Three-phase permanent magnet servo motor with non-uniform air gap and double eccentricity of stator and rotor with pole shoes

Abstract

A three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor solves the positioning torque problem existing in square wave permanent magnet servo motors and sine wave permanent magnet servo motors. The motor is a fractional slot concentrated winding motor with the number of slots per pole per phase q=Z / (2Pm)≤1 / 2, 2P is the number of poles, and Z is the number of slots. Its rotor core is an eccentric rotor, and the rotor eccentricity P r =r1 / r2=(1.05~(1+2δcos(180° / 2P)); Its stator core is an eccentric stator, and the stator eccentricity P R =R1 / R2=(0.95~1 / (1+δcos(180° / Z)), (where r1 is the rotor radius, r2 is the rotor eccentric radius, R1 is the stator radius, and R2 is the stator eccentric radius), the motor is a stator-rotor double eccentric non-uniform air gap motor.

Description

Technical Field

[0001] The invention discloses a three-phase permanent magnet servo motor, in particular to a three-phase permanent magnet servo motor with a rotor having pole shoes and a stator and rotor with double eccentricity and non-uniform air gap. The motor is suitable for direct drive and position and speed servo control applications. Background Art

[0002] Permanent magnet motors can be divided into two categories: sinusoidal and square waves according to the driving current and back EMF waveform. Sine wave permanent magnet motors are generally called permanent magnet synchronous motors (PMSM) or sinusoidal AC servo motors. Another type of square wave permanent magnet motor is called a square wave brushless DC motor (BLDCM).

[0003] The biggest drawback of square wave permanent magnet motors is the large fluctuation of the fundamental commutation torque. In response to this, researchers have proposed a variety of compensation measures, but the actual application results are not ideal.

[0004] The torque fluctuation of the sine wave permanent magnet motor is much smaller than that of the square wave permanent magnet motor, and it has become the mainstream of industrial applications today. However, in order to reduce its torque fluctuation, the traditional sine wave permanent magnet motor adopts the "fractional slot distributed winding structure". The air gap harmonic magnetic field and positioning torque of the "fractional slot distributed winding motor" are small, but it will lead to the complication of the motor structure and manufacturing process. In addition, the complexity of the control system of the sine wave permanent magnet motor leads to a significant increase in the cost of the motor. More importantly, the power energy index of the motor has also decreased.

[0005] Contemporary sinusoidal permanent magnet motors have begun to adopt "fractional slot concentrated winding structure", the most typical example is: 10 poles and 12 slots "fractional slot concentrated winding motor". Since the number of poles and slots of the fractional slot concentrated winding motor are very close, its positioning torque (cogging positioning torque) is relatively large, so the biggest design and manufacturing difficulty of the concentrated winding motor is: how to reduce its positioning torque (cogging positioning torque). Although there have been many studies on it at home and abroad, and there are many methods, these methods all require sacrificing other performance as a prerequisite, and the effect is poor. The reasons are analyzed as follows:

[0006] Since the number of poles and slots of the fractional slot concentrated winding motor is very close, its winding coefficient is very large, that is, the winding utilization rate is very high, and the winding end is minimized, the motor copper loss is small, and the efficiency is high. However, the tooth slot positioning torque of the fractional slot concentrated winding motor may be very large and difficult to suppress. In the extreme case, the positioning torque reaches a maximum value when the number of poles is equal to the number of slots. The traditional method is: select reasonable tooth slot matching, use closed slots or small slots, appropriately increase the air gap, use rotor skew slots, use rotor eccentricity and other commonly used methods to suppress the positioning torque. However, the above methods will make the winding coefficient smaller, the leakage magnetic flux larger, the air gap magnetic density smaller, and the motor material utilization rate reduced, at the expense of the motor power energy index and performance, and it is not enough to suppress the positioning torque to less than a few ten-thousandths. Even if all the above methods are used at the same time, it is difficult to suppress the positioning torque to less than a few ten-thousandths in many engineering applications. Therefore, suppressing the positioning torque is still a major problem in the current design and manufacturing of permanent magnet motors. In particular, large diameter torque motors in direct drive systems still use the traditional "fractional slot distributed winding structure", although the motor structure and manufacturing process are complex and the production cost is high. Summary of the invention

