JP7039322B2 - Variable field motor - Google Patents

Description

The present invention relates to a variable field motor having a stator and a rotor including a plurality of magnets arranged so as to face the stator with a gap.

In a magnet motor provided with a permanent magnet in the rotor, there is a demand that the countercurrent magnetic flux at high speed rotation does not become too large.

Patent Document 1 discloses a method for manufacturing a motor in which a magnetic material is arranged at an end of a rotor having a permanent magnet. The maximum rotation speed of the motor is adjusted by changing the thickness of the end plate made of magnetic material placed at the end of the rotor. That is, by using the end plate, a part of the magnetic flux generated from the permanent magnet is short-circuited inside the rotor, and by changing the thickness of the end plate, the magnetic flux interlinking the winding is finely adjusted. The maximum number of revolutions is finely adjusted.

In Patent Document 2, in a motor having a rotor provided with a permanent magnet, a magnetic short-circuit member is provided at at least one axial end portion of the rotor. Then, it is shown that the magnetic short-circuit member is brought close to or separated from the permanent magnet by an actuator to control the field by the permanent magnet.

In Patent Document 3, a short-circuit member provided with a plurality of proximity portions arranged close to the magnetic poles and a connecting portion connecting the plurality of proximity portions at at least one end in the axial direction of a rotor having a plurality of magnetic poles. To prepare for. Then, the magnetic flux of the rotor due to the short-circuit member is controlled by changing the relative position of the rotor and the short-circuit member in the circumferential direction.

Patent Document 4 shows that a rotor of an electric motor provided with a permanent magnet has a movable iron core whose position changes in a direction close to the rotor core to form a magnetic path as the rotation speed of the rotor increases. Has been done. Since the movable iron core is close to the rotor core at high rotation speed, the field magnetic flux generated by the rotor can be weakened.

International Publication WO02 / 0194999 Japanese Unexamined Patent Publication No. 2001-275326 Japanese Unexamined Patent Publication No. 2012-143055 Japanese Unexamined Patent Publication No. 2001-25190

In Patent Document 1, the short-circuit amount of the magnetic flux is controlled by changing the thickness of the end plate. However, it is difficult to change the thickness of the end plate in the actual drive state.

In Patent Document 2, an actuator is used to separate the magnetic short-circuit member (iron plate) on the upper part of the rotor. However, when the amount of short-circuit magnetic flux to the magnetic short-circuit member increases due to field weakening or the like, the attractive force of the magnetic short-circuit member increases. Therefore, the force for pulling the magnetic short-circuit member apart becomes large, and the size of the actuator becomes large.

In Patent Document 3, the short-circuit amount of the magnetic flux from the magnet is controlled by skewing the short-circuit member (iron piece) on the upper part of the rotor in the circumferential direction by using an actuator. However, the structure of the actuator for skewing becomes complicated.

In Patent Document 4, the movable iron core is moved to the outside of the rotor by centrifugal force at high rotation speed, thereby short-circuiting the magnetic flux. However, a spring is provided between the movable iron core and the rotor to control the movement of the movable iron core according to the centrifugal force, and in order to bring the movable iron core closer to and in contact with the rotor, there is a space inside the rotor to accommodate the spring. It is necessary and the structure is complicated.

An object of the present invention is to provide a variable field motor having a simple structure and capable of effectively generating torque while reducing a countercurrent magnetic flux during high-speed rotation.

INDUSTRIAL APPLICABILITY The present invention is a variable field motor having a stator and a rotor including a plurality of magnets arranged so as to face the stator with a gap, from a magnet on an axial end surface of the rotor. By arranging a magnetic material that short-circuits the magnetic flux of the above, and setting the average magnetic flux density of the magnetic flux from the magnet in the magnetic material to 70 to 80% of the saturated magnetic flux density, the said at the time of no load. The average magnetic flux density with respect to the magnetic field of the magnetic material is set in the transient region of the linear region and the saturation region, and the average magnetic flux density of the magnetic material under a predetermined load or more is set in the saturation region .

