A high thrust density cylindrical linear motor based on wave-shaped air gap

Abstract

The application discloses a high thrust density cylindrical linear motor based on a wave-shaped air gap, which is composed of a wave-shaped stator core, an armature winding, a wave-shaped permanent magnet and a mover core, a wave-shaped air gap is arranged between the stator and the mover in the circumferential direction, the air gap area is increased, the air gap magnetic flux density distribution is adjusted, and the output thrust quality is improved. A wave-shaped permanent magnet excitation structure is arranged on the mover, the stator tooth top is arranged in a wave-shaped distribution same as the permanent magnet excitation structure distribution in the circumferential direction, and the air gap length is ensured to be equal everywhere. The wave-shaped permanent magnet excitation structure is composed of a plurality of pairs of permanent magnets arranged in a wave-shaped distribution in the circumferential direction and stacked in the axial direction, can generate a magnetic aggregation effect, and improve the excitation capacity in the motor. The cylindrical linear motor disclosed by the application has the characteristics of large output thrust, high thrust density and high efficiency, and is suitable for application occasions such as numerical control machine tool machining, electromagnetic launching and automobile suspension systems which require high thrust and high efficiency.

Description

A high thrust density cylindrical linear motor based on a wave-shaped air gap Technical Field

[0001] This invention belongs to the field of motor design, specifically a high thrust density cylindrical linear motor based on a wave-shaped air gap. Background Technology

[0002] As the primary electromechanical energy conversion device, the electric motor can convert fossil fuels or other clean energy sources into electrical energy, and can also convert electrical energy into mechanical energy to provide driving force. In terms of electric motor drives, with the rapid development of industrial production and transportation, there is a need to innovate the structure and design methods of drive motors to further improve motor efficiency and torque density, thereby enhancing the motor's driving capability.

[0003] Linear motion is one of the most widely used types of motion control in industrial production. Traditional linear drive systems use a combination of a rotary motor and a ball screw to convert rotary motion into linear motion. However, such linear drive systems have many intermediate reduction stages, resulting in low drive system efficiency.

[0004] To address this issue, British researchers proposed the concept of a linear motor. In a drive system centered on a linear motor, the primary and secondary structures are relatively independent, allowing for unrestricted linear motion, which is advantageous for long-distance linear motion applications such as electromagnetic catapults. The motor is directly connected to the load without intermediate transmission links, resulting in low system inertia, a simple structure, and ease of maintenance. Traditional permanent magnet linear motors have ends in their windings, leading to three-phase asymmetry after energization, causing large thrust fluctuations and making precise control difficult.

[0005] Therefore, motor researchers proposed the cylindrical linear motor. Compared with traditional long-distance linear motors, the cylindrical linear motor has advantages such as no lateral ends, high winding utilization, high thrust density, and no magnetic pull.

[0006] In recent years, there has been continuous innovation and development in the structural design of novel cylindrical linear motors. N. Bianchi, S. Bolognani, and ADFCappello optimized the axial length of the permanent magnet in a cylindrical linear motor, adjusted the air gap magnetic flux density waveform, and suppressed the positioning force fluctuation of the cylindrical linear motor. Researchers such as Li Huaishu and Xue Zhiqiang from the Naval University of Engineering proposed using a permanent magnet arrangement with unequal pole pitches on the stator and mover to weaken the cogging force of the motor and suppress the thrust fluctuation. However, optimizing the permanent magnet length and using unequal pole pitch permanent magnets have not yet been able to further reduce thrust fluctuation while increasing thrust, and the small air gap area of ​​the motor cannot further improve thrust density and efficiency. Summary of the Invention

[0007] Purpose of the Invention: To further enhance the electromechanical conversion capability of motors, increase thrust density, and reduce thrust fluctuation, this invention discloses a cylindrical linear motor based on a wave-shaped air gap. This motor employs a wave-shaped air gap, increasing the air gap area and optimizing the air gap distribution, thereby improving the air gap magnetic flux density and reducing the air gap magnetic flux density harmonic distortion rate. The wave-shaped permanent magnet excitation structure on the mover and the stator tooth tips both exhibit the same wave shape. The motor disclosed in this invention features a large air gap area, strong magnetic focusing ability, high thrust density, and high operating efficiency, showing promising development prospects in applications requiring high thrust density, such as CNC machine tool processing, electromagnetic catapults, and automotive suspension systems.

