Flat core-less direct-current motor - Patent Review 5498919

I claim:

1. A 3 phase flat brushless and core-less direct-current motor of axial gap type comprising a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is even number and an armature current control device for controlling armature current by detecting the positions of field magnet poles of the magnetic rotor characterized in that

plural fan-shaped and flatly-wound armature coils in which an included angle are constituted by each of their coil portions effective for producing a torque is nearly equal to that of the poles of magnetic rotor,

a flat annular magnet body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally,

an annular stationary armature constituted by the (3/2) n armature coils arranged at equal pitches with their outside surfaces made radial and so that they do not lap over each other, the annular magnetic body to which the armature coils are fixed, wirings among the armature coils with their terminals lead out and plastic in which they are buried,

a means for connecting a wiring to the said annular stationary armature after fixing it on a printed board of a steel base with wirings, and

a shaft which is supported by bearings set in a central portion of a stationary rotor so that it rotates freely and fixed to the magnetic rotor with its pole surface facing the armature coils with a small gap therebetween, first, second and third Hall elements set on contact surfaces and near circumferences of the armature coils arranged in contact with the stationary armature and a pole position detection device for obtaining the first position detection signals of rectangular wave of 180 degrees in electrical angle in breadth at intervals of equal angle followed by second position detection signals of the same wave with a phase delay of 120 degrees in electrical angle from first ones at intervals of equal angle in turn and next by third position detection signals of the same wave with a phase delay of 120 degrees in electrical angle from second ones at intervals of equal angle in turn through the detection of the positions of the magnetic rotor poles by the first, the second and the third Hall elements.

2. A 3 phase flat brushless and core-less direct-current motor of axial gap type comprising a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is an even number and an armature current control device for controlling armature current by detecting positions of field magnet poles of the magnetic rotor characterized in that

plural fan-shaped and flatly-wound armature coils in which an included angle constituted by each of their coil portions effective for producing a torque is nearly equal to that of the poles of the magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally,

an annular stationary armature constituted by (3/2)n armature coils arranged at equal pitches with outside surfaces made radial and so that they do not lap over each other, the annular magnetic body to which the armature coils are fixed, wirings among the armature coils with their terminals lead out and plastic in which they are buried, and

a shaft supported by bearings set in central portions of the stationary armature so that it rotates freely and fixed to the magnetic rotor with its pole surface facing the armature coils with a small gap therebetween, first, second and third Hall elements set on the contact surfaces and near the circumferences of the armature coils arranged in contact with the stationary armature and a pole position detection device for obtaining the first position detection signals of rectangular wave of 180 degrees in electrical angle in breadth at intervals of equal angle followed by second position detection signals of the same wave with a phase delay of 120 degrees in electrical angle from first ones at intervals of equal angle in turn and next by third position detection signals of the same wave with a phase delay of 120 degrees in electrical from second ones at intervals of equal angle in turn through the detection of the positions of the magnetic rotor poles by the first, the second and the third Hall elements.

3. A 3 phase flat brushless and core-less direct-current motor of axial gap type comprising a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is an even number and an armature current control device for controlling armature current by detecting the positions of field magnet poles of the magnetic rotor characterized in that

plural fan-shaped and flatly-wound armature coils in which an included angle constituted by each of their coil portions effective for producing a torque is nearly equal to that of the poles of the magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally with a plastic ring of equal thickness set inside it,

an annular stationary armature constituted by (3/2)n armature coils arranged at equal pitches with outside surfaces made radial and so that they do not lap over each other, the annular magnetic body to which the armature coils is fixed, wirings among the armature coils with their terminals lead out and plastic in which they are buried,

a position detection device comprising 3 magnetism-electricity conversion elements set face to face with the poles of the field magnet between two adjacent armature coils near a circumference of the stationary armature,

a rotor speed detection device set near the circumference of the stationary armature for obtaining electric signals in proportion to rotor speed,

a means for inserting a short downward columnar projection of the stationary armature into a central bore of a printed board and fixing the armature to the printed board,

a means for giving wirings among the wiring of the printed board, the terminals of the armature coils, the terminals of 3 magnetism-electricity conversion elements used for detecting positions and those of the rotor speed detection device, and

a shaft which is supported by bearings set in a central portion of the stationary armature so that it rotates freely and fixed to the magnetic rotor so that its pole surface optionally faces a armature coil surface with a small gap therebetween.

