JP2009284568A - Electromagnetic structure of slotless brushless dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slotless brushless DC motor which suppresses an iron loss in a PWM control by increasing inductance. <P>SOLUTION: The slotless brushless DC motor is constituted in such a manner that: the motor is composed of a rotor core 5 having a stator core 3 concentrically formed with a prescribed air gap 7 and a hollow hole; a concentrated winding coil 2 is firmly adhered on the peripheral face of the stator core 3 which opposes the air gap 7 via an insulating body 6 at an equal interval; and permanent magnets 4 are arranged in the rotor core 5 so that they constitute prescribed magnetic poles. The stator core 3 is formed into a cylindrical shape by using laminated electromagnetic steel plates, and a soft magnetic protrusion 1 is formed in an air core of the concentrated winding coil 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a configuration of an armature of a slotless brushless DC motor stator in a brushless DC motor used for FA and OA.

A stator of a conventional slotless brushless DC motor is configured by fixing an armature coil to a cylindrical laminated electromagnetic steel sheet having no slot via an insulating sheet. For example, FIG. 3 is an example shown in Japanese Utility Model Publication No. 7-50867. In the gap 21 between the permanent magnet rotor 18 and the stator core 11 having a laminated structure surrounding the permanent magnet rotor 18, FIG. An insulating cover 12 that covers the cylindrical inner surface and both end surfaces of the stator core 11 and is fixed to the stator core 11, and is projected on the inner surface of the insulating cover 12 by a number three times the number of magnetic pole pairs. The single-layer wound coil 13 has a projection 17 on which the single-layer wound coil 13 is mounted. The single-layer wound coil 13 is aligned with the inner surface of the insulating cover 12 with the coil sides 14 in contact with each other. It is comprised so that the both end surfaces of 12 may be covered.
No. 7-50867 JP-A-1-315243

In the conventional slotless brushless DC motor, the magnetic gap is large and the armature winding inductance is small. Therefore, since the electric time constant of the motor becomes small, when driving in combination with a PWM amplifier, there is a problem that the harmonic component contained in the current waveform becomes large and the iron loss increases. As a method for increasing the armature winding inductance, the present applicant has applied for a motor in which a small slot is provided in a stator and the armature winding is divided into a small slot and a gap (Japanese Patent Laid-Open No. Hei 1). No. 315243), and the coil is divided and disposed, so that there is a problem that productivity is poor.
Accordingly, an object of the present invention is to provide a slotless brushless DC motor that can increase inductance and suppress motor iron loss during PWM driving.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 is composed of a stator core disposed concentrically with a predetermined gap and a rotor core having a hollow hole, and an insulator is provided on a circumferential surface of the stator core facing the gap. In the slotless brushless DC motor, in which concentrated winding coils are fixed at regular intervals, and permanent magnets are arranged at regular intervals so as to constitute predetermined magnetic poles in the rotor core,
The stator iron core is formed into a cylindrical shape with laminated electromagnetic steel sheets, and a soft magnetic projection is provided on the air core of the concentrated winding coil.
According to a second aspect of the present invention, in the slotless brushless DC motor according to the first aspect, a cylindrical magnetic body is provided in the gap so as to be in close contact with the protrusion.
A third aspect of the present invention is the slotless brushless DC motor according to the first or second aspect, wherein the ratio of the air core width to the coil pitch of the concentrated winding coil is 0.45 or more. It is.