[0007] In view of the above-mentioned shortcomings that the permanent magnet motors in the prior art cannot take into account both the positioning torque and the force energy indicators, or have complex structures and manufacturing processes and high production costs, the present invention proposes a three-phase permanent magnet servo motor with double eccentricity of stator and rotor and non-uniform air gap. Combined with the method of adding pole shoes, the positioning torque can be very well suppressed, the air gap harmonic magnetic field can be reduced, and the performance of the motor in all aspects can be comprehensively improved. This method is applicable to both square wave and sine wave permanent magnet motors, and is also particularly suitable for large-diameter torque motors in direct drive systems.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and a double eccentric stator and rotor, the motor is an inner rotor motor, the rotor is equipped with more than one pair of permanent magnets, the slots of the stator are equipped with three-phase windings, the motor is a fractional slot concentrated winding motor with the number of slots per pole per phase q=Z / (2Pm)≤1 / 2, wherein Z is the number of slots, 2P is the number of poles, and m is the number of phases;

[0009] The rotor core of the motor is an eccentric rotor core.

[0010] Rotor eccentricity P r =r1 / r2=(1.05~(1+2δcos(180° / 2P))), where r1 is the rotor radius and r2 is the eccentric rotor radius.

[0011] The stator core of the motor is an eccentric stator core.

[0012] Stator eccentricity P R=R1 / R2=(0.95~1 / (1+δcos(180° / Z))), where R1 is the stator radius, R2 is the eccentric stator radius, and the tooth pitch angle θ=360 / Z,

[0013] The motor is a non-uniform air-gap motor with double eccentricity of the stator and rotor, and a permanent magnet rotor with pole shoes;

[0014] The length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1.

[0015] The technical solution adopted by the present invention to solve the technical problem further includes:

[0016] The number of slots of the motor is Z=9N, the number of poles is 2P=8N or the number of poles is 2P=10N, wherein N=2, 3, 4, 5, ... N is a natural number greater than or equal to 2.

[0017] The length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1, which is 0.2-10 mm.

[0018] For a motor with slot number Z=12 and pole number 2P=10, the length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1, which is 0.2-2 mm.

[0019] The permanent magnet is a square magnetic steel, and is embedded between the pole shoe and the rotor yoke (301).

[0020] The length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1 is 0.2~3mm, the material of the pole shoe is one of low carbon steel, cast steel, silicon steel sheet, ferrite, SMC composite soft magnetic material or other soft magnetic materials, and the pole shoe and the rotor yoke are respectively provided with grooves, and the pole shoe and the rotor yoke are bonded into an integral rotor core through square magnetic steel using anaerobic glue or epoxy glue specially used for magnetic steel.

[0021] The rotor core of the motor is an eccentric rotor core, and the rotor eccentricity Pr=r1 / r2=(1.05~(1+1.5δcos(180° / 2P))), wherein r1 is the rotor radius, r2 is the eccentric rotor radius, and the stator core of the motor is an eccentric stator core, and the stator eccentricity P R =R1 / R2=(0.95~1 / (1+0.95δcos(180° / Z))), where R1 is the stator radius, R2 is the eccentric stator radius, and the tooth pitch angle θ=360 / Z.

[0022] The rotor core or at least the two axial end faces of the rotor core use rotor end plates in which the pole shoes and the rotor yoke are integrated. The square magnetic steel, the pole shoes and the rotor yoke are inlaid with each other through the rotor end plates to form an integral rotor core. The material of the rotor end plates is silicon steel sheets or other high-strength metal or non-metal composite materials; the number of rotor end plates in which the pole shoes and the rotor yoke are integrated is greater than or equal to 2, and the thickness of the rotor end plates is 0.35 to 2.1 mm.

[0023] The material of the rotor end piece is the same silicon steel sheet as that of the rotor yoke, and the width of the magnetic bridge is Q≤δ.

[0024] The rotor core includes square magnets, pole shoes, rotor yokes and T-shaped wedges. The pole shoes and rotor yokes are respectively provided with grooves. The pole shoes and rotor yokes are bonded and embedded together by square magnets. The rotor yoke is provided with wedge grooves on both sides of the grooves for mounting the magnets thereon, which are used to insert the T-shaped wedges into the rotor yoke. When the T-shaped wedges are axially inserted into the wedge grooves of the rotor yoke, the square magnets, pole shoes and rotor yokes can be embedded together to form a solid rotor core that is embedded with each other as a whole. Anaerobic glue or epoxy glue is applied to the joints of the rotor core to enhance the bonding strength.