4. A 3 phase flat brushless and core-less direct-current motor of axial gap type comprising a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is an even number and an armature current control device for controlling armature current by detecting positions of field magnet poles of the said magnetic rotor characterized in that

plural fan-shaped and flat armature coils of alignment winding in which an included angle constituted by each of the coil portions effective for producing a torque is equal to that of the poles of the magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally inside which a plastic ring of equal thickness is set,

a plane stationary armature constituted by (3/2)n armature coils arranged at equal pitches with the outside surfaces made radial and so that they do not lap over each other, the annular magnetic body to which the armature coils are fixed, a first printed board of an annular thin plastic base fixed concentrically on an opposite side of the annular magnetic body and plastic in which the above three elements are buried,

a position detection device comprising 3 magnetism-electricity conversion elements set at proper positions on the first printed board of the stationary armature face to face with poles of the said field magnet,

a rotor speed detection device for obtaining electric signals of a frequency in proportion to rotor speed through induction output of a zigzag wiring arranged near the circumference of the first printed board so as to form a circle at the same pitches with those of the N and S poles which face the first printed board and are magnetized at alternate equal pitches divided into pieces along the circumference of the field magnet,

a means for inserting a short downward columnar projection of the stationary armature into a central portion of a second printed board and fixing the former to the latter,

a means for giving necessary wirings between the output and input terminals of the [said]armature coils, the 3 magnetism-electricity conversion elements and the zigzag wiring of the first printed board and the terminals of the second printed board, and

a shaft supported by bearings set in a central bore of the stationary armature so that it rotates freely and fixed to the magnetic rotor whose pole surface faces an armature coil surfaces with a small gap therebetween.

5. A 3 phase flat brushless and core-less direct-current motor of axial gap type comprising a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is an even number and an armature current control device for controlling armature current by detecting positions of field magnet poles of the said magnetic rotor characterized in that

plane fan-shaped and flat armature coils of alignment winding in which an included angle constituted by each of coil portions effective for producing a torque is equal to that of the poles of the said magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally inside which a plastic ring of equal thickness is set,

an annular stationary armature constituted by (3/2)n armature coils arranged at equal pitches with the outside surfaces made radial and so that they do not lap over each other, the annular magnetic body to which the armature coils are fixed, a first printed board of an annular thin plastic base fixed concentrically to the annular magnetic body and plastic in which the above three elements are buried,

a position detection device comprising 3 magnetism-electricity conversion elements which are set at proper positions of the stationary armature face to face with poles of the field magnet,

a rotor speed detection device set near the circumference of the stationary armature and the field magnet,

a means for inserting a short downward columnar projection of the stationary armature into a central bore of a second printed board,

a means for giving necessary wirings between the output and input terminals of the armature coils, the 3 magnetism-electricity conversion elements and the first printed board of the rotor speed detection device and the necessary terminals of the second printed board, and

a shaft supported by bearings set in a central portion of the stationary armature so that it rotates freely and fixed to the said magnetic rotor whose pole surface faces an armature coil surface with a small gap therebetween.

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TECHNICAL FIELD

This invention relates to a core-less direct-current motor which is used as a power source for every industrial machine or apparatus necessitating a flat shape, particularly also necessitating a high speed and a high torque.

BACKGROUND TECHNOLOGY

We disclosed our inventions on a flat core-less direct-current motor through the Patent Gazettes of Tokukosho No. 58-26263 and Tokukosho No. 58-26264.

A strong point of the core-less direct-current motor is that it can be shaped in a flat shape, therefore it can be used in a big industrial field as mentioned above and said that it is a very useful motor.

