JP4058095B1 - DC motor - Google Patents

Abstract

[PROBLEMS] To improve the fitting accuracy between a rotor shaft and a bearing by improving the fastening accuracy between the end cap and the case, thereby reducing the sliding noise and vibration of the shaft, and uneven wear of the rotor shaft and the bearing. A small DC motor with significantly improved accuracy, reliability, and durability by eliminating excessive lubrication and reducing additional lubrication to the bearing.
A DC motor according to the present invention is provided with an engagement cap that is provided on the end cap with a locking lid having a diameter larger than the inner diameter of the opening of the case, and that is fitted to the inner wall of the case without a gap. Is provided in the circumferential direction, and a plurality of snap-fit engagement pieces are provided outside the front end of the fitting wall, and a snap-fit engagement hole is provided in the side wall portion on the opening side of the case. The end cap and the case are fastened by snap-fit engagement.
[Selection] Figure 1

Description

  The present invention relates to a direct current motor, and more specifically, an armature, a rotor shaft provided at the center in the radial direction of the armature, two bearings that rotatably support the rotor shaft, and one of the bearings including the armature. The present invention relates to a small DC motor including a case to be disposed and an end cap for closing the opening of the case and the other bearing being disposed.

  There are various sizes of DC motors, and there are various types of structures depending on the application and required characteristics. Recently, coupled with the downsizing of electronic device equipment, there is a great demand for small DC motors. On the other hand, as the performance of these electronic devices increases, the accuracy and reliability required for small DC motors are remarkably high.

  Here, as an example of a conventional small DC motor, there is a DC motor 100 described in Patent Document 1 (FIG. 6). The DC motor 100 includes a case 101 having a permanent magnet 102 fixed to an inner peripheral surface, a rotor 105 having an armature core 103 and a commutator 104, a holder base 107 having a brush 108, and an opening of the case 101. And an end cap 106 to be fitted into the.

  By the way, one of the factors that greatly affects the accuracy and reliability of a small DC motor is a fastening structure between an end cap and a case. In a conventional small DC motor, a caulking structure is used as a method for fastening the end cap and the case. The caulking structure will be described by taking a small DC motor 100 as an example. A bent edge 121 is formed on the periphery of the end cap 106, and the inner diameter of the bent edge 121 is made larger than the outer diameter of the opening of the case 101. The locking claw 122 is formed on a part of the bent edge portion 121 of the end cap 106, and the locking claw 122 corresponds to the outer periphery of the opening of the case 101 and the positioning projection 129. This is a structure in which the concave portion 123 provided at the portion to be bent is locked.

JP-A-7-322551

  However, the caulking structure conventionally used as a fastening structure between the end cap and the case in a small DC motor has a problem that the end cap is displaced in the radial direction with respect to a predetermined design position. May occur. This is due to the fact that radial stress generated when the locking claw is bent acts on the end cap. In order to solve this problem, conventionally, a method of eliminating the influence of the positional deviation by increasing the inner diameter of the bearing supporting the rotor shaft and keeping the assembly position of the rotor shaft within an allowable limit has been adopted. However, when the inner diameter of the bearing is increased, the fitting clearance between the rotor shaft and the bearing is increased, so that mechanical noise such as shaft sliding noise is increased and uneven wear occurs at the contact portion. Furthermore, in order to prevent such noise and uneven wear, additional oil must be frequently added. As a result, secondary problems such as excessive oil causing dust adhesion may occur. . Such a problem acts in a superimposed manner, and has a problem that the durability of the motor is remarkably lowered.

  The present invention has been made in view of the above circumstances, and particularly with respect to a small DC motor, by improving the fastening accuracy between the end cap and the case, the accuracy of the fitting clearance between the rotor shaft and the bearing is improved. Reduces mechanical noise such as shaft sliding noise generated during motor operation and vibration, prevents uneven wear and intrusion of dust on the rotor shaft and bearing, and reduces additional lubrication to reduce noise on the bearing. Thus, it is an object of the present invention to provide a direct current motor that significantly improves accuracy, reliability, and durability by eliminating problems caused by excessive oil amount.

