JP2006280172A - Dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC motor that provides compatibility between the reduction in cogging torques and the enhancement of torque characteristics by optimizing magnetic balance. <P>SOLUTION: A DC motor is configured such that the inner center of curvature of a magnet arranged within the case of DC motor is deviated toward a radiant direction from its outer center of curvature, and the inner center of curvature of teeth ends of an armature core is deviated toward an opposite-end direction from its outer center of curvature. Further, the following respective areas are set at the values that meet equation 1 (P8/P7)×P6×P1=1.6 to 2.2, equation 2 (P5/(π×P2))×P1≥0.24, equation 3 P3/P4≤1.6; where the reference symbols notify number of core slots P1, core outside diameter P2, core slot width P3, curvature radius of teeth end of inner curved surface end P4, teeth width P5, thickness of teeth end P6, deviation of center of curvature of teeth end P7, and deviation of center of curvature of magnet P8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of DC motors, and more particularly, to a DC motor that optimizes the magnetic balance of the stator and armature that are housed therein.

  The structure of a direct current motor, for example, a direct current motor with a brush, includes a magnet arranged in an outer motor case to form a stator (stator), and the armature rotates with a predetermined gap (air gap) inside the stator. What is freely arranged is common.

  The armature includes a laminated core formed by laminating a plurality of substantially T-shaped teeth in a cross-sectional view, and laminating electromagnetic steel plates that are radially formed with slots between the teeth, and substantially at the center of the laminated core. The shaft on which the commutator is disposed is fixed, and further, the winding portion of the laminated core teeth is insulated, and then a winding made of a copper material or the like is wound. As the winding method, a so-called flyer method is widely adopted in which the two slots in the laminated core are wound between teeth at positions close to 180 degrees (close to the axial symmetry of the shaft). The start and end of winding are connected to the commutator. The principle of rotating the armature uses the magnetic force of the magnet and the repulsive force and attractive force of the electromagnetic force obtained when the winding is energized, and it is continuously switched by switching the polarity of the current flowing through the winding with the brush and commutator. It is intended to rotate.

  The laminated core of the armature having the above structure has a portion having a low magnetic resistance (tooth) and a portion having a high magnetic resistance (winding portion). If this magnetic resistance difference is large, the peak-to-peak value of the cogging torque is increased. As a result, it has been a cause of uneven rotation in the DC motor.

  The structure of a laminated core of a DC motor that reduces such cogging torque is disclosed in the following patent documents.

  First, in Patent Document 1, the slots of the laminated core of the electric motor are formed at equal pitches and equal widths, and the teeth bases are formed at equal widths at unequal pitches. An invention characterized by reducing the change of the above is disclosed.

Further, in Patent Document 2, double flyers are formed by forming slots of DC motor laminated cores with unequal pitches and equal widths, and forming teeth bases with equal pitches and equal widths to limit the number of slots to an even number. There has been disclosed a device characterized in that the productivity is improved by the winding of the system and the change in magnetic resistance is reduced.
JP 2002-291210 A (page 5-6, FIG. 1) Japanese Utility Model Publication No. 5-23756 (page 3-4, Fig. 2)

By the way, since the shape of the laminated core of the magnet and the armature has a great influence on the performance of the DC motor, it is necessary to appropriately set the shape of the magnet and the laminated core and optimize the state of the magnetic flux density flowing through them. . However, the following problems need to be considered in the setting.
(1) When the number of slots in the laminated core is increased, the cogging torque is reduced, but the winding transition length is increased, the winding resistance is increased, and the torque characteristics are lowered.
(2) When the tooth width of the laminated core is narrowed, the number of windings can be increased, so the electromagnetic force increases. However, the magnetic flux density of the core may increase and magnetic saturation may occur, resulting in a decrease in torque characteristics. To do.
(3) When the slot width of the laminated core is increased, winding becomes easier, but the difference in magnetic resistance increases and the cogging torque also increases.
(4) Increasing the radius of curvature (the so-called R dimension) of the tip of the teeth forming the slot of the laminated core can facilitate the die structure of a press for punching a steel sheet and reduce the manufacturing cost. The gap between the laminated core and the magnet at the slot position increases, the magnetic resistance increases, and the torque characteristics deteriorate.
(5) When the outer curvature center and the inner curvature center of the substantially C-shaped magnet are decentered in a cross-sectional view, the gap between the opposing armature and the magnet changes, and the switching between the N pole and the S pole of the magnet is smooth. Thus, the cogging torque is reduced, but the torque characteristic is lowered because there is a portion where the gap with the rotor is increased. In general, the surface magnetic flux density of the magnet is highest at the center.

