ELECTROMAGNETIC DRIVING DEVICE

An electromagnetic driving device includes a panel, and an electromagnetic driver attached to the panel and configured to vibrate the panel in a vibrating direction to generate sound. The electromagnetic driver includes a housing, a cover, and a driving unit disposed between the housing and the cover. The cover is attached to the panel. The driving unit includes a magnetic core, a coil wound around the magnetic core and mounted to the cover with a gap formed between the coil and the housing, and a pair of magnetic assemblies mounted to the housing and disposed on opposite axial sides of the coil. Magnetic fluxes emitted from one of the magnetic assemblies arrive at the other of the magnetic assemblies after passing through the coil. Screens of mobile terminals using the electromagnetic driving device have good acoustic effect and good reliability.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority of Chinese Application 201921118963.6, filed on Jul. 16, 2019, the content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to the field of electroacoustic conversion, and in particular to a portable electromagnetic driving device.

BACKGROUND

With the advent of the mobile internet era, the number of smart mobile devices has been continuesly increasing. Among various mobile devices, mobile phones are undoubtedly the most common and most portable mobile devices. Currently, the functions of mobile phones are very diverse, and one of them is the high-quality music function. With the growing demand for larger screen space available for user operation and better acoustic performance of the mobile phones, screen sounding technology has become a trend in the mobile phone industry. Electromagnetic driving devices are important parts for the mobile phones with the screen sounding technology.

An electromagnetic driving device in the related art generally comprises a casing, a screen covering the casing, and a driver. The casing and the screen cooperatively form an accommodation space, and the driver is installed in the accommodation space for driving the screen to vibrate and generate sound.

However, the mobile terminal devices of the related art generally adopt a piezoelectric-type driver, a moving coil type driver or an electromagnetic-type driver. The piezoelectric-type driver requires a large voltage, which means the mobile terminal needs to adjust the battery arrangement and the cost is therefore increased. The moving coil type driver has a limited driving force which limits the acoustic performance of the mobile terminal. Although the electromagnetic type driver of the related art can meet the driving force requirement, it makes the screen subject to a great suction force and imposes a high assembly requirement for the screen and middle frame of the mobile terminal device, which reduces the reliability and assemblability of the screen.

Therefore, it is desired to provide an improved electromagnetic driving device which can overcome at least one of the above problems.

SUMMARY

Accordingly, the present disclosure is directed to an electromagnetic driving device with improved acoustic performance and reliability.

In one aspect, the present disclosure provides an electromagnetic driving device comprising a panel and an electromagnetic driver attached to the panel and configured to vibrate the panel in a vibrating direction to generate sound. The electromagnetic driver comprises a housing, a cover spaced from the housing, and a driving unit disposed between the housing and the cover, one of the housing and the cover being attached to the panel. The driving unit comprises a magnetic core made of magnetic conductive material, a coil wound around the magnetic core and mounted to the cover with a gap formed between the coil and the housing, and at least one pair of magnetic assemblies mounted to the housing, the coil defining an axial direction around which the coil is wound, the axial direction being perpendicular to the vibrating direction, the at least one pair of magnetic assemblies being disposed on opposite axial sides of the coil, magnetic flux emitted from one of the at least one pair of magnetic assemblies arriving at the other of the at least one pair of magnetic assemblies after passing through the coil.

In some embodiments, the magnetic core is made of iron.

In some embodiments, the magnetic core comprises a surface on which a layer of copper is covered to form a short-circuit ring.

In some embodiments, the magnetic assembly comprises a first magnetic member, a second magnetic member and a third magnetic member, the first magnetic member being sandwiched between the second magnetic member and the third magnetic member in the vibrating direction.

In some embodiments, the first magnetic member is polarized in the vibrating direction, and the second magnetic member and the third magnetic member are polarized in the axial direction of the coil, polarized directions of the second magnetic member and the third magnetic member being reversed to each other.

In some embodiments, the first magnetic member is a permanent magnet, and the second and third magnetic members are made of permanent magnet material or magnetic conductive material.

In some embodiments, the first magnetic member is made of magnetic conductive material, and the second and third magnetic members are made of permanent magnet material.