[0008] Technical solution: To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A high thrust density cylindrical linear motor based on a wave-shaped air gap specifically includes: a stator, a wave-shaped air gap, a wave-shaped permanent magnet excitation structure, and a mover core.

[0010] The stator includes a stator core, stator tooth tips, and armature windings. The stator tooth tips have the same circumferential shape as the wave-shaped air gap, and the stator teeth are arranged axially to form stator slots. The disc-shaped armature windings are embedded in the stator slots. When a three-phase sinusoidal current flows through the armature windings, an axial armature traveling wave magnetic field is generated.

[0011] Furthermore, the armature winding adopts a fractional slot winding method, which can improve the winding utilization rate and optimize the motor speed range.

[0012] The wave-shaped air gap is composed of a wave-shaped permanent magnet excitation structure attached to the mover core and the stator tooth tip, and the length of the wave-shaped air gap is equal everywhere.

[0013] The wave-shaped permanent magnet excitation structure is attached to the mover core and consists of several pairs of circumferentially wave-shaped permanent magnets stacked axially. Each pair of wave-shaped permanent magnets includes a wave-shaped permanent magnet that is magnetized radially outward and a wave-shaped permanent magnet that is magnetized radially inward.

[0014] The moving core is distributed in a wave-like shape in the circumferential direction near the air gap surface, which is the same as the shape of the wave-shaped air gap structure. The permanent magnet magnetic field generated by the wave-shaped permanent magnet excitation structure and the traveling wave magnetic field generated by the armature winding can drive the moving core to cut the magnetic induction lines and generate axial electromagnetic thrust.

[0015] The wave-shaped air gap increases the air gap area, optimizes the air gap distribution, improves the air gap magnetic flux density and reduces the harmonic distortion of the air gap magnetic flux density, thereby improving thrust characteristics and operating efficiency.

[0016] The wave-shaped permanent magnet excitation structure generates a magnetic focusing effect between the two wave peaks, which has a strong magnetic focusing ability and further improves the thrust density.

[0017] Furthermore, the stator tooth tip, wave-shaped permanent magnet excitation structure, and mover core of the motor are formed by additive manufacturing using laser sintering, while other structures are formed by subtractive manufacturing, thereby increasing the design freedom of the motor.

[0018] Furthermore, the wavy permanent magnet excitation structure can have a periodic wave shape, a periodic wave shape composed of a set of sinusoidal shapes, or an aperiodic wave shape in the circumferential direction.

[0019] Beneficial effects: Compared with the prior art, the motor disclosed in this invention has the following significant advantages:

[0020] (1) High efficiency. The motor disclosed in this invention adopts a wave-shaped air gap, which increases the air gap area without increasing the motor volume. The air gap magnetic field utilization rate is high, the motor electromechanical energy conversion efficiency is high, and the thrust fluctuation is small.

[0021] (2) Small harmonic distribution distortion. The wavy stator tooth tip can optimize the air gap magnetic permeability and reduce the harmonic distribution distortion rate of the magnetic flux density in the wavy air gap.

[0022] (3) High thrust density. In the wave-shaped permanent magnet excitation structure, a magnetic focusing effect can be generated between the two wave crests, which enhances the permanent magnet magnetic field and further increases the thrust density, resulting in superior thrust characteristics.

[0023] (4) Ease of manufacture. The stator tooth tip, permanent magnet excitation structure and mover core shape are changed only by the wave-shaped air gap. The mover is only composed of the core pole and the mover yoke. The motor structure is simple and easy to manufacture and assemble.

[0024] (5) Design flexibility. The stator tooth tips with the same wave shape in the circumference, the wave-shaped permanent magnet excitation structure, and the mover core are formed by additive manufacturing, which allows for flexible design and high utilization of permanent magnet materials.

[0025] (6) High applicability. The wave-shaped air gap can be formed by the wave-shaped permanent magnet excitation structure attached to the stator tooth tip and the mover core, forming a stator permanent magnet cylindrical linear motor based on the wave-shaped air gap, which has broad prospects for industrial application. Attached Figure Description

[0026] Figure 1 is a schematic diagram of a quarter-axial cross-section of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in an embodiment of the present invention.

[0027] Figure 2 is a schematic diagram of the overall three-dimensional structure of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in an embodiment of the present invention.

[0028] Figure 3 is a schematic diagram of the three-dimensional structure of the circumferentially periodic wave-shaped permanent magnet excitation structure of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in an embodiment of the present invention.