Further, it is preferable that the magnetic material has a moving mechanism for relatively moving the magnetic material with respect to the axial end surface of the rotor, and the distance between the magnetic material and the axial end surface of the rotor can be adjusted.

Further, it is preferable that the moving mechanism can change the state 1 in which the magnetic material is close to the axial end face and the state 2 in which the magnetic material is separated from the axial end face.

Further, when moving the magnetic material, it is preferable to advance the phase angle of the current supplied to the stator from the current advance angle that minimizes the loss to increase the magnetic flux density of the magnetic material.

Further, it is preferable to have an IPM structure in which the stator is arranged on the outer peripheral side of the rotor via a gap and a core exists between the stator, the gap between the rotors and the magnet.

Further, it is preferable that the magnetic material has an annular shape and its outer diameter is smaller than the outer diameter of the rotor.

According to the present invention, by appropriately setting the magnetic flux density of the magnetic material when there is no load, the magnetic flux due to the current is magnetic due to the magnetic saturation of the magnetic material while reducing the countercurrent magnetic flux when there is no load. It is possible to effectively generate torque by suppressing the transfer to the material.

(A) is a diagram showing a system configuration of the variable field motor 10 according to the embodiment, and (b) is a diagram showing a mechanical configuration seen from the axial direction of the variable field motor 10. (A) is a view explaining the arrangement of magnets, and (b) is a side view of a rotor. (A) and (b) are diagrams showing other examples of magnet arrangement. It is a figure which shows the magnetization characteristic of a magnetic material. It is a figure which shows the relationship between the magnetic flux density at no load of a magnetic material, torque, backlash magnetic flux, and attractive force. (A) is a diagram showing a state 1 in which the magnetic material is close to the rotor, and (b) is a diagram showing a state 2 in which the magnetic material is separated from the rotor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described here.

"overall structure"
FIG. 1A is an explanatory diagram schematically showing the overall configuration of the variable field motor 10 according to the embodiment, and FIG. 1B is a mechanical configuration seen from the axial direction of the variable field motor 10. It is a schematic diagram which shows. The variable field motor 10 has an annular stator 12. The stator 12 has a stator core 12a and a plurality of phases (for example, three phases) stator coils 12b wound around the teeth of the stator core 12a, and a rotating magnetic field is formed by supplying a predetermined current to the stator coils 12b. In the figure, the teeth are not shown, and the stator coil 12b shows only the coil end portion.

The control device 14 controls the current supply to the stator coil 12b according to the output torque (required torque) of the variable field motor 10. If the variable field motor 10 is a motor for driving a vehicle, the required torque is determined according to the amount of operation of the accelerator, and the control device 14 controls the supply current to the stator coil 12b by PWM control or the like. ..

A cylindrical rotor 16 is arranged inside the annular stator 12 with a predetermined gap, and a rotating shaft 18 is arranged at the center of the rotor 16. A magnet (permanent magnet) 20 constituting a predetermined number of magnetic poles is arranged on the peripheral side of the rotor 16. Therefore, the rotor 16 rotates according to the rotating magnetic field formed by the stator 12, and the rotating shaft 18 becomes its output shaft.

In the present embodiment, the annular magnetic material 22 is arranged on the axial end surface of the rotor 16. The magnetic material 22 covers the axial end faces of the plurality of magnets 20 in the peripheral portion of the rotor 16 so as to short-circuit the magnetic fluxes of the plurality of magnets 20. As the magnetic material 22, any magnetic material may be used, but a soft magnetic material is preferable.

In this example, the magnets 20 are arranged at intervals in the circumferential direction and inserted and fixed in the magnet holes extending in the axial direction. Therefore, the outer diameter of the magnet 20 is smaller than the outer diameter of the rotor 16, and a part of the rotor core exists between the outside of the magnet 20 and the outer peripheral surface of the rotor 16. That is, the variable field motor 10 has a structure in which a magnet 20 is embedded in the rotor 16, in other words, an IPM (Interior Permanent Magnet) in which a rotor core exists between the stator 12 and the gap between the rotor 16 and the magnet. ) It is a motor.

