JPS6336795Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an improvement in a planar speaker using a disk diaphragm having a Sanderch structure, and particularly to a means for coupling the diaphragm to a voice coil bobbin or a drive cone. One of the characteristics of a flat speaker using a disk diaphragm is that it expands the reproduction band to high-order resonance by driving the nodal circle of the resonance mode of the disk diaphragm (called mode drive or node drive). It is possible. FIGS. 1 and 2 are cross-sectional views showing an example of a planar speaker using a conventional disk diaphragm. In each figure, 1 is a disk diaphragm, 2 is a voice coil, 2' is a voice coil bobbin, 3 is an edge, 4 is a centering spider, 5 is a drive cone, 6 is a magnetic circuit, and 7 is a frame that supports these. In Figure 1, the voice coil 2 is directly connected to the nodal circle (node) of the first resonance mode of the disk diaphragm 1.
FIG. 2 shows a method of driving via a drive cone 5 between the disk diaphragm 1 and the voice coil 2 (drive cone method). Generally, the resonant frequency of a disk diaphragm driven by a nodal circle is

It is represented by [Formula]. However, K: Constant α: Radius of the diaphragm D: Bending rigidity σ: Areal density The disk diaphragm 1 generally has a sandwich structure as shown in Fig. 3 in order to increase the bending rigidity D and decrease the areal density σ. is used. here,
8 and 8' are surface materials (skin or face), 9
is a core material, and 10 and 10' are adhesives. The surface materials 8 and 8' are generally foils or thin plates made of aluminum, plastic, fiber-reinforced plastic (FRP), etc., and the core material 9 is aluminum, plastic, paper, etc. formed into a honeycomb shape, or foamed material. Plastics, light alloys, etc. are used. It is well known that the surface materials 8, 8' and the core material 9 are generally bonded together with adhesives 10, 10' to form a panel. In both the systems shown in FIGS. 1 and 2, the disk diaphragm 1 of the Sanderch structure is connected to the voice coil bobbin 2' or the drive cone 5 at the surface material 8' on one side. Here, the driving force F generated by the signal current applied to the voice coil 2 is transmitted to the disk diaphragm 1 via the voice coil bobbin 2' or the voice coil bobbin 2' and the drive cone 5. However, since this disc diaphragm 1 has the Sanderch structure described above, the driving force F is transmitted to the surface material 8' of the disc diaphragm 1, and the driving force F is transmitted to the surface material 8' of the disc diaphragm 1, and the adhesive 10', the core material 9, and the adhesive 10.
is transmitted to the surface material 8 via. For this reason, adhesive 1
0, 10', a loss occurs in the driving force F in the core material 9. In the Sanderch structure, the surface materials 8, 8' and the core material 9 are often made of different materials. Therefore, the propagation velocity (sound velocity) of longitudinal waves (sound waves) between the surface material and the core material
There is a difference. In general, the core material has a lower sound velocity and a larger internal loss. Furthermore, in order to increase the bending rigidity D, the core material 9
Since the thickness of the surface material 8' is often increased,
and the surface material 8 are out of phase and a difference in amplitude occurs.
Therefore, the disk diaphragm 1 no longer vibrates uniformly. The connection between the disk diaphragm 1 and the voice coil bobbin 2' or the drive cone 5 is, from a local point of view, a strong connection between the surface material 8' and the voice coil bobbin 2' or the drive cone 5. If you look at it as a whole, it's nothing but a soft body connection with losses. Therefore, the bending rigidity D of the diaphragm
can only take a small value, and the resonant frequency also becomes low. The same applies to sander beach structures such as foams having a skin layer formed on the surface. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, increase the resonant frequency, and provide a speaker with a wide band and good flatness. In order to achieve the above object, the speaker of the present invention has a structure in which the driving force F is uniformly and simultaneously propagated to the entire area corresponding to the nodal circle of the diaphragm (surface materials 8, 8' and core material 9). . As one idea, we considered the structure shown in Figure 4. This disc diaphragm is made by cutting a disc diaphragm at a nodal point, dividing it into a ring-shaped diaphragm 1a and a disc diaphragm 1b, and joining them to the outside and inside of a voice coil bobbin 2', respectively. In this method, the surface material and core material of the disk diaphragm were cut, and the bending rigidity D was significantly reduced, making it impossible to put it to practical use. The present invention is a further improvement of the above structure. That is, a plurality of discontinuous slits are provided in the part corresponding to the nodal circle of the resonance mode of the disk diaphragm with the Sanderch structure, and the driving force F is applied to this part.
A plurality of tongues provided on the top of the voice coil bobbin or the top of the drive cone that transmit the information are inserted and fixed. By doing this, the driving force F can be uniformly transmitted to the entire diaphragm, and since both the surface material and the core material are suppressed, the bending rigidity D also takes a large value, and resonance The frequency also becomes higher. Hereinafter, the present invention will be explained in detail with reference to Examples. FIG. 5 is a sectional view showing an embodiment of the present invention, and is an example in which the present invention is applied to the direct drive system of FIG. 1. In the figures, the same reference numerals as those mentioned above indicate the same or equivalent parts. 11