[0025] The stator core is assembled by positioning more than one identical pole slot through an inner circle or an outer circle, and the more than one identical stator pole slot has the same eccentricity.

[0026] The beneficial effects of the present invention are as follows: the non-uniform air gap three-phase permanent magnet servo motor with double eccentricity of stator and rotor proposed by the present invention can better suppress the detent torque, reduce the air gap harmonic magnetic field, and comprehensively improve the performance of the motor in all aspects by adding rotor pole shoes. The method is applicable to both square wave and sine wave permanent magnet motors, and is also particularly suitable for large diameter torque motors in direct drive systems. The three-phase permanent magnet servo motor of the present invention has the advantages of concentrated windings, can be driven by three-phase square wave current or three-phase sine wave current, can generate stable torque, and has a series of advantages such as minimizing winding ends, minimizing air gaps, minimizing materials, minimizing detent torque, and minimizing losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the eccentric structure of the motor rotor in a preferred embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the eccentric structure of the motor stator in a preferred embodiment of the present invention.

[0029] Figure 3 It is a schematic diagram of the stator eccentric structure of a 12-slot 10-pole motor in a preferred embodiment of the present invention.

[0030] Figure 4It is a schematic diagram of the assembly of a stepless shoe double eccentric 10-pole 12-slot motor.

[0031] Figure 5 It is a schematic diagram of assembling a stepless shoe double eccentric 10-pole 12-slot motor in another embodiment.

[0032] Figure 6 It is a schematic diagram of the rotor core structure of a 10-pole 12-slot motor with a rotor pole shoe.

[0033] Figure 7 It is a schematic diagram of the magnetic pole structure of two types of rotors with pole shoes.

[0034] Figure 8 Schematic diagrams of two types of rotor yokes with pole shoes.

[0035] Fig. 9 This is a lamination diagram of a 10-pole 12-slot motor with an eccentric pole shoe rotor.

[0036] Fig.10 It is a schematic diagram of the assembly of a 10-pole 12-slot motor with an eccentric pole shoe rotor using 3 end pieces.

[0037] Fig.11 It is a schematic diagram of the stator core structure composed of Z=12 identical pole slots.

[0038] Fig.12 This is a schematic diagram of the stator punching of a torque motor with a large diameter and an eccentric stator and the number of slots Z=9N=36.

[0039] Fig.13 The stator punching of a torque motor with a large diameter rotor, pole shoes and eccentricity is shown in Figure 2.

[0040] intention.

[0041] Fig.14 It is a stator eccentricity parameter diagram of the best embodiment motor with 10 poles and 12 slots.

[0042] Fig.15 It is a schematic diagram of a 10-pole 12-slot optimal embodiment rotor with pole shoes and a double eccentric motor.

[0043] Fig.16 This is the positioning torque waveform diagram without using an eccentric magnetic pole.

[0044] Fig.17 It is the positioning torque waveform diagram under one magnetic pole after the rotor is eccentric.

[0045] Fig.18 This is the positioning torque waveform under one magnetic pole after the rotor and stator are double eccentric.

[0046] Fig.19This is the positioning torque waveform diagram without using an eccentric magnetic pole with a pole shoe.

[0047] Fig. 20 This is the positioning torque waveform diagram under one magnetic pole after the rotor is eccentric with pole shoes.

[0048] Fig.21 This is the waveform diagram of the positioning torque under one magnetic pole after the rotor and stator are double eccentric with pole shoes.

[0049] In the figure, 1-stator core, 2-rotor core, 3-rotor yoke, 4-pole shoe, 5-rotor end piece, 6-square magnet, 7-rotor assembly, 8-rotor punching sheet, 9-slot, 10-T-shaped wedge, 11-magnetic bridge. DETAILED DESCRIPTION

[0050] This embodiment is a preferred implementation mode of the present invention. Other embodiments whose principles and basic structures are the same or similar to those of this embodiment are within the protection scope of the present invention.