  The present invention solves the above-described problems by the solving means described below.

A DC motor according to the present invention includes an armature, a rotor shaft provided at the center in the radial direction of the armature, two bearings that rotatably support the rotor shaft, and the one armature that includes the armature. In a DC motor comprising a case provided and an end cap that closes the opening of the case and in which the other bearing is disposed, the end cap has an outer diameter larger than the inner diameter of the opening of the case And a fitting wall that fits on the case-side surface without any gap with the inner wall of the case without any gaps, and is provided on all or part of the circumferential direction, and outside the front end of the fitting wall. a plurality of snap-fit engagement piece is provided on the said fitting inner wall of the snap-fit engagement piece is provided on the outside is the case insertion side Formed on a substantially straight wall surface extending from the end portion to the locking lid portion, and provided with a brush installation space inside the fitting wall, and the snap-fit engagement piece is formed on the fitting wall. The case is configured to protrude from the end on the case insertion side toward the outside of the fitting wall from a position close to the locking lid, and the case is formed on the side wall on the opening side. A snap fit engagement hole for engaging a snap fit engagement piece is provided, and the armature is positioned at a predetermined position by fastening the end cap and the case by snap fit engagement. .

Further, the engaging Tomefuta portion is brought into contact with the locking cap abutting surface is a plurality of ribs which strengthen the engagement between the end cap and the case is provided at the case opening portion, said plurality of ribs, said end When the cap and the case are fastened by the snap-fit engagement, the cap and the case are formed to a height that is crushed to generate an elastic force .

  Further, the fitting wall is characterized in that a slit formed in the direction from the front end portion of the fitting wall to the locking lid portion is provided on both sides of the snap-fit engagement piece.

  According to the first aspect of the present invention, the end cap is locked at a predetermined position with respect to the case by the contact of the locking lid portion with the locking lid contact surface of the case, and the movement in the axial direction (movement in the mounting direction). ) Is regulated. Further, when the fitting wall provided on the inner surface of the end cap is fitted with the inner wall of the case without a gap, movement of the end cap in the radial direction is restricted. Further, the snap-fit engagement piece provided on the outer end of the fitting wall is snap-fit engaged with the snap-fit engagement hole of the case, thereby restricting the axial movement (moving in the removal direction) of the end cap. Is done. Thus, the end cap and the case can be fastened without adopting a caulking structure. As a result, it is possible to prevent the end cap from being displaced from a predetermined position.

  According to claim 2, when the end cap is fastened to the case, the end cap is deformed so as to be compressed and crushed by the compression force generated between the locking lid portion and the locking lid contact surface. The ribs that cause the elastic force generate an elastic force to restore the deformation, and the force acts in a direction to separate the locking lid portion and the locking lid contact surface. As a result, it is possible to prevent and eliminate axial shakiness that may occur during end cap fastening.

  According to claim 3, by providing the slit, it is possible to reduce the amount of bending of the fitting wall that occurs when the end cap and the case are fastened by snap-fit engagement, and the fitting wall is bent. It is possible to prevent the occurrence of fastening “play” due to the cause.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of a DC motor 1 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of the case 21 of the DC motor 1. FIG. 3 is a side view showing the configuration of the end cap 31 of the DC motor 1. FIG. 4 is a front view showing the configuration of the end cap 31 of the DC motor 1. FIG. 5 is a bottom view showing the configuration of the end cap 31 of the DC motor 1.

The DC motor 1 shown in FIG. 1 is configured by assembling an end cap 31 so as to close the opening 22 of the case 21 after the magnet 10 and the armature 11 are assembled in the case 21. In the armature 11, a rotor shaft 12 provided at the center in the radial direction is rotatably supported by two bearings 2 and 3. Here, the bearing 2 is configured to be fitted into the through hole 25 of the case 21. The bearing 2 supports one end of the rotor shaft 12 and restricts the armature 11 from moving in the direction of the through hole 25 inside the case 31. On the other hand, the bearing 3 is configured to be fitted into a surface 33 (hereinafter referred to as “end cap inner surface”) that closes the opening 22 of the case 21 in the end cap 31. The other end side of the rotor shaft 12 is supported by the bearing 3. Here, the end of the rotor shaft 12 is in contact with the end cap 31, and the armature 11 is restricted from moving toward the opening 22 inside the case 21. The brush 4 is held by an end cap 31.
In the present application, the term “axial direction” is used as the direction parallel to the longitudinal direction of the rotor shaft 12, and the term “radial direction” is used as the direction orthogonal to the axial direction.

