Magnetic gathering type non-magnetic track linear motor

Abstract

The invention discloses a magnetic-gathering type non-magnetic-track linear motor, and the motor comprises a mover which comprises a mover iron core, a plurality of permanent magnet groups disposed at the lower end of the mover iron core, and a plurality of coils disposed on the mover iron core, the mover iron core is provided with a plurality of armature teeth which are distributed at intervals, and the coils are disposed at the peripheries of the armature teeth in a surrounding manner; the permanent magnet group is embedded and fixed at the lower ends of the armature teeth and exposed on the lower end surfaces of the armature teeth; the stator is formed by superposing a plurality of first silicon steel sheets and is positioned below the permanent magnet group, and an air gap is formed between the stator and the permanent magnet group; each permanent magnet group consists of a radial magnetizing permanent magnet as well as a first axial magnetizing permanent magnet and a second axial magnetizing permanent magnet which are clamped on two sides of the radial magnetizing permanent magnet, the magnetizing direction of the second axial magnetizing permanent magnet is axially leftward so as to face the radial magnetizing permanent magnet, the magnetizing direction of the first axial magnetizing permanent magnet is axially rightward so as to face the radial magnetizing permanent magnet, and the magnetizing direction of the second axial magnetizing permanent magnet is axially rightward. The magnetizing direction of the radial magnetizing permanent magnet is downward in the radial direction, and the radial magnetizing permanent magnet faces the stator, so that a Halbach array magnetism gathering structure is formed.

Description

Technical field:

[0001] The invention relates to the technical field of linear motor products, and in particular to a magnetic-collecting type magnetic-trackless linear motor. Background technology:

[0002] A linear motor is a transmission device that converts electrical energy directly into mechanical energy of linear motion without any intermediate conversion mechanism. It is also called a linear motor, linear motor, linear motor, or push rod motor. After being powered on, this motor can directly generate linear motion, so it is particularly suitable for occasions that require linear motion. Compared with traditional rotary motors, linear motors have the characteristics of high speed, high response, high precision, and direct drive, and are widely used in the field of industrial automation.

[0003] In recent years, the demand for linear motors has increased year by year, and the growth rate has been stable, but the price of the material (praseodymium and neodymium) required for the permanent magnets of linear motors has been rising. The increasing demand for linear motors with low magnetic steel, high thrust density, high efficiency, high precision and high reliability has become a research direction favored by researchers in recent years.

[0004] The invention patent with application number 202420521902.9 discloses a linear motor that is easy to maintain, which includes a linear motor body, two guide rails are fixedly installed on the upper surface of the linear motor body, and sliding blocks are provided on the outer surface sliding sleeves of the two guide rails. A magnetic rail is fixedly installed on the upper surface of the linear motor body, and two baffles are fixedly installed on the upper surface of the linear motor body. Buffer rubber gaskets are provided on the opposite surfaces of the two baffles, and the two buffer rubber gaskets are mirror-imaged. A quick disassembly and assembly mechanism is provided on the opposite surfaces of the two baffles. The working principle is: after starting the linear motor body, the sliding block is driven by the magnetic rail to move on the outer surfaces of the two guide rails.

[0005] The above-mentioned linear motor uses a large amount of magnets, and it is necessary to lay multiple magnets on the entire stroke to form a magnetic track, which makes its cost high; moreover, the utilization rate of the magnets on the stator of the linear motor body is low. Only the part overlapping with the mover in the sliding block can provide an effective magnetic field to generate thrust. Although the part that does not overlap with the mover also provides a magnetic field, the magnetic field is harmful rather than beneficial. Not only can it not contribute to thrust, but it will attract magnetic conductive materials. It is impossible to ensure that the working environment is free of the danger of strong magnetism, which reduces the service life of the linear motor and increases the maintenance cost of the linear motor, which is not conducive to improving the market competitiveness of the product.

