JPS5912691A - Small-sized speaker - Google Patents

Abstract

PURPOSE:To prevent a high output sound pressure and sound distortion, and abnormal sound, by providing a recess on a center pole upper surface for ensuring a space where a diaphragm is vibrated in a large amplitude to a large input around the minimum resonance frequency. CONSTITUTION:The recess 20 is formed to a surface opposite to an inverse dome shaped center dome 19 of the center pole 12 in parallel with the shape of the center dome 19. Thus, the space where the diaphragm can be vibrated in a large amplitude to a large input around the minimum resonance frequency is ensured. Thus, high output sound pressure, sound distortion are prevented and abnormal sound is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a small speaker used in an audio output section of a portable small radio receiver, a cassette tape recorder, a translator, an electronic computer, etc.

Structure of a conventional example and its problems FIG. 1 shows a conventional small speaker. In Figure 1,
1 is a permanent magnet, 2 is a center pole, 3 is a high yoke, 4 is a frame, 6 is a voice coil, 6 is an edge portion, 7 is a diaphragm portion, 8 is a voice coil mounting portion, and 9 is a diaphragm dome portion. In the above-mentioned small speaker, light and highly rigid paper, a polymeric material such as polyarylate, etc. are used as the diaphragm material to ensure sound quality and sound pressure. High-performance samarium cobalt-based permanent magnets are also used. Since the shape of the speaker needs to be extremely thin, the overall shape of the diaphragm is inverted conical. The voice coil mounting portion 8 has the widest space, allowing a margin for the amplitude of the voice coil. The dome portion 9 of the diaphragm is also an inverted dome, and has a structure that reduces the thickness of the speaker.

However, there is an increasing demand to lower the lowest resonant frequency fo and expand the reproduction frequency band even in a small speaker having such a configuration, but conventional speakers cannot meet these demands. By increasing the specific elastic modulus of the diaphragm and making the edges thinner, the reproduction frequency band can be expanded, but the lowest resonant frequency f.

By lowering the amplitude, even with the same human power, there will be a large amplitude in the low range. Therefore, at the time of large input, the diaphragm dome portion 98
There was a problem that the center pole 2 came into contact with the center pole 2, causing the sound to be broken or distorted.

OBJECT OF THE INVENTION The present invention overcomes these conventional drawbacks.
It is an object of the present invention to provide a small speaker that can withstand large amplitudes when the lowest resonant frequency fa is expanded to the lower frequency side.

Structure of the Invention The small speaker of the present invention is applied to a diaphragm in which an inverted conical cone and a center dome have an inverted dome shape as a whole. A concave portion having a shape corresponding to the dome shape is provided. When forming a recess in the center of the center pole, the energy product of the permanent magnet is
The material and size of the center pole, and the size and shape of the recess must be selected to optimal values, taking into account the magnetic flow and magnetic flux density within the center pole. By processing the center pole into this shape, the distance between the apex of the center dome and the center pole can be widened, and it is possible to cope with large amplitudes when the lowest resonance frequency 10 is lowered. A technique for lowering the lowest resonant frequency fo can be realized by forming the edge portion relatively thinner than the diaphragm portion and the center dome portion.

, technology that increases the rigidity of the diaphragm and thins the edges of the diaphragm makes it possible to achieve a wide band and high input resistance, and also allows for large input and large amplitude in the low frequency region, especially below the lowest resonant frequency. By using a center pole with a recess, it is possible to obtain a small speaker that can withstand the above conditions.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described. FIG. 2 shows an embodiment of the present invention, and in FIGS. 3 and 4, 11 is a permanent magnet, 12 is a center pole, 13 is a yoke, 14 is a frame, 16 is a voice coil, and 16 is an edge. part, 17 is a diaphragm part, 18 is a voice coil weighted part,
Reference numeral 19 denotes a diaphragm dome portion, which as a whole constitutes a diaphragm having an inverted conicum cone and a center dome.

A recess 2o is formed on the surface of the center pole 12 facing the center dome 19 so as to be parallel to the shape of the center dome 19. As the material for the diaphragm, we used polyarylate, a thermoplastic polymer film whose edge and cone parts can be integrally molded. In addition, polyester films and films made by combining these with mica or talc as reinforcing materials can also be used. This film is thinned only at the edge portions 16 by vacuum forming, and the center dome 19 is formed into an inverted dome shape to increase the reproduction sound pressure in the low range. The center pole 12 is made of iron, a soft magnetic material with high magnetic permeability. In this case, it is necessary to pay attention to the energy product of the permanent magnet 11 and the magnetic flux density distribution within the center pole 12, and to design a design that saturates and suppresses leakage to the outside as much as possible. In this embodiment, since the magnetic flux density distribution within the center pole 12 is concentrated in the voice coil gap,
The magnetic flux density is rough in the central portion of the upper surface of the center pole 12, and even if the recessed portion 2o is provided in the central portion, the influence on the magnetic flux density between the voice coil gaps is small. By using the center pole 19 with this shape,
In a small thin speaker with a total thickness of 6 mm, the distance between the center pole 12 and the center dome 19 apex is 1.6 to 2.
Can be doubled.

Figures 3a and 3b show another embodiment. Figure 3 a, b
is an enlarged sectional view of only the center pole portion. Figure 3a
Figure 3 shows a simple shape, and Figure 3 shows a shape that takes into consideration the magnetic flux density distribution. Even in these shapes, a large space can be secured for the vibration plate's amplitude.

Effects of the Invention As described above, according to the present invention, since the recess is provided on the upper surface of the center pole, a space can be secured in which the diaphragm can generate a large amplitude in response to a large input near the lowest resonance frequency of 10 2 .

This prevents high output sound pressure and sound cracking, and prevents abnormal sounds. As a result, it is possible to improve input resistance characteristics, life characteristics, and reproduced sound quality in a thin and small conductive speaker. Furthermore, since there is a margin for amplitude, there is an advantage that a thinner speaker can be realized.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional small speaker, Fig. 2 is a sectional view showing an embodiment of the small speaker of the present invention, and Figs. 3 a and b.
is a cutaway i1 of the center pole showing another embodiment of the small speaker of the present invention. 11...Permanent magnet, 12...River/center pole, 19...River/inverted dome-shaped center dome, 20...
・・・Concavity. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 (b+ mouth M part

Claims (1)

[Claims] A small speaker characterized in that the surface of the center pole that constitutes the field part, which faces the inverted dome-shaped center dome, is formed into a concave shape.