JPS625560B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a speaker, and particularly to its constituent materials. Ideally, a speaker diaphragm should make a complete piston movement in the frequency band in which it is used, but if the diaphragm deforms during vibration or split vibration occurs, the sound pressure frequency characteristics, distortion rate, phase characteristics, etc. will deteriorate, resulting in high Fidelity playback cannot be expected. In order to solve these problems, in recent years, planar diaphragms using a honeycomb sandwich structure or the like have been used. If a method is used in which a voice coil is bonded to the nodal part of the plane diaphragm at the primary resonance frequency and driven, the primary resonance is canceled out, so that _h (high frequency limit frequency) can be increased significantly. However, normally the diameter of the nodal circle is approximately 65 mm of the outer diameter of the diaphragm.
%, the voice coil has a larger diameter compared to conventional ones. Therefore, the weight of the voice coil increases, which reduces the efficiency of the speaker. Furthermore, the magnetic circuit that drives the large-diameter voice coil is also large and special, resulting in high costs. In order to solve these problems, a method has been proposed in which the conventional-sized voice coil and the nodal part of the plane diaphragm are connected using a cone-shaped coupling material (referred to as a coupling cone), and this method has been adopted in some cases. . However, in the above method, unless a material that is sufficiently lightweight and has high bending rigidity is used for the coupling cone, not only will the efficiency decrease, but also peaks may occur in the sound pressure frequency characteristics due to resonance of the coupling cone. Problems such as increased distortion arise. In addition, in a speaker using a highly rigid plane diaphragm as mentioned above, the internal loss of the diaphragm is small, so the amplitude at the resonant frequency is large, so the resonance peak at _h is lower than that of a speaker using a conventional paper cone diaphragm. There is a phenomenon where the value becomes extremely high. This peak makes speaker system design difficult; even if a planar speaker with a high _h has a high peak level, the level must be lowered from a considerably low frequency in order to attenuate it, which limits the usable frequency band. That will happen. In order to reduce this resonance peak, it is known that an effect can be obtained by providing a damping layer with a large internal loss between the diaphragm and the voice coil to provide the vibration system with internal loss.
_h also decreased, making it impractical. For these reasons, aluminum alloy sheets, paper, etc. are actually used as materials for the coupling cone, but the former has a small decrease in _h , but the internal loss is small, so the resonance peak becomes large, and the latter has _a large resonance peak. However, because the internal loss is large, the resonance peak becomes small. Each has its advantages and disadvantages. In order to solve these problems, the present invention attempts to obtain a planar speaker with a small resonance peak without reducing _h by using a material with high rigidity and large internal loss for the coupling cone. An embodiment of the present invention will be shown and explained below. FIG. 1 shows the appearance of a flat diaphragm used in the speaker of the present invention and the shape of the core material with a portion of the surface material cut away. Figure 1 shows a flat bass diaphragm with a diameter of 19.1 cm and a height of 6 mm, which has a structure in which 40 μm thick aluminum foil 2 is laminated on both sides of an axially symmetrical honeycomb core core 1 made of 20 μm thick aluminum foil. It is. FIG. 2 is a sectional view showing the structure of the speaker of this embodiment. In FIG. 2, numeral 3 denotes the plane diaphragm shown in FIG. 1, which is adhesively held on the frame 5 via edges 4. Reference numeral 6 denotes a coupling cone made of a material to be described later, the upper end of which is connected to the nodal part of the flat diaphragm 3, and the lower end connected to the voice coil bobbin 8 in the magnetic circuit 7.
is glued to the top edge of the In addition, there is a coupling cone 6 inside the circle formed by the leader line.
9 shows the cross-sectional structure of polyethylene foam, 1
0 is a high-density polyethylene sheet reinforced with carbon fibers, and has a sandwich structure in which foamed polyethylene 9 is sandwiched between sheets 10. Next, a method for manufacturing a coupling cone will be explained with reference to FIG. In Figure 2, the fiber length of the high-density polyethylene fiber is 6 mm, and the carbon fiber with a fiber diameter of 10 μm is
Add 15wt% and make paper with a weight of 90g/ ^m2 . This paper sheet was placed on both sides of a polyethylene sheet with a surface density of 80 g/m ² (expansion ratio approximately 5 times) made by adding a foaming agent, and after thermal lamination, the laminated sheet was heated at 200°C for several seconds. Immediately after heating, press molding is performed to obtain the coupling cone used in this example. In the heating process, the high-density polyethylene of the paper sheet melts and covers the surface of the carbon fibers, forming a composite polyethylene sheet with a high elastic modulus. On the other hand, the foamed polyethylene sheet is also foamed at the same time. Then, both polyethylenes are fused and bonded to form a sandwich structure having foamed polyethylene as the core material. Since this sheet is a structural body, it has high bending rigidity, is lightweight, and is an ideal coupling cone material with large internal loss. The physical properties of this sheet are shown in the table below. For comparison, the physical properties of conventionally used aluminum and paper and the physical properties of the carbon fiber reinforced polyethylene sheet alone are also listed.

[Table] According to this example, an ideal coupling cone with overwhelmingly greater bending rigidity and internal loss than those using other materials can be obtained. Next, a speaker was made using the above coupling cone as shown in Figure 2, and a sound pressure frequency characteristic of 1W/1m was measured using a JIS standard box. The results are shown in FIG. 4a (dotted chain line). Further, the characteristics when a speaker is similarly made using an aluminum coupling cone are shown in FIG. 4c (solid line), and the characteristics when a carbon fiber-reinforced polyethylene sheet is used are shown in FIG. 4b (dashed line). As is clear from the results shown in Figure 4, by using the coupling cone of this example, a speaker with excellent characteristics can be obtained, with a much smaller resonance peak and almost no decrease in _h than when aluminum is used. It is something that can be done. Furthermore, it can be seen that the speaker using the carbon fiber reinforced polyethylene sheet is able to reduce the resonance peak, although _h is slightly lowered, and has quite good characteristics. As is clear from the above embodiments, according to the present invention, the high-frequency resonance peak can be significantly reduced in a nodal circle drive type planar speaker using a coupling cone, and the drop in _h is also small, making it extremely excellent. This makes it possible to provide speakers with improved characteristics.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway top view of a flat diaphragm used in the present invention, FIG. 2 is a sectional view showing an embodiment of the speaker of the present invention, FIG. 3 is a manufacturing process diagram of a coupling cone, and FIG. The figure is a sound pressure frequency characteristic diagram of the present embodiment and a conventional speaker. 3...Plane diaphragm, 6...Coupling cone, 7
...magnetic circuit, 8...voice coil, 9...foamed polyethylene, 10...high density polyethylene sheet.

Claims (1)

[Scope of Claims] 1. A planar diaphragm, a voice coil located in a magnetic circuit, and a large diameter opening bonded to the nodal position of the primary resonance of the planar diaphragm to connect the voice coil to a small diameter opening. a cone-shaped connecting member disposed in the opening, and the connecting member is a reinforced sheet made of high-density polyethylene as a base material and mixed with one or more fiber materials such as carbon fiber, aramid fiber, and glass fiber as a reinforcing material. A speaker characterized by comprising a structure using a reinforced sheet material or a reinforced sheet material. 2. Claim 1, characterized in that the structure using the reinforced sheet material is a sandwich structure in which the core material is foamed polyethylene, the surface material is the reinforced sheet material, and the core material is sandwiched between the surface materials. Speakers listed.