JP2835696B2 - Flat speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio speaker, and more particularly to an audio speaker for faithfully reproducing the entire audible frequency range with a single speaker.

[0002]

2. Description of the Related Art In recent years, due to the development of recording technology, the frequency band of an audio signal to be recorded has been widened, and the dynamic range (ratio of strong and weak audio signals) has been extremely large. Generally, a frequency band (20 Hz to 30 KHz) is divided into two or three, and each divided frequency band is shared by a dedicated speaker.

When the audio frequency band is divided into three parts, the loudspeaker is a conical diaphragm having a diameter of at least 20 cm in the low range, a diameter of about 10 cm in the middle range, and a dome-shaped diaphragm having a diameter of several cm or less in the high range. General. In the normal audio field, as described above, a method in which three speakers are shared is referred to as a three-way speaker system, and a method in which the entire frequency band is divided into a low band and a high band, and each is assigned to a dedicated speaker. This is called a two-way speaker system. In order to drive each of these speakers as a dedicated speaker for a divided frequency band, an output signal from the amplifier is shared by a combination of an inductor (L), a capacitor (C), and a resistor (R). The signal is supplied after being divided into frequency bands according to the characteristics of the speaker.

It is natural that the audio waveform reproduced and synthesized by the three speakers is different from the amplifier output signal waveform. The difference between the waveforms is due to the phase difference between the frequency components constituting the actual voice. However, for continuous sounds, acoustically, if the frequency components are the same even if the waveforms are different, the audibility will be lower. No difference is expected. However, continuous sounds are hardly possible in real voices.

For this reason, a single loudspeaker having a conical diaphragm having a diameter of about 10 cm is generally used for all frequency bands. Also in a flat speaker having a flat diaphragm, an attempt was made to make the diaphragm of about 8 cm × 15 cm correspond to the entire frequency band. However, with these speakers, it has been impossible to faithfully reproduce a part of the low frequency from the following points.

That is, in order to reproduce a high sound range with a sufficient sound pressure with a conical diaphragm having a diameter of about 10 cm or a plane diaphragm having a size of 8 cm × 15 cm, it is necessary to increase the driving force per unit area. For this purpose, it is realized by using the divided vibration of the diaphragm or by increasing the magnetic flux density of the magnetic gap. However, in order to reproduce the lowest sound range of a sufficient sound pressure, the amplitude of the diaphragm is required to be about 2 mm or more. There is no way to support the bobbin.

[0007]

SUMMARY OF THE INVENTION The present invention solves such drawbacks of the conventional loudspeaker by using a flat loudspeaker, and can use a single loudspeaker to transmit an audio signal having a large dynamic range in a wide frequency band. It is intended to enable faithful reproduction.

[0008]

According to a first aspect of the present invention, there is provided a flat speaker, comprising: a rectangular drive coil mounted on a flat diaphragm; By means of a flat leaf spring having a plurality of cuts (slits), the flat leaf spring is parallel to the plane diaphragm radially from four directions and, depending on the amplitude of the plane diaphragm, in this radial direction. A sound absorbing system that supports a vibration system consisting of a plane diaphragm, a drive coil, and a winding frame of the drive coil so that it can expand and contract, and is attached to the entire periphery of the plane diaphragm in a plane parallel to the plane diaphragm. Flexible membranes abut or overlap each other.

[0009]

The drive coil or its winding frame is radially supported by a plurality of flat plate springs having notches (slits) which are not connected to each other, and a gap is formed between the entire periphery of the planar diaphragm and the speaker body structure frame. With a sound absorbing flexible membrane, which can sufficiently guarantee the degree of freedom of the vibration system in the direction of vibration. It is a single speaker with a relatively small diaphragm and has a large dynamic range. Full-range faithful reproduction is possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, when a signal current flows through a coil placed in a magnetic field, the frequency of the signal current is generally set at a right angle to the magnetic field lines based on Fleming's left hand rule. It vibrates according to the amplitude, and the vibration of this coil is transmitted to the diaphragm to be taken out as an acoustic signal. In order to vibrate the diaphragm faithfully in response to the signal current, the support structure for supporting the entire vibration system including the drive coil needs to be free in the vibration direction and to exert a restraining force in other directions.