The magnetic material 22 may be fixed to the axial end face of the rotor 16. In this case, an adhesive, bolt tightening, or the like can be used. The magnetic material 22 may be directly contacted and fixed, or may be fixed via a non-magnetic material.

In this example, the magnetic material 22 is not fixed to the axial end face of the rotor 16, but can be moved relative to the axial end face of the rotor 16 by the actuator 24. That is, the distance between the axial end surface of the rotor 16 and the magnetic material 22 can be adjusted by moving the magnetic material 22 by the actuator 24. For example, the actuator 24 can change the state 1 in which the magnetic material 22 is close to the axial end face and the state 2 in which the magnetic material 22 is separated from the axial end face. The control device 14 controls the actuator 24 according to the motor rotation speed and the like. In FIG. 1, the movement of the magnetic material 22 is indicated by an arrow, and the state in which the magnetic material 22 is separated from the end face of the rotor 16 is indicated by a dotted line.

The magnetic material 22 may be supported by providing a support material on the axial end surface of the rotor 16 so as to be movable in the axial direction on the support material. In this case, the actuator 24 may be fixed to the rotor 16. Further, the magnetic material 22 may be moved by controlling the supply and discharge of the fluid through the passage inside the rotating shaft 18.

Further, although the magnetic material 22 rotates together with the rotating shaft 18, it may be fixed so as to be movable in the axial direction. As a result, the moving mechanism of the magnetic material 22 can be made relatively simple.

Further, the magnetic material 22 may be fixed to a case or the like and may be non-rotating. In this case, the magnetic material 22 is not mechanically connected to the rotor 16 and has no mechanical influence on the drive of the variable field motor 10. Further, various moving mechanisms of the magnetic material 22 can be easily adopted. Due to the rotation of the rotor 16, the axial end portion of the magnet 20 rotates with respect to the magnetic material 22, but the magnetic poles of the rotor 16 have their polarities alternately in the circumferential direction, which causes a problem of short circuit of the magnetic flux due to the magnetic material 22. There is no.

"Arrangement of magnet 20"
Here, as shown in FIG. 2A, it is preferable that the number of magnets 20 constituting one magnetic pole is two. The two magnets 20 are arranged in a V-shape that spreads line-symmetrically toward the outside, and the magnetic poles adjacent to each other in the circumferential direction are arranged so as to be N pole and S pole alternately.

Further, as shown in FIG. 3A, one magnet 20 may be used for one magnetic pole. In this case, the magnets 20 are arranged so as to be orthogonal to each other in the radial direction, and serve as magnetic poles of N pole or S pole toward the outside. Further, as shown in FIG. 3B, three magnets 20 may be arranged on one magnetic pole. One magnetic pole is formed by widening the distance between the two magnets 20 of FIG. 2A and arranging the one magnet 20 of FIG. 3A in the middle.

"Action of magnetic materials"
Then, in the present embodiment, the annular magnetic material 22 short-circuits the magnetic flux from the adjacent magnetic poles. As shown in FIG. 2B, the magnet 20 penetrates the rotor 16 in the axial direction, and the magnetic material 22 is arranged so as to face the axial end faces on both sides of the rotor 16 in the axial direction. Therefore, at least a part of the magnetic flux from one magnetic pole (magnet 20) is short-circuited to the adjacent magnetic pole (magnet 20).

FIG. 4 shows the magnetization characteristics of the magnetic material 22. The horizontal axis is the magnetic field H (A / m), and the vertical axis is the magnetic flux density B (T: tesla). In this way, when the magnetic field H increases from 0, the initial magnetic flux density B increases proportionally. This area is called a linear area. Then, when the magnetic field H further increases and reaches saturation, the magnetic flux density does not increase any more. This region is called the saturation region.

Here, in the transient region where the magnetic flux density is about 70 to 80% of the saturated magnetic flux density (the gray region sandwiched between the two broken lines in FIG. 4), the magnetic flux density in the magnetic material 22 is close to the saturated magnetic flux density. , The rate of increase in magnetic flux density decreases.

