JP7047433B2 - motor - Google Patents

Description

The present invention relates to a motor using a permanent magnet.

Patent Document 1 describes a rotor for a motor and a motor having a neodymium magnet as a permanent magnet. Neodium 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.

There are also motors that use permanent magnets made of materials that do not contain Dy or Tb. Normally, in a motor, when the rotation speed of the motor is high, the magnetic flux generated from the rotor causes a counter electromotive force to be generated in the coil on the stator side due to the change in the magnetic flux. When such a counter electromotive force is generated, when the engine is mainly used for high-speed driving, it becomes a load on the engine and high-speed fuel consumption is deteriorated. 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 "weakened 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 power is not applied, the induced power in the coil of the stator becomes small, so that heat generation in the stator is suppressed.

Japanese Unexamined Patent Publication No. 2017-153356 Japanese Unexamined Patent Publication No. 2017-28806

The motor described in Patent Document 2 can be expected to improve the operating efficiency at high speed rotation of the motor without using the expensive Dy and Tb. As the temperature-sensitive magnetic material to be used, a ferricolloid which is a liquid and an iron-based alloy which is fixed are described. As an embodiment of the temperature-sensitive magnetic material, an embodiment in which one kind of temperature-sensitive magnetic material is arranged as one layer around a permanent magnet is illustrated. Also in this embodiment, by using the temperature-sensitive magnetic material, the effective operating temperature of the motor can be made higher than that of the non-used one. However, it is unavoidable that the maximum motor torque in the high temperature range becomes small.

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, the fluctuation range of the maximum torque of the motor in a high temperature range is relaxed to achieve a high temperature. An object of the present invention is to provide a motor capable of further improving the operating efficiency of the motor in the region.

The motor according to the present invention is a motor including a stator provided with a coil and a rotor provided with a permanent magnet, wherein the rotor is a temperature-sensitive magnetic material having two or more layers on at least the side of the permanent magnet facing the coil. The temperature-sensitive magnetic materials constituting each layer are characterized by having different curry temperatures.

In the motor according to the present invention, the temperature-sensitive magnetic material arranged in the rotor is two or more layers in order to reduce the counter electromotive force generated in the coil of the stator during high-speed rotation, and the temperature-sensitive magnetic material constituting each layer is used. The Curie temperature is different for each. As a result, the fluctuation range of the maximum motor torque in the high temperature region caused by the temperature-sensitive magnetic material can be gradually reduced, and the operating efficiency of the motor in the high temperature region can be further improved.

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 magnet coercive force and the maximum reverse magnetic field applied to the magnet in the prior art (FIG. 4 (a)) and a graph showing the relationship between the magnet coercive force and the maximum motor torque in the prior art (FIG. 4 (b)). ). A graph showing the relationship between the magnet coercive force when the temperature-sensitive magnetic material is one layer and the maximum reverse magnetic field applied to the magnet (FIG. 5A), and the magnet coercive force when the temperature-sensitive magnetic material is one layer. The graph which shows the relationship of the motor maximum torque (FIG. 5 (b)). A graph showing the relationship between the magnet coercive force when the temperature-sensitive magnetic material has three layers and the maximum reverse magnetic field applied to the magnet (FIG. 6A), and the magnet coercive force when the temperature-sensitive magnetic material has three layers. The graph which shows the relationship of the motor maximum torque (FIG. 6 (b)).

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 a 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. In the stator 10, an appropriate number of slots 11 penetrating in the direction of the central axis O are formed 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.

FIG. 2 is a cross-sectional view taken along the lines AA, BB, and CC of FIG. As shown in the cross-sectional view of FIG. 2, the rotor 20 is a laminated body of electrical steel sheets 21, and has a rectangular parallelepiped-shaped space 22 that penetrates the laminated body in the central axis O direction and extends in the central axis direction. ing. A permanent magnet 23 having a rectangular parallelepiped shape and a flat plate shape and a temperature-sensitive magnetic material laminate 24 are inserted into the space 22 in a state of being laminated in the radial direction. The temperature-sensitive magnetic material laminate 24 is made of two or more flat plate-shaped temperature-sensitive magnetic materials having different Curie temperatures Tc. In this example, the temperature-sensitive magnetic material laminate 24 has a three-layer structure of a first temperature-sensitive magnetic material layer 24a, a second temperature-sensitive magnetic material layer 24b, and a third temperature-sensitive magnetic material layer 24c.

In the motor 1, when AC power having 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. Rotate within.

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 permanent magnet 23 having a rectangular shape and a flat plate shape and the temperature-sensitive magnetic material laminate 24 are laminated in the radial direction and are permanent magnets. The temperature-sensitive magnetic material laminate 24 is inserted so as to be located on the side of the stator 10 facing the coil 13 in 23.

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. Then, in each of the spaces 22a, 22b, and 22c, a laminate of the permanent magnet 23 and the temperature-sensitive magnetic material laminate 24 is inserted as described above.