According to the first aspect of the present invention, since the equivalent magnetic gap is reduced, the self-inductance of the stator coil can be increased. Therefore, the harmonic component contained in the current waveform when driven in combination with the PWM amplifier is suppressed, and iron loss can be reduced.
Further, in the case of the same permanent magnet input amount, the magnetic flux density of the air gap can be increased, so that the efficiency of the motor is improved. If the gap magnetic flux density is the same, the permanent magnet can be made smaller, so the cost can be reduced.
In addition, the coil is pre-winded using self-bonding wires, and the coil air core is positioned with soft magnetic protrusions so that the coil can be placed accurately and the coil is supported by the stator core. It is possible to manufacture a slotless brushless DC motor with increased strength and high reliability.
According to the second aspect of the present invention, the number of interlinkage magnetic fluxes of the coil is increased by fixing a cylindrical magnetic body made of a soft magnetic material to the surface facing the permanent magnet so as to contact the protrusion. Further improvement in motor efficiency can be realized.
According to the third aspect of the present invention, since magnetic saturation of the protrusion does not occur, the leakage magnetic flux is reduced, the motor efficiency is improved, and a motor excellent in torque linearity with respect to current can be realized.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram (a front sectional view) illustrating a slotless brushless DC motor according to a first embodiment of the present invention. This example shows an example of an inner rotor type motor having 8 poles and 6 coils. The stator core 3 is configured by laminating silicon steel plates. The soft magnetic protrusions 1 are integrated with the stator core 3, and six are punched on the inner peripheral surface of the stator core 3. The shape of the protrusion 1 is substantially the same as the shape of the air core portion of the concentrated winding coil (hereinafter simply referred to as “coil”) 2, and the coil 2 is fixed to the protrusion 1 via an insulator 6. Alternatively, the coil 2 prewinded on the bobbin may be fixed to the protrusion 1.

When the width of the air core part of the coil 2 is x, x is selected so as to satisfy the following expression with respect to the coil pitch Cp.
X / Cp ≧ 0.45 (1)
Hereinafter, the process of deriving the equation (1) will be described. Since the magnetic flux of the permanent magnet 4 is concentrated on the protrusion 1, it is necessary to select the protrusion width Wt so that the protrusion is not saturated. If the magnetic flux density Bg of the air gap is 0.8 T and the saturation magnetic flux density Bs of the protrusion 1 is 1.8 T, the air core width x of the coil 2 is almost the same as the protrusion width Wt, and the following equation is established.
Bg ・ Cp / Wt ≦ Bs (2)
∴ Bg / Bs ≤ Wt / Cp
∴ Bg / Bs ≤ x / Cp
∴ 0.8 / 1.8 ≦ x / Cp
Ｘ x / Cp ≧ 0.444
from this result,
X / Cp ≧ 0.45
It was.

In this example, the coil 2 is R-shaped using a self-bonding wire so as to fit the inner peripheral surface of the stator core 3, and the protrusions 1 are interposed via the insulator 6 so that the coils 2 are equally spaced. By fixing to the coil 2, the coil 2 can be accurately positioned and fixed.
The coil 2 is connected to form a predetermined magnetic pole, and the stator 8 is formed. The permanent magnets 4 are alternately fixed to the surface of the rotor core 5 made of a soft magnetic material so that adjacent magnetic poles are different from each other, and are arranged so as to face the coil 2 through the gap 7. The rotor core 5 is fixed integrally with the shaft, and is rotatably supported by a bearing (not shown) to constitute a motor.

  FIG. 2 is a diagram (a front sectional view) showing a slotless brushless DC motor according to a second embodiment of the present invention. In this example, a cylindrical magnetic body 9 made of a soft magnetic material is fixed to the opposing surface of the permanent magnet 4 so as to be in close contact with the protrusion 1 of the first embodiment. Other configurations are the same as those in the first embodiment.

The figure which shows the slotless type DC brushless motor in Example 1 of this invention (front sectional drawing) The figure which shows the slotless type DC brushless motor in Example 2 of this invention (front sectional drawing) The figure which shows the slotless type DC brushless motor of a prior art example

Explanation of symbols

1 Protrusion 2 Concentrated Winding Coil 3 Stator Core 4 Permanent Magnet 5 Rotor Core 6 Insulator 7 Gap 8 Stator 9 Cylindrical Magnetic Body

Claims (3)

Concentric winding coils are arranged concentrically with a predetermined gap and a rotor core having a hollow hole, and concentrated winding coils are equidistantly arranged on the peripheral surface of the stator core facing the gap via an insulator. In the slotless type brushless DC motor, in which permanent magnets are arranged at equal intervals so as to form a predetermined magnetic pole in the rotor core, while being fixed,
A slotless brushless DC motor, wherein the stator iron core is formed in a cylindrical shape by a laminated electromagnetic steel plate, and a soft magnetic projection is provided on an air core portion of the concentrated winding coil.   2. The slotless brushless DC motor according to claim 1, wherein a cylindrical magnetic body is provided in the gap so as to be in close contact with the protrusion.   3. The slotless brushless DC motor according to claim 1, wherein a ratio of a width of an air core portion of the concentrated winding coil to a coil pitch is 0.45 or more.

Images