FIG. 5 shows the relationship between the average magnetic flux density Babe of the magnetic material 22 in the no-load state, the torque, the amount of countercurrent magnetic flux, and the attractive force in the no-load state. The horizontal axis is the average magnetic flux density Babe in the magnetic material 22 when no load is applied. In this way, the torque increases as the magnetic flux density increases.

The amount of countercurrent magnetic flux in the magnetic material 22 does not change initially. That is, the magnetic material 22 is in the linear region, and the amount of magnetic flux that can be short-circuited increases as the magnetic flux density increases. However, when the magnetic flux density in the magnetic material 22 approaches the saturated magnetic flux density, it becomes difficult to increase the short-circuited magnetic flux, and the amount of countercurrent magnetic flux begins to increase. When the magnetic flux density in the magnetic material 22 reaches saturation, the short-circuited magnetic flux does not increase, which linearly increases the amount of countercurrent magnetic flux.

Further, the attractive force of the magnetic material 22 by the magnet 20 has a characteristic when approaching the saturation magnetic flux density, which is exactly opposite to the above-mentioned amount of countercurrent magnetic flux. That is, the magnetic material 22 is initially in the linear region, and the attractive force does not change. That is, by reducing the thickness of the magnetic material 22, the magnetic flux density increases, but the amount of short-circuited magnetic flux is the same, so that the attractive force of the magnetic material 22 does not change. However, when the thickness of the magnetic material 22 is further reduced and the magnetic flux density approaches the saturated magnetic flux density, the short-circuited magnetic flux decreases and the attractive force begins to decrease. When the magnetic flux density in the magnetic material 22 reaches saturation, the short-circuited magnetic flux does not increase, so that the magnetic flux from the magnet 20 simply passes through the magnetic material 22 and the attractive force becomes small.

Then, in the present embodiment, the magnetic flux density of the magnetic material 22 at no load is set to 70% or more of the saturation magnetization. In particular, it is preferably set to about 70 to 80%. As a result, the magnetic material 22 can be magnetically saturated under a load while reducing the countercurrent magnetic flux when there is no load, and the magnetic flux due to the current supply to the stator coil can be suppressed from being passed to the magnetic material 22, which is effective. Can generate magnetic flux.

Here, the magnetic flux density of the magnetic material 22 is adjusted by changing the thickness, the inner radius, the outer radius, or the like of the magnetic material 22. That is, the magnetic flux density of the magnetic material 22 under no load can be adjusted by adjusting the magnetic permeability of the magnetic material 22, the area covering the end face of the magnet 20, the thickness, and the like.

When the outer peripheral end of the magnetic material 22 approaches the stator 12, it affects the magnetic flux interlinking with the stator 12, so that the outer peripheral end of the magnetic material 22 may be set to be the same as or inside the outer peripheral end of the magnet 20. preferable.

"Movement of magnetic material"
In this embodiment, an actuator 24 is provided to move the magnetic material 22 in the axial direction. Various types of actuators 24 are known, and any actuator 24 may be used as long as the magnetic material 22 can be appropriately moved. Those that utilize the rotation of the motor and the fluid pressure can be used relatively widely and are suitable.

When the rotor 16 rotates at a high speed, the counter electromotive force becomes large. Therefore, field weakening control is performed in order to output torque at high rotation speeds. In the present embodiment, the magnetic material 22 is provided, and by bringing the magnetic material 22 closer to the end face of the rotor 16, the field due to the magnet 20 can be weakened. Therefore, when the rotation speed is equal to or higher than a predetermined value, the magnetic material 22 may be brought closer to the rotor 16 instead of the field weakening control.

For example, the actuator 24 may be configured so that the magnetic material 22 can be moved to two positions, the close state 1 shown in FIG. 6 (a) and the distant state 2 shown in FIG. 6 (b). As a result, when the rotation speed reaches a predetermined value, the magnetic material 22 is set to the state 1, and the magnetic flux density of the magnetic material 22 at no load is set to about 70 to 80% of the saturated magnetic flux density. As a result, as described above, the magnetic material 22 can be saturated and effectively generate torque while reducing the countercurrent magnetic flux when there is no load.

