Patent Description:
Many conventional loudspeakers produce sound by inducing piston-like motion in a diaphragm. Panel audio loudspeakers, such as distributed mode loudspeakers (DMLs), in contrast, operate by inducing uniformly distributed vibration modes in a panel through an electro-acoustic actuator. Typically, the actuators are electromagnetic or piezoelectric actuators.

<CIT> discloses a high efficiency flat sound equipment driver which comprises a vibration system and a magnetic circuit system which are assembled together. The vibration system comprises a circular voice coil plastic driving sheet, a circular pipe voice coil, a voice coil leading wire and a circular ring voice coil ripple positioning sheet. The circular pipe voice coil is fixedly connected with one side of the circular voice coil plastic driving sheet. The voice coil leading wire is fixedly connected with the circular pipe voice coil. The circular ring voice coil ripple positioning sheet is fixedly connected with the circular pipe voice coil. The magnetic circuit system comprises an outer annular magnetic conductive sheet, an outer annular magnet, a bottom magnetic conductive disk, an inner circular magnetic conductive sheet and an inner disk magnet. The outer annular magnet and the inner disk magnet are arranged above the bottom magnetic conductive disk. The outer annular magnetic conductive sheet is arranged above the outer annular magnet. The inner circular magnetic conductive sheet is arranged above the inner disk magnet. A magnetic pole arrangement mode of the outer annular magnet is opposite to a magnetic pole arrangement mode of the inner disk magnet.

<CIT> discloses a transducer magnet for a low profile loudspeaker transducer having a voice coil, surround suspension member, diaphragm, and top plate. The transducer magnet may include a first magnet assembly. The first magnet assembly may include an annular outer magnet having an outer perimeter, an outer diameter and an inner diameter. The inner diameter defines a vacant circular center within the annular outer magnet and the difference in length between the diameter of the circular inner magnet and the inner diameter of annular outer magnet define an annular first magnet assembly air gap. The annular outer magnet includes one or more channels extending inwardly from the outer perimeter of the annular outer magnet to the first magnet assembly air gap, and the first magnet assembly air gap is configured to receive the voice coil and the channels are configured to pass hookup wires from the voice coil to an external device from the transducer magnet.

<CIT> discloses a loudspeaker drive unit comprising a visual display screen, a resonant panel-form member positioned adjacent to the display screen and at least a portion of which is transparent and through which the display screen is visible, and vibration exciting means to cause the panel-form member to resonate to act as an acoustic radiator.

<CIT> discloses a touch sensitive device comprising a touch sensitive display member capable of supporting bending wave vibration and having a user accessible display surface, an array of transducers coupled to the display member with the array of transducers comprising at least some transducers which are configured to both detect physical touching of the input surface by the user and to input impulses into the display member to produce a haptics sensation to the user in response to said detected touching of the display surface, and a signal processor to receive signals from at least some of transducers in the array of transducers and adapted to analyse the signals to determine the location of the physical touch on the display surface.

<CIT> discloses a variety of magnetic circuit arrangements functioning as acoustic drivers. The circuits include a coil former around which is wrapped a conductive coil and a magnetic gap in which the former is at least partially positioned. Further, an output disk is associated with the former to transfer sound to a substrate. Specifically, each embodiment includes a multi-component suspension system comprising various ways to associate at least one spider suspension with the coil former and integrated mounting apparatus variations that include infrastructure brackets allowing for position adjustments and compensation for torque forces on the bracket.

An aspect of the present disclosure is defined by independent claim <NUM>. Preferred embodiments are defined by way of the dependent claims.

According to the invention, the inner magnet is magnetized axially and the outer magnet is magnetized radially.

The inner and outer magnets can be symmetric with respect to axial rotations.

The device can have a maximum dimension in the axial direction of <NUM> or less (e.g., <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less).

We also describe a panel audio according to claim <NUM>.

We also describe a mobile device according to claim <NUM>.

The mobile device can be a mobile phone or a tablet computer.

