Iron core structure having reduced rare earth permanent magnet material consumption

Abstract

An iron core structure having reduced rare earth permanent magnet material consumption, which is improved on the basis of an embedded single V magnetic steel arrangement topological structure. The iron core structure comprises magnetic bridges and magnetic steels, and the magnetic bridges can be classified into single-magnetic-bridge and double-magnetic-bridge structures. The iron core structure enables low-cost and small-proportion permanent magnet materials such as a neodymium-iron-boron permanent magnet material, a permanent magnetic ferrite or a samarium-iron-nitrogen permanent magnet to be perfectly matched in different parts of a motor magnetic circuit, so as to give full play to respective advantages. The magnetic bridges are pre-saturated, and the magnetic steel of a main magnetic circuit generates 100% of main magnetic flux, so that the consumption of the magnetic steel material of the main magnetic circuit is reduced, the cost of a motor is further reduced while the power density of the motor is improved, and precious rare earth resources are saved.

Description

A core structure with reduced rare earth permanent magnet material

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on the Chinese patent application with application number 202311792673.0 and application date of December 25, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference. Technical Field

[0003] The present invention relates to the technical field of magnetic pole structures of permanent magnet motors, and in particular to an iron core structure with reduced rare earth permanent magnet materials. Background Art

[0004] Permanent magnet synchronous motors (PMSMs) have the advantages of simple structure, small size, high efficiency, and high power factor. They have achieved success in electric drive systems in the metallurgical industry (iron mills and sintering plants, etc.), the ceramic industry (ball mills), the rubber industry (internal mixers), the petroleum industry (pumping units), the textile industry (twisters and spinning machines), and the transportation industry (electric vehicles, high-speed rail, and urban rail transit), and have gradually accumulated design and operation experience. Based on the structure of the permanent magnets, PMSMs can be divided into surface permanent magnet synchronous motors (SPMSMs) and interior permanent magnet synchronous motors (IPMSMs). The interior permanent magnet synchronous motor can fully utilize the reluctance torque generated by the asymmetry of the rotor magnetic circuit to increase the motor's power density, resulting in improved dynamic performance compared to surface-mount rotor structures. The manufacturing process is also simpler, and the motor is more conducive to field weakening speed increase, which can easily improve the safety of high-speed rotation of the motor. However, the leakage flux coefficient and manufacturing cost are higher than those of surface-mount rotor structures.

[0005] Depending on the arrangement of the internal magnets, the magnetic pole structures of built-in rotors can be categorized as radial, tangential, and hybrid. The radial structure is widely used in rail transit, electric vehicles, and other fields due to its advantages, such as low magnetic flux leakage coefficient, no need for magnetic isolation measures on the rotor, easy control of the pole arc coefficient, high mechanical strength of the rotor laminations, and resistance to rotor deformation after installation.

[0006] Permanent magnetic materials are of many types and have a wide range of uses. They have mainly gone through three stages of application and development: metal permanent magnetic materials, ferrite permanent magnetic materials and rare earth permanent magnetic materials.

[0007] Metal permanent magnet materials: Their development and application began relatively early. These alloy-type permanent magnets, also known as permanent magnet alloys, are primarily composed of iron and iron-group elements. These primarily include two types of permanent magnet alloys: aluminum-nickel-cobalt (AlNiCo) and iron-chromium-cobalt (FeCrCo). In the early 20th century, these alloys were produced through casting processes, also known as cast permanent magnets. Around 1880, carbon steel was first used to produce permanent magnets, with a maximum magnetic energy product (BHmax) of approximately 1.6 kJ / m³. This development subsequently progressed to metal permanent magnets such as tungsten steel and cobalt steel. In 1931, Japan developed an iron-nickel-aluminum alloy (Fe-Ni-Al), boasting a coercivity exceeding 400 Oe. Later, elements such as cobalt, copper, and titanium (Co, Cu, and Ti) were added to this alloy. By adding the three elements aluminum, nickel, and cobalt (Al, Ni, and Co) to iron, followed by casting and heat treatment, AlNiCo magnets were created, the well-known AlNiCo magnet. From then on, Alnico magnets dominated the permanent magnet market until the 1960s. This material has a low magnetic energy product, a high Curie temperature (up to 890°C), excellent temperature stability, and a low temperature coefficient of magnetic induction. Therefore, its use in certain specialized devices remains irreplaceable and maintains a stable market demand.

