JP2005354798A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor which practically satisfies an increase in an output torque and a reduction in cogging torque, and which is equipped with a rotor good in assembling property. <P>SOLUTION: In the electric motor, plate-like permanent magnets 31 are embedded in the cylindrical rotor 8, a rotary shaft 1 is provided as axially penetrating through the center of the rotor 8, and a non-magnetic part 32 comprising a space extending from the permanent magnet fitting position to the rotor outer periphery is provided to the end in the peripheral direction of the permanent magnets 31. The mutual outer ends of magnetic materials 33 located on the outside of respective permanent magnets 31 are connected to each other, bridges 34 comprising magnetic bodies located on the outside of the non-magnetic parts 32 are provided, and reinforcing ribs 35 are provided with magnetic bodies between the mutual non-magnetic parts 32 extending radially. Notched grooves 37 are formed on the outer peripheral surface of the rotor 8 corresponding to the non-magnetic parts 32, and projections 2 are provided as projecting the reinforcing ribs 35 from the bottom center of the notched grooves 37 to the outer peripheral direction of the rotor 8. <P>COPYRIGHT: (C)2006,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 torque is improved.

  Conventionally, an inner rotor type electric motor has a structure in which a rotor is provided on the inner periphery of a stator as shown in FIG. 5, 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. 6, 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 have a substantially square shape, and are arranged and fixed so as to surround the rotating shaft 85 at the orthogonal position and at the center 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. Thus, the structure is such that the combined torque for the three phases is also increased (see, for example, Patent Document 1).

  However, in the rotor shape of FIG. 6, both ends of each permanent magnet are arranged close to each other, and since there is no means for preventing a short circuit of magnetic flux at both ends of the permanent magnet, 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. 7 is disclosed.

The rotor of FIG. 7 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. 7, 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.

  Incidentally, as shown in FIG. 7, there is a structure shown in FIG. 8 as a structure for improving the torque of the rotor provided with the nonmagnetic portion 93. This structure has a structure in which the main magnetic flux amount is increased without reducing the reluctance torque by cutting and removing the bridge portion 94 of FIG. 7 (see, for example, Patent Document 3).

However, the structure shown in FIG. 8 has a structure in which the inner core portion 61 and the outer core portion 62 are divided, and thus has the following drawbacks in assembly. That is, since the magnet 65 cannot be press-fitted as in the prior art, it takes time to position the magnet 65. Further, the inner iron core portion 61 and the outer iron core portion 62 are sandwiched between end plates (not shown) provided at both ends of these iron cores, and caulking pins 7 and 8 are inserted through the iron core and the end plates from the rotation axis direction. It is fixed with. Therefore, the roundness of the assembled rotor may not be maintained due to dimensional errors or assembly errors of the holes through which the crimping pins 7 and 8 are inserted or the crimping pins themselves, and there is a problem that the assembling property is poor.
Further, as can be seen from the example of the rotor in FIGS. 6 and 7, in general, in an electric motor, an increase in output torque and a reduction in cogging torque are in a contradictory relationship, and it is difficult to satisfy both practically. there were.

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

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

JP-A-10-164784 (page 3, FIG. 1)

  An object of the present invention is to solve the above-described problems, and to provide an electric motor having a rotor with good assemblability and practically satisfying an increase in output torque and a reduction in cogging torque.

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 with a non-magnetic part that extends to the vicinity of the surface continuously to the part,
A notch groove for reducing magnetic flux leakage is provided on the outer peripheral surface of the rotor corresponding to the nonmagnetic portion, and a protrusion for increasing the output torque is provided from the center of the bottom of the notch groove toward the outer periphery.

According to the motor according to the invention,
According to the first aspect of the present invention, a notch groove for reducing magnetic flux leakage is provided on the outer peripheral surface of the rotor corresponding to the non-magnetic portion, and the output torque is increased from the center of the bottom of the notch groove toward the outer periphery. By providing this, an increase in output torque and a reduction in cogging torque can be satisfied practically. Further, since it is not necessary to divide the magnetic steel plate in order to improve the output torque value, the assembling property of the rotor is not impaired.

  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 cross-sectional view of a rotor 8 provided in an electric motor according to the present invention 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. Moreover, the rotating shaft 1 which penetrates the center of the rotor 8 to an axial direction is provided.
And the nonmagnetic part 32 which consists of the space extended toward the rotor outer periphery from the permanent magnet mounting position in the edge part of the circumferential direction of each rectangular permanent magnet 31 is provided.

  In addition, the outer end portions of the magnetic body portions 33 positioned on the outer sides of the permanent magnets 31 are connected to each other, and a bridge portion 34 made of a magnetic body is provided on the outer side of the nonmagnetic portion 32, and the nonmagnetic portion Reinforcing rib portions 35 made of a magnetic material are provided between 32 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. In addition, a hole 36 is provided at substantially the center of the magnetic part 33 so that a rivet for fixing the stacked 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 the leakage flux increases.