  Based on the above-mentioned problem, the invention of Patent Document 1 has a slot having a lot of winding space because the winding space of the slot is different when the winding is wound the same number of times in each slot. . For this reason, as compared with the conventional laminated core shape having the same winding space, the total number of conductors tends to decrease and the magnetic resistance tends to increase, and there is a problem that the torque characteristics deteriorate.

Further, the idea of Patent Document 2 is a rotating lamination that reduces a change in magnetic resistance that is normally performed when a laminated core is manufactured (in order to make the difference in thickness difference and iron loss of each steel sheet equal, There is a problem in the manufacturing method in which the layers are stacked while sequentially rotating. In other words, because the width of the tip of the teeth is set to an unequal pitch, the rotational pitch is doubled when the steel plates are rotationally laminated. There has been a problem that the change in the value tends to increase and the cogging torque increases.
In addition, since the number of slots (the number of teeth) is an even number, the teeth of the laminated core through which the magnetic flux passes are symmetric with respect to the magnet, and the change in the magnetic resistance is larger than in the case of the odd number of slots. Coupled with the problem, there was a problem that the cogging torque increased.

  Accordingly, the present invention has been made in view of the above problems, and provides a DC motor that optimizes the magnetic balance that is affected by the shape of the laminated core and the magnet, and achieves both a reduction in cogging torque and an improvement in torque characteristics. To do.

In order to solve the above problems, the direct current motor of the present invention is configured as follows. The core of the armature is a laminated core formed by laminating electromagnetic steel sheets.
First, the inner curvature center of the magnet arranged following the inner peripheral surface of the cylindrical motor case forming the yoke of the DC motor is decentered by a predetermined amount in the radial direction from the outer curvature center, and the lamination in which the armature slot is formed The center of curvature of the tip of the core teeth is decentered by a predetermined amount from the outer center of curvature toward the anti-tip, and each part of the following (1) to (8) of the DC motor is expressed by Formula 1, It is characterized in that it is set to a value satisfying Equation 2 and Equation 3.
(1) Number of slots P1 in the laminated core
(2) Outer diameter P2 of laminated core
(3) Slot width P3 of the laminated core
(4) Curvature radius P4 of the inner curved end of the teeth tip of the laminated core
(5) Laminated core teeth width P5
(6) Thickness P6 at the center of the tooth tip of the laminated core
(7) Eccentricity P7 between the center of outer curvature and the center of inner curvature of the teeth tip of the laminated core
(8) Eccentricity P8 between the outer curvature center and the inner curvature center of the magnet
Formula 1: (P8 / P7) × P6 × P1 = 1.6 to 2.2
Formula 2: (P5 / (π × P2)) × P1 ≧ 0.24
Formula 3: P3 / P4 ≦ 1.6

  Since the direct current motor of the present invention has the above configuration, the cogging torque is reduced by 30% to 40% and the torque characteristic is 1 as compared with a motor of the same size composed of a conventional magnet and a laminated core. Increase by 20% to 20%.

  The above effect makes it possible to provide a direct current motor in which cogging torque is reduced and torque characteristics are improved, and its contribution to the industry is remarkable.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a DC motor according to the present invention (hereinafter abbreviated as “motor”) will be described in detail with reference to the drawings.

  FIG. 1 is a partially cutaway perspective view showing the structure of the motor of this embodiment, FIG. 2 is a sectional view of the motor of this embodiment, and FIG. 3 is a winding state and magnetic flux in the armature of this embodiment. FIG. 4 is a plan view of the magnet of this example, and FIG. 5 is a plan view (A) and a partially enlarged view (B) of the laminated core of this example.

