Symmetrical three-rotor permanent magnet linear oscillation motor structure parameter design method

Abstract

The invention relates to a symmetric three-rotor permanent magnet linear oscillation motor structure parameter design method. The symmetric three-rotor permanent magnet linear oscillation motor rotor adopts a main and auxiliary three-rotor symmetric structure, the middle rotor is a main permanent magnet, and the two auxiliary permanent magnets are symmetrically arranged on the two sides of the main permanent magnet; according to the method, other structural parameters of the permanent magnet linear oscillation motor are kept unchanged, one parameter is taken as a variable, and the height of an auxiliary permanent magnet, the length of the auxiliary permanent magnet and the height of an air gap are designed by analyzing and comparing the air gap flux density of the parameters and analyzing the relation between the parameters and electromagnetic thrust. The method is simple and easy to operate, and is suitable for symmetric three-rotor permanent magnet linear oscillation motors of different specifications; the magnetic density can be effectively improved, and the purpose of improving the electromagnetic thrust is achieved; the power density of the motor can be improved; thrust fluctuation is effectively reduced, it is guaranteed that the linear oscillation motor generates equal force in the reciprocating motion process, and reliable work of the symmetric three-rotor permanent magnet linear oscillation motor is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechatronic engineering, and particularly relates to a method for designing the structural parameters of a symmetric three-mover permanent magnet linear oscillating motor. Technical Background

[0002] A linear compressor is a new type of compressor that is economical and efficient. It is a direct-drive compressor directly composed of a linear oscillating motor. The compressor driven by a linear oscillating motor has the advantages of simple structure, small volume, low manufacturing cost, energy saving and high efficiency, low noise, long service life, stable and reliable, excellent environmental protection indicators, good control performance, and convenient maintenance. At present, linear oscillating motors have been applied in many industrial, civil, and military fields in Japan, the United States, and many European countries, especially in compressors.

[0003] According to the different materials of the vibrating part, linear oscillating motors can be divided into four categories, namely moving coil type (the vibrating part is a coil), moving iron type (the vibrating part is a laminated iron core), moving magnet type (the vibrating part is a permanent magnet and a non-magnetic and non-conductive bracket), and moving magnet-iron type (the vibrating part is a permanent magnet and a laminated iron core).

[0004] The current movers of moving magnet type permanent magnet linear oscillating motors include various structural forms such as single-mover and three-mover. The three-mover permanent magnet linear oscillating motor is more suitable for applications in some scenarios with high power, large thrust, low vibration, and stable operation, such as precision medical equipment, aerospace systems, cryogenic refrigeration equipment and other fields.

[0005] For the existing three-mover permanent magnet linear oscillating motor, the mover adopts a symmetric structure of main and auxiliary three-movers, with a main permanent magnet in the middle and two auxiliary permanent magnets on both sides of the main permanent magnet. When the motor is in the initial position, the main permanent magnet is located in the middle of the stator tooth part and the slot opening gap, and the two auxiliary permanent magnets are axially symmetrically arranged on both sides of the main permanent magnet. Three mover permanent magnets with N-S poles alternately distributed in the radial magnetization direction are arranged on the permanent magnet bracket. For the symmetric three-mover moving magnet type linear oscillating motor, its structural parameters, including the length and height of the auxiliary permanent magnet and the air gap height of the key position parameter, have a great influence on the electromagnetic thrust of the linear oscillating motor, but there is no selection basis at present, and it is difficult to optimize the electromagnetic thrust. Summary of the Invention

[0006] The present invention provides a method for designing the structural parameters of a symmetric three-mover permanent magnet linear oscillating motor to overcome the problem of difficult optimization of electromagnetic thrust in the prior art.

[0007] To achieve the above object, the technical solution of the present invention is: a method for designing the structural parameters of a symmetric three-rotor permanent magnet linear oscillating motor. The rotor of the symmetric three-rotor permanent magnet linear oscillating motor adopts a symmetric structure of a main and two auxiliary rotors. There is a main permanent magnet in the middle, and two auxiliary permanent magnets are symmetrically arranged on both sides of the main permanent magnet;

[0008] The structural parameters include the height of the auxiliary permanent magnet, the length of the auxiliary permanent magnet, and the air gap height, and are designed according to the formula:

[0009] The height of the auxiliary permanent magnet is obtained by the following formula:

[0010]

[0011] The length of the auxiliary permanent magnet is obtained by the following formula:

[0012]

[0013] The air gap height is obtained by the following formula:

[0014] x3 = 455.4 / F - 1.56 (3)

[0015] Where: F is the electromagnetic thrust.