[0006] In view of this, the inventor proposes the following technical solution. Summary of the invention:

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a magnetic field-concentrating type magnetic trackless linear motor.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: the magnetic concentrating type magnetic trackless linear motor comprises: a mover, which comprises a mover core and a plurality of permanent magnet groups arranged at the lower end of the mover core and a plurality of coils arranged on the mover core and distributed one by one on the periphery of the permanent magnet groups, the mover core having a plurality of armature teeth protruding downward and distributed at intervals, the coils being arranged around the periphery of the armature teeth; the permanent magnet group being embedded and fixed at the lower end of the armature teeth and exposed at the lower end surface of the armature teeth; a stator, which comprises a plurality of first silicon steel sheets superimposed and fixed on the Together, they are located below the permanent magnet group and form an air gap; each permanent magnet group is composed of a radially magnetized permanent magnet and a first axially magnetized permanent magnet and a second axially magnetized permanent magnet clamped on both sides of the radially magnetized permanent magnet, wherein the magnetizing direction of the second axially magnetized permanent magnet is axially to the left, toward the radially magnetized permanent magnet, the magnetizing direction of the first axially magnetized permanent magnet is axially to the right, toward the radially magnetized permanent magnet, and the magnetizing direction of the radially magnetized permanent magnet is radially downward, toward the stator, to form a Halbach array magnetic focusing structure.

[0009] Furthermore, in the above technical solution, a rectangular groove is provided on the lower end surface of the armature tooth; the first axially magnetized permanent magnet and the second axially magnetized permanent magnet are respectively fitted to the two side surfaces of the radially magnetized permanent magnet and then embedded and fixed in the rectangular groove with no gap therebetween.

[0010] Furthermore, in the above technical solution, the longitudinal sections of the first axially magnetized permanent magnet, the second axially magnetized permanent magnet and the radially magnetized permanent magnet are all rectangular, and their heights are equal to the depth of the rectangular groove, so that the lower end surfaces of the first axially magnetized permanent magnet, the second axially magnetized permanent magnet and the radially magnetized permanent magnet are all flush with the lower end surface of the armature tooth, so that the first axially magnetized permanent magnet, the second axially magnetized permanent magnet and the radially magnetized permanent magnet are completely embedded in the rectangular groove of the armature tooth.

[0011] Furthermore, in the above technical solution, the first axially magnetized permanent magnet and the second axially magnetized permanent magnet have the same size, and the widths of the first axially magnetized permanent magnet and the second axially magnetized permanent magnet are both greater than the width of the radially magnetized permanent magnet.

[0012] Furthermore, in the above technical solution, the number of the armature teeth is 6N, wherein N is greater than or equal to 1.

[0013] Furthermore, in the above technical solution, the mover core is composed of a plurality of second silicon steel sheets stacked and fixed.

[0014] Furthermore, in the above technical solution, the first silicon steel sheet has a plurality of equally spaced rectangular teeth, and the rectangular teeth of a plurality of first silicon steel sheets are superimposed to form a rectangular tooth pole.

[0015] Furthermore, in the above technical solution, the extending direction of the rectangular tooth pole is perpendicular to the length direction of the stator.

[0016] Furthermore, in the above technical solution, the angle formed by the extension direction of the rectangular tooth pole and the length direction of the stator is less than 90°, so that the rectangular tooth pole is obliquely distributed at the upper end of the stator.

[0017] Furthermore, in the above technical solution, the spacing dimension between two adjacent rectangular tooth poles is greater than the spacing dimension between two adjacent armature teeth, and the width dimension of the armature teeth is greater than the spacing dimension between two adjacent rectangular tooth poles.

[0018] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0019] 1. The present invention belongs to a topological structure of a flux reversal linear motor, which is characterized in that the coil and the permanent magnet are integrated on the mover, so that the use cost of the linear motor is reduced, the utilization rate of the permanent magnet is high, and it is suitable for long-stroke application scenarios; at the same time, the stator is composed of multiple first silicon steel sheets stacked and fixed together, and its structure is relatively simple, which is convenient for mechanical processing. For long-stroke application fields, it can greatly reduce the use cost of the motor, reduce the amount of permanent magnets, and has good structural stability. At the same time, the stator has no magnets, that is, the present invention has no magnetic track, that is, the stator structure does not contain magnetism. For actual application environments, it ensures that the working environment is free of the danger of strong magnetism, improves the service life of the linear motor, and reduces the maintenance cost of the linear motor. In addition, the magnetic permeability of the first silicon steel sheet is higher than that of air, which is conducive to improving the thrust density and air gap flux density of the motor.

