JPH0734636B2 - Motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called axial air gap type motor in which a rotor and a stator are arranged with their axial end faces facing each other, and in particular, a yoke. The present invention relates to a motor capable of reducing its iron loss while maintaining the thickness dimension of the same as in the conventional case.

[Problems to be Solved by the Related Art and Invention] Generally, a motor used for a rotary drum of a home VTR (video tape recorder) is a so-called axial air gap type motor which is operated by a power source such as a battery. When used in such applications, it is required to reduce the drive current in order to reduce the size and extend the battery life.

Generally, this is the first axial gap type brushless motor.
The structure shown in the figure is known. 2 is a plan view showing the rotor of this motor, and FIG. 3 is a plan view showing the stator.

In FIG. 1, 1 is a rotary shaft, and this rotary shaft 1 has
A rotor yoke 2 that rotates integrally with this is provided. The rotor yoke 2 is formed of a soft magnetic material, and a field rotor magnet 3 uniformly magnetized to 8 poles as shown in FIG. 2 is fixed inside the rotor yoke 2. On the lower end surface of the rotor magnet 3, a three-phase stator coil 4 composed of six coils wound in a fan shape as shown in FIG. 3 is provided. That is, the rotor magnet 3
The stator coil 4 and the stator coil 4 are arranged so that their axial end faces face each other. Reference numeral 5 shown in FIGS. 1 and 3 denotes a Hall element, which is arranged between the three-phase stator coils 4 with a phase difference of 120 degrees in electrical angle. The stator coil 4 and the Hall element 5 are fixed to the stator yoke 7 via the stator substrate 6. The stator yoke 7 is made of a soft magnetic material, the center portion of the stator coil 4 is an air core, and a gap is formed between the rotor magnet 3 and the stator yoke 7.

Further, the hall element 5 detects the position of the rotor magnet 3 and outputs a detection signal thereof, and the rotor magnet 3 causes the stator coil 4 to pass through the hall element 5 through a semiconductor element (not shown) such as a transistor. By sequentially switching according to the output signal of the element 5, a rotational force in a predetermined direction is obtained. That is, the rotor magnet 3
The magnetic flux generated by the magnetomotive force source interlinks with the stator coil 4, and the stator yoke 7 and the rotor magnet 3 form a closed magnetic circuit.

By the way, as the soft magnetic material of the stator yoke 7, structural steel sheets such as SS material (general structural rolled steel material) and SPCC material (cold rolled steel sheet) are generally used. However,
These SS and SPCC materials have low specific resistance (10 μΩ ・ cm
However, there is a drawback that the load due to this iron loss further increases and the drive current of the motor increases because the iron loss mainly due to eddy current loss and hysteresis loss increases.

Therefore, in order to make up for this drawback, a method has been conventionally used to reduce the iron loss by forming the stator yoke 7 using soft ferrite instead of the SS material or SPCC material. However, in this method, although the soft ferrite has a high specific resistance (several tens of Ω · cm), it is possible to reduce iron loss, but the saturation magnetic flux density is 1 / though that of SS materials.
It is as low as about 3, which may cause magnetic saturation easily and the output torque of the motor may be greatly reduced. To prevent such magnetic saturation, make the ferrite thickness three times or more that of SS material. There was a need. Therefore, a motor using such a ferrite has a drawback that the height or thickness in the axial direction becomes large, which leads to an increase in size of the motor itself.

The present invention has been made to solve the above problems, and it is possible to effectively prevent iron loss in the yoke and also to effectively prevent generation of leakage magnetic flux from the yoke. The purpose is to provide a motor.

[Means for Solving the Problems] In the motor according to the present invention, the magnetomotive force source and the armature coil are arranged such that their axial end faces face each other to form an axial gap, and A first coil is formed on each of the end faces that are axially opposite to the opposite end faces of the child coil.
In a motor in which a rotor and a second yoke are provided to form a closed magnetic circuit as a rotor and a stator, the second yoke provided on the armature coil as either the motor or the stator is located on the armature coil side and the electromagnetic field is reduced. An inner layer made of a steel plate that always forms a closed magnetic path, and an inner layer that is located on the opposite side of the inner layer from the armature coil and that is made of a structural steel plate and is magnetically insulated from the inner layer. It is characterized by having a two-layer structure including an outer layer forming a closed magnetic circuit only when magnetic saturation occurs.

