JP2005210826A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor provided with a rotor shape that reduces cogging torque by leak magnetic flux by reducing the leak magnetic flux that is generated from the bridge portion of the rotor via a stator facing the portion, and that results in the reduction of noise. <P>SOLUTION: The rotor 8 is formed into a six-pole rotor iron core by stacking thin magnetic steel sheets. Permanent magnets 31 of a plate shape are embedded inside the rotor 8 of almost a cylindrical shape. The external ends of magnetic materials 33 positioned outside each permanent magnet 31 are connected to each other, and bridges 34, bridging portions made of a magnetic material positioned outside non-magnetic portions 32, are provided. Cutouts 37, which face the inside circumferential surface of a stator with a gap in-between and correspond to the non-magnetic portions 32, are provided on the outside circumferential surface of the rotor 8. Furthermore, salient poles are formed in such a way that its angle becomes approximately 40°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to the shape of a rotor, and more particularly, to an electric motor in which the shape of an inner rotor type rotor core is specified and cogging torque is reduced to reduce noise.

  Conventionally, an inner rotor type electric motor has a structure in which a rotor is provided on the inner peripheral portion of a stator as shown in FIG. 7, and an annular stator 71 includes a stator core 71c and six sets of stator coils. 73u, 73v, 73w and 74u, 74v, 74w. The stator core 71c has a substantially annular shape, and twelve semi-closed slots 71a having opening portions 71b are formed on the inner peripheral surface side of the stator core 71c in a circumferential shape so as to be equally spaced. ing.

  In this semi-closed slot 71a, six sets of stator coils 73u, 73v, 73w and 74u, 74v, 74w are respectively wound and accommodated in predetermined semi-closed slots 71a. Each of the stator coils 73u to 74w is configured to be supplied with a three-phase DC excitation current.

  In addition, a rotor 82 is disposed on the inner circumferential portion of the concentric circle of the stator 71 so that a small gap portion 80 is made uniform with the inner circumferential surface of the stator 71. As shown in FIG. 8, the rotor 82 is fitted to a rotor core 82c formed by laminating a large number of substantially annular thin plate-like silicon steel plates, and a center position of the rotor core 82c. The rotating shaft 85 and four field permanent magnets 86, 87, 88 and 89 made of ferrite.

  The field permanent magnets 86 to 89 are arranged and fixed so as to surround the rotating shaft 85 at a central position at a substantially square position. Of the four field permanent magnets 86 to 89, the pair of field permanent magnets 86 and 88 arranged at positions facing each other is such that the outer peripheral surface of the rotor 82 has an N pole. The field permanent magnets 87 and 89, which are magnetized and form the other pair, are magnetized on the S pole.

  In the rotor core 2c portion sandwiched between the radial outer peripheral surface of the field permanent magnet 86 and the gap portion 80, the energization section for one phase of the stator coil is 120 degrees as described above. The arc-shaped protruding portion 6a is formed in a portion corresponding to 30 to 150 degrees in electrical angle, and in a portion having a central angle corresponding to 15 to 75 degrees in mechanical angle and 60 degrees.

  The field permanent magnets 87, 88, and 89 also have a portion corresponding to 30 to 150 degrees in terms of electrical angle for one pole and a mechanical angle of 15 on the radially outer peripheral side, similarly to the protruding portion 86a. Arc-shaped projecting portions 87a, 88a, and 89a are formed at portions having a central angle of 60 degrees corresponding to degrees to 75 degrees, respectively. That is, it is a configuration in which a gap portion 80 formed of a notch is provided in a portion corresponding to a mechanical angle of 75 ° to 105 °, 165 ° to 195 °, 255 ° to 285 °, or 345 ° to 15 °. When the stator coils 73u to 74w are energized, the protruding portions 86a to 89a are provided at electrical angle positions corresponding to energization angles for one phase, that is, positions corresponding to 120 degrees in electrical angle.

