JP2018011473A - Variable magnetic flux motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable magnetic flux motor that can be used in a wide rotational frequency region and, moreover, indicates high efficiency over the wide rotational frequency region.SOLUTION: A variable magnetic flux motor 10 comprises: an inner rotor 20 having 2n pieces (n≥1) of magnetic poles; an outer stator 40; and relative moving means 50 that relatively moves the outer stator 40 in an axial direction of the inner rotor 20. The inner rotor 20 has a ring magnet 26 joined to a surface opposite to an inner peripheral surface of the outer stator 40. The ring magnet 26 is magnetized such that an N pole and an S pole alternate in a circumferential direction of the inner rotor 20. The axial length of the ring magnet 26 is two or more times as long as that of the outer stator 40. In addition, the ring magnet 26 comprises p pieces (p≥1) of high magnetic flux regions (A), in which 0°≤θ≤1° (θ is a skew angle), and q pieces (q≥1) of medium and low magnetic flux regions (B), in which 1°<θ≤180°/n.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a variable magnetic flux motor. More specifically, the magnitude of an induced voltage (back electromotive force) generated with the rotation of the motor can be varied by variably controlling the magnitude of the magnetic flux flowing between the stator and the rotor. The present invention relates to a variable magnetic flux motor that can be controlled.

The motor has
(A) an induction motor (IM) using an electric conductor for the rotor,
(B) a surface permanent magnet (SPM) motor having a permanent magnet attached to the surface of the rotor;
(C) Those having various structures such as an interior permanent magnet (IPM) motor in which a permanent magnet is embedded in a rotor are known.

  In order to use such a motor as a drive source of an electric vehicle, for example, a predetermined torque is applied in a wide speed range (rotational speed range) from when the vehicle starts (at low speed rotation) to high speed travel (at high speed rotation). It is required to be obtained. However, in any motor having any structure, the induced voltage (counterelectromotive force) increases as the rotor speed increases. Therefore, the motor power supply voltage and the induced voltage become equal at a certain rotational speed, and the rotational speed cannot be increased any more. In order to solve this problem, the counter electromotive force is conventionally reduced by flowing a current having a magnitude that reduces the magnetic flux passing through the field coil to the field coil and reducing the magnetic flux passing through the field coil. A method of making it small (field weakening control) is used.

For example, Patent Document 1 discloses that
A rotor with magnets embedded inside,
A stator provided with a skew in the slot so that an axial force in the + z-axis direction is generated on the rotor shaft during rotation;
A spring mechanism for urging the rotor shaft in the -z-axis direction;
A radial motor is disclosed that includes a governor mechanism that changes a rotor shaft holding position in the axial direction in accordance with the rotational speed of the motor.

In the same document,
(A) During low-speed rotation, the axial force (+ z direction) of the rotor shaft becomes larger than the set load (−z direction) of the spring mechanism, so that the rotor shaft is displaced in the + z direction, and the pressure plate of the rotor shaft is The point where displacement stops when touched,
(B) During high-speed rotation, the axial force of the rotor shaft is smaller than the set load of the spring mechanism, and the governor mechanism opens due to an increase in centrifugal force, so that the rotor shaft is displaced in the −z direction, and
(C) It is described that the gap magnetic flux is reduced by the displacement of the rotor shaft in the -z direction during high-speed rotation, and a field weakening can be realized.

Patent Document 2 does not aim at field-weakening control,
(A) Magnetizing the N pole and the S pole alternately along the circumferential direction of the outer peripheral surface of the magnet surface having a cylindrical shape;
(B) A steep slope (skew) is attached to the portion near the lower end face of the magnet body,
(C) A ring-type permanent magnet is disclosed in which a gentle slope is provided at a portion near the upper end face of the magnet body and at a central portion.
This document describes that cogging torque can be reduced by providing regions having different inclinations on both the stator and the rotor.

