JP2009219183A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet type of motor which can effectively prevent the demagnetization of a permanent magnet by diamagnetic field. <P>SOLUTION: The first air-gap 32 and the second air-gap 33 are formed segmentally in the radial direction of a rotor 3 from the ends of the permanent magnets 5a-5f. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnet-embedded electric motor in which a permanent magnet is embedded in a rotor, and more particularly, to an electric motor having improved demagnetization resistance of the embedded permanent magnet.

  A brushless DC motor is used for an electric motor employed in a compressor or the like for higher efficiency. Conventionally, this type of brushless DC motor has used an SPM type (surface magnet affixed type) in which a permanent magnet bonded to the rotor surface is covered with a metal tube such as stainless steel. However, the SPM type is a metal tube. Since iron loss occurs, the more efficient IPM type (magnet embedded type) has become mainstream at present (see, for example, Patent Document 1).

  As shown in FIGS. 7 and 8, in the IPM type motor, the magnet torque acting in synchronization with the permanent magnet M and the reluctance torque obtained by the salient pole ratio generated by the slit portion in which the permanent magnet is embedded synergistically. By working, higher efficiency drive is possible.

  When this IPM type motor is rotated, the magnetic poles differ between adjacent teeth, so that the magnetic flux leaks from one tooth to the other tooth through a part of the rotor. At this time, a reverse magnetic field that cancels the magnetic flux of the permanent magnet M flows at the end of the permanent magnet M, and the permanent magnet M may be demagnetized.

  Therefore, the IPM type motor described in Patent Document 1 is provided with slit portions F (so-called flux barriers) made of magnetic gaps along the radial direction from both ends of the permanent magnet so that the magnetic flux does not easily pass through the permanent magnet. Prevents demagnetization.

JP 2000-69717 A

  However, the conventional demagnetization measures have the following problems. That is, when the flux barrier is formed from the end of the permanent magnet to the vicinity of the rotor surface as in Patent Document 1, it is possible to make it difficult to pass the magnetic flux that is short-circuited through a part of the rotor surface between adjacent teeth. On the other hand, when the flux barrier F continuous from the magnet insertion hole is provided, the bridging portion that holds the iron core on the front surface (outer periphery) of the magnet becomes long, so that the mechanical strength is lowered.

  Further, in the case where there is a bridging portion only at one place on the rotor surface as in Patent Document 1, when the demagnetizing field is increased, a reverse magnetic field is generated in the vicinity of the permanent magnet M as shown in FIGS. Magnet demagnetization is likely to occur.

  Therefore, in order to solve the above-described problems, the present invention provides a magnet-embedded electric motor that can more effectively prevent demagnetization of a permanent magnet due to a demagnetizing field.

  In order to achieve the above-described object, the present invention has several features described below. The invention described in claim 1 includes a stator that generates a rotating magnetic field, and a rotor in which a permanent magnet is embedded, and is disposed on the inner diameter side of the stator, and the rotor is disposed from an end of the permanent magnet. In the magnet-embedded electric motor provided with a gap between the outer peripheral surface and the outer peripheral surface, the gap includes a first gap extending from the end of the permanent magnet toward the outer peripheral surface of the rotor. The second gap portion disposed between the first gap portion and the outer peripheral surface of the rotor is provided.

  According to a second aspect of the present invention, in the first aspect, the second gap is formed in a slit shape along a circumferential direction of the rotor.

  A third aspect of the present invention is characterized in that, in the first or second aspect, slit-shaped third gap portions are arranged at a predetermined interval in the circumferential direction of the second gap portion.

  According to a fourth aspect of the present invention, in the above third aspect, the circumferential length of the second gap is shorter than the circumferential length of the third gap. It is said.

  According to a fifth aspect of the present invention, in the third or fourth aspect of the invention, the electrical angle connecting the third gap portion arranged opposite to each other with the permanent magnet interposed therebetween and the center point of the rotor is approximately 90 °. It is characterized by being.