[0020] 2. The mover in the present invention uses three permanent magnets with different magnetizing directions to form a permanent magnet group. The armature teeth of each mover contain a permanent magnet group, that is, each permanent magnet group has three different magnetizing directions, but the directions are concentrated at the midpoint position, which improves the utilization rate of the permanent magnets, increases the magnetic flux density on the side close to the air gap, and reduces the magnetic flux density on the side away from the air gap. Description of the drawings:

[0021] Figure 1 It is a structural diagram of the present invention;

[0022] Figure 2 It is a three-dimensional diagram of the mover core in the present invention;

[0023] Figure 3 is a three-dimensional diagram of the mover in the present invention;

[0024] Figure 4 is a three-dimensional diagram of a stator in the present invention;

[0025] Figure 5 It is a schematic diagram of the magnetization direction of the permanent magnet group in the present invention;

[0026] Figure 6 is a top view of a stator of the first structure in the present invention;

[0027] Figure 7 It is a top view of the stator of the second structure in the present invention. Specific implementation method:

[0028] The present invention is further described below in conjunction with specific embodiments and drawings.

[0029] See Figure 1-7 As shown, a magnetic field-concentrating trackless linear motor comprises: a mover 100 and a stator 4, with an air gap formed between the mover 100 and the stator 4. The present invention belongs to a topological structure of a flux reversal linear motor, which is characterized in that the coil and the permanent magnet are integrated on the mover, so that the use cost of the linear motor is reduced, the utilization rate of the permanent magnet is high, and it is suitable for long-stroke application scenarios.

[0030] The structure of the mover 100 is described in detail below:

[0031] The mover 100 includes a mover core 1, a plurality of permanent magnet groups 2 arranged at the lower end of the mover core 1, and a plurality of coils 3 arranged on the mover core 1 and distributed one by one on the periphery of the permanent magnet group 2. The mover core 1 has a plurality of armature teeth 11 protruding downward and distributed at intervals, and the coils 3 are arranged around the periphery of the armature teeth 11; the permanent magnet group 2 is embedded and fixed at the lower end of the armature tooth 11, and exposed at the lower end surface of the armature tooth 11; wherein each permanent magnet group 2 is composed of a radially magnetized permanent magnet 21 and a first axially magnetized permanent magnet 22 and a second axially magnetized permanent magnet 23 clamped on both sides of the radially magnetized permanent magnet 21, wherein the magnetization directions of all the permanent magnets in each permanent magnet group 2 are different, specifically: the second axial The magnetizing direction of the axially magnetized permanent magnet 23 is axially to the left, toward the radially magnetized permanent magnet 21, the magnetizing direction of the first axially magnetized permanent magnet 22 is axially to the right, toward the radially magnetized permanent magnet 21, and the magnetizing direction of the radially magnetized permanent magnet 21 is radially downward, toward the stator 4, so as to form a Halbach array magnetic concentration structure. The radially magnetized permanent magnet 21, the first axially magnetized permanent magnet 22 and the second axially magnetized permanent magnet 23 are arranged in such a way that the magnetic lines of force of each group of permanent magnets are distributed in the middle. Compared with the ordinary permanent magnet array combination, this structure belongs to the Halbach type (Halbach array) magnetic concentration structure, which is characterized in that the magnetic flux density on the side close to the air gap is increased and the magnetic flux density on the side away from the air gap is reduced.

[0032] The stator 4 is a long strip of sawtooth structure, and its length can be determined according to actual use requirements. Specifically, the stator 4 is composed of multiple pieces of first silicon steel sheets stacked and fixed together, and is located below the permanent magnet group 2 to form an air gap. In other words, the structural feature of the present invention is that the coil and the permanent magnet are integrated on the mover, which reduces the use cost of the linear motor, and the permanent magnet utilization rate is high, which is suitable for long-stroke application scenarios. At the same time, the stator 4 is composed of multiple pieces of first silicon steel sheets stacked and fixed together, and its structure is relatively simple and easy to machine. For long-stroke application fields, the use cost of the motor can be greatly reduced, the amount of permanent magnets is reduced, and the structural stability is good. At the same time, the stator 4 has no magnets, that is, the present invention has no magnetic track, that is, the stator structure does not contain magnetism. For actual application environments, it ensures that there is no danger of strong magnetism in the working environment, improves the service life of the linear motor, and reduces the maintenance cost of the linear motor.