Among other advantages, embodiments feature electromagnetic actuators with compact form factors and high force output. For example, use of concentric axially magnetized magnets can allow for maximizing and balancing the flux density experienced at both the inner and outer faces of a magnetic air gap in an electromagnetic actuator, maximizing a total flux density present in the air gap and therefore maximizing the force output. Such configurations may be realized in relatively small form factors, such as actuators that may be incorporated into mobile devices.

Accordingly, embodiments may solve challenges associated with creating a panel audio loudspeaker (alternatively referred to as a distributed mode loudspeaker (DML)) within a limited physical space with sufficient force over a prescribed audio bandwidth capable of exciting vibrational modes within a diaphragm while still fitting within a sufficiently small package size.

Other advantages will be evident from the description, drawings, and claims.

The disclosure features actuators for panel audio loudspeakers, such as distributed mode loudspeakers (DMLs). Such loudspeakers can be integrated into a mobile device, such as a mobile phone. For example, referring to <FIG>, a mobile device <NUM> includes a device chassis <NUM> and a touch panel display <NUM> including a flat panel display (e.g., an OLED or LCD display panel) that integrates a panel audio loudspeaker. Mobile device <NUM> interfaces with a user in a variety of ways, including by displaying images and receiving touch input via touch panel display <NUM>. Typically, a mobile device has a depth of approximately <NUM> or less, a width of <NUM> to <NUM> (e.g., <NUM> to <NUM>), and a height of <NUM> to <NUM> (e.g., <NUM> to <NUM>).

Mobile device <NUM> also produces audio output. The audio output is generated using a panel audio loudspeaker that creates sound by causing the flat panel display to vibrate. The display panel is coupled to an actuator, such as a distributed mode actuator, or DMA. The actuator is a movable component arranged to provide a force to a panel, such as touch panel display <NUM>, causing the panel to vibrate. The vibrating panel generates human-audible sound waves, e.g., in the range of <NUM> to <NUM>.

In addition to producing sound output, mobile device <NUM> can also produces haptic output using the actuator. For example, the haptic output can correspond to vibrations in the range of <NUM> to <NUM>.

<FIG> also shows a dashed line that corresponds to the cross-sectional direction shown in <FIG>. Referring to <FIG>, a cross-section <NUM> of mobile device <NUM> illustrates device chassis <NUM> and touch panel display <NUM>. <FIG> also includes a Cartesian coordinate system with X, Y, and Z axes, for ease of reference. Device chassis <NUM> has a depth measured along the Z-direction and a width measured along the X-direction. Device chassis <NUM> also has a back panel, which is formed by the portion of device chassis <NUM> that extends primarily in the X-Y-plane. Mobile device <NUM> includes an electromagnet actuator <NUM>, which is housed behind display <NUM> in chassis <NUM> and affixed to the back side of display <NUM>. Generally, electromagnet actuator <NUM> is sized to fit within a volume constrained by other components housed in the chassis, including an electronic control module <NUM> and a battery <NUM>.

Referring to <FIG>, an example of an electromagnet actuator <NUM> is shown in a cross-sectional, a sectional isometric, and an exploded isometric view, respectively. Actuator <NUM> includes a pair of axially magnetized magnets, specifically, an inner axially magnetized magnet <NUM> and an outer axially magnetized magnet <NUM>, separated by an air gap <NUM>. An axially magnetized magnet is one for which the magnetic flux lines at the magnet's surface are aligned parallel to the z-axis for the co-ordinate system shown in <FIG>. In other words, the magnet's poles are oriented along the z-axis. Inner and outer magnets <NUM> and <NUM> are arranged with their magnetic poles in opposite directions. In other words, if magnet <NUM> has its north pole facing in the +z direction, then magnet <NUM> has its north pole facing in the -z direction.

In general, the magnets can be formed from a material than can be permanently magnetized, such as rare earth magnet materials. Exemplary materials include neodymium iron boron, samarium cobalt, barium ferrite, and strontium ferrite.

