JP2014165930A - Rotor of brushless motor, brushless motor, and stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient brushless motor capable of downsizing and effectively utilizing magnetic flux of a rotor magnet.SOLUTION: A rotor 100 includes: a rotor magnet 103; a pair of rotor yokes 104, 105 on which a dent into which one end part in an axial direction of the rotor magnet 103 is buried is formed; and a pair of magnetic pole parts 106, 107 each of which has a roughly cylindrical shape of a structure in which a plurality of tabular magnetic materials are laminated in an axial direction and is in contact with an outer circumference of each of the rotor yokes 104, 105.

Description

  The present invention relates to a motor characterized by the structure of a rotor.

  In a brushless DC motor represented by a stepping motor or the like, a hybrid motor (HB motor) in which a rotor core has a hybrid structure of a magnet (permanent magnet) and a rotor yoke is known. HB motors are required to be small and have high performance as equipment becomes smaller and has higher performance.

  FIG. 5 conceptually shows the magnetic circuit of the HB motor in the prior art. In the structure shown in FIG. 5, the rotor core 500 includes a rotor yoke in which a magnet (permanent magnet) 502 magnetized with one pole in the axial direction and an N pole in the other axial direction and a plurality of electromagnetic steel plates laminated in the axial direction. 503. In the case of this structure, as shown in the figure, the magnetic flux from the N pole first proceeds in the axial direction from the magnet 502 toward the rotor yoke 503, then changes direction in the middle, proceeds in the radial direction (direction away from the center of the axis), It reaches the magnetic pole 501 on the stator side.

  In this case, since the magnetic flux traveling in the radial direction is oriented in a direction parallel to the laminated surface of the electromagnetic steel sheets, an effect of reducing the magnetic resistance of the magnetic path is obtained. On the other hand, since the magnetic flux traveling in the axial direction flows in the laminating direction of the electromagnetic steel sheets, the influence of the gap due to the insulation treatment and lamination of the electromagnetic steel sheets appears greatly, and the magnetic resistance increases. That is, the magnetic resistance of the magnetic path in the axial direction in the rotor yoke 503 is increased. This tendency increases as the distance from the magnet 502 increases. Due to the problem that the magnetic resistance of the magnetic path in the axial direction is high, in the structure shown in FIG. 5, the magnetic flux in the axial direction tends to be unevenly distributed and the magnetic flux distribution is poor. Therefore, the magnetic flux efficiency is poor and sufficient torque cannot be obtained.

  As an approach to this problem, a technique described in Patent Document 1 is known. FIG. 6 shows a rotor 600 in the technique described in Patent Document 1. The rotor 600 is fixed to the outside of the rotor yokes 603 and 604 and the rotor yokes 603 and 604 which are adjacent to the shaft 601 which is a shaft member in the axial direction and is adjacent to the rotor magnet 602 and made of an annular magnetic material. It has a structure provided with rotor cores 605 and 606 having a structure in which a plurality of steel plates are laminated in the axial direction.

  In the structure shown in FIG. 6, since the rotor yokes 603 and 604 are not a structure in which electromagnetic steel plates are laminated, the phenomenon that the magnetic flux efficiency described with reference to FIG. 5 deteriorates can be suppressed.

Japanese Utility Model Publication No. 6-52380

  However, in the structure shown in FIG. 6, since the rotor cores 605 and 606 are separated in the axial direction, the motor is increased in size. In particular, in order to obtain a large torque, it is necessary to use a magnet 602 having a large axial dimension, but in that case, an increase in the axial dimension is inevitable. A structure in which the axial dimensions of the rotor yokes 603 and 604 and the rotor cores 605 and 606 are shortened is conceivable. However, if this is done, the effective outer peripheral area of the rotor core 600 cannot be secured, and the magnetic flux is excessively concentrated in a narrow region. The decrease in total magnetic flux and the increase in loss become remarkable, the efficiency decreases, and the torque decreases.

  In such a background, an object of the present invention is to provide a highly efficient brushless motor that can effectively use the magnetic flux of the rotor magnet while achieving downsizing.