[0033] The stator 6 has a relatively simple structure, which is only composed of a plurality of first silicon steel sheets stacked to form a sawtooth structure. This structure is conducive to mechanical processing, and for long-stroke applications, it can significantly reduce the cost of the motor and reduce the amount of permanent magnets.

[0034] The number of the armature teeth 11 is 6N, wherein N is greater than or equal to 1. In this embodiment, N is equal to 1, that is, the number of the armature teeth 11 is 6. That is to say, each mover 100 has six groups of permanent magnets, each of which is composed of three permanent magnets (i.e., radially magnetized permanent magnet 21, first axially magnetized permanent magnet 22 and second axially magnetized permanent magnet 23). The magnetizing directions of the three permanent magnets are different. Specifically, the magnetizing direction of the second axially magnetized permanent magnet 23 is axially to the left, and the magnetizing direction of the first axially magnetized permanent magnet 22 is axially to the right, facing the radially magnetized permanent magnet 21. The magnetizing direction of the radially magnetized permanent magnet 21 is radially downward. The radially magnetized permanent magnet 21, the first axially magnetized permanent magnet 22 and the second axially magnetized permanent magnet 23 are arranged in such a way that the magnetic lines of force of each group of permanent magnets are distributed close to the middle. Compared with ordinary permanent magnet array combinations, this structure belongs to a Halbach type (Halbach array) magnetic concentrating structure, which is characterized in that the magnetic flux density on the side close to the air gap is increased and the magnetic flux density on the side away from the air gap is reduced.

[0035] In other words, the mover 100 in the present invention uses three permanent magnets in different directions to form a unit (i.e., a permanent magnet group), and the armature teeth 11 of each mover contain a unit. A mover has 6 armature teeth and multiples of 6, and can be switched to movers of different lengths at will to adapt to application scenarios under different thrust conditions. Each permanent magnet group has three different magnetization directions, but the directions are concentrated at the midpoint position, which improves the utilization rate of the permanent magnets, increases the magnetic flux density on the side close to the air gap, and reduces the magnetic flux density on the side away from the air gap.

[0036] The armature tooth 11 is rectangular, and a rectangular groove 111 is provided on the lower end surface of the armature tooth 11; the first axially magnetized permanent magnet 22 and the second axially magnetized permanent magnet 23 are respectively fitted with the two side surfaces of the radially magnetized permanent magnet 21 and then embedded and fixed in the rectangular groove 111, and there is no gap between them. The assembly structure is simple and stable, and the mechanical air gap of the assembly structure is smaller than that of the permanent magnet directly attached to the lower surface of the armature tooth 11. In addition, the mover core is composed of multiple pieces of second silicon steel sheets stacked and fixed, and the magnetic permeability of the second silicon steel sheets is higher than that of air, which is beneficial to improve the thrust density and air gap flux density of the motor, reduce thrust fluctuations, and thus better meet the application scenarios of high thrust, so that the present invention has stronger market competitiveness.

[0037] In this embodiment, the rectangular groove 111 passes through the front and rear end surfaces of the armature tooth 11, and the front and rear end surfaces of the first axially magnetized permanent magnet 22, the second axially magnetized permanent magnet 23 and the radially magnetized permanent magnet 21 are flush with the front and rear end surfaces of the armature tooth 11, and the coil 3 is fitted and wrapped around the front and rear end surfaces of the first axially magnetized permanent magnet 22, the second axially magnetized permanent magnet 23 and the radially magnetized permanent magnet 21.

[0038] In some embodiments, an annular groove is disposed on the periphery of the armature tooth 11, and the coil 3 is wrapped in the annular groove. The annular groove can limit the coil 3 to a certain extent, thereby ensuring the stability of the assembly structure.

[0039] The longitudinal sections of the first axial magnetized permanent magnet 22, the second axial magnetized permanent magnet 23 and the radial magnetized permanent magnet 21 are all rectangular, and their heights are equal to the depth of the rectangular groove 111, so that the lower end surfaces of the first axial magnetized permanent magnet 22, the second axial magnetized permanent magnet 23 and the radial magnetized permanent magnet 21 are all flush with the lower end surface of the armature tooth 11, so that the first axial magnetized permanent magnet 22, the second axial magnetized permanent magnet 23 and the radial magnetized permanent magnet 21 are completely embedded in the rectangular groove 111 of the armature tooth 11.