[0029] Figure 4 is a schematic diagram of the magnetic focusing point of the magnetic focusing effect described in a specific embodiment of the present invention;

[0030] Figure 5 is a schematic diagram of the three-dimensional structure of the sinusoidal permanent magnet excitation structure with a periodic sinusoidal wave shape in the circumferential direction in another extended embodiment of the present invention along the axial direction.

[0031] Figure 6 is a schematic diagram of the three-dimensional structure of the semi-wave-type permanent magnet excitation structure with a non-periodic wave shape in the circumferential direction in another extended embodiment of the present invention along the axial direction.

[0032] Figure 7 is a schematic diagram of the three-dimensional structure of the moving core of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in an embodiment of the present invention along the axial direction.

[0033] Figure 8 is a schematic diagram of the three-dimensional structure of a high thrust density cylindrical linear motor based on a wave-shaped air gap along half of the axial section provided in an embodiment of the present invention.

[0034] Figure 9 is a schematic diagram of the three-dimensional structure of the stator half-axial cross section of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in an embodiment of the present invention.

[0035] Figure 10 is a schematic diagram of the axial cross-sectional structure of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in part of the embodiment of the present invention, with the cross-section taken along the peak of the periodic wave shape of the wave-shaped permanent magnet.

[0036] Figure 11 is a schematic diagram of the axial cross-sectional structure of a high thrust density cylindrical linear motor based on a wave-shaped air gap provided in part of an embodiment of the present invention. The cross-section is taken at the connection point of adjacent periodic wave shapes in the wave-shaped permanent magnet.

[0037] Figures 10 and 11 show the variation of the radial thickness of the stator tooth tip and the mover core section with the cutting position, indicating that its circumferential shape is consistent with the shape of the wave-shaped air gap of the motor disclosed in this invention;

[0038] In the diagram: 1-Stator, 101-Stator core, 102-Stator tooth tip, 103-Armature winding, 2-Wave-shaped air gap, 3-Wave-shaped permanent magnet excitation structure, 301-Wave-shaped permanent magnet magnetized radially outward, 302-Wave-shaped permanent magnet magnetized radially inward, 4-Motor core, 501-Wave-shaped permanent magnet magnetized radially outward in a periodic sine wave shape, 502-Wave-shaped permanent magnet magnetized radially inward in a periodic sine wave shape, 601-Wave-shaped permanent magnet magnetized radially outward in a 1 / n periodic wave shape containing crests, 602-Wave-shaped permanent magnet magnetized radially inward in a 1 / n periodic wave shape containing crests, Thick arrow - Schematic diagram of the magnetization direction of stacked pairs of permanent magnets, F - The magnetizing point, Thin arrow - Direction of magnetic field lines perpendicular to the surface of the permanent magnet. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0040] This invention discloses a high thrust density cylindrical linear motor based on a wave-shaped air gap, as shown in Figure 1. The motor includes a stator 1, a wave-shaped air gap 2, a wave-shaped permanent magnet excitation structure 3, and a mover core 4. The stator 1 includes a stator core 101, a stator tooth tip 102, and an armature winding 103. The wave-shaped permanent magnet excitation structure 3 includes a pair of axially stacked wave-shaped permanent magnets 301 that are magnetically magnetized radially outward and wave-shaped permanent magnets 302 that are magnetically magnetized radially inward.

[0041] As shown in Figure 2, the wave-shaped air gap 2 is composed of the stator tooth tip 102 and the wave-shaped permanent magnet excitation structure 3 attached to the mover core 4. The length of the wave-shaped air gap is equal everywhere, and it is distributed in a wave shape in the circumferential direction. Compared with the traditional circular air gap in the circumferential direction, the wave-shaped air gap 2 can effectively increase the air gap area without increasing the size of the motor, thereby further improving the motor efficiency.

[0042] The stator tooth tip 102, the wave-shaped permanent magnet excitation structure 3, and the mover core 4 all have the same wave shape as the wave-shaped air gap 2 in their circumferential direction. These three structures can be formed using additive manufacturing methods such as laser sintering, while other structures are formed using subtractive manufacturing methods. Compared with traditional manufacturing methods such as sintering and bonding, additive manufacturing offers lower material waste and higher flexibility, overcoming the shortcomings of traditional manufacturing processes. The permanent magnet structure formed by additive manufacturing has the advantages of low cost, light weight, and high magnetic concentration capability, enabling high thrust output.

