JPS6130399Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a magnetic circuit for a speaker.

In recent years, the production volume of speakers that use ferrite magnets in their magnetic circuits has been increasing. The reason for this is that ferrite magnets are more cost-effective than conventionally used alnico magnets. However, on the other hand, ferrite magnets have the disadvantage of being easily damaged by stress applied from the outside, and this disadvantage lowers the production efficiency of magnetic circuits for speakers using ferrite magnets.

The first objective of this invention is to improve production efficiency in a magnetic circuit for a speaker using a ferrite magnet.

Figure 1 shows the magnetic circuit of a conventional speaker.
FIG. 3 is a cross-sectional view of the magnetic circuit of the speaker taken along a plane that passes through the diameter of a circle on the top surface of a center pole and is perpendicular to the plane of the circle.

In the figure, 1 is the center pole, 2 is the yoke,
3 is a top plate, 4 is a magnet, 5 is a heat-curable or room-temperature curing adhesive;
A magnet 4 having a through hole in the center is held between the top plate 3 and the top plate 3, and a center pole 1 is provided in the yoke 2 at a position corresponding to the through hole of the magnet 4. The contact surfaces between the top plate 3 and the magnet 4 and between the magnet 4 and the yoke 2 are bonded together with an adhesive 5 over the entire surface. In addition,
Descriptions of parts unnecessary for the explanation of this invention, such as the diaphragm and voice coil, will be omitted.

Conventionally, when assembling a speaker or after assembling, a temperature gradient occurs between the yoke 2 or top plate 3 and the magnet 4 due to a difference in thermal conductivity due to temperature changes in the outside air, and the coefficient of thermal expansion based on this temperature gradient changes. Stress is applied to the magnet 4 due to the difference, and this stress causes distortion of the magnet 4. If this distortion exceeds the limit of the mechanical strength of the magnet 4, an accident has occurred in which the magnet 4 is damaged.

In addition, adhesive 5 is used to compensate for the above drawbacks.
In addition, adhesives that remain elastic even after curing have been used. However, in this conventional example, damage to the magnetic circuit of the speaker can be prevented, but since the adhesive has elasticity, the magnet vibrates during playback of the speaker, compared to when using an adhesive that does not have elasticity after curing. The natural vibration frequency band of the magnetic circuit of the speaker shifts to the lower side, and the amplitude of this vibration increases.

This prevents the diaphragm from properly vibrating in a frequency band that is easy to hear, resulting in poor quality of reproduced sound and reduced efficiency.

This invention does not compensate for these conventional drawbacks,
The purpose of this invention is to obtain a magnetic circuit for a speaker that has high production efficiency, good sound quality, and good efficiency.

This invention will be explained below based on the embodiment shown in the figures.

FIG. 2 shows an embodiment of this invention, and the same parts as in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted.

In this embodiment, the contact surface is approximately 1/2 that of the inner surface.
The structure is such that about 2/3 of the area is bonded with adhesive 5, and a non-bonded portion is provided on the outer periphery.

Generally, when a ring-shaped material with uniform components expands or contracts due to heat or the like, the inner circumference of the link experiences less change in surface area than the outer circumference.
For the same reason, in the magnetic circuit of the speaker,
When the contact surface is bonded except near the outer periphery as in the above-mentioned embodiment, the distortion that occurs in the magnet 4 is smaller than when the entire surface of the contact surface is bonded.
Since the strain does not exceed the limit of the mechanical strength of the magnet 4, the magnet 4 will not be damaged due to temperature changes, and the speaker's magnetic strength will be reduced compared to when using an adhesive that remains elastic even after curing. Due to the high rigidity of the circuit, the natural vibration frequency band of the magnetic circuit shifts to the higher side, and the amplitude of this vibration also decreases, which prevents the correct vibration of the diaphragm in the frequency range between 600 and 1.200 Hz that is easy to hear. This has the effect of reducing the deterioration in the quality of reproduced sound and the decrease in efficiency caused by the noise.

FIG. 3 shows another embodiment, in which a groove 6 is provided near the outer periphery of the surface of at least one of the yoke 2 and the top plate 3 that is in contact with the magnet 4, and the structure and names of the other parts are as follows. , as in the case of FIGS. 1 and 2. This groove 6 is for preventing the adhesive 5 from overflowing to the outer periphery of the contact surface.

In the process of sandwiching the magnet 4 between the yoke 2 and the top plate 3, even if the adhesive 5 is applied or injected only to the vicinity of the inner circumference of the contact surface, the adhesive 5 will not come into contact with the contact surface due to the pressure etc. during sandwiching. There is a good chance that it will show up on the outer periphery of the surface. In this embodiment, the groove 6 allows the adhesive 5 to escape from the contact surface, thereby preventing the adhesive 5 from spreading to the outer periphery of the contact surface, eliminating the need to pay close attention to the bonding work. Therefore, the work becomes easier, and in addition to the effect shown in the embodiment shown in FIG. 2, it has the effect of increasing work efficiency during production.

Further, even if a groove is provided near the outer periphery of the contact surface of the magnet 4, a magnetic circuit having the same effect can be obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the magnetic circuit of a conventional speaker.
FIGS. 2 and 3 are cross-sectional views of magnetic circuits of speakers showing different embodiments of this invention. 1...Center pole, 2...Yoke, 3...
Top plate, 4... magnet, 5... adhesive, 6... groove.

Claims (1)

[Scope of utility model registration request] The outermost periphery of the adhesive surface of at least one of the yoke and the magnet or the top plate and the magnet of an external magnet type magnetic circuit of a speaker in which a yoke and a top plate are arranged so as to sandwich a magnet. A speaker magnetic circuit characterized by having a non-adhesive part near the end.