JP4882715B2 - Electric motor and control method thereof - Google Patents

Description

  The present invention relates to an electric motor and a control method thereof, and more particularly to an embedded permanent magnet electric motor.

  FIG. 15 is a cross-sectional view showing a conventional configuration of a permanent magnet embedded type electric motor. The electric motor includes a rotor 1 and an armature 2 arranged to face the rotor 1.

  The armature 2 has a yoke 21, a tooth portion 22, and an armature winding 23. An armature winding 23 is wound around the tooth portion 22, and the yoke 21 magnetically connects the tooth portion 22 on the side opposite to the rotor 1. By passing an alternating armature current through the armature winding 23, a rotating magnetic field is generated for the rotor 1, and the rotating magnetic field is linked to the rotor 1.

  The rotor 1 has a rotor core 11 and a permanent magnet 12. The rotor core 11 has a shaft hole 10 and a gap 13 formed therein. A rotating shaft (not shown) is inserted into the shaft hole 10, and a permanent magnet 12 is provided in the gap 13. The permanent magnet 12 serves as a generation source of the field magnetic flux of the rotor 1, and the field magnetic flux is linked to the armature 2. In order to prevent the magnetic flux generated from the permanent magnet 12 from flowing in a short circuit inside the rotor core 11, both ends of the air gap 13 are obtained up to the armature 2 side surface of the rotor core 11. The rotor core 11 may further be provided with fastener insertion holes 14 and air holes 15 as shown.

  In addition, the following patent documents 1 thru | or 3 are enumerated as a literature relevant to this application.

Japanese Patent Laid-Open No. 2005-73444 JP 2002-262494 A JP 2002-136002 A

  The embedded permanent magnet motor having the configuration illustrated in FIG. 15 has high efficiency and excellent controllability because the ratio of torque to armature current is substantially constant. However, since the field magnetic flux is generated by the permanent magnet 12, it is difficult to perform field weakening, which was easy when the field was generated by current. Therefore, the induced voltage rises with the rotational speed, the range in which the armature current can flow is limited by the rotational speed, and it is not easy to change the maximum rotational speed or the current that maximizes the efficiency.

  In order to solve such a problem, so-called field-weakening control that substantially weakens the magnetic flux generated by the permanent magnet 12 has been proposed. However, since this control is greatly influenced by the shape of the motor, its application is limited. there were.

  Accordingly, the present invention proposes a technique for substantially weakening field magnetic flux in a permanent magnet embedded electric motor without performing weakening magnetic field control, and an object thereof is to reduce fluctuations in efficiency with respect to rotational speed. .

  A first aspect of the electric motor according to the present invention is an electric motor including a rotor (1) and an armature (2), and the rotor is annularly arranged around the rotation shaft (Q), A first region (131) and a second region (132) extending within a range (θ) of a predetermined central angle around the rotation axis and having different widths (d1, d2) in the extending direction. A plurality of gaps (13) having a rotor core (11) bored therein, and movable between the first region and the second region in the gap, and A permanent magnet (12) to be generated. The armature is opposed to the rotor (1) from the side opposite to the rotating shaft, and armature windings (iu, iv, iw) for supplying a rotating magnetic field to the rotor flow through the armature winding ( 23).

  The 2nd aspect of the electric motor concerning this invention is the 1st aspect, Comprising: The 2nd area | region (132) expands to the said armature (2) side rather than the said 1st area | region (131) ( 130a), the rotor core (11) has a step (111) between the first region and the second region, and the permanent magnet (12) moves to the second region side. However, the insertion of the permanent magnet into the second region is hindered by the step (111).

  The 3rd aspect of the electric motor concerning this invention is the 2nd aspect, Comprising: The said level | step difference is an obtuse angle seeing from the said rotor core side.

  A fourth aspect of the electric motor according to the present invention is the third aspect, wherein the width (d2) in the second region (132) gradually increases as the distance from the first region (131) increases.

  A fifth aspect of the electric motor according to the present invention is the third aspect thereof, wherein the width (d2) in the second region (132) is gradually increased as the distance from the first region (131) increases. Decrease gradually.

  A sixth aspect of the electric motor according to the present invention is the first aspect, in which the second region (132) expands to the rotating shaft (Q) side than the first region (131) ( 130b).

