JPH11289700A - Small motor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To suppress an increase in the permanent magnet length (motor length) to obtain the same torque even when the permanent magnet outer diameter (motor outer diameter) is reduced. SOLUTION: A small motor provided with a stator having a rotating magnetic field forming coil mounted on an inner peripheral surface of a substantially annular housing, a bearing rotatably supporting a rotating shaft, and a permanent magnet type rotor. The rotor including the rotating shaft is integrally formed of a permanent magnet material and magnetized to form a rotor. Alternatively, a rotating shaft is joined to both end surfaces of the cylindrical permanent magnet so as to be coaxial with the permanent magnet, thereby forming a rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor of, for example, a millimachine or less.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a motor having a smaller diameter and a smaller size for the purpose of mounting it on medical equipment such as diagnosis and treatment in a prenatal cavity or industrial equipment such as self-propelled pipe environment confirmation. ing.

[0003] As the motor becomes smaller, the ratio of mechanical loss including bearing sliding loss and brush sliding loss to the internal loss increases. Therefore, a small motor having an outer diameter of 3 mm or less reduces the mechanical loss. The mainstream is a brushless motor which does not require a brush or a commutator, which is advantageous for ensuring a long life. Further, permanent magnet type rotors are often used because the energy efficiency of the motor is increased.

In general, as a motor having a permanent magnet type rotor, as shown in FIG. 4, a rotor in which a rotating shaft 23 is inserted into an inner diameter of a cylindrical permanent magnet 22 and fixed is known. The stator has a housing 1 on which a coil 2 for forming a rotating magnetic field and brackets 6 and 7 on which bearings 4 and 5 are mounted are fixed, and the rotor is rotatably supported by the bearings 4 and 5. I have. 3 is a lead wire for supplying a current to the coil 2. Further, sliding plates 8 and 9 are mounted on the rotating shaft 23, and the play in the thrust direction of the rotor is limited by the sliding plates 8 and 9 and the bearings 4 and 5. The rotor rotates following the rotating magnetic field formed by the coil 2.

As described above, the conventional permanent magnet type rotor is generally manufactured by inserting and fixing a rotating shaft to the inner diameter of a cylindrical permanent magnet.

[0006]

However, in the configuration of the conventional permanent magnet type rotor, the rotating shaft 23 is fixed to the permanent magnet 2.
2, the permanent magnet thickness is reduced by the amount of the rotating shaft penetrated, and the magnetic energy is reduced. Therefore, when trying to secure torque, the permanent magnet length must be increased accordingly. Had. So, in general,
The motor length must be increased.

[0007] There is a limit in reducing the diameter of the rotating shaft in order to ensure mechanical strength, and the permanent magnet thickness decreases as the motor outer diameter and the permanent magnet outer diameter decrease, so the above tendency is further accelerated. This was an obstacle to reducing the diameter and size of the motor.

The present invention relates to a permanent magnet outer diameter (motor outer diameter).
It is intended to suppress the tendency of the permanent magnet length (motor length) to increase with the decrease in the length.

[0009]

According to the present invention, a coil for forming a rotating magnetic field and a bearing for rotatably supporting a rotating shaft are mounted on the inner peripheral surface of a substantially annular housing. In a small motor having a stator and a permanent magnet type rotor, the rotor including a rotating shaft is integrally formed of a permanent magnet material, and the rotor is magnetized to form a rotor.

Alternatively, a rotor is formed by joining a rotating shaft to both end surfaces of a columnar permanent magnet so as to be coaxial with the permanent magnet. It is more preferable that a metal rotary shaft is welded to both end surfaces of the cylindrical sintered magnet so as to be coaxial with the sintered magnet.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the first invention will be described with reference to FIG.
This will be described with reference to FIG. Note that, in FIG. 1, portions denoted by the same reference numerals as those in FIG. 4 are equivalent components having the same functions, and thus description thereof will be omitted. A feature of the present invention is that a rotor including a rotating shaft is integrally formed of a permanent magnet material, and is magnetized to form a rotor 10.
Is formed.