In the present invention, for example, the four corners of the drive coil or the winding frame of the drive coil wound in a rectangular shape are plate springs which are planarly parallel to the plane diaphragm, and the other end is a speaker structure. And supports the entire vibration system. As shown in FIG. 2, the vibration mode of the leaf spring having one end fixed is such that the free end has a degree of freedom in a direction perpendicular to the plane, but has no degree of freedom in a direction parallel to the plane. However, as shown in FIG. 3, when this leaf spring is connected to both ends via the structure of the diaphragm in the middle, there is no flexibility in the vibration direction required of the vibration system.

In order to obtain this degree of freedom, a leaf spring that has been curved in advance is conceivable. In the case of a leaf spring having a curvature, as shown in FIG. It is difficult to fix the position of the vibration system at the zero level of the signal waveform), and the position of the vibration system may be shifted due to a change in the degree of curvature with time.

Therefore, in the present invention, as shown in FIG.
The vibration system is supported by a flat plate spring having a plurality of slits that are not connected to each other. This leaf spring does not have a degree of freedom in the plane direction of the leaf spring at the vibration origin, but has a degree of freedom only in the vibration direction. Moreover, once the vibration system deviates from the vibration origin, the fixed end of the leaf spring is
It expands and contracts according to the amplitude value in the direction connecting the vibration system support ends, and provides sufficient freedom to vibrate in the vibration direction of the vibration system. That is, even if the flat plate spring shown in FIG. 5 is connected at two or more places through the diaphragm structure, the degree of freedom in the required vibration direction of the diaphragm is maintained. Can support the diaphragm structure

Next, a method of shutting off the reproduced sound generated from the front and back of the diaphragm will be described. In general, in the two-way or three-way loudspeaker system described above, the loudspeaker sharing the low frequency band has a sufficiently large diaphragm and a sufficient distance from the driving point of the diaphragm, so that the end of the diaphragm is handled. No special structure is required.For example, a material integrated with the diaphragm is made flexible at the end of the diaphragm, and then fixed to the frame of the speaker body structure by a method of fixing it to the front and back of the diaphragm. Cut off the playback sound.

The flat speaker according to the present invention has a structure which ensures a sufficient degree of freedom of vibration even at the end of the diaphragm and can adapt to vibration of a large amplitude. The sound between the front and back of the diaphragm is blocked by covering the gap between them. A sound-absorbing and flexible film is attached to the entire periphery of the end of the diaphragm so as to cover all or a part of the gap size between the speaker body structure frame and a plane parallel to the diaphragm.

On the other hand, a sound-absorbing and flexible film is attached also to the entire inner periphery of the frame of the speaker body structure, in a plane covering the whole or a part of the gap size, in a plane parallel to the diaphragm, The structure is to overlap with the film attached to the diaphragm. At this time, the film affixed to the diaphragm and the film affixed to the frame are only abutted or overlapped, and only contact each other in a flexible manner. By doing so, the vibration of the diaphragm is not restricted even at the time of a large amplitude, the air flow path is narrowed, and the air vibration is absorbed by the sound absorbing flexible film. Therefore, the sound reproduced from the front and back of the diaphragm is effectively cut off.

The present invention will be described with respect to a case where the winding shape of the driving coil is rectangular. FIG. 6 is an overall view of the embodiment.
However, in order to clarify the gist of the present invention, the magnetic circuit and the structure for supporting the magnetic circuit are omitted, and FIG. 7 shows the relationship between the structure of the magnetic circuit and the driving coil.

In FIGS. 6 and 7, reference numeral 1 denotes a drive coil, which is wound around a rectangular bobbin 2 which is a part of a crossbar 3 mounted in a grid for reinforcing the diaphragm 6. The magnetic circuit is mounted so that most of the drive coil in the longitudinal direction is located at a position intermediate the magnetic gap shown in FIG. In FIG. 7, reference numeral 4 denotes a magnet, the polarity (N, S) of which is shown in FIG.
When the position is as shown in FIG. 7 with respect to the longitudinal portion 1 ′ of the drive coil 1, the longitudinal portion 1 ″ of the drive coil 1
, So that the polarity is opposite to the position shown in FIG.
Two magnetic circuits are mounted. Numeral 5 in FIG. 7 is a yoke for forming a magnetic gap.

