CN1361581A - Brush-less Dc motor for driving washing machine directly - Google Patents

Abstract

The present invention proposes a brushless direct current motor for directly driving a washing machine, which is suitable for direct-driven fully automatic pulsator washing machines and drum washing machines. The number of magnetic poles of the rotor of the present invention is P=24, and the number of slots of the stator core is Z= 27; Uniform tooth groove structure is adopted, the width of the groove is 3.5mm; two square wave Hall position sensors are used, and an engineering plastic sleeve is added between the rotor shell and the mechanical transmission shaft. The present invention has small positioning torque, low noise, stable performance and extensive social and economic benefits.

Description

Direct Drive Brushless DC Motors for Washing Machines

The invention relates to a brushless direct-current motor for directly driving a washing machine, in particular to an outer rotor three-phase brushless permanent-magnet direct-current motor specially used for washing machines, suitable for direct-driven fully automatic pulsator washing machines and drums washing machine.

Traditional washing machines generally use single-phase capacitor-run induction motors as the drive motors of the washing machine. The operating efficiency of the capacitor running induction motor is very low, generally only about 50%, and because the induction motor is used as the driving motor, the reduction gear and pulley must be used, so the operating efficiency is even lower. Therefore, someone switched to a brushless DC permanent magnet motor as the drive motor of the washing machine. The operating efficiency of the brushless DC permanent magnet motor is very high, more than 90%. After the speed control of the electronic circuit, the reduction gear and the pulley can be removed, and the direct drive can be realized, which greatly reduces the noise. Also, the system efficiency is improved. However, due to the large and small structure of the stator used in the prior art, the processing technology of the motor becomes quite complicated, and the production cost increases. Because of the adoption of three Hall position sensors, the production cost is increased, and because the number of poles P=24 and the number of slots Z=36, the number of positioning moments of this gear slot cooperation is 72 times, and its amplitude It will be very large and must be compensated by the use of large and small slots. A large number of slots (Z=36) is beneficial to reduce the positioning torque, and the positioning torque is the most important source of electromagnetic noise of the motor. The more slots, the more complex the production process and the higher the production cost. The iron loss of the motor with more poles (P=24) increases.

The object of the present invention aims at the deficiencies in the prior art, and proposes a direct-drive brushless DC motor with simple structure, low cost and high efficiency.