  A first aspect of the motor control method according to the present invention is a method for controlling the motor according to the first to sixth aspects of the motor according to the present invention, wherein the armature current (iu, iv, iw) is controlled. The current phase is advanced by 70 to 110 degrees with respect to the phase of the induced voltage caused by the permanent magnet (12) generated in the armature winding (23), and the permanent magnet is arranged on the second region side.

  A second aspect of the motor control method according to the present invention is the first aspect, and generates the current phase of the armature current (iu, iv, iw) in the armature winding (23). The permanent magnet is arranged toward the first region with a delay of 70 to 110 degrees with respect to the phase of the induced voltage by the permanent magnet (12).

  A third aspect of the motor control method according to the present invention is the second aspect, in which the permanent magnet is disposed on the first region side at a predetermined speed or less, and when the predetermined speed is exceeded, the permanent magnet is disposed. A magnet is disposed on the second region side.

  According to the first aspect of the electric motor of the present invention, in the state where the permanent magnet is located near the second region, the permanent magnet and the rotor core are compared with the state where the permanent magnet is located near the first region. The gap between the two becomes wider and the magnetic resistance becomes higher. Therefore, it is possible to substantially change the field magnetic flux while using the permanent magnet as the field magnetic flux generating source, thereby reducing the fluctuation of the efficiency with respect to the rotation speed.

  According to the 2nd aspect of the electric motor concerning this invention, the intensity | strength of the magnetic pole generate | occur | produced on the side facing the armature of a rotor core can be changed effectively.

  According to the third aspect and the fourth aspect of the electric motor according to the present invention, the permanent magnet is smoothly movable between the first region and the second region, and the substantial change in the field magnetic flux is also smooth. Become.

  According to the fifth aspect of the electric motor of the present invention, since the movement of the permanent magnet to the end of the second region on the opposite side of the first region is blocked while buffering, the permanent magnet is prevented from being damaged. To do.

  According to the sixth aspect of the electric motor of the present invention, the permanent magnet does not move unnecessarily even when subjected to the centrifugal force generated with the rotation of the rotor, and is stably arranged.

  According to the first aspect of the motor control method of the present invention, the position of the permanent magnet can be easily arranged on the second region side even when the rotor is rotating.

  According to the second aspect of the motor control method of the present invention, the position of the permanent magnet can be easily arranged on the first region side even when the rotor is rotating.

  According to the third aspect of the motor control method of the present invention, field weakening is realized during high-speed rotation.

  The basic idea of the present invention is that even if the magnetic flux generated from the permanent magnet itself cannot be controlled, the field magnetic flux interlinked with the armature is substantially controlled by controlling the magnetic resistance of the magnetic circuit for the magnetic flux. To try to control. Specifically, the control of the magnetic resistance is realized by moving the permanent magnet within the gap that houses the permanent magnet.

First embodiment.
FIG. 1 is a cross-sectional view illustrating the configuration of an electric motor according to a first embodiment of the invention. The electric motor has a rotor 1 and an armature 2. The rotor 1 functions as a field element. The sectional view shows a section perpendicular to the rotation axis Q of the rotor 1.

  The armature 2 faces the rotor 1 from the side opposite to the rotation axis Q. Similarly to the configuration of FIG. 15, the armature 2 includes a yoke 21, a tooth portion 22, and an armature winding 23, and a rotating magnetic field generated by an armature current flowing in the armature winding 23 is applied to the rotor 1. Supplied. Although the form of a present Example is the shape which wound the armature winding 23 directly on the tooth part 22, the shape of the distributed winding in which the armature winding 23 straddles the several tooth part 22 may be sufficient.

  The rotor 1 includes a rotor core 11 and a permanent magnet 12. A plurality of gaps 13 are formed in the rotor core 11. A plurality of the gaps 13 are annularly arranged around the rotation axis Q. The permanent magnet 12 is accommodated in the gap 13. The permanent magnet 12 generates a field magnetic flux. Similarly to the configuration of FIG. 15, the rotor 1 may have a shaft hole 10, and may further have a fastener insertion hole 14 and an air hole 15.