Further, Patent Document 3 is not intended for field-weakening control,
(A) The skew angle of the high coercive force portion is the optimum skew angle theoretical value or more,
(B) A method of magnetizing a cylindrical or ring magnet is disclosed in which the skew angle of the low coercive force portion is skewed with a skew angle smaller than the theoretical value of the optimal skew angle.
In the same document,
(A) Since cylindrical or ring magnets are not uniform in the axial magnet characteristics, if they are uniformly skew magnetized, the cogging torque cannot be reduced sufficiently, and
(B) It is described that the cogging torque can be sufficiently reduced by increasing or decreasing the skew angle with respect to the theoretical value in accordance with non-uniform magnet characteristics.

  As described above, when the field weakening control is used, the motor can be used in a wide rotational speed range. However, all the conventional motors have only one combination of the rotational speed and the torque that provides the highest efficiency, and the efficiency decreases in a region other than the optimal combination. For this reason, it is difficult for conventional motors to achieve both high-efficiency use in a wide rotational speed range.

JP 2010-268571 A JP 2003-169552 A JP 2005-033879 A

  The problem to be solved by the present invention is to provide a variable magnetic flux motor that can be used in a wide rotational speed range and exhibits high efficiency over a wide rotational speed range.

In order to solve the above problems, the gist of a variable magnetic flux motor according to the present invention is as follows.
(1) The variable magnetic flux motor
An inner rotor having 2n (n ≧ 1) magnetic poles;
An outer stator having a built-in coil for applying a rotating magnetic field to the inner rotor;
Relative movement means for relatively moving the outer stator along the axial direction of the inner rotor.
(2) The inner rotor includes a ring magnet joined to a surface facing the inner peripheral surface of the outer stator,
The ring magnets are alternately magnetized to N or S poles along the circumferential direction of the inner rotor,
The axial length of the ring magnet is at least twice the axial length of the outer stator.
(3) The ring magnet is
P (p ≧ 1) high magnetic flux regions (A _p ) where 0 ° ≦ θ ≦ 1 ° (where θ is a skew angle);
Q (q ≧ 1) medium / low magnetic flux regions (B _q ) satisfying 1 ° <θ ≦ 180 ° / n.
However, “the skew angle θ” means
(A) fixing the outer stator to an arbitrary position in the axial direction of the inner rotor;
(B) an intersection (point A) between a plane passing through the upper end of the outer stator and perpendicular to the axial direction of the inner rotor and one boundary line between the magnetic poles formed on the surface of the ring magnet; In addition, an intersection (point B) between a plane passing through the lower end of the outer stator and perpendicular to the axial direction of the inner rotor and the boundary line is obtained.
(C) When the point A and the point B are projected on a cross section perpendicular to the axial direction of the inner rotor,
An angle formed by a line (AC line) connecting the center of the inner rotor (C point) and the projected A point (AC line) and a line connecting the C point and the projected B point (BC line). .

When the axial length of the ring magnet on the inner rotor surface is made longer than the axial length of the outer stator and a plurality of regions (high magnetic flux region, medium / low magnetic flux region) having different skew angles θ are formed in the ring magnet, By controlling the position of the outer stator, it is possible to variably control the motor device constant (that is, the magnitude of the gap magnetic flux).
For example, on the inner rotor surface,
(A) a region (first high magnetic flux region (A ₁ )) where the highest efficiency is obtained in a low speed region;
(B) Region where the highest efficiency is obtained in the medium speed range (first medium / low magnetic flux region (B ₁ )), and (c) Region where the highest efficiency is obtained in the high speed region (second medium / low magnetic flux region (B) ₂ ))
If the position of the outer stator is controlled in accordance with the rotational speed of the motor, it can be used in a wide rotational speed range, and high efficiency can be obtained over a wide rotational speed range.

It is a schematic diagram for demonstrating the definition of skew angle (theta). It is a schematic diagram of the various ring magnets from which the magnetization method differs. It is a cross-sectional schematic diagram of the variable magnetic flux motor which concerns on one embodiment of this invention. It is a block diagram for demonstrating the control method of a variable magnetic flux motor.