On the other hand, its output torque is small and approximately a third of that of a cored direct-current motor of the same volume. In order to increase its output torque, the number of turns of its coil may be increased on condition that its coil material is thinner, but such a coil lowers its power efficiency. It is a problem. The space for the winding of the core-less direct-current motor must be small because to enlarge the space makes the axial length of a gap between the magnetic poles and the armature longer resulting in reducing magnetic field and decreasing the output torque.

A flat brushless and core-less direct-current motor is well-known itself, and used as a power source for a flexible disk, a hard disk and the others, but there are the following problems to be solved.

The first problem is that a mild steel plate or a silicon steel plate whose iron loss and copper loss are high are used as a magnetic body to be attached to the rear surfaces of the fan-shaped armature coils of the motor so that the magnetic flux from the poles of magnetic rotor of the motor which penetrates the said armature coils may close its magnetic path at the said magnetic body.

Consequently the maximum allowable speed of such a motor is approximately 600 rpm and its power efficiency is low resulting in narrowing its applicable field.

Because of its high speed, its output torque is reduced without the magnetic body, so it is used only in the limited special field.

The second one is that its power efficiency is low by the above-mentioned reason.

The third one is that its structure is apt to be unsuitable for a mass production because of its flatness.

Thus the purpose of this invention is to supply people with a core-less direct-current motor of high output torque, high speed, high power efficiency which is suitable for a mass production.

DISCLOSURE OF THE INVENTION

A 3 phase flat core-less direct-current motor comprises an annular stationary field magnet, a disk-shaped rotary armature, a commutator for controlling the armature current and commutator brushes characterized by comprising the said disk-shaped rotary armature constituted by fan-shaped, alignment-wound and flat armature coils in which an included angle constituted by each of coil portions effective for producing a torque exceeds 180 degrees in electrical angle and plastic in which the said armature coils are buried, the said armature coils being six in all with their outside surfaces made radial so that each adjacent two of them may be in contact with each other and arranged at equal pitches within a same plane.

A 3 phase flat core-less direct-current motor comprises disk-shaped stationary armature, a magnetic rotor including an annular field magnet and an armature current control device for controlling the said armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by comprising the said stationary armature constituted by fan-shaped, alignment-wound and flat armature coils in which an included angle constituted by each of coil portions effective for producing a torque exceeds 180 degrees in electrical angle and plastic in which the said armature coils are buried, the said armature coils being six in all with their outside surfaces made radial so that each adjacent two of them may be in contact with each other and with a disk-shaped magnetic body of a little iron loss functioning as a magnetic path on their one side surfaces.

A 3 phase flat core-less direct-current motor. comprises an annular field magnet including 2 N poles and 2 S poles, a disk-shaped rotary armature, a commutator for controlling the armature current and commutator brushes characterized by comprising the said disk-shaped rotary armature constituted by fan-shaped, alignment-wound and flat armature coils in which an included angle constituted by each of coil portions effective for producing a torque exceeds 180 degrees in electrical angle and plastic in which the said armature coils are buried, the said armature coils being three in all with their outside surfaces made radial so that each adjacent two of them may be in contact with each other and arranged at equal pitches within a plane.

A 3 phase flat core-less direct-current motor comprises a disk-shaped stationary armature, a magnetic rotor including an annular field magnet of 2 N poles and 2 S poles and an armature current control device for controlling the said armature current by detecting the field magnet pole positions of the said magnetic rotor characterized by comprising the said disk-shaped stationary armature constituted by fan-shaped, alignment-wound and flat armature coils in which an included angle constituted by each of the coil portions effective for producing a torque exceeds 180 degrees in electrical angle and plastic in which the said armature coils are buried, the said armature coils being three in all with their outside surfaces made radial so that each adjacent two of them may be in contact with each other and with a disk-shaped magnetic body of a little iron loss functioning as a magnetic path on their one side surfaces.

