JP2019146422A - Variable field motor - Google Patents

Abstract

To effectively short-circuit a magnetic flux of a rotor magnet.SOLUTION: A variable field motor 10 includes: a stator 12; and a rotor 16 including a plurality of magnets 20 arranged to face the stator 12 with a gap therebetween. On an axial end surface of the rotor 16, a magnetic material 22 for short-circuiting a magnetic flux from the magnets 20 is disposed. An average magnetic flux density of the magnetic material 22 at no load is set to 70% or more of saturation magnetic flux density.SELECTED DRAWING: Figure 1

Description

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

  In a magnet motor having a rotor provided with a permanent magnet, there is a demand for preventing the back electromotive force from becoming too large during high-speed rotation.

  Patent Document 1 discloses a method for manufacturing a motor in which a magnetic material is disposed at an end of a rotor having a permanent magnet. The maximum number of revolutions of the electric motor is adjusted by changing the thickness of the end plate made of a magnetic material arranged 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 interlinked with the winding is finely adjusted, The maximum number of rotations 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 of the rotor. In addition, it is shown that the magnetic short-circuit member is moved closer to or away from the permanent magnet by the actuator to control the field by the permanent magnet.

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

  Patent Document 4 shows that a rotor of an electric motor provided with a permanent magnet has a movable iron core that forms a magnetic path by changing its position in a direction close to the rotor core when the rotational speed of the rotor increases. Has been. When the movable iron core comes close to the rotor core during high rotation, the field magnetic flux generated by the rotor can be weakened.

International Publication No. WO02 / 0194999 JP 2001-275326 A JP 2012-143055 A JP 2001-25190 A

  In patent document 1, the thickness of an end plate is changed and the short circuit amount of magnetic flux is controlled. However, it is difficult to change the thickness of the end plate in the actual driving state.

  In Patent Document 2, the magnetic short-circuit member (iron plate) at the top of the rotor is pulled away using an actuator. However, when the amount of short-circuit magnetic flux to the magnetic short-circuit member increases, such as during field weakening, the attractive force of the magnetic short-circuit member increases. For this reason, the force for pulling away the magnetic short-circuit member is increased, and thus the actuator is increased in size.

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

  In Patent Document 4, at the time of high rotation, the movable iron core is moved to the outside of the rotor by centrifugal force, thereby causing a magnetic flux short circuit. 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 there is a space for accommodating the spring inside the rotor so that the movable iron core approaches and contacts the rotor. It is necessary and the structure is complicated.

  An object of the present invention is to provide a variable field motor that has a simple structure and can effectively generate torque while reducing a counter electromotive flux during high-speed rotation.

  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 therebetween. A magnetic material for short-circuiting the magnetic flux is arranged, and the average magnetic flux density of the magnetic material at no load is set to 70% or more of the saturation magnetic flux density.

  In addition, when the average magnetic flux density of the magnetic material at the time of no load is set in a transient region between a linear region and a saturated region, and when the average magnetic flux density of the magnetic material at a predetermined load or more is set in the saturated region Good.

  In addition, the average magnetic flux density of the magnetic material at no load may be set to 70% to 80% of the saturation magnetic flux density.

  Further, it is preferable that the magnetic material has a moving mechanism that moves relative 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.

  Moreover, it is good for the said moving mechanism to change to the state 1 which the said magnetic material adjoins to the said axial direction end surface, and the state 2 which leaves | separates from the said axial direction end surface.

  Further, when the magnetic material is moved, the phase angle of the current supplied to the stator may be advanced from the current advance angle that minimizes the loss to increase the magnetic flux density of the magnetic material.

  The stator may be an IPM structure in which the stator is disposed on the outer peripheral side of the rotor via a gap, and a core exists between the stator and the gap between the rotor and the magnet.

  In addition, the magnetic material may have an annular shape, and the outer diameter thereof may be smaller than the outer diameter of the rotor.