It is a figure which shows the relationship between the rotation speed (RPM) and torque (Nm) of the conventional IPM motor (exhibition: Evaluation of the 2010 Toyota Prius hybrid synergy drive syste. Thecnical report, Oak Ridge National Laboratory (2011)). It is a schematic diagram which shows the relationship between the rotation speed of an IPM motor, and a voltage. It is a figure which shows the relationship between the motor rotation speed and motor torque of a SPM motor, an IPM motor, and a variable magnetic flux motor. It is a figure which shows the relationship between the rotation speed and efficiency of IM motor, SPM motor, IPM motor, and variable magnetic flux motor.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Variable magnetic flux motor]
The variable magnetic flux motor according to the present invention has the following configuration.
(1) The variable magnetic flux motor
An inner rotor having 2n (n ≧ 1) magnetic poles;
An outer stator having a built-in coil for applying a rotating magnetic field to the inner rotor;
Relative movement means for relatively moving the outer stator along the axial direction of the inner rotor.
(2) The inner rotor includes a ring magnet joined to a surface facing the inner peripheral surface of the outer stator,
The ring magnets are alternately magnetized to N or S poles along the circumferential direction of the inner rotor,
The axial length of the ring magnet is at least twice the axial length of the outer stator.
(3) The ring magnet is
P (p ≧ 1) high magnetic flux regions (A _p ) where 0 ° ≦ θ ≦ 1 ° (where θ is a skew angle);
Q (q ≧ 1) medium / low magnetic flux regions (B _q ) satisfying 1 ° <θ ≦ 180 ° / n.

[1.1. Inner rotor]
[1.1.1. Number of magnetic poles]
The inner rotor has 2n (n ≧ 1) magnetic poles. The number of magnetic poles is not particularly limited, and an optimum number can be selected according to the purpose. Generally, as the number of magnetic poles increases, the number of times of switching of magnetic flux linked to the coil increases. Even when the decrease in the magnet amount in each pole is taken into consideration, at the same rotation speed, the torque and the power generation amount improve as the number of magnetic poles increases. In order to obtain such an effect, the number of magnetic poles is preferably four or more. More preferably, the number of magnetic poles is 8 or more.
On the other hand, if the number of magnetic poles is too large, there is a problem that the stator shape and the winding are complicated, and the motor size is enlarged, which is particularly noticeable in a small motor. Therefore, the number of magnetic poles is preferably 16 poles or less. More preferably, the number of magnetic poles is 12 poles or less.

[1.1.2. Ring magnet]
The inner rotor includes a ring magnet joined to a surface facing the inner peripheral surface of the outer stator. The ring magnets are alternately magnetized to the N or S poles along the circumferential direction of the inner rotor.

[A. Ring magnet length]
In the present invention, the axial length (H _R ) of the ring magnet is at least twice the axial length (H _S ) of the outer stator. This point is different from the conventional one. In general, the more H _R becomes longer, it becomes easy to variable control of the skew angle theta. H _R is preferably at least 3 times H _S.
On the other hand, even if unnecessarily large H _R, there is no practical benefit. Therefore, H _R is preferably 20 times or less of H _S. H _R is more preferably 10 times or less of H _S.

[B. High magnetic flux region and medium / low magnetic flux region]
In the present invention, the ring magnet is
(A) p (p ≧ 1) high magnetic flux regions (A _p ) where 0 ° ≦ θ ≦ 1 ° (where θ is a skew angle);
(B) q (q ≧ 1) medium / low magnetic flux regions (B _q ) satisfying 1 ° <θ ≦ 180 ° / n.

Here, in the present invention, the “skew angle θ” refers to an angle calculated by the following method. FIG. 1 is a schematic diagram for explaining the definition of the skew angle θ.
(A) The outer stator 40 is fixed at an arbitrary position in the axial direction of the inner rotor 20.
(B) An intersection (point A) between a plane passing through the upper end of the outer stator 40 and perpendicular to the axial direction of the inner rotor 20 and one boundary line 26a between the magnetic poles formed on the surface of the ring magnet 26; In addition, an intersection (point B) between a plane passing through the lower end of the outer stator 40 and perpendicular to the axial direction of the inner rotor 20 and the boundary line 26a is obtained.
(C) The points A and B are projected on a cross section perpendicular to the axial direction of the inner rotor 20.
(D) An angle formed by a line (AC line) connecting the center (C point) of the inner rotor 20 and the projected A point (AC line) and a line (BC line) connecting the C point and the projected B point, It is defined as a skew angle θ.

