JP2017099176A - Field permanent magnet - Google Patents

Abstract

The present invention provides a field permanent magnet capable of suppressing noise of a rotating machine caused by dust such as dust and fine metal particles.
A field permanent magnet according to the present invention comprises a cylindrical ring magnet (1) having a constant thickness in which different magnetic poles extending in the axial direction are alternately arranged in the circumferential direction. Used for field of machine (M). The ring magnets are alternately arranged in the axial direction in the transition region where the magnetic poles transition from one to the other, and are longitudinal grooves (11 to 14) that open on one end side in the axial direction and extend to the other end side. have. At least one of the longitudinal grooves has a groove height ratio (H) that is a ratio of a groove height (H) that is a length from the open end to the deepest portion with respect to a magnet length (L) that is an axial length of the ring magnet. / L) is 1/2 to 2/3, and the sum of the heights of the vertically arranged vertical grooves is equal to or greater than the magnet length.
[Selection] Figure 2

Description

  The present invention relates to a permanent magnet for a field of a rotating machine (electric motor or generator).

  Some rotating machines do not require permanent magnets, such as induction machines (a type of AC machine), but from the viewpoint of efficiency, controllability, etc., a field consisting of permanent magnets and an armature are combined. Rotating machines are often used.

  In particular, DC motors (a type of direct current machine) that are frequently used in various devices and equipment are strongly required to be small, light, and low in cost, and ring magnets are used as permanent magnets for their fields. There are many. The description regarding such a ring magnet exists in the following patent document, for example.

Japanese Patent No. 5559600 Japanese Utility Model Publication No. 4-111279

  In Patent Document 1, a cylindrical magnet (ring magnet) having a substantially regular n-gonal shape on the outer peripheral side and a circular cross section on the inner peripheral side is formed, and extends in the axial direction into a thin portion (a substantially regular n-gonal planar portion). There is a description relating to a magnet for a DC motor in which elongated cutout portions are alternately arranged (FIG. 2 or FIG. 3). In Patent Document 1, in order to avoid deformation of the uneven-thick DC motor magnet due to thermal expansion into distortion, the entire thermal expansion is absorbed by a notch provided in a thin-walled portion that is easily deformed. .

  Patent Document 2 describes a magnet ring in which opposed V-shaped cut portions are provided only on both ends in the axial direction in order to reduce the cogging torque of a DC rotating machine (FIG. 3).

  Noise reduction is a problem related to a rotating machine that is not described in Patent Document 1 or Patent Document 2. Although there are a plurality of causes of noise generation, foreign matters (dust, metal fine particles, etc.) that enter and adhere to a slight air gap formed between the rotor and the stator are one of the causes of noise generation. If such a foreign substance contacts the rotor or stator intermittently during operation of the rotating machine, noise (abnormal noise) is generated.

  This invention is made | formed in view of such a situation, and it aims at providing the permanent magnet for fields which can aim at the noise reduction of a rotary machine.

  The present inventor has intensively studied to solve this problem, and has come up with the idea that a longitudinal groove capable of collecting foreign matter is provided in the boundary region (transition region) of the ring magnet where the magnetic poles are reversed. By developing this idea, the present invention described below has been completed.

<Permanent magnet for field>
(1) The field permanent magnet of the present invention comprises a cylindrical ring magnet having a constant thickness in which different magnetic poles extending in the axial direction are alternately arranged in the circumferential direction. Permanent magnets for field use, wherein the ring magnets are alternately arranged in the axial direction in the transition region where the magnetic poles transition from one side to the other, and open at one end side in the axial direction. A longitudinal groove extending to the end side, and at least one of the longitudinal grooves is a length from the opening end to the deepest portion with respect to a magnet length (L) which is an axial length of the ring magnet. The groove height ratio (H / L), which is the ratio of a certain groove height (H), is 1/2 to 2/3, and the sum of the groove heights of the alternately arranged longitudinal grooves is equal to or greater than the magnet length. It is characterized by that.