  Since the rotor structure is provided with the gap portion 80 formed of the notches in this way, when the stator coils 83u to 84w are energized, the magnetic flux distribution in the gap portion 80 is magnetically protruding. The magnetic flux density of this part is increased, and the magnetic flux density for one pole increases the magnetic flux at a position corresponding to 30 to 150 degrees in terms of the electrical angle for one pole, so the torque for one phase is also increased. Therefore, the combined torque of the three phases is increased (see, for example, Patent Document 1).

  However, in the rotor shape of FIG. 8, both ends of each permanent magnet are arranged close to each other, and there is no means for preventing short circuit of the magnetic flux at both ends of the permanent magnet, so that leakage flux is generated in the adjacent permanent magnet. There is a problem of doing. As a conventional technique for solving this problem, a rotor structure shown in FIG. 9 is disclosed.

The rotor of FIG. 9 is a rotor applied to a permanent magnet motor such as a brushless DC motor, and a plate-like permanent magnet 92 is embedded in a substantially cylindrical rotor 1. Reference numeral 96 denotes a rotary shaft member that passes through the center of the rotor 91 in the axial direction.
The circumferential end of each permanent magnet 92 has a circumferential length larger than the thickness of the permanent magnet 92 (the radial length of the permanent magnet 92), and the rotor outer circumference from the permanent magnet mounting position. The fan-shaped nonmagnetic part 93 which consists of the space extended toward is provided.

  In addition, a bridge portion 94 made of a magnetic material is provided to connect the outer end portions of the magnetic body portions 91a located outside the permanent magnets 92, and located outside the nonmagnetic portion 93, and also nonmagnetic. Reinforcing rib portions 95 made of a magnetic material are provided between the portions 93 and extend in the radial direction.

  Such a structure concentrates the flow of magnetic flux caused by the permanent magnet 92 on the magnetic body portion 91a by preventing a short circuit of the magnetic flux at both ends of each permanent magnet (see, for example, Patent Document 2). .

  However, in the rotor shape of FIG. 9, non-magnetic portions that prevent short-circuiting of magnetic flux are provided at both ends of each permanent magnet, but leakage from the bridge portion to the adjacent magnetic body portion via the opposing stator. A magnetic flux is generated, and the cogging torque is increased by the leakage magnetic flux, resulting in a problem that noise increases.

JP-A-5-236688 (page 3-4, FIG. 1)

JP 2002-44888 (5th page, FIG. 1)

  The present invention solves the above-mentioned problems and reduces the cogging torque caused by this leakage flux by reducing the leakage flux generated from the rotor bridge through the opposing stator, resulting in noise. It aims at providing the electric motor provided with the rotor shape to reduce.

In order to solve the above-mentioned problems, the present invention faces a stator and an inner peripheral surface of the stator with a gap therebetween, and a plurality of permanent magnets are disposed inside the iron core. In an electric motor composed of a rotor having a plurality of non-magnetic parts extending to the vicinity of the surface continuously to the part,
A notch for reducing magnetic flux leakage is provided on the outer peripheral surface of the rotor corresponding to the nonmagnetic portion.

  Moreover, the depth dimension of the said notch part is made larger than the thickness dimension of the bridge part which consists of the said rotor core from which the gap between the said clearance gap and the said nonmagnetic part becomes thickness.

  Further, the number of poles of the rotor is six, and the protrusion is an angle from the rotation center that defines the outer peripheral width of the arc-shaped salient pole part formed on the outer peripheral surface of the rotor by forming the notch part. The polar angle is about 40 °.

  Alternatively, the number of poles of the rotor is 6, and the protrusion is an angle from the rotation center that defines the outer peripheral width of the arc-shaped salient pole part formed on the outer peripheral surface of the rotor by forming the notch part. The polar angle is in the range of 37 ° to 40.5 °.