When the rotation speed is low, the magnetic material 22 is separated from the rotor 16 by setting the state 2 by the actuator 24, and the short-circuit magnetic flux is reduced or set to 0, so that the magnetic flux generated by the magnet 20 can be effectively used.

Note that FIGS. 6A and 6B show only predetermined angles of the stator 12 and the rotor 16 taken out, and in the figure, the stator coil 12b is not shown and the teeth around which the stator coil 12b is wound are omitted. 12c is shown. Further, both sides of the teeth 12c are slots in which coils are housed.

Further, it is preferable to increase the d-axis current by advancing the phase angle of the current supplied to the stator from the current advance angle that minimizes the loss during movement. That is, the magnetic flux created by the stator current increases by passing the d-axis current, but the magnetic flux short-circuited in the magnetic material 22 increases when the magnetic materials 22 are in close proximity to each other. Therefore, by passing a d-axis current, the magnetic flux density of the magnetic material becomes saturated. Therefore, the adsorptive force of the magnetic material 22 is reduced. Therefore, the magnetic material 22 can be separated from the rotor 16 with a small force to bring the state 2 into the state 2. As a result, the force required for the actuator 24 is reduced, and the actuator 24 can be miniaturized.

"Effect of embodiment"
By providing the magnetic material 22, the countercurrent magnetic flux at no load can be reduced, so that field weakening at high rotation is possible. That is, since the magnetic material is not saturated when there is no load, a large amount of magnetic flux can be short-circuited between the magnetic material and the magnet, and the countercurrent magnetic flux can be reduced.

By setting the average value of the magnetic flux density of the magnetic material when there is no load to 70% or more of the saturation magnetization, the magnetic flux due to the stator current does not pass to the magnetic material in the saturated state but flows to the rotor when the load is applied, and torque is effectively generated. That is, the torque decrease due to the arrangement of the magnetic material 22 can be suppressed as much as possible.

The magnetic flux density of the magnetic material 22 when there is no load is set high. When the magnetic material 22 becomes saturated, the attractive force becomes small, so that the magnetic material can be moved with a small force, and the load on the actuator 24 can be reduced. In particular, by passing a d-axis current when the magnetic material moves, the magnetic material is more saturated and the attractive force is reduced, so that the force required for adjusting the axial position of the magnetic material can be reduced.

10 variable field motor, 12 stator, 12a stator core, 12b stator coil, 14 controller, 16 rotor, 18 rotary shaft, 20 magnet, 22 magnetic material, 24 actuator.

Claims (6)

A variable field motor having a stator and a rotor comprising a plurality of magnets arranged to face the stator with a gap.
A magnetic material that short-circuits the magnetic flux from the magnet is placed on the axial end face of the rotor.
By setting the average magnetic flux density of the magnetic flux from the magnet in the magnetic material at no load to 70 to 80% of the saturated magnetic flux density, the average magnetic flux density with respect to the magnetic field of the magnetic material at no load is in a linear region. And is set in the transient region of the saturation region, and the average magnetic flux density of the magnetic material under a predetermined load or more is set in the saturation region .
Variable field motor. The variable field motor according to claim 1 .
It has a moving mechanism that moves the magnetic material relative to the axial end face of the rotor.
The distance between the magnetic material and the axial end face of the rotor is adjustable.
Variable field motor. The variable field motor according to claim 2 .
By the moving mechanism, the state 1 in which the magnetic material is close to the axial end face and the state 2 in which the magnetic material is separated from the axial end face can be changed.
Variable field motor. The variable field motor according to claim 2 or 3 .
When moving the magnetic material, the phase angle of the current supplied to the stator is advanced beyond the current advance angle that minimizes the loss to increase the magnetic flux density of the magnetic material.
Variable field motor. The variable field motor according to any one of claims 1 to 4 .
The stator is arranged on the outer peripheral side of the rotor via a gap.
An IPM structure in which a core exists between the stator, the gap between the rotors, and the magnet.
Variable field motor. The variable field motor according to any one of claims 1 to 5 .
The magnetic material is annular and its outer diameter is smaller than the outer diameter of the rotor.
Variable field motor.

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