For this reason, in the present invention, as shown in FIG. 1, by providing a notch groove 37 on the outer peripheral surface of the rotor 8 corresponding to the nonmagnetic portion 32, the gap between the inner peripheral surface of the stator and the bridge portion 34 is widened. Leakage is reduced and noise caused by cogging torque is reduced.
By providing this notch groove 37, leakage magnetic flux through the stator is reduced, and as a result, the magnetic force generated from the permanent magnet 31 is generated by the arc-shaped salient pole portion 33a formed in the magnetic body portion 33. The structure is such that the efficiency of the electric motor is increased by concentrating on the salient pole portion 33a.

The position of the notch groove 37 is determined by a salient pole angle that is an angle from the rotation center that defines the outer peripheral width of the arc-shaped salient pole part 33 a formed on the outer peripheral surface of the rotor 8. That is, when the salient pole angle is 38 ° and the number of magnetic poles is 6 poles, (360 ° −38 ° × 6 poles) ÷ 6 poles, the salient pole angle is 22 ° and the salient pole angle is 38 °. Alternatingly arranged with the poles 33a.
And the non-magnetic part 32 is provided in the steel plate of the inner peripheral side of this notch groove 37 by the arrangement | positioning which clamps the reinforcement rib part 35 mentioned above, and the steel plate between the notch groove 37 and the non-magnetic part 32 exists. A bridge portion 34 is provided.

  The present invention is characterized in that the protrusion is extended from the center of the bottom of the notch groove 37, that is, the protrusion 2 in which the reinforcing rib portion 35 extends in the outer peripheral direction of the rotor 8 is provided. The height of the protrusion 2 is the same as the height of the salient pole portion 33 a, and the tip of the protrusion 2 is formed in an arc shape so as to correspond to the outer periphery of the rotor 8. The width of the protrusion 2 is defined as W.

  Since the projection 2 can increase the q-axis inductance and increase the reluctance component when the axis shifted by 90 ° in electrical angle is the q-axis with the central axis of the magnetic pole as the d-axis, the reluctance component can be increased. Can be improved. However, as described in the background art section, it is necessary not to increase the cogging torque as much as possible.

  As a result of various experiments, there is a certain relationship among the width W of the protrusion 2, the cogging torque, and the output torque of the electric motor. By setting the width W of the protrusion 2 to a specific range of dimensions, the cogging torque It has been found that the output torque of the motor can be improved without increasing as much as possible.

  In order to confirm the effect of improving the output torque by the protrusions 2, the following six rotors having different widths W of the protrusions 2 were created, and the motor was configured by combining these with one type of stator. Then, each rotor was rotated using another driving means, and the induced voltage generated in the stator winding, the cogging torque value, and the output torque value were measured.

FIG. 1 shows the structure of the rotor according to the present invention described above, and the width W (unit: mm) of the protrusion 2 is set to no protrusion (w = 0), w = 1.5, w = 2.0, w. Six rotors with 2.5 = w, 3.0 = w, and 3.5 = w were created.
Each rotor has a maximum diameter of 68.8 mm, a hole diameter of the rotating shaft portion is 26 mm, and a salient pole angle which is an angle in the circumferential direction of the salient pole portion 33a is 38.0 °. The depth of the notch groove 37 of the rotor (height of the salient pole portion) is 1.4 mm.

As shown in FIG. 1, at least the thickness dimension b of the rotor notch groove 37 (between the nonmagnetic part 32 and the notch groove 37) a (b) (between the nonmagnetic part 32 and the notch groove 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 groove 37 must be increased in proportion to the thickness dimension of the bridge portion 34.
In this embodiment, the thickness dimension a of the bridge portion 34 is 0.5 mm, the depth dimension b of the notch groove 37 is 1.4 mm, and the notch groove depth dimension is approximately three times that of the bridge portion. .

FIG. 2 shows the measurement results of six rotors having different widths W of the protrusions 2. FIG. 2A is a table showing the induced voltage, cogging torque value, and output torque value for each protrusion width, and FIG. 2 (A) is graphed.
In FIG. 2 (A), the width of the protrusion in the horizontal item, the maximum value (V) and effective value (Vrms) in the induced voltage (for one phase) in the vertical direction, and the induced voltage (between two phases). The maximum value (V) and effective value (Vrms), and the cogging torque value (Nm) and the output torque value (Nm) are the measurement items, and the results are listed 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 rotation state.

  In the graph of FIG. 2B, the left vertical direction is the output torque value (Nm), the right vertical direction is the cogging torque value (Nm), and the horizontal direction is the protrusion width (mm) of each rotor. ing. Here, “no protrusion” indicates a rotor structure as a reference for comparison.