The high magnetic flux region (A _p ) is a region where the gap magnetic flux is maximized, and is mainly used in a low-speed rotation region where high torque is required. The inner rotor may be provided with one high magnetic flux region (A _q ), or may be provided with two or more.
In order to obtain the maximum gap magnetic flux, the skew angle θ is preferably 0 °. Even when the skew angle θ is larger than 0 °, a relatively large gap magnetic flux can be obtained. However, if the skew angle θ is excessively large, high torque cannot be obtained in the low speed rotation range. Therefore, the skew angle θ of the high magnetic flux region (A _p ) is preferably 1 ° or less. The skew angle θ is more preferably 0.5 ° or less.

The middle / low magnetic flux region (B _q ) is a region where the gap magnetic flux becomes medium to low, and is mainly used in the medium to high speed rotation region. The inner rotor may be provided with one medium / low magnetic flux region (B _q ), or may be provided with two or more.
In order to reduce the induced voltage (back electromotive force), it is better that the skew angle θ of the middle / low magnetic flux region (B _q ) is larger. Specifically, the skew angle θ of the middle / low magnetic flux region (B _q ) is preferably more than 1 °. The skew angle θ is more preferably 45 ° / n (= the angle at which the maximum induced voltage of square wave magnetization is 25%) or more.
On the other hand, when the skew angle θ exceeds the angle per magnetic pole (= 360 ° / 2n), the gap magnetic flux increases. Therefore, the skew angle θ of the middle / low magnetic flux region (B _q ) is preferably 180 ° / n or less.

The arrangement order of the high magnetic flux region (A _p ) and the middle / low magnetic flux region (B _q ) in the axial direction of the inner rotor is not particularly limited. In order to smoothly perform variable control of magnetic flux, the ring magnet is moved from one end of the inner rotor to the other end.
(A) a monotonically increasing region in which the θ monotonously increases, and / or
(B) It is preferable to provide a monotonously decreasing region in which the θ monotonously decreases.

The number of high flux region (A _p) and medium and low flux regions (B _q), as well as the skew angle θ of the medium and low flux regions (B _q), depending on the number of poles and motor applications, optimum It is preferred to select a value. In order to obtain high efficiency over a wide rotational speed range, the ring magnet
A _first high magnetic flux region (A ₁ ) satisfying 0 ° ≦ θ ≦ 1 °;
A first medium / low magnetic flux region (B ₁ ) where 1 ° <θ <120 ° / n;
A second medium / low magnetic flux region (B ₂ ) satisfying 120 ° / n ≦ θ ≦ 180 ° / n;
Is preferably provided.
The skew angle θ of the first middle / low magnetic flux region (B ₁ ) is more preferably 60 ° / n ≦ θ <120 ° / n.

Here, “60 ° / n (= 360 ° / (3 × 2n))” is a skew having an induced voltage of about 2/3 of the induced voltage generated in the A ₁ region when compared at the same rotation speed. Represents a corner.
“120 ° / n (= 2 × 360 ° / (3 × 2n))” is an induced voltage that is about 1/3 of the induced voltage generated in the A ₁ region when compared at the same rotation speed. Represents the skew angle.

For example, when the number of magnetic poles is 8 (n = 4), the ring magnet is
A _first high magnetic flux region (A ₁ ) satisfying 0 ° ≦ θ ≦ 1 °;
A first medium / low magnetic flux region (B ₁ ) satisfying 15 ° ≦ θ <30 °;
A second medium / low magnetic flux region (B ₂ ) satisfying 30 ° ≦ θ ≦ 45 °;
The thing provided with is preferable.

FIG. 2 shows schematic diagrams of various ring magnets having different magnetization methods.
FIG. 2A shows an example in which the skew angle θ monotonously increases from the upper end to the lower end of the ring magnet 26, and the boundary line 26a between the magnetic poles changes in a curved shape. The region at the upper end of the ring magnet 26 is a high magnetic flux region (A _p ) where the skew angle θ is minimum. The lower end region of the ring magnet 26 is a middle / low magnetic flux region (B _q ) where the skew angle θ is maximum. Further, the central region of the ring magnet 26 is a medium / low magnetic flux region (B _{q ′} ) in which the skew angle θ is an intermediate value between A _p and B _q .

