JP2018057052A - DC motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor that has an elongated brush life by securing a sufficient brush length while reducing the axial length of the motor.SOLUTION: Provided is a DC motor in which an axial center position of an armature core does not coincide with that of a field magnet and which contains a brush device at an inner diameter side of the field magnet. The DC motor is provided with a tapered portion of which polarizability gradually decreases towards an axial end on an inter peripheral surface of the field magnet not opposing an outer peripheral surface of the armature core, or a step portion structured to form a gap between a yoke inner peripheral surface and an outer peripheral surface of the field magnet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a direct current motor, and more particularly to a direct current motor used for a motor for driving automobile auxiliary equipment.

  Since a direct current motor can obtain a high output relatively easily, for example, it is often used as a motor for driving an automobile auxiliary machine.

  In recent years, in order to improve the low fuel consumption rate of automobiles, automobile auxiliary machines represented by hydraulic pumps have been electrified, and the number of DC motors mounted per vehicle is increasing. The mounting space of the automobile is limited, and considering the mounting property in the engine room, it is required to shorten the axial dimension of the motor.

  Patent Documents 1 and 2 are listed as prior art. In Patent Document 1, an armature is fixed to a shaft rotatably supported by two bearings so as to be integrally rotatable, the armature is a core, a resin molded portion that supports the core so as to be integrally rotatable, and a resin. An armature coil wound around the core in a state in which insulation with the core is ensured by the molded part, provided with a recess in the resin molded part, and disposed on the side of the bearing close to the brush The bearing and the brush and commutator are arranged in the recess so as to be arranged within the axial length of the armature, the positioning part is recessed in the resin molded part, and the armature coil is arranged in the positioning part The length of the resin molded portion in the axial direction of the armature is the same as the length of the core armature in the axial direction. Thus, the size of the motor in the axial direction can be reduced as compared with the conventional configuration.

  In Patent Document 2, the second bearing is disposed on the inner peripheral side of the core bottom passage, and is disposed between the longitudinal ends of the output shaft of the winding in the longitudinal direction of the output shaft. A through hole through which the shaft passes is formed, and the through hole is formed so as to surround the first bearing. A part of the first bearing is exposed from the motor case, and the thickness of the through hole in the longitudinal direction of the output shaft is the first. The motor shaft direction is shortened by forming it thinner than the height of one bearing.

Japanese Patent No. 4518187 Japanese Patent No. 4557754

  The problem to be solved by the present invention is to extend the brush life by ensuring a sufficient brush length while shortening the axial direction of the motor. Another problem is to reduce the thrust force acting on the bearing by reducing the magnetic attractive force acting on the armature core, thereby reducing unnecessary frictional force during rotation. It is another object of the present invention to provide a high-performance DC motor that stabilizes commutation by equalizing the magnetic flux density of the gap.

In order to solve the problems, a DC motor according to the present invention feeds power while slidingly contacting a yoke having a field magnet, a rotary armature having an armature coil, a commutator, and an armature core, and the commutator. The axial length of the field magnet is longer than the axial length of the armature core, and the axial center position of the armature core and the axial center position of the field magnet. Are inconsistent in the axial direction, the brush is disposed on the inner diameter side of the field magnet, and the field magnet that does not face the outer peripheral surface of the armature core is provided with a magnetomotive force reducing means.

  The direct current motor of the present invention stabilizes the rectifying action by ensuring a sufficient brush length and equalizing the magnetic flux density of the gap while achieving improvement in motor characteristics and shortening in the axial direction. Brush life can be extended. Further, by reducing the magnetic attractive force (thrust force) acting on the armature core, the frictional force during rotation can be reduced, and a small and high-performance motor can be provided.

It is the fragmentary sectional view which looked at the direct-current motor concerning this embodiment from the side. It is an external appearance perspective view of the field magnet 4 concerning this embodiment. It is a related figure of the motor axial direction position of the DC motor concerning this embodiment, and the magnetic flux density of a gap. It is sectional drawing of the DC motor concerning other embodiment. It is a perspective view of the field magnet of the direct-current motor concerning other embodiments. It is sectional drawing seen from the side surface of the conventional DC motor. It is a perspective view of the field magnet of the conventional DC motor. It is a related figure of the motor axial direction position of the conventional DC motor and the magnetic flux density of a gap.

  Embodiments of a DC motor according to the present invention will be described below.