  According to the present invention, by appropriately setting the magnetic flux density of the magnetic material at no load, the back electromotive force flux at the time of no load is reduced, and the magnetic flux due to the current is magnetized by the magnetic saturation of the magnetic material at the time of load. It is possible to effectively generate torque while suppressing crossing over the material.

(A) is a figure which shows the system configuration | structure of the variable field motor 10 which concerns on embodiment, (b) is a figure which shows the mechanical structure seen from the axial direction of the variable field motor 10. FIG. (A) is a figure explaining arrangement | positioning of a magnet, (b) is a side view of a rotor. (A), (b) is a figure which shows the other example of arrangement | positioning of a magnet. 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 the time of no load of a magnetic material, a torque, a counter electromotive flux, and attractive force. (A) is a state 1 in which the magnetic material is close to the rotor, and (b) is 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. Note that the present invention is not limited to the embodiments described herein.

"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 shows a mechanical configuration viewed from the axial direction of the variable field motor 10. It is a schematic diagram shown. The variable field motor 10 has an annular stator 12. The stator 12 has a stator core 12a and a plurality of (for example, three-phase) stator coils 12b wound around the teeth of the stator core 12a, and forms a rotating magnetic field by supplying a predetermined current thereto. In the figure, teeth are not shown, and the stator coil 12b shows only the coil end portion.

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

  A cylindrical rotor 16 is disposed inside the annular stator 12 with a predetermined gap, and a rotating shaft 18 is disposed at the center of the rotor 16. The rotor 16 is provided with magnets (permanent magnets) 20 constituting a predetermined number of magnetic poles in the circumferential direction on the peripheral side thereof. Accordingly, the rotor 16 rotates in accordance with the rotating magnetic field formed by the stator 12, and the rotating shaft 18 becomes the output shaft.

  In the present embodiment, an annular magnetic material 22 is disposed on the axial end surface of the rotor 16. The magnetic material 22 covers the axial end surfaces of the plurality of magnets 20 around the rotor 16 so as to short-circuit the magnetic fluxes of the plurality of magnets 20. The magnetic material 22 may be any magnetic material, but is preferably a soft magnetic material.

  In this example, the magnet 20 is inserted and fixed in a magnet hole that is arranged at intervals in the circumferential direction and extends 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 outer side 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 the 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. ) Motor.

  The magnetic material 22 may be fixed to the axial end surface of the rotor 16. In this case, an adhesive or bolting can be used. The magnetic material 22 may be fixed in direct contact, or may be fixed via a nonmagnetic material.

  In this example, the magnetic material 22 is not fixed to the axial end surface of the rotor 16, and can be moved relative to the axial end surface 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 transition between a state 1 in which the magnetic material 22 is close to the axial end surface and a state 2 in which the magnetic material 22 is separated from the axial end surface. Note that the control device 14 controls the actuator 24 in accordance with 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 where the magnetic material 22 is separated from the end surface of the rotor 16 is indicated by a dotted line.

  The magnetic material 22 is preferably provided with a support material on the axial end surface of the rotor 16 and supported by the support material so as to be movable in the axial direction. 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 rotary shaft 18.

  Further, although the magnetic material 22 rotates together with the rotary shaft 18, it may be fixed so as to be movable in the axial direction. Thereby, 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 not rotated. In this case, the magnetic material 22 is not mechanically coupled to the rotor 16 and has no mechanical influence on the driving of the variable field motor 10. Various moving mechanisms for the magnetic material 22 can be easily adopted. As the rotor 16 rotates, the axial end of the magnet 20 rotates with respect to the magnetic material 22, but the magnetic poles of the rotor 16 have alternating polarities in the circumferential direction, causing a problem of short-circuiting of the magnetic flux by the magnetic material 22. There is no.

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

  Further, as shown in FIG. 3A, one magnet 20 may be provided for one magnetic pole. In this case, the magnet 20 is disposed so as to be orthogonal to the radial direction, and becomes an N-pole or S-pole magnetic pole toward the outside. Further, as shown in FIG. 3B, three magnets 20 may be arranged on one magnetic pole. A magnetic pole is configured by widening the interval between the two magnets 20 in FIG. 2A and arranging the one magnet 20 in FIG. 3A in the middle.