The purpose of the present invention is achieved in that the present invention is mainly composed of a stator, a rotor, a permanent magnet, a sensor and a plastic cover formed by lamination of punched silicon steel sheets. The main point of the present invention is that the number of magnetic poles of the rotor 1 is P = 24, the number of slots of the stator core 2 Z = 27, a uniform slot structure is adopted, the width of the slot 3 is 3.5 mm, and the sensor adopts two Hall switches distributed at an electrical angle of 90° in space. The Hall sensor is a switch-type Hall switch, so the requirement for the accuracy of the installation position is not high. It is only necessary to align the magnetic sensitivity direction of the Hall position sensor with the normal direction of the rotor, install it on the inner stator support 8, and keep an air gap of 1-2mm between the inner circle of the rotor magnetic steel, and the Hall sensors 10, 11 Arranged on the same circumference, the space included angle is 1/2 pole pitch, that is, 90° electrical angle. The Hall sensor of the present invention can also be installed on the stator bracket 9, and maintain an air gap of 1-2 mm between the outer circle of the rotor magnetic steel, and the Hall sensors 10, 11 are arranged on the same circle, and the space included angle is 1 /2 pole distance, that is, 90° electrical angle. The punching sheet 14 of each layer of silicon steel sheet is composed of three 120° fan-shaped punching sheets 15 with exactly the same shape. The yoke of the 120° fan-shaped punching sheet has two through holes 16 with a diameter of 3-5mm. The angle between them is 60°, and they are symmetrically distributed on the yoke of the fan-shaped punches. Three fan-shaped punches form a ring-shaped stator punch on a plane. Therefore, the ring-shaped stator punch has three joints. In order to reduce the The influence of small seams on the magnetic circuit of the stator core, when chipping each ring-shaped stator punch, start from the lowest layer of a ring-shaped stator punch, and each additional ring-shaped stator punch, clockwise or counterclockwise The wrong piece is 60°. Due to the symmetry, there are still 6 through holes 16 on the stator iron core stacked by the above-mentioned staggered pieces, and then the upper and lower pressure rings 17, 18 and thin iron rods of the stator iron core are used to pass through the 6 through holes on the stator iron core. Rivet the stator core into a whole. In the present invention, the two through holes of the yoke of each fan-shaped punch can be changed into two grooves 19 on the inner circle of the yoke, the groove width is about 3-6mm, and the groove depth is about 1-2mm. The punched sheet is staggered by 60° according to the above method, and then pressed with the upper and lower pressure rings 17 and 18 of the stator core, and then the stator core is welded into a complete stator core by using 6 grooves. In order to further simplify the processing of the stator core and solve the problem of material utilization, the present invention can also change the two through holes 16 in the yoke of each fan-shaped punch or the two grooves 19 located in the inner circle of the yoke to be located at 120° Two stamped blind holes 21 formed on the inner circle of the yoke of the fan-shaped punching sheet, the diameter of the blind hole is about 2-3mm, and the depth of the blind hole is 1/2 the thickness of the punching sheet; the angle between the two blind holes is 60°; three sheets The fan-shaped punching sheet constitutes a ring-shaped stator punching sheet on a plane. Therefore, the ring-shaped stator punching sheet has three seams. In order to reduce the impact of the seams on the magnetic circuit of the stator core, each ring-shaped stator punching sheet When chipping, starting from the lowest layer of a ring-shaped stator punch, every time a ring-shaped stator punch is added, the clockwise or counterclockwise staggered angle of 60°, due to the symmetry of the distribution of the blind holes 21, after the staggered stacking Each fan-shaped stamping sheet of the stator core that comes is self-positioning, and then the stator core is molded into a complete stator core by injection molding after pressing with the upper and lower pressure rings 17, 18 of the stator core. In the present invention, an engineering plastic sleeve 20 is added between the rotor shell and the mechanical transmission shaft. Since the engineering plastic is connected in series between the rotor steel body and the mechanical transmission shaft, its elastic characteristics greatly buffer the transmission strength of harmonic torque. The overall free oscillation property of the washing machine is improved, so that the overall noise level of the washing machine is further improved.

The invention has the advantages of reasonable structure, stable performance, small positioning torque, low noise, reduced production cost, large motor output and wide application prospects.

Fig. 1 is a principle structural diagram of the present invention.

Fig. 2 is a schematic structure diagram of the stator of the present invention.

Fig. 3 is a principle structure diagram of the magnetic steel of the present invention.

Fig. 4 is a schematic structural diagram of the magnetic steel of the present invention.

Fig. 5 is a schematic structural diagram of a sector punching sheet according to the present invention.

Fig. 6 is a schematic structural diagram of a circular punching sheet according to the present invention.

Fig. 7 is a schematic structural diagram of a circular punching sheet according to the present invention.

Fig. 8 is a schematic diagram of positioning blind holes in the yoke of a circular punch according to the present invention.

Fig. 9 is a schematic diagram of positioning blind holes in the yoke of a circular punch according to the present invention.

Fig. 10 is a schematic diagram of stator installation of the present invention.

Fig. 11 is a schematic structure diagram of the second embodiment of the present invention.

Example:

The technique of the invention is used to realize an outer rotor three-phase brushless DC permanent magnet motor specially used for directly driving washing machines. The number of magnetic poles P of the rotor 1 of the DC permanent magnet motor is 24, the number of slots Z of the stator core 2 is 27, the width of the notch 3 is 3.5mm, and the position sensor used is two hall switches in the form of square wave output The spatial phase difference of the two Hall switches is 90° electrical angle, the motor adopts a uniform slot structure, and the slot width is 3.5mm, which is very suitable for the wires of different diameters of various washing machines to pass through and wind in the slot of this size coil.