  FIG. 1 is a partial cross-sectional view of a DC motor according to the present embodiment as viewed from the side. A portion surrounded by a dotted square A is a cross-sectional view.

  The DC motor 1 has a yoke 3 and a field magnet 4 disposed on the inner peripheral wall of the yoke 3. The armature 30 is disposed on the inner diameter side of the field magnet 4 and is opposed to the field magnet 4 via the gap 15.

  The shaft 10 passes through the central portion of the armature 30 and is fixed to the armature 30. The output shaft side bearing 6 a is provided on one side of the end bracket 20 and the shaft 10 in the axial direction. The non-output shaft side bearing 6 b is supported by the yoke 3 and supports one side of the shaft 10 in the axial direction.

  The commutator 7 and the armature core 2 are arranged in the axial direction of the shaft 10. The armature coil 5 is wound around a slot (not shown) of the armature core 2.

  The armature coil 5 is connected to a commutator piece 11 constituting the commutator 7. When a voltage is applied to the DC motor 1, a current flows through the brush 8, energized to the armature 30, and power is supplied through the other brush 8 (not shown).

  In the transfer of current by mechanical sliding contact to the commutator 7, the brush 8 is urged to the commutator 7 by the brush pressurizing spring 9 so that stable power feeding can be performed even during rotation. A current accompanying the rectification action flows through the armature coil 5, and a continuous rotational torque is generated by the interaction between the magnetic field generated by the field magnet 4 and the magnetic field generated by the armature 30, and the machine starts from the output shaft end of the shaft 10. I am getting output.

  The armature 30 is configured to be accommodated within the axial length of the field magnet 4. Further, a part of each of the brush device including the brush 8 and the brush pressurizing spring 9 and the commutator 7 is configured to be accommodated within the axial length of the field magnet 4. Note that the entire brush device including the brush 8 and the brush pressing spring 9 and the commutator 7 may be accommodated within the axial length of the field magnet 4.

  At the position of the armature core 2 in the axial direction, the central part of the armature core 2 in the axial direction is disposed at a position that is biased toward the side opposite to the output shaft side bearing 6b with respect to the central part of the field magnet 4 in the axial direction. Is done. In the other space of the field magnet 4 where the armature core 2 is not disposed, a brush device including a brush 8 and a brush pressing spring 9 is disposed. Thus, the brush device including the armature 30, the brush 8, and the brush pressing spring 9 is configured to be included in the field magnet 4 with respect to the motor axial direction.

  The field magnet 4 is provided with a taper portion 12 having a decreasing rate from the end on the output shaft side of the armature core 2 toward the output shaft. Thus, the length of the brush 8 can be set longer by increasing the outer diameter of the brush device within a range that does not interfere with the inner peripheral surface of the tapered portion 12 of the field magnet 4.

  FIG. 2 is an external perspective view of the field magnet 4 according to the present embodiment.

  The outer peripheral surface of the field magnet 4 is arc-shaped along the inner peripheral surface of the cylindrical yoke 3, and the field magnet 4 is fixed to the yoke 3 with an adhesive.

  FIG. 3 is a diagram showing the relationship between the position in the motor axial direction and the magnetic flux density of the gap according to the present embodiment. The upper diagram of FIG. 3 is a peripheral cross section of the field magnet 4. The lower diagram of FIG. 3 plots the magnetic flux density of the gap 15 along the direction of the arrow added to the upper diagram.

  3 corresponds to the end position of the armature core 2 on the side opposite to the output shaft. Part B corresponds to the end position of the armature core 2 on the output shaft side.

  In the armature core 2, the magnetic flux density of the gap 15 is set high because the magnetic flux focusing action is enhanced. Due to the magnetomotive force of the field magnet 4 that is greatly overhanged with respect to the armature core 2, the magnetic flux density of the gap in the B portion is higher than that in the A portion. This tendency is remarkable in the conventional example (see FIGS. 6, 7 and 8). That is, in the conventional example of FIGS. 6 to 8, 12 is not formed in the field magnet 4, and a plane is formed on the armature core 2 side of the field magnet 4.

  In general, the magnetomotive force of the magnet is proportional to the magnet thickness and the surface area facing the outer peripheral surface of the armature core 2. In other words, by providing the field magnet 4 with a tapered portion that gradually decreases in the polarity on the output shaft side, the field magnet 4 is operated so that the thickness of the field magnet 4 is reduced, so that the magnetomotive force is reduced. Can be adjusted.