According to the motor according to the invention,
In the invention according to claim 1, by providing a notch portion for reducing magnetic flux leakage on the outer peripheral surface of the rotor corresponding to the non-magnetic portion,
Since the gap between the stator inner peripheral surface and the bridge portion that is the bridge portion of the rotor is widened to reduce magnetic flux leakage, noise due to cogging torque can be reduced while maintaining the strength of the rotor by the bridge portion. .
In addition, by providing this notch, the leakage magnetic flux through the stator is reduced without widening the entire gap between the rotor and the stator, and as a result, the arc-like shape formed in the magnetic body portion. With the salient pole portion, the magnetic force generated from the permanent magnet can be concentrated on the salient pole portion to increase the efficiency of the electric motor.

In the invention according to claim 2, by making the depth dimension of the notch portion larger than the thickness dimension of the bridging portion made of the rotor core having a thickness between the gap and the nonmagnetic portion,
Even when the bridge portion is thick and the leakage magnetic flux is large, this influence can be reduced in proportion to the bridge portion thickness.

  In the invention according to claim 3, the number of poles of the rotor is six, and the angle from the rotation center that defines the outer peripheral width of the arc-shaped salient pole part formed on the outer peripheral surface of the rotor by forming the notch part. By setting a certain salient pole angle to about 40 °, noise due to cogging torque can be most reduced.

  In the invention according to claim 4, the number of poles of the rotor is six, and the angle from the rotation center that defines the outer peripheral width of the arc-shaped salient pole part formed on the outer peripheral surface of the rotor by forming the notch part. By setting a certain salient pole angle within an angle range of 37 ° to 40.5 °, noise due to cogging torque can be reduced.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail as examples based on the attached drawings. The bridge portion described in the background art is a bridge portion that connects the outer end portions of adjacent magnetic body portions. However, in order to facilitate understanding, this bridge portion is also bridged in the following embodiments. Part.

FIG. 1 is a side sectional view of a hermetic scroll compressor equipped with an electric motor according to the present invention.
In this compressor, a sealed container 1 is partitioned into a compressor chamber 3 and a motor chamber 4 by a main frame 2, and an oil reservoir chamber 6 partitioned by a subframe 5 is provided below the motor chamber 4. .
The electric motor chamber 4 is provided with an electric motor unit 11 including a stator 47, a rotor 8, and a crankshaft 10 having a turning shaft 9.
A discharge chamber 12 is provided in the upper portion of the compressor chamber 3 and a scroll-type compression portion 13 is provided in the lower portion. The scroll-type compression portion 13 is formed between the wraps 14 a and 15 a provided in the fixed scroll 14 and the orbiting scroll 15. The rotating scroll 15 is driven to rotate by the action of the Oldham ring 17 with the rotation of the crankshaft 10 as the crankshaft 10 rotates, and the refrigerant gas is sucked and compressed from the suction pipe 18, and is discharged from the discharge hole 19 to the discharge chamber 12. Discharging.
The high-pressure refrigerant gas discharged into the discharge chamber 12 is guided to the upper portion of the electric motor chamber 4 through the first refrigerant passage 20 and is led out to a refrigerating cycle (not shown) from a discharge pipe 21 provided at the upper portion of the electric motor chamber 4. ing.

In addition, a second refrigerant passage 22 is provided between the stator 47 provided with an insulator 47a made of resin on both sides and the sealed container 1, and a cross-sectional arc shape connecting the first refrigerant passage 20 and the second refrigerant passage 22. The oil discharge guide 30 is provided on the inner peripheral surface of the sealed container 1.
The high-pressure refrigerant gas discharged into the discharge chamber 12 passes through the first refrigerant passage 20, the oil discharge guide 30, and the second refrigerant passage 22, respectively, as indicated by the arrows in FIG. The oil reservoir 6 is also filled, and the motor unit 11 is cooled by the high-pressure refrigerant gas.

  Then, the high-pressure refrigerant gas filling the oil reservoir 6 is cooled while passing between the stator 47 and the rotor 8 from the oil reservoir 6 as indicated by the arrows in FIG. A discharge pipe 21 provided at the upper part is led out to a refrigeration cycle (not shown).