[0008] Ferrite permanent magnet materials, also known as permanent ferrite, are made from strontium oxide (SrO) or barium oxide (BaO) and ferric oxide (Fe2O3). They are manufactured through ceramic processes, including pre-sintering, crushing, ball milling, pulverizing, molding, sintering, and machining. Ferrite permanent magnets were discovered in the 1930s and invented by Philips in the 1940s. Due to their cheap raw materials, simple manufacturing process, and low price, they experienced rapid development in the 1970s, reaching the top of the production output list.

[0009] Rare earth permanent magnet materials: This refers to a magnetic material made by pressing and sintering an alloy composed of samarium and neodymium mixed with a transition metal (such as cobalt or iron) using powder metallurgy, followed by magnetization in a magnetic field. These include samarium cobalt (SmCo) permanent magnets and neodymium iron boron (NdFeB) permanent magnets. The magnetic energy product of SmCo magnets ranges from 15 to 30 MGOe, while that of NdFeB magnets ranges from 27 to 50 MGOe. Rare earth permanent magnet materials have evolved through the first generation, SmCo5, the second generation, precipitation-hardened Sm2Co17, and finally the third generation, Nd-Fe-B permanent magnets. NdFeB currently possesses the highest magnetic energy product in the world and is known as the "king of modern permanent magnets." The advent of NdFeB rare earth permanent magnets marked a revolutionary change in the field of permanent magnet materials, a milestone of epoch-making significance. In recent years, the fourth generation of rare earth permanent magnets represented by rare earth iron nitrogen and rare earth iron carbon have made breakthroughs and entered the application stage.

[0010] Drive motors in the transportation sector almost all utilize neodymium iron boron permanent magnets. To accommodate the ever-increasing speeds of these motors, a single-V or double-V magnet arrangement is employed. The topology of an embedded single-V magnet arrangement is shown in Figure 1. To overcome centrifugal force, magnetic bridges are installed on the magnetic poles: upper and lower magnetic bridges 2 and 3 are positioned above and below the main magnet 1, respectively. Due to the presence of these bridges, a portion of the magnetic flux from the magnets is short-circuited along the bridges, bypassing the air gap. This flux is known as leakage flux, as shown in Figure 2. To maximize magnet utilization, a narrow bridge is desirable to minimize leakage flux. However, an excessively narrow bridge leads to excessive stress at the bridge, limiting further increases in motor speed. To balance this conflict, domestic and international researchers have devised various approaches, such as developing high-strength silicon steel and employing dual-phase silicon steel. However, these approaches struggle to balance the material's electromagnetic and mechanical properties with cost, resulting in a dilemma. Summary of the Invention

[0011] In order to overcome the technical defect in the prior art that it is difficult to achieve a balance between the electromagnetic properties and mechanical properties of the material and reduce costs, the present invention provides an iron core structure that reduces rare earth permanent magnet materials.

[0012] The present invention provides an iron core structure that reduces the use of rare earth permanent magnets. This structure is an improvement on the embedded single V-shaped magnet topology described in the prior art. Permanent ferrite is embedded in the central through-holes of the two lower magnetic bridges, allowing the lower magnetic bridges on both sides to achieve pre-saturation. The permanent ferrite can be replaced with samarium iron nitride permanent magnets. The iron core has a single-magnet double-bridge structure, using a single piece of ferrite permanent magnet material to achieve pre-saturation of the magnetic bridges on both sides, thus achieving a magnetic isolation effect for the main magnet. Both permanent ferrite and samarium iron nitride permanent magnets are relatively low-cost and low-density permanent magnet materials.

[0013] The present invention also provides an iron core structure that reduces the use of rare earth permanent magnet materials. This structure is an improvement on the embedded single V-shaped magnet arrangement topology described in the background art. A permanent ferrite is embedded in the original lower magnetic bridge position of the main magnet, eliminating the through hole between the two lower magnetic bridges. An intermediate magnetic bridge is formed between the permanent ferrites on the lower sides of two adjacent main magnets, and the intermediate magnetic bridge is pre-saturated using the permanent ferrites on both sides. The permanent ferrites can be replaced with samarium iron nitride permanent magnets. This structure is a single-bridge dual-magnet structure, using two pieces of ferrite permanent magnet material to achieve pre-saturation of the intermediate magnetic bridge; it also achieves a magnetic isolation effect for the main magnet. Permanent ferrite and samarium iron nitride permanent magnets are both relatively low-cost and low-density permanent magnet materials.