[0051] The present invention aims to solve the problems existing in the existing square wave permanent magnet motors and sine wave permanent magnet motors, and proposes a three-phase permanent magnet servo motor with a new design principle, new structure, high performance, low cost, and a stator and rotor double eccentric non-uniform air gap using fractional slot concentrated windings.

[0052] In order to solve the problem of large positioning torque in existing square wave permanent magnet servo motors and sine wave permanent magnet servo motors, in the present invention, the motor is a fractional slot concentrated winding motor with the number of slots per pole per phase q=Z / (2Pm)≤1 / 2, wherein q is the number of slots per pole per phase, Z is the number of slots, 2P is the number of poles, and m is the number of phases.

[0053] The rotor core 2 of the motor is an eccentric rotor core, and the rotor eccentricity P r =r1 / r2=(1.05~(1+2δcos(180° / 2P))), where r1 is the rotor radius and r2 is the eccentric rotor radius.

[0054] The stator core 1 of the motor is an eccentric stator core, and the stator eccentricity P R =R1 / R2=(0.95~1 / (1+δcos(180° / Z))), where R1 is the stator radius and R2 is the eccentric stator radius.

[0055] The motor is a non-uniform air gap motor with double eccentricity of stator and rotor. Figure 4 and Figure 5 When the eccentricity Pr=P R When =1, r1=r2, R1=R2, when both the stator and the rotor are not eccentric, the motor with non-uniform air gap becomes a motor with uniform air gap. At this time, the length of the equivalent uniform air gap is: δ=R1-r1.

[0056] Since the number of poles and slots of the fractional slot concentrated winding motor is very close, its winding coefficient is very large, that is, the winding utilization rate is very high. However, the cogging torque of the fractional slot concentrated winding motor may be very large and difficult to suppress. The limit is that the cogging torque reaches the maximum value when the number of poles is equal to the number of slots.

[0057] The traditional methods are: selecting reasonable tooth-slot matching, using closed slots or small slots, appropriately increasing the air gap, using rotor skew slots, using rotor eccentricity, etc., which are commonly used methods to suppress the detent torque. However, the above methods will make the winding coefficient smaller, the leakage magnetic flux larger, the air gap magnetic density smaller, and the motor material utilization rate reduced, at the expense of the motor's power energy indicators and performance. It is not enough to suppress the detent torque to less than a few ten-thousandths. Even if all the above methods are used at the same time, it is difficult to suppress the detent torque to less than a few ten-thousandths in many engineering applications.

[0058] Choose a reasonable tooth-slot match: the closer the number of poles is to the number of slots, the larger the winding coefficient is, the higher the utilization rate of the winding is, but the positioning torque may be greater. The present invention adopts a non-uniform air gap structure and electromagnetic design with double eccentricity of the stator and rotor, and the ability to suppress the positioning torque is doubled, so the tooth-slot match with the closest number of poles to the number of slots can be used, for example:

[0059] In this embodiment, the number of slots Z=9N, the number of poles 2P=8N or the number of poles 2P=10N, where N=1, 2, 3, 4, 5, ... wherein N is a natural number greater than or equal to 2; the length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1 is 0.2-10mm, and the winding coefficient of the motor is 0.945. When N is relatively large, the diameter of the motor is also relatively large. At this time, the length of the equivalent uniform air gap can also be relatively large. In the best embodiment of the present invention, a torque motor with the number of slots Z=9N=36, the number of poles 2P=32, and the stator outer diameter of 358mm is taken as an example. The positioning torque of the motor is better than 0.006Nm.

[0060] In this embodiment, a motor 103 with slot number Z=12 and pole number 2P=10 is taken, and the length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1, which is 0.2~2mm. The winding coefficient of the motor is 0.933, and the positioning torque of the motor is better than 0.00045Nm.

[0061] In order to illustrate the influence of eccentricity on the suppression of the detent torque, the following example is taken as an example a motor with the number of slots Z = 12, the number of poles 2P = 10, the air gap δ = 0.4mm, the slot opening 0.2mm, and the outer diameter 110mm:

[0062] (1) When eccentricity is not used and the air gap is uniform, since the number of slots and the number of poles are close, even if the best pole-slot match and the best air gap and slot size match are used, the motor detent torque is still 0.011Nm, which is not practical. The detent torque waveform under one magnetic pole is as follows: Fig.16 The positioning torque waveform consists of a main wave with a larger amplitude and a secondary wave with a smaller amplitude caused by the slot. Relative to a pair of magnetic pole waves, the positioning torque wave is a double frequency harmonic.

