Primary permanent magnet linear motor with low cogging force

Abstract

The application discloses a low-tooth-groove primary permanent magnet linear motor and belongs to the technical field of motors. The application aims at the problem of high tooth groove force of the primary permanent magnet linear motor. The primary permanent magnet linear motor comprises a primary and a secondary, the primary comprises a primary iron core, an armature winding and permanent magnets, the armature winding is wound on the armature tooth of the primary iron core, the armature winding is composed of concentrated windings, the tooth top of the armature tooth is processed with a plurality of unequal-width split teeth to form an odd number of split tooth grooves, the permanent magnets are embedded in the split tooth grooves, the permanent magnet in the middle split tooth groove is higher than the permanent magnets in the split tooth grooves on the two sides, and the plurality of permanent magnets form a non-uniform air gap magnetic field between the primary and the secondary. The application is suitable for high-precision direct drive motion control occasions.

Description

Technical Field

[0001] This invention relates to a primary permanent magnet linear motor with low cogging force, belonging to the field of motor technology. Background Technology

[0002] Permanent magnet linear motors can achieve linear motion without intermediate transmission mechanisms, and have advantages such as high thrust density and fast response speed, which have attracted widespread attention in the field of linear motion.

[0003] Traditional permanent magnet synchronous linear motors require a long array of magnetic poles, while the structural feature of primary permanent magnet linear motors is that both the winding excitation source and the permanent magnet excitation source can be placed on the same side of the motor, and the stator is made entirely of stacked silicon steel sheets, which reduces the amount of permanent magnets used in the motor. Therefore, this type of motor has received widespread attention in the field of long stroke.

[0004] Because both the winding excitation source and the permanent magnet excitation source are located on the primary side of the primary permanent magnet linear motor, the magnetic field situation of the primary iron core is complex, resulting in high cogging force in this type of motor. This high cogging force is the main reason why the practical application of this type of motor is limited. Summary of the Invention

[0005] To address the problem of high cogging force in primary permanent magnet linear motors, this invention provides a primary permanent magnet linear motor with low cogging force.

[0006] The present invention discloses a primary permanent magnet linear motor with low cogging force, comprising a primary and a secondary. The primary includes a primary iron core, an armature winding, and permanent magnets. The armature winding is wound on the armature teeth of the primary iron core, and the armature winding is composed of concentrated windings. The tips of the armature teeth are machined with multiple unequal-width slots to form an odd number of slots. Permanent magnets are embedded in the slots, with the permanent magnets in the middle slot being higher than those in the slots on both sides. The multiple permanent magnets form a non-uniform air gap magnetic field between the primary and secondary.

[0007] According to the low cogging force primary permanent magnet linear motor of the present invention, each armature tooth has three slots, and auxiliary holes are symmetrically arranged on both sides of the middle slot and above the two side slots.

[0008] According to the low cogging force primary permanent magnet linear motor of the present invention, there are two auxiliary holes on one side of the middle tooth groove. The two auxiliary holes are arranged in an upper and lower position, with the lower auxiliary hole close to the middle tooth groove and the upper auxiliary hole away from the middle tooth groove.

[0009] In the primary permanent magnet linear motor with low cogging force according to the present invention, the auxiliary hole is a circular hole, an elliptical hole, or a rectangular hole.

[0010] According to the low cogging force primary permanent magnet linear motor of the present invention, the secondary core of the secondary stage is provided with periodically arranged modulation teeth, satisfying the following relationship:

[0011] ,

[0012] In the formula The number of harmonic pole pairs of the armature magnetic field. The number of harmonic pole pairs in the magnetic field of a permanent magnet. The number of modulation teeth;

[0013] The tip edge of the modulation tooth is chamfered or rounded.

[0014] According to the low cogging force primary permanent magnet linear motor of the present invention, the first pole distance between the permanent magnet in the middle slot and the permanent magnets in the two side slots is... and the second pole distance corresponding to the permanent magnets in the slots on both sides satisfy:

[0015] ,

[0016] In the formula The first polar distance Second polar distance The absolute value of the difference This is the polar distance scaling factor. The pole spacing is uniform for a permanent magnet array; In the formula This is the circumferential length of the motor.

[0017] According to the low cogging force primary permanent magnet linear motor of the present invention, the permanent magnets are magnetized in parallel; the magnetization directions of adjacent permanent magnets are opposite.

[0018] According to the present invention, the primary permanent magnet linear motor with low cogging force has the same axial length for both the primary and secondary stages.