FIG. 2B shows an example in which the skew angle θ monotonously increases from the upper end of the ring magnet 26 toward the center and monotonously decreases from the center toward the lower end. It changes in a curved line. The regions at the upper and lower ends of the ring magnet 26 are high magnetic flux regions (A _p ) where the skew angle θ is minimum. Region under the region and center of the upper from the center of the ring magnet 26, the skew angle θ is A _p larger in Low flux region (B _q). Furthermore, the region at the center of the ring magnet 26 is a high magnetic flux region (A _{p ′} ) where the skew angle θ is minimum.

FIG. 2C shows an example in which the skew angle θ monotonously decreases from the upper end of the ring magnet 26 toward the center and increases monotonously from the center toward the lower end. The boundary line 26a between the magnetic poles is It changes in a curved line. The central region of the ring magnet 26 is a high magnetic flux region (A _p ) where the skew angle θ is minimum. Upper and lower ends of the region of the ring magnet 26, the skew angle θ is A _p larger in Low flux region (B _q).

FIG. 2D shows an example in which the skew angle θ monotonously increases from the upper end to the lower end of the ring magnet 26, and the boundary line 26a between the magnetic poles changes in a stepped manner. The region from the upper end to the center of the ring magnet 26 is a high magnetic flux region (A _p ) where the skew angle θ is minimum. Region from the center of the ring magnet 26 to the lower end, the skew angle θ is A _p larger in Low flux region (B _q).

[1.2. Outer stator]
The outer stator is provided with a through hole for inserting the inner rotor at the center, and teeth serving as iron cores of field coils are radially arranged on the inner surface of the through hole. The outer stator has a built-in coil for causing a rotating magnetic field to act on the inner rotor. In the present invention, the structure of the outer stator (for example, the structure of teeth, the winding method of the coil, etc.) is not particularly limited, and an optimal structure can be selected according to the purpose.

[1.3. Relative moving means]
The variable magnetic flux motor according to the present invention includes relative moving means for relatively moving the outer stator along the axial direction of the inner rotor. The structure of the relative movement means is not particularly limited as long as the outer stator can be relatively moved. The relative movement means may limit the movement of the inner rotor in the axial direction and move the outer rotor along the axial direction of the inner rotor. Alternatively, the relative movement means may limit the movement of the outer rotor in the axial direction and move the inner rotor in the axial direction. In order to facilitate the connection between the inner rotor and the load, it is preferable that the relative movement means move the outer stator along the axial direction of the inner rotor.

[2. Specific example of variable magnetic flux motor]
[2.1. Constitution]
FIG. 3 is a schematic cross-sectional view of a variable magnetic flux motor according to an embodiment of the present invention. In FIG. 3, the variable magnetic flux motor 10 includes an inner rotor 20, an outer stator 40, and relative movement means 50. The inner rotor 20 and the outer stator 40 constitute a main motor of the variable magnetic flux motor 10.

The inner rotor 20 includes a shaft (output rotating shaft of the main motor) 22, a rotor yoke 24 joined to the outer periphery of the shaft 22, and a ring magnet 26 joined to the surface of the rotor yoke 24. The ring magnet 26 is alternately magnetized with N or S poles along the circumferential direction of the inner rotor 20 and has a total of 2n (n ≧ 1) magnetic poles. Further, the axial length of the ring magnet 26 is at least twice the axial length of the outer stator 40. Further, the ring magnet 26 includes at least one high magnetic flux region (A _p ) having different skew angles θ and at least one medium / low magnetic flux region (B _q ).

A bracket 30 having a bearing 28 is disposed on the left side of the rotor yoke 24, and the left end of the shaft 22 is inserted into the bearing 28. A bracket 34 having a bearing 32 is disposed on the right side of the rotor yoke 24, and the right portion of the shaft 22 is inserted into the bearing 32. Furthermore, the right end of the shaft 22 is connected to a load (not shown).
The left and right brackets 30 and 34 are connected by linear movement guides 36 and 38. The linear movement guides 36 and 38 constitute a part of relative movement means 50 that moves the outer stator 40 in the axial direction.