A voice-coil <NUM>, including voice coil windings <NUM>, is located in air gap <NUM> between inner and outer soft magnetic plates <NUM> and <NUM> connected, via an actuator coupling plate <NUM>, to a diaphragm (e.g., display <NUM>) to generate a constant force to the diaphragm in order to excite multiple vibrational modes of said diaphragm, e.g., to generate both acoustic output and haptic feedback. Voice-coil <NUM> is sited in air gap <NUM> and is mechanically connected to the diaphragm to impart the force created by the actuator to the diaphragm. Specifically, an AC signal to voice-coil windings <NUM> present with an axial magnetic field from the coil which generates a force on actuator <NUM> to displace it back and forth in the axial (i.e., z) direction.

Soft magnetic plates (inner top plate <NUM>, outer top plate <NUM>, and back plate <NUM>) sandwich axially magnetized magnets <NUM> and <NUM>. Soft magnetic plates <NUM>, <NUM> and <NUM> can be formed from a material or materials that are readily magnetized in the presence of an external magnetic field. Typically, such materials have high relative magnetic permeability. The soft magnetic material used in embodiments of the present disclosure may have a relative permeability equal to or more than <NUM>, equal to or more than <NUM>, or equal to or more than <NUM>. Examples include high carbon steel and vanadium permendur. Accordingly, soft magnetic plates <NUM>, <NUM> and <NUM> serve to guide the magnetic flux lines from axially magnetized magnets <NUM> and <NUM> across air gap <NUM>.

Actuator coupling plate <NUM> is coupled to the magnet assembly composed of magnets <NUM> and <NUM>, top plates <NUM> and <NUM>, and back plate <NUM> by one or more suspension element (not shown) that may take various geometric forms to provide a desired stiffness in order to tune the fundamental resonance (Fo) of the actuator to a desired frequency. The material used for this suspension may be a polymer, metal or hybrid material.

The use of concentric axially magnetized magnets can provide increased magnetic field flux and/or increased uniformity in magnetic flux density across the entire air gap compared with actuators that simply feature a single magnet circuit topology. Accordingly, actuators with concentric axial magnets can provide increased force output compared to other designs.

The actuator shown in <FIG> can be compact. For example, the thickness of the actuator in the axial direction can be on the order of a few mm, e.g., <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less. The lateral dimensions can also be relatively small. For example, the outer axially magnetized magnet can have a lateral diameter (i.e., the diameter orthogonal to the symmetry axis) of <NUM> or less (e.g., <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less). In implementations where actuator <NUM> is for use in a mobile device, such as mobile phone <NUM>, the actuator can be sized and shaped to fit within the available space in the device chassis along with other components of the device.

An exemplary force vs. frequency characteristic for actuator <NUM> is shown in the plot in <FIG>. Here, the vertical axis shows a magnitude of force, while the horizontal axis shows frequency from <NUM> to <NUM>. Both axes are shown with logarithmic scales. The actuator force peaks at a resonance frequency, F0, in this case at about <NUM>. At higher frequencies, e.g., <NUM> to <NUM> in the example shown, the force v. frequency response is relatively constant. At higher frequencies (e.g., <NUM> to <NUM>), the force factor monotonically decreases as the voice coil inductance increasingly influences the response.

Actuators, such as actuator <NUM>, may be designed to specify the actuator/diaphragm fundamental resonance frequency at such a bandwidth optimized to provide haptic feedback and a constant force bandwidth.