[0019] In the primary permanent magnet linear motor with low cogging force according to the present invention, an insulating layer is laid between the armature teeth and the armature winding.

[0020] The primary permanent magnet linear motor with low cogging force according to the present invention has both the primary core and the secondary core made of laminated silicon steel sheets.

[0021] The beneficial effects of this invention are as follows: This invention suppresses cogging force through the design of the primary structure of the motor. By adjusting the motor pole pitch and the height of the permanent magnet, and introducing an auxiliary hole structure design, it achieves non-uniform reconstruction and harmonic component optimization of the air gap magnetic field, thereby effectively weakening the main harmonic components of the cogging force. This invention can reduce the amplitude of the cogging force, improve the smoothness of motor operation and the accuracy of position control, and is suitable for high-precision direct drive motion control applications.

[0022] The primary permanent magnet linear motor described in this invention does not require additional auxiliary side teeth or tilted magnetic pole structures, reducing assembly difficulty. By designing a non-uniform magnetic pole array structure, this invention significantly suppresses and cancels out harmonics of cogging forces, improving system control stability. Among similar motors, it is simple to implement and offers reliable performance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a primary permanent magnet linear motor;

[0024] Figure 2 This is a schematic diagram of the primary core structure of a primary permanent magnet linear motor;

[0025] Figure 3 This is a schematic diagram of the secondary core structure of a primary permanent magnet linear motor;

[0026] Figure 4 This is a schematic diagram of the specific structure of the primary iron core armature gear;

[0027] Figure 5 This is a schematic diagram of the non-uniform magnetic pole parameters of a permanent magnet on an armature tooth;

[0028] Figure 6 This is a schematic diagram of the specific structure of the secondary iron core;

[0029] Figure 7 This is a schematic diagram of a primary iron core embedded with a permanent magnet;

[0030] Figure 8 This is a schematic diagram of the armature winding layout on the primary iron core;

[0031] Figure 9 This is a waveform diagram of the spatial distribution of the armature magnetic field;

[0032] Figure 10 This is the armature magnetic field harmonic spectrum diagram;

[0033] Figure 11 This is a waveform diagram of the spatial distribution of the magnetic field of a permanent magnet;

[0034] Figure 12 This is a harmonic spectrum diagram of the magnetic field of a permanent magnet;

[0035] Figure 13 A comparison diagram of the cogging force waveforms of the primary permanent magnet linear motor described in this invention and a traditional primary permanent magnet linear motor;

[0036] Figure 14 This is a comparison diagram of the cogging force harmonic order of the primary permanent magnet linear motor described in this invention and a traditional primary permanent magnet linear motor;

[0037] Figure 15This is a curve showing the output thrust current characteristics of the primary permanent magnet linear motor described in this invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Specific Implementation Method 1: Combination Figures 1 to 8 As shown, this invention provides a primary permanent magnet linear motor with low cogging force, comprising a primary and a secondary. The primary includes a primary core, an armature winding, and permanent magnets. The armature winding is wound around the armature teeth of the primary core, and the armature winding is composed of concentrated windings. The tips of the armature teeth are machined with multiple unequal-width slots to form an odd number of slotted grooves, and permanent magnets are embedded in the slots. The permanent magnets in the middle slot are higher than those in the slots on both sides. The multiple permanent magnets form a non-uniform air gap magnetic field between the primary and secondary. The non-uniform air gap magnetic field formed by the non-uniform permanent magnet array suppresses cogging force.

[0040] In this embodiment, the secondary stage only includes the secondary core.

[0041] The concentrated winding is a double-layer concentrated winding.

[0042] In this embodiment, the linear motor has a double-sided or single-sided structure, with the primary winding serving as the mover and the secondary winding serving as the stator.

[0043] As an example, combined Figure 4 As shown, each armature tooth has four slots and three slots. Auxiliary holes are symmetrically arranged on both sides of the middle slot and above the slots on both sides.

[0044] As an example, combined Figure 7 As shown, there are two auxiliary holes on one side of the middle tooth groove. The two auxiliary holes are arranged in an upper and lower position, with the lower auxiliary hole closer to the middle tooth groove and the upper auxiliary hole farther away from the middle tooth groove.

[0045] The auxiliary hole can be a circular hole, an elliptical hole, or a rectangular hole.

[0046] Furthermore, combined with Figure 3 As shown, the secondary core of the secondary winding is provided with periodically arranged modulation teeth, satisfying the following relationship:

[0047] ,

[0048] In the formula The number of harmonic pole pairs of the armature magnetic field. The number of harmonic pole pairs in the magnetic field of a permanent magnet. The number of modulation teeth;

[0049] The tip edge of the modulation tooth is chamfered or rounded.

