JP2021175342A - Rotary motor-driven device - Google Patents

Abstract

To provide a rotary motor-driven device capable of increasing output, increasing revolution speed, and further increasing efficiency at the time of low revolution speed by suppressing constraint caused by counter electromotive voltage.SOLUTION: A permanent magnet 9 provided in a rotor 8 has: an outer layer permanent magnet 9a arranged on an outer surface side of the rotor 8; and an inner layer permanent magnet 9b arranged inside the outer layer permanent magnet 9a in a radial direction of the rotor 8. Coercive force of one permanent magnet 9b, of the outer layer permanent magnet 9a and the inner layer permanent magnet 9b, is less than the coercive force of the other permanent magnet 9a. Magnetic force changing parts 6 and 7 are further provided that reduce or increase magnetic force of the other permanent magnet 9b with less coercive force.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electric motor such as a surface magnet type motor (SPM motor) and a rotary electric device including a device for controlling the torque thereof.

In an electric motor provided with a permanent magnet in the rotor (hereinafter, simply referred to as a motor), a rotating magnetic field is formed around the rotor by a stator coil, so that the rotor rotates and outputs torque. Since the output torque is a torque corresponding to the voltage applied to the stator coil and the magnetic force generated by the permanent magnet of the rotor, the motor can be miniaturized by using a permanent magnet having a high magnetic flux density.

On the other hand, the magnetic flux density of a permanent magnet and the coercive force are in a so-called trade-off relationship, and a permanent magnet having a high magnetic flux density has a low coercive force. Therefore, in a motor that has been miniaturized by using a permanent magnet with a large magnetic force, the coercive force is low, so that the magnetic force generated by the permanent magnet gradually decreases due to the demagnetic field during use of the motor, and the torque that can be output decreases at an early stage. Probability is high. Patent Document 1 describes a surface magnet type motor configured to suppress a decrease in magnetic force due to such a demagnetic field to achieve miniaturization and high output.

The motor described in Patent Document 1 is a motor configured to maintain a large magnetic force by changing the coercive force of a permanent magnet in a rotor according to the degree of influence of a demagnetizing field. According to the description of Patent Document 1, when the permanent magnet provided on the surface side of the rotor is divided into the transition between the magnetic poles in the inner layer, the outer layer and the outer layer, the influence of the demagnetic field is the smallest in the inner layer, and the transition between the outer layer and the magnetic poles. Therefore, the coercive force is set in the order of the degree of influence of this demagnetizing field, that is, in the order of inner layer <outer layer <magnetic pole transition.

Therefore, the inner layer, which has a relatively small coercive force and can increase the coercive force accordingly, can easily maintain the coercive force because the influence of the demagnetic field is small, and the outer layer and the transition of the magnetic poles have a relatively large coercive force. Therefore, the magnetic force can be maintained even if the influence of the demagnetic field is large. As a result, according to the motor described in Patent Document 1, it is said that a large magnetic force can be maintained as a whole of the rotor or the motor as a whole, and the size and output of the motor can be increased.

Japanese Unexamined Patent Publication No. 2010-98863

In the configuration described in Patent Document 1, the magnetic force due to the permanent magnet in the rotor can be increased and maintained. However, since the counter electromotive voltage is generated by the rotation of the rotor, the output torque decreases as the rotation speed of the rotor increases. That is, if the magnetic force of the rotor is simply increased, a high torque can be output at a low rotation speed, but the counter electromotive voltage increases as the rotation speed increases, and the torque that can be output is low torque accordingly. Become. In that case, the output torque can be maintained by increasing the voltage applied to the stator coil, but doing so causes inconveniences such as an increase in the terminal voltage of the inverter in a synchronous motor, for example. Alternatively, it is possible to maintain the torque by weakening the magnetic field control, but since power is consumed for the control, the energy efficiency may decrease.

The present invention has been made by paying attention to the above technical problems, and suppresses the restriction due to the counter electromotive voltage to increase the output at a low rotation speed, increase the rotation speed, and further improve the efficiency. It is an object of the present invention to provide a rotary electric device capable of providing a rotary electric device.

In the present invention, in order to achieve the above object, a rotor in which permanent magnets are arranged on an outer surface is rotatably arranged inside a cylindrical stator having a coil, and the coil is rotatably arranged. In a rotary electric device that rotates the rotor by energizing the rotor to generate a rotating magnetic field, the permanent magnets are an outer layer permanent magnet arranged on the outer surface side of the rotor and the outer layer in the radial direction of the rotor. It has an inner layer permanent magnet arranged inside the permanent magnet, and the coercive force of one of the outer layer permanent magnet and the inner layer permanent magnet is smaller than the coercive force of the other permanent magnet. It is characterized in that it further includes a magnetic force changing portion that reduces and increases the magnetic force of the other permanent magnet having a small size.