  According to the first aspect of the present invention, the first air gap is provided from the end of the permanent magnet toward the outer peripheral surface of the rotor, and the second air gap is provided between the first air gap and the rotor outer peripheral surface. Since a bridging portion is formed at both ends in the radial direction of the second gap portion, it is possible to prevent a magnetic field (reverse magnetic field) acting in the direction of weakening the magnetic field of the magnet in the vicinity of the magnet. Thus, it is possible to improve the demagnetization resistance due to the demagnetizing field. Here, in the present invention, the demagnetizing field refers to a magnetic field that enters from the stator side to the rotor side.

  According to the second aspect of the present invention, the second gap is formed in a slit shape along the circumferential direction of the rotor, so that the bridge adjacent to the second gap in the radial direction is more Since it is located on the outer peripheral surface side, it is possible to further prevent a reverse magnetic field.

  According to the third aspect of the present invention, the third gap is formed at a predetermined interval on the side surface in the circumferential direction of the second gap, so that the demagnetization due to the demagnetizing field is suppressed and the stator is moved to the stator. The magnetic flux heading toward can be concentrated on the portion where there is no gap.

  According to the fourth aspect of the present invention, since the circumferential length of the third gap is formed longer than the circumferential length of the second gap, the mechanical stress is generated at the gap portion. It is possible to concentrate the magnetic flux from the magnet in a portion where there is no gap while suppressing a decrease in mechanical strength due to the gap at the place where the gap is applied most.

  According to the fifth aspect of the present invention, since the electrical angle connecting the third gap portion disposed opposite to each other across the permanent magnet and the center point of the rotor is approximately 90 °, magnetically Since the salient pole portion is formed to concentrate the magnetic flux and the peak of the induced voltage can be increased, the motor characteristics can be improved.

  FIG. 1 is a cross-sectional view of a main part of an electric motor according to an embodiment (Example 1) of the present invention, FIG. 2 is a partial enlarged view of the rotor of the electric motor, and FIG. 4 is a magnetic flux diagram of the rotor and the stator, FIG. 4 is a partially enlarged view showing a modified example (Example 2) of the rotor, and FIG. 5 is a magnetic flux diagram of the rotor and the stator at the maximum magnetic field position. 6 is a graph showing the demagnetization limit. In the figure, an increase in the demagnetizing current represents an increase in the demagnetizing field.

  As shown in FIG. 1, the electric motor 1 is an inner rotor type synchronous motor that includes a cylindrical stator 2 and a rotor 3 that is coaxially disposed along the inner diameter of the stator 2. The rotation shaft 4 is integrally provided at the center of the.

  The stator 2 has nine pole teeth portions 21a to 21i, and a coil 22 is wound around the outer periphery of each of the tooth portions 21a to 21i. In the present invention, the specific configuration of the stator 2 is arbitrary, and the specification is not particularly limited as long as it functions as a synchronous motor.

  The rotor according to the present invention will be described in detail with reference to FIG. The rotor 3 has a cylindrical shape formed by laminating electromagnetic steel plates along the axial direction of the rotary shaft 4, and six permanent magnets 5 a to 5 f are constant on a concentric circle centering on the rotary shaft 4. Arranged at intervals.

  Each permanent magnet 5 a to 5 f is embedded along the through holes 31 a to 31 f formed along the axial direction of the rotor 3. The permanent magnets 5a to 5f are both plate magnets having the same shape. The properties of the permanent magnets 5a to 5f, such as specific materials and shapes, are optional matters.

  The rotor 3 is formed with a first gap 32 along the radial direction from the end of each of the permanent magnets 5a to 5f. Hereinafter, the permanent magnet 5a will be described as an example. The first gap portion 32 is formed in a rectangular shape along the radial direction from the end portion of the permanent magnet 5 a, and penetrates along the axial direction of the rotor 3. The first gap portion 32 can prevent the lines of magnetic force from the N-pole side of the permanent magnet 5a from closing in the rotor core without going through the stator 2 (around the S-pole side of the permanent magnet 5a). It can be prevented from lowering.

  A second gap portion 33 is provided on the tip side of the first gap portion 32 with a predetermined interval. The second gap portion 33 is formed of a gap disposed between the first gap portion 32 and the outer peripheral surface of the rotor 3, and is formed in a long and narrow slit shape along the circumferential direction of the rotor 3.