  As shown in FIG. 1, the motor 1 of this embodiment has a brush 12 disposed on one end side inside a motor case 11 (annular yoke) and two magnets having anisotropy on the inner peripheral surface thereof. 2 is arranged, and the armature 3 is rotatably arranged with a predetermined gap with the magnet 2. These configurations are the same as those of a conventional motor.

  As shown in FIGS. 2 and 3, the magnet 2 is substantially C-shaped in cross-sectional view, and the center of curvature is decentered by a predetermined amount in the radial direction from the center of curvature of the outer side. It is formed in a thick shape. In other words, the center of curvature of the outer curved surface 21 of the magnet 2 coincides with the center of the motor 1 to follow the inner peripheral surface of the motor case 11, but the center of curvature of the inner curved surface 22 extends from the center of the motor 1 to the anti-magnet. It will be eccentric by a predetermined amount in the radial direction.

  Due to the shape of the magnet 2 described above, the surface magnetic flux density at both ends of the inner curved surface 22 is lower than when there is no eccentricity. Further, the gap between the outer edge portion of the rotating armature 3 and the magnet 2 changes, and the vicinity of the central portion of the inner curved surface 22 is closest to the armature 3. As a result, the switching between the N pole and the S pole when the armature 3 rotates becomes smooth, and the cogging torque decreases.

  By the way, for magnetizing the magnet, a method of inserting an iron core with a magnetized coil wound inside to generate a strong magnetic field with the magnet fixed to the motor case, and magnetizing the armature and brush peripheral parts There is a method in which a strong magnetic field is generated and magnetized by placing it in the center of the air-core coil in a state of being assembled and fixed in the motor case. In the magnet 2 of this embodiment, the surface magnetic flux density at the center portion of the inner curved surface 22 is reduced by about 3% to 10% from the conventional one by the magnetizing method appropriately selected at the time of magnetic field shaping. .

  The armature 3 fixes the shaft 32 having the commutator 32a disposed substantially at the center of the laminated core 31 and insulates the winding portions of the seven slots 31d, 31d,. The copper wire 33 is wound around the slot 31d, and the winding end is connected to the commutator 32a. The commutator 32 a is in contact with the brush 12 disposed in the motor case 11 and switches the polarity of the current flowing through the winding 33.

  The laminated core 31 is formed by laminating a plurality of electromagnetic steel sheets punched into a predetermined shape by press working, and reduces the change in magnetic resistance by equalizing the difference in sheet thickness deviation and iron loss. Therefore, each steel plate is formed by being laminated while rotating at a predetermined pitch. In addition, the rotation pitch at the time of lamination | stacking of an electromagnetic steel plate is the same as the arrangement | positioning pitch of the teeth 31a mentioned later.

  As shown in FIGS. 2 and 3, the cross-sectional shape of the laminated core 31 is substantially the same as that of the belt-like base 31b. In addition to forming a letter-shaped tooth 31 a, a plurality of teeth 31 a are arranged radially from the center, and the outer peripheral surface of the tip 31 c is made to coincide with the outer diameter of the armature 3. The center of curvature of the outer peripheral surface of the tip 31c coincides with the center of the laminated core 31, but each center of curvature of the inner peripheral surface is decentered by a predetermined amount from the center of the laminated core 31 in the radial direction on the side opposite to the tip. Yes.

  As shown in FIG. 3, the winding method to the laminated core 31 employs a flyer method in which slots 31d are arranged between slots close to 180 degrees (similar to the shaft axis symmetry) as in the conventional case. ing.

  Note that the flow of magnetic flux of the motor configured as described above is as shown by the arrow a in FIG. 3, where the N pole is on the left side and the S pole is on the right side, the N pole magnet 2, the gap, the laminated core 31, the gap, S The order is the pole magnet 2, the motor case 1, and the N pole magnet 2.

  The motor 1 of the present embodiment has the above-described configuration, but the shape of the magnet 2 and the shape of each part of the laminated core 31 are set as follows in order to optimize the magnetic balance.