"Action of magnetic material"
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 passes through the rotor 16 in the axial direction, and the magnetic material 22 is disposed so as to face the axial end surfaces on both sides in the axial direction of the rotor 16. 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). Thus, when the magnetic field H increases from 0, the initial magnetic flux density B increases in proportion. This region is called a linear region. When the magnetic field H further increases and reaches saturation, the magnetic flux density does not increase any more. This region is called a saturation region.

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

  FIG. 5 shows the relationship between the average magnetic flux density Bave of the magnetic material 22 in the no-load state, the torque, the amount of counter electromotive flux, and the attractive force at the time of no load. The horizontal axis represents the average magnetic flux density Bave in the magnetic material 22 when no load is applied. Thus, the torque increases as the magnetic flux density increases.

  The amount of back electromotive force in the magnetic material 22 does not change initially. That is, the magnetic material 22 is in a 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 saturation magnetic flux density, it becomes difficult to increase the magnetic flux to be short-circuited, and the amount of back electromotive force starts to increase. When the magnetic flux density in the magnetic material 22 reaches saturation, the magnetic flux that is short-circuited does not increase, thereby increasing the amount of back electromotive force linearly.

  Further, the attractive force of the magnetic material 22 by the magnet 20 has a characteristic that is close to the saturation magnetic flux density and is just opposite to the above-described counter electromotive flux amount. That is, the magnetic material 22 is initially in a linear region, and the attractive force does not change. That is, by decreasing the thickness of the magnetic material 22, the magnetic flux density increases, but the amount of magnetic flux to be short-circuited is the same, so 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 saturation magnetic flux density, the magnetic flux that is short-circuited decreases and the attractive force starts to decrease. When the magnetic flux density in the magnetic material 22 reaches saturation, the magnetic flux that is short-circuited does not increase, so that the magnetic flux from the magnet 20 simply passes through the magnetic material 22 and the attractive force decreases.

  And in this embodiment, the magnetic flux density of the magnetic material 22 at the time of no load is set to 70% or more of saturation magnetization. In particular, it is preferably set to about 70 to 80%. As a result, while reducing the back electromotive force when there is no load, the magnetic material 22 is magnetically saturated when there is a load, and it is possible to suppress the magnetic flux due to the current supply to the stator coil from passing over the magnetic material 22. Torque can be generated.

  Here, the magnetic flux density of the magnetic material 22 is adjusted by changing the thickness, inner radius, and outer radius of the magnetic material 22. That is, 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, the magnetic flux density when the magnetic material 22 is unloaded can be adjusted.

  When the outer peripheral end of the magnetic material 22 approaches the stator 12, the magnetic flux interlinked with the stator 12 is affected. Therefore, the outer peripheral end of the magnetic material 22 may be set to be the same as or more than the outer peripheral end of the magnet 20. preferable.

"Movement of magnetic material"
In the present embodiment, an actuator 24 is provided to move the magnetic material 22 in the axial direction. Various actuators 24 are known, and any actuator may be used as long as the magnetic material 22 can be appropriately moved. A motor that uses rotation of a motor or fluid pressure is suitable because it can be used relatively widely.

  When the rotor 16 rotates at high speed, the back electromotive force increases. Therefore, field weakening control is performed in order to output torque during high rotation. In the present embodiment, the magnetic material 22 is provided, and the magnetic material 22 can be brought close to the end surface of the rotor 16, whereby the field by the magnet 20 can be weakened. Therefore, when the rotational speed is equal to or greater 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 shifted to two positions, ie, a close state 1 shown in FIG. 6A and a distant state 2 shown in FIG. 6B. Thus, when the rotational 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 saturation magnetic flux density. Thereby, as described above, the magnetic material 22 is saturated and the torque can be effectively generated when the load is applied while reducing the counter electromotive flux when no load is applied.