FIG. 2 is a cross-sectional view of the motor chamber 4 of FIG. 1 as viewed from above (in the axial direction).
A cylindrical stator 47, a rotor 8, and a crankshaft 10 are sequentially disposed on the inner periphery of the cylindrical sealed container 1, respectively.
The stator 47 is formed by laminating thin magnetic steel plates, and further winding a winding. The outer circumferential surface of the stator 47 is provided with second coolant passages 22 by notches at equal intervals. Each of the windings 47b is provided.
On the other hand, arc-shaped balance weights 25 are fixed to both side surfaces of the rotor 8 using fixing rivets, and notches 37 are provided at equal intervals on the outer peripheral surface. In FIG. 2, a part of the side plate of the rotor 8 is cut away so that the iron core of the rotor 8 can be seen.

FIG. 3 is a cross-sectional view of the rotor 8 as seen from the axial direction.
This rotor 8 is formed by laminating thin magnetic steel plates to form a 6-pole rotor core, and a plate-like permanent magnet 31 is embedded in a substantially cylindrical rotor 8. Further, a crankshaft 10 that is a rotating shaft member that passes through the center of the rotor 8 in the axial direction is provided.
And the nonmagnetic part 32 which consists of the space extended toward a rotor outer periphery from the permanent magnet mounting position in the edge part of the circumferential direction of each permanent magnet 31 is provided.
In this embodiment, since it is described as an electric motor of a compressor, the crankshaft 10 is arranged at the center of the rotor 8. However, in the case of a normal electric motor, the rotating shaft is arranged at the center of the rotor 8. Moreover, the shape of the permanent magnet 31 is a rectangle.

  In addition, the outer end portions of the magnetic body portions 33 located outside the permanent magnets 31 are connected to each other, and a bridge portion 34 made of a magnetic body located outside the nonmagnetic portion 32 is provided, and the nonmagnetic portion A reinforcing rib portion 35 made of a magnetic material is provided between the 32 members and extending in the radial direction. The magnetic body portion 33, the bridge portion 34, and the reinforcing rib portion 35 are formed by being simultaneously punched when the magnetic steel plate is press-formed into the shape of the rotor 8. Further, a hole 36 is provided at substantially the center of the magnetic body portion 33 so that the balance weight 25 described in FIG. 2 is fixed and a rivet for fixing the laminated steel plates is inserted.

As described in the background art section, in such a rotor shape, when the adjacent permanent magnets 31 are close to each other, the permanent magnets cause direct magnetic flux leakage. The structure is as far apart as possible.
Moreover, in the conventional rotor shape, the nonmagnetic part 32 which prevents the short circuit of magnetic flux is provided in the both ends of each permanent magnet 31, However, The stator (not shown) which opposes from the bridge part 34 which consists of a magnetic body. ) Occurs, and there is a problem that the cogging torque due to this leakage flux increases.

For this reason, in the present invention, as shown in FIG. 3, by providing a notch 37 on the outer peripheral surface of the rotor 8 that faces the inner peripheral surface of the stator with a gap and that corresponds to the nonmagnetic portion 32, The feature is that the gap between the peripheral surface and the bridge portion 34 is widened to reduce magnetic flux leakage, and noise due to cogging torque is reduced.
Further, by providing the notch 37, the leakage magnetic flux through the stator is reduced, and as a result, the arc-shaped salient pole portion 33a formed in the magnetic body portion 33 generates the permanent magnet 31. The magnetic force is concentrated on the salient pole portion 33a to increase the efficiency of the electric motor.

  In order to confirm the effect of reducing the cogging torque of the notch 37, a rotor having the following six shapes is created, and an electric motor is configured by combining these with one type of stator, and each rotor is driven separately. The induced voltage generated in the stator winding and the value of the cogging torque were measured.

  4A and 4B are diagrams showing four rotor shapes, and FIG. 4A is a shape without a cutout portion and a salient pole portion (a shape based on the concept of Japanese Patent Application Laid-Open No. 2002-44888), and FIGS. ) Are provided with salient pole parts by notches, and the angles (salient pole angles) from the rotation center that define the outer peripheral width of the salient pole parts are 35 °, 37.5 °, 40 °, 42, 5 °, 45, respectively. The shape is °. The rotors (A) to (F) are model Nos. Called 1-6.