  The outer stator 40 is made of a laminate of electromagnetic steel plates. Teeth (not shown) are radially arranged on the inner peripheral surface of the outer stator 40, and a coil (not shown) is wound around the teeth. The outer stator 40 is provided with a through hole for inserting the linear movement guides 36 and 38. The outer stator 40 is movable in the left-right direction along the linear movement guides 36 and 38. Furthermore, a male screw is formed on the outer peripheral surface of the outer stator 40.

  The relative moving means 50 includes an auxiliary electric motor 52 and a rotating bracket 54. The auxiliary electric motor 52 is for rotating the rotating bracket 54 forward and backward. The rotating bracket 54 has a cylindrical shape, and the bottom surface is connected to the rotating shaft of the auxiliary motor 52. Further, an internal thread portion that is screwed with the external thread portion of the outer stator 40 is formed on the inner peripheral surface at the tip of the rotary bracket 54.

  In such a variable magnetic flux motor 10, when the auxiliary electric motor 52 is rotated forward or backward, the rotating bracket 54 is rotated, and the rotational force is transmitted to the outer peripheral surface of the outer stator 40 through the female screw portion. The outer stator 40 tends to rotate as the rotary bracket 54 rotates, but the rotation is limited by the linear movement guides 36 and 38. Therefore, the outer stator 40 moves horizontally to any position in the axial direction along the linear movement guides 36 and 38 without rotating.

[2.2. control]
FIG. 4 is a block diagram for explaining a control method of the variable magnetic flux motor. First, using various sensors (not shown), current information of the main motor (for example, main motor rotation information, main motor output torque information, main motor stator (outer stator 40) position information, etc.) is acquired. , Input to the controller. Further, the output destination operation information of the main motor (for example, the operation information of the accelerator and the brake in the case of an electric vehicle) is acquired and input to the controller using another sensor (not shown).

  The controller calculates control parameters such as the amount of current flowing through the coil, the rotational speed of the rotating magnetic flux, and the optimal device constant (skew angle θ) based on the acquired current information of the main motor and the output destination operation information of the main motor. To do. Next, the main motor inverter and the auxiliary motor inverter are operated using the calculated control parameters. When electric power is supplied to the auxiliary motor inverter, the auxiliary motor 52 rotates forward or backward, and the outer stator 40 moves along the axial direction of the inner rotor 20. When the outer stator 40 has moved to the optimum position, the auxiliary motor 52 is stopped. At the same time, when necessary electric power is supplied to the main motor inverter, the inner rotor 20 of the main motor rotates at a predetermined rotation speed.

[3. Action]
FIG. 5 shows the relationship between the rotational speed (RPM) and torque (Nm) of a conventional IPM motor (exhibition: Evaluation of the 2010 Toyota Prius hybrid synergy drive syste. Thecnical report, Oak Ridge National Laboratory (2011)). The IPM motor is known for being able to be used in a wide rotational speed range and having a large torque. However, all conventional motors have only one maximum efficiency range. Therefore, there is a problem that the efficiency decreases when the rotation speed and / or torque deviates from the maximum efficiency range. In the example shown in FIG. 5, the region where the rotational speed is about 5,000 rpm and the torque is about 60 Nm is the highest efficiency region, and an efficiency close to 100% is obtained. However, outside this region, the efficiency decreases.

  FIG. 6 shows the relationship between the rotational speed of the IPM motor and the voltage. In an IPM motor that can be used in a wide rotational speed range, an induced voltage (counterelectromotive force) increases with an increase in the rotational speed of the rotor due to a field magnetic flux generated by a magnet. Therefore, the motor power supply voltage and the induced voltage become equal at a certain rotational speed, and the rotational speed cannot be increased any more. In order to solve this problem, field-weakening control is started when the induced voltage approaches the power supply voltage, and the maximum rotational speed is improved. In the case of an IPM motor, field weakening control is generally performed by exciting the field coil and reducing the induced voltage so as to reduce the magnetic flux passing through the field coil. However, reducing the induced voltage by field weakening control itself does not contribute to torque, so the field weakening current becomes a loss and high efficiency cannot be obtained. Further, the IPM motor has only one maximum efficiency region, and greatly decreases at the number of revolutions away from the region.