[0043] As shown in FIG. 3, a wave-shaped permanent magnet 301 magnetized radially outward and a wave-shaped permanent magnet 302 magnetized radially inward are axially stacked to form a wave-shaped permanent magnet excitation structure 3. The wave-shaped permanent magnet 301 and the wave-shaped permanent magnet 302 have the same structure and axial thickness, and the radial height of each permanent magnet in the wave-shaped permanent magnet excitation structure 3 is equal everywhere. The direction of the thick arrow indicates the magnetization directions of the paired wave-shaped permanent magnet 301 radially outward and the wave-shaped permanent magnet 302 radially inward.

[0044] As shown in FIG. ********, compared with traditional structures such as U-shaped and interior permanent magnet structures, the wave-shaped permanent magnet excitation structure 3 has a magnetic focusing effect and has one or more magnetic focusing points. The lines perpendicular to the surface of the permanent magnet intersect at the magnetic focusing points, thereby enhancing the permanent magnet excitation ability in the motor and improving the output thrust. In practical applications, the number of magnetic focusing points can be determined according to the design requirements of the motor, the magnetic focusing and excitation capabilities of the excitation structure.

[0045] The shape of the wave-shaped permanent magnet excitation structure 3 in the circumferential direction can be a periodic wave shape, a periodic wave shape composed of a group of sine shapes, and an aperiodic wave shape:

[0046] As shown in FIG. 5, a sine-shaped permanent magnet 501 magnetized radially outward with a periodic sine wave shape in the circumferential direction and a sine-shaped permanent magnet 502 magnetized radially inward with a periodic sine wave shape are axially stacked to form a sine-shaped permanent magnet excitation structure. The direction of the arrow indicates the magnetization directions of the paired sine-shaped permanent magnet 501 radially outward and the sine-shaped permanent magnet 502 radially inward.

[0047] As shown in FIG. 6, a semi-wave-shaped permanent magnet 601 magnetized radially outward with a 1 / n-period wave shape including wave peaks in the circumferential direction and a semi-wave-shaped permanent magnet 602 magnetized radially inward with a 1 / n-period wave shape including wave peaks are axially stacked to form a semi-wave-shaped permanent magnet excitation structure with an aperiodic wave shape. The direction of the arrow indicates the magnetization directions of the paired semi-wave-shaped permanent magnet 601 radially outward and the semi-wave-shaped permanent magnet 602 radially inward, where 1 < n < 6. In this embodiment, n = 2 is selected, and different n values can be selected according to design needs in practical applications to design different aperiodic wave shapes.

[0048] When using the above two permanent magnet excitation structures to form a motor, compared with a traditional cylindrical linear motor, only by changing the stator tooth tip, the permanent magnet excitation structure, and the shape of the mover core, a sine-shaped air gap and a semi-wave-shaped air gap are formed, increasing the air gap area and improving the thrust density and efficiency of the motor.

[0049] It should be noted that in the translation of , the number in "As shown in FIG. ********" needs to be filled in according to the actual figure number in the original text.As shown in Figure 7, the mover core 4 only has core poles and a mover yoke. Compared to mover structures with built-in permanent magnets or slotted modulation poles, the motor using the mover core 4 can increase thrust density without increasing the amount of permanent magnets. It avoids the high errors caused by complex mover shapes during motor operation adjustment, making the positioning accuracy during manufacturing and the dynamic performance of the motor through position detection during operation simpler. To clearly illustrate the motor structure, the axial lengths of the mover core 4 and stator 1 are the same in the accompanying drawings of the motor embodiment disclosed in this invention. However, in practical applications, the manufacturing process of the secondary-side wave-shaped permanent magnet excitation structure 3 and the mover core 4 is simpler than that of the primary-side stator 1 structure. Therefore, a short primary and long secondary structure should be adopted.

[0050] As shown in Figure 1, the stator tooth tips 102 are arranged axially to form stator slots. The slots are semi-closed, and the armature windings 103 are embedded in the stator slots in a disc shape.

[0051] As shown in Figure 1, the armature winding 103 is a single-layer winding, with one coil in each primary slot. When a fractional-slot double-layer winding is used, each primary slot contains two coils. The number of coils is twice the number of slots, and the number of slots is an integer multiple of the number of phases. For an m-phase motor, Z = km; the number of slots per phase per stage q = Z / 2pm; where k is a constant, Z is the number of slots, and p is the number of permanent magnet pole pairs. When q is less than 1, it is a fractional-slot winding.