  Ideally, the induced voltage and the output torque value are high and the cogging torque value is low as the rotor characteristics, but in reality, the output torque value and the cogging torque value tend to be proportional. . Therefore, as a realistic design, a rotor shape having the highest possible output torque value and the smallest possible cogging torque value is selected.

For this reason, in the present invention, it is determined that a shape that has an output torque value sufficiently higher than “no protrusion” and that does not significantly increase the cogging torque value is effective.
In the graph of FIG. 2B, the output torque value is higher in the structure with protrusions (w = 1.5 to w = 3.5) than in the case of “no protrusion”. However, if the protrusion width becomes wider than w = 3.0, the output torque value decreases while the cogging torque value increases, which is not a practical allowable range. Accordingly, it has been found that the protrusion width w = 1.5 to w = 3.0 contributes to the increase of the output torque value and the cogging torque value does not increase significantly.

  2A shows a unit torque value that is a ratio of the output torque value to the cogging torque value in order to objectively determine the effect when the output torque value and the cogging torque value are both compatible. It is described. This unit torque value is obtained by dividing the output torque value by the cogging torque value. For example, in the case of “no protrusion”, the unit torque value = 10.060 ÷ 0.157 = 64.08, which is the comparison value. The standard. Similarly, the cases of other protrusion widths are calculated and listed in the corresponding table column. This unit torque value indicates that the larger the value, the greater the effect.

  In the unit torque value of FIG. 2A, the value larger than the case of “no protrusion” (64.08) indicates a case where the protrusion width w = 1.5 (64.28), and w = 2. 0 (64.45), and when the protrusion width is within this range, it indicates that the increase rate of the output torque value is higher than the increase rate of the cogging torque value, and is very effective. Is shown. It can also be seen that the effect is highest when the protrusion width is 2.0 mm.

  As described above, the output torque value can be improved by providing a notch groove corresponding to the magnetic pole on the outer periphery of the rotor and providing a protrusion at the center of the notch groove. Further, since the magnetic steel plate constituting the rotor is not divided into a plurality of pieces as in the conventional structure of FIG. 6, the assemblability is not impaired even if the output torque value is improved. In addition, by setting the width of the protrusion in the range of 1.5 mm to 3.0 mm, it is possible to improve the output torque value and to suppress an increase in the cogging torque value. Further, the case where the protrusion width is 2.0 mm is most effective when both the output torque value and the cogging torque value are made compatible.

FIG. 3 is a diagram showing detailed dimensions (unit: millimeters) of a magnetic steel sheet used for a rotor having a protrusion (W = 2 mm) according to the present invention, FIG. 3 (A) is a plan view, and FIG. 3 (B). These are the A section detailed enlarged views in FIG. 3 (A).
In addition, since this electromagnetic steel plate is formed of a silicon steel plate having a thickness of 0.35 mm, and a rotor using this electromagnetic steel plate is used as an electric motor of a hermetic compressor, as shown in FIG. 6 holes for circulating the refrigerant are provided to cool the rotor with the refrigerant.

4 is an explanatory view showing a rotor created using the electrical steel sheet shown in FIG. 3, FIG. 4 (A) is a side sectional view, and FIG. 4 (B) is a view from the front (rotation axis direction). FIG.
This rotor has a structure in which laminated electromagnetic steel plates are sandwiched from both sides by end plates made of stainless steel, rivets are inserted, and fixed by caulking. Note that a balancer is provided on one of the side surfaces so as to balance the rotational load when used in a compressor. All units are millimeters.

The structure shown in FIGS. 3 and 4 (excluding the balancer) has the same structure and dimensions as the data shown in FIG. 2, and the data was collected by changing only the width of the protrusions.
Moreover, the permanent magnet used for this rotor is a rare earth magnet of 69 mm × 20 mm and a plate thickness of 2.8 mm, and has the characteristics shown in FIG.

It is sectional drawing which shows the Example of the rotor of the electric motor by this invention. It is data of a measurement result, (A) is represented as a table, and (B) is a graph of this data. It is a figure which shows the detailed dimension of the electromagnetic steel plate by this invention, (A) is a top view, (B) is the A section detailed enlarged view in FIG. 3 (A). It is explanatory drawing which shows the rotor by this invention, (A) is a sectional side view, (B) is explanatory drawing seen from the front (rotation axis direction), (C) is a characteristic table | surface of a magnet. 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. It is sectional drawing which shows the conventional rotor provided with the projection part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Protrusion 8 Rotor 31 Permanent magnet 31 Each permanent magnet 32 Nonmagnetic part 33 Magnetic body part 33a Salient pole part 34 Bridge part 35 Reinforcement rib part 36 Hole 37 Notch groove

Claims (1)

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,
A notch groove for reducing magnetic flux leakage is provided on the outer peripheral surface of the rotor corresponding to the nonmagnetic part, and a protrusion for increasing output torque is provided from the bottom center of the notch groove toward the outer periphery. Features an electric motor.

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