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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
multi-function sounding body capable of generating an output of acoustic frequency and a low
frequency vibration output with a single device.
2. Description of the Related Art For example, in a mobile phone, two types of electro-mechanical
transducers are needed: a speaker for voice and a generator of low-frequency vibration that can
sense an incoming call silently. Therefore, a proposal has been made to put together these two
types of converters and attempt to reduce the size, weight and cost of devices such as mobile
phones. The structure of a conventional example in the multi-function sounding body (referred to
as such since signals of a plurality of types of frequencies including audio signals can be output
by one device) will be described below. This is described, for example, in JP-A-5-85192.
In this prior art example, the electromechanical transducer for voice generally follows the
structure of a conventional dynamic speaker. That is, a thin cylindrical voice coil fixed to the
voice diaphragm is inserted in the cylindrical air gap of the magnetic circuit, and when the voice
current flows through the voice coil, the diaphragm vibrates in the axial direction at voice
frequency. Sound is generated. On the other hand, a magnetic circuit having a considerable mass
is suspended on a frame by a plate spring or the like so as to be axially displaceable, and is given
a low frequency natural frequency of about 100 to 300 Hz. Therefore, when a low frequency
drive current approximate to the natural frequency is supplied to the voice coil, the voice
diaphragm does not vibrate so much because the natural frequency is far apart, and the magnetic
circuit resonates and vibrates with a large amplitude. Do. The reaction reaction of the vibration of
the large mass magnetic circuit gives a sensational vibration to a portable telephone or the like.
However, in the prior art, since the magnetic circuit is spring-suspended and is displaceable in
the same vibration direction (axial direction of the voice coil) as the voice coil, the influence of
the vibration characteristic of the magnetic circuit As a result, the audio diaphragm does not
vibrate faithfully following the audio signal. That is, it is inevitable that the reproduction quality
of the sound is somewhat degraded. In particular, when an acoustic signal and a low frequency
signal are superimposed and input to the voice coil, the magnetic circuit drives the voice coil
while being displaced at a low frequency and the acoustic output is further disturbed, and the
reproduction of the sound becomes practically impossible. Another problem with the
conventional example is that the thickness of the transducer tends to be large because two types
of vibration mechanisms in the same direction are overlapped.
Therefore, in order to solve these problems, the present applicant has already proposed, in
Japanese Patent Application No. 2000-286414, a configuration of a novel multifunctional
sounding body which is believed not to be known yet. The magnetic circuit can not move in the
axial direction, but it can rotate around the central axis of the sound generator (the central axis of
the voice coil), and the eccentric weight is mounted as a rotor and fixed outside The rotor is
driven to rotate similarly to the motor, and an oscillating force which is a low frequency output
that can be sensed by a centrifugal force that changes direction due to the rotation of the
eccentric weight is obtained. FIG. 2 shows a cross-sectional view of the structure.
The main parts of the sound generator of FIG. 2 are rotationally symmetrical with respect to the
central axis included in the cross section. In FIG. 2, the frame 1 is made of a synthetic resin or
metal and has a shallow cylindrical shape with a bottom, and a sound output cover 2 having a
large number of sound output holes fixed to the upper end surface of the surrounding cylindrical
portion 1a The peripheral edge portion of the thin, disk-like sound diaphragm 4 for sound with
the cylindrical voice coil 3 fixed to the lower surface is adhered and held to the step 1b which
goes around the upper end. (These bonding is done at the final stage of assembly. The structure
and operation of this sounding body (multifunctional acoustic device) are described in detail in
the above-mentioned Japanese Patent Application No. 2000-286414.
A rotor shaft 5 is implanted at the center of the bottom plate 1 c of the frame 1. A rotor 6
includes a cup-shaped yoke 7 made of soft magnetic material, a ring-shaped permanent magnet 8
magnetized in the axial direction, and a top yoke 9 made of soft magnetic material, which are
press-fitted to the sleeve 10. The motor permanent magnet 11 (one or more N and S poles are
alternately magnetized so as to appear alternately at equal intervals on the outer cylindrical
surface) is fitted and fixed to the outer peripheral portion of the cup-shaped yoke 7 Also, an
eccentric weight 12 (having a semicircular annular shape) is fixed which produces a centrifugal
force which becomes an excitation force by the rotation of the rotor 6.
The sleeve 10 is rotatably mounted on the rotor shaft 5 with the washer 13 as a spacer, and is
stopped by the stop ring 14. Since the voice coil 3 is concentrically inserted in the magnetic field
of the cylindrical voice gap formed by the upper end of the inner periphery of the cup-shaped
yoke 7 and the outer peripheral side of the top yoke 9, voice current is supplied to the voice coil
3. The voice diaphragm 4 vibrates in the axial direction of the sounding body regardless of the
rotation of the rotor 6 and emits a voice output, as in a normal speaker.
A stator 15 is disposed to surround the outer periphery of the rotor 6. In order to form a
magnetic circuit so as to surround the cross section of the stator coil 16 cylindrically wound, the
stator upper yoke 17 and the stator lower yoke 18 arranged on the upper and lower surfaces
thereof, and the stator coil 16, they are used as outer peripheries. It consists of a ring-shaped
yoke 19 connected by a part. The upper stator yoke 17 and the lower stator yoke 18 have the
same number of toothed magnetic pole pieces 17a and 18a (the illustration of the shape
developed in the plane is omitted) on the inner circumference, and they are bent to form a stator
coil They are alternately arranged in contact with the inner cylindrical surface 16 and are
opposed to the outer peripheral surface of the motor permanent magnet 11 across the motor gap
20. When a low frequency oscillating current is applied to the stator coil 16, the magnetic poles
appear to be rotationally moved on the respective pole pieces 17a, 18a, and these magnetic poles
and N, S appearing on the outer cylindrical surface of the motor permanent magnet 11 Rotation
is given to the rotor 6 by attraction and repulsion with the poles.
