JPS59215200A - Electromagnetic speaker - Google Patents

Abstract

PURPOSE:To realize the thin profile of a unit and to improve the acoustic transducing efficiency without increasing the resonance frequency of a diaphragm by making the thickness of the center part of the diaphragm or a plate thicker than the thickness of the circumferential part. CONSTITUTION:The relation of t1<t2 is obtained in an electromagnetic speaker, where t1 is the thickness of the diaphragm 9 and t2 is the thickness of a center pole 8. Thus, the magnetic saturation is mostly caused by the diaphragm. Then, in changing the thickness of the center part of the diaphragm 9 from t1 to t2, the cross section to the magnetic flux passing through the diaphragm is increased, the magnetic saturation is reduced remarkably, the magneto-resistance is reduced and the magnetic flux between the diaphragm and the center pole 11 giving a large effect on the acoustic transducing efficiency of the electronic unit is increased, then the efficiency of the speaker is improved without increasing the thickness of the circumference of the diaphragm deciding the resonance frequency of the diaphragm and without increasing the height of the unit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a small speaker used in small audio equipment such as radios and cassette tape recorders with radios.

Conventional configurations and their problems In recent years, small audio equipment such as radios and cassette tape recorders with radios have become increasingly compact. Among these, one factor that hinders miniaturization is the shape of the speaker. Conventional speakers are mainly electrodynamic type speakers consisting of a cone diaphragm and a magnetic circuit, and have become one of the largest components of a set. To solve this problem, a regeneration method has been considered in which a vibrator is attached to a part of the cabinet that makes up the set and the cabinet is used as a diaphragm.

A conventional speaker of this type will be explained below.

FIG. 1 shows a cross-sectional view of a conventional vibrator type speaker, where 7 is a center ball integrally or mechanically connected to a plate 8, 6 is an excitation coil wound around the center pole 7, and 5 is a plate. A ring-shaped magnet 3 is placed on the plate 8, and 3 is a vibrating plate made of a ferromagnetic material such as soft iron, and its periphery is supported by a support 4 made of a non-magnetic material fixed on the plate 8. There is. An electromagnetic unit composed of the above-mentioned components includes a spacer 2 provided on the diaphragm 3 in a part of the cabinet 1 constituting the set.
are strongly connected via.

The operation of the conventional vibrator type speaker configured as described above will be described below.

In the speaker having the above configuration, an electromagnetic unit is attached to a part of the cent cabinet 1, and the cabinet is vibrated by this electromagnetic vibrator to reproduce sound. That is, the magnetic force acting on the diaphragm 3 changes in response to changes in the current flowing through the excitation coil 6, and the diaphragm 3 vibrates due to this magnetic force. The vibrations of the diaphragm 3 are transmitted to the cabinet 1 via the spacer 2 provided above. The gear vignette 1 has a wider vibration area compared to the unit's diaphragm 3, so the vibration from the diaphragm 3 is efficiently absorbed.
It can be converted into sound waves. Compared to conventional electrodynamic speakers, the small electromagnetic unit has a simpler structure because it does not require a voice coil, which is a moving part, and can realize a thin unit.

However, in the above configuration, as shown by the arrow in FIG. Gap q2 between 3 and 7 ball 7
The flow passes through the center pole 7, plate 8, and then reaches the magnet 5. Therefore, the magnetic flux concentrates at the center of the diaphragm 1 or the plate 8, resulting in magnetic saturation, which increases magnetic resistance and reduces the magnetic flux, resulting in a decrease in the acoustic conversion efficiency of the unit. Further, K to solve the above problem is the material thickness t1 of the diaphragm 1 and the plate 8
The material thickness t2 of the diaphragm 3 may be increased to the extent that magnetic saturation does not occur, but if tl is made thicker, the resonant frequency of the diaphragm 3 will increase, making it difficult to reproduce low frequencies. However, there were problems such as an increase in the height and difficulty in making it thinner.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and aims to increase the acoustic conversion efficiency and reduce the thickness of the unit without increasing the resonant frequency of the diaphragm. be.

Structure of the Invention The present invention makes the center part of the diaphragm or plate thicker than the periphery, and changes the height of the center pole and the shape of the excitation coil in response to changes in the thickness of the diaphragm or plate. This is an electromagnetic unit with a structure that provides a certain magnetic gap between the excitation coil and the center ball.The above structure reduces magnetic saturation at the center of the diaphragm and plate, increases acoustic conversion efficiency, and makes the unit thinner. It is something that can be formalized.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows a structural diagram of a vibrator type speaker in a first embodiment of the present invention.