  As shown in FIG. 2, the case 21 is provided with an opening 22 on one end side and a through hole 25 on the other end side. When the DC motor 1 is assembled, the magnet 10 and the armature 11 are inserted into the case 21 through the opening 22. The surface of the end portion of the case 21 on the opening 22 side is a locking lid contact surface 24. Further, a snap fit engagement hole 23 is provided near the opening 22 of the side wall 26 in the case 21. As an example, the snap-fit engagement holes 23 are provided at two opposing flat portions of the side wall portion 26, but may be provided at opposing curved surface portions. Also, the number provided may be two or more. In any case, it is desirable that the rotor shaft 12 to be incorporated is provided in a radial direction.

  As shown in FIGS. 3, 4, and 5, the end cap 31 is provided with a locking lid 32 having an outer diameter larger than the inner diameter of the opening 22 of the case 21. When the end cap 31 is fastened to the case 21, the end cap 31 contacts the case 21 with respect to the case 21 by the contact of the locking lid 32 with the locking lid contact surface 24 in the opening 22 of the case 21. The end cap 31 is locked at the position, and movement of the end cap 31 in the axial direction (movement in the mounting direction) is restricted. In addition, a fitting wall 34 that fits on the inner surface 33 of the end cap without a gap is provided over the whole or a part of the circumferential direction. Due to the fitting, movement of the end cap 31 in the radial direction is restricted. Further, a snap fit engagement piece 35 is provided on the outer side of the distal end portion of the fitting wall 34. The position and the number of the snap fit engagement pieces 35 are provided so that they can be engaged according to the position and the number of the snap fit engagement holes 23 of the case 21. By causing the snap fit engagement piece 35 to snap fit into the snap fit engagement hole 23, movement of the end cap 31 in the axial direction (movement in the removal direction) is restricted. Here, slits 41 are provided at positions on both sides of the snap-fit engagement piece 35 from the distal end portion of the fitting wall 34 toward the locking lid portion 32. In addition, the structure which forms the fitting wall 34 and the snap-fit engagement piece 35 continuously without providing the slit 41 may be sufficient. Further, a groove portion for fitting the bearing 3 is provided in the center portion of the end cap inner surface 33.

  Further, as shown in FIGS. 3, 4, and 5, the locking lid portion 32 may be provided with a rib 40 having a minute height. In that case, when the end cap 31 is fastened to the case 21, the end cap 31 is locked to the case 21 at a predetermined position by the rib 40 coming into contact with the locking lid contact surface 24. Movement of the end cap 31 in the axial direction (movement in the assembling direction) is restricted. At this time, the rib 40 is compressed in the height direction and deformed so as to be crushed by the compression force generated between the locking lid portion 32 and the locking lid contact surface 24 at the time of fastening. At this time, an elastic force that causes the deformation to return is generated. The rib 40 may be formed integrally with the end cap 31 or may be formed separately. In addition, as an example, the ribs 40 are provided at four positions that are symmetrical in the vertical direction and the horizontal direction of the end cap 31. The number of ribs 40 may be four or less or four or more, or may be an asymmetric arrangement. The height and the like of the rib 40 are appropriately set according to the number of the ribs 40 provided, the material of the end cap 31, and the like.

  Normally, the end cap 31 is made of a resin material, and the locking lid portion 32, the fitting wall 34, the snap fit engagement piece 35, and the rib 40 are integrally formed. However, any of those configurations may be formed as separate bodies. Also, the material is not limited to resin.