In the motor of the present invention, the rotor is rotated and torque is output by energizing the coil of the stator to generate a rotating magnetic field. In that case, the rotation speed becomes the rotation speed according to the rotating magnetic field, and the torque becomes the torque according to the magnetic force of the rotor and the voltage applied to the coil. The magnetic force of the rotor is the magnetic force of the outer layer permanent magnet and the inner layer permanent magnet, but one permanent magnet having a small coercive force is demagnetized (or demagnetized) and magnetized by the magnetic force changing portion.

When demagnetized (or degaussed), the magnetic force of the rotor as a whole becomes small, so that the counter electromotive voltage due to the rotation of the rotor becomes small. Therefore, the rotor can be rotated at a high rotation speed, or a predetermined torque can be output even when the rotor is rotating at a high rotation speed. In that case, since the magnetic force of the rotor is small, it is not necessary to flow a weak magnetic field current when increasing the rotation speed. Therefore, the efficiency can be improved by the amount that the current for the weak magnetic field can be reduced. Can be done. On the other hand, if a permanent magnet having a small coercive force is magnetized at the magnetic force changing portion, the magnetic force of the rotor becomes large, so that the output torque can be increased when the rotation speed of the rotor is low. That is, the output can be increased without increasing the size.

It is a schematic cross-sectional view for demonstrating embodiment of this invention. It is a partial cross-sectional view which shows that a permanent magnet has a two-layer structure. It is a diagram which shows the relationship between the rotation speed and the back electromotive force in a fully magnetized state and a partially demagnetized state.

The present invention will be described based on the embodiments shown in the figure. It should be noted that the embodiments described below are merely examples of cases where the present invention is embodied, and do not limit the present invention.

The motor as an embodiment of the present invention is characterized by the structure of the rotor or its permanent magnet, so the overall structure is similar to that of other common permanent magnet motors, except for the rotor. be. 1 and 2 show a schematic diagram for explaining the structure of the motor 1. The cylindrical stator 2 has a stator core 3 formed by laminating a large number of electromagnetic steel sheets, and a coil 5 is wound around a plurality of teeth 4 projecting toward a central portion on an inner peripheral surface thereof. .. A rotating magnetic field is generated by controlling the current flowing from the controller 6 including a secondary battery or an inverter to the coil 5 by an electronic control device (ECU) 7 mainly composed of a microcomputer. ing.

Inside the stator 2, the rotor 8 is rotatably arranged with a slight air gap between it and the teeth 4. The rotor 8 is provided with a permanent magnet 9 on its outer surface. A plurality of permanent magnets 9 are provided so that the north and south poles are alternately positioned in the circumferential direction of the rotor 8. Further, the permanent magnets 9 are provided in two layers in the radial direction of the rotor 8, and are provided inside the outer layer permanent magnets 9a on the outer surface side of the rotor 8 and the outer layer permanent magnets 9a in the radial direction of the rotor 8. It is configured so that the coercive force is different from that of the inner layer permanent magnet 9b.

FIG. 2 shows a schematic partial cross-sectional view of an example in which the outer layer permanent magnet 9a is a high coercive magnet and the inner layer permanent magnet 9b is a low coercive magnet. Both the outer layer and the inner layer are cylindrical, and they are formed in a cylindrical shape with different magnet materials and fitted so as to be integrated, or different magnet materials are arranged in two layers, the inner layer and the outer layer. It may be any of the configurations integrally formed by molding. The magnet materials may be appropriately selected from those conventionally known.

Further, a magnetic force changing portion for changing the magnetic force of a permanent magnet having a small coercive force (inner layer permanent magnet 9b in the example shown in FIG. 2) is provided. The magnetic force changing portion applies a demagnetizing field to the inner layer permanent magnet 9b in the direction opposite to the magnetic field already magnetized to reduce the magnetic force of the inner layer permanent magnet 9b, and also a magnetic field in the same direction (temporarily). (Referred to as a positive magnetic field) is applied to increase the magnetic force of the inner layer permanent magnet 9b, or to magnetize the inner layer permanent magnet 9b.

Such demagnetization (or demagnetization) and magnetization may be performed by the controller 6 and the ECU 7 described above. For example, the d-axis current may be controlled to cause a demagnetizing field or a positive magnetic field to act on the inner layer permanent magnet 9b, thereby demagnetizing (or demagnetizing) or magnetizing the inner layer permanent magnet 9b. In that case, the controller 6 and the ECU 7 correspond to the magnetic field changing unit in the embodiment of the present invention. When a demagnetizing magnetic field or a positive magnetic field is generated as described above, the magnetic field also acts on the outer layer permanent magnet 9a, but since the outer layer permanent magnet 9a is a permanent magnet having a large coercive force, the inner layer having a small coercive force is small. The permanent magnet 9b is preferentially demagnetized (or demagnetized) and magnetized.