[0052] The motor disclosed in this invention uses a fractional-slot winding, which can obtain more poles with a limited number of slots to achieve the effect of speed reduction. It can improve the winding utilization rate, reduce high-order harmonics, improve the electromagnetic performance of the motor, further optimize the speed range of the motor, suppress cogging torque, and can be extended to applications requiring a wide speed range and low thrust fluctuation.

[0053] As shown in Figure 1, after a three-phase sinusoidal alternating current is applied to the annular armature winding 103, an axially sinusoidally distributed traveling wave magnetic field is generated in the wave-shaped air gap 2. This magnetic field couples with the permanent magnet magnetic field generated by the wave-shaped permanent magnet excitation structure 3. The force generated by this coupling can drive the mover core 4 to cut the magnetic induction lines, producing an axial electromagnetic thrust. The axial speed v of the motor is related to the power supply frequency f and the permanent magnet pole pitch τ, where v = 2τf.

[0054] As shown in Figures 8, 9, 10, and 11, the internal structures of the stator 1, the wave-shaped permanent magnet excitation structure 3, and the mover core 4 of the motor disclosed in this invention are further explained.

[0055] When the motor is unloaded, the motor disclosed in this invention exhibits a high sinusoidal back electromotive force waveform. When the motor is loaded, it exhibits high magnetic saturation induction intensity and high motor line load, thereby improving the motor's load-carrying capacity and thrust output capability. The motor of this invention has the advantages of high thrust density and high operating efficiency, making it suitable for applications such as CNC machine tool processing, electromagnetic catapults, and automotive suspension systems.

[0056] The above embodiments are merely illustrative of the technical concept of the present invention and are only some embodiments of the present invention. They cannot be used to limit the scope of protection of the present invention. All other embodiments obtained by those skilled in the art based on the technical concept proposed by the present invention without creative effort are within the scope of protection of the present invention.

Claims

1. A high thrust density cylindrical linear motor based on a wave-shaped air gap, characterized in that: The motor comprises a stator (1), a wave-shaped air gap (2), a wave-shaped permanent magnet excitation structure (3), and a mover core (4). The stator (1) consists of a stator core (101), stator tooth tips (102), and armature windings (103). The wave-shaped permanent magnet excitation structure (3) consists of several pairs of radially outwardly magnetized wave-shaped permanent magnets (301) and radially inwardly magnetized wave-shaped permanent magnets (302). The motor uses a wave-shaped air gap (2) formed by the wave-shaped permanent magnet excitation structure (3) and stator tooth tips (102) with a wave shape. A magnetic focusing effect is generated between the two peaks in the wave-shaped permanent magnet excitation structure (3). The wave-shaped stator tooth tips optimize the air gap permeability and reduce the magnetic flux density harmonic distribution distortion rate in the wave-shaped air gap. The length of the wave-shaped air gap (2) is equal everywhere and close to the mover core (4). The surfaces of the air gap, the stator tooth tip (102) near the air gap, and the wave-shaped permanent magnet excitation structure (3) are distributed in the same circumferential direction; the wave-shaped air gap (2) has a periodic wave shape or a periodic wave shape composed of a set of sinusoidal shapes or a non-periodic wave shape in the circumferential direction; the axially adjacent radially outward magnetized wave-shaped permanent magnets (301) and radially inward magnetized wave-shaped permanent magnets (302) in the wave-shaped permanent magnet excitation structure (3) have the same structure and axial thickness, and the radial height of each permanent magnet is equal everywhere; lines perpendicular to the surface of the permanent magnet intersect at the magnetization point, and the radially outward magnetized wave-shaped permanent magnets (301) or radially inward magnetized wave-shaped permanent magnets (302) have one or more magnetization points; wherein, the number of magnetization points is determined according to the motor design requirements, the magnetization and excitation capacity of the excitation structure.

2. The high thrust density cylindrical linear motor based on a wave-shaped air gap according to claim 1, characterized in that: The motor is formed by a combination of additive and subtractive manufacturing methods. The mover core (4), stator tooth tip (102), and the radially outwardly magnetized wave-shaped permanent magnet (301) and radially inwardly magnetized wave-shaped permanent magnet (302) are formed by laser sintering additive manufacturing, while the other structures of the motor are formed by subtractive manufacturing.

3. The high thrust density cylindrical linear motor based on a wave-shaped air gap according to claim 1, characterized in that: The wave-shaped permanent magnet excitation structure (3) is applied to the mover and the stator to form a mover permanent magnet linear motor and a stator permanent magnet linear motor, respectively.

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