A plural phase flat brushless and core-less direct-current motor comprises a plane stationary armature, a magnetic rotor including an annular field magnet of 2n N and S poles where n is a positive integer and an armature current control device for controlling the armature current by detecting the field magnet poles of the said magnetic rotor characterized by comprising the said plane stationary armature constituted by a fan-shaped winding type flat armature coils in which an included angle constituted by each of the coil portions effective for producing a torque is equal to that constituted by the poles of the said magnetic rotor and plastic in which the said armature coils are buried, the said armature coils whose volumes are large being arranged at equal pitches within a plane with their outside surfaces made radial and so that they may not lap over each other, and the rear surfaces of the said armature coils being coated with an annular magnetic body made of silicon steel rolled thinly and coiled spirally so that the magnetic flux of the said magnetic rotor which faces the front surfaces of the said armature coils may close its magnetic path at it after penetrating the said armature coils

A plural phase flat brushless and core-less direct-current motor comprises a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is 1 to 4 and an armature current control device for controlling the said armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by consisting of:

a cup-shaped first casing,

a flat-bottomed second casing made of mild steel whose flange is fixed to that of the said first casing,

a shaft supported by bearings set in the central bores of both the said casings so that it may rotate freely,

a ring-shaped said magnetic rotor fixed by adhesive to a mild steel disk mounted on the said shaft,

plural flat fan-shaped winding type armature coils in which an included angle constituted by each of the coil portions effective for producing a torque is equal to that of the poles of the said magnetic rotor,

a stationary armature fixed to the said second casing and constituted by the said armature coils arranged at equal pitches within a plane with their outside surfaces made radial and so that they may not lap over each other and an annular magnetic body made of silicon steel rolled thinly and coiled spirally which is fixed by adhesive to one side surfaces of the said armature coils so that the magnetic flux of the said magnetic rotor may close its magnetic path, both the said armature coils and the annular magnetic body being buried in plastic charged into the space necessary for forming the said stationary armature,

a mild steel disk whose central portion is fixed to the shaft on the outside of the said second casing,

an annular magnet fixed to the said mild steel disk, and

a means for canceling a magnetic absorption force between the said magnetic rotor and the said annular magnetic body by a reverse magnetic absorption force between the said annular magnet which is magnetized in N and S poles distributed axially and the said second casing whose outside surface faces the said annular magnet with a small gap therebetween.

A 3 phase flat brushless and core-less direct-current motor of axial gap type comprises a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is even number and an armature current control device for controlling the said armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by consisting of:

plural fan-shaped and flatly-wound armature coils in which an included angle constituted by each of their coil portions effective for producing a torque is nearly equal to that of the poles of the said magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally,

an annular stationary armature constituted by (3/2)n said armature coils arranged at equal pitches with the outside surfaces made radial and so that they may not lap over each other, the said annular magnetic body to which the said armature coils are fixed, wirings among the said armature coils with their terminals lead out and plastic in which they are buried,

a means for giving a wiring to the said annular stationary armature after fixing it on a printed board of a steel base with wirings, and

a shaft which is supported by bearings set in the central portion of the said stationary rotor so that it may rotate freely and fixed to the said magnetic rotor with its pole surface facing the said armature coils with a small gap therebetween.

A 3 phase flat brushless and core-less direct-current motor of axial gap type comprises a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is even number and an armature current control device for controlling the said armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by consisting of:

plural fan-shaped and flatly-wound armature coils in which an included angle constituted by each of their coil portions effective for producing a torque is nearly equal to that of the poles of the said magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally,

an annular stationary armature constituted by (3/2)n said armature coils arranged at equal pitches with the outside surfaces made radial and so that they may not lap over each other, the said annular magnetic body to which the said armature coils are fixed, wirings among the said armature coils with their terminals lead out and plastic in which they are buried, and

a shaft supported by bearings set in the central portions of the said stationary armature so that it may rotate freely and fixed to the said magnetic rotor with its pole surface facing the armature coils with a small gap therebetween.

