Vibration speaker

Details Vibration speaker Vibration speaker

2001-06-27

2002-10-15

Tran, Sinh (Department: 2643)

Electrical audio signal processing systems and devices

Electro-acoustic audio transducer

Electromagnetic

C381S396000, C381S412000

Reexamination Certificate

active

06466682

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration speaker used in mobile communication terminals including cellular phones and pagers for simultaneously generating a sound and a vibration, and in particular, to transferring a stable vibratory force to a set including a vibration speaker for eliminating a touch sound of a vibrating mass and generating a minimum vibrating force during vibration by expanding inputted frequency bandwidth.
The general principle of generating vibration in a vibration speaker used for cellular phones, pagers, etc. is to use a resonance frequency of a vibration system inside of the vibration speaker.
In this regard, the vibrating mass inside of the vibration speaker performs a vertical movement, and touching phenomenon occurs when the vibration mass collides with objects in the upward and downward directions in accordance with the intensity or frequency of inputted vibration signals. Therefore, certain limitations need to be laid on intensity and frequency of the inputted vibration signals when using the vibration speaker as a vibration generator so as not to cause the touching phenomenon in the upward and downward directions.
FIG. 1
is a cross-sectional view of a conventional vibration speaker. Referring to
FIG. 1
, the conventional vibration speaker comprises a case
8
having an inner space, a magnet
4
and a voice coil
2
housed in the case
8
, and a vibrating plate
1
for generating a sound.
In the conventional vibration speaker constructed above as shown in
FIG. 2
, electromagnetic force is generated if an alternated current, which is a high frequency, is applied to the voice coil
2
within a magnetic field consisting of an upper plate
3
, the magnet
4
seated in a vertical direction, and a yoke
5
through a lead wire (not shown in
FIG. 2
) from outside. The voice coil
2
performs a vertical movement due to the generated electromagnetic force. At this stage, a sound is generated by a fine vibration of the vibrating plate
1
, to which a tip of the voice coil
2
is attached.
Also, if a low frequency signal (preferably of 100-200 Hz) as shown in the left part of
FIG. 2
is applied to the voice coil
2
, a vibration is generated by triggering a vertical movement of the vibrating mass including the weight
6
and parts constituting the magnetic field suspended on an upper suspension spring
7
and a lower suspension spring
9
.
The amount of movement of the vibrating mass varies according to the intensity and frequency of the inputted low frequency signals for generating a vibration. Here, touching phenomenon occurs such that the vibrating mass collides with the vibrating plate
1
and the voice coil
2
at the upper side and other attachments at the lower side.
To limit the vertical movement of the vibrating mass for protecting the collided objects from the touching phenomenon, a stopper structure
6
a
that can limit the vertical displacement is included in the vibrating mass. Finger stops
8
a
,
9
b
are installed at upper and lower sides of the inner wall surface of the case facing the stopper structure
6
a.
Even if the stopper
6
a
and the finger stops
8
a
,
8
b
may be able to protect major parts, the touching phenomenon per se cannot be prevented due to the stopper
6
a
, and the touching noise is still generated.
Therefore, to prevent the touching phenomenon of the vibrating mass and the noise caused thereby, it is critical to limit the intensity and frequency width of the signals inputted to the voice coil
2
, etc.
In other words, as the intensity and the frequency bandwidth of the input signals for generating a vibration, which affect the amplitude of the vibrating mass, should prevent the touching phenomenon and the accompanying noise while satisfying the minimum function of incoming calls, the intensity and the frequency need to be limited.
This means that the amplitude and the inputted frequency bandwidth are determined according to the vibrating characteristics of a product itself constituting the vibration system with the mass and spring. Therefore, the inputted frequency is determined by the natural frequency of the vibration system (&ohgr;
n
=2&pgr;f
n
), thereby affecting the amplitude of the vibrating mass.
FIG. 10A
shows the conventional vibration speaker represented by a simplified vibration system. Assuming that the vibrating mass by the magnet
4
, the yoke
5
, the upper plate
3
and the weight
6
is simplified into “m”, and that the suspension springs
7
,
9
are simplified into a spring coefficient “k”, the natural frequency of the vibration system constructed as above is determined by the values of “m” and “k” as follows.
&ohgr;
n={square root over (k/m)}
Since the natural frequency forming the characteristics of the vibration system is affected by the initial conditions or amplitude, a strict management of the parts related to the vibrating characteristics is required when manufacturing the product in order to resolve the above problem caused by the touching phenomenon. The burden of the managing items is added when assembling the product, thereby increasing the unit cost. Ignorance of these factors results in a product of low quality.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a vibration speaker used for mobile communication terminals including cellular phones and pagers that can transfer a stable vibrating force to a set, on which a device is mounted for eliminating a touch sound of a vibrating mass and generating a minimum vibrating force during vibration, by expanding inputted frequency bandwidth.
To achieve the above object, there is provided a vibration speaker for transferring a stable vibrating force to a set, on which a device is mounted for eliminating a touch sound of a vibrating mass and generating a minimum vibrating force during vibration, by expanding inputted frequency bandwidth, the speaker comprising: a case having a space on an inner wall surface; a vibrating plate fixed on an upper end portion of the case at an external tip thereof for generating a sound; a voice coil wound around the vibrating plate so that an upper end thereof can be fixed on the vibrating plate; a plate, an external tip of which is fixed onto a lower end portion of the case; a magnet seated in a vertical direction; an upper plate attached to the magnet for forming a magnetic field; a weight provided on a lower portion of the voice coil to constitute a vibrating mass together with a yoke; a suspension spring for suspending the vibrating mass; and a magneto-rheological fluid having a viscosity inside thereof.
As shown in
FIG. 3
, the magneto-rheological fluid is positioned between a yoke
15
and a plate
20
. The magneto-rheological fluid is, as shown in
FIG. 7
, a fluid comprising fine magnetic particles
22
having magnetism, and a liquid
24
containing a surfactant
23
surrounding the magnetic particles
22
and oil. The magneto-rheological fluid
21
has characteristics of maintaining a consistent form if laid within the magnetic field of higher than a certain intensity so as not to flow out of or run over the rim. If the magnetic field is formed in the upper plate
13
, the magnet
14
, the yoke
15
, etc. constituting the magnetic field, as shown in
FIG. 7
, the vibrating mass performs a vertical movement so that the cleft made with the plate
20
, which is attached to the lower side of the upper plate
13
, becomes narrow due to the vertical movement of the vibrating mass. Because of the facilitation of the magneto-rheological fluid
21
having viscosity as shown in
FIGS. 3 and 4
, the magneto-rheological fluid
21
is always placed between the vibrating mass and the attachment of the lower side.
The magneto-rheological fluid
21
placed between the vibrating mass and the attachment of the lower side functions as a kind of damper due to the viscosity of itself. The following is an explanation of the function.
FIG. 10B
shows a vibrating modeling that simplifies the vibrating speaker acc

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