[0063] (2) When the rotor is eccentric, even if the eccentricity is relatively large, the optimal positioning torque is 0.0026Nm, and the positioning torque waveform is as follows Fig.17 However, at this time, the amplitude of the positioning torque has been reduced by 4.3 times, and the side waves caused by slotting have been basically completely suppressed. However, for high-performance motors, its positioning torque index is not ideal enough.

[0064] (3) Further adopting the double eccentricity of the rotor and stator, even if the eccentricity is not too large, the positioning torque can be optimized to 0.00045Nm. The positioning torque waveform is as follows Fig.18 . It can be seen that after adopting the double eccentricity of the rotor and stator, the amplitude of the positioning torque is reduced by 13.4 times compared with the case without eccentricity, and the frequency is doubled. Since the eccentricity of the rotor and stator when the rotor and stator are double eccentric is not too large, there is no obvious difference between the non-uniform air gap and the uniform air gap without eccentricity. Therefore, the average air gap magnetic flux of the non-uniform air gap motor of the present invention is also not significantly different from that of the case with uniform air gap without eccentricity. That is, for the motor with double eccentricity of the rotor and stator, the average air gap magnetic flux decreases very little.

[0065] In the above three-phase permanent magnet servo motor, due to the eccentricity of the permanent magnet rotor, r1>r2, the rotor radius r1 is larger than the eccentric rotor radius r2, and the effect is similar to the circular chamfer. Obviously, the utilization rate of the permanent magnet steel is reduced, and the processing cost of the circular permanent magnet is also relatively high. In order to adopt low cost and improve the utilization rate of the magnet steel, the permanent magnet rotor described in the present invention has a pole shoe 4, and the permanent magnet is a square magnet steel 6. The permanent magnet is embedded between the pole shoe 4 and the rotor yoke 3 301, and the length of the equivalent uniform air gap between the stator and the rotor is: δ = R1-r1 is 0.2~3mm.

[0066] After the rotor of the present invention is provided with a pole shoe 4, a square magnetic steel 6 can be used, and the cost of the magnetic steel can be reduced by about 25%. More importantly, for the present invention, after the rotor is provided with a pole shoe 4, the principle electromagnetic air gap of the motor is greatly reduced. The reason is that if the rotor does not have a pole shoe 4, since the magnetic permeability of the magnetic steel is close to the magnetic permeability of the air, the principle electromagnetic air gap of this radial magnetic circuit should include the thickness of the magnetic steel. Therefore, after the rotor is provided with a pole shoe 4, the principle electromagnetic air gap of the motor is reduced by a magnetic steel thickness, which is greatly reduced. Obviously, when the principle electromagnetic air gap is small, the rotor and stator are eccentric, and the relative change of the eccentricity to the principle electromagnetic air gap is relatively large, so the eccentricity becomes more sensitive to suppressing the positioning torque. That is, the positioning torque optimization design and better optimization effect can be achieved through a smaller eccentricity change. The eccentricity change is small, and of course the influence on the air gap magnetic density is also smaller. Therefore, after the rotor of the present invention is provided with a pole shoe 4, the rotor and stator are double eccentric, and the influence on the air gap magnetic density is smaller than that of the traditional motor.

[0067] As analyzed above, with the pole shoe 4, the influence of eccentricity is more sensitive. The rotor core 2 of the motor is an eccentric rotor core 2. The rotor eccentricity P of the motor with the pole shoe 4 is r =r1 / r2=(1.05~(1+1.5δcos(180° / 2P))), where r1 is the rotor radius and r2 is the eccentric rotor radius.

[0068] The stator core 1 of the motor is an eccentric stator core with a pole shoe 4. The stator eccentricity of the motor is P R =R1 / R2=(0.95~1 / (1+0.95δcos(180° / Z))), where R1 is the stator radius, R2 is the eccentric stator radius, and the tooth pitch angle θ=360 / Z.