Preferably, the temperature-sensitive magnetic material laminate 24 is in contact with the surface of the permanent magnet 23 so as to be orthogonal to the direction in which the magnetic flux flows between the stator 10 and the permanent magnet 23 during operation of the motor 1, and is on the stator 10 side. It is placed facing the. Although not shown, the three spaces 22a, 22b, and 22c are not essential and may be any one or two selected spaces.

In the present embodiment, the materials of the first temperature-sensitive magnetic material layer 24a, the second temperature-sensitive magnetic material layer 24b, and the third temperature-sensitive magnetic material layer 24c constituting the temperature-sensitive magnetic material laminate 24 are not limited. It is preferably a Mn—Zn-based ferrite magnetic material, and as an example _, an Fe ₂ O3 based oxide magnetic material containing Mn · Zn can be mentioned. The Curie temperature Tc of the first temperature-sensitive magnetic material layer 24a, the second temperature-sensitive magnetic material layer 24b, and the third temperature-sensitive magnetic material layer 24c are different from each other. This kind of material is available on the market.

The characteristics of the temperature-sensitive magnetic material described above will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the saturation magnetic flux density (G) and the temperature (° C.) of the temperature-sensitive magnetic material, and the horizontal axis shows the temperature (° C.) and the vertical axis shows the saturation magnetic flux density (G). As the graph shows, the temperature-sensitive magnetic material has a characteristic that the magnetic resistance is low and the magnetic flux easily passes at a low temperature, and the magnetic resistance is high and the magnetic flux is difficult to pass at a high temperature. For example, in the temperature-sensitive magnetic material a having Tc = 150 ° C., since it is ferrimagnetic at 150 ° C. or lower, magnetic magnetic flux is passed through, but at higher temperatures, it becomes paramagnetic and becomes the same state as the air layer. This makes it difficult for magnetic flux to pass through. As shown in FIG. 3, various types of temperature-sensitive magnetic materials having different Curie temperature Tc (here, seven types of temperature-sensitive magnetic material a to temperature-sensitive magnetic material e) are easily available.

In the motor 1 according to the present embodiment, as described above, the temperature-sensitive magnetic material laminate 24 is located on the surface side of the permanent magnet 22 (the side facing the coil 13 of the rotor 10), so that when the temperature becomes high, A reverse magnetic field is no longer applied to the permanent magnet 22, making it difficult to demagnetize. Further, since the magnetic field from the permanent magnet 22 is difficult to flow in the stator, a self-weakening magnetic field (self-variable magnetic field) action is applied. It will be described in detail below.

In a motor equipped with a rotor, the relationship between the reverse magnetic field and the magnet holding force and the relationship between the maximum torque of the motor at the rotor outer diameter side surface α point (see FIG. 2) of the permanent magnet 23 arranged in the rotor 20 will be described. do. FIG. 4 shows the relationship between them in a conventional motor, that is, a motor that does not use the temperature-sensitive magnetic material described above, and FIG. 4A shows a magnet coercive force (Hcj (kA / m)) and a magnet. FIG. 4B shows the relationship between the magnet coercive force and the maximum motor torque (Nm).

When the maximum reverse magnetic field (Hmax (kA / m)) applied to the magnet becomes larger than the coercive force Hcj of the permanent magnet, the magnet is demagnetized. Therefore, as shown in FIG. 4A, the magnet use limit temperature Tu1 in the motor is set. As shown in FIG. 4B, the maximum motor torque (Nm) is also determined. If the magnet usage limit temperature is Tu1 or higher, it becomes difficult to control the motor.

By using the temperature-sensitive magnetic material, the magnet use limit temperature Tu1 can be changed to a higher temperature Tu2. The state will be described with reference to FIG. FIG. 5 (a) shows the relationship between the magnet coercive force and the maximum reverse magnetic field applied to the magnet, and FIG. 5 (b) shows the relationship between the magnet coercive force and the maximum motor torque, which are shown in FIGS. 4 (a) and 4 (a), respectively. It is a figure corresponding to b).

Here, one kind of temperature-sensitive magnetic material is used, and one layer thereof is laminated on a permanent magnet. Assuming that the Curie temperature Tc of the temperature-sensitive magnetic material used is Tck, at temperatures above Tck, the magnetic field from the stator 10 side becomes difficult to pass through the temperature-sensitive magnetic material, and as a result, the reverse magnetic field to the permanent magnet is small. Therefore, it becomes difficult to demagnetize the permanent magnet. As a result, the maximum reverse magnetic field Hmax (kA / m) is reduced, and the magnet use limit temperature can be raised to a higher temperature Tu2 (> Tu1). However, in that case, as shown in FIG. 5 (b), the maximum motor torque (Nm) becomes a value depending on the Curie temperature Tc of the temperature-sensitive magnetic material used, that is, Tck, and is used in a high temperature range, in other words, used. The maximum motor torque (Nm) in the temperature range above Tck of the temperature-sensitive magnetic material (the temperature range in the vicinity of Tu1 to Tu2) must be small.

The motor according to the present embodiment has improved the inconvenience, and by using the temperature-sensitive magnetic material in a state of being laminated in two or more layers having different Curie temperature Tc instead of one layer. Resolve the inconvenience.