(2) According to the present invention, even if dust (foreign matter) such as dust, metal burrs, and abrasion powder enters the gap (air gap) between the rotor and the stator constituting the rotating machine, the permanent magnet for the field The dust is surely collected (trapped) by the longitudinal grooves provided in the magnet. Therefore, if the field permanent magnet of the present invention is used, even when a minute foreign matter (simply referred to as “dust”) enters the air gap, it is possible to sufficiently suppress the noise of the rotating machine that may be generated. .

  The reason why dust is reliably trapped by the longitudinal grooves according to the present invention is as follows. First, the ring magnet according to the present invention has a first groove that opens at one end side in the axial direction and extends toward the other end side, and a first groove that opens at the other end side and extends toward the one end side. The existing (second) vertical grooves are arranged alternately (so-called “alternate”). At least one of the longitudinal grooves has a length (groove height: H) from the opening end to the deepest portion that is 1/2 or more of the magnet length (L) of the ring magnet, and is alternately arranged. The sum of the groove heights of the vertical grooves is longer than the magnet length.

  For this reason, dust that can enter the air gap (cylindrical space) and come into contact with the rotor and the stator is located in any vertical groove provided in the ring magnet as the rotor rotates at any position. It will be trapped in contact.

  Thus, the ring magnet according to the present invention and the above-described magnet ring of Patent Document 2 are greatly different in that dust is reliably trapped. In the case of the magnet ring of Patent Document 2, the dust adhering to the vicinity of the center in the axial direction is not trapped by the cut portions provided on both ends, and continues to be a noise generation source.

  Next, the ring magnet of the present invention has a constant thickness, and the longitudinal groove formed in a part thereof has the same thickness (depth in the radial direction) as the periphery (magnet portion). Here, the thickness of the ring magnet is usually sufficiently larger than the air gap (gap width). For this reason, even if the dust has a size that contacts the stator and the rotor (such as a particle size larger than the air gap), the dust does not contact the stator or the rotor by being taken into the vertical groove. In this way, noise caused by dust is reliably suppressed.

  In this respect, the ring magnet according to the present invention is greatly different from the magnet of Patent Document 1 described above. In the case of the magnet of Patent Document 1, the notch is intentionally provided in a portion having a small thickness. For this reason, when dust having a relatively large size enters the air gap, it is difficult to capture the dust at the cutout portion of Patent Document 1. Even if the dust is partially taken into the notch, there is a high possibility that it will continue to contact the stator or the rotor. Therefore, in the notch part like patent document 1, the noise of the rotary machine resulting from dust cannot be suppressed reliably.

《Rotating machine》
The present invention can be grasped not only as the above-described field permanent magnet but also as a rotating machine using the same. That is, the present invention can also be grasped as a rotating machine including a field magnet using the above-described field permanent magnet as a magnetomotive source and an armature. At this time, if the thickness of the ring magnet according to the present invention is larger than the air gap which is the gap between the field and the armature (or the gap between the stator and the rotor), dust is reliably trapped as described above. The noise of the rotating machine due to the dust is effectively suppressed.

  Incidentally, the rotating machine may be an electric motor (motor) or a generator (generator). In the rotating machine, the field side may be a stator (stator) and the armature side may be a rotor (rotor), or the field side may be a rotor and the armature side may be a stator. Further, the rotating machine may be an AC machine in addition to a DC machine as long as it uses a permanent magnet as a field magnetomotive source. For example, the rotating machine is a general DC motor or the like, as well as a synchronous machine, a hall element, and a rotary encoder whose rotational speed changes in synchronization with the frequency of an alternating current supplied to a coil (armature winding) provided in a stator. Further, a brushless direct current (DC) motor or the like that generates a rotating magnetic field on the stator side based on the position of the rotor detected by a detecting means such as a resolver may be used.

<Others>
(1) The field permanent magnet of the present invention is reduced in weight by at least the provision of the longitudinal groove. Further, since the longitudinal groove is provided in the transition region, there is almost no decrease in the amount of interlinkage magnetic flux penetrating the armature coil. Furthermore, since the vertical groove is opened from the end, it can be manufactured by a method similar to that of a conventional ring magnet.