  According to the first aspect of the present invention, there is provided a rotor magnet having a substantially columnar shape or a substantially cylindrical shape, a pair of rotor yokes in which one end of the rotor magnet in the axial direction is buried, and a plate-like magnetic A brushless motor rotor having a substantially cylindrical shape having a structure in which a plurality of materials are laminated in the axial direction, and a pair of magnetic pole portions in contact with the outer periphery of the pair of rotor yokes.

  According to the first aspect of the present invention, since both ends of the rotor magnet in the axial direction are buried in the recess of the rotor yoke, a rotor with a reduced axial dimension can be obtained. Further, by providing the magnetic pole part on the outer periphery, a rotor yoke having a property that the magnetic resistance does not depend on the direction can be adopted, and the phenomenon that the magnetic resistance increases in the direction of the magnetic path in the rotor yoke can be suppressed. For this reason, both downsizing and high efficiency (high torque) can be achieved.

  According to a second aspect of the present invention, in the first aspect of the invention, the pair of rotor yokes are spaced apart in the axial direction, and the outer surface of the rotor magnet is covered with the rotor yoke except for the spaced portions. The outer periphery of the rotor yoke is further covered with the magnetic pole portion.

  According to the second aspect of the present invention, since the effective area of the magnetic pole on the rotor side can be secured large, it is possible to further pursue both miniaturization and high efficiency.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the pair of end faces in the axial direction of the pair of rotor yokes are covered with a magnetic shield material.

  According to the third aspect of the present invention, leakage of magnetic flux from the end faces at both ends in the axial direction of the rotor yoke is suppressed, and the magnetic flux generated by the rotor magnet can be used more effectively.

  The invention according to claim 4 is the invention according to claim 3, wherein the magnetic shield material is a laminate of electromagnetic steel plates in the axial direction.

  According to the fourth aspect of the present invention, a magnetic shield material having a property of high magnetic resistance in the axial direction and low magnetic resistance in the direction perpendicular to the axis is obtained, and suppression of leakage of magnetic flux from the axial end face is obtained. The effect and the effect of reducing the magnetic resistance of the magnetic path of the magnetic flux entering and exiting from the outer peripheral surface of the rotor core can be obtained more effectively.

  The invention according to claim 5 is the invention according to claim 4, characterized in that the magnetic steel sheet has a property that the magnetic resistance in the thickness direction is larger than the magnetic resistance in the direction parallel to the surface.

  According to the fifth aspect of the invention, the magnetic shield material can further suppress the leakage magnetic flux from the axial end surface of the rotor core, and can further reduce the magnetic resistance of the magnetic flux traveling in the direction perpendicular to the axis within the magnetic shield material. Can be obtained.

  A sixth aspect of the present invention is a brushless motor using the rotor according to any one of the first to fifth aspects.

  A seventh aspect of the present invention is a stepping motor having the structure of the brushless motor according to the sixth aspect.

  ADVANTAGE OF THE INVENTION According to this invention, the highly efficient brushless motor which can utilize effectively the magnetic flux of a rotor magnet, achieving size reduction is obtained.

It is sectional drawing of the rotor of embodiment. It is sectional drawing of the rotor core of embodiment. It is a key map of the magnetic circuit in the rotor core of an embodiment. It is sectional drawing of the rotor core of other embodiment. It is a conceptual diagram of the magnetic circuit in the rotor core of a prior art. It is sectional drawing of the rotor in a prior art. It is sectional drawing of the rotor core of a comparative example. It is sectional drawing of the rotor core of a modification.

1. First embodiment (structure)
FIG. 1 shows a rotor 100 according to the embodiment, and FIG. 2 shows a rotor core 101. The difference between FIG. 1 and FIG. 2 is only the presence or absence of the shaft 102 which is a shaft member. The rotor 100 is a rotor of a stepping motor. The rotor 100 includes a rotor core 101 and a shaft 102. The shaft 102 is fixed in a state of penetrating through the center of the rotor core 101. The shaft 102 is rotatably held by a stator-side member (for example, an outer casing) (not shown) by a bearing structure (not shown), and the rotor 100 can be rotated by this structure. Although not shown, the structure on the stator side of the stepping motor provided with the rotor 100 is the same as that of a general stepping motor.