[Operation] In the motor according to the present invention, the second yoke provided in the armature coil is in a state of being magnetically insulated from the inner layer made of an electromagnetic steel plate and always forming a closed magnetic circuit, and the inner layer made of a structural steel plate. Since it has a two-layer structure with the outer layer that adheres to the inner layer and forms a closed magnetic circuit only when magnetic saturation of the inner layer occurs, the iron loss in the yoke is effectively reduced by the inner layer made of magnetic steel sheet. In addition, even if the magnetic flux leaking from the inner layer is exceptionally generated, the magnetic flux leaking from the yoke is effectively prevented by the outer layer made of the structural steel sheet.

[Embodiment of the Invention] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 is a vertical cross-sectional view showing a schematic configuration of a motor according to the present invention, and corresponds to FIG. 1 showing a conventional example. Therefore, the same numbers are given to the same components, and duplicate explanations are omitted. Further, FIG. 5 is an enlarged view of a main part to show a state where the rotor and the stator in FIG. 4 face each other.

As shown, the stator yoke 7 is a thin plate-shaped inner layer 9 made of an electromagnetic steel plate called a silicon steel plate, and a thin plate-shaped outer layer 10 made of a structural steel plate such as SS or SPCC.
And are magnetically insulated and closely adhered to each other to form a two-layer structure. Then, the inner layer 9 of the stator yoke 7 is formed in a structure which faces the lower end surface of the rotor magnet 3 in a plane. In this state, the magnetic flux B having the rotor magnet 3 as a magnetomotive force source forms a closed magnetic circuit between the stator yoke 7 and the rotor magnet 3 with a gap between the motor magnet and the stator yoke 7 interposed. The electromagnetic steel sheet such as a silicon steel sheet forming the inner layer 9 of the stator yoke 7 is a material having a small iron loss per unit weight, and the iron loss mainly due to the eddy current loss and the hysteresis loss in this motor configuration is small. Can be suppressed. That is, in the axial air gap type motor, since the air gap length between the motor magnet 3 and the stator yoke 7 is long, the rotor magnet 3 is used in a state of a low permeance coefficient, and particularly the rotor magnet 3 Since most of the materials used are magnets such as barium ferrite and strontium ferrite, the magnetic flux density in the void is small (usually about 2 to 3 KG), and therefore the silicon steel sheet is relatively thin (about 1 mm or less). Even if is adopted as the inner layer 9,
Since the saturation magnetic flux density can be obtained to about 15 KG, the inner layer 9 is hardly magnetically saturated, and the iron loss reducing effect can be sufficiently obtained.

In addition, a rare earth magnet having a large residual magnetic flux density or a large coercive force has recently been used as a material of the rotor magnet 3, and the magnetic flux density in the void may be larger than that of a ferrite magnet. For example, even if the inner layer 9 is magnetically slightly saturated, since the outer layer 10 formed of a structural steel plate is provided in close contact with the inner layer 9,
The magnetic flux passing through the inner layer 9 can form a closed magnetic circuit by the outer layer 10. Therefore, if the motor configured as described above is used for the rotating drum of the VTR, it is possible to prevent the influence on the magnetic tape, the magnetic head or other parts.

Furthermore, since the magnetic saturation of the inner layer 9 is very small, the output reduction of the motor is extremely small, and the iron loss reducing effect can be sufficiently exerted.

The thickness of the outer layer 10 may be thin because it is made of a structural steel plate having a high saturation magnetic flux density. Therefore, the thickness of the entire stator yoke 7 is almost the same as that of the conventional SS material or SPCC material, and the iron loss of the motor can be reduced to reduce the drive current of the motor.

In the above embodiment, the rotor magnet 3 is 8
Although the brushless motor having the structure in which the poles and the stator coils 4 are composed of three-phase six-coil has been shown, the number of poles of the rotor magnet 3 and the number of phases or coils of the stator coil 4 are limited as long as the principle of the configuration of the brushless motor is followed. It may be any number.