A 3 phase flat brushless and core-less direct-current motor of axial gap type comprises a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is even number and an armature current control device for controlling the said armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by consisting of:

plural fan-shaped and flatly-wound armature coils in which an included angles constituted by each of their coil portions effective for producing a torque is nearly equal to that of the poles of the said magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally with a plastic ring of equal thickness set inside it,

an annular stationary armature constituted by (3/2)n said armature coils arranged at equal pitches with the outside surfaces made radial and so that they may not lap over each other, the said annular magnetic body to which the said armature coils is fixed, wirings among the said armature coils with their terminals lead out and plastic in which they are buried,

a position detection device comprising 3 magnetism-electricity conversion elements set face to face with the poles of the said field magnet between two adjacent armature coils near the circumference of the said stationary armature,

a rotor speed detection device set near the circumference of the said stationary armature for obtaining electric signals in proportion to the rotor speed,

a means for inserting a short downward columnar projection of the said stationary armature into the central bore of a printed board and fixing the former to the latter,

a means for giving wirings among the wiring of the said printed board, the terminals of the said armature coils, the terminals of the said 3 magnetism-electricity conversion elements used for detecting positions and those of the said rotor speed detection device, and

a shaft which is supported by bearings set in the central portion of the said stationary armature so that it may rotate freely and fixed to the said magnetic rotor so that its pole surface may face the said armature coil surface with a small gap therebetween.

A 3 phase flat brushless and core-less direct-current motor of axial gap type comprises a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is even number and an armature current control device for controlling the armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by consisting of:

plural fan-shaped and flat armature coils of alignment winding in which an included angle constituted by each of the coil portions effective for producing a torque is equal to that of the poles of the said magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less in thickness rolled thinly and coiled spirally inside which a plastic ring of equal thickness is set,

a plane stationary armature constituted by (3/2)n said armature coils arranged at equal pitches with the outside surfaces made radial and so that they may not lap over each other, the said annular magnetic body to which the said armature coils are fixed, the first printed board of an annular thin plastic base fixed concentrically on the opposite side of the said annular magnetic body and plastic in which the above three elements are buried,

a position detection device comprising 3 magnetism-electricity conversion elements which are set at proper positions on the said first printed board of the said stationary armature face to face with the poles of the said field magnet,

a rotor speed detection device for obtaining electric signals of a frequency in proportion to the rotor speed through the induction output of a zigzag wiring arranged near the circumference of the said first printed board so as to form a circle at the same pitches with those of the said N and S poles which face the said first printed board and are magnetized at alternate equal pitches divided into pieces along the circumference of the said field magnet,

a means for inserting a short downward columnar projection of the said stationary armature into the central portion of a second printed board and fixing the former to the latter,

a means for giving necessary wirings between the output and input terminals of the said armature coils, the said 3 magnetism-electricity conversion elements and the said zigzag wiring of the said first printed board and the terminals of the said second printed board, and

a shaft supported by bearings set in the central bore of the said stationary armature so that it may rotate freely and fixed to the said magnetic rotor whose pole surface faces the armature coil surface with a small gap therebetween.

A 3 phase flat brushless and core-less direct-current motor of axial gap type comprises a plane stationary armature, a magnetic rotor including an annular field magnet with 2n N and S poles where n is even number and an armature current control device for controlling the armature current by detecting the positions of the field magnet poles of the said magnetic rotor characterized by consisting of:

a plane fan-shaped and flat armature coils of alignment winding in which an included angle constituted by each of the coil portions effective for producing a torque is equal to that of the poles of the said magnetic rotor,

a flat annular magnetic body made of silicon steel of about 0.1 mm or less rolled thinly and coiled spirally inside which a plastic ring of equal thickness is set,

an annular stationary armature constituted by (3/2)n said armature coils arranged at equal pitches with the outside surfaces made radial and so that they may not lap over each other, the said annular magnetic body to which the said armature coils are fixed, the first printed board of an annular thin plastic base fixed concentrically to the said annular magnetic body and plastic in which the above three elements are buried,

a position detection device comprising 3 magnetism-electricity conversion elements which are set at the proper positions of the said stationary armature face to face with the poles of the said field magnet,

a rotor speed detection device set near the circumferences of the said stationary armature and the said field magnet,

a means for inserting the short downward columnar projection of the said stationary armature into the central bore of the second printed board,

a means for giving necessary wirings between the output and input terminals of the said armature coils, the said 3 magnetism-electricity conversion elements and the said first printed board of the said rotor speed detection device and the necessary terminals of the said second printed board, and

a shaft supported by bearings set in the central portion of the said stationary armature so that it may rotate freely and fixed to the said magnetic rotor whose pole surface faces the said armature coil surface with a small gap therebetween.