  The rotor core 101 includes a rotor magnet 103, rotor yokes 104 and 105, and magnetic pole portions 105 and 106. The rotor magnet 103 has a substantially columnar shape (or a substantially cylindrical shape) having a hole through which the shaft 102 penetrates at the center, and one end portion (for example, the upper end portion in the figure) in the axial direction has an N or S pole. The other end (for example, the lower end in the figure) is a permanent magnet magnetized with S or N poles. The rotor yoke 104 has a substantially cylindrical structure, and has a substantially crucible shape having a cylindrical recess 104a in which one end in the axial direction of the rotor magnet 103 is buried at one end. . The rotor yoke 105 is the same member as the rotor yoke 104 and is used in a state where the direction in the axial direction is reversed. A recess 105 a is also formed in the rotor yoke 105.

  The rotor yokes 104 and 105 are a single member obtained by forging or pressing a carbon steel for mechanical structure or a rolled steel for general structure, and are not an integrated structure in which a plurality of electromagnetic steel sheets are stacked. Further, the rotor yokes 104 and 105 are made of a magnetically non-directional material that has no difference in magnetoresistance between the axial direction and the direction perpendicular to the axis.

  In this example, one end (upper end in the figure) of the rotor magnet 103 is embedded in the recess 104a of the rotor yoke 104, and the rotor magnet 103 and the rotor yoke 104 are coupled. Further, the other end portion (the lower end portion in the figure) of the rotor magnet 104 is embedded in the recess 105a of the rotor yoke 105, and the rotor magnet 103 and the rotor yoke 105 are coupled.

  The rotor yokes 104 and 105 are separated from each other in the axial direction, and the side surface of the rotor magnet 103 can be seen in this separated portion when viewed from the direction perpendicular to the axis. The outer periphery of the rotor magnet 103 in the portion embedded in the recess 104a of the rotor yoke 104 and the portion embedded in the recess 105a in the rotor yoke 103 is covered with the rotor yokes 104 and 105. Further, the outer periphery thereof is covered with the magnetic pole portion 106. , 107. In other words, the portion of the outer periphery of the rotor magnet 103 other than the portion where the rotor yokes 104 and 105 are separated in the axial direction is covered with the rotor yokes 103 and 104, and the outer periphery thereof is covered with the magnetic pole portions 106 and 107. ing. Here, the area covered by the rotor yokes 104 and 105 and the magnetic pole portions 106 and 107 on the outer periphery of the rotor magnet 103 is larger than the area of the outer periphery of the rotor magnet 103 in the portion where the rotor yokes 104 and 105 are separated.

  The magnetic pole portions 106 and 107 have a substantially cylindrical shape with a small thickness. The magnetic pole portions 106 and 107 have a structure in which a plurality of magnetic steel sheets punched into an annular shape having a tooth shape on the outside are stacked in the axial direction. The axial dimensions of the magnetic pole portions 106 and 107 are substantially the same as those of the rotor yokes 104 and 105. The rotor yoke 104 is fitted and fixed inside the magnetic pole part 106, and the rotor yoke 105 is fitted and fixed inside the magnetic pole part 107.

(Function)
As shown in FIG. 3, the magnetic flux emitted from the N pole of the rotor magnet 103 first proceeds in the axial direction in the rotor yoke 104, and then proceeds in the radial direction (direction away from the axis) by changing the direction. Here, since there is a component that wraps around the side surface of the rotor magnet 103, the magnetic flux is bent in the rotor yoke 104 as shown in the figure. In this magnetic path, there is a portion where the magnetic flux proceeds in the axial direction, but the magnetic resistance in the rotor yoke 104 is not directional, so even if there is a magnetic flux traveling in the axial direction, there is no increase in the magnetic resistance there. The tendency for magnetic flux to be unevenly distributed is also suppressed. This is the same in the rotor yoke 105.