[0050] Combination Figure 5 As shown, permanent magnets of different sizes are embedded in the primary armature teeth. The position of the slotted teeth is non-uniformly treated so that the height of the middle permanent magnet and the height of the two side permanent magnets satisfy the following relationship:

[0051] ,

[0052] In the formula For height ratio, The height of the intermediate permanent magnet. The height of the permanent magnets on both sides.

[0053] This embodiment disrupts the periodicity of the magnetic field by using a non-uniform permanent magnet pole array, thereby reducing the main harmonic amplitude of the cogging force.

[0054] Furthermore, combining Figure 5 As shown, the first pole distance between the permanent magnet in the middle slot and the permanent magnets in the slots on both sides is... and the second pole distance corresponding to the permanent magnets in the slots on both sides satisfy:

[0055] ,

[0056] In the formula The first polar distance Second polar distance The absolute value of the difference This is the polar distance scaling factor. The pole spacing is uniform for a permanent magnet array; In the formula This is the circumferential length of the motor.

[0057] generally The possible values ​​are 0.1-0.2.

[0058] In this embodiment, the permanent magnets are magnetized in parallel; the magnetization directions of adjacent permanent magnets are opposite.

[0059] In this embodiment, the height and width of the middle permanent magnet and the two side permanent magnets can be different.

[0060] The primary and secondary stages have the same axial length.

[0061] An insulating layer is laid between the armature teeth and the armature winding.

[0062] Both the primary and secondary cores are made of laminated silicon steel sheets.

[0063] The motor structure of the present invention will be described in detail below:

[0064] Primary core structure such as Figure 2 As shown, the primary core material, which serves as the main magnetic conductor and structural support of the magnetic circuit, is preferably silicon steel sheet with high permeability and low iron loss (such as DW series or equivalent amorphous or nanocrystalline alloy sheets). This minimizes eddy current losses. The mutually insulated silicon steel sheets are tightly stacked along the motor axis and then cured into a single unit by welding, riveting, or epoxy bonding.

[0065] Multiple armature teeth are periodically arranged circumferentially on the primary core for winding and fixing the armature winding. The top of each armature tooth is divided into multiple cleavages, such as two or four. The width of the cleavages at the top of the same armature tooth varies. For example, for a four-cleavage design, the width can be non-uniformly distributed in a "narrow-wide-wide-narrow" pattern. This differentiated cleavage width design fundamentally changes the distribution pattern of the air gap magnetic field, effectively weakening the harmonics generated by the periodic magnetic permeability, thereby significantly suppressing the amplitude of the cogging torque.

[0066] Between the teeth at the top of adjacent armature teeth, a rectangular cross-section slot-like space is formed for fixing and installing the permanent magnet. Structural details are as follows... Figure 4 As shown, the permanent magnet is installed as follows Figure 7 As shown, these permanent magnets are magnetized in parallel, with adjacent permanent magnets magnetized in opposite directions (NS alternating) to form the required excitation magnetic field. Corresponding to the differences in tooth width, the dimensions (width or height) of the embedded permanent magnets are also designed to be different. For example, three permanent magnets can be embedded at the top of an armature tooth in a four-tooth design, with the height distribution of the permanent magnets being "low-high-low". This differentiated layout of the permanent magnet array can further optimize the air gap magnetic flux density waveform, reducing harmonic components that generate cogging torque from the excitation source.

[0067] To further reduce the cogging effect and optimize local magnetic field saturation, auxiliary holes can be made at specific locations in the armature teeth. Structural details are as follows: Figure 4 As shown, the auxiliary holes are preferably located in the armature tooth yoke region corresponding to the top of the permanent magnet. These auxiliary holes can be circular, elliptical, or rectangular in shape. By introducing controllable magnetic bridges into the overall magnetic circuit, the magnetic flux path of the magnetic circuit is adjusted, smoothing the magnetic reluctance gradient. The location, size, and number of the auxiliary holes need to be determined through electromagnetic field finite element analysis.

[0068] Secondary core structure such as Figure 3As shown, the secondary core is also made of low-loss silicon steel sheets laminated together, maintaining consistency in materials and processes with the primary core to balance magnetic circuit performance. The secondary core has no windings, only periodically arranged modulation teeth. These modulation teeth interact with the armature magnetic field and permanent magnet magnetic field on the primary side, modulating the air gap magnetic field and thus generating effective electromagnetic thrust.