In some embodiments, polarized directions of the first magnetic members of the at least one pair of magnetic assemblies are reversed to each other.

In some embodiments, the housing comprises an bottom plate and a side wall extending from a periphery of the bottom plate toward the cover, the bottom plate defining a recess for forming the gap between the coil and the bottom plate of the housing, the side wall surrounding the driving unit.

In some embodiments, the bottom plate has a rectangular shape, the side wall comprises a pair of first side plates and a pair of second side plates connected between the first side plates, the recessing extending from one of the second side plates to the other of the second side plates.

In some embodiments, the cover comprises a surface facing the coil, a protrusion protrudes from the surface in the vibrating direction, and the coil is fixed to the protrusion.

In some embodiments, an orthographic projection of the coil in the axial direction toward the magnetic assembly falls into a periphery of the magnetic assembly.

In another aspect, the present disclosure provides an electromagnetic driver configured to drive a screen of a mobile terminal device to vibrate and sound. The electromagnetic driver comprises a housing, a driving unit received in the housing, and a cover covering the driving unit.

The driving unit comprises a coil mounted to the cover, and two magnetic assemblies mounted to the housing, the coil defining an axial direction around which the coil is wound, the coil comprising two parts spaced arranged in a vibrating direction along which the coil and the cover is vibrated when the coil is energized. Each magnetic assembly comprises a first magnetic member, a second magnetic member and a third magnetic member, the first magnetic member being sandwiched between the second magnetic member and the third magnetic member in the vibrating direction, the second magnetic member and the third magnetic member respectively facing the two parts of the coil in the axial direction, magnetic flux emitted from one of the second magnetic members arriving at the other of the second magnetic members after passing through one of the two parts of the coil, magnetic flux emitted from one of the third magnetic members arriving at the other of the third magnetic members after passing through the other of the two parts of the coil.

In some embodiments, the first magnetic member is polarized in the vibrating direction, the second magnetic member and the third magnetic member are polarized in the axial direction of the coil, polarized directions of the second magnetic member and the third magnetic member of the same magnetic assembly are reversed to each other, and polarized directions of the first magnetic members of the two magnetic assemblies are reversed to each other.

In some embodiments, the housing comprises a bottom plate and a side wall extending from a periphery of the bottom plate toward the cover, the bottom plate defines a recess facing the coil to provide a space for vibration of the coil in the vibrating direction, the two magnetic assemblies are mounted on the bottom plate and located at opposite sides of the recess, and the side wall surrounds the two magnetic assemblies.

In some embodiments, the cover comprises a surface facing the coil, a protrusion protrudes from the surface in the vibrating direction, and the coil is fixed to the protrusion.

Compared with the related art, in the electromagnetic driving device of the present disclosure, one of the cover and the housing is contacted and fixed to the panel, and the coil and the magnetic assembly are respectively fixed to the cover and the housing. The coil and the magnetic assembly generate an electromagnetic driving force which directly drives the cover and the panel to vibrate and generate sound. The above structure can obtain a flatter electromagnetic driving force and a stable driving force output, and reduce assembly requirements. The magnetic suction force between the panel and the magnetic assembly is balanced and the requirements on the panel are reduced. The electromagnetic driving device of the present disclosure is applicable to panels of different types of screens. The side wall of the housing and the second and third magnetic members cooperate to reduce the magnetic leakage. Thus, a magnet field with high usage efficiency is achieved and interference of the magnet field with other components is avoided. The attenuation of the high frequency performance is reduced and the acoustic performance of the acoustic screens is improved.

DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be further illustrated with reference to the accompanying drawings. It shall be noted that the elements of similar structures or functions are represented by like reference numerals throughout the figures. The embodiments described herein are not intended as an exhaustive illustration or description of various other embodiments or as a limitation on the scope of the claims or the scope of some other embodiments that are apparent to one of ordinary skills in the art in view of the embodiments described in the Application. In addition, an illustrated embodiment need not have all the aspects or advantages shown.

Referring toFIG. 1, an electromagnetic driving device100in accordance with an exemplary embodiment of the present disclosure comprises a panel1, and an electromagnetic driver2attached to the panel1for driving the panel1to vibrate and sound.