  Each of the rotors has a maximum diameter of 68.8 mm, a hole diameter of the rotating shaft portion is 26 mm, and the depth of the notch of the rotor (B) to (F) (saliency pole portion). Is 1.4 mm in each case. Further, although the permanent magnet is not shown in the figure, a rotor equipped with the permanent magnet is used in actual measurement.

As shown in FIG. 3, the depth dimension b of the rotor notch 37 (between the non-magnetic part 32 and the notch 37) a (at least) (b) (between the nonmagnetic part 32 and the notch 37). The rotor structure is determined so that the maximum depth) increases. This is because the magnitude of the magnetic flux of the bridge portion 34 made of a magnetic material increases in proportion to the width when the circumferential length is constant, and in order to reduce this influence, the stator ( This is because the distance from the inner peripheral surface (not shown), that is, the depth dimension b of the notch portion 37 must be increased in proportion to the thickness dimension of the bridge portion 34.
In the present embodiment, the thickness dimension a of the bridge portion 34 is set to 0.5 mm, the depth dimension b of the notch portion 37 is set to 1.4 mm, and the notch portion depth dimension is approximately three times that of the bridge portion. .

FIG. 5 shows the measurement results of the four rotors. It is the table | surface showing the induced voltage and cogging torque value for every, (B) graphed FIG. 5 (A).
In FIG. 5A, models 1 to 6 are displayed in the horizontal direction, the maximum value [V] and effective value [Vrms] in the induced voltage (for one phase) in the vertical direction, and the induced voltage (between the two phases). ), The maximum value [V] and the effective value [Vrms], and the cogging torque value [Nm] are the measurement items, and the results are shown in the corresponding columns of the table.
The induced voltage may be measured only for one phase of the winding, but the winding induced voltage between the two phases was also measured in order to correspond to the actual driving situation.

In the graph of FIG. 5 (B), the effective value [Vrms] of the induced voltage is set to two types of scales between two phases and one phase in the left vertical direction, and the cogging torque value [Nm] scale is set in the right vertical direction. , Each rotor model No. Represents. Here, model no. 1 shows a conventional rotor structure as a reference for comparison. Reference numerals 2 to 6 show rotor structures having notches according to the present invention, and salient pole angles of 35 °, 37.5 °, 40 °, 42, 5 °, and 45 °, respectively.
The dotted line is a graph representing the induced voltage (between two phases), the solid line is the induced voltage (for one phase), and the thick line is the cogging torque value.

  Ideally, the rotor has a high induced voltage and a low cogging torque value, but in reality, the induced voltage and the cogging torque value tend to be proportional. Therefore, as a practical design, a rotor shape having a cogging torque value as small as possible and a small decrease in induced voltage is selected.

Therefore, in the present invention, model No. A shape having a cogging torque value lower than 1 (a rotor having a conventional structure) is determined to be effective in reducing noise.
Model No. 1, the cogging torque value at the induced voltage (for one phase) is 0.295 [Nm]. It was found that the salient pole angle was around 40 ° with 4 as the center. When calculated backward from the graph of the cogging torque value, it can be read that the salient pole angle is in the range of approximately 37 ° to 42.5 °. Therefore, this angle range is the range of the effect of reducing the cogging torque. Among them, it was found that the effect of reducing the cogging torque is greatest when the salient pole angle is 40 ° compared to other salient pole angles.

Model No. with the lowest cogging torque value. 4 (0.157 Nm), model no. Compared to 1 (0.259 Nm), the cogging torque is improved by 0.102 Nm, which is an improvement ratio of 39.4%. The induced voltage (for one phase) at this time is model No. Compared to 1 (76.5 Vrms), the decrease is only 0.6 Vrms, and the reduction rate is 0.8%. Therefore, a significant cogging torque can be improved with almost no decrease in the induced voltage.
Note that the induced voltage (between two phases) has almost the same tendency as the induced voltage (for one phase) as shown in the dotted line graph of FIG. 5B, and the same effect can be obtained in the actual driving of the electric motor. .

