A low torque pulsation IPM servo motor

Abstract

The present invention discloses a low-torque pulsation IPM servo motor, comprising a motor rotor core, wherein the motor rotor core is evenly provided with a plurality of permanent magnet slots along the circumference of the cross section, and permanent magnets are arranged in the permanent magnet slots. At least one pole shoe magnetic adjustment hole is arranged between each pair of adjacent permanent magnet slots of the motor rotor core near the surface of the core. Compared with an IPM servo motor without magnetic adjustment holes, the cogging torque and torque pulsation of the motor can be further reduced, and the torque output performance of the motor can be improved. Compared with an IPM motor with inclined slots or inclined poles, it has higher power density and torque density, higher production efficiency and lower manufacturing cost. An IPM motor with magnetic adjustment holes on the surface of the rotor core has lower wind wear loss, lower manufacturing cost and higher production efficiency.

Description

Technical Field

[0001] The invention relates to a permanent magnet servo motor, in particular to a low torque pulsation IPM servo motor. Background Art

[0002] Permanent magnet servo motors have a flexible and simple structure. According to the relative position of the permanent magnet and the rotor core, they are mainly divided into two categories: surface-mounted permanent magnet (SPM) servo motors and interior permanent magnet (IPM) servo motors. Compared with SPM servo motors, IPM servo motors have higher power density and overload capacity, which has attracted the attention of servo motor manufacturers. However, due to the relatively small air gap of IPM servo motors, their cogging torque and torque fluctuation are relatively large, thereby reducing the torque output quality of the motor. Generally, the torque performance of the motor is improved by adopting closed slots, skewed slots and skewed poles design schemes at the expense of the motor's torque density.

[0003] According to the energy method, the cogging torque is the energy stored in the air gap magnetic field with respect to the rotor position α The rate of change of can be expressed as

[0004] (1)

[0005] In the formula, λ( θ ) represents the air gap permeability, B( θ , α ) represents the air gap magnetic flux. Through Fourier expansion, we can get

[0006] (2)

[0007] Substituting equation (2) into equation (1), the cogging torque expression can be specifically expressed as

[0008] (3)

[0009] In the formula, L a Indicates the axial length of the core; R 1 and R 2 represent the outer radius and inner radius of the air gap respectively; Q Indicates the number of stator slots; p Indicates the number of motor pole pairs; μ 0 is the relative magnetic permeability; N L Represents the least common multiple of the number of stator slots and the number of rotor poles.

[0010] It can be seen from equation (3) that adjusting the relative permeability of the air gap or the air gap flux density can optimize the cogging torque of the motor. Based on this, many scholars and engineering technicians at home and abroad have done a lot of research work.

[0011] Chongqing University scholar Han Li and others proposed a method to suppress the cogging torque of SPM motors by opening rectangular slots on the surface of permanent magnets. By optimizing the size, location and number of permanent magnet slots, finite element calculation results show that the cogging torque of the motor can be effectively weakened. In addition, this method can further increase the surface area of ​​the rotor magnetic poles, improve heat dissipation performance, and reduce the risk of high-temperature demagnetization of permanent magnets on the rotor side by opening different numbers of rectangular slots on the surface of the magnetic poles.

[0012] Fan Ying from Southeast University and Xu Rong from Shanghai Institute of Electric Power have studied the cogging torque suppression method of IPM servo motors with V-shaped magnetic steel, and proposed a method to improve the surface slotting of rotor core pole shoes. Rotor slotting can reduce the cogging torque and torque pulsation of the motor while ensuring other motor performance, improve the control accuracy of the motor, and effectively improve the vibration and noise of the motor. In addition, this method can also adjust the salient pole ratio of the motor and improve the power density and overload capacity of the motor. This method is easy to implement, and the silicon steel sheet can be quickly stamped by a punch press to form an integral one at a time.

[0013] At present, domestic and foreign servo companies are still in the exploratory stage in terms of IPM servo motor torque pulsation suppression technology, and have not yet launched IPM servo motor products that use special torque pulsation suppression strategies. Summary of the invention

[0014] The purpose of the present invention is to overcome the defects of the prior art and propose a low torque pulsation IPM servo motor, which adopts a rotor core to set a pole shoe magnetic adjustment hole to suppress the torque pulsation of the motor and is suitable for batch and large-scale production.