Next, operations and effects based on the above configuration will be described.
First, when the case 21 and the end cap 31 are fastened, the snap fit engagement hole 23 of the case 21 and the snap fit engagement piece 35 of the end cap 31 are snap-fit engaged, so that the axial direction of the end cap 31 is increased. Movement (movement in the removal direction) is restricted. Here, in the conventional DC motor, the end cap is tightened by a structure for tightening, and the movement in the axial direction (movement in the removal direction) is regulated. It is difficult to carry out evenly in the vertical direction, and as a result, radial stress acts on the end cap, resulting in radial displacement from a predetermined position. In that respect, according to the fastening structure of the end cap 31 by the snap-fit engagement according to the present invention, it is possible to eliminate uneven radial stress acting on the end cap 31. Thereby, it is possible to prevent the end cap 31 from being displaced from the predetermined position in the radial direction. Thereby, the accuracy of the assembly position of the rotor shaft 12 can be increased. As a result, it is not necessary to take measures for adjusting the displacement by increasing the inner diameters of the bearing 2 and the bearing 3, and the bearing 2 and the bearing 3 having a smaller inner diameter can be employed. By eliminating the need to increase the inner diameters of the bearing 2 and the bearing 3, the assembly accuracy (fitting clearance accuracy) between the rotor shaft 12, the bearing 2 and the bearing 3 can be improved, and thereby the shaft generated during motor operation. Mechanical noise such as sliding noise and vibration can be significantly reduced, and the durability of the motor can be improved. This not only prevents uneven wear of the rotor shaft 12 and the bearing 2 and the bearing 3 and prevents intrusion of dust, but also reduces the number of additional lubrication, and causes various problems caused by excessive oil amount ( For example, it leads to the elimination of dust adhesion). By these things, it becomes possible to improve the durability of a motor remarkably.

  As a result of fastening with a caulking structure in the conventional DC motor, the end cap may be displaced from the predetermined position in the radial direction. The position of the end cap is struck by the “intuition” of the assembly operator. I was correcting the gap. However, the fastening structure of the end cap 31 by the snap-fit engagement according to the present invention can prevent the end cap 31 from being displaced from the predetermined position in the radial direction, so that the position deviation correcting step in the motor manufacturing process can be omitted. It becomes possible. This makes it possible to shorten the time required for manufacturing the motor, and has the remarkable effect that the cost can be reduced accordingly.

  In addition, the conventional DC motor end cap fastening process includes two processes (the above-described misalignment correcting process): a process of inserting and locking the end cap to a predetermined position of the case and a process of fixing by crimping. And 3 steps). On the other hand, in the present invention, only the operation of inserting the end cap 31 into the case 21 is engaged so that both the axial direction and the radial direction are in predetermined positions, and the fastening is completed. Therefore, the fastening process is labor-saving, and the time can be reduced accordingly. Furthermore, since the operation direction of the assembly work is only a linear operation, the assembly apparatus can be simplified.

  However, there may be problems with the snap-fit connection during fastening. In that case, when the snap fit engagement hole 23 and the snap fit engagement piece 35 are formed, the processing accuracy is lower than the design value. The problem is that the snap-fit engagement between the snap-fit engagement hole 23 of the case 21 and the snap-fit engagement piece 35 of the end cap 31 restricts movement in the removal direction in the axial movement of the end cap 31. Is the main function. For example, when the processing accuracy of the snap fit engagement hole 23 is low and the formation position of the snap fit engagement hole 23 is closer to the end cap 31 than the design position, the end cap The snap-fit engagement is completed before the engagement lid portion 32 and the engagement lid contact surface 24 of the case 21 are brought into contact with each other. At that time, the movement of the end cap 31 in the axial direction is restricted, but the movement of the end cap 31 is restricted. Since the restriction of the movement direction has not occurred, the end cap 31 is movable in the mounting direction in the axial direction, the movable length is that would cause looseness in the axial direction.

  The above problem can be solved by providing the rib 40. That is, when the end cap 31 is fastened to the case 21, the end cap 31 is deformed so as to be compressed and crushed by the compressive force generated between the locking lid portion 32 and the locking lid contact surface 24. The rib 40 to be generated generates an elastic force for returning the deformation, and the force acts in a direction in which the locking lid portion 32 and the locking lid contact surface 24 are separated. Due to this action, the movement of the attachment direction in the movement of the end cap 31 in the axial direction is restricted. As a result, it is possible to eliminate shakiness in the axial direction when the end cap 31 is fastened.