The included angle constituted by each of the coil portions of the fan-shaped armature coils of a conventional core-less direct-current motor effective for producing a torque is 180 degrees in electrical angle as shown in broken lines B and C in FIG. 3, so the coil breadth is small as shown in a broken line 2c-3 in FIG. 3.

According to this invention, the coil is about two times wider than the conventional one as shown in a coil 2c in FIG. 3.

The conventional coil breadth is shown in F.

On the other hand, the coil breadth related to this invention is shown in E.

According to this invention, the space which the coil occupies is about two times larger than the conventional one.

Therefore the output torque related to this invention becomes about two times higher than the conventional one keeping a high power efficiency. It is an action of this invention.

In this invention, the winding type of the coils is alignment winding and the outside portions of each adjacent two of 6 coils are kept in contact with each other as shown in FIG. 3.

Therefore plastic can be charged easily into the space necessary for forming a disk-shaped armature by an injection machine.

It is a strong point of this invention.

The included angle constituted by each of the coil portions effective for producing a torque may as well exceed 180 degrees.

It is (180+60) degrees in electrical angle in this working example.

Therefore the outside surface of the conductive body constituting a coil tilts by about 10 degrees in mechanical angle from a radial broken line B or C.

As a result, the torque it produces is reduced a little, but it is no problem because it is negligible.

A magnetic body is attached to the rear surfaces of the armature coils as a means for closing the passage of the magnetic flux from the poles of a magnetic rotor.

It is made by a process in which a silicon steel plate is thinned so as to be about 50 microns in thickness followed by being coiled spirally by rolls.

Adhesive agent is coated on its surface and stiffened thereafter.

Next, it is cut into plural rings of a few millimeters in length.

Thus a magnetic ring is completed.

Such a magnetic ring is attached to the rear surfaces of the armature coils to make a magnetic path and plastic is charged into a metal mold including them to form a stationary armature with them buried in it.

Accordingly its iron loss is lowered remarkably while its power efficiency and speed are kept high.

Thus the first problem is resolved.

A casing to which the stationary armature is fixed is made of mild steel.

The central portion of a mild steel disk is fixed to a shaft and the magnetic ring is attached to it.

The magnetic ring surface which constitutes a magnetic path faces the outside surface of the casing with a small gap therebetween.

The magnetic ring is magnetized in N pole on one side and in S pole on the other.

As clarified from the constitution mentioned above, a magnetic absorption force produced between the magnetic rotor and the magnetic body acts opposite to the other magnetic absorption force produced between the casing and the magnetic ring resulting in the reduction of the axial load of a bearing of the shaft.

Thus the second problem can be solved.

A means for making a magnetic ring by cutting a silicon steel plate coiled spirally using a cutter is shown in FIG. 23 and FIG. 24 which are explained in detail later.

It enables a mass production of thin magnetic rings.

The assembly of the magnetic ring and the armature coils and plastic charged into a metal mold including the assembly by a plastic injection machine followed by the removal of the metal mold constitute a flat stationary armature.

Thus a flat motor suitable for a mass production is realized.

The stationary armature is shaped in a disk-like body in which the armature coils and the magnetic ring forming a passage of the magnetic flux are buried through a plastic injection process.

The first printed board is fixed to the upper surface or the rear surface of the armature coils if necessary before plastic is injected.

The second printed board is also fixed to the lower surface of the stationary armature thereat.

The necessary terminals of the second printed board are connected with the input and the output terminals of the armature coil of the first printed board and the other elements.

Thus the stationary armature is structured.

Bearings for the magnetic rotor are set in the stationary armature.

Such a structure enables flattening and a mass production and the third problem can be solved.

As described above, the output torque of a flat core-less direct-current motor related to this invention is two or more times higher than the conventional one though the volume of the former