[0069] To reduce the fluctuation of cogging force caused by abrupt changes in the magnetic field at the edge of the modulation tooth, the tip edge of the secondary modulation tooth can be chamfered or rounded, such as... Figure 6 As shown, this subtle structural optimization can significantly smooth the effect of the secondary side on the air gap permeability.

[0070] The primary core and the secondary core have the same axial length.

[0071] To ensure that the above differentiated design achieves globally optimal cogging force suppression, simulation calculations can be used to determine the selection of each parameter. For example, it can be made... =0.12.

[0072] Experiments have verified that... This can suppress cogging forces. It is important to emphasize that this is different from the pole pitch proportionality factor. , The magnitude of the air gap magnetic flux density has a significant impact; that is, this coefficient affects not only the cogging force but also the output thrust. Therefore... The selection of the coefficient requires a balance between the motor's output thrust requirements.

[0073] The armature windings employ a concentrated winding configuration, with each coil tightly wound on an independent primary armature tooth, significantly shortening the end length and reducing copper usage and losses. Before embedding the windings into the armature tooth slots, insulating paper (or insulating film) is pre-laid into the slots to ensure reliable electrical insulation between the windings and the primary core. After all windings are installed, the entire primary module is vacuum pressure impregnated and potted with high-performance epoxy resin. This process not only strengthens the winding fixation and prevents damage from vibration, but more importantly, it establishes an efficient heat conduction path between the windings and the core. Epoxy resin has significantly better thermal conductivity than air, greatly improving the overall heat dissipation capacity of the motor and allowing it to operate continuously at higher current densities.

[0074] This invention, based on air gap magnetic field modulation theory, determines the number of principal harmonic pole pairs of the permanent magnet magnetic field, the number of principal harmonic pole pairs of the winding magnetic field, and the number of secondary modulation teeth to ensure the motor can output thrust. By changing the dimensions of the permanent magnet pole pitch and height, cogging force harmonics are suppressed, improving the stability of motor operation. This non-uniform magnetic pole array concept is applicable to any primary permanent magnet linear motor.

[0075] Specific Implementation Example 1: In practical applications, the design of the motor includes the following steps:

[0076] Step 1: Based on the motor size and performance requirements, determine the number of primary armature teeth, permanent magnets, and secondary modulation teeth. These numbers must satisfy the flux modulation principle to ensure effective thrust generation. Where N... w =N slot / 3 or N slot / 6; If the winding is a double-layer concentrated winding, N w =N slot / 3; or the winding is a single-layer concentrated winding, N w =N slot / 6; where N slot This represents the number of primary slots.

[0077] Step 2: Determine the pole pitch of the uniform permanent magnet array based on the length of the primary module and the number of main harmonic pole pairs of the permanent magnet magnetic field. , It represents the average distance between the center lines of adjacent opposite magnetic poles when the permanent magnets are uniformly arranged.

[0078] Step 3: To effectively suppress cogging force, it is necessary to break the magnetic field symmetry of traditional motors and adjust the reference pole pitch. Differentiation adjustments are made. This means that the motor's pole array should have at least two different pole pitches. Considering the difficulty of subsequent finite element calculations, it is usually sufficient to define two pole pitch sizes. Polar distance ratio coefficient The optimal value needs to be determined through electromagnetic calculations, and it is usually taken as 0.1-0.2.

[0079] Step 4: Adjust the permanent magnet height. Define two permanent magnet heights. The optimal value needs to be determined through electromagnetic calculations. Specific Implementation Example 2:

[0081] An embodiment with 12 armature teeth and 12 windings is described below. The windings are installed in a one-to-one correspondence with the tooth slots; that is, winding 1 is installed on tooth 1, winding 2 on tooth 2, ..., winding 12 on tooth 12. These 12 windings are arranged in physical order, with every three consecutive windings forming a unit group: windings 1-3 form the first group (ABC three-phase winding unit), windings 4-6 form the second group (ABC three-phase winding unit), windings 7-9 form the third group (ABC three-phase winding unit), and windings 10-12 form the fourth group (ABC three-phase winding unit). The winding installation arrangement is as follows... Figure 8 As shown.

[0082] When a three-phase symmetrical sinusoidal alternating current with a phase difference of 120 degrees is passed through the three-phase winding, a traveling wave armature magnetic field with a main harmonic pole pair number of 4 can be generated in the air gap.

[0083] The frequency f of the armature current needs to be precisely matched with the motor's operating speed v to ensure stable thrust output. The calculation formula is as follows:

[0084] .