[0016] Compared with the prior art, the present invention has the following remarkable advantages:

[0017] (1) The design idea of the present invention is to keep other structural parameters of the permanent magnet linear oscillating motor unchanged, take one parameter as a variable, and analyze and compare the air gap magnetic density of the variable parameter. Starting from the structural parameters and position parameters, the relationship between the parameters and the electromagnetic thrust is analyzed. The present invention gives a design scheme through the set thrust, optimizes the length and height of the auxiliary permanent magnet 7 and the key position parameter air gap height, improves the electromagnetic thrust of the permanent magnet linear oscillating motor. The method is simple and easy to operate and is suitable for symmetric three-rotor permanent magnet linear oscillating motors of different specifications;

[0018] (2) The structural parameter formula designed by the present invention starts from the coupling relationship between the electromagnetic thrust and the design parameters, combines the optimization law of the parameters, can effectively improve the magnetic density, and achieves the purpose of improving the electromagnetic thrust. From the perspective of heat transfer, through the parameter design scheme designed by the present invention, the structural characteristics of the three-rotor finally provided increase the effective area of heat exchange between the winding and the iron core, improve the heat dissipation capacity of the excitation winding, and are beneficial to improving the power density of the motor. Through the formula provided by the present invention, the three key parameters of the height of the auxiliary permanent magnet, the length of the auxiliary permanent magnet, and the air gap height can be quickly given. Based on the symmetric design of the main and auxiliary permanent magnets 7, the thrust fluctuation can be effectively reduced, ensuring that the linear oscillating motor generates equal forces during the reciprocating motion, and ensuring the reliable operation of the symmetric three-rotor permanent magnet linear oscillating motor. Description of the Drawings

[0019] Figure 1 is the operating principle diagram of a symmetric three-rotor linear oscillating motor;

[0020] Figure 2 is the structure of a symmetric three-rotor linear oscillating motor;

[0021] Figure 3 is the arrangement of the three-rotor permanent magnets along the axial direction;

[0022] Figure 4 is the relationship between the height of the auxiliary permanent magnet and the electromagnetic thrust;

[0023] Figure 5 is the relationship between the length of the auxiliary permanent magnet and the electromagnetic thrust;

[0024] Figure 6 is the relationship between the air-gap magnetic density and the electromagnetic thrust;

[0025] The reference numerals are as follows:

[0026] 1. Upper plate spring bracket, 2. Permanent magnet bracket, 3. Upper stator core bracket, 4. Outer stator core, 5. Electromagnetic winding, 6. Main permanent magnet, 7. Auxiliary permanent magnet, 8. Lower stator core bracket, 9. Inner stator core, 10. Lower plate spring bracket, 11. Plate spring, 12. Piston shaft. Detailed Description of the Invention

[0027] The present invention will be further described in detail below in conjunction with the drawings and embodiments.

[0028] See Figures 1 - 3The present invention is directed to a symmetrical three-motor permanent magnet linear oscillation motor, comprising an upper leaf spring bracket 1, a permanent magnet bracket 2, an upper stator core bracket 3, an outer stator core 4, an electromagnetic winding 5, a main permanent magnet 6, an auxiliary permanent magnet 7, a lower stator core bracket 8, an inner stator core 9, a lower leaf spring bracket 10, a leaf spring 11 and a piston shaft 12. The mover refers to a component that performs reciprocating motion under the action of electromagnetic force. In the present invention, the mover refers to the permanent magnet bracket 2, the main permanent magnet 6 and the auxiliary permanent magnet 7. The permanent magnet adopts a main-auxiliary three-motor structure, including a main permanent magnet 6 and an auxiliary permanent magnet 7 arranged coaxially. The magnetic rings of the three-motor permanent magnets are fixed to the permanent magnet bracket 2 in an alternating distribution of NS levels in the radial magnetization direction. The main permanent magnet 6 is arranged in the middle, and the axial length of the main permanent magnet 6 is equal to 1 / 2 of the sum of the lengths of the two stator teeth and the slot gap of the outer stator core 4. The axial lengths of the two secondary permanent magnets 7 are equal to the axial length of the main permanent magnet 6. The symmetrical three-motor linear oscillating motor has a cylindrical structure, including the main permanent magnet 6 and the secondary permanent magnets 7. The symmetrical three-motor permanent magnet structure has a main permanent magnet 6 as the center mover and secondary permanent magnets 7 as the side movers. The main permanent magnet 6 is located in the middle of the gap between the stator teeth and the slots, and the two secondary permanent magnets 7 are axially symmetrically arranged on either side of the main permanent magnet 6.