Next, another embodiment of the present invention is shown in FIG. In this embodiment, an axial gap type DC motor with a brush is shown.

In FIG. 6, 1 is a rotating shaft, 2 is a rotor yoke,
The soft magnetic material is formed in a flat plate shape and is configured to rotate integrally with the rotating shaft 1. Reference numeral 11 denotes a rotor coil, which is fixed on the rotor yoke 2. 12 is a commutator, which is connected to the terminal of the rotor coil 11,
It is rotating together with the rotating shaft 1. Reference numeral 13 denotes a field magnet, which is multi-polarized evenly in the circumferential direction and faces each other in parallel with the axial end surface of the rotor coil 11. Reference numeral 7 denotes a stator yoke, which is made of a soft magnetic material and fixes the stator magnet 13. Reference numeral 14 denotes a brush, which has a function of coming into contact with the rotating commutator 12 to supply power to the rotor coil 11, and a brush mounting portion 15
It is attached to the stator case 16 via.

In the brushed DC motor configured as described above, the rotor yoke 2 has an inner layer 9 formed of an electromagnetic steel plate such as a silicon steel plate on the surface facing the stator magnet 13 and an SS layer or SPCC material on the opposite side. The outer layer 10 formed of the structural steel plate is magnetically insulated and formed in close contact with each other. Therefore, the closed magnetic circuit is
A space is provided between the stator magnet 13 and the rotor yoke 2 to form the stator magnet 13 and the rotor yoke 2. That is, the iron loss reducing effect can be obtained while keeping the thickness of the rotor yoke 2 thin, and the axial height or thickness of the motor itself is substantially the same as in the prior art, as in the above-described embodiment. It is possible to reduce the drive current of the motor while maintaining it. Moreover, even if it is used for the rotary drum of a household VTR, there is no magnetic effect on other components other than the motor.

[Advantages of the Invention] As described above, according to the present invention, in the axial air gap type motor, the second yoke provided in the armature coil is provided with an inner layer made of an electromagnetic steel plate and always forming a closed magnetic path, and a structural element. A second layer provided on the armature coil by forming a two-layer structure magnetically insulated from the outer layer formed of a steel plate and forming a closed magnetic circuit only when magnetic saturation of the inner layer occurs.
The iron loss that occurs in the yoke member of can be reduced as much as possible,
The drive current of the motor can be reduced. At the same time, by providing the outer layer, magnetic flux leakage from the second yoke can be effectively prevented when magnetic saturation occurs exceptionally in the inner layer.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a conventional axial gap type motor,
2 is a plan view showing the rotor of FIG. 1, FIG. 3 is a plan view showing the stator of FIG. 1, and FIG. 4 is a side sectional view showing an embodiment of an axial gap type motor according to the present invention. , FIG. 5 is the fourth
FIG. 6 is an enlarged view of an essential part for explaining the facing state of the rotor and the stator yoke in the figure, and FIG. 6 is a side sectional view showing another embodiment of the axial air gap type motor according to the present invention. In the figure, 2 is a rotor yoke, 7 is a stator yoke, 9 is an inner layer, and 10 is an outer layer.

Claims (1)

[Claims] 1. A magnetomotive force source and an armature coil are arranged such that their respective axial end faces face each other to form an axial gap, and said magnetomotive force source and said armature coil have said opposing end faces. In a motor in which first and second yokes are respectively provided on the end faces opposite in the axial direction, and a closed magnetic circuit is formed as a rotor and a stator, the armature coil is provided as either the rotor or the stator. In addition, the second yoke is located on the armature coil side, and is made of an electromagnetic steel plate and always forms a closed magnetic path. An inner layer is formed on the opposite side of the inner layer from the armature coil, and is made of a structural steel plate. A two-layer structure comprising an inner layer magnetically insulated from the inner layer and closely contacting the inner layer, and an outer layer forming a closed magnetic circuit only when magnetic saturation of the inner layer occurs. A motor characterized by being used.