In this structure, the stator 15 is positioned by inserting the stator 15 assembled in advance into
the inside of the cylindrical portion of the frame 1 from above. In this configuration, the intended
purpose of obtaining an excitation force that does not affect voice output is sufficiently achieved,
but there are some problems as follows. (1) The magnetic circuit of the stator can not be
miniaturized further. Alternatively, the freedom of design is limited, and there is no space for
adding additional functions. (2) It is difficult to obtain sufficiently high accuracy in positioning of
the stator. (3) Since the magnetic circuit of the stator is formed by combining the ring-shaped
yoke, the upper stator yoke, and the lower yoke stator, the magnetic resistance at the joint is
large and the magnetic flux leakage occurs. The efficiency as a motor is likely to deteriorate.
The object of the present invention is to further improve the basic structure of the rotary type
multifunctional sounding body already proposed, and it is possible to configure the sound
reproduction quality to be excellent and thin regardless of the driving conditions. In addition to
the features of a certain basic structure, it is possible to make the structure smaller or to allow
extra space, to easily improve the assembly accuracy, and to provide a multi-function sounding
body with excellent magnetic characteristics. It is to be.
In order to achieve the above object, the multifunctional sounding body of the present invention
has the following features.
(1) A rotor is provided with a cylindrical voice coil fixed to a voice diaphragm and a magnetic
circuit provided with a cylindrical air gap into which the voice coil is inserted as a rotor, the rotor
further comprising an eccentric weight member and an outer peripheral portion. It has a
magnetic pole for driving a rotor, and a stator is disposed on the outside of the rotor, and the
stator and a part of the frame holding the rotation axis of the rotor are the magnets of the stator.
It also serves as part of the magnetic members that make up the circuit.
The multifunctional sounding body of the present invention may further have the following
features. (2) The shape of the frame is composed of a substantially flat portion and a cylindrical
portion rising from the peripheral portion, and the cylindrical portion is a main magnetic
member constituting the magnetic circuit of the stator. Double as part of
showing the structure of an improved multifunctional speaker which is an example of the
embodiment of the present invention. The configuration of this example is basically the same as
the configuration before the improvement shown in FIG. 2 except that the parts related to the
frame and the stator are different. Therefore, the reference numerals in FIG. 1 are the same as
those in FIG. 2 and only the essential differences will be described below without adding
repetitive explanations for parts having substantially the same configuration.
In FIG. 1, a soft magnetic material is used as the material of the frame 1. That is, a resin material
mixed with soft magnetic metal powder is insert-molded injection-molded. Alternatively, a metal
material such as permalloy or pure iron is formed into a cup shape by plastic working, and this
molded product is insert-molded injection-molded from a resin material. Also, the ring-shaped
yoke 19 is not used, and instead, a part of the cylindrical portion 1b of the frame 1 can function
as a part of the magnetic circuit of the stator 15 instead of the ring-shaped yoke. The stator
upper yoke 17 has its outer side surface in contact with the inner side surface of the frame
cylindrical portion 1a as shown in the same manner as for the ring shaped yoke in the old
Since the lower surface of the stator lower yoke 18 contacts the upper surface of the bottom
plate 1c of the frame 1 which is also a magnetic material in a large area, the magnetic resistance
of the magnetic flux flowing from the stator lower yoke 18 to the bottom plate 1c is small.
Further, since the bottom plate 1c and the cylindrical portion 1b are integrated, there is almost
no magnetic resistance between them. Therefore, as compared with the old structure having
many end face connection portions of the plate members of the upper stator yoke 17, the lower
stator yoke 18 and the ring yoke 19, the magnetic circuit surrounding the cross section of the
stator coil 16 in the structure of this example There is an advantage that the resistance can be
reduced significantly.
Further, the upper stator yoke 17 and the lower stator yoke 18 having the pole pieces 17a and
18a opposed to the rotor 6 are directly positioned by the inner wall of the cylindrical portion 1a
of the frame 1 directly. Therefore, the positional relationship with the rotor shaft 5 implanted in
the bottom plate 1c is the position accuracy of the pole pieces 17a, 18a with respect to the outer
surface of the motor permanent magnet 11, that is, the motor gap, as compared with the old
structure which is the indirect positioning. It becomes easy to improve the accuracy of 20.
Further, in the present embodiment, since the ring-shaped yoke 19 is not required, it is not a
theory that the diameter of the sound-producing body can be reduced by approximately twice the
thickness. This makes it possible to miniaturize the sounding body, or the spare space obtained
by the reduction can be diverted to other purposes. Although not shown, for example, the frame
1 may be provided with a peripheral portion to provide a margin in the arrangement of the
terminals for the voice coil 5 and the stator coil 16.
Although one example of the embodiment of the present invention has been described above, the
present invention can be implemented in other forms. In particular, various changes can be made
to the detailed structure. For example, the shape of the contact portion between the stator upper
yoke 17 and the cylindrical portion 1a may be modified to make surface contact, thereby further
reducing the magnetic resistance of the stator magnetic circuit. The bottom plate 1c may also be
used in various ways. There is also room for other changes.
According to the present invention, since a part of the frame of the multi-functional sound
generator is shared with the stator magnetic circuit, the sound generator can be miniaturized and
the surplus space can be utilized. At that time, the magnetic characteristics of the stator magnetic
circuit and the positioning accuracy of the main parts such as the pole pieces of the stator can be
easily improved. In particular, when the cylindrical portion of the frame is used as a stator
magnetic circuit, a remarkable effect is obtained.
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