JP2001339902A - Outer rotor type motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise generated by torque pulses in an outer rotor motor having a structure wherein a stator 4 is fixed by use of a stator-fixing screw 11 to a screw hole made at a boss 6 that is integrally formed in one piece with the cover 1. SOLUTION: The structure is configured such that the thickness of an external peripheral of the boss 6 where a twisting energy becomes large in an intrinsic mode wherein the stator 4 and the boss 6 are twisted around the rotating shaft excited by the torque pulses and the thickness of a connecting part CC between the boss 6 and the cover 1 is made thicker than a base material of the cover 1, and then a damping material 50 is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abduction motor in which a control board and an electric motor used in OA equipment such as a copying machine are integrally mounted.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 7-210062 discloses a configuration in which a support plate is placed on a boss united with a resin exterior material and fixed with a screw member screwed into the boss unit, and the drive unit is supported by the support member. In addition, a vibration damping material is provided between the support plate placed on the boss portion and the exterior material.

In Japanese Patent Application Laid-Open No. 11-234956, a damping material is inserted between an outer peripheral portion of a rotor bearing and an outer peripheral portion of a stator and an end cover in an adduction type electric motor.

[0004]

However, the prior art is effective when the support member and the exterior material are configured as separate parts, but Japanese Patent Application Laid-Open No. 7-210062 discloses that the support portion and the exterior material are not provided. The integrally formed structure, Japanese Patent Application Laid-Open No. 11-234965, cannot be applied to a structure in which the stator is screwed to the support at a position other than the circumferential portion.

An object of the present invention is to provide a motor having low vibration and low noise by disposing a damping material in a structure in which a support portion and an exterior portion are integrally formed and a stator is screwed to the support portion. It is in.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotor having a permanent magnet therein, a boss for holding a stator, a printed board and a bearing, and a printed board arranged in parallel at a predetermined interval. A cover integrally formed with the boss so as to be held in a state, and the boss has a plurality of steps concentrically, and the step has at least a hole for connecting to the cover and screwing the stator with a core mounting screw. In an abduction type electric motor, a vibration damping material is arranged on an outer peripheral portion of a step having a hole for connecting a cover and screwing a stator with a core mounting screw, and a joint portion where a boss and a cover are integrally formed. This is achieved by making the plate thickness of the connecting portion where the cover and the cover are integrally formed larger than the plate thickness of the base material of the cover.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of the external appearance of an external rotation type electric motor according to one embodiment of the present invention, and FIG. 2 is a perspective view of the external appearance of a cover and a boss. FIG. 3 is a half sectional view of an epimotor according to one embodiment of the present invention.

The abduction type electric motor includes an abduction type rotor 3 having a permanent magnet 35 therein, a printed circuit board 2, and a stator 4.
, A shaft 12, a bearing 5 for supporting the shaft 12, a boss 6 for holding the bearing 5 and the stator 4, and a cover integrally formed with the boss 6 and connected to another configuration Consists of one.

The boss 6 has a plurality of concentric steps.
Among them, there is a stator mounting screw hole 40 at a stage having a hole for connecting to the cover 1 of the boss 6 and fixing the stator 4 with the stator mounting screw 11.

The damping material 50 is disposed on the outer peripheral portion of the step having the stator mounting screw holes 40 of the boss 6 and on the joint CC between the boss 6 and the cover 1.

It is assumed that the exciting force of the epimotor is torque pulsation. In this case, the torque pulsation is a force that acts on the rotor 3 and the stator 4 in the circumferential direction. What is easily excited by this exciting force is an eigenmode in which the stator 4 and the boss 6 are twisted around the rotation axis.

FIG. 4 is a diagram showing a strain energy distribution obtained by calculation according to one embodiment of the present invention. In this figure, only the boss 6 and the cover 1 are taken out and displayed in the eigenmode in which the stator 4 and the boss 6 are twisted around the rotation axis. In FIG. 4, the strain energy contours 60 are concentrated on the outer peripheral portion of the step having the stator mounting screw holes 40 of the boss 6 and the joint CC between the boss 6 and the cover 1. According to FIG. 4, the distortion energy is increased in this eigenmode because of the outer peripheral portion of the step having the stator mounting screw hole 40 of the boss 6 and the joint CC between the boss 6 and the cover 1.
It can be seen that it is.

The j-th order loss coefficient by the mode distortion energy method using the finite element method is expressed by the following equation.