  The demagnetization resistance of the rotor will be described below with reference to FIG. FIG. 3 shows the lines of magnetic force in the stator / rotor arrangement where the demagnetizing field from the stator to the rotor is the largest. During normal motor operation, the rotor position is detected by an induced voltage generated in the Hall element and stator winding, and a rotating magnetic field is generated according to the motor position to rotate the rotor. Will not be larger than necessary.

  However, when the position of the rotor 3 cannot be accurately grasped (especially when starting up), the stator winding 22 is energized in a stator / rotor arrangement in which the demagnetizing field from the stator 2 to the rotor 3 increases as shown in FIG. It can happen.

  In the case of the rotor 3 according to the first embodiment, the first gap portion 32 in which the gap portion (flux barrier) extends from the end of the permanent magnet 5a toward the rotor outer circumferential surface side, the first gap portion 32, and the rotor outer circumferential surface. Between the poles formed by the permanent magnet 5a embedded in the rotor 3 and between the poles (between the poles), and the outer peripheral surface of the rotor. There are two iron core portions (first bridging portion 35 and second bridging portion 36) extending in the circumferential direction in the vicinity.

  As a result, even when a large current is passed through the stator winding 22 when the stator / rotor arrangement is in a positional relationship in which the demagnetizing field is particularly large at the time of starting, as shown in FIG. The magnetic lines of force from 21a flow not only through the first bridging portion 35 but also through the second bridging portion 36 to the adjacent teeth 21b.

  When magnetic lines of force are short-circuited between adjacent teeth 21a and 21b in this way, a magnetic path is formed in the vicinity of the outer peripheral surface of the rotor. The reverse magnetic field can be reduced.

In this embodiment, the predetermined interval, that is, the widths t _s1 and t _{s2 in} the short direction (radial direction) of the first bridging portion 35 and the second bridging portion 36 are the thicknesses of the electrical steel sheets. About 1.5 times. However, the widths t _s1 and t _s2 are such that the lines of magnetic force emitted from the N pole side of the magnetic flux of the permanent magnet 5 embedded in the rotor 3 do not increase the amount of magnetic flux (wraparound) that closes in the rotor core without passing through the stator. Can be set as appropriate, and is not limited to this width.

Incidentally, more preferably, the width _{t s1, t s2} in the short direction of the first bridge junction 35 and the second bridge junction 36, the width _{t l1, t l2} in the longitudinal direction (circumferential _{direction), t s2>} It is preferable that t _s1 , t _l2 <t ₁₁ . If it does in this way, when punching out a rotor core from an electromagnetic steel plate, the intensity of the 2nd bridge part 36 pinched by the 1st and 2nd crevice part can be made higher.

  According to this, by dividing the gap (flux barrier) into the first gap 32 and the second gap 33, as shown in FIG. Even if the demagnetizing field is dispersed in the path and the demagnetizing field is increased, it is difficult to generate a reverse magnetic field at the end of the magnet.

  Next, a modified example (Example 2) of the rotor will be described with reference to FIGS. In the circumferential direction of the second gap portion 33, third gap portions 34 are arranged with a predetermined interval. The third gap portion 34 is disposed on the circumferential side surface (side surface near the magnetic pole center) of the second gap portion 33, and preferably has the same elongated slit shape as the second gap portion 33, and the second gap portion It is preferable that they are provided on the same circumference of 33.

  The demagnetization resistance of the rotor 3 according to the second embodiment will be described below with reference to FIG. FIG. 5 shows the lines of magnetic force in the stator-rotor arrangement where the demagnetizing field from the stator 2 to the rotor 3 is the largest, as in FIG.

  As can be seen from FIG. 5, in the modified example, the third gap portion 34 is disposed on the side surface near the magnetic pole center of the second gap portion 33. Therefore, the magnetic field lines that are short-circuited from one tooth 21a to the other adjacent tooth 21b pass closer to the rotor magnet 5a than the magnetic field lines in FIG. 3, but as can be seen from the magnetic field lines (the wavy lines in FIG. 5), the second bridge is also used. The reverse magnetic field in the vicinity of the permanent magnet 5 is reduced by going through the entangled portion 36 as well.