One form thereof will be described with reference to FIG. The example shown in FIG. 6 is a diagram corresponding to FIGS. 5 (a) and 5 (b) in the case where the temperature-sensitive magnetic material laminate 24 composed of three layers is laminated on the permanent magnet 23. This corresponds to the case of the rotor 20 described with reference to FIG. 2, and is not limited, but as an example, the first temperature-sensitive magnetic material layer 24a referred to in FIG. 2 is the temperature-sensitive magnetic material exemplified in FIG. a (Tc = 150 ° C.), a temperature-sensitive magnetic material b (Tc = 120 ° C.) for the second temperature-sensitive magnetic material layer 24b, and a temperature-sensitive magnetic material c (Tc = 120 ° C.) for the third temperature-sensitive magnetic material layer 24c. Tc = 90 ° C.) can be mentioned respectively. In FIG. 6, the Curie temperature Tc of the temperature-sensitive magnetic material a corresponding to the first temperature-sensitive magnetic material layer 24a is Tca, and the Curie temperature Tc of the temperature-sensitive magnetic material b corresponding to the second temperature-sensitive magnetic material layer 24b is set. Tcb, the Curie temperature Tc of the temperature-sensitive magnetic material c corresponding to the third temperature-sensitive magnetic material layer 24c is shown as Tcc.

As shown in FIG. 6 (a), by using temperature-sensitive magnetic materials having different Curie temperatures Tc, it is possible to gradually reduce the maximum reverse magnetic field in the high temperature region, and as a result, FIG. 6 (b) shows. As shown, the maximum motor torque in the high temperature range can also be gradually reduced. Therefore, the torque in the high temperature region can be maintained at a high value on average as compared with the one shown in FIG. 5 (b). Further, although it depends on the selection of the temperature-sensitive magnetic material, the magnet use limit temperature Tu3 can be raised to the vicinity of the temperature Tu2, which is almost the same as the case where the temperature-sensitive magnetic material is one layer.

In the motor according to the present invention, the layer of the temperature-sensitive magnetic material is not limited to three layers, and any two or more layers can achieve the intended purpose. Further, the combination order of the two or more layers of the temperature-sensitive magnetic material is not limited to the order of the Curie temperature high temperature material → the Curie temperature low temperature material, and the arrangement order is arbitrary. For example, when the temperature of the permanent magnet is high, a material with a low Curie temperature Tc is placed on the permanent magnet side, and when the temperature on the stator side is high and the temperature on the rotor surface is high, the Curie temperature is on the rotor surface side. It is preferable to arrange a material having a low temperature Tc. Further, as shown in the figure, the layer of the temperature-sensitive magnetic material may be only on the rotor surface side (stator side) of the permanent magnet, or may be on the opposite side, that is, only on the central axis side of the rotor. Similar effects can be achieved by arranging them on both sides of the rotor on the surface side of the rotor on the central axis side. It is suitable for motor control that the temperature-sensitive magnetic material to be used is appropriately selected from materials having a Curie temperature Tc of 60 ° C. to 200 ° C.

In the motor 1 of the present embodiment, a temperature-sensitive magnetic material having a rectangular shape and a flat plate shape is used as the temperature-sensitive magnetic material, and a permanent magnet having a rectangular shape in the axial space formed in the rotor. A rotor with a structure in which a radial laminate of a temperature-sensitive magnetic material and a temperature-sensitive magnetic material is inserted, and a rotor that is easier to manufacture and has high long-term reliability as compared with a rotor that uses a liquid temperature-sensitive magnetic member. It becomes a structure.

Further, the temperature-sensitive magnetic material is a Mn—Zn-based ferrite magnetic material, and when a temperature-sensitive magnetic material which is an iron-based alloy is used, the Curie temperature is high in the iron-based alloy, and the Curie temperature is greatly changed by changing the composition. It is difficult to obtain a material that changes the Curie temperature, but since a ferrite-based temperature-sensitive magnetic material has a Curie temperature that is relatively suitable for motor control, it is not possible to prepare materials with different Curie temperatures by changing the composition without damaging the magnetism. It's relatively easy. Therefore, there is an advantage that it becomes easy to select a material according to the control temperature.

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 sheet is hindered, and the magnet and the electromagnetic steel sheet 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 ... Slot,
12 ... Teeth,
13 ... coil,
20 ... Rotor,
22 (22a, 22b, 22c) ... A rectangular parallelepiped space,
23 ... Permanent magnet,
24 ... Temperature-sensitive magnetic material laminate,
24a ... First temperature-sensitive magnetic material layer,
24b ... Second temperature-sensitive magnetic material layer,
24c ... Third temperature-sensitive magnetic material layer.

Claims (1)

A motor consisting of a hollow columnar stator equipped with a coil and a rotor equipped with a permanent magnet.
The rotor is provided with two or more layers of temperature-sensitive magnetic material on at least the side of the permanent magnet facing the coil, and the temperature-sensitive magnetic materials constituting each layer have different Curie temperatures.
A motor characterized in that two or more layers of a temperature-sensitive magnetic material are laminated in the radial direction of the stator .

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