[0085] The distribution characteristics of the armature magnetic field are as follows Figure 9 and Figure 10 As shown, the main magnetic flux density harmonics of the armature magnetic field are the 4th, 8th, 20th, 24th, 28th, and 36th harmonics. Among them, the harmonics directly generated by the armature magnetic field are mainly the 4th and 8th harmonics. The 24th and 36th harmonics are generated by the modulation of the armature magnetic field through the secondary teeth.

[0086] The distribution characteristics of the magnetic field of a permanent magnet are as follows: Figure 11 and Figure 12 As shown, the main magnetic flux density harmonics of the permanent magnet magnetic field are the 4th, 8th, 12th, 24th, and 36th harmonics. Among them, the harmonics directly generated by the permanent magnet magnetic field are mainly the 24th and 36th harmonics. The 4th and 8th harmonics are generated by the modulation of the permanent magnet magnetic field through the secondary teeth.

[0087] The air gap of the motor contains air gap harmonics with the same number of pole pairs, originating from the armature magnetic field and the permanent magnet magnetic field, which ensures the normal operation of the motor.

[0088] When adjusting the pole pitch ratio and height ratio of a motor, the priority is to adjust the pole pitch difference first, and then adjust the height ratio.

[0089] Figure 13 The diagram shows a comparison of the cogging force waveforms of the non-uniform structure of this invention and the traditional uniform structure of the motor. It is clear that the motor structure proposed in this invention has a significantly lower cogging force. Specifically, the cogging force of the traditional structure is 60 N, while the cogging force of the motor structure of this invention is 27 N, representing a 55% reduction in cogging force. Figure 14 The comparison results of the main harmonic orders of the two cogging force waveforms show that the low-order harmonics with high positioning force amplitude in the traditional structure are greatly suppressed in this invention.

[0090] Depend on Figure 15 It can be seen that the motor of the present invention does not have a saturation problem, and the output thrust has a good linear relationship with the current.

[0091] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A primary permanent magnet linear motor with low cogging force, characterized in that, It includes a primary and a secondary. The primary includes a primary iron core, an armature winding, and a permanent magnet. The armature winding is wound on the armature teeth of the primary iron core. The armature winding is composed of a concentrated winding. The tips of the armature teeth are machined with multiple unequal-width slots to form an odd number of slots. Permanent magnets are embedded in the slots. The permanent magnets in the middle slot are higher than the permanent magnets in the slots on both sides. The multiple permanent magnets form a non-uniform air gap magnetic field between the primary and secondary.

2. The primary permanent magnet linear motor with low cogging force according to claim 1, characterized in that, Each armature tooth has three slots, with auxiliary holes symmetrically arranged on both sides of the middle slot and above the two side slots.

3. The primary permanent magnet linear motor with low cogging force according to claim 2, characterized in that, There are two auxiliary holes on one side of the central tooth groove. The two auxiliary holes are arranged vertically, with the lower auxiliary hole closer to the central tooth groove and the upper auxiliary hole further away from the central tooth groove.

4. The primary permanent magnet linear motor with low cogging force according to claim 3, characterized in that, The auxiliary hole can be a circular hole, an elliptical hole, or a rectangular hole.

5. The primary permanent magnet linear motor with low cogging force according to claim 1, characterized in that, The secondary core of the secondary winding is provided with periodically arranged modulation teeth, satisfying the following relationship: ， In the formula The number of harmonic pole pairs of the armature magnetic field. The number of harmonic pole pairs in the magnetic field of a permanent magnet. The number of modulation teeth; The tip edge of the modulation tooth is chamfered or rounded.

6. The primary permanent magnet linear motor with low cogging force according to claim 5, characterized in that, The first pole distance between the permanent magnet in the middle slot and the permanent magnets in the two side slots and the second pole distance corresponding to the permanent magnets in the slots on both sides satisfy: ， In the formula The first polar distance Second polar distance The absolute value of the difference This is the polar distance scaling factor. The pole spacing is uniform permanent magnet array; In the formula This is the circumferential length of the motor.

7. The primary permanent magnet linear motor with low cogging force according to claim 1, characterized in that, The permanent magnets are magnetized in parallel; adjacent permanent magnets are magnetized in opposite directions.

8. The primary permanent magnet linear motor with low cogging force according to claim 1, characterized in that, The primary and secondary stages have the same axial length.

9. The primary permanent magnet linear motor with low cogging force according to claim 1, characterized in that, An insulating layer is laid between the armature teeth and the armature winding.

10. The primary permanent magnet linear motor with low cogging force according to claim 5, characterized in that, Both the primary and secondary cores are made of laminated silicon steel sheets.

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