TECHNICAL FIELD

The present invention relates to the field of electro-acoustic conversion technology, and particularly relates to a sound producing device.

BACKGROUND

A sound producing device is an electroacoustic device for converting audio electric signal into sound signal, without leak of sound, and is widely used in telecommunication terminal devices, such as mobile telephones, landline telephones and hearing aids, for realizing audio (voice, music) replay. The main principle of a sound producing device is utilizing electromagnetic induction effect and piezoelectric effect, while there are also capacitive earphones utilizing the principle of a capacitor. Sound producing devices utilizing the principle of electromagnetic induction mainly include moving-iron type sound producing devices and moving-coil type sound producing devices. The existing moving-iron type sound producing devices are mostly like the sound producing device with a modified housing as disclosed in Chinese patent literature CN103747374A, which comprises a housing, a vibration membrane and an electromagnetic driving mechanism, wherein the vibration membrane is provided in the housing and separates an inner cavity of the housing into a front cavity and a rear cavity, and the electromagnetic driving mechanism is fixed in the rear cavity.

The electromagnetic driving mechanism comprises a transmission rod, an armature, two permanent magnets and a coil; wherein, the armature has one end fixed on an inner surface of a side wall of the housing and the other end connected to the vibration membrane through the transmission rod; the coil is sleeved on the armature and disposed close to the junction between the armature and the housing; the two permanent magnets are respectively disposed on an upper side and a lower side of the end of the armature close to the transmission rod, and are fixed on an inner wall surface of the housing. As for a sound producing device having such a structure, when alternating current is supplied to the coil, the coil generates alternating magnetic field, the armature is magnetized by the alternating magnetic field so as to generate magnetic poles with alternately changing size and direction, and under the action of the fixed magnetic field of the permanent magnets, the armature produces vibration in various frequencies and amplitudes, thereby driving the vibration membrane to produce sound.

However, like other sound producing device in prior art, the sound producing device with the above-mentioned structure only has one sound producing cavity and mainly produces sound waves in medium-and-high frequency bands, with poor capability for producing sound waves in low frequency bands, which eventually causes poor low-frequency characteristics of the sound producing device with this structure.

SUMMARY OF THE INVENTION

Hence, a technical problem to be solved by the present invention is the poor low-frequency characteristics of the sound producing devices in the prior art.

Thus, the present application provides a sound producing device comprisinga housing, having a hollow cavity;a vibration membrane mechanism, including at least one layer of first sound producing membrane that is mounted on the housing and separates the hollow cavity into a first cavity and a second cavity not communicated with each other; and also including a main vibration component that is mounted in the second cavity and has a vibration plate sealedly mounted on the housing; anda driving mechanism, provided in the second cavity, for driving the vibration plate to vibrate reciprocally in a direction that intersects the vibration membrane mechanism;wherein, the main vibration component separates the second cavity into a main sound producing cavity and a mounting cavity that are arranged side by side with the first cavity and not communicated with each other, the main sound producing cavity is adjacent to the first sound producing membrane; a first sound outlet hole and a second sound outlet hole are respectively opened in wall portions of the housing that correspond to the main sound producing cavity and the first cavity.

Preferably, in the aforementioned sound producing device, at least two layers of the first sound producing membrane are provided, and every two neighboring layers of the first sound producing membrane are spaced apart by a prescribed distance; at least two layers of the first sound producing membrane separate the first cavity into at least two secondary sound producing cavities that are arranged side by side with the main sound producing cavity and not communicated with one another; second sound outlet holes are respectively opened in wall portions of the housing that correspond to the secondary sound producing cavities.

Preferably, the aforementioned sound producing device further comprises an insulation member that matches the first sound producing membrane, wherein the insulation member is mounted on an inner wall of the housing and is provided with a first through-hole communicating the first cavity and the main sound producing cavity, the first sound producing membrane is mounted on the housing by being mounted on the first through-hole.

Preferably, in the aforementioned sound producing device, the main vibration component also comprises a fastening frame, one end of the vibration plate is fastened on the fastening frame, and the other end of the vibration plate is hanging in an inner space of the fastening frame; the main vibration component also comprises a second sound producing membrane which is mounted on the fastening frame and at least sealedly covers the gap between the fastening frame and the vibration plate; the fastening frame is sealedly mounted on the housing; or, at least an end portion of the fastening frame bends toward the first cavity and is sealedly fixed on the first sound producing membrane or the insulation member, with end surfaces of peripheral edges of the fastening frame being sealedly mounted on an inner wall of the housing.

Preferably, in the aforementioned sound producing device, the driving mechanism comprises at least one first permanent magnet mounted on the housing and placed to face a side of the main vibration component; a soft magnet having one end fixed on the housing and the other end fixed on the vibration plate, and placed opposite to the first permanent magnet; and a coil sleeved on the soft magnet.

Further preferably, in the aforementioned sound producing device, the driving mechanism also comprises a second permanent magnet; the second permanent magnet and the first permanent magnet are respectively placed in the main sound producing cavity and in the mounting cavity, the second permanent magnet is placed to be opposite to the first permanent magnet with mutually opposing ends having opposite polarities; the soft magnet and the coil are placed in the mounting cavity; the main vibration component and the soft magnet are placed between the second permanent magnet and the first permanent magnet; and in a vibration direction of the vibration plate, a first gap is preserved between the main vibration component and the second permanent magnet, and a second gap is preserved between the soft magnet and the first permanent magnet.