(2) If the groove height ratio of the longitudinal grooves is excessive, the transition region (bridge region) between the magnetic poles is excessively small, and it is difficult to maintain the ring magnet (cylindrical shape retention) in terms of strength. Moreover, if the groove height ratio is too small, the dust trap may be insufficient. Therefore, the groove height ratio is preferably 1/2 to 2/3, 1/2 to 4/7, and further preferably 1/2 to 5/9.

(3) “x to y” in this specification includes the lower limit value x and the upper limit value y unless otherwise specified. Any numerical value included in various numerical values or numerical ranges described in the present specification can be newly established as a range such as “ab” as a new lower limit value or upper limit value.

(4) The “shaft” in this specification is a rotating shaft of a rotating machine. The “axial direction” is a direction in which the rotation axis (center axis) extends. The “circumferential direction” is a direction around the rotation axis. As appropriate, the axial direction is referred to as “vertical direction”, and the direction orthogonal to the vertical direction is also referred to as “lateral direction”. The “end” is an axial end unless otherwise specified. “End” means the vicinity of the “end”. Further, the side closer to the rotation axis is called “inner (circumference) side”, and the side farther from the rotation axis is called “outer (circumference) side”.

It is a perspective view which shows the outline | summary of the DC motor which is one Example of a rotary machine. It is a perspective view which shows the ring magnet used as the permanent magnet for fields. It is a graph which shows the relationship between the inclination angle ((theta)) of the V-shaped vertical groove provided in the ring magnet, and the weight reduction rate of a ring magnet. It is a graph which shows the relationship between the inclination angle ((theta)) and a flux linkage amount fall rate. It is a graph which shows the relationship between the inclination angle ((theta)) and a cogging torque reduction rate.

  The contents described in the present specification can be applied not only to the field permanent magnet or the rotating machine of the present invention but also to the manufacturing method thereof. One or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. In this case, the components related to the manufacturing method are in a certain case (a situation where it is impossible or impractical (impossible / unpractical circumstances), etc.) In some cases, it can be a component of “things” as a product-by-process. Note that which embodiment is the best depends on the target, required performance, and the like.

《Vertical groove》
The longitudinal groove may be a concave shape that is open on one side and closed on the other side (bottom side), and may take various shapes within a range that can be formed in the transition region of the ring magnet. The longitudinal groove may be, for example, an elongated rectangular shape (rectangular shape) having a substantially constant groove width from the opening end to the vicinity of the deepest portion, or may have a substantially V shape or a substantially U shape in which the groove width monotonously decreases. Further, the outline of the vertical groove (outline extending from the opening end to the deepest part) may be linear or curved. The curve constituting the contour line may be a smoothly connected arc-shaped line, a sine curve or the like. In any case, it is preferable that the contour line of the longitudinal groove is symmetrical with respect to the center line from the viewpoint of manufacturing the ring magnet or the characteristics of the rotating machine.

  If the longitudinal grooves arranged alternately are all the same shape (same shape and size), they become ring magnets balanced in the axial direction and circumferential direction, and the design and production of ring magnets and control of rotating machines Etc. are also preferable because of ease. When multiple types of vertical grooves with different shapes or sizes (groove heights) are provided, adjacent vertical grooves are alternately arranged, and the amount of magnetic flux and weight of each ring magnet are balanced so that the entire ring magnet is balanced. It is good to adjust the shape and arrangement.

  In addition, in order to suppress generation | occurrence | production of a chip | tip, a burr | flash, etc., it is preferable that the corner | angular part near an opening end is round chamfering (R chamfering) or chamfering (C chamfering). Further, the corner of the deepest part (bottom part) is preferably curved or rounded (corner R) in order to avoid stress concentration as a fracture starting point.