[0015] The low torque pulsation IPM servo motor proposed in the present invention comprises a motor rotor core, wherein a plurality of permanent magnet slots are evenly arranged along the circumference of the cross section of the motor rotor core, and permanent magnets are arranged in the permanent magnet slots; the motor rotor core is characterized in that at least one pole shoe magnetic adjustment hole is arranged between each pair of adjacent permanent magnet slots of the motor rotor core near the core surface (located at the pole shoe portion).

[0016] If the number of the pole shoe magnetic adjustment holes between the adjacent permanent magnet slots is an odd number, one of them is located on the center line of the pole shoe, and the rest are symmetrical about the center line of the pole shoe; if the number of the pole shoe magnetic adjustment holes between the adjacent permanent magnet slots is an even number, the pole shoe magnetic adjustment holes are symmetrically distributed about the center line of the pole shoe.

[0017] The cross-sectional shape of the pole shoe magnetic adjustment hole can be a circular hole, a polygonal hole such as a triangular hole and a rectangular hole, a composite hole composed of a circular and a polygonal hole, an irregular hole, or a composite hole composed of a regular hole and an irregular hole.

[0018] The shortest distance between the pole shoe magnetic adjustment hole and the rotor core surface l min Should be greater than 0.5 times the air gap length δ , and less than 3 times the air gap length δ , that is, satisfying 0.5 δ < l min <3 δ .

[0019] When the pole shoe magnetic adjustment holes between adjacent permanent magnet slots are circular holes and the number is 3, the radii of the pole shoe magnetic adjustment holes on both sides of the pole shoe center line are equal; when the pole shoe magnetic adjustment holes between adjacent permanent magnet slots are circular holes and the number is 4, the radii of the pole shoe magnetic adjustment holes at symmetrical positions on both sides of the pole shoe center line are equal.

[0020] If the pole shoe magnetic adjustment hole is a composite hole composed of a circular hole and a polygon, its arc should be close to the air gap side.

[0021] When the pole shoe magnetic adjustment hole is an irregularly shaped hole, its overall outline should be parallel to the direction of the magnetic lines of force, and the wider part should be close to the air gap side, and the narrower part should be away from the air gap side.

[0022] The motor rotor core may be a spoke-type IPM motor rotor core, or may be an IPM motor rotor core of a straight line, V-type, U-type or W-type.

[0023] The IPM servo motor may be an inner rotor IPM motor, an outer rotor IPM motor, a linear IPM motor, or an axial magnetic field IPM motor.

[0024] The present invention analyzes the mathematical model of the cogging torque and proposes to slot the rotor core close to the air gap to adjust the air gap permeability and the air gap magnetic flux distribution, thereby improving the cogging torque and reducing the torque pulsation of the motor.

[0025] Compared with an IPM servo motor without adjustable magnetic holes, the low-torque pulsation IPM servo motor of the present invention can further reduce the cogging torque and torque pulsation of the motor and improve the torque output performance of the motor; compared with an IPM motor with inclined slots or inclined poles, it has higher power density and torque density, higher production efficiency and lower manufacturing cost; and compared with an IPM motor with adjustable magnetic holes on the surface of the rotor core, it has lower wind friction loss, lower manufacturing cost and higher production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 (a) is a cross-sectional view of a low torque pulsation IPM servo motor, where: 1 is the rotor core on the rotor side, 2 is the permanent magnet on the rotor side, 3 is the stator core on the stator side, and 4 is the armature winding on the stator side.

[0027] Figure 1 (b) is a schematic diagram of the rotor core on the rotor side (three circular hole-shaped pole shoe magnetic adjustment holes), where: 1.1, 1.2 and 1.3 are pole shoe magnetic adjustment holes.

[0028] Figure 2 Schematic diagram of the rotor core on the rotor side (1 circular pole shoe magnetic adjustment hole).

[0029] Figure 3 Schematic diagram of the rotor core on the rotor side (two circular pole shoe magnetic adjustment holes).

[0030] Figure 4 Schematic diagram of the rotor core on the rotor side (4 circular pole shoe magnetic adjustment holes).