[0040] The first axial magnetized permanent magnet 22 and the second axial magnetized permanent magnet 23 have the same size, and the width of the first axial magnetized permanent magnet 22 and the second axial magnetized permanent magnet 23 are both greater than the width of the radial magnetized permanent magnet 21 .

[0041] The first silicon steel sheet has a plurality of rectangular teeth distributed at equal intervals, and the rectangular teeth of the plurality of first silicon steel sheets are superimposed to form a rectangular tooth pole 41, that is, a sawtooth structure. In other words, since the stator 4 adopts a sawtooth structure formed by superimposing a plurality of first silicon steel sheets, it is beneficial for the mover to cut the magnetic flux line in the running state, thereby improving the thrust density of the linear motor and thus improving the thrust performance of the linear motor.

[0042] The extending directions of the rectangular tooth pole 41 include at least the following two directions:

[0043] The first one is that the extending direction of the rectangular tooth pole 41 is perpendicular to the length direction of the stator 4 .

[0044] The second type is: the angle formed by the extension direction of the rectangular tooth pole 41 and the length direction of the stator 4 is less than 90°, so that the rectangular tooth pole 41 is obliquely distributed at the upper end of the stator 4. The use of obliquely distributed rectangular tooth poles 41 (i.e., oblique poles) can reduce the high thrust fluctuation caused by the linear motor, that is, solve the problem of large magnetic resistance caused by the disconnection of both sides of the mover of the linear motor and the double salient pole structure, which is conducive to optimizing the performance of the linear motor.

[0045] The spacing dimension between two adjacent rectangular tooth poles 41 is greater than the spacing dimension between two adjacent armature teeth 11, and the width dimension of the armature tooth 11 is greater than the spacing dimension between two adjacent rectangular tooth poles 41, which can better enable the mover to cut the magnetic flux line in the running state, improve the thrust density of the linear motor, and thus improve the thrust performance of the linear motor.

[0046] The above-mentioned magnetic flux density, that is, magnetic flux density, also known as magnetic induction intensity, is an important physical quantity that describes the strength and direction of the magnetic field.

[0047] When the present invention is actually used, the stator is laid on the machine base, and the machine base is also equipped with a linear rail, which is distributed outside the stator and parallel to the stator; the sliding seat is installed on the linear rail through a slider and is located above the stator, and the sliding seat can slide along the length direction of the linear rail, and the mover core 1 of the mover is fixed at the lower end of the middle part of the sliding seat, and the mover core 1 is positioned above the stator, and the air gap is formed therebetween. When the coil of the mover is energized, the mover can slide relative to the stator, which can drive the sliding seat to move linearly on the machine base through the linear rail.

[0048] To sum up, the present invention belongs to a topological structure of a flux reversal linear motor, which is characterized in that the coil and the permanent magnet are integrated on the mover, so that the use cost of the linear motor is reduced, the utilization rate of the permanent magnet is high, and it is suitable for long-stroke application scenarios; at the same time, the stator 4 is composed of multiple first silicon steel sheets stacked and fixed together, and its structure is relatively simple, which is convenient for mechanical processing. For long-stroke application fields, the use cost of the motor can be greatly reduced, the amount of permanent magnets is reduced, and the structural stability is good. At the same time, the stator 4 has no magnets, that is, the present invention has no magnetic rails, that is, the stator structure does not contain magnetism. For actual application environments, it ensures that there is no danger of strong magnetism in the working environment, improves the service life of the linear motor, and reduces the maintenance cost of the linear motor.

[0049] The mover 100 in the present invention uses three permanent magnets with different magnetizing directions to form a permanent magnet group. The armature tooth 11 of each mover contains a permanent magnet group, that is, each permanent magnet group has three different magnetizing directions, but the directions are concentrated at the midpoint position, which improves the utilization rate of the permanent magnets, increases the magnetic flux density on the side close to the air gap, and reduces the magnetic flux density on the side away from the air gap.

[0050] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. All equivalent changes or modifications made according to the structure, characteristics and principles described in the patent application scope of the present invention should be included in the patent application scope of the present invention.