<FIG>, which is outside the scope of the present disclosure, shows another panel audio loudspeaker magnet actuator <NUM> that does not feature a pair of axially magnetized magnets. Rather, actuator <NUM> includes a single axially-magnetized magnet <NUM>, which sits within a soft magnetic cup <NUM>. Actuator <NUM> also includes a voice coil <NUM> with voice coil windings <NUM> that are located in an air gap <NUM> between pole plate <NUM> and cup <NUM>. Voice coil <NUM> is attached to a coupling plate <NUM>. Coupling plate <NUM> includes posts <NUM> to which one or more suspension elements (not shown) are used to connect coupling plate <NUM> to cup <NUM>. A top plate <NUM>, formed from a soft magnetic material, is located on the top surface of magnet <NUM>. Such systems may have performance limitations arising from the soft magnetic top plate <NUM> and cup <NUM> increasing inductance and electrical impedance with increasing frequency. This increase in electrical inductance can reduce the acoustic output at high frequency.

The temperature and electrical resistance of the voice coil conductor can also increase with increasing current which causes power compression and limits the maximum force generated by the actuator. It is therefore often desirable to maximize (or at least, increase) the efficiency of the force generated by the actuator.

When the package size of an actuator is limited, the use of a thin magnet disc is often used in conjunction with a ferrous cup and pole piece (such as illustrated in <FIG>, in which actuator <NUM> features cup <NUM> and top plate <NUM>). However, this topology is often limited in its force generation due to the reduced flux density experienced at the outer face of the air gap compared to the flux density experienced at the inner face of the air gap created by the pole piece. This reduces the total flux density present in the air gap which corresponds to a reduction in force output.

While the foregoing examples feature axially-magnetized magnets, in some examples, actuators can utilize radially magnetized magnets. In such actuators, the magnets are magnetized such that the magnetic field lines at the magnet's surface extend in a radial direction (i.e., parallel to the x-y plane) relative to the vertical z-axis of the actuator at the magnet surfaces.

Referring to <FIG>, an example of an actuator <NUM> with radially magnetized magnets is shown in cross-sectional, sectional isometric, and exploded isometric views, respectively. Actuator <NUM> includes an inner radially-magnetized magnet <NUM> and an outer radially-magnetized magnet <NUM> both centered on a vertical axis and separated by an air gap <NUM> in which voice coil windings <NUM> of a voice coil <NUM> are placed. In the current example, a soft magnetic yoke <NUM> provides a frame to which magnets <NUM> and <NUM> are attached. An actuator coupling plate <NUM> (for attaching to a load, such as a flat panel display) is attached to voice coil <NUM>. Actuator <NUM> can also include one or more suspension elements (not shown) connecting yoke <NUM> to coupling plate <NUM>.

The use of a concentric, radially magnetized actuator (e.g., as shown in <FIG>) creates a relatively long magnetic air gap which may allow a comparatively smaller length voice coil windings to be situated within the magnetic air gap such that the magnetic field experienced by the voice coil and therefore the force generated would be linear and constant. The exclusion of soft magnetic material facing and over the length the air gap can reduce the electrical inductance and/or linearize the electrical inductance of the voice coil compared to an equivalent magnetic circuit that has soft magnetic material facing and over the length of the air gap. The use of concentric radial magnets can be used to maximize and balance the flux density experienced at both the inner and outer faces. Accordingly, such as design can increase (e.g., maximize) the total flux density present in the air gap and therefore increase (e.g., maximize) the force output.

According to the invention, electromagnetic actuators combine an axially magnetized magnet within an annular radially magnetized wall. It is believed that such actuators are able to produce more power per physical size and mass than conventional actuators. This increased power is believed to be made possible by combining, for example, both a thin, flat axially magnetized neodymium magnet and a thin wall radially magnetized magnet(s).

<FIG> depict an example of such an actuator in cross-sectional, sectional isometric, and exploded isometric views, respectively. Specifically, <FIG> show an actuator <NUM> that includes an axially magnetized disc magnet <NUM>, a radially magnetized cylindrical magnet <NUM> and a voice-coil <NUM> located in a magnetic air gap <NUM> between the radial magnet <NUM> and top plate <NUM>. Actuator <NUM> also includes a soft magnetic top plate <NUM> and a soft magnetic yoke <NUM>. The soft magnetic top plate <NUM> and yoke <NUM> serve to guide the magnetic flux lines from the axially magnetized magnet <NUM> across air gap <NUM>. Voice coil <NUM> is connected to an actuator coupling plate <NUM> to generate a constant force to a diaphragm attached to plate <NUM> in order to excite multiple vibrational modes of said diaphragm to generate both acoustic output and haptic feedback. Actuator <NUM> can also include one or more suspension elements (not shown) connecting yoke <NUM> to coupling plate <NUM>.

