Magnetic assembly and electro-acoustic transducer using same

An magnetic assembly and an electro-acoustic transducer using the same are disclosed. The magnetic assembly includes a lower plate, a main magnet positioned on a central portion of the lower plate, an auxiliary magnet positioned on a periphery portion of the lower plate, surrounding the main magnet with space, and having an inner surface facing the main magnet and an outer surface opposite to the inner surface, and a first pole plate. The first pole plate includes a base body attached on the auxiliary magnet, and a magnetic conduction member connected with the base body and overlapping the outer surface of the auxiliary magnet for forming a loop of magnetic flux together with the base body and the lower plate as well as the auxiliary magnet.

FIELD OF THE INVENTION

The present invention relates to the art of electro-acoustic transducers, more particularly to a speaker having an improved magnetic assembly.

DESCRIPTION OF RELATED ART

With the rapid development of wireless communication technologies, portable electronic devices are widely used. Users require portable electronic devices to not only have voice function, but also have high quality acoustic performance. A portable electronic device also provides the users with entertainment contents, such as music, video, game, and so on. For converting electrical signals into audible sounds, a speaker is a necessary component used in the portable electronic device for generating sounds. With the portable electronic device, such as a mobile phone, designed to be smaller and smaller, the speaker used therein is also required to have a low profile with small size.

An electro-acoustic transducer related to the present disclosure includes an vibration unit and a magnetic assembly for driving the vibration unit to vibrate. The magnetic assembly includes a lower plate, a main magnet positioned on a central portion of the lower plate, a pair of auxiliary magnets positioned away from two sides of the main magnet and a pair of second pole plates attached on upper surfaces of the auxiliary magnets, respectively. A magnetic gap is accordingly formed between the main magnet and the auxiliary magnets for partially receiving a voice coil. The magnets, including the main magnet and the auxiliary magnets, are all attached to the lower plate by adhesive, or soldering. Therefore, with such configuration of the magnetic assembly, a magnetic flux leakage would occur at the sides of the auxiliary magnets away from the main magnet, which will badly affect the acoustic performance of the electro-acoustic transducer.

Therefore, it is desirable to provide an improved magnetic assembly which can overcome the above-mentioned problems.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

Referring toFIG. 1andFIG. 2, an electro-acoustic transducer100according to an exemplary embodiment comprises a frame3, a magnetic assembly2accommodated in the frame3, a vibration unit1fixed to the frame3and driven to vibrate along a vibration direction by the magnetic assembly2, and a cover4pressing a periphery of the vibration unit1to the frame3for fixing the vibration unit1to the frame. In an alternative embodiment, the vibration unit1could also be fixed to the magnetic assembly2.

The vibration unit (comprises a diaphragm11and a voice coil12connected with the diaphragm11for driving the diaphragm11to vibrate. Optionally, the voice coil12may be connected to the diaphragm11via a medium which is directly connected with the diaphragm11. In other words, the voice coil12may be connected to the diaphragm11directly or indirectly. Therefore, the term “connect” here means to connect something to another via a medium or to connect something to another directly without any medium.

Referring toFIG. 3, The diaphragm11is made from stretchable and soft material. The diaphragm11takes a rectangular shape and defines a center line L. The diaphragm11includes a dome111and a suspension112connected with the dome111and surrounding the dome111, both of which are optionally symmetrical with respect to the center line L. The suspension112includes a ring edge1121assembled with the frame3and a supporting part1122connected with the dome111for supporting the dome111. The supporting part1122has groups of corrugations1123located on two sides of the supporting part1122parallel to the center line L and spaced with each other for increasing structural strength of the suspension. A plurality of long ribs1111is provided on the top face of the dome111. The long ribs1111each extending parallel to the center line L are arranged in a direction perpendicular to the center line L and spaced with each other in an uniform interval, which can increase structural strength of the dome111.

Referring toFIGS. 4 and 7-9, the magnetic assembly2comprises a base plate21, a main magnet221disposed on a center portion of the base plate21, and an auxiliary magnets222disposed on a periphery portion of the base plate21for forming a magnetic gap223together with the main magnet221. In this embodiment, two separated auxiliary magnets222are provided to surround the main magnet221. Alternatively, four separated auxiliary magnets222may be provided. In other embodiment, the amount of the auxiliary magnets222is variable corresponding to actual requirements. The voice coil12has one end accommodated in the magnetic gap223and the other end connected with the diaphragm11.