[0029] The motion principle of the symmetrical three-motor permanent magnet linear oscillation motor is that when a sinusoidal alternating current is passed through the coil winding, an alternating electromagnetic thrust is generated on the mover, thereby driving the three movers and the supporting components to perform reciprocating linear motion. Figure 1 shown.

[0030] The air gap magnetic field under the action of the symmetrical three-motor permanent magnet alone has two characteristics:

[0031] First, when the three-motor permanent magnet linear oscillation motor is in an ideal state, when the permanent magnet of the mover is in the middle position, the air gap magnetic field on the left side of the air gap magnetic flux density B pm1 Equal to the right air gap magnetic flux density B pm2 ,Right now:

[0032] B pm1 =B pm2 (1)

[0033] Second, when the symmetrical three-motor permanent magnet linear oscillation motor is in an ideal state, the permanent magnet of the mover is located in a non-static

[0034] When the magnetic flux density generated in the left and right air gaps is equal to the magnetic flux density of the left and right air gaps when the magnetic flux density is at rest, that is:

[0035] B' pm1 =B pm1 , B' pm2 =B pm2 (2)

[0036] For a symmetric three-rotor permanent magnet, regardless of the position of the rotor, the air-gap magnetic flux densities on its left and right sides are equal.

[0037] According to the principle of air-gap magnetic flux continuity, the magnetic flux generated by the main permanent magnet 6 in the upper and lower equivalent air-gaps is equal to the sum of the magnetic fluxes in the upper and lower air-gaps of the auxiliary permanent magnet 7 and the magnetic fluxes generated in the left and right air-gaps, that is:

[0038] B pm W pm =B pm1 W rpe +2B pma W pma (3)

[0039] In the formula, B pm is the air-gap magnetic flux density of the main permanent magnet 6, B pma is the air-gap magnetic flux density of the upper and lower parts of the auxiliary permanent magnet 7, W pm is the length of the main permanent magnet 6, W pma is the length of the auxiliary permanent magnet 7, W rpe is the width of the auxiliary permanent magnet 7.

[0040] The magnetic flux B pm of the main permanent magnet 6 is:

[0041] B pm =(B pm1 W rpe +2B pma W pma ) / W pm (4)

[0042] When the rotor permanent magnet moves to the left, the magnitude of the electromagnetic thrust is related to the sum of the magnetic field densities generated by the main permanent magnet 6 and the left-side auxiliary permanent magnet 7 in the air-gap, the current, the number of turns of the coil, and the circumferential length of the rotor permanent magnet, that is:

[0043] F e1 =iN w l r (B pm +B pm1 ) (5)

[0044] Among them, F e1 is the electromagnetic thrust when the rotor permanent magnet moves to the left, i is the magnitude of the current, N w is the number of turns of the coil, l r is the circumferential length of the rotor permanent magnet, B pm is the magnetic flux density formed by the main permanent magnet 6 in the moving air-gap of the rotor, and B pm1 is the magnetic field density generated by the auxiliary permanent magnet 7 at the left air-gap.

[0045] When the mover permanent magnet moves to the right, the magnitude of the electromagnetic thrust generated on the right side is:

[0046] F e2 = iN w l r (B pm + B pm2 ) (6)

[0047] Since B pm1 = B pm2 , the symmetric three-mover linear oscillating motor has the same electromagnetic thrust when moving to the left and right sides, that is:

[0048] F e1 = F e2 (7)

[0049] At this time, the linear oscillating motor runs smoothly, and this symmetric structure ensures that the three-mover linear oscillating motor has very little fluctuation during reciprocating motion.

[0050] Based on the above theoretical description, the symmetric three-mover linear oscillating motor of the present invention designs the parameters such as the length, height, and air-gap magnetic density of the main and auxiliary permanent magnets 7 according to the comparison of the air-gap magnetic density.

[0051] The design idea of the present invention is to keep other structural parameters of the permanent magnet linear oscillating motor unchanged, take one parameter as a variable, and analyze and compare the air-gap magnetic density of the variable parameter to analyze the relationship between the parameter and the electromagnetic thrust.