  Further, since the magnetic pole portion 106 having a structure in which electromagnetic steel plates are laminated in the axial direction is arranged on the outer periphery of the rotor yoke 104, the magnetic flux is effectively emitted from the rotor 100 in the radial direction, and the magnetic pole on the stator side An efficient magnetic circuit is formed with 110. That is, in the magnetic pole portion 106, the magnetic flux travels in the radial direction due to the influence of the gap between the insulating layer and the lamination of the magnetic steel sheet, and thus proceeds naturally in the radial direction and exits from the magnetic pole portion 106 toward the radially outer side. To do. Note that the magnetic flux emitted from the magnetic pole 110 on the stator side returns to the south pole of the rotor magnet 103 along the reverse path described above, but an efficient magnetic circuit is formed in the magnetic pole portion 107 as well as the magnetic pole portion 106. The

(Superiority)
The rotor core 101 has a two-body structure made of different materials, and the portions in contact with the rotor magnet 103 are rotor yokes 104 and 105 made of general steel. According to this structure, the flow of magnetic flux from the rotor magnet 103 can be efficiently guided to the magnetic pole portion 106 formed of an electromagnetic steel plate. Further, by making the rotor yokes 104 and 105 into crucibles, the axial dimension can be shortened while using the thick rotor magnet 103. That is, since both ends in the axial direction of the rotor magnet 103 are buried in the recesses 104a and 105a of the rotor yokes 104 and 105, even when the rotor magnet 103 having a large axial dimension is used, the axial direction of the rotor core 101 itself. An increase in the size of the can be suppressed.

  If the rotor yokes 104 and 105 shown in FIG. 3 and the L1 and L2 in the magnetic pole portions 106 and 107 are not present, that is, in the state shown in FIG. 6, the thickness of the magnetic pole portions 106 and 107 in the axial direction is reduced. There arises a problem that the magnetic flux is reduced or the loss due to magnetic saturation is increased, and the efficiency is lowered as compared with the structure of FIGS. In the case where the magnetic pole portions 106 and 107 are not provided, that is, only the rotor yoke is used, the component of the magnetic flux emitted in the axial direction (that is, leakage magnetic flux) increases, and the efficiency is also lowered.

Also, if the rotor yokes 104 and 105 in the portions L ₁ and L ₂ shown in FIG. 3 do not exist (see FIG. 7), the magnetic path from the rotor yoke 104 to the magnetic pole part 106 and the magnetic path from the rotor yoke 105 to the magnetic pole part 107. Since the path is interrupted at the portions L ₁ and L ₂ , an effective magnetic circuit is not formed and the efficiency is lowered. That is, in the portions of L ₁ and L ₂ , the magnetic flux has to travel in the axial direction in the magnetic pole portions 106 and 107, but the magnetic pole portions 106 and 107 have a structure in which electromagnetic steel plates are laminated, and the axial magnetoresistance Therefore, the efficiency of the magnetic circuit is inevitably reduced.

(Confirmation of effect)
The rotor core shown in FIGS. 1 to 3 has the same dimensions, and the structure shown in FIG. 5 was prepared as a comparative example. A sample of a stepping motor having the same structure was prototyped, and holding torque (torque capable of maintaining a stopped state at a certain angular position), which is one of the performances required for the stepping motor, was measured under the same conditions. As a result, in the sample of this embodiment shown in FIGS. 1 to 3, the holding torque was 510 mNm, whereas in the comparative example, the holding torque was 450 mNm. That is, compared with the stepping motor which employ | adopted the structure of the rotor core shown in FIG. 5, the stepping motor which employ | adopted the structure of the rotor core of the structure shown in FIGS.

2. Second Embodiment Hereinafter, an example of a structure in which a magnetic shield structure is added to the rotor core of the first embodiment will be described. FIG. 4 shows the rotor core 200. The rotor core 200 has a structure in which magnetic shield plates 201 and 202 are disposed on two end faces in the axial direction of the rotor core 101 of FIGS. The magnetic shield plates 201 and 202 have a structure in which a plurality (for example, four) of disk-shaped electromagnetic steel plates each having a hole in the center are laminated in the axial direction. This electromagnetic steel sheet has a characteristic that the magnetic resistance in a direction parallel to the surface is relatively low and the magnetic resistance in a direction perpendicular to the surface is relatively large. Specifically, the magnetic shield plate 201 is made of an electromagnetic steel plate having a magnetic anisotropy having a relatively large permeability in a direction parallel to the surface and a relatively small permeability in a direction perpendicular to the surface. , 202 are configured.