In FIG. 3, the same parts as in FIGS. 1 and 2 are labeled with the same number. In the figure, the material thickness of the diameter D2, which is the surface of the diaphragm 9 facing the center pole 11, is t1', which is t1') 11 relative to the peripheral material thickness t1. The material thickness t1 is constant from the outer circumference to the inner diameter D1 of the magnet 5, and the distance between D1 and D2 is tapered from t1 to t2. Furthermore, diaphragm 97 magnet 5. The width of the magnetic gap ~ between the center pole 11 and the center pole 11 is constant, and the surface of the exciting coil 1o inserted therein facing the diaphragm 9 is tapered along the shape of the diaphragm, and the gap is about 2 degrees. The combs are also the same or large, and the diaphragm 9 even at large amplitudes.
Take into consideration that the insulating coating of the coil will not be destroyed if it hits the excitation coil.

The operation of the speaker of this embodiment configured as described above will be described below.

In general, in an electromagnetic speaker, the material thickness t of the diaphragm 9 is in the relationship tl<t2 compared to the material thickness t2 of the center pole 8. Therefore, it can be considered that magnetic saturation is mostly caused by the diaphragm. Therefore, the thickness of the moon at the center of the diaphragm 9 is t
By changing from l to t2, the cross-sectional area for the magnetic flux passing through the diaphragm disappears, greatly reducing magnetic saturation and magnetic resistance, which greatly affects the acoustic conversion efficiency of electromagnetic units. Since the magnetic flux between the diaphragm 9 and the center pole 11 increases, the efficiency of the speaker can be improved without increasing the thickness of the material around the diaphragm, which determines the resonance frequency of the diaphragm, and without increasing the overall height of the unit.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same parts as in FIG. 3 are given the same numbers. In the same figure, the difference from the first embodiment shown in FIG. 3 is that the thickness of the plate 14 is changed from t2' from the periphery to the inner diameter D1 of the magnet 5 to t3 at the joint of the center pole 13. It is located at 12' and t3. Therefore, the shape of the excitation coil 12 disposed on the plate 14 is also made to follow the taper of the plate 14. In this embodiment, the material thickness is made thinner at the peripheral part of the plate 14 where magnetic flux does not concentrate and magnetic saturation is not a problem, and is thickened at the center part where magnetic saturation is a problem. By setting t3, it is possible to reduce the total height of the unit by reducing t2' compared to a conventional electromagnetic unit without causing magnetic saturation in the plate.

According to the present invention, by making the material thickness at the center of the diaphragm or plate thicker than the thickness at the periphery, magnetic saturation due to concentration of magnetic flux at the center can be reduced. This increases the magnetic flux in the magnetic gap between the diaphragm and the center ball, improving the acoustic conversion efficiency of the speaker, and by reducing the thickness of the diaphragm and center pole at the periphery, A thin electromagnetic unit can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a structural cross-sectional view showing a conventional example, FIG. 2 is a view showing the flow of magnetic flux, FIG. 3 is a structural cross-sectional view showing a first embodiment of the present invention, and FIG. It is a structural sectional view showing a second embodiment. 1...cabinet, 3,9...diaphragm, 8゜14...play), 7.11...
... Center pole, 6.10.12 ... Excitation coil. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4

Claims (4)

[Claims] (1) A vibration plate made of a ferromagnetic material such as soft iron, which is arranged with a center pole around which an excitation coil is wound around a "plate" and an excitation section with a ring-shaped magnet arranged, and a predetermined gap between the excitation section. An electromagnetic speaker having
An electromagnetic speaker characterized in that a central portion of at least one of the plate and the diaphragm is thicker than a peripheral portion. (2) The electromagnetic speaker according to claim 1, characterized in that the material thickness of the peripheral portions of the plate and the diaphragm is constant on the surfaces or opposing surfaces of the ring-shaped magnet. (3) A patent characterized in that the material thickness at the center of the plate and diaphragm is maximum at the joint with the center pole or at the opposing surface, and tapers between the material thickness at the periphery. An electromagnetic speaker according to claim 1. (4) The electromagnetic type according to claim 1, characterized in that the soil surface of the diaphragm is fixed to the wall, furniture, etc. of a gear vignette-sized room of an audio device such as a radio or a power tape recorder with a radio. speaker.