[0031] Figure 5 This is a schematic diagram of the rotor core on the rotor side (two rectangular pole shoe magnetic adjustment holes).

[0032] Figure 6 Schematic diagram of the rotor core on the rotor side (two pole shoe magnetic adjustment holes, which are composite holes composed of circles and polygons).

[0033] Figure 7 Schematic diagram of the rotor core on the rotor side (two pole shoe magnetic adjustment holes, which are composite holes composed of circles and polygons).

[0034] Figure 8 Schematic diagram of the rotor core on the rotor side (three pole shoe magnetic adjustment holes, two irregular holes, and one round hole).

[0035] Fig. 9 This is an example of a finite element calculation of the motor magnetic field diagram after the rotor core is slotted on the rotor side.

[0036] Fig.10 This is a comparison diagram of the cogging torque optimization before and after the rotor core hole is opened on the rotor side.

[0037] Fig.11 This is a comparison diagram of electromagnetic torque optimization before and after the rotor core hole is opened on the rotor side. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described in detail with reference to the accompanying drawings.

[0039] Embodiment 1:

[0040] like Figure 1As shown in (a), it is a cross-sectional view of a low torque ripple IPM servo motor. 1 is the rotor core on the rotor side, 2 is the permanent magnet on the rotor side, 3 is the stator core on the stator side, and 4 is the armature winding on the stator side. To further illustrate the implementation, as Figure 1 shown in (b), it is the corresponding rotor core. There are 3 round hole-shaped pole shoe magnetic modulation holes near the surface of the core between every two adjacent permanent magnet slots. Among them, the round hole-shaped pole shoe magnetic modulation holes 1.1 and 1.3 are symmetric about the magnetic pole center line, the round hole-shaped pole shoe magnetic modulation hole 1.2 is located on the magnetic pole center line, and the distance from the center of the round hole-shaped pole shoe magnetic modulation hole 1.2 to the center of the motor may not be equal to the distance from the center of the round hole-shaped pole shoe magnetic modulation hole 1.1 or 1.2 to the center of the motor. The radii of the round hole-shaped pole shoe magnetic modulation holes 1.1, 1.2, and 1.3 are R1, R2, and R3 respectively, and the sizes of the three round holes satisfy R1 = R3 < R2, and the shortest distance from the 3 round holes to the surface of the rotor core l min should all be greater than 0.5 times the air gap length (defining the unilateral air gap length as δ ), and less than 3 times the air gap length, that is, 0.5 δ < l min <3 δ .

[0041] Example 2:

[0042] As Figure 2 shown, there is 1 round hole-shaped pole shoe magnetic modulation hole near the surface of the core between every two adjacent permanent magnet slots of the rotor core. The center of the pole shoe magnetic modulation hole is located on the magnetic pole center, and the shortest distance from this round hole-shaped pole shoe magnetic modulation hole to the surface of the rotor core l min is greater than 0.5 times the air gap length, and less than 3 times the air gap length, that is, 0.5 δ < l min <3 δ .

[0043] Example 3:

[0044] As Figure 3 shown, there are 2 round hole-shaped pole shoe magnetic modulation holes near the surface of the core between every two adjacent permanent magnet slots of the rotor core, that is, the round hole-shaped pole shoe magnetic modulation holes 1.1 and 1.2, with corresponding radii of R1 and R2 respectively. Among them, the round hole-shaped pole shoe magnetic modulation holes 1.1 and 1.2 are symmetric about the magnetic pole center line, and their radius sizes satisfy R1 = R2, and the shortest distance from the round hole-shaped pole shoe magnetic modulation holes to the surface of the rotor core l min are all greater than 0.5 times the air gap length, and less than 3 times the air gap length, that is, 0.5 δ < l min <3 δ .

[0045] Embodiment 4:

[0046] like Figure 4 As shown, there are 4 circular pole shoe magnetic adjustment holes (1.1, 1.2, 1.3, 1.4) near the surface of the rotor core between each two adjacent permanent magnet slots, with corresponding radii of R1, R2, R3, R4, R1=R4, R2=R3, and the shortest distance between the circular pole shoe magnetic adjustment holes and the rotor core surface is l min Both are greater than 0.5 times the air gap length and less than 3 times the air gap length, i.e. 0.5 δ < l min <3 δ .

