JP4415634B2 - Permanent magnet rotating electric machine - Google Patents

Description

  The present invention relates to a permanent magnet type rotating electrical machine such as an electric motor, and more particularly to a permanent magnet type rotating electrical machine designed to reduce cogging torque.

  In a general configuration of a permanent magnet type rotating electric machine, a rotor is disposed in a stator. The stator is provided with a plurality of stator windings on the inner periphery of a cylindrical stator core to form a plurality of magnetic poles. The rotor is provided with a rotor core so that the rotor can be rotated about the center of the stator, and a permanent magnet is provided on or inside the rotor core. The permanent magnet has alternating N and S poles. It is arranged to line up. In this rotating electrical machine, the rotor is rotated around the rotation axis by appropriately energizing the stator windings to form a rotating magnetic field.

  In the permanent magnet type rotating electrical machine as described above, a fluctuation in rotational torque called cogging torque occurs. The cogging torque not only generates vibration and noise, but also causes a decrease in the control performance of the rotating electrical machine.

Conventionally, in order to reduce the cogging torque, a plurality of permanent magnets are arranged in the axial direction of the rotor core and shifted in the circumferential direction of the rotor core. The permanent magnets are aligned with the stator core surface at a skew angle θ _m (hereinafter referred to as a “step skew angle”) so that the circumferential position of the permanent magnet is shifted depending on the axial position of the rotor core. For example, see Patent Document 1).

As the step skew angle θ _m (mechanical angle), a theoretically obtained angle (hereinafter referred to as a theoretical angle) is used. The theoretical angle (mechanical angle) at which the cogging torque is minimized is determined by (360 / the least common multiple of the number of stator magnetic poles and the number of rotor magnetic poles) / the number of stages of the axial permanent magnet. Stator poles of the rotating electric machine 12, when the rotor poles 8, a number of permanent magnet 2, the row-to-row skew angle theta _m 7.5 ° (30 ° in electrical angle theta _e. Incidentally, (Calculated from a relational expression of electrical angle = mechanical angle × number of poles / 2) (for example, see Patent Document 2).

However, when the step skew angle θ _m is theoretically determined as described above and applied to an actual rotating electrical machine, it is considered that the reduction of the cogging torque is still insufficient. The reason is that the axial leakage magnetic flux is generated by adopting the step skew, but the influence of magnetic saturation due to this leakage magnetic flux is not taken into consideration. The leakage magnetic flux that causes the cogging torque includes the stepped portion of the permanent magnet and the leakage magnetic flux inside the rotor core, but the leakage magnetic flux inside the stator core is the main cause of the cogging torque.

Japanese Utility Model Laid-Open Publication No. 61-17876 (page 4-6, FIG. 1-6) Japanese Unexamined Patent Publication No. 2000-308286 (page 3-4, FIG. 2, FIG. 3)

  As described above, the conventional rotating electric machine that employs the step skew has a problem that the cogging torque cannot be sufficiently reduced because the theoretical angle is adopted as the step skew angle.

  The present invention solves the above-described problems, and can reduce the cogging torque more efficiently than the case where the theoretical angle is adopted as the step skew angle, and can also reduce the torque ripple. A rotating electrical machine is provided.

In the permanent magnet type rotating electrical machine according to the present invention, two stages of permanent magnets are provided in the axial direction on the outer peripheral surface of the rotor core, and the step skew angle θe is provided in the circumferential direction of the rotor core between the two stages of the permanent magnets. (Electric angle) Rotors that are staggered,
A cylindrical fixed iron core is divided into upper, middle, and lower blocks, and no stage skew is applied between the upper block and the lower block, and the middle stage with respect to the upper block and the lower block. the block row skew applied to, placing the rotor therein, comprising a stator winding stator and provided for generating a rotating magnetic field for rotating the rotor,
The lower limit value of the step skew angle θe is a theoretical angle θs (electrical angle) obtained by the following formula (1),
From the relationship between the cogging torque when the rotor is step skewed and the step skew angle θe, the range of the step skew angle θe that is equal to or less than the cogging torque at the theoretical angle θs is obtained, and the upper limit value of the step skew angle θe is obtained. Is the maximum value in the above range,
The step skew angle θe of the rotor core is set to be larger than the lower limit value and smaller than the upper limit value ,
The electrical angle of the step skew of the stator core is set to a value that is ½ of the theoretical angle θs .
(180 × number of rotor magnetic poles / number of stator magnetic poles and least common multiple of rotor magnetic poles) / 2 (electrical angle) (1)