[0015]

(Equation 1)

Here, η _j : j-order loss coefficient U _ij : strain energy of j-th mode of element i U _total : total strain energy η _{e, i} : loss coefficient of damping material added to element i The mode damping ratio ζ _j is obtained by the following equation.

[0017]

(Equation 2)

That is, by disposing the damping material 50 having a large loss coefficient in a portion where the strain energy of a specific eigenmode is concentrated, the mode damping ratio for the specific eigenmode can be increased.

Accordingly, the outer peripheral portion of the step having the stator mounting screw holes 40 of the boss 6, the boss 6 and the cover 1
By arranging the damping material 50 at the coupling portion CC, the mode damping ratio for this eigenmode can be effectively increased.

This effect is not limited to the structure of the present motor, and the same applies to other similar structures in that the vibration damping material is arranged by focusing on a portion having a large strain energy distribution.

The mode attenuation ratio is predicted using (Equation 1) and (Equation 2). Assuming that the loss coefficient of the damping material is 10%, the mode damping ratio with respect to the eigenmode in FIG. 2 when the damping material 50 is arranged on the cover 1 and the boss 6 and when the damping material 50 is arranged at the position shown in FIG. Is shown in Table 1.

[0022]

[Table 1]

That is, the screw holes 4 for fixing the stator of the boss 6
0, outer peripheral portion of the step having the boss 6 and the connecting portion C of the boss 6 and the cover 1
Just by disposing the damping material 50 on C, it is possible to obtain a sufficiently large mode damping ratio equivalent to the disposition of the damping material 50 on the entire boss 6 and cover 1.

Table 2 shows the predicted noise values at the same evaluation position for the eigenmode in which the stator 4 and the boss 6 are twisted around the rotation axis. In Table 2, the noise level without the damping material 50 is set to 0 dB.

[0025]

[Table 2]

According to Table 2, when the damping material 50 is disposed at the position of the embodiment of FIG. 1, the same noise reduction effect as when the damping material 50 is disposed on the entire cover 1 and boss 6 can be obtained. As a result, the amount of the damping material 50 used can be reduced.

To reduce vibration and noise, it is also effective to increase the rigidity of a portion having a large strain energy. FIG.
FIG. 1 shows a half sectional view of an epimotor according to an embodiment from this viewpoint.

The embodiment shown in FIG. 5 is different from the embodiment shown in FIG. 3 in that the plate thickness of the joint CC between the boss 6 and the cover 1 where the strain energy is increased is larger than the plate thickness of the base material of the cover 1. is there. This makes it difficult for vibrations due to torque pulsation to be transmitted to the cover 1 and further reduces noise.

[0029]

According to the present invention, vibration and noise can be effectively reduced while reducing the amount of the vibration damping material used.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external appearance of an epimotor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an external appearance of a cover and a boss of the epimotor according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a half cross section of an epimotor and an arrangement of a vibration damping material in the embodiment of the present invention.

FIG. 4 is a perspective view showing a distribution of distortion energy of the epimotor in the embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a half cross-section of an epimotor and an arrangement of a vibration damping material in the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cover, 2 ... Printed circuit board, 3 ... Rotor, 4 ... Stator, 5 ... Bearing, 6 ... Boss, 11 ... Stator mounting screw,
12 ... shaft, 40 ... stator mounting screw holes, 50 ...
Damping material, 60: strain energy contour, CC: joint between boss and cover.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironori Shiobata 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratories, Hitachi, Ltd. (72) Inventor Toshimi Abkawa 7-chome, Kandami-doshiro-cho, Chiyoda-ku, Tokyo F-term (reference) 5H605 AA05 BB05 BB19 CC01 CC02 CC03 DD05 EA02 EA06 EA15 EA19 GG04 GG21 5H621 AA04 GA01 GA04 HH03 JK08 JK14

Claims (1)

[Claims] A rotor for holding a permanent magnet therein, a boss for holding a stator, a printed circuit board, and a bearing; and a boss for holding the printed circuit board in a parallel state at a predetermined interval. The formed cover and the boss have a plurality of steps concentrically, and the steps are at least connected to the cover and in the abduction type electric motor having a hole for screwing the stator with the core mounting screw, the cover and Vibration damping material is arranged at the joint where the boss and the cover are integrally formed with the outer periphery of the step having a hole for connecting and fixing the stator with the core mounting screw, and the boss and the cover are integrally formed. An abduction type electric motor characterized in that the plate thickness of the connecting portion is greater than the plate thickness of the base material of the cover.