CN112311191B

CN112311191B - Hybrid stepping motor rotor

Info

Publication number: CN112311191B
Application number: CN202011130707.6A
Authority: CN
Inventors: 郗珂庆; 李敏哲; 杨凡; 胡博; 高俊丽; 胡昊; 苏倩; 郭炳岐
Original assignee: Xian Aerospace Propulsion Institute
Current assignee: Xian Aerospace Propulsion Institute
Priority date: 2020-10-21
Filing date: 2020-10-21
Publication date: 2022-12-27
Anticipated expiration: 2040-10-21
Also published as: CN112311191A

Abstract

The invention provides a hybrid stepping motor rotor which comprises a rotor shaft, a magnetism isolating ring, a magnetic yoke and magnetic steel, wherein the magnetic steel is embedded into the magnetic yoke, and the magnetic steel is of a bidirectional conical structure with a large outer diameter at the axial middle position and small outer diameters at the axial two ends. And the taper angle of the conical structure is related to the outer diameter of the rotor, and the taper angle iteration is carried out by presetting an initial taper angle and adopting a mode of judging the relation between the maximum magnetic flux density of the magnetic circuit and the magnetic flux density saturation value of the magnetic material by electromagnetic simulation to obtain the optimal taper angle. The invention can improve the local saturation of the magnetic circuit of the magnetic yoke, further improve the magnetic flux phi of the rotor and improve the output torque of the motor.

Description

Hybrid stepping motor rotor

Technical Field

The invention belongs to the technical field of electromechanics, and particularly relates to a hybrid stepping motor rotor.

Background

The hybrid stepping motor rotor mainly has two typical magnetic circuit structures, as shown in fig. 1 and fig. 2, and has the following common characteristics:

1. part characteristics: the rotor bearing carries torque output, so that the hardness of the metal material is improved by heat treatment, but the used materials also have magnetic conductivity; the magnetism isolating ring is mainly used for shielding the magnetic leakage of the main magnetic circuit of the rotor to the rotor shaft; the magnetic yoke is made of soft magnetic materials, so that the magnetic resistance of a magnetic circuit is reduced; the magnetic steel provides a magnetic source for the whole stepping motor; the materials of parts used by different rotor structures are all of the same grade, so that advantages and disadvantages of different structures can be compared conveniently;

2. the staggered tooth structure is as follows: two magnetic yokes are arranged in the rotor, and the positions of the two magnetic yokes are presented with characteristics of tooth-to-groove and groove-to-tooth (see cross sections E-E and F-F), commonly called staggered teeth, when viewed from the axial direction. The main reason for the staggered teeth is that the continuous operation of the rotor can be realized when the stepping motor receives continuous pulses, namely the working principle of the stepping motor;

3. rotor magnetic path direction: in the rotor shown in fig. 1 and 2, the directions of magnetic circuits of the rotor are consistent, an external magnetic circuit enters a tooth part of a magnetic yoke, the magnetic circuit penetrates through the magnetic yoke and then axially penetrates through magnetic steel, then enters a tooth part of another magnetic yoke, finally goes out of the rotor and enters the external magnetic circuit; a typical local magnetic path is shown in fig. 3 and 4 (the arrow indicates the magnetic path direction):

4. the rotor magnet yoke is required to be in an unsaturated state during magnetic circuit design, otherwise, the basic design requirements of the stepping motor are not met;

5. the magnetic flux of the rotor is the product of the sectional area of the tooth part of the magnetic yoke and the magnetic density of the tooth part of the magnetic yoke, and the magnetic flux of the rotor is in direct proportion to the output torque of the stepping motor.

Φ＝B×S (1)

S＝b×L×Z (2)

In the formula: phi, rotor magnetic flux, B, magnetic flux density of a magnetic yoke tooth part, S, sectional area of the magnetic yoke tooth part, B, single tooth width of the magnetic yoke, L, length of the magnetic yoke, Z and tooth number of the magnetic yoke.

As can be seen from the schematic view of the rotor structure and the magnetic circuit in fig. 1 and 2, the difference between the two characteristics is as follows:

(1) Fig. 2 is an enlarged yoke tooth section area S: compared with the structure shown in fig. 1, the structural difference of fig. 2 is that the magnetic steel is embedded into the magnetic yoke, the length L of the magnetic yoke is increased, the tooth width b and the tooth number Z are fixed, and the sectional area of the tooth part of the magnetic yoke is increased by S;

(2) In fig. 2, the magnetic flux density B of the yoke tooth is increased: the axial sectional area and the axial length of the magnetic steel are positively correlated with the magnetic density B of the magnetic yoke tooth part (the magnetic path of the magnetic yoke is unsaturated), and the structural difference of FIG. 2 is that the axial length of the magnetic steel is increased and the sectional areas are the same, so that the magnetic density B of the magnetic yoke tooth part is increased, the magnetic flux of the final rotor is large, and the output torque is large under the same control condition;

