devices. According to this, it is possible to appropriately change the magnetic field generated in the magnet unit by appropriately adjusting the arrangement of the magnetization switching devices and the magnetic field of each magnetization switching device.

In a further embodiment of the present invention, the mover (20) is formed of a ferromagnetic material without using a permanent magnet, and has a plurality of salient pole portions (21) along the arrangement direction of the magnet portions. It may be. According to this, the movement along the moving magnetic field can be given to the mover by attracting the salient pole part of the mover by the moving magnetic field generated by the plurality of magnet parts. Since it is not necessary to dispose a permanent magnet on the mover side, an electric motor having a simple structure can be realized.

Claims

A plurality of magnet parts having a coercive force functioning as a permanent magnet and capable of reversing the magnetization direction by a predetermined magnetization reversal action are provided side by side in a predetermined direction, and the magnetization reversal action is given to each magnet part. A stator in which a magnetization adjustment unit is provided in association with each magnet unit;
A mover arranged to be movable along the direction in which the magnet parts are arranged;
By the magnetization adjustment unit, the magnetization direction of each of the plurality of magnet units is alternately reversed, and a moving magnetic field is generated along the arrangement direction of the magnet units due to a shift in the magnetization direction reversal time in each magnet unit. Magnetization control means for controlling the magnetization reversal action;
With electric motor.
The magnet portion is formed of a ferromagnetic material that can be a permanent magnet,
As the magnetization adjusting portion, a winding portion is provided that causes an external magnetic field to act on the magnet portion as the magnetization reversal effect by supplying current,
The magnetization control means is supplied to the winding portion so that the magnetization directions of the plurality of magnet portions are alternately reversed and the moving magnetic field is generated due to a shift in the magnetization direction reversal timing in the magnet portions. The electric motor according to claim 1, wherein the electric current to be controlled is controlled.
The electric motor according to claim 2, wherein the magnet portion is formed of a hard magnetic material.
4. The electric motor according to claim 2, wherein the magnetization control means supplies a pulsed current to the winding portion to reverse the magnetization direction of the magnet portion.
The magnet portion has a magnetization direction in a direction coinciding with a direction in which the mover and the stator face each other, and the magnetization direction is reversed according to the direction of an external magnetic field or an external current supplied. At least one magnetization reversal device having a variable layer is provided such that the magnetization variable layer faces the mover,
The electric motor according to claim 1, wherein the magnetization adjusting unit supplies the external electric field or the external current to the magnetization switching device as the magnetization switching action.
The electric motor according to claim 5, wherein the single magnet unit is configured by combining a plurality of magnetization reversal devices.
7. The mover according to claim 1, wherein the mover is made of a ferromagnetic material without using a permanent magnet, and has a plurality of salient pole portions along an arrangement direction of the magnet portions. The electric motor described.