《Magnetic pole》
The ring magnet has at least one pair of magnetic poles having different polarities (magnetic flux directions). That is, magnetic poles having the N pole on the outer peripheral surface side of the ring magnet and magnetic poles having the S pole on the outer peripheral surface side are alternately arranged along the peripheral side surface of the ring magnet. The number of magnetic poles of the ring magnet is selected according to the specifications of the rotating machine, but if it is 4 poles or more, a highly efficient rotating machine is easily obtained.

  The magnetic pole is formed by orientation or magnetization. The orientation is made when the anisotropic magnet powder is formed. In the present specification, the case where the magnetic pole is formed mainly by magnetization will be described, but the contents can also be applied to the case where the magnetic pole is formed by orientation.

  The magnetic poles may be straight magnetized or skew magnetized. Straight magnetization is magnetization in which the boundary between different magnetic poles is parallel to the axis of the ring magnet, and skew magnetization is magnetization in which the boundary is twisted with respect to the axis of the ring magnet. Therefore, when straight magnetization is performed, the transition region becomes parallel to the axial direction. On the other hand, when skew magnetization is performed, the transition region is twisted with respect to the axial direction.

  The use of a skew magnetized ring magnet is preferable in that the cogging torque or torque ripple of the rotating machine can be reduced. Straight magnetization is preferable because it can reduce the initial cost of the equipment, its maintenance cost (running cost), and the like, rather than skew magnetization. However, when the longitudinal groove according to the present invention is substantially V-shaped or substantially U-shaped, even if straight magnetization is performed, the magnetic pole becomes the same as that when skew magnetized as a result, and cogging torque is reduced. obtain.

  Magnetization (or orientation) of the ring magnet is preferably performed in a magnetic field having a radial distribution or a semi-radial distribution. The radial distribution is a distribution in which the entire magnetic field is directed in the radial (radiation) direction. The semi-radial distribution indicates that the magnetic field is oriented in the normal direction of the circumferential side surface in the main area of the magnetic pole, and gradually moves around as the magnetic field approaches the neutral point (magnetic pole boundary point) in the transition area between the main areas. It is a distribution in which the magnetic field gradually turns to the normal direction of the circumferential side surface as it goes away from the neutral point after turning in the tangential direction and becoming the circular tangential direction at the neutral point (boundary point of the magnetic pole). The semi-radial distribution (orientation) and the like are also described in detail in JP-A-2005-312166, International Publications (WO2010 / 029642, WO2011 / 1226026, WO2011 / 126023) and the like.

《Ring magnet》
The ring magnet may be a sintered magnet obtained by sintering magnet powder, or a bonded magnet (plastic magnet) in which magnet powder is bonded with resin. Bonded magnets have a high degree of freedom in form, are excellent in productivity, handleability, and the like, and can be easily integrated with a ring magnet and a field yoke (such as a case).

  There are various types of magnet powders that can be used as raw materials for bonded magnets. The magnet powder may be, for example, an inexpensive ferrite magnet powder or a rare earth magnet powder with high magnetic properties. The rare earth magnet powder is, for example, Nd—Fe—B magnet powder, Sm—Fe—N magnet powder, Sm—Co magnet powder or the like. These rare earth magnet powders may be composed of a plurality of types as well as one type. Incidentally, the plurality of types of magnet powders are not limited to those having different component compositions but may have different particle size distributions. For example, a combination of coarse powder and fine powder of Nd-Fe-B magnet powder or a combination of coarse powder of Nd-Fe-B magnet powder and fine powder of Sm-Fe-N magnet powder may be used. The bonded magnet according to the present invention may be a mixture of rare earth anisotropic magnet powder and / or rare earth isotropic magnet powder and ferrite magnet powder.

  When rare earth anisotropic magnet powder is used, bonded magnets (ring magnets) with high magnetic properties can be obtained by performing the above-mentioned magnetization after molding (such as compression molding, injection molding or transfer molding) in an orientation magnetic field. It is preferable. As described above, the orientation during molding may be performed in a radially distributed magnetic field or a semi-radially distributed magnetic field.