According to the permanent magnet type rotating electrical machine of the present invention, the cogging torque fundamental wave component can be reduced to a value lower than or less than the case where the step skew angle θe is set to the theoretical angle θs, and the torque ripple can be further reduced . Ru can be reduced harmonic components of the cogging torque.

Hereinafter, a preferred embodiment of a permanent magnet type rotating electrical machine according to the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1, 2, 3 and 4 are a perspective view, a cross-sectional view, a side view and a plan view showing the first embodiment of the present invention, and FIGS. 1 to 3 show the arrangement of permanent magnets in the rotor. Is described.

As shown in FIGS. 1 to 3, the rotor 30 has an upper stage permanent magnet 32 a and a lower stage permanent magnet 32 b attached to the outer peripheral surface of the rotor core 31, and is circular by a stage skew angle θ _e (electrical angle). The N poles and the S poles are alternately arranged so as to be shifted in the circumferential direction. The number of magnetic poles of the rotor 30 is 8, and the number of stages of permanent magnets is 2.

  As shown in FIG. 4, the stator 20 has a plurality of stator windings 22 provided on the inner periphery of a cylindrical stator core 21 to form a plurality of magnetic poles. The rotor 30 is provided with a rotor core 31 so as to be able to rotate with the center of the stator 20 as a rotation axis. By appropriately energizing the stator winding 22 and forming a rotating magnetic field, the rotor 30 is It rotates around the axis of rotation.

As shown in FIGS. 2, 3 and 4, the lower permanent magnet 32b is shifted in the circumferential direction by 36 ° in electrical angle (8 ° in mechanical angle) with respect to the reference line A of the upper permanent magnet 32a. Yes. That is, the step skew angle θ _e is calculated by the following formula: (180 × number of rotor magnetic poles / number of stator magnetic poles and least common multiple of the number of rotor magnetic poles) / 2 (theoretical angle θ _s ( 30 °). As described above, the equation representing the step skew angle in terms of the mechanical angle is (360 / the least common multiple of the number of stator magnetic poles and the number of rotor magnetic poles) / 2 (the number of steps of the axial permanent magnet). The required theoretical angle (mechanical angle) is larger than 7.5 °.

The step skew angle θ _e is larger than the theoretical angle θ _s and is set to be equal to or smaller than the maximum value of the step skew angle θ _e obtained according to the magnetic characteristics of the stator core 21 and the rotor core 31 as described later. The cogging torque can be reduced more efficiently than the case where the step skew angle θ _{e is set} to the theoretical angle θ _s, and the torque ripple can also be reduced. Hereinafter, it describes the relationship between the cogging torque and torque ripple and row-to-row skew angle theta _e, in this embodiment, indicate that it is possible to reduce the cogging torque and torque ripple.

  FIGS. 5 and 6 performed a three-dimensional magnetic field analysis on the rotor and the rotating electrical machine (the number of rotor magnetic poles is 8, the number of stator magnetic poles is 12, and the number of permanent magnet stages is 2) shown in FIGS. The result is shown.