[0014] The present invention also provides an iron core structure that reduces the use of rare earth permanent magnet materials. This structure is an improvement on the embedded single V-shaped magnet arrangement topology described in the background art. Permanent ferrite is embedded in the through-hole between the upper end of the main magnet and the upper magnetic bridge, and permanent ferrite is embedded in the through-hole between the lower end of the main magnet and the lower magnetic bridge, so that both the upper and lower magnetic bridges are pre-saturated. The permanent ferrite can be replaced with samarium iron nitride permanent magnets. This structure is a single-magnet double-bridge structure, using special-shaped ferrite magnets to fill both ends of the main magnet to construct a non-magnetic magnetic bridge, achieving a magnetic isolation effect for the main magnet. Permanent ferrite is low-cost, and its high resistivity is utilized to avoid eddy current heating of the magnet. This achieves efficient utilization of the main magnet and improves the power density of the motor. Permanent ferrite and samarium iron nitride permanent magnets are both relatively low-cost and low-density permanent magnet materials.

[0015] The high price of NdFeB permanent magnets, while they can achieve high motor efficiency, increases motor costs. Considering the low price, high resistivity, low eddy current loss, low specific gravity, and lower centrifugal force of ferrite permanent magnets, the magnetic circuit design of the rotor laminations uses inexpensive ferrite permanent magnets to achieve pre-saturation of the magnetic bridge, thereby avoiding magnetic flux leakage from the main magnet. This, together with the main magnet, forms a magnetic circuit isolation structure, ensuring full utilization of the NdFeB permanent magnets.

[0016] The aforementioned core structures can be divided into magnetic bridges and pre-saturated magnets. The magnetic bridges can be categorized as single or double bridges. The design of the magnetic bridges only considers the mechanical stress they withstand. Pre-saturated magnets are selected so that their saturation magnetic induction intensity meets the requirements for saturating the magnetic bridges. Because the magnetic bridges are pre-saturated, magnetic flux leakage in this area need not be considered, thus saving on magnetic material in the main magnetic circuit.

[0017] Compared with the prior art, the technical solution provided by the present invention has the following technical effects: based on the different characteristics and requirements of each part of the motor magnetic circuit and combined with the characteristics of existing engineered hard magnetic materials, the present invention proposes a low-cost combined iron core topology structure that utilizes various hard magnetic materials to achieve high performance, that is, it provides a variety of iron core structures that reduce rare earth permanent magnet materials, specifically, permanent magnet ferrite or samarium iron nitride permanent magnets are added at different positions; the structure of the present invention enables neodymium iron boron permanent magnet materials, permanent magnet ferrite or samarium iron nitride and other low-cost and small-specificity permanent magnet materials to be perfectly matched in different parts of the motor magnetic circuit, giving full play to their respective advantages, so that the magnetic circuit of the traction motor has higher magnetic induction intensity and lower implementation cost, so that the main magnetic circuit magnetic steel generates 100% main magnetic flux, while improving the power density of the motor, ensuring that the cost of the motor is further reduced, saving precious rare earth resources, and making my country's precious rare earth resources more effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic diagram of the topological structure of the embedded single V-shaped magnetic steel arrangement described in the background art;

[0019] FIG2 is a schematic diagram of leakage flux generated by the embedded single V-shaped magnetic steel arrangement topology structure described in the background art;

[0020] FIG3 is a schematic structural diagram of an iron core structure with reduced rare earth permanent magnet material according to Example 1 of the present invention;

[0021] FIG4 is a schematic structural diagram of an iron core structure with reduced rare earth permanent magnet material according to Example 2 of the present invention;

[0022] FIG5 is a schematic structural diagram of an iron core structure with reduced rare earth permanent magnet material according to Example 3 of the present invention. DETAILED DESCRIPTION

[0023] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0024] In the description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance. It should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, removable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms based on specific circumstances.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] The specific embodiments of the present invention will be described in detail below with reference to Figures 1 to 5 .

[0027] In Example 1, as shown in FIG3 , a core structure that reduces rare earth permanent magnet material is disclosed. This is an improvement based on the embedded single V-shaped magnet arrangement topology structure in the background art. Permanent ferrite 4 is embedded in the middle through-holes of the two lower magnetic bridges 3, so that the lower magnetic bridges 3 on both sides are pre-saturated. The permanent ferrite 4 can be replaced with samarium iron nitride permanent magnets, or other permanent magnet materials with lower cost and lower specific gravity. This structure is a single-magnet double-bridge structure, using a single piece of ferrite permanent magnet material to achieve pre-saturation of the magnetic bridges on both sides, achieving a magnetic isolation effect for the main magnetic steel 1. Permanent ferrite 4 and samarium iron nitride permanent magnets are both permanent magnet materials with lower cost and lower specific gravity.