Claims (6)

1. A brushless DC motor for directly driving a washing machine, comprising a stator, a rotor, a permanent magnet, and a sensor formed by laminating punched silicon steel sheets; Between the rotor shell and the mechanical transmission shaft, the number of magnetic poles P of the rotor [1] is 24, the number of slots Z of the stator core [2] is 27; the width of the notch [3] is 3.5mm, and the position sensor used is two Hall switch of the square wave output type, the phase difference of the two Hall switches in space is 90° electrical angle, the size of the magnetic steel pole pitch [13] is 28-35mm, and the magnetic sensitivity direction of the Hall position sensor and the rotor The normal direction is consistent, installed on the inner stator bracket [8], and maintains an air gap of 1-2mm between the inner circle of the rotor magnetic steel, and the two Hall sensors [10], [11] are arranged on the same circle , the space angle is 1/2 pole pitch, that is, 90° electrical angle. 2. The motor according to claim 1, characterized in that: the magnetic sensitivity direction of the Hall position sensor is consistent with the normal direction of the rotor, installed on the stator bracket [9], and between the outer circle of the rotor magnetic steel Keep an air gap of 1-2mm. 3. The motor according to claim 1, characterized in that: when the permanent magnet is a bonded NdFeB magnet, the difference between the two radii is 3-4mm; when the permanent magnet is a ferrite magnet, the difference between the two radii The difference is 6-8mm, the two sides [6], [7] of the inner circle of the tile-shaped magnetic steel are chamfered by straight lines or arcs, and the lengths of the two straight lines or arcs corresponding to the chamfered parts, They are 1/3 of the total arc length of the inner circle, and the two straight lines or arcs corresponding to the chamfered part intersect with the inner circle _{respectively .} 1/3 of the difference. 4. The motor according to claim 1, characterized in that: the punching sheet [14] of the first silicon steel sheet is composed of three 120° fan-shaped punching sheets [15] with exactly the same shape, and the 120° fan-shaped punching sheet The yoke has two through holes [16] with a diameter of 3-5mm, and the angle between the two through holes is 60°, which are symmetrically distributed on the yoke of the fan-shaped punches, and three fan-shaped punches form a ring on a plane When chipping each ring-shaped stator punch, start from the lowest layer of a ring-shaped stator punch, and each time a ring-shaped stator punch is added, the clockwise or counterclockwise angle is staggered by 60°, because Symmetry, there are still 6 through holes [16] on the stator core after staggered stacking, and then the stator core upper and lower pressure rings [17], [18] and thin iron rods pass through the 6 through holes on the stator core. A through hole is used to rivet the stator core into a whole. 5. The motor according to claim 1, characterized in that: each silicon steel sheet punch [14] is composed of three 120° fan-shaped punches [15] with exactly the same shape, and the 120° fan-shaped punch There are two grooves [19] in the inner circle of the yoke, the groove width is about 3-6mm, the groove depth is about 1-2mm, the angle between the two grooves is 60°, and three fan-shaped punches form a ring-shaped stator on a plane For punching, when chipping each ring-shaped stator punch, start from the lowest layer of a ring-shaped stator punch, and each time a ring-shaped stator punch is added, the electrical angle is staggered clockwise or counterclockwise by 60°, because Symmetry, the stator core that has been stacked by staggered pieces still maintains 6 grooves [19], and then the upper and lower pressure rings [17] and [18] of the stator core are used to compress the stator core and use 6 grooves to weld the stator core into a Complete stator core. 6. The motor according to claim 1, characterized in that: each silicon steel sheet punch [14] is composed of three 120° fan-shaped punches [15] with exactly the same shape, and the 120° fan-shaped punch There are two punched blind holes [21] in the inner circle of the yoke. The diameter of the blind holes is about 2-3mm. The depth of the blind holes is about 1/2 of the thickness of the stator punch. The angle between the two blind holes is 60°. Three fan-shaped punches form a ring-shaped stator punch on a plane. Starting from the lowest layer of a ring-shaped stator punch, each additional ring-shaped stator punch is staggered clockwise or counterclockwise by 60°electrical angle, Due to the symmetry of the distribution of blind holes [21], each fan-shaped stamping piece of the stator core that has been stacked by staggered pieces is self-positioning, and then the upper and lower pressure rings [17] and [18] of the stator core are used to compress the stator core and then press it by injection molding. The stator core is welded into a complete stator core.

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