FIG. 3 is a diagram showing the relationship between the rotation speed of the motor 1 and the counter electromotive voltage. In a fully magnetized state in which both the outer layer permanent magnets 9a and the inner layer permanent magnets 9b are magnetized in the same manner, the magnetic forces of both of these permanent magnets 9a and 9b become magnetic forces that generate torque. Therefore, in the fully magnetized state, the increasing gradient of the counter electromotive voltage with the increase in the rotation speed becomes large. On the other hand, in the state of partial demagnetization in which the magnetic force of the permanent magnet (inner layer permanent magnet 9b) having a small coercive force is demagnetized or demagnetized, the magnetic force of the inner layer permanent magnet 9b is reduced and the torque is increased. The magnetic flux involved in the generation of the above or the magnetic flux crossing the coil 5 of the stator 2 is reduced. Therefore, in the partially demagnetized state, the increasing gradient of the counter electromotive voltage accompanying the increase in the rotation speed becomes smaller than in the case of full magnetism.

When the counter electromotive voltage becomes high, the torque that can be output becomes small enough to be impractical, or the terminal voltage of the inverter becomes excessively high. Therefore, there is an upper limit to the counter electromotive voltage that can be practically allowed, and in FIG. 3, the rotation speed at which the counter electromotive voltage reaches the upper limit in the fully magnetized state (motor rotation speed or rotor 8 rotation speed) is switched. It is described as.

When the motor 1 described above is used as a driving force source for some device such as a vehicle, when the rotation speed is equal to or less than the switching rotation speed, the inner layer permanent magnet 9b is magnetized in the same manner as the outer layer permanent magnet 9a in a fully magnetized state. Used in. Therefore, in that case, the magnetic force involved in the generation of torque becomes large, so that a large torque can be obtained. For example, when the motor 1 is used as the driving force source of the vehicle, the driving force at the time of starting or immediately after the start can be increased to improve the starting acceleration.

In such a so-called fully magnetized state, as shown by the solid line in FIG. 3, the counter electromotive voltage greatly increases, and the counter electromotive voltage at the switching rotation speed reaches the upper limit. At that time, a demagnetizing force is applied to the inner layer permanent magnet 9b by the above-mentioned magnetic force changing portion to demagnetize (or demagnetize) the inner layer permanent magnet 9b, thereby reducing the magnetic force of the inner layer permanent magnet 9b. In such a partially demagnetized state, the magnetic flux across the coil 5 decreases, so that the counter electromotive voltage at the switching rotation speed becomes a voltage lower than the upper limit. Therefore, the rotation speed can be further increased by removing the restriction due to the counter electromotive voltage. The state is shown by a solid line in FIG.

That is, according to the configuration of the motor 1 described above, it is possible to increase the output in a low rotation speed state and reduce the restriction due to the counter electromotive voltage to increase the rotation speed. In other words, even if the magnetic force of the rotor 8 is reduced so as to suppress the counter electromotive voltage at a high rotation speed, the magnetic force of the rotor 8 can be increased at a low rotation speed, so that a high torque can be output. Further, the magnetic force of the rotor 8 can be changed by temporarily generating a demagnetizing field or generating a positive magnetic field. That is, unlike the conventional case where the current is continuously applied so as to generate a weakened magnetic field, the current for changing the magnetic force may be temporary, so that the power consumption can be reduced and the energy efficiency can be improved. Further, since the counter electromotive voltage can be suppressed, for example, the terminal voltage of the inverter can be lowered, so that the cost in that respect can be reduced, and the cost of the rotary motor as a whole can be reduced.

The present invention is not limited to the above-described embodiment, and the magnetic field changing unit may be configured by a coil provided separately from the coil through which a current for generating torque is passed.

Further, in the above-described embodiment, since the inner layer permanent magnet 9b is a permanent magnet having a small coercive force, the influence of the demagnetizing field on the permanent magnet having a small coercive force when the motor 1 is rotated is reduced, which is not intended. It is possible to suppress a decrease in magnetic force. However, in the present invention, the present invention is not limited to such a configuration, and the outer layer permanent magnet 9a may be a permanent magnet having a small coercive force. Further, in the above-described embodiment, it is decided to demagnetize (or demagnetize) or magnetize a permanent magnet having a small coercive force, but in the present invention, such demagnetization (or demagnetization) or magnetism is appropriately performed. Therefore, it may be configured to demagnetize (or demagnetize) or magnetize based on an appropriately selected parameter other than the rotation speed.

1 Motor 2 Stator 3 Stator core 4 Teeth 5 Coil 6 Controller 7 Electronic control unit (ECU)
8 Rotor 9 Permanent magnet 9a Outer layer permanent magnet 9b Inner layer permanent magnet

Claims (1)

Inside a cylindrical stator having a coil, a rotor in which permanent magnets are arranged on the outer surface is rotatably arranged coaxially with the stator, and the rotor is energized to generate a rotating magnetic field. In a rotating electric device that rotates
The permanent magnet has an outer layer permanent magnet arranged on the outer surface side of the rotor and an inner layer permanent magnet arranged inside the outer layer permanent magnet in the radial direction of the rotor.
The coercive force of one of the outer layer permanent magnet and the inner layer permanent magnet is smaller than the coercive force of the other permanent magnet.
A rotary electric device further comprising a magnetic force changing portion that reduces and increases the magnetic force of the other permanent magnet having a small coercive force.

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