  FIG. 7 shows the relationship between the motor speed and the motor torque of the SPM motor, the IPM motor, and the variable magnetic flux motor according to the present invention. SPM motors use only magnet torque. Even in the SPM motor, the maximum efficiency region is only one place. Further, the SPM motor can obtain the same torque as the IPM motor in the low speed rotation range. However, since the SPM motor uses only the magnet torque, even if the field weakening control is performed, the rotational speed increases, but the torque decreases.

  On the other hand, the IPM motor uses both magnet torque and reluctance torque. Therefore, when field weakening control is performed, the magnet torque decreases as in the SPM motor, but the reluctance torque increases conversely. That is, the IPM motor can compensate for a part of the magnet torque decreased during the field weakening control by increasing the reluctance torque. As a result, the IPM motor can be used in a higher rotation range than the SPM motor, and a larger torque can be obtained than the SPM motor. However, since the conventional IPM motor also has only one maximum efficiency region, high efficiency cannot be obtained in the entire rotational speed region.

  On the other hand, in the variable magnetic flux motor according to the present invention, a plurality of regions having different skew angles θ are formed in the ring magnet 26 on the surface of the inner rotor 20, and the outer stator 40 is in the axial direction of the inner rotor 20. Can be moved to. Therefore, the motor device constant can be varied according to the rotational speed of the motor. This corresponds to one motor having a plurality of maximum efficiency ranges.

For example, the variable magnetic flux motor shown in FIG. 7 is an example having two levels of device constants, a low speed region and a medium / high speed region. In the low speed range, equipment constants specialized for high torque are selected. Therefore, the torque in a low speed region of 30 km / h or less is higher than that of a conventional SPM motor or IPM motor.
On the other hand, in the middle / high speed range, equipment constants specialized for high speed are selected. Therefore, the torque is lower than that of the SPM motor in the medium speed range of about 30 to 70 km / h. However, at a high speed range of 70 km / h or higher, a higher torque than that of the conventional IPM motor is obtained.

FIG. 8 shows the relationship between the rotational speed and efficiency of the IM motor, SPM motor, IPM motor, and variable magnetic flux motor according to the present invention. The efficiency of an IM motor that uses only reluctance torque is inferior to other motors in the entire rotational speed range. Further, since the SPM motor uses only the magnet torque, its efficiency is inferior to that of the IPM motor in the entire rotational speed range.
On the other hand, the variable magnetic flux motor according to the present invention has a plurality of device constants, and can select an optimal device constant according to the rotation speed range. Therefore, when the setting and selection of device constants are optimized, the efficiency exceeds that of the IPM motor in the entire rotation speed range.

As described above, in the variable magnetic flux motor according to the present invention, the axial length of the ring magnet on the inner rotor surface is longer than the axial length of the outer stator, and the ring magnet has a plurality of regions with different skew angles θ (high Since the magnetic flux region and the middle / low magnetic flux region are formed, the device constant (that is, the magnitude of the gap magnetic flux) of the motor can be variably controlled by controlling the position of the outer stator.
For example, on the inner rotor surface,
(A) a region (first high magnetic flux region (A ₁ )) where the highest efficiency is obtained in a low speed region;
(B) Region where the highest efficiency is obtained in the medium speed range (first medium / low magnetic flux region (B ₁ )), and (c) Region where the highest efficiency is obtained in the high speed region (second medium / low magnetic flux region (B) ₂ ))
If the position of the outer stator is controlled in accordance with the rotational speed of the motor, it can be used in a wide rotational speed range, and high efficiency can be obtained over a wide rotational speed range.

(Example 1, Comparative Example 1)
[1. Test method]
When the ring magnet 26 was magnetized, the skew angle θ was changed depending on the part, and the following three magnetic flux regions were formed on the surface of the ring magnet 26. This was incorporated into the variable magnetic flux motor 10 shown in FIG.
(A) A _first high magnetic flux region (A ₁ ) in which the skew angle θ is 0 °.
(B) A first medium / low magnetic flux region (B ₁ ) having a skew angle θ of 15 °.
(C) A second medium / low magnetic flux region (B ₂ ) having a skew angle θ of 30 °.