Further preferably, in the aforementioned sound producing device, when an end portion of the fastening frame bends toward the first cavity and is fixed on the first sound producing membrane or the insulation member, the coil is placed in a space delimited, along an extending direction of the vibration membrane mechanism, between the housing and the bending end portion of the fastening frame.

Preferably, the soft magnet comprises a mounting part mounted on the housing; an extending part which is formed on the mounting part and extends parallel to an extending direction of the vibration plate; and a connection part with one end fixed on the extending part and the other end fixed on the vibration plate, wherein, in a vibration direction of the vibration plate, a third gap is preserved between the extending part and the vibration plate.

Preferably, the connection part is perpendicular to the extending part.

Preferably, the driving mechanism is a piezoelectric vibrator mounted in the mounting cavity in a hanged state, wherein the piezoelectric vibrator is connected to the vibration plate through a connector.

Preferably, the housing comprises a first casing formed by a first bottom with side walls, and a second casing formed by a second bottom with side walls; and an opening of the first casing is buckled upon an opening of the second casing so as to delimit the hollow cavity.

The technical solutions provided by the present invention have the following advantages:

1. The sound producing device provided by the present invention comprises a housing, a vibration membrane mechanism and a driving mechanism. The vibration membrane mechanism comprises a first sound producing membrane and a main vibration component; the housing has a hollow cavity which is separated by the first sound producing membrane into a first cavity and a second cavity not communicated with each other; the second cavity is separated by the main vibration component into a main sound producing cavity and a mounting cavity not communicated with each other; a first sound outlet hole and a second sound outlet hole are respectively opened in wall portions of the housing that correspond to the main sound producing cavity and the first cavity. The driving mechanism drives the main vibration component to vibrate, and the vibration of the main vibration component drives the air in the main sound producing cavity to be compressed or expand, so as to cause air pressure change, and when driven by the changing air pressure, the first sound producing membrane generates vibration; the vibration of the main vibration component and the first sound producing membrane produces two sounds respectively in the main sound producing cavity and in the first cavity, the two sounds from the first sound outlet hole and the second sound outlet hole converge together to produce a mixed sound to be transmitted to the external environment.

The vibration frequency of the first sound producing membrane is consistent with the vibration frequency of the main vibration component, but since the main vibration component drives the first sound producing membrane to vibrate through the air, the vibration of the first sound producing membrane has a certain lag relative to the vibration of the main vibration component, so that a reverberation effect is caused by the sound produced by the first sound producing membrane and the sound produced by the main vibration component, thereby improving the low-frequency characteristics of the sound producing device and enhancing the fullness and depth of the sound produced by the sound producing device.

2. In the sound producing device provided by the present invention, there are at least two layers of the first sound producing membrane separating the first cavity into at least two secondary sound producing cavities each of which is provided with a second sound outlet hole.

In the sound producing device with this structure, the vibration of the main vibration component is gradually transmitted, through the main sound producing cavity, to multiple layers of the first sound producing membrane corresponding to the multiple secondary sound producing cavities sequentially, and the sounds produced by the vibration of the multiple layers of the first sound producing membrane and from the second sound outlet holes converge with the sound produced by the main vibration component, so that the reverberation effect between the sounds produced respectively by the main vibration component and the multiple layers of the first sound producing membrane is enhanced, thereby more effectively improving the low-frequency characteristics of the sound producing device.

3. The sound producing device provided by the present invention further comprises an insulation member provided with a first through-hole, the first sound producing membrane is mounted on the housing by being mounted on the first through-hole. Because the first sound producing membrane is an elastic membrane, it is relatively difficult to directly mount the first sound producing membrane onto the housing during an assembling process of the sound producing device, and by mounting the first sound producing membrane onto the housing through the insulation member, the assembling process is made more convenient.

4. In the sound producing device provided by the present invention, the main vibration component comprises a fastening frame and a second sound producing membrane, wherein one end of the vibration plate is fastened on the fastening frame and the other end of the vibration plate is hanging in an inner space of the fastening frame, the second sound producing membrane is mounted on the fastening frame and sealedly covers the gap between the fastening frame and the vibration plate. The vibration plate has one end serving as a fixed end and the other end as a free end, which not only ensures that the main vibration component separates the second cavity into the main sound producing cavity and the mounting cavity that are independent from each other and not communicated with each other, but also increases the degree of freedom of the vibration plate, so that the vibration amplitude of the vibration plate is increased under the same electromagnetic driving force, thereby improving the loudness of the sound producing device.

5. In the sound producing device provided by the present invention, the driving mechanism comprises at least one first permanent magnet, a second permanent magnet placed to be opposite to each first permanent magnet, a soft magnet and a coil. When alternating current flows in the coil, an alternating magnetic field is generated, and as a result of being magnetized by the alternating magnetic field, the alternating magnetic field is concentrated on the soft magnet, the soft magnet is placed to face the permanent magnets, so that the soft magnet would produce vibration under the action of the fixed magnetic field of the first permanent magnet and the second permanent magnet, thereby driving the main vibration component to produce vibration.

6. In the sound producing device provided by the present invention, an end portion of the fastening frame bends toward the first cavity and is sealedly fixed on the first sound producing membrane or the insulation member; the coil is placed in a space delimited, along an extending direction of the vibration membrane mechanism, between the housing and the bending end portion of the fastening frame. This space has a height larger than that of the rest of the mounting cavity, and mounting of the coil with a relatively large volume within this space may reduce the overall height of the mounting cavity, thereby making the entire sound producing device thinner.