Referring toFIGS. 2 and 3, the electromagnetic driver2comprises a housing21, a cover22spaced from the housing21, and a driving unit23arranged between the housing21and the cover22. One of the housing21and the cover22is fixed to the panel1. In this embodiment, the cover22is plate-shaped which is fixed to and closely contacts the panel1.

Specifically, the housing21includes a bottom plate211, and a side wall212extending from the periphery of the bottom plate211toward the cover22. The side wall212is spaced from the cover22. A recess213is formed in a surface of the bottom plate211facing the cover22. The recess213extends from the surface of the bottom plate211in a direction away from the cover22.

In the illustrated embodiment, the bottom plate211has a rectangular shape. The side wall212comprises a pair of first side plates2121spaced from each other, and a pair of second side plates2122spaced from each other and respectively connected between the pair of first side plates2121. The recess213extends from one of the second side plates2122to the other of the second side plates2122.

The driving unit23comprises a coil231fixed to the cover22, a iron core232around which the coil231is wound, and at least one magnetic assembly233fixed to the housing21.

The coil231defines an axial direction around which the coil231is wound. The axil direction of the coil231is perpendicular to a vibrating direction of the panel1. In this exemplary embodiment, the first side plate2121is perpendicular to the axil direction of the coil2311, and the bottom plate211and the cover22are parallel to the axil direction of the coil231. The coil231comprises an upper part facing and fixed to the cover22, and a lower part away from the cover22. The lower part of the coil231facing the bottom plate231of the housing2is spaced apart from the bottom plate2311in the vibration direction.

The magnetic assembly233comprises a first magnetic member2331, a second magnetic member2332and a third magnetic member2333. The first magnetic member2331is sandwiched between the second magnetic member2332and the third magnetic member2333in the vibrating direction. In the illustrated embodiment, the first magnetic member2331is implemented as a main magnetic member2331, and the second magnetic member2332and the third magnetic member2333are implemented as auxiliary magnetic members. In this embodiment, there are two such magnetic assemblies233that are respectively located on opposite sides of the recess213. The coil231is disposed between the two magnetic assemblies233in the axial direction of the coil231, with axial gaps formed between the coil231and the magnetic assemblies233such that the coil231is movable relative to the magnetic assemblies233in the vibrating direction. Understandably, the number of the magnetic assemblies233can be four, six or other even numbers. The side wall212of the housing21made of magnetic conductive material is disposed to surround the magnetic assemblies233, which can reduce magnetic leakage and hence enhance usage efficiency of the magnetic field of the magnetic assemblies233. As a result, the driving force of the driving unit23can be increased, such that the acoustic effect of the sound generated by vibration of the panel1can be improved.

In the illustrated embodiment, an orthographic projection of the coil231on the housing211in the vibrating direction completely falls within the periphery of the recess213. The recess213in the bottom plate211provides a space for vibration of the coil231in the vibrating direction and prevents the coil231from bumping against the bottom plate211to generate noise during vibration, which further improves the acoustic effect of the sound generated by vibration of the screen. Furthermore, the provision of the recess213can reduce magnetic leakage through the bottom wall211.

Preferably, a protrusion221protrudes from a surface of the cover22facing the coil231in the vibrating direction, and the coil231is fixed to the protrusion221. With the provision of the protrusion221, the upper part of the coil231can be disposed at the same level or lower than an upper surface of each magnetic assembly233, such that an orthographic projection of the coil231in the axial direction onto the magnetic assembly233falls completely within the periphery of the magnetic assembly233, which further increases the magnetic driving force of the driving unit23.

In this embodiment, the first magnetic member2331is a permanent magnet such as a ferrite magnet or a rare earth magnet. The first magnetic member2331is polarized in the vibrating direction of the coil231. The second magnetic member2332and the third magnetic member2333are also permanent magnets. The second magnetic member2332and the third magnetic member2333are fixed to opposite ends of the first magnetic member2331along the vibrating direction. The second magnetic member2332is fixed to the housing21, for example, fixed to the bottom plate211of the housing21. The third magnetic member2333faces the cover22with a gap formed therebetween in the vibrating direction.