[0047] Embodiment 5:

[0048] like Figure 5 As shown, there are two rectangular pole shoe magnetic adjustment holes (1.1, 1.2) near the surface of the rotor core between each two adjacent permanent magnet slots. The two rectangular pole shoe magnetic adjustment holes are symmetrical about the center line of the magnetic pole, and their sizes are equal. The shortest distance between the rectangular holes and the rotor core surface is l min Both are greater than 0.5 times the air gap length and less than 3 times the air gap length, i.e. 0.5 δ < l min <3 δ .

[0049] Embodiment 6:

[0050] like Figure 6 As shown in the figure, there are two pole shoe magnetic adjustment holes near the surface of the rotor core between each two adjacent permanent magnet slots. They are composite holes composed of circular holes and triangles and are symmetrical about the center line of the magnetic poles. The relevant feature sizes are equal, and their arcs are close to the air gap side, and the corresponding vertices of the triangles should be away from the air gap side. In addition, the shortest distance between the pole shoe magnetic adjustment hole and the rotor core surface is l min Both are greater than 0.5 times the air gap length and less than 3 times the air gap length, i.e. 0.5 δ < l min <3 δ .

[0051] Embodiment 7:

[0052] like Figure 7As shown in the figure, there are two irregular pole shoe magnetic adjustment holes near the surface of the rotor core between each two adjacent permanent magnet slots, which are symmetrical about the center line of the magnetic pole, and the relevant feature sizes are equal. The overall outline of the shape should be parallel to the direction of the magnetic lines of force, and the wider part should be close to the air gap side, and the narrower part should be away from the air gap side. In addition, the shortest distance between the pole shoe magnetic adjustment hole and the rotor core surface is l min Both are greater than 0.5 times the air gap length and less than 3 times the air gap length, i.e. 0.5 δ < l min <3 δ .

[0053] Embodiment 8:

[0054] like Figure 8 As shown, there are three pole shoe magnetic adjustment holes (1.1, 1.2, 1.3) near the surface of the rotor core between each two adjacent permanent magnet slots. The pole shoe magnetic adjustment holes (1.1, 1.3) are irregular holes and are symmetrical about the center line of the magnetic pole. The overall outline of the shape should be parallel to the direction of the magnetic lines of force, and the wider part should be close to the air gap side, and the narrower part should be away from the air gap side. The pole shoe magnetic adjustment hole 1.2 is on the center line of the magnetic pole. In addition, the pole shoe magnetic adjustment hole is the shortest distance from the surface of the rotor core. l min Both are greater than 0.5 times the air gap length and less than 3 times the air gap length, i.e. 0.5 δ < l min <3 δ .

[0055] The low-torque pulsation IPM servo motor of the present invention can be applied to the servo IPM motor industry field, and can also be widely used in the field of household electrical appliance motors, new energy IPM motors, all-electric aircraft motors and other transportation fields.

Claims

1. A low torque pulsation IPM servo motor, comprising a motor rotor core, wherein the motor rotor core is evenly provided with a plurality of permanent magnet slots along the circumference of the cross section, and permanent magnets are arranged in the permanent magnet slots; wherein the characteristics are: Three pole shoe magnetic adjustment holes are arranged between each pair of adjacent permanent magnet slots of the motor rotor core near the core surface; one of the pole shoe magnetic adjustment holes is located on the pole shoe center line and is a circular hole, and the others are symmetrical about the pole shoe center line and are composite holes composed of circles and polygons, the arc of the composite hole is close to the air gap side, and the part of the composite hole away from the air gap side is gradually narrower than the arc part; The shortest distance between the pole shoe magnetic adjustment hole and the rotor core surface l min Greater than 0.5 times the air gap length δ , and less than 3 times the air gap length δ , that is, satisfying 0.5 δ < l min <3 δ .

2. The low torque pulsation IPM servo motor according to claim 1, characterized in that: The IPM servo motor is an inner rotor IPM motor, an outer rotor IPM motor, a linear IPM motor or an axial magnetic field IPM motor.

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