  FIG. 2 is an enlarged sectional view showing only the vicinity of one gap 13 in FIG. In order to avoid complication of the drawing, the fastener insertion hole 14 and the air hole 15 are omitted. Each of the gaps 13 extends in a predetermined center angle range θ around the rotation axis Q, and has a first region 131 and a second region 132.

  The first region 131 and the second region 132 have mutually different widths d1, d2 (> d1) in the direction in which the gap 13 extends. The permanent magnet 12 is movably provided in the gap 13 between the first region 131 and the second region 132.

  The air gap 13 also has protrusions 133 and 134 on the first region 131 and second region 132 sides, respectively, which prevent the magnetic flux generated from the permanent magnet 12 from flowing in a short circuit in the rotor core 11. .

  FIG. 1 shows a state in which the permanent magnet 12 is located in the vicinity of the first region 131. FIG. 3 is a cross-sectional view showing a state in which the permanent magnet 12 is located in the vicinity of the second region 132 in the present embodiment.

  Compared with the state in which the permanent magnet 12 is positioned in the vicinity of the first region 131, the gap 13 that exists between the permanent magnet 12 and the rotor core 11 is present in the state in which the permanent magnet 12 is positioned in the vicinity of the second region 132. Become wider. This is because the second region 132 has an enlarged portion 130 a as compared with the first region 131. Therefore, in terms of the magnetic path of the magnetic flux generated by the permanent magnet 12, the state where the permanent magnet 12 is positioned near the second region 132 is compared to the state where the permanent magnet 12 is positioned near the first region 131. The magnetic resistance increases.

  Therefore, by providing the permanent magnet 12 movably between the first region 131 and the second region 132 in the gap 13, the field magnetic flux can be substantially changed while the permanent magnet 12 is used as the field magnetic flux generating source. Can do. That is, the field weakening can be substantially performed. Thereby, since the induced voltage of the electric motor can be changed, the maximum number of rotations can be changed. For example, the maximum rotation speed can be changed to 7200 rotations per minute when a high speed operation is required while the maximum rotation speed is normally 3600 rotations per minute.

  FIG. 4 is a graph illustrating the above effect. Graphs G <b> 1 and G <b> 2 correspond to a state where the permanent magnet 12 is positioned in the vicinity of the first region 131 and a state where the permanent magnet 12 is positioned near the second region 132, respectively. In the state where the permanent magnet 12 is positioned in the vicinity of the first region 131, the field magnetic flux is large, and the efficiency peak is exhibited at a relatively low rotational speed. In the state where the permanent magnet 12 is located in the vicinity of the second region 132, the field magnetic flux is small, and the efficiency peak is exhibited at a relatively high rotational speed. In this way, the graphs G1 and G2 have intersections, and the graph G1 indicates that the motor efficiency is high below the rotation speed corresponding to the intersection, and the graph G2 indicates high motor efficiency above the rotation speed. Therefore, the permanent magnet 12 is arranged on the first region 131 side below the predetermined speed, and the permanent magnet 12 is arranged on the second region 132 side when the predetermined speed is exceeded, whereby a field weakening is realized at high speed rotation. The This makes it possible to increase the motor efficiency by making the dependency of the efficiency on the rotational speed as shown in the graph G0, and to reduce the fluctuation of the efficiency with respect to the rotational speed.

  Here, a case where four gaps 13 are provided is illustrated, and θ is less than 90 degrees. The extending direction of the gap 13 is substantially perpendicular to the direction connecting the center of the gap 13 and the rotation axis Q, but it is not necessary to be perpendicular to the above direction. Further, the extending direction of the gap 13 may be curved. However, in order to change the field magnetic flux, it is not desirable that the extending direction of the air gap 13 is parallel to the above direction.

  Furthermore, the enlarged portion 130a extends to the armature 2 side from the first region 131. Therefore, the rotor core 11 has a step 111 between the first region 131 and the second region 132. The step 111 prevents the permanent magnet 12 from being inserted into the second region 132 even if the permanent magnet 12 moves toward the second region 132. Thereby, the strength of the magnetic pole generated on the side of the rotor core facing the armature can be effectively changed. In other words, the length of the second region 132 along the direction in which the gap 13 extends is preferably shorter than that of the permanent magnet 12.

Second embodiment.
In the second embodiment, a specific method for moving the permanent magnet 12 described in the first embodiment will be described.

