US-12620851-B2 - Rotor structure

US12620851B2US 12620851 B2US12620851 B2US 12620851B2US-12620851-B2

Abstract

A rotor having a changeable magnetic force is provided, which includes a rotor core and magnetic pole parts disposed therein. The rotor core includes a flange part opposing a stator, a base part located inward of the flange part, and a connecting part coupling the base part to the flange part. Each magnetic pole part includes a fixed magnetic-force magnet and a variable magnetic-force magnet disposed in the flange part, and a cavity part defined by the connecting part, between the flange part and the base part. By bisecting each fixed magnetic-force magnet in line symmetry into a pair of magnet pieces, an inside coupling part is provided in the flange part. A first pillar part is comprised of outside coupling parts that bridge the flange part and the base part, and are disposed circumferentially inward of the center position of the circumferential width of each magnet piece.

Inventors

Naoki ITASAKA

Assignees

MAZDA MOTOR CORPORATION

Dates

Publication Date: 20260505
Application Date: 20240110
Priority Date: 20230131

Claims (7)

1 . A structure of a rotor that constitutes a drive motor and has a changeable magnetic force, the structure comprising: a rotor core disposed inside a stator and opposing the stator via a given gap; and a plurality of magnetic pole parts disposed in the rotor core so that N-poles and S-poles are lined up alternately in a circumferential direction of the rotor core along an opposing surface, wherein the rotor core includes: a flange part opposing the stator and having an annular shape in an axial cross-section; a base part located inward of the flange part and separated from the flange part by a given distance; and a connecting part coupling the base part to the flange part, wherein each of the magnetic pole parts includes: a fixed magnetic-force magnet elongated in the circumferential direction and disposed in the flange part centering on a d-axis so that a magnetic force thereof is oriented in a radial direction of the rotor core; a variable magnetic-force magnet disposed in a part of the flange part on an opposing surface side of the fixed magnetic-force magnet, at a position adjacent in the circumferential direction to the fixed magnetic-force magnet so that a magnetic force thereof is oriented in the circumferential direction; and a cavity part defined by the connecting part, between the flange part and the base part, wherein the connecting part includes a first pillar part located radially inward of the fixed magnetic-force magnet, wherein, by bisecting the fixed magnetic-force magnet in line symmetry with respect to the d-axis into a pair of magnet pieces, a bar-shaped inside coupling part is provided in a part of the flange part, the part corresponding to a center part of a circumferential width of the fixed magnetic-force magnet, the inside coupling part having an axial cross-section extending in the radial direction, wherein the first pillar part is comprised of a plurality of outside coupling parts that bridge between the flange part and the base part and have a pillar-shape axial cross-section, and the outside coupling parts are disposed circumferentially inward of a center position of the circumferential width of each of the pair of magnet pieces, wherein the first pillar part is comprised of two outside coupling parts, and the center position of the circumferential width of each of the outside coupling parts is located on a d-axis side of the center position of the circumferential width of each of the pair of magnet pieces, wherein the variable magnetic-force magnet is disposed at a position centering on a q-axis, and wherein the connecting part includes a second pillar part having a pillar shape in the axial cross-section, and the second pillar part is located in a part radially-inward of the variable magnetic-force magnet and bridges between the flange part and the base part.
2 . The structure of claim 1 , wherein the second pillar part has a wider circumferential width than that of the variable magnetic-force magnet, and wherein by including a nonmagnetic material extending along the second pillar part in a part radially inward of the variable magnetic-force magnet, a pair of coupling arm parts having a bar shape in the axial cross-section are formed, the pair of coupling arm parts being located at both sides of the nonmagnetic material, circumferentially outward of the variable magnetic-force magnet.
3 . A structure of a rotor that constitutes a drive motor and has a changeable magnetic force, the structure comprising: a rotor core disposed inside a stator and opposing the stator via a given gap; and a plurality of magnetic pole parts disposed in the rotor core so that N-poles and S-poles are lined up alternately in a circumferential direction of the rotor core along an opposing surface, wherein the rotor core includes: a flange part opposing the stator and having an annular shape in an axial cross-section; a base part located inward of the flange part and separated from the flange part by a given distance; and a connecting part coupling the base part to the flange part, wherein each of the magnetic pole parts includes: a fixed magnetic-force magnet elongated in the circumferential direction and disposed in the flange part centering on a d-axis so that a magnetic force thereof is oriented in a radial direction of the rotor core; a variable magnetic-force magnet disposed in a part of the flange part on an opposing surface side of the fixed magnetic-force magnet, at a position adjacent in the circumferential direction to the fixed magnetic-force magnet so that a magnetic force thereof is oriented in the circumferential direction; and a cavity part defined by the connecting part, between the flange part and the base part, wherein the connecting part includes a first pillar part located radially inward of the fixed magnetic-force magnet, wherein, by bisecting the fixed magnetic-force magnet in line symmetry with respect to the d-axis into a pair of magnet pieces, a bar-shaped inside coupling part is provided in a part of the flange part, the part corresponding to a center part of a circumferential width of the fixed magnetic-force magnet, the inside coupling part having an axial cross-section extending in the radial direction, wherein the first pillar part is comprised of a plurality of outside coupling parts that bridge between the flange part and the base part and have a pillar-shape axial cross-section, and the outside coupling parts are disposed circumferentially inward of a center position of the circumferential width of each of the pair of magnet pieces, wherein the variable magnetic-force magnet is disposed at a position centering on a q-axis, and wherein the connecting part includes a second pillar part having a pillar shape in the axial cross-section, the second pillar part is located in a part radially-inward of the variable magnetic-force magnet and bridges between the flange part and the base part.
4 . The structure of claim 3 , wherein the second pillar part has a wider circumferential width than that of the variable magnetic-force magnet, and wherein by including a nonmagnetic material extending along the second pillar part in a part radially inward of the variable magnetic-force magnet, a pair of coupling arm parts having a bar shape in the axial cross-section are formed, the pair of coupling arm parts being located at both sides of the nonmagnetic material, circumferentially outward of the variable magnetic-force magnet.
5 . The structure of claim 3 , wherein the cavity part is formed between the first pillar part and the second pillar part, both sides of the cavity part in the circumferential direction are defined by the first pillar part and the second pillar part, and a radially inward part of the cavity part is defined by the base part.
6 . The structure of claim 5 , wherein a radially-outward part of the cavity part is defined by a curved surface extending from a radially-outward end part of the first pillar part to a radially-outward end part of the second pillar part.
7 . The structure of claim 3 , wherein a radially-outward part of the cavity part is defined by a curved surface extending from a radially-outward end part of the first pillar part to a radially-outward end part of the second pillar part.