  Each of the magnetic shield plates 201 and 202 has a laminated structure of electromagnetic steel plates, and each of the electromagnetic steel plates has a magnetic resistance in the axial direction larger than that in a direction parallel to the surface. For this reason, the tendency that the magnetic flux tends to flow in the direction parallel to the surface in the vicinity of the upper surface of the rotor yoke 104 and the lower surface of the rotor yoke 105 in FIG. 4 is stronger than when the magnetic shield plates 201 and 202 are not provided. That is, near the upper surface of the rotor yoke 104 and near the lower surface of the rotor yoke 105, the magnetic flux hardly travels in the axial direction and easily travels in the surface direction, so that a magnetic path in the surface direction is easily formed. For this reason, the generation of magnetic flux (leakage magnetic flux) leaking in the axial direction from the upper surface of the rotor yoke 104 and the lower surface of the rotor yoke 105 is suppressed, and on the other hand, a low-loss magnetic path is formed between the magnetic pole portions 106 and 107, A more efficient magnetic circuit is formed.

(Other)
FIG. 8 shows a modification of the present invention. In the rotor core 101 shown in FIG. 8, the height (axial dimension) of the crucible rotor yokes 104 and 105 is set to be larger than the height (axial dimension) of the cylindrical magnetic pole portions 106 and 107. Yes. By doing so, the side surfaces of the rotor yokes 104 and 105 need to be in contact with the entire inner periphery of the magnetic pole portions 106 and 107, and the edge portions of the rotor yokes 104 and 105 are rounded (added with R). Can do.

  The rotor core of the present embodiment described in the above examples is preferably used for low frequency applications where eddy current loss and hysteresis loss are not particularly important. The use of the present invention is preferably used for a stepping motor, but can also be used for a brushless motor that is not a stepping motor.

  The aspect of the present invention is not limited to the individual embodiments described above, and includes various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the contents described above. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  The present invention can be used for a brushless motor.

  DESCRIPTION OF SYMBOLS 100 ... Rotor, 101 ... Rotor core, 102 ... Shaft, 103 ... Rotor magnet, 104 ... Rotor yoke, 104a ... Depression, 105 ... Rotor yoke, 105a ... Depression, 106 ... Magnetic pole part, 107 ... Magnetic pole part, 110 ... Magnetic pole on the stator side, DESCRIPTION OF SYMBOLS 200 ... Rotor core, 201 ... Magnetic shield plate, 202 ... Magnetic shield plate, 500 ... Rotor core, 501 ... Stator side magnetic pole, 600 ... Rotor core, 601 ... Shaft, 602 ... Rotor magnet, 603 ... Rotor yoke, 604 ... Rotor yoke, 605 ... Rotor core, 606 ... Rotor core.

Claims (7)

A rotor magnet having a substantially cylindrical shape or a substantially cylindrical shape;
A pair of rotor yokes formed with depressions in which one end in the axial direction of the rotor magnet is buried;
A rotor of a brushless motor, comprising: a substantially cylindrical shape having a structure in which a plurality of plate-like magnetic materials are laminated in the axial direction; and a pair of magnetic pole portions in contact with outer peripheries of the pair of rotor yokes. The pair of rotor yokes are separated in the axial direction,
Except for the separated portion, the outer surface of the rotor magnet is covered with the rotor yoke,
The rotor of the brushless motor according to claim 1, wherein an outer periphery of the rotor yoke is further covered with the magnetic pole portion.   3. The rotor of a brushless motor according to claim 1, wherein the pair of end faces in the axial direction of the pair of rotor yokes are covered with a magnetic shield material.   The rotor of a brushless motor according to claim 3, wherein the magnetic shield material is a laminate of electromagnetic steel plates in the axial direction.   5. The rotor of a brushless motor according to claim 4, wherein the electromagnetic steel sheet has a property that a magnetic resistance in a thickness direction is larger than a magnetic resistance in a direction parallel to the surface.   A brushless motor using the rotor according to any one of claims 1 to 5.   A stepping motor having the structure of the brushless motor according to claim 6.

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