The maximum torque and average efficiency of the variable magnetic flux motor 10 were evaluated. The evaluation procedure is as follows. In the evaluation, field weakening control was not performed.
(1) The corresponding rotation speed range is divided into four equal parts, and the rotation speeds corresponding to the second, third, and fourth positions are selected from the low speed side. For example, when the corresponding rotation speed range is 0 to 5000 rpm, 1250 rpm, 2500 rpm, and 3750 rpm are selected as the rotation speed. Hereinafter, the rotation speed selected in this way is referred to as “average target rotation speed”.
(2) The torque range (from 0 torque to the maximum torque) at the average target rotational speed is divided into four equal parts, and the torque corresponding to the second, third, and fourth counts from the low torque side is selected. For example, when the maximum torque is 400 Nm (that is, when the torque range at the average target rotational speed is 0 to 400 Nm), 100 Nm, 200 Nm, and 300 Nm are selected as the torque. Hereinafter, the torque thus selected is referred to as “average target torque”.
(3) The efficiency at each of the nine operating points in the matrix of the average target rotational speed and average target torque is obtained, and the average value is defined as “average efficiency”.

  Furthermore, a test similar to Example 1 was performed using a commercially available IPM motor (maximum rotational speed: 10,000 rpm, maximum torque: 100 Nm) (Comparative Example 1).

[2. result]
Table 1 shows the results. Table 1 shows the following.
(1) In the first embodiment, the position of the outer stator 40 is moved according to the rotational speed, and the skew angle θ is changed. Therefore, in Example 1, the maximum torque and the average efficiency were higher than in Comparative Example 1 in any rotation speed range.
(2) The upper limit of the rotation speed of Comparative Example 1 was 10,000 rpm. On the other hand, the rotation speed of Example 1 exceeded 10,000 rpm.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

  The variable magnetic flux motor according to the present invention can be used as a drive motor for an electric vehicle or a hybrid car.

DESCRIPTION OF SYMBOLS 10 Variable magnetic flux motor 20 Inner rotor 26 Ring magnet 40 Outer stator 50 Relative moving means

Claims (3)

A variable magnetic flux motor having the following configuration.
(1) The variable magnetic flux motor
An inner rotor having 2n (n ≧ 1) magnetic poles;
An outer stator having a built-in coil for applying a rotating magnetic field to the inner rotor;
Relative movement means for relatively moving the outer stator along the axial direction of the inner rotor.
(2) The inner rotor includes a ring magnet joined to a surface facing the inner peripheral surface of the outer stator,
The ring magnets are alternately magnetized to N or S poles along the circumferential direction of the inner rotor,
The axial length of the ring magnet is at least twice the axial length of the outer stator.
(3) The ring magnet is
P (p ≧ 1) high magnetic flux regions (A _p ) where 0 ° ≦ θ ≦ 1 ° (where θ is a skew angle);
Q (q ≧ 1) medium / low magnetic flux regions (B _q ) satisfying 1 ° <θ ≦ 180 ° / n.
However, “the skew angle θ” means
(A) fixing the outer stator to an arbitrary position in the axial direction of the inner rotor;
(B) an intersection (point A) between a plane passing through the upper end of the outer stator and perpendicular to the axial direction of the inner rotor and one boundary line between the magnetic poles formed on the surface of the ring magnet; In addition, an intersection (point B) between a plane passing through the lower end of the outer stator and perpendicular to the axial direction of the inner rotor and the boundary line is obtained.
(C) When the point A and the point B are projected on a cross section perpendicular to the axial direction of the inner rotor,
An angle formed by a line (AC line) connecting the center of the inner rotor (C point) and the projected A point (AC line) and a line connecting the C point and the projected B point (BC line). . The ring magnet is directed from one end of the inner rotor to the other end.
(A) a monotonically increasing region in which the θ monotonously increases, and / or
(B) The variable magnetic flux motor according to claim 1, further comprising a monotonously decreasing region in which the θ monotonously decreases. The ring magnet is
A _first high magnetic flux region (A ₁ ) satisfying 0 ° ≦ θ ≦ 1 °;
A first medium / low magnetic flux region (B ₁ ) where 1 ° <θ <120 ° / n;
A second medium / low magnetic flux region (B ₂ ) satisfying 120 ° / n ≦ θ ≦ 180 ° / n;
The variable magnetic flux motor according to claim 1, comprising:

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