  FIG. 5 is a graph showing the dependence of torque on the current phase, which is typical for an embedded permanent magnet electric motor. Here, the current phase is a phase of the armature current with respect to the phase of the induced voltage generated by the permanent magnet (12) generated in the armature winding (23).

  Graph Tm shows magnet torque and takes the maximum value when the current phase is 0 degree. Graph Tr shows reluctance torque, and takes positive when the current phase is advanced, negative when the current phase is late, and becomes 0 when the current phase is 0 degrees. The graph Tt shows the torque obtained by combining the magnet torque and the reluctance torque. As described above, in a permanent magnet embedded type motor, a large torque can be obtained when the current phase is advanced. Therefore, during normal operation of the motor, the current phase is, for example, -30 to 70 degrees, or narrower to 0 to 0. Selected at 70 degrees.

  FIG. 6 is a cross-sectional view illustrating an operation state when the permanent magnet 12 is on the first region 131 side. In order to avoid complication of the figure, the armature winding 23 is actually a plurality of windings, but is illustrated as one, and only for one tooth portion 22 and one permanent magnet 12. Only illustrated. The same applies to FIGS. 7 to 9 to be described later.

  In addition, the rotation direction is counterclockwise in the drawing, and the second region 132 is on the reverse side of the first region 131. In the drawing, the arc-shaped arrow indicates the rotational direction, and the linear arrow indicates that the permanent magnet 12 is attracted to the tooth portion 22.

  In the present embodiment, an angle exceeding 70 degrees that is not normally employed as the current phase, for example, 90 degrees to 110 degrees is employed, and the permanent magnet 12 is moved to the first region 131 side using the armature current having the current phase. To the second region 132 side.

  FIG. 7 shows a state in which the permanent magnet 12 is attracted to the tooth portion 22 in the direction of the arrow by the armature current having the above current phase. FIG. 8 shows a state after the permanent magnet 12 is moved from the first region 131 side to the second region 132 by such attraction. FIG. 9 is a cross-sectional view illustrating an operation state when the permanent magnet 12 is on the second region 132 side.

  FIG. 10 is a graph showing changes in the armature current when the permanent magnet 12 is moved, and exemplifies a case where three-phase currents iu, iv, and iw are employed as the armature current. One scale on the horizontal axis indicates an electrical angle of 120 degrees. It can be seen that the current phase of each armature current is advanced in the current phase change section where the current phase changes.

  It is desirable that each armature current takes a value necessary for attracting the permanent magnet 12 at least in the current phase change section. On the other hand, it is not desirable for the permanent magnet 12 to move during normal operation. In normal operation, the current phase is selected to be -30 to 70 degrees, so that an attractive force that moves the permanent magnet 12 is unlikely to work. However, it is desirable to reduce the magnitude of the armature current so that the permanent magnet 12 does not move during normal operation.

  In order to move the permanent magnet 12 from the second region 132 side to the first region 131 side, an armature current that employs −70 degrees to −110 degrees that is not normally employed as a current phase is used.

  In this way, by moving the permanent magnet 12 inside the gap 13 using the armature current, the position of the permanent magnet 12 can be easily moved to the first region 131 side or the second region even when the rotor 1 is rotating. It can be arranged on the 132 side.

Third embodiment.
In the third embodiment, various modifications of the gap 13 will be described.

  As shown in FIG. 2, the second region 132 extends to the armature 2 side (here, the outer peripheral side). This is desirable from the viewpoint that the strength of the magnetic pole generated on the side of the rotor core 11 facing the armature 2 can be effectively changed. From this point of view, if the armature 2 is a so-called outer rotor type facing from the inside of the rotor 1, it is desirable that the second region 132 extends to the inner peripheral side (rotation axis Q side).

  However, even if the armature 2 is a so-called inner rotor type in which the armature 2 is opposed from the outside of the rotor 1 as shown in FIG. 1, it is desirable that the second region 132 expands to the inner peripheral side. FIG. 11 is a cross-sectional view showing the configuration of the gap 13 thus deformed, and the second region 132 has an enlarged portion 130b that extends from the first region 131 to the rotation axis Q side. According to such a structure, even if it receives the centrifugal force which generate | occur | produces with rotation of the rotor 1, the permanent magnet 12 does not move unnecessarily but is arrange | positioned stably.