[0069] In the above-mentioned three-phase permanent magnet servo motor, the material of the pole shoe 4 is one of low carbon steel or cast steel, silicon steel sheet, ferrite, SMC composite soft magnetic material or other soft magnetic materials, and there are grooves on the pole shoe 4 and the rotor yoke 3 respectively, so that the pole shoe 4 and the rotor yoke 3 can be bonded into an integral rotor core 2 through the square magnetic steel 6, and the adhesive used can be an anaerobic adhesive or epoxy adhesive specially used for magnetic steel; in order to simplify the production process or for small-sized motors, the square magnetic steel 6, the pole shoe 4 and the rotor yoke 3 can be bonded after being positioned by a mold, and at this time, no grooves may be provided on the pole shoe 4 and the rotor yoke 3.

[0070] The above-mentioned three-phase permanent magnet servo motor, the integral rotor core 2, at least the rotor core 2

[0071] The two axial end faces use rotor end pieces 5 in which the pole shoes 4 and the rotor yoke 3 are integrated. The square magnetic steel 6, the pole shoes 4 and the rotor yoke 3 are mutually inlaid through the rotor end pieces 5 to form an integral rotor core 2. The material of the rotor end pieces 5 can be silicon steel sheets, or other metal or non-metal composite materials with high strength. For motors with a relatively long axial length, in order to increase the strength, the number of rotor end pieces 5 in which the pole shoes 4 and the rotor yoke 3 are integrated is not limited to 2 to 3 pieces, and can even be more. The thickness of the rotor end pieces 5 is 0.35 to 2.1 mm. In this embodiment, rotor punchings 8 are arranged between adjacent rotor end pieces 5.

[0072] In order to simplify and maintain process consistency, in the above three-phase permanent magnet servo motor, the material of the rotor end piece 5 is the same silicon steel sheet as the rotor yoke 3, and in order to reduce magnetic leakage, the width Q of the magnetic bridge is ≤δ.

[0073] In order to simplify assembly, the three-phase permanent magnet servo motor, the rotor core 2 is composed of: square magnetic steel 6, pole shoes 4, rotor yoke 3 and T-shaped wedges 10, the pole shoes 4 and rotor yoke 3 are respectively provided with grooves, so that the pole shoes 4 and rotor yoke 3 can be glued and embedded together through the square magnetic steel 6, and the two sides of the groove for mounting the magnetic steel on the rotor yoke 3 are provided with wedge grooves 9 of the rotor yoke 3 for inserting the T-shaped wedges 10. When the T-shaped wedges 10 are axially inserted into the wedge grooves 9 of the rotor yoke 3, the square magnetic steel 6, pole shoes 4, and rotor yoke 3 can be embedded together to form a solid rotor core 2 that is embedded with each other as a whole; in order to increase the strength, anaerobic glue or epoxy glue is applied to each joint of the rotor core 2.

[0074] In order to further illustrate the eccentricity after the rotor is provided with pole shoes 4 and analyze its influence on suppressing the positioning torque, a motor with slot number Z=12, pole number 2P=10, air gap δ=0.4mm, slot opening 0.2mm and outer diameter 110mm is taken as an example.

[0075] (1) When the motor rotor has pole shoes 4, no eccentricity is used, and the air gap is uniform, since the number of slots and the number of poles are close, even if the best pole-slot match and the best air gap and slot size match are used, the motor positioning torque is still 0.010Nm, which is not practical. The positioning torque waveform under one magnetic pole is as follows: Fig.19 The positioning torque waveform mainly consists of: a main wave with a larger amplitude superimposed on a secondary wave with a smaller amplitude caused by slotting. Relative to a pair of magnetic pole waves, the positioning torque wave is a double frequency harmonic.

[0076] (2) When the rotor has pole shoes 4 and uses rotor eccentricity, even if the eccentricity is relatively large, the optimal positioning torque is 0.001Nm. The positioning torque waveform is as follows Fig. 20 However, the amplitude of the positioning torque has been reduced by 10 times, and the side wave caused by slotting has been basically completely suppressed. For high-performance motors, the positioning torque index is not ideal.