  The resin (binder resin) that binds the magnet powder is appropriately selected from known materials including rubber according to the molding method, the specifications of the rotating machine, and the like. For compression molding, for example, epoxy resin, unsaturated polyester resin, amino resin, phenol resin, polyamide resin, polyimide resin, polyamideimide resin, urea resin, melamine resin, urea resin, direal phthalate resin, polyurethane, etc. These thermosetting resins can be used. In this case, it is preferable that a heat curing process (curing process) is performed after the molding. Thereby, the ring magnet excellent in a magnetic characteristic, heat resistance, intensity | strength, etc. can be obtained, reducing the amount of resin.

  For injection molding, for example, polyethylene, polypropylene, polystyrene, acrylonitrile / styrene resin, acrylonitrile / butadiene / styrene resin, methacrylic resin, vinyl chloride, polyamide, polyacetal, polyethylene terephthalate, ultrahigh molecular weight polyethylene, polybutylene terephthalate, Thermoplastic resins such as methylpentene, polycarbonate, polyphenylene sulfide, polyetheretherketone, liquid crystal polymer, polytetrafluoroethylene, polyetherimide, polyarylate, polysulfone, polyethersulfone, and polyamideimide can be used.

《Field》
The field of the rotating machine is usually configured by combining the field permanent magnet of the present invention and a field yoke (a case made of a soft magnetic material or the like). For example, the field magnet of the rotating machine is formed by housing and integrating the ring magnet according to the present invention in a substantially cylindrical case (housing). In this case, the ring magnet and the case can be integrated by, for example, press-fitting or bonding. Further, a field magnet may be configured by disposing a ring magnet on the outer peripheral side of a substantially cylindrical shape or a substantially columnar shape.

  The field according to the present invention may be a stator or a rotor. The rotor may be an inner rotor or an outer rotor.

《Rotating machine》
The rotating machine using the field permanent magnets of the present invention is used, for example, as a drive motor for each device mounted on an automobile or a drive motor for home appliances.

"Constitution"
FIG. 1 shows a rotor R (armature) and a stator S (field) which are the main parts of a DC motor M which is an embodiment of the rotating machine of the present invention. The ring magnet 1 (field permanent magnet) constituting the stator S is shown in FIG. The DC motor M is a 4-pole 14-slot type. The DC motor M is used for driving an in-vehicle device.

  The rotor R has 14 slots formed by laminating electromagnetic steel plates (soft magnetic materials), and a coil (not shown) formed by winding an electric wire in each slot. The end of each coil is connected to a commutator that rotates integrally with a rotating shaft (not shown). When each commutator comes into contact with a brush (not shown), DC power is supplied to each coil.

  The stator S includes a ring magnet 1 and a case 2 made of soft steel (soft magnetic material) formed into a bottomed cylindrical shape. The ring magnet 1 is fitted in the case 2 and both are integrated by press-fitting or bonding. In addition, in FIG. 1, in order to show the whole ring magnet 1, case 2 was shown with the half cross section.

  As shown in FIG. 1 or FIG. 2, the ring magnet 1 has a substantially cylindrical shape, and four vertical grooves 11 to 14 are alternately formed between the four magnetic poles (transition region). The ring magnet 1 is a bonded magnet made of Nd—Fe—B rare earth anisotropic magnet powder and epoxy resin (binder resin). More specifically, the ring magnet 1 is first heated in a semi-radially oriented magnetic field by filling a compound (magnet raw material) made of rare earth anisotropic magnet powder and binder resin into a cylindrical cavity. Thereby, each magnet particle changes its posture in the softened or melted resin so that the easy axis of magnetization is oriented along the orientation magnetic field. When compression molding and cooling and solidification are performed in this state, a substantially cylindrical shaped body is obtained. By curing the molded body and thermosetting the binder resin, a substantially cylindrical bonded magnet can be obtained. A ring magnet 1 according to an embodiment of the present invention is obtained by attaching the bond magnet to the case 2 and performing straight magnetization.

  By the way, the vertical grooves 11 to 14 are easily formed by making the tip of the punch used when compressing the compound filled in the cylindrical cavity into a convex shape corresponding to the concave shape of the vertical grooves 11 to 14. Is possible. In addition, the manufacturing process of the bonded magnet is also described in detail in, for example, the aforementioned International Publication (WO2011 / 126023).

