Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electromagnetic
Reexamination Certificate
1999-12-06
2002-11-12
Kuntz, Curtis (Department: 2643)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Electromagnetic
C381S191000
Reexamination Certificate
active
06480614
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a flat acoustic converting device, and more particularly to a flat acoustic converting device such as a flat speaker, a flat microphone, a flat speaker which can be used as a microphone, a flat speaker which can be used as an antenna or the like.
BACKGROUND OF THE INVENTION
FIG. 1
shows the fundamental structure of a conventional flat speaker. The flat speaker comprises a plurality of bar magnets
1
which are arranged in parallel on a yoke
4
, a vibrating diaphragm
2
which is provided to be close to and in parallel with the magnetic pole surfaces of the bar magnets
1
, and a plurality of coils
3
each of which is formed on the surface of the vibrating diaphragm
2
at a position which corresponds to the magnetic pole surface of each of the bar magnets. A large portion of the internal periphery of each of the coils
3
is situated at a position facing the magnetic pole surface of each of the bar magnets, and the remaining portion of the coil is positioned outside of the position which corresponds to the external edge of the bar magnet. Alternating currents are supplied into the coils
3
in accordance with Fleming's left-hand rule, and each of the alternating currents is subjected to a force from the magnetic field of each bar magnet. Accordingly, the vibrating diaphragm
2
is vibrated in the direction which is perpendicular to the surface of the vibrating diaphragm
2
so that electric signals can be converted into sound signals.
Further, the vibrating diaphragm
2
is vibrated in the direction which is perpendicular to the surface of the vibrating diaphragm
2
so as to convert sound signals into electrical signals in accordance with Fleming's right-hand rule. Accordingly, this flat speaker can be used as a microphone.
However, in the above-described conventional flat speaker, because a large portion of the coil is disposed at a position on the surface of the vibrating diaphragm so as to face the magnetic pole surface of each bar magnet, a magnetic field whose orientation is perpendicular to the surface of the vibrating diaphragm acts upon the coil portion which is disposed at a position on the surface of the vibrating diaphragm and which faces the magnetic pole surface of the bar magnet. For this reason, the orientation of the force that an electric current supplied into the aforementioned coil portion receives from the magnetic field is along the surface of the vibrating diaphragm. As a result, problems arise in that the force applied along the surface of the vibrating diaphragm causes twisted portions on the surface of the vibrating diaphragm and thereby forms noise components with respect to the sound signals so that the quality of sound may be deteriorated.
Further, since a plurality of bar magnets are disposed in parallel with each other in the longitudinal directions thereof, the length of each of the bar magnets which link to the magnetic field of each coil is approximately twice as long as the product determined by multiplying the value of the longitudinal side of the bar magnet by the number of windings of the coil. The proportion of the surface area of the vibrating diaphragm occupied by the portion of a coil linking to the magnetic field along the length of the longitudinal side of the bar magnets is low. Therefore, there has been a problem that acoustic conversion efficiency deteriorates so that a sufficient amount of volume and a satisfactory quality of sound cannot be obtained.
Further, the configuration of the speaker is determined by the length of each of the bar magnets and the number of the bar magnets disposed on a vibrating diaphragm, the freedom in designing the configuration of a speaker is limited. Moreover, because a coil is disposed for each of the bar magnets along the longitudinal direction thereof, there arises the problem that there is a lack of flexibility in setting the impedance of a speaker to an appropriate value.
The present invention has been accomplished in order to solve the aforementioned drawbacks of the prior art. It is a first object of the present invention to provide a flat acoustic converting device in which the amount of twisted portions which may form on the vibrating diaphragm is decreased so that noise components can be reduced.
Further, it is a second object of the present invention to provide a flat acoustic converting device in which the length of the portion of the coil linking to the magnetic field is made longer, the proportion of the surface area of the vibrating diaphragm occupied by the portion of the coil is increased to enhance acoustic conversion efficiency and improve the quality of sound.
Further, it is a third object of the present invention to provide a flat acoustic converting device whose configuration can be designed with a high degree of freedom, which can be manufactured simply, and in which the impedance of a speaker can be set with high degree of flexibility.
DISCLOSURE OF THE INVENTION
In order to attain the aforementioned objects, the first object of the present invention is a flat acoustic converting device, comprising: a first magnet in which a first magnetic pole surface of the first magnet is disposed so as to be substantially in parallel with a predetermined face; a second magnet which is disposed so as to be spaced apart from the first magnet at a predetermined distance and so as to be adjacent to the first magnet so that a second magnetic pole surface whose polarity is different from the polarity of the first magnetic pole surface is substantially in parallel with the predetermined face and faces the same side as the first magnetic pole surface of the first magnet; a vibrating diaphragm which is disposed so as to face the predetermined face; a first coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the first magnetic pole surface; and a second coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the second magnetic pole surface.
In accordance with the first aspect of the present invention, the first magnet is disposed so that the first magnetic pole surface having the first polarity (for example, N pole) is provided substantially in parallel with the predetermined face. Further, the second magnet is disposed to be spaced apart from the first magnet and to be adjacent thereto so that the second magnetic pole surface having a second polarity (for example, S pole) which is different from the first polarity is disposed so as to be substantially in parallel with the predetermined face and so as to be directed in the same direction as the first magnetic pole surface of the first magnet. Accordingly, the first magnet and the second magnet are provided so as to be adjacent to each other so that each of the magnetic pole surfaces thereof is provided substantially in parallel with the predetermined face, and the magnetic pole surfaces whose polarities are different from each other are directed in the same direction. Moreover, the first and second magnets can be disposed on the predetermined face. However, the external peripheral portions of the first and second magnets can be supported by a frame body or the like.
A vibrating diaphragm is disposed so as to face the predetermined face. Accordingly, the orientation of the magnetic flux which is generated from each of the magnets is from the first magnetic pole surface to the second magnetic pole surface or from the second magnetic pole surface to the first magnetic pole surface. Accordingly, the orientation of the magnetic flux between the first magnetic pole surface and the second magnetic pole surface, i.e., the orientation of the magnetic flux between the first magnet and the second ma
Denda Sakuzo
Miyazaki Toshiiku
Dabney P.
FPS Inc.
Kuntz Curtis
Oliff & Berridg,e PLC
LandOfFree
Planar acoustic transducer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Planar acoustic transducer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Planar acoustic transducer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2926689