With the rotor structure as described above, since the rotating shaft does not penetrate the permanent magnet, the thickness of the permanent magnet is increased by the amount of the rotating shaft penetrating and the magnetic energy is increased as compared with the related art. Therefore, even if the outer diameter of the permanent magnet (outer diameter of the motor) is reduced, an increase in the length of the permanent magnet (motor length) for obtaining the same torque can be suppressed.

Next, the second and third inventions will be described with reference to FIG.
This will be described with reference to FIG. Note that, in FIG. 2, portions denoted by the same reference numerals as those in FIG. 4 are equivalent components having the same functions, and thus description thereof is omitted.

A feature of the present invention is that a rotating shaft 1 is provided on both end surfaces of a cylindrical permanent magnet 11 so as to be coaxial with the permanent magnet 11.
2 and 13 are joined to form a rotor. Particularly, a rotor having high mechanical strength is formed by forming a cylindrical permanent magnet with a sintered magnet and welding and joining a metal rotating shaft to both end surfaces of the magnet so as to be coaxial with the magnet. Is obtained.

With the above-described rotor structure, since the rotating shaft does not penetrate the permanent magnet, the thickness of the permanent magnet is increased by the amount of the rotating shaft penetrating and the magnetic energy is increased as compared with the related art. Therefore, even if the outer diameter of the permanent magnet (outer diameter of the motor) is reduced, an increase in the length of the permanent magnet (motor length) for obtaining the same torque can be suppressed.

In the present invention, in order to further secure the mechanical strength of the rotor, as shown in FIG. 3A, rotating shaft insertion recesses 17 and 18 are provided on both end surfaces of the columnar permanent magnet 14, and are provided there. In order to form a rotor by inserting and fixing the rotating shafts 15 and 16 and to increase the joining area, as shown in FIG.
May be joined to both end surfaces of the columnar permanent magnet 19 to form a rotor.

[0017]

As described above, according to the present invention, even if the outer diameter of the permanent magnet (outer diameter of the motor) is reduced, an increase in the length of the permanent magnet (motor length) for obtaining the same torque is suppressed. This is effective for reducing the diameter and size of the motor.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a rotor structure of a first invention.

FIG. 2 is an explanatory view of a rotor structure according to the second and third aspects of the invention;

FIG. 3 is an explanatory view of another rotor structure of the second and third inventions.

FIG. 4 is an explanatory view of a conventional rotor structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Coil 3 Lead wire 4,5 Bearing 6,7 Bracket 8,9 Sliding plate 10 Rotor 11,14,19,22 Permanent magnet 12,13,15,16,20,21,23 Rotating shaft 17, 18 Rotation shaft insertion recess

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shohei Kawai 3-8-22 Nitta, Adachi-ku, Tokyo Namiki Seiki Co., Ltd.

Claims (5)

[Claims] 1. A small motor having a stator having a rotating magnetic field forming coil mounted on an inner peripheral surface of a substantially annular housing, a bearing rotatably supporting a rotating shaft, and a permanent magnet type rotor. 3. The small-sized motor according to claim 1, wherein the rotor including the rotating shaft is integrally formed of a permanent magnet material and magnetized to form a rotor. 2. A small motor having a stator having a coil for forming a rotating magnetic field, a bearing for rotatably supporting a rotating shaft mounted on an inner peripheral surface of a substantially annular housing, and a permanent magnet type rotor. , A rotor is formed by joining a rotating shaft to both end surfaces of a cylindrical permanent magnet so as to be coaxial with the permanent magnet, thereby forming a rotor. 3. The rotor according to claim 2, wherein a metal rotary shaft is welded and joined to both end surfaces of the cylindrical sintered magnet so as to be coaxial with the sintered magnet. Small motor. 4. A small-sized motor according to claim 2, wherein a rotating shaft insertion recess is provided on both end surfaces of the columnar permanent magnet, and the rotating shaft is inserted and fixed therein to form a rotor. 5. A rotating shaft provided with a flange at one end,
3. The small motor according to claim 2, wherein the rotor is formed by joining to both end surfaces of the cylindrical permanent magnet.