[0077] (3) When the motor rotor has pole shoes 4 and adopts double eccentricity of the rotor and stator, even if the eccentricity is not too large, the positioning torque can be designed to be 0.00059Nm. The positioning torque waveform is as follows Fig.21 , the amplitude of the positioning torque is reduced by 17.6 times compared with the case without eccentricity, and the frequency is doubled. It can be seen that the rotor with pole shoes 4, the effect of suppressing the positioning torque is better after the rotor and stator are double eccentric, and because the eccentricity of the rotor and stator is not too large, there is no obvious difference between the non-uniform air gap and the uniform air gap without eccentricity, so the average air gap magnetic flux of the non-uniform air gap motor of the present invention is almost the same as that of the uniform air gap without eccentricity. That is, the average air gap magnetic flux of the motor with double eccentricity of the rotor and stator decreases very little.

[0078] In addition, the stator core 1 of the three-phase permanent magnet servo motor is assembled from Z identical pole slots 10. Fig.11 The stator core 1 is assembled by inner or outer circle positioning, and the Z identical stator pole slots 10 have the same eccentricity.

[0079] A preferred embodiment of the present invention is Figure 3 , Fig. 9 , Fig.10 and Fig.14 As shown in the figure, it can be seen that this three-phase brushless permanent magnet DC motor is a fractional slot concentrated winding motor with the number of slots per pole and per phase q=Z / (2Pm)=12 / 10m=12 / 30≤1 / 2, in which the number of slots Z is 12, the number of poles 2P is 10, and the number of phases m is 3.

[0080] The rotor core 2 of the motor is an eccentric rotor core 2, and the rotor eccentricity P r =r1 / r2=(1.05~(1+1.5δcos(180° / 2P))), take 2.02, where the rotor radius r1=42mm and the eccentric rotor radius r2=21mm.

[0081] The stator core 1 of the motor is an eccentric stator core 12, and the stator eccentricity P R =R1 / R2=(0.95~1 / (1+0.95δcos(180° / Z))), take 0.794, where the stator radius R1=40.50mm, and the eccentric stator radius R2=53.50mm. Fig.15 This is a schematic diagram of the best embodiment of the 10-pole 12-slot rotor with pole shoes 4 and a double eccentric motor. The positioning torque can reach less than 593.5e -6 Nm, such as Fig.21 shown.

[0082] This motor is a non-uniform air gap motor with double eccentricity of stator and rotor. R =1, r1=r2, R1=R2 When both the stator and the rotor are not eccentric, the motor with non-uniform air gap becomes a motor with uniform air gap. At this time, the length of the equivalent uniform air gap is: δ=R1-r1=0.5mm.

[0083] Another preferred embodiment of the present invention is Fig.12 and Fig.13 As shown. It can be seen from the figure that this three-phase brushless permanent magnet DC motor is a fractional slot concentrated winding motor with the number of slots per pole and phase q=Z / (2Pm)=36 / 32m=36 / 96=0.375≤1 / 2, wherein the number of slots Z=9N=36, the number of poles 2P=8N=32, and the number of phases m is 3. In the best embodiment of the present invention with 32 poles and 36 slots, the rotor has pole shoes 4 and adopts a stator-rotor double eccentric motor. The positioning torque of the large diameter torque with diameter D=360mm can reach the order of less than a few ten-thousandths.

[0084] The stator-rotor double eccentric non-uniform air gap three-phase permanent magnet servo motor proposed by the present invention can better suppress the positioning torque, reduce the air gap harmonic magnetic field, and comprehensively improve the performance of the motor in all aspects by adding the rotor pole shoe 4. The method is applicable to both square wave and sine wave permanent magnet motors, and is also particularly applicable to large diameter torque motors in direct drive systems.

[0085] The three-phase permanent magnet servo motor of the present invention has the advantages of concentrated windings, can be driven by three-phase square wave current or three-phase sine wave current, can generate stable torque, and has a series of advantages such as minimizing winding ends, minimizing air gaps, minimizing materials, minimizing positioning torque, and minimizing losses.