  Normally, since the end cap 31 is made of a resin material, even if a configuration in which the fitting wall 34 and the snap fit engagement piece 35 are continuously formed is employed, the snap fit engagement is performed due to the elasticity of the resin material. The piece 35 can be elastically deformed and snap-fit engaged with the snap-fit engagement hole 23. However, when the continuous configuration is adopted, when the end cap 31 and the case 21 are fastened by snap-fit engagement, the fitting wall 34 may bend, and as a result, looseness of the fastening may occur. . As a means for solving this problem, it is preferable to provide slits 41 from the front end of the fitting wall 34 toward the locking lid 32 at both sides of the snap fit engagement piece 35. That is, by providing the slit 41, it is possible to reduce the amount of deflection of the fitting wall 34 at the time of the fastening and prevent the occurrence of rattling. The above effect can be exhibited not only in the case of a resin material but also in the case of a metal material.

  The present invention is particularly suitable for small motors with a diameter of 20 mm or less. The above-described effects are more remarkably exhibited when applied to such a small motor. Here, the effectiveness of the present invention is proved by showing an example of numerical data achieved by the DC motor 1 according to the present embodiment in Table 1. The numerical value achieved by the direct current motor 1 according to the present invention is higher than that of a conventional motor, and it can be said that the effect itself is a great effect. It can be said that the greatest effect of the present invention is that it is realized by a simple and easy assembling method and at low cost without passing through a correction process.

  The DC motor according to the present invention can be applied not only to a small motor but also to a large motor.

It is the schematic which shows an example of the DC motor which concerns on embodiment of this invention. It is the schematic which shows the structure of the DC motor shown in FIG. It is a side view which shows the structure of the end cap of the DC motor shown in FIG. It is a front view which shows the structure of the end cap of the DC motor shown in FIG. It is a bottom view which shows the structure of the end cap of the DC motor shown in FIG. It is the schematic which shows an example of the DC motor which concerns on the conventional embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC motor 2 Bearing 3 Bearing 4 Brush 10 Magnet 11 Armature 12 Rotor shaft 21 Case 22 Opening part 23 Snap fitting engagement hole 24 Locking lid contact surface 25 Through-hole 26 Side wall part 31 End cap 32 Locking lid part 33 End Cap inner surface 34 Fitting wall 35 Snap fit engagement piece 40 Rib 41 Slit

Claims (3)

An armature, a rotor shaft provided at the center of the armature in the radial direction, two bearings that rotatably support the rotor shaft, a case that encloses the armature and in which the one bearing is disposed, and the case In a DC motor comprising an end cap on which the other bearing is disposed while closing the opening of
The end cap is provided with a locking lid portion having an outer diameter larger than the inner diameter of the opening portion of the case, and a fitting wall that fits on the case-side surface without any gap with the case inner wall in the circumferential direction. Or provided in a part, and a plurality of snap-fit engagement pieces are provided on the outer end of the fitting wall,
The inside of the fitting wall provided with the snap-fit engagement piece on the outside is formed on a substantially straight wall surface extending from the case insertion side end to the locking lid, There is a brush installation space inside,
The snap-fit engagement piece is configured in a shape that protrudes from the end of the fitting wall toward the outside of the fitting wall by a slight amount from the end of the case insertion side.
The case is provided with a snap fit engagement hole for engaging the plurality of snap fit engagement pieces on the side wall portion on the opening side,
The DC motor according to claim 1, wherein the armature is positioned at a predetermined position by fastening the end cap and the case by snap-fit engagement. The locking lid portion is provided with a plurality of ribs to be brought into contact with the locking lid contact surface in the case opening ,
The plurality of ribs are formed at a height that is crushed and generates an elastic force when the end cap and the case are fastened by the snap-fit engagement. The DC motor according to claim 1. The said fitting wall is provided with the slit formed in the direction of a latching cover part from the front-end | tip part of this fitting wall in the both-sides position of a snap fitting engagement piece. 2. The DC motor according to 2.

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