The second magnetic member2332faces one side of the coil231with the axial gap formed therebetween. The third magnetic member2333faces the other side of the coil231with the axial gap formed therebetween. The second magnetic member2332and the third magnetic member2333are polarized in the axial direction of the coil231. The polarity of an end of the second magnetic member2332near the coil231is the same as the polarity of one end of the first magnetic member2331near the second magnetic member2332, and the polarity of an end of the third magnetic member2333near the coil231is the same as the polarity of the other end of the first magnetic member2331near the third magnetic member2333. The second magnetic member2332and the third magnetic member2333are configured to conduct magnetic flux from one end of the first magnetic member2331to one part of the coil231and back to the other end of the first magnetic member2331from the other part of the coil231.

In this embodiment, the magnetization directions of the first magnetic members2331of the two magnetic assemblies233are opposite to each other. For example, as shown inFIG. 3, the end of the left first magnetic member2331facing the cover22is a north pole, and the end of the left first magnetic member2331facing the bottom plate211is a south pole; the end of the right first magnetic member2331facing the cover22is a south pole, and the end of the right first magnetic member2331facing the bottom plate211is a north pole.

In this embodiment, the second magnetic member2332and the third magnetic member2333are implemented as permanent magnets. The magnetization directions of the second magnetic member2332and the third magnetic member2333are opposite to each other and are each perpendicular to the vibrating direction. For example, in the same magnetic assembly233at the left side of the coil231, the end of the second magnetic member2332adjacent the coil231is a south pole, and the end of the second magnetic member2332away from the coil231is a north pole; the end of the third magnetic member2333adjacent the coil231is a north pole, and the end of the third magnetic member2333away from the coil231is a south pole.

Two ends of the two second magnetic members2332of the two magnetic assemblies233facing the same part of the coil231have opposite polarity. For example, as shown inFIG. 3, for the two first magnetic members2332in the two magnetic assemblies233respectively located on left and right sides of the coil231, the end of the second magnetic member2332located on the left side of the coil231facing the coil231is a south pole, and the end of the second magnetic member2332located on the left side of the coil231away from the coil231is a north pole; the end of the second magnetic member2332located on the right side of the coil231facing the coil231is a north pole, and the end of the second magnetic member2332located on the right side of the coil231away from the coil231is a south pole. Magnetic flux emitted from the north pole of the second magnetic member2332located on the right side of the coil231arrives at the south pole of the second magnetic member2332located on the left side of the coil231after passing through the lower part of the coil231.

Two ends of the two third magnetic members2333of the two magnetic assemblies233facing the same part of the coil231have opposite polarity. For example, as shown inFIG. 3, for the two third magnetic members2333in the two magnetic assemblies233respectively located on left and right sides of the coil231, the end of the third magnetic member2333located on the left side of the coil231facing the coil231is a north pole, and the end of the third magnetic member2333located on the right side of the coil231away from the coil231is a south pole; the end of the third magnetic member2333located on the right side of the coil231facing the coil231is a south pole, and the end of the third magnetic member2333located on the right side of the coil231away from the coil231is a north pole. Magnetic flux emitted from the north pole of the third magnetic member2333located on the left side of the coil231arrives at the south pole of the third magnetic member2333located on the right side of the coil231after passing through the upper part of the coil231.

During operation, an alternating current is applied to the coil231which is therefore driven by the magnetic field generated by the magnetic assemblies233to vibrate in the vibrating direction, thereby driving the cover22and the panel1to vibrate and sound.

Referring toFIG. 4, according to an alternative embodiment, the first magnetic member62331is a permanent magnet, while the second magnetic member62332and the third magnetic member62333are implemented as magnet conductive members made of a magnetic conductive material such as iron. The working principle of the alternative embodiment is similar to that of the embodiment described above. Each of the second magnetic member62332and the third magnetic member62333is magnetized by the first magnetic members62331being of permanent magnets. For example, in the same magnetic assembly6233on the left side of the coil6231, the end of the second magnetic member62332adjacent the coil6231is magnetized to form a south pole, and the end of the third magnetic member62333adjacent the coil6231is magnetized to form a north pole. Except for the second magnetic member62332and the third magnetic member62333, the other components in the alternative embodiment are the same as in the embodiment described above and therefore explanations thereof are not repeated.