(3) The magnetic circuit of the yoke of fig. 1 must not be saturated: at present, the highest magnetic density of the magnetic steel is 1.46T, the lowest allowable magnetic density of a magnetic circuit of a common silicon steel sheet is 1.65T, and the sectional area of a magnetic yoke is larger than that of the magnetic steel, so that the magnetic circuit in the figure 1 is certainly unsaturated;

(4) The yoke of fig. 2 may be saturated in the local magnetic circuit: fig. 2 is easy to appear that the magnetic circuit is slightly small to cause magnetic circuit saturation (see the local saturation point shown in fig. 5), and at this time, the sectional area of the magnetic steel can only be reduced to reduce the magnetic density B of the teeth of the magnetic yoke. By establishing a three-dimensional model and performing checking calculation by using finite element software simulation, the optimal size of the magnetic steel is selected by comparing the length and the sectional area of the magnetic steel with the variation trend of the magnetic density B of the tooth part of the magnetic yoke.

Specifically, the following can be analyzed:

fig. 1 and fig. 2 are both conventional rotor structures of the hybrid stepping motor, and both can realize normal operation of the hybrid stepping motor; fig. 1 certainly does not show a yoke local saturation point, but the output torque is smaller; fig. 2 shows that the magnetic steel length is increased to increase the rotor magnetic flux, thereby increasing the output torque, but local saturation points are likely to occur, and if the local saturation points are to be avoided, the idea in the prior art is to reduce the magnetic steel sectional area to reduce the magnetic density B of the tooth portion of the magnetic yoke, and to perform iterative verification by using finite element simulation software of a three-dimensional model.

Disclosure of Invention

Analysis of the background art shows that the structure of fig. 2 is superior to the structure of fig. 1 in terms of output torque on the whole, but has a local saturation point, and the rotor flux Φ is not sufficiently increased, so that the output torque of the motor still has a lifting space. Therefore, the invention redesigns the magnetic path of the rotor, provides a new rotor of the hybrid stepping motor and a design method thereof, improves the local saturation of the magnetic path of the magnetic yoke, further improves the magnetic flux phi of the rotor, and improves the output torque of the motor.

The technical scheme of the invention is as follows:

the utility model provides a hybrid stepper motor rotor, includes the rotor shaft, separates magnetic ring, yoke, magnet steel, inside the magnet steel embedding yoke, its characterized in that: the magnetic steel adopts a bidirectional conical structure with a large outer diameter at the axial middle position and small outer diameters at the axial two ends.

Further, the taper angle of the bidirectional conical structure magnetic steel is determined through the following steps:

step 1: setting an initial taper angle;

step 2: after a taper angle is given, carrying out magnetic density simulation, when the maximum magnetic density of a magnetic circuit is equal to a saturation value of the magnetic density of the material, considering the taper angle as the optimal taper angle, or modifying the taper angle according to the set step length according to the maximum magnetic density of the magnetic circuit obtained by simulation, and re-simulating until the optimal taper angle is obtained; if the maximum magnetic flux density of the magnetic circuit is lower than the saturation value of the magnetic flux density of the material, the taper angle is reduced; if the maximum magnetic flux density of the magnetic circuit is higher than the saturation value of the magnetic flux density of the material, the taper angle is increased; the taper angle is an included angle between the conical surface and the axial direction of the magnetic steel.

Further, the initial taper angle is set to 20 °.

Further, the step size is set to 2 °.

Furthermore, magnetic flux density simulation is carried out by adopting ansys finite element electromagnetic simulation software.

Advantageous effects

The invention provides a novel hybrid stepping motor rotor and a design method thereof, which improve the local saturation of a magnetic yoke magnetic circuit, further improve the rotor magnetic flux phi and improve the motor output torque.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1: the existing typical magnetic circuit structure 1;

FIG. 2: the existing typical magnetic structure 2;

wherein: 1. the rotor comprises a rotor shaft, 2, a magnetism isolating ring, 3, a magnet yoke, 4 and magnetic steel;

FIG. 3: the partial magnetic path schematic in the structure of fig. 1;

FIG. 4: the partial magnetic path schematic in the structure of fig. 2;

FIG. 5: local saturation point of the structure of fig. 2;

FIG. 6: the shape of the magnetic steel is shown schematically;

FIG. 7: a novel rotor structure schematic diagram;

FIG. 8: the novel rotor structure is a magnetic circuit schematic diagram.

Detailed Description

The following detailed description of embodiments of the invention is intended to be illustrative, and not to be construed as limiting the invention.

