JPS58171198A - Electromagnetic speaker - Google Patents

Abstract

PURPOSE:To improve the efficiency of the titled speaker, by putting a hollow disc-like upper york on a magnetic plate and forming the shape of a moving iron piece like a hollow discs or a hollow cylinder. CONSTITUTION:An iron core 9 is fitted to the center of a lower york 8 and a york 10 having outer diameter larger than that of the iron core 9 is fixed on the upper surface of the magnetic core 9. A coil 11 is wound around the periphery of the magnetic core 9 and a hollow ring-like magnet 12 is arranged on the lower york 8 at the periphery of the coil 11. A hollow ring-like upper york 13 is put on the upper surface of the magnet 12. Hollow disc-like moving iron pieces 14 are arranged with proper spaces from the upper surfaces of the yorks 10, 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of an electromagnetic speaker, and in particular aims at increasing efficiency by improving the magnetic circuit configuration.

FIG. 1 is a cross-sectional view showing the structure of a conventional electromagnetic speaker. In Figure 1, 1 is the lower yoke, the lower yoke 1
A magnetic core 2 is provided in the center, and a coil 5 is wound around it. 4 is a ring-shaped magnet, which is placed on the lower yoke 1. A movable iron piece 5 is fixed to the center of a bent diaphragm 6, and the periphery of the diaphragm 60 is supported by a support frame 7. The above configuration is the well-known 111
This is a guide to magnetic speakers. In this structure, a magnetic force acts in the direction of the movable iron piece and the magnetic core, and the force F can be expressed as follows. Here, 8... magnetic core cross-sectional area μ. ...Aia ratio of air B+a...Magnetic flux density of the magnetic gap due to the magnetic flux generated from the magnet B6...Magnetic flux density of the magnetic ear due to the magnetic flux generated by the coil current. Be is proportional to the coil current69, and when a signal current is passed through the coil, the following force is generated in the movable iron piece in proportion to the signal current due to the second load of equation (A).

In equation (A), the first peak is the force due to the magnetic flux from the magnet, which indicates a static attractive force.In order to efficiently obtain the signal sound, the value of the second term in equation (A) must be made large. This means that in the magnetic gap, the magnetic flux density Bm from the magnet and the magnetic flux density due to the coil @ B c 1! r will be increased.

On the other hand, when considering the entire speaker, a method is taken that uses KFi to obtain flat frequency characteristics, and an inertial control region in a band above the resonance frequency of the imaging plate. The sound pressure level in this inertial control region is greatly influenced by the mass of the imaging system, and the smaller the mass, the higher the efficiency.

From the above points, in the case of further improving the electromagnetic speaker shown in Fig. 1, attention should be paid to reducing the quality of the rotating iron piece, but since the movable iron piece is a component of the magnetic circuit, the magnetic flux density Bm , Be must not have the opposite effect of decreasing them. In addition, it acts in a direction that exceeds the resonant frequency of the imaging plate, which is not desirable in this respect, and involves changing the hole size and the thickness to make the vibration fit easier to deflect. Loss of balance,
It is also possible that the movable iron piece and the magnetic core come into contact and are attracted by fCjL and cannot be separated. Therefore, as the spring constant of the imaging plate is reduced, the attractive force (static attractive force) by the magnet is reduced, resulting in a decrease in Bm.

In other words, improvements to improve efficiency must be more effective than the inconsistencies, and of course, if all the dimensions are increased, it cannot be said to be highly efficient.

The structure example according to the present invention is as shown in FIG. 2. In FIG. 2, 8 is a lower yoke, a magnetic core 9 is provided in the center of the lower yoke, and the upper surface thereof is as follows: A wooden yoke 10 is fixed to the outer diameter of the magnetic core 9.

A coil 11 is wound around the outer periphery 4C of the magnetic core 9.
A hollow ring-shaped magnet 12 is placed on the outer periphery of the lower yoke 8. A hollow ring-shaped upper yoke 13 is also mounted on the upper end surface of the magnet 12. These yokes 10, and 1
A hollow disk-shaped movable iron piece 14 is placed apart from the upper end surface of 3 and the clean air FJf.

Since it is larger than the diameter, it plays the role of bending the magnetic flux in the magnetic core 9 to the periphery, and makes it possible to make the movable iron piece hollow so that it has approximately the same cross-sectional area as the conventional one in the magnetic gap with the movable iron piece. Although the yoke 10 is placed on the magnetic core 9 in this example, it can also be formed integrally with the magnetic core 9.
In that case, it is not necessarily necessary to have the shape of this example, and depending on the diameter of the magnetic core 9, the shape shown in FIG. 1 can also be realized.

The storage size of the movable iron piece 14 is determined in consideration of not causing magnetic saturation, but due to the volume reduction of the magnet 120,
It also decreases due to a decrease in the magnetic flux passing through the movable iron piece.

As described above, according to the present invention, the quality t of the movable iron piece can be reduced and the sound pressure level in the inertia control region can be increased. It is possible to improve efficiency without causing problems such as an increase in size or an increase in resonance frequency.

The inner diameter of the movable iron piece 14 is at least smaller than the outer diameter of the yoke 10, and the outer diameter is larger than at least the inner diameter of the upper yoke 13. The movable iron piece 14 is fixed to the camera wjing plate 15, and the periphery of the vibration @15 is supported by a support frame 16.

According to the above structure R, the movable iron piece 14 is not thin and is hollow, so that its mass is reduced. The result is an increase in efficiency, and I will describe it in a sexual way.

First, in order to prevent the co-image frequency from increasing, the thickness or elastic modulus of the diaphragm 15 is set to be small. In order to eliminate the collapse of the magnetic gap balance associated with this, the thickness of the magnet 12 is made small, and the static attraction force is set to be low. Saravc, (A)
From the relationship in the equation, a decrease in Bm results in a decrease in signal driving force, so the upper yoke 13 is arranged to compensate for this. Upper yoke 13
By setting , the magnetic resistance seen from the coil magnetomotive force becomes smaller, and Be becomes larger as a result. That is, this is because the yoke exists in the conventional magnet exclusive area.

In addition, the yoke 10 is arranged on the magnetic core 9, and the yoke 10 is placed on the magnetic core 9.

[Brief explanation of drawings]

Figure W41 is a cross-sectional view of a conventional electromagnetic speaker, and Figure 2 is a cross-sectional view of an 11@-type speaker according to an embodiment of the present invention. 1.8... Lower yoke 2.9... Magnetic core 6.11... Coil 4.12... Magnet 5.14... ...Movable iron piece 6.15 ...Diaphragm 7.16 ...Support frame 10 ...Yoke 13 ......Top Applicant: Daini Seikosha Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A lower yoke, a magnetic core provided on the lower yoke, a coil wound around the magnetic core, a magnet placed on the lower yoke around the coil, and the magnetic core and a suitable air V4. In an electromagnetic speaker that includes a movable iron piece that is arranged so as to maintain a diaphragm and is fixed to a diaphragm, a hollow disc-shaped relay iron is placed on the magnet, and the shape of the movable iron piece is changed to a hollow disc shape, or , an electromagnetic speaker characterized by having a hollow cylindrical shape.