[0052] For the symmetric three-mover permanent magnet linear oscillating motor, other structural parameters are kept unchanged, the height value range of the permanent magnet is 2 mm to 6 mm, and the step size is 0.5 mm. When the height of the permanent magnet increases from 2 mm to 4 mm, the electromagnetic thrust increases greatly. When the height of the permanent magnet increases from 4 mm to 6 mm, the electromagnetic thrust only increases slightly. According to the electromagnetic thrust, the expression of the height x1 of the auxiliary permanent magnet is obtained:

[0053]

[0054] The change trend of the height of the auxiliary permanent magnet and the electromagnetic thrust of the linear oscillating motor is shown in Figure 4 as follows.

[0055] Keeping other structural parameters of the symmetric three-mover permanent magnet linear oscillating motor unchanged, the length value range of the auxiliary permanent magnet 7 is 8 mm to 32 mm, and the step size is 6 mm. When the length of the auxiliary permanent magnet is 26 mm and 30 mm, the air-gap magnetic density generated is close and the air-gap magnetic density is the largest. According to the electromagnetic thrust, the expression of the length x2 of the auxiliary permanent magnet is:

[0056]

[0057] The variation trend of the length of the auxiliary permanent magnet and the electromagnetic thrust of the linear oscillating motor is shown in Figure 5 the following figure.

[0058] Keeping other structural parameters of the symmetric three-moving-magnet linear permanent magnet oscillating motor unchanged, the air gap height ranges from 4 to 10 mm, and the step size is 1 mm. As the air gap height increases, the magnetic permeability of the air gap is much worse than that of ferromagnetic materials, and the magnetic resistance of the closed magnetic circuit increases significantly, resulting in a decrease in the magnetic flux density value in the working air gap, so the electromagnetic thrust also decreases. According to the electromagnetic thrust, the expression of the air gap height x3 is:

[0059] x3 = 455.4 / F - 1.56 (10)

[0060] The variation trend of the air gap height and the electromagnetic thrust of the linear oscillating motor is shown in Figure 6 the following figure.

[0061] According to the above formula, the decoupling parameters of the three-moving-magnet linear permanent magnet oscillating motor can be designed. The following is a detailed description through an example:

[0062] Applying the three-moving-magnet linear permanent magnet oscillating motor to a free-piston Stirling refrigerator, assuming that the power of the three-moving-magnet linear oscillating motor is 300 W, the outer diameter of the three-moving-magnet linear permanent magnet oscillating motor is Φ200 mm, and the length is 207 mm. After calculation and optimization using formulas (8)-(10), the optimal solution for the height of the permanent magnet should be 4 mm. When the length of the auxiliary permanent magnet 7 is 26 mm, the air gap magnetic flux density is the largest. At this time, the lengths of the main and auxiliary permanent magnets 7 are the same, and the air gap height of 4 mm is the optimal. After calculation using the parameter optimization formula provided by the present invention, by using the optimized height of the auxiliary permanent magnet, the length of the auxiliary permanent magnet, and the air gap height, the electromagnetic thrust increases from the original 75 N to 111 N, and the thrust of the optimized three-moving-magnet linear oscillating motor is increased by 48%.

[0063] For those of ordinary skill in the art, any obvious changes made without departing from the essential spirit of the present invention will fall within the protection scope of the present invention. The examples mentioned in the present invention are only for illustrative purposes to explain the implementation manner of the three-moving-magnet linear permanent magnet oscillating motor of the present invention, and should not be construed as a limitation on the protection scope of the invention.

Claims

1. A design method for the structural parameters of a symmetric three-moving-magnet permanent magnet linear oscillating motor, characterized in that: The mover of the symmetric three-mover permanent magnet linear oscillating motor adopts a symmetric structure of a main and two auxiliary movers. There is a main permanent magnet (6) in the middle, and two auxiliary permanent magnets (7) are symmetrically arranged on both sides of the main permanent magnet (6). The structural parameters include the height of the auxiliary permanent magnet, the length of the auxiliary permanent magnet, and the air gap height, which are designed according to the formula: The height of the auxiliary permanent magnet is obtained by the following formula: The length of the auxiliary permanent magnet is obtained by the following formula: The air gap height is obtained by the following formula: x3 = 455.4 / F - 1.56 (10) Where: F is the electromagnetic thrust.

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