JP6939474B2 - motor - Google Patents

Description

The present invention relates to a motor that uses a permanent magnet.

Patent Document 1 describes a rotor for a motor and a motor having a neodymium magnet as a permanent magnet. Neodymium magnets are materials with high magnetic flux density and high coercive force, but since the coercive force decreases at high temperatures, heavy rare earth metals Dy and Tb are added to secure the coercive force at high temperatures. However, since Dy and Tb are rare elements, they are expensive and have a high resource risk.

In a motor that uses a permanent magnet made of a material that does not contain Dy or Tb, when the rotation speed of the motor is high, the magnetic flux generated from the rotor causes a counter electromotive force in the coil on the stator side due to the change in the magnetic flux. appear. When such a counter electromotive force is generated, when the engine is mainly used for high-speed driving, the load on the engine becomes large and the high-speed fuel consumption deteriorates. Therefore, in order to reduce the magnetic flux of the magnet from the stator, the magnetic flux of the magnet is reduced by applying a reverse magnetic field in synchronization with the rotation of the magnet. This is called "weakening field". Such a weakened field may cause an increase in power loss (copper loss), heat generation of the motor, and the like. A motor capable of avoiding this is described in Patent Document 2.

In Patent Document 2, the rotor is provided with a temperature-sensitive magnetic material. When the rotation speed of the motor is high, the temperature of the rotor rises, so that the temperature of the temperature-sensitive magnetic material rises and the magnetic permeability decreases. By reducing the magnetic permeability of the temperature-sensitive magnetic material, the magnetic flux of the permanent magnets alternated by the coil of the stator is reduced. Therefore, the counter electromotive force becomes small, and even if a large field weakening field power is not applied, the induced power in the coil of the stator becomes small, so that heat generation in the stator can be suppressed and the operating efficiency of the motor can be improved. ..

JP-A-2017-153356 JP-A-2017-28806

In the motor described in Patent Document 2, the operating efficiency at high speed rotation of the motor can be improved without using expensive Dy or Tb. As the temperature-sensitive magnetic material to be used, a liquid ferricolloid and a fixed iron-based alloy are described. Placing a temperature-sensitive magnetic material that is a liquid in the rotor is not structurally easy. Further, iron-based alloys generally have a high Curie temperature and are not always effective in actual use.

Further, the position of the temperature-sensitive magnetic material is on the rotor surface side with respect to the magnet V-shaped arrangement, and there is a problem that the reluctance torque is drastically reduced when the temperature becomes high, and the motor torque is lowered.

The present invention has been made in view of the above circumstances, and in a motor provided with a rotor in which a temperature-sensitive magnetic material is arranged together with a permanent magnet in the rotor, the permanent magnet and the temperature-sensitive magnetic material can be easily arranged in the rotor. An object of the present invention is to provide a motor capable of reliably reducing the magnetic flux emitted from a permanent magnet during high-speed rotation.

The motor according to the present invention is a motor including a stator having a coil and a rotor having a rectangular permanent magnet, and the motor is a temperature-sensitive magnetism having a rectangular shape on the surface side of the rotor in the space of the rotor. It is characterized in that the material is provided and the permanent magnet is arranged on the shaft side of the rotor.

In the motor according to the present invention, in order to reduce the counter electromotive force generated in the coil of the stator during high-speed rotation, a rectangular body-shaped temperature-sensitive magnetic material is used as the temperature-sensitive magnetic material arranged in the rotor. Assembling the temperature-sensitive magnetic material is extremely easy. Further, in preparation for the rotor, the rectangular parallelepiped-shaped temperature-sensitive magnetic material is arranged so as to be in contact with the rectangular parallelepiped-shaped permanent magnet, and from this point as well, the rotor can be assembled extremely easily.

A cross-sectional view showing a part of a motor. A cross-sectional view taken along the line AA, line BB, and line CC of FIG. The graph which shows the temperature characteristic of a temperature-sensitive magnetic material. A graph showing the relationship between the coercive force of a magnet and the maximum reverse magnetic field applied to the magnet. The graph which shows the maximum reverse magnetic field reduction effect by using the temperature-sensitive magnetic material. The graph which shows the magnet magnetic flux reduction effect by using the temperature-sensitive magnetic material.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a part of the motor according to the present embodiment.

The motor 1 is composed of a hollow columnar stator 10 and a rotor 20 rotatably provided in the hollow portion of the stator 10. The stator 10 is formed with an appropriate number of slots 11 penetrating in the direction of the central axis O at equal intervals in the circumferential direction of the stator 10. A tooth 12 is formed between adjacent slots 11, and a coil 13 is provided so as to wind the tooth 12.