Understandably, when the second magnetic member2332and the third magnetic member2333are made of permanent magnet material, the first magnetic member2331may be made of a magnetic conductive material and configured to conduct magnetic flux from one of the second magnetic member2332and the third magnetic member2333to the other of the second magnetic member2332and the third magnetic member2333.

Referring again toFIGS. 1-3, the iron coreless driving unit23can provide a more flat magnetic field driving force and a more stable output, which reduces the assembly requirements and does not cause too much attenuation of high-frequency performance. At the same time, the magnetic suction force between the panel1and the magnetic assembly233is balanced and the requirements on the panel1are therefore reduced, which makes the electromagnetic driver2suitable for various types of screens such as hard OLED screen, soft OLED screen, or LCD, and improves the reliability of the screens. The magnetic circuit of the magnetic assembly233can be split or used together according to different application scenarios. The side wall212of the housing21and the second magnetic member2332and the third magnetic member2333cooperate to reduce magnetic leakage, thereby achieving a high-efficiency magnetic field and avoiding interference with other components.

In order to further improve the driving force and optimize the effect of sound generation by vibrating the screen, in the electromagnetic driving device100of the present disclosure, the driving unit23may further comprise a magnetic core232, and the coil231is wound around the magnetic core232. The magnetic core232is made of magnetic conductive material such as iron.

For the same magnetic assembly233, magnetic flux emitted from one of the second magnetic member2332and the third magnetic member2333passes through one part of the coil231and enters into the other of the second magnetic member2332and the third magnetic member2333after passing through the other part of the coil231. During operation, the coil231is charged with an alternating current, and a first driving force in the vibrating direction is formed between the coil231and the magnetic field generated by magnetic assemblies233. After the coil231is energized, the coil231generates an induced magnetic field passing through the magnetic core232. The magnetic core232produces an electromagnet effect and becomes an electromagnet, the polarization direction of which is along the axial direction of the coil231. The magnetic core232interacts with the magnetic assemblies233to produce a second driving force in the vibrating direction. The first driving force and the second driving force are superimposed and the directions of the first driving force and the second driving force are the same, thereby further increasing the efficiency of the magnetic field and improving the acoustic effect of the sound generated by vibration of the panel1.

More preferably, the surface of the magnetic core232is plated with copper or a copper ring is attached around the magnetic core232to form a short-circuit ring in order to solve the problem of high frequency performance attenuation.

When the magnetic assembly233includes the magnetic core such as an iron core, a higher magnetic field driving force can be obtained. The high frequency performance may be attenuated to some extent due to the use of the iron core232, and the short-circuit ring can be formed to effectively address the high frequency performance attenuation issue.

Compared with the related art, in the electromagnetic driving device of the present disclosure, one of the cover and the housing is fixed to the panel, and the coil and the magnetic assemblies are respectively fixed to the cover and the housing. The coil and the magnetic assemblies cooperate to generate an electromagnetic driving force which directly drives the cover to vibrate. The vibrating cover in turn drives the panel to vibrate and generate sound. The electromagnetic driving device of the present disclosure can obtain a more flat electromagnetic driving force and a more stable driving force output, thus reducing the assembly requirements of the screen and frame of the mobile terminal using the electromagnetic driving device of the present disclosure. The magnetic suction force between the panel and the magnetic assemblies is balanced and the requirements on the panel are reduced, which makes the electromagnetic driving device of the present disclosure suitable for panels of various types of screens. The side wall of the housing and the second and third magnetic members are provided to reduce the magnetic leakage, such that a high usage efficiency magnet field can be achieved without interfering with other components of the mobile terminal. In addition, the attenuation of the high frequency performance is reduced, and the acoustic effect of the sound generation by vibrating the panel is improved.

Although the invention is described with reference to one or more embodiments, the above description of the embodiments is used only to enable people skilled in the art to practice or use the invention. It should be appreciated by those skilled in the art that various modifications are possible without departing from the spirit or scope of the present invention. The embodiments illustrated above should not be interpreted as limits to the present invention, and the scope of the invention is to be determined by reference to the claims that follow.