The magnets can be formed from a material than can be permanently magnetized, such as rare earth magnet materials. Exemplary materials include neodymium iron boron, samarium cobalt, barium ferrite, and strontium ferrite.

The use of both an axially magnetized and radially magnetized magnets provides a way to increase (e.g., maximize) and balance the flux density experienced at both the inner and outer faces of the soft magnetic top plate and yoke maximizing the total flux density present in the air gap and to therefore optimize (e.g., maximize) the force output.

In some embodiments, radially magnetized magnet <NUM> can be realized by arc segments of a magnetic material constructed in such a way to create a continuous cylinder.

The use of a complementary radially magnetized magnet surrounding the outside of the voice coil and contained by a soft magnetic yoke contains the magnetic flux within the structure of the magnetic motor circuit minimizing leakage of magnetic flux from the magnetic circuit thereby minimizing interactance of the electromagnetic field with other sensitive components that may be in close proximity to the electromagnetic actuator. Additionally, the extended vertical length of the radially magnetized magnet provides a consistent field strength over the full length of the mechanical excursion capability of the voice coil.

While the components of the actuators described above are axisymmetric (e.g., composed of continuously rotationally symmetric components, such as annular discs and the like), other implementations are also possible. For example, the actuators can have elliptical or polygonal footprints. For example, a magnetic circuit topology within an elongated (e.g., oblong) package as shown in <FIG>, which show a cross-sectional and a sectional isometric view of an actuator <NUM>. Here, actuator <NUM> includes an inner axially magnetized magnet <NUM> shaped to be concentrically slightly smaller than a corresponding soft magnetic top plate <NUM> that is also shaped to be concentrically slightly smaller than a corresponding voice coil <NUM> with voice coil windings <NUM>. A radially magnetized outer magnet <NUM> is separated from inner magnet <NUM> by an air gap <NUM>, within which voice coil <NUM> sits. Outer magnet <NUM> can be constructed, for example, from linear magnetic blocks that would be situated along the outer, linear sides of the voice coil. Actuator <NUM> further includes a soft magnetic yoke <NUM> and a coupling plate <NUM>, which is attached to voice coil <NUM>.

In general, the disclosed actuators are controlled by an electronic control module, e.g., electronic control module <NUM> in FGI. <NUM> above. In general, electronic control modules are composed of one or more electronic components that receive input from one or more sensors and/or signal receivers of the mobile phone, process the input, and generate and deliver signal waveforms that cause actuator <NUM> to provide a suitable haptic response. Referring to <FIG>, an exemplary electronic control module <NUM> of a mobile device, such as mobile phone <NUM>, includes a processor <NUM>, memory <NUM>, a display driver <NUM>, a signal generator <NUM>, an input/output (I/O) module <NUM>, and a network/communications module <NUM>. These components are in electrical communication with one another (e.g., via a signal bus) and with actuator <NUM>.

Processor <NUM> may be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, processor <NUM> can be a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or combinations of such devices.

Memory <NUM> has various instructions, computer programs or other data stored thereon. The instructions or computer programs may be configured to perform one or more of the operations or functions described with respect to the mobile device. For example, the instructions may be configured to control or coordinate the operation of the device's display via display driver <NUM>, waveform generator <NUM>, one or more components of I/O module <NUM>, one or more communication channels accessible via network/communications module <NUM>, one or more sensors (e.g., biometric sensors, temperature sensors, accelerometers, optical sensors, barometric sensors, moisture sensors and so on), and/or actuator <NUM>.