Claims

1. A magnetic concentrating trackless linear motor, characterized in that: It includes: A mover (100) comprises a mover core (1), a plurality of permanent magnet groups (2) arranged at the lower end of the mover core (1), and a plurality of coils (3) arranged on the mover core (1) and distributed one-to-one on the periphery of the permanent magnet groups (2); the mover core (1) has a plurality of armature teeth (11) protruding downward and distributed at intervals, and the coils (3) are arranged around the periphery of the armature teeth (11); the permanent magnet groups (2) are embedded and fixed at the lower ends of the armature teeth (11) and exposed on the lower end surfaces of the armature teeth (11); The stator (4) is composed of a plurality of first silicon steel sheets stacked and fixed together, and is located below the permanent magnet group (2) to form an air gap; Each permanent magnet group (2) is composed of a radially magnetized permanent magnet (21) and a first axially magnetized permanent magnet (22) and a second axially magnetized permanent magnet (23) clamped on both sides of the radially magnetized permanent magnet (21), wherein the magnetizing direction of the second axially magnetized permanent magnet (23) is axially to the left, so as to face the radially magnetized permanent magnet (21), the magnetizing direction of the first axially magnetized permanent magnet (22) is axially to the right, so as to face the radially magnetized permanent magnet (21), and the magnetizing direction of the radially magnetized permanent magnet (21) is radially downward, so as to face the stator (4), so as to form a Halbach array magnetic concentrating structure.

2. The magnetic field-concentrating trackless linear motor according to claim 1, characterized in that: The lower end surface of the armature tooth (11) is provided with a rectangular groove (111); the first axial magnetized permanent magnet (22) and the second axial magnetized permanent magnet (23) are respectively fitted with the two side surfaces of the radial magnetized permanent magnet (21) and then embedded and fixed in the rectangular groove (111), with no gap therebetween.

3. The magnetic field-concentrating trackless linear motor according to claim 2, characterized in that: The longitudinal sections of the first axial magnetized permanent magnet (22), the second axial magnetized permanent magnet (23) and the radial magnetized permanent magnet (21) are all rectangular, and their heights are all equal to the depth of the rectangular slot (111), so that the lower end surfaces of the first axial magnetized permanent magnet (22), the second axial magnetized permanent magnet (23) and the radial magnetized permanent magnet (21) are all flush with the lower end surface of the armature tooth (11), so that the first axial magnetized permanent magnet (22), the second axial magnetized permanent magnet (23) and the radial magnetized permanent magnet (21) are completely embedded in the rectangular slot (111) of the armature tooth (11).

4. The magnetic field-concentrating trackless linear motor according to claim 3, characterized in that: The first axial magnetized permanent magnet (22) and the second axial magnetized permanent magnet (23) have the same size, and the widths of the first axial magnetized permanent magnet (22) and the second axial magnetized permanent magnet (23) are both greater than the width of the radial magnetized permanent magnet (21).

5. A magnetic concentrating trackless linear motor according to any one of claims 1 to 4, characterized in that: The number of the armature teeth (11) is 6N, wherein N is greater than or equal to 1.

6. A magnetic field concentrated trackless linear motor according to any one of claims 1 to 4, characterized in that: The mover core is composed of a plurality of second silicon steel sheets stacked and fixed.

7. A magnetic field concentrated trackless linear motor according to any one of claims 1 to 4, characterized in that: The first silicon steel sheet has a plurality of rectangular teeth distributed at equal intervals, and the rectangular teeth of a plurality of first silicon steel sheets are superimposed to form a rectangular tooth pole (41).

8. The magnetic field concentrated trackless linear motor according to claim 7, characterized in that: The extending direction of the rectangular tooth pole (41) is perpendicular to the length direction of the stator (4).

9. The magnetic field-concentrating trackless linear motor according to claim 7, characterized in that: The angle formed by the extension direction of the rectangular tooth pole (41) and the length direction of the stator (4) is less than 90°, so that the rectangular tooth pole (41) is obliquely distributed at the upper end of the stator (4).

10. A magnetic field concentrated trackless linear motor according to claim 8 or 9, characterized in that: The spacing dimension between two adjacent rectangular tooth poles (41) is greater than the spacing dimension between two adjacent armature teeth (11), and the width dimension of the armature teeth (11) is greater than the spacing dimension between two adjacent rectangular tooth poles (41).

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