FIG. 5 shows the result regarding the cogging torque fundamental wave component, and FIG. 6 shows the result regarding the second harmonic of the cogging torque. The ratio of the cogging torque when the step skew is applied to the cogging torque when there is no step skew, respectively. As for the relationship between the cogging torque ratio and the step skew angle (electrical angle) θ _e , when the magnetic characteristic of the stator core 20 is ideal (magnetic characteristic A), the magnetic characteristic deteriorates during the machining process. The case (magnetic property B) and the case where the magnetic property is further deteriorated by machining (magnetic property C) are shown.

  FIG. 7 shows magnetic characteristics A, B, and C (relationship of BH characteristics) of the stator core 20 used for the analysis. The magnetic flux density ratio in the figure represents the ratio to the reference value with the saturation magnetic flux density of the material having the magnetic property A as the reference value. The magnetic characteristic A is a magnetic characteristic corresponding to the catalog value, and shows the case where there is no influence of processing, the magnetic characteristic B corresponds to the actual machine state, and the magnetic flux density ratio in the vicinity of the magnetic force H = 1000 A / m is the magnetic characteristic A. The magnetic characteristic C has a characteristic in which the magnetic flux density ratio in the vicinity of the magnetizing force H = 1000 A / m is reduced by about 40% compared to the magnetic characteristic A. is there.

From FIG. 5, for the cogging torque fundamental wave component, the step skew angle θ _{e at} which the cogging torque ratio becomes the minimum as the magnetic characteristics of the stator core gradually deteriorate from the magnetic characteristics A to the magnetic characteristics B and C. (This is because, as described above, when the step skew is employed, axial leakage magnetic flux is generated inside the stator core). That is, with the magnetic properties of the stator core is degraded, row-to-row skew angle theta _e cogging torque is minimized is larger than the theoretical angle of 30 °. Thus, the magnetic characteristic B, when the theoretical angle of 30 ° the row-to-row skew angle theta _e, whereas becomes cogging torque ratio (about 0.18) at a point (1), beyond the theoretical angle of 30 ° by less cogging torque ratio at a point (1) (0.18) or less to become the maximum value of the row-to-row skew angle theta _e ((row-to-row skew angle theta _e in point 2) (about 37 °)), The fundamental component of the cogging torque can be reduced to a value lower than or lower than that when the theoretical angle is 30 °. Similarly, in the magnetic properties C, (3) the cogging torque ratio at a point (about 0.23) or less and consisting stage skew angle theta maximum value of _e ((4-row skew angle at a point) theta _{e =} about 43 °) or less, the fundamental wave component of the cogging torque can be reduced to a value lower than or less than the theoretical angle of 30 °.

In the above, the case where the ratio between the number of rotor magnetic poles and the number of stator magnetic poles is 2: 3 has been described. As is apparent from the above description of FIG. 5, the number of rotor magnetic poles and the number of stator magnetic poles in case where the ratio is a predetermined value, the lower limit of stage skew angle theta _e to set the actual machine, and a larger value than the theoretical angle theta _s, the upper limit of the row-to-row skew angle theta _e, the cogging torque ratio and the stepped skew angle theta from the relationship between _e, depending on the magnetic properties of the stator core (BH property), by less than the maximum value of the row-to-row skew angle theta _e to be less cogging torque ratio at the theoretical angle theta _s, the theoretical angle theta _s The fundamental wave component of the cogging torque can be reduced to a value lower than or lower than the above case.

Next, from FIG. 6, regarding the second harmonic component of the cogging torque, the cogging torque ratio becomes minimum at 1/2 or 3/2 of the theoretical angle θ _s (electrical angle 15 °, electric angle 45 °). I understand. This cogging torque harmonic component is due to the fact that less susceptible to axial leakage flux (influence of magnetic saturation), theory stage skew angle theta _e in reducing cogging torque second harmonic component It is considered that the angle θ _s should be 1/2 or 3/2.

On the other hand, the relationship between the torque ripple during energization and the stage skew angle is generally examined using a winding coefficient called a skew coefficient. The skew coefficient κ _sv for the ν th harmonic component in the rotating electrical machine is given by the following equation (2). Where γ is a skew angle.