  As a result, the steep rise and peak values of the magnetic flux density of the gap 15 at the portion B shown in the relationship diagram (FIG. 8) between the position in the motor axial direction of the conventional DC motor and the magnetic flux density of the gap can be reduced. it can. Since the magnetic flux density of the gap 15 is directly related to the motor torque, it is desired to set it high. However, if it is too high, the rectifying action may be affected, and a lot of rectifying sparks may be generated.

  The steep rise of the magnetic flux density in the gap 15 also affects an increase in magnetic attractive force acting in the axial direction of the armature core 2. This force is a thrust force acting on the armature core 2 in the axial direction, and is applied to the output shaft side bearing 6a and the non-output shaft side bearing 6b via the armature core 2 and the shaft 10, and unnecessary rotational friction force Become.

  For this reason, it is important to reduce the thrust force, that is, the magnetic attractive force, in order to maintain the motor characteristics. In the case of this embodiment, if it is suppressed to 0.5 T or less in order to suppress the rectifying spark, the influence of the magnetic attractive force on the thrust force is small. That is, by reducing the axial length of the motor while stabilizing the rectification and reducing the magnetic attractive force, a small and high-performance DC motor with a long brush life and a small rotational frictional force can be obtained. Can do.

In the present embodiment, the shape of the field magnet 4 is described as an arc shape. In the case where the field magnet 4 is plate-shaped, the thickness of the field magnet 4 that does not face the outer periphery of the armature core 2 is gradually reduced toward the end in the axial direction. The effect of can be obtained.
FIG. 4 shows a cross-sectional view of a DC motor according to another embodiment. FIG. 5 is a perspective view of a field magnet of a DC motor according to another embodiment.

  A step portion 13 is provided on the outer peripheral surface of the field magnet 4 so as to form a gap between the inner peripheral surface of the yoke 3. The gap may be left as air (air) or may be filled with an adhesive to firmly fix the field magnet 4 to the yoke 3. The air gap portion has a magnetic permeability lower than that of a soft magnetic material such as iron. The magnetomotive force can be reduced by setting the thickness of the field magnet 4 to be thin by adding this step portion 13 and the stepped portion 13, and the same effect as when the tapered portion is provided in the field magnet 4 of the above embodiment. Play.

  In addition, this invention is not limited to each above-mentioned embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. . Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

    DESCRIPTION OF SYMBOLS 1 ... DC motor, 2 ... Armature core, 3 ... Yoke, 4 ... Field magnet, 5 ... Armature coil, 6a ... Output shaft side bearing, 6b ... Anti-output shaft side bearing, 7 ... Commutator, 8 ... Brush, DESCRIPTION OF SYMBOLS 9 ... Spring for brush pressurization, 10 ... Shaft, 11 ... Commutator piece, 12 ... Tapered part, 13 ... Step part, 15 ... Gap, 20 ... End bracket, 30 ... Armature

Claims (6)

A yoke having a field magnet;
A rotary armature having an armature coil, a commutator, and an armature core;
A brush that rectifies by supplying power while slidingly contacting the commutator,
The axial length of the field magnet is longer than the axial length of the armature core,
The axial center position of the armature core and the axial center position of the field magnet are inconsistent in the axial direction,
The brush is disposed on the inner diameter side of the field magnet,
The field magnet that does not face the outer peripheral surface of the armature core is a direct current motor provided with a magnetomotive force reducing means. The DC motor according to claim 1,
The magnetomotive force reducing means is a direct current motor in which the thickness of a field magnet that does not face the outer peripheral surface of the armature core is gradually reduced toward the end in the axial direction. The DC motor according to claim 1,
The magnetomotive force reducing means is a direct current motor which is a taper portion formed by gradually reducing the pole rate toward the end portion in the axial direction on the inner peripheral surface of the field magnet not facing the outer peripheral surface of the armature core. The DC motor according to claim 1,
The magnetomotive force reducing means is a direct current motor in which a step portion is provided on the outer peripheral surface of the field magnet that does not face the outer peripheral surface of the armature core so as to form a gap with the inner peripheral surface of the yoke. The DC motor according to claim 2,
The direct current motor in which the starting position of the taper portion coincides with the position of the end portion in the axial direction of the armature core. The DC motor according to claim 3,
The DC motor has a start position of the stepped portion that coincides with an axial end position of the armature core.

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