JPH1189123A - Motor provided with auxiliary magnetic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor casing provided with an efficient auxiliary magnetic circuit which causes neither cost nor weight to be raised. SOLUTION: A cylindrical body 5 having high magnetic permeability is fitted into and fixed onto the inside of a casing 1b. A pair of permanent magnets 6a, 6b are mounted onto the inside of this cylindrical body 5 in such a way as to face each other, and a rotor 7 is arranged between these permanent magnets 6a, 6b. This structure enables an efficient auxiliary magnetic circuit to be formed by converging the leakage of magnetic flux from the permanent magnets 6a, 6b through the cylindrical body 5. Also, it makes it possible to cut the cost of a motor and to reduce its weight by shortening the height of the permanent magnets 6a, 6b by just the thickness of the cylindrical body 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a motor provided with an auxiliary magnetic circuit.

[0002]

2. Description of the Related Art In a DC motor, an N-pole permanent magnet 6a and an S-pole permanent magnet 6b form a magnetic field inside a motor case, and a rotor 7 having a winding wound in the magnetic field is supported. , A DC current is passed through the winding to form an electromagnet,
The rotor 7 is rotated by the electromagnet and the magnetic field, and the direction of the DC current is alternately switched through the brush 8 to continuously rotate the rotor 7. Recently, permanent magnets with a large maximum energy product (B × H) have been developed and used in DC motors. However, all improvements in permanent magnets do not lead to an improvement in DC motor efficiency, but lead to an increase in leakage magnetic flux. Therefore, measures such as increasing the thickness of the motor case 1a constituting the magnetic circuit and suppressing the leakage magnetic flux have been taken. Generally, in order to increase the efficiency of the magnetic circuit, it is necessary to lower the magnetic resistance of the magnetic circuit.
The ratio depending on the gap between the rotor core b and the rotor core 7b and the cross-sectional area of the motor case 1a forming the yoke is large. Since there is a limit on the air gap due to the dimensional accuracy of the rotor core 7b, a method of increasing the plate thickness of the motor case 1a and increasing the cross-sectional area is employed to reduce the magnetic resistance. As shown in FIGS. 5 and 6, the motor case 1a forming the yoke portion is provided with a ring 11 made of a material having good magnetic permeability from the outside.
As shown in FIG. 7, a connecting plate 12 made of a material having good magnetic permeability is inserted into both ends of the permanent magnet 6a and the permanent magnet 6b, thereby forming an auxiliary magnetic circuit, and forming a magnetic field of the yoke. A method of reducing the resistance has been adopted. However, if the thickness of the motor case 1a is increased, or if the ring 11 is attached to the outside of the motor case 1a, the weight of the motor increases correspondingly and the cost increases, and the connecting plate 12 as shown in FIG. It took a lot of time to install, and it was not an effective means.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an efficient auxiliary magnetic circuit, and to provide a motor which does not increase its cost or increase its weight.

[0004]

According to the present invention, a cylinder having a high magnetic permeability is fitted and fixed inside a case, and a pair of permanent magnets are mounted inside the cylinder so as to face each other, and a rotor is placed between the magnets. Distribute.

[0005]

Embodiments of the present invention will be described with reference to the drawings. 1 is a cross-sectional view of a DC motor embodying the present invention, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, FIG. 3 is a cross-sectional view of the motor case, and FIG. FIG. Reference numeral 1 denotes a motor case, which is a cylindrical motor case having a bottom.
a and a motor cover 1 that covers the opening side and is integrally connected
a shaft hole 2 is provided through the center of the motor case 1a and the motor cover 1b, and a bearing press-fitting portion 3 is formed around the shaft hole 2 so as to protrude outward. 4. Press-fit.

A cylindrical body 5 made of a material having high magnetic permeability (for example, permalloy) is fitted into a predetermined position inside the motor case 1a and fixed to the motor case 1a. Inside the cylindrical body 5, opposing arc-shaped permanent magnets 6a and 6
b is bonded to form a stator. A rotor 7 penetrates the laminated rotor core 7b, fixes the rotor shaft 7a, press-fits a commutator 8 from one side of the rotor shaft 7a, winds a rotor winding around the rotor core, and rectifies the terminal. The rotor 7 is formed by connecting to the segments of the child 8. Next, the rotor 7 is inserted into the motor case 1a, and the rotor shaft 7a is rotatably supported between the bearing 4 of the motor case 1a and the bearing 4 of the motor cover 1b so that the motor case 1a and the motor cover 1b are integrated. To join. Further, a pair of brushes 10 that are in contact with the segments of the commutator 8 are arranged to face each other, and lead wires are respectively drawn from the pair of brushes 10 to form a DC commutator motor.

With the above configuration, the stator forms a magnetic field from the N-pole permanent magnet 6a to the rotor core 7b through the gap and to the S-pole permanent magnet 6b through the gap. The magnetic flux from the magnetic field forms a magnetic circuit from the N-pole permanent magnet 6a to the rotor core 7b, the gap, the S-pole permanent magnet 6b, the motor case 1a and the cylindrical body 5, and the N-pole permanent magnet 6a through the gap.

In this magnetic circuit, by providing the cylindrical body 5 in parallel with the motor case 1a, the magnetic resistance can be reduced by the cylindrical body 5 made of a material having good magnetic permeability. Further, by providing the cylindrical body 5 inside the motor case 1a, the magnetic flux concentrates on the cylindrical body 5, and the leakage of the magnetic flux can be prevented by the motor case 1a made of an iron plate, and the efficiency of the magnetic circuit can be increased. Further, even if the motor case 1a is made of a non-ferrous material and the magnetic circuit is not formed, the magnetic circuit can be formed by the cylindrical body 5, and the motor can be reduced in weight. Further, by providing the cylindrical body 5 inside the motor case 1a, the height of the permanent magnets 6a and 6b forming the stator can be reduced by that much, and the cost of the permanent magnets 6a and 6b can be reduced. it can. According to the above effects, the efficiency can be increased by about 10% without changing the shape and the plate thickness of the motor case 1a. Further, the weight can be reduced by about 15% as compared with a case where only the plate thickness of the motor case 1a is increased without providing the auxiliary magnetic circuit.

[0009]

As described above, in the present invention, since the cylindrical body made of a material having high magnetic permeability is fitted and fixed inside the motor case, the leakage of the magnetic flux from the permanent magnet is converged through the cylindrical body, and the efficiency is improved. A good auxiliary magnetic circuit can be formed. In addition, the height of the permanent magnet is reduced by the thickness of the cylindrical body, so that the cost of the motor can be reduced and its weight can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a DC motor embodying the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view of a motor case of the present invention.

FIG. 4 is a sectional view taken along the line AA of FIG. 3;

FIG. 5 is a sectional view of a conventional DC motor.

FIG. 6 is a sectional view taken along the line BB of FIG. 5;

FIG. 7 is a sectional view of another conventional example.

[Explanation of symbols]

 1a Motor case 1b Motor cover 2 Shaft hole 3 Bearing press-fit part 4 Bearing 5 Cylindrical body 6a Permanent magnet 6b Permanent magnet 7 Rotor 7a Rotor shaft 7b Rotor core 8 Commutator 9 Lead wire 10 Brush 11 Ring 12 Connecting plate

Claims (1)

[Claims] 1. An auxiliary magnetic circuit comprising a cylindrical body having a high magnetic permeability fitted and fixed inside a case, a pair of permanent magnets mounted opposite to each other inside the cylindrical body, and a rotor arranged between the permanent magnets. Motor provided.