κ _sv = sin (νγ / 2) / (νγ / 2) (2)

Here, _assuming that the step skew angle is γ _d , γ _d = γ / 2. Therefore, the skew coefficient κ _dsv when the step skew is employed is given by the following equation (3).

κ _dsv = sin (νγ _d ) / (νγ _d ) (3)

  In addition, the torque ripple of the permanent magnet type rotating electrical machine is dominated by a component 6 times the power frequency (hereinafter referred to as 6f component). Generally, the torque ripple 6f component is generated due to the fifth and seventh harmonic components.

FIG. 8 is a diagram showing fifth-order and seventh-order skew coefficients with respect to the step skew angle γ _d calculated from the above equation (2). The degree of influence of the fifth and seventh harmonic components on the torque ripple 6f component is considered to be approximately related to the reciprocal of the square of the order, and the degree of influence of the fifth component is 1/5 ² = 0.04, 7 The degree of influence of the next component is considered to be 1/7 ² = 0.02.

FIG. 9 is a diagram showing the torque ripple 6f component coefficient with respect to the step skew angle in consideration of the skew coefficient of FIG. 8 and the degree of influence regarding the fifth and seventh order torque ripple 6f components. From the figure, the torque ripple 6f component coefficient is smaller than the torque ripple 6f component coefficient at 30 ° when the step skew angle γ _d exceeds 30 °. Therefore, it is considered that the torque ripple 6f component can be reduced by setting the step skew angle γ _d to be 30 ° or more which is the theoretical angle θ _s with respect to the cogging torque fundamental wave component.

Embodiment 2. FIG.
10 is a perspective view showing a second embodiment of the present invention, and FIG. 11 is a cross-sectional view in a direction perpendicular to the axial direction of the rotor core 31 of FIG.

As shown in FIG. 10, row-to-row skew angle theta _e of the upper permanent magnet 32a and the lower permanent magnet 32b is the same as in the first embodiment.

  Moreover, as shown in FIG. 11, the adhering position of the permanent magnets 32a, 32b in each stage with respect to the rotor core 31 for each of the two poles (N-S) is shifted, and the adjacent electrical angle for each two poles is One is close to 15 ° (mechanical angle 3.75 °) from the same angle, and the other is 15 ° (mechanical angle 3.75 °) away from the same angle.

According to this embodiment, it is possible to reduce the cogging torque fundamental wave component by stage skew angle theta _e of the upper permanent magnet 32a and the lower permanent magnet 32b, the permanent magnets 32a in each stage, two-pole 32b Cogging is performed by shifting the adhering position with respect to the rotor core 31 every (N-S) and moving the adjacent electrical angle of every two poles closer to 15 ° from the same angle, and 15 ° away from the other. Torque harmonic components can be reduced.

From the above, it is clear that the electrical angle shifted from the equal angle may be ½ of the theoretical angle θ _s .

Embodiment 3 FIG.
FIG. 12 is a perspective view showing a third embodiment of the present invention, FIG. 13 is a perspective view showing a configuration of the stator block in the third embodiment, and FIG. 14 is a block diagram of the stator in the third embodiment. It is sectional drawing.

In this embodiment, when the ratio between the number of rotor magnetic poles and the number of stator magnetic poles is a predetermined value, the lower limit value of the stage skew angle θ _e set in the actual machine is set to a value larger than the theoretical angle θ _s , the upper limit of the row-to-row skew angle theta _e, the relationship between the cogging torque ratio and row-to-row skew angle theta _e, depending on the magnetic properties of the stator core (BH property), the following cogging torque ratio at the theoretical angle theta _s stage configuration for the maximum value of the skew angle theta _e are the same as in the first embodiment.