  That is, as shown in FIGS. 4 and 5, each part of the magnet 2 and the laminated core 31 is set to parameters P1 to P8 shown in the following (1) to (8), and Equation 1 is substituted for these parameters. To be within a range satisfying Formula 3. These parameters and equations are selected to optimize the magnetic flux density flowing through the magnet 2 and the laminated core 31 in the motor. Note that the radius of curvature r of the outer curved end of the tooth tip 31c is set to 0.15 mm or less, so that the magnetic flux is easily concentrated.

(1) Number of slots P1 in the laminated core
(2) Outer diameter P2 (mm) of laminated core
(3) Slot width P3 (mm) of laminated core
(4) Curvature radius P4 (mm) of the inner curved end of the teeth tip of the laminated core
(5) Teeth base width P5 (mm) of laminated core
(6) Thickness P6 (mm) at the center of the teeth tip of the laminated core
(7) Eccentricity P7 (mm) between the center of outer curvature and the center of inner curvature of the teeth tip of the laminated core
(8) Eccentricity P8 (mm) between the outer and inner curvature centers of the magnet
Formula 1: (P8 / P7) × P6 × P1 = 1.6 to 2.2
Formula 2: (P5 / (π × P2)) × P1 ≧ 0.24
Formula 3: P3 / P4 ≦ 1.6

  In each part of the motor 1 of this embodiment, for example, when the motor size is 30 mm in outer diameter and 47 mm in length, the rate of decrease in surface magnetic flux density at the center of the inner curved surface 22 of the magnet 2 is 8.5. %, The value of Equation 1 is set to 1.960, the value of Equation 2 is set to 0.244, and the value of Equation 3 is set to 1.538.

  In the above setting, the radius of curvature r of the outer curved end portion of the tip end portion of the same size is 0.3 mm or more, the decrease rate of the surface magnetic flux density is 0%, the value of Equation 1 is 1.375, and the value of Equation 2 is Compared with the conventional motor in which the value of 0.218 and Equation 3 is set to 4.667, the cogging torque is reduced by about 34.6%, and the torque characteristics are improved by about 11.4%.

It is a partially cutaway perspective view showing the structure of the motor of the present embodiment. It is sectional drawing of the motor of a present Example. It is explanatory drawing which shows the winding state in the armature of a present Example, and the flow of magnetic flux. It is a top view of the magnet of a present Example. It is the top view (A) and partial enlarged view (B) of the lamination | stacking core of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 11 Motor case 12 Brush 2 Magnet 21 Outer curved surface 22 Inner curved surface 3 Armature 31 Laminated core 31a Teeth 31b Base (of teeth)
31c Tip (of teeth)
31d Slot 32 Shaft 32a Commutator 33 Winding P1 Number of slots of laminated core P2 Outer diameter P3 of laminated core Slot width P4 of laminated core P4 Curvature radius of inner curved end of tooth tip of laminated core P5 of teeth base of laminated core Width P6 Thickness P7 of the center of the core of the laminated core P7 Eccentricity of the outer and inner curvature centers of the teeth of the laminated core P8 Eccentricity of the outer and inner curvature centers of the magnet r Radius of curvature of the outer curved end of the section

Claims (1)

While decentering the inner curvature center of the magnet arranged following the inner peripheral surface of the annular yoke by a predetermined amount in the radial direction from the outer curvature center,
A DC motor is constructed by decentering the inner curvature center of the tooth tip of the core forming the armature slot by a predetermined amount from the outer curvature center toward the opposite tip,
A direct-current motor characterized in that each of the following parts (1) to (8) of the direct-current motor is set to a value satisfying expressions 1, 2 and 3.
(1) Number of core slots P1
(2) Core outer diameter P2
(3) Core slot width P3
(4) Curvature radius P4 of the inner curved end of the core tooth tip
(5) Core teeth width P5
(6) Thickness P6 at the center of the tooth tip of the core
(7) Eccentricity P7 between the outer curvature center and the inner curvature center of the core tooth tip
(8) Eccentricity P8 between the outer curvature center and the inner curvature center of the magnet
Formula 1: (P8 / P7) × P6 × P1 = 1.6 to 2.2
Formula 2: (P5 / (π × P2)) × P1 ≧ 0.24
Formula 3: P3 / P4 ≦ 1.6

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