JP3878687B2 - Flat motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a small DC motor, and relates to a flat motor used, for example, in an automobile indoor air cleaner or a blower motor for blowing indoor air.
[0002]
[Prior art]
In recent years, flat motors have been used as fan motors for automobile interiors, taking advantage of their thinness and light weight. For this reason, lower noise is required than ever before.
[0003]
A conventional flat motor will be described below.
FIG. 5 shows a cross-sectional view of a conventional flat motor. In FIG. 5, 1 is a first bracket, 2 is a rotor formed by resin-molding a polygonal single coil, 3 is a second bracket, 4 is Substantially annular magnets 10 are applied to the joint surfaces of the first bracket 1 and the second bracket 2 with a sealant.
[0004]
About the flat motor comprised as mentioned above, the operation | movement is demonstrated below. After inserting the rotor 2 into the second bracket 3 having the substantially annular magnet 4 and applying the sealant 10 to the joint surface of the second bracket 3 with the first bracket 1, the first bracket 1 is put on and the motor is assembled. The sealing agent 10 at this time is urethane-based moisture curable, reacts with moisture in the atmosphere and cures, and after curing, the first bracket 1 and the second bracket 3 are bonded and sealed in cooperation. .
[0005]
FIG. 3 shows the result of investigating the natural frequency of the first bracket 1 when the first bracket 1 is vibrated by the impulse hammer method. It can be seen that the conventional flat motor has a natural frequency in the vicinity of 2.5 kHz after the sealant 10 is cured.
[0006]
[Problems to be solved by the invention]
However, in the conventional configuration, the first bracket is likely to vibrate after the sealant is cured. When the rotor becomes an excitation source within the operating voltage range of the motor, and the nth-order component of the excitation frequency matches the natural frequency of the bracket, the bracket resonates and a resonance noise is generated near 2.5 kHz, for example. Had problems.
[0007]
The present invention solves the above-described conventional problems, and an object thereof is to provide a highly reliable flat motor that has the same cost and realizes noise reduction.
[0008]
[Means for Solving the Problems]
In order to solve this problem, the present invention has a structure in which a liquid gasket that does not semi-permanently cure is interposed on the joint surface between the first bracket and the second bracket.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, there is provided a flat rotor formed by resin-molding a polygonal single coil on a commutator, and a first bracket on one side facing the rotor. And a flat motor provided with a second bracket having a substantially annular magnet on the other side, and assembled by interposing a liquid gasket that does not semi-permanently cure on the joint surface between the first bracket and the second bracket. Yes, as can be seen from FIG. 3, the first bracket has a structure that hardly vibrates, and even if the nth-order component of the excitation frequency of the motor matches the natural frequency of the first bracket, the resonance noise is less likely to occur. It has the effect of reducing noise in the vicinity of 2.5 kHz.
[0010]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(Embodiment 1)
FIG. 1 is a half sectional view of a flat motor according to an embodiment of the present invention, and FIG. 2 is a plan view of a second bracket according to the embodiment of the present invention.
[0011]
1 and 2, 1 is a first bracket, 2 is a rotor formed by resin-molding a polygonal single coil, 3 is a second bracket, 4 is a substantially annular magnet, and 11 is a sealing agent. It is applied to the joint surface between the first bracket 1 and the second bracket 2.
[0012]
The operation of the flat motor configured as described above will be described below.
[0013]
After inserting the rotor 2 into the second bracket 3 having the substantially annular magnet 4 and applying a sealing agent to the joint surface of the second bracket 3 with the first bracket, as in the conventional flat motor. Then, the motor is assembled by covering the first bracket. The sealing agent 11 at this time is applied with a liquid gas mat that does not cure semipermanently.
[0014]
FIG. 3 shows the result of investigating the natural frequency of the first bracket 1 when the first bracket 1 is vibrated by the impulse hammer method. FIG. 4 shows the vibration when the vibration frequency of the motor is 770 Hz. It is a frequency analysis result of noise in a motor + fan state when a third-order component of frequency matches the natural frequency of the first bracket 1.
[0015]
At this time, in the conventional flat motor, before the sealant is cured, the natural frequency of the first bracket 1 is in the vicinity of 2.3 kHz as in the embodiment of FIG. By firmly bonding and sealing the first bracket 1 and the second bracket 3, the natural frequency of the first bracket 1 is easily shifted by about 200 Hz in the vicinity of 2.5 kHz. Further, in this state, it can be seen in FIG. 4 that when the third-order component of the excitation frequency of the motor matches the natural frequency of the first bracket 1, a noise of about 69 dB is generated.
[0016]
Therefore, in this embodiment, the natural frequency of the first bracket 1 exists in the vicinity of 2.3 kHz by using a liquid gas mat in which the sealant does not harden semi-permanently. Even if this is taken into consideration, the first bracket 1 has a structure that hardly vibrates. Therefore, in FIG. 4, when the third-order component of the excitation frequency of the motor matches the natural frequency of the first bracket 1, noise of about 64 dB is generated, but about 5 dB compared to the conventional example. The noise reduction effect of this appears.
[0017]
In addition, the sealing agent of this embodiment is excellent in heat resistance, and the viscosity is lowered even when the temperature reaches 80 ° C., and a material that does not flow and sag is used, for example, an ester-based viscosity of about 300,000 cp. Is desirable.
[0018]
As described above, by having a structure in which the liquid gas mat that does not semipermanently intervene on the joint surface between the first bracket 1 and the second bracket 3, the resonance of the bracket near 2.5 kHz is equivalent to the cost. Can reduce the noise by about 5dB.
[0019]
【The invention's effect】
As described above, according to the present invention, since the liquid gas mat that does not semi-permanently intervene on the joint surface between the first bracket 1 and the second bracket 3, the cost is equivalent. It is possible to provide an excellent flat motor with high reliability in which noise due to bracket resonance in the vicinity of 5 kHz is reduced by about 5 dB.
[Brief description of the drawings]
FIG. 1 is a half sectional view of a flat motor according to an embodiment of the present invention. FIG. 2 is a plan view of a second bracket according to the embodiment of the present invention. Fig. 4 is a diagram showing the frequency analysis result of noise in the motor and fan state according to the embodiment. Fig. 5 is a half sectional view of a conventional flat motor.
DESCRIPTION OF SYMBOLS 1 1st bracket 2 Rotor 3 2nd bracket 4 Substantially annular magnets 10 and 11 Sealing agent

Claims (1)

A flat rotor formed by resin-molding a polygonal single coil on a commutator, a second bracket having a first bracket on one side and a substantially annular magnet on the other side facing the rotor. A flat motor provided with a bracket, wherein a liquid gasket that is not semi-permanently cured is interposed only on the joint surface between the first bracket and the second bracket.

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