12 and 13, the stator core is divided into an upper block 21a, a middle 21b, and a lower 21c, and the upper block 21a and the lower 21c and the middle are divided. of are those of the block 21b to-row skew shifted in the opposite direction along the circumference from one another, the row-to-row skew angle theta _e, it shifted in the opposite direction and a block 21a and 21c and the block 21b from the reference line a, respectively, stage The skew angle θ _e is a theoretical angle represented by ½ of the theoretical angle θ _s for the reduction of the cogging torque fundamental wave component.

FIG. 14 shows a case where the ratio of the number of rotor magnetic poles to the number of stator magnetic poles is 2: 3. As shown in FIG. 14, the electrical angle is 15 ° (mechanical angle is 3.75 °). By doing so, the harmonic component of the cogging torque can be reduced. Note that the height of the upper block 21a and the lower block 21c is ½ that of the middle block 21b.

1 is a perspective view showing a first embodiment of a permanent magnet type rotating electric machine according to the present invention. It is sectional drawing which shows Embodiment 1 of the permanent-magnet-type rotary electric machine which concerns on this invention. It is a side view which shows Embodiment 1 of the permanent magnet type rotary electric machine which concerns on this invention. It is a top view which shows Embodiment 1 of the permanent magnet type rotary electric machine which concerns on this invention. It is a figure which shows the result of the cogging torque fundamental wave component obtained by implementing a three-dimensional magnetic field analysis about the rotor and rotary electric machine shown in FIGS. It is a figure which shows the result of the cogging torque 2nd harmonic component obtained by implementing a three-dimensional magnetic field analysis about the rotor and rotary electric machine shown in FIGS. It is a figure which shows the magnetic characteristic of the rotor core used for the three-dimensional analysis. It is a figure which shows the 5th-order and 7th-order skew coefficient with respect to a stage skew angle. It is a figure which shows the torque ripple 6f component coefficient with respect to a step skew angle. It is a perspective view which shows Embodiment 2 of the permanent magnet type rotary electric machine which concerns on this invention. It is sectional drawing which shows Embodiment 2 of the permanent-magnet-type rotary electric machine which concerns on this invention. It is a perspective view which shows Embodiment 3 of the permanent magnet type rotary electric machine which concerns on this invention. FIG. 10 is a perspective view showing a configuration of a stator block in a third embodiment. FIG. 6 is a cross-sectional view of a stator block in a third embodiment.

Explanation of symbols

20 Stator, 21 Stator core, 21a Upper block,
21b Middle block, 21c Lower block, 22 Stator winding, 30 Rotor,
31 Rotor core, 32a upper permanent magnet, 32b lower permanent magnet.

Claims (1)

A rotor in which two stages of permanent magnets are provided in the axial direction on the outer peripheral surface of the rotor core, and the permanent magnets are shifted by a stage skew angle θe (electrical angle) in the circumferential direction of the rotor core between the two stages; ,
The cylindrical stator core is divided into upper, middle and lower blocks, and no stage skew is applied between the upper and lower blocks, and the upper block and the lower block are A stage skew is applied to the middle block, the rotor is disposed inside, and a stator provided with a stator winding that generates a rotating magnetic field that rotates the rotor is provided.
The lower limit value of the step skew angle θe of the rotor core is a theoretical angle θs (electrical angle) obtained by the following formula (1),
From the relationship between the cogging torque when the rotor is step skewed and the step skew angle θe, the range of the step skew angle θe that is equal to or less than the cogging torque at the theoretical angle θs is obtained, and the upper limit value of the step skew angle θe is obtained. Is the maximum value in the above range,
The step skew angle θe is set to be larger than the lower limit value and smaller than the upper limit value,
A permanent magnet type rotating electrical machine characterized in that the electrical angle of the step skew of the stator iron core is set to a value ½ of the theoretical angle θs.
(180 × number of rotor magnetic poles / number of stator magnetic poles and least common multiple of rotor magnetic poles) / 2 (electrical angle) (1)

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