As shown in the cross-sectional view in the central axial direction of FIG. 2, the rotor 20 is a laminated body of electromagnetic steel plates 21, and is a rectangular parallelepiped-shaped space that penetrates the laminated body in the central axial direction and extends in the central axial direction. Has 22. A permanent magnet 23 having a rectangular parallelepiped shape and a flat plate shape and a temperature-sensitive magnetic material 24 are inserted into the space 22 in a state of being laminated in the radial direction.

When AC power of a predetermined drive frequency is supplied to the coil 13 of the stator 10, a rotating magnetic field is generated at a predetermined timing. The rotating magnetic field generated by the coil 13 of the stator 10 acts on the permanent magnet 23 of the rotor 20, and the coil 13 and the permanent magnet 23 are attracted or repelled to generate a rotational driving force, so that the rotor 20 is fixed to the stator. Rotate within the child 10.

In the present embodiment, the space 22 is formed as a space set of three spaces 22a, 22b, and 22c, and an appropriate number of the space sets are formed at equal intervals in the circumferential direction of the rotor 20. In each of the spaces 22a, 22b, and 22c, the rectangular parallelepiped and flat plate-shaped permanent magnet 23 and the temperature-sensitive magnetic material 24 are inserted in a state of being laminated in the radial direction.

In the illustrated example, the space 22a is formed near the outer peripheral edge of the rotor 20 in a direction orthogonal to a straight line extending in the radial direction from the central axis O of the rotor 20. The space 22b and the space 22c are formed in an inverted C shape (V shape) in which the stator 10 side is open so as to sandwich the space 22a from both sides at a position closer to the central axis O than the space 22a.

As shown in FIG. 1, in the spaces 22a, 22b, and 22c, in the laminated body of the permanent magnet 23 and the temperature-sensitive magnetic material 24, the temperature-sensitive magnetic material 24 faces the stator 10 side (the surface side of the rotor 20). It is inserted in the space as if it were. That is, the temperature-sensitive magnetic material 24 is in contact with the surface of the permanent magnet 23 so as to be relatively orthogonal to the direction in which the magnetic flux flows between the stator 10 and the permanent magnet 23 during the operation of the motor 1, and is on the stator 10 side. It will be arranged facing each other.

In the present embodiment, the temperature-sensitive magnetic material 24 is a Mn—Zn-based ferrite magnetic material, and as an example, an Fe ₂ O _3- based oxide magnetic material containing Mn · Zn can be mentioned. Further, although not shown, the three spaces 22a, 22b, and 22c are not essential and may be any one or two selected spaces.

The characteristics of the temperature-sensitive magnetic material 24 will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the saturation magnetic flux density and the temperature characteristics of the temperature-sensitive magnetic material, in which the horizontal axis shows the temperature (° C.) and the vertical axis shows the saturation magnetic flux density (G). As shown in the graph, the temperature-sensitive magnetic material has a characteristic that magnetic flux easily passes through at low temperature and magnetic flux does not easily pass through at high temperature. For example, in a material having Tc = 150 ° C., since it is ferrimagnetic at 150 ° C. or lower, magnetic magnetic flux is passed through, but at high temperature, it becomes paramagnetic and becomes the same state as the air layer. This makes it difficult for magnetic flux to pass through. Here, Tc is the Curie temperature of the temperature-sensitive magnetic material.

Therefore, in the motor 1 shown in FIG. 1, at a temperature of Tc or higher, the magnetic field from the stator 10 side becomes difficult to pass through the temperature-sensitive magnetic material 24, and as a result, the reverse magnetic field to the permanent magnet 23 becomes small. Therefore, it becomes difficult to demagnetize the permanent magnet 23. When the temperature-sensitive magnetic material 24 is not provided, the magnetic field from the permanent magnet is large in the case of high-temperature and high-speed rotation. You will need it.

In the motor 1 of the present embodiment, field weakening control is required for high-speed rotation at a low temperature as in the conventional case, but when the temperature becomes high, the temperature-sensitive magnetic material 24 is non-magnetic (paramagnetic) as described above. Therefore, it becomes difficult for magnetic flux to be generated from the permanent magnet 23, and the required weakening field magnetic field can be reduced.

Next, the maximum reverse magnetic field reduction effect due to the use of the temperature-sensitive magnetic material 24 in the motor 1 of the present embodiment will be described. 4 and 5 are graphs showing the relationship between the magnet holding force Hcj and the maximum reverse magnetic field Hmax applied to the magnet, FIG. 4 is a graph when the temperature-sensitive magnetic material 24 is not used, and FIG. It is a graph in the case of the motor 1 of the form. In both graphs
Hmax (kA / m): Maximum reverse magnetic field applied to the permanent magnet at temperature T,
Hcj (kA / m): Coercive force of permanent magnet at temperature T,
Tc: Curie temperature of temperature-sensitive magnetic material,
T1: High Br / low Hcj material use limit temperature,
T2: Use limit temperature of low Br / high Hcj material,
Is. Br is a unit of the residual magnetic density of the permanent magnet, and Hcj indicates the strength of the applied magnetic field at which the magnetization of the permanent magnet itself becomes zero, and represents the true resistance force of the permanent magnet to the reverse magnetic field.