The base plate21is made of magnetic conduction materials for effectively conducting magnetic fluxes. At least one of the main magnet and auxiliary magnet221,222is a permanent magnet. In this embodiment, both the main magnet221and the auxiliary magnet222are permanent magnets. In an alternative embodiment, the main magnet is a permanent magnet and the auxiliary magnet is made of magnetic conduction materials for effectively conducting magnetic fluxes. Furthermore, the auxiliary magnet and the base plate may be integrally formed as one unit. Or, the main magnet is made of magnetic conduction materials for effectively conducting magnetic fluxes and the auxiliary magnets are permanent magnets. The main magnet and the base plate may be integrally formed as one unit. In this embodiment, the auxiliary magnet222takes a cuboid shape, and comprises an inner surface2222facing the main magnet221, and an outer surface2221opposite to the inner surface2222.

The magnetic assembly2further comprises a first pole plate232attached on top face of the auxiliary magnet222and a second pole plate231attached on a top face of the main magnet221. In this embodiment, two separated first pole plates232are provided to cover the auxiliary magnets respectively. The first pole plate232has a top face being coplanar with that of the second pole plate231thereby providing a greater vibration space to the diaphragm11. While electrified, the voice coil12drives the diaphragm11to vibrate along the vibration direction by the interaction between the voice coil12and the magnetic assembly2. Generally, the vibration direction is perpendicular to the base plate21.

In this embodiment, each first pole plate232includes a base body2321attached on the top face of the auxiliary magnet222and a magnetic conduction member2322connected with the base body2321and overlapping the outer surface2221of the auxiliary magnet222for forming a loop of magnetic flux together with the base body2321and the lower plate21as well as the auxiliary magnet222so as to reduce the amount of magnetic flux leakage of the magnetic assembly that occurs at the outer surface2221of the auxiliary magnet222. The base body2321and the magnetic conduction member2322are made of magnetic conduction materials for effectively conducting magnetic fluxes.

In this embodiment, the base body2321takes a rectangular shape, which is shaped to match that of the auxiliary magnets222. The base body2321includes a first side2321afacing the main magnet221and a second side2321bopposite to the first side2321a. The magnetic conduction member2322includes three separated magnetic conduction parts2322each extending substantially perpendicularly from the second side2321bsubstantially to the lower plate21so as to be close to the lower plate21. Three separated magnetic conduction parts2322are spaced with each other. Optionally, one of the magnetic conduction parts2322locates in the central portion of the second side2321b, and the other two magnetic conduction part2322locates in the both ends of the second side2321brespectively. Each magnetic conduction part2322is a flat plate, parallel to the outer surface2221of the auxiliary magnet222with space and positioned outside the outer surface2221of the auxiliary magnet222. A bottom surface of the magnetic conduction part2322may be in contact with the lower plate21. Alternatively, the bottom surface of the magnetic conduction part2322may be close to the lower plate21as far as possible. The number of magnetic conduction parts2322is not limited to this, and is variable according to actual requirements. Alternatively, the magnetic conduction part may be separated element which is connected to the base body by gluing, soldering, or the like.

In this embodiment, the first pole plate232further comprises a plurality of connecting parts2323each locating between two adjacent magnetic conduction parts2322and extending substantially horizontally from the second side2321bin a direction away from the first side2321a. Each connecting part2323is configured for connecting to the frame3. Optionally, the connecting part2323is integrated with the frame3by insert-molding.

The first pole plate232defines a plurality of recesses2324each formed on the second side2321band located between the connecting part2323and the magnetic conduction part2322. Each recess2324is depressed from the second side2321btoward the first side2321a.

Referring toFIG. 5throughFIG. 9andFIG. 2, the frame3includes a pair of first sidewalls31arranged opposite to each other and a pair of second sidewalls32arranged opposite to each other. Each first sidewall31is adjacent to each second sidewall32. The first and second sidewalls31,32are connected with each other one by one, in order from a beginning to an end, to form a receiving space30. In this embodiment, each second sidewall32faces the second side2321bof the first pole plate232. Each second sidewall32defines a plurality of engaging grooves322corresponding to the connecting parts2323one by one for receiving the connecting part2323. Each second sidewall32further comprises a plurality of projections321corresponding to the recesses2324one by one for inserting into the recesses2324. While assembled, the magnetic assembly2is received in the receiving space30. The connecting part2323is received in the engaging groove322, the projection321is received in the recess2324and the magnetic conduction part2322is embedded into the second sidewall32of the frame3. By virtue of the configuration of the frame3, the first pole plate232can be fixed to the frame3firmly.