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

  6A and 6B show only a predetermined angle of the stator 12 and the rotor 16, and in the figure, the stator coil 12b is not shown, and the teeth around which the stator coil 12 is wound are shown. 12c is shown. Further, both sides of the teeth 12c are slots in which coils are accommodated.

  Furthermore, it is preferable to increase the d-axis current by moving the phase angle of the current supplied to the stator more than the current advance angle at which the loss is minimized during movement. That is, the magnetic flux generated by the stator current is increased by passing the d-axis current, but the magnetic flux that is short-circuited in the magnetic material 22 is increased when the magnetic material 22 is in close proximity. Accordingly, the magnetic flux density of the magnetic material is saturated by passing the d-axis current. Accordingly, the attractive force of the magnetic material 22 is reduced. For this reason, the magnetic material 22 can be separated from the rotor 16 with a small force, and the state 2 can be obtained. As a result, the force required for the actuator 24 is reduced, and the actuator 24 can be miniaturized.

"Effect of the embodiment"
By providing the magnetic material 22, the counter electromotive flux when no load is applied can be reduced, so that field weakening can be achieved during high rotation. That is, since the magnetic material is not saturated at the time of no load, many magnetic fluxes can be short-circuited between the magnetic material and the magnet, and the counter electromotive flux can be reduced.

  By setting the magnetic material magnetic flux density average value at the time of no load to 70% or more of the saturation magnetization, the magnetic flux generated by the stator current at the time of loading is not transferred to the magnetic material in the saturated state but is transferred to the rotor and effectively generates torque. That is, the torque reduction 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 at no load is set higher. When the magnetic material 22 is saturated, the attractive force is reduced, 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 flowing a d-axis current during the movement of the magnetic material, the magnetic material is more saturated and the attractive force is reduced, and the force required for adjusting the axial position of the magnetic material can be reduced.

DESCRIPTION OF SYMBOLS 10 Variable field motor, 12 Stator, 12a Stator core, 12b Stator coil, 14 Control apparatus, 16 Rotor, 18 Rotating shaft, 20 Magnet, 22 Magnetic material, 24 Actuator.

Claims (8)

A variable field motor having a stator and a rotor including a plurality of magnets arranged to face the stator via a gap,
On the axial end surface of the rotor, a magnetic material for short-circuiting the magnetic flux from the magnet is disposed,
The average magnetic flux density of the magnetic material at no load is set to 70% or more of the saturation magnetic flux density.
Variable field motor. The variable field motor according to claim 1,
The average magnetic flux density of the magnetic material at no load is set in a linear region and a transient region of a saturation region, and the average magnetic flux density of the magnetic material at a load of a predetermined load or more is set in a saturation region.
Variable field motor. The variable field motor according to claim 2,
The average magnetic flux density of the magnetic material at no load is set to 70% to 80% of the saturation magnetic flux density,
Variable field motor. The variable field motor according to any one of claims 1 to 3,
A moving mechanism for moving the magnetic material relative to the axial end surface of the rotor;
The distance between the magnetic material and the axial end surface of the rotor is adjustable.
Variable field motor. The variable field motor according to claim 4,
By the moving mechanism, the magnetic material can transition to a state 1 approaching the axial end surface and a state 2 separating from the axial end surface.
Variable field motor. The variable field motor according to claim 4 or 5,
When moving the magnetic material, increase the magnetic flux density of the magnetic material by advancing the phase angle of the current supplied to the stator more than the current advance angle that minimizes the loss,
Variable field motor. The variable field motor according to any one of claims 1 to 6,
The stator is arranged on the outer peripheral side of the rotor via a gap,
It is an IPM structure in which a core exists between the stator and a gap between the rotor and a magnet.
Variable field motor. The variable field motor according to any one of claims 1 to 7,
The magnetic material has an annular shape, and the outer diameter thereof is smaller than the outer diameter of the rotor.
Variable field motor.