are a plurality of tongues provided on the voice coil bobbin 2'. FIGS. 6 and 7 are perspective views showing the structures of the voice coil bobbin and disk diaphragm used in the speaker of the present invention (FIG. 5), respectively. Reference numeral 12 designates a plurality of arcuate or straight thin slits provided in the nodal portion of the disk diaphragm 1, and the tongue portion 11 is passed through the slits 12 to join the entire disk diaphragm 1 and the voice coil bobbin 2'. It's becoming like that. For this joining, epoxy,
A hard adhesive such as acrylic adhesive may be used.
Furthermore, if it is desired to reduce the resonance sharpness at the resonance frequency, a rubber-based adhesive with high loss may be used. Figure 8 shows the drive cone method (second
FIG. A plurality of tongues 11 are provided similar to those shown in FIG. It goes without saying that the tongue portion 11 may be constructed as a separate component without being provided integrally with the voice coil bobbin 2' or the drive cone 5. According to the present invention described above, the driving force F generated by the voice coil 2 is transmitted to the nodal portion of the disk diaphragm 1, and uniformly and simultaneously to the surface material 8', the core material 9, and the surface material 8. Since the bending rigidity D also takes a larger value than that of the conventional method, the resonant frequency can be set high. FIG. 9 is a characteristic diagram showing sound pressure frequency characteristics of tweeters using the present invention and a conventional disk diaphragm. 13 (solid line) is the frequency characteristic of a tweeter with a conventional structure (FIG. 1). 14 (dotted line) is the frequency characteristic obtained by the configuration of the present invention, the resonance frequency is increased by about 20% compared to the conventional one, and the effect is remarkable. Furthermore, the configuration of the present invention described above also provides the following effects. That is, in the conventional configuration (Fig. 1), the voice coil bobbin 2' is joined to the part corresponding to the nodal circle of the first resonance mode as a diaphragm with a free periphery, so the schematic diagram is shown in Fig. 10. As shown in , a part of the disc diaphragm is
A new resonance mode occurs when it is supported (or fixed) by the ring 15 (corresponding to the voice coil bobbin 2'). This resonant mode indicated by the dotted line is very similar to the first resonant mode of a peripherally free disk diaphragm. However, this resonance occurs between the first and second resonance frequencies of the peripherally free disk diaphragm, and the 9th
A sharp peak g is generated in the frequency characteristic 13 shown in the figure. When this resonance occurs, the nodal portions of the disk diaphragm perform expansion and contraction movements as indicated by the arrows in FIG. In the configuration of the present invention shown in FIG. 5, a plurality of tongues 11 are passed through and joined to the disc diaphragm 1, so that the top of the fulcrum (support) is reinforced as shown in FIG. The circular part becomes difficult to expand and contract, and resonance is suppressed, resulting in the frequency characteristic 14 shown in Figure 9.
Broadband characteristics with good flatness can be obtained as shown in FIG. These effects are more pronounced when foamed plastic is used for the core material 9 of the disc diaphragm 1.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a speaker using a conventional disk diaphragm, FIG. 3 is a perspective view showing the sanderch structure of the disk diaphragm, and FIG. 4 is a cross-sectional view of the structure before this invention was developed. Fig. 5 is a sectional view of a speaker showing an embodiment of the invention, Fig. 6 is a perspective view showing the structure of the voice coil bobbin used in the speaker of the invention, and Fig. 7 is a disk diaphragm used in the speaker of the invention. Fig. 8 is a perspective view of the drive cone, Fig. 9 is a sound pressure frequency characteristic diagram of the tweeter using the present invention and the conventional disc diaphragm, and Fig. 10 is the new structure of the conventional method. A schematic diagram showing resonance, Figure 11 is the 10th diagram according to the present invention.
It is a schematic diagram which suppresses the resonance of a figure. 1... Disc diaphragm, 2... Voice coil,
2'...Voice coil bobbin, 3...Edge, 4
...Centering spider, 5...Drive cone, 6...Magnetic circuit, 7...Frame, 8,8'
... Surface material, 9 ... Core material, 10, 10' ... Adhesive material, 11 ... Tongue, 12 ... Slit, 13 ...
Conventional frequency characteristics (solid line), 14... Frequency characteristics of the present invention (dotted line).

Claims (1)

[Scope of utility model registration request] In a flat speaker using a disk diaphragm with a Sanderch structure, a plurality of discontinuous slits are provided in the portion of the diaphragm that corresponds to the nodal circle of the resonant mode, and the voice is further fitted with the slits provided in the diaphragm. A plurality of tongues are provided on the top of the coil bobbin or the top of the drive cone, and the tongues are bonded to both the front and back surface materials or the surface material and the core material of the disk diaphragm with a sanderch structure to each other to produce high frequency sound. A speaker characterized by a high resonance frequency.