JPH0690495

Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH0690495
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electrodynamic speaker for use in sound reproduction equipment and the like.
[0002]
2. Description of the Related Art A typical prior art will be described with reference to FIG. FIG. 4
(a) is a half sectional view of a conventional electrodynamic speaker, in which a ring-shaped main
magnet 14 magnetized in the thickness direction is attached in the vicinity of the outer periphery
of the upper surface of the disk-like bottom plate 15. A ring-shaped top plate 13 is attached to
the top, and a ring-shaped sub magnet 16 magnetized in the direction opposite to the magnet is
attached near the outer periphery of the bottom surface of the bottom plate 15. Further, a frame
17 is attached to the upper surface of the top plate 13, and a suspension 19 whose outer
periphery is fixed to the frame 17 is provided in a magnetic gap portion formed by the pole
portion at the top center of the top plate 13 and the bottom plate 15. There is a voice coil 18
supported, and the outer periphery is fixed to the frame 17 at its upper part, the inner periphery
is fixed to the voice coil 18, and a diaphragm 20 with an edge 21 having a dust cap 22 at its
center is attached The structure was FIG. 4B is a front view of the diaphragm, but as shown in
this drawing, the physical property values (Young's modulus, density) of the diaphragm are
substantially uniform over the entire surface.
[0003]
11-05-2019
1
However, in the above-described conventional structure, the inherent high-frequency resonance
occurs depending on the material and shape of the diaphragm, resulting in a very unpleasant
sound. In order to clarify this cause, we simulated a typical speaker with an aperture of 18 cm.
The frequency characteristics are shown in FIG. Thus, it can be confirmed that the secondary
resonance exists at 6.4 kHz. The vibration mode of this secondary resonance is shown in FIG. The
prototype model is shown in FIG. 7 for reference. From this result, it can be confirmed that
uniform deformation in the circumferential direction is concentrated on an arbitrary
circumference in the middle part of the diaphragm. In addition, it was confirmed that higher
order resonances increase the number of deformation points. This is because the bonding portion
between the diaphragm and the voice coil is a fixed end and the edge is a free end, causing the
diaphragm to undergo axial symmetry deformation, and as a result, the position of the antinode
of the second resonance or higher is inside the diaphragm. It is because it becomes from the
abdomen to the outer periphery, and the position of this belly becomes the maximum point of
amplitude. Moreover, it is because the number of this belly increases as it becomes high-order.
Therefore, in order to prevent the generation of the second resonance or the third resonance or
more, it is necessary to reduce the deformation of the middle portion of the diaphragm or not to
concentrate on an arbitrary circumference. Therefore, as a conventional solution to this problem,
a damping material having a large internal loss has been attached to the diaphragm middle
portion or the outer peripheral portion and braking is performed. However, the workability is
poor, and the attachment position, Since it is difficult to keep the damping material shape
uniform, problems such as variations in frequency characteristics have occurred.
[0004]
The present invention solves such conventional problems and makes it possible to provide stable
frequency characteristics while hardly generating high-frequency resonance (more than
secondary resonance).
[0005]
[Means for Solving the Problems] In order to solve the above problems, the speaker of the
present invention is different in either density or Young's modulus, and the ratio of its
constituting area in the same circumferential portion of the diaphragm is vibration. A papermade diaphragm is used in which different shape parts are dispersed in the diaphragm middle
part or at least one place in the outer peripheral part in the part near the plate center and the
part near the outer periphery.
[0006]
11-05-2019
2
[Operation] With this configuration, the portion where the antinodes of the amplitude occur is
not uniform on the same circumference, and the diaphragm mid-abdominal portion or the outer
peripheral portion that caused the occurrence of high-frequency resonance (secondary resonance
or more) The phenomenon of uniform deformation concentration in the circumferential direction
at an arbitrary diameter of the above becomes less likely to occur.
[0007]
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 (a) is a half sectional view of the 18 cm diameter electrodynamic speaker of the present
invention, which is magnetized in the thickness direction in the vicinity of the outer peripheral
edge of the upper surface of a disk-shaped bottom plate 3 having an outer diameter φ80
thickness t = 6 mm. Ring-shaped main magnet 2 of diameter φ90 inner diameter φ50 thickness
t = 15 mm is attached, and further, ring-shaped top plate 1 of outer diameter φ85 inner
diameter φ40.8 thickness t = 6 mm is attached thereon, and bottom plate 3 A ring-shaped sub
magnet 4 with an outer diameter of φ80, an inner diameter of φ40, and a thickness of t = 15
mm, which is magnetized in the direction opposite to the magnet, is attached in the vicinity of the
outer peripheral edge of the lower surface.
In addition, a frame 5 with a diameter of 18 cm is attached to the upper surface of the top plate
1, and the outer periphery is fixed to the frame 5 in the magnetic gap portion constituted by the
pole portion at the upper center of the top plate 1 and the bottom plate 3. There is a voice coil 6
supported by a suspension 7. Further, an outer periphery is fixed to the frame 5 at an upper
portion thereof, an inner periphery is fixed to the voice coil 6, and an edge having a dust cap 10
with an outer diameter φ 58 at its central portion 9 attached diaphragm 8 was attached.
[0008]
Moreover, the front view of only the speaker diaphragm by this invention is shown in FIG.1 (b).
As shown in the figure, the present diaphragm is a diaphragm made of paper making, and the
high density part 11 (density: 680 kg / m 3, Young's modulus: 1.09 × 10 10 N / m 2) and the
low density part 12 (density: 480 kg / m 3, Young There are four low density parts at the
11-05-2019
3
axisymmetric position, and the area from φ54 to φ80 has an area ratio of 1⁄5 of the entire
circumference, and from φ80 to The area up to φ114 has an area ratio of 2/5. The thickness of
the material is different, and the high density part is t = 0.4 mm, and the low density part is t =
0.6 mm. It is needless to say that the low density portion shape is not necessarily the above
shape, and may not be axially symmetrical.
[0009]
FIG. 2 shows simulation results of frequency characteristics when the diaphragm according to
the present invention is used, and FIG. 3 shows vibration modes at 6.4 kHz. Thus, it can be
confirmed by comparison of FIG. 2 and FIG. 5 that the sound pressure at the resonance of 6.4
kHz is reduced by about 5 dB. Further, comparison of FIG. 3 and FIG. 6 reveals that uniform
concentration of deformation is eliminated in the circumferential direction of the diaphragm
middle portion, which is the cause of resonance at 6.4 kHz, and that the deformation is dispersed.
[0010]
As described above, in the electrodynamic speaker using the diaphragm according to the present
invention, the level of high frequency resonance (secondary resonance or more) is lowered, and
unpleasant sounds are less likely to be heard, and smooth reproduction is possible. It becomes.
11-05-2019
4