  FIG. 6 shows cogging torque measurement data. The vertical axis represents torque [Nm], and the horizontal axis represents the electrical angle. 1, 2, 4, and 6 are extracted as graphs of cogging torque values. Each model No. Since the maximum values on the plus side and the minus side of the torque value are the same, the values on the plus side are shown in FIG.

  The notch of the rotor according to the present invention has other effects in addition to the effect of reducing the cogging torque. For example, when the compressor shown in FIG. 1 is used, the high-pressure refrigerant gas filled in the oil reservoir 6 passes between the stator 47 and the rotor 8 from the oil reservoir 6 as indicated by the arrows in FIG. However, the cooling effect is improved because the notched portion of the present invention can serve as a refrigerant passage and promote smooth refrigerant circulation when cooling.

Although not shown, another effect is that the rotor 8 can be easily positioned in the magnetizing operation of the rotor 8 in the compressor manufacturing process. If a jig that fits into the notch of the rotor 8 is inserted from the side surface (rotation axis direction) of the rotor 8, the rotor 8 can be fixed at a predetermined rotation angle, so that positioning becomes easy and the magnetizing operation is smooth. Can be done.
As a matter of course, the present invention is applicable not only to a compressor but also to a general electric motor, and has the above-described effects.

It is sectional drawing which shows the Example of the compressor carrying the electric motor by this invention. It is sectional drawing which looked at the electric motor chamber of the compressor from upper direction (axial direction). It is sectional drawing which looked at the rotor of the electric motor by this invention from the axial direction. It is sectional drawing for demonstrating each rotor for performing a comparative experiment. It is data of a measurement result, (A) is represented as a table, and (B) is a graph of this data. It is a graph which shows the waveform of the cogging torque for every rotor which performed the comparative experiment. It is sectional drawing which shows the conventional electric motor. It is sectional drawing which shows the rotor of the conventional electric motor. It is sectional drawing which shows the other conventional rotor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 2 Main frame 3 Compressor room 4 Electric motor room 5 Sub frame 6 Oil reservoir room 8 Rotor 9 Turning shaft 10 Crankshaft 11 Electric motor part 12 Discharge chamber 13 Compression part 14 Fixed scroll 14a Each wrap 15 Turning scroll 16 Compression space DESCRIPTION OF SYMBOLS 17 Oldham ring 18 Intake pipe 19 Discharge hole 20 Refrigerant passage 21 Discharge pipe 22 Refrigerant passage 25 Balance weight 30 Oil drain guide 31 Permanent magnet 32 Nonmagnetic part 33 Magnetic body part 33a Salient pole part 34 Bridge part (bridge part)
35 Reinforcement rib part 36 Hole 37 Notch part 40 Salient pole angle 47 Stator 47a Insulator 47b Winding

Claims (4)

The stator is opposed to the stator inner circumferential surface with a gap, and a plurality of permanent magnets are disposed inside the iron core, and are continuous to the circumferential end of the permanent magnet and extend to the vicinity of the surface. In an electric motor composed of a rotor having a magnetic part,
An electric motor comprising a notch portion for reducing magnetic flux leakage on an outer peripheral surface of the rotor corresponding to the non-magnetic portion.   The depth dimension of the said notch part is made larger than the thickness dimension of the bridging part which consists of the said rotor core from which the gap between the said clearance gap and the said nonmagnetic part becomes thickness. Electric motor.   The number of poles of the rotor is six, and the salient pole angle is an angle from the rotation center that defines the outer circumferential width of the arc-shaped salient pole part formed on the outer circumferential surface of the rotor by forming the notch part. The electric motor according to claim 1, wherein the angle is about 40 °.   The number of poles of the rotor is six, and the salient pole angle is an angle from the rotation center that defines the outer circumferential width of the arc-shaped salient pole part formed on the outer circumferential surface of the rotor by forming the notch part. The electric motor according to claim 1 or 2, wherein an angle range of 37 ° to 40.5 ° is set.

Images