  The third gap 34 has an electrical angle of approximately 90 ° (mechanical angle of approximately 30) connecting the second gaps 33 and 33 disposed opposite to each other across the permanent magnet 5a and the center of the rotor 3. °) is designed to be. According to this, by forming the magnetic salient pole portion and concentrating the magnetic flux, the peak of the induced voltage can be increased, and the motor characteristics can be improved.

The third gap 34 is formed such that its circumferential length is longer than the circumferential length of the second gap 33. According to this, since the length of the circumferential direction of the 2nd space | gap part 34 is restrained by lengthening the length of the 3rd space | gap part 34, the circumferential direction of the 1st and 2 bridge parts 35 and 36 is suppressed. The widths t _l1 and t _l2 are suppressed. Therefore, it is possible to suppress a decrease in magnetic field strength at a location where mechanical stress is most applied at the inter-electrode portion.

  Next, the difference in the demagnetization resistance between the rotor of the present invention and the conventional rotor will be described with reference to FIG. FIG. 6 shows the demagnetization factor when the rotors of Examples 1 and 2 of the present invention and the conventional example are used, that is, the relationship between the current applied to the stator winding (demagnetization current) and the demagnetization factor of the rotor magnet. ing. The demagnetization limit line in FIG. 6 represents an acceptable demagnetization factor for the product, and the rotor magnet is not allowed to demagnetize beyond this demagnetization limit.

  As can be seen from FIG. 6, in Examples 1 and 2, the demagnetization current value that reaches the demagnetization limit is larger than that in the conventional example. This is because the motor using the rotor according to the present invention is the conventional one. This shows that the rotor magnet is less likely to be demagnetized than the motor, and the demagnetization resistance is increased.

  In the first and second embodiments, a 6-pole permanent magnet embedded electric motor has been described as an example. However, the number of poles is not limited to this, and may be another pole number such as 4 poles or 8 poles. . Various modifications can be made to the magnet shape, the stator shape, and the like.

The principal part sectional view of the electric motor concerning one embodiment of the present invention. (A) The elements on larger scale of the said motor, (b) The enlarged view of the bridge part periphery of the said motor. The magnetic flux diagram of the electric motor of the said Example. The elements on larger scale which show the modification of the said electric motor. The magnetic flux diagram of the electric motor of the said modification. The graph which represented the demagnetization limit peak of an Example and a prior art example by ratio. The elements on larger scale of the conventional rotor. Magnetic flux diagram of a conventional electric motor.

Explanation of symbols

1 Electric motor 2 Stator (stator)
21a-22i Teeth 22 Coil 3 Rotor (Rotor)
31a-31f Through-hole 32 1st space | gap part 33 2nd space | gap part 34 3rd space | gap part 35 1st bridge part 36 2nd bridge part 4 Rotating shaft 5a-5f Magnet

Claims (5)

A stator that generates a rotating magnetic field, and a rotor in which a permanent magnet is embedded and disposed on the inner diameter side of the stator, and a gap is formed between the end of the permanent magnet and the outer peripheral surface of the rotor. In the built-in magnet motor,
The air gap is a first air gap extending from the end of the permanent magnet toward the outer peripheral surface of the rotor, and a second air gap disposed between the first air gap and the outer peripheral surface of the rotor. An electric motor comprising a gap portion.   The electric motor according to claim 1, wherein the second gap portion is formed in a slit shape along a circumferential direction of the rotor.   3. The electric motor according to claim 1, wherein slit-shaped third gap portions are arranged at a predetermined interval in a circumferential direction of the second gap portion.   The electric motor according to claim 3, wherein a length of the second gap portion in the circumferential direction is shorter than a length of the third gap portion in the circumferential direction.   5. The electric motor according to claim 3, wherein an electrical angle connecting the third gap portion arranged opposite to each other across the permanent magnet and the center point of the rotor is approximately 90 °.

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