The embodiment redesigns a rotor magnetic circuit path, provides a new hybrid stepping motor rotor and a design method thereof, improves the local saturation of a magnetic yoke magnetic circuit, further improves the rotor magnetic flux phi, and improves the motor output torque.

In order to further eliminate the local saturation point shown in fig. 5, a conical magnetic steel structure is adopted in the embodiment, the sectional area of the local saturation point is increased, so that the local saturation phenomenon can not occur under the same magnetic flux condition, the whole magnetic circuit is unobstructed, the magnetic resistance is reduced, and the output torque of the motor is improved. Fig. 6 is a novel magnetic steel rotor structure with taper, a schematic diagram of the novel rotor structure is shown in fig. 7, and a schematic diagram of a magnetic circuit of the novel rotor structure is shown in fig. 8.

The rotor belt taper angle theoretically avoids saturation points, but different outer diameter rotors certainly have only one optimum taper angle. Under the optimal taper structure, when the motor operates according to rated output torque, the maximum magnetic flux density point of a magnetic circuit is equal to the allowable magnetic flux density of a material; if the taper angle is less than the optimal taper angle, then local saturation points must occur, except that the degree of saturation must be less than in the configuration of FIG. 5; if the taper angle is greater than the optimal taper angle, then it is certain that local saturation points do not occur, except that maximization of magnetic material use is not achieved, and the output torque does not achieve a maximum. Combining the theoretical analysis and the actual engineering experience, the following taper angle iterative design method is formed:

1. using a tool: ansys finite element electromagnetic simulation software;

2. the design idea is as follows: giving an initial taper angle, obtaining the maximum flux density of a magnetic circuit by using finite element analysis software, judging whether the maximum flux density is equal to the flux density saturation value of the magnetic material or not, and reducing the taper angle if the maximum flux density is lower than the flux density saturation value; if the flux density is higher than the saturation value of the flux density, the taper angle is increased to continue iteration.

3. The method comprises the following specific steps:

step 1: initial taper angle: combining engineering experience, setting the initial taper angle to be 20 degrees, and enabling the initial taper angle to be closer to the optimal taper angle;

and 2, step: and (3) magnetic density determination: and (3) performing magnetic flux density simulation after a taper angle is given, wherein when the maximum magnetic flux density of the magnetic circuit is equal to a saturation value (1.65T in the embodiment) of the magnetic flux density of the material, the taper angle is the optimal taper angle, and otherwise, continuing to increase/decrease the taper angle for iterative simulation. The iteration principle is shown in the design idea;

and step 3: iteration quantity of taper angle: in order to improve the simulation efficiency and reduce the workload, the taper iteration quantity is measured by 2 degrees.

Comparing fig. 4 and fig. 6, it can be known that, through magnetic circuit optimization, the magnetic circuit saturation point existing in fig. 4 does not exist in fig. 6, and the magnetic circuit path in fig. 6 is short, which is beneficial to the magnetic circuit to reduce the magnetic resistance, improve the rotor magnetic flux Φ, and improve the motor output torque.

In this embodiment, taking a J35BYG250 two-phase hybrid stepping motor as an example, the same control conditions, stator parameters and rotor outer envelope parameters are set to compare the output torques of three different rotor structures. Under the condition of 20Hz rotating speed, the output torque of the structure in the figure 1 is 0.07Nm, the output torque of the structure in the figure 2 is 0.11Nm, and the output torque of the structure in the figure 3 (the taper angle is 26 degrees) is 0.13Nm. The data shows that the magnetic reluctance of the rotor magnetic circuit of the structure shown in fig. 3 is reduced relative to the magnetic circuits of the structures shown in fig. 1 and 2, and the rotor magnetic flux is maximum.

Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and not to be construed as limiting the present invention, and that those skilled in the art may make variations, modifications, substitutions and alterations within the scope of the present invention without departing from the spirit and scope of the present invention.

Claims

1. The utility model provides a hybrid step motor rotor, includes the rotor shaft, separates magnetic ring, yoke, magnet steel, inside the magnet steel embedding yoke, its characterized in that: the magnetic steel adopts a bidirectional conical structure with a large outer diameter at the axial middle position and a small outer diameter at the axial two ends; the taper angle of the bidirectional conical structure magnetic steel is determined through the following steps:

step 1: setting an initial taper angle;

2. A hybrid stepper motor rotor as recited in claim 1, wherein: the initial taper angle is set to 20 °.

3. A hybrid stepper motor rotor as recited in claim 1, wherein: the set step size is 2 °.

4. A hybrid stepper motor rotor as recited in claim 1, wherein: and performing magnetic flux density simulation by using ansys finite element electromagnetic simulation software.