In FIG. 6, reference numeral 6 denotes a plane diaphragm to which the winding frame 2 of the driving coil is fixed, and which vibrates the driving coil 1 when an electric signal is inputted to the driving coil 1 from its ends 1a and 1b. Is transmitted to the plane diaphragm 6. A vibration system including the drive coil 1, the winding frame 2 and the plane diaphragm 6 has one end of four flat plate springs 7 fixed to four corners of the winding frame 2 in parallel with the diaphragm 6 in plane. The ends are fixed to the speaker body structure frame 8 and are supported radially from all sides.

FIG. 5 shows the shape of the flat plate spring 7 as an embodiment. Three cuts (slits) of a U-shape, an L-shape, and an inverted L-shape are arranged with the center line in the length direction of the short resin plate having a plate thickness of 0.5 mm as a symmetric axis. The side fixed to the bobbin 2 has a right-angled tip along the corner of the crosspiece 3 of the girder.

Next, the film 9 that covers the gap between the diaphragm 6 and the speaker body structure frame 8 will be described. In FIG. 8 showing a cross section of FIG. 6, a sound-absorbing flexible film 9a is attached to the entire periphery of the end portion of the planar diaphragm 6 so as to cover the gap in a plane parallel to the diaphragm 6. A sound-absorbing flexible film 9b is attached all around the inside of the speaker body structure frame 8 so as to cover the gap in a plane parallel to the diaphragm 6 and overlap the film 9a. It should be noted that in FIG. 8, the membranes 9 a and 9 b are illustrated with a gap to show that they are merely overlapped due to their flexibility and are not integrated. In the case of a material having a high sound absorbing property, it is only necessary to butt without overlapping. FIG. 8 also shows the positional relationship of the drive coil 1, the winding frame 2, the leaf spring 7, and the vibration plate 6 in the vibration direction. However, the positional relationship between the films 9a and 9b may be upside down as shown.

The diaphragm 6 in the embodiment of the present invention
Is made of lightweight balsa wood with a thickness of 1.5 mm.
mm × 148 mm rectangular plate, and the flat plate spring 7
A 0.5 mm thick, 12 mm × 39 mm polycarbonate resin plate with a notch shown in FIG. 5 is used to support the vibration system, and as flexible films 9 a and 9 b, a tanned leather is used. About 9 between the diaphragm and the speaker body structural frame
mm gap.

[0023]

As described above, the flat plate spring having a plurality of slits which are not connected to each other and which are not connected to each other as shown in FIG. By providing a structure in which the gap between the entire circumference of the diaphragm and the frame of the speaker body structure is covered with a sound-absorbing flexible film, the degree of freedom in the vibration direction of the vibration system can be sufficiently ensured. A single loudspeaker with a small diaphragm makes it possible to faithfully reproduce the entire audio frequency range with a large dynamic range.

[Brief description of the drawings]

FIG. 1 illustrates Fleming's left hand rule, which is the principle of operation of a speaker.

FIG. 2 illustrates a mode of vibration of a leaf spring.

FIG. 3 shows a state in which the vibration structure is supported at both ends by a flat plate spring.

FIG. 4 shows a state in which a vibrating structure is supported at both ends thereof by a curved leaf spring.

FIG. 5 illustrates a shape of an embodiment of a flat plate spring which is an element of the present invention.

FIG. 6 is a perspective view showing an entire embodiment of the present invention.

FIG. 7 is a diagram showing a part of a magnetic circuit and showing a relative position between the magnetic circuit and a drive coil.

FIG. 8 is a sectional view of FIG. 6;

[Description of Signs] 1 Drive coil 2 Winding frame 6 Planar diaphragm 7 Flat plate spring 8 Speaker body structural frame 9 Sound absorbing flexible film

Claims (1)

(57) [Claims] 1. A flat plate spring having a plurality of notches (slits) that are not connected to each other at four corners of a rectangular drive coil or a winding frame of a drive coil mounted on a plane diaphragm, The plane diaphragm, the drive coil, and the drive coil are arranged so that the plane leaf spring can expand and contract in the radial direction according to the amplitude of the plane diaphragm. Ri Na and supports the vibration system consisting of the bobbin, etc., and the flat diaphragm to the entire circumference of the diaphragm
The sound-absorbing flexible film attached parallel to the surface is
A flat speaker that is abutting or overlapping.