  By the way, the vertical grooves 11 to 14 (also simply referred to as “longitudinal grooves 11 and the like”) are arranged in a reversed direction (alternately arranged) one by one in each transition region. In addition, the basic shape of each of the longitudinal grooves 11 is the same. Specifically, for example, the vertical groove 11 is bilaterally symmetric with respect to the rotation axis l, opens at one end 111 of the ring magnet 1, and has a substantially V shape with the deepest portion 112 on the other end side as a vertex. The shape is cut into a letter shape. However, the corner of the one end 111 and the corner of the deepest part 112 are both rounded, and the contour line (outline) of the vertical groove 11 is smoothly continuous.

<Evaluation>
The relationship between the shape of the vertical groove 11 and the like and each characteristic (weight, magnetic flux amount or cogging torque) was obtained by simulation. These relationships are shown in FIGS. 3A to 3C (they are simply referred to as “FIG. 3”).

At this time, the ring magnet was calculated with an outer diameter: φ30.0 mm, an inner diameter: φ27.0 mm, a wall thickness: 1.5 mm, and a length (magnet length L): 35.0 mm. The vertical groove has a groove width at the opening end: 5 mm (constant), a depth from the opening end to the deepest part (groove height H): 23 mm, and the inclination angle (θ) shown in FIG. 2 is 0 °, 2 °. Calculations were made for each case of 4 ° or 6 °. Here, the inclination angle (θ) is an angle at which the side surface of the vertical groove is inclined with respect to the center line of the vertical groove extending in the axial direction, and the opening angle of the V-shaped vertical groove (V-shaped angle). Or the apex angle) is 2θ. Since the groove width at the opening end is constant, θ = 0 ° indicates a case where the vertical groove has a rectangular shape (5 mm × 23 mm). In each figure, the vertical axis represents the characteristic (X) of each sample made of a ring magnet provided with vertical grooves 11 and the like, and the characteristic (X) of a reference sample made of a complete cylindrical ring magnet not provided with vertical grooves 11 and the like. ₀ ) and the change rate calculated based on (100 × (X−X ₀ ) / X ₀ %).

  A ring magnet having a thickness larger than the air gap (0.5 mm) between the rotor and the stator, and a longitudinal groove having a groove height ratio (H / L) of 1/2 to 2/3 (example: H / L = 0) .66≈2 / 3), first of all, a reliable dust trap becomes possible. In addition to this, as is clear from FIG. 3, by devising the shape of the longitudinal groove, the weight and cogging torque can be reduced without substantially reducing the amount of magnetic flux of the ring magnet that is a field permanent magnet. It became clear that they could be compatible.

M DC motor (rotary machine)
S Stator R Rotor 1 Ring magnet 11 Vertical groove

Claims (4)

A permanent magnet for a field used for a field of a rotating machine, comprising a cylindrical ring magnet with a constant thickness in which different magnetic poles extending in the axial direction are alternately arranged in the circumferential direction,
The ring magnet is alternately arranged in the axial direction in a transition region in which the magnetic pole transitions from one to the other, and has a longitudinal groove that opens on one end side in the axial direction and extends to the other end side,
At least one of the longitudinal grooves is a groove height that is a ratio of a groove height (H) that is a length from the opening end to a deepest portion with respect to a magnet length (L) that is an axial length of the ring magnet. The ratio (H / L) is 1/2 to 2/3,
The permanent magnet for field, wherein the sum of the heights of the vertically arranged vertical grooves is equal to or greater than the magnet length.   2. The permanent magnet for a field according to claim 1, wherein the vertical groove has a substantially V-shape or a substantially U-shape in which the groove width monotonously decreases from the opening end to the deepest portion.   The field permanent magnet according to claim 2, wherein the magnetic pole is magnetized straight.   The field ring permanent magnet according to claim 1, wherein the ring magnet is formed of a bonded magnet in which magnet powder is bonded with resin.

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