As shown in FIG. 4, when the conventional technique, that is, the temperature-sensitive magnetic material 24 is not used, the maximum reverse magnetic field Hmax (kA / m) is constant regardless of the temperature, so that the permanent magnet 23 is made by using the high coercive force material. However, in the motor 1 of the present embodiment, as shown in FIG. 5, the temperature-sensitive magnetic material 24 is arranged on the stator 10 side of the permanent magnet 23 at a high temperature. It is possible to reduce the maximum demagnetizing field of the magnet, raise the operating temperature, or use a permanent magnet 23 as a permanent magnet with a low magnetic force.

Next, the effect of reducing the magnetic flux of the magnet by using the temperature-sensitive magnetic material 24 in the motor 1 of the present embodiment will be described with reference to FIG. In FIG. 6, the horizontal axis represents the temperature (° C.) and the vertical axis represents the no-load magnetic flux (B) due to the magnet. As shown in FIG. 6, in the motor 1 of the present embodiment, by arranging the temperature-sensitive magnetic material 24 in the rotor 20, the magnet magnetic flux can be reduced in the vicinity of Tc (Curie temperature), so that the field weakening current can be reduced. ..

Further, in the conventional case, that is, when the temperature-sensitive magnetic material is not used, the magnetic flux in Tc is Bj, the field weakening current is Ij, and the copper loss due to the field weakening is Wj. If the magnetic flux of the magnet is Bh, the field weakening current is Ih, and the copper loss due to the field weakening is Wh, then Wh / Wj ∝ (Ih / Ij) ^ 2 ∝ (Bh / Bj) ^ 2, which is the weakening field. The copper loss due to magnetism can be reduced.

In the case of using a liquid temperature-sensitive magnetic material as described in Patent Document 2, the liquid temperature-sensitive magnetic material is sealed in the laminated electromagnetic steel sheet, and the thermal expansion and contraction is repeated in the rotating body and due to the temperature change. Therefore, it is necessary to have a structure in which the rotor is sealed for a long period of time so as not to leak, and it is not easy to manufacture and guarantee the rotor.

In the motor 1 of the present embodiment, the temperature-sensitive magnetic material 24 has a rectangular parallelepiped shape and a flat plate shape, and further, the temperature-sensitive magnetic material 24 has a rectangular parallelepiped shape in the axial space formed in the rotor. It has a structure in which a radial laminate of a permanent magnet and a temperature-sensitive magnetic material is inserted, which also makes it easy to manufacture a rotor and has a rotor structure with high long-term reliability.

Further, the temperature-sensitive magnetic material 24 is a Mn—Zn-based ferrite magnetic material, and when a temperature-sensitive magnetic material which is an iron-based alloy is used, the iron-based alloy has a high Curie temperature, and the Curie temperature is changed to a large Curie. It is difficult to obtain a material that changes the temperature, but since a ferrite-based temperature-sensitive magnetic material has a Curie temperature that is relatively suitable for motor control, it is necessary to prepare materials with different Curie temperatures by changing the composition without impairing the magnetism. Is relatively easy. Therefore, there is an advantage that the material selection according to the control temperature becomes easy.

Further, when the temperature-sensitive magnetic material is a ferrite magnetic material, the ferrite magnetic material is an _{insulator because it is an iron oxide material of Fe 2} O ₃ , and the direct contact between the magnet and the electromagnetic steel plate is hindered, and the magnet and the electromagnetic steel plate are used. The generation of eddy current at the contact interface of the magnet is eliminated, and the effect of eliminating the eddy current loss is also brought about.

1 ... Motor,
10 ... stator,
11 ... Slots,
12 ... Teeth,
13 ... Coil,
20 ... Rotor,
22 (22a, 22b, 22c) ... A rectangular parallelepiped space,
23 ... Permanent magnet,
24 ... Temperature-sensitive magnetic material.

Claims (2)

A motor consisting of a stator equipped with a coil and a rotor equipped with a rectangular parallelepiped permanent magnet.
The motor is provided with a temperature-sensitive magnetic material which is a rectangular parallelepiped Mn—Zn-based ferrite magnetic material on the surface side of the rotor in the space of the rotor, and the permanent magnet is arranged on the shaft side of the rotor. A motor characterized by that. The space of the rotor is formed at equal intervals in the circumferential direction of the rotor, and the space of the rotor is orthogonal to a straight line extending in the radial direction from the central axis of the rotor near the outer peripheral edge of the rotor. A space 22a formed in the direction, and a space 22b and a space formed in an inverted C shape with the stator side open so as to sandwich the space 22a from both sides at a position closer to the central axis than the space 22a. The motor according to claim 1, wherein the motor is one or more selected from a space set consisting of 22c.

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