Description

TECHNICAL FIELD The art disclosed herein relates to a structure of a rotor which constitutes a drive motor suitable for driving an automobile. BACKGROUND OF THE DISCLOSURE In recent years, electrification of automobiles, such as hybrid vehicles and electric vehicles, has progressed. Drive motors mounted on automobiles are required to achieve low-speed but high-torque output when operating at low speeds, and on the other hand, required to achieve high-speed but low-torque output when operating at high speeds. Within such a wide range, the drive motors are required to achieve a stable output. A permanent magnet synchronous motor is used widely for this kind of drive motor, and in order to output the high torque, a permanent magnet with a powerful magnetic force is incorporated into a rotor. The onboard drive motor uses a battery as its power source, and is driven by an inverter controlling electric current supplied to the drive motor. Therefore, current exceeding the voltage of the battery or the capacity of the inverter cannot be supplied to the drive motor. Although a counter electromotive force also increases with the increase of the rotational speed, since the current amount is limited, the rotational speed which can be outputted by the drive motor is limited. Therefore, in the control of the drive motor, a magnetic-flux weakening control which weakens an interlinkage flux by supplying a given current to the stator is generally performed. The magnetic-flux weakening control enables the high-speed output exceeding the limitation, but copper loss and iron loss increase. On the other hand, lately, a drive motor which is able to change the magnetic force of the rotor by using a permanent magnet with a small coercive force (hereinafter, referred to as a “variable magnetic-force motor”) has attracted attention. If the magnetic force of the rotor can be changed according to the driving state, increase in the output, improvement in efficiency, etc. of the drive motor can be realized as well as the reduction in the counter electromotive force, and therefore, fuel efficiency and electricity efficiency of the automobile can be improved. For example, JP2021-027700A discloses a variable magnetic-force motor in which permanent magnets able to change their magnetic force (variable magnetic-force magnets) are attached to the rotor along with permanent magnets not able to change their magnetic force (fixed magnetic-force magnets). When the drive motor of an automobile is a variable magnetic-force motor, the magnetic force of the rotor changes during operation of the automobile. Therefore, operation scenes in which the motor performance is influenced, such as a scene of increasing the magnetic force of the rotor and a scene of decreasing the magnetic force of the rotor, increase more than in the conventional drive motor in which the magnetic force of the rotor does not change. Therefore, in order to utilize the variable magnetic-force motor effectively, it is necessary to optimize the structure of the rotor for each of such various operation scenes. For this purpose, it is necessary to devise rotor elements, such as a fixed magnetic-force magnet, a variable magnetic-force magnet, and a cavity. As a result, the number of rotor elements increases, and therefore, it cannot be avoided that the structure of the rotor, such as the layout and the shapes of the elements, become complicated. In addition, these rotor elements are unevenly distributed in the outer circumferential part of the rotor on which a strong centrifugal force acts when the rotor rotates. Therefore, the percentage of the rotor core which is used as the base structure decreases in the outer circumferential part of the rotor, which is disadvantageous with respect to the strength. Therefore, in the case of the variable magnetic-force motor, it is not only necessary to devise the rotor element(s), but also necessary to secure the strength so that it can stand against a centrifugal force breakage. SUMMARY OF THE DISCLOSURE The disclosed art aims at realization of a structure of a rotor which can be effectively adapted to various operation scenes of a variable magnetic-force motor, and particularly, the art for securing strength of the rotor which would be complicated in connection with the adaptation is disclosed. The disclosed art relates to a structure of a rotor that constitutes a drive motor and has a changeable magnetic force. The structure includes a rotor core disposed inside a stator and opposing the stator via a gap, and a plurality of magnetic pole parts disposed in the rotor core so that N-poles and S-poles are lined up alternately in a circumferential direction of the rotor core along an opposing surface. The rotor core includes a flange part opposing the stator and having an annular shape in an axial cross-section, a base part located inward of the flange part and separated from the flange part by a given distance, and a connecting part coupling the bas