[0028] In Example 2, as shown in FIG4 , a core structure that reduces the use of rare earth permanent magnets is disclosed. This structure is an improvement on the embedded single V-shaped magnet arrangement topology described in the background art. A permanent ferrite 4 is embedded in the original lower magnetic bridge 3 of the main magnetic steel 1, eliminating the through-hole between the two lower magnetic bridges 3. The through-hole between the two lower magnetic bridges 3 forms the rotor core 6 body. An intermediate magnetic bridge 5 is then formed between the permanent ferrites 4 on the lower sides of two adjacent main magnetic steels 1. The intermediate magnetic bridge 5 is presaturated using the permanent ferrites 4 on both sides. The permanent ferrites 4 can be replaced with samarium iron nitride permanent magnets or other low-cost, low-density permanent magnet materials. This structure is a single-bridge, dual-magnet structure, using two ferrite permanent magnets to achieve presaturation of the intermediate magnetic bridge 5. This achieves a magnetic isolation effect for the main magnetic steel 1. Both the permanent ferrite 4 and the samarium iron nitride permanent magnets are low-cost, low-density permanent magnet materials.

[0029] In Example 3, as shown in FIG5 , a core structure that reduces the use of rare earth permanent magnets is disclosed. This structure is an improvement on the embedded single V-shaped magnet topology described in the prior art. A permanent ferrite 4 is embedded in the through-hole between the upper end of the main magnet 1 and the upper magnetic bridge 2, and a permanent ferrite 4 is embedded in the through-hole between the lower end of the main magnet 1 and the lower magnetic bridge 3, achieving presaturation of both the upper and lower magnetic bridges 2 and 3. The permanent ferrite 4 can be replaced with samarium iron nitride permanent magnets or other low-cost, low-density permanent magnet materials. This structure is a single-magnet double-bridge structure, employing shaped ferrite magnets at both ends of the main magnet 1 to create a non-magnetic bridge, achieving a magnetic isolation effect for the main magnet 1. The permanent ferrite 4 is low-cost, and its high resistivity prevents eddy current heating of the magnets. This achieves efficient utilization of the main magnet 1 and improves the power density of the motor. Both the permanent ferrite 4 and the samarium iron nitride permanent magnets are low-cost, low-density permanent magnet materials.

[0030] The high price of NdFeB permanent magnets, while they can achieve high motor efficiency, increases motor costs. Considering the low price, high resistivity, low eddy current loss, low specific gravity, and reduced centrifugal force of ferrite permanent magnets, the magnetic circuit design of the rotor laminations uses inexpensive ferrite permanent magnets or samarium iron nitride permanent magnets to achieve pre-saturation of the magnetic bridge, thereby preventing magnetic flux leakage from the main magnet 1. This, together with the main magnet, forms a magnetic circuit isolation structure, ensuring full utilization of the NdFeB permanent magnets.

[0031] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. A core structure for reducing rare earth permanent magnet materials, wherein, It is improved based on the embedded single-V permanent magnet arrangement topology. A permanent ferrite magnet is embedded in the through-hole between the two lower magnetic bridges, causing the two lower magnetic bridges on both sides to reach pre-saturation; the permanent ferrite magnet can be replaced with a samarium-iron-nitrogen permanent magnet.

2. A core structure for reducing rare earth permanent magnet materials, wherein, It is improved based on the embedded single-V permanent magnet arrangement topology. The through-hole between the two lower magnetic bridges is cancelled, and a permanent ferrite magnet is embedded at the original position of the lower magnetic bridge of the main permanent magnet. An intermediate magnetic bridge is formed between the permanent ferrite magnets on the lower sides of two adjacent main permanent magnets, and the intermediate magnetic bridge is pre-saturated by the permanent ferrite magnets on both sides; the permanent ferrite magnet can be replaced with a samarium-iron-nitrogen permanent magnet.

3. A core structure for reducing rare-earth permanent magnet materials, wherein, It is improved based on the embedded single-V permanent magnet arrangement topology. A permanent ferrite magnet is embedded in the through-hole between the upper end of the main permanent magnet and the upper magnetic bridge, and a permanent ferrite magnet is embedded in the through-hole between the lower end of the main permanent magnet and the lower magnetic bridge, causing both the upper magnetic bridge and the lower magnetic bridge to reach pre-saturation; the permanent ferrite magnet can be replaced with a samarium-iron-nitrogen permanent magnet.

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