  12 to 14 are cross-sectional views showing other modified examples of the gap 13. In any deformation, the step 111 is an obtuse angle when viewed from the rotor core 11. In particular, in the structure shown in FIG. 13, the width d <b> 2 in the second region 132 gradually increases as the distance from the first region 131 increases. As a result, the permanent magnet 12 is smoothly movable between the first region 131 and the second region 132, and the substantial change in the field magnetic flux is also smoothed.

  In particular, in the structure shown in FIG. 14, the width d <b> 2 in the second region 132 gradually increases and then gradually decreases as the distance from the first region 131 increases. Thereby, the movement of the permanent magnet 12 to the end of the second region 132 on the side opposite to the first region 131 is prevented while buffering. This is desirable from the viewpoint of preventing the permanent magnet 12 from being damaged.

It is sectional drawing which illustrates the structure of the electric motor concerning 1st Embodiment of this invention. It is sectional drawing which expands and shows only one vicinity of the space | gap 13 in 1st Embodiment of this invention. It is sectional drawing which shows the state of the electric motor in 1st Embodiment of this invention. It is a graph which illustrates the effect of a 1st embodiment of this invention. It is a graph which shows the dependence with respect to the electric current phase of a general torque about a permanent magnet embedded type motor. It is sectional drawing which shows the state of the electric motor in 2nd Embodiment of this invention. It is sectional drawing which shows the state of the electric motor in 2nd Embodiment of this invention. It is sectional drawing which shows the state of the electric motor in 2nd Embodiment of this invention. It is sectional drawing which shows the state of the electric motor in 2nd Embodiment of this invention. It is a graph which shows the change of the armature current in 2nd Embodiment of this invention. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows the conventional structure of the permanent magnet embedded type electric motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor 11 Rotor core 111 Step 12 Permanent magnet 13 Air gap 130a, 130b Enlarged part 131 1st area 132 2nd area 2 Armature 23 Armature winding iu, iv, iw Armature current d1, d2 Width Q Rotation axis θ Center angle range

Claims (9)

Arranged in a ring around the rotation axis (Q), each extends within a range (θ) of a predetermined center angle around the rotation axis, and the widths (d1, d2) in the extending direction are mutually A plurality of voids (13) having different first regions (131) and second regions (132), a rotor core (11) bored therein;
A rotor (1) including a permanent magnet (12) provided movably between the first region and the second region in the gap and generating the field magnetic flux;
An armature that includes an armature winding (23) that faces the rotor (1) from the side opposite to the rotating shaft and flows an armature current (iu, iv, iw) that supplies a rotating magnetic field to the rotor. An electric motor comprising (2). The second region (132) has an enlarged portion (130a) that extends to the armature (2) side than the first region (131),
The rotor core (11) has a step (111) between the first region and the second region,
The electric motor according to claim 1, wherein even if the permanent magnet (12) moves toward the second region, the stepping of the permanent magnet into the second region is inhibited by the step (111).   The electric motor according to claim 2, wherein the step is an obtuse angle when viewed from the rotor core side.   The electric motor according to claim 3, wherein the width (d2) in the second region (132) gradually increases as the distance from the first region (131) increases.   The electric motor according to claim 3, wherein the width (d2) in the second region (132) gradually increases and then gradually decreases as the distance from the first region (131) increases.   The electric motor according to claim 1, wherein the second region (132) has an enlarged portion (130b) that extends toward the rotating shaft (Q) with respect to the first region (131). A method for controlling an electric motor according to any one of claims 1 to 6,
The current phase of the armature current (iu, iv, iw) is advanced by 70 to 110 degrees with respect to the phase of the induced voltage by the permanent magnet (12) generated in the armature winding (23), and the permanent A method for controlling an electric motor, wherein a magnet is arranged toward the second region.   The current phase of the armature current (iu, iv, iw) is delayed by 70 to 110 degrees with respect to the phase of the induced voltage by the permanent magnet (12) generated in the armature winding (23), and the permanent The motor control method according to claim 7, wherein a magnet is arranged toward the first region.   The motor control method according to claim 8, wherein the permanent magnet is disposed toward the first region at a speed lower than a predetermined speed, and the permanent magnet is disposed toward the second region when the predetermined speed is exceeded.

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