Signal generator <NUM> is configured to produce AC waveforms of varying amplitudes, frequency, and/or pulse profiles suitable for actuator <NUM> and producing acoustic and/or haptic responses via the actuator. Although depicted as a separate component, in some embodiments, signal generator <NUM> can be part of processor <NUM>.

Memory <NUM> can store electronic data that can be used by the mobile device. For example, memory <NUM> can store electrical data or content such as, for example, audio and video files, documents and applications, device settings and user preferences, timing and control signals or data for the various modules, data structures or databases, and so on. Memory <NUM> may also store instructions for recreating the various types of waveforms that may be used by signal generator <NUM> to generate signals for actuator <NUM>. Memory <NUM> may be any type of memory such as, for example, random access memory, read-only memory, Flash memory, removable memory, or other types of storage elements, or combinations of such devices.

As briefly discussed above, electronic control module <NUM> may include various input and output components represented in <FIG> as I/O module <NUM>. Although the components of I/O module <NUM> are represented as a single item in <FIG>, the mobile device may include a number of different input components, including buttons, microphones, switches, and dials for accepting user input. In some embodiments, the components of I/O module <NUM> may include one or more touch sensor and/or force sensors. For example, the mobile device's display may include one or more touch sensors and/or one or more force sensors that enable a user to provide input to the mobile device.

Each of the components of I/O module <NUM> may include specialized circuitry for generating signals or data. In some cases, the components may produce or provide feedback for application-specific input that corresponds to a prompt or user interface object presented on the display.

As noted above, network/communications module <NUM> includes one or more communication channels. These communication channels can include one or more wireless interfaces that provide communications between processor <NUM> and an external device or other electronic device. In general, the communication channels may be configured to transmit and receive data and/or signals that may be interpreted by instructions executed on processor <NUM>. In some cases, the external device is part of an external communication network that is configured to exchange data with other devices. Generally, the wireless interface may include, without limitation, radio frequency, optical, acoustic, and/or magnetic signals and may be configured to operate over a wireless interface or protocol. Example wireless interfaces include radio frequency cellular interfaces, fiber optic interfaces, acoustic interfaces, Bluetooth interfaces, Near Field Communication interfaces, infrared interfaces, USB interfaces, Wi-Fi interfaces, TCP/IP interfaces, network communications interfaces, or any conventional communication interfaces.

In some implementations, one or more of the communication channels of network/communications module <NUM> may include a wireless communication channel between the mobile device and another device, such as another mobile phone, tablet, computer, or the like. In some cases, output, audio output, haptic output or visual display elements may be transmitted directly to the other device for output. For example, an audible alert or visual warning may be transmitted from the electronic device <NUM> to a mobile phone for output on that device and vice versa. Similarly, the network/communications module <NUM> may be configured to receive input provided on another device to control the mobile device. For example, an audible alert, visual notification, or haptic alert (or instructions therefor) may be transmitted from the external device to the mobile device for presentation.

Claim 1:
An actuator (<NUM>), comprising:
an actuator coupling plate (<NUM>);
a yoke (<NUM>):
an inner magnet (<NUM>) arranged relative to an axis wherein the inner magnet is axially magnetized;
an outer magnet (<NUM>) arranged at a radial distance from the axis, an inner radial wall of the outer magnet facing an outer radial wall of the inner magnet, the outer magnet surrounding the outside of a voice coil (<NUM>) and contained by the yoke (<NUM>),
wherein the outer magnet (<NUM>) is radially magnetized;
a magnetic plate (<NUM>) co-axial with the inner magnet and proximate to the actuator coupling plate (<NUM>);
wherein the voice coil (<NUM>) is arranged in an air gap separating the outer magnet (<NUM>) and the magnetic plate (<NUM>);
wherein the yoke (<NUM>) and the magnetic plate (<NUM>) are formed from a soft magnetic material; and
wherein during operation of the actuator (<NUM>), electrical activation of the voice coil (<NUM>) causes axial motion of the actuator coupling plate (<NUM>).