Claims

1. A three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor, wherein the motor is an inner rotor motor, wherein the rotor is equipped with one or more permanent magnets, and the slots of the stator are equipped with three-phase windings, characterized in that: The motor is a fractional slot concentrated winding motor with the number of slots per pole per phase q=Z / (2Pm)≤1 / 2, where Z is the number of slots, 2P is the number of poles, and m is the number of phases; The rotor core of the motor is an eccentric rotor core. Rotor eccentricity P r =r1 / r2=(1.05~(1+2δcos(180° / 2P))), where r1 is the rotor radius and r2 is the eccentric rotor radius. The stator core of the motor is an eccentric stator core. Stator eccentricity P R =R1 / R2=(0.95~1 / (1+δcos(180° / Z))), where R1 is the stator radius, R2 is the eccentric stator radius, and the pitch angle θ=360 / Z, The motor is a non-uniform air-gap motor with double eccentricity of the stator and rotor, and a permanent magnet rotor with pole shoes; The length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1.

2. The non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor according to claim 1 is characterized in that: The number of slots of the motor is Z=9N, the number of poles is 2P=8N or the number of poles is 2P=10N, wherein N=2, 3, 4, 5, ... N is a natural number greater than or equal to 2.

3. The non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor according to claim 1, characterized in that: The length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1 is 0.2~10mm.

4. According to claim 1, the non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor is characterized in that: For a motor with slot number Z=12 and pole number 2P=10, the length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1, which is 0.2-2 mm.

5. The three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor with non-uniform air gap according to any one of claims 1 to 4, characterized in that: The permanent magnet is a square magnetic steel, and the permanent magnet is embedded between the pole shoe and the rotor yoke. The length of the equivalent uniform air gap between the stator and the rotor is: δ=R1-r1 is 0.2-3mm. The material of the pole shoe is one of low carbon steel, cast steel, silicon steel sheet, ferrite, SMC composite soft magnetic material or other soft magnetic materials. The pole shoe and the rotor yoke are respectively provided with grooves. The pole shoe and the rotor yoke are bonded into an integral rotor core through the square magnetic steel using anaerobic glue or epoxy glue specially used for the magnetic steel.

6. The non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor according to claim 5, characterized in that: The rotor core of the motor is an eccentric rotor core, and the rotor eccentricity Pr=r1 / r2=(1.05~(1+1.5δcos(180° / 2P))), wherein r1 is the rotor radius, r2 is the eccentric rotor radius, and the stator core of the motor is an eccentric stator core, and the stator eccentricity P R =R1 / R2=(0.95~1 / (1+0.95δcos(180° / Z))), where R1 is the stator radius, R2 is the eccentric stator radius, and the tooth pitch angle θ=360 / Z.

7. The non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor according to claim 6, characterized in that: The rotor core or at least the two axial end faces of the rotor core use rotor end plates in which the pole shoes and the rotor yoke are integrated. The square magnetic steel, the pole shoes and the rotor yoke are inlaid with each other through the rotor end plates to form an integral rotor core. The material of the rotor end plates is silicon steel sheets or other high-strength metal or non-metal composite materials; the number of rotor end plates in which the pole shoes and the rotor yoke are integrated is greater than or equal to 2, and the thickness of the rotor end plates is 0.35 to 2.1 mm.

8. The non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor according to claim 7, characterized in that: The material of the rotor end piece is the same silicon steel sheet as that of the rotor yoke, and the width of the magnetic bridge is Q≤δ.

9. The non-uniform air gap three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor according to claim 6, characterized in that: The rotor core includes square magnets, pole shoes, rotor yokes and T-shaped wedges. The pole shoes and rotor yokes are respectively provided with grooves. The pole shoes and rotor yokes are bonded and embedded together by square magnets. The rotor yoke is provided with wedge grooves on both sides of the grooves for mounting the magnets thereon, which are used to insert the T-shaped wedges into the rotor yoke. When the T-shaped wedges are axially inserted into the wedge grooves of the rotor yoke, the square magnets, pole shoes and rotor yokes can be embedded together to form a solid rotor core that is embedded with each other as a whole. Anaerobic glue or epoxy glue is applied to the joints of the rotor core to enhance the bonding strength.

10. The three-phase permanent magnet servo motor with a rotor with pole shoes and double eccentricity of the stator and rotor with non-uniform air gap according to claim 6, characterized in that: The stator core is assembled by positioning more than one identical pole slot through an inner circle or an outer circle, and the more than one identical stator pole slot has the same eccentricity.

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